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Activation and functionalization of C-H bonds catalyzed by oxygen and nitrogen ligated late transition metal complexes

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Activation and functionalization of C-H bonds catalyzed by oxygen and nitrogen ligated late transition metal complexes

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ACTIVATION AND FUNCTIONALIZATION OF C-H BONDS CATALYZED
BY OXYGEN AND NITROGEN LIGATED LATE TRANSITION METAL
COMPLEXES

by
Somesh Kumar Ganesh

A Dissertation Presented to the
FACULTY OF THE GRADUATE SCHOOL
UNIVERSITY OF SOUTHERN CALIFORNIA
In Partial Fulfillment of the
Requirements for the Degree
DOCTOR OF PHILOSOPHY
(CHEMISTRY)

December 2008

Copyright 2008 Somesh Kumar Ganesh
ii
DEDICATION

TO MY GRAND PARENTS
(Mr. and Mrs. Bharatha Iyer)
iii
ACKNOWLEDGEMENTS
As I advance into the final phase towards obtaining my PhD, I would like to
thank my advisor, Prof Roy A. Periana, for giving me this wonderful opportunity to
work with him and guiding me how to properly think about science and pursue
cutting-edge research. This wouldn’t have been possible without his endless support,
inspiration, patience and above all his positive criticism.
I would also like to thank Professor G.K.Surya Prakash and Professor Nicos
Petasis for their excellent support and encouragement. Their profound knowledge in
both chemistry and philosophy has truly inspired me and they would be ideal role
models for me to follow in life.
I must acknowledge all the past and present members of the Periana group
for providing such a competitive and fertile scientific environment. I must personally
acknowledge Dr. Kenneth J. H. Young for teaching me how to make and
characterize complexes and ligands, Dr.Gaurav Bhalla, Dr.Xiang Yang Liu, and
Dr.Oleg Mironov for helping me from very beginning in doing rigorous science. My
thanks are also due to Bill Tenn, Brian Conley, and Steven Meier for making the lab
over the past 4 years a friendly and fun place to work. I would like to thank the
following Periana Group members and Caltech Goddard Group members for their
contributions to my science: C. J. Jones, Vadim Ziatdinov, Joo-Ho Lee, Steven
Bischof, Claas Hövelmann, Joyanta Choudhury, Chinnappan Sivasankar, Daniel Ess,
Robert Nielsen, Jonas Oxgaard, Marten Alhquist, Professor Bill Goddard, and Jason
iv
Gonzales. I would also like to thank Professor William Kaska for helpful
discussions.
I would like to thank various members of the chemistry department which
keep it running like a well oiled machine: Michele, Heather, Jaime, Bruno, Carole,
David, Jessy, Allan, and Ross. I would like to thank Professor Robert Bau’s group,
Dr. Muhammed Yousufuddin, Timothy Stewart and Professor Bau for solving the
various crystal structures which are presented in this thesis. I would also like to thank
many other friends and Collegues including Sujith, Kalyan, Panja, Habiba, Anand,
Gopal, Babu, Dr.Thomas Mathew and Chris Sucato for all the encouragement.
I would also like to thank the professors who have been part on my thesis and
candidacy exam committees: Prof. G. K. Surya Prakash, Prof. Nicos A. Petasis, Prof.
Roy A. Periana, Prof. Kyung Jung, and Prof. Katherine Shing. Thank you for
sacrificing your invaluable time to educate me so that I may become a better
scientist.
I would also like to thank the Department of Energy, that National Science
Foundation, the Loker Hydrocarbon Institute, the University of Southern California,
and most importantly Chevron for funding which allowed me to practice this
chemistry over the course of last four years. Last but not the least; I convey my deep
appreciation to my family. Without their belief, sacrifices and support this wouldn’t
have been possible.
v
TABLE OF CONTENTS
DEDICATION .............................................................................................................ii
ACKNOWLEDGEMENTS ........................................................................................iii
LIST OF TABLES .....................................................................................................vii
LIST OF FIGURES .....................................................................................................x
LIST OF SCHEMES.................................................................................................xiv
ABSTRACT...............................................................................................................xv
Chapter 1: Introduction ................................................................................................1
1.1 Background...................................................................................................1
1.2 CH activation................................................................................................6
1.2.1 Systems undergoing CH activation via electrophillic mechanism..........17
1.2.2 Electrophilic CH activation by Pt(II) ......................................................21
1.2.3 CH activation in strongly acidic media: catalyst inhibition by ground
state stabilization.....................................................................................25
1.3 CH activation and functionalization based on oxidative addition
mechanism...............................................................................................34
1.4 Iridium in an oxygen ligand environment...................................................38
1.5 Metal-Carbon bond functionalization pathways .........................................41
1.6 Chapter 1 References ..................................................................................43
Chapter 2: Non-planar Tetradentate Diamine-Bis(phenolate) Ligated
Rhodium(III) Complexes: Synthesis and Structures................................50
2.1 Introduction.................................................................................................50
2.2 Results and discussion................................................................................52
2.3 Conclusion..................................................................................................59
2.4 Experimental section...................................................................................59
2.5 Chapter 2 References ................................................................................105
Chapter 3: Mechanistic Insights Into Benzene C-H Activation With
Cyclometallated Ir(NNC)(R)(TFA)(CH
3
CN) Complexes ....................107
3.1 Introduction...............................................................................................107
3.2 Results and Discussion..............................................................................110
3.2.1 Synthesis of active catalyst ...................................................................110
3.2.2 Catalyst stability....................................................................................113
3.2.3 Mechanism of H/D exchange................................................................114
3.2.4 Reaction order of substrates..................................................................117
vi
3.2.5 Kinetic Dependence on acetonitrile (NCCH
3
) concentration ...............121
3.2.6 Evidence for ion-pair mechanism .........................................................122
3.3 Conclusion................................................................................................128
3.4 Experimental Section................................................................................128
3.5 Chapter 3 References ................................................................................152
Chapter 4: Mechanism of Anti-Markovnikov Olefin Hydroarylation Catalyzed
by Homogeneous O-Donor Ir(III) Complexes.......................................154
4.1 Introduction...............................................................................................154
4.2 Results and Discussion..............................................................................158
4.2.1 Rates of Hydroarylation for (acac-O,O)
2
Ir(III) Complexes..................158
4.2.2 Catalyst stability....................................................................................161
4.2.3 Thermodynamic vs. Kinetic control of regioselectivity........................162
4.2.4 Is the active catalyst a dinuclear or mononuclear species? ...................165
4.2.5 Why is no β-hydride elimination observed? .........................................167
4.2.6 Reaction order of substrates..................................................................176
4.2.7 Evidence for proposed mechanism .......................................................179
4.3 Conclusion................................................................................................189
4.4 Experimental Section................................................................................190
4.5 Chapter 4 References ................................................................................203
Bibliography.............................................................................................................206

vii
LIST OF TABLES

Table 2.1. Calculated relative energies for cis-O,O and trans-O,O
isomers of 1, 2 and 3. Energies are in kcal/mol. 56
Table 2.2. Crystal data and structure refinement for Rh(NNOO-
but,py)(Cl)( CH
3
OH) 64
Table 2.3. Atomic coordinates ( x 10
4
) and equivalent isotropic
displacement parameter (Å
2
x 10
3
) for Rh(NNOO-
bu
t
,py)(Cl)( CH
3
OH). U(eq) is defined as one third of the
trace of the orthogonalized U
ij
tensor. 64
Table 2.4 Bond lengths [Å] and angles [°] for Rh(NNOO-but,py)(Cl)(
CH
3
OH). 66
Table 2.5. Anisotropic displacement parameters (Å
2
x 10
3
) for
Rh(NNOO-bu
t
,py)(Cl)( CH
3
OH) The anisotropic
displacement factor exponent takes the form: -2 π
2
[ h
2

a
*2
U
11
+ ... + 2 h k a* b* U
12
]. 72
Table 2.6. Hydrogen coordinates ( x 10
4
) and isotropic displacement
parameters (Å
2
x 10
3
) for Rh(NNOO-bu
t
,py)(Cl)( CH
3
OH). 74
Table 2.7. Crystal data and structure refinement for Rh(NNOO-
Me,Py)(Cl)(H
2
O). 76
Table 2.8. Atomic coordinates ( x 10
4
) and equivalent isotropic
displacement parameters (Å
2
x 10
3
) for Rh(NNOO-
Me,Py)(Cl)(H
2
O). U(eq) is defined as one third of the
trace of the orthogonalized Uij tensor. 77
Table 2.9. Bond lengths [Å] and angles [°] for Rh(NNOO-
Me,Py)(Cl)(H
2
O). 78
Table 2.10. Anisotropic displacement parameters (Å
2
x 10
3
) for C
24
H
27

Cl N
2
O
4
Rh. The anisotropic displacement factor exponent
takes the form: 81
Table 2.11. Hydrogen coordinates ( x 10
4
) and isotropic displacement
parameters (Å
2
x 10
3)
for C
24
H
27
Cl N
2
O
4
Rh. 83
Table 2.12. Crystal data and structure refinement for C
31
H
34
N
2
O
5
Rh. 84
viii
Table 2.13. Atomic coordinates ( x 10
4
) and equivalent isotropic
displacement parameters (Å
2
x 10
3
) for C
31
H
34
N
2
O
5
Rh.
U(eq) is defined as one third of the trace of the
orthogonalized Uij tensor. 85
Table 2.14. Bond lengths [Å] and angles [°] for C
31
H
34
N
2
O
5
Rh. 86
Table 2.15. Anisotropic displacement parameters (Å
2
x 10
3
) for C
31
H
34

N
2
O
5
Rh. The anisotropic displacement factor exponent
takes the form: 90
Table 2.16. Hydrogen coordinates ( x 10
4
) and isotropic displacement
parameters (Å
2
x 10
3
) for C
31
H
34
N
2
O
5
Rh. 92
Table 3.1. Crystal data and structure refinement for C
30
H
29
C
l2
F
3
Ir
N
3
O
2
. 137
Table 3.2. Atomic coordinates ( x 10
4
) and equivalent isotropic
displacement parameters (Å
2
x 10
3
) for C
30
H
29
C
l2
F
3
Ir N
3

O
2
. U(eq) is defined as one third of the trace of the
orthogonalized U
ij
tensor. 138
Table 3.3. Bond lengths [Å] and angles [°] for NNCethym. 139
Table 3.4. Anisotropic displacement parameters (Å
2
x 10
3
) for C
30
H
29

Cl
2
F
3
Ir N
3
O
2
. The anisotropic displacement factor
exponent takes the form: -2 π
2
[ h
2
a
*2
U
11
+ ... + 2 h k a* b*
U
12
]. 143
Table 3.5.

Hydrogen coordinates ( x 10
4
) and isotropic displacement
parameters (Å
2
x 10
3
) for C
30
H
29
C
l2
F
3
Ir N
3
O
2
. 145
Table 3.6. C
6
H
6
/Tol-d
8
H/D exchange (170
o
C) with Phenyl-Ir-TFA
and catalyst stability. 146
Table 3.7. Eyring plot for C
6
H
6
/Tol-d
8
H/D exchange for Phenyl-Ir-
TFA. 147
Table 3.8. Eyring plot for C
6
H
6
/Tol-d
8
H/D exchange for Ethyl-Ir-
TFA 148
Table 3.9. Kinetic dependence of H/D exchange on benzene
concentration. 148
Table 3.10. Kinetic dependence on catalyst concentration. 149
ix
Table 3.11. Kinetic dependence on trifluroacetate (TFA) concentration. 150
Table 3.12. Kinetic dependence on acetonitrile (NCCH
3
) concentration. 150
Table 4.1. Hydroarylation of propylene and styrene with benzene
catalyzed by R-(acac-O,O)
2
Ir(III)(L) complexes. Values
taken from reference 85b. 159
Table 4.2. Comparison of thermodynamic and experimental ratio for
Hydroarylation with various olefins. 162
Table 4.3. Insertion products of olefins (mono-substituted ethylenes)
with Ph-Ir-Py
a
185
Table 4.4. Eyring Plot for pyridine exchange with Ph-Ir-Py. 196
Table 4.5. Eyring plot for pyridine exchange for CH
3
-Ir-Py. 197
Table 4.6. Kinetic dependence of Hydroarylation on olefin
concentration. 198
Table 4.7. Kinetic dependence of Hydroarylation on catalyst
concentration 198
Table 4.8. Kinetic dependence of Hydroarylation on pyridine
concentration. 199
Table 4.9. Rate difference between Ph-Ir-Py and Ph-Ir-H
2
O 200
Table 4.10. Comparitive rate of Hydroarylation between trans-Ph-Ir-Py
Vs cis-Ph-Ir-Py. 201
Table 4.11. Comparison of thermodynamic and experimental ratio for
Hydroarylation with various olefins. 202

x
LIST OF FIGURES
Figure 1.1. Oxidative conversion of fossil fuels is a foundational
technology 2
Figure 1.2. Examples of products potentially impacted by next
generation, low temperature, selective, hydrocarbon
oxidation catalysts 3
Figure 1.3. Many complexes capable of CH activation have now been
reported. Catalytic systems that generate functionalized
products have been boxed. 5
Figure 1.4. Advantage of CH actviation over classical methods, greater
selectivity. 7
Figure 1.5. Incorporating the “CH activation” reaction into a catalytic
system requires integration with a functionalization
reaction and stable systems 8
Figure 1.6. Key requirements for any efficient catalyst 10
Figure 1.7. The various mechanisms for CH cleavage in CH activation 11
Figure 1.8. Catalytic cycle for alkane metathesis. 15
Figure 1.9. Electrophilic activation of methane by “Soft” electrophiles 16
Figure 1.10. Orbital interaction between the low lying compact HOMO
of a CH bond and the low lying, polarizable LUMO of a
“Soft” electrophile 17
Figure 1.11. Proposed mechanism for methane oxidation by the
Pt(bpym)Cl
2
/H
2
SO
4
. 25
Figure 1.12. Generalized energy diagram for CH Activation via alkane
coordination and CH cleavage showing ground state
stabilization 27
Figure 1.13. Comparison of the likely active catalyst in the
Pt(bpym)Cl
2
/H
2
SO
4
system with the weakly coordinating
BARF anion. 32
Figure 1.14. Correlation of CH activation rates (Measured by H/D
exchange rates between CH
4
and D
2
SO
4
) with solvent
acidity, H
0
(98 % H
2
SO
4
= 10.4 H
0
and 85% = 8 H
0
). 34
xi
Figure 1.15. Some notable C-H activation complexes based on OA
mechanism 35
Figure 1.16. Ir(PCP)H
2
catalyzed dehydrogenation of Alkanes. 36
Figure 1.17. Friedel Crafts Alkylation 37
Figure 1.18. Murai reaction catalyzed by Ru complex. 37
Figure 1.19. Oxygen transfer on Iridium center using polyoxoanion
(Klemperer) 39
Figure 1.20. Reported examples of Ir(V) Complexes. 39
Figure 1.21. Examples of Oxygen donor ligands. 40
Figure 1.22. Comparision of Baeyer-Villiger reaction to a possible
transition metal analog. 41
Figure 2.1. (a) tetradentate amine-phenol ligand(NNOO) (b) structure
classes of amine-phenolate complexes 51
Figure 2.2. Molecular structure of 1, Rh(NNOO-bu
t
,py)(Cl)( CH
3
OH). 53
Figure 2.3. Molecular structure of 3, Rh(NNOO-Me,Py)(Cl)(H
2
O). 55
Figure 2.4. Molecular structure of 4, Rh(NNOO-Me,Py)(Ph)(CH
3
OH). 58
Figure 3.1. Possible catalytic schemes for hydrocarbon hydroxylation. 108
Figure 3.2. Synthesis of Ethyl-Ir-TFA complex 111
Figure 3.3. ORTEP diagram of Ethyl-Ir-TFA, showing ellipsoids at the
50% probability level. 112
Figure 3.4. Synthesis of Phenyl-Ir-TFA by stoichometric CH
activation. 113
Figure 3.5. Plot of C
6
H
6
/Tol-d
8
H/D exchange with Phenyl-Ir-TFA as
catalyst. 114
Figure 3.6. Proposed mechanism for CH activation with a dissociative
loss of acetonitrile 116
Figure 3.7. Ion-pair mechanism where TFA labilizes and forms a tight
ion-pair 117
xii
Figure 3.8. Benzene concentration dependence 119
Figure 3.9. Dependence on catalyst concentration with excess L(TFA) 120
Figure 3.10. Dependence of rate on [TFA]. 121
Figure 3.11. Dependence of rate of H/D exchange of [NCCH
3
] 122
Figure 3.12. Addition of excess chloride salt to Phenyl-Ir-TFA. 123
Figure 3.13. NMR showing treatment of Phenyl-Ir-TFA with tetrabutyl
ammonium chloride. 124
Figure 3.14. Phenyl-Ir-TFA in presence of excess acetonitrile 125
Figure 3.15. VT-NMR showing formation of new acetonitrile species. 126
Figure 3.16. B3LYP potential energy surface (ΔH
solv
) for C
6
H
6
/C
6
D
6

H/D exchange. 127
Figure 4.1. Comparison of a) Friedel-Crafts acylation, followed by
reduction and b) Hydroarylation of olefins. 155
Figure 4.2. Proposed reaction mechanisms for H/D exchange of
benzene and hydroarylation of ethylene catalyzed by R-Ir-L
and [R-Ir]
2
complexes. 157
Figure 4.3. Acetylacetonate based Ir(III) O-donor complexes studied. 159
Figure 4.4. Time-dependent hydroarylation of propylene using Ph-Ir-Py
as catalyst. 162
Figure 4.5. TOF vs. 1/Py catalyzed by Ph-Ir-Py. 167
Figure 4.6. Reversible versus irreversible β-hydride elimination 169
Figure 4.7. Possible products expected from heating CH
3
13
CH
2
-Ir-Py in
C
6
D
6
to generate ethane by CH Activation. 171
Figure 4.8. Time dependent
13
C NMR spectra for the reaction of
CH
3
13
CH
2
-Ir-Py (-9 ppm) with C
6
D
6
to form
13
CH
3
CH
2
-Ir-
Py (18 ppm) and two regioisomers of ethane (8 ppm). 172
Figure 4.9. B3LYP potential energy surface for β-hydride elimination,
olefin hydride formation, and CH activation (kcal/mol). 175
xiii
Figure 4.10. Kinetic dependence of hydroarylation on benzene
concentration 177
Figure 4.11. Kinetic dependence of hydroarylation on olefin
concentration. 178
Figure 4.12. Rate vs. catalyst concentration for Ph-Ir-Py with excess
Py. 179
Figure 4.13. Stoichiometric products after treatment of Ph-Ir-Py with R-
CH=CH
2
, R= C
6
H
5
, CH
3
, C
4
H
9
. 185
Figure 4.14. Comparison of previously reported B3LYP (ΔH
solv
top and
ΔH
gas
bottom) and experimental values for the
hydroarylation (shown only for ethylene). Experimental
values in blue boxes. Values taken from references 9 and
10 (kcal/mol). 189
xiv
LIST OF SCHEMES
Scheme 1.1. C-H bond cleavage by sigma bond metathesis. 13
Scheme 1.2. Methane activation by HgSO
4
. 18
Scheme 1.3. Possible Transition states for generation of methanol from
CH
3
HgX 20
Scheme 1.4. Methane activation by (bpym)PtCl
2
22
Scheme 1.5. Acetic acid formation using (bpym)PtCl
2
with CH
4
and
CO. 23
Scheme 2.1. Synthesis of bisphenolate based Rh (III) chloro complexes 52
Scheme 2.2. Synthesis of Rh (III) Phenyl complex by transmetallation. 57
Scheme 3.1. Proposed rate law 118
Scheme 4.1. TOF dependence on [L] for dinuclear and mononuclear
complexes. 166
Scheme 4.2. Kinetic scheme for CH activation and α to β
13
C-migration. 173
Scheme 4.3 Proposed rate law. 176

xv

ABSTRACT
This dissertation describes the usage of nitrogen and oxygenated ligand sets such
as acetylacetone (acac), 6-phenyl-4,4’-bis(tert-butyl)-2,2’-bipyridine(NNC) on
Iridium metal and diamine-bisphenolate (NNOO) on Rhodium for the activation of
the C-H bonds of arenes and functionalization such as hydroarylation of olefins.
The first chapter is an introduction to CH activation and its importance
towards CH bond functionalization. The use of acidic solvents for CH activation are
also addressed and the catalyst inhibition by water or methanol. Approaches for the
next generation of CH functionalization of catalysts are also addressed.
Chapter two addresses synthesis and characterization of air and thermally
stables biamine-bisphenolate (NNOO)Rh(III)Cl(S) (X= Cl ,Ph; S = H
2
O , CH
3
OH)
type complexes with the objective of designing new CH activation catalyst
precursors having predisposed cis coordination states for CH activation. NMR and
X-ray diffraction studies revealed that the NNOO ligands coordinate to Rh as non-
planar tetradentate ligands, with O,O donors either in a cis or trans position,
depending on fairly subtle differences. DFT studies suggest that the preference for
cis/trans-O,O is controlled by the bulk of the phenolate substituents, and the rigidity
of the N-C-C-N bridge. Finally, transmetalation of the Rh-Cl bond with Ph
2
Hg led to
a Rh-Phenyl complex with conserved geometry.
xvi
Our group has been exploring the chemistry of electron rich, tridentate
pincer, NNC ligated, Ir(III) homogeneous complexes in order to identify systems that
could be sufficiently thermally, protic and oxidant stable to allow coupling of the CH
activation and M-R Functionalization reactions to generate functionalized products
in new catalytic systems. We had earlier demonstrated that Ir(NNC)(C
2
H
5
)(TFA)(L)
complexes where NNC is 6-phenyl-4,4'-(di-tert-butyl)-2,2'-bipyridine and L is
NCCH
3
or ethylene(C
2
H
4
) undergo stochiometric C-H activation of hydrocarbons at
110
o
C. In chapter 3 we examine the mechanism for the catalytic H/D exchange
between benzene and toluene with this system where R = Ph.
Chapter 4 summarizes the usage of air and water stable O-donor ligated, late
metal complexes, (acac-O,O)
2
Ir(R)(L), based on the simplest β-diketonate,
acetylacetonate for the anti-Markovnikov, hydroarylation of unactivated olefins,
which has been shown to operate by arene C-H activation followed by olefin
insertion.

1
Chapter 1: Introduction

1.1 Background

The conversion of fossilized hydrocarbons to energy and materials is a
foundational technology of our petroleum industry.
1
While it is important that we
consider a switch to future alternative forms, such as wind, solar and hydrogen-based
economy. It is critical that we develop short term solutions as a bridge to this long
term future and to address the energy crisis facing the world today. As a result, we
need to develop more environmentally benign, greener technologies for these
essential fossil fuel based processes currently being used and will continue to be
important in the next decade. As shown in Figure 1.1, the key objectives of such
future processes must be to minimize emissions and capital costs while maximizing
energy and product output. By reducing the dependence on petroleum and increasing
the use of underutilized, abundant natural gas would facilitate this movement
lifetime to these greener technologies while extending the lifetime of these limited
fossilized resources.

2
ENERGY
$$$
EMISSIONS
-$$
MATERIALS
$$$
FOSSIL FUELS
+
AIR
CAPITAL
-$$
Minimize
Maximize
Minimize
Maximize
Global warming
Lessen dependence
on oil
Currently:
Primarily oil
Future:
Natural gas

Figure 1.1. Oxidative conversion of fossil fuels is a foundational technology

Alkanes from natural gas and petroleum are among the world’s most
abundant and low-cost feedstocks. Currently petrochemical technologies to convert
these feed stocks to energy, chemicals, and fuels operate at high temperatures and
utilize multi-step processes which lead to inefficient, capital intensive processes.
The development of low temperature, selective, direct alkane oxidation chemistry
could lead to a new paradigm in energy and petrochemical technologies in the 21
st

century that are environmentally cleaner, economically superior and allow the large
reserves of untapped remote natural gas to be used as primary feedstocks for fuels
and chemicals.
2
Alcohols are among the highest volume commodity chemicals and
most versatile feedstocks.
2b
A primary reason that technologies for direct, selective
hydroxylation of alkanes to alcohols remain a challenge is that the current
commercial catalysts for alkane oxidation (typically solid metal oxides) are not
sufficiently active for the functionalization of alkane CH bonds. As a result, high
3
temperatures and harsh conditions must be employed that lead to low reaction
selectivity.
2a

The development of next generation catalysts that would allow the selective
conversion of methane and higher alkanes to alcohols or other chemical commodities
at low temperatures (~200–250
o
C), in inexpensive reactors, with fewer steps and
high yields. Examples of products that could be dramatically impacted by such low
temperature conversion catalysts are shown in Figure 1.2.
R-H R-X
Phenol
1,4-Butane Diol
Propylene Glycol
t-Butanol
1,3-Propane Diol
Ethanol
Ethylene Glycol
Methanol
(DMM)
Low Temperature
Fuel Cells
Acetic Acid
Lower
Temperatures
~200
o
C
Higher efficiencies
Lower capital
Today
High Temperatures
>600
o
C
High capital
Lower atom and
energy efficiency
Cinnamates
Linear Alkyl Benzene
MSA
Methyl Chloride
Divinyl Benzene
Cyclohexanol
Neoacids
Diphenyl Carbonates
Hydrogen peroxide
Liquid Fuels
Styrene
Isobutyl Benzene

Figure 1.2. Examples of products potentially impacted by next generation, low
temperature, selective, hydrocarbon oxidation catalysts

The primary basis for direct alkane conversion chemistry impacting the
petrochemical industry is that, unlike the fine chemical industry, the bulk of the
production costs are process costs as opposed to material costs. Depending on the
process, as much as 50 to 75% of these process costs can be related to the cost of the
plant itself, the capital costs. Consequently, in addition to improvements related to
4
environmental considerations, so-called “Green chemistry”, key improvements to
developing new petrochemical processes must involve significant reductions in
capital costs in order to warrant the risks of developing new processes. This is
because in general, petrochemical processes involve enormously large capital on the
order of hundreds of millions of dollars. One key to reducing the capital costs in
new processes is to reduce the number of process steps since this is related to the
number of process units in the plant.
Significant advances in the chemistry of the hydrocarbons have been made
since the 1970’s. Particularly relevant to the development of low temperature,
selective, heteroatom hydrocarbon functionalization catalysts has been the discovery
of homogeneous metal complexes that cleave the CH bonds of unactivated
hydrocarbons at low temperatures and with extraordinary selectivity via the CH
activation reaction.
3
Some of the notable homogeneous complexes that catalyse the
activation of alkanes and functionalization to products are shown in Figure 1.3.
5

N
N
N
N N
N
Ru
Ph
3
PH
L
B
H
Periana
Periana
Green
W
H
H
Ir CO
CO
Graham
Pt
P
H P
Whitesides
H
Os
PR
3
R
3
P PR
3
R
3
P
Flood
N N
Pt
CH
3
B
N
N
N
N
H
Goldberg
Watson
Lu
CH
3
NN
NN
Pt
Cl
Cl
Goldman, Jensen, Kaska
Lau
Pt
N CH
3
L N
Bercaw Hartwig
P
P
Ir
H
H
Ir
Me
3
P
H
H
Bergman
Hg(II)
Ir
Sen
Pd(II)
Pt
Cl H
2
O
H
2
O Cl
Shilov
Me
5
Ir
Me
3
P
Me
Bergman
Ir
O O
O O
CH
3
N
Periana
[(Por)
2
Rh
II
]
2
Wayland
Re
Me
3
P
H
PMe
3
H
W. D. Jones
NR Zr
RHN
RHN
Wolczanski

Figure 1.3. Many complexes capable of CH activation have now been reported.
Catalytic systems that generate functionalized products have been
boxed.

It is well understood that the C-H bond in methanol (~90 kcal/mol) a carbon-
heteroatom functionalized product, is more reactive than the parent alkane (methane
~105 kcal/mol). Therefore, the method chosen for the functionalization of C-H
bonds must be one that shows selectivity. Through the mechanistic study of some of
these systems (Figure 1.3), it was observed that the CH activation reaction (cleavage
of CH bonds 1
o
> 3
o
and aromatic > aliphatic) has a unique selectivity.
4
Therfore,
since this discovery, there has been and continues to be intense interest in
incorporating the CH activation reaction into catalytic cycles to convert hydrocarbon
to more useful functionalized products. However, to date relatively few catalyst
systems that are based on the CH activation reaction have been developed that allow
the functionalization of hydrocarbons
5,6,7,8,9,10,11
and there are still large gaps in our
fundamental knowledge of how to design such catalysts.
12
In this chapter, the focus
6
is discussion of some of the challenges and approaches to developing the next
generation of alkane hydroxylation catalysts based on the CH activation reaction.

1.2 CH activation

Homogeneous transition metal catalysis has had a substantial impact on
organic chemistry. From polymerizations to hydrogenations there are few aspects of
organic chemistry that have not been touched by this field of research. Most of the
organic chemistry, characterized by mild reaction conditions and high reaction
selectivity, can be classified as inner-sphere coordination chemistry at carbon
centers; i.e. chemistry that occurs within the first-coordination sphere of three, four
and five coordinate carbon species. While the coordination chemistry of carbon in
functionalized organic molecules is well-developed, the coordination chemistry of
alkanes is much less so and is characterized by reactions with super acids, super
bases, free-radicals or carbenes. These very reactive species (Figure 1.4) are either
generated under high energy conditions, or with high energy precursors and are
generally not amenable to efficient syntheses with alkanes as starting materials.
7
C + H C + H C + H
zz
+ - -
+
C H C H
C-M + H-X C-M + H-X
C
H
X-M
MX
Electrophilic Substitution Insertion
Sigma bond metathesis
C
H
C
Classical Chemistry
High Energy Intermediates
Classical Chemistry
High Energy Intermediates
CH Activation
Low Energy Intermediates
CH Activation
Low Energy Intermediates
Highly Selective
Highly Selective
Non Free Radical
Non Free Radical

Figure 1.4. Advantage of CH actviation over classical methods, greater selectivity.

The majority of these catalytic reactions take place in the inner, or first
coordination sphere of the homogeneous metal catalyst and in many cases lead to the
formation of organometallic, M-C, intermediates. The advantage of these inner
sphere, organometallic reactions is that the reactant of interest is bound to the
catalyst center during conversion to products and as a result, the catalyst can
effectively mediate both rate and selectivity in the conversion of the reactants to
desired products.

8
C H
C-M + X-H C-M + H-X
C
H
X-M
MX
1/2 O
2
C-OH
+
Functionalization
CH Activation
<250
o
C
Stable
Catalysis!
Stable
Catalysis!
MX +
Electrophilic
Substitution
Insertion
Sigma bond
metathesis

Figure 1.5. Incorporating the “CH activation” reaction into a catalytic system
requires integration with a functionalization reaction and stable
systems

There are many definitions of “CH activation.” We define CH activation as a
two step process by which 1) coordination of the substrate C-H bond to the inner-
sphere of an M-X species followed by the facile cleavage of the CH bond by the M-
X species to generate an M-C intermediate and HX (Figure 1.5). Functionalization
of the resulting M-C intermediate by reactions at the inner-sphere of the metal or
through an attack on or by the carbon bound to the metal results in the functionalized
product. Important to this definition is the requirement that during the CH cleavage
the hydrocarbyl species remains in the inner-sphere and under the influence of “M”.
Theoretical studies as well as experimental studies support this view that classically
unreactive CH bonds can be cleaved by such inner-sphere mechanism.
13
This
emphasis on inner-sphere coordination is based on the presumption that cleavage
reactions of the CH bond that proceed in this manner, with strong interaction
9
between the CH bond and “M”, can be expected to show unique high selectivity and
activities A process such as this could be run in a small inexpensive reactor which
would reduce the capital costs associated with the multi-step Fisher-Tropsch process
From the list of catalysts (Figure 1.3) only a few have been shown to generate
functionalized products.
14,15,16,17,18,19,20,21
The reason for the limited number of
catalysts that are capable of generating functionalized products when there are a
significant number of catalysts that are competent for CH activation can likely be
attributed to what some call “the devil’s triangle,” Figure 1.6. Three successive
criteria must be met for any catalyst to be efficient in any catalytic reaction. These
three criteria are rate, life and selectivity. The problem arises because these three
criteria are interdependent on the molecular structure and composition of the catalyst
and the reaction conditions.

For example, a highly reactive catalyst might not be
stable under the conditions of the reaction and therefore have a short lifetime, or
even display low selectivity. Vice versa, a relatively stable catalyst might have a
sufficiently long lifetime but will likely have slow rates. Therefore, all three criteria
must be met simultaneously in order to generate an efficient catalyst.
10
These requirements
should be simultaneously
considered for efficient
catalyst design

Figure 1.6. Key requirements for any efficient catalyst

As might be expected from the wide variety of complexes that cleave C-H
bonds by such inner-sphere reaction there are several recognized mechanisms for CH
activation (the transition state for the CH cleavage step). Several of these CH
cleavage classifications are shown in Figure 1.7. As shown, all of these
classifications are related in that they require the alkane (R-H) be coordinated to the
inner-sphere of the metal either as intermediate or via a transition state leading to the
formation of an organometallic M-C intermediate. The specifics of the actual mode
of cleavage depend on the electronic configuration of the metal, the X group and
various variations of these classifications have been observed. Of these, the most
common modes are Electrophilic Substitution (ES), Oxidative Addition (OA) and
Sigma Bond Metathesis and in all cases unique CH cleavage selectivity patterns are
observed.
12

11

Figure 1.7. The various mechanisms for CH cleavage in CH activation

This cleavage of the CH bond mediated via formation of a M-C species can
be contrasted to other reactions of alkane CH bonds such as metal mediated
generation of alkyl free radicals, acid or base catalyzed generation of carbocations or
carbanions that are not as selective. In these processes, unlike the CH activation
reaction as defined above, the reactive alkyl fragments that are generated are not
under the influence of the catalyst (because they are not strongly bound to the
catalyst center) and consequently, can exhibit intrinsic reactivities that are generally
undesirable. This may be a reason that the commercially available oxidation catalysts
based on metal oxides and utilized at high temperatures are not selective for the
conversion of methane to methanol: such catalysts may operate by the generation of
12
free radical species that exhibit intrinsic reactivity that cannot be controlled by the
catalyst.
While several pathways for CH cleavage, Figure 1.7, have been proposed
only a few of the pathways have been observed in the generation of functionalized
products.
6-13
This is likely a result of the need to have a highly active starting
material, and further functionalization of the M-C intermediate results in the
formation of a less active metal species that can not be returned to its original state as
M-X. Some of the pathways are discussed below:
1. Metalloradical pathways were discovered and popularized by Wayland et al.
22

These reactions occur via a Rh(II) porphyrin complex. The Rh(II) porphyrin
complexes exist in a dimeric-monomeric equilibrium., and the CH Activation
occurs when two monomeric Rh(II) centers interact with the C-H bond of
methane in a termolecular reaction. These reactions through experimental
evidence do not suggest that it is free radical based. Further analysis of the Rh-H
bond strength (~60 kcal/mol compared to the C-H bond strength (~105
kcals/mol) suggest that a free radical H atom abstraction would be highly
endothermic.
23
No functionalization pathways have been observed for these
systems.
2. Sigma-bond metathesis was discovered by Patricia Watson in the early 1980’s.
24

These reactions are characteristic of early group 3 metals, Sc, lathanides and
actinides. These reactions occur as shown in Scheme 1.1. After analysis of the
reaction, the reaction appears to be an interchange reaction with no net alkane
13
activation. To my knowledge only one form of functionalization has been
observed via a sigma-bond metathesis pathway. Recently the Tilley group
showed that Cp*
2
ScCH=C(CH
3
)
2
was competent for the hydromethaylation of
isobutylene to neopentane. However, the conversions were low (TON ~2), and
side reactions such as polymerization were competitive.
25

Scheme 1.1. C-H bond cleavage by sigma bond metathesis.

3. A more recent pathway that has been given consideration due to the possibility of
a proposed pathway existing for the functionalization of alkanes is alkane
activation by 1,2-addition. These reactions have typically been reported by group
4 and 5 metals in high oxidation states, usually containing amido’s, or imido
ligands.
23
Bergman and Wolczanksi studied that 1,2-addition of CH bonds to
early transition metal imido complexes, Zr and Ti.
26
The appeal of this pathway
is that the resulting metal alkyl is one step away from functionalized products
through a reductive elimination/functionalization pathway. However, to date
there have been no reported examples of functionalization using this pathway.
While some of the previous CH cleavage pathways have failed to show
functionalized products catalytically, there have been two of the pathways that have
generated functionalized products in catalytic reactions. The first pathway to be
14
discussed is oxidative addition. Oxidative addition reactions are usually observed for
low oxidation state, electron rich, late transition metals, group VII-X metals.
Oxidative addition can be described as a loss of two electrons by the metal center
changing the electron count about the metal while increasing the coordination
number of the metal. Brookhart and Goldman recently published a work in Science
where they used the well known Ir(PCP) pincer complex to dehydrogenate alkanes
which are then coupled via Schrock olefin metathesis catalysts to generate higher
and lower olefin products. These olefins are then hydrogenated by the iridium
dihydride intermediates to regenerate the iridium catalyst and the higher and lower
alkane products. This process is called alkane metathesis and the CH cleavage step to
generate the metal alkyl proceeds through oxidative addition.
27
A simplified catalytic
cycle can be seen in Figure 1.8.
15
PR
2
PR
2
Ir
H
H
PR
2
PR
2
Ir
H
H
PR
2
PR
2
Ir
H
PR
2
PR
2
Ir
C
2
H
4
2
2
2
2
2
2
Metathesis
Reaction
(metathesis
catalyst)
Alkane dehydrogenation
+
C
2
H
6 +

Figure 1.8. Catalytic cycle for alkane metathesis.

Recent work by Hartwig has shown that alkanes can be functionalized by
boron reagents to generate alkylboron products.
28
Mechanistic work; however, failed
to distinguish whether the pathway for CH cleavage was oxidative addition or sigma
bond metathesis with the Ir-Boron complex.
The other predominantly utilized pathway is electrophilic substitution shown
in Figure 1.9. The CH activation by an ES pathway the coordination of the CH of the
alkane to an electrophilic center followed by loss of a proton can also be described as
attack of a nucleophile, “sol”, on the coordinated CH bond that leads to CH cleavage
and generation an intermediate E-CH
3
species. While this is a valid comparison, it
would be expected that as the C=C double bond is considerably more electron rich
16
than that of an alkane C-H bond, that more reactive electrophilies would be required
for similar coordination and cleavage of the CH bond.

CH ACTIVATION
H
+
1/2 O
2
+ 2 H
+
H
2
O
CH
3
OH + H
+
[CH
3
-E
N
]
(n-1)
CH
4
[E
N
]
n
H
2
O
FUNCTIONALIZATION
OXIDATION
[E
(N-2)
]
(n-2)
C
H
H
H
H
E
Sol
[E
N
sol]
n
CH
4
sol
CH Cleavage
CH coordination
sol-H
+

Figure 1.9. Electrophilic activation of methane by “Soft” electrophiles

Alkane C-H activation can also be compared to well known Wacker reaction
which is an inner-sphere process.
1
As identified in the Wacker reaction (activation,
functionalization and reoxidation), following steps can also be seen in catalytic,
alkane C-H activation and functionalization systems that operate with electrophilic
catalysts. Thus, the coordination of the double bond of the olefin to electrophilic
Pd(II) followed by cleavage of the coordinated double bond by nucleophilic attack of
water can be compared to C-H activation of CH
4
by an Electrophilic Substitution
(ES) pathway as shown in Figure 1.9. Some of the more common ones are those
developed by our group which uses electrophilic species such as Pd(II), Th
+
, I
+
,
17
Hg(II), and Pt(II) to generate methane functionalized products in strongly acidic
media, H
2
SO
4
.
29

Frontier orbital considerations of this interaction between the CH bond and
electrophiles, Figure 1.10, indicate, given the low energy, σ-symmetry, and low
polarizability of the HOMO
CH
that “soft”, electrophiles characterized by low lying,
polarizable LUMO’s with σ-symmetry would be effective for this mode of CH
activation.

