Toward a catalytic cycle for the hydroxylation of methane: oxy-functionalization of electron rich M-CH3 bonds

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Content TOWARD A CATALYTIC SYSTEM FOR THE HYDROXYLATION OF METHANE:
OXY-FUNCTIONALIZATION OF ELECTRON RICH M-CH
3
BONDS

by

Brian Lee Conley

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 Brian Lee Conley
ii

DEDICATION

For my scientific predecessors.

iii

ACKNOWLEDGEMENTS

To me it is quite unbelievable that it has been four years since I walked off the
campus at Elon University in North Carolina, destined for the fun and sun of Los
Angeles, California. I would never have been able to get here without my family, who
has loved and supported me unconditionally in every way I could imagine. I especially
want to acknowledge my brother, Philip, who has been my roommate and friend for the
past three years; the presence of family when undertaking feats of this magnitude is much
underrated and I feel blessed to have had his company. Also, my parents, Tom and
Kathy, who have been the link to my past and will always be my biggest fans, no matter
how many papers I ever publish. I owe my grandparents, Jason and JoAnn Conley and
Al and Martha Bennett, for bringing my parents into the world and for the lessons they
have taught me throughout my life. Grandma and Grandpa Conley have donated to Brian
Conley’s poor college student fund for 8 years now, always without my asking, and it is
unbelievable how their financial support has kept me going. I have to thank Laura Wulf,
my fiancé, for her tremendous emotional support and understanding. She has been my
sounding board for all of my successes and failures and for that I am eternally grateful.
I hold a special place in my heart for three scientists in particular who believed in
me and inspired me to take up chemistry: Dr. Karl Sienerth, Dr. Joel Karty, and Dr.
Eugene Grimley at Elon University. Dr. Sienerth was my research director and afforded
me some of the best opportunities of my early career in chemistry, from national
meetings to funding for several semesters. I am thankful to Dr. Grimley for his passion
in building the chemistry department at Elon, which allowed me access to phenomenal
iv

resources as an undergraduate and to Dr. Karty for his dedication to teaching and
intellectual stimulation.
A special thanks to my research group. My advisor, Roy Periana, has been the
source of a lot of growth in my life, both scientifically and personally. Though we do not
always agree, I will always respect his well thought out philosophy on life, his desire to
do quality science, and his unique style of leadership. I do hope one day the Periana
group solves the methane problem, and that it may benefit our world in ways we cannot
yet predict. I also hope that the way of doing science I learned here will be as infectious
to the scientific community as it has been to the people that have come through the group.
Certainly it advances the idea that science is a tool we should use for the betterment of
our way of life. I truly feel that my training goes well beyond chemistry and I hope that
present and future group members feel the same. To those in the group that have made a
lasting impression I thank you: Gaurav, Oleg, Vadim, Bill (a special thanks for your
training and friendship), Steve Meier, Steve Bischof, Somesh, Dr. Liu, and Kenny.
Lastly I thank God, while acknowledging that I often struggle to understand what
that really means. Without a deeper sense of purpose I would have been lost and
defeated in this journey long ago. I am grateful for the beauty and complexity of the
world in which I get to live and for the experiences that allow a glimpse of the divine, of
which the marvel of chemistry is certainly one. I hope one day human passions on this
subject can convene in some way.
v

TABLE OF CONTENTS

DEDICATION ii 
ACKNOWLEDGEMENTS iii 
LIST OF TABLES vii 
LIST OF FIGURES ix 
LIST OF SCHEMES xiv 
ABSTRACT xv 
1 Chapter 1: Introduction 1 
1.1 Background - Methane as a Feedstock 1 
1.2 Overall Strategy: Selective Hydroxylation of Methane 4 
1.3 CH Activation of Methane: General Considerations 13 
1.4 Functionalization Reactions of M-CH
3
Fragments 22 
1.5 Chapter 1 References 37

2 Chapter 2: Oxy-Functionalization of Methyltrioxorhenium, a Model M-CH
3
41 
2.1 Introduction 41 
2.2 Results and Discussion 44 
2.3 Experimental Details 54 
2.4 Chapter 2 References 72

3 Chapter 3: Oxy-Functionalization of Electron-Rich Metal Alkyl with OsO
4
74 
3.1 Introduction 74 
3.2 Results and Discussion 77 
3.3 Experimental Section 87 
3.4 Chapter 3 References 111 

vi

4 Chapter 4: Catalytic Oxy-functionalization of a Low Valent Metal Alkyl with
Se(IV) 114
4.1 Introduction 114 
4.2 Results and Discussion 120 
4.3 Experimental 130 
4.4 Chapter 4 References 153

5 Chapter 5: Synthesis, Characterization, and CH Activation Reactions of
Organometallic, O-Donor Ligated, Rh(III) Complexes 155
5.1 Introduction 155 
5.2 Results and Discussion 159 
5.3 Experimental 166 
5.4 Chapter 5 References 200

Bibliography 201

vii

LIST OF TABLES
Table 2.1: Yield of Methanol (%) and Relative Transition State Energies
for BV and η
2
-Peroxo Pathways for Several O-atom Donors. 49
Table 5.1: Crystal data and structure refinement for
(acac)
2
Rh(Cl)(CH
3
OH). 169
Table 5.2: Atomic coordinates ( x 10
4
) and equivalent isotropic
displacement parameters (Å
2
x 10
3
) for
(acac)
2
Rh(Cl)(CH
3
OH). U(eq) is defined as one third of the
trace of the orthogonalized U
ij
tensor. 170
Table 5.3: Bond lengths [Å] and angles [°] for (acac)
2
Rh(Cl)(CH
3
OH). 171
Table 5.4: Anisotropic displacement parameters (Å
2
x 10
3
) for
(acac)
2
Rh(Cl)(CH
3
OH). The anisotropic displacement factor
exponent takes the form: -2π
2
[ h
2
a*
2
U
11
+ ... + 2 h k a*
b* U
12
]. 174
Table 5.5: Hydrogen coordinates ( x 10
4
) and isotropic displacement
parameters (Å
2
x 10
3
) for (acac)
2
Rh(Cl)(CH
3
OH). 176
Table 5.6: Crystal data and structure refinement for trans-
(acac)
2
Rh(CH
3
)(Py). 177
Table 5.7: Atomic coordinates ( x 10
4
) and equivalent isotropic
displacement parameters (Å
2
x 10
3
) for trans-
(acac)
2
Rh(CH
3
)(Py). U(eq) is defined as one third of the
trace of the orthogonalized U
ij
tensor. 179
Table 5.8: Bond lengths [Å] and angles [°] for trans-
(acac)
2
Rh(CH
3
)(Py). 180
Table 5.9: Anisotropic displacement parameters (Å
2
x 10
3
) for trans-
(acac)
2
Rh(CH
3
)(Py). The anisotropic displacement factor
exponent takes the form: -2π
2
[ h
2
a*
2
U
11
+ ... + 2 h k a*
b* U
12
]. 183
viii

Table 5.10: Hydrogen coordinates ( x 10
4
) and isotropic displacement
parameters (Å
2
x 10
3
) for trans-(acac)
2
Rh(CH
3
)(Py). 185
Table 5.11: Crystal data and structure refinement for cis-
(acac)
2
Rh(CH
3
)(Py). 186
Table 5.12: Atomic coordinates ( x 10
4
) and equivalent isotropic
displacement parameters (Å
2
x 10
3
) for cis-
(acac)
2
Rh(CH
3
)(Py). U(eq) is defined as one third of the
trace of the orthogonalized U
ij
tensor. 187
Table 5.13: Bond lengths [Å] and angles [°] for cis-(acac)
2
Rh(CH
3
)(Py). 189
Table 5.14: Anisotropic displacement parameters (Å
2
x 10
3
) for cis-
(acac)
2
Rh(CH
3
)(Py). The anisotropic displacement factor
exponent takes the form: -2π
2
[ h
2
a*
2
U
11
+ ... + 2 h k a*
b* U
12
]. 195
Table 5.15: Hydrogen coordinates ( x 10
4
) and isotropic displacement
parameters (Å
2
x 10
3
) for cis-(acac)
2
Rh(CH
3
)(Py). 196

ix

LIST OF FIGURES
Figure 1.1: World Natural Gas Reserves, 2004. 3
Figure 1.2: Progression of Technology of Industrial Processes Through
Successive “Generations” 5
Figure 1.3: The Hydroxylation of the Methane CH bond with O
2
6
Figure 1.4: Thermodynamically Feasible Pathways for Direct Use of
Methane 7
Figure 1.5: Susceptibility of Methane to Overoxidation and Reduced
Rate of Cyanomethane 9
Figure 1.6: Direct Conversion of Alkanes to Alcohols Requires New
Hydroxylation Catalysts 10
Figure 1.7: Wacker Type System for Conversion of Alkanes to Alcohols. 12
Figure 1.8: Examples of Some of the Reported C-H Activation Systems
with Catalytic Systems That Generate Functionalized
Products Highlighted 16
Figure 1.9: Generalized Energy Diagram Emphasizing the Two Key
Steps Involved in the C-H Activation Reaction: C-H
Coordination and C-H Cleavage. 17
Figure 1.10: Classification of Various Modes of C-H Activation 19
Figure 1.11: Two modes of Interaction between C-H bonds and Metals
with Occupied d-Orbitals in the Valence Shell 22
Figure 1.12: Proposed Mechanism for Pt(bpym)Cl
2
/H
2
SO
4
System for
Methane Oxidation to Methanol 24
Figure 1.13: Reductive Functionalization of Methyl Platinum Bonds to
Form Esters and Ethers 26
Figure 1.14: Intramolecular Reductive Functionalization with Rh
III

Porphyrin System. 27
Figure 1.15: Proposed Mechanism for Alkane Borylation by Ru(II)
Species. 28
x

Figure 1.16: Conversion of Pd-Ar bond to Pd-OAr through putative
Pd
IV
=O species. 30
Figure 1.17: (a) Migration of Phenyl (Ph) to Bound Oxo-Group of Re(VII)
Generated In Situ (b) Overoxidation of Alkyl Ligands by α-
Hydrogen Shift to Bound Oxo 32
Figure 1.18: Proposed Mechanism for Insertion of O into Ni-Ar Bond 34
Figure 1.19: Insertion of Oxygen from N
2
O into Hf-H and Hf-Ph Bonds is
Proposed to Occur by Migration to the N
2
O Adduct. 35
Figure 2.1: Ideal Catalytic Cycle for the Hydroxylation of Methane by
Non-Redox C-H Activation and O-Atom Insertion 42
Figure 2.2: Contrasting Catalytic Cycles for Hydrocarbon
Functionalization by (A) Redox Catalysis and (B) Non-
Redox Catalysis 43
Figure 2.3: BV-type Transition State for O-Insertion into Re-CH
3
Bond 44
Figure 2.4: Methyl Migration to Electrophilic Oxygen in Bound
Hydroperoxide Anion 47
Figure 2.5: B3LYP/LACVP++** Transition State for Reaction of MTO
and IO
4
-
. 50
Figure 2.6: Overall Catalytic Cycle Showing Three (3) Mechanistic
Possibilities for Functionalization by O-Atom Transfer: Cis-
Dioxo, BV-Type, and Oxo-Insertion 53
Figure 2.7: Fragmentation pattern for CH
3
16
OH in H
2
O (absolute
intensity vs. m/z). 55
Figure 2.8: Fragmentation pattern for CH
3
18
OH in H
2
O (absolute
intensity vs. m/z). 56
Figure 2.9: Fragmentation pattern for CH
3
18
OH from MTO + NaI
18
O
4

reaction in H
2
18
O (absolute intensity vs. m/z). 56
Figure 2.10: Control. Fragmentation pattern of
16
O-MTO in H
2
16
O
(absolute intensity vs. m/z). 57
Figure 2.11: Fragmentation pattern of
16
O-MTO in H
2
18
O after 90 minutes
(absolute intensity vs. m/z). 58
xi

Figure 2.12: Fragmentation pattern of
16
O-MTO in H
2
18
O after 135
minutes (absolute intensity vs. m/z). 58
Figure 2.13:
1
H NMR (py-d
5
/THF-d
8
) of MTO + pyO reaction at t=0
(bottom) and t=1h (top): δ 3.58 and δ 1.67 (residual THF
resonances); δ 8.19 (d, 2H, o-pyO); δ 7.25 (m, overlapping
m-pyO and pyridine-h
5
); δ 7.12 (t, 1H, p-pyO); δ 8.58 (d, 2H,
pyridine
h5
); δ 7.65 (t, 1H, pyridine
h5
); δ 4.48 (s, CH
3
O-Re);
δ1.70 (s, 3H, MTO methyl); δ 1.40 (cyclohexane I.S.). 59
Figure 2.14:
1
H NMR of MTO in D
2
O with cyclohexane internal standard.
δ 2.38 (s, 3H, MTO methyl); δ1.57 (s, cyclohexane I.S.); δ
4.79 (H
2
O residual peak). 60
Figure 2.15:
1
H NMR of MTO + H
2
O
2
in D
2
O with cyclohexane internal
standard: δ 2.70 (s, 3H, MTO methyl); δ1.40 (s, cyclohexane
I.S.); 3.14 (s, 3H, methanol). 61
Figure 2.16:
1
H NMR of MTO + PhIO in D
2
O with cyclohexane internal
standard: δ 1.52 (cyclohexane); δ 2.36 (s, 3H, MTO methyl);
δ 3.28 (s, 3H, methanol); δ 4.79 (H
2
O residual peak). 61
Figure 2.17:
1
H NMR of MTO + NaIO
4
in D
2
O with cyclohexane internal
standard: δ 1.56 (cyclohexane); δ 3.28 (s, 3H, methanol); δ
4.79 (H
2
O residual peak). 62
Figure 2.18: B3LYP/LACVP/6-311G** BV-type Transition State for
MTO + IO
4
-
63
Figure 3.1: General Activation/Functionalization Catalytic Cycle for
Hydroxylation of Hydrocarbons. 75
Figure 3.2: BV and (3+2) Transition States for Functionalization of M-R
with YO and cis-LMO
2
. 76
Figure 3.3: 400 MHz
1
H NMR of (a) MTO + OsO
4
(1:1) in D
2
O and (b)
MTO + OsO
4
(1:1) in D
2
O with 3 equivalents added KOD. 78
Figure 3.4: Pathways for MTO functionalization by OsO
4
in basic
aqueous media (B3LYP/LACVP**, bond distances in Å, kcal
mol
-1
). 81
Figure 3.5: HOMO orbitals and energies (eV), Re-C bond lengths (Å),
and Mulliken carbon atomic charges (e) of MTO Species. 84
xii

Figure 3.6: 400MHz
1
H NMR of MTO in D
2
O with benzene/CCl
4
co-
axial internal standard (bottom) and MTO in D
2
O with added
isonicotinic acid/OsO
4
solution (top). The peak at ~ δ 3.3 is
CH
3
OH. 91
Figure 3.7: Proposed structure for product of reaction between MTO and
OsO
4
in neat pyridine. 93
Figure 3.8: ORTEP diagram for [(C
5
H
5
-CH
2
)Re(NC
6
H
5
)
3
(O)
2
][ReO
4
]
with 50% ellipsoids. 95
Figure 3.9: 400 MHz
1
H NMR (aromatic region) of reaction product
from MTO + OsO
4
in neat pyridine dissolved in py-d
5
. 96
Figure 3.10: 400 MHz
13
C NMR of reaction product from MTO + OsO
4
in
neat pyridine dissolved in py-d
5
97
Figure 3.11: FMO and TS orbital interactions 100
Figure 3.12: Transition State HOMO (53) 108
Figure 3.13: Ground state CH
3
ReO
4
-
.

HOMO (29). 108
Figure 3.14: Ground state OsO
4
. HOMO (24). 109
Figure 3.15: Ground state OsO
4
. LUMO (25). 109
Figure 3.16: Ground state OsO
4
. LUMO + 1 (26). 110
Figure 4.1: Methyl Transfer from Re to Se Through a 4-centered
Transition State. 116
Figure 4.2: Plausible pathways, A and B, for oxy-functionalization of M-
R intermediates generated by CH activation. 118
Figure 4.3: First Known Insertion of SO
2
into M-R bonds (R = -CH
3
, -
CH
2
CH
3
, -C
6
H
5
) 119
Figure 4.4: Reported Oligomerization During Attempted Synthesis of
(CO)
5
ReOH in Acetone. 121
Figure 4.5: Electrospray Ionization Mass Spectrum of (CO)
3
bpyReCH
3
+
H
2
SeO
3
in CH
3
CN/H
2
O (9:1) 126
Figure 4.6: Lowest energy pathway for methyl transfer to H
2
SeO
3
. 128
xiii

Figure 4.7: Transition State (top left) and Snapshot Views from the IRC
of the Subsequent Decomposition to O-seleninate Product. 129
Figure 4.8: 400MHz
1
H-NMR of (CO)
5
ReCH
3
in CD
3
CN. 132
Figure 4.9: 400MHz
1
H-NMR of (CO)
5
ReCH
3
in C
6
D
6
. 133
Figure 4.10: 400MHz
13
C-NMR of (CO)
5
ReCH
3
in C
6
D
6
. 134
Figure 4.11: 400MHz
1
H NMR of (CO)
3
(bpy)ReCH
3
in CD
3
CN. 137
Figure 4.12: 400MHz
1
H NMR of (CO)
3
(bpy)ReCH
3
in CDCl
3
. 138
Figure 4.13: 400MHz
13
C NMR of (CO)
3
(bpy)ReCH
3
in THF-d
8
. 139
Figure 4.14: 400MHz
1
H NMR of CO
3
bpyRe(SeO
2
CH
3
) in wet CD
2
Cl
2
.
Se satellites on the methyl group at δ 2.04 are indicative of
Se-CH
3
(J=7Hz). 141
Figure 4.15: 400MHz
1
H NMR of (CO)
3
(bpy)Re(SeO
2
OH) in CD
3
OD. 143
Figure 4.16: Eyring Plot for Transfer of Methyl from (CO)
5
ReCH
3
to
H
2
SeO
3
145
Figure 5.1: Hydroarylation of Ethylene to form Ethyl Benzene. 156
Figure 5.2: Conceptual Mechanism for Catalytic Hydroarylation 157
Figure 5.3: ORTEP of 1 (50% probability thermal ellipsoids). A
molecule of co-crystallized methanol has been omitted for
clarity. The hydrogen atom on the methanol was not located. 160
Figure 5.4: ORTEP plot of 2 (50% probability thermal ellipsoids).
Selected bond lengths (Å): Rh1-N1, 2.236(3); Rh1-C16,
2.031(3). 161
Figure 5.5: ORTEP plot of 3 (50% probability thermal ellipsoids).
Selected bond lengths (Å): Rh1-N1, 2.017(5); Rh1-C16,
2.026(5). 162
Figure 5.6: ORTEP plot of 6 (50% probability thermal ellipsoids). 164

xiv

LIST OF SCHEMES
Scheme 1.1: Overall Hydroxylation of Methane in Acidic Medium by
(bpym)PtCl
2
Catalyst 21
Scheme 2.1: Degradation of Tri-alkyl Boranes by O
2
is Proposed to
Proceed through Peroxide Linkage 45
Scheme 2.2: Conversion of Tri-alkyl Boranes with Amine-N-oxides by O-
atom Insertion 46
Scheme 2.3: Formation of Mono-η
2
peroxo and Bis- η
2
peroxo Species
from H
2
O
2
and Methyltrioxorhenium (MTO). 46
Scheme 2.4: Density Functional Theory (B3LYP/LACVP**) Reaction
Pathways for Methanol Production from MTO and IO
4
-
.
50
Scheme 5.1: Synthesis of (hfac-O,O)
2
Rh(III) Complexes. 159
Scheme 5.2: Hydrocarbon activation by 3. 163
xv

ABSTRACT
The chemistry discussed herein involves the strategy of selective oxy-
functionalization of well defined, electron-rich (and nucleophilic), M-CH
3
bonds by O-
atom insertion or methyl transfer reaction and a homogeneous system that exhibits C-H
activation of a variety of bonds. These projects were undertaken with the goal of adding
conceptual and practical knowledge to the development of a catalytic cycle for the
conversion of hydrocarbons (particularly methane) to alcohols (methanol).
Chapter one introduces the strategy of C-H activation of methane as it pertains to
using natural gas as a feedstock. It discusses the utility of employing selective reactions
at C-H bonds, some pitfalls of current systems, and the strategy of incorporating an oxy-
functionalization reaction for more nucleophilic metals.
Chapter two describes oxy-functionalization of a model transition metal-methyl
species, methyltrioxorhenium (MTO) by a variety of O-atom donors to produce methanol
including theoretical work used to supplement and validate the experimental findings.
Chapter three is a research that elucidates a new (3+2) mechanism for oxy-
functionalization of M-C bonds using cis-dioxo oxidants like OsO
4
and describes the
required base activation of the M-CH
3
species.
Chapter four conveys a new strategy for functionalization of low-valent M-CH
3

bonds by transfer of the methyl to a co-catalyst and subsequent oxidation/reduction steps
to produce methanol.
xvi

Chapter five is research directed at finding new catalyst for hydroarylation of
olefins, highlighting a novel Rh system that affords stoichiometric reactions with C-H
bonds.

1

1 Chapter 1: Introduction
1.1 Background - Methane as a Feedstock

Hydrocarbons derived from petroleum reserves provide the world with a
plethora of products including pharmaceuticals, polymers for plastics, and fuels,
among others. The bulk of the petroleum is used as fuel after relatively simple
distillation processes. Petroleum can also be converted to value added products
by a variety of industrial processes yielding products that can be used in chemical
synthesis. As worldwide resources of hydrocarbons dwindle, we are shunted
toward a future wherein both products and fuels will become increasingly less
available and thereby less affordable. Though most experts agree that a litany of
technological advances must be made in the areas of renewable energy (and/or
alternative non-renewable energy) if we continue to increase our energy demand
worldwide at the current rate, our dependence on fossil fuels cannot be
immediately alleviated. This necessitates intermediate technologies that can be
implemented in the next 25-50 years that maximize the efficiency of current
feedstock conversion to products or energy and tap into underutilized feedstocks
in an atom economical manner, which will greatly extend the lifetime of our
reserves, slow the release of the critical greenhouse gas, CO
2
, and accordingly
lower the prices of fuel and food until more sustainable technologies can take
over the majority of the demand.
2

Our group has focused on implementing methane as an alternative
feedstock, although chemistry developed for this molecule will be useful for
other hydrocarbons in general (and potentially for many small molecules, i.e. N
2
,
H
2
O, CO
2
, O
2
, etc) since the focus is activation of the C-H bond, which, in
alkanes, is among the most inert bonds on the planet. Methane is an attractive
molecule on which to focus chemical research, as it is the main component of
natural gas, which is an abundant (Figure 1.1), relatively untapped hydrocarbon
resource. It has the highest ratio of hydrogen to carbon of any hydrocarbon (4:1),
and thus represents a cleaner source of energy than longer chain alkanes (~2:1) or
coal (variable depending on source, but typically ~1:1)
1
. In addition, its
corresponding alcohol, CH
3
OH, has been proposed to be used widely as an
electron reservoir for fuel (direct methanol fuel cells, diesel synthesis) and
chemical applications (methanol-to-olefins, MTO).
1
As the world looks to
maximize efficiency and minimize CO
2
emissions, it should naturally seek out
the cleanest energy source in the process if adequate technology for its use is
available, as well as focusing intense efforts on converting all products back to
useful starting materials to ultimately create a manmade “carbon cycle.”

3

Figure 1.1: World Natural Gas Reserves, 2004.

In spite of the large reserves and desirable characteristics of natural gas,
petroleum remains the primary feedstock for chemicals and fuels, because
implementing the use of natural gas faces a couple major obstacles. First, it is a
gas at standard conditions which precludes it from being transferred
economically due to a low “energy density.” Second, in spite of the high carbon
yields (>50%) of commercially available technologies for conversion to
transportable liquids, such as methane to methanol or methane to liquid paraffins
(Fischer-Tropsch chemistry), they are still too expensive to compete with
processes creating materials from petroleum. Consequently, in order to have
natural gas augment or replace petroleum as the primary feedstock, and thereby
lessen the World’s dependence on oil,
2
new technology that is both substantially
less costly and more energy and atom-efficient needs to be developed.
4

The bulk of the cost to produce large scale products such as electricity,
fuels and commodity chemicals results from the capital cost of the plant, unlike
the production of lower volume products such as drugs in which most of the cost
is associated with lengthy trial phases that use limited amounts of energy. In the
case of converting methane to methanol or paraffins, >65% of the costs are
related to the capital. This is because the current processes for conversion of
methane to liquid products are based on high-temperature (~900
o
C) chemistry for
the production of syngas followed by its conversion to the end products. As a
result of the high temperatures utilized in the generation of syngas, the
specialized reactor and process controls required are capital intensive. In the
case of electricity production, methane is combusted at ~1000°C in a gas turbine
(a heat engine). Here, also, the high temperatures lead to capital intensive,
complicated plants. The efficiency (~30%) of the gas turbine results from the
practical upper limit of the temperature in the combustion zone. The key to
moving to a methane economy will be the development of lower temperature
methane conversion processes that can be practiced in less capital intensive
plants and with high energy and atom-efficiency.

1.2 Overall Strategy: Selective Hydroxylation of Methane

The chemistry with the broadest potential for developing new technology
(and paradoxically facing the greatest technical challenges) for the conversion of
5

methane to both power and materials is the selective, low-temperature
hydroxylation of the alkane C-H bond. Thus, as shown in Figure 1.3, chemistry
for the conversion of the methane C-H bond to a C-OH bond (hydroxylation) with
O
2
from air as the terminal oxidant could enable the development of next
generation technologies for the direct, selective, low temperature conversion of
methane to methanol and other materials. The generations of technology for other
notable processes are represented in Figure 1.2; it is obvious that the trend is
toward more efficient, less energy intensive conversions requiring fewer steps.

Figure 1.2: Progression of Technology of Industrial Processes Through
Successive “Generations”

Significantly, as shown in Figure 1.3, the low temperature oxidation of
methane to CO
2
can be viewed as the complete, anodic, hydroxylation of the C-H
bonds of methane in liquid water, coupled with the reduction of oxygen. Viewed
6

this way, the connection to CH hydroxylation is clear as a necessary goal to
developing maximally efficiently direct methane fuel cells that operate at low
temperatures. The key to implementing C-H hydroxylation chemistry with
oxygen for both methanol and electricity production will be to develop the next
generation of catalysts that will facilitate C-H hydroxylation reactions with low
activation barriers (<25 kcal/mol) and with high selectivity.

Figure 1.3: The Hydroxylation of the Methane CH bond with O
2

In addition to new technologies involving the direct conversion of methane to
methanol and electricity as shown in Figure 1.3, if selective C-H conversion
chemistry could be developed for methane, less obvious advances (such as the
ones shown in Figure 1.4) could be developed that reduce the number of process
steps and overall costs for the production of some of the other large scale
7

commodities on the planet such as ammonia, acetic acid and hydrogen peroxide.
The direct reactions of methane shown in Figure 1.4 serve to illustrate that, in
addition to being one of the most abundant, cheapest, carbon-based raw materials
on the planet, it can also be considered the least expensive reductant (as apposed
to H
2
which is produced from methane). The key to unleashing the largely
underutilized potential of this molecule is increasing the rate of reaction; that is,
making methane a kinetically facile reductant.

Figure 1.4: Thermodynamically Feasible Pathways for Direct Use of Methane

The primary reason that new technologies for the conversion of methane to
methanol remain a challenge is that the current commercial catalysts for alkane
oxidation (typically solid metal oxides) have high barriers for the oxy-
functionalization reaction which requires that high temperatures or expensive
8

reactive reagents be utilized, ultimately leading to low reaction selectivity and
inefficient chemistry. We believe that more active catalysts that operate in the
temperature range of ~200–250
o
C would allow for the selective functionalization
of methane to methanol at low temperatures in inexpensive reactors, with fewer
steps and in high yields.
Combustion of fuel in the presence of air is the ultimate oxy-
functionalization reaction, which results in the complete oxidation of the carbon-
hydrogen and carbon-carbon bonds to form water and CO
2
(carbon oxidation state
formally changes from -4 to +4). Because of the radical generating combustion
reaction, there is no way to “control the burn” to selectively generate alcohols
(trapping at an intermediate oxidation state). This is a direct result of the high
homolytic C-H bond strength of methane (~105 kcal/mol) relative to that of
methanol (93 kcal/mol). This chemistry also governs the bulk of the known
oxidation catalysts that utilize free radical chemistry. They show a correlation
between activation barriers (≈rates) and homolytic bond strengths, Figure 1.5. As
a result, methanol is substantially more reactive than methane with known free-
radical based catalysts. The rate for hydrogen atom abstraction from methane (2.4
x 10
8
s
-1
) by a hydroxyl radical is compared to that for methanol (8 x 10
8
s
-1
) in
Figure 1.5. However, the reactivity of C-H bonds by transition metal catalyzed C-
H activation has been shown to possess the opposite correlation due to the
resultant bond strengths of the intermediate metal alkyl/aryl species.
3
This is a
pillar of our group’s strategy to use homogeneous transition metal catalysts for
9

hydroxylation, and is discussed in more detail below. In addition, as illustrated in
Figure 1.5, the C-H bonds of methanol can be protected by the presence of
electron withdrawing groups, such as substitution by cyanide or conversion to
esters, as shown by Periana, et. al.
4
Protection of methanol by chemical
modification allows for high concentrations to accumulate in solution with
minimal conversion to unwanted over-oxidation products, such as formaldehyde
or CO
2
.

Figure 1.5: Susceptibility of Methane to Overoxidation and Reduced Rate of
Cyanomethane

As shown in Figure 1.6, new catalysts for the hydroxylation of methane must
reduce the activation barrier for the oxidation of methane relative to the barrier for
over-oxidation of methanol.

10

Figure 1.6: Direct Conversion of Alkanes to Alcohols Requires New
Hydroxylation Catalysts

The issues of selectivity in methane hydroxylation are exacerbated by the low
solubility of methane (1mM at STP) relative to the complete miscibility of
methanol in water (the cheapest, most readily available, and environmentally
friendly reaction medium). Thus, because the concentration of methanol builds
up in the reactor, the intrinsic reactivity of methane must be much higher than that
of methanol to maintain high reaction selectivity. Assuming a reactor with a 1:1
gas to liquid ration and 500 psig methane pressure, kinetic models
5
show that the
relative rate constants for reaction of methane to methanol and methanol to CO
2
,
k
1
and k
2
respectively in Figure 1.6, must be at least 20:1 for high reaction
selectivity to methanol to be maintained at conversions of methane over 15%.
Given this requirement to reverse the typical reactivity of methane and methanol,
11

it is clear that the next generation of catalysts must operate by non-free radical
reactions.
In developing this next-generation direct methane to methanol process,
several key considerations are important. As a general consideration it should be
expected that any new process not only substantially reduces the capital costs for
the process (ideally by >50%) but also meets (and desirably exceeds) the overall
yield and atom-efficiency of the existing process. Significantly, giving the
economic challenges, the only other starting material that can be utilized in any
large scale process to functionalize methane is air. Indeed, even pure or enriched
oxygen (obtained from air) could be too expensive. Thus, other oxidants such as
hydrogen peroxide, nitrous oxide, ozone, peroxides, or persulfates would not be
useful since these materials cannot be regenerated from air.
Since capital cost of the plant is critical, it is instructive to consider the
type of process design, and the impact on the required chemistry, that could lead
to sufficiently low capital costs to compete with petroleum. Many schemes can
be considered for reacting air and methane (assuming that suitable catalysts are
available) to generate methanol at low costs. Reactions involving direct
combination of the alkane and air would seem to be theoretically ideal.
However, practical considerations, such as avoiding explosive gaseous mixtures
and minimizing likely free radical reactions due to the triplet ground state of
oxygen, suggest that a Wacker type scheme, that employs inexpensive, liquid-
phase bubble column reactors and a stoichiometric, air recyclable oxidant (YO)
12

in direct reaction with the methane could be preferred. A simplified process
diagram for such a scheme is shown in Figure 1.7. In the original Wacker system
for the oxidation of ethylene to acetaldehyde catalyzed by Pd(II), the role of this
stoichiometric, air recyclable oxidant was met with Cu(II).
6

Two key advantages of utilizing this process design are: A) air, instead of
pure oxygen, can be utilized for the re-oxidation and B) that inexpensive gas-
liquid bubble column reactors can be employed. Since these reactors can be
designed to operate at comparable pressures and temperatures, there is no
disadvantage to separating the alkane reaction from reactions with air.

Figure 1.7: Wacker Type System for Conversion of Alkanes to Alcohols.

Overall Reaction:
RH + YO  ROH + Y (1)
Y + ½ O
2
 YO (2)
13

RH + ½ O
2
 ROH (Net)

In the “oxidation” side of the reactor setup, a homogeneous transition metal
complex catalyzes C-H activation, followed by functionalization (vide infra) to
yield methanol and spent oxidant (Y). From this reaction mixture must be
separated CH
3
OH, Y (for regeneration by air), and H
2
O.
Next, we will briefly look at some of the important details of the C-H
activation reaction of methane that takes place in the left reactor of Figure 1.7,
examples of working systems, and how the knowledge of their mechanisms has
determined our course in the stubsequent study of oxidation reactions, namely
the conversion of the resultant M-CH
3
to methanol.

