THEORETICAL STUDIES ON OXIDATIVE ADDITION OF AMMONIA TO IRIDIUM COMPLEXES AND METATHESIS REACTIONS OF TRIPLE BONDS INVOLVING TUNGSTEN, MOLYBDENUM, CARBON AND NITROGEN EMPLOYING DENSITY FUNCTIONAL THEORY

Presented in Partial Fulfillment of the Requirements for

the Degree Doctor of Philosophy in the Graduate

School of The Ohio State University

By

Shentan Chen, M.S.

*****

The Ohio State University 2009

Dissertation Committee: Approved by Professor Bruce E. Bursten, Advisor

Professor Malcolm H. Chisholm, Advisor

Professor Sheldon G. Shore ______Professor Patrick M. Woodward Advisor Graduate Program in Chemistry

ABSTRACT

Activation and cleavage of element-hydrogen bonds, E-H, where E = H, C, N and

O, via oxidative addition to a transition metal complex is an important step in many

catalytic cycles. Hence, an understanding of the factors that influence the oxidative

addition and reductive elimination of H–E bonds is necessary to develop efficient

catalysts. Density functional theory (DFT) has been used to investigate the oxidation

addition of an N-H bond to iridium complexes. Both the electronic properties and steric

properties of the ancillary ligands (Ln) play important roles in affecting the relative

stability of LnIr(III)(NH2)H and LnIr(I)(NH3). Under similar steric effects, LnIr(I)(NH3) is more stable than LnIr(III)(NH2)H when Ln is a poor electron donating ligand and

LnIr(III)(NH2)H becomes more stable than LnIr(I)(NH3) when Ln is a good donating

ligand. The relative stability of LnIr(III)(NH2)H and LnIr(I)(NH3) can thus be manipulated by changing the electronic donating ability of Ln.

Like metal-alkylidyne complexes that are active as catalysts for alkyne metathesis

reactions, metal-nitride complexes can undergo metathesis reactions with M≡M

complexes, nitriles and alkynes. Theoretical studies employing DFT methods on the

ii reactions between the model compounds (MeO)3M≡N and CH3C≡N, where M = Mo and

W, show that the reactions proceed through a cyclobutadiene-like transition state. The

calculated energy of the transition state for M = Mo is 13 kcal/mol higher than that for M

= W. This is consistent with the experimental observation that nitrogen atom exchange

only occurs at elevated temperatures for M = Mo.

The reactivity of metal-nitride molecules is greatly influenced by the metal, the

electron configuration of the metal, and the particular set of attendant ligands. The

t electronic structures of the molecules ( BuO)3M≡N(M = Cr, Mo, W) have been studied by using the gas phase photoelectron spectroscopy and the density functional calculations.

It is found that the alkoxide orbitals mix strongly with the M≡N triple bond orbitals and contribute substantially to the valence electronic structure. The first ionization of

t ( BuO)3Cr≡N is from an orbital of a2 symmetry that is oxygen based and contains no

metal or nitrogen character by symmetry. In contrast, the first ionizations of the

molybdenum and tungsten analogs are from orbitals of a1 and e symmetry that derive

form the highest occupied M≡N σ and π orbitals mixed with the appropriate symmetry

combinations of the oxygen p orbitals. The polarity of the M≡N bond increases down the

group such that W≡N has the highest charge separation. In addition to investigation of

the effects of the metals, the electronic influences of substitution at the alkoxide ligands

have been examined for the molecules (RO)3Mo≡N (R=C(CH3)2H, C(CH3)3, and

C(CH3)2CF3). The introduction of CF3 groups stabilizes the molecular orbital energies,

iii but does not alter the overall electronic structure.

DFT has been applied to study the metathesis reaction between W2(OMe)6 and

MeCN. The reaction begins with the coordination of acetonitrile to W2(OMe)6 to give an

adduct with a planar cyclobutadiene-like W2CN core and is then followed by the cleavage

of the C-N and W-W bond in this adduct to give tungsten alkylidyne and tungsten nitride.

The rate-determining step is the cleavage step. The ditungstenazacyclobutadiene

t intermediate that is structurally related to ( BuO)6Mo2(NCNMe2) can also be readily

obtained from the starting reagents. This structure is calculated to be thermodynamically

unfavorable relative to the metathesis products and thus no such analogue for tungsten is observed in experiment.

iv

DEDICATION

To my parents and Lu

v

ACKNOWLEDGEMENTS

Fist of all, I would like to express my gratitude and thanks to two of my advisors,

Dr. Bruce E. Bursten and Dr. Malcolm H. Chisholm, not only for their patient guidance through the course of this dissertation but also for their encouragement and support throughout my Ph.D. study.

I also would like to thank Dr. Russell M. Pitzer for providing helpful suggestions and lots of education in quantum chemistry. I appreciate that many faculty members in chemistry department gave me a tremendous education. I would give my special thanks to Dr. Shore and Dr. Woodward as my committee members.

I would like to extend my gratitude to all group members in Bursten and Chisholm group, for their friendship, encouragement, and discussions. Sharing an office with Mike

Mrozik was a wonderful experience. He gave me a lot help both within and outside the office. I thank Dr. Benjamin Lear for teaching me how to use the Schlenk line techniques and dry box as well as some other experimental techniques. I thank Chandrani Chatterjee for helping me with the mass spectrum. I appreciate Lacey O'Neal for her help.