CH
CH
E
+
E
+
LUMO of a
“soft”
electrophile
HOMO of a
C-H bond

Figure 1.10. Orbital interaction between the low lying compact HOMO of a CH
bond and the low lying, polarizable LUMO of a “Soft” electrophile

1.2.1 Systems undergoing CH activation via electrophillic mechanism
1.2.1.1 Electrophillic CH activation by Hg

C-H bond activation has been demonstrated with the “soft,” powerful
electrophilic species, [XHg]
+
, generated by dissolving HgX
2
salts in strongly acidic
18
solvent such as sulfuric acid or Triflic acid. These stable, active oxidation catalysts
that operate via the alkane C-H activation reaction utilize metals that can be readily
dissolved with suitable oxidants to generate “soft”, electrophilic, oxidizing metal
cations in poorly coordinating solvents. Reasoning that “soft”, electrophilic,
oxidizing, third or second row metal cations, MX, could form relatively stable
covalent bonds to methyl groups and M-CH
3
intermediates that can subsequently be
oxidized, use of soluble Hg(II) cations in sulfuric acid as an effective catalyst for the
selective oxidation of methane to methanol.
30
Thus, reaction of methane (500 psig)
with 96% sulfuric acid at ~180 °C containing 20 mM concentration of Hg(HSO
4
)
2

efficiently generates methanol at concentrations of ~1 M with selectivities >90% and
yields of ~40% based on added methane, Scheme 1.2. The reaction can be carried
out in triflic acid to generate methyl triflate, but in this case the reaction is
stoichiometric in Hg(II) which serves as both the catalyst and stoichiometric oxidant.

Scheme 1.2. Methane activation by HgSO
4
.
CH
4
+ H
2
SO
4
CH
3
OH + SO
2
+ H
2
O
H
2
SO
4
HgSO
4

As shown in Figure 1.9, the proposed mechanism of the Hg system is
characterized by the same three steps: C-H activation of methane, functionalization
of the CH
3
-Hg to generate methanol and the reoxidation of the resulting Hg(I)
species.
30
This system seems to be the simplest case of C-H activation of methane
by an ES pathway. It is proposed that the soft and powerful electrophilic species,
19
[XHg]
+
, is generated upon dissolution of HgX
2
salts in hot sulfuric acid and readily
reacts with methane. It seems likely that the high solvation energy of the proton in
sulfuric acid and the formation of the strong Hg-CH
3
bond are the driving force of
this step.
The intermediacy of the CH
3
HgX species in this step is confirmed by the
direct observation of this species in the reaction media.
30, 31
It is also found that
approximately the same catalytic activity (TOF) is obtained with the use of CH
3
HgX
directly in place of HgSO
4
. Additionally, under the reaction conditions,
independently synthesized CH
3
HgX is readily converted to both methane, methanol
and the reduced Hg
2
(II) species (Hg
2
X
2
). It is interesting to speculate on how the
methanol is formed in this reaction. Kinetic studies show that the rate of formation
of CH
3
OH is independent of the concentration of added Hg(II). This rules out a free
Hg(II)-assisted bimolecular electrophilic substitution pathway as shown in Scheme
1.3. It is also well known that Hg(II) with strong field ligands such as CH
3
-

adopts a
linear, two coordinate geometry. This would suggest that a concerted reductive
elimination is unlikely. On the basis of preliminary theoretical and experimental
studies, we propose that the reaction occurs by solvent assisted heterolysis of the
[CH
3
-Hg]
+
species with simultaneous capture of the departing incipient fragment,
CH
3
+
, by H
2
SO
4
(or by either HSO
4
-
or H
2
O) to generate CH
3
OSO
3
H, or CH
3
OH and
Hg(0). The Hg(0) is not observed because Hg(II) is known to react rapidly with
Hg(0) to generate Hg
2
(II), which is observed. Kinetic studies on [CH
3
HgX] in
sulfuric acid show that the activation energy of the functionalization step is higher
20
than that for the C-H activation step. The Hg
2
(II) species generated in the
functionalization step has been shown to reoxidize to Hg(II) in hot sulfuric acid.
Experiments suggest that Hg
2
(II) is the resting state of the catalyst and suggests that
the oxidation step is rate-determining in the overall catalytic cycle. It should be
noted that the possibility of a free-radical pathway operating concurrently has been
suggested by other researchers.
32
However, based on the observation of high yields
and selectivities and that added oxygen does not change the reaction rates or
selectivities, we do not believe that free-radical pathways play a significant role in
this system.
Scheme 1.3. Possible Transition states for generation of methanol from CH
3
HgX

.
HX
XHg CH
3
XHg
HX
XHg CH
3
HX
α+
α+
Unimolecular solvent
Assisted Heterolysis
Bimolecular Electrophilic
Substitution

The basis for the high selectivity in this system, confirmed by both theoretical
and experimental results, is that the active catalyst [XHg]
+
reacts at least 1000 times
faster with the C-H bonds of methane compared to the those of CH
3
OH, which exists
primarily as the protonated, or sulfated forms, [CH
3
OH
2
]
+
or CH
3
OSO
3
H
respectively, in sulfuric acid. This greater reactivity of the methane C-H bonds
compared to those of methanol can be traced to substantially lower reactivity of the
21
electrophilic [XHg]
+
catalyst towards the C-H bonds of methanol, which due to the
electron withdrawing effect of protonation or sulfonation are substantially less
electron rich than those of methane.
The properties of Hg(II) that lead to this efficient reaction with methane in
strongly acidic media can be described as “soft”, “redox active” and “electrophilic”.
These properties are also shared by the late third and second row elements of the
periodic table due to their high Z
eff
, high principal quantum number and large size.
Consistently, we have found that the cations (bpym)PtCl
2
, Au(III), Au(I), Tl(III) and
Pd(II) all react readily with methane in strongly acid media to generate methanol
presumably via an ES C-H activation reaction mechanism. Consistent with the
important electrophilic properties, all of these systems are inhibited by good ligands
such as water or methanol or anions such as HSO
4
-
or Cl
-
.
1.2.2 Electrophilic CH activation by Pt(II)

Durring the 1970’s Shilov published extensively on the reactions of alkanes
in aqueous solutions of platinum(II) complexes.
33
The reactions are typically carried
out at < 100 °C with chloride salts of Pt(II) as catalyst and the chloride salts of
Pt(IV) as the oxidant in aqueous hydrochloric acid as solvent. Typical reaction
yields, based on added methane are less than 3% with >90% selectivities to methanol
and methyl chloride. The reaction was proposed to proceed via a C-H activation
reaction to generate alkyl platinum intermediates in reactions with alkanes and later
studies by other are consistent with this proposal.
34
This system is one of the first
22
systems that was proposed to operate via the C-H activation reaction and to generate
potentially useful functionalized products. The key disadvantages of the Shilov
system were the low rates (catalyst turn-over-frequency, TOF of <10
-5
s
-1
), short
catalyst life (turn-over-number, TON of < 20) and the use of Pt (IV) as a
stoichiometric oxidant.
Scheme 1.4. Methane activation by (bpym)PtCl
2

CH
4
+ H
2
SO
4
CH
3
OH + SO
2
+ H
2
O
H
2
SO
4
NN
NN
Pt
Cl
Cl

One of the advantages of the use of transition metals for the C-H activation
reaction is that, as a result of the multiple available coordination sites, spectator
ligands can be utilized to mediate the chemistry of the metal center. Utilizing
ligands and alternative oxidants with Pt(II), a very efficient catalyst for the oxidation
of methane to methanol based on the C-H Activation reaction was developed. This
system, dichloro(κ-2-{2,2’-bipyrimidyl})platinum(II), Pt(bpym)Cl
2
, is stable and
active for the conversion of methane to methanol in concentrated sulfuric acid
(Scheme 1.4) with yields of over 70% methanol (based on added methane) with
selectivities of >90% with a catalyst TOF of ~10
-3
s
-1
at 500 psig of methane.
35
The
Pt(bpym)Cl
2
complex is stable in hot concentrated sulfuric acid for weeks and
catalyst TON of > 300 have been observed without decomposition. The chemistry is
applicable to higher alkanes and reactions with ethane lead to the generation of
23
ethylene glycol. Reactions with higher alkanes are less selective but oxygenated
products can be obtained. The key issues with this system for alkane oxidation are
the slow rates (TOF of ~1 s
-1
are desirable) and the inhibition of the catalyst by water
and methanol that limit concentration of products to ~1.5 M. It has been estimated
that at concentrations below ~3 M, the cost of separation of the products from
sulfuric acid is not economical. To overcome this separation issue, the possibility of
using this stable, active system to generate acetic acid by the oxidative carbonylation
reaction shown in Scheme 1.5 is being examined. Initial studies indicate that in the
presence of low levels of CO, the oxidation of methane with the Pt(bpym)Cl
2
/ H
2
SO
4

system can be selectively diverted to generate acetic acid instead of methanol.
36

Scheme 1.5. Acetic acid formation using (bpym)PtCl
2
with CH
4
and CO.

CH
4
+ CO CH
3
CO
2
H + SO
2
+ H
2
O
CF
3
SO
3
H
NN
NN
Pt
Cl
Cl

Experimental and theoretical studies are consistent with the Pt(bpym)Cl
2

system proceeding via the electrophilic substitution (ES) C-H activation reaction
mechanism shown in. Figure 1.11.
37
This is likely due to the increased
electrophilicity of the metal upon protonation of the bpym ligand. Consistent with
the proposed formation of a Pt-CH
3
intermediate, when the reactions are carried out
in D
2
SO
4
, multiple deuterium incorporation occurs into both methane and methyl
products.
24
Experimental and theoretical studies show that the high stability of
Pt(bpym)Cl
2
complex is likely due to the unique structure and composition of the
bpym ligand.
37
These studies show that the bpym ligand is protonated in strongly
acidic media which prevents decomposition from irreversible formation of insoluble
(PtCl
2
)n or Pt black formation. The presence of two nitrogens in the same aromatic
ring in the bipyrimidine ligand, along with the chelate structure, allows electronic
communication between these N-centers and prevents loss of the ligand that could
result from exhaustive protonation of all the ring nitrogens. Consistent with this
proposal, while (PtCl
2
)
n
and Pt black are both insoluble in hot sulfuric acid, addition
of one equivalent of bpym ligand leads to dissolution and generation of an active and
stable catalyst. Significantly, this dissolution is not observed with simpler ligands
such as bipyridine.

25
CH
4
H
2
SO
4
CH Activation
Functionalization
Oxidation
NN
HN N
Pt
Cl
CH
3
SO
2
+ 2 H
2
O 3 H2SO
4
2+
H
2
O
2+
2 HSO
4
-
[CH
4
]
NN
HN N
Pt
OSO
3
H
CH
3
OSO
3
H
Cl
HSO
4
-
2 HSO
4
-
HSO
4
-
+
+
NN
NN
Pt
Cl
Cl
Sol
- HCl
NN
HN N
Pt
Cl
[Sol]
NN
HN N
Pt
Cl
CH
3
OH
H
2
SO
4
Sol
H
+
Sol
Pt
N Cl
N
H
C
H
H
H
2+
Electrophilic
Substitution

Figure 1.11. Proposed mechanism for methane oxidation by the
Pt(bpym)Cl
2
/H
2
SO
4
.

1.2.3 CH activation in strongly acidic media: catalyst inhibition by ground state
stabilization

The CH activation is typically a rapid reaction only when the reaction is
carried out by the generation of high energy species and where the reaction system is
carefully chosen such that the alkane is the most (or only) reactive species present,
and under these conditions it is understandable that CH Activation is rapid.
However, in a medium that consists of things other than neat alkane, most of these
highly reactive systems would suffer poor rates.
One reason for this is that alkane C-H bonds, unlike C=C double bonds of
olefins or other functional groups, are poorly ligating and are unlikely to compete
26
with the more coordinating species in the reaction mixture. Consistent with the poor
ligating capability of alkanes, only by spectroscopic studies has an alkane complex
been observed and to date, there has only been one reported in the literature.
38
,
39

The coordination of an alkane to the first coordination sphere of a metal center in the
CH activation reaction (either leading to an intermediate alkane complex or a
transition state that leads directly to CH cleavage) can be viewed as inner sphere
ligand displacement or either through an associative, dissociative or interchange
mechanism.
4,40
This depends on the binding constant of the ligand being displaced
by the alkane but given the poor binding characteristics of alkanes, it is reasonable
that there is will be substantial dissociative character to the displacement reaction in
all cases except with extremely poor ligands. The ligand that is to be displaced by
the alkane can be represented as “X” in Figure 1.12. This “X” molecule will likely
be the most nucleophilic or ligating reagent in the medium and it can either be a
reactant, a product, a solvent molecule, or a ligand. The main point to make is that
this “X” ligand will be more coordinating than the alkane substrate.
27
Coordination
Alkane Complex
CH Cleavage
Cleavage TS
M
X L
L L
M
CH
4
L
L L
M
C
H
3
L
L L
H
X
M
CH
3
L
L L
Activation
Barrier for
CH Activation

Figure 1.12. Generalized energy diagram for CH Activation via alkane
coordination and CH cleavage showing ground state stabilization

These considerations demonstrate a fundamental challenge in performing CH
activation that must be overcome. Inner sphere ligand displacement mechanisms
with alkanes (whether associative or dissociative) lead to weakly bound, intermediate
alkane complexes, or directly to a transition state leading to CH cleavage which can
be expected to be subject to severe ground state inhibition in most media that would
be useful for CH functionalization catalysis. This ground state stabilization
fundamentally arises from strong binding of other possible ligands to the catalyst in
the reaction system. This leads to drop in energy of the catalyst resting state and as
can be seen from Figure 1.12, the more stable this state, the higher the expected
activation barrier for CH activation.
28
For example, it is challenging to imagine how methane coordination could
occur to sufficient extent to allow efficient catalysis in a solvent such as liquid water,
given the excellent coordinating properties of water that would lead to stable water
complexes and extensive ground state inhibition. This is heightened by the poor
solubility of methane in most useful media and the high concentration of the solvent.
Of course, the reaction does not have to be carried out in solvents as ligating as
water. However, if the objective is the hydroxylation of methane to methanol, then
at a minimum, (if as desired, the catalyst is expected to operate at high turn over
numbers before separation of product) methanol, which can be expected to bind
more tightly to the catalyst than methane, will be present in the system and catalyst
inhibition may be observed.
As might be anticipated this issue of ground state inhibition is observed in
many catalytic alkane functionalization systems that operate by the CH activation
reaction. Thus, of the systems that are known or likely to activate and hydroxylate
alkanes by the CH activation reaction, the Shilov, Sen and Periana systems, this issue
of inhibition is present. Thus, for the Sen Pd(II) and Periana Hg(II) and Pt(bpym)Cl
2

systems shown in Figure 1.3, independent of stabilities, the slow rates or eventual
inhibition of these catalyst systems that prevent their utility can be traced to water (or
methanol) binding that leads to ground state inhibition. Other CH
activation/functionalization systems that operate by other mechanisms such as the
Ir(PCP)H
2
system for the dehydrogenation of alkanes to olefins inhibition is
observed through coordination of the olefin to the metal.
16
The slow rates of the
29
Shilov system that is proposed to operate by through an oxidative addition
mechanism is also likely due to strong ground state inhibition from water binding.
3g

One of the early pioneers for the direct conversion of methane is George Olah
at the University of Southern California. His approach was based upon the use of
acidic catalysts such as superacids for the direct conversion of methane to
methylhalides through a selective halogenations process, and the conversion of
methane to higher hydrocarbons through condensation of methanol or methyl
halides. The methane and methyl halides used for the condsentation could ultimately
be generated from methane via the superacid catalysts.
41
This work is very similar to
that of Hg(II) CH Activation system which operates in sulfuric acid. In both cases
they operate by electrophilic substitution of methane. The electrophile interacts with
the C-H bond in a 3 centered 2 electron interaction. Olah also indicates that the
methanol generated likely becomes protonated, CH
3
OH
2
+
, which further prevents
over oxidation of the methanol product. This protection is also what likely occurs in
sulfuric acid either in the form of CH
3
OH
2
+
or CH
3
OSO
3
H. In either case the C-H
bond has become electron deficient relative to methan and thus less reactive towards
electrophiles. The primary difference between the superacid and Hg systems is the
fact that the Hg(II) system has alternative orbitals open to it like s and p orbitals. It is
also a 6
th
row metal which allows it to be very polarizable and thus more tolerable to
water.
The idea behind using acidic solvents (Lewis, or Bronsted) is that in
principle, the strongest base that can exist in such a solvent is the conjugate base of
30
the acid solvent. In the case of a strong acid, the conjugate base should be weakly
basic and thus be expected to be poorly coordinating. As a result, ground state
stabilization by the solvent and the conjugate base will be minimized. The solvent is
the item in the largest quantity in the reaction medium; therefore, it only makes sense
to use the acid as a solvent rather than in stochiometric amounts. It is also likely that
other reactants and products will be larger than stochiometric amounts assuming
catalysis occurs.
The general use of Lewis or Bronsted acids to facilitate coordination of
reactants is a well-known fact in coordination chemistry.
42
Thus, one of the most
active complexes known for catalytic CH activation was developed by Bergman
group at Berkley,
43
[Cp
*
Ir(PMe)
3
Me(CH
2
Cl
2
)]
+
[MeB(C
6
F
5
)
3
]
-
. This complex is
generated by reaction of the Lewis acid, B(C
6
F
5
)
3
, with Cp
*
Ir(PMe)
3
Me
2
in the
poorly coordinating solvent, dichloromethane. One reason that this complex is quite
reactive with methane (at -10
o
C) is that all of the possible competing ligands in the
reaction system [MeB(C
6
F
5
)
3
]
-
and CH
2
Cl
2
, are poorly coordinating. Therefore, this
makes the coordinating ability of methane more comparable to these ligands. This
use of a stochiometric weakly coordinated complex leads to very active catalysts;
however, in the presence of more coordinating species such as reactants or products
including methanol these systems would likely be severely inhibited. Consequently,
this approach of stoichiometric use of weakly coordinating groups would not be
suitable for catalytic systems where the desired product is methanol and many
catalyst turnovers are required.
31
An alternative approach would be to run the reaction in liquid BARF,
B(C
6
F
5
)
3,
as solvent. Under these conditions any methanol produced would form a
strong acid-base adduct with the excess B(C
6
F
5
)
3
, and thus the methanol produced
would be unavailable for coordination to the metal thereby preventing inhibition or
ground state stabilization. The key issue with this strategy is that B(C
6
F
5
)
3
is
expensive and the cost of separating MeOH from the MeOH: B(C
6
F
5
)
3
complex to
recycle the B(C
6
F
5
)
3
would be too great. However, if the Lewis acid utilized is
inexpensive and thermally robust, this could be a useful strategy.
This was the idea behind the use of an inexpensive solvent like sulfuric acid
for facilitating the selective functionalization of methane.
29
By the definition of an
acid, liquid sulfuric acid, is a polar, strongly Lewis acidic, poorly nucleophilic liquid.
The strongest nucleophile or ligand that can exist in this solvent is the conjugate
base, HSO
4
-
. Bisuflate is a poorly coordinating substrate which is less coordinating
that water or methanol. At high concentrations of acid solvent (>85%), any water or
methanol generated (or any other species more basic than HSO
4
-
) is essentially fully
protonated and not available for coordination to the metal center. As a result, this
helps to minimize catalyst inhibition by ground state stabilization. As the acid
concentration drops below 85% the acidity
41b
drops rapidly and water or methanol
can become available for coordination to the metal center which should lead to
inhibition of the CH activation reaction.
The key challenge to utilizing this strategy is the identification of catalysts,
reactants and products that are thermally stable in such a medium. Both methane and
32
methanol are thermally stable in sulfuric acid at temperature below 250
o
C and we
have identified several catalyst systems that are stable in this media for the selective
oxidation of methane to methanol. As noted above both the Hg(II) and Pt(bpym)Cl
2

system have been found to be an efficient catalyst for methane oxidation to methanol
at ~200
o
C in this solvent as both are very stable in this media. Consistent with the
concept of basicity leveling, theoretical studies show that, at sulfuric acid
concentrations > 90%, the ground state of these catalysts, [(Hbpym)PtCl(HSO
4
)]
+

and Hg(HSO
4
)
2
, are coordinated to weakly binding HSO
4
-
that is most likely
extensively hydrogen bonded to solvent H
2
SO
4
molecules as shown in Figure 1.13
for the Pt(bpym)Cl
2
/H
2
SO
4
system. As can be seen, this weakly coordination of
HSO
4
-
in sulfuric acid leads to a highly dispersed anion that is similar to the weakly
coordinating anion, B(C
6
F
5
)
3
Me]
-
and that can be expected to be displaced by
methane more readily than water.
BARF anion
Weak coordinating
Ligands that can be
displaced by methane
Likely active Pt(II) Catalyst
NN
HN N
S
O
O
OH
OH
H
S
O
O
O
O
H
S
O
O
O
OH
H
S
O
OH
O
O
Pt
Cl
+
F
F
F
F
F
B
F
F
F F
F
F
F
F
F
F
F
F
F
F
F
-

Figure 1.13. Comparison of the likely active catalyst in the Pt(bpym)Cl
2
/H
2
SO
4

system with the weakly coordinating BARF anion.

Calculations show that replacement of the HSO
4
-
ligand by methane in the
Pt(bpym)Cl
2
/H
2
SO
4
system is uphill 24 kcal/mol with a barrier of ~33 kcal/mol. This
is comparable to the ~28-30 kcal/mol barrier obtained experimentally for the CH
33
activation step by carrying out the reaction in D
2
SO
4
and monitoring the rate of H/D
exchange between methane and the solvent. Interestingly, the calculations as well
as experimental results indicate that in the Pt(bpym)X
2
system that operates via an
ES mechanism, the formation of this methane complex, rather than the CH cleavage
step, is the rate determining step. Importantly, as a result of the large excess of
solvent sulfuric acid (the catalyst concentration is typically 5 – 50 mM), substantially
more than one equivalent of methanol can be generated in this system before catalyst
inhibition due to water or methanol binding slows reaction to impractical rates.
Thus, with a catalyst concentration of 50mM, and starting with 100% sulfuric acid
solvent, ~300 turnovers have been demonstrated with the generation of >1.5 M
methanol at ~80% conversion of methane with >90% selectivity to methanol. At
these high levels of water and methanol concentrations, the activity of water and
methanol are considerably higher because the sulfuric acid concentration is reduced.
Experimental studies show that at acid concentrations below 80% sulfuric acid the
reaction rates are too low to be useful (~10
-7
s
-1
) at 200
o
C. In this acid concentration
range, the CH activation step is rate limiting and is at least 1000 times slower than at
96% sulfuric acid solvent concentration. The basis for this large difference in rate
can be explained by theoretical calculations, which show that the water complex
(which is expected to be formed at lower concentrations of acid),
[(Hbpym)PtCl(H
2
O)]
2+
is ~7-8 kcal/mol more stable than the [(Hbpym)PtCl(HSO
4
)]
+

complex. Consistent with the expected dependence on solvent acidity, as can be
34
seen from, Figure 1.14, the drop off in rate below 85% sulfuric acid solvent
correlates well with the solvent acidity.

Figure 1.14. Correlation of CH activation rates (Measured by H/D exchange rates
between CH
4
and D
2
SO
4
) with solvent acidity, H
0
(98 % H
2
SO
4
=
10.4 H
0
and 85% = 8 H
0
).

Critically, while the use of sulfuric acid allows the catalytic reaction to
proceed efficiently, the rapid inhibition of the catalysts by water or methanol below
90% sulfuric acid leads to uneconomical catalyst rates (for the Pt system) and high
separation costs for the methanol (for both the Pt and Hg systems). Calculations
show that if catalyst inhibition can be minimized to allow an ~5M solution of
methanol to be obtained, with an overall catalyst TOF of ~1 s
-1
that a process based
on the use of sulfuric acid could potentially be useful.

1.3 CH activation and functionalization based on oxidative
addition mechanism

Indeed, the first indications for C-H activation came from the reactions with
Iridium centers especially of arylphosphine ligands via orthometalation reactions.
0.0
0.5
1.0
1.5
2.0
6 7 8 9 10 11
D
2
SO
4
acidity, –H
0
k
H/D
x10
4
, s
-1
0.0
0.5
1.0
1.5
2.0
6 7 8 9 10 11
D
2
SO
4
acidity, –H
0
k
H/D
x10
4
, s
-1
NN
NN
Pt
Cl
Cl
35
Bergman and Janowicz were the first ones to show the intermolecular C-H activation
reactions using Cp*Ir(PMe
3
)H
2
.

Using photolysis, a very highly reactive molecule
was generated after the loss of hydrogen, which would then react with alkanes to
yield alkylhydrido Iridium complexes (Figure 1.15). Other notable systems based on
Iridium for C-H activation are shown in Figure 1.15 and all have been shown to
follow an oxidative addition mechanism. All these complexes are efficient C-H
activation catalyst as evident fromH/D exchange but lack functionalization.

N
N
N
N
N
N
Ir
H
L
B
H
Ir CO
CO
Graham
Carmona
Ir
Me
3
P
H
H
Bergman
Me
5
Ir
Me
3
P
Me
Bergman

Figure 1.15. Some notable C-H activation complexes based on OA mechanism

Catalysts based on ES pathways are not the only stable, active systems that
operate by alkane C-H activation and functionalization. In the case of the (PCP)IrH
2

system, which is the one of the most efficient system known for the low temperature
dehydrogenation of alkanes (conversion of alkanes to olefins, Figure 1.16)
44
C-H
activation has been shown to operate by an OA, β-hydride elimination sequence.
This catalyst is quite stable and reaction of alkanes can be carried out at reasonable
rates at temperatures above 200
o
C where both hydrogenation (transfer of hydrogen
to an olefin as hydrogen acceptor) and “acceptorless” dehydrogenation (loss of
36
hydrogen gas) is observed. While many systems are known that can cleave C-H
bonds by OA mechanism and may also be capable of β-hydride elimination
reactions, it is likely that an important property of the catalyst is the unique, high
thermal stability imparted by the tri-dentate, PCP ligand and strong Ir-C and Ir-P
bonds.
200° C
H
2
P
P
Ir
H
H

Figure 1.16. Ir(PCP)H
2
catalyzed dehydrogenation of Alkanes.

The general scheme for generating functionalized products involves C-H
activation followed by oxidation or insertion of small molecules (CO or olefins).
Based on differences in mechanism of Electrophilic substitution (ES) and oxidative
addition (OA) mechanism, one could expect some novel selectivity (regio, stereo,
enantio) in the products. An example where one can witness this difference is the
Friedel Crafts based alkylation, where one observes 100% branched product, as the
mechanism proceeds via carbocations (Figure 1.17).

37
X
R
R
H
R
X
+
+
R
X
+
+
HX
X
-
X
- - HX

Figure 1.17. Friedel Crafts Alkylation

Whereas novel selectivity is observed in the case of Murai reaction,
45
which
is the hydroarylation of olefins, proposed to go via chelation assisted, C-H activation.
This reaction is catalyzed by Ru(H
2
)(CO)(PPh
3
) and the mechanism is shown in
Figure 1.18. This complex is very high yielding reaction and results primarily in
linear alkylated benzenes. One of the limitations is the requirement of the acetyl
group which is needed for the reaction to proceed. As shown in mechanism, this
assists in C-H activation of the benzene followed by insertion of the olefin.
CH
3
O
Si(OEt)
2
+
CH
3
O
Si(OEt)
2
High Yield
1 : 1 ratio
Ru(H)
2
(CO)(PPh
3
)
3
Toluene
135 C, 1 hr
RuH
2
(CO)(PPh
3
)
3
[ Ru
0
]
R
O
R
O
R
O
Ru
R
O
Ru
H
R
O
Y
Ru
H
Y
Y
Ru
R
O
Y
CH
3
O
Si(OEt)
2
+
CH
3
O
Si(OEt)
2
High Yield
1 : 1 ratio
Ru(H)
2
(CO)(PPh
3
)
3
Toluene
135 C, 1 hr
RuH
2
(CO)(PPh
3
)
3
[ Ru
0
]
R
O
R
O
R
O
Ru
R
O
Ru
H
R
O
Y
Ru
H
Y
Y
Ru
R
O
Y

Figure 1.18. Murai reaction catalyzed by Ru complex.

38

1.4 Iridium in an oxygen ligand environment

Most of the catalysis using Iridium compounds has typically exploited
neutral, soft donor ligands such as phosphines, arsines, cyclopentadienes, etc.
Iridium in atypical environment such as oxygen could support very active catalysts
and may actually be more akin to the environment that exists around a metal when it
is supported on an oxide support.
Finke’s and Klemperer’s
46
group have attached polyoxoanions on Iridium
metal centers and suggest some novel reactivity with molecular oxygen to yield a
oxometallacyclobutane unit derived from insertion of oxygen into the M-C bond
(Figure 1.19). The mechanism has been proposed through coordination of oxygen,
which then bridges with another Iridium center. This undergoes internal oxidation
whereby the oxygen atoms are inserted into Ir-C bonds to complete the
transformation. This suggests that placing an Iridium metal center in this
environment might provide the platform to do some unusual catalytic reactions.
Analogous oxygen atom transfer from the Ir(III) oxo complex, [C
5
Me
5
)Ir(O)]
2
, to
PPh
3
has also been observed.
47

39
P
O
P
O
P
O
O
O
O
O
O
O
Ir
2
2
P
O
P
O
P
O
O
O
O
O
O
O
Ir
HO
O
2
1,2 dichloroethane
2
O
Ir(P
3
O
9
)
O
Mechanism O
2
4
O
Ir(P
3
O
9
)
O
Ir(P
3
O
9
)
4
O
Ir(P
3
O
9
)
O
Ir(P
3
O
9
)
O
Ir(P
3
O
9
)
2
X-Ray
X-Ray
X-Ray

Figure 1.19. Oxygen transfer on Iridium center using polyoxoanion (Klemperer)

Crabtree has also investigated the oxygen donor ligand effect on the Iridium
centers using the ligand “triso” (HC(Ph
2
P=O), shown in Figure 1.20. Crabtree’s
group showed that this ligand could stabilize the Iridium in not only +1 oxidation
state but also in +3 and +5 as well. Well all these cases involving insertion and
stabilization of high oxidation state Iridium complexes suggest that lone pair
donation might be involved and help in C-H activation and oxidation chemistry.
Ir
O H
H O
H
PCy
3
SiEt
3
Esteruelas, et. al.,
Organometallics, 1996, 823.
Ir
PMe
3
Si
H
H
Bergman, et. al.,
J. Am. Chem. Soc. 2000, 1816.
Ir
O
SiR
3
H O
2
RP
2
RP
H
SiR
3
2
RP O
Tanke, R. S.; Crabtree, R. H.
Organometallics, 1991, 415.

Figure 1.20. Reported examples of Ir(V) Complexes.

40
There are lots of oxygen donor ligands available in literature as shown in
Figure 1.21. These ligand sets provide an oppourtunity to control or tune the
reactions of interest either by changing the electronics or by changing the sterics. For
example, one might expect a difference in reactivity with acetylacetone (acac) and
tropolone, on the basis of their different bite angle. Given the ubiquity of the OA
mechanism, most of the systems shown in Figure 1.3 operate by this mechanism, it
would be desirable to identify complexes that operate via this mechanism and that
are stable to the protic, thermal, oxidizing conditions required for functionalization
of alkanes to alcohols or other insertion reactions such as olefin. In such an effort to
develop new stable motifs that operate via the OA pathway and that may lead to the
development of new, stable oxidation catalysts, we have been exploring the use of O-
donor ligands.
M
O
O
R
R
M
O
O
R
M
O
O
O
AcAc Tropolone Ethyl Maltol
O
O
M
Hydroxy
Acetophenone
PR
2 PR
2
PR
2
O
O
O
Co
PR
2
O
P
O
PR
2
O
Klaui's Ligand
HO
P O
HO
Crabtree's Bipo Grim's Triso
O
O
M
Catecholates
O
O
M
Alkoxides
OM
4
Calixarenes

Figure 1.21. Examples of Oxygen donor ligands.

41
1.5 Metal-Carbon bond functionalization pathways

As new systems are created that are capable of activating the CH bond, it also
possible that other pathways for functionalization of the resulting M-C intermediates
exist. Our group has been investigating alternative pathways by which these low
valent metal alkyls could be functionalized to generate new products. Early work by
Conley et al. of our group showed that methyl trioxorhenium, MTO, can be
functionalized by a wide variety of O-atom donors. Further mechanistic studies,
suggested that the functionalization occurs by insertion of the oxygen into the Re-Me
bond via Bayer-Villiger type transition state.
48
While this result was exciting, it is
also important that we look for functionalization possibilities with low valent metal
alkyls. In MTO, the metal is Re(VII); whereas as we expect the CH activation to
occur at a low valent metal like Re(I) which should be more electron rich and show
faster rates for CH activation. However, this result provided inspiration for future
work in our group.
Ph R
O
O R
O
Ph
YO
OH
-
YO = HO-O
-
,Et
3
N-O,RCO
2
-O
-
,etc
-
OOH
Ph R
O
-
O
OH
Baeyer-Villiger Reaction
MCH
3
O
YO
YO = HO-O
-
,IO
4
-
,etc
M CH
3
O
-
O
Y
Transition Metal Analog
L
n
L
n
MOCH
3
O
L
n
+
Y +

Figure 1.22. Comparision of Baeyer-Villiger reaction to a possible transition metal
analog.

42
Later to address, this issue of functionalizing a low valent metal alkyl, Tenn
et al. within our group found another pathway in the process of functionalizing a
Re(I)-Me complex, Re(CO)
5
Me. Preliminary results show that the methyl is being
transferred to Se(IV) to yield Me-Se products in a quantitative fashion. This Me-Se
can then be further functionalized to yield methanol. Further work is ongoing to
investigate the mechanism of this reaction.
49
We believe that by coupling the CH
Activation to these new functionalization pathways it should be possible to convert
alkanes to R-heteroatom products by catalysts that are not inhibited by the products.

43

1.6 Chapter 1 References

1
Copyright: Conley, B. L.; Tenn, W. J. III.; Young, K. J. H.; Ganesh, S. K.;
Meier, S. K.; Ziatdinov, V. R.; Mironov, O.; Oxgaard, J.; Gonzales, J.;
Goddard, W. A. III.; Periana, R. A. J. Mol. Cat. A. 2006, 251(1-2), 8-.
License (date/number): Mar 18, 2008, 1912030616728

2
(a) Wolf. E. E. Ed Methane Conversion by Oxidative Processes,.; Van
Nostrand Reinhold; New York, 1992 (b) , Derouane, E. G.; Haber, J.; Lemos,
F.; Ribeiro, F. R.; Guisnet, M. Eds Catalytic Activation and
Functionalization of Light Alkanes. Advances and Challenges.; Nato ASI
Series, Kluwer Academic Publishers, Dordrecht, The Netherlands, 1997 (c)
Lunsford, J. H. Catalysis Today, 2000, 63, 165. (d) Periana, R. A. “Cooler
Chemistry for the 21
st
Century.” C&E News, 2001, 79, 287. (e) Curry-Hyde,
H.E.; Howe, R. F. Eds. Natural Gas Conversion II, Elsevier, New York,
1994

3
(a) Arndtsen, B. A.; Bergman, R. G.; Mobley, T. A.; Peterson, T. H. Acc.
Chem. Res. 1995, 28, 154. (b) Shilov, A. E.; Shulpin, G. B. Activation and
Catalytic Reactions of Saturated Hydrocarbons in the Presence of Metal
Complexes, Kluwer Academic; Dordrecht, 2000. (c) Jia, C.; Kitamura, T.;
Fujiwara, Y. Acc. Chem. Res. 2001, 38, 633. (d) Jones, W. D. Acc. Chem.
Res. 2003, 36, 140. (e) Crabtree, R. H. J. Chem. Soc., Dalton Trans. 2001,
19, 2437. (f) Labinger, J. A.; Bercaw, J. E. Nature 2002, 417, 507. (g)
Periana, R. A.; Bhalla, G.; Tenn III, W. J.; Young, K. J. H.; Liu, X. Y.;
Mironov, O.; Jones, C.; Ziatdinov, V. R. J. Mol. Cat. A- Chem. 2004, 220, 7.

44

4
(a) Labinger, J. A.; Herring, A. M.; Bercaw, J. E. J. Am. Chem. Soc. 1990,
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Mol. Catal. A: Chem. 1997, 116, 269. (j) Wick, D. D.; Goldberg, K. I. J. Am.
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6
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45

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47

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R.; Voss, G.; Masuda, T. Stud. Surf. Sci. Catal. 1994, 81, 533.

31
CH
3
HgX species is also an intermediate of sulfonation of methane in oleum.
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Tenn, W. J. III.; Conley, B. L.; Oxgaard, J.; Goddard, W. A. III; Periana, R.
A. manuscript in preparation.

50
Chapter 2: Non-planar Tetradentate Diamine-
Bis(phenolate) Ligated Rhodium(III) Complexes:
Synthesis and Structures

2.1 Introduction

We have long been interested in the use of bis-acetylacetonate complexes for CH
activation and functionalization, and have previously discovered that: (1)
(acac)
2
Ir(III) complexes can activate a variety of CH bonds and are capable of
functionalization arene CH bonds by coupling with olefins.
50
(2) These types of
complexes are readily synthesized.
50
(3) The bis-bidentate acac skeleton in
(acac)
2
Ir(III) complexes
50b
and related (acac)
2
Rh(III) complexes
51
(which have
recently been synthesized and characterized) are robust under reaction conditions
such as air, moisture and acid media. (4) These complexes must undergo a rate-
determining planar to non-planar isomerization prior to C-H activation.
50
Clearly, it
would be interesting to develop ligands with similar reactivity as bis-acac, but
already predisposed towards non-planar tetradentate ligand coordination.
In designing new ligands for CH activation, it has been noted that Cp*LIr(III)
52
and Cp*LRh(III)
53
complexes have been used as precursors for complexes capable
of C-H activation reactions with high reactivity. In addition, these Cp* ligands are
essential to many of the new class of homogenous polymerization catalysts, the
metallocenes. However, diamine-bisphenols (NNOO, Figure 2.1) have recently
emerged as alternative ligands in developing new non-Cp type catalysts for
polymerization of α-olefins.
54
Presumably, one of the keys to the high activities is
51
that N
2
O
2
ligating atoms adopt non-planar coordination sites where the co-ligands
are forced to take up cisoid positions (see Fig 1b), as such conformations have been
found to be essential for metallocene catalysts.
55

N
OH HO
N
R
R
R
R
amine-phenol
N
N
O
X
X
O
O
N
X
X
O
N
trans O-O
cis O-O
a
b

Figure 2.1. (a) tetradentate amine-phenol ligand(NNOO) (b) structure classes of
amine-phenolate complexes

Given that NNOO ligands have been successfully used to substitute Cp type
ligands for polymerization catalysts, that Cp type ligands have been used for C-H
activation catalysts, and that NNOO is isoelectronic to bis-acac O
,
O; O,O (albeit
with somewhat different bonding and more electron donating character), this could
make amine-bisphenol ligands excellent for group VIII metal CH activation
catalysts. Indeed, preliminary computational work suggests that this is the case.
Furthermore, NNOO has some additional advantages, such as the possibility of
tuning the electronic environment through modification of the R groups, as well as
an automatic assumption of the desired non-planar tetradentate coordination. In
contrast, bis-acac is significantly harder to modify, as modifications of the ligand can
easily prevent the acac* from binding to the metal center, and in almost all cases
prefer a planar tetra-dentate geometry. We now report the synthesis and structural
52
studies of four biamine-bisphenolate Rh(III) complexes, which to our knowledge are
the first group VIII complexes to incorporate such ligands .