1.3 CH Activation of Methane: General Considerations
There are many definitions of CH activation. From the discussion above,
one could conclude that the combustion reaction is a C-H activation reaction that
happens when a radical, originating from O
2
, breaks the C-H bond
heterolytically. One could also consider more classic deprotonation reactions as
C-H activation, such as the formation of an enolate from deprotonation of α-C-H
bonds in ketones or aldehydes. Other prominent chemistry features the use of
super acid media for the effective protonation of hydrocarbons, which allows for
polymerization and oxy-functionalization.
7
Realizing the need for distinction
14

amongst these chemistries because of the vastly different mechanisms (and
therefore strategies employed) we define C-H activation as a facile C-H cleavage
reaction with an “MX” species that proceeds by coordination of an alkane to the
inner-sphere of “M” (either via an intermediate alkane complex or a transition
state) leading to a M-C intermediate.
3
Important to this definition is the
requirement that during the C-H cleavage, the hydrocarbyl species remains in the
inner-sphere and under the influence of the metal. Theoretical as well as
experimental studies support this view that unactivated C-H bonds can be
cleaved by such an inner-sphere mechanism.
8
This emphasis on inner-sphere
coordination is based on the presumption that cleavage reactions of the C-H bond
that proceed in this manner, with strong interaction between the C-H bond and
“M”, can be expected to show uniquely high selectivity and activity, vide infra.
It is also important to point out that utilizing C-H activation for hydroxylation of
unactivated hydrocarbons necessitates an intermolecular reaction. Recent
important advances in the broader field of C-H activation have focused on
substrates with inherently higher reactivity (they are “activated”) because of the
availability of coordinating heteroatom groups such as nitrogen or oxygen.
9

Paradoxically, the major strength and weakness of this approach is that typically
the chemist has access to only one proton as dictated by steric and electronic
effects that accompany a cyclic, intramolecular transition state. In terms of
scope, catalysts that activate substrates in an intramolecular fashion often do not
15

activate more robust substrates, such as methane, because the entropic
component of the activation barrier is no longer minimized.
Since its original discovery in the late 1960s/early 1970s by the Shilov
group,
10
catalytic C-H activation (as defined herein) has been achieved by several
systems. Importantly, isolation of key intermediates generated by C-H activation
of alkanes and subsequent mechanistic studies by the Bergman group and others
has established the course of the C-H activation reaction. Details of “Shilov”
chemistry have been thoroughly considered, conceptually and experimentally by
Bercaw
11
, Tilset
12
, and others.
13
However, despite the wealth of knowledge
about the chemical events composing C-H activation, relatively few system have
been identified that catalytically generate heteroatom products (such as alcohols)
from unactivated hydrocarbons. Shown in Figure 1.8 are several representative
systems.
16

Figure 1.8: Examples of Some of the Reported C-H Activation Systems with
Catalytic Systems That Generate Functionalized Products Highlighted

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, Figure 1.9. The advantage
of these inner-sphere/coordination reactions is that the reactants are bound to the
catalyst center during conversion to products. As a result, the catalyst can
17

effectively mediate both rate and selectivity in the conversion of the reactants to
desired products.

Figure 1.9: Generalized Energy Diagram Emphasizing the Two Key Steps
Involved in the C-H Activation Reaction: C-H Coordination and C-H
Cleavage.

Since the C-H bond of methane is characteristically strong (ΔH
f
= 105
kcal/mol) a key characteristic of the C-H activation reaction is the formation of
strong M-C bonds that compensate for breaking the C-H bond. This is one of the
key bases for the involvement of second and third row transition metals in the
many C-H activation reaction that have been reported. Interestingly, while the
involvement of these metals facilitates C-H cleavage, these metals are among the
kinetically least labile. This can lead to slow rates for the C-H activation reaction
in the presence of good ligands (those that impart sufficient stability), which
18

forces the chemisty to balance rate, life, and selectivity by catalyst design (the so-
called “Devil’s Triangle” of catalysis).
There are several proposed mechanisms that share in common required
coordination of the alkane C-H bond to the inner-sphere of the metal center,
either as an intermediate or in a transition state, leading to the formation of
organometallic M-C intermediates. The mode of cleavage depends on the
electronics of the metal. Of these, the most common modes are Electrophilic
Substitution (ES), Oxidative Addition (OA) and Sigma Bond Metathesis (SBM)
and in all cases high selectivities are observed. To utilize the unique properties
of the C-H activation reaction the M-C species must be more easily
functionalized than the C-H bond to yield a useful C-X product with regeneration
of the MX species. Ideally, to maintain high reaction selectivity and catalyst
control, it may be desirable that this functionalization also occur within the inner
sphere of “M”.
19

Figure 1.10: Classification of Various Modes of C-H Activation

This cleavage of the C-H bond mediated via formation of an M-C species can be
contrasted to other, more “classical” coordination reactions of alkane C-H bonds,
such as those based on free radical, carbocation or carbanion intermediates.
Since these reactions are based on intermediates that are highly energetic species,
they require either very harsh conditions, such as extreme temperatures, or very
energetic (and expensive) reagents such as superacids or peroxides that are not
desirable for bulk conversions.
2a
Additionally, in these classical C-H bond
breaking reactions, unlike the C-H activation reaction as defined above, the
20

reactive alkyl fragments 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 undesirable.
Work toward a practical, industrially practiced process can be viewed
from two perspectives: 1) modification and optimization of the original Shilov
system and 2) de novo design of highly active systems. We have undertaken
both approaches, focusing more recently on the latter. However, it is very
instructive to understand the Shilov system, as many parallels in reactivity can be
drawn to other working systems. The primary issue with the Shilov system,
14

PtCl
2
(H
2
O)
2
, which is proposed to operate via oxidative addition, is catalyst
instability due to irreversible decomposition to platinum metal or insoluble,
polymeric Pt salts such (PtCl
2
)
n.
This was addressed by the use of ligands that
stabilized Pt(II) in neat sulfuric acid, leading to a high yield system
(Pt(bpym)Cl
2
/H
2
SO
4
) where bpym = κ
2
-{2,2'-bipyrimidyl}.
4
This system is
stable and active for the conversion of methane to methanol in concentrated
sulfuric acid (Eq 2) and yields of over 70% methanol (based on methane) with
selectivities of >90% and turnovers of ~1000 have been observed with turnover-
frequencies of ~10
-3
s
-1
.

21

Scheme 1.1: Overall Hydroxylation of Methane in Acidic Medium by
(bpym)PtCl
2
Catalyst

Theoretical and experimental studies show that this cationic Pt
II
catalyst operates
via an ES reaction pathway. This switch to an ES pathway, whereas the Shilov
Pt
II
system is proposed to operate via an OA pathway, is due to the increased
electrophilicity of the metal imparted by the protonation of the bpym ligand and
the electron-withdrawing HSO
4
-
groups. In spite of the high efficiency, this
system is strongly inhibited by the reaction product, methanol, and water. In this
case, the inhibition limits product concentration to ~1.5 M, which remains too
low for commercialization.
In an effort to design catalysts that may not be as susceptible to water
inhibition but retain the stability of the bpym ligated Pt
II
system, we have moved
to more electron rich systems that we believe operate via donation from occupied
d-orbitals on the metal to the σ-antibonding orbitals of the C-H bond. This
paradigm shift is important, and will be laid out in pending publications from our
group in due time. The two extremes (donation to or from

the metal) are shown
in Figure 1.11.
22

Figure 1.11: Two modes of Interaction between C-H bonds and Metals with
Occupied d-Orbitals in the Valence Shell

1.4 Functionalization Reactions of M-CH
3
Fragments

Thus far the discussion has focused on the impetus for using C-H activation
by transition metals as the basis of functionalizing hydrocarbons, which follows
the actual progression of events in our lab. The origins of our group, as most
know, were in a small Silicon Valley company, Catalytic, Inc. of which Dr.
Periana was a group leader. The electrophilic mercury and platinum systems
were developed there, though a large chunk of the experimental verification of
mechanism and all of the theoretical work was done in the USC/Caltech (William
A. Goddard, III group) collaboration. Prior to my entering the group, we had
published papers from USC on a new motif for C-H activation, (acac)
2
Ir
III
(R)(L)
that activates C-H bonds efficiently in weak acid and organic solvents and is
shown to catalyze the anti-Markovnikov hydroarlyation and hydrovinylation of
23

olefins.
15
In addition, the group had begun its shift to more electron donating
metals to carry out the C-H activation reaction, such as osmium, ruthenium, and
rhenium as well as the modification of the electronics around Ir
III
such that it may
exhibit higher reactivity in non-acidic media. I was charged with investigating
oxy-functionalization reactions of the more electron rich metal-alkyl fragments
that would be ideally be generated by C-H activation catalysts. In order to follow
the emerging story of functionalization of these species, it is necessary to examine
the known functionalization reactions of M-C bonds including the character of the
M-C bond and reagents known to effect the transformation.
Fortunately, the recently amassed work done with the late transition
metals and the pioneering work in functionalization of hydrocarbons with these
catalysts provides us with a wealth of knowledge, both empirical and
mechanistically elucidated, about the functionalization step. These catalysts are
widely known to operate through “reductive elimination” or nucleophilic attack
on a polarized M
δ-
-C
δ+
bond. Though reductive elimination is a mechanistically
sound description, we prefer to call the reaction that produces a heteroatom
product “reductive functionalization” or more specifically “reductive oxy-
functionalization” (when oxygen is the heteroatom) as this distinguishes it from
degenerate reactions, i.e. reductive elimination of RH from a species that
originated from the oxidative addition of RH. Both pathways transform a M
n+2
-R
and X
-
species into M
n
+ RX, the most important distinction being that reductive
functionalization requires cis orientation of the R
+
and X
-
fragments at the metal
24

center and nucleophilic attack is subject to steric impedance by groups attached to
the carbon undergoing reaction.
16

In the case of [(bpym)Pt
II
]/H
2
SO
4
system, functionalization is proposed to
occur by elimination of HSO
4
CH
3
from (bpym)Pt
IV
(CH
3
)(HSO
4
). The overall
mechanistic picture is shown in Figure 1.12, though it should be noted that several
nuances of this mechanism are still under investigation in our group and others.
13

Figure 1.12: Proposed Mechanism for Pt(bpym)Cl
2
/H
2
SO
4
System for Methane
Oxidation to Methanol

A field that benefits greatly from reductive functionalization is coupling
chemistry that employs activated alkyl and aryl species and palladium
17
and
25

copper
18
catalysts, such as Stille, Sonogashira, Suzuki/Miyaura
19
coupling to form
C-C bonds and the Buchwald
20
-Hartwig
17
systems for C-N and C-O coupling.
Recently Vigalok
21
and Sanford
22,23
have released accounts of isolated Pt
IV

and Pd
IV
species that undergo reductive eliminations of R-X, further supporting
this mechanism as the predominate functionalization pathway in electron deficient
M-C species. Most of this chemistry, though, is only peripherally related to
alkane functionalization. The most common coupling fragments are arenes
originating from aryl-X, aryl-B, or aryl-M, which are not formed by a prior,
selective, C-H activation reaction occurring in the same reaction vessel; coupling
to heteroatom substituents and to other other arenes dominates this methodology.
However, Sanford has recently begun to tie C-H activation into a catalytic cycle
for the functionalization of arene C-H bonds in aromatic systems. Bergman and
Ellman, and Fagnou
24
have also demonstrated impressive “direct coupling”
reactions in seminal papers. Of course, the ultimate goal is the direct coupling
25

of two unactivated fragments such as alkane C-H bonds. Though the researchers
have made a compelling argument, the acidity of the indole C-H bond probably
does not qualify it to most as “unactivated.” Therefore this methodology
probably will remain isolated to molecules with similar reactivity, and
emphasizes again that discovery of new, more active catalysts for alkanes is still a
priority. Nonetheless, it is apparent that groups are actively investigating this area
of chemistry, seeking to move away from aryl-X type molecules and
stoichiometric quantities of often toxic metal reagents (i.e. R-Sn).
26

What this survey of systems serves to illustrate is the proclivity of late
transition metals to undergo reductive functionalization. There numerous
examples and this is a prolific method for the formation of C-C and C-heteroatom
bonds.
26
Interestingly though, examples that feature alkyl group are rare, as this
represents the reductive functionalization of a metal-C(sp
3
) bond. Recently,
interest in this area has grown with more examples populating the literature. Of
note are Goldberg’s mechanistic studies of reductive functionalization of
(dppe)Pt
IV
-CH
3
, Figure 1.13, that produces methyl esters or ethers.

Figure 1.13: Reductive Functionalization of Methyl Platinum Bonds to Form
Esters and Ethers

In another example Sanford and Groves used a Rh
I
/Rh
III
porphyrin cycle for the
intramolecular anti-Markovnikov functionalization of olefins, which expels the
cyclic product by reductive functionalization, Figure 1.14. Likely, since this
reaction takes place from a coordinatively saturated porphyrin complex, the
reaction mechanism is actually a nucleophilic attack by the nitrogen on the alkyl
group. A base was used in every example in this paper, so deprotonation of the
amine could be proposed to precede the functionalization step. However, it is
27

more likely it either participates directly in the transition state as an external base
or deprotonates the ammonium ion formed from attack of the amine lone pair on
carbon.

Figure 1.14: Intramolecular Reductive Functionalization with Rh
III
Porphyrin
System.

One of the more intriguing, recent research programs for the
functionalization of alkanes is the catalytic borylation of linear alkanes by
iridium, rhodium, and ruthenium boryl complexes
27
synthesized in the labs of
John Hartwig.
28
In this work R-Bpin is the product of reductive
functionalization, Figure 1.15, likely from Ru
IV
generated in situ by
disproportionation of the Ru
III
dimer and oxidative addition of (Bpin)
2
.

28

Figure 1.15: Proposed Mechanism for Alkane Borylation by Ru(II) Species.

Another interesting proposal for oxy-functionalization in the chemical
literature pertains to the net insertion of oxygen into metal carbon bonds, which
has been demonstrated for the functionalization of cyclometallated M-Ar species,
commonly called “metaloxylation.” The field can be traced back to the seminal
research at the University of Newcastle reporting the cleavage of Pt-CH
2
Ph and
Pd-CH
2
Ph bonds by m-chloroperoxybenzoic acid (m-CPBA). Several groups
have expanding upon this research since 1984, reporting several synthetic
examples of the conversion M-Ar to M-OAr (M=Pd, Ru) in cyclometallated
azoaryl species with m-CPBA,
29a-e
H
2
O
2
,
30
t-BuOOH radicals and iodosyl
29

benzene
31
(and its perfluoronated analog). Early mechanistic studies by Harvie
and McQuillin suggested that the insertion (referred to as the cleavage of the Pt-C
bond) occurred with retention of stereochemistry of the α-carbon
32
providing
evidence against a free radical mechanism, which would most likely give some
degree of racemization.
33
Further, D. Banyopadhyay reports preliminary evidence
that supports the formation of a high energy Pd
IV
=O species.
34
The electrophilic
oxygen then induces either the migration of the aryl group or insertion of the oxo
species into the M-R bond, as shown in Figure 1.16. Pt
IV
=O and Pd
IV
=O are
structural motifs with little precedent, and likely will never be observed for simple
organometallic species. Because the platinum group is beyond the “oxo-wall” it
is not expected, due to repulsion between filled d-orbitals and lone pairs on
oxygen, that an oxo ligand would be stable. This is contrasted to the extreme
oxophilicity of the nucleophilic metals to the left in the periodic table. In fact,
only one Pt=O has been isolated, by Craig Hill,
35
which employs large, diffuse
and thereby powerful polyoxometallate ligands to remove considerable electron
density from the platinum metal. This allows for donation into empty d-orbitals
and the formation of a true oxo ligand (based on the relative bond lengths of oxo
and hydroxide/alkoxide), as evidenced by high level diffraction studies.
35

Nonetheless, high energy species that cannot be isolated are often still postulated
in chemistry, i.e. carbocations and alkane complexes (concrete evidence of both
took decades). In proposing high energy species, however, the author must speak
to the expected thermodynamics of such an intermediate. If in fact it does exist in
30

an intermediate in this case, the oxygen of a putative Pd
IV
species would be
electrophilic in nature and could be expected to induce an intramolecular
reduction as the hydrocarbyl ligand transfers as R
-
and electron density from the
double bond drains into d-orbitals. One must be mindful, however, in considering
these reactions for incorporation into practical catalytic systems, especially for
substrates that are ligated and utilize the intramolecular C-H activation reaction,
vide supra. As highlighted by Sanford, et. al.,
36
the “functionalized ligand” must
be able to detach from the metal as a free organic in order for turnover to be
achieved. Therefore, the kinetic parameters for cyclometallation/demetallation
are extremely important and must not be prohibitively high.

Figure 1.16: Conversion of Pd-Ar bond to Pd-OAr through putative Pd
IV
=O
species.

Though this functionalization pathway is distinct from reductive
functionalization, it is comparably less prevalent and, at least for the moment,
represents an exception to the rule, which is that late transition metal M-C bonds
are polarized M
δ-
-C
δ+
and are attacked by O-nucleophiles. It is obvious from a
complete scan of the literature, also, that reductive functionalization abounds for
31

late metal systems but examples taper as one looks at metals to the left of
platinum, especially in the low oxidation states needed for C-H activation in these
complexes. It became obvious to us that, when considering low valent metal
alkyls that would be generated on more electron rich metal centers (metals farther
to the left of the Pt triad), the polarization of the bond should change substantially
so that it is either neutral or M
δ+
-C
δ-
.
Interestingly, the general transformation (M
n
R  M
n+2
(O)(R)  M
n
-OR)
that was proposed for the functionalization of cyclometallated Pd species was also
proposed by Mayer, et. al for the insertion of oxygen into (tp)Re
V
-Ph bonds
37
. In
this case, the relatively weak oxidant dimethyl sulfoxide (DMSO) is able to
oxidize Re
V
-Ph to a Re
VII
(Ph)(O) intermediate (Figure 1.17) which rearranges to a
Re
V
phenoxide by proposed formal Ph
-
migration. Pyridine-N-oxide, a stronger
oxidant, was also able to induce the insertion as well, even providing the
thermodynamic driving force that favored the formation of Re
VII
to Re
V
and
allowed [(tp)Re(O)
2
Ph]
+
to be observed directly by
1
H NMR. However,
overoxidation of the phenoxide ligand to form a chelating chatecolate highlights a
notable drawback to this strategy, namely that the system is too oxidizing for a
simple insertion reaction alone. This [1,2] shift also occurs with hydride ligands
to form Re-OH. Unfortunately, the R-ligands more relevant to our research, i.e.
Et-, n-Bu-, and Me-, undergo α-hydrogen migration to the bound oxo, followed
by further reaction with py-O to yield the corresponding acetaldehyde,
38,37b
as
shown in Figure 1.17b.
32

Figure 1.17: (a) Migration of Phenyl (Ph) to Bound Oxo-Group of Re(VII)
Generated In Situ (b) Overoxidation of Alkyl Ligands by α-
Hydrogen Shift to Bound Oxo

Like the palladium system, the proposed mechanism for this reaction
involves a formal redox reaction at the metal, though there is no formal change in
oxidation state from reactants to products (from the perspective of the metal
center) and overall the reaction is an insertion. In these types of transformations,
one can follow the flow of electrons by assigning carbon an oxidation state of -1
in the metal aryl/alkyl species and +1 in the phenoxide/alkoxide. The carbon is
transferred as a carbanion and electron density is transfered through the acceptor
oxygen to formally reduce the metal with concomitant formal oxidation of the
carbon atom.
The opening to Mayer’s 2000 Organometallics paper
37b
serves to
punctuate the importance of finding more reactions that will allow for conversion
of M-C intermediates; “Selective oxidations are among the least explored and
least understood areas of organometallic chemistry.” With that in mind, utilizing
33

high oxidation state transition metal species to hydroxylate hydrocarbons is
generally not compatible with our strategy because selective, catalytic C-H
activation is not active for these systems and high-valent metal oxo compounds
often react with hydrocarbons through one-electron chemistry which would be
deleterious and possibly even dangerous in an industrial application. To
juxtapose the above research and our own strategy is useful. Migration of the
phenyl moiety in the above example is contingent on the formation of a highly
electrophilic oxo group,
37a
which is intimately linked to the oxidation state of the
metal. It is critical to realize that in these migration reactions, the R-group is
already intact, such that stoichiometric oxidation reactions could be investigated.
The generation of the M-C bond by C-H activation will be a necessity and we are
proposing a nucleophilic substitution of the C-H bond with our catalysts instead
of the electrophilic substitution of the earlier reported Hg and Pt systems. Thus, it
follows that low oxidation state (i.e. d
6
-
Os
II
) metal centers are active.
39
Of course,
oxos at lower oxidation states (i.e. Os
IV
=O) will not be electrophilic enough to
induce alkyl migration.
Another “net insertion” that attracted our attention turns out to operate in a
different manner. The complex (bpy)Ni(CH
2
CH
3
)
2
reacts with N
2
O at 50 °C in
benzene to make (bpy)Ni(OEt)(CH
2
CH
3
) + N
2
.
40
The authors present their
mechanistic proposal for reaction in a subsequent paper, suggesting that N
2
O
reacts as a heterocumulene, first coordinating end-on through nitrogen, followed
by –R transfer to the nitrogen (Figure 1.18). Rearrangement inserts oxygen into
34

the M-C bond and liberates nitrogen.
41
This prior “activation” of N
2
O by nickel
seems somewhat fortuitous and probably not generally applicable to the type of
M-C species we are examining, though we have routinely included N
2
O as an
oxidant in our experimental and theoretical screens.

Figure 1.18: Proposed Mechanism for Insertion of O into Ni-Ar Bond

With our main considering being to keep our catalysts in lower oxidation
states, we are examining species that are viable for direct insertion into the M-C
bond, realizing that this reaction mechanism lacks the precedent of other modes of
35

functionalization. Thus we began looking for reagents that could deliver
electrophilic oxygen that would not result in the net donation of 2 metal electrons
resulting in oxidation to the M
n+2
state in the process.
There is scant evidence for the direct insertion of electrophilic oxygen into
a M-alkyl bond that does not proceed through what we perceive as “prohibitory”
redox reactions. The closest known are reactions of electron rich d
0
-Hf hydrido
phenyl complexes with the thermodynamically powerful (but kinetically slow)
N
2
O molecule
42
as shown in Figure 1.19. Conversion of both the Hf-H and Hf-Ph
bonds are proposed to occur through a concerted transfer of the ligand to the
incoming oxygen of N
2
O. Though these are not alkyl complexes, the involvement
of a σ-bond is encouraging.

Figure 1.19: Insertion of Oxygen from N
2
O into Hf-H and Hf-Ph Bonds is
Proposed to Occur by Migration to the N
2
O Adduct.

36

Unfortunately, the only evidence for this pathway is that the intermediacy of
Cp*
2
Hf(ONNPh)(H), resulting from the complete insertion of N
2
O into the Hf-Ph
bond, is not reasonable given the high activation barrier expected for the
subsequent migration of Ph- to oxygen from nitrogen due to the double bond
character of the Ph-N linkage. Also, as we have seen with methyltrioxorhenium
(see Chapter 2), these complexes benefit from having no d-electrons which could
result in formal oxidation of the metal. It is quite possible that other more facile
reactions, such as the heterocumulene reaction (vide supra), will be favored for
N
2
O in complexes with d-electrons.
Given the state of the field of nucleophilic metal-alkyl functionalization
reactions, we decided that advances could be made to enhance the possibility of
incorporating functionalization reactions into catalytic cycles for C-H
hydroxylation. The observation that no direct insertion reactions of electrophilic
oxygen into a metal-alkyl bond were known encouraged us to investigate this
mode of reactivity.

37

1.5 Chapter 1 References

1 Beyond Oil and Gas: The Methanol Economy, Olah, G.A.; Goeppert, A.;
Prakash, G.K.S.; Wiley-VCH, Weinheim 2006, pp. 1-259.

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

3 (a) Arndtsen, B. A.; Bergman, R. G.; Mobley, T. A.; Peterson, T. H. Acc. Chem.
Res. 1995, 28, 154 and citations therein. (b) 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 and citations therein.

4 Periana, R.A.; Taube, D.J.; Evitt, E.R.; Loffler, D.G.; Wentreek, P.R.; Voss, G.;
Masuda, T. Science 1993, 259, 340.

5 Periana, R.A.; Nielsen, R.; Mironov, O.; Ziatdinov, V.R.; Oxgaard, J.;
Goddard, W.A., III. Unpublished results.

6 Smidt, J.; Hafner, W.; Jira, R.; Sieber, R.; Sedlmeier, J.; Sabel, A. Angew.
Chem. Int. Ed. 1962, 1, 80.

7 Olah, G.A.; Parker, D.G.; Yonea, N. Angew. Chem. Int. Ed. 1978, 17, 909 and
references therein.

8 (a) Xu, Xin; Kua, Jeremy; Periana, Roy A.; Goddard, William A. III
Organometallics 2003, 22, 2057. (b)Kua, Jeremy; Xu, Xin; Periana, Roy A.;
Goddard, William A. III. Organometallics 2002, 21, 511.

9 (a) Ryabov, A.D. Chem. Rev. 1990, 90, 403. (b) Pfeffer, M. Pure Appl. Chem.
1992, 64, 335. (c) Tan, K.L.; Bergman, R.G.; Ellman, J.A. J. Am. Chem. Soc.
2001, 123, 2685. (d) Dick, A.R.; Hull, K.L.; Sanford, M.S. J. Am. Chem. Soc.
2004, 126, 2300.

38

10 (a) Gol’dshleger, N.F.; Tyabin, M.B.; Shilov, A.E.; Shteinmann, A.A. Zh. Fiz.
Khim. (Engl. Transl.) 1969, 43, 1222. (b) Gol’dshleger, N.F.; Es’kova, V.V.;
Shilov, A.E.; Shteinmann, A.A. Zh. Fiz. Khim. (Engl. Transl.) 1972, 46, 785.

11 (a) Zhong, H.A.; Labinger, J.A.; Bercaw, J.E. J. Am. Chem. Soc. 2002, 124,
1378. (b) Heyduk, A.F.; Driver, T.G.; Labinger, J.A.; Bercaw, J.E. J. Am. Chem.
Soc. 2004, 126, 15034. (c) Driver, T.G.; William, T.J.; Labinger, J.A.; Bercaw,
J.E. Organometallics 2007, 26, 294.

12 Lersch, M.; Tilset, M. Chem. Rev. 2005, 105, 2471.

13 (a) Paul, A.; Musgrave, C.B. Organometallics 2007, 26, 793. (b) Zhu, H.;
Ziegler. Organometallics 2007, 26, 2277. (c) Kua, J.; Xu, X.; Periana, R.A.;
Goddard, W.A., III. Organometallics 2002, 21, 511.

14 (a) Kushch, K. A.; Lavrushko, V. V.; Misharin, Yu. S.; Moravsky, A. P.;
Shilov, A. E. New J. Chem. 1983, 7, 729.

15 (a) Matsumoto, T.; Periana, R.A.; Taube, D.J.; Yoshida, H. J. Mol. Cat. A
2002, 180, 1. (b) Bhalla, G.; Liu, X.Y.; Oxgaard, J.; Goddard, W.A., III; Periana,
R.A. J. Am. Chem. Soc. 2005, 127, 11372. (c)Oxgaard, J.; Muller, R.P.; Goddard,
W.A., III; Periana, R.A. J. Am. Chem. Soc. 2004, 126, 352. (d)Oxgaard, J.;
Bhalla, G.; Periana, R.A.; Goddard, W.A., III. Organometallics 2006, 25, 1618.

16 Collman, J.P.; Hegedus, L.S.; Norton, J.R.; Finke, R.G. in Principles and
Applications of Organotransition Metal Chemistry. University Science Books,
Sausalito, CA, 1987, 7, 401-431.

17 Hartwig, J.F. in Handbook of Organopalladium Chemistry for Organic
Synthesis; Negishi, E.I., Ed.; Wiley-Interscience: New York, 2002, Vol. 1, p
1051.

18 Ley, S.V.; Thomas, A.W. Ang. Chem. Int. Ed. 2003, 42, 5400.

19 Miyaura, N.; Suzuki, A. Chem. Rev. 1995, 95, 2457.

20 (a) Wolfe, J.P.; Wagaw, S.; Marcoux, J.-F.; Buchwald, S.L. Acc. Chem. Res.
1998, 31, 805 and references therein. (b) Billingsley, K.L.; Barder, T.E.;
Buchwald, S.L. Ang. Chem. Int. Ed. 2007, 46, 1.

21 Yahav-Levi, A.; Goldberg, I.; Vigalok, A. J. Am. Chem. Soc. 2006, 128, 8710.

39

22 (a) Dick, A.R.; Kampf, J.W.; Sanford, M.S. J. Am. Chem. Soc. 2005, 127,
12790. (b) Whitfield, S.R.; Sanford, M.S. J. Am. Chem. Soc. 2007, 129, 15142.

24 Stuart, D.R.; Fagnou, K. Science 2007, 316, 1174.

25 Alberico, D.; Scott, M.E.; Lautens, M. Chem. Rev. 2007, 107, 174.

26 Hartwig, J.F. Acc. Chem. Res. 1998, 31, 852.

27 Hartwig, J.F.; Cook, K.S.; Hapke, M.; Incarvito, C.D.; Fan, Y.; Webster, C.E.;
Hall, M.B. J. Am. Chem. Soc. 2005, 127, 2538.

28 Chen, H.; Schlecht, S.; Semple, T.C.; Hartwig, J.F. Science 2000, 287, 1995.

29 a) Mahapatra, A.K.; Bandyopadhyay, D.; Bandyopadhyay, P.; Chakravorty, A.
J. Chem. Soc., Chem. Commun. 1984, 999. b) Mahapatra, A.K.; Bandyopadhyay,
D.; Bandyopadhyay, P.; Chakravorty, A. Inorg. Chem. 1986, 25, 2214. c) Sinha,
C.; Bandyopadhyay, D.; Chakravorty, A. J. Chem. Soc., Chem. Commun. 1988,
468. d) Bhawmick, R.; Das, P.; Neogi, D.N.; Bandyopadhyay, P. Polyhedron
2006, 25, 1177. e) Rath, R.K.; Nethaji, M.; Chakravarty, A.R. J. Organomet.
Chem. 2001, 633, 79.

30 Wadhwani, P.; Bandyopadhyay, D. Organometallics 2000, 19, 4435.

31 Bhawmick, R.; Biswas, H.; Bandyopadhyay, P. J. Organomet. Chem. 1995,
498, 81.

32 Harvie, I.J.; McQuillin, F.J. J. Chem. Soc. Chem. Comm. 1977, 8, 241.

33 Free radical oxidations of M-R bonds usually result in the formation of
mixtures of enantiomeric products.

34 Kamaraj, K.; Bandyopadhyay, D. Organometallics 1999, 18, 438.

35 Anderson, T.M.; Neiwart, W.A.; Kirk, M.L.; Piccoli, P.M.B.; Schultz, A.J.;
Koetzle, T.F.; Musaev, D.G.; Morokuma, K.; Cao, R.; Hill, C.L. Science 2004,
306, 2074.

36 Dick, A.R.; Hull, K.L.; Sanford, M.S. J. Am. Chem. Soc. 2004, 126, 2300.

40

37 a) Brown, S.N.; Mayer, J.M. J. Am. Chem. Soc. 1996, 118, 12119. b) Matano,
Y.; Northcutt, T.O.; Brugman, J.; Bennett, B.K.; Lovell, S.; Mayer, J.M.
Organometallics 2000, 19, 2781.

38 DuMez, D.D.; Mayer, J.M. J. Am. Chem. Soc. 1996, 118, 12416.

39 Conley, B.L.; Young, Kenneth, J.H.; Mironov, O.; Nielsen, R.; Periana, R.A.
Several unpublished systems catalyze H/D exchange of the CH bonds of
hydrocarbons.

40 Matsunaga, P.T.; Hillhouse, G.L. J. Am. Chem. Soc. 1993, 115, 2075.

41 Koo, K.; Hillhouse, G.L.; Rheingold, A.L. Organometallics 1995, 14, 456.

42 Vaughan, G.A.; Rupert, P.B.; Hillhouse, G.L. J. Am. Chem. Soc. 1987, 109,
5538.
41

2 Chapter 2: Oxy-Functionalization of
Methyltrioxorhenium, a Model M-CH
3

2.1 Introduction

As discussed above, one of the most daunting challenges to developing
selective, low temperature hydrocarbon oxidation catalysts based on C-H
activation is integration with a compatible functionalization reaction.
1,2
We
recently reported a C-H activation reaction, Figure 1, with an methoxo complex,
Ir-OCH
3
, that simultaneously generates a functionalized product, CH
3
OH, and a
metal aryl, Ir-Ph, where M is Ir(III).
3
The related iridium hydroxide, which is
formed by the hydrolysis of the methoxo ligand in water to form methanol, is also
active for H-D exchange of the C-H bonds of protio-benzene for the deuterium in
D
2
O.

42

Figure 2.1: Ideal Catalytic Cycle for the Hydroxylation of Methane by Non-
Redox C-H Activation and O-Atom Insertion

We realized that a catalytic cycle for the conversion of RH to ROH could be
possible by regeneration of M-OCH
3
from M-CH
3
, as shown in Figure 2.1, if
these types of M-heteroatom systems are able to activate alkanes such as CH
4
.
The contrast to redox-active systems, such as the electrophilic [(bpym)Pt] system,
is shown in Figure 2.2.

43

Figure 2.2: Contrasting Catalytic Cycles for Hydrocarbon Functionalization by
(A) Redox Catalysis and (B) Non-Redox Catalysis

Functionalization of these M-Rs may be facile in non-redox, insertion
reactions with electrophilic O-atom donors, YO, shown generically in Eq 1, if
free-radical pathways or formal oxidation of the metal centers could be
minimized.
4
Conversion of Y to YO with O
2
could complete the overall catalytic
cycle as in Figure 2.1.

M-R + YO  M-OR + Y (1)

The conversion of M-R to M-OR is not well known and the few reported
examples proceed with O
2
by free-radicals pathways,
5
by redox reactions
involving alkyl to metal oxo migration,
6
or through mechanisms that are not
general enough to be applied to the types of systems we are currently
investigating, vide supra, Chapter 1. Consequently, identification of a facile
pathway for Eq 1, especially with non peroxo
7
YOs (which have a proclivity to
form radical species) that could potentially be recycled with O
2
, could be useful.
44

2.2 Results and Discussion

We report here combined experimental and theoretical evidence for a
facile Re-CH
3
to Re-OCH
3
bond conversion with non peroxo YOs that proceeds
via a low energy, Baeyer-Villiger (BV) type, electrophilic O-atom insertion,
Figure 2.3. In addition we report that, though there is a lower barrier for
functionalization of the methyl group through a η
2
-peroxo transition state for
hydrogen peroxide, there also exists a low energy pathway for the BV type
reaction with peroxide donors.

