Close
About
FAQ
Home
Collections
Login
USC Login
Register
0
Selected
Invert selection
Deselect all
Deselect all
Click here to refresh results
Click here to refresh results
USC
/
Digital Library
/
University of Southern California Dissertations and Theses
/
Hydrogen energy system production and storage via iridium-based catalysts
(USC Thesis Other)
Hydrogen energy system production and storage via iridium-based catalysts
PDF
Download
Share
Open document
Flip pages
Contact Us
Contact Us
Copy asset link
Request this asset
Transcript (if available)
Content
HYDROGEN ENERGY SYSTEM
PRODUCTION AND STORAGE VIA IRIDIUM-BASED CATALYSTS
by
VAN KHANH DO
A Dissertation Presented to the
FACULTY OF THE USC GRADUATE SCHOOL
UNIVERSITY OF SOUTHERN CALIFORNIA
In Partial Fulfillment of the
Requirements for the Degree
DOCTOR OF PHILOSOPHY
(CHEMISTRY)
MAY 2023
© Copyright 2023 by Van K. Do, 2023. All rights Reserved.
ii
Dedication
In the loving memory of my grandmother, bà ngoại.
To my family bố mẹ, my sister Uyên, and my friends in my hometown in Vietnam
To my special friends – Sherri, Joe, and Lâm
To my loving and supporting fiancé William and the Richards Family
iii
Acknowledgments
Above all, I would like to express my appreciation for my academic advisor, Professor
Travis J. Williams. There are many lessons, even outside of Chemistry, that Travis taught me
over the past five years, besides Chemistry. Thank you, Travis, for providing me guidance in this
very challenging program. Thanks to you, I’m a different person now than I was years ago.
I would like to thank my qualification and dissertation committee members: professors
Barry Thompson, Valery Fokin, Jessie Yen, and Dr. Andy Chang for their advice and time.
Thanks to the Department of Energy-Hydrogen Material Advanced Research Consortium (DOE-
HyMARC) at Los Alamos, Pacific Northwest, Oak Ridge National Laboratories, and National
Renewable Energy Laboratory: Dr. Robert Currier, Dr. John Gordon, Dr. Pavel Dub, Dr. Thomas
Autrey, Dr. Katherina Grubel, Dr. Samantha Johnson, Dr. Mark Bowden, Dr. Ryan Klein, Dr.
Craig Brown, Dr. Xiaoping Wang, and Dr. Yongqiang Cheng, for various technical advice and
support on the hydrogen program and neutron diffraction crystallography.
Thanks to all former and current Williams group members, especially to Dr. Ivan
Demianets who was the first to introduce organometallic chemistry to me. A special thank you to
A.J. Chavez for being an amazing undergraduate researcher and friend. And to the great
colleagues in the Williams group, I thank you for being yourselves and providing me a
professional working environment for me to grow as a chemist: Dr. Carlos Navarro, Dr. Valeriy
Cherepakhin, Adriane Tam, Stephanie Sun, Andrew Rice Rander, Justin Lim, Long Zhang,
Yuhao Chen, Brandon Wong, and Davin Nguyen. My graduate studies would have been so much
more challenging without the emotional support of my cohort friends at USC, thank you for the
fun, gossip, relationship advice, and the coffee/lunches: Dr. Keying Chen, Dr. Bryce Tappan, Dr.
iv
Carlos Navarro, Dr. Nicolas Hartel, Alexander Schmitt, Xanath Ispizua-Rodriguez, and C.J.
Koch.
To all excellent faculty and staff members of the USC Chemistry Department and Loker
Hydrocarbon Institute: Dr. Allan Kershaw, Dr. Shawn Wagner, Dr. Ralf Haiges, Dr. Robert
Aniszfeld, David Hunter, Philip Sliwoski, Joseph Lim, Michele Dea, Carol Philips, Magnolia
Benitez, and Jessie May. I thank you for the endless support in the program from instruments to
infrastructures.
Last but not least, I am eternally grateful for my family: my grandmother, my parents, my
siblings, my fiancé William, my future in-laws, the Richards family, and my dearest friends
Sherri Sawicki and Lam Bui. Your love and support have carried me on through many hardships
and successes in life.
v
Table of Contents
Dedication ....................................................................................................................................... ii
Acknowledgments.......................................................................................................................... iii
List of Figures .............................................................................................................................. viii
List of Schemes ............................................................................................................................ xiv
Preparative Procedures................................................................................................................. xvi
Abstract ........................................................................................................................................ xix
Chapter 1. Catalyst Carbonylation in Metal-Catalyzing Alcohol Dehydrogenation in
Homogeneous Catalyst Development .......................................................................................... 1
1.1 Introduction ............................................................................................................................... 1
1.2 How Do Organics Decarbonylate? ........................................................................................... 3
1.3 Metal-Catalyzing Alcohol Oxidation/Dehydrogenation ........................................................... 6
1.4 Hydrogen Borrowing Amination ............................................................................................ 11
1.5 Carbonylation Reactions ......................................................................................................... 15
1.6 Conclusions and Outlook ........................................................................................................ 17
1.7 References ............................................................................................................................... 19
Chapter 2 Pressurized Formic Acid Dehydrogenation: An Entropic Spring Replaces
Hydrogen Compression Cost ..................................................................................................... 23
2.1 Introduction ............................................................................................................................. 23
2.2 Catalysts for FA Dehydrogenation at Ambient and Self-Pressurizing Conditions................. 25
2.3 Impact of Applied H2 and CO ................................................................................................. 33
2.4 Regeneration, Activity, and Selectivity of 11 in High Pressure Gas Stream Production ....... 39
2.5 Conclusions ............................................................................................................................. 39
vi
2.6 References ............................................................................................................................... 42
Chapter 3 Bonding and Reactivity in Triiridium Polyhydride Clusters. Reversible
CO2-Formate Conversion ........................................................................................................... 46
3.1 Introduction ............................................................................................................................. 47
3.2 Synthesis and Characterizations of Complex 3.1-O and 3.1-H .............................................. 49
3.3 Structural Analysis and Bonding via First Principle Calculations and Neutron Vibrational
Spectroscopy ................................................................................................................................. 58
3.4 CO2 Hydrogenation and Formic Acid Dehydrogenation ........................................................ 62
3.5 Conclusion .............................................................................................................................. 64
3.6 References ............................................................................................................................... 65
Chapter 4 Mechanistic Study of Prolific Ir-Catalyzing Formic Acid Dehydrogenation
and Blended Fuel......................................................................................................................... 70
4.1 Iridium-Catalyzing Dehydrogenation of Neat Formic Acid ................................................... 70
4.2 On-Demand Formic Acid Release Scale-up and H2 Purification ........................................... 76
4.3 Synthesis of Bifunctional Photobasic Iridium Catalyst for Methanol Dehydrogenation at
Room Temperature ....................................................................................................................... 79
4.4 Conclusion .............................................................................................................................. 80
4.5 References ............................................................................................................................... 82
Chapter 5 Experimental and Spectral Data ............................................................................. 88
5.1. General Procedures ................................................................................................................ 88
5.1.1. Reagents .................................................................................................................. 88
5.1.2. Instrumentations ...................................................................................................... 88
5.1.3. Experimental Procedures ........................................................................................ 89
vii
5.2. Chapter 2 Experimental and Spectral Data ............................................................................ 89
5.3. Chapter 3 Experimental and Spectral Data ............................................................................ 97
5.4. Chapter 4 Experimental and Spectral Data .......................................................................... 139
5.5. Crystallography Data (X-ray & Neutron Diffraction) ......................................................... 154
5.5.1 Crystal Structure Data for 2.11-Rh ........................................................................ 154
5.5.2 X-ray Crystal Structure Data for 3.1-H ................................................................. 164
5.5.3 Neutron Diffraction Crystallographic Data of 3.1-H ............................................. 183
5.5.4 X-ray Crystal Structure Data for 3.1-O ................................................................. 185
5.5.5 Crystal Structure Data for 3.1-Au .......................................................................... 195
5.5.6 Crystal Structure Data for 3.2-Cl ........................................................................... 215
5.5.7 Crystal Structure Data for 4.2 ................................................................................ 225
5.5.8 Crystal Structure Data for 4.9 ................................................................................ 227
5.5.9. References ............................................................................................................. 236
viii
List of Figures
Figure 1.1 PNN monomer (1.5a) and dimer (1.5b) pre-catalysts for primary and secondary
alcohol dehydrogenation ................................................................................................................ 6
Figure 2.1 Late Transition metal complexes tested for formic acid dehydrogenation in this
study .............................................................................................................................................. 25
Figure 2.2 Gas evolution of formic acid dehydrogenation by complexes 2.1-2.21 at ambient
pressure over time (Left: 0 - 25 hours; Right: 0-5 hours) ............................................................. 28
Figure 2.3 Structural analogy between the common Noyori-type, Milstein-type pincer and
our pseudo-pincer active catalytic species .................................................................................... 30
Figure 2.4 Gas evolution of formic acid dehydrogenation by complex 2.1-2.21 over time
at ambient pressure condition (opened system) – grey triangles; at self-pressurized condition
(closed system) – blue diamonds. ................................................................................................. 32
Figure 2.5 Pressurized dehydrogenations of FA: control (black squares), pretreated with 8
bar of H2 (green triangles), (orange circles) pre-treated with 1 bar of CO following by N2
purging. Top left. complex 2.5; Top right. complex 2.15; Bottom left. complex 2.10;
Bottom right. complex 2.14 .......................................................................................................... 33
Figure 2.6 Left: Kinetic profile of FA dehydrogenation by 2.9 (black circles) and 2.9-CO
(orange circles).............................................................................................................................. 36
Figure 2.7 (Top) Gas evolution of formic acid dehydrogenation by complex 2.9, 2.9-CO,
and 2.10 over time pretreated with 0 bar CO ................................................................................ 37
Figure 2.8 Catalyst recycling study in FA dehydrogenation by complex 2.11 ............................ 40
Figure 3.1
1
H NMR intergration of hydrides illustrated in H/D exchange rate of complex
3.1-H in neat triflic acid-d1 ........................................................................................................... 54
ix
Figure 3.2 Experimental FTIR spectrum for 3.1-H (black curve, top) and NV spectrum for
3.1-H(d72) (black curve) with simulated spectra for the full material (red curve) and for the
compound with scattering cross-section set to 0 for all non-Ir3H7 atoms (blue curve). Error
bars represent ±1σ ......................................................................................................................... 59
Figure 3.3 Neutron molecular structure of 3.1-H ........................................................................ 60
Figure 4.1 Computed thermodynamic equilibria – formic acid dehydrogenation (red),
methanol dehydrogenation (blue), blended fuel dehydrogenation (green) 73
Figure 4.2 Catalytic dehydrogenation with 2.11 in aqueous methanol-formic acid blended
fuel solution at 110 °C .................................................................................................................. 74
Figure 4.3
31
P NMR time-course study of blended fuel dehydrogenation with 2.11 resulting
in formation of resting state 2.11-CO (bottom) after 48 hours ..................................................... 75
Figure 5.2.1
1
H NMR spectrum of 2.5 in CD2Cl2 ........................................................................ 89
Figure 5.2.2
31
P{
1
H} NMR spectra of 2.5 in CD2Cl2 .................................................................. 90
Figure 5.2.3
1
H{
31
P} NMR spectrum of 2.11-CO in CD2Cl2 ...................................................... 92
Figure 5.2.4
13
C NMR spectrum of 2.11-CO in CD2Cl2 ............................................................. 93
Figure 5.2.5
19
F NMR spectra of 2.11-CO in CD2Cl2 ................................................................. 93
Figure 5.2.6
31
P{
1
H} NMR spectra of 2.11-CO in CD2Cl2 ......................................................... 94
Figure 5.3.1 a. Full
1
H{
31
P} spectrum of 3.1-O; b. Proton region; c. Hydride region ........... 97-98
Figure 5.3.2
31
P{
1
H} NMR spectrum of 3.1-O ............................................................................ 99
Figure 5.3.3
19
F NMR spectrum of 3.1-O .................................................................................. 100
Figure 5.3.4
13
C NMR spectra of 3.1-O .............................................................................. 101-102
Figure 5.3.5 IR spectrum of 3.1-O in KBr pellet ....................................................................... 102
x
Figure 5.3.6
1
H{
31
P} NMR spectrum of 3.1-H .......................................................................... 104
Figure 5.3.7
13
C NMR spectrum of 3.1-H ................................................................................. 105
Figure 5.3.8
13
P{
1
H} NMR spectrum of 3.1-H .......................................................................... 106
Figure 5.3.9
19
F NMR spectrum of 3.1-H .................................................................................. 107
Figure 5.3.10 IR spectrum of 3.1-H in KBr pellet ..................................................................... 107
Figure 5.3.11 UV-Vis spectrum of 3.1-H in methanol .............................................................. 108
Figure 5.3.12
1
H{
31
P} NMR spectrum of 3.1-Au ...................................................................... 110
Figure 5.3.13
13
C NMR spectrum of 3.1-Au ............................................................................. 111
Figure 5.3.14
31
P{
1
H} NMR spectrum of 3.1-Au ...................................................................... 112
Figure 5.3.15
19
F NMR spectrum of 3.1-Au .............................................................................. 113
Figure 5.3.16 IR spectrum of 3.1-Au in KBr pellet ................................................................... 113
Figure 5.3.17
1
H{
31
P} NMR spectrum of 3.2-I ......................................................................... 115
Figure 5.3.18
31
P{
1
H} NMR spectrum of 3.2.I .......................................................................... 116
Figure 5.3.19
13
C NMR spectrum of 3.2-I ................................................................................. 116
Figure 5.3.20
2
H NMR spectrum of 2-picoline-d7 in H2O ......................................................... 118
Figure 5.3.21
13
C{
1
H} NMR spectrum of 2-picoline-d7 in D2O ................................................ 118
Figure 5.3.22
2
H NMR spectrum of [(CD3)3C]2PCl in C6H6 ..................................................... 120
Figure 5.3.23
13
C{
1
H} NMR spectrum of [(CD3)3C]2PCl in CDCl3 ......................................... 121
Figure 5.3.24
31
P{
1
H} NMR spectrum of [(CD3)3C]2PCl in C6D6 ............................................ 121
Figure 5.3.25
2
H NMR spectrum of PN-d24 in CH2Cl2 .............................................................. 123
Figure 5.3.26
13
C{
1
H} NMR spectrum of PN-d24 in C6D6 ........................................................ 123
Figure 5.3.27
31
P{
1
H} NMR spectrum of PN-d24 in CD2Cl2 ..................................................... 124
Figure 5.3.28
1
H NMR spectrum of [Ir(COD)(PN-d24)]OTf in CD2Cl2 .................................... 126
xi
Figure 5.3.29
2
H NMR spectrum of [Ir(COD)(PN-d24)]OTf in CD2Cl2 .................................... 127
Figure 5.3.30
13
C{
1
H} NMR spectrum of [Ir(COD)(PN-d24)]OTf in CD2Cl2 ........................... 127
Figure 5.3.31
31
P{
1
H} NMR spectrum of [Ir(COD)(PN-d24)]OTf in CD2Cl2 ........................... 128
Figure 5.3.32 IR spectrum of [Ir(COD)(PN-d24)]OTf ............................................................... 128
Figure 5.3.33
2
H NMR spectrum of 3.1-H(d72) in CH2Cl2 ........................................................ 130
Figure 5.3.34
31
P{
1
H} NMR spectrum of 3.1-H(d72) in CD2Cl2 .............................................. 131
Figure 5.3.35
19
F NMR spectrum of 3.1-H(d72) in CD2Cl2 ...................................................... 132
Figure 5.3.36 IR spectrum of 3.1-H(d72) ................................................................................... 132
Figure 5.3.37 Table 3.1, entry 1 spectrum –
1
H{
31
P} NMR (500 MHz, CD2Cl2) ..................... 133
Figure 5.3.38 Table 3.1, entry 2 spectra –
1
H{
31
P} (600 MHz, CD2Cl2) and
2
H NMR (600
MHz, CD2Cl2) ............................................................................................................................. 134
Figure 5.3.39 Table 3.1, entry 3 spectrum –
1
H{
31
P} (600 MHz, CD2Cl2) ............................... 134
Figure 5.3.40 Table 3.1, entry 4 spectrum –
1
H{
31
P} (600 MHz, CD2Cl2) ............................... 135
Figure 5.3.41 Formation of Ir3H6(µ3-S)(PN)
+
in D2/D2S condition ........................................... 135
Figure 5.3.42 Cyclic voltammetry of complex 3.1-H (1.0 mM in CH2Cl2, 0.1 M
[Bu4N][PF6], and FeCp*2 as reference at two scan rates, 50 mV/s and 200 mV/s).................... 136
Figure 5.4.1
1
H NMR spectrum of 4.5 at 25 °C in CDCl3 ......................................................... 139
Figure 5.4.2
13
C NMR spectrum of 4.5 at 25 °C in CDCl3 ........................................................ 140
Figure 5.4.3 IR spectrum of 4.5 ................................................................................................. 140
Figure 5.4.4
1
H NMR spectrum of 4.6 at 25 °C in CDCl3 ......................................................... 142
Figure 5.4.5
13
C NMR spectrum of 4.6 at 25 °C in CDCl3 ........................................................ 143
Figure 5.4.6 IR spectrum of 4.6 ................................................................................................. 143
Figure 5.4.7
1
H NMR spectrum of 4.7 at 25 °C in CDCl3 ......................................................... 145
xii
Figure 5.4.8
13
C NMR spectrum of 4.7 at 25 °C in CDCl3 ........................................................ 146
Figure 5.4.9 IR spectrum of 4.7 ................................................................................................. 146
Figure 5.4.10
1
H NMR spectrum of 4.8 at 25 °C in CDCl3 ....................................................... 148
Figure 5.4.11 Stacked FTIR spectra of CO experiments ........................................................... 150
Figure 5.4.12 CO experiment. Condition: 60 mL FA, 25.3 mg of 2.11, 25.3 g NaOOCH,
120 °C. Headspace gas was collected at 1458 psi ...................................................................... 151
Figure 5.4.13 CO experiment via demonstration reactor ........................................................... 151
Figure 5.4.14 CO experiment via demonstration reactor ........................................................... 152
Figure 5.4.15 CO experiment via demonstration reactor ........................................................... 152
Figure 5.5.1.1 Molecular structure of 2.11-Rh shown with 50% probability ellipsoids.
Hydrogen atoms are omitted for clarity ...................................................................................... 153
Figure 5.5.2.1 Molecular structure of 3.1-H shown with 50% probability ellipsoids.
Hydrogen atoms and counteranions are omitted for clarity, except hydrides............................. 163
Figure 5.5.3.1 Neutron molecular structure of 3.1-H shown with 50% probability
ellipsoids. Hydrogen atoms and counteranions are omitted for clarity, except hydrides ........... 182
Figure 5.5.4.1 Molecular structure of 3.1-O shown with 50% probability ellipsoids.
Hydrogen atoms are omitted for clarity, except hydrides ........................................................... 184
Figure 5.5.5.1 Molecular structure of 3.1-Au shown with 50% probability ellipsoids.
Hydrogen atoms are omitted for clarity, except hydrides ........................................................... 194
Figure 5.5.6.1 Molecular structure of 3.2-Cl shown with 50% probability ellipsoids.
Hydrogen atoms are omitted for clarity, except hydrides ........................................................... 214
Figure 5.5.7.1 Molecular structure of 4.2 shown with 50% probability ellipsoids.
Hydrogen atoms are omitted for clarity, except hydrides ........................................................... 224
xiii
Figure 5.5.8.1 Molecular structure of 4.9 shown with 50% probability ellipsoids.
Hydrogen atoms are omitted for clarity, except hydrides ........................................................... 226
xiv
List of Schemes
Scheme 1.1 General mechanism for primary alcohol dehydrogenation and aldehyde
decarbonylation using a generic MXL3 pre-catalyst ....................................................................... 5
Scheme 1.2 Catalytic dehydrogenation of alcohol step-by-step: a computational study by
Morton and Cold-Hamilton............................................................................................................. 8
Scheme 1.3 Catalyst speciation pathway to initiation and termination via carbonylation ............. 9
Scheme 1.4 Carbonylation of a bromoruthenium pre-catalyst enables selectivity for alkene,
rather than alkane, products in biomass dehydroxylation ............................................................. 11
Scheme 1.5 Mechanism for hydrogen borrowing amination ....................................................... 13
Scheme 1.6 Activation, evolution, and deactivation of amination catalyst 1.21 .......................... 14
Scheme 1.7 Different catalytic carbonylation pathways leading to different speciation
scopes. Precatalyst 1.26 for alcohol amine coupling; Catalyst 1.22 deactivated amination;
Catalyst 1.17c resting state for alcohol oxidation ......................................................................... 15
Scheme 1.8 A. Amination of a simple alcohol. B. High-yielding synthesis of tetrahydro-
β-carbolines from N-benzyltryptamine. C. One-pot synthesis of harmicine (1.31) ..................... 16
Scheme 1.9 A. Hydroformylation of substituted olefins. B. One proposed mechanism
where CO was involved in carbonylation on the metal centre ..................................................... 18
Scheme 2.1 Synthesis and molecular structures of 2.9-CO and 2.11-CO. CCDC
2142637 contains supplementary crystallographic data for 2.11-CO .......................................... 38
Scheme 3.1 Common iridium dimeric structure transformation under H2/H
+
/H
−
environment .................................................................................................................................. 48
Scheme 3.2 Synthesis of trinuclear complexes family, including 3.1-O, 3.1-H, and 3.1-S,
from precursor 2.11 ....................................................................................................................... 50
xv
Scheme 3.3 Synthesis of 3.1-Au, 3.2-I, and 3.2-Cl ..................................................................... 56
Scheme 3.4 Synthesis of deuterated compound 3.1-H(d72) ......................................................... 58
Scheme 3.5 Reversible CO2 hydrogenation with 3.1-H and 3.1-H’ ............................................ 63
Scheme 4.1 Reported prolific formic acid dehydrogenation by 2.11 by Celaje (2016) ............... 71
Scheme 4.2 Catalytic cycles involve catalyst carbonylation and catalyst methylation ................ 72
Scheme 4.3 Photobase-mediated methanol dehydrogenation ...................................................... 79
Scheme 4.4 A complete proposed synthetic pathway to target complex 4.10 ............................. 80
xvi
Preparative Procedures
Complex 3.1-H
Complex 3.1-O
Complex 3.1-Au
Complex 3.2-I
xvii
Complex 3.2-Cl
Compound 4.5
Compound 4.6
Compound 4.7
xviii
Compound 4.8
Complex 4.9
xix
Abstract
This dissertation contains research contributing to the development of homogeneous
transition-metal catalysis for hydrogen production and storage. The main focus of the study is the
synthesis of novel complexes and the H-transfer mechanism of iridium catalysts in
dehydrogenation and hydrogenation of liquid organic hydrogen carriers (LOHCs). Chapter 1 is
an overview of a common catalyst deactivation pathway in alcohol: catalyst carbonylation and
the underexplored benefits of catalyst carbonylation in transition-metal complex initiation.
Since the Williams group specializes in precious transition metals (Ir, Ru, and Rh),
twenty-one catalysts were investigated and categorized into four common ligand types:
bidentate, tridentate, piano-stool, and metal precursors discussed in Chapter 2. They were found
to have economic advantages in on-demand H2 release from formic acid under self-pressurizing
condition. Demonstrated herein is the first direct comparison of catalyst efficiency between
ambient pressure and self-pressurized conditions through in-situ activation by trace amounts of
CO and H2 gases.
Discussed in chapter 3 is the discovery of novel trinuclear iridium complexes derived
from (pyridylphosphine)iridium precursor, and the application thereof to formic acid
dehydrogenation reactions in aqueous methanol environments. This chapter describes the
synthesis, characterization, and reactivity of this family of iridium-based molecular cluster
complexes, including neutron and X-ray single crystal diffraction measurements. One complex,
which comprises an Ir3H6(μ3-H) trinuclear core, exhibits reactivity for reversible CO2
hydrogenation via hydride transfer. This reactivity is unlike previous reports of the known
Ir3H6(μ3-H) complex, which is chemically inert. A detailed investigation into the origins of this
xx
CO2-reducing reactivity was performed, including of analysis chemical bonding, redox reactions,
metal electrophilic substitution, neutron vibrational spectroscopy, and theoretical calculations.
Novel metal clusters were analyzed via nuclear magnetic resonance (NMR), X-ray diffraction
(XRD), neutron diffraction, and inelastic neutron scattering (INS). The same series of trinuclear
iridium complexes was the subject of an investigation on the catalytic hydrogenation of CO2 to
formate.
Chapter 4 recounts important findings and contributions in structural identification of
catalytic intermediates in an Ir-catalyzed neat formic acid dehydrogenation mechanism,
demonstration of an on-demand H2 release scaleup, and a synthesis of a photobase-mediated
complex. The investigation of formic acid dehydrogenation in aqueous methanol solutions
reveals a robust catalyst carbonylation process while operating at room temperature, which
previously was found to happen at an elevated reaction temperature (90°C). In addition, a scale-
up H2 release (2.35 million turnover numbers) from formic acid and a complete removal of CO 2
from the product gas stream were demonstrated experimentally in a laboratory-built high-
pressure reaction vessel via water and a potassium hydroxide solution partition. This chapter also
describes a photobase-mediated methanol dehydrogenation concept and the step-by-step
synthetic route towards a quinoline-containing Ir
(I) complex.
Chapter 5 discuss experimental procedures, spectral data, and other characterizations of
the compounds in chapters 2, 3, and 4.
1
1 Chapter 1. Catalyst Carbonylation in Metal-Catalyzing Alcohol Dehydrogenation in
Homogeneous Catalyst Development
This chapter describes a common pathway in catalytic systems that gives rise to the
carbonylation of homogeneous catalysts in alcohol oxidation. It is an important aspect in the
design of novel catalysts and necessitates mechanistic studies to further advance on-demand
hydrogen production from liquid organic hydrogen carriers (LOHCs). This work is a published
minireview in the journal Catalysis Science & Technology.
1
I would like to acknowledge my co-
authors, Nick Alfonso, A.J. Chavez, and Yuhao Chen, for their extensive literature research and
analysis for this manuscript. Reproduced from Ref. 1 with permission from the Royal Society of
Chemistry.
1.1 Introduction
Green energy production is in increasing demand, hence the emergence of an efficient
renewable fuel source becomes a critical global priority. In recent years, there has been
significant interest in the scientific community in zero-carbon fuel sources, e.g. hydrogen gas
(H2), from various hydrogen carriers. Yet, the commodity usage of H2 energy must meet
practical standards and demands of the modern world. Although hydrogen gas is an attractive
fuel, commonly used in fuel cell electric vehicles (FCEVs), its combustible gaseous nature
becomes an impediment in transportation and storage to end users. Thus, widespread adoption of
H2 energy is practically difficult to achieve. Due to the high H2 density in natural chemical
liquid mediums, e.g. MeOH (12.6 wt%), ammonia borane (19.6 wt%), and formic acid (4.4
wt%), production of H2 from liquid media is a strategic solution to production, transportation,
and storage of H2.
2-11
Advancement in H2 production can potentially change the global energy
landscape and encourage the deployment of fuel-cell technology.
2
Almost like the proliferation of cross-coupling reactions 10 years earlier, there is an
emergence of increasingly impactful catalytic dehydrogenation and hydrogen transfer reactions
in organic synthesis. Some key examples include alcohol oxidation, hydrogen borrowing
amination, asymmetric carbonyl hydrogenation, carbonyl transfer, and many other useful
manipulations of oxygenated and aminated functional groups. Widespread use of these methods
through the organic chemistry community has been transformative, enabling displacement of
stoichiometric, often metallic, waste streams generated by reactions like chromate oxidation,
reductive amination, lithium aluminum hydride reduction, and related pathways, while
simultaneously introducing game-changing approaches for carbon–heteroatom bond formation
and asymmetric induction in small molecules.
Organometallic homogeneous catalysis offers robust reaction selectivity, prolific product
efficiency, and well-behaved catalytic transformation. Precious metal catalysts, particularly
ruthenium and iridium, prove to have higher recyclability and better lifetimes, therefore
providing higher turnover numbers and greater value than non-precious metal catalysts and
heterogeneous systems in metal-catalyzed H-transfer reactions. As new catalysts and conditions
emerge for these high-value synthetic methods, more thought-provoking, mechanistic studies are
also emerging that show that in many cases the mechanistic story is much more complicated than
the simple template of β-hydride elimination and insertion that were characterized in early
examples.
Catalytic precursors for many useful dehydrogenation catalysts are completely
transformed by metal carbonylation. While this role of a starting alcohol in some of the recent
work in the Williams group, it is one that has been characterized in the mechanisms of several
3
high-value synthetic transformations, yet it is generally omitted from the discussions of hydrogen
transfer reactions that proliferate in the synthetic literature.
Catalyst carbonylation is certainly not a necessary feature for hydrogen transfer catalysts.
A great many scaffolds show reactivity in this area, with pathways utilizing both inner- and
outer-sphere proton- and hydride-transfer mechanisms. There are a few case studies in which a
CO ligand anticipated or unanticipated changed the course of the mechanism of a catalytic
hydrogen transfer reaction. Catalyst carbonylation has been known to organometallic chemistry
since the first metal-carbonyl complex was reported in 1868 by Schutzenberger.
12
Throughout
the 20th century, carbonyl-containing metal complexes have been used as catalysts for reactions
ranging from Monsanto's acetic acid process to reductive hydrosilylation of amides.
13
The metal
carbonyl can be directly involved in catalysis, as in the case of olefin hydroformylations, or a
spectator ligand, as in reactions of Milstein's ruthenium-pincer complexes.
14-15
Either way, the
metal carbonyl group plays an important role in defining the electronic environment of the
catalyst and thus governs energetics of the catalytic cycle. Catalyst carbonylation changed the
fate of a catalytic reaction sequence and created an active catalyst that is considerably different
than its precursor.
1.2 How Do Organics Decarbonylate?
Rhodium-mediated decarbonylation was first reported by Tsuji and Ohno in the mid-
1960s as a stoichiometric reaction to decarbonylate various aldehydes.
6
They found that
Wilkinson's catalyst will form carbonylated rhodium complexes in the presence of aldehydes,
which they characterized by FTIR spectroscopy. They correctly identified that this reaction is
closely related to a similar one in which Vaska found that osmium halides tend to
hydrocarbonylate by reaction with various alcohols.
16
Tsuji and Ohno also reported palladium-
4
catalyzed hydroformylation of olefins in a separate article in the same year.
17
Their reactions
would be stepping stones for further reaction development over the next 50 years and lead to
numerous high utility catalytic carbonylation and decarbonylation systems.
The general mechanism (Scheme 1.1) for alcohol dehydrogenation or aldehyde
decarbonylation using an MXL3 generic pre-catalyst (1.1, center) begins with oxidative addition
of either the hydroxyl bond of the alcohol or the acyl C–H bond of the aldehyde. In the former
case, the alcohol then undergoes β-hydride elimination to produce coordinated aldehyde 1.2,
which subsequently releases H2 and activates the aldehyde to form 1.3. The (acyl) metal group of
1.3 then undergoes migratory extrusion and reductive elimination of the decarbonylated product
to give carbonylated species 1.4. The reaction rate and selectivity depend on both the metal and
its ligand set. The process is common and facile; in fact, Morton and co-workers published a
study of this with Wilkinson's catalyst,
18
in which they discovered that decarbonylation of the
intermediate aldehyde is so facile that it is difficult to prevent. Moreover, once the catalyst is
carbonylated in this case, the catalytic alcohol oxidation reaction is poisoned. This could be
either because the CO ligand is blocking a metal coordination site needed for alkoxide binding or
because back-bonding to the CO depletes electron density needed for alcohol oxidative addition.
Morton showed that the active catalyst could be regenerated either by photo dissociation of the
CO, this worked moderately, or by decarboxylation via hydroxide attack. Strategically, Morton
intended to dehydrogenate alcohols with this method, and catalyst poisoning by aldehyde
decarbonylation presented a complication. Thus, this was an early case of the dilemma of how to
design catalysts selectively to achieve dehydrogenation over decarbonylation. This sort of
poisoning by CO is seen in many different types of hydrogenation and dehydrogenation
5
catalysts, including proton-exchange membrane fuel cells, but there are also cases in which
catalyst carbonylation is beneficial, or even essential.
In a more recent case study, Zhang and co-workers developed electron-rich ruthenium
complexes that dehydrogenate secondary alcohols. The pre-catalysts form complexes with
terminal (1.5a) or bridging (1.5b) dinitrogen ligands (Fig. 1.1), allowing facile access by
substrate alcohols. The mechanism then follows the same general path in Scheme 1.1, except that
since they use secondary alcohols, migratory extrusion cannot occur, so the ketone is released as
a product. The authors attempted to use primary alcohols in these experiments, but this resulted
in catalyst poisoning by carbonylation. Like Morton's case, these investigators encountered CO
poisoning, but this time in a rigidly defined (pincer)ruthenium environment. The resulting CO
.........
Scheme 1.1. General mechanism for primary alcohol dehydrogenation and aldehyde
decarbonylation using a generic MXL3 pre-catalyst.
6
complex was characterized by X-ray diffraction. Despite these findings, secondary alcohols are
not completely safe from decarbonylation. There are a few rare cases of catalyst carbonylation
by secondary alcohols, including one that was well-characterized by the Ozerov group. They
found that their ruthenium PNP pincer complex could oxidize isopropanol to acetone, then
carbonylate to release two equivalents of methane. This is unique, because C–C oxidative
addition is much less facile than aldehyde activation.
19
Figure 1.1. PNN monomer (1.5a) and dimer (1.5b) pre-catalysts for primary and secondary
alcohol dehydrogenation.
1.3 Metal-Catalyzing Alcohol Oxidation/Dehydrogenation
The first step of primary alcohol oxidation, especially methanol, is highly endothermic
(∆H°rxn = 130 kJ/mol).
20
With a high thermodynamic barrier, one-carbon alcohol
dehydrogenation, such as methanol, is energy intensive; strategically, the utilization of highly
selective catalysts, high temperature, and a strong base is essential to overcome this energy
barrier and formation of deactivation pathways. The Beller group demonstrated an efficient low-
temperature dehydrogenation case (ca. 65-95 ºC), in which Ru-PNP and Fe-PNP catalysts
achieved up to 350,000 TON.
6, 11
A base-free iron-based RPNP (R = iPr or Cy) pincer system
reported by Bielinski and co-workers exhibited up 50,000 turnover numbers (TON), the highest
TON for non-precious metal-based MeOH dehydrogenation.
21
A few photochemical
dehydrogenation cases at near room temperature were documented. Notably, first reported in
1985, a cis-[Rh2Cl2(CO)2(dpm)2]2 catalytic system by Takahashi and co-workers, where a
7
photosensitizer, e.g. acetone, is required. Although the presence of acetone enhanced H2, it also
lowers the catalytic selectivity.
22
Wakizaka developed a non-photosensitizer o-aminophenol-
based photocatalyst for anhydrous methanol dehydrogenation facilitated via photo-induced
formation of a hydrogen radical with a high quantum yield.
8
Interestingly, Shen and coworkers
dehydrogenate methanol at 30 °C with an enzyme-Ir cooperative dehydrogenation system:
alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH) oxidize MeOH to formic
acid, then in tandem with Cp*IrCl2(ppy) catalysis, dehydrogenate formic acid near-room
temperature.
7
Traditional alcohol oxidation methods usually require the alcohol to be activated as
a leaving group (e.g., halide or sulfonate) or that a stoichiometric amount of strong and toxic
metal-containing oxidants such as potassium permanganate, pyridinium dichromate (PDC),
chromium(VI) oxide, a hypervalent iodine compound, DMSO (Swern oxidation), peroxide, or
pressurized oxygen is used. These produce harmful waste streams. The catalytic community is
working to move away from such strategies by introducing transfer and acceptorless
dehydrogenation systems that reduce waste and reagent costs.
20
Herns oxidation was the first to
introduce the usage of catalytic platinum under aerobic conditions for alcohol oxidation in the
1940s, followed by Sharpless’ modified procedure with ruthenium tetraoxide RuO4.
23
So doing,
the community has confronted the catalyst carbonylation issue laid out above, with CO poisoning
catalysis in some cases
24-25
and enabling it in others.
26-27
8
Scheme 1.2. Catalytic dehydrogenation of alcohol step-by-step: a computational study by
Morton and Cole-Hamilton.
9
Morton and co-workers documented a particularly instructive example of alcohol
dehydrogenation (Scheme 1.2) in which the precursor [RuH2(X2)(PPh3)3] (X = H2, N2, PPh3) 1.6
has two catalytic cycles originating from the parent and carbonylated metal species: (1) the
parent dehydrogenation pathway, TOF = 148.1 h
−1
, with complex 1.7 as the active catalyst and
(2) the carbonylated pathway, TOF 62 h
−1
,
with complex 1.16 as the active catalyst.
18, 28
Eqn (I) and (II) highlight the driving force
for catalyst carbonylation in this system.
Further, while dehydrogenation (eqn (I)) is
an overall endergonic process which
requires an energy input of 50.5 kJ mol
−1
,
catalyst carbonylation (eqn (II)) is highly
exergonic at −84.5 kJ mol
−1
. Formation of
M–CO complex 1.15 proceeds through
activation of aldehyde complex 1.12.
Formation of agostic complex 1.13 favors
the acyl activation step, thus facilitating the
exergonic pathway to complex 1.14.
Complex 1.14 then proceeds to the cycle of
the carbonylated catalyst. While this cycle is slow compared to the parent, CO ligand
dissociation is enthalpically prohibitive, so a re-activation step would be required to return to the
parent cycle.
Scheme 1.3. Catalyst speciation pathway to
initiation and termination via carbonylation.
10
While examples of carbonylation of rhodium
17, 24
and iridium
29
dehydrogenation catalysts
span 1974 to the present day, this is the first report to characterize initiation of iridium- or
ruthenium-catalyzed dehydrogenation systems that require metal carbonylation for activation. In
these two systems, [Ir(2-PyCH2P
t
Bu2)(COD)]OTf
26
and [(η
6
-cymene)RuCl(2-
PyCH2P
t
Bu2)]OTf,
20, 27
the active catalysts are carbonylated dinuclear complexes 1.19 (Scheme
1.3) and 1.22 (vide infra, Scheme 1.6), respectively. Species 1.19 contains a (chelate)MH(CO)
structural fragment, a common substructure in the alcohol dehydrogenation literature. This
arrives through two initiating steps in which initial carbonylation leads to dimerization.
26
A
singly-carbonylated dimer is the active dehydrogenation catalyst. Our observation of the
carbonylation event is consistent with the observed facility of carbonylation of late metal
complexes: this sits well with conventional wisdom about the energetics of late metal back
bonding. Our situation is different than the earlier ones, though, because the CO does not inhibit
catalysis: in fact, it is necessary. While it is uncertain which iridium center is the locus of
reactivity, there is no catalytic activity of iridium alkoxides like 1.18a without first generating a
carbonylated dimer.
Alcohol decarbonylation can be used as an efficient tandem reaction to convert primary
alcohols to alkanes. Andersson and Madsen have shown a productive (BINAP)iridium system
for such defunctionalization of benzylic alcohols.
29
In this case, it is the same (BINAP)Ir
I
Cl(CO)
species that mediates both the dehydrogenation and decarbonylation pathways. The same process
introduced a hiccup in a glycol upgrading reaction reported by Heinekey and Goldberg.
30
In this
case, as (POCOP)IrH2 carbonylates to give (POCOP)Ir(CO), which appears to be the active
catalyst for conversion of propylene glycol to 1-propanol. Another example, a recent study from
De Vos and co-workers showed that a CO ligand is essential in a Ru-mediated dehydroxylation
11
of biomass alcohols (Scheme 1.4).
31
This particular process is a tandem combination of alcohol
dehydration and ketone reduction, ultimately to give alkene products in high selectivity. The
homogenous ruthenium catalyst is required for the ketone reduction step. In this case, the active
catalyst contains a BrRu–CO fragment. The authors show that the CO ligand plays the essential
role of preventing overreduction of the product alkene. Thus, CO acts as a catalyst poison in this
system, but it serves the very important purpose of poisoning a value-decreasing side reaction in
which the product alkene could have been downgraded to an alkane.
Scheme 1.4. Carbonylation of a bromoruthenium pre-catalyst enables selectivity for alkene,
rather than alkane, products in biomass dehydroxylation.
1.4 Hydrogen Borrowing Amination
Amination by hydrogen borrowing has been one of the most synthetically attractive
reactions that has come out of the literature of catalytic hydrogen transfer.
32-33
Conceptually, this
is a way to do reductive amination without pre-forming an aldehyde, supplying a hydride
reagent, or generating a waste stream other than water. Like the parent oxidation pathway, the
importance of catalytic carbonylation in catalyst speciation can be observed. The mechanism of
hydrogen borrowing amination involves alcohol dehydrogenation, followed by condensation of
the intermediate carbonyl with an amine to form an imine. This imine is then hydrogenated to
12
form the amine product (Scheme 1.5). Our P–N chelated ruthenium catalyst (1.20) is one of a
great number of catalysts for this reaction. It is special for 2 reasons: first, the reversible alcohol
dehydrogenation step is faster than the condensation step, which changes the reaction's
selectivity pattern and enables incredible functional group tolerance, e.g. it will couple alkyl
amines in the present of anilines.
34
Second, its speciation, lifecycle, and deactivation are known
(Scheme 1.6).
20
In this system, catalyst initiation commences with n-butoxide displacement of chloride.
The butoxide complex (1.20-OBu) undergoes β-hydride elimination to form butyraldehyde and
hydride 1.21 (Scheme 1.6). Another example, a recent study from De Vos and co-workers
showed that a CO 1.20-OBu can affect alcohol oxidation and that 1.21 can regenerate 1.20-
OBu under the conditions, this path is much slower than our catalytic reaction. Rather, in the
catalytic conditions, 1.21 converts on to a carbonylated species, which takes up another metal to
generate singly-carbonylated ruthenium dimer 1.22, itself an intermediate seen only by MALDI-
MS and NMR spectroscopy, that is suspected to be the active catalyst. An additional equivalent
of 1.20 reacts quickly with 1.22 to generate dormant species 1.23, from which the active species
can regenerate. The catalyst slowly deactivates by carbonylating a second time to
form 1.24 and 1.25 over the course of about 24–72 hours, depending on the ruthenium loading.
Like iridium species 1.20, 1.22 contains the shared (chelate)MH(CO) fragment (X = H for at
least one X in 1.22), which is derived through metal carbonylation and dimerization. Further, and
analogous to Morton's observation of Wilkinson's catalysis, here CO can shut down catalysis:
some CO is necessary, too much CO is a poison.
13
Scheme 1.5. Mechanism for hydrogen borrowing amination.
Our original report of our amination system featured only the more reactive benzylic
alcohols as electrophiles, because aliphatic alcohol is less reactive.
34
We were able to expand this
reaction scope once we understood the non-intuitive conclusion of our mechanistic study: less
catalyst is more. An initial catalyst carbonylation activates the catalyst, but formation of a resting
trimer (1.23) sets up a second carbonylation that was killing the system (as 1.24/1.25). Applying
the conventional wisdom of adding more catalyst only increased [1.22] and accelerated catalyst
deactivation. By lowering ruthenium loading, simple primary alcohols (e.g. butanol), and general
amines (e.g. aminohexane) can be utilized to give useful amination yields (e.g. 90%, Scheme
1.8A).
27
From a fascination with the recurrence of this (chelate)MH(CO) fragment in the active
species, observing an analogy to other (pincer)metal hydrogen transfer systems:
26, 34-35
it seems
to be a special case of the Milstein pincer system, where a second metal is serving as a very
special hemilabile arm on the pincer.
26-27, 35
While Milstein has carefully designed pincers that
feature a labile arm (e.g. 1.27), the Williams group was forming analogous structures in
situ (Scheme 1.6).
14
Understanding our catalyst deactivation mechanism, the Williams group was able to
extend the reaction first to aliphatic alcohols, then to tandem reactions (Scheme 1.8A).
36
For
example, Nalikezhathu took up the application of hydrogen borrowing amination to the synthesis
of indole alkaloids.
36
This required conditions to execute an acid-mediated Pictet–Spengler
reaction in situ with the base-promoted amination sequence. This conundrum was resolved with
the use of In(OTf)3 as a co-catalyst. These conditions were developed first for the efficient
construction of tetrahydro-β-carbolines from tryptamine (Scheme 1.8B).
36
Further optimization
of this strategy enabled the one-step total synthesis of the indole alkaloid harmicine (1.32,
Scheme 1.8C).
6
Scheme 1.6. Activation, evolution, and deactivation of amination catalyst 1.22.
15
Scheme 1.7. Different catalytic carbonylation pathways leading to different speciation scopes.
Precatalyst 1.27 for alcohol amine coupling; Catalyst 1.23 deactivated amination; Catalyst 1.18c
resting state for alcohol oxidation.
1.5 Carbonylation Reactions
Among reagents for organic synthesis, CO gas itself is very useful and generally
underutilized building block. Still, the carbonylation of organic molecules has been widely
applied in the industrial scale production of commodity chemicals from designer surfactants and
lubricants to acetic acid. To understand the difficulties in reaction selectivity and rate that are
intrinsic to such a simple and reactive building block, many modern studies have been conducted
in the stoichiometric CO insertion with organometallic catalysts, avoiding the direct involvement
of CO gas.
30, 38-39
The dehydrogenation reactions above feature examples of a CO ligand
appearing in the catalyst's lifecycle in cases where no CO is intrinsic to the reaction. Of course,
there are numerous catalytic processes that engage CO as a reagent, and in such cases, CO must
16
necessarily interact with the catalyst. The flagship example of these is olefin hydroformylation, a
process originally reported in pre-war Germany and practiced at scale today.
40
Scheme 1.8. A. Amination of a simple alcohol. B. High-yielding synthesis of tetrahydro-β-
carbolines from N-benzyltryptamine. C. One-pot synthesis of harmicine (1.32).
a
NMR yield with
mesitylene as internal standard.
b
Isolated yield.
George Stanley and co-workers contributed “the first major discovery in
hydroformylation in 50 years” by designing a catalyst carbonylation equilibrium that lowers the
key kinetic barrier intrinsic to the process' seminal HCo(CO)4 catalyst.
41
These workers reported
that a (chelate)Co(II) complex can form a unique 19 e
−
triply-carbonylated complex that exploits
the antibonding of the 19th electron to labialize CO and enable alkene access to the metal: thus,
this third CO ligand makes an enabling modification to the mechanism by opening alkene access
to the metal centre. The new catalyst can achieve reaction rates similar to HCo(CO)4 at half the
CO pressure. The key to the new system is the ability to coordinate bulky olefins with an open
equatorial position.
17
Another series of synthetically useful carbonylation reactions is CO insertion into
palladium coupling reactions, as in the conversion of aryl halides to carboxylic acid
derivatives.
42
Beller recently reported a related reaction, carboxylation of allylic systems, in
which catalyst carbonylation by formic acid played a critical, but anticipated role.
43
The overall
reaction in this case is hydrocarboxylation of an allylic system with tandem allylic transposition
(Scheme 1.9A).
24
The overall scheme utilizes CO to carbonylate the allylic substrate and an
appropriate alcohol converts the intermediate (formyl) palladium to a product ester. This case is
a logical complement to those that we found in our group's dehydrogenation systems: the
reaction scheme necessarily involves catalyst carbonylation, but the CO must be displaced from
palladium for the allylic functionalization to proceed; e.g., CO must be formed by the catalyst,
then must somehow leave the catalyst to enable the process (Scheme 1.9B). Thereby, with the
formation of the desired product, the catalyst can be converted back to its active form for the new
catalytic cycle. Our cases differ in that CO must be formed by the catalyst, then must remain
bound to enable the catalytic process.
1.6 Conclusions and Outlook
The metal–CO bond is one of the most versatile and well-studied functionalities in
organometallic chemistry. Despite this, its appearance in the mechanisms of many hydrogen-
transfer systems appears to us to be underappreciated. Catalyst carbonylation has long been
known as an unproductive or poisoning mechanism to be avoided in catalyst design. We have
shown that unanticipated catalyst carbonylation can also be productive, or even essential, in
18
Scheme 1.9. A. Hydroformylation of substituted olefins. B. One proposed mechanism where
CO was involved in carbonylation on the metal centre.
several cases of catalytic hydrogen transfer, whether as a beneficial poison or essential activating
group. We hope that this analysis provides useful food for thought for the numerous groups
introducing transformative, new technology in the hydrogen transfer space.