2.2 Results and discussion

Our particular NNOO ligands (R = Me, t-Bu; N = C
6
H
4
N, CH
2
N(CH
3
)
2
, see
Scheme 2.1) reacted readily with RhCl
3
(H
2
O)x in the presence of NaHCO
3
at 80
o
C in
a mixture of water and acetone, to give air stable complexes 1-3 as brick red or
orange crystalline solids. These solids were found to contain a methanol or water
solvate molecule after recrystallization using a mixture of methanol and
dichloromethane.
Scheme 2.1. Synthesis of bisphenolate based Rh (III) chloro complexes
N
N
OH HO
tBu
tBu tBu
tBu
N
N
OH HO
Me
Me Me
Me
Rh
N
S
N
O
Cl
O
Me
Me Me
Me
Rh
N
Cl
N
O
S
O
tBu
tBu
tBu
tBu
Rh
N
Cl
N
O
S
O
Me
Me
Me
Me
N
N
OH HO
Me
Me Me
Me
RhCl
3
xH
2
O
NaHCO
3
trans-O,O
cis-O,O
1
2
3
RhCl
3
xH
2
O
NaHCO
3
RhCl
3
xH
2
O
NaHCO
3
S=MeOH
S=MeOH
S=H
2
O

53
The
1
HNMR spectra of 1 and 2 show an AX system for the Ar-CH
2
-N methylene
units, corresponding to two symmetry-related phenolate rings. This indicates the
formation of C
s
symmetrical complexes, in which the phenolate rings are in a trans
configuration, as shown in Scheme 2.1. The solid state structure of 1 (see Figure 2.2) is
fully consistent with the solution NMR data for the C
s
symmetry. The structure
features a slightly distorted octahedral geometry with the oxygen atoms trans to each
other, and the chlorine atom trans to the coordinating sidearm nitrogen atom, which
forms the non-planar tetradentate NNOO fragment. As expected, 1 features a
relatively short Rh-N(2) [pyridine, trans to O] distance of 1.977 Å, which should be
compared to the Rh-N(1) [amine, trans to Cl] distance of 2.040 Å (Scheme 2.1 and
Figure 2.2). The NMR spectra of complex 2 exhibits a similar pattern as that of 1, and
a similar trans-geometry is thus assumed for 2 (Scheme 2.1).

Figure 2.2. Molecular structure of 1, Rh(NNOO-bu
t
,py)(Cl)( CH
3
OH).

54
Figure 2.2: Continued
The H atoms were omitted for clarity. Key atoms are labeled. Selected bond
distances (Å) and angles (deg): Rh(1)-O(1) = 2.041(2), Rh(1)-O(2) = 1.999(2),
Rh(1)-O(3) = 2.093(2), Rh(1)-N(1) = 2.040(2), Rh(1)-N(2) = 1.977(3), Rh(1)-Cl(1) =
2.3757(9), O(2)-Rh(1)-O(1) = 176.08(9), N(2)-Rh(1)-N(1) = 84.19(11), N(2)-Rh(1)-
O(2) = 86.11(11), O(2)-Rh(1)-N(1) = 89.40(10), N(2)-Rh(1)-O(1) = 93.09(10), N(1)-
Rh(1)-O(1) = 94.33(10)

Conversely, the
1
HNMR spectrum of 3 exhibits two chemically distinct phenolate
ring environments, which give rise to four resonance signals for the Ar-CH
2
-N
methylene units, implying a C1 symmetric cis-O,O geometry. A similar observation
has been reported for LZrCl
2
complexes,
56
where the geometry of both C1 and Cs
symmetrical isomers were assigned by NMR or X-ray diffraction studies. By
comparing our NMR data for complex 3 to these known LZrCl
2
complexes, it is
reasonable to assume a cis-O,O geometry. However, the assignment of the
coordination positions for the Cl atom and the solvate molecule is ambiguous by
NMR data, and therefore a X-ray diffraction determination for 3 was carried out. The
solid structure of complex 3 is shown in Figure 3, where it can be observed that the
phenolate ligands adopt mutually cis positions, and the Cl is trans to one of the
phenolates. The Rh center in 3 is approximately octahedral, and the R-N bond length
of 1.958 Å suggests that the pyridyl moiety is as tightly bound as it is in 1.
55

Figure 2.3. Molecular structure of 3, Rh(NNOO-Me,Py)(Cl)(H
2
O).
The H atoms were omitted for clarity. Key atoms are labeled. Selected bond
distances (A) and angles(deg): Rh(1)-O(1) = 1.992(6), Rh(1)-O(2) = 2.081(5), Rh(1)-
O(3) = 1.971(5), Rh(1)-N(1) = 2.029(6), Rh(1)-N(2) = 1.958(6), Rh(1)-Cl(1) =
2.3821(19), O(3)-Rh(1)-O(1) = 91.1(2), N(2)-Rh(1)-N(1) = 81.2(3), N(2)-Rh(1)-
O(2) = 94.9(3), O(2)-Rh(1)-N(1) = 175.4(2), N(2)-Rh(1)-O(1) = 87.7(3), N(1)-
Rh(1)-O(1) = 93.6(2), O(1)-Rh(1)-Cl(1) = 174.26(17)

It is perhaps not surprising that a cis-O,O geometry is more favorable for the
methyl substituted complex 3 than it is for the analogous t-Bu substituted complex 1,
as it can be assumed that the bulky tert-butyl (t-Bu) groups would significantly repel
each other in a cis geometry. However, it is not a priori obvious why the methyl
substituted complex 2 also favors the trans configuration. Consequently, we turned to
DFT calculations (B3LYP/LACVP** using the Jaguar 6.5 program suite,
57
see
supporting information for more detailed information). Our calculations (see Table
2.1) on the six complexes cis/trans-1, cis/trans-2 and cis/trans-3 qualitatively
reproduced the observations, i.e. the cis form is only favored for 3. Comparison of
56
cis and trans-1 readily confirms the assumption of sterics, as the t-Bu groups on each
phenolate in cis-3 bump into their counterpart on the other phenolate.
Table 2.1. Calculated relative energies for cis-O,O and trans-O,O isomers of 1, 2
and 3. Energies are in kcal/mol.

cis-O,O trans-
O,O
1 3.4 0
2 2.8 0
3 0 1.5

Moreover, as expected, the methyl analogues 2 and 3 do not have any steric
issues, in either cis or trans forms. However, trans-3 exhibits some fairly substantial
angle/ring strain in the Rh-N-CH
2
-C=N-Rh ring, as the coordination of the two
phenolates trans to each other “push” the ring in the middle into a planar
configuration. This is not a problem in trans-2, as the second sp
3
-hybridized -CH
2
-
group in the Rh-N-CH
2
-CH
2
-N-Rh bridge can readily accommodate any reasonable
angle. Indeed, the Rh-N-CH
2
-C dihedral angles in trans-2 and trans-3 are 42° and
17°, respectively, showing how much more planar the ring in trans-3 is. The
equivalent dihedrals in cis-2 and cis-3 are 48° and 42°, respectively, i.e. fairly similar
and without measurable strain.
Thus, we can draw the conclusion that electronically, the trans-form is the most
stable form for this type of complex, by ~3 kcal/mol (based on structure 2). Making
the N-C-C-N bridge more rigid increases the energy of the trans-form, causing cis-3
57
to be favored, while the introduction of steric substituents on the phenolates
increases the energy of the cis-form, pushing the favorability back to the trans-form
for 1.
Scheme 2.2. Synthesis of Rh (III) Phenyl complex by transmetallation.
Rh
N
S
N
O
Cl
O
Me
Me Me
Me
Rh
N
S
N
O
Ph
O
Me
Me Me
Me Ph
2
Hg
CH
3
OH/CH
2
Cl
2
3 4
S=CH
3
OH S=CH
3
OH

As our ultimate goal is the synthesis of isoelectronic analogues of known CH
activation catalysts such as (acac)
2
Ir(Ph)(L),
50
transmetalation of complex 3 was
carried out. Mixing 3 with Ph
2
Hg at room temperature led to the new phenyl species
4 (Scheme 2). Complex 4 was obtained as a yellow-orange solid. The most distinct
feature of the
1
HNMR spectrum of 4 is a set of signals at ~6.8 ppm, corresponding to
resonance signals for the phenyl group. The measured integral ratio of these signals
to those of the other ligand protons matches very close the ratio found for the
complex (acac)
2
Rh(Ph)(CH
3
OH).2 Again, the asymmetric related phenolate ring
resonance suggests that the geometry is similar to complex 3, i.e. featuring a cis-O,O
arrangement. Confirmation of the cis-O,O geometry and the position of the phenyl
group was established by X-ray diffraction. The structure (shown in Figure 2.4) closely
resembles complex 3, with the only notable difference being the expected
replacement of the Cl ligand with a Ph group.
58

Figure 2.4. Molecular structure of 4, Rh(NNOO-Me,Py)(Ph)(CH
3
OH).
The H atoms were omitted for clarity. Key atoms are labeled. Selected bond
distances (Å) and angles(deg): Rh(1)-O(1) = 2.013(6), Rh(1)-O(2) = 2.161(6), Rh(1)-
O(3) = 2.101(6), Rh(1)-N(1) = 2.045(8), Rh(1)-N(2) = 2.025(6), Rh(1)-C(25) =
2.037(9), O(1)-Rh(1)-O(3) = 87.2(3), N(2)-Rh(1)-N(1) = 82.4(3), N(2)-Rh(1)-O(2) =
88.5(3), N(1)-Rh(1)-O(2) = 90.7(3), O(1)-Rh(1)-N(2) = 175.6(3), O(1)-Rh(1)-N(1) =
94.5(2), C(25)-Rh(1)-O(2)= 174.26(17).

It is anticipated that the synthetic strategies described here might also be of
potential use for preparing Ir(III) and other late transition metal biamine-
bisphenolate complexes. The exchange of the aqua or methanol ligands during
recrystallization implies a facial dissociation of these ligands at the Rh center, which
suggests the possibility of an accessible unsaturated 16e
-
Rh species, which is
essential for CH bond activation. We investigated complex 4 for catalysing H/D
scrambling of a C
6
H
6
/C
6
D
6
mixture, we found that the complex falls apart above 160
o
C.
59
2.3 Conclusion
The first air and thermally stable biamine-bisphenolate (NNOO)Rh(III)Cl(S) (X=
Cl or Ph; S = H
2
O or CH
3
OH) type complexes have been synthesized and
characterized. The NNOO ligands coordinate to Rh as non-planar tetradentate
ligands, with O,O donors either in a cis or trans position. DFT studies suggest that
the preference for cis/trans-O,O is controlled by sterics and the rigidity of the N-C-
C-N bridge.

2.4 Experimental section.

General considerations.
Materials and Analyses, Spectroscopy All air and water sensitive procedures were
carried out either in an MBraun inert atmosphere glove box (under nitrogen), or
using standard Schlenk techniques under argon. All deuterated solvents (Cambridge
Isotopes), was degassed and filled with argon prior to use. GC/MS analysis was
performed on a Shimadzu GC-MS QP5000 (ver. 2) equipped with cross-linked
methyl silicone gum capillary column (DB5) and a Gas-pro column. The retention
times of the products were confirmed by comparison to authentic samples. NMR
spectra were obtained on a Varian Mercury-400 spectrometer at room temperature.
All chemical shifts are reported in units of ppm and referenced to the residual
protonated solvent. All high-resolution mass spectra were obtained by UCLA
Pasarow Mass Spectrometry Laboratory on either an ESI, or a MALDI-TOF mass
spectrometer. Elemental Analysis was performed by Desert Analytics of Tucson,
Arizona.
60
X-ray Crystallography. Diffraction data for 1 was collected at low temperature (T =
128 K) on a Bruker SMART APEX CCD diffractometer with graphite-
monochromated Mo K α radiation ( λ= 0.71073 Å). The cell parameters for the Ir
complex were obtained from the least-squares refinement of the spots (from 60
collected frames) using the SMART program. A hemisphere of the crystal data was
collected and the intensity data was processed using the Saint Plus program. All
calculations for structure determination were carried out using the SHELXTL
package (version 5.1).Initial atomic positions were located by direct methods using
XS, and the structure was refined by least-squares methods using SHELX.
Absorption corrections were applied by using SADABS.3 Calculated hydrogen
positions were input and refined in a riding manner along with the attached carbons.

Ligands:N-(2-Pyridylmethyl)-N,N-bis(2´-hydroxy-3´,5´-di-tert-
butylbenzyl)amine
58
, N-(2-N´,N´-dimethylethyl)-N,N-bis(2´-hydroxy-3´,5´-
dimethylbenzyl)amine
58
and N-(2-Pyridylmethyl)-N,N-bis(2´-hydroxy-3´,5´-
dimethylbenzyl)amine
59
(2) were prepared as described in the literature.
Synthesis of 1,Rh(NNOO-bu
t
,py)(Cl)( CH
3
OH). To a 20 ml vial, 230 mg of
RhCl
3
(H
2
O)x (40% of Rh, 0.89 mmol) in 5 ml of H
2
O and 485 mg (0.89 mmol)of
H
2
L in 10 ml of acetone was mixed heated at 80
o
C for 5 minutes to get a
homogenous orange solution. 150 mg of NaHCO
3
(1.78 mmol) was added. The
mixture was heated at 80
o
C for 7 hours. The yellow micro crystalline was collected
by filtering. More crystalline was obtained by cooling the reaction solution at -30
o
C
to give 414 mg (72%) complex Rh(NNOO-but,py)(Cl)(CH
3
OH). Recrystalization is
61
performed in a mixture of methanol and methylene dichloride at -30oC, from which
cystals for X-ray diffraction selected.
1
HNMR (CD
3
OD/CDCl
3
): δ 9.41(d, J
HH
= 6
Hz, 1H, Py), 7.41(t, J
HH
= 7.5 Hz, 1H, Py), 7.00(t, J
HH
= 7 Hz, 1H, Py), 6.90(d,J
HH
=
3 Hz, 2H, Ar), 6.87(d, J
HH
= 3 Hz, 2H, Ar), 6.75(d, J
HH
= 8 Hz, 1H, Py), 4.90(d, J
HH

= 13 Hz, 2H, CHAr, CHAr´), 4.29(s, 2H, CH
2
Py), 3.53(d, J
HH
= 13 Hz, 2H, CHAr´,
CHAr), 1.22(s, 18H, t-Bu), 1.19(s, 18H, t-Bu),
13
C{
1
H}NMR(CD
3
OD/CDCl
3
): δ
166.4(s), 155.6(s), 153.2(s), 140.8(s), 138.6(s), 125.9(s),124.8(s) 122.8(s), 121.7(s),
119.7(s),65.6(s CH
2
Ar),62.8(s, CH
2
Py).
Synthesis of 3, Rh(NNOO-Me,Py)(Cl)(H
2
O). To a 20 ml vial, 250 mg of RhCl
3
(H
2
O)
x

(40% of Rh, 0.97 mmol) in 5 ml of H
2
O and 365 mg (0.97 mmol) of H
2
L in 10 ml of
acetone was mixed heated at 80
o
C for 5 minutes to get a homogenous orange
solution. 163 mg of NaHCO
3
(1.94 mmol) was added. The mixture was heated at 80
o
C for 5 hours. The orange micro crystalline was collected by filtering and dried. The
reaction solution was cooled at -30
o
C to get more product as micro crystalline.
Totally 360 mg (70%) of complex Rh(N
2
O
2
-Me,Py)(Cl)(H
2
O) was obtained.
1
HNMR (CD
3
OD/CDCl
3
): δ 8.50(d, J
HH
= 5.5 Hz, 1H, Py), 7.59(t, J
HH
= 6 Hz, 1H,
Py), 7.13(m, 2H, Py), 6.79(s, 1H, Ar), 6.70(s, 1H, Ar), 6.41(s, 1H, Ar), 6.35(s, 1H,
Ar), 5.53(d, J
HH
= 13 Hz, 1H, CHAr), 4.98(d, J
HH
= 15 Hz, 1H, CHAr), 4.19(d, J
HH
=
15 Hz, 1H, CHPy), 3.77(d, J
HH
= 13 Hz, 1H, CHPy), 3.53(d, J
HH
= 13 Hz, 1H,
CHAr), 2.75(d, J
HH
= 13 Hz, 1H, CHAr), 2.33(s, 3H, Me), 2.15(s, 3H, Me), 2.00(s,
3H, Me), 1.85(s, 3H, Me).
13
C{
1
H}NMR(CD
3
OD/CDCl
3
): δ 163.0(s), 149.6(s),
149.5(s), 139.5(s), 132.7(s), 132.6(s),130.1(s) 129.4(s), 128.8(s), 128.3(s), 127.0(s),
62
126.5(s), 124.1(s), 123.9(s), 122.1(s), 121.8(s),69.7(s CH
2
Ar), 66.8(s, CH
2
Ar),
61.8(s, CH
2
Py, 20.50(s, MeAr), 20.46(s, MeAr), 18.1(s, MeAr), 17.2(s, MeAr).
Synthesis of 2b, Rh(NNOO-Me,NMe
2
)(Cl)(H
2
O). To a 20 ml vial, 306 mg of
RhCl
3
(H
2
O)
x
(40% of Rh, 1.19 mmol) in 5 ml of H
2
O and 423 mg (1.19 mmol)of
H
2
L in 10 ml of acetone was mixed heated at 80
o
C for 5 minutes to get a
homogenous orange solution. 200 mg of NaHCO
3
(2.38 mmol) was added. The
mixture was heated at 80
o
C for 6 hours. The orange micro crystalline was collected
by filtering and dried. The reaction solution was cooled at -30
o
C to get more product
as micro crystalline. Totally 420 mg (69%) of complex Rh(NNOO-Me,
NMe
2
)(Cl)(H
2
O) was obtained.
1
H NMR (CD
3
OD/CDCl
3
): δ 6.78(d,J
HH
= 2 Hz, 2H,
Ar), 6.65(d, J
HH
= 2 Hz, 2H, Ar), 5.39(d, J
HH
= 13 Hz, 2H, CHAr, CHAr´), 3.26(d,
J
HH
= 13 Hz, 2H, CHAr, CHAr´), 2.84(t, J
HH
= 6 Hz, 2H,CH
2
N), 2.17(s, 6H, Me),
2.15(s, 6H, Me), 2.13(s, 6H, Me), 2.06(t, J
HH
= 6 Hz, 2H,CH
2
N).
13
C{
1
H}NMR(CD
3
OD/CDCl
3
): δ 161.1(s), 133.1(s), 129.8(s),128.6(s) 124.1(s),
121.0(s),67.3(s CH
2
N),64.7(s, CH
2
N), 57,5(s CH
2
N),50.3(s, CH
3
N), 20.4(s,
Me),17.7(s, Me). Anal. Calcd for C
22
H
32
ClN
2
O
3
Rh(H
2
O): C, 50.79; H, 6.86; Cl, 6.52
N, 5.15. Found: C, 50.86; H, 6.29; Cl, 6.53 N, 5.45.
Synthesis of Rh(NNOO-Me,Py)(Ph)(CH
3
OH) To a schlenk bomb containing 100
mg (0.184 mmols) of Rh(NNOO-Me,Py)(Cl)(H
2
O) and 72 mg of diphenylmercury
(0.202 mmols) was added 20 mL of dichlorormethane and 10 ml of methanol. The
reaction was stirred for 30 minutes.The resulting solution was filitered over celite
and washed with cold methanol.Recrysallised with dichlormethane/hexane. Totally
63
65 mg (60%) of complex Rh(NNOO-Me,Py)(Ph)(CH
3
OH) was obtained
1
H NMR
(CDCl
3
/CD
3
OD): δ 8.34(br, d, J
HH
=6, 1H, Py), 7.51(t, J
HH
=7.5, 1H, Py), 7.06 (t,
J
HH
=6.5, 2H, Py), 6.84(s, 1H, Ar), 6.81(s, 5H, Ph), 6.55(br, s, 1H, Ar), 6.24(br, s, 2H,
Ar), 4.59(d, J
HH
=13, 1H, CHN), 4.17(d, J
HH
=12.5, 1H, CHN), 3.97(d, J
HH
=15, 1H,
CHN), 3.79(d, J
HH
=15, 1H, CHN), 3.18(d, J
HH
=13, 1H, CHN), 2.55(d, J
HH
=12, 1H,
CHN), 2.35(s, 3H, MeAr), 2.14(s, 3H, MeAr), 1.96(s, 6H, MeAr).
13C{1H}NMR(CD
3
OD/CDCl
3
): δ 148.5(s), 137.5(s), 137.2(br, s), 133.0(s),
132.0(s), 129.0(s),128.7(s), 127.7(br, s), 123.9(br, s), 123.7(s), 120.9(s).
Synthesis of N,N-bis(2-Pyridylmethyl)-N-(2´-hydroxy-3´,5´-
dimethylbenzyl)amine. 2,4-dimethylphenol (2.44 g, 20 mmol), N,N-bis(2-
Pyridylmethyl)amine (3.98 g, 20 mmol)and HCHO (2 mL of 37%, 24 mmol) were
dissolved in 10 ml of methanol in a 20 mL vial. The mixture was stirred at 80
o
C for
24 hours. The volatiles were removed under vacuo to leave yellowish oil. This oil
was extracted by a mixture of hexane and ethyl acetate and filtered through a silica
gel column. After concentration of filtrate, 4.5 g of white crystalline product (67%)
was obtained.

64
Table 2.2. Crystal data and structure refinement for Rh(NNOO-but,py)(Cl)(
CH
3
OH)
Empirical formula C38 H54 Cl N2 O4 Rh
Formula weight 740.18
Temperature 298(2) K
Wavelength 0.71073 Å
Crystal system Monoclinic
Space group P2(1)/c
Unit cell dimensions a = 15.7408(13) Å α = 90
0

b = 17.9422(10) Å β = 119.7460(10)
0

c = 15.7257(9) Å γ  = 90°.
Volume 3856.1(4) Å
3

Z 4
Density (calculated) 1.275 Mg/m
3

Absorption coefficient 0.551 mm
-1

F(000) 1556
Crystal size 0.118 x 0.106 x 0.08 mm
3

Theta range for data collection 1.49 to 26.42°.
Index ranges -19<=h<=17, -17<=k<=22, -
19<=l<=19

Reflections collected 22172
Independent reflections 7877 [R(int) = 0.0366]
Completeness to theta = 26.42° 99.6 %
Transmission Factors min/max ratio: 0.882
Refinement method Full-matrix least-squares on
F
2

Data / restraints / parameters 7877 / 0 / 440
Goodness-of-fit on F
2
1.030
Final R indices [I>2sigma(I)] R1 = 0.0467, wR2 = 0.1132
R indices (all data) R1 = 0.0684, wR2 = 0.1237
Largest diff. peak and hole 1.367 and -0.559 e.Å
-3

Table 2.3. Atomic coordinates ( x 10
4
) and equivalent isotropic displacement
parameter (Å
2
x 10
3
) for Rh(NNOO-bu
t
,py)(Cl)( CH
3
OH). U(eq) is
65
defined as one third of the trace of the orthogonalized U
ij
tensor.

x y z U(eq)
Rh(1) 5667(1) 8338(1) 8407(1) 39(1)
Cl(1) 5797(1) 9644(1) 8253(1) 62(1)
O(1) 4544(2) 8347(1) 6993(2) 45(1)
O(2) 6754(2) 8404(1) 9794(2) 51(1)
O(3) 6588(2) 8177(2) 7817(2) 68(1)
O(4) 5650(3) 8937(2) 6184(3) 105(1)
N(1) 5597(2) 7216(1) 8574(2) 40(1)
N(2) 4774(2) 8393(1) 8951(2) 39(1)
C(1) 4354(3) 9017(2) 9055(3) 54(1)
C(2) 3775(3) 9005(3) 9483(3) 74(1)
C(3) 3601(4) 8331(3) 9794(4) 85(2)
C(4) 4035(3) 7699(3) 9695(3) 70(1)
C(5) 4626(3) 7739(2) 9279(2) 44(1)
C(6) 5194(3) 7087(2) 9238(3) 47(1)
C(7) 3767(3) 7900(2) 6756(2) 42(1)
C(8) 2790(3) 8142(2) 6162(2) 48(1)
C(9) 2537(3) 8936(2) 5728(3) 58(1)
C(10) 3011(4) 9107(3) 5114(4) 94(2)
C(11) 2878(4) 9497(3) 6552(4) 93(2)
C(12) 1432(4) 9037(3) 5053(5) 115(2)
C(13) 2044(3) 7638(2) 5991(3) 51(1)
C(14) 2200(3) 6914(2) 6355(3) 48(1)
C(15) 1363(3) 6387(2) 6197(3) 64(1)
C(16) 1475(4) 6219(3) 7205(4) 98(2)
C(17) 352(3) 6728(3) 5567(4) 83(1)
C(18) 1440(4) 5666(3) 5720(4) 92(2)
C(19) 3163(3) 6686(2) 6893(2) 49(1)
Table 2.3: Continued
C(20) 3934(3) 7156(2) 7082(2) 43(1)
C(21) 4956(3) 6872(2) 7583(3) 47(1)
66
C(22) 6591(3) 6869(2) 8985(3) 48(1)
C(23) 7349(2) 7138(2) 9984(2) 44(1)
C(24) 8086(3) 6643(2) 10569(3) 49(1)
C(25) 8842(3) 6826(2) 11488(3) 48(1)
C(26) 9678(3) 6279(2) 12095(3) 56(1)
C(27) 10538(6) 6662(4) 12945(7) 101(3)
C(28) 10084(5) 5996(4) 11431(5) 92(3)
C(29) 9312(6) 5644(5) 12406(8) 100(3)
C(30) 8781(3) 7520(2) 11845(3) 50(1)
C(31) 8059(2) 8040(2) 11316(2) 44(1)
C(32) 8003(3) 8783(2) 11763(3) 56(1)
C(33) 8765(4) 8827(3) 12859(3) 88(2)
C(34) 8185(3) 9435(2) 11240(3) 73(1)
C(35) 6979(3) 8859(2) 11658(3) 71(1)
C(36) 7359(2) 7867(2) 10327(2) 43(1)
C(37) 7601(4) 8416(3) 8360(5) 98(2)
C(38) 6126(7) 9585(4) 6137(5) 145(3)
C(39) 9682(14) 5572(11) 11560(13) 55(6)
C(40) 10680(20) 6625(15) 12510(20) 74(8)
C(41) 9513(15) 5959(12) 12992(16) 59(6)

Table 2.4 Bond lengths [Å] and angles [°] for Rh(NNOO-but,py)(Cl)(
CH
3
OH).

Rh(1)-N(2) 1.977(3)
Rh(1)-O(2) 1.999(2)
Rh(1)-N(1) 2.040(3)
Rh(1)-O(1) 2.041(2)
Rh(1)-O(3) 2.093(3)
Rh(1)-Cl(1) 2.3757(9)
Table 2.4: Continued
O(1)-C(7) 1.352(4)
O(2)-C(36) 1.323(4)
67
O(3)-C(37) 1.451(6)
O(4)-C(38) 1.406(8)
N(1)-C(6) 1.485(4)
N(1)-C(22) 1.499(4)
N(1)-C(21) 1.506(4)
N(2)-C(5) 1.348(4)
N(2)-C(1) 1.351(4)
C(1)-C(2) 1.375(6)
C(2)-C(3) 1.382(6)
C(3)-C(4) 1.371(6)
C(4)-C(5) 1.379(5)
C(5)-C(6) 1.494(5)
C(7)-C(20) 1.406(4)
C(7)-C(8) 1.414(5)
C(8)-C(13) 1.397(5)
C(8)-C(9) 1.545(5)
C(9)-C(11) 1.514(6)
C(9)-C(10) 1.516(6)
C(9)-C(12) 1.534(6)
C(13)-C(14) 1.392(5)
C(14)-C(19) 1.381(5)
C(14)-C(15) 1.539(6)
C(15)-C(17) 1.523(6)
C(15)-C(18) 1.530(6)
C(15)-C(16) 1.536(6)
C(19)-C(20) 1.383(5)
C(20)-C(21) 1.488(5)
C(22)-C(23) 1.505(5)
C(23)-C(24) 1.387(5)
C(23)-C(36) 1.411(4)
Table 2.4: Continued
C(24)-C(25) 1.380(5)
C(25)-C(30) 1.389(5)
68
C(25)-C(26) 1.536(5)
C(26)-C(29) 1.465(8)
C(26)-C(40) 1.51(3)
C(26)-C(27) 1.516(8)
C(26)-C(39) 1.524(18)
C(26)-C(28) 1.555(8)
C(26)-C(41) 1.66(2)
C(30)-C(31) 1.385(5)
C(31)-C(36) 1.424(5)
C(31)-C(32) 1.531(5)
C(32)-C(33) 1.536(5)
C(32)-C(34) 1.537(6)
C(32)-C(35) 1.542(6)
N(2)-Rh(1)-O(2) 86.11(11)
N(2)-Rh(1)-N(1) 84.19(11)
O(2)-Rh(1)-N(1) 89.40(10)
N(2)-Rh(1)-O(1) 93.09(10)
O(2)-Rh(1)-O(1) 176.08(9)
N(1)-Rh(1)-O(1) 94.33(10)
N(2)-Rh(1)-O(3) 174.89(11)
O(2)-Rh(1)-O(3) 94.92(12)
N(1)-Rh(1)-O(3) 90.81(11)
O(1)-Rh(1)-O(3) 86.22(11)
N(2)-Rh(1)-Cl(1) 96.35(8)
O(2)-Rh(1)-Cl(1) 88.99(7)
N(1)-Rh(1)-Cl(1) 178.26(8)
O(1)-Rh(1)-Cl(1) 87.29(7)
O(3)-Rh(1)-Cl(1) 88.68(8)
C(7)-O(1)-Rh(1) 118.13(19)
C(36)-O(2)-Rh(1) 127.3(2)
Table 2.4: Continued
C(37)-O(3)-Rh(1) 120.0(3)
C(6)-N(1)-C(22) 110.5(3)
69
C(6)-N(1)-C(21) 111.2(3)
C(22)-N(1)-C(21) 107.2(3)
C(6)-N(1)-Rh(1) 108.26(19)
C(22)-N(1)-Rh(1) 110.8(2)
C(21)-N(1)-Rh(1) 108.9(2)
C(5)-N(2)-C(1) 119.1(3)
C(5)-N(2)-Rh(1) 114.7(2)
C(1)-N(2)-Rh(1) 126.1(2)
N(2)-C(1)-C(2) 122.0(4)
C(1)-C(2)-C(3) 118.9(4)
C(4)-C(3)-C(2) 119.1(4)
C(3)-C(4)-C(5) 120.1(4)
N(2)-C(5)-C(4) 120.9(3)
N(2)-C(5)-C(6) 116.3(3)
C(4)-C(5)-C(6) 122.6(3)
N(1)-C(6)-C(5) 112.5(3)
O(1)-C(7)-C(20) 118.9(3)
O(1)-C(7)-C(8) 122.6(3)
C(20)-C(7)-C(8) 118.5(3)
C(13)-C(8)-C(7) 117.6(3)
C(13)-C(8)-C(9) 120.2(3)
C(7)-C(8)-C(9) 122.2(3)
C(11)-C(9)-C(10) 109.5(4)
C(11)-C(9)-C(12) 108.3(4)
C(10)-C(9)-C(12) 106.4(4)
C(11)-C(9)-C(8) 109.3(3)
C(10)-C(9)-C(8) 111.5(3)
C(12)-C(9)-C(8) 111.7(4)
C(14)-C(13)-C(8) 124.3(3)
C(19)-C(14)-C(13) 116.4(3)
Table 2.4: Continued
C(19)-C(14)-C(15) 120.6(3)
C(13)-C(14)-C(15) 123.0(3)
70
C(17)-C(15)-C(18) 109.4(4)
C(17)-C(15)-C(16) 107.3(4)
C(18)-C(15)-C(16) 110.1(4)
C(17)-C(15)-C(14) 113.2(4)
C(18)-C(15)-C(14) 109.2(4)
C(16)-C(15)-C(14) 107.7(3)
C(14)-C(19)-C(20) 122.0(3)
C(19)-C(20)-C(7) 121.0(3)
C(19)-C(20)-C(21) 120.5(3)
C(7)-C(20)-C(21) 118.5(3)
C(20)-C(21)-N(1) 113.6(3)
N(1)-C(22)-C(23) 115.8(3)
C(24)-C(23)-C(36) 119.5(3)
C(24)-C(23)-C(22) 117.1(3)
C(36)-C(23)-C(22) 123.3(3)
C(25)-C(24)-C(23) 123.1(3)
C(24)-C(25)-C(30) 116.1(3)
C(24)-C(25)-C(26) 121.8(3)
C(30)-C(25)-C(26) 122.1(3)
C(29)-C(26)-C(40) 132.3(11)
C(29)-C(26)-C(27) 112.6(6)
C(40)-C(26)-C(27) 31.2(9)
C(29)-C(26)-C(39) 69.4(8)
C(40)-C(26)-C(39) 107.2(12)
C(27)-C(26)-C(39) 128.1(8)
C(29)-C(26)-C(25) 110.3(4)
C(40)-C(26)-C(25) 113.3(11)
C(27)-C(26)-C(25) 111.9(4)
C(39)-C(26)-C(25) 115.2(7)
C(29)-C(26)-C(28) 109.4(5)
Table 2.4: Continued
C(40)-C(26)-C(28) 74.9(10)
C(27)-C(26)-C(28) 104.7(6)
71
C(39)-C(26)-C(28) 40.8(7)
C(25)-C(26)-C(28) 107.6(4)
C(29)-C(26)-C(41) 36.3(7)
C(40)-C(26)-C(41) 109.9(12)
C(27)-C(26)-C(41) 81.6(8)
C(39)-C(26)-C(41) 103.1(10)
C(25)-C(26)-C(41) 107.6(8)
C(28)-C(26)-C(41) 138.5(8)
C(31)-C(30)-C(25) 124.2(3)
C(30)-C(31)-C(36) 118.0(3)
C(30)-C(31)-C(32) 121.9(3)
C(36)-C(31)-C(32) 120.2(3)
C(31)-C(32)-C(33) 111.7(3)
C(31)-C(32)-C(34) 110.4(3)
C(33)-C(32)-C(34) 108.2(3)
C(31)-C(32)-C(35) 108.8(3)
C(33)-C(32)-C(35) 108.0(4)
C(34)-C(32)-C(35) 109.8(3)
O(2)-C(36)-C(23) 124.4(3)
O(2)-C(36)-C(31) 117.2(3)
C(23)-C(36)-C(31) 118.4(3)
Symmetry transformations used to generate
equivalent atoms:

72
Table 2.5. Anisotropic displacement parameters (Å
2
x 10
3
) for Rh(NNOO-
bu
t
,py)(Cl)( CH
3
OH) The anisotropic displacement factor exponent
takes the form: -2 π
2
[ h
2
a
*2
U
11
+ ... + 2 h k a* b* U
12
].

U
11
U
22
U
33
U
23
U
13
U
12

Rh(1) 44(1) 29(1) 46(1) 1(1) 25(1) 3(1)
Cl(1) 72(1) 34(1) 85(1) 5(1) 42(1) -2(1)
O(1) 56(2) 42(1) 41(1) 5(1) 26(1) 0(1)
O(2) 50(2) 32(1) 55(1) -6(1) 13(1) 7(1)
O(3) 75(2) 54(2) 101(2) -2(2) 64(2) 1(1)
N(1) 41(2) 32(1) 44(2) 0(1) 18(1) 4(1)
N(2) 43(2) 39(2) 34(1) 3(1) 19(1) 7(1)
C(1) 62(3) 48(2) 53(2) 7(2) 28(2) 20(2)
C(2) 86(3) 83(3) 68(3) 21(2) 50(3) 42(3)
C(3) 86(4) 113(4) 83(3) 33(3) 62(3) 38(3)
C(4) 75(3) 76(3) 77(3) 33(2) 51(3) 16(2)
C(5) 46(2) 45(2) 41(2) 7(2) 21(2) 3(2)
C(6) 53(2) 36(2) 49(2) 6(2) 23(2) 3(2)
C(7) 58(2) 35(2) 36(2) 0(1) 26(2) 2(2)
C(8) 59(2) 44(2) 39(2) 3(2) 24(2) 9(2)
C(9) 63(3) 50(2) 56(2) 15(2) 26(2) 14(2)
C(10) 110(4) 93(4) 86(3) 48(3) 55(3) 29(3)
C(11) 135(5) 55(3) 88(3) 10(3) 55(3) 30(3)
C(12) 78(4) 88(4) 135(5) 58(4) 18(4) 27(3)
C(13) 46(2) 55(2) 45(2) 3(2) 18(2) 7(2)
C(14) 50(2) 45(2) 46(2) -2(2) 20(2) -1(2)
C(15) 55(3) 59(3) 66(3) 0(2) 20(2) -9(2)
C(16) 97(4) 95(4) 106(4) 17(3) 54(4) -20(3)
C(17) 60(3) 81(4) 97(4) -1(3) 30(3) -5(2)
C(18) 70(3) 62(3) 122(4) -22(3) 29(3) -14(2)
C(19) 57(2) 38(2) 41(2) 2(2) 17(2) 3(2)
C(20) 47(2) 36(2) 39(2) -2(1) 15(2) 1(2)
C(21) 53(2) 34(2) 47(2) -7(2) 18(2) 4(2)
73
Table 2.5: Continued
C(22) 48(2) 34(2) 56(2) -4(2) 20(2) 8(2)
C(23) 42(2) 35(2) 50(2) -2(2) 19(2) 4(1)
C(24) 53(2) 31(2) 60(2) -2(2) 26(2) 8(2)
C(25) 41(2) 41(2) 60(2) 1(2) 23(2) 4(2)
C(26) 45(2) 46(2) 64(2) 10(2) 18(2) 11(2)
C(27) 76(5) 75(5) 90(6) 10(4) -6(4) 34(4)
C(28) 73(5) 85(5) 118(6) 25(4) 49(4) 40(4)
C(29) 89(5) 86(6) 140(8) 62(6) 68(5) 47(4)
C(30) 45(2) 43(2) 51(2) 1(2) 16(2) 1(2)
C(31) 41(2) 35(2) 51(2) -3(2) 20(2) -1(2)
C(32) 52(2) 46(2) 53(2) -11(2) 14(2) 2(2)
C(33) 90(4) 63(3) 66(3) -21(2) 4(3) 15(3)
C(34) 62(3) 36(2) 98(3) -7(2) 23(2) -7(2)
C(35) 75(3) 64(3) 80(3) -19(2) 42(3) 6(2)
C(36) 40(2) 34(2) 51(2) 1(2) 19(2) 6(1)
C(37) 77(4) 99(4) 147(5) 19(4) 78(4) 10(3)
C(38) 208(8) 110(6) 106(5) 15(4) 69(5) 3(5)
74
Table 2.6. Hydrogen coordinates ( x 10
4
) and isotropic displacement parameters
(Å
2
x 10
3
) for Rh(NNOO-bu
t
,py)(Cl)( CH
3
OH).
x y z U(eq)
H(1) 4460 9468 8831 65
H(2) 3505 9443 9561 89
H(3) 3196 8306 10067 102
H(4) 3931 7243 9910 84
H(6A) 5728 6983 9892 57
H(6B) 4772 6652 9016 57
H(10A) 2811 9592 4826 141
H(10B) 2813 8740 4605 141
H(10C) 3710 9095 5521 141
H(11A) 3575 9462 6962 139
H(11B) 2568 9395 6933 139
H(11C) 2708 9991 6284 139
H(12A) 1104 8976 5425 173
H(12B) 1197 8671 4540 173
H(12C) 1304 9527 4770 173
H(13) 1401 7798 5608 61
H(16A) 929 5926 7124 147
H(16B) 1496 6678 7528 147
H(16C) 2070 5946 7594 147
H(17A) 270 6862 4940 125
H(17B) 289 7165 5884 125
H(17C) -139 6372 5481 125
H(18A) 1379 5778 5095 139
H(18B) 927 5332 5632 139
H(18C) 2063 5437 6134 139
H(19) 3297 6202 7135 58
H(21A) 5242 6968 7171 57
H(21B) 4944 6336 7660 57
H(22A) 6831 6961 8534 58
H(22B) 6522 6334 9017 58
75
Table 2.6: Continued
H(24) 8071 6166 10331 59
H(27A) 10361 6804 13425 152
H(27B) 10714 7097 12712 152
H(27C) 11085 6326 13236 152
H(28A) 10612 5654 11793 137
H(28B) 10319 6412 11222 137
H(28C) 9573 5749 10868 137
H(29A) 8756 5432 11846 150
H(29B) 9124 5810 12869 150
H(29C) 9817 5275 12706 150
H(30) 9256 7643 12481 60
H(33A) 8656 8429 13201 132
H(33B) 8704 9297 13117 132
H(33C) 9410 8784 12942 132
H(34A) 8813 9376 11286 110
H(34B) 8171 9896 11542 110
H(34C) 7685 9440 10563 110
H(35A) 6493 8870 10976 107
H(35B) 6947 9312 11965 107
H(35C) 6860 8442 11967 107
H(37A) 7630 8927 8554 147
H(37B) 7894 8368 7954 147
H(37C) 7950 8110 8933 147
H(39A) 10240 5274 11984 82
H(39B) 9713 5702 10984 82
H(39C) 9095 5293 11375 82
H(40A) 11163 6280 12956 111
H(40B) 10704 7072 12860 111
H(40C) 10806 6743 11992 111
H(41A) 8892 5712 12719 88
H(41B) 9528 6367 13394 88
H(41C) 10025 5613 13383 88
76
Table 2.7. Crystal data and structure refinement for Rh(NNOO-
Me,Py)(Cl)(H
2
O).
Identification code rhnnoom
Empirical formula C24 H27 Cl N2 O4 Rh
Formula weight 545.84
Temperature 153(2) K
Wavelength 0.71073 Å
Crystal system Triclinic
Space group P-1
Unit cell dimensions a = 9.2566(18) Å α= 76.053(3)°.
b = 9.2615(18) Å β= 77.247(3)°.
c = 13.978(3) Å γ = 81.376(3)°.
Volume 1128.4(4) Å
3

Z 2
Density (calculated) 1.607 Mg/m
3

Absorption coefficient 0.909 mm
-1

F(000) 558
Crystal size 0.13 x 0.10 x 0.02 mm
3

Theta range for data collection 1.53 to 27.54°.
Index ranges -11<=h<=10, -11<=k<=11, -
17<=l<=18

Reflections collected 6872
Independent reflections 4846 [R(int) = 0.0315]
Completeness to theta = 27.54° 93.0 %
Transmission factors min/max ratio: 0.574
Refinement method Full-matrix least-squares on
F
2

Data / restraints / parameters 4846 / 0 / 289
Goodness-of-fit on F
2
1.045
Final R indices [I>2sigma(I)] R1 = 0.0684, wR2 = 0.1880
R indices (all data) R1 = 0.0970, wR2 = 0.2514
Largest diff. peak and hole 1.573 and -2.497 e.Å
-3

77
Table 2.8. Atomic coordinates ( x 10
4
) and equivalent isotropic displacement
parameters (Å
2
x 10
3
) for Rh(NNOO-Me,Py)(Cl)(H
2
O). U(eq) is
defined as one third of the trace of the orthogonalized Uij tensor.
x y z U(eq)

Rh(1) 7855(1) 5957(1) 6193(1) 23(1)
Cl(1) 7139(2) 5617(2) 4732(1) 29(1)
O(1) 8632(7) 6328(7) 7323(4) 36(1)
O(2) 9878(6) 6637(8) 5340(4) 39(2)
O(3) 8829(6) 3893(6) 6392(4) 28(1)
O(4) 766(14) 8368(17) 6719(11) 134(5)
N(1) 5852(7) 5455(7) 7060(5) 25(1)
N(2) 6822(7) 7981(7) 6062(4) 25(1)
C(1) 4742(8) 6588(9) 6618(6) 28(2)
C(2) 5314(10) 8070(10) 6341(6) 33(2)
C(3) 4442(11) 9403(10) 6378(6) 39(2)
C(4) 5133(14) 10751(10) 6063(6) 48(3)
C(5) 6659(14) 10655(11) 5754(7) 50(3)
C(6) 7480(12) 9296(11) 5756(7) 43(2)
C(7) 8423(9) 5257(10) 8182(6) 32(2)
C(8) 9641(10) 4577(13) 8644(7) 49(3)
C(9) 9373(11) 3465(15) 9516(7) 59(3)
C(10) 7961(10) 3018(11) 9936(7) 41(2)
C(11) 6809(9) 3723(9) 9490(6) 28(2)
C(12) 7015(9) 4823(8) 8630(5) 24(2)
C(13) 11183(12) 5060(19) 8183(8) 83(5)
C(14) 7776(12) 1732(13) 10841(7) 53(3)
C(15) 5732(9) 5615(9) 8130(6) 27(2)
C(16) 5569(8) 3913(9) 7041(6) 26(2)
C(17) 6665(8) 2662(8) 7437(5) 21(1)
C(18) 6129(9) 1413(9) 8140(6) 29(2)
C(19) 7047(10) 216(9) 8492(6) 33(2)
C(20) 8559(12) 268(12) 8168(8) 59(3)
C(21) 9172(10) 1477(11) 7473(7) 48(3)
78
Table 2.8: Continued
C(22) 8221(9) 2708(9) 7093(6) 29(2)
C(23) 6464(11) -1118(10) 9250(7) 43(2)
C(24) 10833(16) 1576(17) 7144(11) 81(4)

Table 2.9. Bond lengths [Å] and angles [°] for Rh(NNOO-Me,Py)(Cl)(H
2
O).