Figure 2.3: BV-type Transition State for O-Insertion into Re-CH
3
Bond

BV and alkyl borane oxidation reactions to generate oxy-esters and alkoxy
boranes, respectively, are well-known organic reactions involving electrophilic O-
insertions with YOs (vid infra). Significantly, both peroxo and non peroxo YOs
can be utilized and the reactions

proceed without free-radicals or formal redox
changes.
8
Hydroboration is well known to proceed through a migration of R
-
to
electrophilic oxygen of the incoming deprotonated peroxide or peracid. Alkyl
45

boranes are air sensitive, though the reaction with oxygen is reported to be
relatively slow and complicated. H.C. Brown reported on the possible
mechanisms of degradation of trialkyl boranes by oxygen,
9
which, at least for
oxidation of some of the B-R bonds, occurs with simultaneous reduction of the
peroxide linkage as shown in Scheme 2.1.

Scheme 2.1: Degradation of Tri-alkyl Boranes by O
2
is Proposed to Proceed
through Peroxide Linkage

Precedent also exists for the conversion of alkyl boranes to alcohols using
non-peroxide pathways, such as the selective insertion of oxygen by anhydrous
trimethylamine-N-oxide and pyridine-N-oxide to form the corresponding boric
esters in quantitative yield, as reported by Koster in 1966.
10
The presence of a
protic source induces hydrolysis and affords the desired alcohol, as shown in
Scheme 2.2.

46

Scheme 2.2: Conversion of Tri-alkyl Boranes with Amine-N-oxides by O-atom
Insertion

Methyltrioxorhenium, MTO, is well known to catalyze olefin epoxidation
and O-atom transfer reactions with H
2
O
2
via Re η
2
-peroxo intermediates.
11
There
are two forms of the oxidizing species that predominate; a mono-peroxo and a
bis-peroxo, both of which are capable of O-atom transfer, Scheme 2.3.

Scheme 2.3: Formation of Mono-η
2
peroxo and Bis- η
2
peroxo Species from
H
2
O
2
and Methyltrioxorhenium (MTO).

The scope of this reaction is truly huge (the correlation in the number of papers
published about this molecule is a testament) and MTO is a veritable industrial
catalyst.
12
A reported observation that attracted our attention was that an
undesirable “side reaction” is the decomposition of MTO to methanol at room
temperature.
13
We were intrigued because, in spite of the high Re
VII
oxidation
state, unlike Pt
IV
alkyls, treatment of MTO in basic or acidic water does not
generate Re
V
and methanol by reductive functionalization. Another intriguing
result was that addition of base, not acid, facilitates the hydrolysis of the Re-
47

methyl bond to form methane and perrhenate (ReO
4
-
), as eloquent pH dependent
studies done by Abu-Omar and Espenson show.
13
These results indicated to us
that the addition of hydroxide to MTO (a known Lewis acid) could be increasing
the polarization of the metal carbon bond by donation of electron density to the
metal center. In the presence of HOO
-
, which is more nucleophilic than OH
-
, we
imagined the coordination of the peroxo anion and subsequent transfer of the
methyl group to the electrophilic oxygen (the oxygen connected to the remaining
hydrogen) as shown in Figure 2.4.

Figure 2.4: Methyl Migration to Electrophilic Oxygen in Bound Hydroperoxide
Anion

Consistent with the observations of the initial investigators,
13
we found that the
formation of methanol from MTO in water requires added H
2
O
2
as the oxidant.
The reaction is extremely facile (complete upon mixing at room temperature),
selective (yields methanol with no formation of methane from base induced
decomposition or overoxidation), quantitative, and proceeds without a change in
oxidation state of the Re to generate the Re
VII
O
4
-
anion.
In the initial studies of decomposition of MTO to methanol, only H
2
O
2
was
investigated and two non BV-type mechanisms proposed: intramolecular transfer
48

of the methyl reaction via a η
2
-peroxo intermediate (Scheme 2.3) or by direct
methyl migration to the hydroxo of Re coordinated OOH
-
. We considered that
since nature tends to conserve low energy pathways, the reaction may proceed via
the BV-type pathway where the leaving group, Y, could be OH
-
or H
2
O. More
significantly, given the ease of functionalization of the Re-CH
3
bond and the d
0

electron configuration, this system could be a useful model to determine if a BV-
type pathway was viable without complication from metal centered oxidations.
Establishing that a BV-type pathway is feasible with M-Rs would be useful
because, to our knowledge, this functionalization pathway has not been fully
elucidated, it should be lower energy than η
2
-peroxo pathways
7
and accessible
with a broader range of potentially more practical, non peroxo YOs.
To investigate this possibility we compared the reaction of MTO with H
2
O
2
and
three non peroxo YOs: PhIO, PyO and IO
4
-
in water. As can be seen in Table 2.1,
PhIO and IO
4
-
are as efficient as

H
2
O
2
for generation of methanol. Controls show
that the selectivities and yields are independent of added O
2
indicating that free-
radicals are likely not involved, since oxygen would trap highly reactive one
electron intermediates. Facile methanol formation with the non peroxo YOs is
consistent with a low energy BV-type pathway. Also, there is no possibility for
transfer to oxygen in the β-position for the non-peroxo YOs. However, these
observations alone cannot rule out a η
2
-peroxo pathway with non peroxo YOs.
Significantly, density functional theory calculations
14
show that a BV-type
49

pathway is both viable and, as shown in Table 1, lower in energy than the η
2
-
peroxo pathways for all the non peroxo YOs.

Table 2.1: Yield of Methanol (%) and Relative Transition State Energies for BV
and η
2
-Peroxo Pathways for Several O-atom Donors.

YO % MeOH
a
BV TS
b
η-2 peroxo TS
b
H
2
O
2
80 20 13
PyO 0 32 47
IO
4
-
100 17 25
PhIO 90 8 18

a
Yields based on added MTO (0.1mM) with 2 equivalents of YO at 25
o
C for 1
h under air or argon.
b
B3LYP/LACVP/6-311G
**
++ enthalpies in kcal/mol,
implicitly solvated in water.

For IO
4
-
the BV-type and η
2
-peroxo pathways shown in Scheme 2.4 have
calculated barriers of 17 and 25 kcal/mol, respectively. The products of the BV
pathway are IO
3
-
and the methoxide species, MeORe(O)
3
, which we propose
readily hydrolyses to methanol and Re(O)
3
OH. The BV-type transition state
involves concerted methyl migration and IO
3
-
loss as observed by stretching of the
C-Re bond from 2.168 Å to 2.516 Å and the I-O bond from 1.803 Å to 2.399 Å.
Similar to BV or alkyl borane oxidation reactions in organic chemistry, this
50

transition state can be described as a formal insertion of an electrophilic O into the
Re-CH
3
bond. While it is possible that a more exhaustive investigation could lead
to alternative low-energy pathways, these results emphasize that a BV-type
pathway can be considered as a particularly facile option for M-R
functionalizations.

Figure 2.5: B3LYP/LACVP++** Transition State for Reaction of MTO and IO
4
-
.

The 17 kcal/mol activation energy calculated for IO
4
-
is remarkably low
for a M-C to M-O-C transformation given the significant change in electronic
configurations. However, this value is consistent with the facile reaction
observed at room temperature.

Scheme 2.4: Density Functional Theory (B3LYP/LACVP**) Reaction Pathways
for Methanol Production from MTO and IO
4
-
.

51

As the BV-type transition state is calculated to be significantly favored
over a η
2
-peroxo pathway, the O in the MeOH product should be derived almost
exclusively from YO and not from MTO. Consistently, the reaction of
16
O-MTO
with [I
18
O
4
]
-
,
15
followed by GC-MS analysis of the reaction mixture at low
conversion of MTO showed that only CH
3
18
OH was formed. While this
observation supports a BV-pathway, it does not rule out reaction proceeding via
an unsymmetrical η
2
- peroxo species, where the oxygen closest to the methyl
group would be the favored site for transfer and that oxygen would preferentially
be
18
O.
The relatively high calculated BV barrier for PyO of 32 kcal/mol is
consistent with the observation that methanol was not formed at room
temperature. Realizing that the known MeOReO
3
complex
16
should be generated
but not hydrolyzed in aprotic media at moderate temperature, we examined the
reaction of MTO with one equivalent of PyO in THF-d
8
at 125
o
C in the presence
of excess pyridine-d
5
by
1
H NMR. It is known
13
and we observe that MTO is
quantitatively converted to the MTO-Py-d
5
adduct
17
(s, 1.70 ppm) at room
temperature. Upon heating, loss of this adduct is observed along with clean
formation of free pyridine-h
5
and the MeOReO
3
-Py-d
5
adduct (s, 4.48 ppm) based
on comparison to the chemical shift of the known MeOReO
3
-amine adduct.
16

52

While these results taken individually do not prove a specific mechanism,
it is our belief that the convergence between the experimental and theoretical
results strongly supports a BV-style mechanism for the functionalization of MTO
by non peroxo YOs.
Calculations of the reaction of MTO with H
2
O
2
in water were found to be
considerably more complicated than the reaction with non peroxo YOs due to the
multiple possible hydrogen and oxygen rearrangements. Nevertheless, the
calculations show two low energy pathways: one via a η
2
-peroxo and the other via
a BV-type pathway, Table 2.1. The complete mechanism for MTO-H
2
O
2
has
been addressed in a more thorough theoretical study,
18
but it is clear that the BV
mechanism is feasible even for peroxo YOs such as H
2
O
2
.
These results are encouraging and may point to a facile pathway for
heteroatom functionalization of M-R intermediates of more electron rich metals
via a BV-type pathway with electrophilic, O-atom donors, YO. However, there
are some key considerations that must be addressed before we can determine if
this pathway will be broadly applicable for M-R functionalizations. In MTO,
rhenium is pseudo tetrahedral and formally a d
0
metal. Consequently, competitive
oxidation of the metal center, versus O-atom insertion is not an issue in reactions
of MTO with YO. In fact, we believe that one of the most difficult tasks will be
to predict which mechanisms a systems will follow and what dictates those
choices for the functionalization step, though our conceptual understanding has
grown significantly through the research presented herein. A simplified
53

schematic (Figure 2.6) shows some of the options for functionalization by a
generic M-R species.

Figure 2.6: Overall Catalytic Cycle Showing Three (3) Mechanistic Possibilities
for Functionalization by O-Atom Transfer: Cis-Dioxo, BV-Type,
and Oxo-Insertion

The BV-type mechanism was discussed in this chapter. The next chapter
contains the details of novel (3+2) transition states employing cis-dioxo oxidants.
The third pathway in Figure 2.6, oxo insertion, has been reported elsewhere and is
referenced in the introduction to this dissertation. The nature of our research
program dictates that we stay aware of all of these examples and probe our
systems both by theory and experiment for the different types of mechanisms.
54

Thus, a key question we are investigating is whether the concerted, low
energy, BV-type transition state can be extended to a range of YOs and M-Rs
with other geometries and electronic configurations and the feasibility of
incorporation into catalytic cycles of the type shown in Figure 2.1. In addition, we
hope to elucidate what factors favor this desirable insertion pathway to formal
oxidation at the metal or other potentially deleterious pathways.

2.3 Experimental Details

General Considerations: All air and water sensitive procedures were carried out
either in a MBraun inert atmosphere glove box under N
2
, or using standard
Schlenk techniques under argon. Pyridine oxide was purified by sublimation.
Labeled reagents H
2
18
O (Cambridge Isotopes) and CH
3
18
OH (Sigma-Aldrich)
were used as purchased. Methyltrioxorhenium was purchased from Strem.
GC/MS analysis was performed on a Shimadzu GC-MS QP5000 (ver. 2)
equipped with cross-linked methyl silicone gum capillary column (DB5). 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.

55

Oxygen labeling:
16
O-MTO + I
18
O
4
-
CH
3
18
OH : 50.5 mg NaIO
4
(2 equivalents)
were added to 0.5 mL H
2
18
O and allowed to equilibrate for 30 minutes at room
temperature with sonication (the exchange of
16
O for
18
O under such conditions is
extremely fast
19
). 25.2 mg MTO were added directly to this solution. The
reaction quickly turned yellow, then clear within one minute of addition. The
reaction mixture was allowed to sit at room temperature for 10 minutes. 1 µL was
analyzed by GC/MS for methanol content. The fragmentation pattern of methanol
produced from the reaction was compared to patterns for CH
3
18
OH and CH
3
16
OH.
Appearance and relative intensities of peaks in the fragmentation pattern matched
that of CH
3
18
OH. No evidence of CH
3
16
OH was present by comparison of the
fragmentation pattern to known mixtures of CH
3
18
OH and CH
3
16
OH. The rate of
18
O incorporation into MTO was slow relative to the incorporation into IO
4
-
and
the production of methanol as measured by GC/MS.

Figure 2.7: Fragmentation pattern for CH
3
16
OH in H
2
O (absolute intensity vs.
m/z).

56

Figure 2.8: Fragmentation pattern for CH
3
18
OH in H
2
O (absolute intensity vs.
m/z).

Figure 2.9: Fragmentation pattern for CH
3
18
OH from MTO + NaI
18
O
4
reaction in
H
2
18
O (absolute intensity vs. m/z).

18
O-MTO labeling:
16
O-MTO + H
2
18
O: To verify that the incorporation of
18
O
into MTO was slow compared to the incorporation into the oxidant, IO
4
-
, we
studied this reaction by GC/MS. 28.5 mg MTO was dried thoroughly in vacuo
inside a flame dried schlenk tube, sealed with a Chemglass Teflon valve. 1.0 g
H
2
18
O was added using standard schlenk technique. The solution was sonicated
57

for 90 minutes to increase the solubility of MTO in solution and promote the
incorporation of
18
O. The solution was analyzed by GC/MS at this point and the
fragmentation pattern compared to the blank (
16
MTO in H
2
O). The solution was
then sonicated for 45 minutes and analyzed again by GC/MS. Though the rate of
incorporation was not explicitly measured, as this would require deconvolution
due to the natural abundance of Re isotopes (
187
Re: 62.60%,
185
Re: 37.4%) it is
clear from the fragmentation intensities that incorporation is slow relative to the
instantaneous reaction of H
2
18
O with IO
4
-

at room temperature. Ignoring the
m/z=248 and 250 peaks as possibly having no incorporation (of course m/z=250
may have one
18
O swapped for a
16
O atom), one concludes that the lower limit of
incorporation at 135 minutes is 57.9% based on fragmentation intensities.

Figure 2.10: Control. Fragmentation pattern of
16
O-MTO in H
2
16
O (absolute
intensity vs. m/z).
58

Figure 2.11: Fragmentation pattern of
16
O-MTO in H
2
18
O after 90 minutes
(absolute intensity vs. m/z).

Figure 2.12: Fragmentation pattern of
16
O-MTO in H
2
18
O after 135 minutes
(absolute intensity vs. m/z).

(CH
3
)ReO
3
(py) + pyO CH
3
O-ReO
3
(py): 12.0 mg MTO were dissolved
in 155 µL pyridine-d
5
. To this solution was added 0.40 mL THF-d
8
, 9.2 mg pyO
(2 eq), and co-axial capillary containing cyclohexane internal standard (3.2 µL
cyclohexane in 50 µL CCl
4
). The
1
H NMR was taken at this point (t
0
). The
solution was heated at 125 °C for 1 h. The solution turned orange and
59

precipitated an orange solid on the walls of the J-Young tube. A yield of 40%
was calculated based on conversion of MTO to methoxide, though this does not
take into account the precipitated product. No other products were detected by
NMR.
MTO + pyO + py-d5 in THF-d8

Figure 2.13:
1
H NMR (py-d
5
/THF-d
8
) of MTO + pyO reaction at t=0 (bottom)
and t = 1 h (top): δ 3.58 and δ 1.67 (residual THF resonances); δ 8.19 (d, 2H, o-
pyO); δ 7.25 (m, overlapping m-pyO and pyridine-h
5
); δ 7.12 (t, 1H, p-pyO); δ
8.58 (d, 2H, pyridine
h5
); δ 7.65 (t, 1H, pyridine
h5
); δ 4.48 (s, CH
3
O-Re); δ1.70 (s,
3H, MTO methyl); δ 1.40 (cyclohexane I.S.).

60

MTO + YO + D
2
O CH
3
OH: All reactions were carried out under air in
D
2
O in eight inch J-Young NMR tubes. Approximately 16 mg (0.067 mmol)
MTO was dissolved in D
2
O with the aid of sonication. 2 equivalents of YO were
added and allowed to react for 1-1.5 hours. The reaction with OsO
4
required 2
equivalents of KOD to produce methanol and thus is reported in Table 1 as [OsO
4

(OH)
2
]
2-
. All appropriate blanks were taken to assign solvent peaks, oxidant
peaks, and product (methanol) formation. NMR spectra were obtained on a
Varian Mercury 400 spectrometer (400.151 MHz for
1
H). Chemical shifts are
given in ppm relative to residual solvent proton resonances (D
2
O at 4.79 ppm).
Cyclohexane (5 µL in 2 mL CCl
4
) was used as an external standard. All
reactions were carried out under air at room temperature.

Figure 2.14:
1
H NMR of MTO in D
2
O with cyclohexane internal standard. δ 2.38
(s, 3H, MTO methyl); δ1.57 (s, cyclohexane I.S.); δ 4.79 (H
2
O
residual peak).
61

Figure 2.15:
1
H NMR of MTO + H
2
O
2
in D
2
O with cyclohexane internal
standard: δ 2.70 (s, 3H, MTO methyl); δ1.40 (s, cyclohexane I.S.);
3.14 (s, 3H, methanol).

Figure 2.16:
1
H NMR of MTO + PhIO in D
2
O with cyclohexane internal
standard: δ 1.52 (cyclohexane); δ 2.36 (s, 3H, MTO methyl); δ 3.28
(s, 3H, methanol); δ 4.79 (H
2
O residual peak).

62

Figure 2.17:
1
H NMR of MTO + NaIO
4
in D
2
O with cyclohexane internal
standard: δ 1.56 (cyclohexane); δ 3.28 (s, 3H, methanol); δ 4.79
(H
2
O residual peak).

Theoretical Considerations: All theoretical calculations were performed with
the B3LYP
20,21
density functional, in combination with the Jaguar 6.0
22

computational package. Rhenium and osmium were described with the effective
core potential of Hay and Wadt,
23
iodine with the effective core potentials of
Ermler and colleagues
24
while all other atoms used the 6-31G**
25
all electron
basis set. The effects of diffuse functions (namely 6-31G**++) were included
with single point calculations. Solvation effects, in water, (computed via single
point corrections) were modeled implicitly with the PCM
26,27
model (ε = 80.37,
r
solv
= 1.4).

63

Figure 2.18: B3LYP/LACVP/6-311G** BV-type Transition State for MTO +
IO
4
-

As shown in Figure 7, the BV-type transition state involves concerted methyl
migration and IO loss as observed by stretching of the C-Re bond from 2.168 Å
to 2.516 Å and the I-O bond from 1.803 Å to 2.399 Å
Cartesian coordinates, enthalpies of key reactants, intermediates and products:

MTO: Enthalpy -344.735079
Re 0.0225076773 -0.0389976943 0.9841137885
O -0.0412669306 0.0721630199 -0.7188448601
O -0.8650944722 -1.3564082344 1.6111155616
O 1.6068674707 0.0713482115 1.6119648144
C -0.9620317510 1.6659935371 1.6802485195
H -0.4377146603 2.5502800084 1.3083854987
H -0.9545215728 1.6546922393 2.7734008924
H -1.9904965715 1.6534915104 1.3097371021

OOH- reaction
64

HOOH: Enthalpy -151.524452
H -1.0954082085 -0.5181115430 -0.1127101386
O -0.6955460318 0.2156509838 0.3804764064
O 0.6951350748 -0.2155547136 0.3803823417
H 1.0951998361 0.5183769146 -0.1123842364

OOH-: Enthalpy -151.094175
O -0.7310552170 0.2271846813 0.3801763264
O 0.7306760620 -0.2271883720 0.3807340958
H 1.0946951166 0.5199633660 -0.1132043404

OH-: Enthalpy -75.971064
O 0.7302746777 -0.2280123124 0.3812787519
H 1.1010653770 0.5330398984 -0.1218484279

Complex: Enthalpy -495.832953
Re 0.0298271438 -0.0255134190 0.9853726224
O 0.7791697496 0.6990804187 -0.4016481557
O -0.3480621300 -1.6513396528 0.3984820841
O 1.1841411740 -0.0772697496 2.2620460995
C -0.9084243165 1.9526485893 1.2227400199
H -0.0950584448 2.6837576753 1.2000729724
H -1.4685507152 2.0070682718 2.1550157327
H -1.5740067000 2.1296874465 0.3744139270
O -1.7823399141 -0.2282879115 1.8730081936
O -2.2045452262 -1.6020674937 2.1093129530
H -1.6651819166 -2.0383345475 1.4026224542

Baeyer-Villager Transiton State: Enthalpy -495.800542
Re 0.0925144043 0.0569160102 -0.0015241948
O -0.5923406510 -0.4016474321 1.5326356769
O 1.6806269868 0.5655635261 0.4701284185
O 0.0984742678 -1.4222616653 -0.8890690619
C -2.1595823735 1.2856073095 0.0884650738
H -2.6995686603 0.3396596418 0.0882243655
65

H -2.5725467561 2.0002569508 -0.6169751156
H -2.0270673552 1.6830849346 1.0914193806
O -0.5029402316 1.4013033038 -1.1387515027
O 0.9672094661 1.1653969133 -2.2162263003
H 1.5574174855 1.7306991857 -1.6926802475

Product: Enthalpy -419.958234
Re 0.0960135290 -0.0252090513 0.0083133782
O 0.3207157605 0.3447293605 1.6623250847
O 1.5749838015 0.0830802637 -0.8394712242
O -0.5557180356 -1.6010380673 -0.1149101093
C -2.4434719506 1.4583523647 -0.3570414263
H -3.0467614877 0.5509411150 -0.4585325560
H -2.8165460393 2.2307213282 -1.0323814459
H -2.4762597794 1.8177760364 0.6760502544
O -1.0845566309 1.1937849604 -0.7443093694

PyO reaction
PyO: Enthalpy -323.379837
C -1.2453415647 -0.1912252723 0.0002757594
C 0.1376857259 -0.2051196657 0.0002519491
C 0.8606448469 0.9894878081 -0.0004860143
C 0.1377958141 2.1841618802 -0.0011930686
C -1.2452333159 2.1703967678 -0.0011578157
H -1.8754819987 -1.0700577673 0.0008263226
H 0.6412578248 -1.1663931709 0.0008209650
H 1.9444614065 0.9894369751 -0.0005091501
H 0.6414583301 3.1453876167 -0.0017836474
H -1.8752944511 3.0492868349 -0.0016814267
N -1.9494849913 0.9896184123 -0.0004258756
O -3.2228763298 0.9896770390 -0.0003983688

Py: Enthalpy -248.209568
C -1.2692437223 -0.1526414456 0.0002607430
C 0.1256196330 -0.2088805465 0.0002601027
66

C 0.8378780829 0.9895048952 -0.0004872800
C 0.1257009862 2.1879409818 -0.0011950523
C -1.2691601068 2.1318083715 -0.0011244425
H -1.8544479484 -1.0711281496 0.0008267178
H 0.6355253817 -1.1673526370 0.0008236424
H 1.9243557612 0.9894656194 -0.0005195675
H 0.6357047258 3.1463601195 -0.0017910419
H -1.8542958606 3.0503385868 -0.0016694354
N -1.9675430946 0.9896093263 -0.0004161403

Complex: Enthalpy -668.115827
Re -0.0283353162 -0.0733140427 -0.0126672563
O 1.4077973818 -0.4457883853 1.9559748106
O -0.7203858684 0.2978608126 -1.5312043221
O -0.7834254794 0.9500135419 1.1442046657
O -0.2262522282 -1.7643207189 0.2258446822
C 1.9263645389 0.5164038542 -0.5679251586
H 2.2238926494 -0.1000125853 -1.4215845614
H 2.6153896524 0.3921580538 0.2645744965
H 1.8761728020 1.5615871146 -0.8872520501
C 0.6231529854 -2.2762308891 3.1280073772
C 0.1722926673 -0.0791814816 3.8739393289
C -0.0610522622 -2.8035256214 4.2104016616
H 1.0879725743 -2.8538759817 2.3421701342
C -0.5185736486 -0.5730646916 4.9676506634
H 0.3039801788 0.9672102254 3.6396881816
C -0.6412627991 -1.9510336707 5.1505502790
H -0.1355977339 -3.8811732038 4.3030774794
H -0.9587811770 0.1306185122 5.6650911409
H -1.1793041601 -2.3507619180 6.0029450169
N 0.7395875377 -0.9297256451 2.9773588070

Baeyer-Villager Transition State: Enthalpy -668.064204
Re -0.0085348126 0.0290036580 0.0706414122
O 0.0152669732 -0.1380269548 2.0014431810
C 1.9750188822 0.3546044552 1.3422552660
N -1.5421420243 -0.5486446055 2.7296410086
O 0.7883687521 -1.1709062413 -0.8638872680
O 0.1659723515 1.5967691918 -0.6076644779
O -1.6997419577 -0.3533622093 0.0939073618
67

H 2.3407366463 -0.5453400860 1.8238346055
H 1.9467833083 1.2239316601 1.9894633639
H 2.4972231267 0.5587852592 0.4035031909
C -1.7614126666 -1.8240817633 3.0400960969
C -2.3245601959 0.4412178904 3.1539240251
C -2.8543185891 -2.1734085416 3.8286732307
H -1.0565287764 -2.5456265183 2.6421944871
C -3.4351880055 0.1629536311 3.9457465962
H -2.0497801776 1.4425878913 2.8418922604
C -3.7016736746 -1.1637613004 4.2868974195
H -3.0307278051 -3.2152588015 4.0718550242
H -4.0729902378 0.9733119815 4.2809354368
H -4.5609087832 -1.4081642203 4.9029513384

η
2
-peroxo Transition State: Enthalpy -668.040308
Re 0.0624229735 0.0929855350 0.1148554018
O 0.0933715171 -0.8053029649 1.6800524689
O 1.7356600616 -0.6198029599 1.0061822269
N 3.4699882358 -0.4453954372 0.3691885905
O -0.8991264370 -0.7929565791 -0.9828237174
O -0.5891737295 1.6434640809 0.4071879039
C 1.4478843099 0.7658959342 -1.3833084208
H 0.8075840941 1.2646379865 -2.1159161738
H 1.9623377373 -0.0716671894 -1.8531111502
H 2.1671784651 1.4753709839 -0.9766532877
C 4.0111083681 -1.4772025588 -0.2791437339
C 4.2270085764 0.4976189804 0.9307649587
C 5.3923698382 -1.5870294166 -0.4256780056
H 3.3179013542 -2.2132616043 -0.6740860070
C 5.6157507994 0.4583647350 0.8272943445
H 3.6986644502 1.2792150484 1.4674375639
C 6.2052414845 -0.6013006229 0.1362000026
H 5.8141786307 -2.4296661764 -0.9626928985
H 6.2145620006 1.2383136356 1.2849218171
H 7.2849767733 -0.6620723931 0.0430527563

Product: Enthalpy -419.958234
Structure same as OOH- product.
68

IO
4
- Reaction
IO
4
-: Enthalpy -412.288013
I -0.3488049918 0.3729442403 -0.0095806512
O 0.2665189166 1.2826546404 -1.4392713358
O -2.1499153212 0.3142055189 -0.0638167927
O 0.3080813504 -1.3057771050 -0.0372813961
O 0.1800028342 1.2006511465 1.5022063895

IO
3
-: Enthalpy -337.145366
I -0.3391880367 0.3879665852 0.0178202602
O 0.2618689636 1.2755533045 -1.4573055975
O -2.1582312765 0.3057806960 -0.0796754760
O 0.3038257539 -1.3169447465 -0.0528848218

Baeyer-Villager Transition State: Enthalpy -756.996419
Re 0.0125788072 -0.0317477788 0.0160164527
O -0.0534120389 0.0082720311 1.7367133655
O 1.6598328991 -0.1326246661 -0.4891221793
O -0.2777119564 1.6046665450 -0.8558098364
O -0.8569993435 -1.3820537344 -0.6062302405
C -2.1375939174 1.2733802799 -0.0180711596
H -2.5734694769 1.3251801555 -1.0070006458
H -2.0523133382 2.2126597196 0.5122241572
H -2.5058240134 0.4462201087 0.5910786957
I 1.5805998896 2.5405607427 -2.0508271140
O 0.6240116586 3.9792654094 -2.5811742513
O 2.9926767633 3.1222770178 -1.0773436265
O 2.1546598663 1.6623581215 -3.5269952758

η
2
-peroxo Transition State: Enthalpy -756.964939
Re -0.0589378784 0.0003845822 -0.0153604521
O -0.0604775362 -0.0022140352 1.8322308989
O 1.4627757478 -0.0001385500 1.2554496647
I 4.0502734276 0.0033312041 0.6251010514
O -0.8314905435 -1.4173712439 -0.5710615777
O -0.8317733230 1.4192945439 -0.5675807072
69

C 1.4823839491 0.0021137889 -1.4815235915
H 0.9351553858 0.0026515109 -2.4289955277
H 2.1043224281 -0.8905829802 -1.3863569759
H 2.1037130463 0.8951104476 -1.3850593024
O 4.3726874336 1.4736518689 -0.3998671866
O 4.3757652622 -1.4666957526 -0.3993406744
O 5.2069415444 0.0047727063 2.0230808793

Product: Enthalpy -419.958234
Structure same as OOH- product

PhIO Reaction
PhIO: Enthalpy -418.142340
C -2.5331172743 0.6144599249 -0.0617961204
C -1.1508928402 0.4238865499 0.0188825993
C -0.3281927309 1.5423128353 -0.0580449172
C -0.8229275879 2.8318810894 -0.2098995559
C -2.2074217087 3.0039132056 -0.2874632030
C -3.0591784144 1.8991978279 -0.2150230612
H -3.1948234494 -0.2451974248 -0.0046737500
H -0.7415038221 -0.5757123678 0.1385802180
H -0.1282214064 3.6684160667 -0.2648751230
H -2.6193820817 4.0021358626 -0.4067247953
H -4.1347945506 2.0377465035 -0.2785718398
I 1.8245299593 1.4062976055 0.0495021421
O 2.2937770171 3.2194862384 -0.1044916291

PhI: Enthalpy -343.019569
C -2.5292103574 0.4387685805 0.0002127487
C -1.1325406835 0.4307501315 0.0006156919
C -0.4460895929 1.6459698872 0.0001828524
C -1.1324470471 2.8612315692 -0.0008902187
C -2.5291042359 2.8533199227 -0.0013423806
C -3.2292367927 1.6460730597 -0.0007603293
H -3.0659632985 -0.5056010328 0.0006343804
70

H -0.5907046282 -0.5088195556 0.0015881560
H -0.5905197053 3.8007512670 -0.0012188136
H -3.0658097355 3.7977169249 -0.0020932946
H -4.3149104335 1.6461455571 -0.0011219934
I 1.6964303864 1.6458386763 0.0010554152

Complex: Enthalpy -762.887453
Re -0.1136171847 0.4606042883 0.1380386389
O 0.5058859271 1.7311349611 1.0961640391
O 1.2909028156 -0.2260926545 -0.7856905771
O -0.6631263436 0.7473893459 -1.7681078828
O -0.7402017034 -0.8136438972 1.0868680222
C -2.0933796894 1.4263069046 0.0046520384
H -2.3377318370 1.5405749261 1.0635471986
H -2.7932665673 0.7682192360 -0.5031437142
H -2.0072398468 2.3872440922 -0.4952721889
I 0.7993732932 0.0461318866 -3.0098384667
C -0.4829214991 0.6315260344 -4.6334598857
C -0.7830409384 -0.3104461790 -5.6198199055
C -0.9684944832 1.9395046896 -4.7147336214
C -1.5620266745 0.0709753652 -6.7155734697
H -0.4239349490 -1.3325619932 -5.5405545969
C -1.7572755032 2.3051093347 -5.8054544506
H -0.7454893768 2.6584664387 -3.9336367488
C -2.0490663644 1.3749477150 -6.8068596198
H -1.7958816839 -0.6564039256 -7.4871695551
H -2.1414783569 3.3185352679 -5.8740312189
H -2.6599089608 1.6666933405 -7.6556996266

Baeyer-Villager Transition State: Enthalpy -762.874390

Re 0.1928708004 -0.3016777024 -0.1767187369
O 1.2324198720 -0.0915942402 1.1717919619
O 1.1859973200 -0.6631682246 -1.6018958902
O -0.3122450370 1.2296488538 -1.2103682050
O -0.9330497395 -1.5781150108 0.0382282749
C -1.3342839207 1.1717809747 0.7972955940
H -1.3972332617 0.5734052067 1.7073742463
H -2.2490982693 1.1870079151 0.2184230210
H -0.8725836605 2.1406404103 0.9409032974
I 0.7070655384 1.2589495901 -3.1826753009
C 2.1258169685 0.1038501647 -4.3062640134
71

C 3.4829110640 0.4190794980 -4.2153636526
C 1.6698503945 -0.9255194031 -5.1319401307
C 4.3955591990 -0.2954766034 -4.9929376951
H 3.8277364368 1.2064198292 -3.5535152776
C 2.5946764567 -1.6307259071 -5.9031531558
H 0.6154646024 -1.1758761520 -5.1777396137
C 3.9532498600 -1.3172197919 -5.8346208443
H 5.4525955962 -0.0543002916 -4.9333553385
H 2.2498548448 -2.4290131201 -6.5534465535
H 4.6680395888 -1.8732857721 -6.4333489646

η
2
-Peroxo Transition State: Enthalpy -762.852895
Re 0.1584963588 -0.2252561677 -0.1977264655
O -0.1422985097 -1.0079163833 1.3711162699
O 1.6689188727 -0.3106101807 1.2637376383
I 3.6779057475 0.4708184523 1.4887971073
O 0.3771228085 -1.4022153266 -1.4113658015
O -1.2543164580 0.6843723125 -0.5148702239
C 1.4041575765 1.3367334722 -1.0000491578
H 0.8946450388 1.6255793919 -1.9229438528
H 2.4079369344 0.9865978592 -1.2351172339
H 1.4418331457 2.1919274924 -0.3232835593
C 5.0423828702 0.1064738130 -0.1102023200
C 5.3651931145 1.1490852195 -0.9835150809
C 5.5878953056 -1.1717226021 -0.2584899177
C 6.2779005748 0.9052092917 -2.0111095601
H 4.9229582047 2.1323865208 -0.8641837528
C 6.4942530555 -1.3980249011 -1.2943774231
H 5.3148756749 -1.9733377042 0.4190564664
C 6.8407169348 -0.3628538256 -2.1653350169
H 6.5436280034 1.7091924337 -2.6899905213
H 6.9272379163 -2.3854653869 -1.4180050302
H 7.5484394447 -0.5459736273 -2.9675012243

Product: Enthalpy -762.875227
Product Structure Same as OOH- case

72

2.4 Chapter 2 References

1 We define the CH activation reaction as a coordination reaction that proceeds
without the involvement of free-radicals, carbocations or carbanions, to generate
discrete M-R intermediates. (a) Arndtsen, B. A.; Bergman, R. G.; Mobley, T. A.;
Peterson, T. H. Acc. Chem. Res. 1995, 28, 154 and citations therein. (b) 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 and citations therein.