19
1.7. References
1. Alfonso, N.; Do, V. K.; Chavez, A. J.; Chen, Y.; Williams, T. J., Catalyst Carbonylation:
a Hidden, but Essential, Step in Reaction Initiation. Catal. Sci. Technol. 2021, 11 (7), 2361-2368.
2. Onishi, N.; Kanega, R.; Kawanami, H.; Himeda, Y. Recent Progress in Homogeneous
Catalytic Dehydrogenation of Formic Acid. Molecules, 2022, 27 (2). 455.
3. Campos, J.; Sharninghausen, L. S.; Manas, M. G.; Crabtree, R. H., Methanol
Dehydrogenation by Iridium N-Heterocyclic Carbene Complexes. Inorg. Chem. 2015, 54 (11),
5079-5084.
4. Conley, B. L.; Guess, D.; Williams, T. J., A Robust, Air-Stable, Reusable Ruthenium
Catalyst for Dehydrogenation of Ammonia Borane. J. Am. Chem. Soc. 2011, 133 (36), 14212-
14215.
5. Jia, K.; Wei, X.; Xu, Y.; Wang, Z.; Chen, J., Asymmetric Potential Barrier Lowering
Promotes Photocatalytic Nonoxidative Dehydrogenation of Anhydrous Methanol. APPL CATAL
A-GEN. 2023, 650, 119009.
6. Nielsen, M.; Alberico, E.; Baumann, W.; Drexler, H.-J.; Junge, H.; Gladiali, S.; Beller,
M., Low-Temperature Aqueous-Phase Methanol Dehydrogenation to Hydrogen and Carbon
Dioxide. Nature 2013, 495 (7439), 85-89.
7. Shen, Y.; Zhan, Y.; Li, S.; Ning, F.; Du, Y.; Huang, Y.; He, T.; Zhou, X., Hydrogen
Generation from Methanol at Near-Room Temperature. Chem. Sci. 2017, 8 (11), 7498-7504.
8. Wakizaka, M.; Matsumoto, T.; Tanaka, R.; Chang, H.-C., Dehydrogenation of
Anhydrous Methanol at Room Temperature by o-Aminophenol-Based Photocatalysts. Nat.
Commun. 2016, 7 (1), 12333.
9. Yang, H.; Chen, Y.; Cui, X.; Wang, G.; Cen, Y.; Deng, T.; Yan, W.; Gao, J.; Zhu, S.;
Olsbye, U.; Wang, J.; Fan, W., A Highly Stable Copper-Based Catalyst for Clarifying the
Catalytic Roles of Cu(0) and Cu
+
Species in Methanol Dehydrogenation. Angew. Chem. Int. Ed.
2018, 57 (7), 1836-1840.
10. Zhang, X.; Kam, L.; Williams, T. J., Dehydrogenation of Ammonia Borane through the
Third Equivalent of Hydrogen. Dalton Trans. 2016, 45 (18), 7672-7677.
11. Boddien, A.; Loges B Fau - Junge, H.; Junge H Fau - Beller, M.; Beller, M., Hydrogen
Generation at Ambient Conditions: Application in Fuel Cells. ChemSusChem 2008, 1, 751-758.
12. Herrmann, W. A., 100 Years of Metal Carbonyls: a Serendipitous Chemical Discovery of
Major Scientific and Industrial Impact. J. Organomet. Chem. 1990, 383 (1), 21-44.
13. Dombray, T.; Helleu, C.; Darcel, C.; Sortais, J.-B., Cobalt Carbonyl-Based Catalyst for
Hydrosilylation of Carboxamides. Adv. Synth. Catal. 2013, 355 (17), 3358-3362.
20
14. Dawe, L. N.; Karimzadeh-Younjali, M.; Dai, Z.; Khaskin, E.; Gusev, D. G., The Milstein
Bipyridyl PNN Pincer Complex of Ruthenium Becomes a Noyori-Type Catalyst under Reducing
Conditions. J. Am. Chem. Soc. 2020, 142 (46), 19510-19522.
15. Gunanathan, C.; Milstein, D., Bond Activation and Catalysis by Ruthenium Pincer
Complexes. Chem. Rev. 2014, 114 (24), 12024-12087.
16. Vaska, L., Hydridocarbonyl Complexes of Osmium by Reaction with Alcohols. J. Am.
Chem. Soc. 1964, 86 (10), 1943-1950.
17. Tsuji, J.; Ohno, K.; Kajimoto, T., Organic Syntheses by Means of Noble Metal
Compounds XX. Decarbonylation of Acyl Chloride and Aldehyde Catalyzed by Palladium and
its Relationship with the Rosenmund Reduction. Tetrahedron Lett. 1965, 6 (50), 4565-4568.
18. Morton, D.; Cole-Hamilton, D. J.; Utuk, I. D.; Paneque-Sosa, M.; Lopez-Poveda, M.,
Hydrogen Production from Ethanol Catalysed by Group 8 Metal Complexes. J. Chem.
Soc., Dalton Trans. 1989, (3), 489-495.
19. Çelenligil-Çetin, R.; Watson, L. A.; Guo, C.; Foxman, B. M.; Ozerov, O. V.,
Decarbonylation of Acetone and Carbonate at a Pincer-Ligated Ru Center. Organometallics
2005, 24 (2), 186-189.
20. Cherepakhin, V.; Williams, T. J., Direct Oxidation of Primary Alcohols to Carboxylic
Acids. Synthesis 2020, 53 (06), 1023-1034.
21. Bielinski, E. A.; Lagaditis, P. O.; Zhang, Y.; Mercado, B. Q.; Würtele, C.; Bernskoetter,
W. H.; Hazari, N.; Schneider, S. Lewis Acid-Assisted Formic Acid Dehydrogenation Using a
Pincer-Supported Iron Catalyst. J. Am. Chem. Soc. 2014, 136, 10234– 10237.
22. Takahashi, T.; Shinoda, S.; Saito, Y., The Mechanisms of Photocatalytic
Dehydrogenation of Methanol in the Liquid Phase with Cis-[Rh2Cl2(CO)2(dpm)2] Complex
Catalyst. Mol. Catal. 1985, 31 (3), 301-309.
23. Tojo, G.; Fernandez, M. I., Oxidation of Primary Alcohols to Carboxylic Acids A Guide
to Current Common Practice. 1st ed. 2007. ed.; Springer New York: New York, NY, 2007.
24. Fristrup, P.; Kreis, M.; Palmelund, A.; Norrby, P.-O.; Madsen, R., The Mechanism for
the Rhodium-Catalyzed Decarbonylation of Aldehydes: A Combined Experimental and
Theoretical Study. J. Am. Chem. Soc. 2008, 130 (15), 5206-5215.
25. Melnick, J. G.; Radosevich, A. T.; Villagrán, D.; Nocera, D. G., Decarbonylation of
Ethanol to Methane, Carbon Monoxide and Hydrogen by a [PNP]Ir Complex. ChemComm.
2010, 46 (1), 79-81.
26. Cherepakhin, V.; Williams, T. J., Iridium Catalysts for Acceptorless Dehydrogenation of
Alcohols to Carboxylic Acids: Scope and Mechanism. ACS Catal. 2018, 8 (5), 3754-3763.
21
27. Cherepakhin, V.; Williams, T. J., Catalyst Evolution in Ruthenium-Catalyzed Coupling
of Amines and Alcohols. ACS Catal. 2020, 10 (1), 56-65.
28. Lorusso, P.; Ahmad, S.; Brill, K.; Cole-Hamilton, D. J.; Sieffert, N.; Bühl, M., On the
Catalytic Activity of [RuH2(PPh3)3(CO)] (PPh3=triphenylphosphine) in Ruthenium-Catalysed
Generation of Hydrogen from Alcohols: a Combined Experimental and DFT study.
ChemCatChem 2020, 12 (11), 2995-3009.
29. Olsen, E. P. K.; Singh, T.; Harris, P.; Andersson, P. G.; Madsen, R., Experimental and
Theoretical Mechanistic Investigation of the Iridium-Catalyzed Dehydrogenative
Decarbonylation of Primary Alcohols. J. Am. Chem. Soc. 2015, 137 (2), 834-842.
30. Ahmed Foskey, T. J.; Heinekey, D. M.; Goldberg, K. I., Partial Deoxygenation of 1,2-
Propanediol Catalyzed by Iridium Pincer Complexes. ACS Catal. 2012, 2 (6), 1285-1289.
31. Stalpaert, M.; Janssens, K.; Marquez, C.; Henrion, M.; Bugaev, A. L.; Soldatov, A. V.;
De Vos, D., Olefins from Biobased Sugar Alcohols via Selective, Ru-Mediated Reaction in
Catalytic Phosphonium Ionic Liquids. ACS Catal. 2020, 10 (16), 9401-9409.
32. Yang, Q.; Wang, Q.; Yu, Z., Substitution of Alcohols by N-Nucleophiles via Transition
Metal-Catalyzed Dehydrogenation. Chem. Soc. Rev. 2015, 44 (8), 2305-2329.
33. Irrgang, T.; Kempe, R., 3D-Metal Catalyzed N- and C-Alkylation Reactions via
Borrowing Hydrogen or Hydrogen Autotransfer. Chem. Rev. 2019, 119 (4), 2524-2549.
34. Celaje, J. J. A.; Zhang, X.; Zhang, F.; Kam, L.; Herron, J. R.; Williams, T. J., A Base and
Solvent-Free Ruthenium-Catalyzed Alkylation of Amines. ACS Catal. 2017, 7 (2), 1136-1142.
35. Balaraman, E.; Srimani, D.; Diskin-Posner, Y.; Milstein, D., Direct Synthesis of
Secondary Amines From Alcohols and Ammonia Catalyzed by a Ruthenium Pincer Complex.
Catal. Letters 2015, 145 (1), 139-144.
36. Nalikezhathu, A.; Cherepakhin, V.; Williams, T. J., Ruthenium Catalyzed Tandem
Pictet–Spengler Reaction. Org. Lett. 2020, 22 (13), 4979-4984.
37. Sahoo, A. R.; Lalitha, G.; Murugesh, V.; Bruneau, C.; Sharma, G. V. M.; Suresh, S.;
Achard, M., Direct Access to (±)-10-Desbromoarborescidine A from Tryptamine and Pentane-
1,5-diol. Asian J. Org. Chem. 2020, 9 (6), 910-913.
38. Morimoto, T.; Kakiuchi, K., Evolution of Carbonylation Catalysis: No Need for Carbon
Monoxide. Angew. Chem. Int. Ed. 2004, 43 (42), 5580-5588.
39. Odell, L. R.; Russo, F.; Larhed, M., Molybdenum Hexacarbonyl Mediated. Synlett 2012,
23 (05), 685-698.
40. Cornils, B.; Herrmann, W. A.; Rasch, M., Otto Roelen, Pioneer in Industrial
Homogeneous Catalysis. Angew. Chem. 1994, 33 (21), 2144-2163.
22
41. Hood, D. M.; Johnson, R. A.; Carpenter, A. E.; Younker, J. M.; Vinyard, D. J.; Stanley,
G. G., Highly Active Cationic Cobalt(II) Hydroformylation Catalysts. Science 2020, 367 (6477),
542-548.
42. Cao, J.; Zheng, Z.-J.; Xu, Z.; Xu, L.-W., Transition-Metal Catalyzed Transfer
Carbonylation with HCOOH or HCHO as Non-Gaseous C1 Source. Coord. Chem. Rev. 2017,
336, 43-53.
43. Sang, R. A.-O.; Kucmierczyk, P.; Dong, K.; Franke, R.; Neumann, H.; Jackstell, R.;
Beller, M. A.-O., Palladium-Catalyzed Selective Generation of CO from Formic Acid for
Carbonylation of Alkenes, 2018, J. Am. Chem. Soc. 2018, 140 (15), 5217–5223 1520-5126.
23
2. Chapter 2 Pressurized Formic Acid Dehydrogenation: An Entropic Spring Replaces
Hydrogen Compression Cost
This chapter describes the work, which was performed in collaboration with Dr. John
Gordon, Dr. Robert Currier, and Dr. Pavel Dub at the Los Alamos National Laboratory and my
undergraduate co-worker A.J. Chavez, my graduate co-worker Nicholas Alfonso, Long Zhang,
Dr. Valeriy Cherepakhin, and Dr. Zhiyao Lu at the University of Southern California. A.J., Nick,
and Long helped acquire data. Dr. Lu and Dr. Cherepakhin synthesized and characterized
carbonylated species. Dr. Dub, Dr. Gordon, and Dr. Currier participated in project
conceptualization and the many catalyst supplies. We thank Dr. Tom Autrey, Dr. Sam Johnson,
Dr. Katarzyna Grubel, and the DOE HyMARC team at Pacific Northwest National Laboratory
for valuable discussions. We further thank Dr. Grubel for her work to replicate FA
dehydrogenation with 2.11 under pressure at PNNL under fast heating conditions. A manuscript
for this work has been published in the journal Catalysis Science & Technology.
1
Reproduced
from Ref. 1 with permission from the Royal Society of Chemistry.
2.1 Introduction
The production of hydrogen gas on demand is an enabling technology for the widespread
deployment of hydrogen fuel cell vehicles. One approach to providing H2 on demand is to
release it catalytically from a liquid organic hydrogen carrier (LOHC), provided that the
economics of such a system can overcome the costs of pressurizing and delivering the gas. Gas
compression contributes 49% to 83% of the total refueling cost for light-duty and heavy-duty
vehicles, respectively, in US retail cases. Thus, the ability to produce pressurized H2 on demand
reduces the cost of H2 in vehicle refueling. Yet, most catalyst development work on LOHC
dehydrogenation has been under ambient pressure conditions.
24
Formic acid (FA, available from biomass fermentation or CO2 electrolysis), is a low cost,
sustainable hydrogen carrier with desirable volumetric density (1.22 g mL
−1
) and H2 content (4.4
wt%).
2-3
Its dehydrogenation is significantly entropically driven, with ΔH°rxn = +7.4 kcal
mol
−1
and ΔS°rxn = +51 cal mol
−1
K
−1
, so entropic energy released upon dehydrogenation serves
as a type of spring, capable of delivering compressed hydrogen without the cost of compression.
Self-pressurization of FA or alcohol dehydrogenation creates a unique environment for catalysis,
where H2, CO2, and/or CO can govern catalyst initiation (e.g. in situ catalyst synthesis),
speciation, and decomposition. While carbonylation is a known poisoning pathway in many
cases,
4-5
I find that it can be essential to catalyst activation in others: for example, CO can play a
healing role, extending the life of systems that would be deactivated without it. Despite these key
advantages, I know of no broad studies of how closed-reactor conditions impact dehydrogenation
catalysis;
4
the healing role of CO has been missed; and there are not generalizations for when
this behavior might be expected or what the role of pressurization might have in directing it.
Hydrogen release from FA has been studied extensively in homogeneous and
heterogeneous systems based on precious (Ir,
6-8
Ru,
6, 9-10
Pd,
11-12
and Au
13-14
) and non-precious
metal (Fe
15-16
and Mn
17-18
) catalysts, but I see only a few systems that are known to produce
pressurized products while maintaining catalytic reactivity and selectivity.
19-24
Pioneering work
by Fellay et al. described one of the first examples of high-pressure dehydrogenation of aqueous
formic acid using a ruthenium catalyst.
19-20
Since then, several groups have reported similar
findings,
21-24
however, industrially relevant turnover frequencies (TOF) and turnover numbers
(TON) have not been achieved using neat formic acid. Most recently, Milstein recently reported
a ruthenium PNP pincer catalyst for the dehydrogenation of neat FA, demonstrating the catalyst's
tolerance of headspace H2/CO2 pressure (10–100 bar).
25
25
I provide here the first general study of how FA dehydrogenation catalysts respond to
self-pressurizing conditions. We demonstrate a broad survey of activity and stability of catalysts
in both ambient and pressurized reaction conditions and find striking reactivity improvements for
some catalysts when pressurized. We ultimately show how such improvements are realized,
sometimes by transforming a monomeric catalyst into a two-metal pseudo-pincer type species
upon carbonylation.
2.2 Catalysts for FA Dehydrogenation at Ambient and Self-Pressurizing Conditions
Figure 2.1. Late Transition metal complexes tested for formic acid dehydrogenation in this
study.
26
Table 2.1. Dehydrogenation of neat FA at ambient pressure versus under self-pressurized
operation
Entry
a
Catalyst
precursor
Conversion at
ambient pressure
c
Conversion in pressurized vessel
(Evolved pressure in bar)
d
1a 2.1 6 % 42 % (16)
1b
b
2.1 6 % 82 % (31)
2a 2.2 8 % 29 % (11)
2b
b
2.2 9 % 58 % (22)
3 2.3 9 % 71 % (27)
4a 2.4 2 % 40 % (15)
4b
b
2.4 3 % 79 % (30)
5 2.5 3 % 79 % (30)
6a 2.6 9 % 84 % (32)
6b
b
2.6 3 % 84 % (32)
7 2.7 63 % 74 % (28)
8 2.8 10 % 32 % (12)
9a
9b
2.9
2.9-CO
12 %
35 %
86 % (33)
92 % (35)
10 2.10 6 % 55 % (21)
11 2.11 >99 % 100 % (38)
12 2.12 >99 % 100 % (38)
13 2.13 0 % 32 % (12)
14 2.14 1 % 74 % (28)
15 2.15 2 % 16 % (6)
16 2.16 3 % 16 % (6)
17 2.17 23 % 42 % (16)
18 2.18 3 % 32 % (12)
19
e
2.19 >99 % 100 % (38)
20 2.20 33 % 100 % (38)
21 2.21 5 % 84 % (32)
a
Conditions: catalyst (0.00795 mmol, 100 ppm), FA (3.0 mL, 79.5 mmol), and NaO2CH (1.2 g,
17.6 mmol) at 110 °C.
b
Pre-activation with 2.0 eq. of KO
t
Bu in toluene (0.5 mL) at 25 °C.
c
FA
conversion in opened system.
d
FA conversion in closed system (3.0 ml) calculated based on full
conversion (38 bar) of entry 11.
e
Reported best yield of 3 replications.
27
We surveyed a wide range of complexes that generally fit into four classes: (1) Noyori-
type tridentate complexes 2.1–2.8, (2) bidentate chelate complexes 2.9–2.12 and their
analog 2.13, (3) cyclopentadienyl piano stools complexes 2.14–2.17, and (4) metal precursors for
the ligated complexes 2.18–2.21 (Fig 2.1). Each was examined in FA dehydrogenation both
under ambient pressure and self-pressurizing conditions to determine catalyst activity and
efficiency (Table 2.1). While every complex is different under these conditions, some
generalizations of each class can be identified.
Table 2.1 shows the results of FA dehydrogenation conducted under both ambient and
self-pressurizing conditions. All twenty-one complexes react with FA at a higher rate when
pressurized than they do at ambient pressure, each without detectable reversibility (see Fig.2.2.
and Fig.2.4. for time course data). The overall improvement in conversion efficiency varied
between a minimum of +16% (entries 15 and 16) and a maximum of +72% (entry 14) as
conditions changed from open to closed vessels. For example, mildly active complex 2.20 at
ambient pressure promoted complete conversion when in a closed system (entry 20). Perhaps
most startling, complexes 2.1–2.6, 2.8, 2.10, 2.13, and 2.21 exhibit little reactivity at ambient
pressure but are dramatically more reactive under self-pressurizing conditions. An exception was
observed in complex 2.7 which has competitive reaction conversion at both ambient and
pressurized conditions.
26
Complexes 2.1–2.8 in the well-studied Noyori-type tridentate family, generally featuring
M(PNL) (L = PPh2, P(
i
Pr)2, S(CH3)2) structures, tend to have lower reactivity than other catalysts
at ambient pressure, giving conversions between 2% and 10%; but they are the highly impacted
by pressurization relative to the other classes, reaching conversions from 58% to 84% under self-
whereas in an ester hydrogenation reaction, complex 2.7 is one order of magnitude less
28
Figure 2.2. Gas evolution of formic acid dehydrogenation by complexes 2.1-2.21 at ambient
pressure over time (Left: 0 - 25 hours; Right: 0-5 hours): complex 2.1 – lavender crosses;
complex 2.1 w/
t
BuOK – purple squares; complex 2.2 – orange asterisks; complex 2.2 w/
t
BuOK
– grey circles; complex 2.3 – yellow plusses; complex 2.4 – blue squares; complex 2.4 w/
t
BuOK
– peach squares; complex 2.5 – green triangles; complex 2.6 – cream crosses; complex 2.7 – red
asterisks; complex 2.8 – red circles; complex 2.9-CO – blue plusses; complex 2.10 – orange
hyphens; complex 2.11 – black triangles;–; complex 2.12 – navy diamonds; complex 2.13 – grey
hyphens; complex 2.14 – yellow crosses; complex 2.15 – blue asterisks; complex 2.16 – lavender
diamonds; complex 2.17 – pink squares; complex 2.18 – green hyphens; complex 2.19 – grey
triangles; complex 2.20 –green circles; complex 2.21 – yellow diamonds.
efficient than complex 2.4.
26
Often, complexes in this class require pre-
activation via hydrodechlorination with KOH or KO
t
Bu to generate their active hydride forms.
9,
26-31
Nevertheless, under self-pressurizing conditions, there is an increase in conversion from
29% (entry 2a) to 84% (entry 6a) without such pre-activation. For example, self-pressurization
enables complex 2.4 (entry 4b) to achieve 79% conversion, comparable to its activated dihydride
29
derivative (entry 5, 79%). Complex 2.6 can be initiated under pressurizing conditions without
any base to convert 84% FA, while at ambient pressure only 3.0% FA is converted, even if the
catalyst is activated with KO
t
Bu. This dramatic enhancement of reactivity upon pressurization
suggests that one of the reaction products, like H2 or CO, is necessary to enable or maintain
catalytic activity. Hydrogenation is known to activate amine-containing Noyori-type complexes
such as 2.1–2.6 in the presence of base,
9, 29-31
which is a possible explanation. Further, we
observe that thermal decarbonylation of FA is possible at our operating temperature (vide infra).
We expect that the trace CO generated through this pathway is oxidized rapidly by the catalyst,
but that its continued supply installs or maintains a CO ligand on the catalyst.
Bidentate chelate complexes 2.9-CO, 2.11,
8, 28, 32-34
and 2.12 are the most reactive
precursors that we encountered at ambient pressure.
35
Complex 2.11 exhibits the highest rate of
the entire library, where in 79.5 mmol of FA were fully converted within 1.2 hours. We found
these complexes to be pressure-tolerant, but with little enhancement in reactivity because of their
high baseline efficiency at ambient pressure. We believe the unique reactivity of these complexes
to be a function of a novel self-assembly pathway: these convert to two-metal pseudo-pincer
structures in the presence of a CO (isolated and characterized from reaction mixtures),
exemplified by cases of our (pyridyl)phosphine ligand bound to ruthenium and iridium (Fig.
2.3).
8, 35
These pathways are available at ambient pressure either from FA or an alcohol.
8, 28, 32-
34
The resulting bimetallic complexes have high activity and stability at ambient or elevated
pressure. The active complexes have structural homology with some prolific Noyori-type and
Milstein-type pincer complexes, where one arm of the tridentate ligand is replaced by the second
metal.
36-37
Carbene-ligated compound 2.10 in this class lacks the reactivity of 2.9-CO, 2.11,
or 2.12. While the reactivity of carbene-ligated systems 2.9-CO and 2.10 should be different than
30
their phosphine-ligated congeners 2.11 and 2.12, it is surprising that 2.10 does not react
analogously to 2.9-CO under pressurized conditions, especially whereas 2.9-CO is prepared
from its cyclooctadiene-ligated precursor 2.9 at ambient pressure (vide infra). Crabtree's
catalyst 2.13 also exhibits low reactivity compared to its bidentate analog 2.11. We infer that
tethering the pyridine and phosphine groups is important for proper catalyst self-assembly.
Figure 2.3. Structural analogy between the common Noyori-type, Milstein-type pincer and our
pseudo-pincer active catalytic species.
Piano stool Cp*Ir complexes 2.15–2.17 are not very efficient in this study, although they
are moderately aided by pressure. Complexes 2.16 and 2.17 have been known to have excellent
reactivity in alcohol dehydrogenation,
27, 37
but their activity towards FA is moderate, respectively
16% and 42% conversion under pressurizing conditions. Notably, Shvo's cyclopentadienone-
ligated catalyst 2.14 is much more reactive than Cp*Ir systems under pressurizing condition. The
Shvo system is known to rest in its dimeric form 2.14 in the presence of H2,
38-40
so we reason
that the availability of CO to trap the system's oxidized monomer and prevent formation
of 2.14 could account for its rate advantage upon pressurization, because it is known that
H2 pressure will drive the system back to dimer 2.14.
38-39, 41
31
While several of the ligated species in Table 2.1 are efficient catalysts—they were
designed as such—we were surprised to find that their synthetic precursors 2.18–2.21
8, 35-36
have
reactivity that rivals their ligated congeners. We find, however, that unlike the ligated congeners,
the unligated precursors seem to deactivate easily. Overall, one piece of traditional wisdom that
seems to be preserved is that ligated complexes tend to have good stability, sometimes at the cost
of reaction rate. For example, we had difficulty replicating entries 2.18–2.21 whilst other entries
were very reliable. Apparently, these more naked species tend to react quickly, yet the reactivity
is short-lived and difficult to replicate.
32
Figure 2.4. Gas evolution of formic acid dehydrogenation by complex 2.1-2.21 over time at
ambient pressure condition (opened system) – grey triangles; at self-pressurized condition
(closed system) – blue diamonds.
33
2.3 Impact of Applied H2 and CO
Whereas many of the complexes we
screened are more productive under self-
pressurizing conditions, I conclude that initially
formed products, probably CO and H2, are
involved in activating the precatalysts
4, 7
and
healing the active catalyst by preempting
deactivation processes. I propose that these
processes could be emulated by adding CO or
H2 at the outset of the reaction. To test this,
reactions involving four catalyst
precursors, 2.5, 2.10, 2.14, and 2.15, were
examined representing the 3 respective classes
of ligated precatalysts that benefitted
significantly from self-pressurizing conditions.
These were alternatively pretreated with H2 or
CO in FA and their catalytic activity was
evaluated (Fig. 2.5).
Neither H2 (green triangles) nor CO
(orange circles) uniformly improved catalytic
activity over baseline (black squares) of every catalyst tested. While
complexes 2.15 and 2.10 benefit respectively from H2 and CO pretreatment, other combinations
Figure 2.5. Pressurized dehydrogenations
of FA: control (black squares), pretreated
with 8 bar of H2 (green triangles), (orange
circles) pre-treated with 1 bar of CO
following by N2 purging. Top left.
complex 2.5; Top right. complex 2.15;
Bottom left. complex 2.10; Bottom right.
complex 2.14.
34
of catalyst and treatment did not significantly improve reactivity: there is not a generalization
that explains why these four complexes are accelerated by pressure. By contrast,
both 2.10 and 2.5 are deactivated by H2 pretreatment. In the case of the Shvo system 2.14,
H2 pressure slows the reaction but did not affect maximum total pressure (27–28 bar), consistent
with the above proposal of dimer formation.
Notably, after 2.10 was pretreated with CO, the activity was significantly improved,
reaching 89% conversion in five hours, surpassing its carbonylated homolog 2.9-CO. This is an
interesting contrast to the relatively low reactivity of 2.9 under self-pressurizing conditions (vide
supra): apparently insufficient CO is generated by formic acid dehydrogenation to realize the full
benefit of carbonylation. Also very interesting about this catalyst system is that at ambient
pressure, reactivity slows after about 3 minutes, which is not observed under pressurizing
conditions. We view this as evidence that CO heals the catalyst and maintains fast kinetics when
it does not have the opportunity to escape the reactor. Despite numerous cases of catalyst
poisoning by metal carbonylation,
4-5
complexes 2.9-CO and 2.10 exhibit the opposite effect: in
the absence of CO, 2.10 has low activity for FA decomposition, but when CO is introduced,
either by self-generation or pretreatment, complex 2.10 performed ca. three times (added CO,
Fig. 2.5) to four times (self-generated CO, Table 2.1, entry 10) better.
Whereas CO is essential to the activation of these catalyst systems, it must be available in
the reactor, although it is not detected in the product stream of FA dehydrogenation as reported
in many studies from our lab and others.
4
Although there has not been a full explanation of this,
we believe that formation of CO occurs thermally,
42-43
possibly catalyzed by traces of metals in
the reactor vessel, and that CO is oxidized rapidly by the catalyst in our conditions. We tested
these ideas with two experiments: (1) when the reaction was run with precursor 2.11 under
35
pressurizing conditions and utilizing rapid heating, the reactor reaching over 129 °C at times, we
detected CO concentration up to 0.63%, concurrent with fast H2 generation (107 L h
−1
). No CO
(< 10 ppm) is observed under analogous conditions below 100 °C. This suggests that thermal
decarbonylation of FA can produce significant CO concentration if not controlled;
42-43
(2) in an
aqueous methanol photodehydrogenation experiment (Table 2.2), 6% of CO was generated in the
absence of catalyst 2.10, whereas none can be detected when 2.10 is present. Complex 2.10 was
chosen for this experiment for its relatively slow reactivity in FA dehydrogenation, thus to allow
longer life and easier observation of C1 intermediates. We infer from this observation that, when
CO is produced by a non-catalytic reaction, the presence of an appropriate metal complex will
reform the CO efficiently: CO is available, but not detectable. We suspect that this is a general
feature of homogeneous catalysts for formic acid dehydrogenation that has not previously been
described.
Table 2.2. CO formation of 2.10.
Whereas CO is vital to the initiation and speciation of some catalysts, we attempted to
prepare species by independent synthesis that could be responsible for the observations. Upon
treating 2.10 with 1 atm CO, we found that 2.10-CO was not stable to isolation. Treatment
of 11 with CO results in a broad diversity of structures, which we have previously
reported.
28
While these systems failed, the clean carbonylated species 2.9 readily yielded 2.9-
CO upon carbonylation.
28
We measured the kinetics of dehydrogenation with 2.9 and 2.9-CO at
36
ambient pressure to test the hypothesis that CO plays a role in precatalyst activation. At ambient
pressure, complex 2.9-CO dehydrogenates FA faster than precursor 2.9 (Fig. 2.6): both show
saturation catalysis through a 4-hour experiment, with 2.9-CO at 24.6% conversion (16.5(1) ×
10
−2
TOF) relative to 2.9 at 11.7% conversion (8.3(1) × 10
−2
TOF). These data indicate an
important role for CO in the reactivity of catalyst 2.9.
Further investigation of CO pressure revealed the expected inhibitory role at higher
loading (Fig. 2.6 and 2.7.). At low concentration of CO either from FA decomposition or
treatment with 2 bar of CO, 2.9 initiates at a faster rate than in the absence of CO. By contrast,
under 8 bar of CO, we observe slower conversion of the catalytic reaction following rapid
initiation as shown in Fig. 2.6. As expected, 2.9-CO performed substantially similar
to 2.9 when 2.9 is treated with 2 bar CO, but like 2.9, 2.9-CO exhibits inhibited rate when 8 bar
CO is applied.
Figure 2.6. Left: Kinetic profile of FA dehydrogenation by 2.9 (black circles) and 2.9-CO
(orange circles). Conditions: catalyst loading (0.00795 mmol, 100 ppm), FA (3.0 mL, 79.5
mmol), and NaO2CH (1.2g, 17.6 mmol) at 110 °C. Right: Gas evolution of FA dehydrogenation
by complex 2.9 (orange) and 2.9-CO (blue) over time upon treatment of 0 bar CO – diamond; 2
bar CO – triangles; 8 bar CO – circles.
37
Figure 2.7. (Top) Gas evolution of formic acid dehydrogenation by complex 2.9, 2.9-CO, and
2.10 over time pretreated with 0 bar CO – orange circles; pretreated with 2 bar CO – grey
triangles; pretreated with 8 bar CO – blue diamonds. (Bottom) Cross-comparison CO initiation
between 2.9 and 2.9-CO showed that after 2.9 was synthesized in-situ (initiation via catalyst
carbonylation), excess CO gas becomes inhibitory to reaction kinetics.
38
While seeking to understand the activation pathway of our most active precursor 2.11, a
stable species 2.11-CO was isolated from a FA dehydrogenation reaction at ambient pressure
(Scheme 2.1). Complex 2.11-CO was characterized by
1
H,
13
C,
19
F, and
31
P NMR spectroscopy
and its molecular structure was established by single-crystal X-ray diffraction. Formation of
carbonyl complex 2.11-CO under these conditions is a remarkable development, since FA
dehydrogenation catalyzed by 2.11 is known to produce no free CO gas (< 10 ppm) and returns
non-carbonylated catalytic species when operated at 90°C.
8
This teaches us that at sufficient
temperature and pressure, the previously characterized resting species from the 2.11-catalyzed
dehydrogenation of FA can be further converted into a carbonylated system 2.11-CO. Again, we
see that while FA decarbonylation happens during catalysis, CO is reformed rapidly to products
and remains undetectable in the product stream.
Scheme 2.1. Synthesis and molecular structures of 2.9-CO and 2.11-CO. CCDC 2142637
contains supplementary crystallographic data for 2.11-CO.
39
2.4 Regeneration, Activity, and Selectivity of 11 in High Pressure Gas Stream Production.
To the best of my knowledge, precursor 2.11 continues to demonstrate comparable or
superior activity to all known homogeneous systems for dehydrogenation of neat FA (Fig. 2.3).
It also provides excellent stability, longevity (TON > 2 million) and selectivity (H2:CO2 1:1, CO
< 10 ppm).
8
I thus scaled this system to generate a pressurized product stream (> 103 bar) while
demonstrating longevity and exceptional kinetics. To acquire high resolution data, we used a 600
mL stirred pressure vessel equipped with an internal temperature probe and a pressure
transducer. I report volumetric flow rate (standardized to 1 atm at 0°C) in units of liters per hour
(L/hr corrected to ambient conditions) for all H2 evolution rates.
A 20-cycle pressure experiment was accomplished using 99.6 mg (145 µmol) of complex
2.11 and 20 g (294 mmol) of sodium formate co-catalyst in 55 mL of FA (Fig. 2.8). During each
cycle, ca. 50 mL of FA was added (1 L, 17.9 mol over 20 cycles), the reactor was sealed and
heated to 120 °C, then the pressure was allowed to build to 117 bar (approximately 25 L of H 2).
Once the desired pressure was achieved, the reaction was quenched by rapid cooling in a dry-ice
bath and then depressurized to repeat the cycle. The reaction rate in the form of evolved H 2 per
hour is plotted in Fig. 2.8. This experiment illustrates that once pre-catalyst 2.11 is initiated,
there is no detectable deactivation of the catalyst through 200,000 turnovers as evidenced by the
consistently high peak reaction rates, varying only due to concentration differences between
individual experiments. Cycle 4 demonstrated that when allowed to run near dryness, the peak
reaction rate exceeded 160 L/hr, corresponding to a TOF of nearly 50,000 hr
-1
.
2.5 Conclusions
Among a library of late-transition metal complexes, I found that in every case studied the
dehydrogenation of neat FA is more productive under self-pressurizing reaction conditions. This
40
is a stunning outcome, whereas the cost of hydrogen provided for retail vehicle filling is
dominated by the cost of compressing the gas yet I have few detailed and broad-based studies
that show how pressure evolution impacts the efficacy of homogeneous FA dehydrogenation
catalysts. I grouped catalysts for neat FA dehydrogenation into four general classes, pincers,
bidentate chelates, piano stool complexes, and metal precursors. Each structural class uniquely
responds to pressurized condition. The bidentate chelates excel beyond others, which we
attribute to a transformation from monomers to two-metal pseudo-pincer complexes in which the
second metal seems to impart special reactivity. I find an enabling role for CO and/or H2 in a
number of cases, typically impacting catalyst initiation (in-situ catalyst synthesis) and defining
the course of catalyst speciation. This hypothesis is supported by previous studies,
5, 37
namely,
the observation and isolation of the carbonylation derivative of 2.11, and the 3-fold increase in a
healing process of 2.10 by CO. In addition, complex 2.11, which exhibits exceptional catalytic
activity, stability, and selectivity, supersedes existing systems in the production of a high-
pressure product stream from neat FA dehydrogenation. This catalyst was used to convert over 1
L of formic acid into pressurized H2/CO2 product over the course of 30 hours, proving that the
Figure 2.8. Catalyst recycling study in FA dehydrogenation by complex 2.11.
41
catalytic activity could be maintained at a high level for 200,000 turnovers at 117 bar without
any loss of reactivity. Due to the favorable economics of producing H2 at pressure, fully
automated H2 generation using a continuous feed, stirred tank reactor will be developed to
evaluate the ultimate longevity of the catalyst. This technology and the discovery of a detailed
mechanism and speciation of 2.11 will be reported in future work.
42
2.6 References
1. Do, V. K.; Alfonso Vargas, N.; Chavez, A. J.; Zhang, L.; Cherepakhin, V.; Lu, Z.;
Currier, R. P.; Dub, P. A.; Gordon, J. C.; Williams, T. J., Pressurized Formic Acid
Dehydrogenation: an Entropic Spring Replaces Hydrogen Compression Cost. Catal. Sci.
Technol. 2022, 12 (23), 7182-7189.
2. Mazloomi, K.; Gomes, C., Hydrogen as an Energy Carrier: Prospects and Challenges.
Renew. Sust. Energ. Rev. 2012, 16 (5), 3024-3033.
3. Sponholz, P.; Mellmann, D.; Junge, H.; Beller, M., Towards a Practical Setup for
Hydrogen Production from Formic Acid. ChemSusChem 2013, 6 (7), 1172-1176.
4. Alfonso, N.; Do, V. K.; Chavez, A. J.; Chen, Y.; Williams, T. J., Catalyst Carbonylation:
a Hidden, but Essential, Step in Reaction Initiation. Catal. Sci. Technol. 2021, 11 (7), 2361-2368.
5. Iguchi, M.; Onishi, N.; Himeda, Y.; Kawanami, H., Ligand Effect on the Stability of
Water-Soluble Iridium Catalysts for High-Pressure Hydrogen Gas Production by
Dehydrogenation of Formic Acid. ChemPhysChem 2019, 20 (10), 1296-1300.
6. Siek, S.; Burks, D. B.; Gerlach, D. L.; Liang, G.; Tesh, J. M.; Thompson, C. R.; Qu, F.;
Shankwitz, J. E.; Vasquez, R. M.; Chambers, N.; Szulczewski, G. J.; Grotjahn, D. B.; Webster,
C. E.; Papish, E. T., Iridium and Ruthenium Complexes of N-Heterocyclic Carbene- and
Pyridinol-Derived Chelates as Catalysts for Aqueous Carbon Dioxide Hydrogenation and Formic
Acid Dehydrogenation: The Role of the Alkali Metal. Organometallics 2017, 36 (6), 1091-1106.
7. Wang, Z.; Lu, S.-M.; Li, J.; Wang, J.; Li, C., Unprecedentedly High Formic Acid
Dehydrogenation Activity on an Iridium Complex with an N,N′-Diimine Ligand in Water. Chem.
Eur. J. 2015, 21 (36), 12592-12595.
8. Celaje, J. J. A.; Lu, Z.; Kedzie, E. A.; Terrile, N. J.; Lo, J. N.; Williams, T. J., A Prolific
actalyst for Dehydrogenation of Neat Formic Acid. Nat. Commun. 2016, 7 (1), 11308.
9. Agapova, A.; Alberico, E.; Kammer, A.; Junge, H.; Beller, M., Catalytic
Dehydrogenation of Formic Acid with Ruthenium-PNP-Pincer Complexes: Comparing N-
Methylated and NH-Ligands. ChemCatChem 2019, 11 (7), 1910-1914.
10. Thevenon, A.; Frost-Pennington, E.; Weijia, G.; Dalebrook, A. F.; Laurenczy, G., Formic
Acid Dehydrogenation Catalysed by Tris(TPPTS) Ruthenium Species: Mechanism of the Initial
“Fast” Cycle. ChemCatChem 2014, 6 (11), 3146-3152.
11. Qin, X.; Li, H.; Xie, S.; Li, K.; Jiang, T.; Ma, X.-Y.; Jiang, K.; Zhang, Q.; Terasaki, O.;
Wu, Z.; Cai, W.-B., Mechanistic Analysis-Guided Pd-Based Catalysts for Efficient Hydrogen
Production from Formic Acid Dehydrogenation. ACS Catal. 2020, 10 (6), 3921-3932.
12. Zhong, H.; Iguchi, M.; Song, F.-Z.; Chatterjee, M.; Ishizaka, T.; Nagao, I.; Xu, Q.;
Kawanami, H., Automatic High-Pressure Hydrogen Generation from Formic Acid in the
43
Presence of Nano-Pd Heterogeneous Catalysts at Mild Temperatures. Sustain. Energy Fuels
2017, 1 (5), 1049-1055.
13. Huang, Y.; Zhou, X.; Yin, M.; Liu, C.; Xing, W., Novel PdAu@Au/C Core−Shell
Catalyst: Superior Activity and Selectivity in Formic Acid Decomposition for Hydrogen
Generation. Chem. Mater. 2010, 22 (18), 5122-5128.
14. Liu, Q.; Yang, X.; Huang, Y.; Xu, S.; Su, X.; Pan, X.; Xu, J.; Wang, A.; Liang, C.;
Wang, X.; Zhang, T., A Schiff Base Modified Gold Catalyst for Green and Efficient H2
Production from Formic Acid. Energy Environ. Sci. 2015, 8 (11), 3204-3207.
15. Bielinski, E. A.; Lagaditis, P. O.; Zhang, Y.; Mercado, B. Q.; Würtele, C.; Bernskoetter,
W. H.; Hazari, N.; Schneider, S., Lewis Acid-Assisted Formic Acid Dehydrogenation Using a
Pincer-Supported Iron Catalyst. J. Am. Chem. Soc. 2014, 136 (29), 10234-10237.
16. Léval, A.; Agapova, A.; Steinlechner, C.; Alberico, E.; Junge, H.; Beller, M., Hydrogen
Production from Formic Acid Catalyzed by a Phosphine Free Manganese Complex:
Investigation and Mechanistic Insights. Green Chem. 2020, 22 (3), 913-920.
17. Sun, Q.; Chen, B. W. J.; Wang, N.; He, Q.; Chang, A.; Yang, C.-M.; Asakura, H.;
Tanaka, T.; Hülsey, M. J.; Wang, C.-H.; Yu, J.; Yan, N., Zeolite-Encaged Pd–Mn Nanocatalysts
for CO2 Hydrogenation and Formic Acid Dehydrogenation. Angew. Chem. Int. Ed. 2020, 59
(45), 20183-20191.
18. Zell, T.; Butschke, B.; Ben-David, Y.; Milstein, D., Efficient Hydrogen Liberation from
Formic Acid Catalyzed by a Well-Defined Iron Pincer Complex under Mild Conditions. Chem.
Eur. J. 2013, 19 (25), 8068-8072.
19. Fellay, C.; Dyson, P.; Laurenczy, G. A Viable Hydrogen-Storage System Based On
Selective Formic Acid Decomposition with a Ruthenium Catalyst. Angew. Chem. Int. Ed. 2008,
47, 3966–3968.
20. Fellay, C.; Yan, N.; Dyson, P. J.; Laurenczy, G., Selective Formic Acid Decomposition
for High-Pressure Hydrogen Generation: A Mechanistic Study. Chem. Eur. J. 2009, 15 (15),
3752-3760.
21. Himeda, Y., Highly Efficient Hydrogen Evolution by Decomposition of Formic Acid
Using an Iridium Catalyst with 4,4′-Dihydroxy-2,2′-Bipyridine. Green Chem. 2009, 11 (12),
2018-2022.
22. Iguchi, M.; Himeda, Y.; Manaka, Y.; Kawanami, H., Development of an Iridium-Based
Catalyst for High-Pressure Evolution of Hydrogen from Formic Acid. ChemSusChem 2016, 9
(19), 2749-2753.
23. Iguchi, M.; Zhong, H.; Himeda, Y.; Kawanami, H., Effect of the ortho-Hydroxyl Groups
on a Bipyridine Ligand of Iridium Complexes for the High-Pressure Gas Generation from the
Catalytic Decomposition of Formic Acid. Chem. Eur. J. 2017, 23 (70), 17788-17793.
44
24. Manaka, Y.; Wang, W.-H.; Suna, Y.; Kambayashi, H.; Muckerman, J. T.; Fujita, E.;
Himeda, Y., Efficient H2 Generation from Formic Acid Using Azole Complexes in Water. Catal.
Sci. Technol. 2014, 4 (1), 34-37.
25. Kar, S.; Rauch, M.; Leitus, G.; Ben-David, Y.; Milstein, D., Highly Efficient Additive-
Free Dehydrogenation of Neat Formic Acid. Nat. 2021, 4 (3), 193-201.
26. Dub, P. A.; Batrice, R. J.; Gordon, J. C.; Scott, B. L.; Minko, Y.; Schmidt, J. G.;
Williams, R. F., Engineering Catalysts for Selective Ester Hydrogenation. Org. Process Res.
Dev. 2020, 24 (3), 415-442.
27. Demianets, I.; Cherepakhin, V.; Maertens, A.; Lauridsen, P. J.; Sharada, S. M.; Williams,
T. J., A New Mechanism of Metal-Ligand Cooperative Catalysis in Transfer Hydrogenation of
Ketones, Polyhedron 2020, 182, 114508.
28. Lu, Z.; Demianets, I.; Hamze, R.; Terrile, N. J.; Williams, T. J., A Prolific Catalyst for
Selective Conversion of Neat Glycerol to Lactic Acid. ACS Catal. 2016, 6 (3), 2014-2017.
29. Padmanaban, S.; Gunasekar, G. H.; Yoon, S., Direct Heterogenization of the Ru-
MACHO Catalyst for the Chemoselective Hydrogenation of α, β-Unsaturated Carbonyl
Compounds. Inorg. Chem. 2021, 60 (10), 6881-6888.
30. Dub, P. A., Alkali Metal Alkoxides in Noyori-Type Hydrogenations. Eur. J. Inorg. 2021,
2021 (47), 4884-4889.
31. Otsuka, T.; Ishii, A.; Dub, P. A.; Ikariya, T., Practical Selective Hydrogenation of α-
Fluorinated Esters with Bifunctional Pincer-Type Ruthenium(II) Catalysts Leading to
Fluorinated Alcohols or Fluoral Hemiacetals. J. Am. Chem. Soc. 2013, 135 (26), 9600-9603.
32. Cherepakhin, V.; Williams, T. J., Iridium Catalysts for Acceptorless Dehydrogenation of
Alcohols to Carboxylic Acids: Scope and Mechanism. ACS Catal. 2018, 8 (5), 3754-3763.
33. Lauridsen, P. J.; Lu, Z.; Celaje, J. J. A.; Kedzie, E. A.; Williams, T. J., Conformational
Twisting of a Formate-Bridged Diiridium Complex Enables Catalytic Formic Acid
Dehydrogenation. Dalton Trans. 2018, 47 (38), 13559-13564.
34. Lu, Z.; Cherepakhin, V.; Demianets, I.; Lauridsen, P. J.; Williams, T. J., Iridium-Based
Hydride Transfer Catalysts: from Hydrogen Storage to Fine Chemicals. ChemComm. 2018, 54
(56), 7711-7724.
35. Cherepakhin, V.; Williams, T. J., Catalyst Evolution in Ruthenium-Catalyzed Coupling
of Amines and Alcohols. ACS Catal. 2020, 10 (1), 56-65.
36. Gonçalves, T. P.; Huang, K.-W., Metal–Ligand Cooperative Reactivity in the (Pseudo)-
Dearomatized PNx(P) Systems: The Influence of the Zwitterionic Form in Dearomatized Pincer
Complexes. J. Am. Chem. Soc. 2017, 139 (38), 13442-13449.