Rh(1)-N(2) 1.958(6)
Rh(1)-O(3) 1.971(5)
Rh(1)-O(1) 1.992(6)
Rh(1)-N(1) 2.029(6)
Rh(1)-O(2) 2.081(5)
Rh(1)-Cl(1) 2.3821(19)
O(1)-C(7) 1.358(10)
O(3)-C(22) 1.380(10)
N(1)-C(1) 1.478(10)
N(1)-C(16) 1.498(10)
N(1)-C(15) 1.516(9)
N(2)-C(2) 1.360(11)
N(2)-C(6) 1.376(11)
C(1)-C(2) 1.478(12)
C(2)-C(3) 1.375(11)
C(3)-C(4) 1.418(14)
C(4)-C(5) 1.379(15)
C(5)-C(6) 1.369(14)
C(7)-C(12) 1.389(11)
C(7)-C(8) 1.413(12)
C(8)-C(9) 1.395(14)
C(8)-C(13) 1.517(14)
C(9)-C(10) 1.390(13)
C(10)-C(11) 1.357(12)
C(10)-C(14) 1.512(13)
79
Table 2.9: Continued
C(11)-C(12) 1.374(11)
C(12)-C(15) 1.514(10)
C(16)-C(17) 1.505(10)
C(17)-C(18) 1.399(11)
C(17)-C(22) 1.418(10)
C(18)-C(19) 1.353(11)
C(19)-C(20) 1.377(14)
C(19)-C(23) 1.503(12)
C(20)-C(21) 1.393(14)
C(21)-C(22) 1.404(11)
C(21)-C(24) 1.515(17)
N(2)-Rh(1)-O(3) 177.1(2)
N(2)-Rh(1)-O(1) 87.7(3)
O(3)-Rh(1)-O(1) 91.1(2)
N(2)-Rh(1)-N(1) 81.2(3)
O(3)-Rh(1)-N(1) 96.3(2)
O(1)-Rh(1)-N(1) 93.6(2)
N(2)-Rh(1)-O(2) 94.9(3)
O(3)-Rh(1)-O(2) 87.6(2)
O(1)-Rh(1)-O(2) 83.8(2)
N(1)-Rh(1)-O(2) 175.4(2)
N(2)-Rh(1)-Cl(1) 92.18(18)
O(3)-Rh(1)-Cl(1) 89.32(17)
O(1)-Rh(1)-Cl(1) 174.26(17)
N(1)-Rh(1)-Cl(1) 92.05(18)
O(2)-Rh(1)-Cl(1) 90.53(17)
C(7)-O(1)-Rh(1) 115.1(5)
C(22)-O(3)-Rh(1) 123.8(4)
C(1)-N(1)-C(16) 110.8(6)
C(1)-N(1)-C(15) 107.2(6)
C(16)-N(1)-C(15) 110.8(6)
C(1)-N(1)-Rh(1) 105.5(5)
80
Table 2.9: Continued
C(16)-N(1)-Rh(1) 110.4(4)
C(15)-N(1)-Rh(1) 112.0(5)
C(2)-N(2)-C(6) 117.8(7)
C(2)-N(2)-Rh(1) 115.9(6)
C(6)-N(2)-Rh(1) 126.3(6)
N(1)-C(1)-C(2) 109.3(7)
N(2)-C(2)-C(3) 122.8(8)
N(2)-C(2)-C(1) 112.5(7)
C(3)-C(2)-C(1) 124.7(8)
C(2)-C(3)-C(4) 118.8(9)
C(5)-C(4)-C(3) 118.1(8)
C(6)-C(5)-C(4) 120.8(9)
C(5)-C(6)-N(2) 121.7(10)
O(1)-C(7)-C(12) 120.9(7)
O(1)-C(7)-C(8) 120.3(8)
C(12)-C(7)-C(8) 118.7(8)
C(9)-C(8)-C(7) 118.1(9)
C(9)-C(8)-C(13) 122.2(9)
C(7)-C(8)-C(13) 119.7(9)
C(10)-C(9)-C(8) 122.1(9)
C(11)-C(10)-C(9) 118.3(9)
C(11)-C(10)-C(14) 122.6(9)
C(9)-C(10)-C(14) 119.1(8)
C(10)-C(11)-C(12) 121.8(8)
C(11)-C(12)-C(7) 120.9(7)
C(11)-C(12)-C(15) 122.0(7)
C(7)-C(12)-C(15) 117.1(7)
C(12)-C(15)-N(1) 115.2(6)
N(1)-C(16)-C(17) 115.8(6)
C(18)-C(17)-C(22) 119.6(7)
C(18)-C(17)-C(16) 119.0(7)
C(22)-C(17)-C(16) 121.3(7)
81
Table 2.9: Continued
C(19)-C(18)-C(17) 122.2(8)
C(18)-C(19)-C(20) 118.2(8)
C(18)-C(19)-C(23) 121.9(8)
C(20)-C(19)-C(23) 119.8(8)
C(19)-C(20)-C(21) 122.7(9)
C(20)-C(21)-C(22) 119.2(9)
C(20)-C(21)-C(24) 123.2(9)
C(22)-C(21)-C(24) 117.5(9)
O(3)-C(22)-C(21) 119.1(7)
O(3)-C(22)-C(17) 122.8(7)
C(21)-C(22)-C(17) 118.1(7)
Symmetry transformations used to generate
equivalent atoms

Table 2.10. Anisotropic displacement parameters (Å
2
x 10
3
) for C
24
H
27
Cl N
2
O
4

Rh. The anisotropic displacement factor exponent takes the form:
-2 π
2
[ h
2
a*
2
U
11
+ ... + 2 h k a* b* U
12
]
U
11
U
22
U
33
U
23
U
13
U
12

Rh(1) 15(1) 32(1) 21(1) -5(1) 0(1) -6(1)
Cl(1) 21(1) 41(1) 24(1) -11(1) -3(1) -3(1)
O(1) 36(3) 49(4) 24(3) 5(3) -7(2) -24(3)
O(2) 21(3) 66(4) 28(3) -16(3) 11(2) -18(3)
O(3) 14(3) 32(3) 30(3) 5(2) -4(2) 10(2)
O(4) 106(10) 158(13) 146(12) -35(10) -19(9) -44(9)
N(1) 19(3) 33(3) 24(3) -13(3) 0(2) -3(3)
N(2) 30(4) 25(3) 18(3) 5(2) -17(3) 6(3)
C(1) 20(4) 36(4) 26(4) -7(3) -1(3) 0(3)
C(2) 38(5) 41(5) 24(4) -17(4) 0(3) -5(4)
C(3) 49(6) 38(5) 29(4) -14(4) -9(4) 12(4)
C(4) 88(9) 37(5) 25(4) -9(4) -32(5) 12(5)
C(5) 77(8) 39(5) 42(5) -12(4) -21(5) -18(5)
82
Table 2.10: Continued
C(6) 61(7) 44(5) 28(4) -7(4) -9(4) -24(5)
C(7) 29(4) 46(5) 20(4) -5(3) -3(3) -12(4)
C(8) 26(5) 88(8) 30(5) 4(5) -9(4) -16(5)
C(9) 23(5) 116(10) 30(5) 6(5) -9(4) -11(5)
C(10) 30(5) 60(6) 28(4) 1(4) -9(4) 1(4)
C(11) 24(4) 37(4) 23(4) -9(3) -3(3) -6(3)
C(12) 26(4) 28(4) 20(4) -4(3) -7(3) -2(3)
C(13) 32(6) 171(15) 39(6) 14(7) -14(5) -38(8)
C(14) 45(6) 70(7) 36(5) 4(5) -4(4) -7(5)
C(15) 26(4) 32(4) 23(4) -9(3) -1(3) 0(3)
C(16) 19(4) 32(4) 29(4) -9(3) 0(3) -8(3)
C(17) 16(4) 25(4) 19(3) -3(3) -2(3) -2(3)
C(18) 24(4) 31(4) 32(4) -10(3) 0(3) -8(3)
C(19) 35(5) 28(4) 26(4) 6(3) -4(3) 3(3)
C(20) 44(6) 58(7) 52(6) 5(5) 16(5) 6(5)
C(21) 23(5) 49(6) 47(6) 22(4) 2(4) 13(4)
C(22) 23(4) 38(4) 21(4) -5(3) 4(3) 0(3)
C(23) 48(6) 33(5) 39(5) -3(4) 3(4) 5(4)

83
Table 2.11. Hydrogen coordinates ( x 10
4
) and isotropic displacement parameters
(Å
2
x 10
3)
for C
24
H
27
Cl N
2
O
4
Rh.
x y z U(eq)

H(2) 10009 6426 4773 58
H(1A) 3793 6614 7110 34
H(1B) 4551 6326 6015 34
H(3) 3396 9421 6609 47
H(4) 4561 11693 6064 58
H(5) 7147 11543 5538 59
H(6) 8530 9260 5540 51
H(9) 10183 2998 9834 71
H(11) 5833 3449 9781 33
H(13A) 11891 4503 8602 125
H(13B) 11167 6133 8143 125
H(13C) 11488 4857 7507 125
H(14A) 6738 1784 11199 80
H(14B) 8430 1795 11290 80
H(14C) 8039 783 10620 80
H(15A) 5654 6692 8131 33
H(15B) 4799 5224 8539 33
H(16A) 5564 3881 6338 31
H(16B) 4562 3725 7438 31
H(18) 5085 1404 8377 34
H(20) 9211 -553 8429 71
H(23A) 5374 -1006 9368 65
H(23B) 6793 -1192 9882 65
H(23C) 6846 -2027 8995 65
H(24A) 11146 1472 6445 122
H(24B) 11363 773 7574 122
H(24C) 11066 2547 7200 122

84
Molecular structure 4
Table 2.12. Crystal data and structure refinement for C
31
H
34
N
2
O
5
Rh.
Identification code rhn2o2m
Empirical formula C31 H34 N2 O5 Rh
Formula weight 617.51
Temperature 163(2) K
Wavelength 0.71073 Å
Crystal system Orthorhombic
Space group P2(1)2(1)2(1)
Unit cell dimensions a = 10.3395(14) Å α= 90°.
b = 14.753(2) Å β= 90°.
c = 23.961(3) Å γ = 90°.
Volume 3654.9(8) Å
3

Z 4
Density (calculated) 1.122 Mg/m
3

Absorption coefficient 0.500 mm
-1

F(000) 1276
Crystal size 0.42 x 0.18 x 0.03 mm
3

Theta range for data collection 1.62 to 25.68°.
Index ranges -12<=h<=12, -16<=k<=17, -
19<=l<=29

Reflections collected 20150
Independent reflections 6911 [R(int) = 0.0598]
Completeness to theta = 25.68° 99.9 %
Transmission factors min/max ratio: 0.252
Refinement method Full-matrix least-squares on
F
2

Data / restraints / parameters 6911 / 0 / 352
Goodness-of-fit on F
2
1.066
Final R indices [I>2sigma(I)] R1 = 0.0690, wR2 = 0.2131
R indices (all data) R1 = 0.1005, wR2 = 0.2348
Absolute structure parameter 0.47(8)
Largest diff. peak and hole 1.445 and -0.657 e.Å
-3

85
Table 2.13. Atomic coordinates ( x 10
4
) and equivalent isotropic displacement
parameters (Å
2
x 10
3
) for C
31
H
34
N
2
O
5
Rh. U(eq) is defined as one
third of the trace of the orthogonalized Uij tensor.
x y z U(eq)

Rh(1) 2532(1) 2081(1) 1423(1) 37(1)
O(1) 1034(6) 2729(4) 1063(2) 39(2)
O(2) 2657(6) 3178(4) 2018(2) 49(1)
O(3) 1178(6) 1480(5) 1962(3) 51(2)
O(4) 9609(8) 116(6) 1663(4) 84(2)
O(5) 1041(10) 4432(7) 2319(4) 98(3)
N(1) 3899(7) 2686(5) 931(3) 38(2)
N(2) 4109(8) 1521(6) 1786(3) 45(2)
C(1) 3405(8) 2809(6) 358(3) 41(2)
C(2) 2287(9) 3418(5) 322(3) 42(2)
C(3) 2329(10) 4102(6) -83(3) 47(2)
C(4) 1312(11) 4715(7) -167(4) 54(2)
C(5) 187(10) 4605(7) 153(4) 51(2)
C(6) 113(9) 3902(6) 556(3) 44(2)
C(7) 1183(8) 3327(6) 654(3) 39(2)
C(8) 1403(12) 5462(7) -578(5) 70(3)
C(9) -1079(9) 3781(8) 890(4) 60(3)
C(10) 4291(9) 3593(7) 1146(4) 50(2)
C(11) 4781(9) 3590(6) 1745(4) 45(2)
C(12) 6049(9) 3761(7) 1872(4) 54(2)
C(13) 6451(10) 3747(7) 2445(4) 57(3)
C(14) 5538(10) 3569(7) 2844(4) 56(3)
C(15) 4269(9) 3386(7) 2723(4) 50(2)
C(16) 3866(8) 3396(6) 2167(4) 43(2)
C(17) 7839(9) 3953(9) 2599(5) 75(3)
C(18) 3278(11) 3149(8) 3168(4) 66(3)
C(19) 5036(8) 2065(7) 933(4) 44(2)
C(20) 5202(9) 1619(7) 1507(4) 47(2)
C(21) 6359(10) 1289(7) 1702(4) 57(3)
86
Table 2.13: Continued
C(22) 6384(11) 857(8) 2181(6) 73(3)
C(23) 5245(12) 752(7) 2511(5) 69(3)
C(24) 4135(11) 1091(7) 2285(5) 58(3)
C(25) 2247(7) 985(6) 920(3) 40(2)
C(26) 2870(9) 149(6) 1040(4) 49(2)
C(27) 2563(14) -630(6) 738(4) 67(3)
C(28) 1668(10) -599(7) 307(4) 60(3)
C(29) 1082(12) 229(8) 191(5) 74(3)
C(30) 1368(11) 971(7) 492(4) 56(3)
C(31) 114(14) 2055(11) 2182(6) 94(4)

Table 2.14. Bond lengths [Å] and angles [°] for C
31
H
34
N
2
O
5
Rh.
Rh(1)-O(1) 2.013(6)
Rh(1)-N(2) 2.025(8)
Rh(1)-C(25) 2.037(9)
Rh(1)-N(1) 2.045(8)
Rh(1)-O(3) 2.101(6)
Rh(1)-O(2) 2.161(6)
O(1)-C(7) 1.329(10)
O(2)-C(16) 1.339(11)
O(3)-C(31) 1.486(16)
N(1)-C(1) 1.476(10)
N(1)-C(19) 1.490(11)
N(1)-C(10) 1.490(12)
N(2)-C(20) 1.319(12)
N(2)-C(24) 1.355(12)
C(1)-C(2) 1.467(12)
C(2)-C(7) 1.397(12)
C(2)-C(3) 1.401(11)
C(3)-C(4) 1.401(14)
C(4)-C(5) 1.403(14)
87
Table 2.14: Continued
C(4)-C(8) 1.481(14)
C(5)-C(6) 1.418(13)
C(6)-C(7) 1.414(12)
C(6)-C(9) 1.481(12)
C(10)-C(11) 1.522(12)
C(11)-C(12) 1.369(13)
C(11)-C(16) 1.415(13)
C(12)-C(13) 1.436(13)
C(13)-C(14) 1.367(14)
C(13)-C(17) 1.513(14)
C(14)-C(15) 1.370(13)
C(15)-C(16) 1.395(12)
C(15)-C(18) 1.520(13)
C(19)-C(20) 1.534(12)
C(20)-C(21) 1.374(13)
C(21)-C(22) 1.312(16)
C(22)-C(23) 1.426(17)
C(23)-C(24) 1.364(15)
C(25)-C(30) 1.371(12)
C(25)-C(26) 1.420(12)
C(26)-C(27) 1.394(12)
C(27)-C(28) 1.389(14)
C(28)-C(29) 1.391(16)
C(29)-C(30) 1.343(14)
O(1)-Rh(1)-N(2) 175.6(3)
O(1)-Rh(1)-C(25) 90.7(3)
N(2)-Rh(1)-C(25) 92.7(3)
O(1)-Rh(1)-N(1) 94.5(2)
N(2)-Rh(1)-N(1) 82.4(3)
C(25)-Rh(1)-N(1) 96.1(3)
O(1)-Rh(1)-O(3) 87.2(3)
N(2)-Rh(1)-O(3) 95.8(3)
88
Table 2.14: Continued
C(25)-Rh(1)-O(3) 86.1(3)
N(1)-Rh(1)-O(3) 177.2(3)
O(1)-Rh(1)-O(2) 88.5(2)
N(2)-Rh(1)-O(2) 88.5(3)
C(25)-Rh(1)-O(2) 173.2(3)
N(1)-Rh(1)-O(2) 90.7(3)
O(3)-Rh(1)-O(2) 87.1(3)
C(7)-O(1)-Rh(1) 122.9(5)
C(16)-O(2)-Rh(1) 114.3(5)
C(31)-O(3)-Rh(1) 118.1(7)
C(1)-N(1)-C(19) 110.6(7)
C(1)-N(1)-C(10) 107.8(7)
C(19)-N(1)-C(10) 109.6(7)
C(1)-N(1)-Rh(1) 110.5(5)
C(19)-N(1)-Rh(1) 106.0(5)
C(10)-N(1)-Rh(1) 112.4(5)
C(20)-N(2)-C(24) 118.7(9)
C(20)-N(2)-Rh(1) 115.4(6)
C(24)-N(2)-Rh(1) 125.9(7)
C(2)-C(1)-N(1) 113.7(7)
C(7)-C(2)-C(3) 119.2(9)
C(7)-C(2)-C(1) 123.5(7)
C(3)-C(2)-C(1) 117.2(8)
C(2)-C(3)-C(4) 122.8(9)
C(3)-C(4)-C(5) 118.0(8)
C(3)-C(4)-C(8) 121.9(9)
C(5)-C(4)-C(8) 120.2(10)
C(4)-C(5)-C(6) 120.1(9)
C(7)-C(6)-C(5) 120.6(8)
C(7)-C(6)-C(9) 119.3(8)
C(5)-C(6)-C(9) 120.1(9)
O(1)-C(7)-C(2) 125.3(8)
89
Table 2.14: Continued
O(1)-C(7)-C(6) 115.5(7)
C(2)-C(7)-C(6) 119.2(8)
N(1)-C(10)-C(11) 114.5(8)
C(12)-C(11)-C(16) 121.2(8)
C(12)-C(11)-C(10) 121.9(8)
C(16)-C(11)-C(10) 116.9(8)
C(11)-C(12)-C(13) 119.2(9)
C(14)-C(13)-C(12) 118.1(9)
C(14)-C(13)-C(17) 121.6(9)
C(12)-C(13)-C(17) 120.3(10)
C(13)-C(14)-C(15) 123.4(9)
C(14)-C(15)-C(16) 119.1(9)
C(14)-C(15)-C(18) 122.8(9)
C(16)-C(15)-C(18) 118.1(8)
O(2)-C(16)-C(15) 122.1(8)
O(2)-C(16)-C(11) 118.8(8)
C(15)-C(16)-C(11) 119.0(8)
N(1)-C(19)-C(20) 110.8(7)
N(2)-C(20)-C(21) 122.3(9)
N(2)-C(20)-C(19) 113.8(8)
C(21)-C(20)-C(19) 123.7(9)
C(22)-C(21)-C(20) 119.1(10)
C(21)-C(22)-C(23) 121.4(10)
C(24)-C(23)-C(22) 115.8(10)
N(2)-C(24)-C(23) 122.6(11)
C(30)-C(25)-C(26) 116.0(8)
C(30)-C(25)-Rh(1) 123.4(7)
C(26)-C(25)-Rh(1) 120.3(6)
C(27)-C(26)-C(25) 120.5(8)
C(28)-C(27)-C(26) 120.7(9)
C(27)-C(28)-C(29) 117.8(9)
C(30)-C(29)-C(28) 120.9(10)
90
Table 2.14: Continued
C(29)-C(30)-C(25) 124.0(10)
Symmetry transformations used to generate
equivalent atoms:

Table 2.15. Anisotropic displacement parameters (Å
2
x 10
3
) for C
31
H
34
N
2
O
5
Rh.
The anisotropic displacement factor exponent takes the form:
-2 π
2
[ h
2
a*
2
U
11
+ ... + 2 h k a* b* U
12
]

U
11
U
22
U
33
U
23
U
13
U
12

Rh(1) 37(1) 42(1) 33(1) 2(1) 1(1) 0(1)
O(1) 35(3) 44(4) 38(3) 11(3) -5(3) 2(3)
O(2) 45(4) 53(3) 48(3) -10(2) 16(3) 8(3)
O(3) 48(4) 63(5) 41(4) 17(3) 9(3) -4(3)
O(4) 59(5) 96(6) 98(6) 22(5) -3(4) -18(4)
N(1) 44(4) 44(5) 26(4) -1(3) -2(3) 5(3)
N(2) 58(5) 50(5) 28(4) 6(3) -3(3) -6(4)
C(1) 38(4) 50(5) 37(4) -5(4) 5(4) -3(4)
C(2) 54(6) 37(4) 35(4) -1(3) -6(4) -12(4)
C(3) 53(6) 52(5) 35(4) -1(3) -9(4) -5(5)
C(4) 78(7) 50(6) 33(5) 1(4) -4(5) -8(5)
C(5) 61(6) 56(6) 36(5) 0(4) -10(4) 5(5)
C(6) 44(5) 49(5) 39(5) -4(4) -2(4) 2(4)
C(7) 39(5) 49(5) 28(4) -10(4) 0(4) 5(4)
C(8) 92(9) 54(6) 65(7) 18(5) -18(6) 1(6)
C(9) 42(5) 91(8) 46(6) 7(5) 9(4) 24(5)
C(10) 48(5) 57(6) 46(5) 6(4) 4(4) -7(5)
C(11) 44(5) 46(5) 46(5) -14(4) 1(4) -1(4)
C(12) 41(5) 67(7) 54(6) -10(5) 3(4) -7(5)
C(13) 52(6) 55(6) 64(7) -10(5) -20(5) -6(5)
C(14) 70(7) 52(6) 45(6) -18(5) 4(5) -8(5)
C(15) 57(6) 56(6) 36(5) -11(4) 3(4) -5(5)
C(16) 38(5) 42(5) 48(5) -8(4) 1(4) -2(4)
91
Table 2.15: Continued
C(17) 48(7) 91(9) 85(8) -25(7) -13(5) 8(5)
C(18) 77(7) 76(8) 45(6) -8(5) 4(5) -15(6)
C(19) 38(5) 52(5) 43(5) 1(4) 5(4) 3(4)
C(20) 41(5) 53(5) 46(5) -12(4) -10(4) -3(4)
C(21) 61(6) 63(6) 46(6) -5(5) -16(5) 7(5)
C(22) 43(6) 81(8) 94(9) -11(7) -21(6) 17(6)
C(23) 89(9) 45(6) 72(8) 8(5) -38(7) -1(6)
C(24) 62(6) 53(6) 60(6) -13(5) -24(5) -1(5)
C(25) 34(6) 47(5) 37(4) 13(3) 0(3) -7(4)
C(26) 50(6) 46(5) 51(5) 2(4) -13(4) -3(4)
C(27) 81(7) 44(5) 75(6) 3(4) -28(8) -3(7)
C(28) 63(6) 53(6) 65(7) -17(5) -11(5) -7(5)
C(29) 77(8) 75(8) 71(7) 10(6) -34(6) -16(6)
C(30) 73(7) 44(6) 50(6) -6(5) -13(5) -3(5)
C(31) 93(10) 115(11) 74(9) 24(8) 6(7) -22(9)

92
Table 2.16. Hydrogen coordinates ( x 10
4
) and isotropic displacement parameters
(Å
2
x 10
3
) for C
31
H
34
N
2
O
5
Rh.

x y z U(eq)

H(1A) 4109 3053 121 50
H(1B) 3159 2209 205 50
H(3) 3078 4153 -310 56
H(5) -526 5002 100 61
H(8A) 1664 6021 -388 106
H(8B) 559 5552 -756 106
H(8C) 2046 5307 -863 106
H(9A) -1512 3219 778 90
H(9B) -1660 4296 827 90
H(9C) -854 3749 1287 90
H(10A) 3539 4007 1121 60
H(10B) 4979 3839 901 60
H(12) 6655 3887 1584 65
H(14) 5796 3573 3224 67
H(17A) 7859 4339 2931 112
H(17B) 8262 4267 2288 112
H(17C) 8298 3385 2676 112
H(18A) 3694 3153 3535 99
H(18B) 2923 2545 3093 99
H(18C) 2578 3597 3162 99
H(19A) 5826 2411 839 53
H(19B) 4916 1590 646 53
H(21) 7131 1372 1494 68
H(22) 7177 609 2311 88
H(23) 5260 465 2866 82
H(24) 3348 1022 2486 70
H(26) 3500 121 1328 59
H(27) 2971 -1188 829 80
H(28) 1462 -1126 97 72
93
Table 2.16: Continued
H(29) 471 270 -104 89
H(30) 935 1519 402 67
H(31A) 407 2369 2519 141
H(31B) -633 1674 2272 141
H(31C) -134 2503 1899 141

Theoretical: All theoretical calculations were performed with the B3LYP
60,61

density functional, in combination with the Jaguar 6.5
62
computational package.
Rhenium was described with the effective core potential of Hay and Wadt
63
, while
all other atoms used the 6-31G** all electron basis set.
64
The following includes the
Cartesian coordinates (in Angstroms) and gas-phase electronic energies (in Hartrees)
for cis-O,O and trans-O,O isomers of species 1, 2 and 3.

Compound 1 – trans-O,O R=t-Bu S=CH
3
OH, N=C
6
H
4
N
Electronic Energy: -2347.50313294350
H 1.3882676385 -1.1450654190 -0.1925091806
C 1.9601820507 -1.8680241226 0.3771649273
C 3.4253624592 -3.6992899083 1.8164713244
C 1.2929742616 -2.5938710515 1.3660641263
C 3.3290294121 -1.9958251591 0.0756010642
C 4.0413030042 -2.9316074755 0.8200006743
C 2.0516542731 -3.5427127430 2.1282311962
H 5.1010033079 -3.0899402186 0.6387522649
O 1.4640098086 -4.2767369583 3.0705722035
C 4.2537471741 -4.6845240873 2.5883080142
H 3.8788537465 -5.7089571554 2.5036611630
H 5.2871704635 -4.6707186804 2.2154410403
Rh 2.3671729761 -4.8190465104 4.8481732539
N 2.4948134485 -2.9223569833 5.5365170826
C 2.9177776345 -0.3777210373 6.5352993879
94
Compound 1 – trans-O,O R=t-Bu S=CH
3
OH, N=C
6
H
4
N
C 1.5490401015 -2.3323947384 6.2955054645
C 3.6461600626 -2.2778221249 5.2524762573
C 3.8844328701 -0.9968977775 5.7496431531
C 1.7292690880 -1.0551015758 6.8075168871
H 0.6606163752 -2.9275083147 6.4726492272
H 4.8199444359 -0.4995775739 5.5143522232
H 0.9480508476 -0.6102345455 7.4138711082
H 3.0894297393 0.6194271673 6.9297568692
C 4.6310042424 -2.9604597425 4.3390442603
H 5.6340380392 -2.8914852679 4.7687139632
H 4.6316781499 -2.4246736617 3.3853193446
O 3.1697120519 -5.6750295348 6.5679107701
N 4.2881855037 -4.3965709655 4.0712036938
C 5.2792919579 -5.3188735533 4.7345056346
H 4.9117588231 -6.3311274719 4.5401270433
H 6.2430733585 -5.2010915085 4.2203090977
C 5.4460566282 -5.0540361896 6.2014428833
C 5.7962158953 -4.6543080331 8.8975471977
C 4.3456971879 -5.2764726797 7.0629730543
C 6.6782208491 -4.6023627671 6.6873672357
C 6.8815323727 -4.3761366751 8.0464401819
C 4.5428998021 -5.1007945251 8.4698345155
H 7.4825963835 -4.4448024031 5.9745580897
H 5.9443558284 -4.5051999342 9.9605713469
C 3.4205406200 -5.4205332143 9.4805047185
C 8.2075230355 -3.8524720849 8.6296508188
C -0.2147163927 -2.3878463150 1.6302439505
C 3.9681911861 -1.1150712114 -1.0142657252
Cl 0.1763779072 -5.2700884217 5.7667679112
O 2.4487309180 -6.8895591599 4.2552097860
C 1.3421232069 -7.4688437900 3.5193004061
H 1.6087293866 -8.4917077137 3.2365395410
H 0.4315978883 -7.4407979177 4.1188590027
H 1.2111674907 -6.8436462192 2.6374712999
H 2.4940467842 -7.2531533950 5.1585092799
C -0.4412003469 -1.9346327297 3.0931703055
H -0.1030585135 -2.6996785038 3.7918483495
H 0.0945535259 -0.9992710900 3.2971164103
H -1.5085505794 -1.7539699682 3.2692386679
C -0.9742978180 -3.7131745647 1.3790048517
H -2.0458435927 -3.5759211625 1.5677797332
H -0.8542129041 -4.0350191104 0.3381697816
95
Compound 1 – trans-O,O R=t-Bu S=CH
3
OH, N=C
6
H
4
N
H -0.6061905531 -4.5013759494 2.0371461787
C -0.8283668824 -1.3143116641 0.7082645735
H -0.3668761162 -0.3306720773 0.8531320189
H -0.7435647535 -1.5804162976 -0.3512958865
H -1.8950763070 -1.2118491945 0.9351087819
C 3.8024744139 0.3774854935 -0.6389143600
H 4.2451635252 1.0220670835 -1.4079398141
H 2.7490219288 0.6548263274 -0.5385660264
H 4.2967705352 0.5981376478 0.3138249050
C 3.2757805364 -1.3777851990 -2.3726285338
H 2.2046974616 -1.1577845319 -2.3312063168
H 3.7145685294 -0.7510868788 -3.1584079515
H 3.3888848383 -2.4253883132 -2.6703197486
C 5.4733573366 -1.3984074293 -1.1825757069
H 6.0304965406 -1.2004036550 -0.2599796402
H 5.6620186973 -2.4357786380 -1.4794311726
H 5.8890720108 -0.7513332249 -1.9626122140
C 2.1839343792 -4.5307357479 9.2118991741
H 2.4464350184 -3.4691419249 9.2981990356
H 1.7728026142 -4.7181203833 8.2197294682
H 1.4029901389 -4.7421013579 9.9524779279
C 3.0220786783 -6.9111622724 9.3465060592
H 3.8768043125 -7.5628595801 9.5627544954
H 2.2233986492 -7.1549615403 10.0571758192
H 2.6633663224 -7.1261935334 8.3387610618
C 3.8610720387 -5.1830328377 10.9394400902
H 3.0333251349 -5.4356011611 11.6107743620
H 4.7150766416 -5.8085128750 11.2224376325
H 4.1252438667 -4.1359106375 11.1271584174
C 8.7916009711 -4.8891151844 9.6189865804
H 9.7324296878 -4.5252528253 10.0494535320
H 8.1043138079 -5.0924972432 10.4457550486
H 8.9944483016 -5.8393599572 9.1134161105
C 9.2602574430 -3.5900740761 7.5353862031
H 9.5150179411 -4.5031918587 6.9865271278
H 8.9171867230 -2.8416335621 6.8122161368
H 10.1823970119 -3.2106609390 7.9889277824
C 7.9548704562 -2.5205301754 9.3774332690
H 7.5557949542 -1.7602399682 8.6966453237
H 7.2380451210 -2.6424796177 10.1950487017
H 8.8874224503 -2.1345735216 9.8066873364

96
Compound 1 ′ – cis-O,O R=t-Bu S=CH3OH, N=C6H4N
Electronic Energy: -2347.49778372243
H 2.8091897068 -1.2107471942 0.5650202719
C 2.1892182646 -0.9612251739 1.4176666623
C 0.5688425516 -0.2658012850 3.5288556883
C 1.1664880542 -1.8478954613 1.7639670774
C 2.4707375720 0.2369999586 2.0965799996
C 1.6132435434 0.5779488677 3.1394665149
C 0.3792360261 -1.5239073780 2.9116200186
H 1.7346021732 1.5175802011 3.6694597749
O -0.5810370519 -2.3442605972 3.3582377576
C -0.4989389892 0.2643248097 4.4474333430
H -0.2564627484 1.2927538955 4.7431359079
H -1.4443276692 0.2911944721 3.8935783460
Rh -0.9671799828 -2.5043561354 5.3697865054
N -2.9323610801 -1.9960893389 4.9321664691
C -5.4054443753 -0.9318010975 4.3130574988
C -3.8088984933 -2.7186360076 4.2219051369
C -3.2477990732 -0.7521101453 5.3502313444
C -4.4830756711 -0.1861454533 5.0465932410
C -5.0661628881 -2.2188268388 3.8972150653
H -3.4733507843 -3.7063342217 3.9269130464
H -4.7126692538 0.8211698169 5.3789239024
H -5.7566094272 -2.8263862337 3.3223212294
H -6.3745967236 -0.5097084695 4.0644088266
O 0.9700062400 -2.9225388199 5.8085577476
N -0.8209469328 -0.4893764522 5.7222754735
C 0.1754143679 -0.2400696287 6.8169179491
H 0.1749376190 0.8397992591 7.0202346681
H -0.2308140359 -0.7564220041 7.6915314089
C 1.5862826676 -0.6963897065 6.5509594028
C 4.2306386531 -1.4781194437 6.5437074380
C 1.8918357598 -2.0316596232 6.1762633142
C 2.6038424522 0.2178066032 6.8574906320
C 3.9476717474 -0.1367167670 6.8517199543
C 3.2705822957 -2.4353005527 6.2202352713
H 2.3078981859 1.2275291751 7.1284035636
H 5.2676124902 -1.7905687661 6.5677052292
C 3.6814045010 -3.9052758107 5.9770960639
C 5.0906678267 0.8309240349 7.2109500284
C 0.8471526763 -3.0765916287 0.8794100244
C 3.6679997822 1.1019186746 1.6588914473
C -2.1884981823 -0.0773552556 6.1841878701
97
Compound 1 ′ – cis-O,O R=t-Bu S=CH3OH, N=C6H4N
H -2.2862521586 1.0150179435 6.1550755067
H -2.2935612604 -0.4213734695 7.2176009831
O -1.2383909456 -4.5593240136 4.7380768468
C -0.7037661844 -5.6487880594 5.5256217692
H -1.1888880311 -5.5821893816 6.4980618087
H -0.9512292395 -6.5948291652 5.0337708000
H 0.3745741400 -5.5405441001 5.6473664088
Cl -1.6426196831 -2.9965206492 7.6553806133
H -0.7609549656 -4.4798726890 3.8932200207
C -0.6301505411 -3.0067514655 0.4183433366
H -1.3113262917 -2.9922375021 1.2711666034
H -0.8039520194 -2.1007276543 -0.1724979468
H -0.8730890673 -3.8713143918 -0.2117928750
C 1.0938987414 -4.3973751439 1.6399965388
H 2.1533906825 -4.5211281225 1.8788517507
H 0.5460465130 -4.4182619899 2.5830238071
H 0.7761573521 -5.2553683036 1.0352199936
C 1.7193839646 -3.1265162675 -0.3931225299
H 1.4281678050 -3.9926367759 -0.9976807650
H 1.5923301113 -2.2329608223 -1.0130711728
H 2.7843511882 -3.2352145928 -0.1613676222
C 3.8031678807 2.3773140971 2.5113553216
H 4.6756006790 2.9534539815 2.1841909334
H 2.9255158637 3.0264099075 2.4153655115
H 3.9391908914 2.1414330265 3.5719484729
C 3.5044496492 1.5301635177 0.1807274810
H 4.3610954276 2.1349465056 -0.1409705711
H 3.4389235819 0.6676612512 -0.4898436828
H 2.5966165261 2.1280436090 0.0438731581
C 4.9716503832 0.2808606496 1.8101190199
H 4.9550115059 -0.6208511867 1.1896853049
H 5.8425217612 0.8761622290 1.5092653217
H 5.1141704133 -0.0336793035 2.8491812251
C 3.2702025700 -4.3537724684 4.5568071564
H 2.1985019873 -4.2344630345 4.4089475923
H 3.7849273920 -3.7526209082 3.7988078859
H 3.5390993706 -5.4055974633 4.3946039627
C 3.0001241791 -4.8016121059 7.0408901192
H 3.2079897230 -5.8605543785 6.8402843319
H 3.3836891235 -4.5684139140 8.0405218410
H 1.9205480465 -4.6474668372 7.0522986091
C 5.2031223703 -4.1274959778 6.1032388040
98
Compound 1 ′ – cis-O,O R=t-Bu S=CH3OH, N=C6H4N
H 5.5752527412 -3.8743100036 7.1016225469
H 5.4269024850 -5.1862963965 5.9302056712
H 5.7700036640 -3.5481389617 5.3659587991
C 5.7924975970 0.3398177148 8.5010733638
H 6.6161031908 1.0102415630 8.7765494396
H 5.0873873010 0.3041427052 9.3384648204
H 6.2083118976 -0.6648100401 8.3754098693
C 4.5837240238 2.2645301525 7.4590962669
H 3.8928109706 2.3096399948 8.3077516843
H 5.4275395526 2.9249067415 7.6877628916
H 4.0722436527 2.6721746293 6.5799816574
C 6.1272448683 0.8819982788 6.0639109609
H 6.5492767977 -0.1055473065 5.8554756432
H 5.6723219501 1.2506773840 5.1383972163
H 6.9579596156 1.5499662084 6.3228165481