2 Crabtree, R. H. J. Organomet. Chem. 2004, 689, 4083.

3 (a)Tenn, W. J., III; Young, K. J. H.; Bhalla, G.; Oxgaard, J.; Goddard, W. A.,
III; Periana, R. A. J. Am. Chem. Soc. 2005, 127, 14172. *A related heteroatom C-
H activation reaction that does not generate a functionalized product is found
herein: Feng, Y.; Lail, M.; Barakat, K., Cundari, T.; Gunnoe, T.B.; Peterson, J.L.
J. Am. Chem. Soc. 2005, 127, 14174.

4 Formal oxidation of electropositive metals is likely to inhibit the CH activation
reaction and free-radicals would react with the alcohol product.

5 Kim, S.; Choi, D.; Lee, Y.; Chae, B.; Ko, J.; Kang, S. Organometallics 2004,
23, 559 and references therein.

6 (a) Matano, Y.; Northcutt, T. O.; Brugmann, J.; Bennett, S. L.; Mayer, J. M.
Organometallics 2000, 19, 2781. (b) Brown, S.; Mayer, J.M. J. Am. Chem. Soc.
1996, 118, 12119.

7 A peroxo bond is a weak O-O high energy bond, DH = 33 kcal/mol

8 Smith, M. B. Organic Synthesis; McGraw Hill: New York, 2004.

9 Brown, H.C.; Midland, M.M.; Kabalka, G.W. Tetrahedron 1986, 20, 5523.

10 Köster, R.; Morita, Y. Angew. Chem. Int. Ed. 1966, 5, 580.

11 (a) Kuhn, F.E., Scherbaum, A.; Herrmann, W.A. J. Organomet. Chem. 2004,
4149.(b) Owens, G. S.; Arias, J., Abu-Omar, M. M. Catalysis Today 2000, 55,
317. (c) Espenson, J. H. Chem. Comm. 1999, 479 and references therein.

12 Owens, G.S.; Arias, J.; Abu-Omar, M.M. Catalysis Today 2000, 55, 317.

13 Abu-Omar, M. M.; Hansen, P. J.; Espenson, J. H. J. Am. Chem. Soc. 1996,
118, 4966.

73

14 Solvent optimized B3LYP/LACVP** (with corrections for diffuse functions)
enthalpies are in kcal mol-1.

15 The rate of O-atom exchange between IO
4
-
and MTO is slow compared to the
rate of formation of methanol as explained in the Experimental section.

16 Edwards, P.; Wilkinson, G. J. Chem. Soc. Dalton Trans. 1984, 2695.

17 Wang, W.D.; Espenson, J.H. J. Am. Chem. Soc. 1998, 120, 11335.

18 Gonzales, J. M.; Distasio, R., Jr.; Periana, R. A.; Goddard, W. A., III;
Oxgaard, J. J. Am. Chem. Soc. 2007, 129, 15794.

19 Pecht, I.; Luz, Z. J. Am. Chem. Soc. 1965, 87, 4068-4072.

20 Becke, A. D., J. Chem. Phys. 1993, 98, 5648.

21 Lee, C.; Yang, W.; Parr, R. G., Phys. Rev. B. 1988, 37, 785.

22 Jaguar 6.0. Schrodinger, LLC: Portland, Oregon, 2005.

23 Hay, P. J.; Wadt, W. R., J. Chem. Phys. 1985, 82, 299.

24 LaJohn, L. A.; Christiansen, P. A.; Ross, R. B.; Atashroo, T.; Ermler, W. C.,
J. Chem. Phys. 1987, 87, 2812.

25 Harihara, P. C.; Pople, J. A., Theo. Chim. Acta. 1973, 28, 213.

26 Tannor, D. J.; Marten, B.; Murphy, R.; Friesner, R. A.; Sitkoff, D.; Nicholls,
A.; Ringnalda, M.; Goddard, W. A.; Honig, B., J. Am. Chem. Soc. 1994, 116,
11775.

27 Marten, B.; Kim, K.; Cortis, C.; Friesner, R. A.; Murphy, R.; Ringnalda, M.;
Sitkoff, D.; Honig, B., J. Phys. Chem. 1996, 100, 9098.

74

3 Chapter 3: Oxy-Functionalization of Electron-Rich
Metal Alkyl with OsO
4

3.1 Introduction

Selective, low temperature hydroxylation of alkanes catalyzed by
transition metal complexes is an important area of study given the possible
applications to natural gas conversion as well as more efficient production of bulk
chemicals and energy (see Chapter 1 for a full introduction). Several promising
electrophilic catalysts that couple C-H activation to facile oxy-functionalization of
the resulting electron-poor M-R intermediates have been reported (Figure 1).
1
To
address practical challenges with these electrophilic catalysts, such as water and
product inhibition,
2
we are currently designing new systems based on more
electron rich metals, such as iridium, osmium, ruthenium, and rhenium. However,
while oxy-functionalization reactions of electron-poor M-R intermediates are
known,
2
there are no reports of facile oxy-functionalization reactions of more
electron-rich M-R species
3
that can potentially be coupled to C-H activation with
electron-rich catalysts to develop efficient catalytic cycles.

75

Figure 3.1: General Activation/Functionalization Catalytic Cycle for
Hydroxylation of Hydrocarbons.

We recently reported a Baeyer-Villiger (BV) type O-atom transfer
mechanism (Chapter 2) for the non-redox oxy-functionalization of the metal-
carbon bond in methyltrioxorhenium (MTO), a convenient model for water stable
and soluble M-R species of a more electron-rich metal.
4
The proposed mechanism
for this functionalization reaction is fundamentally different than for more
electron-poor M-R species,
2
featuring the transfer of a nucleophilic methyl group
(R = -CH
3
α-
) to the electrophilic oxygen of an incoming O-atom donor, YO
(Figure 3.2, BV). To expand the scope of electron-rich M-R functionalization
reactions that could potentially be coupled to C-H activation we are currently
exploring a range of mechanisms for oxy-functionalization with O-donors. An
important goal is to identify pathways that do not involve free-radicals, that are
compatible with C-H activation reactions of electron-rich metals, and that are
sufficiently fast and selective to intercept and convert electron-rich M-R
intermediates to oxygenated products.
76

Figure 3.2: BV and (3+2) Transition States for Functionalization of M-R with
YO and cis-LMO
2
.

One intriguing possibility is the use of cis-metal dioxo compounds that
can react with M-R σ-bonds via a (3+2) type addition reaction (Figure 3.2).
Related mechanisms are well known for the cis-dihydroxylation of alkenes by
OsO
4
,

5
and have recently been implicated in the oxidation of hydrogen,
6

silanes,
7

and alkanes.
8
Significantly, in all of these examples OsO
4
is activated by
coordination of a Lewis base (including hydroxide) to the osmium center,
followed by addition of the substrate bond across the three atom moiety
(O=Os=O). The nature of this activation is discussed in detail in the chemical
literature, though a personal favorite is the account by Roald Hoffmann in the
Journal of the American Chemical Society in 1986.
9
The reaction of OsO
4
with
ethylene and OsO
4
(py) with ethylene are contrasted using a simple MO
description that shows that OsO
4
(py) is more reactive with the interacting HOMO
and LUMO of ethylene.

77
3.2 Results and Discussion

Here we report the facile oxy-functionalization of MTO to methanol by
reaction with OsO
4
in aqueous basic media at room temperature. The
stoichiometry is given in Eq 1. Interestingly, this reaction requires coordination
of a base to the MTO rather than OsO
4
. Density Functional Theory (DFT) suggest
that this reaction proceeds via a novel, cyclic (3+2) transition state (TS) featuring
transfer of a nucleophilic methyl group.

Treatment of MTO at room temperature with basic, aqueous (D
2
O)
solutions containing excess OsO
4
resulted in the quantitative conversion (>95%)
to CH
3
OD upon mixing in the presence or absence of air. High yields of
methanol required a 5-10 fold molar excess of both OsO
4
and OH
-
. Under these
reaction conditions, no intermediates or other species were detected by in situ
1
H
NMR, except for trace amounts of CH
3
D attributed to the known hydroxide
induced decomposition of MTO.
10
The reactions are very rapid and even at
temperatures as low at -40
o
C (using diglyme-d
14
solvent) the reaction is
essentially complete on mixing. Notably, no reaction occurred between OsO
4
and
MTO in D
2
O in the absence of added KOD.

78

Figure 3.3: 400 MHz
1
H NMR of (a) MTO + OsO
4
(1:1) in D
2
O and (b) MTO +
OsO
4
(1:1) in D
2
O with 3 equivalents added KOD.

In situ
1
H-NMR studies of the reaction of stoichiometric quantities of
OsO
4
, MTO and OH
-
at room temperature showed that ~75% of the MTO is
converted to methanol (46%, at δ 3.30), another methyl species (29%, at δ 4.30),
and base coordinated CH
3
ReO
3
(11%, at δ 1.69, Figure 3.3B).
11
It is possible
that the species at δ 4.30 is an intermediate containing either a Re-OCH
3
or Os-
OCH
3
fragment (that could be generated from BV or (3+2) type mechanisms,
respectively). This species is not seen at any time when excess OsO
4
and OH
-
are
used, or when the system is buffered at high pH (vide infra), and could not be
isolated as a discrete, well characterized compound.
Since hydroxide is consumed in the reaction, we examined the reactions at
room temperature with various pH buffers. Importantly, in situ
1
H NMR analysis
of the stoichiometric reaction in a NaH
2
PO
4
/Na
2
HPO
4
buffer at pH 7.8 showed
79
that free MTO is completely consumed after 2 hours and that a dark, unidentified
precipitate is generated along with a 15% yield of methanol. In contrast, reaction
in a pH 11.1 buffer (Na
2
HPO
4
/Na
3
PO
4
) resulted in 70% yield of methanol in the
same time (relative to added MTO) with no other detectable methyl products. As
noted above, with excess NaOH and OsO
4
the reaction is essentially quantitative
on mixing. We are currently investigating the pH dependence of this reaction as
well as the identity and reactivity of the observed intermediates and precipitate.
Significantly, reactions of
16
O-MTO with
18
O-enriched OsO
4
unequivocally show
that the methanol oxygen is derived either from OsO
4
or H
2
O but not from
MTO.
12
Since O-atom exchange between H
2
O and OsO
4
is fast (but slow with
MTO)
4
in aqueous base on the time scale of the reaction we could not
unambiguously determine if the methanol oxygen is derived from OsO
4
or H
2
O.
There are several plausible mechanisms that can account for this
functionalization reaction and its acceleration by hydroxide. One possibility is a
BV-type reaction with base coordinated OsO
4
playing the role of O-donor.
4

Another is a (3+2) type reaction between the various possible hydroxide adducts
of MTO and OsO
4
. Given the experimental challenges in distinguishing between
these different mechanisms, we have used B3LYP DFT to investigate pathways
for the reaction of OsO
4
and MTO under basic conditions.
B3LYP predicts the transformation of [OsO
4
(OH)]
-
and [CH
3
ReO
4
]
2-
(the
ground state base adducts of OsO
4
and MTO, respectively, in aqueous basic
media) to methanol, [OsO
2
(OH)
4
]
2-
and [ReO
4
]
-
to be highly exothermic (ΔH = -
82.6 kcal mol
-1
, Figure 4).
13
Since the various methyl Re and Os oxo anions likely
80
equilibrate (Eqs 2-5), we explored plausible TSs from the various combinations of
these reactants.

OsO
4
+ OH
-
 [OsO
4
(OH)]
-
ΔH = -1.5 kcal mol
-1

(2)
[OsO
4
(OH)]
-
+ OH
-
 [OsO
5
]
2-
+ H
2
O ΔH = -3.9 kcal mol
-1

(3)
CH
3
ReO
3
+ OH
-
 [CH
3
ReO
3
(OH)]
-
ΔH = -6.4 kcal mol
-1

(4)
CH
3
ReO
3
(OH)
-
+ OH
-
[CH
3
ReO
4
]
2-
+ H
2
O ΔH = -3.4 kcal mol
-1

(5)
81

Figure 3.4. Pathways for MTO functionalization by OsO
4
in basic
aqueous media (B3LYP/LACVP**, bond distances in Å, kcal mol
-1
).
Figure 3.4: Pathways for MTO functionalization by OsO
4
in basic aqueous media (B3LYP/LACVP**, bond
distances in Å, kcal mol
-1
.
82

Consistent with the observed rapid reaction at room temperature, a low
energy pathway with an activation enthalpy of only 11.7 kcal mol
-1
was found for
the reaction of [CH
3
ReO
4
]
2-
with uncoordinated OsO
4
(Figure 4A, (2+3)). In this
pathway, one of the oxygen atoms on the [CH
3
ReO
4
]
2-
coordinates to the metal
center of OsO
4
as the methyl group is transferred to a cis-oxygen on OsO
4
.
Interestingly, by the (2+3) pericyclic nomenclature, this makes the Os=O bond the
two atom fragment, and [CH
3
ReO
4
]
2-
the three atom fragment. In the well-known
Sharpless dihydroxylation reaction between ligated OsO
4
and olefins, the cis-
OsO
2
motif is the three-atom fragment and the alkene is the two-atom fragment.
Similarly, in the recently reported reactions of H
2
with base coordinated OsO
4
,
[OsO
4
(OH)]
-
, the H-H σ-bond is the two-atom fragment and the cis-OsO
2
the
three-atom fragment.
6
(3+2) pathways where cis-OsO
2
acts as the three-atom
fragment with the two-atom fragment of MTO (and hydroxide adducts) were also
located, but have considerably higher activation enthalpies (e.g. Figure 4C,
(3+2)).
One possible explanation for why the (2+3) TS in pathway A is favored
with added base is that, similar to the BV-type reaction of MTO, in spite of the
high formal oxidation state of the Re
VII
center, it features a nucleophilic methyl
group transfer to an electrophilic oxygen. Significantly, this is opposite to that
typically found for oxy-functionalization of electron-poor M-R species
2
where the
oxygen acts as the nucleophile and the carbon as the electrophile. Given the
83
dearth of facile functionalization reactions of electron-rich M-R species and the
unusually low barrier for this reaction, it is important to establish the nature this
(2+3) TS as this could provide guidance to develop new strategies and reactions
for the functionalization of other electron-rich M-R intermediates.
Nucleophilic, rather than electrophilic, methyl transfer is consistent with
the lowest TS resulting from reaction with [CH
3
ReO
4
]
2-
; the methyl group in O
2-

activated MTO is expected to be the most nucleophilic methyl group of all the
equilibrated MTO species, while the oxygens in uncoordinated OsO
4
would
plausibly be the most electrophilic. The very low activation enthalpy of 11.7 kcal
mol
-1
for this pathway is contrasted to the lowest energy TS, a BV-type at 36.7
kcal mol
-1
(Figure 4B), that could be indentified for the methyl transfer between
uncoordinated MTO and OsO
4
. Other combinations involving hydroxide
coordinated MTO reacting with uncoordinated and base coordinated OsO
4
as well
as base coordinated OsO
4
with uncoordinated MTO were also examined. In some
cases, such as the reaction of [CH
3
ReO
3
(OH)]
-
with OsO
4
and the reaction of
[OsO
5
]
2-
with uncoordinated MTO, no transition states were located after
extensive searching. In cases where TSs were located, activation enthalpies were
all greater than 20 kcal mol
-1
. The next lowest activation enthalpy is for a BV-
type reaction of [OsO
4
(OH)]
-
with uncoordinated MTO (22.7 kcal mol
-1
, Figure
4C). The (3+2) TS for this reaction has an even larger activation enthalpy of 27.8
kcal mol
-1
. The lowest barrier found for reaction of [OsO
4
(OH)]
-
with
[CH
3
ReO
3
(OH)]
-
was 23.5 kcal mol
-1
(see Experimental Section).
84
The relative ranking of these activation enthalpies is consistent with the
fastest reaction proceeding when the methyl group is most nucleophilic and the
oxygen is most electrophilic. As can be seen in Figure 5, coordination of the
strong base, O
2-
, to MTO to generate [CH
3
ReO
4
]
2-
localizes the highest occupied
molecular orbital (HOMO) on the methyl group and increases the negative
polarization while significantly stretching the Re-CH
3
bond. Figure 5 shows this
activation of the Me-Re bond relative to MTO as hydroxide and then O
2-
is
coordinated to the Re center. As can be seen, the CH
3
-Re bond increases from
2.086Å to 2.218Å to 2.368Å while the negative carbon atom Mulliken charge and
the energy of HOMO both increase. Combined, these factors serve to facilitate
interaction of the nucleophilic methyl group with the electrophilic oxygen of
uncoordinated OsO
4
, ultimately providing a low barrier for oxy-functionalization
and provides a basis for the enormous acceleration of the reaction by added base.

Figure 3.5: HOMO orbitals and energies (eV), Re-C bond lengths (Å), and
Mulliken carbon atomic charges (e) of MTO Species.

85
The major frontier orbital interaction in the low energy TS involves the
Re-CH
3
bond (HOMO of [CH
3
ReO
4
]
2-
) interacting with the LUMO+1 orbital on
the Os bound oxygen through a σ-interaction as well as a π-interaction of the Re-
O lone pair with an unoccupied d-orbital on the Os center (see Experimental
Section for details). This π-interaction helps stabilize the cyclic transition state; no
lower energy TSs for pathways where osmium remains four-coordinate were
found (e.g. S
N
2 type attack of the methyl on an Os=O bond). In this TS, the Re-C
bond is almost completely broken (2.920 Å), and the incipient O-C bond length is
2.540 Å, which indicates possible radical character.
4b
Therefore, we explored the
singlet and triplet surfaces along the intrinsic reaction coordinate to show that this
TS does not decompose to discrete free radicals. The possibility of a free radical
mechanism is important, particularly considering the recent investigation of
possible radical mechanisms for oxidation of alkanes by OsO
4
.
14
Also, since MTO
and its congeners have relatively low homolytic Re-C bond strengths,
15
there
could be a proclivity for radical functionalization pathways. Significantly, the
observation that there are no changes in reaction yield or methanol selectivity
when the reactions are carried out under ~200 psig of pure O
2
is evidence against
a free-radical mechanism.
We also considered that activation of the MTO might be possible using
other bases by similar mechanisms. Common Lewis bases such as pyridine and
amines are well known to activate OsO
4
in alkene cis-dihydroxylation
16
reactions
and to bind well to MTO. Hydroxide was thus replaced with the water soluble,
substituted pyridine, isonicotinic acid (the p-carboxylic acid). The reaction of
86
MTO with OsO
4
and 3 equivalents of isonicotinic acid buffered at pH 7.8 resulted
in 65% yield of methanol. The significantly higher yield upon addition of a
pyridine base (relative to 15% without pyridine base, vide infra) is evidence for
the possibility of general base activation of the MTO and could potentially lead to
methods for the stereoseletive oxy-functionalization of M-R intermediates by the
use of chiral bases as activating agents.
The work communicated here establishes the viability of using cis-metal
dioxo compounds, such as OsO
4
, as reagents for the facile, selective
functionalization of electron-rich metal alkyl species. We have also established
the concept of activation of electron-rich M-R species by coordination of bases
that can lead to low energy TSs by increasing the nucleophilicity of the R group.
Here, this involves a novel, cyclic (2+3) transition state leading to methyl group
transfer from the activated [CH
3
ReO
4
]
2-
species to unactivated OsO
4
. These
results serve to advance efforts toward the de novo design of catalytic systems for
hydroxylation of hydrocarbons based on integrating non-radical functionalization
reactions with CH activation using more electron-rich metals that are expected to
be less sensitive to water inhibition.

87
3.3 Experimental Section

All air and water sensitive procedures were carried out either in a
MBraun inert atmosphere glove box under N
2
, or using standard Schlenk
techniques under argon. Labeled reagents D
2
O, H
2
18
O (Cambridge Isotopes) and
KOD solution (40% wt. 98+ atom % D, Sigma-Aldrich) were used as purchased.
Water, D
2
O, and KOD were degassed by thoroughly purging with dry argon gas.
Methyltrioxorhenium was purchased from Strem. OsO
4
was purchased from
Pressure Chemical. Na
3
PO
4
was purchased from J.T. Baker Chemical Company,
Na
2
HPO
4
from Mallinckrodt, and KH
2
PO
4
from EMD. Sodium isonicotinate
was purchased from TCI America. Extra dry grade oxygen used was purchased
from Gilmore. GC/MS analysis was performed on a Shimadzu GC-MS QP5000
(ver. 2) equipped with cross-linked methyl silicone gum capillary column (DB5).
The retention times of the products were confirmed by comparison to authentic
samples. NMR spectra were obtained on a Varian Mercury-400 MHz (measured
at 399.96 MHz) spectrometer at room temperature. All chemical shifts are
reported in units of ppm and referenced to the residual protonated solvent.
Standard C,H,N elemental analysis was performed by Desert Analytics
Laboratory in Tucson, AZ.

Procedure for Reaction of OsO
4
and MTO: Appropriate quantities of OsO
4

were weighed in a well ventilated fume hood, taking extra precaution with regard
to sash level and air flow setting due to the unusual volatility and toxicity of the
88
compound. Due to its volatility, osmium tetroxide is sticky and hard to manage at
room temperature, but can easily be handled by dropping the glass vial in which it
is stored into liquid nitrogen for a short time just prior to weighing, or by cooling
inside the glove box freezer. The OsO
4
was dissolved in 0.5 mL D
2
O followed by
addition of KOD to form hydroxylated OsO
4
in situ. Methyltrioxorhenium was
weighed out and dissolved in 0.5 mL D
2
O inside a Teflon fitted J-Young tube and
sonicated and/or shaken until fully dissolved. Typical quantities that easily
dissolve are between 10-15 mg. The
1
H NMR of MTO and D
2
O was first taken
with a benzene/CCl
4
co-axial external standard. The oxidant solution was then
added, the valve was sealed and the tube was inverted several times to mix the
solutions. The
1
H NMR was then taken again. Integration of the methanol peak
was multiplied by 2 to account for dilution and yields were calculated.

Pressurization with O
2
: An MTO solution in D
2
O was prepared as above. The
1
H NMR was taken after which the solution was transferred to a small (~0.75 mL)
vial, which was made by sealing a glass pipet. A stainless steel, 5 mL (total
volume) Swagelok reactor was filled with oxidant solution as prepared above.
The small vial was carefully set in the reactor (thus keeping the solutions
partitioned) and the reactor was subsequently sealed. It was pressurized to 180
psi (12.2 atm) using Swagelok fittings and valve connected to the oxygen tank.
After 5 minutes, the reactor was inverted and shaken to mix the two solutions.
After mixing the reactor was opened and the resultant solution was transferred to
the same NMR tube with co-axial standard. As reported in this communication,
89
yields and selectivity to methanol of this reaction and of a similarly run control
reaction (with no oxygen added) were statistically identical.

18
O-labeling Experiment: 15.0 mg of OsO
4
was dissolved in 0.25mL H
2
18
O.
Percent incorporation was determined by GC/MS analysis of the resulting
solution immediately. OsO
4
elutes at ~3.4 minutes on the DB-5 column and has
the following fragmentation patter: m/z 256 (100%), m/z 254 (64.4%), m/z 253
(39.6%), m/z 252 (32.5%), m/z 251 (4.8%), m/z 250 (3.9%). Since the
predominant fragments in the spectrum are due to Os isotopes, the fragmentation
pattern for Os
18
O
4
(fully enriched) should simply be shifted by 8 mass units (i.e.
at full incorporation m/z 264 would be the 100% peak). Thus, we deconvoluted
by setting all the fragments in the MS spectrum relative to a 100% peak at m/z
264, subtracted all of the theoretical values (so for the m/z 264 peak 100%-100%,
m/z 262 100%-64.4%, m/z 260 63.0%-32.5%, etc.). This removes all intensity
for the fully incorporated molecule. We set the moles of OsO
4
equal to 1. The
new value for the m/z 262 peak is 35.6% and thus we have a 1.0:0.356 ratio of
Os
18
O
4
to Os
18
O
3
16
O. We similarly deconvolute the whole spectrum to get the
following values:
Table 3.1: Isotopic distribution of
18
O enriched osmium tetroxide as determined
by GC/MS analysis.

isotope Os
18
O
4
Os
18
O
3
16
O Os
18
O
2
16
O
2
Os
18
O
16
O
3
Os
16
O
4
mol 1.000 0.356 0.214 0 0

90
To get the total moles of incorporated
18
O, we multiplied the moles of isotope by
the corresponding number of oxygens (i.e. Os
18
O
3
16
O has 1.068 moles of
18
O and
0.356 moles of
16
O). The total number of moles of oxygen was 6.28, 5.496 of
which were
18
O for a total incorporation of 87%.
This solution was mixed with a 0.25 mL solution of 15.0mg MTO and
0.01 mL 40 % KOH in H
2
18
O. The methanol produced from this reaction was
labeled to ~95%
18
O as determined by GC/MS analysis. Methanol elutes
simultaneously with water. We “find” the methanol by multiplying the m/z 32 or
34 GC trace by 1,000-10,000, then selecting the middle of that peak to look for
relevant MS data. We compare the relative ratios of m/z 34 to m/z 32 for
incorporation analysis.
A complementary experiment used the same amount of reagents, but MTO was
dissolved in H
2
16
O before addition to the Os
18
O
4-n
16
O
n
solution. The product
contained a 50:50 mixture of CH
3
16
OH to CH
3
18
OH. Since we know that the
incorporation of
18
O into MTO is slow on the time scale of the reaction, we are
confident that the label in the product does not come from an oxygen on the Re
starting material. The observed product ratio from this experiment suggests that
oxygen can wash back into OsO
4
faster than the reaction to form methanol occurs.

Reaction of MTO and OsO
4
/Isonicotinate: 0.5 mL of a 10mM MTO in D
2
O
solution was treated with 0.5mL of a 100mM OsO
4
solution containing 28.5 mg
sodium isonicotinate. The following NMR spectra are typical for this experiment.

91

Figure 3.6: 400MHz
1
H NMR of MTO in D
2
O with benzene/CCl
4
co-axial
internal standard (bottom) and MTO in D
2
O with added isonicotinic
acid/OsO
4
solution (top). The peak at ~ δ 3.3 is CH
3
OH.

Buffered Experiments: Phosphate buffers were prepared in D
2
O using Na
3
PO
4
,
Na
2
HPO
4
, and KH
2
PO
4
followed by adjustment of pH using a 40% KOD in D
2
O
solution.

Attempted Isolation of Methoxide Intermediate: In attempting to isolate a
methoxide intermediate by trapping, MTO was reacted with OsO
4
in neat
pyridine. My intent was to provide an activating, non-protic media which we had
previously demonstrated useful for the reaction of other O-atom donors.
4
The
original solution became yellow-orange upon addition of equimolar amounts of
MTO and OsO
4
. Over the course of 24 h, the solution gradually turned darker,
the resultant solution a deep forest green. After removal of solvent by reducing
92
the pressure (~100mTorr) on a vacuum manifold, we were able to isolate the
green solid and analyze it by
1
H NMR,
13
C NMR, elemental analysis, and infrared
spectroscopy. This material was extremely difficult to manipulate, remaining
sticky, probably due to an association with pyridine solvent molecules despite
drying for days under reduced pressure. Attempts to wash the crude compound
with solvents such as ethanol and THF were deleterious, resulting in dark black
insoluble species and yellow-orange colored solutions.
1
H NMR and
13
C spectra
were obtained in py-d
5
, the only NMR solvent in which the compound was
soluble (Figure 3.9 and Figure 3.10). The proton NMR is consistent with the
sticky nature of the compound, as free pyridine-h5 is seen in solution upon
dissolution in pyridine-d
5
(these are distinguishable from residual protons in the
solvent). Three more equivalents of bound, protiated pyridine can be accounted
for based on the integration of the aromatic region, shown in Figure 3.9. The 2:1
ratio of peaks at δ 9.11, δ 8.86, δ 7.19 vs. δ 7.92, δ 7.50, δ 7.45 indicates that two
of the bound pyridine molecules are symmetrical. Over time these resonances
decay and the free pyridine resonances increase as the bound molecules exchange
with the deuterated solvent. I believe that the peaks at δ 6.16 and δ 6.28 account
for the methyl originally associated with MTO. Consistently, the intensity of
these peaks does not change over the same time period necessary for complete
pyridyl exchange. The methyl peak of the known pyridyl adduct of MTO shows
up much further upfield and is concentration dependent (~ δ 1.7-2.0). I have not
been able to discern the origin of the 2:1 integration of these two peaks, though
the total integration of the two singlets is ~3, consistent with our assignment to
93
the methyl protons. I suspect that the singlets are due to methyl association with a
heteroatom, given their high chemical shifts, and have tentatively assigned them
as methoxide protons.
13
C NMR of the same solution accounts for 10 carbon
peaks, consistent with the
1
H NMR, one peak being located upfield at δ 55.6.
Elemental analysis suggests the molecular formula is C
21
H
23
N
4
O
7
OsRe. Expected
for this molecular weight: C, 30.76; H, 2.83; N, 6.83; O, 13.66; Os, 23.20; Re,
22.71. Found for the sample: C, 30.54; H, 2.28; N, 6.90 and duplicate C, 30.00;
H, 2.49; N, 6.80. Based on this combined evidence we have proposed the
structure seen in Figure 3.7 without implication of the orientation of the ligands
around the rhenium fragment. We believe the oxygen based ligands are planar,
given the symmetry of the pyridyl peaks in the NMR spectra.

Figure 3.7: Proposed structure for product of reaction between MTO and OsO
4
in
neat pyridine.

Attempts, by several methods, to obtain crystals from this material suitable
for X-ray diffraction studies have failed, though they are ongoing and will be
presented if successful. Interestingly, a minor impurity crystallized from a
94
saturated pyridine solution upon slow diffusion of ether or pentane under nitrogen
atmosphere. This orange crystalline material was identified as a Re(VI)/Re(VII)
salt, as shown in the ORTEP plot (Figure 3.8). A nearly identical species,
synthesized in high yield with the aid of (CH
3
)
2
SnCl
2
, has been reported
previously.
17
We presume the mechanism for formation of the complex reported
here mirrors the known chemistry,
17
namely the tautomer of MTO forms by
migration of a proton to one of the three oxo groups, forming an electrophilic
methylene group; the basic lone pair of pyridine is then able to attack at the
carbon atom which causes the dissociation of one equivalent of hydroxide.
Subsequently, the liberated hydroxide hydrolyzes a molecule of MTO to form
methane and one equivalent of perrhenate. As this was a small impurity (~2-5%)
isolated from large scale-up reactions, we expect protons associated with this
structure did not reveal themselves in the
1
H NMR of smaller reactions due to the
low concentration expected in solution.
95

Figure 3.8: ORTEP diagram for [(C
5
H
5
-CH
2
)Re(NC
6
H
5
)
3
(O)
2
][ReO
4
] with 50%
ellipsoids.
96

Figure 3.9. 400 MHz
1
H NMR (aromatic region) of reaction product
from MTO + OsO
4
in neat pyridine dissolved in py-d
5
.
Figure 3.9: 400 MHz
1
H NMR (aromatic region) of reaction product from MTO + OsO
4
in neat
pyridine dissolved in py-d
5
.
 
97

Figure 3.10.

Figure 3.10: 400 MHz
13
C NMR of reaction product from MTO + OsO
4
in neat pyridine dissolved in py-d
5
 
98
Theoretical Considerations: The following includes the geometric structures (in
Angstroms) and solution phase enthalpies (in kcal mol
-1
) for the necessary
reactants, transition states and products. In addition to the species mentioned in
the communication additional reaction pathways of higher enthalpy are included.
Quantum mechanical computations were performed using the B3LYP density
functional. This functional is a combination of the hybrid three-parameter Becke
exchange functional (B3)
18
and the Lee-Yang-Parr correlation functional (LYP).
19

The basis sets used with B3LYP were constructed as follows. For rhenium we
used the core-valence effective core potential of Hay and Wadt,
20
while the Pople-
style 6-31G** basis set
21
was utilized for hydrogen, carbon and oxygen atoms.
Since some reactions include negatively charged species, the effects of diffuse
functions were included by computing single point energies with the 6-11G**++
basis set.
22,23
The combination of the ECP and basis set is referred to as
LACVP** or LACVP**++.
All calculations corrected for the effect of solvent interactions by using the
polarizable continuum model (PCM) of solvation.
24,25
We solvated with water,
with a dielectric constant of 80.37 and a probe radius of 1.40 Å. The final
enthalpy was computed as:

Where is the B3LYP/LACVP**++//B3LYP/LACVP energy. For hydroxide
the solvation energy used was the experimental value of -102.90 kcal mol
-1

measured by Tissandier et al.
26

99
Figure 3.11 shows the important frontier orbitals and their interaction in
the TS. Both TSs use very similar orbitals. The HOMO of CH
3
ReO
4
2-
interacts
with the LUMO+1 orbital on the Os bound oxygen through a σ-interaction as well
as through a π-interaction of the Re-O lone pair with an unoccupied d-orbital on
osmium. In the bottom TS, the orbital interactions involve two σ-interactions.