45
37. Gunanathan, C.; Milstein, D., Metal–Ligand Cooperation by Aromatization–
Dearomatization: A New Paradigm in Bond Activation and “Green” Catalysis. Acc. Chem. Res.
2011, 44 (8), 588-602.
38. Casey, C. P.; Johnson, J. B., Isomerization and Deuterium Scrambling Evidence for a
Change in the Rate-Limiting Step during Imine Hydrogenation by Shvo's
Hydroxycyclopentadienyl Ruthenium Hydride. J. Am. Chem. Soc. 2005, 127 (6), 1883-1894.
39. Conley, B. L.; Pennington-Boggio, M. K.; Boz, E.; Williams, T. J., Discovery,
Applications, and Catalytic Mechanisms of Shvo’s Catalyst. Chem. 2010, 110 (4), 2294-2312.
40. Nakamura, H.; Yoshida, M.; Matsunami, A.; Kuwata, S.; Kayaki, Y., Oxy-tethered
Cp*Ir(III) Complex as a Competent Catalyst for Selective Dehydrogenation from Formic Acid.
ChemComm. 2021, 57 (45), 5534-5537.
41. Gusev, D. G.; Spasyuk, D. M., Revised Mechanisms for Aldehyde Disproportionation
and the Related Reactions of the Shvo Catalyst. ACS Catal. 2018, 8 (8), 6851-6861.
42. Akiya, N.; Savage, P. E., Role of Water in Formic Acid Decomposition. AIChE J. 1998,
44 (2), 405-415.
43. Yu, J.; Savage, P. E., Decomposition of Formic Acid under Hydrothermal Conditions.
Ind. Eng. Chem. Res. 1998, 37 (1), 2-10.
46
3 Chapter 3 Bonding and Reactivity in Triiridium Polyhydride Clusters. Reversible CO2-
Formate Conversion
This chapter describes the synthesis, reactivities, and chemical properties of a family of
rare trinuclear iridium complexes. These complexes were discovered in the dehydrogenation of
formic acid in an aqueous methanol solution (blended fuel), as a part of improving the H2 content
in LOHCs study (Chapter 4). Even though, catalyst 2.11 could not realize high selectivity toward
methanol dehydrogenation, I was able to accomplish a thorough chemical study on a series of
novel complexes isolated from the formic acid-methanol solution. This work contains a
publishable preprint in preparation for submission. I would like to take this opportunity to thank
my co-colleagues, Dr. Valeriy Cherepakhin, my undergraduate mentee A.J. Chavez, Jacob
Kelber (NSF-REU program student) for the many intense hours in the lab. I want to especially
thank my DOE-HyMARC collaborator at the National Renewable Energy Laboratory and Oak
Ridge National Laboratory, Dr. Ryan A. Klein, Dr. Eric Novak (ORNL), and Dr. Xiaoping
Wang (ORNL), for their specialty in VISION and TOPAZ neutron beamlines at ORNL and the
detailed structural analysis. Thank you to Dr. Yongqiang Cheng (ORNL) for the important
theoretical calculations via neutron vibrational spectroscopy/first principles calculations on
complex 3.1-H, and lastly Dr. Craig Brown at National Institutes of Standards and Technology
for overseeing the neutron analysis study.
47
3.1 Introduction
Metal hydrides are ubiquitous in organometallic chemistry. Such M–H bonds occur
frequently in hydride transfer hydrogenation/dehydrogenation,
1-3
hydrogen borrowing
alkylation,
4-8
and as sorbent hydrogen storage materials.
9-10
Multinuclear metal hydride
complexes have special reactivity that comes from cooperativity among the multiple metals and
ligands available,
11
hence these complexes can exhibit unique chemistries that are not available
to their mononuclear counterparts. For example, such cooperativity has been seen in activation of
small and inert molecules, such as benzene groups,
12
dinitrogen (N2),
13-15
carbon monoxide
(CO),
16-18
and carbon dioxide (CO2).
11, 19-23
In the latter case, developing new catalysts that
convert CO2 to upcycled commodity chemicals is especially important to mitigate atmospheric
CO2,
24-27
Specifically, the generation of formate from CO2 is highly desirable as formic acid has
several industrial uses including H2 storage for on-demand release.
28
Moreover, formic acid is a
preservative and antibacterial agent in livestock feed,
29
and has been proposed as for CO2 capture
technology. Since late-transition metals are useful for CO2 activation,
23, 30
I hypothesized that
multinuclear IrxHy small molecular clusters may have special reactivity for catalytic
hydrogenation of CO2 to formate.
48
While hundreds of mononuclear and
dinuclear iridium hydride species are known,
there are fewer reports of multinuclear IrxHy
clusters. For instance, there are only five
previous reports for the synthesis and
structural analysis of trinuclear iridium
Ir3H6(µ3-H) type complexes. The first
discovery of such an iridium heptahydride
trimer was as a deactivated form of
Crabtree’s catalyst for olefin hydrogenation.
Later, Crabtree (1978),
31-32
Pignolet (1980
and 1988),
33-34
Albinati (2003),
35
and Inagaki
(2018),
36
found that other analogous
triiridium species also are inert in catalytic hydrogenation conditions. These strongly suggests
that doubly cationic. Therefore, there has been little attention to their potential reducing
reactivity.
Typically, molecular H2 undergoes oxidative addition to iridium(I) complexes to form
octahedral iridium(III) dihydride species,
37-39
with supporting ancillary ligands having a
significant electronic effect on stabilizing any subsequent reactive dimeric intermediates.
(Pincer)iridium systems are not prone to Ir–Ir bond formation and, as such, tend to remain
mononuclear in hydrogenation reactions.
37, 40
These pincer complexes have been extensively
studied for catalytic H-transfer, in part due to the highly tunable electronic properties imparted
by the ligand environment. On the other hand, while bidentate ligands allow more spatial site
Scheme 3.2. Common general iridium dimeric
structure transformation under H2/H
+
/H
−
environment.
Scheme 3.1. Common iridium dimeric
structure transformation under H2/H
+
/H
−
environment.
49
access to the Ir center upon treatment of a hydride donor, a plethora of possible dinuclear Ir
38, 41
and in some rare cases trinuclear structure can be formed (Scheme 3.1).
31-34, 36
Herein, I utilized a bidentate ((di-tert-butylphosphino)methyl)pyridy ligand, reminiscent
of two thirds of a Milstein-like PNP ligand,
37
to synthesize a new family of IrxHy cluster
compounds, including a novel Ir3H6(μ3-O) oxo complex, 3.1-O, and an Ir3H6(μ3-H) complex,
3.1-H. We then characterized the structure and reactivity of these compounds using both liquids
methods (like NMR) and solid-state single crystal X-ray and neutron diffraction to find the first
detailed views of how hydrides are positioned in the Ir3H6(μ3-H) complex. Finally, we conducted
neutron vibrational spectroscopic measurements, coupled with calculations, to investigate the
chemical bonding in these hydrides. The structural model used in the calculations is validated by
vibrational spectroscopy measurements, and further DFT calculations were conducted to
investigate CO2 complexation to the Ir3H6(μ3-H) cluster. The results of these investigations help
shed light on the mechanism of CO2 hydrogenation in this system.
3.2 Synthesis and Characterizations of Complex 3.1-O and 3.1-H
I first encountered the oxo-centered cluster [Ir3(µ3-O)H6(PN)]
+
(PN =
t
Bu2PCH2(2-py))
(3.1-O) in an experiment in which we initiated our very successful formic acid dehydrogenation
catalyst in the presence of methanol. With some experimentation, I discovered an efficient and
selective preparation of 3.1-O that proceeds in the absence of H2 gas in 54% yield. By contrast,
in an H2-rich environment, precursor 2.11 favors the formation of analog Ir3H6(µ3-H) 3.1-H,
selectively (Scheme 3.2). However, I observed a mixture of both 3.1-O and 3.1-H when both
sodium formate and H2 were present in the solution. In fact, the synthesis of 3.1-O requires
sodium formate and water, and the addition of H2 was unnecessary. While 3.1-O and 3.1-H may
appear to be a redox pair, I do not observe interconversion between the two under hydrogen-
50
Scheme 3.2. Synthesis of trinuclear complexes family, including 3.1-O, 3.1-H, and 3.1-S, from
precursor 2.11.
transfer conditions: in a methanol/H2O with an atmosphere of H2 (1 atm). I attempted to employ
similar synthetic approach to the mononuclear rhodium analog of 2.11 Rh(
t
Bu2PCH2(2-
py))(COD)
+
, but this material is unreactive to H2 in various reaction conditions.
33, 42-45
Tracking the formation of 3.1-O in solution by
31
P{
1
H} NMR revealed the conversion to
a major species at 33 ppm, presumbly a dimeric structural analogs similarly in Scheme 3.1. This
material proceeds to a doublet of a doublet signal at 58 ppm upon reaction completion. I
suspected that the prolonged reaction time of 3.1-O overnight could allow a small amount of H2
within the mixture to react with dimeric intermediate to form [Ir3(µ3-H)H6(PN)3]
+
(PN =
51
t
Bu2PCH2(2-py)) analog 3.1-H. As aforementioned, there are only a handful of structural analogs
of this trimer family, and no examples of Ir3H6(µ3-O)-type complexes have been reported.
To further investigate the reaction mechanism, I performed isotopic labeling studies on
the formation of 3.1-O (Table 3.1). Previous studies of the precursor 2.11 system suggested that
the Ir–H bond formation was initiated by sodium formate complexed to the iridium center or in
situ with H2 via oxidative addition.
46
In this case, hydrides then seem to exchange with protic
groups in solution (CH3OH and D2O) and rearranges into the trinuclear product. The resulting
complex 3.1-O has six hydrides which originate from both hydridic and protic sources (Table
3.1, entries 1–3). When complex 2.11 was treated with NaOOCD-d1 (Table 3.1, entry 1), only
10% deuteration was incorporated on hydrides via
1
H NMR analysis. This is consistent with a
view that while there is a mechanism for installation of of the metal hydrides from formate, this
must either not be the primary mechanism, or an initially-formed Ir–D bond is exchanged for
proton later in the mechanism. I favor the latter. Entries 2-4 further confirmed the hydrides of the
product cluster must partially exchange with a protic source. For example, comparing entries 2
and 3 shows that depriving the system of its only hydritic deuterium source results in
incorporation of less deuterium in the product cluster. Therefore, C–D groups must not be the
only source of deuterium in the system. In entry 5, I observed a significant H/D kinetic isotopic
effect on product formation, as this entry results in only 5% conversion, insufficient accurately to
quantify the H/D ratio in the product. When Cherepakhin treated 2.11 with D2/D2S/D2O, he
detected a mixture of 3.1-H:3.1-O:3.1-S (72%:19%:4%) via
1
P NMR and MALDI-MS (Scheme
3.2). These results establish that there is facile H/D exchange between hydride groups in the
trimer family formation mechanism. Cherepakhin was not able to isolate a supply of complex
3.1-S for further structural characterization.
52
Table 3.1. Isotopic labelling experiments and identification of hydride carriers in the synthesis of
3.1-O. Formation of products determined by
31
P{
1
H} and
1
H{
31
P} NMR measurements.
Entry Methanol Water Formate Deuteration (%)
[a]
1 CH3OH H2O NaOOCD 10
2 CD3OD D2O NaOOCH 30
3 CH3OD D2O NaOOCH 40
4 CD3OH H2O NaOOCH 0
5 CD3OD D2O NaOOCD 39
Deuterium incorporation in products determined by
1
H and
2
H NMR measurements.
Next, I optimized the synthesis of complex 3.1-H to high yielding (81%) by
hydrogenating precursor 2.11 with H2 (1 atm) at room temperature. Importantly in this synthesis,
the selection of solvents plays a major role in selecting for Ir3 formation. Treatment of 2.11 with
H2 (1 atm) in CD2Cl2 resulted in an equilibrium between Ir dimer (
1
H NMR: −3.5 ppm, doublet,
2
JHP(trans) = 45 Hz) and 3.1-H (−4.0 ppm, quartet,
2
JHP(trans) = 45 Hz). Complex 3.1-H has lower
solubility in methanol, hence, the reaction equilibrium is shifted towards the less soluble product
3.1-H, avoiding dimeric intermediates, which are seen in the reaction solution. The efficiency of
the formation of 3.1-H was optimized in methanol achieve 81% isolated yield.
To investigate the crystal structures of 3.1-O and 3.1-H, we grew single crystals suitable
X-ray and neutron diffraction measurements. Suitable crystals for X-ray were obtained from the
slow diffusion of diethyl ether into saturated dichloromethane solution of both 3.1-O and 3.1-H.
X-ray analysis enabled structural characterization of the non-H atoms in these systems, but we
turned to neutron diffraction measurements to locate the hydride groups of 3.1-H.
47
These
measurements were carried out using the TOPAZ high resolution single crystal neutron
53
diffractometer (BL-12) at the Spallation Neutron Source at Oak Ridge National Laboratory
(USA). Both complexes display partially distorted octahedral geometries at the metal centers,
which form equilateral triangular Ir
III
3 cores with ∠(Ir-Ir-Ir) angles of 60.08(8)° and Ir–Ir bond
distances of 2.7 Å.
Table 3.2. The selected bond angles (deg) and distances (Å) of complexes 3.1-H and 3.1-O.
Crystallographic analysis showed that complexes 3.1-O and 3.1-H are structurally
analogous (Table 3.2). Neutron crystallographic analysis reveals the locations and bond distances
of three distinct Ir–H moieties which were inferred in previous studies—there are three terminal
hydrides (H1, H2, H3) pointing out of the plane of the Ir3 triangle and trans to H12, H23, H13
with Ir–H distances 1.582(7) Å. The µ3-bridging H ligand has Ir–H distances of 1.945(7) Å. The
three µ2-bridging Ir–H–Ir atoms are asymmetric between the Ir atoms with two distinct Ir–H
distances of 1.679(7) Å and 1.946(8) Å, respectively. This is a key structural insight that
oresages a path for CO2 incorporation into the cluster, which could not have been found in prior
X-ray studies.
31-35
The nature of the Ir–H moieties (i.e. terminal, μ2, and μ3) determined
crystallographically agrees well with our NMR analysis.
Complex 3.1-O
(X=O)
3.1-H
(X=H)
Reported analogs
(X=H)
d, Ir-Ir (Å) 2.834 2.768 2.755 – 2.793
d, Ir-H (Å) 1.425 1.580 Not reported
d, Ir-(µ2-H) (Å) 1.986
1.626
1.945
1.684
Not reported
d, Ir-(µ3-X) (Å) 2.071 1.926 1.7
∠, Ir-Ir-Ir (deg) 60 60 60
∠, Ir-(µ3-X)-Ir (deg) 86.31 89.93 Not reported
54
Interestingly, complex 3.1-H retained its structure in neat triflic acid (CF3SO3D-d1) over
7 days, but
1
H NMR analysis shows H/D exchange of the hydrides at a noticeable rate (Fig. 3.1).
The terminal hydrides (H1, H2, H3) exchanged at the highest rate (94%
2
H) realizing the most
labile H among the three types, followed by μ3-H (55%
2
H) and μ2-H (44%
2
H) (Fig. 3.1) over
the 7-day experiment.
In search for a correlation between hydricity and H/D exchange rate, we calculated the
number of valence electrons of H within the Wigner-Seitz radius for each hydride based on the
Vienna Ab-initio Simulation Package (VASP): Density Functional Theory (DFT) calculated
electron density distribution and summarized the relative comparison in Table 3.3. While the
terminal hydrides have the shortest bond distance to Ir (1.58 Å), possibly due to greater negative
Figure 3.1.
1
H NMR integration of hydrides illustrated in H/D exchange rate of complex 3.1-H
in neat triflic acid-d1. Integration of hydrides was referenced to aromatic protons (3 equivalent).
µ3-H
µ2-H
terminal-H
55
charged, H123 (μ3-H) has the longest bond distance to Ir (1.9 Å) and the most positively charged
distribution (Table 3.3, entry 2-3). Thus, the µ3-H group seems to possess electrophilic character
appropriate to participate in an acidic exchange reaction.
Table 3.3. Comparison the relative chemical properies between hydride modes of 3.1-H.
To further investigate the electrophilic behavior of the µ3-H group, I investigated this
hypothesis with 3.1-H using strong electrophiles, e.g. methyl iodine, methyl triflate, and a
(triphenylphosphine)gold(I)
+
to substitute µ3-H group (H123) with CH3
+
and AuPPh3
+
(Scheme
3.3). Complex 3.1-H was stable in solution with both methyl iodine and methyl triflate, however,
we successfully substitute µ3-H group with Au(I)PPh3 to give a tetranuclear Ir3Au cluster, 3.1-A,
in 54% isolated yield. To our surprise, despite Hg
2+
being an isoelectronic cation of Au
+
, reaction
of 3.1-H with Hg(OAc)2 displace the µ3-H group from the cluster.
Further, an electrochemical study of 3.1-H was performed to examine the redox potential
of the complex. A solution of 3.1-H (1.0 mM) in CH2Cl2 with 0.1 M [Bu4N][PF6] and FeCp
*
was
applied with potential ranging from −2.5 V to 2.5 V at a slow scan rate (50 mV/s) and high scan
rate (200 mV/s). The cyclic voltammogram showed multiple electrochemical irreversibility
events: Ep ≈ 0.36 V and 1.41 V vs SHE in the positive potential and Ep ≈ −1.89 V and −1.06 V vs
SHE in the negative potential environment. Oxidation of 3.1-H with TEMPO in an acidic
Entry Property Comparison
1 H/D exchange rate Hterminal > μ2-H ≈ μ3-H
2 Calc. Charged Distribution (negative) Hterminal > μ2-H > μ3-H
3 Ir–H Length Hterminal < μ2-H ≈ μ3-H
56
environment fully oxidizes the seven hydrides in the cluster to yield complex 3.2-Cl (Table 3.4,
entry 1). This compound has Cl
−
ions coordinating two octahedral Ir
III
centers, as determined by
NMR and X-ray diffraction measurements. We noted that the Ir3 triangular plane in the trinuclear
complexes resembles the electronic density of an aromatic ring, and we hypothesized that a
selection of oxidants which can facilitate classic aromatic electrophilic substitution, such as
halogens, may affect similar chemical reactions at the Ir3 triangular core in 3.1-H (Table 3.4,
entries 2–4).
Scheme 3.3. Synthesis of 3.1-Au, 3.2-I, and 3.2-Cl.
When I treated 3.1-H with the more weakly oxidizing halogenating agent, I2 (E° = 0.54 V
vs SHE), I see selective conversion 3.1-H to a thermodynamically stable product 3.2-I.
48
X-ray
diffraction measurements for 3.2-I reveal that this complex is a dinuclear Ir with side on η
2
-
coordination of the iodine to the Ir atoms. The compound has two chemically inequivalent Ir
III
centers with two µ2-bridging iodine atoms, one µ2-bridging hydride ion (dd,
2
JPH = 51, 12 Hz),
57
and two terminal hydrides (Table 3.4, entry 2). Next 3.1-H was treated with Br2, which generates
an intractable mixture. Likewise, treatment of 3.1-H with the brominating reagent N-
bromosuccinamide (NBS) did not yield any isolable product even at elevated temperature (70
°C) (Table 3.4, entry 4). Evidently, complex 3.1-H can be oxidized to remove its hydride ions
either partially with an oxidant, I2, or fully by using a stronger oxidant like Br2 (E° = 1.09 V vs
SHE) and TEMPO.
49
Complex 3.1-H also facilitates multi-electron reduction transferring all
seven hydride ions from H2SO4 (98%) to H2S and decomposing the trimer (Table 3.4, entry 5).
Further investigations with H2S revealed that multiple Ir–H species formed and none was
isolable from the mixture. A mix of complexes forms possibly due to an unquantifiable amount
of H2S gas in the reaction.
Table 3.4. Redox and electrophilic substitution reactions with complex 3.1-H resulting in the
formation of 3.1-Au, 3.2-Cl, and 3.2-I
Entry Reagents E° (V) Product
1 TEMPO-HCl -0.376 3.2-Cl
2 I2 (I2 +2e
−
= 2I
−
) 0.5355 3.2-I
3 Br2 (Br2 + 2e
−
= 2Br
−
) 1.087 Reactive products mix
4 N-bromosuccinamide (NBS) 0.944 No reaction
5 H2SO4 N/A H2S↑
6 CH3I, CH3O3SCF3, [Ph3C][BF4] N/A No reaction
58
3.3 Structural Analysis and Bonding via First Principle Calculations and Neutron Vibrational
Spectroscopy
Scheme 3.4. Synthesis of deuterated compound 3.1-H(d72).
To better understand the structure and bonding in 3.1-H, neutron vibrational
spectroscopic (NVS) measurements were performed (Fig. 3.2). NVS measurements probe the
vibrational states of the crystalline sample without the selection rules that apply to optical
spectroscopies. In addition, the technique probes all vibrations across the entire Brillouin zone,
and modes involving displacements of hydrogen atoms are particularly intense because of the
total neutron scattering cross section of hydrogen. Lastly, experimental NVS spectra can be
readily simulated using quantum chemistry computations, which both greatly facilitates mode
assignments in the NVS spectra and validates the structural model used as an input in the
calculations—allowing for greater confidence in further calculations using the experimentally
validated theoretical model. To facilitate the investigation, a partially deuterated analog of 3.1-H
was synthesized, 3.1-H(d72) (Scheme 3.4). The NVS spectrum of 3.1-H(d72) should display
intense features for the phonon modes involving the Ir3H7 core and much weaker intensity modes
for the phonons associated with the ligands because of the large total scattering cross section of
H (82.03 barn) compared to D (7.64 barn).
47
59
To determine which modes in the spectra arise specifically from phonons involving the H
atoms in the Ir3H7 core, a second simulation was conducted in which the scattering cross sections
for all other atoms were set to 0. The result is plotted as the blue curve in Fig. 3.2. The modes
identified by this second calculation are indeed intense in the experimental (black curve) and
simulated spectra (red curve), justifying our choice to synthesize a perdeuterated analog of 3.1-H
for this measurement. From this calculation, we identified several intense modes specific to the
Ir3H7 cluster involving the three distinct hydride species at energy transfer values of ≈ 550, 800,
Figure 3.2. Experimental FTIR spectrum for 3.1-H (black curve, top) and NVS spectrum for
3.1-H(d72) (black curve) with simulated spectra for the full material (red curve) and for the
compound with scattering cross-sections set to 0 for all non-Ir3H7 atoms (blue curve). Error
bars represent ±1σ.
60
1050, 1250, 1750, and 2250 cm
–1
. Other modes in the experimental spectrum arise from phonons
involving ligand atoms and from the aluminum sample can.
The calculations allow us to visualize atomic displacements and assign the Ir3H7 phonon
modes in the experimental spectrum. Visualization of the intense mode in the Ir3H7-only
spectrum (blue curve in Fig. 3.2) at ≈ 550 cm
–1
reveals that this mode involves a symmetric
rocking motion of the H12, H1, and H13 atoms in the IrH3N plane about the P–Ir–H123 axis
(Fig. 3.4). Likewise, the mode at ≈ 800 cm
–1
corresponds to a scissoring mode for the H1–Ir1–
H13 atoms (Fig. 3.4). At higher energy transfers, the mode at ≈ 1050 cm
–1
corresponds to a
symmetric stretching motion of the Ir1–H13 bond, where H13 bridges Ir1 and Ir2 and is trans to
the terminal hydride H1. The mode at ≈ 1250 cm
–1
arises from a vibration of the μ3-H123 ion
perpendicular to and into/out of the Ir3 triangular plane. The feature at ≈ 1750 cm
–1
corresponds
Figure 3.4. Neutron molecular structure of 3.1-H.
61
to a symmetric stretching of the Ir1–H12 bond (trans to the N atom). This phonon mode involves
the same atoms and the same type of symmetric stretching as the mode calculated at 1050 cm
–1
but along the N–Ir–H axis instead of along the H–Ir–H axis. The difference in νsym(Ir–H)
frequencies for the μ2-H ion is very large, ca. 700 cm, and we attribute this very large difference
to the trans effect. Indeed, the trans effect is much larger for a M–H moiety trans to a terminal
metal hydride than it is for a M–H bond trans to a pyridine or amine.
53
We hypothesize that, in
addition to greatly modulating the symmetric stretching modes for the μ 2-H hydride, the trans
effect may play a role in directing reactivity in the cluster and determining the degree of
hydricity for this ion.
Finally, the mode at ≈ 2250 cm
–1
corresponds to a symmetric stretching of the Ir1–H1
terminal hydride moiety. Typically, mononuclear Ir
III
–H symmetric stretching frequencies for
terminal hydrides have a strong trans ligand dependence and occur between ca. 2000 cm
–1
and
2300 cm
–1
.
50
The terminal Ir–H stretching frequency observed for 3.1-H(d72) is comparable to
those observed in many mononuclear Ir
III
terminal hydrides.
50-52,53
Conversely, the νsym(Ir–
Hterminal) stretching frequencies in trinuclear Ir3H6(μ3-H) systems exist over a much smaller
energy range, ca. 2200 cm
–1
to 2250 cm
–1
, possibly because of the similarity of the local
coordination environment for the Ir ions, and because the trans μ2-H ligand is chemically similar
in these specific cases. For example, the complexes [Ir3H7(dppp)3](BF4)2 and [Ir3(PN)3(H)7](X)2
(X = PF6, BF4) all have reported stretching frequencies of νsym(Ir–H) = 2200 cm
–1
, and the cluster
compounds [(IrH2LL')3(μ3-H)](BF4)2 (L = PCy3 or P(
i
Pr)3, L' = py; L = PCy3, L' = MeCN) and
[{IrH2(PCy3)(C5H5N)}3(μ3-H)] [PF6]2 display νsym(Ir–H) frequencies of 2240 cm
–1
. This suggests
that the local electronics for the terminal hydrides are similar in these cases, potentially ruling
62
out electronic structure differences at the terminal hydride as the underlying causes for the
disparate reactivities towards CO2.
3.4 CO2 Hydrogenation and Formic Acid Dehydrogenation
Table 3.5. CO2 hydrogenation to formate salt in various conditions.
a
Conditions: catalyst (1.0 mg), THF:H2O (1:5 v/v in mL).
b
Yield was calculated based on K2CO3
conversion determined by
1
H NMR with DMF as internal standard.
c
TON = mol formate/mol
catalyst.
Our initial reactivity studies showed that our complexes 3.1-O and 3.1-H do not facilitate
H-atom transfer to 1-hexene and are thermally stable in various solvents (e.g. water, acetone),
ambient O2, and H2 (1 atm), similar to the previous reports on Ir3H6(μ3-H) complexes.
32-35
I was
Entry Cat PTotal
(PH2: PCO2)
K2CO3
(eq)
Temp.
(°C)
Time
(h)
Yield
b
(%)
TON
c
1
2.11 35
(30:5)
4,970 50 24 19 379
2 3.1-O 45
(35:10)
10,560 50 24 2 336
3 3.1-H 45
(35:10)
1,145 70 24 100 1145
4 3.1-H 45
(35:10)
11,440 50 24 5 1,063
5 3.1-H 90
(70:20)
11,440 50 24 6 1,243
6 3.1-H 90
(70:20)
11,440 120 24 94 21,286
7 3.1-H 90
(70:20)
57,185 120 48 22 24,735
8
3.1-H 90
(45:45)
57,185 120 70 25 28,385
63
therefore surprised to find that 3.1-H is reactive for reversible catalytic hydrogenation of CO2
under H2 to yield formate, with a turnover number (TON) over 28,000 over 70 h.
While several existing metal-catalyzing CO2 hydrogenations normally undergo a metal-
ligand cooperative mechanism, especially when tridentate pincer complexes are involved.
11
Multinuclear metal-metal cooperation in CO2 hydrogenation can also play a pivotal role in
improved catalytic performance.
11
Intrigued by this metal-metal cooperating H-transfer
mechanism, I investigated the reactivities of 2.11, 3.1-O, and 3.1-H towards CO2 hydrogenation
(Table 3.5). Complex 2.11 employs a pyridylphosphine arm fragment of common tridentate
pincer ligands which can be activated by a strong base before H2/CO2 abstraction via a so-called
dearomatization mechanism.
37
In these conditions, complex 2.11 achieves 379 TON which is
comparable to trimer 3.1-O (entries 1-2). Complex 2.11 forms dinuclear and higher order
clusters over time, both allowing reactivity towards CO2 activation but also ultimately hindering
the total TON achieved, based on the reactivity observed during optimization of synthesis for
3.1-H. Complex 3.1-H is presumed to be the active species possibly attributed to its high
complexity of Ir–H characters for intramolecular single-hydride transfer to CO2. Trimer 3.1-H
exhibits the highest catalytic performance among the three studied complexes (Table 3.5, entries
1-3). In entry 3, 3.1-H catalyzed over 1,000 TON under moderate conditions.
Scheme 3.5. Reversible CO2 hydrogenation with 3.1-H and 3.1-H’.
64
While seeking to understand the catalytic mechanism of 3.1-H with H2:CO2 (1:1, 1 atm)
at room temperature, I did not observe newly formed iridium species via
1
H NMR, I was able to
detect formation of formate product over 3 hours. It suggested that 3.1-H is either the catalytic
resting state or dormant species. Upon increasing gas pressure and temperature to 90 bar and 120
°C (Table 3.5, entries 5-6), we achieved approximately 25,000 TON over 48 hours (Table 3.5,
entry 7). There was little efficiency improvement prolonging the reaction time (entries 8). In fact,
this realized that catalyst 3.1-H was slowly deactivated and ultimately became deactivated after
70 hours. In a 5 mL series 2550 micro-batch Parr pressure non-stirred reactor vessel, we isolated
the deactivated species 3.1-H‘ structurally identified by
1
H{
31
P} and
31
P{
1
H} NMR to be an
asymmetrical iridium dimer containing two hydrides (µ2-H and Hterminal). Further structural
analysis was not obtained due to low isolated yield. Since the hydrogenation of CO2 reaction
required a cation source (K2CO3) to trap formate ion, I hypothesized that in the absence of a
base, catalyst 3.1-H is reactive toward catalyzing formic acid dehydrogenation. To investigate
this hypothesis, we tested catalyst 3.1-H in neat formic acid. A total of ≈ 162,000 TON of formic
acid was readily dehydrogenated to H2 and CO2 over 13 repeatable cycles. As expected, I
isolated and identified 3.1-H’ presence in the post-catalytic mixture (Scheme 3.5).
3.5 Conclusion
Multinuclear complexes containing iridium-hydride bonds of the type [Ir3H6(µ3-
H)(PN)3]
2+
have been underexplored for decades since its first analogous complex was
discovered. Herein, I synthesized a family of trinuclear iridium complexes and unlocked the
versatile chemical reactivities of 3.1-H in noncatalytic reactions using several oxidants and metal
electrophiles. Moreover, I could also activate H-transfer capability of 3.1-H in reversible CO2
hydrogenation (max TON ≈ 28,000) and formic acid dehydrogenation (TON ≈162,000).
65
3.6 References
1. Baidilov, D.; Hayrapetyan, D.; Khalimon, A. Y., Recent Advances in Homogeneous
Based-Metal Catalyzed Transfer Hydrogenation Reactions. Tetrahedron 2021, 98, 132435.
2. Crabtree, R. H., Transfer Hydrogenation with Glycerol as H-Donor: Catalyst Activation,
Deactivation and Homogeneity. ACS Sustain. Chem. Eng. 2019, 7 (19), 15845-15853.
3. Dobereiner, G. E.; Crabtree, R. H., Dehydrogenation as a Substrate-Activating Strategy
in Homogeneous Transition-Metal Catalysis. Chem. Rev. 2010, 110 (2), 681-703.
4. Cabrero-Antonino, J. R.; Adam, R.; Papa, V.; Beller, M., Homogeneous and
Heterogeneous Catalytic Reduction of Amides and Related Compounds Using Molecular
Hydrogen. Nat. Commun. 2020, 11 (1), 3893.
5. Nalikezhathu, A.; Cherepakhin, V.; Williams, T. J., Ruthenium Catalyzed Tandem
Pictet–Spengler Reaction. Org. Lett. 2020, 22 (13), 4979-4984.
6. Nalikezhathu, A.; Tam, A.; Cherepakhin, V.; Do, V. K.; Williams, T. J., Synthesis of 1,4-
Diazacycles by Hydrogen Borrowing. Org. Lett. 2023, 25(10), 1754–1759.
7. Qu, R.; Cheng, Y.; Yang, S.; Zhao, C.; Liu, H.; Huang, X., Iron-Catalyzed N-Alkylation
of Secondary Amines with Alcohols Using Borrowing Hydrogen Strategy. ChemistrySelect
2021, 6 (17), 4089-4097.
8. Yin, Z.; Zeng, H.; Wu, J.; Zheng, S.; Zhang, G., Cobalt-Catalyzed Synthesis of Aromatic,
Aliphatic, and Cyclic Secondary Amines via a “Hydrogen-Borrowing” Strategy. ACS Catal.
2016, 6 (10), 6546-6550.
9. Manickam, K.; Mistry, P.; Walker, G.; Grant, D.; Buckley, C. E.; Humphries, T. D.;
Paskevicius, M.; Jensen, T.; Albert, R.; Peinecke, K.; Felderhoff, M., Future Perspectives of
Thermal Energy Storage with Metal Hydrides. Int. J. Hydrog. Energy 2019, 44 (15), 7738-7745.
10. Schneemann, A.; White, J. L.; Kang, S.; Jeong, S.; Wan, L. F.; Cho, E. S.; Heo, T. W.;
Prendergast, D.; Urban, J. J.; Wood, B. C.; Allendorf, M. D.; Stavila, V., Nanostructured Metal
Hydrides for Hydrogen Storage. Chem. Rev. 2018, 118 (22), 10775-10839.
11. Kanega, R.; Onishi, N.; Tanaka, S.; Kishimoto, H.; Himeda, Y., Catalytic Hydrogenation
of CO2 to Methanol Using Multinuclear Iridium Complexes in a Gas–Solid Phase Reaction. J.
Am. Chem. Soc. 2021, 143 (3), 1570-1576.
12. Hu, S.; Shima, T.; Hou, Z., Carbon–Carbon Bond Cleavage and Rearrangement of
Benzene by a Trinuclear Titanium Hydride. Nature 2014, 512 (7515), 413-415.
13. Singh, D.; Buratto, W. R.; Torres, J. F.; Murray, L. J., Activation of Dinitrogen by
Polynuclear Metal Complexes. Chem. Rev. 2020, 120 (12), 5517-5581.
66
14. McWilliams, S. F.; Holland, P. L., Dinitrogen Binding and Cleavage by Multinuclear
Iron Complexes. Acc. Chem. Res. 2015, 48 (7), 2059-2065.
15. Lee, Y.; Sloane, F. T.; Blondin, G.; Abboud, K. A.; García-Serres, R.; Murray, L. J.,
Dinitrogen Activation Upon Reduction of a Triiron(II) Complex. Angew. Chem. Int. Ed. 2015,
54 (5), 1499-1503.
16. Brenner, A.; Hucul, D. A., Clusters and Catalysis: On the Requirement for Multinuclear
Centers to Catalyze the Hydrogenation of Carbon Monoxide. J. Am. Chem. Soc. 1980, 102 (7),
2484-2487.
17. Ghosh, A. C.; Duboc, C.; Gennari, M., Synergy Between Metals for small molecule
activation: Enzymes and bio-inspired complexes. Coord. Chem. Rev. 2021, 428, 213606.
18. Mahajan, D., Atom-Economical Reduction of Carbon Monoxide to Methanol Catalyzed
by Soluble Transition Metal Complexes at Low Temperatures. Top Catal. 2005, 32 (3), 209-214.
19. Moret, S.; Dyson, P. J.; Laurenczy, G., Direct Synthesis of Formic Acid from Carbon
Dioxide by Hydrogenation in Acidic Media. Nat. Commun. 2014, 5, 4017.
20. Tanaka, R.; Yamashita, M.; Nozaki, K., Catalytic Hydrogenation of Carbon Dioxide
Using Ir(III)−Pincer Complexes. J. Am. Chem. Soc. 2009, 131 (40), 14168-14169.
21. Wang, W.-H.; Hull, J. F.; Muckerman, J. T.; Fujita, E.; Himeda, Y., Second-
Coordination-Sphere and Electronic Effects Enhance Iridium(iii)-Catalyzed Homogeneous
Hydrogenation of Carbon Dioxide in Water Near Ambient Temperature and Pressure.
Energy Environ. Sci. 2012, 5 (7), 7923-7926.
22. Westhues, N.; Belleflamme, M.; Klankermayer, J., Base-Free Hydrogenation of Carbon
Dioxide to Methyl Formate with a Molecular Ruthenium-Phosphine Catalyst. ChemCatChem
2019, 11 (21), 5269-5274.
23. Miller, A. J. M.; Labinger, J. A.; Bercaw, J. E., Trialkylborane-Assisted CO2 Reduction
by Late Transition Metal Hydrides. Organometallics 2011, 30 (16), 4308-4314.
24. Hanifa, M.; Agarwal, R.; Sharma, U.; Thapliyal, P. C.; Singh, L. P., A Review on CO2
Capture and Sequestration in the Construction Industry: Emerging Approaches and
Commercialised Technologies. J. CO2 Util. 2023, 67, 102292.
25. Huhe, F. N. U.; King, J.; Chuang, S. S. C., Amine-Based Sorbents for CO2 Capture from
Air and Flue Gas—A Short Review and Perspective. Res. Chem. Intermed. 2023, 49 (3), 791-
817.
26. Koch, C. J.; Galvan, V.; Goeppert, A.; Surya Prakash, G. K., Metal Hydroxide Assisted
Integrated Direct Air Capture and Conversion to Methane with Ni/Al2O3 Catalysts. Green Chem.
2023, 25 (5), 1803-1808.
67
27. Shao, B.; Wang, Z.-Q.; Gong, X.-Q.; Liu, H.; Qian, F.; Hu, P.; Hu, J., Synergistic
Promotions between CO2 Capture and In-Situ Conversion on Ni-CaO Composite Catalyst. Nat.
Commun. 2023, 14 (1), 996.
28. Ma, Z.; Legrand, U.; Pahija, E.; Tavares, J. R.; Boffito, D. C., From CO 2 to Formic Acid
Fuel Cells. Ind. Eng. Chem. Res. 2021, 60 (2), 803-815.
29. Ricke, S. C.; Dittoe, D. K.; Richardson, K. E., Formic Acid as an Antimicrobial for
Poultry Production: A Review. Frontiers 2020, 7, 2297-1769.
30. Evans, H. A.; Mullangi, D.; Deng, Z.; Wang, Y.; Peh, S. B.; Wei, F.; Wang, J.; Brown, C.
M.; Zhao, D.; Canepa, P.; Cheetham, A. K., Aluminum Formate, Al(HCOO)3: An Earth-
Abundant, Scalable, and Highly Selective Material for CO2 capture. Sci. Adv. 2022, 8 (44), 1473.
31. Chodosh, D. F.; Crabtree, R. H.; Felkin, H.; Morris, G. E., A Tri-Coordinate Hydrogen
Ligand in a Trinuclear Iridium Cluster. J Organomet Chem 1978, 161 (3), C67-C70.
32. Chodosh, D. F.; Crabtree, R. H.; Felkin, H.; Morehouse, S.; Morris, G. E., Trinuclear
Iridium Cluster Containing a Tricoordinate Bridging Hydrogen Ligand: Structural and Chemical
Studies. Inorg. Chem. 1982, 21 (4), 1307-1311.
33. Wang, H. H.; Pignolet, L. H., Cationic Polyhydride Cluster Complexes of Iridium with
Chelating Diphosphine Ligands. X-ray Crystal and Molecular Structures of
[Ir2H5(Ph2P(CH2)3PPh2)2]BF4 and [Ir3H7(Ph2P(CH2)3PPh2)3](BF4)2. Inorg. Chem. 1980, 19 (6),
1470-1480.
34. Wang, H. H.; Casalnuovo, A. L.; Johnson, B. J.; Mueting, A. M.; Pignolet, L. H.,
Cationic Polyhydrido Cluster Complexes. Crystal and Molecular Structures of Tris[1,3-
Bis(diphenylphosphino)propane]carbonylheptahydridotriiridium(2+) and Heptahydridotris[1-(2-
Pyridyl)-2-(Diphenylphosphino)ethane]triiridium
2+
. Inorg. Chem. 1988, 27 (2), 325-331.
35. Smidt, S. P.; Pfaltz, A.; Martínez-Viviente, E.; Pregosin, P. S.; Albinati, A., X-ray and
NOE Studies on Trinuclear Iridium Hydride Phosphino Oxazoline (PHOX) Complexes.
Organometallics 2003, 22 (5), 1000-1009.
36. Shitaya, S.; Nomura, K.; Inagaki, A., Synthesis of Di- and Trinuclear Iridium
Polyhydride Complexes Surrounded by Light-Absorbing Ligands. Dalton Trans. 2018, 47 (35),
12046-12050.
37. Gunanathan, C.; Milstein, D., Metal–Ligand Cooperation by Aromatization–
Dearomatization: A New Paradigm in Bond Activation and “Green” Catalysis. Acc. Chem. Res.
2011, 44 (8), 588-602.
38. Chadwick, F. M.; Olliff, N.; Weller, A. S., A Convenient Route to a Norbornadiene
Adduct of Iridium with Chelating Phosphines, [Ir(R2PCH2CH2PR2)(NBD)][BAr4F] and a
Comparison of Reactivity with H2 in Solution and the Solid–State. J. Organomet. Chem. 2016,
812, 268-271.
68
39. Schnabel, R. C.; Carroll, P. S.; Roddick, D. M., Polyhydride (Fluoroalkyl)phosphine
Complexes of Iridium. Synthesis, Dynamics, and Reactivity Properties of (dfepe)2Ir2(μ-H)3(H).
Organometallics 1996, 15 (2), 655-662.
40. Prichatz, C.; Alberico, E.; Baumann, W.; Junge, H.; Beller, M., Iridium–PNP Pincer
Complexes for Methanol Dehydrogenation at Low Base Concentration. ChemCatChem 2017, 9
(11), 1891-1896.
41. Ghaffari, B.; Vanchura, B. A., II; Chotana, G. A.; Staples, R. J.; Holmes, D.; Maleczka,
R. E., Jr.; Smith, M. R., III, Reversible Borylene Formation from Ring Opening of Pinacolborane
and Other Intermediates Generated from Five-Coordinate Tris-Boryl Complexes: Implications
for Catalytic C–H Borylation. Organometallics 2015, 34 (19), 4732-4740.
42. Fischer, C.; Kohrt, C.; Drexler, H.-J.; Baumann, W.; Heller, D., Trinuclear rhodium
hydride complexes. Dalton Trans 2011, 40 (16), 4162-4166.
43. Kohrt, C.; Hansen, S.; Drexler, H.-J.; Rosenthal, U.; Schulz, A.; Heller, D., Molecular
Vibration Spectroscopy Studies on Novel Trinuclear Rhodium-7-Hydride Complexes of the
General Type {[Rh(PP*)X]3(μ2-X)3(μ3-X)}(BF4)2 (X = H, D). Inorg. Chem. 2012, 51 (13), 7377-
7383.
44. Maitlis, P. M., (Pentamethylcyclopentadienyl)rhodium and Iridium complexes:
Approaches to New Types of Homogeneous Catalysts. Acc. Chem. Res. 1978, 11 (8), 301-307.
45. Nutton, A.; Bailey, P. M.; Braund, N. C.; Goodfellow, R. J.; Thompson, R. S.; Maitlis, P.
M. In Synthesis and Structure (X-ray Diffraction and Spectroscopy) of an Extremely Rigid and
Non-Fluxional Trinuclear Trihydride, [Rh3H3(η
5
-C5Me5)3O]PF6·H2O, J. Chem. Soc., Chem.
Commun. 1980, 13, 631-633.
46. Celaje, J. J. A.; Lu, Z.; Kedzie, E. A.; Terrile, N. J.; Lo, J. N.; Williams, T. J., A prolific
catalyst for dehydrogenation of neat formic acid. Nat. Commun. 2016, 7 (1), 11308.
47. Sears, V. F., Neutron Scattering Lengths and Cross Sections. Neutron News 1992, 3 (3),
26-37.
48. Cotton, F. A.; Lahuerta, P.; Sanau, M.; Schwotzer, W., Preparation and Structures of
Novel Di- and Trinuclear Clusters of Iridium(II) without Carbonyl Ligands. J. Am. Chem. Soc.
1985, 107 (26), 8284-8285.
49. Connelly, N. G.; Geiger, W. E., Chemical Redox Agents for Organometallic Chemistry.
Chem. 1996, 96 (2), 877-910.
50. Morris, R. H., Estimating the Wavenumber of Terminal Metal-Hydride Stretching
Vibrations of Octahedral d6 Transition Metal Complexes. Inorg. Chem. 2018, 57 (21), 13809-
13821.
69
51. Esteruelas, M. A.; Oliván, M.; Vélez, A., POP-Pincer Silyl Complexes of Group 9:
Rhodium versus Iridium. Inorg. Chem. 2013, 52 (20), 12108-12119.
52. Lee, J. C.; Rheingold, A. L.; Muller, B.; Pregosin, P. S.; Crabtree, R. H., Complexation of
an Amide to Iridium via an Iminol Tautomer and Evidence Ir–H ⋯ H–O Hydrogen Bond.
J. Chem. Soc., Chem. Commun. 1994, (8), 1021-1022.
53. Jmol: An Open-Source Java Viewer for Chemical Structures in 3D. http:www.jmol.org.
54. Smith, S. A.; Blake, D. M.; Kubota, M., Hydridocarboxylato Complexes of Iridium.
Inorg. Chem. 1972, 11 (3), 660-662.
70
4 Chapter 4 Mechanistic Study of Prolific Ir-Catalyzing Formic Acid Dehydrogenation
and Blended Fuel
This chapter contains the catalytic mechanism study of our most prolific neat formic acid
dehydrogenation system. This chapter is largely based on work that is either part of a manuscript
in preparation for publication or part of other, ongoing studies centered around formic acid,
methanol, and blended fuel dehydrogenation. Here, we explored the potential of improving H2-
content density in the C1 LOHCs through a new fuel medium called blended fuel and elucidated
the structures of several catalytic intermediates in Ir-catalyzed formic acid dehydrogenation
system involving catalyst carbonylation and catalyst methylation under multiple reaction
conditions and the application in formic acid dehydrogenation at scale in methanol blended fuel
and in a laboratory-built demonstration reactor. I would like to acknowledge Dr. Valeriy
Cherepakhin, who studied and characterized complex 2.11 and its five intermediates in neat
formic acid. I want to thank Nicolas Alfonso, A.J. Chavez, and the DOE-HyMARC team, Dr.
Thomas Autrey, Dr. Katherina Grubel, Dr. Samantha Johnson, and Dr. Mark Bowden, at Pacific
Northwest National Laboratory (PNNL) for the prototype demonstration reaction setup,
programs, and useful chemical/technical advice. Also, I thank C.J. Koch for all mixture analysis
in gas chromatography (GC) and Fourier-transform infrared spectrometer (FT-IR).
4.1 Iridium-Catalyzing Dehydrogenation of Neat Formic Acid
Global energy demand increases on an exponential trajectory giving rise to an imperative
energy-climate challenge – a sustainable carbon-neutral energy source to replace fossil fuels. A
commonly studied LOHCs, such as formic acid (FA), containing up to 4.4 wt% H2, can be
converted to H2 and CO2 (∆G
o
rxn = −32.8 kJ mol
-1
). Coffey (1967) first reported an efficient
formic acid dehydrogenation (FAD) by Ir(H3)(PPh3)3 with > 11,000 TON. In the recent decades,
71
extensive efforts in the development of highly efficient heterogeneous
1-11
and homogeneous
12-29
FAD have resulted in a number of prominent systems, some of which featuring millions of
turnover numbers (TON) under various conditions. For instance, Iguchi et.al. reported TON of 5
million for a water-soluble, recyclable [Cp*Ir(DHPT)(H2O)][SO4] catalyst,
30
Celaje and Kar
et.al. independently reported an iridium-based FAD system, which performed efficiently with
neat formic acid resulting in 2.16 and 1.7 million TON, respectively.