Compound 2 – trans-O,O R=Me S=CH3OH, N=CH2N(CH3)2
Electronic Energy: -1801.92856443459
H 0.9386203159 -1.8188115608 -0.6645450435
C 1.6353441341 -2.2648329705 0.0443304654
C 3.3956142238 -3.4435774250 1.8577834051
C 1.1150757549 -2.9417524312 1.1426290096
C 3.0146759389 -2.1317654120 -0.1796191506
C 3.8676032671 -2.7317443828 0.7428971961
C 1.9991447846 -3.5403739715 2.0863055954
H 4.9438808557 -2.6694321424 0.5858801514
O 1.4569518794 -4.1413603890 3.1391156694
C 4.3998911741 -4.2073160873 2.6837186340
H 4.2819231250 -5.2837059571 2.5360581146
H 5.4127721098 -3.9243631730 2.3674617555
Rh 2.4728125557 -4.6387060480 4.8422568095
N 2.2798589370 -2.6188753421 5.6352741294
C 3.6994047218 -2.1761783986 5.7721569759
C 4.5062528074 -2.5599059282 4.5364840744
H 5.5682523770 -2.3530440497 4.7105468631
H 4.1871967589 -1.9786587676 3.6687553968
O 3.1502462735 -5.2332059191 6.6928984077
99
Compound 2 – trans-O,O R=Me S=CH3OH, N=CH2N(CH3)2
N 4.3309630483 -4.0112383766 4.1822731291
C 5.3951662910 -4.8846240724 4.8006206360
H 5.1590925468 -5.8965293214 4.4599160791
H 6.3539033389 -4.5855657157 4.3561617387
C 5.5118342236 -4.8478092984 6.3007922470
C 5.9070887356 -5.0918269517 9.0448405055
C 4.3985042631 -5.1225440485 7.1335952511
C 6.7818582200 -4.6662082137 6.8672910191
C 7.0108038407 -4.7787604937 8.2365195057
C 4.6238607065 -5.2626577945 8.5339392180
H 7.6199623440 -4.4499789098 6.2054263458
H 6.0531215452 -5.2024048273 10.1188648427
C 3.4634167354 -5.6108324131 9.4321441044
H 2.6937945106 -4.8284512230 9.4323588807
H 2.9682805901 -6.5301648781 9.0989979820
H 3.7962110053 -5.7543748288 10.4644756836
C 8.3885834295 -4.5974214624 8.8310454275
H 8.3784640280 -3.8950901253 9.6733676086
H 8.7962081509 -5.5434440584 9.2101510125
H 9.0947924004 -4.2126765801 8.0885397341
C -0.3722084543 -3.0761218041 1.3523420199
H -0.6747191970 -4.1297681519 1.3819539477
H -0.6878255698 -2.6379478006 2.3072183454
H -0.9290387837 -2.5828014066 0.5501687847
C 3.5416498941 -1.3690107948 -1.3736520358
H 3.1127449403 -1.7406132822 -2.3121068131
H 3.3002977558 -0.2997046975 -1.3149982360
H 4.6298790997 -1.4554128634 -1.4522931465
O 0.4450296007 -5.1659307203 5.3864909625
C 0.2232438317 -6.3604840472 6.1744809550
H -0.8360399143 -6.4121850251 6.4450575758
H 0.5384084273 -7.2457791977 5.6203128877
H 0.8454372232 -6.2525932949 7.0614330654
H 0.1114618267 -5.2878178920 4.4802403463
Cl 2.7363230210 -6.8641738841 3.9773732541
H 4.1136637314 -2.6579615750 6.6569462765
H 3.7414897143 -1.0872601485 5.9221885416
C 1.5196469750 -1.7053403495 4.7472515641
H 1.4380202872 -0.7176455917 5.2211621070
H 2.0092427165 -1.6062516331 3.7802619499
H 0.5256572040 -2.1186490647 4.5807532399
C 1.6180511425 -2.6458344283 6.9628260182
100
Compound 2 – trans-O,O R=Me S=CH3OH, N=CH2N(CH3)2
H 0.5754370379 -2.9347096718 6.8228575359
H 2.1109753601 -3.3905217231 7.5845938108
H

1.6633087132 -1.6535634688 7.4316545881

Compound 2 ′ – cis-O,O R=Me S=CH
3
OH, N=CH
2
N(CH
3
)
2

Electronic Energy: -1801.92416317448
H 3.1005709538 -1.2846638064 0.8657245647
C 2.4162721575 -0.9527691439 1.6458074090
C 0.6538653114 -0.1069345165 3.6086814684
C 1.3140059295 -1.7534489909 1.9422265963
C 2.6858496418 0.2492666177 2.3179139370
C 1.7826979590 0.6561955806 3.2987950153
C 0.4125808048 -1.3301481851 2.9510885001
H 1.9575772514 1.5863171358 3.8364227373
O -0.6817941715 -2.0543426648 3.2302292846
C -0.4036291001 0.4350706639 4.5271871281
H -0.0689692807 1.3766862301 4.9782993812
H -1.2916255817 0.6569562302 3.9300087060
Rh -1.0339365469 -2.4668211319 5.1974390879
N -3.1839641596 -2.0503857383 4.8363442186
C -3.2752418947 -0.5690683948 5.0064063264
O 0.9248329503 -2.8457761696 5.4820629618
N -0.8754700142 -0.4536866268 5.6640002211
C 0.0386101053 -0.3245045148 6.8534980085
H 0.0169658850 0.7265670130 7.1737131450
H -0.4107878603 -0.9355365056 7.6402243172
C 1.4647518260 -0.7400896731 6.5975120712
C 4.1465175013 -1.4437485026 6.3427455905
C 1.7973807892 -1.9708033961 5.9803141106
C 2.4837407395 0.1054043814 7.0603760457
C 3.8324555040 -0.2217879404 6.9557801645
C 3.1749524013 -2.3088875941 5.8534709798
H 2.2029962428 1.0501469605 7.5255037296
H 5.1926303947 -1.7266889382 6.2311714311
C 3.5482984442 -3.6008712645 5.1736205827
H 3.1232162325 -4.4658407111 5.6967553479
H 3.1608933551 -3.6295979471 4.1483100438
H 4.6349149266 -3.7250992765 5.1351894064
C 4.9169063452 0.6843575000 7.4910991482
101
Compound 2 ′ – cis-O,O R=Me S=CH
3
OH, N=CH
2
N(CH
3
)
2

H 5.3025049223 0.3345054739 8.4581953420
H 5.7717539608 0.7344506863 6.8072125539
H 4.5496778957 1.7052165825 7.6388776293
C 1.0653821640 -3.0418374803 1.1987630178
H 0.0325323147 -3.1070850847 0.8411069872
H 1.7346697650 -3.1326154136 0.3379948332
H 1.2337063548 -3.9104772231 1.8459659609
C 3.9158430265 1.0622973642 1.9861405115
H 4.8363339523 0.5125713841 2.2186007044
H 3.9563788525 1.3179228022 0.9203217556
H 3.9407319690 1.9977466403 2.5532024020
C -2.2738237916 -0.0686666715 6.0458553534
H -2.3446259598 1.0232954131 6.1477587518
H -2.4765481654 -0.5183494159 7.0202896921
O -1.2984984454 -4.6019805775 4.8428514777
C -0.2539467347 -5.2978040408 4.1264742384
H 0.7251859211 -4.9907055642 4.4984928961
H -0.4033359661 -6.3764908092 4.2375379259
H -0.3584935374 -5.0124388533 3.0812195207
Cl -1.4454498846 -3.2773670161 7.5015979177
H -1.2577658747 -4.8384041205 5.7918774374
H -3.0802806329 -0.1124335485 4.0343892698
H -4.2929593061 -0.2793029056 5.3018473870
C -4.0964515586 -2.7314084821 5.7876857482
H -5.1392393176 -2.4888835374 5.5379884925
H -3.9456247507 -3.8087144334 5.7166520086
H -3.8740384521 -2.4312783131 6.8094131521
C -3.5659239215 -2.4384427285 3.4555630180
H -4.5831687260 -2.0923032657 3.2253921483
H -2.8422450468 -2.0210398131 2.7565690642
H -3.5317797655 -3.5270038652 3.3829262974

Compound 3 – cis-O,O R=Me S=CH
3
OH, N=C
6
H
4
N
Electronic Energy: -1875.73808553718
H 3.2860966340 -1.6854986324 1.0798840404
C 2.5380092764 -1.2897579222 1.7656348864
C 0.6242686318 -0.2908007099 3.5137494396
C 1.4652145494 -2.1060116923 2.1185008261
C 2.6991167656 0.0091576994 2.2706684025
C 1.7258879678 0.4881473749 3.1468133713
C 0.4889069889 -1.6026137993 3.0115096778
H 1.8240968921 1.4912678096 3.5582121141
102
Compound 3 – cis-O,O R=Me S=CH
3
OH, N=C
6
H
4
N
O -0.5669638410 -2.3598458056 3.3389816364
C -0.4928219148 0.3011445414 4.3279944505
H -0.2564309537 1.3389580015 4.5947988934
H -1.4061246122 0.3094695529 3.7222822851
Rh -1.0927750945 -2.4362139101 5.3123251769
N -3.0200100276 -1.8704891280 4.7862474942
C -5.4410212895 -0.7509655210 4.0650916739
C -3.8985500889 -2.5868139097 4.0722579796
C -3.3080983534 -0.6050353712 5.1580524244
C -4.5161180032 -0.0112341399 4.8015617032
C -5.1304445837 -2.0598506514 3.6972614021
H -3.5855098432 -3.5927458095 3.8156074001
H -4.7242524425 1.0115948390 5.0986261685
H -5.8237272508 -2.6641223446 3.1225554102
H -6.3899550842 -0.3080447463 3.7781440069
O 0.8098362603 -2.9039564308 5.7910379568
N -0.8878032589 -0.4061785119 5.6140392512
C 0.0758773573 -0.1604239178 6.7440542199
H 0.1063776663 0.9232622631 6.9237030774
H -0.3806157242 -0.6450807949 7.6122867766
C 1.4747586499 -0.6733293736 6.5232382600
C 4.1144771853 -1.5458833358 6.3715902328
C 1.7365177102 -2.0043284298 6.1144173807
C 2.5403984594 0.1824727235 6.8379553848
C 3.8693544140 -0.2249179132 6.7775266578
C 3.0941688363 -2.4281724276 6.0358544139
H 2.3135096472 1.2013647172 7.1505764252
H 5.1434939210 -1.8978106197 6.3061266104
C 3.3889371413 -3.8355114762 5.5847272804
C 5.0067762564 0.7112946217 7.1154996804
C 1.3190443961 -3.5025414982 1.5687267045
C 3.8810633336 0.8575501147 1.8617892719
C -2.2571083110 0.0612795062 6.0102320000
H -2.3207735763 1.1548432312 5.9482115436
H -2.4114315382 -0.2506375017 7.0476487480
O -1.3107750429 -4.4942084478 4.6891944939
C -0.7106258153 -5.5156560507 5.5229399088
H -1.3244522547 -5.5713206753 6.4203392398
H -0.7304630420 -6.4678457869 4.9839424330
H 0.3059803155 -5.2256397388 5.7925735599
Cl -1.8770205769 -2.8351345640 7.5837270693
H -0.7694592252 -4.3444300294 3.8886030787
103
Compound 3 – cis-O,O R=Me S=CH
3
OH, N=C
6
H
4
N
H 2.1364987673 -3.7435078662 0.8829508469
H 0.3732297867 -3.6273123619 1.0281268154
H 1.3259140386 -4.2484662878 2.3741415485
H 4.0048682385 1.7166336295 2.5280078498
H 4.8138646642 0.2830354555 1.8839531892
H 3.7687610926 1.2466920670 0.8413928421
H 5.6064651767 0.9610634712 6.2305883552
H 5.6920294418 0.2686548169 7.8486970351
H 4.6375017504 1.6520497212 7.5362446751
H 2.9549350054 -4.0278141439 4.5964067575
H 4.4672232472 -4.0136249365 5.5294349152
H 2.9545815919 -4.5757527602 6.2678500896

Compound 3 ′ – trans-O,O R=Me S=CH3OH, N=C6H4N
Electronic Energy: -1875.73568430996
H 1.2787389916 -1.0863905510 -0.2372112570
C 1.8985305321 -1.7750306164 0.3362593629
C 3.4645014748 -3.5302898118 1.8177849137
C 1.3128826431 -2.4643133566 1.3928682196
C 3.2535158662 -1.9176207890 -0.0096077935
C 4.0144438056 -2.7991315903 0.7526648099
C 2.1001415223 -3.3689114905 2.1653700771
H 5.0694475870 -2.9353069368 0.5154242133
O 1.4970138752 -4.0248477410 3.1482310352
C 4.3384372578 -4.4869734405 2.5787681164
H 4.0176784266 -5.5275131950 2.4675810884
H 5.3706781981 -4.4135988771 2.2088966508
Rh 2.4320730671 -4.7297713783 4.8387516886
N 2.5972610374 -2.9120860472 5.7127601735
C 3.1223492729 -0.5293253349 7.0172678779
C 1.7052779323 -2.4190594520 6.5949305981
C 3.7432853394 -2.2461955686 5.4525697467
C 4.0335214633 -1.0475850950 6.1022512739
C 1.9372519799 -1.2230044258 7.2612367843
H 0.8186872212 -3.0260436682 6.7414467376
H 4.9648011826 -0.5348199703 5.8848552723
H 1.1994389184 -0.8546596925 7.9654680438
H 3.3348011011 0.4022357475 7.5333610892
C 4.6367993430 -2.8034484271 4.3772515039
H 5.6874764483 -2.6732139422 4.6545433679
H 4.4546007630 -2.2294142403 3.4625681235
104
Compound 3 ′ – trans-O,O R=Me S=CH3OH, N=C6H4N
O 3.2445359358 -5.7200978337 6.4659646175
N 4.3537276457 -4.2414058747 4.0684347796
C 5.3835762152 -5.1414167079 4.7040433330
H 5.0763454684 -6.1607668361 4.4485961997
H 6.3485033859 -4.9426178713 4.2175266772
C 5.5033630776 -4.9619563416 6.1879819601
C 5.7190426012 -4.7196482253 8.9418926255
C 4.3899721326 -5.2896559022 6.9950477054
C 6.6940011499 -4.5076873653 6.7674304418
C 6.8275396362 -4.3775863845 8.1495728254
C 4.5128534048 -5.1670228509 8.4051337916
H 7.5382053984 -4.2649449919 6.1226488909
H 5.7980951651 -4.6224982348 10.0242217281
C 3.3369656856 -5.5238301386 9.2768676258
C 8.1156037532 -3.8979233503 8.7795839888
C -0.1395353238 -2.2852306577 1.7520422804
C 3.8538927877 -1.1285539779 -1.1506280823
Cl 0.2581394690 -5.2361127245 5.7653237632
O 2.4981865011 -6.7353744222 4.0708485990
C 1.3588640621 -7.2484366399 3.3347484878
H 1.6194147754 -8.2315968850 2.9312692274
H 0.4813831871 -7.2959164482 3.9804383066
H 1.1747658229 -6.5343220642 2.5337444040
H 2.5778766977 -7.1725585903 4.9389796945
H 4.9028504798 -1.3965492863 -1.3121107247
H 3.8155709764 -0.0475717240 -0.9634936119
H 3.3198796801 -1.3062050548 -2.0918961559
H -0.6110686803 -1.5235351050 1.1235343640
H -0.6963612668 -3.2224280012 1.6388681522
H -0.2514963881 -1.9962128827 2.8028993071
H 8.6316742295 -4.7047786713 9.3153934344
H 8.8091614275 -3.5114710618 8.0260665457
H 7.9363839475 -3.0974691838 9.5072843978
H 3.5125620858 -5.2319954342 10.3167202332
H 3.1383084184 -6.6021054792 9.2545077148
H 2.4224607891 -5.0417027343 8.9175140286

105
2.5 Chapter 2 References

50
(a) Wong-Foy, A. G; Bhalla, G; Liu, X. Y.; Periana, R. A. J. Am. Chem. Soc.
2003, 125, 14292. (b) Periana, R. A.; Liu, X. Y.; Bhalla, G. Chem. Commun.
2002, 3000.
51 Liu, X.Y.; Tenn III, W. J.; Bhalla, G.; Periana, R.A. Organometallics 2004,
23, 3584.
52 (a) Slugovc, C.; Padilla-Matinez, I.; Sirol, S.; Carmona, E.; Coord. Chem.
Rev. 2001, 213, 129. (b) Buchanan, J. M.; Stryker; J. M.; Bergman R. G. J.
Am. Chem. Soc. 1986, 108, 1537.
53 (a) Periana, R. A.; Bergman, R. Organometallics 1984, 3, 508. (b) Jones W.
D., Acc. Chem. Res., 2003, 36, 140. (c) Chin, R. D.; Dong, L.; Duckett, S. B.;
Jones, W. D., Organometallics 1992, 11, 871.
54 (a) Tshuva, E. Y.; Goldberg, I., Kol, M. Inorg. Chem. 2001, 40, 4263. (b)
Groysman, S.; Goldberg, I.; Kol, M.; Genizi, E.; Goldschmidt, Z.
Organometallics 2004, 23. 1880. (c) Groysman, S.; Goldberg, I.; Kol, M.;
Goldschmidt, Z. Organometallics 2003, 22. 3793. (d) Tshuva, E. Y.;
Groysman, S.; Goldberg, I.; Kol, M.; Goldschmidt, Z. Organometallics
2002, 21. 662. (e) Tshuva, E. Y.; Groysman, S.; Goldberg, I.; Kol, M.;
Goldschmidt, Z. Organometallics 2001, 20. 3017. (f) Tshuva, E. Y.;
Groysman, S.; Goldberg, I.; Kol, M.; Weitman, H.; Goldschmidt, Z. Chem.
Commun. 2000, 379.
55 (a) Collman, J. P.; Hegedus, J. R.; Norton, J. R.; Finke, R. G. Principles and
Applications of Organotransition Metal Chemistry, University Science
Books, Mill Valley, CA, 1987. (b) Brintzinger, H. H.; Fischer, D.; Mulhaupt,
R.; Rieger, B.; Waymouth, R. M. Angew. Chem. Int. Ed. 1995, 34, 1143.
56 Toupance, T.; Dubberley, S. R.; Rees, N. H.; Tyrrell B. R.; Mountford, P.
Organometallics 2002, 21, 1367.
57 Jaguar, version 6.5, Schrodinger, LLC, New York, NY, 2005.
58 Tshuva, E.Y.; Goldberg , I.; Kol, M. Organometalllics 2001, 20, 3017.
59 Toupance, T.; Dubberley, S. R.; Rees, N. H.; Tryyell, B. R.; Mountford, P.
Organometalllics 2002, 21, 1367.
60 Becke, A. D. J. Chem. Phys. 1993, 98, 5648.
61 Lee, C.; Yang, W.; Parr, R. G., Phys. Rev. B. 1988, 37, 785.
106

62 Jaguar 6.0. Schrodinger, LLC: Portland, Oregon, 2005.
63 Hay, P. J.; Wadt, W. R., J. Chem. Phys. 1985, 82, 299.
64 Harihara, P. C.; Pople, J. A., Theo. Chim. Acta. 1973, 28, 213.

107
Chapter 3: Mechanistic Insights Into Benzene C-H
Activation With Cyclometallated
Ir(NNC)(R)(TFA)(CH
3
CN) Complexes

3.1 Introduction

The CH activation reaction has been of interest for the selective
functionalization of CH bonds.
65
Several systems have been shown to convert
methane into functionalized products. However, all of these systems rely on
electrophilic metals, such as Pt(II), Pd(II), Hg(II), and Au(I)/Au(III), and all of these
operate in strongly acidic media, sulfuric acid.
66
The most well known of these
systems is the Catalytica system, Pt(bipyrimidine)Cl
2
, developed by Periana et al.
which converts methane to methylbisulfate in a 72% one-pass yield at 90%
selectivity.
2a
Fortuitously, the functionalized product, methanol, is protected in the
form of methylbisulfate by the sulfuric acid. It is believed that formation of
methylbisulfate prevents the methanol from being over oxidized to CO
2
. However,
the separation of the product, methanol, from the sulfuric acid is expensive at the
concentrations the catalyst generates, ~1M. The water produced in the
functionalization step also inhibits the electrophilic Pt(II) center.
67
Therefore, our
research efforts have been directed towards developing more electron rich CH
activation catalysts that are thermally stable to protic and oxidizing media. Key
challenges to designing these new catalysts are: A) thermal stability to the protic,
oxidizing conditions likely required and B) identification of new, compatible,
functionalization reactions.

108

CH Activation
RH
Functionalization
HOZ
M
n
-OZ
M
n
-R
M
n-2
R-OH
M
n
-R
O
M
n+2
-R
OZ
OZ
M
n
-OR
R-OH
R-OH
R-OH
Ox
Ox
Ox
Ox
A
B
C
D
HOZ
HOZ
HOZ
HOZ

Figure 3.1. Possible catalytic schemes for hydrocarbon hydroxylation.

Ir complexes are among the most active alkane CH activation catalysts, and
show the desired reduced sensitivity to methanol inhibition compared to
isoelectronic Pt complexes. However, most of the reported systems are not expected
to be stable under oxidizing protic conditions likely required for functionalization.
Additionally, given the lower oxidation potentials of Ir relative to the isoelectronic
(bpym)Pt(II)/(IV) system, Figure 3.1-b we considered that an Ir(I)/(III) cycle, Figure
3.1 may not be feasible. Therefore, along with designing more stable Ir complexes,
we are examining two plausible catalytic cycles that involve CH activation with
Ir(III) followed by oxidation to Ir(V)-R and reductive functionalization, (Figure 3.1-
B,D), or O-atom insertion and hydrolysis, (Figure 3.1-C).
Recently, we reported an example of efficient alkyl functionalization from an
Ir(III)-methyl species. When (NN)(NC)Ir(III)(Me)OTf complex was treated with

109
PhI(OAc)
2
or PhI(TFA)
2
, methyl acetate (MeOAc) and methyl trifluoroacetate
(MeTFA) were formed respectively. We proposed that this reaction could involve
reductive functionalization via an Ir(V)-Me intermediate. Unfortunately this Ir(III)
motif, although stable to oxidizing conditions and active for arene CH activation was
not active for alkane CH activation. Therefore we decided to make more electron
rich iridium complex. Given the success use of pincer ligands and complexes for
organic transformations,
68,70
we decided to explore pincer motifs.Recently we
reported that the pincer (NNC)Pt(TFA) complex (NNC = κ
3
6–phenyl-4, 4′–di-tert–
butyl,-2, 2 ′-bipyridine) was sufficiently thermally and protic stable to catalyze CH
activation of benzene but not alkanes in DTFA. Since this pincer motif formed stable
and competent catalysts for CH activation with Pt we envisioned that by replacing
platinum with the more electropositive metal such as iridium that this could lead to
more active CH activation catalysts that would be less inhibited by water. Using
density functional theory (DFT), we identified the (NNC)Ir(III) analogue as a
potential efficient catalyst for methane hydroxylation via a catalytic sequence
involving CH activation, oxidation to Ir(V)-CH
3
, followed by reductive
functionalization (Figure 3.1). Previous to our investigation of this ligand motif only
the related Pd, Pt, Rh, and Ru NNC complexes were known. However recently our
group reported the first example of a NNCIr(III) complex, (NNC)IrEt(X)(C
2
H
4
) (X=
Cl or TFA), where (NNC) = 6-phenyl-4,4’-di-tert-butyl-2,2’-bipyridine and TFA =
trifluoroacetate.These new complexes are active catalyst for the H/D exchange
reaction between hydrocarbons (alkanes and benzene) and trifluoroacetic acid
69
or

110
toluene-d
8
.Rate of benzene activation were faster than methane activation. Herein we
report, a systematic study on (NNC)Ir complexes to elucidate the mechanism for
arene CH activation inorder to better understand the reactivity and selectivity of this
complex and design more reactive catalysts. We present a detailed experimental
study to answer the following questions:
(1) How stable is the catalyst?
(2) Is the mechanism ion-pair based or not?
(3) What are the reaction orders of the substrates?
(4) Which one is the labile ligand: TFA or NCCH
3
?
(5) Consistency between experimental and DFT calculations?

3.2 Results and Discussion
3.2.1 Synthesis of active catalyst
It is now well established that the tridentate pincer ligand motif can impart both
thermal stability and reactivity to transition metal complexes.
70
This has been
demonstrated with the thermally stable PCP-Ir systems of Kaska, Jensen and
Goldman
71
that catalyzes the thermal dehydrogenation of alkanes. The tridentate
ligand 6-phenyl-2, 2’-bipyridine (NNC-H) and its derivatives have been shown to
readily form stable, cyclometalated complexes with platinum, Pt(NNC)X
72
and only
recently our group demonstrated it on Iridium.
69
However besides our investigation
of these complexes for CH activation, there are no other examples of catalysis with
the platinum or iridium complexes with this ligand motif. The cyclometalated NNC

111
Iridium (III) chloride complex, trans(Cl,Et)-(NNC)IrCl(C
2
H
4
)Et complex (Ethylene-
Ir-Cl ) and NNC is 6-phenyl-4, 4’-di-tert-butyl,-2,2’-bipyridine, was prepared by
treatment of 6-phenyl-4, 4’-di-tert-butyl,-2,2’-bipyridine with [Ir(C
2
H
4
)
2
Cl]
2
under
an ethylene atmosphere and isolated in ~66% yield as an air stable solid. Ethylene-
Ir-Cl, is stable upon dissolution in DTFA (deuterated trifluroacetic acid) and upon
heating to 140
o
C for 2h, deuterium incorporation into the ligand is observed but the
NNC ligand remains cyclometalated to the Ir center. Ethylene-Ir-Cl also catalyses
H/D exchange between methane and DTFA with a TOF ~ 5 x 10
-4
s
-1
(180
o
C). This
result is significant because under similar conditions the other protic, thermally
stable complexes studied, (NNC)Pt(II) and Pt(bpym)Cl
2
73
showed no H/D exchange.
Ethylene-Ir-Cl is significantly more active towards aromatic CH bonds and
catalyzes H/D exchange between benzene/ toluene-d
8
and benzene/DTFA.
acetonitrile
110
o
C, 2h
AgTFA (1.05 eq)
48h, rt. CH
2
Cl
2
Ir
N
NCCH
3
N
TFA
Ir
N
NCCH
3
N
Cl
Ir
N
N
Cl
Ethylene-Ir-Cl
(1)
Acetonitrile-Ir-Cl
Ethyl-Ir-TFA
(2) (3)

Figure 3.2. Synthesis of Ethyl-Ir-TFA complex

Since it’s less complicated (no solubility, mass-transfer issues) to perform
dependence studies when we have the potentially labile ligand as a liquid
(acetonitrile, pyridine) than a gas (ethylene). We treated Ethylene-Ir-Cl with
acetonitrile and it lead to the replacement of ethylene with acetonitrile and formation

112
of Acetonitrile-Ir-Cl in quantitative yields. In quest to create potentially active
catalyst, the chloride was replaced by a more labile leaving group using silver
trifluoroacetate to obtain the corresponding trifluoroacetate complex (3), Ethyl-Ir-
TFA in good yields (Figure 3.2). Complex 3 is air stable and was fully characterized
by
1
H,
13
C NMR, X-ray as well as mass spectroscopy and elemental analysis. An
ORTEP diagram of this complex is shown in (Figure 3.3) and we observe that the
ethyl group is trans to TFA and acetonitrile is trans to the central pyridine of the
NNC ligand.

Figure 3.3. ORTEP diagram of Ethyl-Ir-TFA, showing ellipsoids at the 50%
probability level.
Selected bond distances ( Ǻ): Ir(1)-N(2), 1.962(8); Ir(1)-N(3),
1.984(10); Ir(1)-C(1), 2.004(12); Ir(1)-C(27), 2.083(11); Ir(1)-N(1),
2.086(11); Ir(1)-O(2), 2.239(8).

In order to understand the mechanism by which these complexes operate we
decided to investigate the H/D exchange mechanism between C
6
H
6
and toluene-d
8
.

113
Since the active catalyst involved in this exchange would be the phenyl species, we
synthesized the phenyl analogue of 3 by heating Ethyl-Ir-TFA with benzene
yielding the stoichometric CH activation product 4, Phenyl-Ir-TFA in about ~95%
yield and 4 was characterized by
1
H,
13
C NMR, elemental analysis. Phenyl-Ir-TFA
was found to be stable to air, protic solvents, silica and alumina and soluble in most
common organic solvents.

Ethyl-Ir-TFA
Phenyl-Ir-TFA
160C,20 min
C
6
H
6 Ir
N
NCCH
3
N
TFA
Ir
N
NCCH
3
N
TFA
3
4

Figure 3.4. Synthesis of Phenyl-Ir-TFA by stoichometric CH activation.

3.2.2 Catalyst stability

Figure 3.5 is a plot of turnover number (TON) versus time for H/D exchange
reaction between C
6
H
6
and toluene-d
8
with catalyst Phenyl-Ir-TFA. The linear
relationship between TON and time shows that the catalyst is active and thermally
stable at 170
o
C over extended periods with a turnover frequency (TOF) of 5.3 x 10
-3
s
-1
. Heating in neat benzene for 12h at 150
o
C we recover Phenyl-Ir-TFA back in >
95% yield . The activation parameters, ΔH
‡
= 29.0 (± 2.8) kcal/mol, ΔG
‡
(T=298K) =
27.7 ± 2.9 kcal/mol was derived from a linear regression analysis of the Eyring plot

114
using rate data obtained from 415 K to 447 K . When Ethyl-Ir-TFA, 3 was used as
the catalyst, activation parameter ( ΔH
‡
= 25.7 (± 4.8) kcal/mol) was obtained
experimentally which is in agreement with the value obtained with Phenyl-Ir-TFA
as 3 gets converted to 4 under reaction conditions.

d
8
+
+
d
8-n
d
n
0.1ml
1.0ml
7mg (8mM)
Ir
N
NCCH
3 N
TFA
R
2
= 0.9992
0
20
40
60
80
100
120
0 50 100 150 200 250 300
time(min)
TON

Figure 3.5. Plot of C
6
H
6
/Tol-d
8
H/D exchange with Phenyl-Ir-TFA as catalyst.

3.2.3 Mechanism of H/D exchange
CH activation with Phenyl-Ir-TFA is expected to go through ligand
substitution pathway followed by cleavage of the C-H bond to form the phenyl(or
hydrocarbyl) intermediate.Benzene coordination can occur through either an

115
associative substitution mechanism (benzene coordination to form an intermediate
with increased coordination number follwed by labile ligand dissociation) or an
dissociative mechanism (dissociation of the ligand to form a 5-coordinated Ir(III)
followed by benzene coordination). If benzene binding is occurring through an
dissociative mechanism (more likely since Phenyl-Ir-TFA is a 18 electron
octahedral species) then there are two ligands, acetonitrile or TFA that can
potentially dissociate to generate the active catalyst. The plausible pathway for the
arene CH activation via dissociative mechanism may involve (a) Initial dissociative
loss of acetontrile from Phenyl-Ir-TFA to generate an unsaturated 5 Coordinate
complex, which then can bind benzene in a η
2
fashion followed by slippage to an
agnostic CH interaction followed by cleavage of the arene C-H bond as shown in
Figure 3.6 (Oxidative Hydrogen migration mechanism shown).

116

Cat-L
Cat
Ir
N
NCCH
3
N
TFA

D
7
H

NNCIr
TFA
D
D
7
NNCIr
TFA

NNCIr
TFA

D
8

NNCIr
TFA
H
D
7

NNCIr
TFA
D
7
NNCIr
TFA
D
7
D
8
C-H ACTIVATION
Ir(NNC) =
Ir
N
N
- NCCH
3
D

Figure 3.6. Proposed mechanism for CH activation with a dissociative loss of
acetonitrile

(b) An ion-pair mechanism where TFA dissociates to form a tight ion-pair
with cationic Ir species.Since the reaction is carried in non-polar solvent mixture of
benzene and toluene this five coordinated Ir(III) complex then binds benzene and
undergoes CH activation .In the extreme case TFA could be completely dissociated

117
in which case the mechanism would be similar to the one with acetonitrile loss ie
mechanism (a).
Ir
N
NCCH
3
N
TFA

D
7
H

NNCIr
NCCH
3
D
D
7
NNCIr
NCCH
3

NNCIr
NCCH
3

D
8

NNCIr
H
D
7

NNCIr
NCCH
3
D
7
NNCIr
NCCH
3
D
7
D
8
ION-PAIR MECHANISM
Ir(NNC) =
Ir
N
N
TFA
D
NCCH
3
TFA
TFA
TFA
TFA
TFA

Figure 3.7. Ion-pair mechanism where TFA labilizes and forms a tight ion-pair

3.2.4 Reaction order of substrates
Based on the proposed mechanism(s) and the above results, we can formulate
a suggested rate law using the usual steady state approximation and the assumption
that the pre-equilibrium term involving L is small. As can be seen in this rate law,
under conditions where L = L
0
(at small K and L
0
= ML
0
) it is predicted that the

118
reaction rate will be inversely dependent on added L
0
(Acetontrile or TFA) with a
first order dependence on benzene. In the presence of excess L (Acetontrile or TFA),
there should also be a first order dependence on catalyst concentration. The results of
the kinetic investigation of the components of the proposed rate law are shown in
Scheme 3.1 below.
Scheme 3.1. Proposed rate law

3.2.4.1 Kinetic dependence on benzene concentration

The rate law indicates a linear dependence on arene concentration. The
reaction order on benzene was determined using toluene-d
8
as the other solvent with
Phenyl-Ir-TFA as the catalyst. Figure 3.8 shows a linear relationship between
benzene concentration and TOF, which is expected for a first-order dependence on
benzene.

119
R
2
= 0.9916
0.000E+00
2.500E-03
5.000E-03
7.500E-03
1.000E-02
1.250E-02
01 2 3 45 6
Benzene conc(M)
TOF(10% conv)

Figure 3.8. Benzene concentration dependence

3.2.4.2 Kinetic dependence on catalyst concentration

As the concentration of free L during catalysis could not be easily determined,
we carried out reactions in the presence excess L (L
0
= 5 equivalents of added
catalyst) as this allows for the assumption that the concentration of L (NCCH
3
and
TFA) under experimental conditions would be equal to L
0
, given the small value of
K. Under these conditions, approximations to the rate law predict that the rate should
be first-order dependant on catalyst concentration. Figure 3.9 shows a plot of catalyst
concentration versus rate of H/D exchange which is consistent with the above
prediction.

120
R
2
= 0.9356
0.0
2.0
4.0
6.0
8.0
10.0
12.0
0 5 10 15 20 25
Cat conc(mM)
TON(rate of H/D exchange)

Figure 3.9. Dependence on catalyst concentration with excess L(TFA)

3.2.4.3 Kinetic dependence on trifluroacetate (TFA) concentration

The rate law indicates an inverse dependence on TFA concentration. The
reaction order on TFA was determined by varying the amount of added cesium
trifluroacetate (1 eq-100 eq) with Phenyl-Ir-TFA as the catalyst. Plotting TOF vs.
[1/TFA] yields a straight line with a linear correlation (R
2
= 0.99), at constant
catalyst ([M-L]) and the maximum decrease in TOF is observed between 1-10 eq of
TFA.

121

1/TFA Plot
y = 0.0007x
R
2
= 0.9931
0.0E+00
1.0E-04
2.0E-04
3.0E-04
4.0E-04
5.0E-04
6.0E-04
7.0E-04
8.0E-04
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
1/TFA eq
TO F

Figure 3.10. Dependence of rate on [TFA].

3.2.5 Kinetic Dependence on acetonitrile (NCCH
3
) concentration

Based on the fact that we observe inverse dependence on rate with increasing
concentration of TFA it would be interesting to observe effect of acetonitrile on the
rate of H/D exchange. The reaction order on acetonitrile was determined by varying
the amount of added acetonitrile (1 eq-100 eq) with Phenyl-Ir-TFA as the catalyst.
Plotting TOF vs. [1/NCCH
3
] yields a straight line with a linear correlation (R
2
=
0.99).

122
R
2
= 0.9975
0.00E+00
2.00E-04
4.00E-04
6.00E-04
8.00E-04
0 0.02 0.04 0.06 0.08 0.1
1/[NCCH3]
TOF

Figure 3.11. Dependence of rate of H/D exchange of [NCCH
3
]

3.2.6 Evidence for ion-pair mechanism
Since we observe similar decrease in rate of H/D exchange with increasing
[TFA] and [NCCH
3
] suggesting that kinetic dependence studies for labile liagnd is
inconclusive but suggest a TFA loss mechanism. Since in an ion-pair mechanism
involving TFA loss we will observe an inverse dependence on acetonitrile due to
formation of diacetonitrile complex(discussed later).

123

Figure 3.12. Addition of excess chloride salt to Phenyl-Ir-TFA.

We decided to investigate the treatment of Phenyl-Ir-TFA with ion
exchange salt like tetrabutylammonium chloride with the assumption that if TFA is
the labile ligand it should result in its exchange with chloride. Addition of chloride
salt to Phenyl-Ir-TFA resulted in formation of Phenyl-Ir-Cl at room temperature
which was further confirmed by spiking the reaction mixture with separately
synthesized Phenyl-Ir-Cl. Figure 3.13 depicts the aromatic region of Phenyl-Ir-
TFA and Phenyl-Ir-Cl in CDCl
3
when 0.4 eq of chloride salt is added and we
observed upfield shifting of the ortho hydrogen peak of the terminal pyridine ring of
the NNC ligand in Phenyl-Ir-TFA from 8.99 ppm to 8.84 ppm which is where it
appears in B, Phenyl-Ir-Cl. Similar result was obtained on treatment of Ethyl-Ir-
TFA with tetrabutylammonium salt yielding Ethyl-Ir-Acetonitrile.