100

Figure 3.11: FMO and TS orbital interactions
 
101
1. OH
-
Enthalpy: -75.955491
O 0.7302746777 -0.2280123124 0.3812787519
H 1.1010653770 0.5330398984 -0.1218484279

2. H
2
O
Enthalpy: -76.420422
H .0000000000 .0000000000 .0000000000
O .0000000000 .0000000000 .9649402977
H .9364263498 .0000000000 1.1977829378

3. OsO4
Enthalpy: -391.930337
O 0.0580513741 -0.0799777376 2.0275567689
O -0.3111609038 -0.4946330240 4.7692073023
O 2.1303871511 -1.1537146471 3.5714106973
O -0.1498148848 -2.6815580210 3.0320616728
Os 0.4322595916 -1.1022648261 3.3503172382

4. OsO
4
(OH)
-
axial OH
Enthalpy: -467.888104
Os -0.7469096428 0.5576507081 0.0173290251
O -0.7637114383 1.2980769646 -1.5538190199
O -0.4928462051 1.6854137375 1.3397633142
O 1.3326161226 0.6068129092 0.0163285283
O -2.4789825822 0.4045639619 0.2902956412
O -0.4101600155 -1.1508304982 -0.0123632053
H 1.5480623797 1.4302391906 0.4733945980

5. OsO
4
(OH)
-
equatorial OH
Enthalpy: -467.885892
Os -.5469180388 .5511094912 .0411472503
O -.7461968755 1.4020750110 -1.7705257399
O -.4711852344 1.4217645354 1.5469552965
O 1.1473198077 .8255045493 -.4641704353
O -2.2956643442 .6173811250 -.1891451525
102
O -.4117008387 -1.1595733285 .3363458895
H .1901774621 1.5317960446 -2.0015749951

6. CH
3
ReO
3
(MTO)
Enthalpy: -344.734004
Re 0.0226800516 -0.0393152074 0.9840731779
O -0.0420342788 0.0746283099 -0.7182474158
O -0.8669297413 -1.3548667404 1.6113574231
O 1.6062793176 0.0731071735 1.6127014857
C -0.9608811120 1.6639885884 1.6791620604
H -0.4362739067 2.5475384299 1.3061421460
H -0.9522639110 1.6521171554 2.7722114888
H -1.9892317515 1.6500741802 1.3086276706

7. CH
3
ReO
3
(OH)
-
[MTO(OH)-]
Enthalpy: -420.699546
Re -0.0292208236 -0.2162078937 0.8576259078
O -0.5650016695 0.2905160171 -0.7034612170
O -1.2476939032 -1.1326762065 1.6677200516
O 1.4596893519 0.6950373633 1.8326014643
C -0.8339974559 1.6501175340 1.7467557955
H -0.3017462138 2.5157820319 1.3486719137
H -0.7291330038 1.6243924955 2.8327981832
H -1.8928170607 1.6953969513 1.4690707956
O 1.3006224177 -1.3449648800 0.5632872773
H 2.1932662709 0.0767911007 1.6727549365

8. CH
3
ReO
4
2-

Enthalpy: -420.239992
Re -0.0489822155 0.0070068445 1.1814958263
O 0.5793680322 -1.5990114835 1.5639232620
C 1.6449742034 -0.0954105786 -0.4701513158
H 1.4673799738 -0.9421885561 -1.1574914156
H 2.6385271891 -0.2289390338 -0.0053818870
H 1.6636546797 0.8350750296 -1.0658457516
O -1.3350719649 0.0848463100 2.4300080290
O 0.8920460393 1.4092972930 1.6982429395
O -1.0730273979 0.1787213242 -0.2472744594

103
9. Lower energy(3+2) Transition State from Communication
Enthalpy: -812.154083
Os -0.6342148082 -0.3314518377 0.0880564161
O 0.9368706730 0.5435817591 1.6479416676
Re 2.5801734366 0.4736898765 2.2984154502
C 1.9412747123 -2.3750024600 2.2379696183
O 0.3772667847 -1.7391003159 0.3403825921
O -1.6900231369 0.0123422080 1.4379855794
O 0.1114030905 0.8854382672 -0.9192598366
O -1.8220665878 -0.9824432096 -1.0534552270
H 2.2408303796 -2.8661154361 1.3193254331
H 2.6955284627 -2.3263009415 3.0195846377
H 0.9332464671 -2.5911994668 2.5770304081
O 2.6731936541 -0.0487601442 3.9579984272
O 3.8080420742 -0.2430966611 1.2994611657
O 3.0287602833 2.1603986242 2.3683541570

10. Higher energy(3+2) Transition State from Communication
Enthalpy: -888.555638
Os -0.4801458766 -0.1982250200 0.1672924683
O 0.4958648986 0.4062532482 1.6186132612
Re 2.4950467826 0.3455165976 2.4032224787
C 1.5962647925 -2.2278732301 2.2313405581
O 0.2861380278 -1.7738557514 0.2578389176
O -2.0280077519 -0.1094757724 0.9660788780
O 0.2364753868 0.8627283441 -1.0205022605
O -1.6767156132 -0.7969018965 -1.4582619798
H 1.9624251411 -2.8333907709 1.4114376771
H 2.3030734830 -2.1223619941 3.0525801657
H 0.5850150370 -2.4414740557 2.5562238234
O 3.8099015260 -0.2369398051 3.3760275169
O 1.2914131585 0.1081219566 4.0014034989
O 3.0403926653 -0.0519893525 0.8022147669
O 2.6309027225 2.0755385904 2.4522948801
H 0.3988058796 0.1330729581 3.6282535091
H -1.1006618414 -0.6069735660 -2.2103860265

11. Baeyer-Villiger Transition State from Communication
Enthalpy: -888.545938
Re -0.1167620527 -0.0228849788 -0.0603929754
104
O -0.3687069981 -0.2557126016 1.9076668165
C 1.7119228979 -0.2333244377 1.7797417888
Os -1.4239344052 -0.3497881589 3.5938543425
O 0.5773162276 1.5931785526 -0.0196340015
O -1.8686626682 -0.0065966524 -0.1739293112
O 0.5839065448 -1.5848649077 -0.4061681291
H 1.7042735208 -1.2173894395 2.2334482686
H 1.6875467230 0.6115004549 2.4578923964
H 2.3992486758 -0.1246705032 0.9406295316
O -0.6118485420 1.0884029795 4.1651524309
O -0.7288121205 -1.9165885542 3.9245601147
O -2.7133234981 -0.3966727493 4.8289561788
O -2.9658467879 -0.1769847892 2.4094436612
H -2.6230860590 -0.1191588512 1.4915153243
O 0.0733603083 0.2185255855 -2.0890184818
H 0.0483128224 1.1800545988 -2.1867393985

12. (3+2) Product from Communication
Enthalpy: -888.655941
Os -0.8131302459 1.4760611305 -0.5990818831
O -1.0195240422 3.2043873985 -0.3262679341
O 1.0365435959 1.7557217531 0.2998743977
O -2.6604597745 1.2881438207 -1.1770285617
O -1.4039310821 0.3233840586 0.8402809820
H 1.2349837636 2.6823850767 0.0987165973
O -0.0844489782 0.6780525239 -1.9503082761
C -0.5609807403 -0.0490442870 1.9101355060
H -1.1389918146 0.0251532615 2.8441944879
H -0.2407040293 -1.0981374578 1.7914280153
H 0.3262661659 0.5903038670 1.9619390142
Re -4.1912957866 0.3886114577 -0.2531714584
O -4.8308116134 -0.1930696264 1.2568306997
O -5.5574935549 0.7391801527 -1.2640402962
O -3.5679812663 -1.1104946069 -0.8949207299
O -4.0013148942 2.1465703977 0.7218135491
H -3.3521296524 2.6696105231 0.2276236381

13. Baeyer-Villiger Product A from Communication: OsO
3
(OH)
-
Enthalpy: -392.707503
O 0.7217205546 0.0546634884 1.9002344620
O -0.3093444848 -0.1359127073 4.6413204859
O 2.3363064999 -0.9177805009 3.2692783407
105
O -0.2481085010 -2.5438302316 2.8604687118
Os 0.4245352784 -1.0267602446 3.3517005574
H 2.3543513146 -0.3211197570 2.4632586882

14. Baeyer-Villiger Product B from Communication: CH
3
-O-ReO
3
(OH)
-
Enthalpy: -495.980999
Re -.0080395503 .3977583442 .7909653909
O .7644183454 2.2268421557 .5736506222
O .1323060733 .4016879462 2.5220197054
O 1.3779070065 -.2770628727 -.0306185151
O -1.4502484180 .9830193860 .0320183720
O -.8551250230 -1.4109803465 .7965589021
C -.1064223977 -2.4827100153 1.2773070312
H -.6734675239 -3.4192149691 1.1549198585
H .8525928273 -2.5768533441 .7359057949
H .1368513770 -2.3613779294 2.3496957341
H 1.7195184072 2.1689725111 .7080700347

15. Higher Enthalpy (3+2) Transition State (Connects to 12)
Enthalpy: -888.553605
Os -0.1348301123 -0.0310607493 -0.0115264668
O -0.1444047095 0.0645527247 1.7485801071
C 2.0091002548 0.0071276218 2.8616675530
Re 2.9729650960 -1.8162959382 1.1073393748
O 1.6426474646 -0.5467479599 -0.0129810982
O -2.0929831470 0.6839621927 0.1108980844
O 0.1625206488 1.4252977229 -0.9323152524
H 3.0146150297 -0.2787366786 3.1652237231
H 1.9347590686 1.0321461867 2.5186984849
H 1.2346399643 -0.3116072521 3.5488788728
O 1.5696818325 -2.6824468621 1.6547092868
O 3.4542181838 -2.6976081546 -0.3103858978
O 4.1457782384 -2.2398662304 2.3151696408
O -0.7812221741 -1.4906323800 -0.6981441623
H -2.2874512342 0.5551875451 1.0482176164
O 4.0244352128 -0.1339254742 0.7513164306
H 3.4145109146 0.4198422905 0.2432336566

16. Higher Enthalpy (3+2) Transition State (Connects to 18)
Enthalpy: -888.547570
106
Os -0.2785171412 -0.2767355453 -0.0728094969
O 0.4241188676 0.2890197032 1.5258850405
Re 2.3081159217 0.3571541419 2.5895125123
C 1.9592109320 -2.3247310277 1.8494105581
O 0.7207327706 -1.7563347416 -0.0296414279
O -1.3772649041 1.4904733097 0.0621099277
O 0.3370896524 0.3228219399 -1.5892732329
O -1.8187287045 -1.1042051222 0.0080551218
H -0.9676763030 1.9138975389 0.8277026808
H 2.5237102233 -2.6628512433 0.9908283385
H 2.5552591887 -2.1858173150 2.7507268071
H 1.0160754287 -2.8275633091 2.0238963274
O 3.5820350071 -0.1812889907 3.6364872645
O 0.9759857930 -0.3692967816 3.8971694789
O 3.0830370306 0.3328295201 1.0365740917
O 2.1334974358 2.0478625696 2.9328638690
H 0.1570069615 -0.4561245566 3.3890306620

17. Higher Energy (3+2) Transition State (Connects to 12)
Enthalpy: -888.545569
Os -0.1298328369 0.2034382544 0.1187032475
O 0.0477449213 0.2494259830 1.8686309779
C 2.1284361652 0.1479996136 2.9049545173
Re 2.8088001312 -1.9097032202 0.9481070788
O 1.6710128326 -0.4318500549 0.0476915175
O -1.9087682131 0.0238496920 0.1063207409
O 0.0939605577 1.8032692040 -0.5196438250
H 3.1308802853 -0.2636647446 2.9936435544
H 2.0967964807 1.1897245515 2.6087966305
H 1.4367474798 -0.1464001272 3.6855814001
O 1.3258377960 -2.5635656773 1.5771641474
O 3.0918586295 -2.8586101017 -0.4809644407
O 3.9592476524 -2.4662495514 2.1267444282
O -0.3188288324 -1.2706492145 -1.1990217153
O 4.0828658526 -0.3859959877 0.5889505747
H 3.5174034439 0.2788784301 0.1692068978
H 0.6000855342 -1.5672272100 -1.3106630557

18. Alternative (3+2) Product

Enthalpy: -888.669349
Os -0.9511692321 1.7758568098 -0.5351425447
O -1.0082468894 3.3954763432 0.1056904333
107
O 0.2532327742 0.5101551924 -0.4332357728
O -2.5629388078 1.2620413826 -1.3753847396
O -1.9389342331 0.9700990905 1.0798887543
O -0.2722000914 2.3761197952 -2.3232479384
C -1.2770461084 0.2382132563 2.0630925679
H -0.7482646698 0.9001753202 2.7764377704
H -2.0140356794 -0.3542926599 2.6248278347
H -0.5294518361 -0.4392241093 1.6168010911
Re -3.8974971696 0.1050479490 -0.1716234324
O -4.5701216305 -0.3427310631 1.3662208605
O -5.1339994179 -0.2231137799 -1.3416169062
O -2.7752847597 -1.1960339875 -0.4560730444
O -4.4305589188 2.0035100418 0.1874186858
H -3.8326527526 2.5576584569 -0.3312331883
H -1.0376157839 2.1523323713 -2.8762739375

108
Frontier orbitals for interaction analysis (Figure 3.4B in text):
B3LYP/LACVP** orbitals.

Figure 3.12: Transition State HOMO (53)

Figure 3.13: Ground state CH
3
ReO
4
-
.

HOMO (29).

109

Ground state OsO4
HOMO (24)

Figure 3.14: Ground state OsO
4
. HOMO (24).

Figure 3.15: Ground state OsO
4
. LUMO (25).

110

Figure 3.16: Ground state OsO
4
. LUMO + 1 (26).

111
3.4 Chapter 3 References

1 We define CH activation as a coordination reaction between a reactive species
“M” that proceeds without the involvement of free-radicals, carbocations or
carbanions to generate discrete M-R intermediates. Functionalization is the
conversion of the M-R intermediate to an R-heteroatom product. a) A. E. Shilov,
G. B. Shul’pin, Chem. Rev. 1997, 97, 2879; b) R. A. Periana, O. Mironov, D.
Taube, G. Bhalla, C. Jones, Science 2003, 30, 814 and references therein; c) M.
Lin, T. Hogan, A. Sen, J. Am. Chem. Soc. 1997, 119, 6048; d) M. Muehlhofer, T.
Strassner, W. A. Herrmann, Angew. Chem. Int. Ed. 2002, 41, 1745; Angew. Chem.
2002, 114, 1817; i) H. Chen, S. Schlect, T. Semple, J. Hartwig, Science 2000,
287, 1995.

2 Periana, R.A.; Bhalla, G.; Tenn, W.J., III; Young, K.J.H.; Liu, X.Y.; Mironov,
O.; Jones, C.J.; Ziatdinov, V. J. Mol. Cat. A 2004, 220, 7.

3 a) S. Kim, D. Choi, Y. Lee, B. Chae, J. Ko, S. Kang, Organometallics 2004, 23,
559 and references therein; b) Y. Matano, J. Brugmann, S.L. Bennett, J.M. Mayer,
Organometallics 2000, 19, 2781; c) S. Brown, J.M. Mayer, J. Am. Chem. Soc.
1996, 118, 12119.

4 a) Conley, B.L.; Ganesh, S.K.; Gonzales, J.M.; Tenn, W.J., III; Young, K.J.H.;
Oxgaard, J.; Goddard, W.A., III; Periana, R.A. J. Am. Chem. Soc. 2006, 128,
9018. b) Gonzales, J. M., Distasio, R., Periana, R. A., Goddard, W. A., Oxgaard,
J. J. Am. Chem. Soc. 2007, 129, 15794.

5 (a) DelMonte, A.J.; Haller, J.; Houk, K.N.; Sharpless, K.B.; Singleton, D.A.;
Strassner, T.; Thomas, A.A. J. Am. Chem. Soc. 1997, 119, 9907. (b) Corey, E.J.;
Noe, M.C. J. Am. Chem. Soc. 1996, 118, 11308. For theoretical work view (c)
Norrby, P.-O.; Rasmussen, T.; Haller, J.; Strassner, T.; Houk, K.N. J. Am. Chem.
Soc. 1999, 121, 10186. (d) Torrent, M.; Deng, L.; Duran, M.; Sola, M.; Ziegler, T.
Organometallics 1997, 16, 13.

6 Dehestani, A.; Lam, W.H.; Hrovat, D.A.; Davidson, E.R.; Borden, W.T.;
Mayer, J.M. J. Am. Chem. Soc. 2005, 127, 3423.

7 Valliant-Saunders, K.; Gunn, E.; Shelton, G.R.; Hrovat, D.A.; Borden, W.T.;
Mayer, J.M. Inorg. Chem. 2007, 46, 5215.

8 Bales, B.C.; Brown, P.; Dehestani, A.; Mayer, J.M. J. Am. Chem. Soc. 2005,
127, 2832.

9 Jørgensen, K.A.; Hoffmann, R. J. Am. Chem. Soc. 1986, 108, 1867.

112

10 Abu-Omar, M.; Hansen, P.J.; Espenson, J.H. J. Am. Chem. Soc. 1996, 118,
4966.

11 From theory we suspect the formation of [CH
3
ReO
4
]
2-
as reported in the text
(Eq. 4 and 5). Espenson (Ref. 11) suggests formation of [CH
3
ReO
3
(OH)]
-
under
less basic conditions and reports a chemical shift in D2O of δ 1.9. Our shift of δ
1.69 would be consistent with a more electron rich methyl species formed from
subsequent deprotonation of the bound hydroxide.

12 See Experimental section.

13 CH
3
ReO
4
2-
is the ground state, not CH
3
ReO
3
(OH)
-
, as was found in our
previous investigation in THF containing OH-.

14 Mayer, J.M.; Mader, E.A.; Roth, J.P.; Bryant, J.R.; Matsuo, T.; Dehestani, A.;
Bales, B.C.; Watson, E.J.; Osako, T.; Valliant-Saunders, K.; Lam, W.H.; Hrovat,
D.A.; Borden, W.T.; Davidson, E.R. J. Mol. Cat. A 2006, 251, 24.

15 Mealli, C.; Lopez, J.A.; Calhorda, M.J.; Romão, C.C.; Herrmann, W.A.
Inorg. Chem. 1994, 33, 1139.

16 Kolb, H.; VanNieuwenhze, M.S.; Sharpless; K.B. Chem. Rev. 1994, 94, 2483.

17 Zhang, C.; Guzei, I.A.; Espenson, J.H. Organometallics 2000, 5257.

18 Becke, A. D., J. Chem. Phys. 1993, 98, 5648.

19 Lee, C.; Yang, W.; Parr, R. G., Phys. Rev. B. 1988, 37, 785.

20 Hay, P. J.; Wadt, W. R., J. Chem. Phys. 1985, 82, 299.

21 Hariharan, P. C.; Pople, J. A., Theo. Chim. Acta. 1973, 28, 213.

22 Krishnan, R.; Binkley, J. S.; Seeger, R.; Pople, J. A., J. Chem. Phys. 1980, 72,
650.

23 Clark, T.; Chandrasekhar, J.; Schleyer, P. v. R., J. Comput. Chem. 1983, 4,
294.

24 Tannor, D. J.; Marten, B.; Murphy, R.; Friesner, R. A.; Sitkoff, D.; Nicholls,
A.; Ringnalda, M.; Goddard, W. A.; Honig, B., J. Am. Chem. Soc. 1994, 116,
11775.

113

25 Martin, J. M. L., Chem. Phys. Lett. 1996, 259, 669.

26 Tissandier, M. D.; Cowen, K. A.; Feng, W. Y.; Gundlach, E.; Cohen, M. H.;
Earheart, A. D.; Coe, J. V.; Tuttle, T. R., J. Phys. Chem. A 1998, 102, 7787.

114

4 Chapter 4: Catalytic Oxy-functionalization of a Low
Valent Metal Alkyl with Se(IV)

4.1 Introduction

The evolution of the following chemistry deserves a good description.
This work will soon be published, and though I will not be first author on the
paper when it hits the chemical literature, I will always have a place in my heart
for the chemistry. It is both interesting and potentially broadly applicable and
filled my last year of research with a good deal of excitement about the future of
this program.
My friend and colleague, Dr. Bill Tenn, currently at The Dow Chemical
Company in Freeport, TX was working on low-valent Re systems for the purpose
of C-H activation. His work spanned a solid year at the end of his successful
graduate career, but the result was no working system, highlighting the degree of
difficulty of the synthesis of very electron rich molecules of interest. In his
extensive literature searches he found a Re-CH
3
species which he believed could
be ideal for studying O-atom insertion processes and which he hoped might be
active under some condition for C-H activation, thus demonstrating a complete
catalytic cycle. As we worked closely with each other, I was privy to his thoughts
and ideas about the project and contributed my own ideas in our almost daily
conversations over coffee. Our general protocol with model methyl species, like
115
in the MTO work presented in the chapters above, was to screen the compound
across a range of oxidants we suspected could be useful for insertion of an oxygen
atom into the M-CH
3
bond. As evidenced in the results below, a couple oxidants
yielded low conversion of the methyl to methanol, but one gave way to a new
functionalization strategy altogether.
The turning point came with the use of high valent Se species like selenate
(SeO
4
2-
) and selenite (SeO
3
2-
). We have long been interested in the Periana group
in the use of selenium compounds as O-atom donors with the hope that some of
the resultant molecules could be recycled with air. However, with a variety of Se
reagents Bill noticed the characteristic smell, and verified chemically, the
presence of Me-Se products and the lack of O-atom transfer. Initially, he, Roy,
and I focused on a transalkylation mechanism that we though proceeded through a
4-centered, sigma bond metathesis type transition state, as shown in Figure 4.1.
His primary reagent, H
2
SeO
3
(which is formed by addition of water across SeO
2
),
provided 100% methyl mass balance to CH
3
SeO
2
H when excess SeO
2
was added
to D
2
O solutions for
1
H NMR studies, and it was logical to think that the resultant
species might contain a Re-OH bond. The implication would be that either 1) the
reaction proceeded first with loss of CO to form the 5-coordinate species or 2)
that Re undergo coordination expansion, keeping the 5
th
CO bound to the metal
during the transfer of the methyl group. As Bill lacked one major resource, time,
he moved quickly to reactions with catalytic amounts of H
2
SeO
3
, as will be
described in detail below. With IO
4
-
as the terminal oxidant he was able to see
catalytic production of methanol in aqueous media. This finding was significant,
116
as we had tried to show this type of catalysis with several different systems using
MTO as our methyl source.

Figure 4.1: Methyl Transfer from Re to Se Through a 4-centered Transition State.

At the conception of the project, I was thoroughly involved in
investigating methyl group transfer reactions from reagents such as Me
4
Sn and
MeB(OH)
2
to some of our transition metal species based on osmium and
ruthenium. This necessitated a thorough understanding of the background of
these types of molecules, and in my reading I came across what turned out to be a
general class of insertion reactions with SO
2
. Specifically, I found that treatment
of alkyl tin compounds, such as Me
4
Sn, reacted with SO
2
to form Me
3
Sn-
OSO
2
Me. Of course, this was fascinating and I immediately made the connection
to the SeO
2
work Bill was doing, finding out that complexes of iron and rhenium,
among others, show similar reactivity (see below for references). This suggested
a different mechanism than we originally proposed and provided a starting point
for a thorough mechanistic study. As it turned out, at this time Bill was preparing
his dissertation materials and packing for Texas. Because he and I were close and
I was the only one doing this type of chemistry in the group at the time, I decided
117
to work on the project with the caveat that I would be 2
nd
author on a
communication to be published at a later date. As is the case with most projects,
the chemistry led us away from our initial ideas and even our parent compound,
but ultimately gave way to understanding the chemistry. With that said, I will try
to emphasize my involvement in the project in this chapter and give credit where
credit is due otherwise. My goals in the research were to elucidate the mechanism
of the transformations involved in the catalytic reaction (methyl transfer and
oxidation) and extend our understanding of the chemical processes involved,
which I did successfully with the help of density functional theory (DFT) and
sound chemical characterization techniques.
The design of stable systems that utilize efficient, reversible CH activation
followed by oxy-functionalization reactions could lead to the development of
selective, low temperature, hydrocarbon hydroxylation catalysts.
1,2
In an effort to
overcome the water sensitivity of earlier systems, we have begun the rational
development of catalysts based on more electropositive, less oxidizing metals to
the left of platinum. Pathways involving reductive oxy-functionalization by attack
of O-nucleophiles on M-C
δ+
polarized intermediates with electron poor, oxidizing
species such as Pt(IV), Pd(II), Hg(II), etc. are well known and utilized. However,
reductive functionalization is far less accessible with more electron-rich, less
oxidizing systems.
1b,3
Consequently, we recently proposed a strategy for non-
redox oxy-functionalization of electron-rich M-R species that involves insertion
of electrophilic oxygen from O-atom sources, YO,
4
into M-C
δ-
intermediates,
Figure 4.2A. An alternate strategy is transfer of R to a more electrophilic, redox–
118
active species, N-X, which readily reacts with external oxidants to produce
functionalized products, Figure 4.2B.

Figure 4.2: Plausible pathways, A and B, for oxy-functionalization of M-R
intermediates generated by CH activation.

There are several well-known stoichiometric alkyl group transfer reactions
from low-valent transition metals (Fe, Mn, Re, Ir, Ru, Zr, etc.) to electrophiles
such as Sn(IV)-X, Hg(II)-X,
5
H
+
,
6,7
SO
2
/SeO
2
,
8,9
and CO.
10
These radical-free
reactions are generally quite facile. We were particularly interested in reactivity
of SO
2
with M-CH
3
species that we believed to be analogous to our system, as
well as the lone standing example of SeO
2
with a Fe-CH
3
complex.
The first discrete insertion of SO
2
into a low valent transition metal-carbon
bond was carried out by Andrew Wojcicki in 1964.
11
(η
5
-C
5
H
5
)Fe(CO)
2
R (R = -
CH
3
, -CH
2
CH
3
) was reacted in cold benzene solutions with SO
2
which yielded the
119
S-bound sulfinate complexes as shown in Figure 4.3, though the connectivity was
not elucidated until later.

Figure 4.3: First Known Insertion of SO
2
into M-R bonds (R = -CH
3
, -CH
2
CH
3
, -
C
6
H
5
)

Since the initial discovery, which was directed by the authors’ general interest in
insertion reactions (such as those discovered just prior to the work involving CO),
detailed kinetic and structural work was completed for this complex and others.
Our own entry into these insertion reactions was quite fortuitous in
retrospect, especially considering our interest was insertion of oxygen, not of a
whole molecule of SeO
2
! However, a look back into the literature afforded only
one example of the insertion reaction Bill stumbled upon. This was a purposeful
study presented in the context of studying the Se analogue of the SO
2
chemistry.
Indeed, the reaction was carried out in much the same fashion by Ingo-Peter
Lorenz using the same complex Wojcicki used in the very first known example,
CpFe(CO)
2
CH
3
.
12

None of the above work was done in the context of catalytic oxy-
functionalization.
In addition to our work with O-atom donors such as PhIO, pyO, IO
4
-
and
OsO
4
to generate methanol,
4,13
we are also interested in identifying similar
120
reactions of more electron-rich, d
6
, octahedral, M-R complexes. To minimize
metal centered oxidations and alkyl protonolysis we chose to study the readily
available (CO)
5
Re
I
CH
3
complex that our screens showed was relatively soluble
and stable in aqueous media. Herein, we report conditions for the stochiometric
and catalytic functionalization of (CO)
5
ReCH
3
and (CO)
3
bpyReCH
3
to CH
3
OH
and related heteroatom products.

4.2 Results and Discussion

In contrast to the CH
3
ReO
3
work, reactions of (CO)
5
ReCH
3
with both
PhIO and NaIO
4
in a 9:1 acetonitrile/water solution at 100 ºC gave low yields of
methanol (~20-30%, see SI), and PyO yielded no methanol.
14
Because selenium
oxides are known to act as co-catalysts in hydrocarbon oxidation,
15,16
and our
[(bpym)PtCl
2
]/H
2
SO
4
/CH
4
system is more efficient with added selenium oxides,
17

we examined the reaction of (CO)
5
ReCH
3
with H
2
SeO
3
which was found to give
highly efficient functionalization.
The reaction of (CO)
5
ReCH
3
with excess D
2
SeO
3
(generated in situ from
SeO
2
and D
2
O)
18
in a solution of a 9:1 v/v solution of CD
3
CN/D
2
O produced
methaneseleninic acid, CH
3
-SeO
2
D, in quantitative yield as identified by
comparison of the
1
H and
13
C NMR spectra and mass peaks to that of a
commercially available sample. In addition, (CO)
5
Re
13
CH
3
, when reacted with
D
2
SeO
3
in the same solvent system, produces
13
CH
3
-SeO
2
D in quantitative yield.
121
The product was identified by its large
13
C satellites in the
1
H NMR spectrum and
the strong
13
C spectrum accompanied by Se satellites. This reaction is slow at
room temperature, but heating to 50
o
C for a few hours gives nearly quantitative
formation of CH
3
SeO
2
D as monitored by
1
H NMR. The formation of CH
3
SeO
2
D
follows first order kinetics with an experimental enthalpy of activation of 8.0 ±
1.7 kcal/mol. Given the almost 100% methyl and selenium mass balance between
reactant and CH
3
SeO
2
H product, the likely reaction stoichiometry is shown in Eqs
1 and 2. The expected Re products, (CO)
5
Re(OSeO
2
H) or (CO)
5
ReOH, could not
be observed directly, most likely due to known oligomerization reactions
19

(Figure 4.4) and displacement of labile CO ligands by the coordinating solvent
(CD
3
CN). The oligomerization is a result of the instability of the hydroxide
ligand toward insertion of CO and subsequent bridging capability of the acyl
complex generated. One might question why the methyl is stable at room
temperature toward insertion to the acyl (it is not so at temperatures over 100 °C)
but the hydroxide is not.

Figure 4.4: Reported Oligomerization during Attempted Synthesis of
(CO)
5
ReOH in Acetone.
122

High resolution mass spectrometry taken of resultant solution was not
conclusive, but suggested the presence of (CO)
3
(CH
3
CN)
3
Re
+
. Elemental
analysis of the solid isolated from the solution, washed with water, and dried
thoroughly did not match any meaningful collection of atoms, suggesting again
that there is probably not one discrete monomeric species formed.
13
C NMR
spectroscopy, which might be viewed as one of the most appropriate
characterization methods given the lack of other active nuclei, was devoid of
signals, indicating the lack of a monomeric, well defined species and/or loss of
many of the possible CO ligands. The
13
C NMR was run for over 100,000 scans
after reaction of a saturated solution (~100 mg starting material) in NMR solvent
to provide the best chance of success. As mentioned, the other deleterious
reaction (in terms of following the reaction products) is the labilization and
subsequent substitution of CO ligands. Given the large excess of CH
3
CN (or
CD
3
CN in NMR reactions) and the gaseous nature of CO thus liberated, it stands
to reason that a pentakis CO complex would no longer exist.