12, 14
Other outstanding
examples of first-row metals FADs with excellent turnovers have been reported by Beller
31
(TOF
> 9,400), Bielinski
32
(TON > 983,000), and Anderson
33
(TOF > 8,500).
Scheme 4.1 Reported prolific formic acid dehydrogenation by 2.11 by Celaje (2016).
Although many proposed FAD mechanisms indicate that its catalyst initiation involves
coordination of formate onto the metal center, not all intermediates of transition-metals bearing
formate (M-OC(O)H) can be isolated and characterized. Since the first M-OC(O)H X-ray
structure reported in 1973 by Kolomnikov,
34
a series of transition metal complexes with
established crystal structures containing HCOO–M fragments were observed in 339 first-row
metal complexes (Cu,
35-38
Ni,
39
Fe,
40-41
and Mn
42
) and 48 rare, precious metal complexes
(Ru,
34,43-52
Re,
42
Pd,
39, 53-54
Rh,
55-56
Pt,
57
Os,
58
and Ir
59
). These transition metal complexes bearing
formate (M-OC(O)H) are formed by 3 types of reactions: 1. CO2 insertion to M-H bond in CO2
hydrogenation, 2. coordination via formate salt, 3. formic acid dehydrogenation.
72
Among these, formato iridium-based complexes are scarce, with only one existing
monomeric pincer-type iridium formato structure reported thus far. Previously, we have reported
a highly prolific neat FAD catalyzed by an iridium-pyridylphosphine catalyst, compound 2.11,
12
for which the catalyst initiation involved the formation of the formate-bridging diiridium active
species, carbonylated compounds 2.11-CO, 4.1, 4.1-H2, and methylated compound 4.2. Here, we
reported the initiation and catalytic reactivity of 2.11-CO and 4.2 via catalyst carbonylation and
methylation pathways in various reaction conditions (temperature, solvents, and kinetics).
Scheme 4.2. Catalytic cycles involve catalyst carbonylation and catalyst methylation.
The thermodynamic equilibria of formic acid, methanol, and a blended fuel at 20-120 °C
were computed using HSC Chemistry 10 (Fig. 4.1). Oxidation of a primary alcohol, such as
methanol, is highly endothermic (∆H°rxn = 130 kJ/mol). This reaction requires an alkaline
solution (KOH) at high temperature to surpass its activation barrier at an appreciable rate.
60
73
While methanol dehydrogenation is an obvious uphill battle, dehydrogenation of formic acid is a
much more exergonic reaction (∆G°rxn = −80 kJ/mol at 120 °C) due to its much greater entropic
energy (∆S°rxn = +51 cal mol
−1
K
−1
). Thus, coupling the two reactions together creates a
thermodynamic advantage to drive blended fuel dehydrogenation forward at an energy demand
that is lower than it would be for the respective individual reactions. For these reasons, it is
thermodynamically possible to catalyze methanol dehydrogenation under acidic conditions such
as in a formic acid blended fuel.
Figure 4.1. Computed thermodynamic equilibria – formic acid dehydrogenation (red), methanol
dehydrogenation (blue), blended fuel dehydrogenation (green).
74
The Williams group has long been
interested in the on-demand H2 release from
formic acid and its detailed mechanism. As
part of these efforts, Cherepakhin conducted
a detailed mechanistic study of 2.11 in neat
formic acid and revealed a complex
catalytic transformation, including the
intermediates [(tBu2PCH2(2-
py))Ir(CO)]2(μ2-H)
+
(2.11-CO), [(tBu2PCH2(2-py))Ir(H)]2(μ
2
-H)(μ
2
-κ,κ′-O2CCH3)
+
(4.1), and an
ortho-methylated pyridyl derivative (4.2). In this mechanism sequence, catalyst 2.11 was
initiated to form active formate-bridging Ir dimers at room temperature. This active species is
then carbonylated at elevated temperature (90-110°C) yielding complex 2.11-CO. To our
surprise, this catalyst carbonylation sequence is more robust at room temperature when formed in
formic acid-methanol blend solution. The reaction kinetic reaches an average turnover frequency
of 98 hr
-1
at room temperature (Fig. 4.2). Formation of 2.11-CO with > 95% NMR purity was
observed in a blended fuel solution after 48 hours (Fig. 4.3). Further, we found complex 2.11-
CO is the catalytic resting state in both neat formic acid and blended fuel.
Figure 4.2. Catalytic dehydrogenation with 2.11 in
aqueous methanol-formic acid blended fuel
solution at 110 °C.
75
To determine catalytic selectivity in blended fuel system, we performed a series of
control experiments summarized in Table 4.1. Due to the unknown ratio of gas products, we
employed a strongly basic eudiometry system (4.0 M KOH) to separate CO 2 from our gas stream
and quantify only evolved H2. As expected, 2.11 is much more selective toward neat FAD than
methanol (Table 4.1, entries 1-3). Yet, the efficiency of each fuel in a blended fuel mixture
cannot be drawn from this experiment. For instance, in entry 4 we calculated the H2 yield via
eudiometry, I assumed that 2.11 has 1. a much faster kinetic for FAD and 2. formate salt
dehydrogenation is also thermodynamically feasible. We hypothesize that the aqueous methanol
solution acts as a solvent for 2.11-CO to dehydrogenate formate. To test this hypothesis, we
treated 2.11-CO with sodium formate (Table 4.1, entry 5) and sodium carbonate (Table 4.1,
entry 6) in aqueous methanol solutions. Formate salt was fully converted to carbonate salt by
Figure 4.3.
31
P NMR time-course study of blended fuel dehydrogenation with 2.11 resulting in
formation of resting state 2.11-CO (bottom) after 48 hours.
76
2.11-CO within 6 hours (Table 4.1, entry 5) and only 2% gas evolved when HCOONa was
substituted with Na2CO3. The preliminary results indicate that blended fuel is not kinetically
feasible under these conditions. Future investigations regarding catalyst screening and condition
optimization of reaction conditions need to be performed for an effective H2-densed blended-fuel
system.
Table 4.1. Blended fuel dehydrogenation conditions.
Entry
a
Catalyst(s) VolMeOH
(mL)
VolFormic acid
(mL)
VolDI Water
(mL)
H2 Yield (%)
1 2.11 - 1.5 - 100
2 2.11 - 1.5 1.0 100
3 2.11 3.2 0 1.0 5
4
2.11 3.2 1.5 1.0 27
5
2.11-CO 3.2 - 1.0 15
6
b
2.11-CO 3.2 - 1.0 2
a
Conditions: catalysts (0.016 mmol), HCOONa (17.6 mmol), CH3OH, HCOOH, and
deionized H2O at 110 °C.
b
Replaced HCOONa with Na2CO3 (17.6 mmol). Reaction yield
calculated by total collected H2 gas (by volume)/total theoretical H2 in HCOOH and
CH3OH/H2O.
4.2 On-Demand Formic Acid Release Scale-up and H2 Purification
Of further importance to the utility of this technology is the scale-up process to meet the
Department of Energy (DOE) target flow rate of 300 kg H2/hr on-demand H2. This goal has two
major technicalities: 1. scalability and 2. H2 purity. In a laboratory-built high-pressure
demonstration reactor prototype, Alfonso and Chavez achieved 2.35 million TON of continuous
H2 evolution from 3.25 L of formic acid within 160 hours at 1440 psig without catalyst
deactivation. Although this prototype requires more engineering effort to continuously operate in
an automated fashion, this experiment is a good example demonstrating a case of achieving the
target flow rate.
77
Since the product gas stream from formic acid is contaminated with undesired gases (CO2
and trace CO), additional product processing is required. In a 750 mL Parr pressure vessel,
formic acid (70 mL) was dehydrogenated with catalyst 2.11 to 2300 psig. The product gas was
allowed to partition into a pressurized extraction vessel containing water. Once the pressure had
equalized between the vessels, a 100 mL volumetric pipet containing 80 mL of 3.0 M KOH was
connected to the sampling line of the extraction vessel. The pipet was purged with headspace
gas, the pipet headspace was sampled and injected into a gas GC with an 8.8 ppm detection limit
for CO. The resulting chromatogram showed ≈ 99.9% H2 purity, as no other gas peaks (CO or
CO2) were detected. This experiment shows that after a water absorption step, 50% H2 can be
purified to > 99% H2 (nominally < 10 ppm CO, CO2) using a relatively small amount of CO2
absorption agent (Table 4.2). Partial CO2 removal was achieved by water partitioning H2:CO2
gas mixture at 2300 psig and completely removal of CO and CO2 from product gas stream by
scrubbing at ambient pressure.
Table 4.2. Qualitative gas analysis from formic acid dehydrogenation in gas purification.
Stage Technique H2 CO2 CO
1 High pressure water/gas partition 71.3% 24.7% 4.0%
2 Ambient pressure KOH scrubbing 100% < 10 ppm < 10 ppm
Celaje previously proved the high selectivity of 2.11 for formic acid dehydrogenation
(HCOOH → CO2 + H2) over its energetically competitive dehydration reaction (HCOOH →
H2O + CO), however, quantitative amounts of CO ligand ends up in precursor 2.11 and
detectable quantities by gas analysis (GC, IR) emphasizes the importance of CO in the catalytic
mechanism. I then conducted a set of experiments to determine the CO formation pathways
78
summarized in table 4.3. In entries 1-3, we observed a significant noncatalytic thermal
decomposition of formic acid at 120 °C, which is in agreement with reported chemical properties
of formic acid at elevated temperature. However, a small amount of Ir-catalyzing formic acid
dehydration also occurs in entry 4. The addition of water to the reactions facilitates the reverse
water-gas shift (RWG) reaction hindering formation of the CO product (Table 4.3, entries 5-6).
Our CO2 separation process utilizes a cost-effective water partition method at high pressure to
demonstrate the effectiveness of our proposed CO2 purification scrubbing vessels.
Table 4.3. CO formation under self-pressurized conditions.
Exp
.
Cat
1
(mg)
NaOOCH
(g)
Temp
.(°C)
Additives Collected
Gas
Pressure
(psi)
Gas
Chromatography
Analysis
IR
Analysis
H2
(psi)
CO2
(psi)
CO
(psi)
Free CO
stretch
1 52.6 25.3 120 None 1458 723.
2
714.
4
20.4 Y
2 52.6 25.3 90 None 382 194.
8
183.
7
3.4 Y
3 0 25.3 120 None 7 1.2 0.5 5.3 Not
detected
*
4 52.6 5.4 90 None 64 27.4 33.9 2.7 Y
5 52.6 5.4 90 H2O 90 46.6 42.5 0.9 Y
6 52.6 5.4 90 H2O 7 3.7 3.3 0.02 Y
79
4.3 Synthesis of Bifunctional Photobasic Iridium Catalyst for Methanol Dehydrogenation at
Room Temperature
This work was inspired by early
discoveries of photobase reactivity by Dalawty
61-
63
and preliminary studies on light-driven, base-
and solvent-free formic acid dehydrogenation by
Demianets. This study demonstrates the synthesis
of a silver N-heterocyclic carbene (NHC) (4.5), a
precursor for an Ir
I
complex (4.6) designed by
Demianets as an application of the recently-
discovered form of chemical reactivity, photobasicity, in one of our highly active iridium
catalysts to develop a base-free aqueous methanol dehydrogenation reaction. This system
circumvents the safety hazards of hydrogen gas storage by using liquid methanol and water as
feedstocks and maximizes energy conversion efficiency by using a photo-activating bifunctional
iridium catalyst input. The base-free nature of this process sets it apart from several other
excellent, known approaches.
Development of this concept by the Dawlaty group at USC showed that 5-
methoxyquinoline (Q) achieves a change in pKa
*
to 15.1 (Q*), more basic than methanol which
has a pKa of 15.5, during photoexcitation. This suggests that the 5-methoxyquinoline moiety
could be a substitute for a base in the initiation step by deprotonating aqueous methanol and
subsequently releasing that same proton at the end of its photoexcitation (Scheme 4.3). The
synthesis sequence (Scheme 4.4) starts from selectively reducing the nitro group on a
commercially available compound, followed by a Skraup reaction to form a functionalized
Scheme 4.3 Photobase-mediated methanol
dehydrogenation.
80
quinoline-containing compound 4.5 (74%). Aldehyde 4.6 formation (56%) is a result of
formylating lithiated compound 4.5, via a Bouveault synthesis. Then, compound 4.6
subsequently undergoes nucleophilic acyl substitution and nucleophilic addition resulting in the
in situ generated pyridine alcohol 4.7 (44%), following halogen-functionalization with cyanuric
chloride to substitute the resulting chlorinated compound with a N-methylimidazole. Challenging
purification of compound 4.8 resulted in low yields for the product of the following step, silver
precursor complex 4.9 which was consequently only identified only by X-ray crystallography. I
could not realize the formation of complex 4.10 from this synthetic route.
Scheme 4.4. A complete proposed synthetic pathway to target complex 4.10.
4.4 Conclusion
In conclusion, we presented here several approaches to improve the efficiency of on-
demand H2 release from formic acid, methanol, and blended fuel. The new catalytic LOHCs
dehydrogenation approaches reveal new insight into initiation of catalyst carbonylation. While
thermal decomposition of formic acid is a common source of CO for catalyst carbonylation, this
process has proven experimentally possible at room temperature with 2.11 via a catalytic
81
process. Here, we proposed another approach for the dehydrogenation of methanol including the
partial synthesis towards a novel quinoline-mediated methanol dehydrogenation.
82
4.5 References
1. Grasemann, M.; Laurenczy, G., Formic Acid as a Hydrogen Source – Recent
Developments and Future Trends. Energy & Environmental Science 2012, 5 (8), 8171-8181.
2. Hong, D.; Shimoyama, Y.; Ohgomori, Y.; Kanega, R.; Kotani, H.; Ishizuka, T.; Kon, Y.;
Himeda, Y.; Kojima, T., Cooperative Effects of Heterodinuclear Ir
III
–M
II
Complexes on
Catalytic H2 Evolution from Formic Acid Dehydrogenation in Water. Inorg. Chem. 2020, 59
(17), 11976-11985.
3. Li, X.; Surkus, A.-E.; Rabeah, J.; Anwar, M.; Dastigir, S.; Junge, H.; Brückner, A.;
Beller, M., Cobalt Single-Atom Catalysts with High Stability for Selective Dehydrogenation of
Formic Acid. Angew. Chem. Int. Ed. 2020, 59 (37), 15849-15854.
4. Liu, Q.; Yang, X.; Huang, Y.; Xu, S.; Su, X.; Pan, X.; Xu, J.; Wang, A.; Liang, C.;
Wang, X.; Zhang, T., A Schiff Base Modified Gold Catalyst for Green and Efficient H2
Production from Formic Acid. Energy Environ. Sci. 2015, 8 (11), 3204-3207.
5. Patra, S.; Awasthi, M. K.; Rai, R. K.; Deka, H.; Mobin, S. M.; Singh, S. K.,
Dehydrogenation of Formic Acid Catalyzed by Water-Soluble Ruthenium Complexes: X-ray
Crystal Structure of a Diruthenium Complex. Eur. J. Inorg. 2019, 2019 (7), 1046-1053.
6. Wang, B.; Yang, S.; Yu, Z.; Zhang, T.; Liu, S., Performance Modulation Strategies of
Heterogeneous Catalysts for Formic Acid Dehydrogenation: A review. Mater. Today Commun.
2022, 31, 103617.
7. Yu, Z.; Yang, Y.; Yang, S.; Zheng, J.; Hao, X.; Wei, G.; Bai, H.; Abudula, A.; Guan, G.,
Selective Dehydrogenation of Aqueous Formic Acid over Multifunctional γ-Mo2N Catalysts at a
Temperature Lower than 100 ℃. Appl. Catal. B. 2022, 313, 121445.
8. Zhang, L.; Wu, W.; Jiang, Z.; Fang, T., A Review on Liquid-Phase Heterogeneous
Dehydrogenation of Formic Acid: Recent Advances and Perspectives. Chem. Rev. 2018, 72 (9),
2121-2135.
9. Zhao, X.; Wang, Y.; Shang, M.; Hao, Y.; Wang, J.; Meng, T.; Li, Q.; Zhang, L.; Feng,
C.; Niu, J.; Cui, P.; Wang, C., Mechanism Difference between Nanoparticles and Single-Atom
Sites on Aqueous Formic Acid Dehydrogenation over Cobalt Catalyst. Mol. 2022, 531, 112671.
10. Zhong, H.; Iguchi, M.; Chatterjee, M.; Himeda, Y.; Xu, Q.; Kawanami, H., Formic Acid-
Based Liquid Organic Hydrogen Carrier System with Heterogeneous Catalysts. Adv. Sustain.
Syst. 2018, 2 (2), 1700161.
11. Zhou, X.; Huang, Y.; Xing, W.; Liu, C.; Liao, J.; Lu, T., High-Quality Hydrogen from
the Catalyzed Decomposition of Formic Acid by Pd–Au/C and Pd–Ag/C. ChemComm. 2008,
(30), 3540-3542.
83
12. Celaje, J. J. A.; Lu, Z.; Kedzie, E. A.; Terrile, N. J.; Lo, J. N.; Williams, T. J., A Prolific
Catalyst for Dehydrogenation of Neat Formic Acid. Nat. Commun. 2016, 7 (1), 11308.
13. Mellmann, D.; Sponholz, P.; Junge, H.; Beller, M., Formic Acid as a Hydrogen Storage
Material – Development of Homogeneous Catalysts for Selective Hydrogen Release.
Chem. Soc. Rev. 2016, 45 (14), 3954-3988.
14. Kar, S.; Rauch, M.; Leitus, G.; Ben-David, Y.; Milstein, D., Highly Efficient Additive-
Free Dehydrogenation of Neat Formic Acid. Nat. 2021, 4 (3), 193-201.
15. Sordakis, K.; Tang, C.; Vogt, L. K.; Junge, H.; Dyson, P. J.; Beller, M.; Laurenczy, G.,
Homogeneous Catalysis for Sustainable Hydrogen Storage in Formic Acid and Alcohols. Chem.
Rev. 2018, 118 (2), 372-433.
16. Onishi, N.; Iguchi, M.; Yang, X.; Kanega, R.; Kawanami, H.; Xu, Q.; Himeda, Y.,
Development of Effective Catalysts for Hydrogen Storage Technology Using Formic Acid. Adv.
Energy Mater. 2019, 9 (23), 1801275.
17. Guan, C.; Pan, Y.; Zhang, T.; Ajitha, M. J.; Huang, K.-W., An Update on Formic Acid
Dehydrogenation by Homogeneous Catalysis. Chem.: Asian J. 2020, 15 (7), 937-946.
18. Léval, A.; Agapova, A.; Steinlechner, C.; Alberico, E.; Junge, H.; Beller, M., Hydrogen
Production from Formic Acid Catalyzed by a Phosphine-Free Manganese Complex:
Investigation and Mechanistic Insights. Green Chem. 2020, 22 (3), 913-920.
19. Zell, T.; Langer, R., CO2-Based Hydrogen Storage – Formic Acid Dehydrogenation.
Phys. Sci. Rev. 2018, 3 (12).
20. Mellone, I.; Peruzzini, M.; Rosi, L.; Mellmann, D.; Junge, H.; Beller, M.; Gonsalvi, L.,
Formic Acid Dehydrogenation Catalysed by Ruthenium Complexes Bearing the Tripodal
Ligands Triphos and NP3. Dalton Trans. 2013, 42 (7), 2495-2501.
21. Boddien, A.; Loges, B.; Junge, H.; Gärtner, F.; Noyes, J. R.; Beller, M., Continuous
Hydrogen Generation from Formic Acid: Highly Active and Stable Ruthenium Catalysts. Adv.
Synth. Catal. 2009, 351 (14-15), 2517-2520.
22. Younas, M.; Rezakazemi, M.; Arbab, M. S.; Shah, J.; Rehman, W. U., Green Hydrogen
Storage and Delivery: Utilizing Highly Active Homogeneous and Heterogeneous Catalysts for
Formic Acid Fehydrogenation. Int. J. Hydrog. Energy 2022, 47 (22), 11694-11724.
23. Chen, T.; He, L.-P.; Gong, D.; Yang, L.; Miao, X.; Eppinger, J.; Huang, K.-W.,
Ruthenium(II) Pincer Complexes with Oxazoline Arms for Efficient Transfer Hydrogenation
Reactions. Tetrahedron Lett. 2012, 53 (33), 4409-4412.
24. Dutta, I.; Alobaid, N. A.; Menicucci, F. L.; Chakraborty, P.; Guan, C.; Han, D.; Huang,
K.-W., Dehydrogenation of Formic Acid Mediated by a Phosphorus–Nitrogen PN3P-Manganese
84
Pincer Vomplex: Catalytic Performance and Mechanistic Insights. Int. J. Hydrog. Energy 2022,
0360-3199.
25. Wei, D.; Sang, R.; Sponholz, P.; Junge, H.; Beller, M., Reversible Hydrogenation of
Carbon Dioxide to Formic Acid using a Mn-Pincer Complex in the Presence of Lysine. Nat.
Energy 2022, 7 (5), 438-447.
26. Johnee Britto, N.; Jaccob, M., Unveiling the Mechanistic Landscape of Formic Acid
Dehydrogenation Catalyzed by Cp
∗
M(III) Catalysts (M = Co or Rh or Ir) with Bis(pyrazol-1-
yl)methane Ligand Architecture: A DFT Investigation. Int. J. Hydrog. Energy 2022, 47 (51),
21736-21744.
27. Himeda, Y., Highly Efficient Hydrogen Evolution by Decomposition of Formic Acid
Using an Iridium Catalyst with 4,4′-dihydroxy-2,2′-bipyridine. Green Chem. 2009, 11 (12),
2018-2022.
28. Scotti, N.; Psaro, R.; Ravasio, N.; Zaccheria, F., A New Cu-Based System for Formic
Acid Dehydrogenation. RSC Advances 2014, 4 (106), 61514-61517.
29. Nakajima, T.; Kamiryo, Y.; Kishimoto, M.; Imai, K.; Nakamae, K.; Ura, Y.; Tanase, T.,
Synergistic Cu2 Catalysts for Formic Acid Dehydrogenation. J. Am. Chem. Soc. 2019, 141 (22),
8732-8736.
30. Iguchi, M.; Himeda, Y.; Manaka, Y.; Kawanami, H., Development of an Iridium-Based
Catalyst for High-Pressure Evolution of Hydrogen from Formic Acid. ChemSusChem 2016, 9
(19), 2749-2753.
31. Boddien, A.; Mellmann, D.; Gärtner, F.; Jackstell, R.; Junge, H.; Dyson, P. J.; Laurenczy,
G.; Ludwig, R.; Beller, M., Efficient Dehydrogenation of Formic Acid Using an Iron Catalyst.
Science 2011, 333 (6050), 1733-1736.
32. Bielinski, E. A.; Lagaditis, P. O.; Zhang, Y.; Mercado, B. Q.; Würtele, C.; Bernskoetter,
W. H.; Hazari, N.; Schneider, S., Lewis Acid-Assisted Formic Acid Dehydrogenation Using a
Pincer-Supported Iron Catalyst. J. Am. Chem. Soc. 2014, 136 (29), 10234-10237.
33. Anderson, N. H.; Boncella, J.; Tondreau, A. M., Manganese-Mediated Formic Acid
Dehydrogenation. Chem. Eur. J. 2019, 25 (45), 10557-10560.
34. Kolomnikov, I. S.; Gusev, A. I.; Aleksandrov, G. G.; Lobeeva, T. S.; Struchkov, Y. T.;
Vol'pin, M. E., Structure of the Product Formed in the Reaction of Carbon Dioxide with
Ruthenium Hydride Complexes. J. Organomet. Chem. 1973, 59, 349-351.
35. Sletten, E.; Jensen, L. H., The Crystal Structure of Dimethylammonium Copper(II)
Formate, NH2(CH2)2[Cu(OOCH)3]. Acta Crystallogr., Sect. B 1973, 29 (9), 1752-1756.
85
36. Okada, K.; Kay, M. I.; Cromer, D. T.; Almodovar, I., Crystal Structure by Neutron
Diffraction and the Antiferroelectric Phase Transition in Copper Formate Tetrahydrate.
J. Chem. Phys. 1966, 44 (4), 1648-1653.
37. Bukowska-Strzyzewska, M., The Crystal Structure of Copper(II) Formate Dihydrate.
Acta Crystallogr., Sect. D. 1965, 19 (3), 357-362.
38. Burger, N.; Fuess, H., Crystal Structure and Magnetic Properties of Copper Formate
Anhydrate [α-Cu(HCOO)2]. Solid State Commun. 1980, 34 (8), 699-703.
39. Suh, H.-W.; Schmeier, T. J.; Hazari, N.; Kemp, R. A.; Takase, M. K., Experimental and
Computational Studies of the Reaction of Carbon Dioxide with Pincer-Supported Nickel and
Palladium Hydrides. Organometallics 2012, 31 (23), 8225-8236.
40. Wang, L.; Sun, H.; Zuo, Z.; Li, X.; Xu, W.; Langer, R.; Fuhr, O.; Fenske, D., Activation
of CO2, CS2, and Dehydrogenation of Formic Acid Catalyzed by Iron(II) Hydride Complexes.
Eur. J. Inorg. 2016, 2016 (33), 5205-5214.
41. Zell, T.; Butschke, B.; Ben-David, Y.; Milstein, D., Efficient Hydrogen Liberation from
Formic Acid Catalyzed by a Well-Defined Iron Pincer Complex under Mild Conditions. Eur. J.
Chem. 2013, 19 (25), 8068-8072.
42. Williams, M. T.; McEachin, C.; Becker, T. M.; Ho, D. M.; Mandal, S. K., Synthesis and
X-ray Structures of Manganese(I) and Rhenium(I) Formato Complexes, Fac-
(CO)3(dppp)MOC(H)O. J. Organomet. Chem. 2000, 599 (2), 308-312.
43. Safronov, S. V.; Gutsul, E. I.; Golub, I. E.; Dolgushin, F. M.; Nelubina, Y. V.; Filippov,
O. A.; Epstein, L. M.; Peregudov, A. S.; Belkova, N. V.; Shubina, E. S., Synthesis, Structural
Properties and Reactivity of Ruthenocene-Based Pincer Pd(II) Tetrahydroborate. Dalton Trans.
2019, 48 (33), 12720-12729.
44. Alberico, E.; Lennox, A. J. J.; Vogt, L. K.; Jiao, H.; Baumann, W.; Drexler, H.-J.;
Nielsen, M.; Spannenberg, A.; Checinski, M. P.; Junge, H.; Beller, M., Unravelling the
Mechanism of Basic Aqueous Methanol Dehydrogenation Catalyzed by Ru–PNP Pincer
Complexes. J. Am. Chem. Soc. 2016, 138 (45), 14890-14904.
45. Czaun, M.; Goeppert, A.; Kothandaraman, J.; May, R. B.; Haiges, R.; Prakash, G. K. S.;
Olah, G. A., Formic Acid As a Hydrogen Storage Medium: Ruthenium-Catalyzed Generation of
Hydrogen from Formic Acid in Emulsions. ACS Catal. 2014, 4 (1), 311-320.
46. Konno, H.; Kobayashi, A.; Sakamoto, K.; Fagalde, F.; Katz, N. E.; Saitoh, H.; Ishitani,
O., Synthesis and Properties of [Ru(tpy)(4,4′-X2bpy)H]
+
(tpy = 2, 2′:6′, 2″-terpyridine, bpy = 2,
2′-bipyridine, X = H and MeO), and Their Reactions with CO2. Inorganica Chim. Acta 2000, 299
(2), 155-163.
86
47. Hu, P.; Diskin-Posner, Y.; Ben-David, Y.; Milstein, D., Reusable Homogeneous
Catalytic System for Hydrogen Production from Methanol and Water. ACS Catal. 2014, 4 (8),
2649-2652.
48. Abura, T.; Ogo, S.; Watanabe, Y.; Fukuzumi, S., Isolation and Crystal Structure of a
Water-Soluble Iridium Hydride: A Robust and Highly Active Catalyst for Acid-Catalyzed
Transfer Hydrogenations of Carbonyl Compounds in Acidic Media. J. Am. Chem. Soc. 2003, 125
(14), 4149-4154.
49. Creutz, C.; Chou, M. H.; Hou, H.; Muckerman, J. T., Hydride Ion Transfer from
Ruthenium(II) Complexes in Water: Kinetics and Mechanism. Inorg. Chem. 2010, 49 (21),
9809-9822.
50. Martinez, R.; Simon, M.-O.; Chevalier, R.; Pautigny, C.; Genet, J.-P.; Darses, S., C−C
Bond Formation via C−H Bond Activation Using an in Situ-Generated Ruthenium Catalyst. J.
Am. Chem. Soc. 2009, 131 (22), 7887-7895.
51. Bontemps, S.; Vendier, L.; Sabo-Etienne, S., Borane-Mediated Carbon Dioxide
Reduction at Ruthenium: Formation of C1 and C2 Compounds. Angew. Chem. Int. Ed. 2012, 51
(7), 1671-1674.
52. Dong, W.; Tang, J.; Zhao, L.; Chen, F.; Deng, L.; Xian, M., The Visible-Light-Driven
Transfer Hydrogenation of Nicotinamide Cofactors with a Robust Ruthenium Complex
Photocatalyst. Green Chem. 2020, 22 (7), 2279-2287.
53. Broggi, J.; Jurčík, V.; Songis, O.; Poater, A.; Cavallo, L.; Slawin, A. M. Z.; Cazin, C. S.
J., The Isolation of [Pd{OC(O)H}(H)(NHC)(PR3)] (NHC = N-Heterocyclic Carbene) and Its
Role in Alkene and Alkyne Reductions Using Formic Acid. J. Am. Chem. Soc. 2013, 135 (12),
4588-4591.
54. Bröring, M.; Kleeberg, C.; Scheja, A., Cationic Palladium(II) Complexes of the Sterically
Hindered Bis(4-methylthiazolyl)isoindoline (4-Mebti) with Neutral Group XVI Donor Ligands.
Inorganica Chim. Acta 2011, 374 (1), 572-577.
55. Grushin, V. V.; Kuznetsov, V. F.; Bensimon, C.; Alper, H., A Simple and Convenient
Preparation of [(Ph3P)4Rh2(µ-OH)2] and Its Reactions with C-H, O-H, and M-H Acids.
Organometallics 1995, 14 (8), 3927-3932.
56. Ogo, S.; Nishida, H.; Hayashi, H.; Murata, Y.; Fukuzumi, S., Aqueous Transformation of
a Metal Diformate to a Metal Dihydride Carbonyl Complex Accompanied by H 2 Evolution from
the Formato Ligands. Organometallics 2005, 24 (20), 4816-4823.
57. Immirzi, A.; Musco, A., Reactions of Trans-(PtH2(P(C6H11)3)2) with Carbon Dioxide. X-
Ray Structures of Trans-(PtH(O2CH)(P(C6H11)3)2) and Trans-(PtH(O2COCH3)(P(C6H11)3)2).
Chem. Inf.-Dienst 1977, 8 (27), L35-L36.
87
58. Esteruelas, M. A.; García-Yebra, C.; Martín, J.; Oñate, E., Dehydrogenation of Formic
Acid Promoted by a Trihydride-Hydroxo-Osmium(IV) Complex: Kinetics and Mechanism. ACS
Catal. 2018, 8 (12), 11314-11323.
59. Schmeier, T. J.; Dobereiner, G. E.; Crabtree, R. H.; Hazari, N., Secondary Coordination
Sphere Interactions Facilitate the Insertion Step in an Iridium(III) CO2 Reduction Catalyst. J.
Am. Chem. Soc. 2011, 133 (24), 9274-9277.
60. Cherepakhin, V.; Williams, T. J., Direct Oxidation of Primary Alcohols to Carboxylic
Acids. Synthesis 2020, 53 (6), 1023-1034.
61. Hunt, J. R.; Dawlaty, J. M., Photodriven Deprotonation of Alcohols by a Quinoline
Photobase. J. Phys. Chem. A 2018, 122 (40), 7931-7940.
62. Hunt, J. R.; Tseng, C.; Dawlaty, J. M., Donor–Acceptor Preassociation, Excited State
Solvation Threshold, and Optical Energy Cost as Challenges in Chemical Applications of
Photobases. Faraday Discuss. 2019, 216, 252-268.
63. Voegtle, M. J.; Dawlaty, J. M., Can Brønsted Photobases Act as Lewis Photobases? J.
Am. Chem. Soc. 2022, 144 (18), 8178-8184.
88
5 Chapter 5 Experimental and Spectral Data
5.1. General Procedures
5.1.1. Reagents
All air and moisture sensitive chemicals and procedures were setup and performed under
inert atmosphere (N2) using standard Schlenk technique or a N2-filled glovebox (2-10 ppm O2 for
all manipulations). Metal precursors (Ir, Rh, Ru, Ag, and Au) and starting material were
purchased and used as received without further purification from BTC Beantown Chemicals,
Sigma Aldrich, Strem Chemicals, TCI Chemicals, VWR, Combi Blocks Inc., Alfa Aesar,
Oakwood Chemicals, or Chem-Impex Int’l Inc. Deuterated solvents for NMR references and
isotopic labeling experiments were purchased from Cambridge Isotopes Laboratories or Sigma
Aldrich. Dry solvents for complex synthesis and recrystallization (dichrolomethane, diethyl
ether, hexane, tetrahydrofuran, and benzene) were dried in a J. C. Meyer solvent purification
system with alumina/copper(II) oxide columns.
5.1.2. Instrumentations
NMR spectra were recorded on Varian 400MR, VNMRS-500, or VNMRS-600
spectrometer and processed in MestreNova. Chemical shifts are reported in units of ppm and
referenced to the residual
1
H or
13
C solvent peak and line-listed according to (s) singlet, (bs)
broad singlet, (d) doublet, (t)triplet, (dd) doublet doublet, (td) triplet of doublet, etc.
13
C spectra
are delimited by carbon peaks, not carbon count. Air-sensitive NMR spectra were taken in J-
Young tubes (Willmad or Norell) with Teflon valve plugs. Mass spectra were obtained on
Bruker Autoflex Speed MALDI MS spectrometer using the evaporated drop method on a coated
96-well plate or Agilent Q-Tof tandem mass spectrometer with anthracene matrix and Agilent
electrospray ionization mass spectrometer (ESI-MS). X-ray crystallography data of compound
4.9 were obtained on a Bruker APEX DUO single-crystal diffractometer equipped with an
89
APEX2 CCD detector, Mo fine-focus and Cu micro-focus X-ray sources. All other X-ray
crystallography data were obtained on Rigaku XtaLAB Synergy, Dualflex, Hypix diffractometer
from microfocus sealed tube with Mo and Cu X-ray sources. CHNS elemental analyses of
compounds were collected at Robertson Microlit Laboratories. IR spectra of solid compounds
were obtained using Jasco FT/IR-4600 FT-IR Spectrometer. Gas analysis was obtained on a
Thermo Finnigan gas chromatograph (column: Supelco, Carboxen 1010 plot, 30 m X 0.53 mm)
equipped with a TCD detector (CO detection limit: 0.099 v/v%). CO2 (Gilmore, instrument
grade), 1:3 CO2:H2 mix (Airgas, certified standard-spec grade) and H2 (Gilmore, ultra-high pure
grade 5.0). JASCO FT/IR-4600 spectrometer was used to record gas. IR.spectral data of soid
compounds were obtained on Perkin-Elmer UV-Vis-NIR and Horiba Fluorimeter.
5.1.3. Experimental Procedures
5.2. Chapter 2 Experimental and Spectral Data
Complex 2.5:
In a N2-filled glovebox, a suspension of 2.4 (synthesized by Pavel
Dub from Los Alamos National Lab) (200 mg, 0.27 mmol) in toluene
(5 mL) was added a solution of NaHBEt3 (1.0 M in toluene; 0.54 mL;
0.54 mmol) dropwise at room temperature. The white suspension slowly turned into a
transparent orange-red solution within 1 hour. The reaction was stirring at room temperature for
18 hours giving a dark orange solution. The reaction mixture volume was partially reduced under
vacuum and filtered. The resulting filtrate was concentrated under vacuum, layered with pentane
in the glovebox to obtain turmeric yellow crystalline solid in 2 days. They were filtered, washed
with pentane, and dried in vacuum. The final product was compared to publish procedure.
1
90
1
H NMR (600 MHz, C6D6): δ -11.6 (s, 1H, RuH), -7.5 (dd,
2
JHH = 18 Hz, 1H, RuH), δ 1.72 (s,
3H), δ 1.86-2.35 (m, 7H), δ 2.97 (d, 2H), δ 6.93-7.12 (m, 12H), δ 7.17-7.32 (m, 4H), δ 7.67 (t, J
= 7.67 Hz, 8H).
31
P{
1
H} NMR (243 MHz, C6D6): δ 78.75 (s), δ 50.94 (s).
MALDI-MS: m/z calcd for 669.13, found 669.25.
Figure 5.2.1.
1
H NMR spectrum of 2.5 in CD2Cl2.
91
Figure 5.2.2.
31
P{
1
H} NMR spectra of 2.5 in CD2Cl2.
92
Complex 2.11-CO:
A solution of complex 2.11 (200 mg, 2.91 x 10
–4
mol)
synthesized following published procedure
2
and sodium
formate (99 mg, 1.46 mmol, 5 eq.) in formic acid (20 mL)
was stirred at room temperature under nitrogen for one hour. When the solution became yellow,
it was heated in an oil bath for 4 hours at 90
o
C. Then, the temperature was raised to 115
o
C and
the remaining formic acid was distilled off affording a red solid. The solid was extracted with
CH2Cl2, filtered, and the resulting black-red solution was diluted with diethyl ether. The next day
the product crystallized as dark-red crystals. They were filtered, washed with diethyl ether, and
dried in vacuum (118 mg, 71%).
1
H NMR (500 MHz, CD2Cl2): δ 9.74 (d, J = 5.3 Hz, 2H, ArH), 7.96 (t, J = 7.6 Hz, 2H, ArH),
7.77 (d, J = 7.7 Hz, 2H, ArH), 7.28 (t, J = 6.4 Hz, 2H, ArH), 5.33 (s, 2H, CH2Cl2), 3.75 (d, J =
8.2 Hz, 4H, 2CH2), 1.41 (d, J = 13.7 Hz, 36H, 12CH3), –0.09 (t,
2
JPH = 56.4 Hz, 1H, IrH).
13
C{
1
H} NMR (126 MHz, CD2Cl2): δ 179.13, 166.74, 160.82, 140.51, 124.31, 124.02 (t, J = 4.8
Hz), 37.24 – 36.64 (m), 36.21 – 35.76 (m), 29.22.
19
F NMR (564 MHz, CD2Cl2): δ –78.89.
31
P{
1
H} NMR (243 MHz, CD2Cl2): δ 78.06 (s).
IR (KBr, cm
-1
): 2965, 2905, 2874, 2043, 1960 (νCO), 1612, 1479, 1274, 1151, 1034, 829, 770,
640.
MALDI-MS: m/z calcd for [C30H49Ir2N2O2P2]
+
915.25, found 915.21.
93
Figure 5.2.3.
1
H{
31
P} NMR spectrum of 2.11-CO in CD2Cl2.
94
Figure 5.2.4.
13
C NMR spectrum of 2.11-CO in CD2Cl2.
Figure 5.2.5.
19
F NMR spectra of 2.11-CO in CD2Cl2.
95
Figure 5.2.6.
31
P{
1
H} NMR spectra of 2.11-CO in CD2Cl2.
Theoretical Yield & Reaction Rate Calculations
Based on the Ideal gas law equation and assuming 100% FA conversion from 3.00 mL (79.5
mmol) of FA, we would yield:
a. Ambient Pressure:
nevolved gases = 159 mmol
P = 1 atm
R = 0.08206 L atm K
-1
mol
-1
T = 25 °C + 273 = 298 K
V = (n • R • T) / P = 3.89 Liter
FA conversion % = (Vevolved gas / 3.89)*100
b. Self-Pressurized Conditions:
nevolved gases = 0.159 mol
R = 0.08206 L atm K
-1
mol
-1
T = 110°C + 273.15 = 383.15 K
V = 0.125 L
P = (n • R • T) / V = 39.99 atm = 40.5 bar
High-pressure H2/CO2 mixtures cannot be precisely predicted by the Van der Waals’
equation of state, therefore, I utilized the best catalytic run (Table 2.1, entry 11) to be our standard
96
100% FA conversion yield.
1
H NMR at the end of entry 11 suggested there was no trace of
unreacted FA left. Therefore, under self-pressurized condition conversion was calculated by:
FA conversion % = (Pevolved gas /38 bar)*100
All volumetric rate data are expressed in normal liters per hour (L/hr), standardized to 0
o
C
and 1 atm. An example calculation of a volumetric rate from pressure is shown below.
P1 = 990 psi; T1 = 118
o
C
P2 = 1005 psi; T2 = 120
o
C
V = 600 mL
Δt = 8 s
Δn = [P2 / (273.15 K + T2) - P1 / (273.15 K + T1)] / 14.7 • V / 1000 / R
Rate (L/hr) = Δn • R • 273.15 K / 1 atm / (Δt / 3600) = 126.8 L/hr.
97
5.3. Chapter 3 Experimental and Spectral Data
Complex 3.1-O:
To a Straus flask in the N2-filled glovebox, complex 2.11
(50 mg, 0.0738 mmol) synthesized following published
procedure,
2
NaOOCH (20.6 mg, 0.295 mmol, 4 eq), dry methanol
(0.3 mL) purchased from ThermoFisher Scientific, and deionized
H2O (0.3 mL) were added and let stir under N2 at room temperature. After 3 hours, the red solution
turned to orangish yellow slurry. Crude
31
P NMR showed 100% conversion to a singlet at around
31-33 ppm. Solvent in the crude product was removed under high vacuum to give a glassy oil, then
resuspended in DCM, filtered, and concentrated. The crude product was collected as an oil. The
resulting oil was recrystallized in 1:1 DCM:Et2O over 2 days to yield off-white solid. The solid
was filtered, washed with Et2O, and dried under vacuum to obtain product (54% yield). Single
yellow crystal was crystallized from dichloromethane and hexane suitable for X-ray
crystallographic analysis.
1
H NMR (600 MHz, CD2Cl2): δ 9.92 (d, J = 5.9 Hz, 1H, ArH), 7.67 (dd, J = 7.7, 7.7 Hz, 1H,
ArH), 7.46 (d, J = 7.8 Hz, 1H, ArH), 7.03 (dd, J = 6.7, 6.7 Hz, 1H, ArH), 3.42 (dd, J = 17.2, 9.1
Hz, 1H), 3.05 (dd, J = 17.2, 8.9 Hz, 1H), 1.24 (d, J = 13.2 Hz, 9H), 1.07 (d, J = 13.2 Hz, 9H),
−22.04 (d, J = 25.2 Hz, 1H), −22.51 (s, 1H).
13
C NMR (151 MHz, CD2Cl2): δ 165.01 (s), 154.15 (s), 136.57 (s), 122.02 (s), 121.9 (d, J = 7.6
Hz), 38.14 (d, J = 27 Hz), 34.85 (d, J = 23.0 Hz), 33.59 (d, J = 30 Hz), 29.40 (d, J = 72 Hz).
19
F NMR (564 MHz, CD2Cl2): δ −78.92 (s).
31
P{
1
H} NMR (243 MHz, CD2Cl2): δ 58.10 (dd, J = 26.7, 7.3 Hz).
98
IR (KBr, cm
-1
): 2957, 2905,2873, 2206, 1741, 1608, 1482, 1395, 1367, 1271, 1228, 1155, 1030,
826, 770, 642, 585, 500, 463.
MALDI-MS: m/z calc’d for [C42H78Ir3N3OP3]
+
1310.4 g/mol, found 1310.1 g/mol.
a.
-38 -36 -34 -32 -30 -28 -26 -24 -22 -20 -18 -16 -14 -12 -10 -8 -6 -4 -2 0 2 4 6 8 10 12
1H NMR
1.00
1.00
9.42
9.80
0.94
1.10
0.99
0.98
0.98
0.99
-22.51
-22.06
-22.02
1.06
1.08
1.23
1.26
3.03
3.04
3.05
3.07
3.40
3.41
3.42
3.45
5.32 CD2Cl2
7.02
7.03
7.04
7.45
7.46
7.65
7.67
7.68
9.91
9.92
99
b.
c.
Figure 5.3.1. a. Full
1
H{
31
P} spectrum of 3.1-O; b. Proton region; c. Hydride region.
1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 10.0
1H NMR
9.42
9.80
0.94
1.10
0.99
0.98
0.98
0.99
1.06
1.08
1.23
1.26
3.03
3.04
3.05
3.07
3.40
3.41
3.42
3.45
5.32 CD2Cl2
7.02
7.03
7.04
7.45
7.46
7.65
7.67
7.68
9.91
9.92
100
Figure 5.3.2.
31
P{
1
H} NMR spectrum of 3.1-O.
101
Figure 5.3.3.
19
F NMR spectrum of 3.1-O.
102
-10 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 210 220 230
13C NMR
29.16
29.64
33.49
33.69
34.78
34.93
38.05
38.23
53.84 CD2Cl2
53.84
121.90
122.14
128.71
136.57
154.15
165.01
103
Figure 5.3.4.
13
C NMR spectra of 3.1-O.
Figure 5.3.5. IR spectrum of 3.1-O in KBr pellet.
104
Complex 3.1-H:
Procedure A (PF6 dianion): To a Straus flask in the N2-filled
glovebox, complex 2.11 (200 mg, 0.291 mol) synthesized following
published procedure,
2
sodium hexafluorophosphate NaPF6 (97.8
mg, 0.582 mmol, 2 eq.) in dry CH3OH (10 mL) purchased from
ThermoFisher Scientific, were weighed out. The red solution was purged with H2 (1 atm) and
stirred at room temperature. The red solution gradually turns yellow after 2.5 hours. The resulting
yellow solution was dried under vacuum, resuspend in 3 mL of dry DCM, and filtered to remove
white solids, to yield a neon-yellow solution. The final product was recrystallized slowly with 1:1
DCM:Et2O. The resulting yellow crystalline was filtered, washed with dry ether, and dried under
vacuum to yield 0.124 mg (81% yield). Crystallization from dichloromethane and ether over 3
days produced crystals suitable for X-ray and neutron crystallographic analysis.
Procedure B (OTf dianion): To a Straus flask in the N2-filled glovebox, complex 2.11 (250
mg, 0.364 mol), synthesized following published procedure,
2
was dissolved dry CH3OH (10 mL)
purchased from ThermoFisher Scientific. The red solution was purged with H2 (1 atm) and stirred
at room temperature for 1 hour until the solution turned bright yellow. The resulting yellow
solution was dried under vacuum, resuspended in dry DCM (3 mL), and layered with dry ether
over 3 days yielding bright yellow single crystals. These single crystals suitable for neutron
diffraction were not isolated from their mother liquor to avoid crystal cracks.
1
H NMR (600 MHz, CD2Cl2): δ 9.33 (d, J = 6.0 Hz, 1H, ArH), 7.85 (t, J = 7.7 Hz, 1H, ArH), 7.70
(d, J = 7.6 Hz, ArH, 7.29 (t, J = 6.7 Hz, 1H, ArH), 3.65 (dd, J = 17.6, 8.8 Hz, 3H, CH2), 3.53 (dd, J
= 17.6, 10.3 Hz, 3H, CH2), 1.33 (d, J = 14.3 Hz, 27H, tBu), 1.07 (d, J = 14.5 Hz, 27H, tBu), -4.15
105
(q, 2JPH = 45 Hz, 1H, Ir(µ3-H)), -18.6 (d, J = 12 Hz, 3H, Ir(µ2-H)), -23.07 (d, J = 22 Hz, 3H,
Ir(terminal-H)).
13
C{
1
H} NMR (151 MHz, CD2Cl2): δ 162.88, 158.55, 139.24, 124.17, 123.60 (d, J = 10 Hz),
72.33, 70.78, 59.01, 37.67 (d, J = 32 Hz), 37.0 (d, J = 29 Hz), 35.13 (d, J = 28 Hz), 34.53, 28. 7 (d,
J = 72 Hz), 27.09, 22.74, 14.22.
19
F NMR (564 MHz, CD2Cl2): δ −72.96 (d, J = 710.7 Hz).