124
8.976
8.848
7.890
7.840
7.709
7.260
7.121
6.989
6.647
9.0 8.5 8.0 7.5 7.0 6.5 PPM
A
A + B
8.976
8.848
7.890
7.840
7.709
7.260
7.121
6.989
6.647
9.0 8.5 8.0 7.5 7.0 6.5 PPM
A
A + B

Figure 3.13. NMR showing treatment of Phenyl-Ir-TFA with tetrabutyl
ammonium chloride.

Stoichometric CH activation of Ethyl-Ir-TFA with benzene which results in
formation of Phenyl-Ir-TFA is highly depended on dielectric of the medium. For e.g
when THF is added as the diluent, multiple reaction pathways appear to operate and
the CH activation product couldn’t be isolated. Also reaction shows temperature
dependence, above 165
o
C we speculate that the pathways may be competing and
interfering with the operating mechanism and inturn reducing the yield from >95%
to less than 70%.

125

Figure 3.14. Phenyl-Ir-TFA in presence of excess acetonitrile

Next we decided to investigate the nature of the system when Phenyl-Ir-
TFA is in solution with excess acetonitrile. We followed the reaction by low
temperature VT-
1
H NMR in the temperature ranging from 233 K to 308 K and it
resulted in formation of a new species 6 in equilibrium with 4, Phenyl-Ir-TFA
which we assign as containing two acetonitrile molecules bound to Ir and TFA
forming an ion-pair with the cationic Ir species.

126
0.99
1.01
0.22
1.00
0.25
0.17
1.00
1.01
0.18
1.02
0.17
1.00
0.98
0.17
1.00
0.41
1.00
1.04
0.44
1.08
0.62
1.00
1.04
0.64
25 C
-10 C
-25 C
-40 C
35 C
5 C
0.28
1.00
0.99
1.02
0.29
0.99
1.01
0.22
1.00
0.25
0.17
1.00
1.01
0.18
1.02
0.17
1.00
0.98
0.17
1.00
0.41
1.00
1.04
0.44
1.08
0.62
1.00
1.04
0.64
25 C
-10 C
-25 C
-40 C
35 C
5 C
0.28
1.00
0.99
1.02
0.29

Figure 3.15. VT-NMR showing formation of new acetonitrile species.

In the region where the ortho-hydrogen on the terminal pyridine appears
shows two sets of peaks, whose ratio changes on varying temperature as can be seen
in Figure 3.15. The more downfielded shift is for 4, Phenyl-Ir-TFA and we can infer
that its equilibrium concentration increase from 1:6 (0.17:1) at 233K to about 1:1.6
(0.62:1) at 308K. These results suggest that species 6 is more thermodynamically
favored or it is more stable than 4, Phenyl-Ir-TFA. This is supported by DFT
calculations which predict the diacetonitrile species, 6 to be ~0.8 kcal/mol downhill
from 4, Phenyl-Ir-TFA and in presence of excess acetonitrile the equilibrium is
driven towards species 6 and it becomes the resting state of the catalyst. The DFT

127
also predicts an activation barrier of ~35 kcal/mol, via an ion-pair mechanism as
shown in Figure 3.16 , which corresponds to the barrier for abstraction of proton
from benzene coordinated Iridium complex by TFA, suggesting it to be the rate
determining step. The experimentally calculated value for activation barrier is 29.8
(± 2.8) kcal/mol.

Ir
N
N
O O
F
F
F
C
N
CH
3
Ir
N
N
O O
F
F
F
C
N
CH 3
D 6
Ir
N
N
O DO
F
F
F
C
N
CH 3
D 5
Ir
N
N
O
DO F
F
F
C
N
CH 3
D 5
Ir
N
N
O
O F
F
F
C
N
CH 3
D 5
D
Ir
N
N
O
O
F
F
F
C
N
CH 3
D 5
33.2
33.2
0.0
0.0
24.3
24.3
10.9
10.9
23.8
23.8
8.9
8.9
35.0
35.0
T.S 1
T.S 1 T.S 2
T.S 2
0.0
0.0
Ir
N
N
O O
F
F
F
C
N
CH
3
Ir
N
N
O O
F
F
F
C
N
CH 3
D 6
Ir
N
N
O DO
F
F
F
C
N
CH 3
D 5
Ir
N
N
O
DO F
F
F
C
N
CH 3
D 5
Ir
N
N
O
O F
F
F
C
N
CH 3
D 5
D
Ir
N
N
O
O
F
F
F
C
N
CH 3
D 5
33.2
33.2
0.0
0.0
24.3
24.3
10.9
10.9
23.8
23.8
8.9
8.9
35.0
35.0
T.S 1
T.S 1 T.S 2
T.S 2
0.0
0.0

Figure 3.16. B3LYP potential energy surface (ΔH
solv
) for C
6
H
6
/C
6
D
6
H/D
exchange.

The dissociative mechanism proceeding through acetonitrile loss and C-H
bond cleavage involving OHM (oxidative hydrogen migration) transition state has a
barrier of 42 kcal/mol.

128
3.3 Conclusion

In conclusion, mechanistic investigations on 4,Phenyl-Ir-TFA are in
agreement with a mechanism for CH activation in benzene with an activation barrier
of 29.0 (±2.8) kcal/mol involving an ion-pair. The labile ligand (L) atleast below 160
o
C is TFA and the dependence on acetonitrile concentration is attributed to blocking
the vacant site by binding to Ir center and forming the more thermodynamically
favored diacetonitrile complex, 6. The kinetic investigations show a direct
dependence on catalyst and benzene concentration and inverse dependence on TFA
in accordance with our predicted rate law. The catalyst is stable under the reaction
conditions ( 170
o
C) .These insights should aid in designing better (NNC)Ir based
catalysts and investigating CH activation in weakly acidic conditions.
3.4 Experimental Section

General Considerations: Unless otherwise noted all reactions were
performed using standard Schlenck techniques (argon) or in a MBraun glove box
(nitrogen). GC/MS analysis was performed on a Shimadzu GC-MS QP5000 (ver. 2)
equipped with a cross-linked methyl silicone gum capillary column (DB5).
1
H and
13
C NMR were collected on Varian 400 Mercury plus Spectrometer and referenced
to residual protiated solvent, and fluorine resonances were referenced to CFCl
3
or
hexafluorobenzene. All coupling constants are reported in Hz. Mass Spectroscopy
analyses were performed at UC Riverside Mass Spectrometry Lab or at the
University of Florida. Elemental analyses were performed by Desert Analytical

129
Laboratory, Inc.; Arizona. X-ray Crystallography was collected on a Bruker
SMART APEX CCD diffractometer.
Materials: IrCl
3
•3H
2
O was purchased from Pressure Chemical, Phenyl
Lithium (1.8 M in n-butyl ether, Aldrich), 4,4’-di-tert-butyl-2,2’-dipyridyl (98%,
Aldrich), Manganese(IV) oxide ( ≥90%, Aldrich). All solvents were reagent grade or
better. Benzene, ether, benzene-d
6
, toluene-d
8
and THF were purified by vacuum
transfer from sodium benzophenone ketyl. Dichloromethane (stabilizer removed with
sulfuric acid) was dried over P
2
O
5
and distilled over argon. The ligand 6-phenyl-
4,4’-di-tert-butyl-2,2’-bipyridine,
74
was synthesized according to previously
published procedures. Aluminum oxide neutral for thin layer chromatography was
purchased from EMD.
Synthesis of trans(Cl,Et)-(NNC)IrCl(C
2
H
4
)Et
69
(1,Ethylene-Ir-Cl), and
trans(Cl,Et)-(NNC)IrCl(NCCH
3
)Et (2,Acetonitrile-Ir-Cl)
69
. [Ir(C
2
H
4
)
2
( μ-Cl)]
2

(1.03 g, 1.82 mmol) was dissolved in CH
2
Cl
2
(25 ml) in a Schlenck bomb
75
. In a
separate Schlenck flask, 6-phenyl-4,4’-di-tert-butyl-2,2’-bipyridine (1.25 g, 3.63
mmol) was dissolved in CH
2
Cl
2
(15 ml). Ethylene was then bubbled through the
iridium solution while stirring at –50
o
C for 5 min. Under an ethylene atmosphere
the dissolved ligand was transferred (by cannula) over. The flask was then washed
with CH
2
Cl
2
(15 mL) and transferred over. The red solution was then stirred at –50
o
C for 15 min, then allowed to warm to room temp, and stirred for 16 h. During the
course of the reaction the bomb was opened periodically to relieve excess ethylene
pressure. The solvent was then reduced to 20 ml under reduced pressure
76
, and

130
ethylene was then bubbled through for 5 min. Acetonitrile (20ml) was then added
and the solution was heated at 50
o
C for 30 min. The solvent was then removed, and
the resulting red residue was passed through neutral alumina with CH
2
Cl
2
until the
yellow band came off, then ethyl acetate/methanol gradient to remove 1,Ethylene-
Ir-Cl (orange band) and acetonitrile complex 2, Acetonitrile-Ir-Cl (red band).
Complexes 1,Ethylene-Ir-Cl and 2,Acetonitrile-Ir-Cl were obtained as crystalline
material by recrystalization from CH
2
Cl
2
/Pentane at –25
o
C. Yielding 1.32 g
(57.9%) of 1, Ethylene-Ir-Cl and 301.5mg (13%) of 2, Acetonitrile-Ir-Cl.
1
H
NMR of 1-EtClC
2
H
4
: (CDCl
3
) 9.21(d, 1H,
3
J = 6.1), 8.04(d, 1H,
4
J = 2.0), 7.94(d,
1H,
4
J = 1.6), 7.80(d, 1H,
4
J = 1.6), 7.73(dd, 1H,
3
J = 8.0
4
J = 1.0), 7.68(dd, 1H,
3
J =
7.8
4
J = 1.6), 7.56(dd, 1H,
3
J = 6.1
4
J = 2.1), 7.28(dt, 1H,
3
J = 7.5
4
J = 1.6), 7.13(dt,
1H,
3
J = 7.5
4
J = 1.0), 3.97(s, 4H, C
2
H
4
), 1.52(s, 9H), 1.48(s, 9H), 0.47(dq, 1H,
2
J =
10.8
3
J = 7.7, -CH
2
-), 0.25(dq, 1H,
2
J = 10.8 Hz,
3
J = 7.7 Hz, -CH
2
-), -0.28 (t, 3H,
3
J
= 7.7 Hz, -CH
3
).
13
C NMR (CDCl
3
): 163.88, 163.04, 162.28, 158.40, 153.18,
151.21, 144.76, 144.38, 134.99, 131.67, 124.90, 124.63, 122.74, 119.61, 116.17,
115.13, 65.86(C
2
H
4
), 35.59(CMe
3
), 35.47(CMe
3
), 30.94(CMe
3
), 30.62(CMe
3
),
14.95(-CH
3
), -7.52(-CH
2
-). ESI-MS: 593.2 (M - Cl)
+
, 565.2 (M –Cl -C
2
H
4
)
+
.
Elemental analysis; Found: C 52.98, H 5.52, N 4.24, Cl 5.59 Calculated; C 53.53; H
5.78; N 4.46, Cl 5.64;
1
H NMR of 2,Acetonitrile-Ir-Cl (CDCl
3
) 8.78(d, 1H,
3
J =
5.7), 7.91(d, 1H,
4
J = 1.8), 7.66(d, 1H,
4
J = 1.6), 7.61(d, 1H,
4
J = 1.6), 7.55(m, 2H),
7.48(dd, 1H,
3
J = 5.7
4
J = 1.8), 7.14(dt, 1H,
3
J = 7.7, 7.3,
4
J = 1.4), 6.98(dt, 1H,
3
J =
7.6, 7.4,
4
J = 1.3), 2.69(s, 3H, NCCH
3
), 1.44(s, 9H, -CMe
3
), 1.43(s, 9H, -CMe
3
),

131
0.91(m, 1H), 0.67(m, 1H), 0.21(t, 1H,
3
J = 7.7)
13
C NMR (CDCl
3
) 167.79, 161.83,
160.88, 157.64, 155.59, 154.08, 149.98, 145.21, 133.67, 130.99, 124.90, 124.12,
120.75, 119.32, 115.07, 114.82, 114.06, 35.38(CMe
3
), 31.07, 30.74, 16.05, 5.07, -
9.47. ESI-MS: 647.2(M-Cl +NCCH
3
)
+
606.2 (M-Cl)
+
, 565.2 (M-Cl-NCCH
3
)
+
.
Elemental analysis: Found: C 52.03, H 5.47, N 6.23, Cl 5.62 Calculated; C 52.44, H
5.50, N, 6.55, Cl 5.53.
Synthesis of trans(TFA,Et)-(NNC)Ir(TFA)(C
2
H
4
)Et 69 (Ethylene-Ir-TFA): In a
small schlenk bomb, (200 mg, 0.318 mmol) of 1,Ethylene-Ir-Cl was combined with
(74 mg, 0.334 mmol) of silver trifluoroacetate and dissolved in CH
2
Cl
2
(30 ml). The
reaction was allowed to stir under argon and in the dark for 2 days. The orange
solution was then filtered over celite to remove any AgCl. The filtrate was then
evaporated to dryness. After recrystallization from CH
2
Cl
2
/Pentane at –25
o
C a
yellow solid is obtained (175 mg, 80 % yield).
1
H NMR of Ethylene-Ir-TFA
(CDCl
3
, 400MHz): 9.16(d, 1H,
3
J = 6.1, H-1), 8.00(d, 1H,
4
J = 2.0, H-4), 7.89(d,
1H,
4
J = 1.7, H-9), 7.78(d, 1H,
4
J = 1.8, H-7), 7.69 (dd, 1H,
3
J = 7.9
4
J = 1.1, H-12),
7.63(dd, 1H,
3
J = 7.9
4
J = 1.6, H-15), 7.52(dd, 1H,
3
J = 6.0
4
J = 2.2, H-2), 7.25(dt,
1H,
3
J = 7.4
4
J = 1.6, H-13), 7.13(dt, 1H,
3
J = 7.4
4
J = 1.1, H-14) 3.87(m, 2H,
H
2
C=CH2), 1.50(s, 9H, H-18,19,20), 1.45(s, 9H, H-22,23,24), 0.44(m, 1H, -CH
2
-),
0.24(m, 1H, -CH
2
-), -0.41 (t, 3H,
3
J = 7.4, -CH
3
).
13
C NMR of 4: 164.01(C-10),
163.35(C-3), 162.70(C-8), 162.06 (CO(CF
3
), J = 34.5 Hz) 159.32(C-5), 154.31(C-
6), 151.32(C-1), 145.11(C-16), 143.35(C-11), 135.23(C-12), 131.37(C-13),
124.68(C-15), 124.45(C-2), 123.09(C-14), 119.23(C-4), 115.90(C-9), 115.84

132
(CO(CF
3
), J=294.0Hz), 115.00(C-7), 66.15(C
2
H
4
), 35.61(C-21), 35.47(C-17),
30.87(C-18,19,20), 30.52(C-22,23,24), 15.01(-CH
3
), -7.52(-CH
2
-).
19
F NMR (376
MHz, CDCl
3
) δ -75.35 (s, 3F) Elemental Calcd for C
30
H
36
F
3
IrN
2
O
2
C, 51.05; H,
5.14; F, 8.07; N, 3.97. Found C, 50.75; H, 4.98; F, 8.14; N, 3.96.
Synthesis of trans(TFA,Et)-(NNC)IrTFA(NCCH
3
)Et (3,Ethyl-Ir-TFA): In a
small schlenk bomb, (250 mg, 0.390 mmol) of 2 was combined with (90 mg, 0.409
mmol) of silver trifluoroacetate and dissolved in CH
2
Cl
2
(40 mL). The reaction was
allowed to stir under argon and in the dark for 2 days. The red solution was then
filtered over celite to remove any AgCl. The filtrate was then evaporated to dryness.
After recrystallization from CH
2
Cl
2
/Pentane at –25
o
C a reddish solid is obtained
(192 mg, 70 % yield).
1
H NMR of 3 (CDCl
3
, 400MHz): 8.87(d, 1H,
3
J = 5.8, H-1),
7.84(d, 1H,
4
J = 2.0, H-4), 7.62(d, 1H,
4
J = 1.7, H-9), 7.57 (d, 1H,
4
J = 1.7, H-7),
7.51(dd, 1H,
3
J = 6.2 4J = 1.4, H-15), 7.49(dd, 1H,
3
J = 6.2 4J = 1.7, H-12), 7.45(dd,
1H,
3
J = 5.7
4
J = 2.0, H-2), 7.11(dt, 1H,
3
J = 7.3
4
J = 1.3, H-14) 6.97 (dt, 1H,
3
J = 7.3
4J = 1.5, H-13) 2.68(s, 3H, NCCH
3
), 1.44(s, 9H, H-22,23,24), 1.42(s, 9H, H-
18,19,20), 0.86(m, 1H, -CH
2
-), 0.57(m, 1H, -CH
2
-), 0.09 (t, 3H,
3
J = 8.0,-CH
3
).
13
C
NMR of 3: 168.32 (C-10), 162.33(C-3), 161.55 (C-8),158.01(C-5), 156.68(C-6),
152.94(C-16), 151.50(C-1), 145.94(C-11), 134.08 (C-15), 130.90(C-14), 124.75(C-
12), 123.88(C-2), 121.19(C-13), 118.79(C-4), 116.41(NCCH
3
), 116.30 (CO(CF
3
), J=
294.4Hz), 114.70(C-9), 113.90(C-7), 35.51(-C(CH
3
)
3
), 35.49(-C(CH
3
)
3
), 31.07(C-
22,23,24), 30.73(C-18,19,20), 16.53(-CH
3
), 4.64(NCCH
3
) -15.43(-CH
2
-).
19
F NMR

133
(376 MHz, CDCl
3
) δ -74.90 (s, 3F) Elemental Calcd for C
30
H
35
F
3
IrN
3
O
2
C, 50.13;
H, 4.91; F, 7.93; N, 5.85. Found C, 50.36; H, 4.85; F, 7.86; N, 5.70.
Synthesis of trans(TFA,Ph)-(NNC)IrTFA(NCCH
3
)Ph (4,Phenyl-Ir-TFA): In a
schlenk bomb, (100 mg, 0.136 mmol) of 3 was dissolved in CH
2
Cl
2
(50 ml). The
reaction was heated at 130
o
C for 2h. The solvent was then removed under vacuum.
The residue was redissolved in CH
2
Cl
2
, and reprecipitated with pentane. Yielding
101 mg (95%) of 4, Phenyl-Ir-TFA.
1
H NMR of 4 (CDCl
3
, 400MHz): 8.87(d, 1H,
3
J = 5.8, H-1), 7.84(d, 1H,
4
J = 2.0, H-4), 7.62(d, 1H,
4
J = 1.7, H-9), 7.57 (d, 1H,
4
J
= 1.7, H-7), 7.51(dd, 1H,
3
J = 6.2 4J = 1.4, H-15), 7.49(dd, 1H,
3
J = 6.2 4J = 1.7, H-
12), 7.45(dd, 1H,
3
J = 5.7
4
J = 2.0, H-2), 7.11(dt, 1H,
3
J = 7.3
4
J = 1.3, H-14) 6.97
(dt, 1H,
3
J = 7.3 4J = 1.5, H-13) 2.68(s, 3H, NCCH
3
), 1.44(s, 9H, H-22,23,24),
1.42(s, 9H, H-18,19,20), 0.86(m, 1H, -CH
2
-), 0.57(m, 1H, -CH
2
-), 0.09 (t, 3H,
3
J =
8.0,-CH
3
).
13
C NMR of 3: 168.32 (C-10), 162.33(C-3), 161.55 (C-8),158.01(C-5),
156.68(C-6), 152.94(C-16), 151.50(C-1), 145.94(C-11), 134.08 (C-15), 130.90(C-
14), 124.75(C-12), 123.88(C-2), 121.19(C-13), 118.79(C-4), 116.41(NCCH
3
),
116.30 (CO(CF
3
), J= 294.4Hz), 114.70(C-9), 113.90(C-7), 35.51(-C(CH
3
)
3
), 35.49(-
C(CH
3
)
3
), 31.07(C-22,23,24), 30.73(C-18,19,20), 16.53(-CH
3
), 4.64(NCCH
3
) -
15.43(-CH
2
-).
19
F NMR (376 MHz, CDCl
3
) δ -74.90 (s, 3F). Elemental Calcd for
C
30
H
35
F
3
IrN
3
O
2
C, 53.25; H, 4.60; F, 7.43; N, 5.48, Found C 52.94; H, 4.55; F, 7.24;
N, 5.68.

134
Synthesis of [(NNC)IrPh( μ-Cl)]
2
,[Ph-Ir-Cl]
2
69
and Ph-Ir-Cl. Complex Ethylene-
Ir-Cl (100mg, 0.159 mmol) was heated at 160
o
C in benzene (100ml) in a Schlenck
bomb for 2h. The solvent was then removed under vacuum. The residue was
redissolved in CH
2
Cl
2
, and reprecipitated with pentane to give [Ph-Ir-Cl]
2
. Ph-Ir-Cl
was quantitatively synthesized by heating [Ph-Ir-Cl]
2
(100mg,) at 120
o
C in
acetontrile (50ml) in a schlenk bomb for 2h under argon. Yielding 94.7mg (91.8%)
of [Ph-Ir-Cl]
2
.
1
H NMR (CD
2
Cl
2
) 8.57(d, 1H,
3
J = 5.8), 8.05(d, 1H,
4
J = 1.7),
7.80(bs, 2H), 7.69(dd, 1H,
3
J = 7.9
4
J = 1.3), 7.43(dd, 1H,
3
J = 5.8,
4
J = 1.7), 7.15(dd,
1H,
3
J = 7.4
4
J = 1.3), 7.10(dt, 1H,
3
J = 7.5
4
J = 1.3), 6.91(dt, 1H,
3
J = 7.4
4
J = 1.3),
6.40-6.28(m, 5H, phenyl), 1.53(s, 9H, CMe
3
), 1.52(s, 9H, CMe
3
).
13
C NMR
(CD
2
Cl
2
) 169.20, 162.27, 161.89, 157.41, 157.08, 154.36, 152.14, 147.66, 137.39,
133.73, 130.92, 125.31, 125.11, 124.75, 124.70, 121.35, 119.35, 115.25, 115.20,
35.65, 31.00, 30.69; Elemental analysis: Calculated: C 55.58; H 4.98; N 4.32; Cl
5.47 ; Found: C 55.19; H 4.69; N 4.76; Cl 5.20.
Reaction Procedure for substrate Dependence (Benzene): A 10 mL glass Schlenk
flask fitted with a Teflon valve and equipped with a magnetic stir bar under argon
atomsphere was charged with 6-8 mg (8 mmol, 0.8 mol %) of catalyst. To it benzene
(0.1 to 0.5 mL) was added , keeping the total volume as 1.1ml. The valve was closed
and was heated to 170
o
C and aliquots were drawn every 30 min. The liquid phase
was sampled and the increase of deuterium incorporation in to C
6
H
6
determined by
GC-MS.

135
Reaction Procedure for catalyst (Phenyl-Ir-TFA) Dependence : A 10 mL glass
Schlenk flask fitted with a Teflon valve and equipped with a magnetic stir bar was
charged under Argon atmosphere with dry, distilled benzene (0.1ml) and toluene-d
8
(typically 1.0 mL) and varied amount of Phenyl-Ir-TFA 4-20 mg) with 5 eq of
cesium trifluroacetate to each flask. The valve was closed and was heated to 170
o
C
and aliquots drawn every 30 minutes and the increase of deuterium incorporation in
to C
6
H
6
determined by GC-MS.
Reaction Procedure for TFA Dependence: A 5 mL glass Schlenk flask fitted with
a Teflon valve and equipped with a magnetic stir bar under argon atomsphere was
charged with 6-8 mg (8 mmol, 0.8 mol %) of catalyst. To it were added varying
amount of cesium trifluoroacetate (8.95-895 mmol), and 1.0ml of toluene-d
8
.The
valve was closed and was heated to 170
o
C and aliquots drawn very 30min. The
liquid phase was sampled and the increase of deuterium incorporation in to C
6
H
6

determined by GC-MS.
Reaction Procedure for NCCH
3
Dependence: A 5 mL glass Schlenk flask fitted
with a Teflon valve and equipped with a magnetic stir bar under argon atomsphere
was charged with 6-8 mg (0.008 mmol, 0.008 mol %) of catalyst. To it were added
varying amounts of acetonitrile (0.00895-0.895 mmol), and 1.0ml of toluene-d
8
. The
valve was closed and was heated to 170
o
C and aliquots drawn very 30min. The
liquid phase was sampled and the increase of deuterium incorporation in to C
6
H
6

determined by GC-MS.

136
H-D Exchange between C
6
H
6
and Toluene-d
8
: Catalytic H-D exchange reactions
were quantified by monitoring by the increase of deuterium into C
6
H
6
by GC/MS
analyses for Phenyl-Ir-TFA (8 mM) using toluene-d
8
as the deuterium source at 170
°C. This was achieved by deconvoluting the mass fragmentation pattern obtained
from the MS analysis, using a program developed on Microsoft EXCEL. The mass
range from 78 to 84 (for benzene) was examined for each reaction and compared to a
control reaction where no metal catalyst was added. The program was calibrated with
known mixtures of benzene isotopomers. The results obtained by this method are
reliable to within 5%. Catalytic H/D exchange reactions were thus run for reaction
times in order to be able to detect changes >5% in exchange.

137

Table 3.1. Crystal data and structure refinement for C
30
H
29
C
l2
F
3
Ir N
3
O
2
.

Identification code IrNNCethyl
Empirical formula C30 H29 Cl2 F3 Ir N3 O2
Formula weight 783.66
Temperature 150(2) K
Wavelength 0.71073 Å
Crystal system Monoclinic
Space group P2(1)/n
Unit cell dimensions a = 13.227(3) Å α= 90°.
b = 16.003(3) Å β= 99.627(4)°.
c = 16.192(3) Å γ = 90°.
Volume 3379.0(12) Å
3

Z 5
Density (calculated) 1.926 Mg/m
3

Absorption coefficient 5.193 mm
-1

F(000) 1920
Crystal size 0.51 x 0.27 x 0.20 mm
3

Theta range for data collection 1.80 to 23.30°.
Index ranges -14<=h<=14, -17<=k<=17, -10<=l<=17
Reflections collected 14851
Independent reflections 4861 [R(int) = 0.563]
Completeness to theta = 23.30° 99.6 %
Absorption correction None
Refinement method Full-matrix least-squares on F
2

Data / restraints / parameters 4861 / 0 / 387
Goodness-of-fit on F
2
0.935
Final R indices [I>2sigma(I)] R1 = 0.0549, wR2 = 0.1404
R indices (all data) R1 = 0.0831, wR2 = 0.1494
Largest diff. peak and hole 2.656 and -0.984 e.Å
-3

138
Table 3.2. Atomic coordinates ( x 10
4
) and equivalent isotropic displacement
parameters (Å
2
x 10
3
) for C
30
H
29
C
l2
F
3
Ir N
3
O
2
. U(eq) is defined as
one third of the trace of the orthogonalized U
ij
tensor.

x y z U(eq)
Ir(1) 912(1) 6627(1) 1260(1) 38(1)
C(16) 2211(9) 8155(7) 1443(7) 37(3)
O(2) 1260(6) 6687(4) 2660(5) 47(2)
C(27) 637(9) 6678(7) -44(7) 50(3)
C(7) -576(9) 7902(7) 1303(7) 42(3)
C(8) -934(8) 8715(7) 1350(7) 41(3)
N(2) 419(7) 7776(5) 1339(6) 34(2)
C(9) -288(8) 9381(6) 1460(7) 35(3)
C(11) 1096(8) 8426(6) 1437(6) 34(3)
C(1) -583(9) 6372(7) 1187(7) 43(3)
C(30) 2264(11) 6596(9) 3993(9) 59(4)
C(3) -2194(10) 5602(8) 1074(8) 57(4)
O(1) 2510(6) 5710(5) 2899(6) 61(2)
C(10) 759(8) 9229(7) 1513(7) 38(3)
C(2) -1141(10) 5618(7) 1109(8) 53(4)
C(29) 1987(10) 6282(8) 3087(8) 46(3)
C(6) -1189(10) 7106(7) 1210(8) 43(3)
C(5) -2226(10) 7065(8) 1174(8) 51(3)
C(4) -2743(10) 6318(8) 1103(8) 58(4)
C(28) 1554(12) 6802(9) -466(9) 75(4)
C(18) 3983(9) 8397(7) 1503(7) 42(3)
N(1) 2283(8) 7295(6) 1371(6) 45(3)
C(17) 2996(8) 8698(6) 1524(7) 35(3)
N(3) 1413(7) 5468(6) 1170(7) 48(3)
C(25) 1708(9) 4791(8) 1136(8) 50(3)
C(19) 4094(9) 7538(7) 1431(7) 39(3)
C(20) 3246(10) 7028(8) 1374(8) 52(3)

139
Table 3.2: Continued
C(21) 4915(9) 8964(7) 1555(8) 44(3)
C(12) -660(9) 10301(7) 1530(9) 55(4)
C(26) 2094(12) 3942(7) 1118(10) 80(5)
C(13) -1832(11) 10306(8) 1549(16) 136(9)
C(15) -110(13) 10690(10) 2328(12) 115(7)
F(2) 3144(7) 7013(5) 4104(6) 93(3)
F(3) 2445(8) 5968(6) 4527(6) 111(4)
F(1) 1609(8) 7089(8) 4247(6) 116(4)
C(14) -400(20) 10799(10) 824(14) 163(11)
C(24) 4701(13) 9833(12) 1630(20) 226(18)
C(23) 5752(15) 8659(14) 2210(20) 181(14)
C(22) 5440(20) 8840(20) 850(20) 250(20)
Cl(1) 3831(7) 8061(7) 8947(8) 265(6)
Cl(2) 4665(12) 6431(9) 9023(10) 343(8)
hC(31) 3940(30) 7260(17) 8295(13) 310(30)

Table 3.3.

Bond lengths [Å] and angles [°] for NNCethym.

Ir(1)-N(2) 1.962(8)
Ir(1)-N(3) 1.984(10)
Ir(1)-C(1) 2.004(12)
Ir(1)-C(27) 2.083(11)
Ir(1)-N(1) 2.086(11)
Ir(1)-O(2) 2.239(8)
C(16)-C(17) 1.344(15)
C(16)-N(1) 1.385(13)
C(16)-C(11) 1.536(15)
O(2)-C(29) 1.265(14)
C(27)-C(28) 1.502(17)
C(7)-N(2) 1.323(14)
C(7)-C(8) 1.392(15)

140
Table 3.3: Continued
C(7)-C(6) 1.504(16)
C(8)-C(9) 1.359(14)
N(2)-C(11) 1.364(13)
C(9)-C(10) 1.396(14)
C(9)-C(12) 1.561(14)
C(11)-C(10) 1.372(14)
C(1)-C(2) 1.408(15)
C(1)-C(6) 1.427(16)
C(30)-F(1) 1.289(16)
C(30)-F(3) 1.321(14)
C(30)-F(2) 1.327(15)
C(30)-C(29) 1.536(18)
C(3)-C(4) 1.361(17)
C(3)-C(2) 1.386(16)
O(1)-C(29) 1.215(14)
C(6)-C(5) 1.364(16)
C(5)-C(4) 1.372(17)
C(18)-C(19) 1.390(14)
C(18)-C(17) 1.397(15)
C(18)-C(21) 1.522(15)
N(1)-C(20) 1.342(15)
N(3)-C(25) 1.156(13)
C(25)-C(26) 1.453(17)
C(19)-C(20) 1.377(16)
C(21)-C(24) 1.43(2)
C(21)-C(22) 1.45(2)
C(21)-C(23) 1.48(2)
C(12)-C(14) 1.48(2)
C(12)-C(15) 1.507(19)
C(12)-C(13) 1.557(18)
Cl(1)-C(31) 1.68(3)

141
Table 3.3: Continued
Cl(2)-C(31) 1.92(3)
N(2)-Ir(1)-N(3) 179.5(4)
N(2)-Ir(1)-C(1) 81.9(4)
N(3)-Ir(1)-C(1) 98.3(4)
N(2)-Ir(1)-C(27) 91.5(4)
N(3)-Ir(1)-C(27) 88.0(4)
C(1)-Ir(1)-C(27) 86.9(5)
N(2)-Ir(1)-N(1) 78.9(4)
N(3)-Ir(1)-N(1) 100.9(3)
C(1)-Ir(1)-N(1) 160.8(4)
C(27)-Ir(1)-N(1) 94.0(4)
N(2)-Ir(1)-O(2) 84.8(3)
N(3)-Ir(1)-O(2) 95.7(4)
C(1)-Ir(1)-O(2) 95.8(4)
C(27)-Ir(1)-O(2) 175.0(4)
N(1)-Ir(1)-O(2) 82.1(3)
C(17)-C(16)-N(1) 126.0(10)
C(17)-C(16)-C(11) 122.9(10)
N(1)-C(16)-C(11) 111.1(10)
C(29)-O(2)-Ir(1) 122.7(8)
C(28)-C(27)-Ir(1) 116.7(9)
N(2)-C(7)-C(8) 119.1(10)
N(2)-C(7)-C(6) 113.1(10)
C(8)-C(7)-C(6) 127.9(11)
C(9)-C(8)-C(7) 121.9(10)
C(7)-N(2)-C(11) 121.1(9)
C(7)-N(2)-Ir(1) 118.6(7)
C(11)-N(2)-Ir(1) 120.3(7)
C(8)-C(9)-C(10) 117.9(10)
C(8)-C(9)-C(12) 123.4(10)
C(10)-C(9)-C(12) 118.8(9)

142
Table 3.3: Continued
N(2)-C(11)-C(10) 120.6(10)
N(2)-C(11)-C(16) 113.3(9)
C(10)-C(11)-C(16) 126.2(10)
C(2)-C(1)-C(6) 114.8(11)
C(2)-C(1)-Ir(1) 132.6(9)
C(6)-C(1)-Ir(1) 112.6(8)
F(1)-C(30)-F(3) 108.3(13)
F(1)-C(30)-F(2) 105.6(12)
F(3)-C(30)-F(2) 103.6(11)
F(1)-C(30)-C(29) 116.1(12)
F(3)-C(30)-C(29) 111.3(12)
F(2)-C(30)-C(29) 111.0(12)
C(4)-C(3)-C(2) 121.4(12)
C(11)-C(10)-C(9) 119.4(10)
C(3)-C(2)-C(1) 121.9(12)
O(1)-C(29)-O(2) 131.4(12)
O(1)-C(29)-C(30) 115.5(12)
O(2)-C(29)-C(30) 113.1(11)
C(5)-C(6)-C(1) 121.7(11)
C(5)-C(6)-C(7) 124.5(11)
C(1)-C(6)-C(7) 113.8(11)
C(6)-C(5)-C(4) 121.9(12)
C(3)-C(4)-C(5) 118.4(12)
C(19)-C(18)-C(17) 117.1(10)
C(19)-C(18)-C(21) 120.0(10)
C(17)-C(18)-C(21) 122.9(10)
C(20)-N(1)-C(16) 113.2(11)
C(20)-N(1)-Ir(1) 130.3(8)
C(16)-N(1)-Ir(1) 116.4(7)
C(16)-C(17)-C(18) 119.0(10)
C(25)-N(3)-Ir(1) 178.5(11)

143
Table 3.3: Continued
N(3)-C(25)-C(26) 178.4(14)
C(20)-C(19)-C(18) 119.7(11)
N(1)-C(20)-C(19) 125.0(11)
C(24)-C(21)-C(22) 109.3(19)
C(24)-C(21)-C(23) 113.3(17)
C(22)-C(21)-C(23) 97(2)
C(24)-C(21)-C(18) 114.6(11)
C(22)-C(21)-C(18) 111.2(13)
C(23)-C(21)-C(18) 110.2(11)
C(14)-C(12)-C(15) 107.3(15)
C(14)-C(12)-C(13) 112.1(15)
C(15)-C(12)-C(13) 108.7(13)
C(14)-C(12)-C(9) 109.5(11)
C(15)-C(12)-C(9) 109.8(11)
C(13)-C(12)-C(9) 109.4(10)
Cl(1)-C(31)-Cl(2) 103.1(15)
Symmetry transformations used to generate equivalent atoms:

Table 3.4. Anisotropic displacement parameters (Å
2
x 10
3
) for C
30
H
29
Cl
2
F
3
Ir
N
3
O
2
. The anisotropic displacement factor exponent takes the form:
-2π
2
[ h
2
a
*2
U
11
+ ... + 2 h k a* b* U
12
].

U
11
U
22
U
33
U
23
U
13
U
12

Ir(1) 43(1) 20(1) 47(1) -2(1) -4(1) 3(1)
C(16) 45(7) 31(7) 32(7) 1(5) -2(6) 12(6)
O(2) 48(5) 41(5) 47(5) -4(4) -5(4) 4(4)
C(27) 62(8) 45(7) 38(7) -17(6) -13(6) 0(6)
C(7) 48(8) 33(7) 41(7) -5(6) -4(6) 3(6)
C(8) 26(6) 38(7) 52(8) -3(6) -6(6) 5(5)
N(2) 39(6) 20(5) 41(6) 1(4) -3(5) 4(5)

144
Table 3.4: Continued
C(9) 45(7) 19(6) 40(7) -10(5) 4(6) 0(5)
C(11) 45(7) 23(6) 30(6) 1(5) -8(5) -3(5)
C(1) 47(7) 33(7) 44(8) -6(6) -6(6) 1(6)
C(30) 69(10) 50(8) 54(9) 12(8) 3(8) -8(8)
C(3) 45(8) 49(8) 76(10) 4(7) 5(7) -21(7)
O(1) 65(6) 43(5) 66(6) 5(5) -10(5) 19(5)
C(10) 41(7) 30(7) 40(7) -8(5) -3(6) 8(5)
C(2) 64(9) 21(6) 68(10) 0(6) -9(7) -7(6)
C(29) 44(8) 32(7) 56(9) 0(6) -5(7) -6(6)
C(6) 50(8) 32(7) 45(8) 0(6) 0(6) -6(6)
C(5) 52(9) 44(8) 53(9) -8(7) -3(7) -3(7)
C(4) 50(8) 44(8) 72(10) -8(7) -18(7) -9(7)
C(28) 83(11) 83(11) 59(10) -1(8) 13(9) -11(9)
C(18) 44(7) 37(7) 41(7) 2(6) -3(6) 7(6)
N(1) 56(7) 47(6) 33(6) 5(5) 9(5) 33(5)
C(17) 39(7) 19(5) 41(7) -12(5) -5(6) -3(5)
N(3) 43(6) 23(6) 73(8) -9(5) -3(5) -3(5)
C(25) 47(7) 27(7) 70(9) -10(6) -6(7) -3(6)
C(19) 33(7) 36(7) 47(8) 1(6) 3(6) 8(6)
C(20) 58(9) 35(7) 61(9) 2(7) 5(7) 14(7)
C(21) 41(7) 31(7) 59(9) 8(6) 5(7) -4(6)
C(12) 33(7) 30(7) 99(11) -20(7) -4(7) 6(5)
C(26) 108(12) 30(7) 85(11) -12(7) -30(10) 20(8)
C(13) 64(11) 33(9) 310(30) -32(13) 27(14) 14(8)
C(15) 104(13) 82(12) 148(18) -82(13) -9(13) 19(10)
F(2) 94(6) 53(5) 116(8) -8(5) -30(6) -26(5)
F(3) 170(9) 75(6) 68(6) 27(5) -35(6) -44(6)
F(1) 102(8) 179(11) 62(6) -43(7) -5(6) 22(8)
C(14) 290(30) 50(11) 180(20) 73(13) 130(20) 86(15)
C(24) 53(11) 88(16) 540(60) -40(20) 60(20) -35(11)
C(23) 72(13) 127(18) 320(40) 100(20) -33(19) -27(12)

145
Table 3.4: Continued
C(22) 180(30) 260(40) 350(50) -210(40) 170(30) -140(30)
Cl(1) 192(8) 193(9) 424(18) 37(10) 97(11) 16(7)
Cl(2) 312(15) 283(16) 460(20) -97(14) 134(16) -61(12)
C(31) 720(80) 180(30) 73(16) 69(17) 190(30) 270(40)

Table 3.5.