2 H
2
SeO
3
+ (CO)
5
ReCH
3
 (CO)
5
Re(OSeO
2
H) + CH
3
SeO
2
H (1)
(CO)
5
Re(OSeO
2
H) + H
2
O ↔ (CO)
5
Re(OH) + H
2
SeO
3
(2)

Importantly, no methane was observed in the headspace or solution after the
reaction. This, along with the high reaction yield, suggested that the
functionalization reaction with D
2
SeO
3
is much faster than the protonolysis of the
123
Re-CH
3
bond, which does occur at longer reaction times and elevated
temperature.
It is known that CH
3
Se
VI
(O)
2
OH thermally generates methanol and
H
2
Se
IV
O
3
.
20
Therefore, we considered that if CH
3
Se
IV
O
2
H could be oxidized to
CH
3
Se
VI
(O)
2
(OH), then H
2
Se
IV
O
3
could catalyze oxy-functionalization of
(CO)
5
ReCH
3
. Indeed, heating (CO)
5
ReCH
3
to 100
o
C for 12 hrs in 8.3:1.7 v/v
mixture of CD
3
CN/D
2
O with excess KIO
4
along with 10 mol % D
2
SeO
3
gave an
~80% yield of methanol. The initial result was reported by Bill Tenn in a 9:1 v/v
mixture, but this result could not be reproduced after several attempts. The yield
of methanol in this solvent composition was very meager and I had a hunch that
the solubility of KIO
4
(which is not even terribly soluble in water) could have
resulted in the discrepancy. (CO)
5
ReCH
3
is not soluble in water, but is very
soluble in acetonitrile. To test the limit of the solvent composition, 30mg of
(CO)
5
ReCH
3
was added to 0.5 mL CD
3
CN. D
2
O was slowly added with
subsequent gentle heating (so as not to induce reaction, but increase solubility).
This resulted in the high yield of methanol reported above. It should be noted that
Bill reported NaIO
4
as the oxidant, but I could not locate this in our laboratory,
believing he must have used the potassium salt. For future studies NaIO
4
will
certainly benefit the chemistry as its solubility in water is reportedly much higher.
Importantly, no CO
2
, which is often produced in reactions of metal
carbonyls with strong oxidants, was identified by GC-MS analysis of the
headspace.
124
CH
3
Se
IV
O
2
H was observed as a reaction intermediate at near 10% of the
intial Re-Me concentration (in accordance with the 10 mol % added SeO
2
),
indicating that oxidation of CH
3
Se
IV
O
2
H to CH
3
Se
VI
(O)
2
OH is the rate limiting
step in the overall conversion of (CO)
5
ReCH
3
to methanol. Control experiments
confirm that CH
3
Se
IV
O
2
H generates methanol upon treatment with only IO
4
-
.
In order to definitively comment on the nature of the stoichiometric
methyl transfer from rhenium to selenium, we sought to identify a more reactive
system that could generate a well-defined rhenium product suitable for
characterization by
1
H NMR and mass/elemental analyses. Reasoning that
(CO)
3
(bpy)ReCH
3
,
21
could lead to a cleaner, faster reaction (because bpy would
replace the 2 most labile CO ligands and result in a more electron rich metal-
methyl bond) we reacted (CO)
3
(bpy)ReCH
3
with H
2
SeO
3
in a 1:1 ratio in
CH
3
CN/H
2
O. Indeed the reaction was very efficient at room temperature,
generating (CO)
3
(bpy)Re(OSe(O)CH
3
) in essentially quantitative yield upon
mixing, as evidence by the immediate color change from orange to yellow. The
seleninate species was isolated as a fine yellow solid in 65% yield after
precipitation by diethyl ether, filtration, and copious washings with diethyl ether.
It was characterized by
1
H NMR and elemental analysis. Use of excess H
2
SeO
3

(instead of 1 equivalent) produced the seleninate species,
(CO)
3
(bpy)Re(OSeO
2
H), and CH
3
SeO
2
H as shown in Eq. 2.
(CO)
3
(bpy)Re(OSeO
2
H) was isolated and characterized analogously. This result
supports the original observation that (CO)
5
ReCH
3
with excess H
2
SeO
3
produces
CH
3
SeO
2
H in quantitative yield, as the free H
2
SeO
3
in solution is competent to
125
protonate (CO)
5-x
(CD
3
CN)
x
Re(OSe(O)
2
CH
3
) and its excess drives the acid/base
equilibrium to completion.
High resolution mass spectrometry (ESI/APCI) of the reaction solution of
(CO)
3
(bpy)ReCH
3
with one equivalent of H
2
SeO
3
indicated that several species
are present before purification. The major species has a m/z of 417.0077 which
corresponds to [(CO)
3
bpyRe]
+
. Also present at m/z=455.0042 is [(CO)
4
bpyRe]
+
.
Three dinuclear species at low intensity are identified. Two are bridging
seleninate species and one is the hydroxide as drawn in Figure 4.5. The actual
binding of the bridging species can not be established based on this data, only the
correct collection of atoms. Drawn are the most likely structures. The data
suggests that the monomeric species are either highly labile in solution or that the
Re-O, Re-Se, or Re-CH
3
bonds do not survive the ionization. This is supported
by the observation of large amounts of cationic, 5-coordinate species and 6-
coordinate species which have picked up a labilized CO. The spectrum for
(CO)
3
bpyReCH
3
, shown in , has one set of peaks at 427.01 which is consistent
with a low bond strength.
126

Figure 4.5: Electrospray Ionization Mass Spectrum of (CO)
3
bpyReCH
3
+ H
2
SeO
3

in CH
3
CN/H
2
O (9:1)

127
Attempted reaction of (CO)
3
(bpy)ReCH
3
with IO
4
-
and catalytic amounts
of H
2
SeO
3
led only to formation of methane. Control experiments show that,
consistent with the expected higher degree of M-C
δ-
polarization in
(CO)
3
(bpy)ReCH
3
relative to (CO)
5
ReCH
3
, the rate of protonolysis of the bpy
complex is much faster (CH
3
D is produced at room temperature in less than 10
minutes when (CO)
3
bpyReCH
3
is dissolved in a CD
3
CN/D
2
O mixture without the
presence of H
2
SeO
3
). Though reaction with H
2
SeO
3
is also more efficient,
selenium is present only in catalytic amounts, and the rate limiting step remains
oxidation of Se
IV
to Se
VI
. Thus, the increased rate of protonolysis relative to
oxidation of selenium precludes the formation of methanol above the 10% or so
expected from the instantaneously formed CH
3
SeO
2
H. As expected, using
stoichiometric or excess H
2
SeO
3
in the reaction of (CO)
3
(bpy)ReCH
3
with IO
4
-

generates methanol because the methyl pools to methylseleninic acid.
To further understand how the co-catalyst, H
2
SeO
3
, is involved in the
reaction mechanism we performed B3LYP density functional theory (DFT)
calculations.
22
Early studies of net insertion of SO
2
or SeO
2
into the M-R bond
were proposed to precede via insertion or external attack mechanisms.
23,24,6
Thus,
we investigated several mechanisms for the methyl transfer step. The most
favorable pathway was found to be an electrophilic attack (S
E
2) by Se (Figure 2).
Alternative mechanisms involving prior dissociation of CO or a seven-coordinate
rhenium complex in a four centered associative transition state, were found to
have higher activation barriers.

128

Figure 4.6: Lowest energy pathway for methyl transfer to H
2
SeO
3
.

The initial step is the endothermic conversion of H
2
SeO
3
to SeO
2
(ΔH of 5.5
kcal/mol) with H
2
O weakly bound to selenium. The electrophilic selenium then
accepts the methyl group of (CO)
5
ReCH
3
through an approximately linear (Re-C-
Se > 160°) S
E
2 type transition state with a barrier of 7.6 kcal/mol. Overall ΔH
‡
=
13.2 kcal/mol relative to selenious acid and (CO)
5
ReCH
3
, which is consistent with
the experimental value of 8.0 ± 1.7 kcal/mol. The intrinsic reaction coordinate
(Figure 4.7) from the transition state connects to a structure where one of the
oxygen atoms (as apposed to selenium) of the methyl seleninate moiety is
coordinating to rhenium (Figure 4.6, ΔH = -21.5 kcal/mol).
129

Figure 4.7: Transition State (top left) and Snapshot Views from the IRC of the
Subsequent Decomposition to O-seleninate Product.

This mechanism fits the experimental result that showed no decrease in rate in a
solution saturated with CO, and that more electron-rich Re-CH
3
bonds would
have lower barriers, e.g. (CO)
3
(bpy)ReCH
3
system. In addition, though we were
not able to obtain X-ray quality crystals of the product, theory predicts the
uncommon O-bound seleninate, which was favored over the S-bound congener by
nearly 14 kcal/mol.

130
4.3 Experimental

General Considerations: All air and water sensitive procedures were carried out
either in a Vacuum Atmosphere glove box under argon, or using standard Schlenk
techniques under argon. Labeled solvents, D
2
O and CD
3
CN were purchased from
Cambridge Isotopes and used without further purification. CD
3
CN was dried over
CaH
2
and vacuum transferred for NMR used for compound characterizations.
2,2’-bipyridine (Lancaster Synthesis, Inc. 99+%) was sublimed at 100-120°C and
stored under argon prior to use. CO
5
ReBr and rhenium carbonyl ,Re
2
(CO)
10
,
were purchased from Strem. THF (Mallinckrodt) was refluxed over
Na/benzophenone and distilled under argon before use in synthesis or for column
chromatography. Basic alumina (EMD) was dried for 2 days at 100
o
C in a
vacuum oven, and then kept in the glove box antechamber under vacuum
overnight before use. 48% aqueous HBr, GOLD LABEL SeO
2
(99.9+%),
methaneseleninic acid (CH
3
Se(O)OH, 95%), CH
3
MgI (Grignard, 3.0M in diethyl
ether), and CH
3
I (95.5% stabilized with Cu) were all purchased from Alrich,
degassed and stored under argon.
13
CH
3
I was purchased from Cambridge
Isotopes, degassed, and stored under argon. CH
3
I was vacuum transferred and
stored over molecular sieves. GC/MS analysis was performed on a Shimadzu
GC-MS QP5000 (ver. 2) equipped with cross-linked methyl silicone gum
capillary column (DB5). The retention times of the products were confirmed by
comparison to authentic samples. NMR spectra were obtained on a Varian
Mercury-400 MHz spectrometer at room temperature. All chemical shifts are
131
reported in units of ppm and referenced to the residual protonated solvent.
Standard C,H,N elemental analysis was performed by Desert Analytics
Laboratory in Tucson, AZ. Fast atom bombardment (FAB) high resolution mass
spectra were collected by the University of California, Riverside Mass
Spectrometry facility.

Synthesis of (CO)
5
ReCH
3
: 2.0 g rhenium carbonyl, Re
2
(CO)
10
, were dissolved in
~10mL dry THF under argon atmosphere in the glove box. This solution was
transfer to a vial containing 10 gram Na/Hg amalgam and stirred for 2 hours,
resulting in a deep red solution. The resultant solution was decanted from the
amalgam and to it added 50-100 equivalents of CH
3
I. After stirring for 45
minutes, the solution was removed from the glove box. DI water was added to
the solution until a white solid ((CO)
5
ReCH
3
) precipitated. This solid was
quickly filtered on a fine glass frit to remove bulk water, then transferred to a
small vial for further drying over P
2
O
5
. Care must be taken, as (CO)
5
ReCH
3
is
volatile. Extended vacuum drying will result in loss of compound. After drying
over P
2
O
5
in a sealed container was complete (15-20h), the compound can be
further purified by sublimation at 60
o
C. NMR analyses were conducted in
CD
3
CN and C
6
D
6
. (CO)
5
Re
13
CH
3
was synthesized following the same prep using
13
CH
3
I.

132

Figure 4.8: 400MHz
1
H-NMR of (CO)
5
ReCH
3
in CD
3
CN.
 
133

Figure 4.9: 400MHz
1
H-NMR of (CO)
5
ReCH
3
in C
6
D
6
.
 
134

Figure 4.10: 400MHz
13
C-NMR of (CO)
5
ReCH
3
in C
6
D
6
.
 
135
Synthesis of (CO)
3
(bpy)ReBr: 0.3950 g (CO)
5
ReBr was combined with 2.5 g
bipyridine in a glass schlenk bomb (~50 mL volume) sealed with a Kontes Teflon
valve under argon gas. The reaction was heated at 120 °C for 2 hours with a
moderate flow of argon through the bomb. Bipyridine melts at ~70 °C so the
system is homogeneous throughout. The reaction was cooled and the excess
bipyridine was extracted with excess THF. (CO)
5
ReBr is collected as the
remaining fine yellow powder, washed with more THF on a glass frit followed by
excess diethyl ether. This reaction can also be run in 10-15 mL THF instead of
neat ligand using the same reaction conditions. In this case, yellow product will
fall out of solution and can be filtered followed by washing with THF and ether.
Synthesis of (CO)
3
(bpy)ReCH
3
: The yellow (CO)
3
(bpy)ReBr from the first
reaction was treated with 0.5mL CH
3
MgI solution (3.0 M in ether) and stirred in
7.5 mL rigorously dried THF at room temperature for 2 h under argon in the glove
box. An orange solution results as the insoluble yellow starting material is
methylated and becomes soluble. Decomposition results at longer reaction times
with excess Grignard, possibly due to reduction or substitution of the bpy ligand.
Immediately following reaction, the THF solution was run through a plug of dry
neutral or basic alumina and the orange product eluted with THF. Solvent was
evaporated, leaving analytically pure (CO)
3
(bpy)ReCH
3
. Evidence of unreacted
starting material, or possibly hydrolyzed (CO)
3
(bpy)ReCH
3
(to form presumably
(CO)
3
(bpy)Re(OH) or variants) can be noted as a faint yellow, slowly eluting
band at the top of the alumina plug. Typical yields were between 70-90% based
136
on (CO)
5
ReBr. Elemental analysis: Expected, C, 38.09 H, 2.51 N, 6.35. Found,
C, 37.98 H, 2.62 N, 6.09.

137

Figure 4.11: 400MHz
1
H NMR of (CO)
3
(bpy)ReCH
3
in CD
3
CN.
 
138

Figure 4.12: 400MHz
1
H NMR of (CO)
3
(bpy)ReCH
3
in CDCl
3
.
 
139

Figure 4.13: 400MHz
13
C NMR of (CO)
3
(bpy)ReCH
3
in THF-d
8
.
 
140
Synthesis of (CO)
3
(bpy)Re(SeO
2
CH
3
): 50 mg (0.113 mmol) (CO)
3
(bpy)ReCH
3
was dissolved in 7.5 mL CH
3
CN and treated with 13.0 mg SeO
2
(0.113 mmol) and
0.05 mL H
2
O under air. The reaction turns pale yellow and forms a precipitate. It
was stirred overnight (~12 hr). 3 mL diethyl ether was added to further
precipitate the compound. The precipitate was collected on a frit, washed
thoroughly with water and ether and dried on a vacuum line (~10 mTorr) for 24
hours. Elemental analysis: Expected, C, 30.44; H, 2.01; N, 5.07. Found, C,
30.03; H, 1.83; N, 5.23.

141

Figure 4.14: 400MHz
1
H NMR of CO
3
bpyRe(SeO
2
CH
3
) in wet CD
2
Cl
2
. Se satellites on the methyl group at δ 2.04 are
indicative of Se-CH
3
(J=7Hz).
 
142
Synthesis of (CO)
3
(bpy)Re(SeO
2
OH): 50mg (0.113mmol) (CO)
3
(bpy)ReCH
3
was dissolved in 7.5 mL 9:1 CH
3
CN:H
2
O and treated with ~100 mg SeO
2
(excess). The reaction turns yellow and starts to precipitate solid immediately.
(CO)
3
(bpy)Re(SeO
2
OH) is less soluble than (CO)
3
(bpy)Re(SeO
2
CH
3
) so it is not
necessary to further precipitate the product. A fine yellow solid was collected on
a glass frit by vacuum filtration, washed with water, acetonitrile, and ether and
dried under vacuum for 24 hours. Elemental analysis: Expected, C, 28.16; H,
1.64; N, 5.05. Found, C, 28.57; H, 1.41; N, 5.16.
143

Figure 4.15: 400MHz
1
H NMR of (CO)
3
(bpy)Re(SeO
2
OH) in CD
3
OD.
 
144
Kinetic analysis of (CO)
5
ReCH
3
+ D
2
SeO
3
reaction in 9:1 CD
3
CN:D
2
O: Stock
solutions of (CO)
5
ReCH
3
and H
2
SeO
3
in 9:1 CD
3
CN:D
2
O were prepared in
separate vials at 20.5mM and 0.205 M, respectively so that the concentration of
D
2
SeO
3
was pseudo-first order throughout the reaction with respect to the Re
reactant. A
1
H NMR spectrum of 0.25 mL CO
5
ReCH
3
solution was taken prior to
reaction in an 8” J-Young NMR tube sealed with a Teflon cap and outfitted with a
benzene/CCl
4
co-axial external standard (sealed capillary supported by one fitted
Teflon O-ring). Precisely 0.25 mL D
2
SeO
3
solution was then added and another
1
H NMR spectrum was taken as the t
0
. The production of CH
3
SeO
2
H at ~2.6 ppm
was monitored along with the disappearance of the Re-CH
3
resonance at -0.26
ppm by heating the NMR tubes in the probe. Reactions were run in triplicate at
50, 60, 70, and 80
o
C in order to perform the Eyring analysis shown below.
145

Figure 4.16: Eyring Plot for Transfer of Methyl from (CO)
5
ReCH
3
to H
2
SeO
3
.
 
146
CO inhibition study: 4.2 mg (CO)
5
ReCH
3
was dissolved in 0.6mL of a 9:1
CD
3
CN:D
2
O solution containing ~100 equivalents of D
2
SeO
3
in an 8” J-Young
tube sealed with a Teflon cap. The reaction was blanketed with 1atm CO,
resealed and shaken vigorously, then heated at 70°C in the NMR probe. The
reaction was monitored by
1
H NMR until complete. The rate of reaction was
unchanged in the presence of CO gas.

CH
3
SeO
2
H oxidations by iodine reagents:
KIO
3
- 5.0 mg CH
3
SeO
2
H and 25.3 mg KIO
3
were dissolved in 0.5 mL D
2
O in an
eight inch J-Young NMR tube and heated at 150 °C for ~30 minutes. 21%
conversion to methanol was observed at this short reaction time at δ 3.33 along
with unreacted CH
3
SeO
2
H starting material at δ 2.78. I
2
- 5.0 mg CH
3
SeO
2
H was
heated at 150°C for ~5 hours with 30.0 mg I
2
in D
2
O under argon. No reaction
occurred. 10 µL of degassed 40% KOD was added and the reaction was heated
for 30 minutes at 150°C under argon. This yielded methanol in accordance with
the known reaction of I
2
with OH
-
:
25

I
2
+ 2OH
-
 I
-
+ IO
-
+ H
2
O (K
eq
~30) (1)
3IO
-
 2I- + IO
3
-
(K
eq
~10
20
) (2)

KI - Heating 10.0 mg CH
3
SeO
2
H with 30.0 mg KI in 0.5 mL D
2
O at 150 °C for 4
hours under argon resulted in no reaction. Addition of 10 µL KOD and continued
heating under argon for 5 hours resulted in no reaction as well. Opening the J-
147
Young tube to air and reheating for 5 hours resulted in the formation of methanol
as well as formaldehyde as monitored by
1
H NMR spectroscopy in accordance
with the known air oxidation of I
-
:
2I
-
+ O
2
 I
2
(unbalanced)
(3)

This reaction likely proceeds with the formation of a reduced oxygen species such
as H
2
O
2
which would render the solution basic, i.e.:

2I
-
+ O
2
+ H
2
O  I
2
+ H
2
O
2
+ 2OH
-

(4)

Accordingly, reaction of 5.0 mg CH
3
SeO
2
H with 30.0 mg of KI under air or 1atm
O
2
in D
2
O at 150 °C for 6 hours yields methanol and formaldehyde. The oxygen
species resulting from the air oxidation of I
-
is most likely responsible for the
overoxidation of CH
3
SeO
2
H to formaldehyde, as CH
3
SeO
2
H does not oxidize in
the presence of air under the same conditions. I
2
is also known to be oxidized by
H
2
O
2
:

I
2
+ 5H
2
O
2
 2HIO
3
+4H
2
O (5)

Computational Details: All calculations were performed with using the B3LYP
hybrid density functional as implemented by the Jaguar 6.5 program package. For
all atoms except selenium the LACV3P** basis set was used for geometry
148
optimizations and solvation energies, and LACV3P**++ for single point gas
phase energy corrections. For selenium the all electron basis set MSV augmented
with one d-function was used for geometries and solvation energies (MSV+d),
and MSV augmented with one d-function and one f-function used for the single
point energy corrections (MSV+d,f). In MSV+d the d-function had an exponent α
= 0.5213. In MSV+d,f the additional d-function used α = 0.4530, while the f-
function had α = 0.6850. With the additional d- and f-functions values in good
agreement with experimental data for conversion of Se between different
oxidation states were obtained. Solvation was modeled implicitly with the
Poisson-Boltzmann solver (PBF) implemented in Jaguar. The parameters were set
to e = 36.6 and probe radius = 2.18 to simulate acetonitrile. Vibrational
frequencies were calculated numerically including the PBF. The vibrational
entropies were extracted from the solution phase frequency calculations, while the
translational and rotational entropies were calculated in the gas phase and scaled
by a factor of 0.5, which in our experience yields results in good agreement with
experiments for solution phase entropies.

XYZ-coordinates in Å and energies.

Re(CO)
5
CH
3

E
elctronic
= -685.9789823567 a.u.
149
E
solv
= -0.0053822 a.u.
ZPE= 48.584 kcal/mol
ΔH
298.15
= 9.11288 kcal/mol
ΔS
vib 298.15
= 44.423 cal/(mol K)
ΔS
trans,rot 298.15
= 37.3465 cal/(mol K)
Re1 -0.0010544160 -0.0472494336 -0.0010022568
O2 3.1380786927 -0.3185281196 0.0281484577
C3 2.0049314962 -0.1944401689 0.0171265749
O4 -0.0396258935 -0.3032027012 3.1389737190
C5 -0.0253381093 -0.1855418880 2.0050929572
O6 0.0192700408 3.0809015648 0.0044046050
C7 0.0088229479 1.9317591838 0.0020663897
O8 -3.1420736752 -0.2803168696 -0.0316423906
C9 -2.0073948744 -0.1689185160 -0.0210654967
O10 0.0212469346 -0.2904179137 -3.1417656455
C11 0.0135862209 -0.1754029101 -2.0075073432
C12 0.0208840581 -2.3487950296 0.0052189797
H13 -0.9777709970 -2.7517783259 0.1808812476
H14 0.3793632730 -2.7390398872 -0.9489091321
H15 0.6798489185 -2.7256403905 0.7901283023

H
2
SeO
3

E
elctronic
= -2626.13674273109
E
solv
= -0.0232088
ZPE= 18.287 kcal/mol
ΔH
298.15
= 4.2009 kcal/mol
ΔS
vib 298.15
= 10.965 cal/(mol K)
ΔS
trans,rot 298.15
= 32.827 cal/(mol K)

Se1 1.2707845070 0.4928866478 0.1061707961
O2 0.3074944528 1.1783706000 1.2220162336
150
O3 0.1793035580 -0.5856207100 -0.8344680913
H4 -0.5711403984 -0.8895459265 -0.2919466453
O5 2.1832771134 -0.7669015564 1.0121762108
H6 1.6734374207 -1.0905758079 1.7772103299

SeO
2
(OH
2
)
E
elctronic
= -2626.121521
E
solv
= -0.0295176
ZPE= 18.214 kcal/mol
ΔH
298.15
= 4.2010 kcal/mol
ΔS
vib 298.15
= 11.119 cal/(mol K)
ΔS
trans,rot 298.15
= 33.1355 cal/(mol K)

Se1 -1.5085155729 -1.0483449878 0.0891943415
O2 -2.4532547075 -0.0191205030 -0.7405046266
H3 0.9925176421 -1.2632001503 -1.5502464108
O4 -1.6695604807 -2.5653269500 -0.4708374266
O5 0.6269750019 -0.5073752684 -1.0661618788
H6 0.5288150237 0.1884241558 -1.7336739153

Re(CO)
5
-CH
3
- SeO
2
(OH
2
) (transition state)
E
elctronic
= -3312.077484
E
solv
= -0.0464542
ZPE= 67.343 kcal/mol
ΔH
298.15
= 13.2427 kcal/mol
ΔS
vib 298.15
= 75.018 cal/(mol K)
ΔS
trans,rot 298.15
= 39.515 cal/(mol K)

151

C1 0.0000000000 0.0000000000 0.0000000000
Se2 0.0000000000 0.0000000000 2.3900693319
O3 1.6798071606 0.0000000000 2.6747936700
H11 -1.0696985896 0.1335806793 0.0923257830
H12 0.4731722447 -0.9686108080 0.0923257830
H13 0.6245865390 0.8743093788 -0.1234666410
Re8 -0.4784067729 -0.6696838665 -2.3976267560
O14 -0.5446101614 1.5890726443 2.6747936700
C9 1.4850058584 -0.3730684811 -2.8029977656
O10 2.5813600936 -0.2069265646 -3.0428845619
O11 -1.0326520335 2.3748406923 -3.0428845619
C12 -0.8343708914 1.2838409974 -2.8029977656
O13 -1.0643923999 -1.4899588764 -5.3170357053
C14 -0.8433162133 -1.1804917789 -4.2379670899
O15 -3.5110705427 -1.0664054724 -1.6091719207
C16 -2.4203770872 -0.9261986410 -1.8958213746
O17 0.1295201831 -3.6671598696 -1.6091719207
C18 -0.0914598837 -2.5899236006 -1.8958213746
H15 2.2385001677 1.8432290771 3.1202585879
O16 1.9886989273 2.7838226011 3.0866357406
H17 1.0179233702 2.7151811070 3.1202585879

Re(CO)5-O
2
SeCH
3

E
elctronic
= -3312.156536
E
solv
= -0.0273795
ZPE= 69.668 kcal/mol
ΔH
298.15
= 13.8415 kcal/mol
ΔS
vib 298.15
= 79.877 cal/(mol K)
ΔS
trans,rot 298.15
= 39.002 cal/(mol K)

C7 0.6390385808 1.2755266038 2.1484293134
Se1 -0.4740536308 -0.0808739301 1.2848555934
O2 -1.8933313498 0.7802496448 1.0276204038
Re8 -0.4622391392 -0.9929720399 -2.0397339327
C9 -2.2260483327 0.0152898112 -1.9522441148
152
O10 -3.2397775680 0.5227630727 -2.0079773922
O11 -1.7489632940 -3.3880848709 -0.4403253272
C12 -1.2755731347 -2.5086712263 -0.9829858123
O13 -1.4275073734 -2.3471620538 -4.6526100685
C14 -1.0680476255 -1.8421079538 -3.6874724927
O15 2.2899576452 -2.5456485118 -2.1470508692
C16 1.3043716058 -1.9858058928 -2.1067889289
O17 0.8114883757 1.3119433956 -3.8003436881
C18 0.3567649756 0.5087517709 -3.1409280713
H19 1.6576837190 0.9003865775 2.2391221946
H20 0.2076227426 1.4742594287 3.1306441462
H21 0.5864470089 2.1595219794 1.5136837329
O3 0.3680877823 -0.0279209268 -0.2706128488
H3 -1.3362694462 2.1945798743 -0.1232061045
O5 -0.6673380031 2.6198744133 -0.6959260522
H6 -0.0225978391 1.8997349940 -0.7772344606

153
4.4 Chapter 4 References

1 (a) Arndtsen, B. A.; Bergman, R. G.; Mobley, T. A.; Peterson, T. H. Acc. Chem.
Res. 1995, 28, 154 and citations therein. (b) 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 and references therein.

2 Crabtree, R. H. J. Organomet. Chem. 2004, 689, 4083.

3 Lersch, M.; Tilset, M. Chem. Rev. 2005, 105, 2471.

4 Conley, B.L.; Ganesh, S.K.; Gonzales, J.M.; Tenn, W.J., III; Young, K.J.H.;
Oxgaard, J.; Goddard, W.A., III; Periana, R.A. J. Am. Chem. Soc. 2006, 128,
9018.

5 Sanderson, L.J.; Baird, M.C. J. Organomet. Chem. 1986, 307, C1.

6 Flood, T.C. in Topics in Organic and Organometallic Stereochemistry;
Geoffroy, G.L. Ed. Vol. 12 of Topics in Stereochemisty; Wiley, New York, 1981,
12, 83 and references therein.

7 Labinger, J.A.; Hart, D.W.; Seibert, W.E., III; Schwartz, J. J. Am. Chem. Soc.
1975, 97, 3851.

8 (a) Bibler, J.P.; Wojcicki, A. J. Am. Chem. Soc. 1964, 86, 5051. b) Wojcicki, A.
Acc. Chem. Res. 1971, 4, 344.

9 Lorenz, I.-P. Angew. Chem. Int. Ed. 1978, 17, 53.

10 Calderazzo, F. Angew. Chem. Int. Ed. 1977, 16, 299.

11 Bibler, J.P.; Wojcicki, A. J. Am. Chem. Soc. 1964, 86, 5051.

12 Lorenz, I.P. Angew. Chem. Int. Ed. Engl. 1978, 1, 53.

13 Conley, B.; Ganesh, S.K.; Gonzales, J.M.; Ess, D.H.; Nielsen, R.J.; Ziatdinov,
V.R.; Oxgaard, J.; Goddard, W.A., III; Periana, R.A. Submitted for publication.

14 At >120°C protonolysis of (CO)
5
ReCH3 to yield methane occurs along with
CO insertion to generate acyl derivatives. Reaction rates and selectivities are
independent of added O
2
suggesting that free-radicals are not involved.

15 (a) Sharpless, K. B.; Gordon, K. M. J. Am. Chem. Soc. 1976, 98, 300. (b)
Corey, E. J.; Schaefer, J. P. J. Am. Chem. Soc. 1960, 82, 918. (c) Selenium in
Natural Products Synthesis, Nicolaou, K. C.; Petasis, N. A.; CIS; Philadelphia,

154

1984. (d) Sharpless, K. B.; Lauer, R. F. J. Am. Chem. Soc. 1972, 94, 7154. (e)
Umbreit, M. A.; Sharpless, K. B. J. Am. Chem. Soc. 1977, 99, 5526.

16 (a) Patel, B. M.; Price, G. L. Ind. Eng. Chem. Res. 1990, 29, 730. (b) Mann, R.
S.; Lao, K. C. Ind. Eng. Chem. Res. 1967, 6, 263.

17 Periana, R.A. Private communication.

18 Waitkins, G. R.; Clark, C. W. Chem. Rev. 1945, 36, 235.

19 Beck, W.; Raab, K.; Nagel, U.; Steinmann, M. Ang. Chem. Int. Ed. 1982, 21,
526.

20 Bird, L.; Challenger, F. J. Chem. Soc. 1942, 570.

21 (a) Lucia, L.A.; Burton, R.D.; Schanze, K.S. Inorg. Chim. Acta. 1993, 208,
103. (b) Worl, L.A.; Duesing, R.; Chen, P.; Della Ciana, L.; Meyer, T.J. J. Chem.
Soc. Dalton Trans. 1991, 849.

22 All B3LYP/ LACV3P**// LACV3P**++ (Se atoms used augmented MSV
basis set) calculations performed with Jaguar 6.5 program. See SI.

23 Jacobsen, S.E.; Reich-Rohrwig, P.; Wojcicki, A. Inorg. Chem. 1973, 12, 717.

24 Whitesides, G. M.; Boschetto, D. J. J. Am. Chem. Soc. 1971, 93, 1529.

25 Greenwood, N.N.; Earnshaw, A. in Chemistry of the Elements, 2nd Edition;
Butterworth-Heinemann; Oxford, 1997; pp 862-874.
155
5 Chapter 5: Synthesis, Characterization, and CH
Activation Reactions of Organometallic, O-Donor
Ligated, Rh(III) Complexes

5.1 Introduction

The rational synthesis and characterization of the O-donor, air and water
stable organometallic complexes trans-(hfac-O,O)
2
Rh(CH
3
)(py), 2, and cis-(hfac-
O,O)
2
Rh(CH
3
)(py), 3, trans-(hfac-O,O)
2
Rh(C
6
H
5
)(py), 4, cis-(hfac-
O,O)
2
Rh(C
6
H
5
)(py), 5, and cis-(hfac-O,O)
2
Rh(Mes)(py), 6 (where hfac-O,O = κ
2
-
O,O-1,1,1,5,5,5- hexafluoroacetylacetonate) are reported. These compounds are
analogues to the O-donor (acac)
2
Ir complexes that are active catalysts for the
hydroarylation of olefins and activation of alkanes, and (acac)
2
Rh complexes
which we recently reported
1
. Complex 2 undergoes a quantitative isomerization
in cyclohexane to form 3, which activates C-H bonds in benzene and mesitylene
to form 5 and 6 respectively. All of these compounds are air and water stable to
decomposition. Complex 3 and 5 were tested for hydroarylation reactions.
Highly efficient and selective transition metal mediated methods for the
functionalization of unactivated alkanes is still largely an unsolved problem that
poses significant challenges to homogeneous and heterogeneous chemists alike.
One of the key reasons for this is that the C-H bonds of saturated alkanes are
thermodynamically and kinetically difficult to break. However, significant
advances have been made in this field through the use of well defined,
156
homogeneous organometallic complexes.
2
A specific challenge here is
hydroarylation of alkenes, a conceptually simple transformation that couples
unactivated Ar-H with unactivated olefin to generate alkyl benzene (Figure 5.1).
Despite the seeming simplicity of this transformation only three systems have
been reported that are able to directly catalyze this intermolecular reaction,
3
none
of which are commercially viable. Friedel Crafts alkylation of arenes is a similar
reaction catalyzed by Lewis acids that yields one predominant product, the

Figure 5.1: Hydroarylation of Ethylene to form Ethyl Benzene.

branched alkyl arene (Markovnikov product), due to the intermediacy of a
carbocation. We are interested in transition metal catalyzed reactions for this
transformation, which allows control by the coordination sphere of the metal.
Efficient, selective systems based on CH activation and insertion reactions could
allow access to high demand linear alkyl benzenes (anti-Markovnikov products).
The reported systems all proceed through a common mechanism
characterized by two key steps, [1,2]-insertion of the coordinating olefin into the
M-Ph bond (TS1, see Figure 5.2), and intermolecular hydrogen transfer (C-H
activation) from benzene to M-CH
2
-CH
2
-Ph (TS2, see Figure 5.2), regenerating
157
the M-Ph species and forming the ethyl benzene product.
4
Our theoretical results
suggested that the barriers for these two steps are inversely related to the donating
character of the metal d-orbitals, where more donating d-orbitals lead to higher
insertion barriers (TS1) and lower hydrogen transfer barriers (TS2). Recent
experimental and theoretical work by Gunnoe and Cundari has demonstrated this
framework nicely.
5
Thus, a system without donating d-orbitals would insert
easily (low TS1) but since it could not catalyze the CH activation (high TS2), it
would lead to polymeric products. Conversely, a system with very donating d-
orbitals would easily transfer the hydrogen (low TS2), but since it could not
catalyze insertion (high TS1), no functionalization reaction would occur.

Figure 5.2: Conceptual Mechanism for Catalytic Hydroarylation
158

In investigating possible modifications to the oldest of the three reported
hydroarylation catalysts trans-(acac-O,O)
2
Ir(C
6
H
5
)(py), we considered our
previously reported Rh analog, (acac)
2
Rh(C
6
H
5
)(py) for catalytic activity in
addition to the system reported herein. Our theoretical analysis suggested that
since the Rh d-orbitals are less donating than the Ir d-orbitals, both
(acac)
2
Rh(C
6
H
5
)(py) and 4 should primarily function as a polymerization
catalysts, with low insertion and high C-H activation barriers. Unfortunately, the
acac analog decomposes to biphenyl and unidentified inorganic products.
6

Though we did not investigate this pathway in detail, we have reason to believe it
may be the result of known bimetallic reductive pathways reported previously in
the literature.
7

In addition to investigating the less donating rhodium metal, we realized
that more electron-withdrawing ligands could improve insertion rates while only
marginally inhibiting CH activation. We noted that the hfac analogue of
(acac)
2
Rh(C
6
H
5
)(py) was easily accessible in the cis-form. We thus investigated
the activity of 3 and one of its derivatives.
The synthesis of the (hfac-O,O)
2
Rh(R)(L) motif and stoichiometric CH
activation reactions thereof are reported here along with preliminary data that
suggests the hydroarylation chemistry is prohibited, probably due to large barriers
for CH activation and/or low barriers for olefin insertion.