31
P{
1
H} NMR (243 MHz, CD2Cl2): δ 75.96 (s), δ 144.46 (hept, J = 711.1 Hz).
IR (KBr, cm
-1
): 2959, 2910, 2872, 2255, 1764, 1608, 1482, 1269, 1225, 1152, 1032, 824, 773,
763, 644, 500.
ESI-MS: m/z calc’d for [C42H79Ir3N3P3]
2+
647.7 g/mol, found 647.6 g/mol.
Figure 5.3.6.
1
H{
31
P} NMR spectrum of 3.1-H.
106
Figure 5.3.7.
13
C NMR spectrum of 3.1-H.
107
Figure 5.3.8.
13
P{
1
H} NMR spectrum of 3.1-H.
108
Figure 5.3.9.
19
F NMR spectrum of 3.1-H.
Figure 5.3.10. IR spectrum of 3.1-H in KBr pellet.
109
Figure 5.3.11. UV-Vis spectrum of 3.1-H in methanol.
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
250 350 450 550 650 750
Absorbance
Wavelength, nm
110
Complex 3.1-Au:
To a vial equipped with a stir bar in the N2-filled
glovebox, silver hexafluorophosphate (8 mg, 31.6 mmol, 1 eq)
purchased from Alfa Aesar, was added to a AuPPh3Cl (15.6 mg,
31.5 mmol, 1 eq), purchased from Combi Blocks, in 3 mL acetone (dried in Drydrite) at room
temperature. The solution immediately turned cloudy and white solid was filtered. The resulting
transparent solution was added dropwise to a solution of [Ir3H7(PN)3][PF6]2 3.1-H (50 mg, 31.5
mmol, 1 eq) in acetone (7 mL) purchased from VWR. The resulting dark orange solution was
stirred for 5 minutes, filtered through a PTFE filter to remove undissolved black solid, then
acetone was completely removed under vacuum yielding a dark red glassy oil. The resulting oily
crude product was purified by recrystallization with 1:1 DCM:Et2O over 2 days yielding bright red
crystals on the vial wall and black oil at the bottom of vial. Pure red crystals were isolated with a
spatula in the glovebox to give 40 mg (72% yield). Crystallization from dichloromethane and ether
produced crystals suitable for X-ray crystallographic analysis.
1
H NMR (600 MHz, CD2Cl2): δ 10.04 (d, J = 5.9 Hz, 3H, ArH), 7.64 (d, J = 7.7 Hz, 3H, ArH),
7.53 (dt, J = 34, 15 Hz, 9H, ArH), 7.35 (td, J = 7.5, 2 Hz, 3H, ArH), 7.06 (dd, J = 12.4, 7.5 Hz,
1H), 6.30 (t, J = 6.6 Hz, 3H, ArH), 3.72 (dd, J = 18, 8 Hz, 3H, CH2), 3.54 (dd, J = 18, 9 Hz, 3H,
CH3), 1.24 (d, J = 13.6 Hz, 27H, tBu), 1.18 (d, J = 14.1 Hz, 27H, tBu), −20.62 (s, 3H, Ir-H),
−20.97 (d, J = 22 Hz, 3H, Ir-H).
13
C{
1
H} NMR (151 MHz, CD2Cl2): δ 164.55, 153.89, 138.61, 133.61 (d, J = 14 Hz), 132.05 (d, J
= 3 Hz), 131.17, 130.87, 129.83 (d, J = 12 Hz), 123.50, 122.36, 38.60(d, J = 27 Hz), 37.18 (d, J =
32 Hz), 35.80 (d, J = 22 Hz), 30.09, 29.27 (d, J = 62 Hz), 1.17.
111
19
F NMR (564 MHz, CD2Cl2): δ -72.1 (d, J = 710.6), -152.7 (BF4 impurity in manufactured
reagent).
31
P NMR (243 MHz, CD2Cl2): δ 76.7 (d, J = 42 Hz), δ 62.2 (q, J = 42 Hz), δ 142.44 (hept, J =
709.6 Hz).
IR (KBr, cm
-1
): 2952, 2906, 2877, 2229, 1702, 1604, 1478, 1436, 1395, 1375, 1182, 1104, 1058,
843, 778, 761, 693, 626, 560, 528, 502, 465.
ESI-MS: m/z calc’d for [C60H93AuF12Ir3N3P6]
2+
876.7 g/mol, found 876.8 g/mol.
Elemental Analysis: Anal. Calc’d. for C60H93AuF12Ir3N3P6: C, 35.26; H, 4.59; N, 2.06. Found: C,
35.177; H, 4.380; N, 2.035.
Figure 5.3.12.
1
H{
31
P} NMR spectrum of 3.1-Au.
112
Figure 5.3.13.
13
C NMR spectrum of 3.1-Au.
113
Figure 5.3.14.
31
P{
1
H} NMR spectrum of 3.1-Au.
114
Figure 5.3.15.
19
F NMR spectrum of 3.1-Au.
Figure 5.3.16. IR spectrum of 3.1-Au in KBr pellet.
115
Complex 3.2-I:
2 [Ir3H7(PN)3]
2+
+ 3 I2 → 3 [Ir2H3I2(PN)2]
+
+ 2 H2 + H
+
A solution of iodine (0.02 M in CH2Cl2, 0.95 mL, 1.892 x
10
–5
mol, 1.5 eq.), purchased from Sigma Aldrich, was added
drop-wise to a stirred solution of complex 3.1-H (0.020 g, 1.261 x 10
–5
mol) in CH2Cl2 (1 mL) at
room temperature. After stirring for five hours, the initially orange solution turned yellow, and
then the solvent was evaporated in vacuum to dryness. The residue was redissolved in CH 2Cl2 (0.5
mL) and the product was crystallized over the course of two days by adding (3 x 1 mL) Et2O.
Bright yellow cotton-like crystals of 3.2-I were separated by decantation, washed with ether, and
dried in vacuum. Yield: 18.4 mg (77%). Crystals suitable for X-ray analysis were obtained by slow
evaporation of 1:1 CH2Cl2:hexane solution of 3.2-I.
1
H NMR (600 MHz, CD2Cl2): δ 10.07 (d, J = 5.8 Hz, 1H, ArH), 9.30 (d, J = 6.0 Hz, 1H, ArH),
7.89 (t, J = 7.6 Hz, 1H, ArH), 7.84 (t, J = 7.7 Hz, 1H, ArH), 7.75 (d, J = 7.8 Hz, 1H, ArH), 7.65 (d,
J = 7.9 Hz, 1H, ArH), 7.12 (t, J = 6.6 Hz, 1H, ArH), 7.05 (t, J = 6.7 Hz, 1H, ArH), 3.92–3.79 (m,
2H, CH2), 3.57 (dd, J = 17.0, 9.4 Hz, 1H, CH2), 3.29 (dd, J = 17.2, 9.3 Hz, 1H, CH2), 1.50 (d, J =
14.8 Hz, 18H, 6CH3), 1.39 (d, J = 14.4 Hz, 9H, 3CH3), 1.21 (d, J = 14.3 Hz, 9H, 3CH3), –18.72
(dd,
2
JPH = 48.3, 9.0 Hz, 1H, bridging IrH), –23.30 (d,
2
JPH = 16.3 Hz, 1H, terminal IrH), –24.99
(d,
2
JPH = 18.9 Hz, 1H, terminal IrH).
13
C{
1
H} NMR (151 MHz, CD2Cl2): δ 165.97, 164.44, 159.98, 158.74, 138.91, 138.89, 124.92,
124.28, 123.88 (d,
2
JCP = 8.9 Hz), 123.41 (d,
2
JCP = 9.1 Hz), 38.91 (d,
1
JCP = 29.4 Hz), 38.42 (d,
1
JCP = 29.7 Hz), 37.63 (d,
1
JCP = 19.6 Hz), 36.08 (d,
1
JCP = 18.2 Hz), 35.86 (d,
1
JCP = 20.0 Hz),
35.84 (d,
1
JCP = 20.5 Hz) 30.61 (d,
2
JCP = 2.3 Hz), 30.18, 28.59, 28.42 (d,
2
JCP = 2.8 Hz).
116
19
F NMR (564 MHz, CD2Cl2): δ –73.26 (d,
1
JPF = 710.7 Hz).
31
P NMR (243 MHz, CD2Cl2): δ 70.32 (dd, J = 46.2, 6.4 Hz), 68.84 (t, J = 9.0 Hz), –145.00 (hept,
1
JPF = 710.7 Hz, PF6).
MALDI-MS: m/z calc’d for [C28H51I2Ir2N2P2]
+
1115.08 g/mol, found 1115.03 g/mol.
Elemental Analysis: Anal. Calc’d. for C28H51F6I2Ir2N2P3: C, 26.67; H, 4.08; N, 2.22; S, 0.00.
Found C, 27.05; H, 4.34; N, 2.27; S, 0.000.
Figure 5.3.17.
1
H{
31
P} NMR spectrum of 3.2-I.
117
Figure 5.3.18.
31
P{
1
H} NMR spectrum of 3.2-I.
Figure 5.3.19.
13
C NMR spectrum of 3.2-I.
118
Synthesis of 2-Picoline-d7
2-Picoline (14.90 g, 160 mmol), D2O (96.14 g, 4.800 mol, 30 eq.), NaBH4 (0.18 g, 4.758
mmol), Pd/C 10% (0.15 g), and Pd(dba)2 (0.15 g, 2.6 x 10
–4
mol, 0.16 mol%) were transferred to a
300 mL Straus flask. The reactor was sealed, and the mixture was stirred for 10 days at 130
o
C.
Analysis by
1
H NMR indicates complete H/D exchange with 90% total deuterium content in the
system.
The following steps to separate the product from water are not recommended because of
excessive product degradation. The solution was filtered and treated with excess of concentrated
D2SO4 to form a non-volatile salt (C6D8N)2SO4. Water was distilled off under vacuum and the
residue was mixed with BaO (24 g, 157 mmol). The following distillation gave a yellow liquid (12
g) and a charred solid residue. The liquid was stirred in CaH2 for 1 day and then redistilled (5.80 g,
36%).
2
H NMR (92 MHz, H2O): δ 8.36 (s, CD), 8.11 (s, CD), 7.54 (s, 2CD), 2.44 (s, CD3).
13
C{
1
H} NMR (151 MHz, D2O): δ 157.22 (s, C), 147.05 (tlp,
1
JCD = 27 Hz, CD), 136.90 (tlp,
1
JCD
= 25 Hz, CD), 123.18 (tlp,
1
JCD = 25 Hz, CD), 120.47 (tlp,
1
JCD = 26 Hz, CD), 22.54–21.32 (m,
CD3). (tlp = 1:1:1 three-line pattern).
119
Figure 5.3.20.
2
H NMR spectrum of 2-picoline-d7 in H2O.
Figure 5.3.21.
13
C{
1
H} NMR spectrum of 2-picoline-d7 in D2O.
Synthesis of (CD3)3CMgCl in Diethyl Ether
The following reagents were transferred to a 300 mL Straus flask: tert-butanol (20.00 g,
270 mmol), D2O (135.12 g, 6.746 mol, 25 eq.), and D2SO4 (0.27 g, 2.698 mmol, 1 mol%). The
reactor was sealed and the solution was stirred at 100
o
C for 48 hours. Analysis by
1
H NMR
120
indicates complete H/D exchange with 85% total deuterium content in the system. Then, the
remaining acid in the solution mixture was neutralized with solid K2CO3 and the solution was
heated at 100
o
C overnight while tert-butanol-d10/water azeotrope distilled off as a colorless liquid
(35.8 g).
Azeotrope solution of tert-butanol-d10/water (35.8 and 12.4 g) was stirred with anhydrous
ZnCl2 (18 g, 0.132 mol) and DCl (35 w% in D2O, 50 g, 0.467 mol). After 1 hour, a layer of tert-
butyl chloride-d9 was separated via separatory funnel, washed with K2CO3/D2O solution, then
dried over P2O5 (22.8 g, 55% based on 30 g of tert-butanol). The compound was used in the next
step without characterization.
Synthesis of (CD3)3CMgCl was performed in a three-neck round-bottom flask (0.5 L)
equipped with a dropping funnel, reflux condenser, nitrogen gas inlet, and a large Teflon stirring
bar. A small portion of tert-butyl chloride-d9 (22 g, 0.216 mol) was added to a stirring mixture of
magnesium turnings (15.79 g, 0.650 mol) in dry diethyl ether (300 mL). When the reaction started,
tert-butyl chloride was slowly added to the stirring solution, then the mixture was heated to reflux
for 2 hours. In a glove box, the resulting suspension was decanted from unreacted magnesium
metal (10.59 g, 0.436 mol). The concentration of (CD3)3CMgCl was determined by titration with
1-butanol and 2,2’-bipyridine (0.398 M).
3
121
Synthesis of [(CD3)3C]2PCl
The reaction was performed in a N2-filled glove box in a round-bottom flask (0.5 L)
equipped with a dropping funnel. A solution of (CD3)3CMgCl in diethyl ether (0.398 M, 250 mL,
99.5 mmol) was added in portions to a vigorously stirring solution of PCl3 (6.83 g, 49.7 mmol)
purchased from Sigma-Aldrich, in diethyl ether (100 mL). The resulting white suspension was
stirred overnight, then the precipitate was filtered and washed with ether. Evaporation of the
ethereal solution at room temperature gave a colorless oil, which was purified by vapor transfer
technique (liquid N2 vs. oil bath at 60-80
o
C) affording the product as colorless liquid (8.00 g,
81%).
2
H NMR (92 MHz, C6H6): δ 1.01 (s).
13
C{
1
H} NMR (150 MHz, CDCl3): δ 35.38 (m), 27.27 (m).
31
P{
1
H} NMR (202 MHz, C6D6): δ 147.18 (s).
Figure 5.3.22.
2
H NMR spectrum of [(CD3)3C]2PCl in C6H6.
122
Figure 5.3.23.
13
C{
1
H} NMR spectrum of [(CD3)3C]2PCl in CDCl3.
Figure 5.3.24.
31
P{
1
H} NMR spectrum of [(CD3)3C]2PCl in C6D6.
123
Synthesis of Ligand PN-d24
The reaction was performed in a N2-filled glove box. A solution of n-BuLi (2.55 M in
hexane, 13.8 mL, 35.19 mmol) was added dropwise to a stirring solution of 2-picoline-d7 (3.50 g,
34.94 mmol) in dry THF (50 mL). The resulting black-red mixture was stirred for 10 mins, and
then added dropwise to a stirring solution of [(CD 3)3C]2PCl (6.95 g, 34.94 mmol) in dry THF (50
mL). The reaction was continued overnight, then CD3OD was added dropwise until the solution
turned from red to yellow. The resulting solution was evaporated and mixed with hexane (50 mL)
to precipitate LiCl, which was filtered off and washed with hexane. The hexane solutions were
combined, evaporated, and the resulting yellow oil was distilled under vacuum to give the product
as a pale-yellow liquid (4.80 g, 52%). The product is air sensitive. The concentration of n-BuLi
solution was determined by the standard titration using 1-butanol and 2,2’-bipyridine in THF.
3
2
H NMR (92 MHz, CH2Cl2): δ 1.09 (s, CD3), 3.00 (s, CD2), 7.06 (s, CD), 7.42 (s, CD), 7.58 (s,
CD), 8.44 (s, CD).
13
C{
1
H} NMR (151 MHz, C6D6): δ 162.72 (m), 148.77 (tlp,
1
JCD = 26 Hz, CD), 135.05 (tlp,
1
JCD =
24 Hz, CD), 123.86 (m), 119.91 (tlp,
1
JCD = 24 Hz, CD), 34.10–26.92 (m, CD2, C(CD3)3). (tlp =
1:1:1 three-line pattern)
31
P{
1
H} NMR (202 MHz, CD2Cl2): δ 35.90 (m).
IR was not attempted because a thin film of the material would rapidly air oxidize.
124
Figure 5.3.25.
2
H NMR spectrum of PN-d24 in CH2Cl2.
Figure 5.3.26.
13
C{
1
H} NMR spectrum of PN-d24 in C6D6.
125
Figure 5.3.27.
31
P{
1
H} NMR spectrum of PN-d24 in CD2Cl2.
126
Synthesis of [Ir( η
2
,η
2
-COD)(PN-d24)]OTf
The reaction was performed in a N2-filled glove box in a round-bottom flask (100 mL). A
solution of ligand PN-d24 (2.96 g, 11.320 mmol) in CH2Cl2 (10 mL) was added dropwise to a
stirred suspension of [Ir2Cl2(COD)2] (3.80 g, 5.660 mmol) and NaOTf (3.90 g, 22.640 mmol) in
CH2Cl2 (50 mL). The reaction was stirred for 1 h, then the mixture was filtered and concentrated in
vacuum. Addition of hexane (to 100 mL total volume) initiates formation of ruby-red crystals.
They were filtered, washed with hexane, and dried in vacuum (6.36 g, 79%).
1
H NMR (500 MHz, CD2Cl2): δ 8.26 (s, CH, 90% D), 8.09 (m, CH, 90% D), 8.02 (m, CH, 54%
D), 7.47 (s, CH, 90% D), 4.87 (m, 2H, 2CH, 0% D), 4.48 (m, 2H, 2CH, 0% D), 3.63 (m, CHD,
75% D), 2.45–2.11 (m, 6H, 3CH2, 0% D), 2.03–1.85 (m, 2H, CH2, 0% D), 1.37–1.20 (m, CHD2,
81% D).
2
H NMR (92 MHz, CH2Cl2): δ 8.21 (s, CD), 8.05 (s, CD), 7.99 (s, CD), 7.43 (s, CD), 3.55 (s,
CD2), 1.20 (s, CD3).
13
C{
1
H} NMR (126 MHz, CD2Cl2): δ 167.23 (m), 149.03 (tlp,
1
JCD = Hz, CD), 141.23 (m, CD),
125.12 (m, CD), 124.14 (tlp,
1
JCD = Hz, CD), 121.29 (q,
1
JCF = 321 Hz, CF3), 90.41 (d,
2
JCP = 11
Hz, CH), 63.13 (m, CH), 37.18–36.35 (m, CD2), 34.50–33.66 (m, C(CD3)3), 33.36 (m, CH2),
30.07–28.53 (m, CD3), 28.23 (m, CH2).
31
P{
1
H} NMR (202 MHz, CD2Cl2): δ 57.39 (m).
127
MALDI-MS: m/z calc’d for [C22H17D19IrNP]
+
557.34, found 557.49.
Elemental Analysis: Anal. calcd. for C23H17D19F3IrNO3PS: C, 39.13; H, 7.85; N, 1.98. Found C,
39.43; H, 5.43; N, 2.31.
IR (KBr, cm
−1
): 2957, 2930, 2895, 2843, 2297, 2231, 2216, 2133, 2069, 1589, 1541, 1433, 1277
νas(SO3), 1224 νs(CF3), 1155 νas(CF3), 1032 νs(SO3), 638 δs(SO3).
Figure 5.3.28.
1
H NMR spectrum of [Ir(COD)(PN-d24)]OTf in CD2Cl2.
128
Figure 5.3.29.
2
H NMR spectrum of [Ir(COD)(PN-d24)]OTf in CH2Cl2.
Figure 5.3.30.
13
C{
1
H} NMR spectrum of [Ir(COD)(PN-d24)]OTf in CD2Cl2.
129
Figure 5.3.31.
31
P{
1
H} NMR spectrum of [Ir(COD)(PN-d24)]OTf in CD2Cl2.
Figure 5.3.32. IR spectrum of [Ir(COD)(PN-d24)]OTf.
130
Synthesis of [Ir3H7(PN-d24)3][PF6]2, 3.1-H(d72)
In a N2-filled glovebox, the following reagents were transferred to a 1 L Straus flask:
freshly prepared [Ir(COD)(PN-d24)]OTf (5.00 g, 7.033 mmol) synthesized following published
procedure,
2
NaPF6 (2.36 g, 14.066 mmol, 2 eq.) purchased from Sigma-Aldrich, and dry methanol
(100 mL) purchased from ThermoFisher Scientific. Then, the flask was connected to a Schlenk
line and the reactor headspace was filled with hydrogen gas (1 atm). The flask was sealed, and the
mixture was occasionally shaken to fully dissolve the reagents, followed by slow crystallization of
bright-yellow product [Ir3H7(PN-d24)3][PF6]2. The reaction was continued for 12 hours during
which the reactor was recharged with hydrogen gas three times. The reaction mixture was
concentrated in vacuum to ca. 50 mL, then the crude product was filtered, washed with methanol,
and dried. Further purification requires dissolution in CH2Cl2, filtration, and fractional
crystallization from 3:1:3 CH2Cl2:CH3OH:Et2O solutions. Bright-yellow crystalline powder (1.16
g, 30%).
2
H NMR (92 MHz, CH2Cl2): δ 9.25 (s, CD), 7.81 (s, CD), 7.22 (s, CD), 5.24 (s, CD), 3.48 (s,
CD2), 1.00 (d, CD3).
31
P{
1
H} NMR (202 MHz, CD2Cl2): δ 75.84 (m, PN), –143.83 (hept,
1
JPF = 711 Hz, PF6).
19
F NMR (564 MHz, CD2Cl2): δ –73.00 (d, JFP = 852 Hz, PF6).
MALDI-MS: m/z calcd for [C28H13D38Ir2N2P2]
+
901.52, found 901.44.
131
IR (KBr, cm
−1
): 2930, 2233 (IrH), 3134, 2075, 1772 (IrH), 1590, 1540, 1420, 1384, 1295,
1044, 843 ν(PF6), 558.
Figure 5.3.33.
2
H NMR spectrum of 3.1-H(d72) in CH2Cl2.
132
Figure 5.3.34.
31
P{
1
H} NMR spectrum of 3.1-H(d72) in CD2Cl2.
133
Figure 5.3.35.
19
F NMR spectrum of 3.1-H(d72) in CD2Cl2.
Figure 5.3.36. IR spectrum of 3.1-H(d72).
134
3.1-O Isotopic Labeling Studies
To a Straus flask in the N2-filled glovebox, [Ir(COD)(PN)]OTf 2.11 (20 mg, 0.03 mmol)
synthesized following published procedure,
2
NaOOCD (20.0 mg, 0.29 mmol, 10 eq), dry methanol
(0.3 mL) purchased from ThermoFisher Scientific, and deionized H2O (0.3 mL) from a Milli-Q
water purification system, were added and let stir under N2 environment at room temperature.
After 3 hours, the red solution turned to orangish yellow slurry. Solvent in the crude product was
removed under high vacuum, resuspended in 0.7 mL CD2Cl2, filtered through 0.22 µL PTFE to a
J-Young NMR tube for structural analysis and quantification of deuteration percentage.
Procedure for Table 3.1, E1:
Figure 5.3.37. Table 3.1, entry 1 spectrum –
1
H{
31
P} NMR (500 MHz, CD2Cl2)
Procedure for Table 3.1, E2-4:
To a Straus flask in the N2-filled glovebox, [Ir(COD)(PN)]OTf 2.11 (20 mg, 0.03 mmol)
synthesized following published procedure,
2
NaOOCH (20.0 mg, 0.29 mmol, 10 eq), dry methanol
(0.3 mL) purchased from ThermoFisher Scientific, and deionized H2O (0.3 mL) from a Milli-Q
water purification system, were added and let stir under N2 environment at room temperature.
After 3 hours, the red solution turned to orangish yellow slurry. Solvent in the crude product was
135
removed under high vacuum, resuspended in 0.7 mL CD2Cl2, filtered through 0.22 µL PTFE to a
J-Young NMR tube for structural analysis and quantification of deuteration percentage.
Figure 5.3.38. Table 3.1, entry 2 spectra –
1
H{
31
P} (600 MHz, CD2Cl2) and
2
H NMR (600 MHz,
CD2Cl2).
Figure 5.3.39. Table 3.1, entry 3 spectrum –
1
H (600 MHz, CD2Cl2).
136
Figure 5.3.40. Table 3.1, entry 4 spectrum –
1
H{
31
P} (600 MHz, CD2Cl2).
Figure 5.3.41. Formation of Ir3H6(µ3-S)(PN)
+
in D2/D2S condition.
137
Electrochemical Study
In a N2-filled glove box, complex 3.1-H (0.016 g, 1.0 mM), tetrabutylammonium
hexafluorophosphate (0.387 g, 0.1 M) in 10 mL CH2Cl2. Methanol purchased from Sigma Aldrich
(10 mL) and deionized H2O (10 mL) from a Milli-Q water purification system were added to the
electrolyte reaction mixture via syringe. The homogeneous solution transferred to the voltammetry
cell via syringe. A glassy carbon working electrode (surface area of 0.195 cm
2
), Pt wire counter
electrode, and silver wire pseudo-reference electrode, 50 and 200 mV/s scan rates.
Figure 5.3.42. Cyclic voltammetry of complex 3.1-H (1.0 mM in CH2Cl2, 0.1 M [Bu4N][PF6], and
FeCp*2 as reference at two scan rates, 50 mV/s and 200 mV/s).
CO2 Hydrogenation
In a N2-filled glovebox, 1 mL of catalyst stock solution (10 mg [3.1-H] in 10 mL THF) and
5 mL deionized H2O from a Milli-Q water purification system were added to a 125 mL Parr non-
138
stirred reactor. The reactor was removed from the glovebox and charged with H2:CO2 to the
desired mixture and ratio prior to heating in oil bath. Internal temperature was measured by a
thermal couple connected to a second oil bath for accurate reading. Solvent of the resulting
solution was removed under vacuum to white solid, following by the addition of internal standard
(DMF), and quantification of formate product by
1
H NMR.
Experimental details of neutron vibrational spectroscopic measurement
In a helium-filled glovebox equipped with oxygen and water sensors, 1.1416 g of bright
yellow microcrystalline powder of partially deuterated [Ir3H6(µ3-H)(PN)3][PF6]2 was added to an
aluminum sample can. This was then sealed with a copper gasket and aluminum lid, brought out of
the glovebox and mounted on a sample stick compatible with the top-loading closed cycle
refrigerator at the VISION spectrometer (BL-16B), at the Spallation Neutron Source, Oak Ridge
National Laboratory. The sample was cooled to 5 K and then measured for ≈ 2 h. 6 mm x 30 mm
slits were used to reduce the beam size such to help ensure that only the sample was illuminated
during the experiment.
139
5.4. Chapter 4 Experimental and Spectral Data
8-Bromo-5-methoxyquinoline (4.5)
Following a modified procedure by Miyaji et al., distilled 2-bromo-5-
methoxyaniline (3.00 g, 0.0150 mol, 1 equiv.), sodium 3-nitrobenzenesulfonate
(4.00 g, 0.0178 mol, 1.18 equiv.), FeSO4 . 7 H2O (0.200 g, 0.719 mmol, 0.05
equiv.), glycerol (20 mL, 0.274 mol, 18.2 equiv.) and methanesulfonic acid (20 mL) purchased
from Acros Organics, to a 100 mL round bottom flask with a magnetic stir bar. The flask was
heated to 125 °C and left for 16 hours at this temperature. After that, the flask was cooled down to
room temperature and the brown contents were transferred to a 500 mL beaker with the help of
100 mL of water. The content of the beaker was placed in an ice bath and treated with 20% w/v
NaOH until pH reached 14 by pH paper. The heterogeneous mixture was extracted three times
with diethyl ether (3 150 mL). Layer separation appeared to be slow, in some cases over 30
mins. Combined organic layers were washed with water (3 200 mL) to remove remaining
glycerol, then dried with MgSO4, filtered through a Celite layer and evaporated. The resulting
brown oil was purified by flash column chromatography with Hex:EtOAc 3:1 yielding yellow
solid 2.32 g, 70% that was further analyzed by NMR and proved to be spectroscopically pure.
1
H NMR (400 MHz, Chloroform-d) δ 9.03 (dt, J = 4.3, 1.7 Hz, 1H), 8.59 (dt, J = 8.5, 2.0 Hz, 1H),
7.92 (dd, J = 8.4, 1.9 Hz, 1H), 7.44 (ddd, J = 8.4, 4.3, 1.8 Hz, 1H), 6.74 (dd, J = 8.4, 1.8 Hz, 1H),
3.99 (d, J = 1.9 Hz, 3H).
13
C NMR (101 MHz, Chloroform-d) δ 154.99, 151.39, 145.49, 132.55, 131.42, 122.16, 120.91,
114.78, 105.05, 55.94.
140
FTIR ν 3512.22, 3435.56, 3389.76, 3365.17, 3344.93, 3305.39, 3209.45, 3069.16, 3031.55,
2991.53, 2963.09, 2929.82, 2844.01, 2763.01, 2682.98, 2638.14, 2599.57, 2556.67, 2534.01,
2488.2, 2457.83, 2421.19, 2377.8, 2318.5, 2288.61, 2214.84, 2170.97, 2075.99, 1989.7, 1984.87,
1936.18, 1819.51, 1778.53, 1701.87, 1606.41, 1586.16, 1565.92, 1496.49, 1456.47, 1388.98,
1364.87, 1296.41, 1253.5, 1226.99, 1204.33, 1151.78, 1126.22, 1083.32, 1038.96, 987.375,
914.575, 796.939, 778.136, 711.122, 619.52, 589.629, 525.507, 469.1.
MS (MALDI) calculated for C9H8BrNO 236.98, found 237.68.
Figure 5.4.1.
1
H NMR spectrum of 4.5 at 25 °C in CDCl3.
141
Figure 5.4.2.
13
C NMR spectrum of 4.5 at 25 °C in CDCl3.
Figure 5.4.3. IR spectrum of 4.5.
142
5-Methoxyquinoline-8-carbaldehyde (4.6):
Compound 4.5 (2.58 g, 0.0109 mol, 1 equiv.) was added to a flame dried
50 mL flask with a magnetic stir bar inside of the glove box, followed by the
addition of 20 mL of dry THF. The flask was sealed with a septum, removed
from the glove box, and connected to the nitrogen line. After that flask was cooled to -78
o
C (dry
ice/acetone bath) and n-Buli 2.5 M hexanes solution (5.7 mL, 0.0142 mol, 1.3 equiv.) was added
via syringe dropwise. The reaction mixture was warmed to room temperature with the help of a
water bath and left stirring for 10 minutes. After that flask was cooled to -78
o
C again and DMF
(4.2 mL, 0.0545 mol, 5 equiv.) was added via syringe dropwise and left stirring for 10 minutes at -
78
o
C. The reaction mixture was then poured into a beaker containing 200 mL of a saturated
sodium bicarbonate solution. This solution was extracted with EtOAc (3 150 mL). Combined
organic fractions were dried over MgSO4, treated with activated charcoal, filtered through Celite
pad and evaporated on a rotavapor with a bath set to 25
o
C (Aldehyde product decomposes on air
at elevated temperatures). The resulting yellow oil underwent purification on a flash purification
system (Hex : EtOAc, 4:1) and the collected combined fractions were evaporated and left under
high vacuum overnight. The resulting flaky yellow solid (1.14 g, 0.00610 mol, 56%) was further
analyzed by NMR and proved to be spectroscopically pure.
1
H NMR (600 MHz, Chloroform-d) δ 11.28 – 11.23 (m, 1H), 9.02 (dt, J = 3.6, 1.7 Hz, 1H), 8.62
(dt, J = 8.5, 1.7 Hz, 1H), 8.34 (dd, J = 8.2, 1.4 Hz, 1H), 7.47 (ddd, J = 8.5, 4.2, 1.4 Hz, 1H), 6.98
(dd, J = 8.3, 1.3 Hz, 1H), 4.09 (d, J = 1.4 Hz, 3H).
13
C NMR (151 MHz, Chloroform-d) δ 191.30, 160.20, 151.45, 131.56, 131.35, 125.12, 120.87,
120.11, 104.23, 56.20.
143
FTIR ν 3317.45, 3066.26, 3012.75, 2929.82, 2867.63, 2844.97, 2757.71, 2732.16, 2674.3,
2642.48, 2600.06, 2588.97, 2557.63, 2523.4, 2305.48, 2178.69, 2115.53, 2052.37, 1994.52,
1957.39, 1907.25, 1804.56, 1670.05, 1604.97, 1570.25, 1500.35, 1472.38 ,1445.87, 1411.16,
1397.17, 1364.39, 1307.02, 1277.61, 1248.2, 1237.11, 1215.9, 1168.65, 1142.13, 1083.8, 1028.35,
983.518, 962.305, 819.598, 776.69, 714.979, 662.428, 640.251, 596.861, 481.153.
MS (MALDI) calculated for C11H9NO2 187.06, found 187.87.
Figure 5.4.4.
1
H NMR spectrum of 4.6 at 25 °C in CDCl3.
144
Figure 5.4.5.
13
C NMR spectrum of 4.6 at 25 °C in CDCl3.
Figure 5.4.6. IR spectrum of 4.6.
145
(5-Methoxyquinolin-8-yl)(pyridin-2-yl)methanol (4.7):
2-Iodopyridine (0.8 mL, 6.1 mmol, 1 eq) was added to a previously
flame dried 250 mL flask with a magnetic stir bar inside of the glove box,
followed by the addition of 80 mL of dry DCM. The flask was sealed with a
rubber stopper and taken outside of the glove box, later to be connected to the
nitrogen line. A 3M solution of EtMgBr in diethyl ester (2.0 mL, 6.1 mmol, 1 eq) in a syringe with
a needle was added dropwise to the stirring DCM solution of 2-iodopyridine through the rubber
stopper and left for 1 hour. A solution of compound 4.6 (1.14 g, 6.1 mmol, 1 eq) in 12 mL of dry
DCM was added dropwise in the same way and left for 16 hours. The reaction solution was
washed with saturated NaHCO3 solution of 75 mL, which was then extracted twice with DCM (2
50 mL). Combined DCM fractions were dried over MgSO4, treated with activated charcoal,
filtered through a Celite pad and evaporated. Obtained red oil was redissolved in 20 mL of diethyl
ether and then filtrated. The diethyl ether mixture was evaporated, and the resulting orange oil was
recrystallized from boiling EtOAc resulting in pale yellow crystals (713 mg, 2.7 mmol, 44%) that
were further analyzed by NMR and proved to be spectroscopically pure.
1
H NMR (600 MHz, Chloroform-d) δ 8.86 (dd, J = 4.3, 1.9 Hz, 1H), 8.58 (dd, J = 8.5, 1.8 Hz,
1H), 8.51 (ddd, J = 4.8, 1.7, 0.9 Hz, 1H), 7.68 – 7.66 (m, 1H), 7.61 (td, J = 7.7, 1.8 Hz, 1H), 7.56
(dd, J = 8.1, 0.6 Hz, 1H), 7.38 (dd, J = 8.5, 4.3 Hz, 1H), 7.12 (ddd, J = 7.3, 4.9, 1.3 Hz, 1H), 6.80
(d, J = 8.0 Hz, 1H), 6.61 (s, 1H), 3.96 (s, 3H).
13
C NMR (101 MHz, Chloroform-d) δ 162.87, 154.63, 149.10, 147.82, 146.78, 136.75, 131.60,
128.67, 121.92, 121.25, 121.01, 120.05, 104.07, 74.47, 55.71.
146
FTIR ν 3093.74, 3067.23, 3017.09, 2965.98, 2935.61, 2908.61, 2829.54, 2682.98, 2526.77,
2358.03, 2284.27, 2228.83, 2025.85, 2012.84, 1981.02, 1875.92, 1730.8, 1667.64, 1615.09,
1587.13, 1498.9, 1472.87, 1452.14, 1436.71, 1399.1, 1372.59, 1325.34, 1309.43, 1265.56,
1203.85, 1189.38, 1155.63, 1072.71, 1001.84, 892.88, 826.83, 783.922, 749.209, 709.194,
663.875, 631.573, 602.164, 542.381, 471.028.
Figure 5.4.7.
1
H NMR spectrum of 4.7 at 25 °C in CDCl3.
147
Figure 5.4.8.
13
C NMR spectrum of 4.7 at 25 °C in CDCl3.
Figure 5.4.9. IR spectrum of 4.7.
148
3-((5-methoxyquinolin-8-yl)(pyridin-2-yl)methyl)-1-methyl-1H-imidazol-3-ium (4.8)
2,4,6-Trichloro-[1,3,5]-triazine (145.22 mg, 0.75 mmol) was added to
DMF (0.15 mL), maintained at 25 °C for 30 mins resulting to formation of
white solid. The reaction was monitored by TLC for 1 hour. White solid was
dissolved in CH2Cl2 (1.9 mL) by sonication. Next, compound 4.7 (200 mg,
0.75 mmol) was added to the solution and stirred at room temperature. The
reaction completion was monitored by TLC. After 14 h, the reaction was washed with deionized
H2O, NaHCO3 (saturated), 1M HCl, and brine. The organic layer was extracted, combined, and
dried with Na2SO4. The resulting solution was concentrated under vacuum without other
purifications. Under N2 Schlenk line, acetonitrile (2 mL) was added to the resuspend the solution
and N-methylimidazole (0.825 mmol, 1.1 eq) was slowly added and let stirred for 14 h at room
temperature. The resulting crude mixture was concentrated down and recrystallized with
diethylether (3 mL). This product is highly reactive and decomposed after several hours.
1
H NMR (400 MHz, Chloroform-d) δ 8.87 (dd, J = 4.3, 1.8 Hz, 1H), 8.58 (dd, J = 8.5, 1.8 Hz,
1H), 8.51 (d, 1H), 7.68 – 7.64 (m, 1H), 7.60 (ddd, J = 8.0, 7.3, 1.8 Hz, 1H), 7.55 (d, 1H, J = 7.9
Hz), 7.45 (bs), 7.39 (dd, J = 8.5, 4.2 Hz, 1H), 7.13 – 7.09 (td, 1H), 6.87 (bs, 2H), 6.80 (d, J = 8.1
Hz, 1H), 6.77 – 6.72 (d, J = 6.4 Hz, 1H), 6.61 (d, J = 5.7 Hz, 1H).
149
Figure 5.4.10.
1
H NMR spectrum of 4.8 at 25 °C in CDCl3.
150
(1-((5-methoxyquinolin-8-yl)(pyridin-2-yl)methyl)-3-methyl-2,3-dihydro-1H-imidazol-2-
yl)silver(II) chloride (4.9)
In a N2-filled glovebox, compound 4.8 (0.6 mmol, 1 eq) was
dissolved in DCM (5 mL) and Ag2O (0.6 mmol, 1 eq) was added to the
solution and stirred over 22 hours at room temperature. Solvent of resulting
solution was removed under vacuum and washed with benzene. Crude
product was dried under vacuum and a yellow single crystal suitable for X-
ray crystallography obtained by layering the crude product with DCM and hexane in an NMR tube
after several days. This reaction resulted in low spectroscopically and isolated yield, therefor, no
other structural analysis could be obtained.
151
Catalyst Carbonylation CO Experiments:
To a 750 mL Parr reactor, 2.11 (52.6 mg, mmol), sodium formate (25.3 g, mmol), and
formic acid (60 mL, mol) were added. The reaction was stirred at 90-120 °C and evolved gas was
monitored via LabView. The headspace gas mixtures were collected directly from the reactor at 25
°C.
Figure 5.4.11. Stacked FTIR spectra of CO experiments.
CO
152
Figure 5.4.12. CO experiment via demonstration reactor. Condition: 60 mL FA, 25.3 mg of 2.11,
25.3 g NaOOCH, 120 °C. Headspace gas was collected at 1458 psi.
Figure 5.4.13. CO experiment via demonstration reactor. Condition: 60 mL FA, 25.3 mg of 2.11,
25.3 g NaOOCH, 90 °C. Headspace gas was collected at 382 psi, then depressurized to 102 psi. to
add 15 psi. of CO gas into the reactor before heating it back up to 90 ºC.
153
Figure 5.4.14. CO experiment via demonstration reactor. Condition: 52.6 mg of 2.11, 5.4 g (5
mol%) NaOOCH, 90°C. After 4 hours, headspace gas was collected at 64 psi after the reactor was
cooled down to 25°C. After gas was collected, the reactor was heated it back up to 90 ºC.
Figure 5.4.15. CO experiment via demonstration reactor. Condition: 52.6 mg of 2.11, 5.4 g (5
mol%) NaOOCH, 6.3 mL H2O, 90°C. After 4 hours, headspace gas was collected at 90 psi after
the reactor was cooled down to 25°C. After gas was collected, the reactor was heated it back up to
90 ºC.
154
5.5. Crystallography Data (X-ray & Neutron Diffraction)
We gratefully acknowledge Professor Ralf Haiges (USC) and Dr. Thomas Saals (USC), for
the X-ray acquisition and refinement assistance. We also thank Dr. Xiaoping Wang and Dr.
Yongqiang Cheng at the Spallation Neutron Source, Oak Ridge National Laboratory for the
acquisition of single-crystal and powder neutron diffraction of complex 3.1-H.
5.5.1 Crystal Structure Data for 2.11-Rh
Figure 5.5.1.1 Molecular structure of 2.11-Rh shown with 50% probability ellipsoids. Hydrogen
atoms are omitted for clarity.
Single crystals of C23H36F3N1O3P1Rh1S1 RhPNCOD were layered with DCM and Toluene.
A suitable crystal was selected and mounted on MiTiGen 50um on a XtaLAB Synergy, Dualflex,
HyPix diffractometer. The crystal was kept at 100.00(10) K during data collection. Using Olex2,
the structure was solved with the SHELXT structure solution program using Intrinsic Phasing and
refined with the SHELXL refinement package using Least Squares minimisation.
4-7
Crystal Data for C23H36F3N1O3P1Rh1S1 (M =119.49 g/mol): triclinic, space group P-1 (no.
2), a = 8.8927(3) Å, b = 10.3448(3) Å, c = 14.8521(3) Å, α = 109.951(2)°, β = 100.254(2)°, γ =
94.693(2)°, V = 1248.68(6) Å
3
, Z = 10, T = 100.00(10) K, μ(Mo Kα) = 0.879 mm
-1
, Dcalc =
155
1.589 g/cm
3
, 41340 reflections measured (4.994° ≤ 2Θ ≤ 66.482°), 8380 unique (Rint = 0.0735,
Rsigma = 0.0437) which were used in all calculations. The final R1 was 0.0324 (I > 2σ(I))
and wR2 was 0.0884 (all data). Further crystallographic details can be obtained from the
Cambridge Crystallographic Data Centre (CCDC deposit number: 2206834)
Crystal data and structure refinement for 2.11-Rh.
Identification code RhPNCOD_1
Empirical formula C4.6H7.2F0.6N0.2O0.6P0.2Rh0.2S0.2
Formula weight 119.49
Temperature/K 100.00(10)
Crystal system triclinic
Space group P-1
a/Å 8.8927(3)
b/Å 10.3448(3)
c/Å 14.8521(3)
α/° 109.951(2)
β/° 100.254(2)
γ/° 94.693(2)
Volume/Å
3
1248.68(6)
Z 10
ρcalcg/cm
3
1.589
μ/mm
-1
0.879
F(000) 616.0
Crystal size/mm
3
0.329 × 0.188 × 0.138
Radiation Mo Kα (λ = 0.71073)
2Θ range for data collection/° 4.994 to 66.482
Index ranges -12 ≤ h ≤ 13, -14 ≤ k ≤ 15, -22 ≤ l ≤ 21
Reflections collected 41340
Independent reflections 8380 [Rint = 0.0735, Rsigma = 0.0437]
156
Data/restraints/parameters 8380/0/304
Goodness-of-fit on F
2
1.083
Final R indexes [I>=2σ (I)] R1 = 0.0324, wR2 = 0.0866
Final R indexes [all data] R1 = 0.0353, wR2 = 0.0884
Largest diff. peak/hole / e Å
-3
0.78/-1.04
Fractional Atomic Coordinates (×104) and Equivalent Isotropic Displacement Parameters
(Å
2
×10
3
) for 2.11-Rh. Ueq is defined as 1/3 of the trace of the orthogonalised U IJ tensor.
Atom x y z U(eq)
Rh1 4686.0(2) 8477.9(2) 6871.0(2) 9.28(5)
P1 5564.5(5) 7182.7(4) 7798.9(3) 10.32(8)
N1 6108.1(15) 7317.4(13) 5964.9(9) 11.6(2)
C20 4133(2) 11471.0(17) 6958.4(12) 17.0(3)
C9 8603(2) 6858(2) 8665.9(14) 24.7(4)
C14 2908(2) 5493.7(19) 7658.3(13) 23.2(4)
C10 7488(2) 8925.3(19) 9603.8(12) 21.9(3)
C11 4337(2) 6383.2(16) 8441.1(11) 15.6(3)
C18 3480.2(18) 9013.1(16) 5626.5(11) 12.9(3)
C15 2629.2(18) 9019.3(16) 7386.4(11) 13.6(3)
C13 3772(2) 7500.6(18) 9242.7(12) 19.4(3)
C22 3917.4(18) 9997.0(16) 8008.9(11) 13.7(3)
C16 1412.8(19) 9288.3(18) 6639.6(12) 17.4(3)
C6 5815.1(19) 5649.7(15) 6776.0(11) 13.2(3)
C17 1767.1(18) 8823.9(18) 5608.5(12) 16.7(3)
C4 7574.4(19) 5418.4(17) 5591.3(12) 16.4(3)
C3 8227.7(19) 5926.0(19) 4970.8(12) 17.8(3)
C8 8359(2) 8839(2) 8088.8(13) 23.7(4)
C1 6763.0(18) 7792.7(16) 5358.1(11) 13.4(3)
C21 4359(2) 11434.6(16) 8005.0(12) 17.3(3)
157
C12 5174(3) 5441.5(19) 8895.8(14) 25.6(4)
C2 7821.8(18) 7134.5(18) 4856.8(11) 15.8(3)
C19 4535.4(18) 10167.8(16) 6245.8(11) 13.3(3)
C5 6525.7(18) 6140.0(16) 6081.4(10) 12.6(3)
C7 7581.4(19) 7951.5(16) 8575.1(11) 14.5(3)
S1 8949.9(5) 2415.6(4) 7109.0(3) 14.64(8)
F1 10631.1(17) 2134.3(14) 8656.2(9) 37.7(3)
F2 8432.5(17) 2734.4(18) 8860.1(9) 46.1(4)
F3 10270.1(15) 4242.0(12) 8874.6(8) 30.3(3)
O1 8315.2(15) 964.3(13) 6780.8(9) 21.0(2)
O2 10371.4(17) 2694.2(16) 6820.5(10) 30.9(3)
O3 7830(2) 3313.6(16) 7013.6(12) 36.8(4)
C23 9601(2) 2911.5(19) 8440.2(13) 20.3(3)
Anisotropic Displacement Parameters (Å
2
×10
3
) for 2.11-Rh. The Anisotropic displacement factor
exponent takes the form: -2π
2
[h
2
a*
2
U11+2hka*b*U12+…].