Hydrogen coordinates ( x 10
4
) and isotropic displacement parameters
(Å
2
x 10
3
) for C
30
H
29
C
l2
F
3
Ir N
3
O
2
.

x y z U(eq)
H(27A) 296 6151 -256 61
H(27B) 148 7138 -217 61
H(8) -1651 8807 1305 49
H(3) -2541 5080 1029 69
H(10) 1236 9678 1601 45
H(2) -784 5107 1080 64
H(5) -2601 7569 1198 61
H(4) -3466 6302 1074 70
H(28A) 1863 7349 -309 112
H(28B) 1340 6779 -1075 112
H(28C) 2058 6362 -290 112
H(17) 2882 9278 1594 41
H(19) 4751 7303 1420 47
H(20) 3350 6443 1334 62
H(26A) 2653 3859 1591 120
H(26B) 2351 3849 592 120
H(26C) 1540 3546 1160 120
H(13A) -2077 10884 1541 205
H(13B) -1965 10029 2059 205
H(13C) -2193 10009 1057 205
H(15A) 617 10762 2291 172

146
Table 3.5: Continued
H(15B) -175 10325 2802 172
H(15C) -415 11235 2410 172
H(14A) -524 11392 918 244
H(14B) -822 10617 300 244
H(14C) 329 10717 787 244
H(24A) 5347 10146 1738 339
H(24B) 4326 9917 2099 339
H(24C) 4284 10033 1112 339
H(23A) 5889 8070 2102 271
H(23B) 5549 8716 2758 271
H(23C) 6373 8988 2189 271
H(22A) 5088 9161 366 373
H(22B) 5424 8245 700 373
H(22C) 6148 9028 991 373
H(31A) 4327 7426 7851 371
H(31B) 3253 7053 8031 371

Table 3.6. C
6
H
6
/Tol-d
8
H/D exchange (170
o
C) with Phenyl-Ir-TFA and catalyst
stability.

time(min) Avg TON
15 2.4
30 8.9
60 20.8
120 49.3
255 104.0

147
R
2
= 0.9992
0
20
40
60
80
100
120
0 50 100 150 200 250 300
time(min)
TON

Table 3.7. Eyring plot for C
6
H
6
/Tol-d
8
H/D exchange for Phenyl-Ir-TFA.

Temp(K) TOF ln(TOF/T)
415 4.40E-04 -13.8
427 1.72E-03 -12.4
432 2.26E-03 -12.2
438 2.71E-03 -12.0
442 5.40E-03 -11.3
447 5.97E-03 -11.2

Eyring Plot
y = -14579x + 21.505
R
2
= 0.9634
-14
-13.5
-13
-12.5
-12
-11.5
-11
-10.5
-10
0.0022 0.00225 0.0023 0.00235 0.0024 0.00245
1/T(K)
ln(TOF/T)

148
ΔH
‡
= 29.0 ± 2.8 kcal/mol,
ΔG
‡
(T=298K) = 27.7 ± 2.9 kcal/mol
The error bars were calculated using linest function in Microsoft Excel.

Table 3.8. Eyring plot for C
6
H
6
/Tol-d
8
H/D exchange for Ethyl-Ir-TFA

Temp(K) TOF 1/T(K) ln(TOF/T)
419 2.16E-03 0.002387 -12.1764
421 2.01E-03 0.002375 -12.25248
432 3.31E-03 0.002315 -11.77928
438 5.28E-03 0.002283 -11.32652
442 1.41E-02 0.002262 -10.35421

Eyring Plot
y = -12881x + 18.363
-17
-15
-13
-11
-9
0.00224 0.00229 0.00234 0.00239
1/T(K)
ln(TOF/T)

ΔH
‡
= 25.7 ± 4.7 kcal/mol,

Table 3.9. Kinetic dependence of H/D exchange on benzene concentration.

C6H6
Conc(M)
Mean Avg
TOF
1.018 4.871E-03
2.036 7.045E-03
4.072 9.825E-03
5.09 1.200E-02

149

R
2
= 0.9916
0.000E+00
2.500E-03
5.000E-03
7.500E-03
1.000E-02
1.250E-02
01 2 3 45 6
Benzene conc(M)
TOF(10% conv)

Table 3.10. Kinetic dependence on catalyst concentration.

Cat
Conc(mM)
Mean Avg
TOF Mean TON
4.15 2.510E-04 4.97
8.3 2.545E-04 5.04
16.6 4.032E-04 7.98
20.75 5.186E-04 10.27

R
2
= 0.9356
0.0
2.0
4.0
6.0
8.0
10.0
12.0
0 5 10 15 20 25
Cat conc(mM)
TON(rate of H/D exchange)

150
Table 3.11. Kinetic dependence on trifluroacetate (TFA) concentration.

1/TFA TOF
- 4.871E-03
16.751E-04
0.2 1.250E-04
0.1 2.161E-05
0.04 2.037E-05
0.02 1.918E-05

1/TFA Plot
y = 0.0007x
R
2
= 0.9931
0.0E+00
1.0E-04
2.0E-04
3.0E-04
4.0E-04
5.0E-04
6.0E-04
7.0E-04
8.0E-04
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
1/TFA eq
TO F

Table 3.12. Kinetic dependence on acetonitrile (NCCH
3
) concentration.

No. Eqvts 1/NCCH3 Avg TOF
02.16E-03
10 0.1 7.18E-04
50 0.02 5.79E-05
100 0.01 1.70E-05

151
R
2
= 0.9975
0.00E+00
2.00E-04
4.00E-04
6.00E-04
8.00E-04
0 0.02 0.04 0.06 0.08 0.1
1/[NCCH3]
TOF

152
3.5 Chapter 3 References

65
(a) Shilov, A. E. Activation of Saturated Hydrocarbons by Transition Metal
Complexes, Riedel, Dordrecht, The Netherlands, 1984 (b) Waltz, K. M.;
Hartwig, J. F. Science, 1997, 277, 211. (c) Sen, A. Acc. Chem. Res. 1998, 31,
550. (d) Shilov, A. E.; Shul’pin, G. B. Activation and Catalytic Reactions of
Saturated Hydrocarbons, Kluwer,: Dordrecht, The Netherlands, 2000. (e)
Labinger, J. A.; Bercaw, J. E. Nature 2002, 417, 507. (f) Conley, B. L.; Tenn,
W. J., III.; Young, K. J.H.; Ganesh, S. K.; Meier, S. K.; Ziatdinov, V. R.;
Mironov, O.; Oxgaard, J.; Gonzales, J.; Goddard, W. A., III.; Periana, R. A.
J. Mol. Catal. A 2006, 251, 8.

66
(a) Periana, R. A.; Taube, D. J.; Gamble, S.; Taube, H.; Satoh, T.; and Fujii,
H. Science, 1998, 280, 560. (b) Periana, R. A.; Mironov, O.; Taube, D. J.;
Bhalla, G.; Jones, C.J. Science, 2003, 301, 814. (c) Periana, R. A.; Taube, D.
J.; Evitt, E. R.; Loffler, D. G.; Wentcek, P. R. Science 1993, 259, 340 (d)
Jones, C.J.; Taube, D. J.; Ziatdinov, V. R.; Periana, R. A.; Nielsen, R. J.,
Oxgaard, J.; Goddard, W. A., III. Angew. Chem., Int. Ed. 2004, 43, 4626.

67
Muller, R. P.; Philipp, D. M.; Goddard, W. A., III. Top. Catal. 2003, 23, 181.

68
Goldman, A. S.; Roy, A. H.; Huang, Z.; Ahuja, R.; Schinski, W.; Brookhart,
M. Science 2006, 312, 257-261.

69
Young, K. J.H.; Oxgaard, J.; Goddard, W. A.(III); Periana, R. A.; manuscript
submitted to JACS.
70
Van der Boom, M. E.; Milstein, D. Chem. Rev. 2003, 103, 1759.
71
(a) McLoughlin, M. A.; Flesher, R. J., Kaska, W. C., Mayer, H. A.
Organometallics 1994, 13, 3816. (b) Liu, F.; Pak, E. B.; Singh, B.; Jensen,
C. M.; Goldman, A. S. J. Am. Chem. Soc. 1999, 121, 4086.
72
(a) Constable, E. C.; Henney, R. P. G.; Leese, T. A.; Tocher, D. A. J. Chem.
Soc. Dalton Trans. 1990, 443. (b).Jahng, Y.; Park J. G. Inorganica Chimica
Acta 1998, 267, 265. (c) Lu, W.; Mi, B-X; Chan, M. C. W.; Hui, Z.; Che, C-
M.; Zhu, N.; Lee, S-T. J. Am. Chem. Soc. 2004, 126, 4958.
73
Young K.J.H.; Meier,S.K.;Gonzales,J.M.; Oxgaard,J; Goddard,W.A.III;
Periana,R.A. Organometallics, 2006, 25,4734 and references therein.

74
Lu, W.; Mi, B-X; Chan, M. C. W.; Hui, Z.; Che, C-M.; Zhu, N.; Lee, S-T. J.
Am. Chem. Soc, 2004. 126, 4958.
75
A thick walled glass vessel sealed with a resealable high vacuum PTFE
valve.

153

76
A minor amount of what is believed to be the cis-isomer was also observed,
however, this complex is only stable under an ethylene atmosphere. When
placed under vacuum the red solution turns slightly greenish. Bubbling
ethylene through the solution gives back the ethylene complex, and after
treatment with acetonitrile at 50
o
C for 30 minutes leads to the trapping and
isolation of this side product as the acetonitrile adduct. 1-EtClC
2
H
4
can be
converted to 1-EtClNCCH
3
by heating in acetonitrile.
154
Chapter 4: Mechanism of Anti-Markovnikov Olefin
Hydroarylation Catalyzed by Homogeneous O-Donor
Ir(III) Complexes.

4.1 Introduction

The addition coupling reaction of arenes to olefins, ultimately generating
alkylarene hydrocarbons, continues to be an important C-C bond forming reaction
and CH functionalization route.
77
Classically, straight-chain and branched-chain
alkylbenzene hydrocarbons are generated by the Friedel-Crafts electrophilic
substitution of benzene or acylation followed by reduction (Figure 4.1a).
78

However,
regioselectivity in these reactions are typically determined by the stability of the
carbocation intermediate, and are often difficult to control and predict.
79
Therefore, it
would be highly useful to develop alternative catalysts not based on obligatory
carbocation intermediates that control regio- and stereochemistry, and are applicable
to a broad range of substrates and functional groups. This naturally leads to strategies
based on the CH activation reaction, defined as a coordination reaction between a C-
H bond and a reactive species “M” that proceeds without the intermediate formation
of free-radicals, carbocations, carbanions or carbenes to generate discreet M-C
intermediates.
80
155

Figure 4.1. Comparison of a) Friedel-Crafts acylation, followed by reduction and b)
Hydroarylation of olefins.

The most practical approach to generate the formal Markovnikov
hydroarylation addition was developed by Murai and co-workers using chelation-
assisted reactions of olefins with acylheteroaromatics catalyzed by Ru.
81

The only
practical approach to generate the anti-Markovnikov hydroarylation addition to
ethylene was reported by Periana and co-workers in 2000, and involves CH
activation and functionalization (Figure 4.1b).
82

Here, the hydroarylation of
unactivated olefins
6
,
83,11
with unactivated arenes is catalyzed by an O-donor,
dinuclear, Ir(III) complex based on the bis-acac motif, [Acac-C-Ir]
2
[where -Ir- is
understood to be the trans-(acac-O,O)
2
Ir(III) motif throughout this chapter unless
otherwise specified].
84

The related mononuclear species, R-Ir(acac-O,O)
2
L (R= acac
(acetylacetonate), CH
3
, CH
2
CH
3
, Ph, CH
2
CH
2
Ph), also catalyzes hydroarylation and
benzene H/D exchange.
6
Figure 4.2 shows our previously proposed catalytic scheme
156
based on experimental
85
and theoretical studies.
86
These studies have revealed
several important conclusions. 1) The dinuclear and mononuclear complexes follow
the same mechanistic steps and catalytic cycle. 2) Initiation involves either
dissociation of the dinuclear complex or ligand loss from the mononuclear species to
generate a 5-coordinate species. 3) CH activation involves the cis-5-coordinate
species, requiring trans-cis isomerization of the acac ligand. 4) CH activation is not
the rate determining step.
Also, our density functional theory (DFT) studies have revealed a complex
interplay between CH activation and olefin insertion.
86
By studying several virtual
analogues of our Ir-acac catalyst and Gunnoe’s Tp-Ru(Ph)(CH
3
CN)(CO)
87

system
(which reacts via the same mechanism), it was concluded that the barriers for CH
activation and olefin insertion are correlated with the energy of the metal d-orbitals,
but in opposite fashion. Thus, the barrier for olefin insertion increases with higher
energy d-orbitals, while the barrier for CH activation decreases.

157
O
Ir
O
O
O
O
Ir
O
O
O
Ph
H
O
Ir
O
O
O
Ph
Ir
O O
O O
L
O
Ir
O
O
R
O
O
Ir
O
O
R*
O
C-H ACTIVATION
HYDROARYLATION
O
Ir
O
O
R*
O D
V
R
R*D
RD
R*H
RH
L
Ir
O O
O O
R
Ir
O O
O O
R*
Ir
O O
O O
R
R = Acac, Alkyl, Aryl
L = Py
O
Ir
O
O
R*
O H
R
V
- L
R = Ph
R-Ir-L
cis-Ph-Ir-Ol
PhCH
2
CH
2
-Ir-L
R-Ir- cis-R-Ir- Ir
O O
O O
R
R
Ir
O O
O O
+L
+L
[R-Ir]
2
cis-PhCH
2
CH
2
-Ir-Bz

Figure 4.2. Proposed reaction mechanisms for H/D exchange of benzene and
hydroarylation of ethylene catalyzed by R-Ir-L and [R-Ir]
2
complexes.

Given the importance and potential broad potential utility of hydroarylation
reactions,
88
we have begun a systematic study to understand reactivity and selectivity
in order to design more reactive and more selective catalysts.
89
We have recently
reported a bis-tropolonato Ir(III) analogue which shows a higher rate of CH
activation and comparable hydroarylation reactivity.
90
Here we present a detailed
158
experimental study of hydroarylation catalyzed by O-donor Ir(III) complexes and
answer the following questions:
(1) How are catalytic rates for R-Ir(acac)2-L complexes influenced by various “R”
and “L” groups?
(2) How stable is the catalyst?
(3) Is the observed anti-Markovnikov regioselectivity due to thermodynamic or
kinetic control?
(4) Is the active catalyst a dinuclear or mononuclear species?
(5) Why is no β-hydride elimination observed?
(6) What are the reaction orders of the substrates?
(7) What is the rate-determining step and complete mechanism for hydroarylation?

4.2 Results and Discussion

4.2.1 Rates of Hydroarylation for (acac-O,O)
2
Ir(III) Complexes

Figure 4.3 shows the mononuclear and dinuclear (acac-O,O)
2
Ir(III) complexes
that were studied. These catalysts differ by the R group or the L group on the (acac-
O,O)
2
Ir(III) motif. The naming scheme refers to the two axial substituents. Thus,
“Acac-C-Ir-H
2
O” is an (acac-O,O)
2
Ir(III) complex with an additional acac ligand
bound to the central carbon atom and coordinated with water. Table 4.1 gives the
rates of hydroarylation catalyzed by complexes in Figure 4.3. The most active
catalyst complex is Ph-Ir-H
2
O, with a TOF of 130 X 10
-4
s
-1
. All other catalysts gave
159
slightly slower rates with TOFs ranging from 15 to 110 X 10
-4
s
-1
, depending on the
concentration of catalyst and additive. All five catalysts gave identical ratios of linear
to branched hydroarylation products (61:39 for benzene + propylene and 98:2 for
benzene + styrene), suggesting a common regioselective step. Entries 3-5 in Table
4.1 show that the product ratios are independent of catalyst concentration; entries 6,
8, and 9 shows that the product ratios are also independent of the additive (vida
infra), although the TOF is slightly affected.
R-Ir-L
Ir
O O
O O
R
L
R = Acac, Alkyl, Aryl
L = Py, H
2
O
[R-Ir]
2
Ir
O O
O O
R
Ir
O O
O O
R

Figure 4.3. Acetylacetonate based Ir(III) O-donor complexes studied.

Table 4.1. Hydroarylation of propylene and styrene with benzene catalyzed by
R-(acac-O,O)
2
Ir(III)(L) complexes. Values taken from reference 85b.
S.N
o
[Comple
x]
Propylene Styrene

Complex Additive
mmol
TOF
a
(x 10
-4
s
-
1
)
L: B
(Mol
ratio)
TOF
a
(x 10
-4
s
-
1
)
L:B
(Mol
Ratio)
1 [Acac-C-Ir]
2
-- 5 110 61: 39 160 98: 2
2
Acac-C-Ir-
H
2
O
-- 5 100 61: 39 158 98: 2
160
Table 4.1: Continued

3 Acac-C-Ir-Py

--

5

24

61: 39

53

98: 2
4 Acac-C-Ir-Py -- 10 22 61: 39 -- 98: 2
5 Acac-C-Ir-Py -- 30 22 61: 39 -- 98: 2
6 Ph-Ir-Py -- 5 32 61: 39 62 98: 2
7 Ph-Ir-H
2
O -- 5 130 61: 39 175 98: 2
8 Ph-Ir-Py Acac 5 15 61: 39 -- 98: 2
9 Ph-Ir-Py H
2
O 5 36 61: 39 -- 98: 2

All reactions were carried out at 0.96 MPa of propylene with an extra 2.96 MPa of
nitrogen in benzene at 180 °C for 30min.
a
TOF = [moles of product]/([moles of
added catalyst]*Reaction time)

The mononuclear Ph-Ir-H
2
O complex has a TOF very close to [Acac-C-Ir]
2
(110 X 10
-4

s-1
), while Ph-Ir-Py is slightly less active(5 X 10
-4
s
-1
). Combined with
the identical product selectivities, these results indicate that the same active catalytic
species is formed from [Acac-C-Ir]
2
, Acac-C-Ir-H
2
O, Acac-C-Ir-Py, Ph-Ir-H
2
O or
Ph-Ir-Py, albeit at different concentrations. In addition, we previously showed a
similar correlation by comparing the experimental hydroarylation TOF and the
calculated free energies of the various catalyst precursors,
86
again strongly
supporting the presence of a common catalytic intermediate and a common rate
determining step.
Because Ph-Ir-H
2
O and Ph-Ir-Py both catalyze hydroarylation, this indicates
that neither γ-C bonded acac nor water is essential to catalysis. We confirmed this by
examining the effect of added free acetyl acetone (acac-H) and water on the catalytic
161
activity of Ph-Ir-Py using dry benzene. As can be seen in Table 4.1, (entries 8 and 9)
neither added acac-H or water has any effect on the product selectivity of Ph-Ir-Py.
However, the TOF decreases to 15 X 10
-4
s
-1
when acac-H is added (compare entries
6 and 8). In fact, acetic acid, trifluoroacetic acid, and hydrochloric acid all strongly
inhibit the reaction rate, most likely through a reaction such as HX + R-Ir-L Æ X-Ir-
L + RH, thereby reducing the catalyst concentration of the active catalyst and
reducing the TOF. Since these results show that all active catalysts investigated
involve the same active catalytic species, the remainder of the studies was performed
using only Ph-Ir-Py.

4.2.2 Catalyst stability

Figure 4.4 is a plot of turnover number (TON) versus time for the
hydroarylation of propylene with benzene with catalyst Ph-Ir-Py. The linear
relationship between TON and time shows that the catalyst is active and thermally
stable at 180
o
C over extended periods.
84, 85
162
R
2
= 0.9961
0
5
10
15
20
25
0 2000 4000 6000 8000 10000 12000 14000 16000
Time (s)
Turn Over Number

Figure 4.4. Time-dependent hydroarylation of propylene using Ph-Ir-Py as catalyst.

4.2.3 Thermodynamic vs. Kinetic control of regioselectivity

A key feature of these (acac-O,O)
2
Ir(III) catalysts is the preference for anti-
Markovnikov regioselectivity in olefin hydroarylation giving straight-chain (linear)
alkylbenzenes. However, the 40:60 ratio of iso- and n-propyl benzene is essentially
the same value expected from thermodynamic control (based on DFT calculations
86

and thermodynamic tables
91
, see Supporting Information). In fact, Table 4.2
compares the predicted and observed linear to branched products for several
hydroarylation substrates and shows that they are also very similar. Therefore, we
examined whether the reaction is under thermodynamic control.

Table 4.2. Comparison of thermodynamic and experimental ratio for
Hydroarylation with various olefins.
163
180
o
C
[Ph-Ir-Py]
+
+
R
R
R
Linear Branched

Expected Thermodynamic
Ratio
a

Observed Experimental
Ratio Olefin
Linear Branch Linear Branch
propylene 75 35 61 39
styrene 97 3 98 2
1-hexene 87 13 69 31
isobutylene 96 4 82 18

Based on relative B3LYP/LACV3P++**//LACVP** free energies (see Supporting
Information). Also see reference 10.

For the insertion to be under thermodynamic control it is required that a
facile pathway be available for the intramolecular interconversion of the n-propyl
and isopropyl benzene isomers, on at least the same time scale and under the same
conditions as the hydroarylation reaction. Importantly, such alkylarene
isomerizations must not be accompanied by intermolecular trans-alkylation
(reactions that transfer alkyl groups between different arenes), because in that case
the predicted thermodynamic products would be expected to be poly-alkylarenes,
that are not observed. To test the possibility that a selective intramolecular alkylarene
isomerization catalyst is generated we examined whether isopropyl benzene, under
the hydroarylation conditions (i.e., in the presence of benzene and the catalyst, Ph-Ir-
164
Py), rearranges to the thermodynamically more stable n-propyl benzene isomer (Eq.
1). GC/MS analysis of the resulting reaction mixture showed that the isopropyl
benzene remains unchanged and no n-propyl benzene was generated. To further
mimic the reaction conditions, this reaction was repeated in the presence of ethylene
to rule out the possibility that the potential active catalyst for isomerization is only
generated in the presence of olefins. Under these conditions, while ethyl benzene is
observed (indicating that an active hydroarylation catalyst is formed) the isopropyl
benzene again remains unchanged and no n-propyl benzene is observed. These
experiments rule out the possibility that the anti-Markovnikov reaction selectivity
stems from thermodynamic control during the hydroarylation reaction and that the
similarity between the thermodynamic and the observed product distribution with
propylene is coincidental.
180
o
C
[Ph-Ir-Py]
Eq. 1

It is interesting to note that the same regioisomers are observed in the well
documented Heck reaction.
92
The common step of both the Heck reaction and
hydroarylation is the insertion of olefin into a M-Ph bond, which controls the
selectivity of the products. Based on our theoretical results, electronic and steric
factors both control selectivity, which is further elaborated in reference 86a.

165
4.2.4 Is the active catalyst a dinuclear or mononuclear species?

In the initial report of hydroarylation by the (acac-O,O)
2
Ir(III) complexes, we
utilized the dinuclear complex, [Acac-C-Ir]
2
.
84
Subsequently, we found that the
mononuclear complexes shown in Table 4.1 (Ph-Ir-L, Acac-C-Ir-L (L = H
2
O, Py)
etc.) are also active catalysts. While this suggests that the active catalyst is a
mononuclear (acac-O,O)
2
Ir complex, it could be speculated that the active catalyst
could be a dinuclear Ir species that is formed in situ in a pre-equilibrium step under
the reaction conditions.
The lability of the dinuclear complex [CH
3
-Ir]
2
was studied by dynamic
NMR, and the dissociation to stable 5-coordinate square pyramidal complexes (or 6-
coordinate solvento complexes) occurs with an activation barrier of 14.1 kcal/mol.
Since this barrier is significantly lower than the measured ΔG
‡
for hydroarylation,
either the dinuclear or the mononuclear species could be the active species.
We have previously reported a facile conversion of these dinuclear
complexes to stable mononuclear complexes when treated with coordinating ligands
L (where L = Pyridine),
85
which is inconsistent with dinuclear complexes as the
stable, active catalysts. Examination of the predicted rate laws for a mononuclear
catalytic species versus a dinuclear catalytic species generated in situ shows a
difference in the dependency of the predicted rate on the concentration of L (Scheme
4.1). If we presume that the active catalyst is a dinuclear complex (M-M) and that it
is in equilibrium with the catalyst precursor, M-L, then the rate law will be
proportional to [M-L]
2
/[L]
2
under steady state conditions. This is reasonable if the
166
equilibrium constant for formation of M-M or the amount of L formed from
dissociation of M-L are small. Consistent with these assumptions, VT-NMR analysis
of a C
6
D
6
solution of Ph-Ir-Py at 100
o
C showed no detectable amounts of free
pyridine or dinuclear complexes. These results are also consistent with previous
theoretical calculations that indicate that both the reactions are endoergic reactions
with ΔG > 5 kcal/mol.
86a,b

2 M-L "M-M"
-2L
+2L
=
=
k
obs
Rate
[M-L]
[L]
Rate
[M-L]
2
[L]
2
k
obs
M-L "M"

Rate k
obs
[M-L]
[M-L]
[L]
2
Rate
[M-L] [L]
k
obs
"M-M"
Ol + Ar-H
Ar-R
"M"
Ol + Ar-H Ar-R
-L
+L
Dinuclear Catalyst Mononuclear Catalyst
= TOF = = TOF =

Scheme 4.1. TOF dependence on [L] for dinuclear and mononuclear complexes.

If the catalyst is the dinuclear complex M-M, plotting the TOF (TOF =
Rate/ML
a
; ML
a
= ML) vs. [1/L
2
] should yield a straight line. On the other hand, if
the active catalyst is the 5-coordinate mononuclear species “M” generated by the loss
of L from added M-L, then plotting TOF vs. [1/L] should yield a straight line at
constant [M-L].
Figure 4.5 shows that a plot of TOF versus [1/L] for Ph-Ir-Py gives a linear
correlation (R
2
= 0.99), strongly indicating an active mononuclear catalyst.
167

R
2
= 0.9917
0
0.0002
0.0004
0.0006
0.0008
0.001
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4
1/Py Equivalents
Turn Over Frequency (s
-1
)

Figure 4.5. TOF vs. 1/Py catalyzed by Ph-Ir-Py.

4.2.5 Why is no β-hydride elimination observed?

It is well known that metal-alkyl complexes possessing β-CH bonds are
susceptible to facile β-hydride elimination reactions.
93
However, no olefinic products
are observed during the hydroarylation reactions between benzene and ethylene or
styrene.
84,85
Additionally, in the stoichiometric CH activation reactions of
PhCH
2
CH
2
-Ir-Py and CH
3
CH
2
-Ir-Py with benzene, analysis of the liquid and gas
phases of these reactions by NMR and GC/MS showed that neither olefinic products
(such as styrene or ethylene) were formed, either free or complexed to Ir, nor Ir-
hydride products.
85
Since such products would be expected from irreversible β-
hydride elimination reactions from the coordinatively unsaturated intermediates cis-
PhCH
2
CH
2
-Ir- and cis-CH
3
CH
2
-Ir- , this complete lack of olefinic products could
suggest that β-hydride elimination reactions either do not occur, or are reversible and
unproductive. The observation that only PhCH
2
CH
2
D is quantitatively formed from
168
the stoichiometric CH activation of C
6
D
6
with PhCH
2
CH
2
-Ir-Py naively suggests that
β-hydride elimination reactions do not occur. However, this result would also be
observed if the β-hydride elimination from PhCH
2
CH
2
-Ir-Py is reversible,
unproductive and significantly more stable than the branched alkyl PhCH(CH
3
)-Ir-Py
product, and/or if CH activation from PhCH
2
CH
2
-Ir-Py was competitive with the β-
hydride elimination reaction. Given these plausible possibilities, the selective
formation of PhCH
2
CH
2
D from CH activation of C
6
D
6
with PhCH
2
CH
2
-Ir-Py does
not rule out the possibility that reversible, unproductive, β-hydride elimination
reactions occurs in these O-donor complexes. Also, previous DFT calculations
86
have
suggested that these O-donor Ir-alkyls do undergo reversible β-hydride elimination,
but that such reactions are reversible and unproductive, because the barrier for
dissociative loss of olefin from the saturated, 6-coordinate hydride intermediates is
higher than the barrier for the CH activation step, see Figure 4.6.
169
O
Ir
O
O
Py
O
Ph
Ir
O O
O O
N
Ph
O
Ir
O
O
H
O
O
Ir
O
O
Py
O
Ph
C
6
D
6
PhCH
2
CH
2
D
PhCHD CH
3
C
6
D
6
Ph
- Py Py
D
5
O
Ir
O
O
O
Ph
O
Ir
O
O
O
Ph
- L
- L
D
5
Ir
O O
O O
N
Ir
O O
O O
Ph
N
D
5
Ph-d
5
-Ir-Py
PhCH
2
CH
2
-Ir-Py
Py - Py
cis-PhCH
2
CH
2
-Ir-Py
cis-PhCH(CH
3
)-Ir-Py
Ir
O O
O O
H
Ph
+

Figure 4.6. Reversible versus irreversible β-hydride elimination
Since metal alkyls that possess β-CH bonds, but do not react to generate
olefins, would be useful in a variety of catalytic reactions (polymerization,
hydroarylation, etc.), the α-
13
C-labelled complex, CH
3
13
CH
2
-Ir-Py, was synthesized
and the CH activation with C
6
D
6
was examined. This ethyl-Ir complex was chosen as
an alkyl-Ir-L complex that would not show a steric or electronic bias to possible
[1,2]-Ir-carbon rearrangements from reversible β-hydride elimination reactions.
CH
3
13
CH
2
-Ir-Py was synthesized using
13
C-labelled Et
2
Hg. As shown in Figure 4.7,
if reversible β-hydride elimination does occur with CH
3
13
CH
2
-Ir-Py, this would lead
to migration of the
13
C-label from α to the β-position and formation of the
170
13
CH
3
CH
2
-Ir-Py regio-isotopomer. Additionally, carrying out this reaction in C
6
D
6
as
the reaction solvent is expected to lead to two regio-isotopomers of ethane,
13
CH
3
CH
2
D and
13
CH
2
DCH
3
(formed by C-D activation of the C
6
D
6
solvent and loss
of ethane) if reversible β-hydride elimination does occur, or only
13
CH
2
DCH
3
if no
13
C-migration occurs. Importantly, measurements of the rate of
13
C migration in the
13
C-labelled CH
3
13
CH
2
-Ir-Py and/or the relative ratio of the two regio-isotopomers of
ethane could both be expected to provide information on the relative rates of
reversible β-hydride elimination versus benzene CH activation. For example, if the
reversible β-hydride reaction is fast compared to benzene CH activation, then
approximately equal amounts of Ir-CH
2
13
CH
3
, Ir-
13
CH
2
CH
3
as well as
13
CH
3
CH
2
D
and
13
CH
2
DCH
3
would be observed under arene CH activation conditions. The
labeled olefin is assumed to be able to rotate rapidly around the Ir-C
2
H
4
axis,
equilibrating the cis-
13
CH
3
CH
2
-Ir-L and cis-CH
3
13
CH
2
-Ir-L species.

171
O
Ir
O
O
L
O
Ir
O O
O O
N
*
O
Ir
O
O
H
O
O
Ir
O
O
L
O
C
6
D
6
H
3
CCH
2
D H
3
CCH
2
D
*
*
*
*
*
C
6
D
6
- L L
D
5
O
Ir
O
O
O
O
Ir
O
O
O
O
Ir
O
O
O D
*
D
5
- L
- L
D
5
( )
*
O
Ir
O
O
O D
*
D
5
*
*
L = Pyridine
Ir
O O
O O
N
Ir
O O
O O
N
*
1-
13
CH
2
CH
3 1-CH
2
13
CH
3
D
5
1-Ph-d
5
Ir
O O
O O
H
Ir
O O
O O
H
N
-
13
CH
2
CH
2 + Pyr

Figure 4.7. Possible products expected from heating CH
3
13
CH
2
-Ir-Py in C
6
D
6
to
generate ethane by CH Activation.

As reported earlier,
85
treatment of CH
3
CH
2
-Ir-Py with C
6
D
6
at 110
o
C leads
to quantitative and irreversible formation of Ph-d
5
-Ir-Py and mono-deuterioethane
(C
2
H
5
D) in stoichiometric amounts. This formation of mono-deuterioethane is also
observed upon CH activation of C
6
D
6
with the
13
C-labelled complex, CH
3
13
CH
2
-Ir-
Py. However, monitoring the progress of the CH activation reaction by
13
C{
1
H}
172
(with sufficiently long relaxation delay to afford accurate integration of the
13
C
resonances) and
1
H NMR yielded additional information. As shown in Figure 4.8, a
time dependent study of the reaction progress shows evidence for the migration of
the
13
C label of CH
3
13
CH
2
-Ir-Py (~ -9 ppm) from the α to the β-position, resulting in
a formation of the β-
13
C regio-isotopomer,
13
CH
3
CH
2
-Ir-Py (~18 ppm).
15
165
t=0 min
45
75
105
135
15 10 5 0 -5 -10 -15 PP
15
165
t=0 min
45
75
105
135
15 10 5 0 -5 -10 -15 PP

Figure 4.8. Time dependent
13
C NMR spectra for the reaction of CH
3
13
CH
2
-Ir-
Py (-9 ppm) with C
6
D
6
to form
13
CH
3
CH
2
-Ir-Py (18 ppm) and two
regioisomers of ethane (8 ppm).

Eq. 2

It is also clear from Figure 4.8 that a steady state concentration of the β-
isomer,
13
CH
3
CH
2
-Ir-Py (~18 ppm), is attained that is substantially lower than the
CH
3
*CH
2
-Ir-Py *CH
3
CH
2
-Ir-Py
C
6
D
6
D
+
Ir
O O
O O
N
D
Ir
O O
O O
N
Ph-Ir-Py
+
173
amount of CH
3
13
CH
2
-Ir-Py present (-9 ppm). This indicates that reversible β-hydride
elimination occurs and accounts for the α to β-migration of the
13
C-label of
CH
3
13
CH
2
-Ir-Py, and importantly, the lack of formation of equimolar amounts of
CH
3
13
CH
2
-Ir-Py and
13
CH
3
CH
2
-Ir-Py as ethane is lost with concomitant CH
activation of the benzene solvent strongly indicates that the α to β-migration of the
13
C-label is slower than both the CH activation of benzene and the formation of
ethane and Ph-d
5
-Ir-Py. This result is confirmed by analysis of the dissolved ethane
that is produced from arene CH activation. Thus, both regio-isotopomers of mono-
2
H,
13
C-ethane (8 ppm composed of a singlet from
13
CH
3
CH
2
D and a 1:1:1 triplet
from
2
H-
13
C coupling in
13
CH
2
DCH
3
,) are generated from the CH activation of C
6
D
6

as shown in Eq. 2. Simulation of this pattern readily shows that the predominant
ethane product is
13
CH
2
DCH
3
with ~ 16 mol % of
13
CH
3
CH
2
D and that this ratio is
essentially constant over the course of the reaction to generate ethane. Analyses by
1
H NMR confirm (on the basis of the acac resonances) that Ph-d
5
-Ir-Py is the only
new (acac)
2
Ir product formed on loss of ethane.
Scheme 4.2. Kinetic scheme for CH activation and α to β
13
C-migration.

CH
3
-
13
CH
2
-Ir-Py
13
CH
3
-CH
2
-Ir-Py
PhH PhH
k
CH
k
CH
k
β
k
β
Ph-d
5
-Ir-Py
CH
3
-
13
CH
2
D
+
Ph-d
5
-Ir-Py
CH
2
D-
13
CH
3
+

174

16 . 0
1
] [
] [
] [
] [
≈ = =
β
CH
3
13
2
2
13
3
3
13
2
2
13
3
k
[PhH] k
CH D CH
D CH CH
CH D CH
D CH CH
d
d

5 . 0
] [
] [
≈ =
[PhH] CH D CH
D CH CH
k
k
3
13
2
2
13
3
β
CH

Kinetic analysis of a reaction scheme (Scheme 4.2), assuming steady state
conditions, for the formation of
13
CH
3
CH
2
-Ir-Py and that the CH activation reaction
has a bi-molecular reaction dependency on the concentration of benzene while the
13
C migration occurs via a unimolecular β-hydride elimination reaction pathway
allows the ratio of rate constants for the CH activation to β-hydride elimination (k
CH

: k
β
) gives an ratio of
13
CH
2
DCH
3
and
13
CH
3
CH
2
D of ~0.5 produced during the
reaction.
This comparable value for CH activation and β-hydride elimination would
seem to suggest a common rate determining intermediate for both processes, as was
seen for the CH activation and trans-cis isomerization reaction. As in that case, this
intermediate is most likely the cis-5-coordinate species, cis-R-Ir- , where R =
CH
3
CH
2
-. Indeed, theoretical calculations (Figure 4.9) confirm that the energy of this
cis-Et-Ir- intermediate is approximately equal to the barrier for CH activation, and
the two processes are also predicted to have equivalent rates.
86a, b

175

Figure 4.9. B3LYP potential energy surface for β-hydride elimination, olefin
hydride formation, and CH activation (kcal/mol).

(Red lines show CH activation of C
6
H
6
. Black lines show reversible β-hydride
elimination followed by CH activation. Enthalpies taken from references 10a,b).
These findings should be contrasted to the related but more electron rich Ir(III)
complex, [Cp*(PMe
3
)IrR(OTf)], which does undergo irreversible β-hydride
elimination to form very stable olefin metal hydrides that prevents catalysis.
94
Also,
another closely related molecule, TpIr(olefin)
2
, has been shown to transform into
Ir(III) vinyl hydride isomers, [TpIr(CH=CH
2
)H(C
2
H
4
)], which are also the
thermodynamically most stable products.
95
These results point to an important
characteristic of these less electron-rich O-donor complexes, that is, even though the
β-hydride elimination reaction to generate olefinic metal complexes is kinetically
176
facile, unlike the more electron-rich complexes, the formation of the resulting olefin
metal hydride is reversible.

4.2.6 Reaction order of substrates
Based on the proposed mechanism
8
and the above results, we can formulate a
suggested rate law using the usual steady state approximation and the assumption
that the pre-equilibrium term involving L is small. As can be seen in this rate law,
under conditions where L = L
0
(at small K and L
0
= ML
0
) it is predicted that the
reaction rate will be inversely dependent on added L
0
with a first order dependence
on olefin and benzene. In the presence of excess L, there should also be a first order
dependence on catalyst concentration. The results of the kinetic investigation of the
components of the proposed rate law are shown in below.

Scheme 4.3 Proposed rate law.

177

4.2.6.1 Kinetic dependence of Hydroarylation on benzene concentration

The rate law indicates a linear dependence on arene concentration. Earlier
results from stoichiometric arene CH activation reactions showed that cyclohexane is
an inert solvent and could be used as a diluent. The reaction order on benzene was
determined using cyclohexane solvent with Ph-Ir-Py as the catalyst. Figure 4.10
shows a linear relationship between benzene concentration and TOF, which is
expected for a first-order dependence on benzene.