159
5.2 Results and Discussion

Synthesis of Complexes. The syntheses of new complexes of Rh
III
with
the β-diketonate κ
2
-O,O-1,1,1,5,5,5-hexafluoroacetylacetonate, hfac-O,O, are
summarized in Scheme 1. The synthesis of 1 has been previously reported.
8

Treatment of rhodium(III) trichloride hydrate with hexafluoroacetylacetone in
refluxing anhydrous ethanol for 4 hours, followed by recrystallization from
methanol yields the complex trans-(hfac-O,O)
2
Rh(CH
3
OH)Cl, 1, as an air and
water stable mustard-yellow microcrystalline compound. The
1
H NMR spectrum
of 1 shows single resonance signals for the methine proton of the hfac ligands and
coordinated methanol at their usual chemical shifts, implying a symmetric
environment for the two hfac ligands as expected for the trans geometry. This
assignment was confirmed by eluciation of the molecular structure of 1 via a low
temperature, single crystal X-ray diffraction study, Fig 1. Although the aquo
analog of 1 was previously reported, no structure of the complex had been
reported.

Scheme 5.1: Synthesis of (hfac-O,O)
2
Rh(III) Complexes.
160

Figure 5.3: ORTEP of 1 (50% probability thermal ellipsoids). A molecule of co-
crystallized methanol has been omitted for clarity. The hydrogen
atom on the methanol was not located.

Complex 1 was heated with (CH
3
)
2
Hg in methanol at 75
o
C for 12 hours,
followed by treatment with pyridine. This afforded the methyl complex trans-
(hfac-O,O)
2
Rh(CH
3
)(py), 2 which has also been fully characterized by
1
H,
13
C
NMR spectroscopy, elemental analysis, and X-ray crystallography.

161

Figure 5.4: ORTEP plot of 2 (50% probability thermal ellipsoids). Selected bond
lengths (Å): Rh1-N1, 2.236(3); Rh1-C16, 2.031(3).

Heating complex 2 in cyclohexane at 130
o
C for 12 hours induced trans to
cis isomerization of the complex to afford the cis-(hfac-O,O)
2
Rh(CH
3
)(py)
isomer, 3, in quantitative yield as determined by monitoring the
1
H NMR
throughout the reaction. The reaction was carried out inside an 8-inch J-Young
style NMR tube equipped with a sealed coaxial external standard capillary
containing 1,3,5-trimethoxybenzene in CCl
4
.

162

Figure 5.5: ORTEP plot of 3 (50% probability thermal ellipsoids). Selected bond
lengths (Å): Rh1-N1, 2.017(5); Rh1-C16, 2.026(5).

Treatment of 1 with Ph
2
Hg in CHCl
3
/CH
3
OH at 100
o
C for 12 h, followed
by treatment with pyridine, gave the air and water stable organometallic complex
trans-(hfac-O,O)
2
Rh(Ph)(py), 4. Initial investigations of the chemistry of this
molecule revealed a decomposition pathway. Upon heating in arene solutions or
methanol, 4 was found to decompose to biphenyl (identified by GC-MS and NMR
analysis) and a new (hfac-O,O)
2
Rh complex which has not been fully
characterized. Presumably these decomposition reactions preclude isomerization
to the cis species which would be necessary for the CH activation reaction. This
is analogous to the chemistry of the acac analog.
6

Hydrocarbon Activation. When 3 is heated in benzene at 190°C for 14
hours it is converted to cis-(hfac-O,O)
2
Rh(C
6
H
5
)(py), 5 in 78% yield; as shown in
Scheme 2. The
1
H NMR spectrum revealed the disappearance of the distinctive
doublet of the Rh-CH
3
resonance at 2.48 ppm, which is accompanied by
163
appearance of two new multiplets at 7.10 and 7.36 ppm corresponding to the new
phenyl protons. The reaction in C
6
D
6
reveals an upfield 1:1:1 triplet at 0.18 ppm
due to the formation of CH
3
D. Some decomposition of the starting material is
observed, especially when the reaction was carried out at temperatures greater
than 190
o
C. Complex 5 has been characterized by
1
H,
13
C NMR spectroscopy,
and elemental analysis.
In a closely related reaction, when 3 is heated in mesitylene at 190 °C for
14 hours it is converted to cis-(hfac-O,O)
2
Rh(Mes)(Py), 6, which has also been
fully characterized by
1
H,
13
C NMR spectroscopy, elemental analysis, hi-
resolution FAB mass spectrometry, and X-ray crystallography (Figure 4). 6 was
isolated from the reaction mixture isolated in 51% yield after purification by slow
sublimation at 60
o
C under reduced pressure.

Scheme 5.2: Hydrocarbon activation by 3.

164

Figure 5.6: ORTEP plot of 6 (50% probability thermal ellipsoids).

Catalytic CH Activation. Having established that 3 can stoichiometrically
activate the C-H bonds of benzene, and mesitylene we examined the catalytic CH
activation of benzene by this complex as a first step toward developing new
catalysts for hydrocarbon functionalization. The rates of H/D exchange of a
mixture of C
6
H
6
and toluene-d
8
(1:1 v/v),

at 190 °C catalyzed by the methanol
analog of 2, trans-(hfac-O,O)
2
Rh(CH
3
)(CH
3
OH), were measured. The reaction
mixture is stable over the time period studied (11.5 hr) and turn-over-numbers
(TON) of 114 and turn-over-frequencies (TOF) of 2.8 x 10
-3
s
-1
were observed
based on added catalyst. In addition, when the reaction was carried out using the
pyridyl complex, 2, a TOF of 2.0 x 10
-3
s
-1
was observed. The observation that 2-
py, catalyzes the reaction more slowly than 2-CH
3
OH is consistent with the
requirement for reversible loss of L and supports metal-mediated mechanism
165
involving hydrocarbon coordination prior to CH cleavage since pyridine is a less
labile ligand than methanol.
Hydroarylation Reactions. Having demonstrated the stoichiometric and
catalytic capability of 3 for CH activation of benzene we examined the
competency of 3 and 5 for hydroarylation (CH activation/functionalization) using
a mixture of benzene and styrene. These complexes were not active catalysts for
hydroarylation. Interestingly, 3 yielded traces of dihydrostilbene early in the
reaction, as monitored by GC/MS, but as the reaction was followed for longer
periods significant quantities of polystyrene were generated. No olefinic
products, such as stilbenes, which could result from β–hydride elimination of the
products form the metal center were detected in the analysis of the reaction
mixture. Compound 3 was inactive for reaction between benzene and propylene
as well as benzene and ethylene at 190
o
C, with no observable polymerization
products.
In conclusion, we have prepared several novel bis-
hexafluoroacetylacetonate Rh(III) compounds with the same structure and
composition as the Ir catalysts we previously reported for the hydroarylation of
olefins
1

and have investigated them for catalytic activity in CH activation and
hydroarylation. The cis-(hfac-O,O)
2
Rh(CH
3
)(py) is produced quantitatively from
isomerization of the trans- analog. When 3 was heated at 190
o
C in benzene or
mesitylene the corresponding phenyl- or mesityl- complexes were generated. We
have determined that the trans phenyl species, 4, is not a potential catalyst for
hydroarylation due to the predominating decomposition pathway. The cis species,
166
3 and 5, while carrying out efficient CH activation, seem to be inactive or very
inefficient, as polymerization pathways dominate for styrene and no reaction
occurs with the more inert ethylene and propylene substrates. These results
underscore the need to pair activation and insertion barriers and the connection of
the relative barriers on the metal and ligands.

5.3 Experimental

Warning! Organomercury compounds are highly toxic! There is a danger
of cumulative effects. These compounds may cause serious and irreversible
effects on skin contact. These compounds may be fatal if absorbed through the
skin - even small amounts, such as a single drop, may cause serious injury or
potentially be fatal. They may cause metal fume fever if inhaled or swallowed.
Chronic exposure may cause irreversible CNS damage, sensitization, weight loss,
immunological disease and other serious effects. Dimethylmercury is volatile and
dangerous concentrations can readily build up in poorly ventilated areas. Work
with these dangerously toxic compounds must not begin before a full assessment
of the risks has been made and suitable protocols established.
167
General Methods. All air and water sensitive procedures were carried out
either in an MBraun inert atmosphere glove box, or using standard Schlenk
techniques under argon. The glovebox atmosphere was maintained by periodic
nitrogen purges and monitored by an oxygen analyzer {O
2(g)
< 15 ppm}.
Methanol was dried from Mg/I
2
, and benzene from sodium/benzophenone ketal.
All deuterated solvents (Cambridge Isotopes) were used as received. 1,1,1,5,5,5-
hexafluoroacetylacetone (Synquest) was stored under argon. GC/MS analysis
was performed on a Shimadzu GC-MS QP5000 (ver. 2) equipped with cross-
linked methyl silicone gum capillary column (DB5). The retention times of the
products were confirmed by comparison to authentic samples. NMR spectra were
obtained on a Bruker AM-360 spectrometer, measured at 360.138 MHz for
1
H
and 90.566 MHz for
13
C or on a Bruker AC-250 spectrometer, measured at
250.134 MHz for
1
H and 62.902 MHz for
13
C, or Varian Mercury-400
spectrometer, measured at 399.96 MHz for
1
H, 100.57 MHz for
13
C, and 376.34
MHz for
19
F at room temperature. All chemical shifts are reported in units of ppm
and referenced to the residual protonated solvent. High-resolution mass spectra
were obtained by UCLA Pasarow Mass Spectrometry Laboratory on an ESI mass
spectrometer. Elemental Analysis was performed by Desert Analytics of Tucson,
Arizona.
X-ray Crystallography. Table 1 summarizes the crystallographic data for
all structurally characterized compounds. X-ray data were collected at 85K for
complexes 1 and 2 and at 149K for complex 3, on a SMART APEX CCD
diffractometer with graphite-monochromated Mo-Kα radiation (λ = 0.71073 Å).
168
The cell parameters for each compound were obtained from the least-squares
refinement of the spots (from 60 collected frames) using the SMART program
[1]. In each case, a hemisphere of data was collected up to a resolution of 0.75Å,
and intensity data were processed using the SAINT PLUS program [2]. Empirical
absorption corrections were applied using SADABS [3], and all calculations for
the structural analyses were carried out using the SHELXTL package [4]. Initial
positions of the Rh atoms were located by direct methods, and the rest of the
atoms found using conventional heavy atom techniques. The structures were
refined by least-squares methods using data in the range of 2θ = 3.5 to 55.0º. All
non-hydrogen atoms in the three complexes were anisotropically refined, and
calculated hydrogen positions were varied in a riding manner along with their
attached carbons.
Synthesis of trans-(hfac-O,O)
2
Rh(Cl)(CH
3
OH). This synthesis can be
followed as reported by Chattoraj and Sievers heating 4.0 g RhCl
3
(H
2
O)
x
and 11
mL 1,1,1,5,5,5-hexafluoropentanedione (Hhfac) in 50mL absolute ethanol under
argon or dinitrogen. This makes the workup rather difficult though. The original
paper does not stress the extent to which the reaction must be dried. In practice, it
must either be pumped on in excess of 24 hours on a vacuum line (30 millitorr) or
gently heated at 40-50 °C on a high vacuum line (2 millitorr). Alternatively, heat
can be applied by a heat gun on a low setting, although this can lead to
inadvertent charring of the reaction products. Upon removal of all excess ethanol,
DI water was added. A large amount was added as the desired product is very
insoluble in water. The complex precipitated from solution as mustard-yellow
169
microcrystals. The microcrystalline product is then washed on a medium porosity
frit with copious amounts of water. A second crop of crystals was also recovered
from the mother-liquor as they precipitated over the next four days. During 1.0 g
syntheses this “second yield” neared 0.2 g. Smaller scale reactions were run
using 1.0 g RhCl
3
(H
2
O)
x
and 3.0 mL Hhfac in 15 mL absolute ethanol. These
reactions are easier to dry. The yield obtained for these smaller syntheses was
found to average 48 %. A common impurity seems to be free hfac ligand, whose
methine proton comes slightly upfield from the bound ligand. Recrystallization
from methanol gives trans-(hfac-O,O)
2
Rh(Cl)(CH
3
OH).
1
H NMR (CD
3
OD) 400
MHz: δ 6.60 (s, 2H, hfac C
3
H).
19
F NMR (CD3OD) ref. to CFCl
3
360 MHz: δ
71.87 (s, 12F, hfac-CF3’s).
13
C{
1
H} NMR (C
6
D
6
): δ 179.07 (q, J
CF
= 146.75 Hz,
hfac C=O), 116.78 (q, J
CF
= 1132.75 Hz, hfac CF
3
), 93.34 (s, hfac CH). Single
crystals structure suitable for diffraction were obtained from a concentrated
solution in methanol stored at -30
o
C overnight.

Table 5.1: Crystal data and structure refinement for (acac)
2
Rh(Cl)(CH
3
OH).
Identification code rhf6acam
Empirical formula C12 H9 Cl F12 O6 Rh
Formula weight 615.55
Temperature 123(2) K
Wavelength 0.71073 Å
Crystal system Orthorhombic
Space group Pca2(1)
Unit cell dimensions a = 8.6144(10) Å a= 90°.
b = 19.986(2) Å b= 90°.
c = 11.7027(13) Å g = 90°.
Volume 2014.8(4) Å
3
170
Table 5.1: Continued

Z 4
Density (calculated) 2.029 Mg/m
3

Absorption coefficient 1.117 mm
-1

F(000) 1196
Crystal size 0.50 x 0.29 x 0.10 mm
3

Theta range for data collection 1.02 to 27.52°.
Index ranges -6<=h<=11, -25<=k<=25, -
14<=l<=15
Reflections collected 11495
Independent reflections 4341 [R(int) = 0.0298]
Completeness to theta = 27.52° 99.3 %
Transmission factors min/max ratio: 0.711
Refinement method Full-matrix least-squares on F
2

Data / restraints / parameters 4341 / 1 / 292
Goodness-of-fit on F
2
1.042
Final R indices [I>2sigma(I)] R1 = 0.0346, wR2 = 0.0775
R indices (all data) R1 = 0.0494, wR2 = 0.0842
Absolute structure parameter 0.06(5)
Largest diff. peak and hole 0.942 and -0.400 e.Å
-3

Table 5.2: Atomic coordinates ( x 10
4
) and equivalent isotropic displacement
parameters (Å
2
x 10
3
) for (acac)
2
Rh(Cl)(CH
3
OH). U(eq) is defined as one third
of the trace of the orthogonalized U
ij
tensor.
__________________________________________________________________
_____________
x y z U(eq)
__________________________________________________________________
_____________
Rh(1) 4978(1) 2472(1) 1140(1) 23(1)
Cl(1) 3482(1) 2646(1) 2714(1) 37(1)
F(1) 9079(4) 4025(2) 1695(3) 69(1)
F(2) 7478(4) 4772(1) 2234(3) 59(1)
F(3) 7877(4) 3924(1) 3278(3) 65(1)
171
Table 5.2: Continued

F(4) 3233(4) 4066(1) -1449(3) 61(1)
F(5) 3418(4) 4871(1) -264(3) 71(1)
F(6) 1638(4) 4149(2) -80(4) 93(2)
F(7) 8199(3) 742(1) 2429(3) 54(1)
F(8) 6804(3) 1023(1) 3858(2) 45(1)
F(9) 6278(3) 134(1) 2922(3) 58(1)
F(10) 1848(3) 995(1) -796(3) 53(1)
F(11) 808(3) 936(1) 871(3) 56(1)
F(12) 2326(3) 165(1) 290(3) 47(1)
O(1) 6559(3) 3103(1) 1749(2) 29(1)
O(2) 3805(3) 3174(1) 292(3) 29(1)
O(3) 6179(3) 1779(1) 1985(3) 28(1)
O(4) 3425(3) 1824(1) 523(2) 27(1)
O(5) 6324(3) 2282(2) -282(3) 32(1)
O(6) 8961(3) 2841(2) -312(3) 49(1)
C(1) 7742(7) 4118(2) 2217(5) 42(1)
C(2) 6427(5) 3733(2) 1609(4) 30(1)
C(3) 5340(5) 4086(2) 985(5) 37(1)
C(4) 4146(5) 3790(2) 372(4) 30(1)
C(5) 3081(6) 4229(3) -356(5) 46(1)
C(6) 6748(5) 763(2) 2834(5) 35(1)
C(7) 5711(5) 1186(2) 2035(4) 27(1)
C(8) 4474(6) 878(2) 1519(4) 30(1)
C(9) 3436(5) 1221(2) 804(4) 28(1)
C(10) 2095(6) 823(2) 282(4) 36(1)
C(11) 5617(6) 2308(3) -1407(4) 43(1)
C(12) 9938(5) 2578(2) 522(6) 51(2)

Table 5.3: Bond lengths [Å] and angles [°] for (acac)
2
Rh(Cl)(CH
3
OH).
_____________________________________________________
Rh(1)-O(1) 1.989(3)
Rh(1)-O(3) 1.992(3)
172
Table 5.3: Continued

Rh(1)-O(2) 1.992(3)
Rh(1)-O(4) 1.997(3)
Rh(1)-O(5) 2.064(3)
Rh(1)-Cl(1) 2.2747(16)
F(1)-C(1) 1.317(7)
F(2)-C(1) 1.327(5)
F(3)-C(1) 1.306(6)
F(4)-C(5) 1.327(6)
F(5)-C(5) 1.319(6)
F(6)-C(5) 1.294(6)
F(7)-C(6) 1.338(5)
F(8)-C(6) 1.308(6)
F(9)-C(6) 1.325(5)
F(10)-C(10) 1.325(6)
F(11)-C(10) 1.325(6)
F(12)-C(10) 1.330(5)
O(1)-C(2) 1.275(5)
O(2)-C(4) 1.270(5)
O(3)-C(7) 1.255(5)
O(4)-C(9) 1.250(5)
O(5)-C(11) 1.451(5)
O(6)-C(12) 1.392(6)
C(1)-C(2) 1.542(7)
C(2)-C(3) 1.380(6)
C(3)-C(4) 1.386(6)
C(4)-C(5) 1.529(6)
C(6)-C(7) 1.544(6)
C(7)-C(8) 1.371(6)
C(8)-C(9) 1.403(6)
C(9)-C(10) 1.530(6)
O(1)-Rh(1)-O(3) 84.66(12)
O(1)-Rh(1)-O(2) 94.55(11)
O(3)-Rh(1)-O(2) 179.10(14)
173
Table 5.3: Continued

O(1)-Rh(1)-O(4) 178.81(13)
O(3)-Rh(1)-O(4) 94.43(11)
O(2)-Rh(1)-O(4) 86.36(13)
O(1)-Rh(1)-O(5) 91.19(11)
O(3)-Rh(1)-O(5) 88.87(12)
O(2)-Rh(1)-O(5) 90.73(13)
O(4)-Rh(1)-O(5) 88.03(13)
O(1)-Rh(1)-Cl(1) 90.03(10)
O(3)-Rh(1)-Cl(1) 89.91(11)
O(2)-Rh(1)-Cl(1) 90.50(10)
O(4)-Rh(1)-Cl(1) 90.73(9)
O(5)-Rh(1)-Cl(1) 178.19(10)
C(2)-O(1)-Rh(1) 121.3(3)
C(4)-O(2)-Rh(1) 121.9(3)
C(7)-O(3)-Rh(1) 120.9(3)
C(9)-O(4)-Rh(1) 121.7(3)
C(11)-O(5)-Rh(1) 119.3(3)
F(3)-C(1)-F(1) 108.7(5)
F(3)-C(1)-F(2) 107.1(4)
F(1)-C(1)-F(2) 107.2(4)
F(3)-C(1)-C(2) 110.8(4)
F(1)-C(1)-C(2) 111.0(4)
F(2)-C(1)-C(2) 111.8(4)
O(1)-C(2)-C(3) 129.2(4)
O(1)-C(2)-C(1) 111.6(4)
C(3)-C(2)-C(1) 119.2(4)
C(2)-C(3)-C(4) 124.0(4)
O(2)-C(4)-C(3) 128.6(4)
O(2)-C(4)-C(5) 112.1(4)
C(3)-C(4)-C(5) 119.3(4)
F(6)-C(5)-F(5) 108.1(4)
F(6)-C(5)-F(4) 107.8(5)
F(5)-C(5)-F(4) 107.2(4)
174
Table 5.3: Continued

F(6)-C(5)-C(4) 111.5(4)
F(5)-C(5)-C(4) 112.4(4)
F(4)-C(5)-C(4) 109.7(4)
F(8)-C(6)-F(9) 108.5(4)
F(8)-C(6)-F(7) 107.6(4)
F(9)-C(6)-F(7) 106.5(4)
F(8)-C(6)-C(7) 111.0(4)
F(9)-C(6)-C(7) 112.9(4)
F(7)-C(6)-C(7) 110.1(4)
O(3)-C(7)-C(8) 130.8(4)
O(3)-C(7)-C(6) 111.1(4)
C(8)-C(7)-C(6) 118.2(4)
C(7)-C(8)-C(9) 122.7(4)
O(4)-C(9)-C(8) 129.3(4)
O(4)-C(9)-C(10) 113.0(4)
C(8)-C(9)-C(10) 117.7(4)
F(10)-C(10)-F(11) 108.4(4)
F(10)-C(10)-F(12) 106.7(4)
F(11)-C(10)-F(12) 106.8(4)
F(10)-C(10)-C(9) 111.5(4)
F(11)-C(10)-C(9) 109.6(4)
F(12)-C(10)-C(9) 113.5(4)
_____________________________________________________________
Symmetry transformations used to generate equivalent atoms:

Table 5.4: Anisotropic displacement parameters (Å
2
x 10
3
) for
(acac)
2
Rh(Cl)(CH
3
OH). The anisotropic displacement factor exponent takes the
form: -2p
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

__________________________________________________________________
____________
175
Table 5.4: Continued

Rh(1) 20(1) 25(1) 25(1) 1(1) -1(1) 1(1)
Cl(1) 29(1) 53(1) 29(1) -3(1) 5(1) 4(1)
F(1) 40(2) 79(2) 88(3) -33(2) 7(2) -16(2)
F(2) 74(2) 35(1) 68(2) -14(2) -14(2) -9(1)
F(3) 88(3) 60(2) 46(2) 6(2) -25(2) -31(2)
F(4) 91(2) 50(2) 42(2) 0(1) -18(2) 19(2)
F(5) 109(3) 29(2) 76(2) 2(2) -39(2) 14(2)
F(6) 41(2) 109(3) 130(4) 59(3) 7(2) 35(2)
F(7) 38(2) 57(2) 67(2) 6(2) -1(2) 17(1)
F(8) 54(2) 47(2) 36(2) 3(1) -14(2) 5(1)
F(9) 71(2) 31(1) 72(2) 16(1) -32(2) -7(1)
F(10) 59(2) 57(2) 44(2) 5(1) -21(2) -18(1)
F(11) 25(1) 71(2) 71(2) -18(2) 10(2) -10(1)
F(12) 51(2) 37(1) 53(2) -6(1) -12(1) -10(1)
O(1) 29(2) 27(2) 30(2) -2(1) -2(1) -1(1)
O(2) 28(2) 30(2) 31(2) 1(1) -5(1) 6(1)
O(3) 24(2) 25(2) 35(2) 3(1) -4(1) 1(1)
O(4) 23(2) 30(2) 28(2) 0(1) -4(1) -3(1)
O(5) 27(2) 40(2) 28(2) -3(2) -3(1) 6(1)
O(6) 31(2) 78(3) 37(2) -2(2) 2(2) -6(2)
C(1) 46(3) 39(3) 42(3) -3(2) -4(2) -9(2)
C(2) 33(3) 30(2) 26(2) -5(2) 6(2) 1(2)
C(3) 46(3) 28(2) 36(3) 1(2) 4(3) 4(2)
C(4) 28(2) 32(2) 31(2) -1(2) 6(2) 9(2)
C(5) 48(3) 45(3) 44(3) 8(3) -5(3) 12(2)
C(6) 35(3) 26(2) 43(3) 5(2) -9(2) 3(2)
C(7) 24(2) 31(2) 26(2) 0(2) 4(2) 5(2)
C(8) 28(2) 27(2) 34(3) -3(2) 1(2) -3(2)
C(9) 27(2) 30(2) 26(2) -2(2) 4(2) -1(2)
C(10) 37(3) 36(3) 35(3) -6(2) 2(2) -5(2)
C(11) 38(3) 57(3) 32(3) -6(2) 1(2) 5(3)
C(12) 34(3) 76(4) 43(3) 7(3) 2(2) 15(3)

176
Table 5.5: Hydrogen coordinates ( x 10
4
) and isotropic displacement parameters
(Å
2
x 10
3
) for (acac)
2
Rh(Cl)(CH
3
OH).
__________________________________________________________________
_____________
x y z U(eq)
__________________________________________________________________
_____________

H(6) 9277 2724 -961 73
H(3) 5415 4560 975 44
H(8) 4312 415 1650 36
H(11A) 4926 1923 -1505 64
H(11B) 6430 2297 -1992 64
H(11C) 5017 2723 -1482 64
H(12A) 10289 2938 1028 77
H(12B) 10839 2368 156 77
H(12C) 9374 2242 969 77

Synthesis of trans-(hfac-O,O)
2
Rh(CH
3
)(Py). Approximately 1.0 g of 1
was dissolved in 15 mL of methanol in a 30 mL Schlenk tube fitted with a
resealable Teflon valve. This compound is highly soluble so not much methanol
is required to dissolve large quantities of the compound. Dimethylmercury was
added in a 2:1 molar ratio with respect to the compound. Excess
dimethylmercury was pumped off with the methanol after the reaction was
complete and converted to (CH
3
)Hg(NO
3
) with HNO
3
for disposal with mercury
waste. The reaction mixture was then heated for 14 hours at 75°C under argon
after 5 successive freeze-pump-thaw cycles removed air. The products were
redissolved in a minimal amount of methanol and kept at -30
o
C overnight to
precipitate methylmercuric chloride (grayish black color).
1
H NMR (CDCl
3
) 400
177
MHz: δ 6.4 (s, 2H, hfac CH), 3.0 (d, 3H, CH
3
split by Rh), 3.5 (s, 3H, CH
3
bound
CH
3
OH). Neat pyridine was added to the methanol adduct and the solution
immediately turned red. Heating was found to be necessary to convert the
methanol adduct to the pyridyl complex, as indicated when the process was
followed by
1
H NMR. Thus, the solution was heated for approximately 30
minutes at 65°C. Analytical TLC at this point in every synthesis showed an
impurity that stuck to neutral alumina when run in CH
2
Cl
2
. Prep TLC or an
alumina plug was employed at this point to remove the unwanted impurity.
Excess pyridine was removed in vacuuo. When nearly all pyridine was removed,
a small amount of chloroform was added to dissolve the solid formed in the flask
and the remaining traces of pyridine. This solution was then fully evaporated.
Crystals suitable for X-ray diffraction were grown from methanol at low
temperature (-30°C).
1
H NMR (CDCl
3
) 400 MHz: δ 8.49 (d, 2H, py-o-H’s), 7.93
(t, 1H, py-p-H), 7.54 (t, 2H, py-m-H’s), 6.14 (s, 2H, hfac-CH), 2.43 (s, 3H, CH3).
19
F NMR (CD
3
OD) ref. to CFCl
3
360 MHz: δ 72.17 (s, 12F, hfac-CF3’s).
13
C{
1
H} NMR (C
6
D
6
): δ 175.15 (s, J
FC
= 141.6 Hz, hfac C=O), 148.91 (s, py),
138.75 (s, py), 125.76 (s, py), 115.29 (q, J
FC
= 1118 Hz, hfac CF
3
), 92.23 (q, J
CF
=
84 Hz, hfac CH), 5.87 (d, J
RhC
= 14 Hz, CH
3
). Analysis Calculated for
C
16
H
10
F
12
NO
4
Rh: C, 31.44; H, 1.65; N, 2.29. Found: C, 31.58; H, 1.58; N, 2.24.
Table 5.6: Crystal data and structure refinement for trans-(acac)
2
Rh(CH
3
)(Py).
Identification code rhmetf6m
Empirical formula C16 H10 F12 N O4 Rh
Formula weight 611.16
Temperature 143(2) K
178
Table 5.6: Continued

Wavelength 0.71073 Å
Crystal system Triclinic
Space group P-1
Unit cell dimensions a = 10.8849(12) Å
a=117.822(2)°.
b = 10.9005(12) Å
b=108.698(2)°.
c = 10.9681(12) Å g
=99.217(2)°.
Volume 1012.91(19) Å
3

Z 2
Density (calculated) 2.004 Mg/m
3

Absorption coefficient 0.977 mm
-1

F(000) 596
Crystal size 0.19 x 0.09 x 0.02 mm
3

Theta range for data collection 2.13 to 27.48°.
Index ranges -13<=h<=13, -14<=k<=11, -
11<=l<=14
Reflections collected 6284
Independent reflections 4373 [R(int) = 0.0225]
Completeness to theta = 27.48° 94.1 %
Transmission factors min/max ratio: 0.681
Refinement method Full-matrix least-squares on F
2

Data / restraints / parameters 4373 / 0 / 308
Goodness-of-fit on F
2
1.056
Final R indices [I>2sigma(I)] R1 = 0.0380, wR2 = 0.0890
R indices (all data) R1 = 0.0448, wR2 = 0.0921
Largest diff. peak and hole 0.882 and -0.526 e.Å
-3

179
Table 5.7: Atomic coordinates ( x 10
4
) and equivalent isotropic displacement
parameters (Å
2
x 10
3
) for trans-(acac)
2
Rh(CH
3
)(Py). U(eq) is defined as one
third of the trace of the orthogonalized U
ij
tensor.
__________________________________________________________________
_____________
x y z U(eq)
__________________________________________________________________
_____________
Rh(1) 4418(1) 3002(1) 1277(1) 19(1)
F(1) 1953(2) -2122(2) -1340(3) 40(1)
F(2) 1207(2) -1047(2) 301(3) 43(1)
F(3) -41(2) -1920(2) -2088(3) 49(1)
F(4) 114(3) 3536(4) -777(4) 70(1)
F(5) -374(3) 1750(3) -3043(3) 70(1)
F(6) 1255(2) 3833(3) -1933(3) 47(1)
F(7) 7955(3) 1973(3) 3877(3) 52(1)
F(8) 7361(3) 3149(3) 5601(3) 62(1)
F(9) 9196(3) 4248(3) 5651(4) 76(1)
F(10) 8692(3) 8102(2) 5135(3) 58(1)
F(11) 7091(2) 7836(2) 3190(2) 35(1)
F(12) 6720(3) 8175(2) 5100(3) 61(1)
O(1) 3267(2) 880(2) 331(2) 22(1)
O(2) 2916(2) 3333(2) -20(2) 23(1)
O(3) 5890(2) 2685(2) 2634(2) 23(1)
O(4) 5551(2) 5158(2) 2318(2) 23(1)
N(1) 5240(3) 2315(3) -468(3) 21(1)
C(1) 1266(3) -1222(4) -961(4) 29(1)
C(2) 1994(3) 314(3) -616(3) 22(1)
C(3) 1199(3) 897(4) -1297(4) 26(1)
C(4) 1709(3) 2329(4) -956(4) 24(1)
C(5) 663(4) 2861(4) -1701(5) 37(1)
C(6) 7909(4) 3288(4) 4735(4) 32(1)
C(7) 7008(3) 3751(4) 3759(4) 23(1)
C(8) 7468(3) 5223(4) 4224(4) 25(1)
C(9) 6717(3) 5814(3) 3499(3) 23(1)
180
Table 5.7: Continued

C(10) 7318(4) 7492(4) 4234(4) 32(1)
C(11) 5060(3) 889(4) -1397(4) 25(1)
C(12) 5526(4) 419(4) -2509(4) 31(1)
C(13) 6218(4) 1464(4) -2676(4) 31(1)
C(14) 6412(4) 2939(4) -1727(4) 31(1)
C(15) 5902(3) 3316(4) -655(4) 26(1)
C(16) 3635(4) 3617(4) 2830(4) 28(1)

Table 5.8: Bond lengths [Å] and angles [°] for trans-(acac)
2
Rh(CH
3
)(Py).
_____________________________________________________
Rh(1)-O(1) 1.998(2)
Rh(1)-O(2) 2.001(2)
Rh(1)-O(4) 2.003(2)
Rh(1)-O(3) 2.007(2)
Rh(1)-C(16) 2.031(3)
Rh(1)-N(1) 2.236(3)
F(1)-C(1) 1.322(4)
F(2)-C(1) 1.331(4)
F(3)-C(1) 1.334(4)
F(4)-C(5) 1.326(5)
F(5)-C(5) 1.319(4)
F(6)-C(5) 1.319(4)
F(7)-C(6) 1.319(4)
F(8)-C(6) 1.322(4)
F(9)-C(6) 1.309(4)
F(10)-C(10) 1.333(4)
F(11)-C(10) 1.328(4)
F(12)-C(10) 1.331(4)
O(1)-C(2) 1.259(4)
O(2)-C(4) 1.266(4)
O(3)-C(7) 1.264(4)
O(4)-C(9) 1.262(4)
181
Table 5.8: Continued