Atom U11 U22 U33 U23 U13 U12
Rh1 10.52(7) 9.76(7) 9.07(7) 4.53(4) 3.09(4) 2.89(4)
P1 13.81(18) 8.89(16) 9.02(17) 4.33(13) 2.36(13) 1.47(13)
N1 12.9(6) 12.5(6) 10.1(6) 4.5(4) 2.8(4) 3.3(4)
C20 20.8(8) 13.3(7) 18.8(7) 7.8(6) 3.7(6) 5.2(6)
C9 23.0(9) 22.2(8) 25.8(9) 7.4(7) -1.2(7) 7.5(7)
C14 25.8(9) 20.8(8) 18.9(8) 3.8(6) 7.3(6) -8.1(7)
C10 21.8(8) 22.1(8) 15.5(7) 1.4(6) -0.6(6) 2.9(6)
C11 22.2(8) 12.6(6) 12.8(7) 5.7(5) 5.2(5) -1.4(6)
C18 14.2(7) 15.3(7) 11.6(6) 7.5(5) 2.9(5) 4.5(5)
C15 13.4(7) 15.4(7) 13.7(7) 5.1(5) 6.3(5) 4.3(5)
C13 24.6(8) 19.8(8) 13.8(7) 5.0(6) 8.2(6) 0.1(6)
158
C22 16.9(7) 14.6(7) 10.7(6) 4.0(5) 5.2(5) 5.5(5)
C16 12.4(7) 23.6(8) 16.7(7) 6.9(6) 3.9(5) 5.6(6)
C6 18.8(7) 9.8(6) 12.0(6) 4.3(5) 4.3(5) 3.2(5)
C17 11.9(7) 22.0(8) 15.9(7) 7.2(6) 0.8(5) 4.2(6)
C4 18.0(7) 16.4(7) 15.4(7) 5.2(5) 3.4(5) 9.1(6)
C3 15.5(7) 24.8(8) 13.4(7) 5.2(6) 5.1(5) 8.6(6)
C8 18.9(8) 29.1(9) 21.4(8) 12.5(7) -2.1(6) -6.8(7)
C1 13.2(7) 15.9(7) 12.5(7) 6.4(5) 3.4(5) 3.2(5)
C21 22.1(8) 12.7(7) 16.3(7) 3.6(5) 4.7(6) 4.3(6)
C12 43.3(11) 17.9(8) 22.2(8) 13.6(7) 10.9(7) 3.8(7)
C2 12.2(7) 23.3(8) 12.2(7) 6.3(6) 3.7(5) 3.1(6)
C19 15.8(7) 14.6(7) 13.7(7) 9.2(5) 4.3(5) 5.1(5)
C5 14.2(7) 14.0(7) 9.4(6) 4.3(5) 1.8(5) 3.3(5)
C7 15.2(7) 14.5(7) 12.1(7) 5.0(5) -0.5(5) 1.3(5)
S1 16.70(18) 13.14(17) 15.36(18) 6.57(13) 3.73(13) 2.65(13)
F1 43.2(8) 36.9(7) 30.6(7) 16.1(5) -8.1(5) 11.9(6)
F2 36.1(7) 73.6(11) 25.9(6) 13.7(6) 16.8(5) -9.7(7)
F3 41.2(7) 22.3(5) 20.3(5) 1.2(4) 4.7(5) -0.6(5)
O1 18.9(6) 15.4(5) 26.5(6) 8.3(5) -0.3(5) -0.2(4)
O2 30.3(7) 35.0(8) 20.8(6) 2.9(5) 11.7(5) -13.0(6)
O3 45.3(9) 25.3(7) 35.8(8) 9.6(6) -5.2(7) 20.8(7)
C23 21.1(8) 23.3(8) 18.5(8) 9.4(6) 6.0(6) 2.5(6)
159
Bond Lengths for 2.11-Rh
Atom Atom Length/Å Atom Atom Length/Å
Rh1 P1 2.3136(4) C18 C19 1.383(2)
Rh1 N1 2.1456(13) C15 C22 1.409(2)
Rh1 C18 2.2277(15) C15 C16 1.520(2)
Rh1 C15 2.1490(15) C22 C21 1.509(2)
Rh1 C22 2.1371(15) C16 C17 1.539(2)
Rh1 C19 2.2445(15) C6 C5 1.503(2)
P1 C11 1.8830(16) C4 C3 1.390(2)
P1 C6 1.8458(15) C4 C5 1.393(2)
P1 C7 1.8930(16) C3 C2 1.385(2)
N1 C1 1.3548(19) C8 C7 1.539(2)
N1 C5 1.359(2) C1 C2 1.383(2)
C20 C21 1.545(2) S1 O1 1.4402(13)
C20 C19 1.519(2) S1 O2 1.4429(14)
C9 C7 1.533(2) S1 O3 1.4373(15)
C14 C11 1.538(2) S1 C23 1.8327(18)
C10 C7 1.538(2) F1 C23 1.334(2)
C11 C13 1.541(2) F2 C23 1.334(2)
C11 C12 1.532(3) F3 C23 1.337(2)
C18 C17 1.514(2)
Bond Angles for 2.11-Rh
Atom Atom Atom Angle/˚ Atom Atom Atom Angle/˚
N1 Rh1 P1 80.92(4) C16 C15 Rh1 113.50(10)
N1 Rh1 C18 90.48(5) C15 C22 Rh1 71.27(9)
N1 Rh1 C15 158.59(6) C15 C22 C21 125.89(14)
N1 Rh1 C19 97.32(5) C21 C22 Rh1 110.28(10)
C18 Rh1 P1 160.72(4) C15 C16 C17 112.75(13)
160
C18 Rh1 C19 36.03(6) C5 C6 P1 108.78(10)
C15 Rh1 P1 100.80(4) C18 C17 C16 113.26(13)
C15 Rh1 C18 81.09(6) C3 C4 C5 119.03(15)
C15 Rh1 C19 87.41(6) C2 C3 C4 119.24(15)
C22 Rh1 P1 96.03(4) N1 C1 C2 123.08(15)
C22 Rh1 N1 163.01(6) C22 C21 C20 112.87(13)
C22 Rh1 C18 97.03(6) C1 C2 C3 118.79(15)
C22 Rh1 C15 38.38(6) C20 C19 Rh1 111.51(10)
C22 Rh1 C19 80.38(6) C18 C19 Rh1 71.32(9)
C19 Rh1 P1 161.96(4) C18 C19 C20 125.07(14)
C11 P1 Rh1 124.44(6) N1 C5 C6 116.91(13)
C11 P1 C7 112.03(7) N1 C5 C4 122.10(14)
C6 P1 Rh1 97.25(5) C4 C5 C6 120.99(14)
C6 P1 C11 102.50(7) C9 C7 P1 113.80(12)
C6 P1 C7 105.26(7) C9 C7 C10 109.65(14)
C7 P1 Rh1 111.75(5) C9 C7 C8 108.07(15)
C1 N1 Rh1 122.56(10) C10 C7 P1 109.89(12)
C1 N1 C5 117.76(13) C10 C7 C8 107.61(14)
C5 N1 Rh1 119.22(10) C8 C7 P1 107.61(11)
C19 C20 C21 111.46(13) O1 S1 O2 114.86(9)
C14 C11 P1 106.70(11) O1 S1 C23 103.57(8)
C14 C11 C13 107.89(15) O2 S1 C23 102.09(8)
C13 C11 P1 111.72(11) O3 S1 O1 114.60(9)
C12 C11 P1 112.72(13) O3 S1 O2 115.63(11)
C12 C11 C14 108.48(14) O3 S1 C23 103.60(9)
C12 C11 C13 109.15(13) F1 C23 S1 111.16(13)
C17 C18 Rh1 107.27(10) F1 C23 F2 106.66(16)
C19 C18 Rh1 72.65(9) F1 C23 F3 107.34(15)
C19 C18 C17 124.88(14) F2 C23 S1 111.73(13)
C22 C15 Rh1 70.35(9) F2 C23 F3 107.66(15)
161
C22 C15 C16 124.74(15) F3 C23 S1 112.02(12)
Torsion Angles for 2.11-Rh
A B C D Angle/˚
A B C D Angle/˚
Rh1 P1 C11 C14 54.16(13)
C6 P1 C7 C9 -38.42(14)
Rh1 P1 C11 C13 -63.53(13)
C6 P1 C7 C10 -161.82(11)
Rh1 P1 C11 C12 173.14(10)
C6 P1 C7 C8 81.29(13)
Rh1 P1 C6 C5 41.80(11)
C17 C18 C19 Rh1 99.29(14)
Rh1 P1 C7 C9 -142.88(11)
C17 C18 C19 C20 -4.3(2)
Rh1 P1 C7 C10 93.72(11)
C4 C3 C2 C1 -0.7(2)
Rh1 P1 C7 C8 -23.17(13)
C3 C4 C5 N1 0.7(2)
Rh1 N1 C1 C2 172.31(11)
C3 C4 C5 C6 -178.68(15)
Rh1 N1 C5 C6 6.20(18)
C1 N1 C5 C6 178.58(13)
Rh1 N1 C5 C4 -173.20(12)
C1 N1 C5 C4 -0.8(2)
Rh1 C18 C17 C16 38.02(16)
C21 C20 C19 Rh1 15.09(16)
Rh1 C18 C19 C20 -103.63(14)
C21 C20 C19 C18 96.82(18)
Rh1 C15 C22 C21 101.91(15)
C19 C20 C21 C22 -36.70(19)
Rh1 C15 C16 C17 11.92(17)
C19 C18 C17 C16 -42.5(2)
Rh1 C22 C21 C20 40.70(17)
C5 N1 C1 C2 0.2(2)
P1 C6 C5 N1 -34.59(17)
C5 C4 C3 C2 0.1(2)
P1 C6 C5 C4 144.82(13)
C7 P1 C11 C14 -166.19(12)
N1 C1 C2 C3 0.5(2)
C7 P1 C11 C13 76.12(13)
C11 P1 C6 C5 169.55(11)
C7 P1 C11 C12 -47.22(14)
C11 P1 C7 C9 72.21(14)
C7 P1 C6 C5 -73.15(12)
C11 P1 C7 C10 -51.18(13)
O1 S1 C23 F1 58.35(14)
C11 P1 C7 C8 -168.07(12)
O1 S1 C23 F2 -60.68(16)
C15 C22 C21 C20 -40.4(2)
O1 S1 C23 F3 178.44(12)
C15 C16 C17 C18 -34.1(2)
O2 S1 C23 F1 -61.26(15)
C22 C15 C16 C17 93.60(18)
O2 S1 C23 F2 179.72(15)
162
C16 C15 C22 Rh1 -105.52(14)
O2 S1 C23 F3 58.83(15)
C16 C15 C22 C21 -3.6(2)
O3 S1 C23 F1 178.28(14)
C6 P1 C11 C14 -53.83(13)
O3 S1 C23 F2 59.26(17)
C6 P1 C11 C13 -171.52(12)
O3 S1 C23 F3 -61.63(15)
C6 P1 C11 C12 65.15(13)
Hydrogen Atom Coordinates (Å×10
4
) and Isotropic Displacement Parameters (Å
2
×10
3
) for 2.11-
Rh
Atom x y z U(eq)
H20A 3043.08 11555.22 6727.33 20
H20B 4796.73 12298.31 6974.34 20
H9A 9640.48 7325.53 9048.45 37
H9B 8672.09 6247.5 8009.71 37
H9C 8149.73 6303.77 8997.69 37
H14A 3198.11 4631.72 7243.48 35
H14B 2506.8 6015.17 7251.62 35
H14C 2108.97 5267.39 7981.12 35
H10A 7093.25 8374.8 9957.28 33
H10B 6791.08 9591.68 9542.82 33
H10C 8521.38 9430.14 9966.86 33
H18 3752.17 8521.48 4983.52 15
H15 2209.26 8381.24 7689.44 16
H13A 4665.29 8111.54 9734.43 29
H13B 3135.74 7048.21 9558.71 29
H13C 3154.78 8052.44 8944.49 29
H22 4226.68 9922.38 8668.31 16
H16A 1346.43 10295.45 6865.33 21
H16B 393.64 8785.36 6601.99 21
H6A 6494.2 5084.45 7032.86 16
163
H6B 4800.25 5063.21 6427.71 16
H17A 1327.22 7829.82 5250.79 20
H17B 1250.82 9365.2 5242.9 20
H4 7839.15 4591.77 5679.7 20
H3 8944.13 5449.37 4629 21
H8A 9363.03 9332.75 8512.38 36
H8B 7698.2 9514.69 7992.6 36
H8C 8510.34 8233.02 7451.81 36
H1 6481.73 8616.77 5272.94 16
H21A 5457.16 11777.13 8346.16 21
H21B 3725.29 12072.46 8375.85 21
H12A 5610.2 4777.72 8402.5 38
H12B 4438.5 4932.79 9122.26 38
H12C 6007.85 6011.57 9453.59 38
H2 8262.7 7504.56 4441.91 19
H19 5446.48 10347.33 5972.27 16
164
5.5.2 X-ray Crystal Structure Data for 3.1-H
Figure 5.5.2.1. Molecular structure of 3.1-H shown with 50% probability ellipsoids. Hydrogen
atoms and counteranions are omitted for clarity, except hydrides.
A single clear bright yellow block-shaped crystal of C45H78Cl2F6Ir3N3O6P3S2
[Ir3H7][OTf]2-processed with approximate dimensions 0.35 x 0.14 x 0.07 mm
3
, was mounted on
a Rigaku XtaLAB Synergy, Dualflex, Hypix diffractometer from microfocus sealed tube for X-ray
crystallographic collection. The crystal was kept at a steady T = 160.15 K during data collection.
The structure was solved using SHELXT structure solution program using Intrinsic Phasing and
refined on SHELXL refinement package using Least Squares minimisation.
4-7
All non-hydrogen
atoms were refined anisotropically.
Crystal Data for C45H78Cl2F6Ir3N3O6P3S2, M =1675.63 g/mol, orthorhombic, Pbca (no.
61), a = 19.1876(2) Å, b = 20.3309(2) Å, c = 31.4163(3) Å, V = 12255.5(2) Å
3
, Z = 8, T = 160.15
K, μ(MoKα) = 6.794 mm
-1
, Dcalc = 1.816 g/cm
3
, 351608 reflections measured (4.694° ≤ 2Θ ≤
165
66.54°), 22209 unique (Rint = 0.0681, Rsigma = 0.0305) which were used in all calculations. The
final R1 was 0.0255 (I > 2σ(I)) and wR2 was 0.0520 (all data).
Sample and crystal data for 3.1-H
Identification code [Ir3H7][OTf]2-
processed
Chemical formula C45H78Cl2F6Ir3N3O6P3S2
Formula weight 1675.63 g/mol
Temperature 160.15
Wavelength MoKα (λ = 0.71073) Å
Crystal size 0.35 × 0.14 × 0.07 mm
Crystal system orthorhombic
Space group Pbca
Unit cell dimensions a = 19.1876(2) Å α = 90°
b = 20.3309(2) Å β = 90°
c = 31.4163(3) Å γ = 90°
Volume 12255.5(2) Å
3
Z 8
Density (calculated) 1.816 g/cm
3
Absorption coefficient 6.794 mm
-1
F(000) 6504.0
Data collection and structure refinement for 3.1-H
Diffractometer XtaLAB Synergy, Dualflex,
HyPix
Radiation source MoKα , λ = 0.71073 Å
Theta range for data
collection
4.694 to 66.54°
Index ranges -27 ≤ h ≤ 28, -31 ≤ k ≤ 30, -48 ≤ l
166
≤ 48
Reflections collected 351608
Independent reflections 22209 [Rint = 0.0681, RSigma =
0.0305]
Coverage of independent
reflections
99.9%
Absorption correction multi-scan
Max. and min.
transmission
0.332 and 0.622
Structure solution
technique
direct methods
Structure solution
program
SHELXTL XT 2014/5 (Bruker
AXS, 2014)
Refinement method Full-matrix least-squares on F
2
Refinement program SHELXTL XL 2018/3 (Bruker
AXS, 2018)
Function minimized Σ w(Fo
2
- Fc
2
)
2
Data / restraints /
parameters
22209/0/673
Goodness-of-fit on F
2
1.031
Δ/σmax 0.006
Final R indices I>2σ(I) R1 = 0.0255, wR2
= 0.0488
all data R1 = 0.0379, wR2
= 0.0520
Weighting scheme w=1/[σ
2
(Fo
2
)+(0.0107P)
2
+38.6583P]
where P=(Fo
2
+2Fc
2
)/3
Largest diff. peak and
hole
1.58/-1.02 eÅ
-3
R.M.S. deviation from 0.166 eÅ
-3
167
mean
Fractional Atomic Coordinates (×10
4
) and Equivalent Isotropic Displacement Parameters (Å
2
×10
3
)
for 3.1-H. Ueq is defined as 1/3 of the trace of the orthogonalised U IJ tensor.
Atom x y z U(eq)
Ir1 5284.6(2) 8815.5(2) 6608.2(2) 9.26(2)
Ir2 5398.4(2) 7551.2(2) 6316.5(2) 9.85(2)
Ir3 6545.1(2) 8204.6(2) 6611.6(2) 9.64(2)
S008 5222.3(4) 7216.9(3) 8046.7(2) 19.99(13)
P1 4772.7(3) 9742.5(3) 6380.8(2) 10.96(11)
P2 5155.3(3) 6912.0(3) 5752.0(2) 11.71(11)
P3 7642.2(3) 8431.4(3) 6411.1(2) 12.19(11)
F1 5900(2) 7230.1(14) 8769.0(9) 80.3(11)
F2 6385.5(14) 7783.3(15) 8270.2(12) 75.8(10)
F3 5492.3(15) 8168.8(11) 8587.0(8) 52.4(7)
O1 5171.7(18) 7703.2(12) 7718.1(9) 49.4(8)
O2 5612.5(13) 6636.5(10) 7933.1(8) 29.6(5)
O3 4593.8(13) 7085.1(13) 8277.4(12) 51.4(8)
N1 5542.3(11) 9419.7(10) 7132.5(7) 12.6(4)
N2 4368.8(11) 7292.9(10) 6484.3(7) 12.9(4)
N3 7014.1(11) 7344.1(10) 6847.3(7) 13.1(4)
C1 5735.1(15) 9156.1(12) 7509.6(8) 16.5(5)
C2 5916.3(16) 9540.0(14) 7855.5(9) 20.3(5)
C3 5893.7(16) 10221.4(14) 7817.6(9) 21.3(5)
C4 5683.0(14) 10494.9(13) 7434.1(9) 17.3(5)
C5 5511.5(13) 10086.4(12) 7093.9(8) 13.9(4)
C6 5286.7(14) 10361.2(12) 6670.4(8) 14.7(5)
C7 4903.4(14) 9946.5(12) 5806.9(8) 15.3(5)
C8 4840.5(16) 10691.2(14) 5715.0(9) 22.5(6)
168
C9 5649.2(14) 9731.5(13) 5688.2(8) 17.6(5)
C10 4383.2(15) 9558.7(14) 5538.0(8) 20.3(5)
C11 3843.6(13) 9868.7(12) 6549.4(8) 14.6(5)
C12 3851.4(15) 9916.4(14) 7041.0(8) 18.2(5)
C13 3515.4(15) 10506.0(13) 6377.9(9) 19.2(5)
C14 3386.7(14) 9275.5(14) 6421.6(10) 20.8(5)
C15 4142.0(15) 7348.4(12) 6892.0(9) 17.0(5)
C16 3478.4(16) 7160.2(14) 7010.6(10) 23.4(6)
C17 3026.1(16) 6904.8(15) 6710.8(11) 27.4(6)
C18 3254.1(15) 6842.3(15) 6294.8(10) 23.2(6)
C19 3930.5(14) 7040.4(12) 6187.9(9) 15.6(5)
C20 4200.2(13) 6980.5(13) 5741.0(8) 14.9(5)
C21 5439.4(14) 7211.3(13) 5214.6(8) 16.5(5)
C22 4967.4(17) 6958.3(16) 4851.0(9) 25.3(6)
C23 5382.3(16) 7968.3(13) 5218.6(9) 20.3(5)
C24 6198.4(15) 7015.2(14) 5130.5(10) 23.1(6)
C25 5345.3(14) 6012.4(12) 5822.7(9) 16.2(5)
C26 5152.2(16) 5597.2(13) 5427.4(10) 22.7(6)
C27 6116.9(15) 5901.3(14) 5931.8(10) 22.9(6)
C28 4897.9(16) 5765.1(13) 6199.6(10) 21.6(6)
C29 6682.5(14) 6969.1(12) 7139.0(8) 15.6(5)
C30 6970.1(14) 6396.4(13) 7299.9(9) 19.0(5)
C31 7625.3(15) 6203.0(13) 7161.3(10) 20.4(5)
C32 7975.9(14) 6592.6(12) 6868.2(9) 17.3(5)
C33 7660.2(13) 7165.0(12) 6715.7(8) 13.4(4)
C34 8020.9(13) 7599.6(12) 6395.1(9) 15.8(5)
C35 8182.7(15) 8893.0(13) 6809.9(9) 18.8(5)
C36 8926.2(16) 9038.2(16) 6657.8(11) 28.3(7)
C37 7821.0(18) 9543.1(14) 6935.3(10) 25.6(6)
C38 8240.9(16) 8453.0(14) 7210.1(9) 21.9(6)
169
C39 7761.2(14) 8760.9(13) 5859.4(8) 16.4(5)
C40 8494.9(16) 8643.7(16) 5677.9(11) 26.6(6)
C41 7241.3(16) 8405.6(15) 5568.5(9) 22.4(6)
C42 7581.9(15) 9497.8(13) 5854.3(9) 20.6(5)
C43 5776(2) 7618.2(17) 8440.0(12) 35.0(8)
Cl 8212.6(7) 6856.3(6) 5006.2(5) 67.3(4)
Cl1 8075.6(6) 6147.3(5) 5814.5(3) 46.1(2)
C45 8041(2) 6098(2) 5251.3(14) 43.0(9)
S 8038.5(3) 9956.9(3) 4590.9(2) 16.94(12)
F4 8262.0(12) 10233.0(13) 3784.3(6) 44.7(6)
F5 8090.4(12) 11082.8(10) 4181.8(8) 43.4(6)
F6 9071.9(10) 10567.9(10) 4207.4(7) 35.2(5)
O4 7293.1(11) 10008.8(11) 4541.3(7) 25.4(4)
O5 8311.8(12) 10257.8(12) 4970.7(7) 27.7(5)
O6 8327.1(12) 9321.8(11) 4490.3(8) 31.3(5)
C44 8386.4(17) 10488.3(16) 4170.8(10) 27.3(6)
Anisotropic Displacement Parameters (Å
2
×10
3
) for 3.1-H. The Anisotropic displacement factor
exponent takes the form:-2π
2
[h
2
a*
2
U11+2hka*b*U12+…].
Atom U11 U22 U33 U23 U13 U12
Ir1 11.09(4) 8.00(4) 8.67(4) -0.03(3) -0.68(3) 0.62(3)
Ir2 10.39(4) 8.75(4) 10.42(4) -1.26(3) -0.78(3) 0.00(3)
Ir3 10.14(4) 8.68(4) 10.10(4) -0.11(3) -1.06(3) 0.11(3)
S008 20.4(3) 14.3(3) 25.3(3) 3.9(2) -2.3(3) -2.5(2)
P1 12.5(3) 10.0(3) 10.4(3) 0.8(2) 0.0(2) 1.6(2)
P2 10.5(3) 11.4(3) 13.3(3) -3.3(2) -0.2(2) -0.1(2)
P3 11.3(3) 9.6(3) 15.7(3) 0.6(2) -1.4(2) -0.7(2)
F1 145(3) 48.7(15) 47.6(16) -0.5(12) -53.1(19) 21.7(18)
170
F2 27.9(13) 73.6(19) 126(3) -27.8(2) -14.5(16) -14.5(1)
F3 72.7(18) 29.9(11) 54.7(15) -18.5(1) -17.0(13) 10.9(11)
O1 89(2) 21.9(12) 37.1(15) 11.8(1) -31.0(15) -12.7(1)
O2 34.5(13) 20.3(10) 33.9(13) -1.5(9) 11.8(10) -0.8(9)
O3 23.0(12) 31.5(13) 100(3) -4.6(15) 23.8(15) -3.2(10)
N1 13.5(10) 11.1(9) 13.2(9) -0.8(7) 0.0(8) 0.0(7)
N2 13.7(10) 9.4(9) 15.6(10) -1.6(7) 0.8(8) -0.8(7)
N3 13.2(10) 12.5(9) 13.6(10) 0.0(7) -2.0(8) -1.0(7)
C1 22.5(13) 13.9(11) 13.2(11) 1.9(9) -2.1(10) 0.3(9)
C2 25.5(14) 22.3(13) 13.0(12) -0.9(10) -2.6(10) -1.6(10)
C3 25.0(14) 22.2(13) 16.6(12) -6.9(10) -1.4(11) -3.7(11)
C4 19.1(12) 14.5(11) 18.4(12) -3.9(9) -1.2(10) -1.7(9)
C5 13.2(11) 12.6(11) 15.8(11) -2.1(9) 1.9(9) 1.3(8)
C6 19.1(12) 9.2(10) 15.9(11) 0.8(8) -0.3(9) -1.2(8)
C7 17.8(12) 16.1(11) 12.2(11) 4.0(9) 1.5(9) 5.4(9)
C8 28.8(15) 21.3(13) 17.5(13) 7.4(10) 3.5(11) 8.4(11)
C9 18.3(12) 20.1(12) 14.5(11) 4.6(9) 3.5(10) 4.8(10)
C10 20.7(13) 29.1(14) 11.1(11) -1.4(10) -1.5(10) 7.7(11)
C11 12.9(11) 14.0(11) 17.0(12) 1.4(9) 1.0(9) 2.2(8)
C12 18.8(13) 20.9(12) 15.1(12) 0.0(10) 4.8(10) 2.9(10)
C13 19.5(13) 18.7(12) 19.5(13) 1.0(10) 1.3(10) 7.6(10)
C14 14.4(12) 20.7(13) 27.4(15) -0.9(11) -0.7(10) -1.6(10)
C15 20.9(13) 13.9(11) 16.3(12) -1.5(9) 3.5(10) -2.5(9)
C16 23.9(14) 22.6(13) 23.8(14) -6.1(11) 9.9(11) -6.2(11)
C17 19.7(14) 28.2(15) 34.2(17) -9.1(13) 9.8(12) -7.1(11)
C18 14.2(12) 27.9(14) 27.5(15) -9.1(12) 3.4(11) -4.4(10)
C19 14.3(11) 13.4(11) 19.3(12) -4.0(9) 2.5(9) 0.1(9)
C20 11.8(11) 17.0(11) 16.0(12) -4.5(9) -2.1(9) -0.3(9)
C21 17.5(12) 17.5(11) 14.6(11) -4.2(9) -0.2(9) -0.8(9)
C22 28.9(15) 30.4(15) 16.6(13) -5.9(11) -2.1(11) -4.6(12)
171
C23 27.8(14) 17.4(12) 15.8(12) -0.5(9) -1.5(11) 0.3(10)
C24 20.2(13) 23.3(13) 25.7(14) -4.7(11) 7.3(11) -3.8(11)
C25 16.9(12) 12.0(11) 19.5(12) -4.5(9) 2.0(10) 0.5(9)
C26 21.7(13) 16.6(12) 29.7(15) -11.0(1) 5.5(12) -2.6(10)
C27 19.4(13) 17.3(12) 32.1(16) -1.8(11) 1.1(11) 6.0(10)
C28 25.9(14) 13.1(12) 25.9(14) 0.9(10) 4.2(11) 0.4 (10)
C29 14.9(11) 15.1(11) 16.8(12) 2.8(9) -1.6(9) -1.1(9)
C30 17.1(12) 15.9(12) 24.0(14) 5.4(10) -2.3(10) -1.4(9)
C31 21.2(13) 11.4(11) 28.6(14) 3.3(10) -5.9(11) 1.5(9)
C32 14.9(12) 11.9(11) 25.1(13) -1.7(9) -3.5(10) 1.8(9)
C33 13.8(11) 9.0(10) 17.3(11) -0.6(8) -3.2(9) -0.5(8)
C34 13.4(11) 12.7(11) 21.5(13) 0.8(9) 3.0(9) 2.0(8)
C35 20.0(13) 13.6(11) 22.7(13) -0.6(10) -9.1(10) -3.2(9)
C36 21.3(14) 26.1(15) 37.3(18) 7.3(13) -10.2(13) -10.2(1)
C37 34.1(17) 15.5(12) 27.0(15) -4.5(11) -9.3(13) -2.3(11)
C38 23.1(14) 19.4(13) 23.1(14) 2.2(10) -10.4(11) -3.0(10)
C39 15.2(12) 17.2(12) 16.6(12) 2.9(9) 1.9(9) -2.1(9)
C40 17.6(13) 32.6(16) 29.5(16) 6.2(12) 7.0(12) 1.5(11)
C41 23.3(14) 27.0(14) 16.9(13) 1.0(10) 0.9(11) -5.2(11)
C42 20.4(13) 16.2(12) 25.2(14) 8.1(10) 0.5(11) -2.2(10)
C43 42(2) 29.9(17) 33.0(18) -4.6(13) -15.1(15) 6.5(14)
Cl 67.1(8) 48.8(6) 86.0(9) 1.8(6) 31.6(7) -10.8(6)
Cl1 53.7(6) 34.7(5) 50.0(6) -18.8(4) -7.3(5) 8.8(4)
C45 45(2) 35(2) 49(2) -15.6(2) 3.6(19) -3.5(17)
S 13.1(3) 20.5(3) 17.2(3) -2.5(2) -2.2(2) 3.3(2)
F4 37.0(12) 79.3(17) 17.7(9) 2.7(10) 3.8(8) 9.7(11)
F5 39.7(12) 34.1(11) 56.3(14) 21.4(10) 2.9(11) 12.3(9)
F6 19.9(9) 41.5(11) 44.0(12) 13.1(9) 4.2(8) 0.6(8)
O4 13.7(9) 36.8(12) 25.6(11) -3.9(9) -2.7(8) 4.0(8)
O5 25.8(11) 39.8(13) 17.3(10) -3.9(9) -4.5(8) -5.8(9)
172
Bond Lengths for 3.1-H
O6 25.1(11) 22.7(11) 46.2(15) -3.8(10) 5.7(10) 6.7(9)
C44 22.1(15) 33.7(16) 26.0(15) 6.7(12) 0.2(12) 8.0
Atom Atom Length/Å Atom Atom Length/Å
Ir1 Ir2 2.73764(12) C7 C9 1.542(4)
Ir1 Ir3 2.71881(13) C7 C10 1.527(4)
Ir1 P1 2.2421(6) C11 C12 1.548(4)
Ir1 N1 2.113(2) C11 C13 1.538(4)
Ir2 Ir3 2.73222(13) C11 C14 1.544(4)
Ir2 P2 2.2474(6) C15 C16 1.381(4)
Ir2 N2 2.111(2) C16 C17 1.382(4)
Ir3 P3 2.2452(7) C17 C18 1.384(4)
Ir3 N3 2.102(2) C18 C19 1.400(4)
S008 O1 1.433(2) C19 C20 1.501(4)
S008 O2 1.442(2) C21 C22 1.546(4)
S008 O3 1.432(3) C21 C23 1.543(4)
S008 C43 1.822(4) C21 C24 1.533(4)
P1 C6 1.839(3) C25 C26 1.547(4)
P1 C7 1.867(3) C25 C27 1.536(4)
P1 C11 1.877(3) C25 C28 1.547(4)
P2 C20 1.838(3) C29 C30 1.384(4)
P2 C21 1.876(3) C30 C31 1.387(4)
P2 C25 1.878(3) C31 C32 1.389(4)
P3 C34 1.841(3) C32 C33 1.397(3)
P3 C35 1.878(3) C33 C34 1.508(4)
P3 C39 1.872(3) C35 C36 1.533(4)
F1 C43 1.322(4) C35 C37 1.544(4)
F2 C43 1.329(5) C35 C38 1.547(4)
F3 C43 1.328(4) C39 C40 1.538(4)
173
Bond Angles for 3.1-H
N1 C1 1.352(3) C39 C41 1.534(4)
N1 C5 1.362(3) C39 C42 1.537(4)
N2 C15 1.357(3) Cl C45 1.753(5)
N2 C19 1.356(3) Cl1 C45 1.773(5)
N3 C29 1.351(3) S O4 1.443(2)
N3 C33 1.357(3) S O5 1.440(2)
C1 C2 1.382(4) S O6 1.440(2)
C2 C3 1.391(4) S C44 1.832(3)
C3 C4 1.387(4) F4 C44 1.342(4)
C4 C5 1.393(4) F5 C44 1.336(4)
C5 C6 1.506(4) F6 C44 1.330(4)
C7 C8 1.546(4)
Atom Atom Atom Angle/˚ Atom Atom Atom Angle/˚
Ir3 Ir1 Ir2 60.096(3) C12 C11 P1 106.32(18)
P1 Ir1 Ir2 135.854(17) C13 C11 P1 113.90(18)
P1 Ir1 Ir3 140.799(17) C13 C11 C12 107.5(2)
N1 Ir1 Ir2 142.00(6) C13 C11 C14 109.5(2)
N1 Ir1 Ir3 93.11(6) C14 C11 P1 111.04(18)
N1 Ir1 P1 82.08(6) C14 C11 C12 108.3(2)
Ir3 Ir2 Ir1 59.610(3) N2 C15 C16 121.8(3)
P2 Ir2 Ir1 142.229(17) C15 C16 C17 120.0(3)
P2 Ir2 Ir3 135.733(17) C16 C17 C18 118.7(3)
N2 Ir2 Ir1 94.31(5) C17 C18 C19 119.6(3)
N2 Ir2 Ir3 142.16(6) N2 C19 C18 121.3(3)
N2 Ir2 P2 81.90(6) N2 C19 C20 117.3(2)
Ir1 Ir3 Ir2 60.294(3) C18 C19 C20 121.4(2)
P3 Ir3 Ir1 137.654(16) C19 C20 P2 109.40(18)
P3 Ir3 Ir2 139.432(17) C22 C21 P2 112.77(19)
174
N3 Ir3 Ir1 139.68(6) C23 C21 P2 107.20(18)
N3 Ir3 Ir2 93.42(6) C23 C21 C22 107.2(2)
N3 Ir3 P3 82.43(6) C24 C21 P2 110.3(2)
O1 S008 O2 114.92(17) C24 C21 C22 110.0(2)
O1 S008 C43 102.67(16) C24 C21 C23 109.2(2)
O2 S008 C43 103.38(16) C26 C25 P2 113.0(2)
O3 S008 O1 115.9(2) C27 C25 P2 110.89(18)
O3 S008 O2 114.15(15) C27 C25 C26 109.3(2)
O3 S008 C43 103.4(2) C27 C25 C28 108.4(2)
C6 P1 Ir1 100.51(8) C28 C25 P2 107.42(17)
C6 P1 C7 104.70(12) C28 C25 C26 107.7(2)
C6 P1 C11 106.03(12) N3 C29 C30 122.3(3)
C7 P1 Ir1 115.82(8) C29 C30 C31 119.0(3)
C7 P1 C11 111.69(12) C30 C31 C32 119.0(2)
C11 P1 Ir1 116.17(8) C31 C32 C33 119.5(3)
C20 P2 Ir2 100.26(8) N3 C33 C32 121.0(2)
C20 P2 C21 104.37(12) N3 C33 C34 117.8(2)
C20 P2 C25 105.64(12) C32 C33 C34 121.2(2)
C21 P2 Ir2 117.54(8) C33 C34 P3 109.80(17)
C21 P2 C25 111.47(12) C36 C35 P3 113.7(2)
C25 P2 Ir2 115.43(9) C36 C35 C37 109.4(2)
C34 P3 Ir3 100.89(9) C36 C35 C38 107.3(2)
C34 P3 C35 105.03(12) C37 C35 P3 110.48(19)
C34 P3 C39 104.78(12) C37 C35 C38 108.7(2)
C35 P3 Ir3 115.68(10) C38 C35 P3 107.05(18)
C39 P3 Ir3 116.59(9) C40 C39 P3 113.6(2)
C39 P3 C35 111.82(12) C41 C39 P3 107.69(18)
C1 N1 Ir1 121.11(17) C41 C39 C40 107.6(2)
C1 N1 C5 119.0(2) C41 C39 C42 107.9(2)
C5 N1 Ir1 119.93(17) C42 C39 P3 109.33(19)
175
Torsion Angles of 3.1-H
C15 N2 Ir2 121.00(18) C42 C39 C40 110.6(2)
C19 N2 Ir2 120.20(17) F1 C43 S008 111.6(3)
C19 N2 C15 118.7(2) F1 C43 F2 107.8(4)
C29 N3 Ir3 120.45(17) F1 C43 F3 107.8(3)
C29 N3 C33 119.0(2) F2 C43 S008 110.7(3)
C33 N3 Ir3 120.49(17) F3 C43 S008 112.0(3)
N1 C1 C2 122.3(2) F3 C43 F2 106.7(3)
C1 C2 C3 119.1(3) Cl C45 Cl1 112.5(2)
C4 C3 C2 118.9(2) O4 S C44 103.90(14)
C3 C4 C5 119.8(2) O5 S O4 114.81(13)
N1 C5 C4 121.0(2) O5 S O6 115.02(15)
N1 C5 C6 117.4(2) O5 S C44 102.34(15)
C4 C5 C6 121.6(2) O6 S O4 115.03(14)
C5 C6 P1 109.69(17) O6 S C44 103.33(15)
C8 C7 P1 112.79(18) F4 C44 S 111.0(2)
C9 C7 P1 107.17(17) F5 C44 S 111.1(2)
C9 C7 C8 107.8(2) F5 C44 F4 107.3(3)
C10 C7 P1 109.37(18) F6 C44 S 111.7(2)
C10 C7 C8 110.6(2) F6 C44 F4 107.5(3)
C10 C7 C9 109.1(2) F6 C44 F5 107.9(3)
A B C D Angle/˚
Ir1 P1 C6 C5 -32.57(18)
Ir1 P1 C7 C8 -154.36(17)
Ir1 P1 C7 C9 -35.9(2)
Ir1 P1 C7 C10 82.15(18)
Ir1 P1 C11 C12 62.83(18)
Ir1 P1 C11 C13 -178.97(16)
176
Ir1 P1 C11 C14 -54.8(2)
Ir1 N1 C1 C2 179.0(2)
Ir1 N1 C5 C4 -179.60(19)
Ir1 N1 C5 C6 0.3(3)
Ir2 P2 C20 C19 -33.68(18)
Ir2 P2 C21 C22 -151.45(17)
Ir2 P2 C21 C23 -33.7(2)
Ir2 P2 C21 C24 85.09(18)
Ir2 P2 C25 C26 178.74(16)
Ir2 P2 C25 C27 -58.2(2)
Ir2 P2 C25 C28 60.1(2)
Ir2 N2 C15 C16 -177.7(2)
Ir2 N2 C19 C18 177.6(2)
Ir2 N2 C19 C20 -2.3(3)
Ir3 P3 C34 C33 -29.76(19)
Ir3 P3 C35 C36 -179.79(17)
Ir3 P3 C35 C37 -56.3(2)
Ir3 P3 C35 C38 61.9(2)
Ir3 P3 C39 C40 -156.52(18)
Ir3 P3 C39 C41 -37.6(2)
Ir3 P3 C39 C42 79.43(19)
Ir3 N3 C29 C30 179.5(2)
Ir3 N3 C33 C32 -179.67(19)
Ir3 N3 C33 C34 -0.5(3)
O1 S008 C43 F1 -178.3(3)
O1 S008 C43 F2 -58.1(3)
O1 S008 C43 F3 60.8(3)
O2 S008 C43 F1 -58.5(3)
O2 S008 C43 F2 61.7(3)
O2 S008 C43 F3 -179.4(3)
177
O3 S008 C43 F1 60.8(3)
O3 S008 C43 F2 -179.0(3)
O3 S008 C43 F3 -60.1(3)
N1 C1 C2 C3 0.7(4)
N1 C5 C6 P1 23.2(3)
N2 C15 C16 C17 0.3(4)
N2 C19 C20 P2 25.7(3)
N3 C29 C30 C31 0.8(4)
N3 C33 C34 P3 21.8(3)
C1 N1 C5 C4 0.8(4)
C1 N1 C5 C6 -179.3(2)
C1 C2 C3 C4 0.6(4)
C2 C3 C4 C5 -1.2(4)
C3 C4 C5 N1 0.5(4)
C3 C4 C5 C6 -179.4(3)
C4 C5 C6 P1 -156.9(2)
C5 N1 C1 C2 -1.4(4)
C6 P1 C7 C8 -44.7(2)
C6 P1 C7 C9 73.72(19)
C6 P1 C7 C10 -168.18(18)
C6 P1 C11 C12 -47.82(19)
C6 P1 C11 C13 70.4(2)
C6 P1 C11 C14 -165.41(18)
C7 P1 C6 C5 -153.01(18)
C7 P1 C11 C12 -161.31(17)
C7 P1 C11 C13 -43.1(2)
C7 P1 C11 C14 81.1(2)
C11 P1 C6 C5 88.76(19)
C11 P1 C7 C8 69.6(2)
C11 P1 C7 C9 -171.97(17)
178
C11 P1 C7 C10 -53.9(2)
C15 N2 C19 C18 0.4(4)
C15 N2 C19 C20 -179.5(2)
C15 C16 C17 C18 0.2(5)
C16 C17 C18 C19 -0.3(5)
C17 C18 C19 N2 0.0(4)
C17 C18 C19 C20 179.9(3)
C18 C19 C20 P2 -154.2(2)
C19 N2 C15 C16 -0.5(4)
C20 P2 C21 C22 -41.5(2)
C20 P2 C21 C23 76.3(2)
C20 P2 C21 C24 -164.98(18)
C20 P2 C25 C26 69.0(2)
C20 P2 C25 C27 -167.97(19)
C20 P2 C25 C28 -49.6(2)
C21 P2 C20 C19 -155.78(17)
C21 P2 C25 C26 -43.8(2)
C21 P2 C25 C27 79.3(2)
C21 P2 C25 C28 -162.41(18)
C25 P2 C20 C19 86.58(19)
C25 P2 C21 C22 72.0(2)
C25 P2 C21 C23 -170.16(18)
C25 P2 C21 C24 -51.4(2)
C29 N3 C33 C32 1.8(4)
C29 N3 C33 C34 -179.1(2)
C29 C30 C31 C32 0.6(4)
C30 C31 C32 C33 -0.7(4)
C31 C32 C33 N3 -0.4(4)
C31 C32 C33 C34 -179.6(2)
C32 C33 C34 P3 -159.0(2)
179
Hydrogen Atom Coordinates (Å×104) and Isotropic Displacement Parameters (Å
2
×10
3
) for 3.1-H
C33 N3 C29 C30 -1.9(4)
C34 P3 C35 C36 70.0(2)
C34 P3 C35 C37 -166.5(2)
C34 P3 C35 C38 -48.4(2)
C34 P3 C39 C40 -46.0(2)
C34 P3 C39 C41 73.0(2)
C34 P3 C39 C42 -170.04(19)
C35 P3 C34 C33 90.8(2)
C35 P3 C39 C40 67.2(2)
C35 P3 C39 C41 -173.79(19)
C35 P3 C39 C42 -56.8(2)
C39 P3 C34 C33 -151.23(18)
C39 P3 C35 C36 -43.1(2)
C39 P3 C35 C37 80.4(2)
C39 P3 C35 C38 -161.45(19)
O4 S C44 F4 -68.5(2)
O4 S C44 F5 50.9(3)
O4 S C44 F6 171.5(2)
O5 S C44 F4 171.7(2)
O5 S C44 F5 -68.9(3)
O5 S C44 F6 51.7(3)
O6 S C44 F4 51.9(2)
O6 S C44 F5 171.3(2)
O6 S C44 F6 -68.1(3)
Atom x y z U(eq)
H 5620(20) 8030(20) 6859(14) 43(12)
HA 6260(20) 8890(20) 6440(14) 48(12)
HB 5060(20) 8390(20) 6205(14) 46(12)
180
HC 6180(20) 7700(20) 6175(14) 49(13)
H1 5746.54 8691.02 7537.89 20
H2 6054.52 9341.01 8115.78 24
H3 6020.32 10494.71 8050.32 26
H4 5655.73 10959.07 7403.6 21
H6A 5702 10483.58 6501.06 18
H6B 5002.68 10761.79 6715.11 18
H8A 5156.78 10934.4 5902.71 34
H8B 4360.11 10834.33 5766.56 34
H8C 4964.66 10777.06 5417.59 34
H9A 5985.77 9976.52 5861.15 26
H9B 5733.07 9822.02 5386.1 26
H9C 5702.81 9259.37 5741.86 26
H10A 4514.71 9588.36 5237.23 30
H10B 3915.2 9742.01 5577.13 30
H10C 4385.82 9096.78 5627.21 30
H12A 4086.47 9529.68 7159.57 27
H12B 3371.54 9934.63 7147.3 27
H12C 4100.94 10315.15 7127.57 27
H13A 3821.84 10878.6 6442.14 29
H13B 3061.06 10575.23 6513.16 29
H13C 3454.16 10470.13 6069.07 29
H14A 3355.31 9251.31 6110.65 31
H14B 2918.82 9328.93 6541.8 31
H14C 3596.04 8869.76 6531.24 31
H15 4448.29 7521.48 7101.48 20
H16 3332.8 7206.24 7298.04 28
H17 2567.94 6774.81 6788.63 33
H18 2953.65 6666.05 6083.27 28
H20A 4061.68 7371.91 5573.68 18
181
H20B 3997.53 6586.46 5603.32 18
H22A 4484.22 7089.07 4906.14 38
H22B 4996.8 6477.61 4836.18 38
H22C 5122.13 7147.78 4580.19 38
H23A 4896.19 8096.13 5266.65 31
H23B 5540.19 8143.39 4944.4 31
H23C 5674.31 8146.11 5447.16 31
H24A 6368.05 7242.97 4875.85 35
H24B 6226.26 6538.74 5086.28 35
H24C 6486.18 7138.43 5375.55 35
H26A 4670.26 5691.77 5344.15 34
H26B 5197.86 5128.84 5495.61 34
H26C 5466.04 5707.99 5191.99 34
H27A 6405.88 6020.59 5686.47 34
H27B 6191.79 5437.17 6002.45 34
H27C 6245.23 6175.4 6176.19 34
H28A 4989.83 6037.23 6450.9 32
H28B 5017.08 5306.53 6262.21 32
H28C 4403.13 5795 6124.53 32
H29 6236.24 7103.19 7237.04 19
H30 6722.53 6139.63 7502.21 23
H31 7831.06 5809.6 7265.48 24
H32 8427.27 6470.81 6772.14 21
H34A 7965.87 7411.8 6106.3 19
H34B 8525.04 7622.23 6460.47 19
H36A 9136.6 8634.12 6546.4 42
H36B 9204.53 9201.5 6897.03 42
H36C 8912.55 9371.72 6432.76 42
H37A 7763.47 9818.99 6681.95 38
H37B 8107.21 9775.92 7145.23 38
182
H37C 7362.87 9447.14 7058.4 38
H38A 7774 8316.91 7300.72 33
H38B 8465.64 8700.69 7439.85 33
H38C 8520.09 8062.84 7143.22 33
H40A 8835.99 8894.41 5843.97 40
H40B 8509.4 8787.9 5380.35 40
H40C 8607.09 8174.04 5693.58 40
H41A 7326.58 7930.66 5580.15 34
H41B 7300.02 8560.96 5275.44 34
H41C 6765.15 8498.1 5664.17 34
H42A 7125.19 9565.92 5986.81 31
H42B 7569.44 9655.12 5559.57 31
H42C 7936.89 9742.19 6013.38 31
H45A 8370(20) 5780(20) 5152(15) 52(13)
H45B 7540(40) 5990(30) 5180(20) 110(20)
183
5.5.3 Neutron Difrraction Crystallographic Data of 3.1-H
Figure 5.5.3.1. Neutron molecular structure of 3.1-H shown with 50% probability ellipsoids.
Hydrogen atoms and counteranions are omitted for clarity, except hydrides.
Neutron diffraction data for 3 were measured on the TOPAZ single-crystal time-of-flight
Laue diffractometer at the Spallation Neutron Source (SNS), Oak Ridge National Laboratory.
5
A
plate-shaped crystal of 1, with dimensions of 0.30 x 0.75 x 1.95 mm was mounted on the tip of a
MiTeGen loop using fluorinated grease and transferred to the TOPAZ goniometer for data
collection at 100 K. To ensure good coverage and redundancy, data were collected using 19 crystal
orientations optimized with CrystalPlan software with better than 99% coverage of symmetry-
equivalent reflections of the orthorhombic cell.
9
Each orientation was measured for approximately
5-6 hrs with 25 - 30 C of proton charge at the beam power of 1.4 MW. The integrated raw Bragg
intensities were obtained using the 3-D ellipsoidal Q-space integration in accordance with
previously reported methods.
10
Data reduction, including neutron TOF spectrum, Lorentz, and
184
detector efficiency corrections, was carried out with the ANVRED3 program.
11
Gaussian
numerical absorption correction was applied with µ = 0.13253 +0.14700 mm
−1
. The reduced data
were saved as SHELX HKLF2 format, in which the wavelength is recorded separately for each
reflection, and data were not merged. Starting with the X-ray structure at 100 K as an input model,
the neutron crystal structure was refined using the SHELXL2018/3 program.