R
2
= 0.9711
0.00E+00
1 .00E-03
2.00E-03
3.00E-03
4.00E-03
0 246 8 10 12
Benzene /[M]
Turn Over Frequency (s-1)

Figure 4.10. Kinetic dependence of hydroarylation on benzene concentration

4.2.6.2 Kinetic dependence of Hydroarylation on olefin concentration

178
The hydroarylation of olefins to generate mono-alkylarenes is typically
carried out at ~200 °C with 5 – 10 mM catalyst loading in neat arene (which is both a
reactant and the solvent) and 10 – 20 mol % olefin. Studies of olefin concentration
(with styrene as the olefin) under these conditions show a complicated dependence
(Figure 4.11). The initial increase in the TOF is consistent with the first order
dependence on olefin, as can be seen from the approximately linear dependence on
the styrene concentration up to ~3 M. The inhibition at higher concentrations has
been reported earlier, and is likely a result of ground-state stabilization by the high
concentration of olefin, which is a good ligand for the (acac)
2
Ir center.
84, 86

0.00E+00
1.00E-03
2.00E-03
3.00E-03
4.00E-03
012345
Styrene / [M]
Turn Over Frequency (s-1)

Figure 4.11. Kinetic dependence of hydroarylation on olefin concentration.

4.2.6.3 Kinetic dependence of Hydroarylation on catalyst concentration

As the concentration of free L during catalysis could not be easily determined,
we carried out reactions in the presence excess L (L
0
>1 eq of added catalyst) as this
allows for the assumption that the concentration of L under experimental conditions
179
would be equal to L
0
, given the small value of K. Under these conditions,
approximations to the rate law predict that the rate should be first-order dependant on
catalyst concentration. Figure 4.12 shows a plot of catalyst concentration versus rate
of hydroarylation which is consistent with the above prediction.
0.00E+00
4.00E-06
8.00E-06
2.00E-03 5.00E-03 8.00E-03 1.10E-02
Catalyst [M]
rate of hydroarylation

Figure 4.12. Rate vs. catalyst concentration for Ph-Ir-Py with excess Py.

4.2.7 Evidence for proposed mechanism

The proposed mechanism of the hydroarylation reaction catalyzed by the O-
donor, (acac)
2
Ir(III) complexes is shown in Figure 4.2. As previously reported, the
trans complexes are the kinetic product that are isolated during synthesis, and upon
heating lead to the quantitative formation of the thermodynamically stable cis
product.
85
The reaction mechanism is proposed to proceed via three key steps: A) A
pre-equilibrium, or isomerization step(s), that generates the “active catalyst”,
independent of which R-Ir-L complex is used to catalyze the reaction, B) an olefin
180
insertion step, and C) a CH activation step. An important prediction of the proposed
mechanism is that the two key cis-intermediates, cis-Ph-Ir-Ol and cis-PhCH
2
CH
2
-Ir-
Bz, are proposed to be in equilibrium with the corresponding trans-R-Ir-L
complexes, where L is an added ligand. This is important because it allows entry into
the proposed catalytic cycle from the trans-complexes that can be readily
synthesized. We have been unable to synthesize or isolate the active catalysts
species.
Alternative to CH activation mechanisms, alkylation of arenes can occur
under Lewis acid catalyzed conditions. The (acac)
2
Ir(III) complexes are considered
“soft” Lewis acids,
77
especially given the recent precedent for the use of transition
metal complexes such as Au, Pt and Pd as general Lewis acids for catalyzing
reactions between alkenes/alkynes and arenes.
96
However, the central observation
that the hydroarylation reaction catalyzed by the (acac)
2
Ir(III) complexes generates
alkylarenes with anti-Markovnikov regioselectivity would tend to rule out
mechanisms occurring via carbocation intermediates. Several other observations also
indicate that a carbocation intermediate is not involved:
1) Under Lewis acid catalyzed conditions, alkylarenes are more reactive than
the parent arenes toward alkylation; in the (acac)
2
Ir(III) catalyzed hydroarylation
alkyl benzenes are less reactive.
84

2) Lewis acid catalyzed reactions are typically inhibited by greater than one
equivalent of water relative to the catalyst. However, the (acac)
2
Ir(III) catalysts are
not inhibited by addition of several equivalents of water (Table 4.1, entries 6 and 9).
181
3) Lewis acids readily catalyze the exchange of alkyl groups between
alkylarenes. However, the (acac)
2
Ir(III) complexes do not catalyze reactions of
diethylbenzene with benzene to generate mono-ethyl benzene under hydroarylation
conditions.
4) The reaction rates of Lewis acid catalyzed reactions strongly correlate with
the strength of the Lewis acid. However, while IrCl
3
could be expected to be a
stronger Lewis acid than the (acac)
2
Ir(III) complexes, IrCl
3
does not catalyze the
hydroarylation reactions under identical conditions.
5) The observation that other Ir catalysts show no hydroarylation activity
strongly suggests a unique catalytic activity for the (acac)
2
Ir(III) complexes.
84

Nevertheless, the central approach to experimentally elucidate reaction
mechanisms is to synthesize well-defined complexes that are proposed to be
involved in the catalytic cycle and to show that the chemistry of these complexes is
consistent with the observed catalysis, with respect to rate and selectivity and the
observed resting state of the catalyst. The current mechanism has been divided into
three main sections which constitute the pre-equilibrium steps, olefin insertion, and
CH activation.
4.2.7.1 Pre-equilibrium steps

As can be seen in Figure 4.2, it is proposed that all the various R-Ir-L as well as
dinuclear ([R-Ir]
2
) complexes are catalyst precursors that in a series of pre-
equilibrium steps (that can involve ligand loss, trans-cis isomerization, arene CH
activation and olefin coordination) lead to the same active catalyst, cis-Ph-Ir-Ol,
182
independent of the starting complex. Mechanisms involving C-H activation
84
and
insertion
97
are typically inner-sphere reactions and as such require a vacant
coordination site on the metal for coordination of the substrate.
As shown in Table 4.1, the ligand “L” of the O-donor (acac)
2
Ir(R)(L) complexes
significantly influences the rate of the catalytic hydroarylation reaction. Strongly
donating ligands, such as pyridine (Table 4.1, Entry 3-6), severely inhibit the
catalysis whereas labile ligands, such as CH
3
OH and H
2
O (Table 4.1, Entry 7), are
weaker inhibitors. These TOFs have been correlated to the calculated relative
energies of these complexes, and a linear correlation between the relative energy of
the ground states and TOFs were found.
86

Strong evidence for a pre-equilibrium dissociative loss of L has been shown
previously,
85
where exchange of free pyridine with coordinated pyridine with Ph-Ir-
Py and CH
3
-Ir-Py, is rapid at room temperature and independent of the concentration
of added free Py, as expected for a dissociative process. Previously, the activation
parameters for the rate of exchange for Ph-Ir-Py were measured to ΔH
‡
= 22.8 ± 0.5
kcal/mol; ΔS
‡
= 8.4 ± 1.6 eu; and ΔG
‡
298K
= 20.3 ± 1.0 kcal/mol.
85
Similarly,
pyridine exchange for CH
3
-Ir-Py was found to be dissociative, with activation
parameters of ΔH
‡
= 19.9 ± 1.4 kcal/mol; ΔS
‡
= 4.4 ± 5.5 eu; and ΔG
‡
298K
= 18.6 ±
0.5 kcal/mol.
85
This rapid rate relative to the hydroarylation catalysis is consistent
with the ligand loss being a pre-equilibrium step.
Given that these complexes undergo trans-cis isomerization of the acac groups, we
also investigated the pyridine exchange with cis-Ph-Ir-Py. NMR spectroscopic
183
studies show that pyridine exchange with cis-Ph-Ir-Py is much slower than that of its
trans analog, which is consistent with the theoretical predictions.
8
Thus, Ph-Ir-Py
shows exchange at room temperature, but the cis-Ph-Ir-Py undergoes pyridine
exchange only above 160°C.
4.2.7.2 Olefin insertion

To generate the proposed active catalyst cis-Ph-Ir-Ol, olefin coordination is
required. This most likely occurs in a manner similar to conversion of trans-Ph-Ir-
Py to cis-Ph-Ir-Py, i.e. by ligand loss, cis-trans isomerization and coordination of
olefin. However, while olefin complexes can be observed by in situ NMR
spectroscopy, attempts at generating and isolating such olefin complexes with
various trans-R-Ir-L complexes failed, presumably due to instability of the olefin
complexes. NMR analysis showed that addition of ethylene to the dinuclear
complex, [Acac-Ir]
2
, leads to a new mononuclear complex containing coordinated
ethylene. However, all attempts at isolating this complex failed. The instability of the
olefin complex(es) is consistent with the lability of the Py and H
2
O complexes to
substitution at room temperature. Ethylene does not coordinate as strongly with
Ir(acac)
2
(R) as other π-acids (such as Py and CO), preventing isolation of an olefin
complex. Furthermore, our theoretical calculations showed that the five coordinate
cis-Ph-Ir- species is higher in energy than the insertion transition state, suggesting
that the complex undergoes further reaction under any conditions that allow for its
generation.
86

184
The olefin insertion step with the Ph-Ir olefin intermediate, cis-Ph-Ir-Ol, is
proposed to control the anti-Markovnikov regioselectivity. To investigate this step
we examined the stoichiometric reaction of Ph-Ir-Py with various olefins as shown in
Figure 4.13. As can be surmised from the reaction stoichiometry, a hydrogen donor
is required for the generation of alkylarenes. In the proposed catalytic reaction
mechanism, this is provided by the arene co-reactant in the CH activation step, or
from the olefin via vinylic CH bond activation. However, since the CH activation
step is much faster than insertion, mesitylene was used as a solvent (rather than
benzene) to allow for only stoichiometric reactivity. Control experiments showed
that the olefin hydroarylation reaction with benzene and propylene catalyzed by Ph-
Ir-Py could be carried out in the presence of added mesitylene, suggesting the
mesitylene did not significantly alter the hydroarylation chemistry. NMR spectra of
these reactions show that the organometallic complex after the reaction is either
Mes-Ir-L or Vinyl-Ir-L, the latter being the major product. Both Mes-Ir-L and Vinyl-
Ir-L have been reported previously.
98
,
99
The non-intrusive nature of mesitylene is
also indicated by the experimental observation that there was a significant amount of
deuterium incorporation into the ethylene (10%) when C
6
D
6
was employed for
hydroarylation. Since mesitylene is present in significantly larger concentrations than
C
6
D
6
, this suggests that the CD activation from C
6
D
6
is faster than CH activation
from mesitylene.
The reaction was typically carried out by reacting 15 mmol Ph-Ir-Py with
olefins such as propylene, ethylene, styrene and 1-hexene in liquid mesitylene at 180
185
ºC for 20 min. The gas and liquid phases were then analyzed by GC/MS to identify
and quantify reaction products. The solvent was then removed and the non-volatile
reaction products were dissolved in CDCl
3
and analyzed by NMR.

R
R
+
AB C
+

Figure 4.13. Stoichiometric products after treatment of Ph-Ir-Py with R-CH=CH
2
,
R= C
6
H
5
, CH
3
, C
4
H
9
.

Table 4.3 gives the results of the stoichiometric reactions investigated.
Addition of styrene (R =Ph) to Ph-Ir-Py in mesitylene yields 40% hydroarylated
products, dihydrostilbene and 2,2-diphenylethane in a 98:2 ratio, along with 60%
benzene (the total yield of A + B + C is 100% with respect to Ph-Ir-Py). Similarly,
addition of 1-hexene (R = C
4
H
9
) leads to the formation of 1-phenyl hexane and 2-
phenyl hexane in a 69:31 ratio, along with free benzene. Identical regioselectivity
was observed when cis-Ph-Ir-Py was used in lieu of Ph-Ir-Py.
Table 4.3. Insertion products of olefins (mono-substituted ethylenes) with Ph-Ir-
Py
a

R
A
(%)
B
(%)
A : B C (%)
CH
3
b
40 27 61:3933
Ph 39 1 98:2 60
C
4
H
9
50 25 69:3125

186
a
All reactions carried out with 15mmol of Ph-Ir-Py in 1mL of mesitylene at 180
°C for 20min.
b
0.96 Mpa of propylene with 2 MPa of N
2
.

In addition to hydroarylation products, a substantial amount of benzene is
generated along with derivatives of the corresponding vinyl-Ir-L complex. Benzene
should be the product of the reverse C-H transfer step (Figure 4.2), i.e. Ph-Ir-Py +
CH
2
=CHR Æ cis-Ph-Ir-(CH
2
=CHR) + Py Æ cis-(CH
2
=CR)-Ir-C
6
H
6
+ Py Æ
CH
2
=CR-Ir-Py + C
6
H
6
. During the catalytic cycle, this transformation is expected to
be reversible and would lead back to the olefin intermediate, cis-Ph-Ir-Ol. In the
stoichiometric reaction, however, the concentration of benzene is sufficiently low as
to trap the vinyl intermediate.
From these results, there are two important observations. First, the
stoichiometric reactions of Ph-Ir-Py with olefins results in the same ratio of
branched to linear alkylarene products as observed in olefin hydroarylation catalysis.
This suggests that our catalyst structure is maintained in the catalytic cycle, and no
stoichiometric induction is required for catalysis. Second, the presence of both
hydroarylated product and benzene in the non-complete stoichiometric reactions
shows that both C-H activation and insertion occurs in this system. However, the
observed relative rates of A + B vs. C does not allow us to determine relative rates of
insertion vs. C-H activation, as the C-H activation is reversible while the insertion is
not.
4.2.7.3 CH activation step

187
Ample evidence for this step has been reported earlier
85
and is also observed
in the facile, clean reaction of R-Ir-Py with benzene to generate the Ph-Ir-Py
complex. The activation parameters (ΔH
‡
= 41.1 ± 1.1 kcal/mol; ΔS
‡
=11.5 ± 3.0 eu;
ΔG
‡
298k
= 37.7 ± 1.0 kcal/mol) for CH activation were previously obtained, using
CH
3
-Ir-Py as starting material at a constant ratio of [Py]/[C
6
D
6
] = 0.045.
85
The
PhCH
2
CH
2
-Ir-Py complex was found to react at essentially the same rate as CH
3
-
Ir-Py and showed similar temperature dependence.
Since there is rapid scrambling of mixtures of benzene and deuteriobenzene
(relative to the hydroarylation reaction, see below), a kinetic isotope effect could not
be obtained under hydroarylation conditions using mixtures of C
6
H
6
and C
6
D
6
.
However, comparison of the absolute rates of catalytic hydroarylation reactions
using the same olefin, such as styrene and catalyst, Ph-Ir-Py, in separate
experiments with C
6
H
6
and C
6
D
6
solvents showed no kinetic isotope effect. Carrying
out the catalysis with ethylene and C
6
D
6
also shows no kinetic isotope effect, and
yields as the major product C
6
D
5
-CH
2
-CH
2
D (as identified by
13
C NMR
spectroscopy). Under these conditions, only a low level of deuterium is incorporated
into unreacted ethylene as estimated by GC-MS spectrometry.
4.2.7.4 Resting state of catalyst

The active catalyst is proposed to be composed of a cis-(acac)
2
Ir(III) motif.
Comparative hydroarylation studies between trans-Ph-Ir-Py and cis-Ph-Ir-Py were
carried-out at 180
o
C, and it was determined that the trans isomer is 4.0 ± 0.4 times
more active than the cis isomer, cis-Ph-Ir-Py. The TOF of the trans complex begins
188
to decrease at longer reaction times, most likely because it is converted to the cis
form, which is predicted to be more thermodynamically stable by ~ 2 kcal/mol (see
Figure 4.14).
85
However, it is possible that the active catalyst may be generated by
loss of the acac ligands. Several observations indicate this is unlikely. 1) The catalyst
is long lived (see Figure 4.4). 2) The resting state of the catalyst after >50 turn-overs
(with ethylene) is Ph-Ir-Py. 3) The O-donor (acac)
2
Ir(III) complexes are thermally
stable to exchange in the presence of acac-H and protic acids such as HOAc and
CF
3
CO
2
H. 4) trans-Ph-Ir-Py is thermally stable in benzene and cleanly undergoes
CH activation and olefin insertion reactions to generate the products observed in the
hydroarylation reactions. Furthermore, our reported theoretical results showed that
loss of an acac group costs ~50 kcal/mol, i.e. significantly more than the activation
energy of the reaction.
86
These observations strongly suggest that the (acac)
2
Ir(III)
motif is part of the “active catalyst.”

4.2.7.5 Complete mechanism and comparison to DFT

As mentioned earlier, hydroarylation can be divided into three steps (pre-
equilibrium, insertion of olefin and CH activation of arene). Previously calculated
activation parameters for CH activation, combined with experimental kinetic isotope
studies, revealed that trans to cis isomerization is the rate determining step.
85
Earlier
DFT studies also predicted that this step is rate determining for the hydroarylation
starting from any trans configured Ir(acac)
2
.
86
Figure 4.14 shows a comparison of
189
experimental and DFT results for the potential energy surface of hydroarylation and,
and they are found to be in good agreement. We thus believe that the theoretical
results are a good description of the potential energy surface, not only for our model
catalyst Ph-Ir-Py, but for all Ir(acac)
2
type systems.
-Pyr
+ C
2
H
4
+ C
2
H
4
Ir
O O
O O
Ph
Py
Ir
O O
O O
Ph
O
Ir
O
O Ph
Py
O
O
Ir
O
O Ph
O
CH
3
H
O
Ir
O
O
O
O
Ir
O
O
O
Ph
O
Ir
O
O
Ph
O
TS 3
O
Ir
O
O
O
Ph
TS1
O
Ir
O
O
Ph
O
TS 2
O
Ir
O
O
Ph
O
Ir
O O
O O
Py
Ph
+
+ C
6
H
6
Ir
O O
O O
Ph
Ir
O O
O O
CH
3
Py
OR
41.1
19.9
22.8
0.0
0.0
16.6
21.4
42.0
44.3
36.0
42.8
9.4
9.5
-2.3
-3.3
34.0
34.0
22.6
24.4
11.8
11.1
23.3
22.6
14.3
20.2
-12.3
-13.1
-1.2
2.2
-16.3
-16.9

Figure 4.14. Comparison of previously reported B3LYP (ΔH
solv
top and ΔH
gas

bottom) and experimental values for the hydroarylation (shown only
for ethylene). Experimental values in blue boxes. Values taken from
references 9 and 10 (kcal/mol).
4.3 Conclusion

The O-donor R-Ir-L and [R-Ir]
2
complexes are active and stable catalysts for
the hydroarylation of unactivated olefins with unactivated arenes. All O-donor
complexes studied catalyze the hydroarylation of unactivated olefins, albeit at
varying rates. This reaction is very selective and generates saturated products only,
although it undergoes reversible and unproductive β-hydrogen elimination as
190
determined by labeling studies. The hydroarylation reactions studied are not under
thermodynamic control. The catalyst is a mononuclear species and stable at high
temperatures. Mechanistic studies suggest that the mechanism involves pre-
equilibrium steps, followed by insertion of olefin, and finally CH activation of
benzene to yield the linear alkyl benzene product and regenerate the catalyst.

4.4 Experimental Section

Spectroscopy. Liquid phases of the reaction mixtures were analyzed with a
Shimadzu GC-MS QP5000 (ver. 2) equipped with cross-linked methyl silicone gum
capillary column, DB5. Gas measurements were performed using a GasPro column
on the same instrument. The retention times of the products were confirmed by
comparison to authentic samples. NMR spectra were obtained on a Bruker AM-360
(360.138 MHz for
1
H and 90.566 MHz for 13C), Bruker AC-250 (250.134 MHz for
1H and 62.902 MHz for
13
C) or on a Varian Mercury 400 (400.151 MHz for
1
H and
100.631 MHz for
13
C) spectrometer. Chemical shifts are given in ppm relative to
TMS, or to residual solvent proton resonances. All carbons are singlets unless
otherwise mentioned.
Materials and Analyses. All manipulations were carried out using glovebox
and high vacuum line techniques. Benzene, benzene-d
6
, toluene-d
8
and THF were
purified by vacuum transfer from sodium benzophenone ketyl. CD
2
Cl
2
and pyridine
were dried by vacuum transfer from CaH
2
. Synthetic work involving iridium
complexes was carried out in an inert atmosphere in spite of the air stability of the
complexes. Reagent-grade chemicals and solvents were used as purchased from
191
Aldrich or Strem. CH
3
13
CH
2
I was purchased from Cambridge Isotopes Inc. and was
used as received. Complexes R-Ir-L, [R-Ir]
2
and cis R-Ir-L,
85,100
and
diethylmercury
101
were prepared as described in the literature. Elemental analyses
were done by Desert Analytics laboratory; Tucson, Arizona.
[(CH
3
-
13
CH
2
)Ir(O,O-acac)
2
]
2
[CH
3
13
CH
2
-Ir]
2
: [CH
3
13
CH
2
-Ir]
2
was synthesized in
the same fashion as Acac-C-Ir-H
2
O (97 mg, 0.19 mmol) and
13
C enriched
diethylmercury (630 mg, 0.24 mmol).
85
The crude reaction mixture was developed
on a preparatory silica TLC plate with THF: ether (1:1) as an eluent. After pumping
off the solvent, the solid was redeveloped on a preparatory silica TLC plate using
1:1:2 THF: CH
2
Cl
2
: hexanes. The orange band R
f
= 0.87 was scraped off and
extracted with CH
2
Cl
2
and THF. The solvent was pumped off to yield an orange
powder (0.0410g, 51% yield). (For simplicity, CD
3
OD was chosen)
1
H NMR
(CD
3
OD): δ 5.47 (s, 2H, acac-C
3
H), 2.83 ( dq,
1
JCH = 128.5,
3
J
HH
=7.7, -13CH
2
-Ir),
1.76 (s, 12H, acac-CH
3
), 0.198 (m, 3H, CH
3
-
13
CH
2
-Ir)
13
C {1H} few scans
(CD
3
OD): δ -17.59 (s, -
13
CH
2
-Ir).
[Ir(O,O-acac)
2
(
13
CH
2
CH
3
)(Py)] (CH
3
13
CH
2
-Ir-Py): CH
3
13
CH
2
-Ir-Py was
synthesized from [CH
3
13
CH
2
-Ir]
2
(100mg, 0.119 mmol) in CHCl
3
and pyridine (1
mL, 12.3 mmol).
85
Isolated Yield: 115 mg, >95%.
1
H NMR (C
6
D
6
): δ 8.69 (d, 2H, o-
Py), 6.84 (t,
1
H, p-Py), 6.56 (t, 2H, m-Py), 5.10 (s, 2H, acac-C
3
H), 3.47 (dq, 2H,
1
J
CH

= 125.3, -
13
CH
2
-Ir), 1.60 (s, 12H, acac-CH
3
), 1.23 (m, 3H, CH
3
-
13
CH
2
-Ir).
13
C {
1
H}
NMR (C
6
D
6
): δ 182.69 (acac C=O), 149.57 (o-py), 136.32 (p-py), 124.38 (m-py),
102.76 (acac-CH), 26.66 (acac-CH
3
), 15.99 (d,
1
J
CC
= 34, CH
3
), -10.56 (-
13
CH
2
-Ir).
192

Cis-[Ir(O,O-acac)
2
(Ph)(Py)] (cis-Ph-Ir-Py): In addition to the method for the
synthesis of cis-Ph-Ir-Py we reported previously,
85a
this is another method we have
used as well. A 5 mL thick-walled glass tube equipped with a resealable Teflon valve
and a magnetic stir bar was charged with 2.5 mL of benzene containing Ph-Ir-Py (10
mg, 0.02 mmol). The tube was heated for 100 h in a well-stirred oil bath maintained
at 180 °C. The autoclave was cooled thereafter, and the solvent was removed in
vacuo and the solid obtained was washed with cold methanol to yield the complex.
Isolated yield: >90%.
Reaction Procedure for the Olefin Arylation: A 3 mL stainless steel autoclave,
equipped with a glass insert and a magnetic stir bar was charged with 1 mL of
distilled benzene and 3-5 mg (5 mmol, ~0.1 mol %) of catalyst (unless otherwise
mentioned). The reactor was degassed with nitrogen, pressurized with 0.96 MPa of
propylene with an extra 2.96 MPa of nitrogen. The autoclave was heated for 30 min
in a well stirred heating bath maintained at 180 °C. The liquid phase was sampled
and the product yields were determined by GC-MS using methyl cyclohexane as an
internal standard, introduced into the reaction solution after the reaction.
Insertion Reactions of Olefins with Ph-Ir-Py: A 3 mL stainless steel autoclave,
equipped with a a glass insert and a magnetic stir bar was charged with distilled 1 ml
of mesitylene and 15 mg of Ph-Ir-Py. The autoclave was heated at 180 °C for 10 min
after adding olefin. The liquid phase was sampled and the product yields were
determined by GC-MS using methyl cyclohexane as an internal standard, introduced
193
into the reaction solution after the reaction. Following are the amount of olefin added
in the above insertion reactions: 2 MPa of ethylene, 0.96 MPa of propylene with an
extra 2 MPa of nitrogen, 0.25 mL of styrene with 2 MPa of nitrogen and 0.25 mL of
1-hexene with 2 Mpa of nitrogen.
Reaction Procedure for substrate Dependence (Olefin): A 10 mL glass Schlenk
flask fitted with a Teflon valve, equipped with a magnetic stir bar was charged with
dry, distilled benzene (typically 1 mL) and 3-5 mg (5 mmol, ~0.1 mol %) of catalyst
from a stock solution. To it was added varied amount of styrene (typically 0.1 to
1mL) and 20 μL of methylcyclohexane, added as internal standard. The valve was
closed and was heated to 180
o
C for 30 minutes. The liquid phase was sampled and
the product yields were determined by GC-MS.

Reaction Procedure for substrate Dependence (Benzene): A 10 mL glass Schlenk
flask fitted with a Teflon valve and equipped with a magnetic stir bar was charged
with dry, distilled styrene (typically 0.6 mL) and 3-5 mg (5 mmol, ~0.1 mol %) of
catalyst from a stock solution. To it were added benzene (0.1 to 1 mL) and
cyclohexane (0.1 to 1 mL) and 20 μL of methylcyclohexane, added as internal
standard. The valve was closed and was heated to 180
o
C for 30 minutes. The liquid
phase was sampled and the product yields were determined by GC-MS.
Reaction Procedure for catalyst (Ph-Ir-Py) Dependence : A 10 mL glass Schlenk
flask fitted with a Teflon valve and equipped with a magnetic stir bar was charged
with dry, distilled benzene and styrene (typically 0.6 mL) and varied amount of Ph-
Ir-Py (2-10 mg) with 1 eq of pyridine to each flask. A 20 μL aliquot of
194
methylcyclohexane was added as internal standard. The valve was closed and was
heated to 180
o
C for 30 minutes. The liquid phase was sampled and the product
yields were determined by GC-MS.
CH
3
13
CH
2
-Ir-Py in C
6
D
6
to generate ethane by C-H Activation: CH
3
13
CH
2
I was
form Cambridge Isotopes Inc. used as received. HgCl
2
was obtained from Loker
Hydrocarbon Institute, and used as I found it.
13
C-diethyl mercury
101
method
modified as not to use a Shoxlet extractor.In a 50 mL three necked round bottom
flask fitted with a reflux condenser and addition funnel. Under an argon atmosphere
containing a solution of the
13
C-ethyl Grignard, made form 1g (6.37mmoles) of
13
C-
ethyl iodide, in ether was added dropwise a solution containing 0.4806g (1.77
mmoles) HgCl
2
in 8 mL dry ether and a small amount of THF for solubility. The
solution was then refluxed for 19.5 h, and the excess grinard quenched with 4 mL of
water and the mixture stirred for 3 min, this was then filtered to remove the MgCl
2

and aqueous layer extracted with 5 x 2ml portions of ether. The combined ether
portions were dried with MgSO
4
, filtered and the ether removed under vacuum, the
resulting light yellow liquid was then vacuum transferred to a small flask giving a
clear colorless liquid. 45% yield. (0.1034g) Specta were consistent with reported
values.
[(CH
3
*CH
2
)Ir(O,O-acac)(C-acac)]
2
:In a large vial containing 0.06286g (0.24
mmoles) of
13
C diethylmercury in 10 mL of methanol, was added 0.0968g (0.19
mmoles) of 2-H
2
O the caped vial was then heated to 75
o
C for 2h. The resulting
reaction mixture was then filtered through ceilite and the volatiles removed under
195
dynamic vacuum. The resulting orange solid was then developed on a preparatory
silica TLC plate with 1:1 THF: ether. The orange band with a R
f
value nearly equal
to unity was scraped off and extracted with CH
2
Cl
2
and THF. After rotovaping, the
solid was redeveloped on a preparatory silica TLC plate using 1:1:2 THF:
CH
2
Cl
2
:hexanes. The orange band R
f
= 0.87 was scraped off and extracted with
CH
2
Cl
2
and THF this solution was then rotovaped and redissolved in CH
2
Cl
2
three
times. The solid was then dried under dynamic vacuum giving an orange powder.
51% yield. (0.0410g)
1
H NMR (CD
3
OD): δ 5.47 (s, 2H, acac-C3H), 3.09, 2.58 ( dq,
1
J
CH
= 128.5,
3
JHH =7.7, -
13
CH
2
-Ir), 1.76 (s, 12H, acac-CH
3
), 0.198 (m, 3H, CH
3
-
13
CH
2
-Ir)
13
C NMR few scans (CD
3
OD): δ -17.59 (s, -
13
CH
2
-Ir)
[CH
3
-
13
CH
2
-Ir(O,O-acac)Py] :
1
H NMR (C
6
D
6
): δ 8.69 (d, 2H, o-py), 6.84 (t, 1H, p-
py), 6.56 (t, 2H, m-py), 5.10 (s, 2H, acac-C3H), 3.60,3.35 (dq, 2H,
1
J
CH
= 125.3, -
13
CH
2
-Ir), 1.60 (s, 12H, acac-CH
3
), 1.23 (m, 3H, CH
3
-
13
CH
2
-Ir).
13
C NMR (C
6
D
6
): δ
182.96 (acac C=O), 149.84 (o-py), 136.81 (p-py), 124.87 (m-py), 103.21 (acac-
C3H), 27.2 (acac-CH
3
), 16.4 (d,
1
JCC = 34 CH
3
), -10.19 (-
13
CH
2
-Ir).

196
Table 4.4. Eyring Plot for pyridine exchange with Ph-Ir-Py.

290 K 283 K 297K
time (s) At -Ln(At/Ao) At -Ln(At/Ao) time At -Ln(At/Ao)
30.91 37.1 0 64.5 0 30.91 92 0
91.82 29.5 0.229226706 58.9 0.090824 61.82 66.5 0.324586629
152.7 25.8 0.363242478 57.8 0.109676 92.73 42.6 0.769934324
213.6 20.2 0.607934365 54.1 0.175831 123.6 32.7 1.034413499
274.5 18.3 0.70671591 52 0.215422 154.6 22.8 1.395028041
335.5 14.6 0.932595441 50.4 0.246674 185.5 21 1.477266139
396.4 13 1.048667612 40.3 0.470314 216.4 18 1.631416819
457.3 10.5 1.262241712 44.8 0.364457 247.3 15 1.813738376
518.2 8.84 1.434330093 40.5 0.465363 278.2 14 1.882731247
579.1 8.03 1.530432442 33.9 0.64325 309.1 9.8 2.239406191
640 8.17 1.513148061 33.1 0.667132 340 8 2.442347035
700.9 6.88 1.684998318 30.1 0.76214 370.9 7.5 2.506885557
761.8 6.43 1.752642431 31.9 0.704059 401.8 7 2.575878428
822.7 4.74 30.8 0.739151
883.6 6.12 1.802054873 30.5 0.748939
944.6 5.5 1.908868877 23.6 1.005419
1005 4.5 2.109539573 24.6 0.963919
1065 3.41 2.386904678 23.3 1.018212
1127 2.93 2.538614547 23.2 1.022513
1188 3.05 16
1249 2 2.920469789 17.5 1.304464
1310 1.9 2.971763083 21.4
1371 1.8 3.025830305 14.8 1.472038
1432 13.8 1.541997

T (K) 1/T kobs Ln(K/T)
277 0.00361 0.0004 -13.448064
283 0.003534 0.001 -12.553202
290 0.003448 0.0026 -11.622125
297 0.003367 0.0071 -10.641393

R
2
= 0.9754
R
2
= 0.9722
R
2
= 0.9881
R
2
= 0.9602
0
0.5
1
1.5
2
2.5
3
3.5
0 500 1000 1500
time (s)
-Ln(At/Ao)
290K 283K 277K 297K

197
R
2
= 0.9997
-16
-14
-12
-10
-8
0.0032 0.0034 0.0036 0.0038
1/T (1/K)
Ln(k/T)
ΔH
‡
= 22.8± 0.5 kcal/mol,

ΔS
‡
= 8.4 ± 1.6 eu,

ΔG
‡
(T=298K) = 20.3± 0.5
kcal/mol

Table 4.5. Eyring plot for pyridine exchange for CH
3
-Ir-Py.

264K 272K 281K
time (s) At -Ln(At/Ao) time (s) At -Ln(At/Ao) time (s) At -Ln(At/Ao)
30.91 38 0 30.91 79 0 30.91 10 0
91.82 31 0.203599 71.82 73 0.078988 61.82 6 0.510826
152.7 29 0.27029 112.7 62.8 0.229493 92.73 4 0.916291
213.6 27.7 0.316154 153.6 41.4 0.646167 123.6 2 1.609438
274.5 24.9 0.422718 194.5 37.1 0.755831 154.5 0.89 2.419119
335.5 21 0.593064 235.5 28.1 1.033678 185.5 0.5 2.995732
396.4 18.6 0.714425 278.4 25 1.150572 216.4 0.2 3.912023
457.3 19.9 0.646866 317.3 18.9 1.430286
518.2 14.9 0.936225 358.2 16.4 1.572167
579.1 16.1 0.858767 399.1 15 1.661398
640 12.7 1.095984 440 14 1.730391
700.9 13 1.072637 480.9 13.6 1.759378
761.8 12.5 1.111858 521.8 10.7 1.999204
822.7 11 1.239691 562.7
883.6 9.21 1.417296 603.6
644.7 5.87 2.599593
685.5 3 3.270836

198
T (K) 1/T kobs Ln(k/T)
264 0.003788 0.0016 -12.0137
272 0.003676 0.0042 -11.07847
281 0.003559 0.017 -9.712897

R
2
= 0.975
R
2
= 0.9639
R
2
= 0.9066
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
0 200 400 600 800 1000
time (s)
-Ln(At/Ao)

R
2
= 0.991 6
-15
-13
-11
-9
-7
0.0033 0.0036 0.0039
1/ T ( 1/ K )
ΔH
‡
= 19.9 ± 1.4 kcal/mol,
ΔS
‡
= 4.4 ± 5.5 eu,
ΔG
‡
(T=298K)=18.6±0.5kcal/
mol

Table 4.6. Kinetic dependence of Hydroarylation on olefin concentration.
Styr /
[M] TN
1.454633 1.36
2.493656 2.76
3.272924 5.24
3.879021 2.56
4.363898 1.42
0
1
2
3
4
5
6
12 3 4 5
Styrene / [M]
TN

Table 4.7. Kinetic dependence of Hydroarylation on catalyst concentration
199

0.00E+00
4.00E-06
8.00E-06
2.00E-03 5.00E-03 8.00E-03 1.10E-02
Catalyst [M]
rate of hydroarylation

Catal /
[M] TN
.59E-03 1.55
6.88E-03 1.56
9.17E-03 1.54

Table 4.8. Kinetic dependence of Hydroarylation on pyridine concentration.

R
2
= 0.9917
0
0.0002
0.0004
0.0006
0.0008
0.001
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4
1/Py Equivalents
Turn Over Frequency (s
-1
)

200
1/Py
Eq. TN
0.37 1.63
0.185 0.81
0.123 0.57
0.093 0.49

Table 4.9. Rate difference between Ph-Ir-Py and Ph-Ir-H
2
O

Time / h

TN (H
2
O)

TN (Py)
0

0

0
0.25

14.11

2.3
0.5

14.62

5.21
1

15.13

5.33
1.5

15.3

5.41
2

15.3

5.55

0
2
4
6
8
10
12
14
16
18
00.51 1.522.5
Time / h
Turn Over Number
TN (H2O)
TN (Py)

201
Table 4.10. Comparitive rate of Hydroarylation between trans-Ph-Ir-Py Vs cis-
Ph-Ir-Py.

time(min) Trans % conv cis%conv
0 0.00 0.00
20 0.53 -
40 0.87 -
60 1.23 0.28
120 1.78 0.55
263 3.23 0.84

Trans-Ph-Ir-Py complex was found to be 4.0 ± 0.4 times more active(faster) than
the cis-Ph-Ir-Py.The internal standard used was 1,3,5-trimethoxybenzene.

y = 0.0132x
R
2
= 0.9251
y = 0.0035x
R
2
= 0.9388
0
0.5
1
1.5
2
2.5
3
3.5
4
0 5 0 1 00 15 0 20 0 25 0 3 00
tim e(m in)
Percent con

202
Table 4.11. Comparison of thermodynamic and experimental ratio for
Hydroarylation with various olefins.

Olefin B3LYP-G B3LYP-G dG
kcal/mol
exptal DFT ratio
A(linear) B(branched)
Propylene C
9
H
12
-350.13573 -350.134 0.9 61:39 74:36
Styrene C
14
H
14
-541.87036 -541.865 3.2 98:2 97: 03
1-hexene C
12
H
18
-468.02955 -468.027 1.9 69:31 87: 13
Isobutylene C
10
H
14
-389.43316 -389.428 2.9 82:18 96:4

B3LYP-G values are B3LYP/LACV3P++**//LACVP** gas phase values.

203

4.5 Chapter 4 References

77 Olah, George A. Friedel-Crafts and Related Reactions. Vol. I. General
Aspects.; Vol. II. Alkylation and Related Reactions. Part 1.; Part 2.; 1964,
1031 pp.; 658 pp.; 703 pp. Interscience (Div. of Wiley), New York.
78 (a) Isenberg; Grdinic. J. Chem. Educ. 1969, 46, 601. (b) Grdinic; Isenberg.
Intra-Sci. Chem. Rep. 1970, 4, 145-162.
79 Olah, G. A.; Molnár, Á . Hydrocarbon Chemistry, 2nd ed.; Wiley-
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153. Young, K. J.H.; Oxgaard, J.; Goddard, W. A.(III); Periana, R. A.;
manuscript submitted to JACS.

Abstract (if available)

Abstract This dissertation describes the usage of nitrogen and oxygenated ligand sets such as acetylacetone (acac), 6-phenyl-4,4’-bis(tert-butyl)-2,2’-bipyridine(NNC) on Iridium metal and diamine-bisphenolate (NNOO) on Rhodium for the activation of the C-H bonds of arenes and functionalization such as hydroarylation of olefins.

Linked assets

University of Southern California Dissertations and Theses

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Asset Metadata

Creator Ganesh, Somesh Kumar (author)

Core Title Activation and functionalization of C-H bonds catalyzed by oxygen and nitrogen ligated late transition metal complexes

School College of Letters, Arts and Sciences

Degree Doctor of Philosophy

Degree Program Chemistry

Publication Date 09/12/2008

Defense Date 06/27/2008

Publisher University of Southern California (original), University of Southern California. Libraries (digital)

Tag activation,C-H bonds,functionalization,OAI-PMH Harvest,transition metal complexes

Language English

Contributor Electronically uploaded by the author (provenance)

Advisor Periana, Roy A. (committee chair), Petasis, Nicos A. (committee member), Prakash, G.K. Surya (committee member), Shing, Katherine S. (committee member)

Creator Email skganesh@gmail.com,skganesh@usc.edu

Permanent Link (DOI) https://doi.org/10.25549/usctheses-m1597

Unique identifier UC1121629

Identifier etd-Ganesh-2300 (filename),usctheses-m40 (legacy collection record id),usctheses-c127-94965 (legacy record id),usctheses-m1597 (legacy record id)

Legacy Identifier etd-Ganesh-2300.pdf

Dmrecord 94965

Document Type Dissertation

Rights Ganesh, Somesh Kumar

Type texts

Source University of Southern California (contributing entity), University of Southern California Dissertations and Theses (collection)

Repository Name Libraries, University of Southern California

Repository Location Los Angeles, California

Repository Email cisadmin@lib.usc.edu