N(1)-C(11) 1.337(4)
N(1)-C(15) 1.343(4)
C(1)-C(2) 1.538(4)
C(2)-C(3) 1.384(4)
C(3)-C(4) 1.389(4)
C(4)-C(5) 1.536(5)
C(6)-C(7) 1.533(4)
C(7)-C(8) 1.380(4)
C(8)-C(9) 1.393(4)
C(9)-C(10) 1.525(4)
C(11)-C(12) 1.381(5)
C(12)-C(13) 1.381(5)
C(13)-C(14) 1.379(5)
C(14)-C(15) 1.378(5)
O(1)-Rh(1)-O(2) 94.58(9)
O(1)-Rh(1)-O(4) 177.05(8)
O(2)-Rh(1)-O(4) 85.98(9)
O(1)-Rh(1)-O(3) 85.12(9)
O(2)-Rh(1)-O(3) 177.75(9)
O(4)-Rh(1)-O(3) 94.22(9)
O(1)-Rh(1)-C(16) 88.11(12)
O(2)-Rh(1)-C(16) 88.60(12)
O(4)-Rh(1)-C(16) 89.01(12)
O(3)-Rh(1)-C(16) 89.16(12)
O(1)-Rh(1)-N(1) 91.57(9)
O(2)-Rh(1)-N(1) 90.35(9)
O(4)-Rh(1)-N(1) 91.32(9)
O(3)-Rh(1)-N(1) 91.88(9)
C(16)-Rh(1)-N(1) 178.88(11)
C(2)-O(1)-Rh(1) 121.3(2)
C(4)-O(2)-Rh(1) 121.2(2)
C(7)-O(3)-Rh(1) 121.6(2)
C(9)-O(4)-Rh(1) 121.7(2)
182
Table 5.8: Continued

C(11)-N(1)-C(15) 117.3(3)
C(11)-N(1)-Rh(1) 121.5(2)
C(15)-N(1)-Rh(1) 121.2(2)
F(1)-C(1)-F(2) 106.9(3)
F(1)-C(1)-F(3) 108.0(3)
F(2)-C(1)-F(3) 107.1(3)
F(1)-C(1)-C(2) 112.3(3)
F(2)-C(1)-C(2) 109.2(3)
F(3)-C(1)-C(2) 113.1(3)
O(1)-C(2)-C(3) 129.6(3)
O(1)-C(2)-C(1) 111.9(3)
C(3)-C(2)-C(1) 118.4(3)
C(2)-C(3)-C(4) 123.5(3)
O(2)-C(4)-C(3) 129.4(3)
O(2)-C(4)-C(5) 113.1(3)
C(3)-C(4)-C(5) 117.2(3)
F(6)-C(5)-F(5) 107.5(3)
F(6)-C(5)-F(4) 106.9(3)
F(5)-C(5)-F(4) 107.6(3)
F(6)-C(5)-C(4) 112.4(3)
F(5)-C(5)-C(4) 112.4(3)
F(4)-C(5)-C(4) 109.8(3)
F(9)-C(6)-F(7) 107.6(3)
F(9)-C(6)-F(8) 107.9(3)
F(7)-C(6)-F(8) 105.6(3)
F(9)-C(6)-C(7) 113.1(3)
F(7)-C(6)-C(7) 112.3(3)
F(8)-C(6)-C(7) 109.9(3)
O(3)-C(7)-C(8) 129.0(3)
O(3)-C(7)-C(6) 112.7(3)
C(8)-C(7)-C(6) 118.2(3)
C(7)-C(8)-C(9) 124.2(3)
O(4)-C(9)-C(8) 129.0(3)
183
Table 5.8: Continued

O(4)-C(9)-C(10) 113.3(3)
C(8)-C(9)-C(10) 117.7(3)
F(11)-C(10)-F(12) 106.8(3)
F(11)-C(10)-F(10) 106.6(3)
F(12)-C(10)-F(10) 107.6(3)
F(11)-C(10)-C(9) 112.5(3)
F(12)-C(10)-C(9) 110.0(3)
F(10)-C(10)-C(9) 113.0(3)
N(1)-C(11)-C(12) 123.2(3)
C(13)-C(12)-C(11) 118.9(3)
C(12)-C(13)-C(14) 118.6(3)
C(13)-C(14)-C(15) 119.0(3)
N(1)-C(15)-C(14) 123.1(3)
_____________________________________________________________
Symmetry transformations used to generate equivalent atoms:

Table 5.9: Anisotropic displacement parameters (Å
2
x 10
3
) for trans-
(acac)
2
Rh(CH
3
)(Py). The anisotropic displacement factor exponent takes the
form: -2p
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) 19(1) 16(1) 19(1) 10(1) 7(1) 5(1)
F(1) 43(1) 25(1) 55(1) 21(1) 26(1) 14(1)
F(2) 53(1) 41(1) 47(1) 29(1) 31(1) 11(1)
F(3) 29(1) 34(1) 58(2) 27(1) -3(1) -5(1)
F(4) 75(2) 94(2) 107(2) 75(2) 64(2) 69(2)
F(5) 46(2) 40(2) 70(2) 29(1) -23(1) 3(1)
F(6) 39(1) 47(1) 63(2) 43(1) 11(1) 15(1)
F(7) 67(2) 51(2) 43(1) 29(1) 18(1) 40(1)
F(8) 87(2) 95(2) 57(2) 63(2) 46(2) 61(2)
184
Table 5.9: Continued

F(9) 36(1) 61(2) 93(2) 55(2) -22(1) -6(1)
F(10) 48(1) 28(1) 51(1) 22(1) -16(1) -11(1)
F(11) 41(1) 27(1) 33(1) 20(1) 10(1) 5(1)
F(12) 115(2) 27(1) 60(2) 21(1) 61(2) 32(1)
O(1) 21(1) 18(1) 24(1) 12(1) 9(1) 5(1)
O(2) 25(1) 21(1) 26(1) 14(1) 10(1) 10(1)
O(3) 23(1) 19(1) 25(1) 14(1) 9(1) 7(1)
O(4) 26(1) 16(1) 23(1) 11(1) 8(1) 6(1)
N(1) 21(1) 18(1) 23(1) 13(1) 8(1) 7(1)
C(1) 24(2) 26(2) 30(2) 16(2) 7(2) 5(1)
C(2) 23(2) 21(2) 19(1) 10(1) 9(1) 5(1)
C(3) 23(2) 23(2) 26(2) 12(1) 9(1) 6(1)
C(4) 23(2) 26(2) 23(2) 14(1) 9(1) 10(1)
C(5) 30(2) 33(2) 47(2) 25(2) 10(2) 11(2)
C(6) 32(2) 31(2) 29(2) 19(2) 7(2) 10(2)
C(7) 23(2) 26(2) 21(2) 15(1) 10(1) 10(1)
C(8) 23(2) 24(2) 22(2) 12(1) 6(1) 5(1)
C(9) 29(2) 20(2) 20(2) 10(1) 12(1) 8(1)
C(10) 38(2) 20(2) 21(2) 8(1) 5(2) 3(2)
C(11) 27(2) 23(2) 32(2) 19(1) 14(1) 11(1)
C(12) 39(2) 24(2) 33(2) 14(2) 18(2) 16(2)
C(13) 39(2) 33(2) 31(2) 18(2) 22(2) 18(2)
C(14) 38(2) 29(2) 40(2) 24(2) 24(2) 14(2)
C(15) 29(2) 24(2) 30(2) 16(1) 14(2) 11(1)
C(16) 30(2) 28(2) 26(2) 14(1) 15(2) 10(2)

185
Table 5.10: Hydrogen coordinates ( x 10
4
) and isotropic displacement parameters
(Å
2
x 10
3
) for trans-(acac)
2
Rh(CH
3
)(Py).
__________________________________________________________________
_____________
x y z U(eq)
__________________________________________________________________
_____________
H(3) 253 284 -2038 31
H(8) 8353 5877 5094 30
H(11) 4588 164 -1286 30
H(12) 5373 -606 -3150 38
H(13) 6554 1172 -3430 38
H(14) 6890 3684 -1810 37
H(15) 6024 4331 -19 32
H(16A) 2613 3200 2278 42
H(16B) 3963 4708 3480 42
H(16C) 3952 3238 3481 42

Synthesis of cis-(hfac-O,O)
2
Rh(CH
3
)(py). Quantitative isomerization of
the trans-complex, 2, to the cis-analog, 3, occurs upon heating 2 in cyclohexane
under argon. Complex 2 (45 mg) was dissolved upon heating in cyclohexane (6
mL) at 95
o
C and after 14 h was completely converted to the cis-isomer, 3, as
evidenced by NMR. The yield of the reaction was measured by comparison with
an internal standard, 1,3,5-trimethoxybenzene. Decomposition may occur if the
solution is not fully degassed prior to carrying out the isomerization procedure.
1
H NMR (CDCl
3
) 400 MHz: δ 2.48 (d, 3H, CH
3
, J
RhC
= 2.50 Hz), 5.99 (s, 2H,
hfac CH), 6.22 (s, 2H, hfac C
3
H), 7.43 (t, 2H, m-CH pyridine), 7.88 (t, 1H, p-CH
pyridine), 8.26 (d, 2H, o-CH pyridine).
19
F NMR (CDCl
3
) ref. to CFCl
3
400
MHz: δ 74.37 (s, 3F, hfac-CF3), 74.70 (s, 3F, hfac-CF3), 74.79 (s, 3F, hfac-CF3),
186
76.32 (s, 3F, hfac-CF3).
13
C {
1
H} NMR (CDCl
3
) 400 MHz: δ 7.23 (d, CH
3
, J
RhC

= 26.1), 88.98 (s, hfac CH), 92.08 (s, hfac CH), 115.7 (q, CF
3
, J
CF
= 284 Hz),
115.9 (q, CF
3
, J
CF
= 284 Hz), 116.4 (m, CF
3
, J
CF
= 284 Hz), 117.4 (m, CF
3
, J
CF
=
284 Hz), 125.62(s, m-CH pyridine), 138.70(s, p-CH pyridine), 151.70 (s,o- CH
pyridine), 174.9 (hfac C=O
2
J
CF
= 34.9), 175.1 (hfac C=O
2
J
CF
= 33.7), 175.1
(hfac C=O
2
J
CF
= 36.2), 177.3 (hfac C=O
2
J
CF
= 35.0).

Table 5.11: Crystal data and structure refinement for cis-(acac)
2
Rh(CH
3
)(Py).

Identification code mrhcism
Empirical formula C16 H10 F12 N O4 Rh
Formula weight 611.16
Temperature 153(2) K
Wavelength 0.71073 Å
Crystal system Monoclinic
Space group P2(1)/c
Unit cell dimensions a = 8.0941(15) Å a= 90°.
b = 29.962(6) Å b=
97.310(3)°.
c = 8.7770(17) Å g = 90°.
Volume 2111.2(7) Å
3

Z 4
Density (calculated) 1.923 Mg/m
3

Absorption coefficient 0.937 mm
-1

F(000) 1192
Crystal size 0.20 x 0.18 x 0.01 mm
3

Theta range for data collection 1.36 to 27.53°.
Index ranges -10<=h<=10, -38<=k<=36, -
8<=l<=11
Reflections collected 12955
Independent reflections 4737 [R(int) = 0.0511]
Completeness to theta = 27.53° 97.0 %
187
Table 5.11: Continued

Transmission factors min/max ratio: 0.653
Refinement method Full-matrix least-squares on F
2

Data / restraints / parameters 4737 / 21 / 329
Goodness-of-fit on F
2
1.043
Final R indices [I>2sigma(I)] R1 = 0.0556, wR2 = 0.1262
R indices (all data) R1 = 0.0849, wR2 = 0.1387
Largest diff. peak and hole 0.987 and -0.697 e.Å
-3

Table 5.12: Atomic coordinates ( x 10
4
) and equivalent isotropic displacement
parameters (Å
2
x 10
3
) for cis-(acac)
2
Rh(CH
3
)(Py). U(eq) is defined as one third
of the trace of the orthogonalized U
ij
tensor.
__________________________________________________________________
_____________
x y z U(eq)
__________________________________________________________________
_____________
Rh(1) 6023(1) 8894(1) 3231(1) 30(1)
F(1) 2537(16) 9783(4) 23(14) 80(4)
F(1A) 1717(15) 9631(3) 107(10) 67(3)
F(2) 1033(12) 9985(3) 1744(9) 57(3)
F(2A) 1644(12) 10167(3) 1880(10) 60(3)
F(3) 3586(13) 10247(4) 1494(15) 86(4)
F(3A) 3496(13) 10096(4) 552(15) 86(4)
F(4) 1411(10) 8761(3) 6046(9) 77(3)
F(4A) 2873(14) 8803(4) 7251(13) 77(4)
F(5) 1594(19) 9488(4) 6540(20) 70(5)
F(5A) 1334(19) 9350(6) 6640(20) 55(4)
F(6) 3511(11) 9002(4) 7632(10) 74(3)
F(6A) 3763(13) 9400(5) 7617(10) 98(5)
F(7) 2965(5) 7780(1) 188(4) 61(1)
F(8) 1826(4) 7727(1) 2259(4) 57(1)
F(9) 3660(5) 7244(1) 1763(5) 70(1)
F(10) 9965(5) 7831(2) 4832(5) 81(2)
188
Table 5.12: Continued

F(11) 8252(6) 7320(1) 5258(5) 77(1)
F(12) 8619(5) 7873(1) 6746(4) 57(1)
O(1) 4646(5) 9351(1) 1997(4) 35(1)
O(2) 4704(5) 8928(1) 5029(4) 37(1)
O(3) 4301(4) 8387(1) 2225(4) 37(1)
O(4) 7445(4) 8438(1) 4437(4) 34(1)
N(1) 7400(6) 8822(1) 1486(6) 35(1)
C(1) 2558(9) 9882(3) 1372(9) 61(2)
C(2) 3414(7) 9538(2) 2490(7) 39(1)
C(3) 2794(7) 9474(2) 3866(7) 38(1)
C(4) 3430(6) 9176(2) 5031(6) 36(1)
C(5) 2556(9) 9121(3) 6386(8) 76(3)
C(6) 3253(8) 7677(2) 1679(7) 45(2)
C(7) 4581(6) 7988(2) 2507(6) 31(1)
C(8) 5915(7) 7788(2) 3454(6) 34(1)
C(9) 7170(6) 8022(2) 4305(6) 32(1)
C(10) 8515(7) 7758(2) 5286(7) 41(1)
C(11) 9065(7) 8763(2) 1750(8) 45(2)
C(12) 9988(8) 8691(2) 588(10) 56(2)
C(13) 9222(9) 8680(2) -909(9) 56(2)
C(14) 7522(9) 8741(2) -1192(8) 52(2)
C(15) 6661(8) 8814(2) 31(7) 41(1)
C(16) 7532(7) 9386(2) 4181(7) 44(2)

189
Table 5.13: Bond lengths [Å] and angles [°] for cis-(acac)
2
Rh(CH
3
)(Py).
_____________________________________________________
Rh(1)-O(1) 1.996(4)
Rh(1)-O(4) 2.000(3)
Rh(1)-O(2) 2.017(4)
Rh(1)-N(1) 2.017(5)
Rh(1)-C(16) 2.026(5)
Rh(1)-O(3) 2.171(4)
F(1)-F(1A) 0.817(11)
F(1)-C(1) 1.219(13)
F(1)-F(3A) 1.266(14)
F(1A)-C(1) 1.439(11)
F(2)-F(2A) 0.737(9)
F(2)-C(1) 1.352(10)
F(2A)-C(1) 1.248(10)
F(2A)-F(3) 1.667(14)
F(3)-F(3A) 0.937(12)
F(3)-C(1) 1.369(13)
F(3A)-C(1) 1.281(12)
F(4)-C(5) 1.429(10)
F(4)-F(4A) 1.488(13)
F(4A)-F(6) 0.830(12)
F(4A)-C(5) 1.226(12)
F(5)-C(5) 1.363(12)
F(5A)-C(5) 1.245(17)
F(6)-F(6A) 1.211(14)
F(6)-C(5) 1.307(9)
F(6A)-C(5) 1.597(14)
F(7)-C(6) 1.336(7)
F(8)-C(6) 1.328(7)
F(9)-C(6) 1.337(7)
F(10)-C(10) 1.305(7)
F(11)-C(10) 1.330(7)
F(12)-C(10) 1.319(7)
O(1)-C(2) 1.267(7)
190
Table 5.13: Continued

O(2)-C(4) 1.272(6)
O(3)-C(7) 1.236(6)
O(4)-C(9) 1.270(6)
N(1)-C(15) 1.340(7)
N(1)-C(11) 1.350(7)
C(1)-C(2) 1.529(9)
C(2)-C(3) 1.379(8)
C(3)-C(4) 1.404(8)
C(4)-C(5) 1.468(8)
C(6)-C(7) 1.535(8)
C(7)-C(8) 1.410(7)
C(8)-C(9) 1.374(7)
C(9)-C(10) 1.521(7)
C(11)-C(12) 1.356(9)
C(12)-C(13) 1.380(10)
C(13)-C(14) 1.379(10)
C(14)-C(15) 1.370(8)
O(1)-Rh(1)-O(4) 178.66(15)
O(1)-Rh(1)-O(2) 94.34(15)
O(4)-Rh(1)-O(2) 86.94(15)
O(1)-Rh(1)-N(1) 89.15(17)
O(4)-Rh(1)-N(1) 89.59(17)
O(2)-Rh(1)-N(1) 176.34(16)
O(1)-Rh(1)-C(16) 89.4(2)
O(4)-Rh(1)-C(16) 90.2(2)
O(2)-Rh(1)-C(16) 89.6(2)
N(1)-Rh(1)-C(16) 91.6(2)
O(1)-Rh(1)-O(3) 88.47(15)
O(4)-Rh(1)-O(3) 91.98(14)
O(2)-Rh(1)-O(3) 88.67(15)
N(1)-Rh(1)-O(3) 90.29(16)
C(16)-Rh(1)-O(3) 177.18(19)
F(1A)-F(1)-C(1) 87.7(13)
191
Table 5.13: Continued

F(1A)-F(1)-F(3A) 148.0(18)
C(1)-F(1)-F(3A) 62.0(8)
F(1)-F(1A)-C(1) 57.8(10)
F(2A)-F(2)-C(1) 65.9(10)
F(2)-F(2A)-C(1) 81.4(12)
F(2)-F(2A)-F(3) 134.8(13)
C(1)-F(2A)-F(3) 53.7(6)
F(3A)-F(3)-C(1) 64.4(10)
F(3A)-F(3)-F(2A) 98.1(12)
C(1)-F(3)-F(2A) 47.3(5)
F(3)-F(3A)-F(1) 131.0(15)
F(3)-F(3A)-C(1) 74.4(11)
F(1)-F(3A)-C(1) 57.2(8)
C(5)-F(4)-F(4A) 49.6(5)
F(6)-F(4A)-C(5) 76.2(11)
F(6)-F(4A)-F(4) 138.1(14)
C(5)-F(4A)-F(4) 62.7(7)
F(4A)-F(6)-F(6A) 143.1(14)
F(4A)-F(6)-C(5) 65.7(10)
F(6A)-F(6)-C(5) 78.6(8)
F(6)-F(6A)-C(5) 53.3(7)
C(2)-O(1)-Rh(1) 121.8(4)
C(4)-O(2)-Rh(1) 122.7(3)
C(7)-O(3)-Rh(1) 120.2(3)
C(9)-O(4)-Rh(1) 122.7(3)
C(15)-N(1)-C(11) 118.4(5)
C(15)-N(1)-Rh(1) 120.2(4)
C(11)-N(1)-Rh(1) 121.3(4)
F(1)-C(1)-F(2A) 125.3(9)
F(1)-C(1)-F(3A) 60.8(7)
F(2A)-C(1)-F(3A) 106.3(9)
F(1)-C(1)-F(2) 113.0(9)
F(2A)-C(1)-F(2) 32.6(5)
192
Table 5.13: Continued

F(3A)-C(1)-F(2) 130.3(8)
F(1)-C(1)-F(3) 101.7(9)
F(2A)-C(1)-F(3) 79.0(8)
F(3A)-C(1)-F(3) 41.2(6)
F(2)-C(1)-F(3) 111.4(8)
F(1)-C(1)-F(1A) 34.6(6)
F(2A)-C(1)-F(1A) 113.0(8)
F(3A)-C(1)-F(1A) 94.8(8)
F(2)-C(1)-F(1A) 87.1(7)
F(3)-C(1)-F(1A) 134.6(9)
F(1)-C(1)-C(2) 114.1(8)
F(2A)-C(1)-C(2) 118.2(7)
F(3A)-C(1)-C(2) 116.4(7)
F(2)-C(1)-C(2) 110.6(7)
F(3)-C(1)-C(2) 105.5(7)
F(1A)-C(1)-C(2) 105.8(6)
O(1)-C(2)-C(3) 128.9(5)
O(1)-C(2)-C(1) 113.1(5)
C(3)-C(2)-C(1) 118.0(5)
C(2)-C(3)-C(4) 125.8(5)
O(2)-C(4)-C(3) 126.3(5)
O(2)-C(4)-C(5) 114.2(5)
C(3)-C(4)-C(5) 119.4(5)
F(4A)-C(5)-F(5A) 115.1(11)
F(4A)-C(5)-F(6) 38.1(6)
F(5A)-C(5)-F(6) 113.6(12)
F(4A)-C(5)-F(5) 129.8(10)
F(5A)-C(5)-F(5) 20.4(11)
F(6)-C(5)-F(5) 114.9(9)
F(4A)-C(5)-F(4) 67.7(8)
F(5A)-C(5)-F(4) 86.8(11)
F(6)-C(5)-F(4) 105.4(7)
F(5)-C(5)-F(4) 105.5(8)
193
Table 5.13: Continued

F(4A)-C(5)-C(4) 120.3(7)
F(5A)-C(5)-C(4) 124.0(10)
F(6)-C(5)-C(4) 114.4(6)
F(5)-C(5)-C(4) 109.4(8)
F(4)-C(5)-C(4) 106.4(6)
F(4A)-C(5)-F(6A) 85.7(8)
F(5A)-C(5)-F(6A) 91.3(12)
F(6)-C(5)-F(6A) 48.0(6)
F(5)-C(5)-F(6A) 79.5(9)
F(4)-C(5)-F(6A) 149.4(7)
C(4)-C(5)-F(6A) 100.0(6)
F(8)-C(6)-F(7) 107.3(5)
F(8)-C(6)-F(9) 108.0(5)
F(7)-C(6)-F(9) 106.8(5)
F(8)-C(6)-C(7) 109.9(5)
F(7)-C(6)-C(7) 110.3(5)
F(9)-C(6)-C(7) 114.2(5)
O(3)-C(7)-C(8) 129.5(5)
O(3)-C(7)-C(6) 113.2(5)
C(8)-C(7)-C(6) 117.3(5)
C(9)-C(8)-C(7) 124.2(5)
O(4)-C(9)-C(8) 131.2(5)
O(4)-C(9)-C(10) 110.8(5)
C(8)-C(9)-C(10) 118.0(5)
F(10)-C(10)-F(12) 107.8(5)
F(10)-C(10)-F(11) 107.9(5)
F(12)-C(10)-F(11) 105.4(5)
F(10)-C(10)-C(9) 110.3(5)
F(12)-C(10)-C(9) 111.5(5)
F(11)-C(10)-C(9) 113.7(5)
N(1)-C(11)-C(12) 121.7(7)
C(11)-C(12)-C(13) 119.8(6)
C(14)-C(13)-C(12) 119.0(6)
194
Table 5.13: Continued

C(15)-C(14)-C(13) 118.4(7)
N(1)-C(15)-C(14) 122.7(6)
_____________________________________________________________
Symmetry transformations used to generate equivalent atoms:

195
Table 5.14: Anisotropic displacement parameters (Å
2
x 10
3
) for cis-
(acac)
2
Rh(CH
3
)(Py). The anisotropic displacement factor exponent takes the
form: -2p
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) 28(1) 29(1) 32(1) 0(1) 0(1) 3(1)
F(1A) 91(7) 46(5) 51(5) 14(4) -44(5) -6(5)
F(4) 87(6) 77(6) 79(6) -14(4) 57(5) -44(5)
F(5) 97(10) 55(8) 68(8) 8(6) 53(6) 6(6)
F(5A) 50(6) 65(9) 58(7) 31(7) 32(5) 17(7)
F(6A) 92(8) 172(14) 30(5) -28(6) 3(5) 31(8)
F(7) 69(2) 80(3) 32(2) -13(2) 1(2) -23(2)
F(8) 41(2) 75(3) 58(2) -12(2) 9(2) -20(2)
F(9) 75(3) 42(2) 90(3) -14(2) -6(2) -14(2)
F(10) 41(2) 122(4) 83(3) 46(3) 16(2) 37(2)
F(11) 110(3) 39(2) 72(3) 0(2) -27(3) 28(2)
F(12) 73(2) 60(2) 34(2) -2(2) -7(2) 21(2)
O(1) 37(2) 33(2) 36(2) 3(2) 5(2) 12(2)
O(2) 37(2) 42(2) 30(2) 1(2) 2(2) 6(2)
O(3) 30(2) 41(2) 38(2) 1(2) -1(2) -1(2)
O(4) 28(2) 34(2) 37(2) -2(2) -4(2) 3(2)
N(1) 38(2) 24(2) 44(3) 1(2) 10(2) 3(2)
C(1) 64(4) 68(5) 54(5) 6(4) 21(4) 31(4)
C(2) 38(3) 35(3) 41(4) -3(3) -3(3) 5(2)
C(3) 37(3) 42(3) 35(3) -3(3) 1(2) 8(2)
C(4) 34(3) 43(3) 31(3) -7(2) 2(2) -2(2)
C(5) 68(5) 117(7) 45(4) 24(5) 19(4) 51(5)
C(6) 41(3) 52(4) 41(4) -8(3) 7(3) -8(3)
C(7) 27(3) 36(3) 33(3) -1(2) 10(2) -1(2)
C(8) 39(3) 30(3) 35(3) -1(2) 8(2) 4(2)
C(9) 34(3) 37(3) 25(3) 0(2) 8(2) 12(2)
C(10) 48(3) 41(3) 33(3) 4(3) -1(3) 14(3)
196
Table 5.14: Continued

C(11) 37(3) 38(3) 62(4) -2(3) 12(3) -1(3)
C(12) 41(3) 41(4) 91(6) -5(4) 32(4) 0(3)
C(13) 71(5) 39(4) 69(5) -5(3) 46(4) -10(3)
C(14) 70(5) 45(4) 43(4) 3(3) 18(3) 10(3)
C(15) 49(3) 36(3) 39(3) 5(3) 8(3) 4(3)
C(16) 43(3) 33(3) 54(4) -9(3) 4(3) -2(3)

Table 5.15: Hydrogen coordinates ( x 10
4
) and isotropic displacement parameters
(Å
2
x 10
3
) for cis-(acac)
2
Rh(CH
3
)(Py).
__________________________________________________________________
_____________
x y z U(eq)
__________________________________________________________________
_____________
H(3) 1853 9647 4041 46
H(8) 5947 7472 3508 41
H(11) 9604 8771 2777 54
H(12) 11158 8649 803 67
H(13) 9857 8630 -1733 67
H(14) 6962 8734 -2211 62
H(15) 5492 8861 -160 49
H(16A) 8073 9533 3379 65
H(16B) 8383 9258 4952 65
H(16C) 6871 9605 4672 65

197

Synthesis of trans-(hfac-O,O)2Rh(Ph)(py). 1 (0.1 g) was heated with
diphenyl mercury (0.1 g, ~1.2 mol eq) in 1:1 CHCl
3
/CH
3
OH (15 mL) at 100°C for
12 h in a Schlenk tube fitted with a resealable Teflon valve, after 5 freeze-pump-
thaw cycles, and filled with argon. The solution became dark orange. The
solvent was then removed by vacuum, then 7 mL of dry pyridine was added and
the solution was heated at 50 °C for 15 min. The pyridine was mostly removed
by vacuum, then 1 mL of water was added and a yellow/orange compound
precipitated. The solid was filtered, and washed with two 5 mL portions of cold
water, then dried on the vacuum line and stored under argon until the compound
was found to be air and water stable.
1
H NMR (CDCl
3
) 250MHz: δ 8.62 (d, 2H,
py-o-H’s), 7.96 (t, 1H, py-p-H), 7.57 (t, 2H, py-m-H’s), 7.14 (m, 3H, Ph-H’s),
7.05 (d, 2H, Ph-H’s), 5.91 (s, 2H, hfac-CH).
19
F NMR (CD
3
OD) ref. to CFCl
3
360 MHz: δ 74.98 (s, 12F, hfac-CF3’s).
13
C{
1
H} NMR (C
6
D
6
) 360 MHz: δ 92.72
(s, hfac CH), 175.86 (q, J
CF
= 143.75 Hz, hfac C=O), 149.46 (s, py), 139.41 (s,
py), 133.93 (s, Ph), 127.96 (s, Ph), 126.24 (s, Ph), 125.12 (s, py), 115.43 (q, J
CF
=
1132.25 Hz). Anal. Calcd: C, 37.47; H, 1.80; N, 2.08. Found: C, 35.73; H, 1.80;
N, 2.02.
Synthesis of cis-(hfac-O,O)
2
Rh(Ph)(py). Complex 3 was heated in neat
benzene under argon at 190°C for 24 hours. This produced cis-(hfac)
2
Rh(Ph)(py).
The reaction was done with approximately 25mg of starting material in 15mL
neat benzene. Sublimation of this compound left behind Rh metal precipitated
from the reaction.
1
H NMR (CDCl
3
) 400 MHz: δ 6.06 (s, 2H, hfac C
3
H), δ 6.09
198
(s, 2H, hfac C
3
H), δ 6.86 (d, o-CH phenyl), δ 7.10 (m, m/p-CH phenyl
overlapping), δ 7.36 (t, 2H, m-CH pyridine), δ 7.87 (t, 1H, p-CH pyridine), δ 8.17
(d, 2H, o-CH pyridine).
13
C NMR {
1
H} (CDCl
3
) 400 MHz: δ 89.53 (s, hfac CH),
92.32 (s, hfac CH), 118ppm (m, CF
3
overlapping resonances), 147.70 (d, i-C J
RhC

= 28.6), 177.10 (m, hfac C=O J
2
CF
= 36.2 Hz). Phenyl and pyridine carbons: δ
125.18, 125.52, 127.66, 134.40, 138.98, 52.43. Analysis Calculated for
C
21
H
18
F
12
NO
4
Rh: C, 37.13; H, 2.67; N, 2.06. Found: C, 37.80; H, 2.00; N, 2.08.
Synthesis of cis-(hfac-O,O)
2
Rh(Mes)(py). Complex 3 was heated in neat
mesitylene under argon at 190°C for 28 hours. The synthesis was divided up into
5 batches of about 25 mg apiece. Larger batches took more time for complete
conversion to the mesityl product.
1
H NMR (CDCl
3
) 400 MHz: δ 2.15 (s, CH
3
,
mesityl), doublet of doublets at δ 4.46 (d/d, CH
2
, mesityl) and δ 5.05 (d/d, 1H,
CH
2
mesityl), δ 5.68 (s, 1H, hfac C
3
H), δ 5.96 (s, 1H, hfac C
3
H), δ 6.69 (s, 1H, o-
CH, mesityl), δ 6.79 (s, 1H, p-CH, mesityl), δ 7.45 (t, 2H, m-CH pyridine), δ 7.90
(t, 1H, p-CH pyridine), δ 8.26 (d, 2H, o-CH pyridine). Single crystals suitable for
diffraction were grown from evaporation of a concentrated solution in methanol.
H-D exchange: Catalytic H-D exchange reactions were quantified by
monitoring the increase of deuterium into C
6
H
6
by GC/MS analyses. This was
achieved by deconvoluting the mass fragmentation pattern obtained from the MS
analysis, using a program developed with Microsoft EXCEL. An important
assumption made with this method is that there are no isotope effects on the
fragmentation pattern for the various benzene isotopologs. Fortunately, because
the parent ion of benzene is relatively stable towards fragmentation, it can be used
199
reliably to quantify the exchange reactions. 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 isotopologs. The results obtained by this method are reliable
to within 5%. Thus, analysis of a mixture of C
6
H
6
, C
6
D
6
and C
6
H
5
D
1
prepared in a
molar ratio of 40: 50: 10 resulted in a calculated ratio of 41.2(C
6
H
6
): 47.5(C
6
D
6
):
9.9(C
6
H
5
D
1
). Catalytic H/D exchange reactions were thus run for sufficient
reaction times to be able to detect changes >5% exchange. The methanol analog
of complex 2, trans-(hfac-O,O)
2
Rh(CH
3
)(CH
3
OH), was the catalyst used to carry
out the H/D exchange between benzene and deuterium oxide.
In a typical experiment, a 2 mL Schlenk tube fitted with a resealable
Teflon valve was charged with 5 mg of methanol analog of 2, benzene 1.0 mL,
and 1.0 mL of toluene-d8 under an atmosphere of argon. The tube was then
placed in a temperature controlled oil-bath maintained at 190 °C, and deuteration
was then measured as described above.

200
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Abstract (if available)

Abstract The chemistry discussed herein involves the strategy of selective oxy-functionalization of well defined, electron-rich (and nucleophilic), M-CH3 bonds by O-atom insertion or methyl transfer reaction and a homogeneous system that exhibits C-H activation of a variety of bonds. These projects were undertaken with the goal of adding conceptual and practical knowledge to the development of a catalytic cycle for the conversion of hydrocarbons (particularly methane) to alcohols (methanol).

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Creator Conley, Brian Lee (author)

Core Title Toward a catalytic cycle for the hydroxylation of methane: oxy-functionalization of electron rich M-CH3 bonds

School College of Letters, Arts and Sciences

Degree Doctor of Philosophy

Degree Program Chemistry

Publication Date 12/04/2008

Defense Date 07/08/2008

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

Tag insertion,methane,OAI-PMH Harvest,O-atom donor,oxy-functionalization,oxygen

Language English

Contributor Electronically uploaded by the author (provenance)

Advisor Periana, Roy A. (committee chair), Petruska, John A. (committee member), Prakash, Surya (committee member), Williams, Travis J. (committee member)

Creator Email bconley@usc.edu,brianlconley@gmail.com

Permanent Link (DOI) https://doi.org/10.25549/usctheses-m1870

Unique identifier UC1285084

Identifier etd-Conley-2502 (filename),usctheses-m40 (legacy collection record id),usctheses-c127-134347 (legacy record id),usctheses-m1870 (legacy record id)

Legacy Identifier etd-Conley-2502.pdf

Dmrecord 134347

Document Type Dissertation

Rights Conley, Brian Lee

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