12
Owing to the
negative neutron scattering length for hydrogen atoms, the nuclear positions dominated by the
seven missing hydrides appear as strong negative peaks (or holes) of -6.02 to -6.70 fm Å
3
in the
difference Fourier map. The hydrides atoms located from the difference Fourier map were
included in the refinement of the neutron structure. All atoms, including the hydrogen atoms were
refined anisotropically to convergence. The data is deposited in the CCDC as 2235972.
185
5.5.4 X-ray Crystal Structure Data for 3.1-O
Figure 5.5.4.1. Molecular structure of 3.1-O shown with 50% probability ellipsoids. Hydrogen
atoms are omitted for clarity, except hydrides.
A single clear bright yellow block-shaped crystal of C43H78F3Ir3N3O4P3S Ir3 with
approximate dimensions 0.152 × 0.133 × 0.101 mm
3
, was mounted on a Rigaku XtaLAB Synergy,
Dualflex, Hypix diffractometer from microfocus sealed tube for X-ray crystallographic collection.
The crystal was kept at a steady T = 100.15 K during data collection. The structure was solved
using SHELXT structure solution program using Intrinsic Phasing and refined on SHELXL
refinement package using Least Squares minimization on F
2
.
4-7
All non-hydrogen atoms were
refined anisotropically.
Crystal Data for C43H78F3Ir3N3O4P3S, M = 1459.65 g/mol, triclinic, P-3 (no. 147), a =
13.9561(2) Å, b = 13.9561(2) Å, c = 17.1572(2) Å, V = 2894.04(9) Å
3
, Z = 2, T = 100.15 K,
μ(MoKα) = 7.045 mm
-1
, Dcalc = 1.675 g/cm
3
, 74630 reflections measured (4.748° ≤ 2Θ ≤ 59.15°),
186
5428 unique (Rint = 0.0435, Rsigma = 0.0176) which were used in all calculations. The final R1 was
0.0197 (I > 2σ(I)) and wR2 was 0.0464 (all data).
Identification code Ir3
Chemical formula C43H78F3Ir3N3O4P3S
Formula weight 973.10 g/mol
Temperature 100.01(10)
Wavelength MoKα (λ = 0.71073) Å
Crystal size 0.152 × 0.133 × 0.101 mm
3
Crystal system trigonal
Space group P-3
Unit cell dimensions a = 13.9561(2) Å α = 90°
b = 13.9561(2) Å β = 90°
c = 17.1572(2) Å γ = 120°
Volume 2894.04(9) Å
3
Z 3
Density (calculated) 1.675 g/cm
3
Absorption coefficient 7.045 mm
-1
F(000) 1416.0
187
Data collection and structure refinement for 3.1-O
Diffractometer XtaLAB Synergy,
Dualflex, HyPix
Radiation source MoKα , λ = 0.71073 Å
Theta range for data
collection
4.748 to 59.15 °
Index ranges -19 ≤ h ≤ 19, -19 ≤ k ≤ 19, -
23 ≤ l ≤ 23
Reflections collected 74630
Independent reflections 5428 [Rint = 0.0435, RSigma
= 0.0176]
Coverage of independent
reflections
99.9%
Absorption correction multi-scans
Max. and min.
transmission
0.461 and 0.737
Structure solution
technique
direct methods
Structure solution
program
SHELXTL XT 2014/5
(Bruker AXS, 2014)
Refinement method Full-matrix least-squares
on F
2
Refinement program SHELXTL XL 2018/3
(Bruker AXS, 2018)
Function minimized Σ w(Fo
2
- Fc
2
)
2
Data / restraints /
parameters
5428/0/195
Goodness-of-fit on F
2
1.047
Δ/σmax 0.001
188
Final R indices I>2σ(I) R1 = 0.0197, wR2 =
0.0455
all data R1 = 0.0229, wR2 =
0.0464
Weighting scheme w=1/[σ
2
(Fo
2
)+( 0.0198 P)
2
+
4.6719P]
where P=(Fo
2
+2Fc
2
)/3
Largest diff. peak and
hole
1.61/-0.79 eÅ
-3
R.M.S. deviation from
mean
0.100 eÅ
-3
189
Fractional Atomic Coordinates (×10
4
) and Equivalent Isotropic Displacement Parameters (Å
2
×10
3
)
for 3.1-O. Ueq is defined as 1/3 of the trace of the orthogonalised U IJ tensor.
Atom x y z U(eq)
Ir1 680.5(2) 1353.6(2) 3076.9(2) 15.36(3)
P1 1521.2(6) 2850.9(5) 2313.8(4) 22.37(14)
O1 0 0 3817.4(17) 18.0(6)
N1 2122.3(17) 2219.9(18) 3755.8(12) 18.2(4)
C1 2305(2) 1720(2) 4367.1(14) 20.7(5)
C2 3226(2) 2265(2) 4839.0(15) 24.6(5)
C3 3993(2) 3363(2) 4682.3(16) 26.3(6)
C4 3806(2) 3879(2) 4064.1(16) 23.7(5)
C5 2862(2) 3299(2) 3610.8(14) 19.3(5)
C6 2580(2) 3866(2) 2980.0(15) 25.2(5)
C7 789(3) 3607(2) 1995.3(18) 37.9(8)
C8 -2(3) 3525(3) 2654(2) 45.2(9)
C9 105(3) 3062(3) 1255(2) 45.8(9)
C10 1582(4) 4853(3) 1837(2) 54.3(11)
C11 2340(3) 2745(2) 1477.0(16) 30.8(6)
C12 1576(3) 1713(2) 990.4(16) 28.9(6)
C13 2905(4) 3750(3) 930.4(18) 50.0(10)
C14 3251(2) 2586(3) 1847.8(18) 35.4(7)
S1 6666.67 3333.33 5928.6(7) 21.9(2)
F1 5738.5(15) 2479.3(16) 4581.2(11) 38.1(4)
O2 7756.9(16) 4236.5(16) 6119.6(12) 28.2(4)
C15 6666.67 3333.33 4862(3) 29.4(10)
190
Anisotropic Displacement Parameters (Å
2
×10
3
) for 3.1-O. The Anisotropic displacement factor
exponent takes the form: -2π
2
[h
2
a*2U11+2hka*b*U12+…].
Atom U11 U22 U33 U23 U13 U12
Ir1 16.06(5) 13.56(5) 16.02(5) -0.02(3) -2.89(3) 7.06(4)
P1 30.9(4) 14.2(3) 17.4(3) 0.4(2) -7.9(3) 7.8(3)
O1 19.0(9) 19.0(9) 16.1(14) 0 0 9.5(4)
N1 16.7(10) 19.0(10) 17.0(9) 0.7(8) -2.2(7) 7.6(8)
C1 21.4(12) 20.1(12) 19.5(11) 3.2(9) -1.1(9) 9.5(10)
C2 27.8(13) 29.4(14) 18.9(12) -0.6(10) -7.6(10) 16.0(1)
C3 22.5(13) 29.3(14) 26.5(13) -9.0(11) -9.5(10) 12.5(1)
C4 20.5(12) 19.4(12) 24.4(12) -3.2(10) -2.4(10) 4.9(10)
C5 21.5(12) 20.0(11) 14.4(11) -0.1(9) -1.3(9) 8.9(10)
C6 31.5(14) 15.4(11) 20.2(12) 0.7(9) -7.3(10) 5.4(10)
C7 65(2) 23.4(14) 30.0(15) -3.8(11) -24.6(2) 25.2(2)
C8 68(2) 41.9(19) 48(2) -13.7(2) -28.1(2) 43.8(2)
C9 70(2) 36.6(18) 38.5(18) -9.1(14) -32.1(2) 32.7(2)
C10 98(3) 23.5(15) 40.4(19) -2.4(14) -29(2) 29.6(2)
C11 38.1(16) 19.8(13) 17.3(12) 2.3(10) -0.5(11) 1.6(12)
C12 34.7(15) 21.1(13) 20.4(12) 2.2(10) -1.5(11) 6.0(12)
C13 69(3) 24.6(15) 22.2(14) 4.7(12) 0.7(15) -2.5(16)
C14 25.2(14) 40.1(17) 24.5(14) -0.2(12) 5.4(11) 3.9(13)
S1 18.6(3) 18.6(3) 28.7(5) 0 0 9.28(2)
F1 35.0(10) 35.6(10) 40.0(10) -8.7(8) -10.1(8) 15.0(8)
O2 20.9(9) 22.3(9) 37.8(11) -5.2(8) -2.0(8) 8.2(8)
C15 28.0(15) 28.0(15) 32(3) 0 0 14.0(8)
191
Bond Lengths for 3.1-O
Atom Atom Length/Å Atom Atom Length/Å
Ir1 Ir11 2.83357(16) C4 C5 1.389(3)
Ir1 Ir12 2.83362(16) C5 C6 1.504(3)
Ir1 P1 2.2373(7) C7 C8 1.542(5)
Ir1 O1 2.0713(18) C7 C9 1.542(4)
Ir1 N1 2.106(2) C7 C10 1.549(5)
P1 C6 1.845(3) C11 C12 1.540(4)
P1 C7 1.880(3) C11 C13 1.537(4)
P1 C11 1.886(3) C11 C14 1.534(5)
N1 C1 1.353(3) S1 O2 1.4468(19)
N1 C5 1.357(3) S1 O23 1.4468(19)
C1 C2 1.382(4) S1 O24 1.4468(19)
C2 C3 1.388(4) S1 C15 1.830(5)
C3 C4 1.378(4) F1 C15 1.337(3)
Bond Angles for 3.1-O
Ir1
1
Ir1 Ir1
2
60.0 N1 C5 C6 117.5(2)
P1 Ir1 Ir1
1
132.314(19) C4 C5 C6 121.1(2)
P1 Ir1 Ir1
2
136.728(17) C5 C6 P1 111.19(18)
O1 Ir1 Ir1
2
46.84(5) C8 C7 P1 108.4(2)
O1 Ir1 Ir1
1
46.84(5) C8 C7 C10 107.1(3)
O1 Ir1 P1 176.30(4) C9 C7 P1 109.8(2)
O1 Ir1 N1 93.16(7) C9 C7 C8 108.9(3)
N1 Ir1 Ir1
1
95.68(6) C9 C7 C10 109.1(3)
N1 Ir1 Ir1
2
139.98(6) C10 C7 P1 113.4(3)
N1 Ir1 P1 83.29(6) C12 C11 P1 108.8(2)
192
1
+Y-X, -X, +Z;
2
-Y, +X-Y, +Z;
3
1-Y, +X-Y, +Z;
4
1+Y-X, 1-X, +Z
Torsion Angles for 3.1-O
A B C D Angle/˚ A B C D Angle/˚
Ir1 P1 C6 C5 24.5(2) C6 P1 C7 C10 40.7(3)
Ir1 P1 C7 C8 33.0(2) C6 P1 C11 C12 165.6(2)
Ir1 P1 C7 C9 -85.8(3) C6 P1 C11 C13 -71.0(3)
Ir1 P1 C7 C10 151.8(2) C6 P1 C11 C14 48.5(2)
Ir1 P1 C11 C12 55.2(2) C7 P1 C6 C5 149.9(2)
Ir1 P1 C11 C13 178.6(2) C7 P1 C11 C12 -86.1(2)
C6 P1 Ir1 101.50(8) C13 C11 P1 116.6(2)
C6 P1 C7 101.59(13) C13 C11 C12 108.8(2)
C6 P1 C11 104.35(14) C14 C11 P1 105.90(19)
C7 P1 Ir1 121.05(12) C14 C11 C12 109.0(3)
C7 P1 C11 110.08(15) C14 C11 C13 107.5(3)
C11 P1 Ir1 115.30(9) O2 S1 O2
3
115.03(7)
Ir1
1
O1 Ir1
2
86.32(9) O2
4
S1 O2
3
115.03(7)
Ir1
2
O1 Ir1 86.32(9) O2
4
S1 O2 115.03(7)
Ir1
1
O1 Ir1 86.32(9) O2
3
S1 C15 103.09(10)
C1 N1 Ir1 120.35(17) O2 S1 C15 103.09(10)
C1 N1 C5 118.6(2) O2
4
S1 C15 103.09(10)
C5 N1 Ir1 120.95(16) F1 C15 S1 111.1(2)
N1 C1 C2 122.3(2) F1
3
C15 S1 111.1(2)
C1 C2 C3 119.1(2) F1
4
C15 S1 111.1(2)
C4 C3 C2 118.9(2) F1
3
C15 F1
4
107.8(2)
C3 C4 C5 119.9(2) F1 C15 F1
4
107.8(2)
N1 C5 C4 121.2(2) F1
3
C15 F1 107.8(2)
193
Ir1 P1 C11 C14 -61.9(2) C7 P1 C11 C13 37.3(3)
Ir1 N1 C1 C2 -178.4(2) C7 P1 C11 C14 156.8(2)
Ir1 N1 C5 C4 179.02(19) C11 P1 C6 C5 -95.6(2)
Ir1 N1 C5 C6 3.4(3) C11 P1 C7 C8 171.7(2)
N1 C1 C2 C3 0.0(4) C11 P1 C7 C9 52.9(3)
N1 C5 C6 P1 -19.7(3) C11 P1 C7 C10 -69.5(3)
C1 N1 C5 C4 1.7(4) O2
1
S1 C15 F1
2
54.89(12)
C1 N1 C5 C6 -173.9(2) O2
1
S1 C15 F1
1
174.89(12)
C1 C2 C3 C4 0.6(4) O2 S1 C15 F1
2
-65.11(12)
C2 C3 C4 C5 0.0(4) O2
1
S1 C15 F1 -65.11(12)
C3 C4 C5 N1 -1.2(4) O2 S1 C15 F1 174.89(12)
C3 C4 C5 C6 174.2(3) O2
2
S1 C15 F1 54.89(12)
C4 C5 C6 P1 164.7(2) O2
2
S1 C15 F1
2
174.89(12)
C5 N1 C1 C2 -1.1(4) O2
2
S1 C15 F1
1
-65.11(12)
C6 P1 C7 C8 -78.1(2) O2 S1 C15 F1
1
54.89(12)
C6 P1 C7 C9 163.1(3)
1
1-Y, +X-Y, +Z;
2
1+Y-X, 1-X, +Z
Hydrogen Atom Coordinates (Å×10
4
) and Isotropic Displacement Parameters (Å
2
×10
3
) 3.1-O
Atom x y z U(eq)
H 280(30) 1960(30) 3500(20) 49(11)
HA 1130(40) 400(40) 2520(30) 73(15)
H1 1782.05 968.35 4475.72 25
H2 3333.3 1893.32 5264.76 30
H3 4635.65 3752.59 4996.02 32
194
Solvent Masks Information for 3.1-O
Number X Y Z Volume Electron count Content
1 0.453 -0.443 0 582.0 107.5 6CH3OH
H4 4322.39 4630.55 3948.08 28
H6A 3256.49 4360.92 2680.29 30
H6B 2302.59 4325.86 3219.77 30
H8A -394.54 3911.42 2495.9 68
H8B 425.58 3866.45 3127.77 68
H8C -537.91 2745.26 2755.2 68
H9A 604.66 3216.46 811.88 69
H9B -383.82 3362.9 1148.85 69
H9C -341.43 2260.57 1333 69
H10A 1157.81 5188.81 1640.87 81
H10B 2133.72 4938.97 1447.94 81
H10C 1956.7 5220.52 2321.92 81
H12A 1012.34 1823.32 731.86 43
H12B 1215.15 1065.65 1332.94 43
H12C 2014.67 1593.84 596.8 43
H13A 3340.19 4422.14 1239.43 75
H13B 2340.77 3816.33 633.7 75
H13C 3393.78 3652.11 569.74 75
H14A 3769.69 3260.19 2128.44 53
H14B 3647.08 2433.54 1439.24 53
H14C 2917.31 1962.65 2212.74 53
195
5.5.5 X-ray Crystal Structure Data for 3.1-Au
Figure 5.5.5.1. Molecular structure of 3.1-Au shown with 50% probability ellipsoids. Hydrogen
atoms are omitted for clarity.
A single clear bright red block-shaped crystal of C60H87AuBF10Ir3N3P5 Ir3Au with
approximate dimensions 0.308 × 0.16 × 0.061 mm
3
, was mounted on a Rigaku XtaLAB Synergy,
Dualflex, Hypix diffractometer from microfocus sealed tube for X-ray crystallographic collection.
The crystal was kept at a steady T = 99.98(13) K during data collection. The structure was solved
using SHELXT structure solution program using Intrinsic Phasing and refined on SHELXL
refinement package using Least Squares minimization on F
2
.
4-7
All non-hydrogen atoms were
refined anisotropically.
Crystal Data for C60H87AuBF10Ir3N3P5, M = 1979.55 g/mol, monoclinic, P21/c (no. 14), a
= 13.1450(2) Å, b = 28.6637(3) Å, c = 19.6662(2) Å, β = 97.4670(10) °, V = 7347.08(16) Å
3
, Z =
4, T = 99.98(13) K, μ(MoKα) = 7.577 mm
-1
, Dcalc = 1.790 g/cm
3
, 237485 reflections measured
196
(4.748° ≤ 2Θ ≤ 68.042°), 27065 unique (Rint = 0.0722, Rsigma = 0.0494) which were used in all
calculations. The final R1 was 0.0447 (I > 2σ(I)) and wR2 was 0.0972 (all data).
Sample and crystal data for 3.1-Au
Identification code IrAu
Chemical formula C60H87AuBF10Ir3N3P5
Formula weight 1979.55 g/mol
Temperature 99.98(13)
Wavelength MoKα (λ = 0.71073) Å
Crystal size 0.308 × 0.16 × 0.061mm
3
Crystal system monoclinic
Space group P21/c
Unit cell dimensions a = 13.1450(2) Å α = 90°
b = 28.6637(3) Å β = 97.4670(10)
°
c = 19.6662(2) Å γ = 90°
Volume 7347.08(16) Å
3
Z 4
Density (calculated) 1.790 g/cm
3
Absorption coefficient 7.577 mm
-1
F(000) 3792.0
197
Data collection and structure refinement for 3.1-Au
Diffractometer XtaLAB Synergy, Dualflex, HyPix
Radiation source MoKα , λ = 0.71073 Å
Theta range for data
collection
4.748 to 68.042°
Index ranges -20 ≤ h ≤ 20, -43 ≤ k ≤ 42, -28 ≤ l ≤
29
Reflections collected 237485
Independent
reflections
27065 [Rint = 0.0722, RSigma =
0.0494]
Coverage of
independent reflections
99.9%
Absorption correction multi-scan
Max. and min.
transmission
0.059 and 1.000
Structure solution
technique
direct methods
Structure solution
program
SHELXTL XT 2014/5 (Bruker
AXS, 2014)
Refinement method Full-matrix least-squares on F
2
Refinement program SHELXTL XL 2018/3 (Bruker
AXS, 2018)
Function minimized Σ w(Fo
2
- Fc
2
)
2
Data / restraints /
parameters
27065/12/766
Goodness-of-fit on F
2
1.044
Δ/σmax 0.004
Final R indices I>2σ(I) R1 = 0.0447, wR2 =
0.0863
198
all data R1 = 0.0744, wR2 =
0.0972
Weighting scheme w=1/[σ
2
(Fo
2
)+( 0.0146P)
2
+
99.9299P]
where P=(Fo
2
+2Fc
2
)/3
Largest diff. peak and
hole
3.79/-2.79 eÅ
-3
R.M.S. deviation from
mean
0.248 eÅ
-3
Fractional Atomic Coordinates (×10
4
) and Equivalent Isotropic Displacement Parameters (Å
2
×10
3
)
for 3.1-Au. Ueq is defined as 1/3 of the trace of the orthogonalised U IJ tensor.
Atom x y z U(eq)
Ir1 3263.4(2) 5431.8(2) 2524.3(2) 16.23(4)
P1 -654(2) 4078.2(9) 2068.0(17) 65.1(8)
F1 -454(5) 4235(2) 1332(3) 71.6(17)
N1 1088(4) 5869.1(16) 1234(3) 21.4(9)
C1 3404(5) 4396.0(19) 3082(3) 22.4(11)
B1 6482(6) 8082(2) 1354(3) 25.3(14)
Au1 2008.3(2) 6103.6(2) 2961.7(2) 16.51(4)
Ir2 2557.9(2) 6140.9(2) 1635.6(2) 15.67(4)
F2 -936(8) 3912(3) 2770(5) 134(4)
C2 5365(5) 7237(2) 2544(3) 23.9(12)
F3 -1696(5) 4394(3) 1959(5) 97(2)
C3 1252(5) 6308(2) 179(3) 22.8(11)
Ir3 3991.8(2) 6349.6(2) 2731.3(2) 15.66(4)
F4 -1235(5) 3630(2) 1729(5) 94(2)
C4 3484(5) 6571(2) 5259(3) 25.8(12)
F5 403(5) 3784(2) 2160(4) 75.0(18)
199
P12 3823.0(12) 4704.0(5) 2348.7(7) 19.1(3)
P30 2595.3(11) 6350.7(5) 536.5(7) 18.0(3)
P46 5581.5(12) 6655.9(5) 2918.3(8) 19.4(3)
P62 1023.6(11) 6268.6(5) 3835.2(7) 18.2(3)
N44 3587(4) 7072.6(16) 2721(2) 18.9(9)
N10 3434(4) 5185.9(15) 3562(2) 17.5(9)
C11 120(6) 5396(2) 3679(4) 33.1(15)
C9 3522(4) 5479.3(18) 4108(3) 17.0(10)
F10 7080(5) 7972(2) 1943(3) 70.7(18)
C43 4298(4) 7404.2(19) 2624(3) 19.5(10)
C26 514(5) 5589(2) 1599(3) 26.3(12)
C39 2626(5) 7218.9(19) 2792(3) 20.6(11)
C5 3480(4) 4717.6(18) 3688(3) 18.7(10)
F6 -57(5) 4506.7(19) 2404(3) 59.1(14)
C8 3643(4) 5324.4(19) 4780(3) 18.8(10)
F9 6069(4) 7652.2(17) 1070(3) 53.3(13)
C40 2336(5) 7685.0(19) 2775(3) 22.7(11)
C61 2801(5) 6531.7(19) 4657(3) 22.9(11)
C36 4333(5) 5805(2) 410(3) 30.1(13)
C6 3615(5) 4543.8(19) 4357(3) 21.6(11)
F7 5581(5) 8307(2) 1569(4) 82(2)
C13 3197(5) 4353(2) 1595(3) 25.0(12)
C63 380(4) 6832.9(19) 3744(3) 22.2(11)
C31 2939(5) 6969.7(19) 351(3) 22.0(11)
C47 6601(5) 6400(2) 2440(3) 26.0(12)
C18 5717(5) 4956(2) 1943(3) 26.3(12)
C68 43(5) 6996(2) 3081(3) 28.5(13)
C17 5254(5) 4634.3(19) 2451(3) 20.2(11)
C14 2064(5) 4504(2) 1436(3) 30.8(14)
C69 60(5) 5839(2) 3965(3) 23.9(12)
200
C22 701(5) 5964(2) 572(3) 23.9(12)
C32 2412(6) 7300(2) 816(3) 30.6(14)
C19 5679(5) 4802(2) 3183(3) 24.2(12)
C7 3694(5) 4846.6(19) 4907(3) 22.3(11)
F8 6849(6) 8343(2) 926(3) 87(2)
C56 1852(4) 6310.7(19) 4654(3) 20.2(10)
C48 7063(5) 5961(2) 2805(4) 31.0(14)
C51 6100(5) 6767(2) 3849(3) 25.8(12)
C35 3266(5) 5920(2) 19(3) 23.9(12)
C16 3733(6) 4442(2) 956(3) 28.6(13)
C37 2611(5) 5473(2) -39(3) 28.2(13)
C25 -398(6) 5391(2) 1331(4) 35.9(16)
C34 2587(5) 7112(2) -397(3) 28.2(13)
C52 6112(6) 6321(2) 4268(3) 30.9(14)
C70 -722(5) 5933(2) 4370(3) 27.7(13)
C42 4047(5) 7874.9(19) 2600(3) 27.7(13)
C41 3067(5) 8022(2) 2672(3) 27.0(13)
C67 -430(5) 7433(2) 2992(4) 36.8(17)
C20 5634(5) 4134(2) 2382(3) 27.6(13)
C23 -216(6) 5763(3) 270(4) 36.9(16)
C38 3397(6) 6081(2) -711(3) 34.4(15)
C15 3207(6) 3827(2) 1752(4) 34.7(15)
C33 4115(5) 7036(2) 511(4) 35.0(15)
C50 7466(5) 6748(3) 2344(4) 34.3(15)
C53 5383(5) 7124(2) 4133(3) 27.3(13)
C64 234(5) 7106(2) 4309(4) 29.6(13)
C24 -775(7) 5478(3) 647(4) 45.1(19)
C57 1589(5) 6134(2) 5269(3) 27.8(13)
C66 -558(5) 7708(2) 3555(5) 40.9(19)
C54 7192(5) 6983(3) 3938(4) 32.9(14)
201
C65 -238(6) 7542(2) 4203(5) 40.3(18)
C73 -579(7) 5049(3) 3805(4) 42.6(18)
C59 3206(5) 6395(2) 5868(3) 28.7(13)
C58 2265(6) 6179(2) 5878(3) 32.0(14)
C71 -1398(5) 5580(2) 4506(4) 34.7(15)
C72 -1318(6) 5140(2) 4221(4) 40.6(17)
C49 6084(5) 6262(2) 1728(3) 27.7(13)
Anisotropic Displacement Parameters (Å
2
×10
3
) for Ir3Au_autored. The Anisotropic displacement
factor exponent takes the form: -2π
2
[h
2
a*
2
U11+2hkab*U12+…].
Atom U11 U22 U33 U23 U13 U12
Ir1 22.27(10) 11.75(8) 15.14(9) -0.06(6) 4.23(7) 0.38(7)
P1 68.6(18) 47.9(14) 87(2) -15.1(13) 41.5(16) -18.9(12)
F1 84(4) 81(4) 49(3) -26(3) 3(3) -11(3)
N1 26(2) 12(2) 25(2) -1.2(17) 0.9(19) -1.9(17)
C1 38(3) 12(2) 18(3) -3.6(18) 8(2) -1(2)
B1 51(4) 11(3) 11(3) -1.2(19) -6(3) 4(3)
Au1 19.88(9) 13.60(8) 16.76(9) 0.78(7) 5.07(7) -0.49(7)
Ir2 20.17(10) 12.21(8) 14.99(9) 0.33(6) 3.66(7) -1.14(7)
F2 179(8) 96(6) 157(8) 22(5) 132(7) -14(5)
C2 28(3) 18(3) 26(3) 5(2) 4(2) -6(2)
F3 60(4) 91(5) 147(7) -34(5) 39(4) -7(4)
C3 26(3) 25(3) 16(2) -2(2) -1(2) -1(2)
Ir3 19.74(10) 12.49(8) 15.19(9) 0.52(6) 3.92(7) -1.21(7)
F4 61(4) 57(4) 167(7) -19(4) 23(4) -16(3)
C4 34(3) 18(3) 25(3) -4(2) 3(2) 8(2)
F5 75(4) 56(3) 100(5) -13(3) 32(4) -2(3)
P12 29.3(8) 12.4(6) 15.9(6) -0.3(5) 4.4(5) 1.8(5)
P30 22.8(7) 15.9(6) 15.8(6) 0.3(5) 4.4(5) -0.7(5)
202
P46 21.0(7) 17.1(6) 20.1(7) 2.2(5) 2.2(5) -1.9(5)
P62 19.6(7) 16.2(6) 19.9(6) 2.4(5) 6.7(5) 0.8(5)
N44 23(2) 17(2) 17(2) -1.5(16) 0.9(18) -1.6(17)
N10 23(2) 12.0(19) 17(2) 1.4(15) 2.7(17) 0.2(16)
C11 48(4) 19(3) 36(4) -3(2) 19(3) -9(3)
C9 17(2) 12(2) 22(3) -2.0(18) 1.2(19) 2.1(18)
F10 88(4) 75(4) 43(3) 23(3) -14(3) -41(3)
C43 24(3) 16(2) 17(2) 2.6(18) -4(2) -5(2)
C26 29(3) 20(3) 29(3) 2(2) 1(2) -3(2)
C39 28(3) 16(2) 19(3) 0.6(19) 9(2) -4(2)
C5 26(3) 15(2) 17(2) 1.7(18) 8(2) 2(2)
F6 82(4) 56(3) 42(3) -10(2) 18(3) -8(3)
C8 21(3) 20(2) 16(2) -0.4(18) 4(2) 1(2)
F9 62(3) 45(3) 53(3) -19(2) 3(2) -5(2)
C40 27(3) 16(2) 25(3) -1(2) 3(2) 1(2)
C61 35(3) 14(2) 20(3) -2.7(19) 7(2) 2(2)
C36 31(3) 30(3) 31(3) 0(3) 8(3) 5(3)
C6 33(3) 15(2) 18(2) 4.0(19) 8(2) 0(2)
F7 89(5) 51(3) 112(5) -21(3) 41(4) 10(3)
C13 37(3) 19(3) 20(3) -3(2) 4(2) -2(2)
C63 20(3) 16(2) 32(3) 3(2) 6(2) 1(2)
C31 31(3) 18(2) 18(2) 2.2(19) 2(2) -6(2)
C47 28(3) 29(3) 21(3) 2(2) 4(2) 1(2)
C18 34(3) 18(3) 28(3) 3(2) 10(3) 5(2)
C68 32(3) 21(3) 33(3) 11(2) 7(3) 1(2)
C17 28(3) 16(2) 18(2) -1.6(18) 6(2) 5(2)
C14 32(3) 28(3) 30(3) -5(2) -7(3) -4(3)
C69 28(3) 18(3) 26(3) 7(2) 6(2) -3(2)
C22 29(3) 17(3) 24(3) 0(2) -1(2) -2(2)
C32 54(4) 13(3) 25(3) 0(2) 6(3) -3(3)
203
C19 30(3) 22(3) 20(3) -3(2) 3(2) 3(2)
C7 33(3) 18(2) 17(2) 0.9(19) 9(2) -1(2)
F8 123(6) 80(4) 63(4) 38(3) 28(4) -7(4)
C56 23(3) 15(2) 23(3) 1.4(19) 4(2) 7(2)
C48 30(3) 29(3) 35(3) 0(3) 6(3) 7(3)
C51 28(3) 24(3) 24(3) 0(2) -2(2) -3(2)
C35 32(3) 21(3) 21(3) -2(2) 10(2) 3(2)
C16 42(4) 22(3) 22(3) -1(2) 5(3) 4(3)
C37 42(4) 19(3) 25(3) -3(2) 8(3) -1(2)
C25 37(4) 30(3) 41(4) 10(3) 5(3) -13(3)
C34 40(4) 22(3) 23(3) 3(2) 4(3) 1(3)
C52 35(4) 29(3) 27(3) 2(2) -3(3) 0(3)
C70 25(3) 23(3) 36(3) 5(2) 10(3) 1(2)
C42 36(3) 10(2) 36(3) 4(2) 3(3) -7(2)
C41 34(3) 12(2) 35(3) 6(2) 4(3) 1(2)
C67 22(3) 28(3) 59(5) 21(3) 4(3) -2(3)
C20 43(4) 18(3) 23(3) 3(2) 9(3) 8(2)
C23 39(4) 40(4) 28(3) 3(3) -12(3) -13(3)
C38 49(4) 32(3) 24(3) 1(3) 16(3) 7(3)
C15 52(4) 23(3) 29(3) -4(2) 1(3) -3(3)
C33 31(4) 32(3) 40(4) 12(3) -2(3) -8(3)
C50 24(3) 35(4) 45(4) 2(3) 9(3) -7(3)
C53 38(4) 21(3) 22(3) -4(2) -1(3) -3(2)
C64 24(3) 24(3) 41(4) -2(3) 6(3) 2(2)
C24 44(4) 45(4) 44(4) 5(3) -5(3) -23(4)
C57 30(3) 30(3) 26(3) 5(2) 13(2) 4(3)
C66 25(3) 19(3) 80(6) 6(3) 10(4) 0(2)
C54 24(3) 36(4) 35(4) -1(3) -8(3) -6(3)
C65 32(4) 26(3) 64(5) -10(3) 11(4) 2(3)
C73 57(5) 25(3) 50(5) -4(3) 21(4) -12(3)
204
Bond Lengths for 3.1-Au
C59 40(4) 22(3) 24(3) -1(2) 2(3) 8(3)
C58 43(4) 32(3) 23(3) 4(2) 10(3) 9(3)
C71 26(3) 29(3) 51(4) 12(3) 15(3) -1(3)
C72 44(4) 27(3) 53(5) 5(3) 14(4) -13(3)
C49 25(3) 31(3) 27(3) 0(2) 5(2) 3(2)
Atom Atom Length/Å Atom Atom Length/Å
Ir1 Au1 2.7457(3) C11 C69 1.397(9)
Ir1 Ir2 2.7612(3) C11 C73 1.397(9)
Ir1 Ir3 2.8109(3) C9 C8 1.384(7)
Ir1 P12 2.2536(14) C43 C42 1.389(8)
Ir1 N10 2.143(4) C26 C25 1.368(9)
P1 F1 1.571(7) C39 C40 1.388(8)
P1 F2 1.550(8) C5 C6 1.397(7)
P1 F3 1.632(8) C8 C7 1.392(8)
P1 F4 1.596(7) C40 C41 1.395(8)
P1 F5 1.615(7) C61 C56 1.398(9)
P1 F6 1.558(6) C36 C35 1.544(9)
N1 Ir2 2.137(5) C6 C7 1.380(8)
N1 C26 1.368(8) C13 C14 1.543(9)
N1 C22 1.364(8) C13 C16 1.540(9)
C1 P12 1.836(6) C13 C15 1.538(9)
C1 C5 1.500(7) C63 C68 1.401(9)
B1 F10 1.350(8) C63 C64 1.394(9)
B1 F9 1.431(8) C31 C32 1.542(9)
205
B1 F7 1.458(10) C31 C34 1.538(8)
B1 F8 1.268(9) C31 C33 1.549(9)
Au1 Ir2 2.7972(3) C47 C48 1.535(9)
Au1 Ir3 2.7942(3) C47 C50 1.541(9)
Au1 P62 2.3298(14) C47 C49 1.526(9)
Ir2 Ir3 2.7382(3) C18 C17 1.542(8)
Ir2 P30 2.2503(14) C68 C67 1.399(9)
C2 P46 1.829(6) C17 C19 1.550(8)
C2 C43 1.509(9) C17 C20 1.531(8)
C3 P30 1.818(6) C69 C70 1.405(9)
C3 C22 1.495(8) C22 C23 1.397(9)
Ir3 P46 2.2524(15) C56 C57 1.397(8)
Ir3 N44 2.139(5) C51 C52 1.519(9)
C4 C61 1.394(9) C51 C53 1.545(9)
C4 C59 1.392(9) C51 C54 1.553(9)
P12 C13 1.889(6) C35 C37 1.540(9)
P12 C17 1.877(6) C35 C38 1.538(8)
P30 C31 1.878(6) C25 C24 1.394(11)
P30 C35 1.890(6) C70 C71 1.394(9)
P46 C47 1.884(6) C42 C41 1.379(9)
P46 C51 1.895(6) C67 C66 1.386(12)
P62 C63 1.823(6) C23 C24 1.378(10)
P62 C69 1.807(6) C64 C65 1.399(9)
P62 C56 1.827(6) C57 C58 1.400(10)
N44 C43 1.364(7) C66 C65 1.374(12)
206
Bond Angles for 3.1-Au
N44 C39 1.355(8) C73 C72 1.373(11)
N10 C9 1.356(7) C59 C58 1.386(10)
N10 C5 1.365(7) C71 C72 1.392(10)
Atom Atom Atom Angle/˚ Atom Atom Atom Angle/˚
Au1 Ir1 Ir2 61.054(7) C56 P62 Au1 109.79(19)
Au1 Ir1 Ir3 60.366(7) C43 N44 Ir3 120.1(4)
Ir2 Ir1 Ir3 58.860(7) C39 N44 Ir3 122.2(4)
P12 Ir1 Au1 156.73(4) C39 N44 C43 117.7(5)
P12 Ir1 Ir2 132.37(4) C9 N10 Ir1 122.5(3)
P12 Ir1 Ir3 140.96(4) C9 N10 C5 118.0(5)
N10 Ir1 Au1 85.71(12) C5 N10 Ir1 119.5(4)
N10 Ir1 Ir2 146.08(12) C69 C11 C73 120.2(6)
N10 Ir1 Ir3 100.27(12) N10 C9 C8 123.0(5)
N10 Ir1 P12 81.11(12) N44 C43 C2 117.2(5)
F1 P1 F3 87.6(4) N44 C43 C42 121.1(6)
F1 P1 F4 88.5(4) C42 C43 C2 121.7(5)
F1 P1 F5 90.5(4) N1 C26 C25 123.8(6)
F2 P1 F1 175.6(5) N44 C39 C40 123.5(5)
F2 P1 F3 89.6(5) N10 C5 C1 117.6(5)
F2 P1 F4 88.1(5) N10 C5 C6 121.3(5)
F2 P1 F5 92.4(5) C6 C5 C1 121.1(5)
F2 P1 F6 91.7(5) C9 C8 C7 119.0(5)
F4 P1 F3 92.5(4) C39 C40 C41 118.5(6)
F4 P1 F5 89.1(4) C4 C61 C56 121.0(6)
F5 P1 F3 177.5(4) C7 C6 C5 120.1(5)
F6 P1 F1 91.7(3) C14 C13 P12 108.7(4)
F6 P1 F3 89.2(4) C16 C13 P12 110.7(4)
207
F6 P1 F4 178.3(4) C16 C13 C14 108.6(5)
F6 P1 F5 89.2(4) C15 C13 P12 111.9(4)
C26 N1 Ir2 123.7(4) C15 C13 C14 107.4(5)
C22 N1 Ir2 119.1(4) C15 C13 C16 109.5(5)
C22 N1 C26 117.2(5) C68 C63 P62 118.3(5)
C5 C1 P12 109.5(4) C64 C63 P62 122.0(5)
F10 B1 F9 106.4(5) C64 C63 C68 119.6(6)
F10 B1 F7 105.0(6) C32 C31 P30 109.1(4)
F9 B1 F7 102.3(6) C32 C31 C33 108.5(5)
F8 B1 F10 118.6(7) C34 C31 P30 112.7(4)
F8 B1 F9 114.0(6) C34 C31 C32 107.6(5)
F8 B1 F7 109.0(6) C34 C31 C33 109.3(5)
Ir1 Au1 Ir2 59.746(7) C33 C31 P30 109.6(4)
Ir1 Au1 Ir3 60.974(7) C48 C47 P46 110.4(4)
Ir3 Au1 Ir2 58.645(7) C48 C47 C50 109.6(6)
P62 Au1 Ir1 141.94(4) C50 C47 P46 113.1(5)
P62 Au1 Ir2 156.24(4) C49 C47 P46 107.4(4)
P62 Au1 Ir3 133.46(4) C49 C47 C48 108.5(5)
Ir1 Ir2 Au1 59.200(7) C49 C47 C50 107.7(5)
N1 Ir2 Ir1 100.28(13) C67 C68 C63 119.9(7)
N1 Ir2 Au1 89.97(14) C18 C17 P12 110.0(4)
N1 Ir2 Ir3 150.12(14) C18 C17 C19 106.9(5)
N1 Ir2 P30 82.78(14) C19 C17 P12 107.6(4)
Ir3 Ir2 Ir1 61.477(7) C20 C17 P12 115.1(4)
Ir3 Ir2 Au1 60.623(7) C20 C17 C18 109.9(5)
P30 Ir2 Ir1 139.22(4) C20 C17 C19 107.0(5)
P30 Ir2 Au1 161.14(4) C11 C69 P62 119.0(5)
P30 Ir2 Ir3 126.79(4) C11 C69 C70 119.0(6)
C43 C2 P46 110.2(4) C70 C69 P62 121.9(5)
C22 C3 P30 110.8(4) N1 C22 C3 118.7(5)
208
Au1 Ir3 Ir1 58.661(7) N1 C22 C23 121.1(6)
Ir2 Ir3 Ir1 59.663(7) C23 C22 C3 120.1(6)
Ir2 Ir3 Au1 60.733(7) C6 C7 C8 118.7(5)
P46 Ir3 Ir1 132.83(4) C61 C56 P62 117.6(4)
P46 Ir3 Au1 159.61(4) C57 C56 P62 123.6(5)
P46 Ir3 Ir2 137.97(4) C57 C56 C61 118.9(6)
N44 Ir3 Ir1 145.64(13) C52 C51 P46 111.1(4)
N44 Ir3 Au1 90.55(13) C52 C51 C53 109.0(5)
N44 Ir3 Ir2 93.38(13) C52 C51 C54 109.2(5)
N44 Ir3 P46 81.29(14) C53 C51 P46 107.5(4)
C59 C4 C61 119.3(6) C53 C51 C54 107.1(5)
C1 P12 Ir1 100.82(18) C54 C51 P46 112.8(5)
C1 P12 C13 102.5(3) C36 C35 P30 109.2(4)
C1 P12 C17 105.2(3) C37 C35 P30 106.7(4)
C13 P12 Ir1 119.7(2) C37 C35 C36 108.8(5)
C17 P12 Ir1 115.13(18) C38 C35 P30 115.0(4)
C17 P12 C13 110.9(3) C38 C35 C36 108.9(5)
C3 P30 Ir2 102.27(19) C38 C35 C37 108.1(5)
C3 P30 C31 103.6(3) C26 C25 C24 118.8(6)
C3 P30 C35 104.2(3) C71 C70 C69 120.2(6)
C31 P30 Ir2 118.34(18) C41 C42 C43 121.0(5)
C31 P30 C35 111.8(3) C42 C41 C40 118.3(5)
C35 P30 Ir2 114.37(19) C66 C67 C68 120.4(7)
C2 P46 Ir3 101.3(2) C24 C23 C22 120.5(7)
C2 P46 C47 103.7(3) C63 C64 C65 119.1(7)
C2 P46 C51 104.7(3) C23 C24 C25 118.5(7)
C47 P46 Ir3 118.2(2) C56 C57 C58 120.3(6)
C47 P46 C51 111.0(3) C65 C66 C67 119.3(6)
C51 P46 Ir3 115.6(2) C66 C65 C64 121.6(7)
C63 P62 Au1 113.7(2) C72 C73 C11 120.3(7)
209
Torsion Angles for 3.1-Au
A B C D Angle/˚ A B C D Angle/˚
Ir1 P12 C13 C14 -30.0(5) N10 C5 C6 C7 0.7(9)
Ir1 P12 C13 C16 89.3(4) C11 C69 C70 C71 2.8(10)
Ir1 P12 C13 C15 -148.4(4) C11 C73 C72 C71 1.9(13)
Ir1 P12 C17 C18 -59.3(4) C9 N10 C5 C1 -178.8(5)
Ir1 P12 C17 C19 56.8(4) C9 N10 C5 C6 -0.2(8)
Ir1 P12 C17 C20 175.9(3) C9 C8 C7 C6 -0.4(9)
Ir1 N10 C9 C8 -179.3(4) C43 C2 P46 Ir3 31.8(4)
Ir1 N10 C5 C1 -0.1(7) C43 C2 P46 C47 154.8(4)
Ir1 N10 C5 C6 178.5(4) C43 C2 P46 C51 -88.8(5)
N1 C26 C25 C24 -0.3(11) C43 N44 C39 C40 -0.3(8)
N1 C22 C23 C24 2.8(11) C43 C42 C41 C40 0.5(10)
C1 P12 C13 C14 80.4(5) C26 N1 C22 C3 173.8(5)
C1 P12 C13 C16 -160.4(4) C26 N1 C22 C23 -3.4(9)
C1 P12 C13 C15 -38.0(5) C26 C25 C24 C23 -0.4(12)
C1 P12 C17 C18 -169.3(4) C39 N44 C43 C2 -179.9(5)
C1 P12 C17 C19 -53.2(4) C39 N44 C43 C42 0.1(8)
C1 P12 C17 C20 65.9(5) C39 C40 C41 C42 -0.7(9)
C1 C5 C6 C7 179.2(6) C5 C1 P12 Ir1 -34.4(5)
Au1 P62 C63 C68 33.7(5) C5 C1 P12 C13 -158.4(4)
Au1 P62 C63 C64 -145.1(5) C5 C1 P12 C17 85.6(5)
Au1 P62 C69 C11 16.0(6) C5 N10 C9 C8 -0.7(8)
Au1 P62 C69 C70 -166.7(5) C5 C6 C7 C8 -0.4(9)
Au1 P62 C56 C61 39.6(5) C61 C4 C59 C58 0.5(9)
C63 P62 C56 104.1(3) C58 C59 C4 120.5(6)
C69 P62 Au1 115.6(2) C59 C58 C57 119.9(6)
C69 P62 C63 107.0(3) C72 C71 C70 119.8(6)
C69 P62 C56 105.6(3) C73 C72 C71 120.5(6)
210
Au1 P62 C56 C57 -140.2(4) C61 C56 C57 C58 0.2(9)
Ir2 N1 C26 C25 -175.8(5) C13 P12 C17 C18 80.6(4)
Ir2 N1 C22 C3 -8.1(7) C13 P12 C17 C19 -163.3(4)
Ir2 N1 C22 C23 174.6(5) C13 P12 C17 C20 -44.2(5)
Ir2 P30 C31 C32 -40.9(5) C63 P62 C69 C11 143.9(5)
Ir2 P30 C31 C34 -160.3(4) C63 P62 C69 C70 -38.8(6)
Ir2 P30 C31 C33 77.7(5) C63 P62 C56 C61 -82.5(5)
Ir2 P30 C35 C36 -51.2(5) C63 P62 C56 C57 97.7(5)
Ir2 P30 C35 C37 66.2(4) C63 C68 C67 C66 0.8(10)
Ir2 P30 C35 C38 -173.9(4) C63 C64 C65 C66 -0.2(10)
C2 P46 C47 C48 166.3(5) C31 P30 C35 C36 86.8(5)
C2 P46 C47 C50 43.1(5) C31 P30 C35 C37 -155.8(4)
C2 P46 C47 C49 -75.6(5) C31 P30 C35 C38 -36.0(6)
C2 P46 C51 C52 168.2(5) C47 P46 C51 C52 -80.5(5)
C2 P46 C51 C53 49.0(5) C47 P46 C51 C53 160.3(4)
C2 P46 C51 C54 -68.8(5) C47 P46 C51 C54 42.5(5)
C2 C43 C42 C41 179.8(6) C68 C63 C64 C65 -0.7(9)
C3 P30 C31 C32 71.3(5) C68 C67 C66 C65 -1.7(10)
C3 P30 C31 C34 -48.1(5) C17 P12 C13 C14 -167.7(4)
C3 P30 C31 C33 -170.0(4) C17 P12 C13 C16 -48.5(5)
C3 P30 C35 C36 -162.0(4) C17 P12 C13 C15 73.9(5)
C3 P30 C35 C37 -44.6(5) C69 P62 C63 C68 -95.3(5)
C3 P30 C35 C38 75.3(5) C69 P62 C63 C64 85.9(6)
C3 C22 C23 C24 -174.3(7) C69 P62 C56 C61 164.9(4)
Ir3 P46 C47 C48 -82.6(5) C69 P62 C56 C57 -14.9(6)
Ir3 P46 C47 C50 154.2(4) C69 C11 C73 C72 -1.3(13)
Ir3 P46 C47 C49 35.5(5) C69 C70 C71 C72 -2.3(11)
Ir3 P46 C51 C52 57.6(5) C22 N1 C26 C25 2.2(9)
Ir3 P46 C51 C53 -61.6(4) C22 C3 P30 Ir2 -26.1(4)
Ir3 P46 C51 C54 -179.4(4) C22 C3 P30 C31 -149.6(4)
211
Ir3 N44 C43 C2 -1.4(7) C22 C3 P30 C35 93.3(4)
Ir3 N44 C43 C42 178.6(4) C22 C23 C24 C25 -0.9(13)
Ir3 N44 C39 C40 -178.8(4) C56 P62 C63 C68 153.2(5)
C4 C61 C56 P62 -178.9(4) C56 P62 C63 C64 -25.6(6)
C4 C61 C56 C57 0.9(8) C56 P62 C69 C11 -105.6(6)
C4 C59 C58 C57 0.6(9) C56 P62 C69 C70 71.7(6)
P12 C1 C5 N10 24.6(7) C56 C57 C58 C59 -1.0(10)
P12 C1 C5 C6 -154.0(5) C51 P46 C47 C48 54.4(5)
P30 C3 C22 N1 23.8(7) C51 P46 C47 C50 -68.8(5)
P30 C3 C22 C23 -159.0(6) C51 P46 C47 C49 172.5(4)
P46 C2 C43 N44 -21.8(6) C35 P30 C31 C32 -177.1(4)
P46 C2 C43 C42 158.1(5) C35 P30 C31 C34 63.5(5)
P62 C63 C68 C67 -178.4(5) C35 P30 C31 C33 -58.4(5)
P62 C63 C64 C65 178.0(5) C70 C71 C72 C73 -0.1(12)
P62 C69 C70 C71 -174.5(5) C67 C66 C65 C64 1.4(11)
P62 C56 C57 C58 -180.0(5) C64 C63 C68 C67 0.4(9)
N44 C43 C42 C41 -0.2(9) C73 C11 C69 P62 176.3(6)
N44 C39 C40 C41 0.7(9) C73 C11 C69 C70 -1.1(11)
N10 C9 C8 C7 1.0(9) C59 C4 C61 C56 -1.3(8)
Hydrogen Atom Coordinates (Å×10
4
) and Isotropic Displacement Parameters (Å
2
×10
3
) for 3.1-Au
Atom x y z U(eq)
H1A 2686.74 4289.32 964.23 27
H1B 3842.15 4118.54 3195.48 27
H2A 5876.86 7457.81 2775.1 29
H2B 5449.63 7227.22 2051.34 29
H3A 923.34 6617.87 193.17 27
H3B 1200.72 6208.91 -307 27
H4 4132.76 6715.61 5252.76 31
212
H11 638.38 5329.22 3398.73 40
H9 3498.56 5805.83 4024.44 20
H26 762.17 5528.2 2066.24 32
H39 2123.68 6990.48 2857.46 25
H8 3690.98 5540.77 5148.76 23
H40 1655.56 7772.75 2832.13 27
H61 2983.05 6657.31 4242.1 28
H36A 4764.28 6084.8 436.54 45
H36B 4655.05 5558.18 166.67 45
H36C 4256.34 5698.54 874 45
H6 3652.17 4216.63 4434.03 26
H18A 5500.67 5277.97 2007.74 39
H18B 5477.93 4856.29 1472.65 39
H18C 6467.6 4936.87 2025.73 39
H68 135.66 6811.13 2693.74 34
H14A 2031.07 4832.67 1294.91 46
H14B 1723.33 4465.7 1846.56 46
H14C 1719.42 4311 1064.34 46
H32A 2510.68 7624.14 678.63 46
H32B 2714.64 7256.76 1294.02 46
H32C 1676.97 7230.08 770.59 46
H19A 6429.92 4812.18 3229.98 36
H19B 5461.39 4586.04 3522.06 36
H19C 5413.51 5114.89 3259.01 36
H7 3781.57 4731.22 5364.19 27
H48A 7467.16 5791.41 2499.9 46
H48B 6508.82 5759.73 2923.28 46
H48C 7506.1 6050.57 3223.59 46
H16A 3310.71 4317.21 549.85 43
H16B 4404.24 4288.1 1012.48 43
213
H16C 3826.35 4778.8 899.24 43
H37A 2990.73 5221.02 -228.85 42
H37B 1969.77 5530.77 -340.79 42
H37C 2454.44 5383.2 417.38 42
H25 -766.4 5197.15 1605.44 43
H34A 1855.09 7041.59 -513.31 42
H34B 2981.04 6937.15 -702.19 42
H34C 2699.58 7446.8 -451.65 42
H52A 5410.88 6201.85 4252.71 46
H52B 6394.71 6386.44 4743.97 46
H52C 6538.92 6087.32 4076.06 46
H70 -791.1 6237.03 4550.21 33
H42 4556.97 8099.11 2534.1 33
H41 2894.94 8343.76 2652.5 32
H67 -666.2 7542.21 2543.06 44
H20A 5423.09 4022.59 1913.17 41
H20B 5337.72 3931.71 2706.66 41
H20C 6383.99 4126.48 2480.08 41
H23 -456.06 5823.05 -198.38 44
H38A 3870.68 6346.74 -685.22 52
H38B 2729.55 6175.7 -951.97 52
H38C 3674.57 5824.53 -959.13 52
H15A 2787.48 3765.79 2119.09 52
H15B 3913.81 3725.82 1898.19 52
H15C 2927.34 3655.67 1338.88 52
H33A 4283.65 7367.19 468.55 52
H33B 4457.86 6853.46 186.7 52
H33C 4346.61 6930.64 979.6 52
H50A 7857.74 6817.68 2791.22 51
H50B 7166.78 7036.18 2138.68 51
214
H50C 7922.4 6610.35 2042.49 51
H53A 5444.01 7426.42 3908.9 41
H53B 5577.17 7158.38 4628.83 41
H53C 4671.74 7014.67 4042.01 41
H64 451.67 6997.64 4761.38 36
H24 -1403.99 5343.58 445.31 54
H57 947.89 5981.53 5275.41 33
H66 -862.51 8008.22 3493.12 49
H54A 7686.87 6749.42 3822.57 49
H54B 7375.66 7082.71 4414.95 49
H54C 7204.04 7252.71 3633.33 49
H65 -339.9 7728.09 4588.29 48
H73 -544.27 4750.06 3601.53 51
H59 3666.18 6422.44 6280.61 34
H58 2077.67 6062.78 6296.21 38
H71 -1911.08 5640.82 4793.25 42
H72 -1777.61 4899.38 4314.85 49
H49A 6575.35 6092.98 1484.69 41
H49B 5851.51 6542.75 1470 41
H49C 5494.14 6060.44 1773.5 41
Solvent masks information for 3.1-Au
Number X Y Z Volume Electron
count
Content
1 0.154 0.271 0.926 275.7 70.7 1.7 CH3CH2OCH2CH3
2 0.154 0.229 0.426 275.7 71.0 1.7 CH3CH2OCH2CH3
3 -0.154 0.771 0.574 275.7 71.2 1.7 CH3CH2OCH2CH3
4 -0.154 0.729 0.074 275.7 71.5 1.7 CH3CH2OCH2CH3
215
5.5.6 X-ray Crystal Structure Data for 3.2-Cl
Figure 5.5.6.1. Molecular structure of 3.2-Cl shown with 50% probability ellipsoids. Hydrogen
atoms and a dichloromethane molecule are omitted for clarity.
A single clear light red prism-shaped crystal of C29H50Cl8Ir2N2P2, Ir-TEMPO with
approximate dimensions 0.16 × 0.10 × 0.05 mm
3
, was mounted on a Rigaku XtaLAB Synergy,
Dualflex, Hypix diffractometer from microfocus sealed tube for X-ray crystallographic collection.
The crystal was kept at a steady T = 100(2) K during data collection. The structure was solved
using SHELXT structure solution program using Intrinsic Phasing and refined on SHELXL
refinement package using Least Squares minimization on F
2
.
4-7
All non-hydrogen atoms were
refined anisotropically.
216
Crystal Data for C29H50Cl8Ir2N2P2, M = 1156.65 g/mol, monoclinic, I2/a (No. 15), a =
14.9806(6) Å, b = 14.9616(4) Å, c = 17.5808(7) Å, β = 108.934(4)°, α = γ = 90°, V = 3727.2(2)
Å
3
, Z = 4, Z’ = 0.5, T = 100(2) K, μ(MoKα) = 7.818 mm
-1
, Dcalc = 2.061 g/cm
3
, 18132 reflections
measured (4.748° ≤ 2Θ ≤ 68.042°), 4792 unique (Rint = 0.0866) which were used in all
calculations. The final R1 was 0.0510 (I > 2σ(I)) and wR2 was 0.1323 (all data).
Sample and crystal data for 3.2-Cl.
Identification code Ir-TEMPO
Chemical formula C29H50Cl8Ir2N2P2
Formula weight 1156.65 g/mol
Temperature 100(2)
Wavelength MoKα (λ = 0.71073)
Å
Crystal size 0.16 × 0.10 × 0.05
mm
3
Crystal system monoclinic
Space group I2/a
Unit cell dimensions a = 14.9806(6) Å α = 90°
b = 14.9616(4) Å β =
108.934(4)°
c = 17.5808(7) Å γ = 90°
Volume 3727.2(2) Å
3
Z 4
Z’ 0.5
Density (calculated) 2.061 g/cm
3
Absorption coefficient 7.818 mm
-1
F(000) 2232
217
Data collection and structure refinement for 3.2-Cl
Diffractometer XtaLAB Synergy, Dualflex,
HyPix
Radiation source MoKα , λ = 0.71073 Å
Theta range for data
collection
2.723 to 30.996°
Index ranges -19 ≤ h ≤ 18, -21 ≤ k ≤ 17, -22
≤ l ≤ 24
Reflections collected 18132
Independent reflections 4792 [Rint = 0.0866]
Coverage of independent
reflections
99.9%
Absorption correction multi-scan
Max. and min.
transmission
0.033 and 0.414
Structure solution
technique
direct methods
Structure solution
program
SHELXTL XT 2014/5 (Bruker
AXS, 2014)
Refinement method Full-matrix least-squares on F
2
Refinement program SHELXTL XL 2018/3 (Bruker
AXS, 2018)
Function minimized Σ w(Fo
2
- Fc
2
)
2
Data / restraints /
parameters
4792/0/201
Goodness-of-fit on F
2
0.971
Δ/σmax 0.001
Final R indices I>2σ(I) R1 = 0.0510, wR2 =
0.1229
all data R1 = 0.0650, wR2 =
218
0.1323
Weighting scheme w=1/[σ
2
(Fo
2
)+( 0.0762P)
2
]
where P=(Fo
2
+2Fc
2
)/3
Largest diff. peak and hole 1.923/-2.21 eÅ
-3
R.M.S. deviation from
mean
0.228 eÅ
-3
Fractional Atomic Coordinates (×104) and Equivalent Isotropic Displacement Parameters
(Å
2
×10
3
) for 3.2-Cl. Ueq is defined as 1/3 of the trace of the orthogonalised Uij.
Atom x y z Ueq
Ir1 6204.0(2) 7440.8(2) 2293.1(2) 35.25(11)
Cl3 6229.5(11) 8658.8(9) 3158.2(9) 40.2(3)
Cl2 7600.4(11) 6768.2(9) 3173.6(9) 38.8(3)
Cl1 5117.9(11) 8223.5(9) 1236.0(9) 42.8(3)
P1 5210.8(12) 6589.1(9) 2728.7(9) 36.5(3)
Cl4 2733.7(13) 5514.0(12) 4259.6(11) 55.8(4)
N1 6163(4) 6356(3) 1556(3) 39.1(11)
C8 6368(4) 6720(4) 4348(3) 39.6(13)
C6 5627(4) 5494(4) 2519(3) 36.4(12)
C7 5345(5) 6552(4) 3833(4) 39.1(13)
C5 5907(4) 5542(4) 1767(3) 36.6(12)
C4 5885(4) 4800(4) 1296(4) 41.3(13)
C1 6382(4) 6423(4) 871(4) 39.4(13)
C11 3922(4) 6625(4) 2104(4) 39.7(13)
C2 6347(5) 5704(4) 375(4) 45.0(14)
C14 3833(4) 6329(4) 1243(4) 42.1(13)
C9 4729(5) 7274(4) 4047(4) 40.1(13)
C10 5082(5) 5610(4) 4064(4) 42.4(13)
C12 3538(5) 7582(4) 2096(5) 43.2(16)
219
C13 3304(5) 5980(4) 2398(4) 42.6(13)
C3 6112(5) 4868(4) 597(4) 45.7(15)
C15 2500 6189(6) 5000 61(3)
Anisotropic Displacement Parameters (×104) for 3.2-Cl. The anisotropic displacement factor
exponent takes the form: -2π
2
[h
2
a*
2
× U11+ ... +2hka* × b* × U12]
Atom U11 U22 U33 U23 U13 U12
Ir1 36.09(18) 37.43(16) 31.41(16) 0.40(7) 9.84(12) -0.48(7)
Cl3 45.2(8) 38.6(7) 37.2(7) -1.9(5) 14.0(6) 0.3(5)
Cl2 38.5(8) 42.0(7) 34.9(7) 1.9(5) 10.6(6) -1.4(5)
Cl1 44.2(8) 45.6(7) 36.7(8) 5.3(5) 10.6(6) 2.6(6)
P1 38.1(8) 38.8(7) 32.5(7) 0.5(5) 11.2(6) -0.2(5)
Cl4 56.3(11) 66.4(10) 46.9(9) 2.4(7) 19.9(8) -2.6(8)
N1 33(3) 47(3) 35(3) 0.7(19) 8(2) 0.3(19)
C8 39(3) 50(3) 26(3) -2(2) 6(2) -6(2)
C6 37(3) 38(3) 31(3) -2(2) 7(2) 0(2)
C7 44(3) 41(3) 32(3) 1(2) 12(3) 1(2)
C5 36(3) 42(3) 31(3) 3(2) 9(2) 2(2)
C4 38(3) 42(3) 40(3) 2(2) 6(3) 4(2)
C1 42(3) 42(3) 33(3) 3(2) 11(3) -2(2)
C11 32(3) 45(3) 41(3) -6(2) 10(3) 0(2)
C2 41(4) 59(4) 33(3) -8(2) 10(3) 3(3)
C14 31(3) 55(3) 36(3) 0(2) 6(3) 0(2)
C9 39(3) 48(3) 34(3) -2(2) 12(3) 3(2)
C10 48(4) 43(3) 38(3) 2(2) 16(3) 2(2)
C12 35(4) 48(3) 42(4) 2(2) 6(3) 3(2)
C13 36(3) 52(3) 39(3) -1(2) 12(3) 2(2)
C3 50(4) 46(3) 40(3) -9(2) 12(3) 3(3)
C15 80(8) 46(5) 50(6) 0 13(6) 0
220
Bond Lengths in Å for 3.2-Cl.
Atom Atom Length/Å Atom Atom Length/Å
Ir1 Cl3 2.3661(14) C6 C5 1.513(8)
Ir1 Cl2
1
2.4971(15) C7 C9 1.544(8)
Ir1 Cl2 2.3841(15) C7 C10 1.552(8)
Ir1 Cl1 2.3473(14) C5 C4 1.379(8)
Ir1 P1 2.2724(16) C4 C3 1.382(10)
Ir1 N1 2.066(5) C1 C2 1.376(8)
P1 C6 1.832(6) C11 C14 1.541(9)
P1 C7 1.887(6) C11 C12 1.541(8)
P1 C11 1.886(6) C11 C13 1.537(9)
Cl4 C15 1.770(6) C2 C3 1.390(9)
N1 C5 1.362(7)
N1 C1 1.351(8)
C8 C7 1.527(8)
1
3/2-x, 3/2-y, 1/2-z
Bond Angles in ° for 3.2-Cl
Atom Atom Atom Angle/° Atom Atom Atom Angle/°
Cl3 Ir1 Cl2 94.58(5) Cl1 Cl1 Cl1 Cl1
Cl3 Ir1 Cl2
1
88.99(5) Ir1 Ir1 Ir1 Ir1
Cl2 Ir1 Cl2
1
80.89(5) Cl3 Cl3 Cl3 Cl3
P1 Ir1 Cl3 95.22(5) C8 C7 C9 107.7(5)
P1 Ir1 Cl2
1
173.94(5) C8 C7 C10 106.6(5)
P1 Ir1 Cl2 94.41(5) C9 C7 P1 110.9(4)
P1 Ir1 Cl1 100.67(6) C9 C7 C10 110.5(5)
N1 Ir1 Cl3 178.35(15) C10 C7 P1 110.1(4)
N1 Ir1 Cl2 85.23(14) N1 C5 C6 117.5(5)
N1 Ir1 Cl2
1
92.59(15) N1 C5 C4 120.7(6)
N1 Ir1 Cl1 91.35(14) C4 C5 C6 121.8(5)
221
N1 Ir1 P1 83.16(15) C5 C4 C3 120.6(6)
Ir1 Cl2 Ir1
1
99.11(5) N1 C1 C2 122.4(6)
C6 P1 Ir1 97.5(2) C14 C11 P1 108.1(4)
C6 P1 C7 104.5(3) C14 C11 C12 110.1(5)
C6 P1 C11 105.0(3) C12 C11 P1 109.9(4)
C7 P1 Ir1 120.1(2) C13 C11 P1 113.6(4)
C11 P1 Ir1 116.5(2) C13 C11 C14 106.3(5)
C11 P1 C7 110.3(3) C13 C11 C12 108.8(5)
C5 N1 Ir1 119.0(4) C1 C2 C3 119.1(6)
C1 N1 Ir1 122.3(4) C4 C3 C2 118.3(5)
C1 N1 C5 118.7(5) Cl4 C15 Cl4
2
110.4(5)
C5 C6 P1 110.0(4)
C8 C7 P1 110.9(4)
1
3/2-x, 3/2-y, 1/2-z;
2
1/2-x, +y, 1-z
Torsion Angles in ° for 3.2-Cl
Atom Atom Atom Atom Angle/°
Ir1 P1 C6 C5 -34.9(4)
Ir1 P1 C7 C8 -28.3(5)
Ir1 P1 C7 C9 91.3(4)
Ir1 P1 C7 C10 -146.1(4)
Ir1 P1 C11 C14 58.0(4)
Ir1 P1 C11 C12 -62.2(5)
Ir1 P1 C11 C13 175.7(4)
Ir1 N1 C5 C6 2.6(7)
Ir1 N1 C5 C4 -179.1(4)
Ir1 N1 C1 C2 -179.3(5)
P1 C6 C5 N1 24.5(7)
P1 C6 C5 C4 -153.8(5)
N1 C5 C4 C3 -0.6(9)
222
N1 C1 C2 C3 -2.5(10)
C6 P1 C7 C8 79.5(4)
C6 P1 C7 C9 -160.8(4)
C6 P1 C7 C10 -38.2(5)
C6 P1 C11 C14 -48.5(5)
C6 P1 C11 C12 -168.7(5)
C6 P1 C11 C13 69.1(5)
C6 C5 C4 C3 177.6(6)
C7 P1 C6 C5 -158.7(4)
C7 P1 C11 C14 -160.6(4)
C7 P1 C11 C12 79.2(5)
C7 P1 C11 C13 -43.0(5)
C5 N1 C1 C2 0.8(9)
C5 C4 C3 C2 -1.1(10)
C1 N1 C5 C6 -177.5(5)
C1 N1 C5 C4 0.8(9)
C1 C2 C3 C4 2.6(10)
C11 P1 C6 C5 85.2(5)
C11 P1 C7 C8 -168.1(4)
C11 P1 C7 C9 -48.4(5)
C11 P1 C7 C10 74.2(5)
223
Hydrogen Fractional Atomic Coordinates (×104) and Equivalent Isotropic Displacement
Parameters (Å
2
×10
3
) for 3.2-Cl. Ueq is defined as 1/3 of the trace of the orthogonalised Uij.
Atom x y z Ueq
H8A 6774.05 6262.86 4232.39 59
H8B 6421.52 6692.79 4918.5 59
H8C 6564.03 7312.16 4224.71 59
H6A 6175.69 5305.93 2980.02 44
H6B 5120.16 5045.6 2445.23 44
H4 5711.12 4236.33 1454.51 50
H1 6567.83 6988.31 727.15 47
H2 6480.88 5777.94 -113.68 54
H14A 4234.68 6706.86 1034.79 63
H14B 3174.59 6386.62 897.53 63
H14C 4032.2 5703.98 1250.01 63
H9A 4893.42 7862.75 3886.95 60
H9B 4840 7268.07 4627.57 60
H9C 4061.21 7150.03 3760.71 60
H10A 4452.22 5445.05 3706.06 64
H10B 5082.15 5616.78 4621.48 64
H10C 5544.27 5172.32 4009.8 64
H12A 3568.69 7751.7 2642 65
H12B 2881.72 7604.85 1740.44 65
H12C 3920.53 7996.76 1899.83 65
H13A 3552.2 5371.5 2419.04 64
H13B 2655.5 5999.29 2026.83 64
H13C 3311.84 6160.01 2936.34 64
H3 6107.29 4355.65 276.36 55
H15A 1949.25 6577.39 4743.86 73
H15B 3050.75 6577.4 5256.13 73
224
Atomic Occupancies for all atoms that are not fully occupied in 3.2-Cl
Atom Occupancy
H15A 0.5
H15B 0.5
225
5.5.7 X-ray Crystal Structure Data for 4.2
Figure 5.5.7.1. Molecular structure of 4.2 shown with 50% probability ellipsoids. Hydrogen atoms
are omitted for clarity, except hydrides.
A single crystals of C31H47F3Ir2N2O5P2S [[6]] were layered with DCM and Hexane. A
suitable crystal was selected and mounted on MiTiGen 50µm on a XtaLAB Synergy, Dualflex,
HyPix diffractometer. The crystal was kept at 101.15 K during data collection. Using Olex2, the
structure was solved with the SHELXT structure solution program using Intrinsic Phasing and
refined with the SHELXL refinement package using Least Squares minimisation on F
2
.
4-7
Crystal Data for C31H47F3Ir2N2O5P2S (M =1063.10 g/mol): monoclinic, space group P21/c
(no. 14), a = 13.2885(2) Å, b = 9.79380(10) Å, c = 29.3459(4) Å, β = 91.5730(10)°, V =
3817.78(9) Å
3
, Z = 4, T = 101.15 K, μ(MoKα) = 7.155 mm
-1
, Dcalc = 1.850 g/cm
3
, 112789
reflections measured (5.002° ≤ 2Θ ≤ 66.58°), 13361 unique (Rint = 0.0840, Rsigma = 0.0464) which
were used in all calculations. The final R1 was 0.0531 (I > 2σ(I)) and wR2 was 0.1237 (all data).
Crystal data and structure refinement for 4.2
226
Identification code [6]
Empirical formula C31H47F3Ir2N2O5P2S
Formula weight 1063.10
Temperature/K 101.15
Crystal system monoclinic
Space group P21/c
a/Å 13.2885(2)
b/Å 9.79380(10)
c/Å 29.3459(4)
α/° 90
β/° 91.5730(10)
γ/° 90
Volume/Å
3
3817.78(9)
Z 4
ρcalcg/cm
3
1.850
μ/mm
-1
7.155
F(000) 2056.0
Crystal size/mm
3
0.19 × 0.11 × 0.07
Radiation MoKα (λ = 0.71073)
2Θ range for data collection/° 5.002 to 66.58
Index ranges -20 ≤ h ≤ 20, -13 ≤ k ≤ 14, -45 ≤ l ≤ 42
Reflections collected 112789
Independent reflections 13361 [Rint = 0.0840, Rsigma = 0.0464]
Data/restraints/parameters 13361/0/436
Goodness-of-fit on F
2
1.193
Final R indexes [I>=2σ (I)] R1 = 0.0531, wR2 = 0.1176
Final R indexes [all data] R1 = 0.0719, wR2 = 0.1237
Largest diff. peak/hole / e Å
-3
3.16/-1.39
227
5.5.8 X-ray Crystal Structure Data for 4.9
Figure 5.5.8.1. ORTEP diagram of 4.9 shown with 50% probability ellipsoids. Hydrogen atoms
are omitted for clarity.
A clear colourless prism-like specimen of C20H18AgClN4O, approximate dimensions 0.149
mm x 0.258 mm x 0.363 mm, was used for the X-ray crystallographic analysis. The X-ray
intensity data were measured on a Bruker APEX DUO system equipped with a fine-focus tube
(MoKα , λ = 0.71073 Å) and a TRIUMPH curved-crystal monochromator.
The total exposure time was 3.50 hours. The frames were integrated with the Bruker
SAINT software package using a SAINT V8.38A (Bruker AXS, 2013) algorithm. The integration
of the data using a triclinic unit cell yielded a total of 23231 reflections to a maximum θ angle of
30.52° (0.70 Å resolution), of which 5649 were independent (average redundancy 4.112,
completeness = 98.4%, Rint = 2.90%, Rsig = 1.80%) and 5551 (98.27%) were greater than 2σ(F
2
).
The final cell constants of a = 9.4354(13) Å, b = 9.8010(13) Å, c = 11.9620(16) Å, α =
100.555(2)°, β = 110.768(2)°, γ = 106.606(2)°, volume = 939.9(2) Å
3
, are based upon the
228
refinement of the XYZ-centroids of 9205 reflections above 20 σ(I) with 4.809° < 2θ < 61.04°. Data
were corrected for absorption effects using the multi-scan method (SADABS). The ratio of
minimum to maximum apparent transmission was 0.862. The calculated minimum and maximum
transmission coefficients (based on crystal size) are 0.6630 and 0.8380.
The structure was solved and refined using the Bruker SHELXTL Software Package, using the
space group P -1, with Z = 2 for the formula unit, C 20H18AgClN4O. The final anisotropic full-
matrix least-squares refinement on F
2
with 246 variables converged at R1 = 3.22%, for the
observed data and wR2 = 8.22% for all data. The goodness-of-fit was 1.257. The largest peak in
the final difference electron density synthesis was 1.765 e
-
/Å
3
and the largest hole was -0.985 e
-
/Å
3
with an RMS deviation of 0.098 e
-
/Å
3
. On the basis of the final model, the calculated density was
1.674 g/cm
3
and F(000), 476 e
-
.
Sample and Crystal Data for 4.9
Identification code VDDisilver
Chemical formula C20H18AgClN4O
Formula weight 473.70 g/mol
Temperature 100(2) K
Wavelength 0.71073 Å
Crystal size 0.149 x 0.258 x 0.363 mm
Crystal habit clear colourless prism
Crystal system triclinic
Space group P -1
Unit cell dimensions a = 9.4354(13) Å α = 100.555(2)°
b = 9.8010(13) Å β = 110.768(2)°
c = 11.9620(16) Å γ = 106.606(2)°
Volume 939.9(2) Å
3
Z 2
229
Density (calculated) 1.674 g/cm
3
Absorption coefficient 1.232 mm
-1
F(000) 476
Data collection and structure refinement for 4.9
Diffractometer Bruker APEX DUO
Radiation source fine-focus tube (MoKα , λ = 0.71073 Å)
Theta range for data collection 1.92 to 30.52°
Index ranges -13<=h<=13, -13<=k<=13, -17<=l<=16
Reflections collected 23231
Independent reflections 5649 [R(int) = 0.0290]
Coverage of independent reflections 98.4%
Absorption correction multi-scan
Max. and min. transmission 0.8380 and 0.6630
Structure solution technique direct methods
Structure solution program SHELXTL XT 2014/5 (Bruker AXS, 2014)
Refinement method Full-matrix least-squares on F
2
Refinement program SHELXTL XL 2018/3 (Bruker AXS, 2018)
Function minimized Σ w(Fo
2
- Fc
2
)
2
Data / restraints / parameters 5649 / 0 / 246
Goodness-of-fit on F
2
1.257
Δ/σmax 0.001
Final R indices 5551 data; I>2σ(I) R1 = 0.0322, wR2 = 0.0820
all data R1 = 0.0327, wR2 = 0.0822
Weighting scheme w=1/[σ
2
(Fo
2
)+(0.0187P)
2
+1.9482P]
where P=(Fo
2
+2Fc
2
)/3
Largest diff. peak and hole 1.765 and -0.985 eÅ
-3
R.M.S. deviation from mean 0.098 eÅ
-3
230
Atomic coordinates and equivalent isotropic atomic displacement parameters (Å2) for 4.9.
U(eq) is defined as one third of the trace of the orthogonalized Uij tensor.
x/a y/b z/c U(eq)
C1 0.2500(3) 0.1504(2) 0.6213(2) 0.0155(4)
C2 0.4730(3) 0.3006(3) 0.6089(2) 0.0170(4)
C3 0.4923(3) 0.1702(3) 0.6159(2) 0.0204(4)
C4 0.3299(4) 0.9312(3) 0.6361(3) 0.0288(5)
C5 0.2542(3) 0.4025(2) 0.6079(2) 0.0130(3)
C6 0.2088(2) 0.4303(2) 0.4808(2) 0.0140(4)
C7 0.1874(3) 0.3249(3) 0.3743(2) 0.0177(4)
C8 0.1278(3) 0.3479(3) 0.2581(2) 0.0210(4)
C9 0.0911(3) 0.4745(3) 0.2521(2) 0.0228(5)
C10 0.1205(3) 0.5756(3) 0.3634(2) 0.0205(4)
C11 0.3617(3) 0.5392(2) 0.7237(2) 0.0135(4)
C12 0.4819(3) 0.6614(2) 0.7278(2) 0.0160(4)
C13 0.5823(3) 0.7878(2) 0.8377(2) 0.0186(4)
C14 0.5577(3) 0.7905(3) 0.9442(2) 0.0185(4)
C15 0.4375(3) 0.6646(2) 0.9468(2) 0.0158(4)
C16 0.3402(3) 0.5383(2) 0.8361(2) 0.0135(4)
C17 0.4139(3) 0.6588(3) 0.0561(2) 0.0203(4)
C18 0.3001(3) 0.5319(3) 0.0521(2) 0.0215(4)
C19 0.2085(3) 0.4121(3) 0.9385(2) 0.0188(4)
231
C20 0.7629(4) 0.0358(3) 0.0583(3) 0.0346(6)
Ag1 0.04770(2) 0.09381(2) 0.66216(2) 0.02062(6)
Cl1 0.83734(8) 0.05307(7) 0.73077(7) 0.02900(13)
N1 0.3241(2) 0.2859(2) 0.61185(17) 0.0138(3)
N2 0.3554(3) 0.0807(2) 0.62350(18) 0.0180(4)
N3 0.1773(2) 0.5553(2) 0.47612(19) 0.0178(4)
N4 0.2258(2) 0.4138(2) 0.83367(18) 0.0154(3)
O1 0.6410(2) 0.9069(2) 0.05443(18) 0.0260(4)
Bond lengths (Å) for 4.9
C1-N2 1.353(3) C1-N1 1.359(3)
C1-Ag1 2.085(2) C2-C3 1.355(3)
C2-N1 1.385(3) C2-H2 0.95
C3-N2 1.383(3) C3-H3 0.95
C4-N2 1.460(3) C4-H4A 0.98
C4-H4B 0.98 C4-H4C 0.98
C5-N1 1.474(3) C5-C11 1.513(3)
C5-C6 1.526(3) C5-H5 1.0
C6-N3 1.347(3) C6-C7 1.395(3)
C7-C8 1.391(3) C7-H7 0.95
C8-C9 1.388(4) C8-H8 0.95
C9-C10 1.389(4) C9-H9 0.95
232
C10-N3 1.338(3) C10-H10 0.95
C11-C12 1.373(3) C11-C16 1.429(3)
C12-C13 1.418(3) C12-H12 0.95
C13-C14 1.370(3) C13-H13 0.95
C14-O1 1.364(3) C14-C15 1.431(3)
C15-C17 1.411(3) C15-C16 1.421(3)
C16-N4 1.367(3) C17-C18 1.371(4)
C17-H17 0.95 C18-C19 1.405(3)
C18-H18 0.95 C19-N4 1.323(3)
C19-H19 0.95 C20-O1 1.425(3)
C20-H20A 0.98 C20-H20B 0.98
C20-H20C 0.98 Ag1-Cl1 2.3654(7)
Bond angles (°) for 4.9
N2-C1-N1 103.99(19) N2-C1-Ag1 129.96(16)
N1-C1-Ag1 124.82(15) C3-C2-N1 106.2(2)
C3-C2-H2 126.9 N1-C2-H2 126.9
C2-C3-N2 106.6(2) C2-C3-H3 126.7
N2-C3-H3 126.7 N2-C4-H4A 109.5
N2-C4-H4B 109.5 H4A-C4-H4B 109.5
N2-C4-H4C 109.5 H4A-C4-H4C 109.5
H4B-C4-H4C 109.5 N1-C5-C11 110.49(17)
N1-C5-C6 111.25(17) C11-C5-C6 116.47(17)
N1-C5-H5 106.0 C11-C5-H5 106.0
C6-C5-H5 106.0 N3-C6-C7 122.7(2)
N3-C6-C5 115.82(19) C7-C6-C5 121.24(19)
233
C8-C7-C6 118.8(2) C8-C7-H7 120.6
C6-C7-H7 120.6 C9-C8-C7 118.8(2)
C9-C8-H8 120.6 C7-C8-H8 120.6
C8-C9-C10 118.5(2) C8-C9-H9 120.8
C10-C9-H9 120.8 N3-C10-C9 123.6(2)
N3-C10-H10 118.2 C9-C10-H10 118.2
C12-C11-C16 118.4(2) C12-C11-C5 123.64(19)
C16-C11-C5 117.91(18) C11-C12-C13 122.7(2)
C11-C12-H12 118.7 C13-C12-H12 118.7
C14-C13-C12 119.2(2) C14-C13-H13 120.4
C12-C13-H13 120.4 O1-C14-C13 125.2(2)
O1-C14-C15 114.2(2) C13-C14-C15 120.6(2)
C17-C15-C16 118.2(2) C17-C15-C14 122.7(2)
C16-C15-C14 119.1(2) N4-C16-C15 121.65(19)
N4-C16-C11 118.45(19) C15-C16-C11 119.90(19)
C18-C17-C15 119.2(2) C18-C17-H17 120.4
C15-C17-H17 120.4 C17-C18-C19 119.0(2)
C17-C18-H18 120.5 C19-C18-H18 120.5
N4-C19-C18 123.7(2) N4-C19-H19 118.1
C18-C19-H19 118.1 O1-C20-H20A 109.5
O1-C20-H20B 109.5 H20A-C20-H20B 109.5
O1-C20-H20C 109.5 H20A-C20-H20C 109.5
H20B-C20-H20C 109.5 C1-Ag1-Cl1 173.31(6)
C1-N1-C2 111.56(18) C1-N1-C5 123.50(18)
C2-N1-C5 124.93(18) C1-N2-C3 111.64(19)
C1-N2-C4 124.2(2) C3-N2-C4 124.2(2)
C10-N3-C6 117.6(2) C19-N4-C16 118.3(2)
C14-O1-C20 117.0(2)
234
Anisotropic atomic displacement parameters (Å2) for 4.9. The anisotropic atomic displacement
factor exponent takes the form: -2π
2
[ h
2
a*
2
U11 + ... + 2 h k a*b* U12 ]
U11 U22 U33 U23 U13 U12
C1 0.0181(9) 0.0134(9) 0.0133(9) 0.0037(7) 0.0047(7) 0.0067(8)
C2 0.0150(9) 0.0199(10) 0.0169(9) 0.0049(8) 0.0070(8) 0.0084(8)
C3 0.0214(10) 0.0245(11) 0.0173(10) 0.0048(8) 0.0074(8) 0.0137(9)
C4 0.0417(15) 0.0184(11) 0.0317(13) 0.0101(10) 0.0149(12) 0.0187(11)
C5 0.0139(9) 0.0119(8) 0.0152(9) 0.0055(7) 0.0069(7) 0.0060(7)
C6 0.0115(8) 0.0147(9) 0.0152(9) 0.0055(7) 0.0055(7) 0.0042(7)
C7 0.0171(9) 0.0172(9) 0.0172(10) 0.0047(8) 0.0072(8) 0.0051(8)
C8 0.0175(10) 0.0266(11) 0.0161(10) 0.0052(8) 0.0072(8) 0.0054(9)
C9 0.0179(10) 0.0361(13) 0.0201(11) 0.0151(10) 0.0090(9) 0.0133(10)
C10 0.0172(10) 0.0263(11) 0.0269(11) 0.0160(9) 0.0114(9) 0.0135(9)
C11 0.0128(8) 0.0130(8) 0.0149(9) 0.0047(7) 0.0055(7) 0.0055(7)
C12 0.0160(9) 0.0149(9) 0.0179(9) 0.0063(8) 0.0078(8) 0.0055(8)
C13 0.0165(9) 0.0135(9) 0.0222(10) 0.0063(8) 0.0061(8) 0.0034(8)
C14 0.0171(10) 0.0146(9) 0.0185(10) 0.0024(8) 0.0036(8) 0.0057(8)
C15 0.0156(9) 0.0164(9) 0.0162(9) 0.0057(8) 0.0060(8) 0.0080(8)
C16 0.0131(9) 0.0143(9) 0.0153(9) 0.0057(7) 0.0062(7) 0.0074(7)
C17 0.0201(10) 0.0245(11) 0.0148(10) 0.0046(8) 0.0060(8) 0.0097(9)
C18 0.0215(11) 0.0298(12) 0.0163(10) 0.0087(9) 0.0095(8) 0.0114(9)
C19 0.0166(10) 0.0227(10) 0.0190(10) 0.0099(8) 0.0080(8) 0.0076(8)
C20 0.0318(14) 0.0186(11) 0.0347(15) -0.0011(10) 0.0083(12) -0.0024(10)
Ag1 0.01765(9) 0.01578(8) 0.03109(10) 0.01239(7) 0.01086(7) 0.00654(6)
Cl1 0.0251(3) 0.0244(3) 0.0429(4) 0.0150(3) 0.0182(3) 0.0097(2)
N1 0.0136(8) 0.0142(8) 0.0143(8) 0.0044(6) 0.0059(6) 0.0065(6)
N2 0.0235(9) 0.0159(8) 0.0149(8) 0.0040(7) 0.0059(7) 0.0113(7)
N3 0.0167(8) 0.0189(9) 0.0222(9) 0.0097(7) 0.0093(7) 0.0097(7)
N4 0.0137(8) 0.0171(8) 0.0173(8) 0.0080(7) 0.0068(7) 0.0066(7)
235
O1 0.0261(9) 0.0171(8) 0.0216(8) -0.0011(7) 0.0050(7) 0.0012(7)
Hydrogen atomic coordinates and isotropic atomic displacement parameters (Å
2
) for 4.9
x/a y/b z/c U(eq)
H2 0.5469 0.3852 0.6031 0.02
H3 0.5823 0.1451 0.6157 0.025
H4A 0.3738 -0.1206 0.5868 0.043
H4B 0.2123 -0.1264 0.6049 0.043
H4C 0.3866 -0.0598 0.7250 0.043
H5 0.1485 0.3598 0.6141 0.016
H7 0.2130 0.2390 0.3812 0.021
H8 0.1125 0.2782 0.1841 0.025
H9 0.0468 0.4916 0.1737 0.027
H10 0.0992 0.6641 0.3593 0.025
H12 0.4984 0.6612 0.6539 0.019
H13 0.6656 0.8696 0.8376 0.022
H17 0.4759 0.7418 1.1316 0.024
H18 0.2835 0.5250 1.1250 0.026
H19 0.1297 0.3251 0.9369 0.023
H20A 0.8083 1.1140 1.1396 0.052
H20B 0.7135 1.0735 0.9900 0.052
H20C 0.8507 1.0085 1.0481 0.052
236
5.5.9 References
1. Zhang, L.; Raffa, G.; Nguyen, D. H.; Swesi, Y.; Corbel-Demailly, L.; Capet, F.; Trivelli,
X.; Desset, S.; Paul, S.; Paul, J.-F.; Fongarland, P.; Dumeignil, F.; Gauvin, R. M., Acceptorless
Dehydrogenative Coupling of Alcohols Catalysed by Ruthenium PNP Complexes: Influence of
Catalyst Structure and of Hydrogen Mass Transfer. J. Catal. 2016, 340, 331-343.
2. Celaje, J. J. A.; Lu, Z.; Kedzie, E. A.; Terrile, N. J.; Lo, J. N.; Williams, T. J., A Prolific
Catalyst for Dehydrogenation of Neat Formic Acid. Nat. Commun. 2016, 7 (1), 11308.
3. Ireland, R. E.; Meissner, R. S., Convenient Method for the Titration of Amide Base
Solutions. J. Org. Chem. 1991, 56 (14), 4566-4568.
4. Sheldrick, G. M. SHELX-97. Acta Crystallogr., Sect. A 2008, 64, 112–122.
5. Sheldrick, G. M. Crystal Structure Refinement with SHELXL. Acta Crystallogr., Sect. C
2015, 71, 3–8.
6. Hübschle, C. B.; Sheldrick, G. M.; Dittrich, B. ShelXle: A Qt Graphical User Interface for
SHELXL. J. Appl. Crystallogr. 2011, 44, 1281–1284.
7. CrysAlisPro. Rigaku, V1.171.41.120a, 2021.
8. Coates, L.; Cao, H.; Chakoumakos, B. C.; Frontzek, M. D.; Hoffmann, C.; Kovalevsky, A.
Y.; Liu, Y.; Meilleur, F.; dos Santos, A. M.; Myles, D. A. A Suite-Level Review of the Neutron
Single-Crystal Diffraction Instruments at Oak Ridge National Laboratory. Rev. Sci. Instrum. 2018,
89, 092802.
9. Zikovsky, J.; Peterson, P. F.; Wang, X. P.; Frost, M.; Hoffmann, C. CrystalPlan: An
ExperimentPlanning Tool for Crystallography. J. Appl. Crystallogr. 2011, 44, 418-423.
10. Schultz, A. J.; Jørgensen, M. R. V.; Wang, X.; Mikkelson, R. L.; Mikkelson, D. J.; Lynch,
V. E.; Peterson, P. F.; Green, M. L.; Hoffmann, C. M. Integration of Neutron Time-of-Flight
Single-Crystal Bragg Peaks in Reciprocal Space. J. Appl. Crystallogr. 2014, 47, 915-921.
11. Schultz, A. J.; Srinivasan, K.; Teller, R. G.; Williams, J. M.; Lukehart, C. Single-Crystal,
Time-of-Flight, Neutron-Diffraction Structure of Hydrogen cis-Diacetyltetracarbonylrhenate,[cis-
(OC)4Re(CH3CO)2]H: A Metallaacetylacetone Molecule. J. Am. Chem. Soc. 1984, 106, 999-1003.
12. Sheldrick, G. M. SHELXT–Integrated Space-Group and Crystal-Structure Determination.
Acta Crystallogr. A 2015, 71, 3-8.
13. Sheldrick, G. M. A Short History of SHELX. Acta Cryst. 2008, A64, 112-122.
Abstract (if available)
Abstract
This dissertation contains research contributing to the development of homogeneous transition-metal catalysis for hydrogen production and storage. The main focus of the study is the synthesis of novel complexes and the H-transfer mechanism of iridium catalysts in dehydrogenation and hydrogenation of liquid organic hydrogen carriers. Chapter 1 is an overview of catalyst carbonylation pathway in alcohol and the underexplored benefits of catalyst carbonylation in catalyst initiation.
Chapter 2 discusses the economic advantages in on-demand H2 release from formic acid under self-pressurizing condition of 21 transition-metal catalysts (Ir, Ru, and Rh). Demonstrated herein is the first direct comparison of catalyst efficiency between ambient pressure and self-pressurized conditions through in-situ catalyst activation.
Discussed in chapter 3 is the discovery of novel trinuclear iridium complexes derived from (pyridylphosphine)iridium precursor and the application thereof to formic acid dehydrogenation reactions in aqueous methanol environments. This chapter describes the synthesis, investigation into the origins of this CO2-reducing reactivity, and reactivity of this family of iridium-based molecular cluster complexes, including of analysis chemical bonding, redox reactions, metal electrophilic substitution, neutron vibrational spectroscopy, and theoretical calculations. Novel metal clusters were analyzed via nuclear magnetic resonance, X-ray diffraction, neutron diffraction, and inelastic neutron scattering.
Chapter 4 recounts important findings and contributions in structural identification of catalytic intermediates in an Ir-catalyzed neat formic acid dehydrogenation mechanism, demonstration of an on-demand H2 release scaleup, and a step-by-step synthesis of a photobase-mediated complex. Chapter 5 discusses experimental procedures, spectral data, and other characterizations of the compounds in chapters 2, 3, and 4.
Linked assets
University of Southern California Dissertations and Theses
Conceptually similar
PDF
Iridium and ruthenium complexes for catalytic hydrogen transfer reactions
PDF
Development of new bifunctional iridium complexes for hydrogenation and dehydrogenation reactions
PDF
Hydrogen transfer reactions catalyzed by iridium and ruthenium complexes
PDF
New bifunctional catalysts for ammonia-borane dehydrogenation, nitrile reduction, formic acid dehydrogenation, lactic acid synthesis, and carbon dioxide reduction
PDF
Ruthenium catalyzed hydrogen-borrowing amine alkylation reactions
PDF
Carbon-hydrogen bond activation: radical methane functionalization; unactivated alkene coupling; saccharide degradation; and carbon dioxide hydrogenation
PDF
Ruthenium catalysis for ammonia borane dehydrogenation and dehydrative coupling
PDF
Transition metal complexes of pyridylphosphine and dipyridylborate ligands in dehydrogenation reactions
PDF
Rhenium bipyridine catalysts with pendant amines: substituent and positional effects on the electrocatalytic reduction of CO₂ to CO
PDF
Design and modification of electrocatalysts for use in fuel cells and CO₂ reduction
PDF
Dithiolate-based metal-organic frameworks for electrocatalytic hydrogen evolution
PDF
Novel methods for functional group interconversions in organic synthesis and structural characterization of new transition metal heterogeneous catalysts for potential carbon neutral hydrogen storage
PDF
Rational design of simple and complex rare earth metal catalyst systems to enable reactive, controlled and selective block copolymerization of chemically dissimilar monomers
PDF
Integrated carbon dioxide capture and utilization: catalysis enabled carbon-neutral methanol synthesis and hydrogen generation
PDF
Integrated capture and conversion of carbon dioxide from air into methanol and other C1 products
PDF
Harnessing fluorinated C1 nucleophilic reagents for the direct fluoroalkylation of ubiquitous C(sp2)-X and C(sp)-H centers
PDF
Electrochemical pathways for sustainable energy storage and energy conversion
PDF
Investigations in cooperative catalysis: synthesis, reactivity and metal-ligand bonding
PDF
Catalytic applications of palladium-NHC complexes towards hydroamination and hydrogen-deuterium exchange and development of acid-catalyzed hydrogen-deuterium exchange methods for preparative deut...
PDF
Photophysical properties of luminescent iridium and coinage metal complexes
Asset Metadata
Creator
Do, Van Khanh
(author)
Core Title
Hydrogen energy system production and storage via iridium-based catalysts
School
College of Letters, Arts and Sciences
Degree
Doctor of Philosophy
Degree Program
Chemistry
Degree Conferral Date
2023-05
Publication Date
11/15/2023
Defense Date
05/15/2023
Publisher
University of Southern California
(original),
University of Southern California. Libraries
(digital)
Tag
homogeneous catalysis,hydrogen energy,hydrogen production,hydrogen storage,iridium catalysts,OAI-PMH Harvest,production and storage reversibility
Format
theses
(aat)
Language
English
Contributor
Electronically uploaded by the author
(provenance)
Advisor
Williams, Travis (
committee chair
), Fokin, Valery (
committee member
), Yen, Jesse (
committee member
)
Creator Email
vando@usc.edu
Permanent Link (DOI)
https://doi.org/10.25549/usctheses-oUC113122794
Unique identifier
UC113122794
Identifier
etd-DoVanKhanh-11848.pdf (filename)
Legacy Identifier
etd-DoVanKhanh-11848
Document Type
Dissertation
Format
theses (aat)
Rights
Do, Van Khanh
Internet Media Type
application/pdf
Type
texts
Source
20230515-usctheses-batch-1044
(batch),
University of Southern California
(contributing entity),
University of Southern California Dissertations and Theses
(collection)
Access Conditions
The author retains rights to his/her dissertation, thesis or other graduate work according to U.S. copyright law. Electronic access is being provided by the USC Libraries in agreement with the author, as the original true and official version of the work, but does not grant the reader permission to use the work if the desired use is covered by copyright. It is the author, as rights holder, who must provide use permission if such use is covered by copyright.
Repository Name
University of Southern California Digital Library
Repository Location
USC Digital Library, University of Southern California, University Park Campus MC 2810, 3434 South Grand Avenue, 2nd Floor, Los Angeles, California 90089-2810, USA
Repository Email
cisadmin@lib.usc.edu
Tags
homogeneous catalysis
hydrogen energy
hydrogen production
hydrogen storage
iridium catalysts
production and storage reversibility