Finally I would like to thank my parents and my wife for their unconditional love and support, all the other family members and all my friends, for their encouragement.

vi

VITA

May 18, 1977………………………....Born – Fujian, P. R. China

1994 – 1998…………………………..B.S. Chemistry Nankai University, Tianjin, China

1998 – 2000…………………………..Analyst, Xiamen 3-Circles Battery Co., LTD Fujian, China

2000 – 2003…………………….…….M.S. Chemistry Nankai Univeristy, Tianjin, China

2003 – 2009………………………..…Graduate Teaching and Research Associate, The Ohio State University

PUBLICATIONS

Research publication

1. Chen, Shentan; Chisholm, Malcolm H.; Davidson, Ernest R.; English, Jason B.; Lichtenberger, Deenis L. Theoretical and Spectroscopic Investigations of the Bonding and Reactivity of (RO)3M≡N Molecules, where M = Cr, Mo and W. Inorganic Chemistry 2009, 48, 828-837.

2. Burroughs, Beth A.; Bursten, Bruce E.; Chen, Shentan; Chisholm, Malcolm H.; Kidwell, Andy R. Metathesis of Nitrogen Atoms within Triple Bonds Involving Carbon, Tungsten, and Molybdenum. Inorganic Chemistry 2008, 47, 5377-5385.

3. Bursten, Bruce E.; Chen, Shentan; Chisholm, Malcolm H. Ligand effects on the stability of the insertion products: A DFT study of oxidative addition of NH3 to iridium(I) complex. Journal of Organometallic Chemistry 2008, 693,1547-1551.

vii 4. Du, Miao; Chen, Shen-Tan; Guo, Ya-Mei; Bu, Xian-He; Ribas, Joan. Synthesis, crystal structure, spectroscopy and magnetic properties of a dinuclear Cu(II) complex with 3,5-bis(2-pyridyl)pyrazole bridging ligand. Journal of Molecular Structure 2005, 737,17-21.

5. Du, Miao; Guo, Ya-Mei; Chen, Shen-Tan; Bu, Xian-He; Batten, Stuart R.; Ribas, Joan; Kitagawa, Susumu. Preparation of Acentric Porous Coordination Frameworks from an Interpenetrated Diamondoid Array through Anion-Exchange Procedures: Crystal Structures and Properties. Inorganic Chemistry 2004, 43, 1287-1293.

6. Huang, Zheng; Song, Hai-Bin; Du, Miao; Chen, Shen-Tan; Bu, Xian-He; Ribas, Joan. Coordination Polymers Assembled from Angular Dipyridyl Ligands and CuII, CdII, CoII Salts: Crystal Structures and Properties. Inorganic Chemistry 2004, 43, 931-944.

7. Du, Miao; Bu, Xian-He; Huang, Zheng; Chen, Shen-Tan; Guo, Ya-Mei; Diaz, Carmen; Ribas, Joan. From Metallacyclophanes to 1-D Coordination Polymers: Role of Anions in Self-Assembly Processes of Copper(II) and 2,5-Bis(3-pyridyl)-1,3,4- oxadiazole. Inorganic Chemistry 2003, 42, 552-559.

8. Du, Miao; Chen, Shen-Tan; Bu, Xian-He; Ribas, Joan. Crystal structure and properties of a CuII coordination polymer with 2-D grid-like host architecture for the inclusion of organic guest molecule. Inorganic Chemistry Communications 2002, 5(11), 1003-1006.

9. Du, Miao; Chen, Shen-Tan; Bu, Xian-He. {[Cd(bpo)(SCN)2]CH3CN}n: A Novel Three-Dimensional (3D) Noninterpenetrated Channel-Like Open Framework with Porous Properties. Crystal Growth & Design 2002, 2(6), 625-629.

FIELDS OF STUDY

Major Field: Chemistry

viii

LIST OF TABLE

Table page

2.1 Selected bond lengths and bond angles of complexes 1a, 1b, 2a and 2b …….….. 35

2.2 Relative energies and relative Gibbs free energies (298K) were

given in kcal/mol. Ir-NH3 refers to ammonia coordinated compound while HIr-NH2 refers to hydrido amido compound. …………………………….. 38

4.1 Relative areas of the He I spectra regions (A, A*, B+C) of t t BuOH and ( BuO)3M≡N relative to the total area (A+A*+B+C) …….………… 90

4.2 Prominent features in the He I photoelectron spectra, and the calculated lowest ionization potentials (IP) by ADF2007.01. See Figure 4.4 for definitions of peaks. ……………………………………….… 92

4.3 Comparison of the ADF2007.01 optimized geometrical parameters t with the crystal structure parameters for ( BuO)3M≡N…………………………..100

4.4 The calculated orbital energies (in eV) of the highest six occupied t orbitals for ( BuO)3M≡N. …………………………………………………...….101

t 4.5 Calculated primary orbital characters for ( BuO)3M≡N. ………………………. 102

4.6 Mulliken charges, molecular dipole moment (µ) and M≡N bond

dissociation energies (BDE) calculated by ADF2007.01 for (RO)3M≡N. ……... 107

5.1 Free energies (kcal/mol) and selected bond distance (Å) for intermediates and transition states on the pathway from ditungstenazatetrahedrane to tungsten alkylidyne and nitride. ………………. 128

5.2 Free energies (kcal/mol) and selected bond distance (Å) for intermediates and transition states on the pathway from ditungstenazacyclobutadiene to tungsten alkylidyne and nitride. …………….... 133

ix

LIST OF FIGURE

Figure page

1.1 π-interaction between p-π lone pair orbital on N and the empty and filled d orbitals of a transition metal ……………………………………….….6

1.2 Bonding modes for bent (A) and linear (B) or (C) imido complexes ……………...7

1.3 Synthesis of tungsten-based imido alkylidene complexes form alkyldyne complexes ………………………………………………………..…….10

1.4 Catalytic intramolecular hydroamination ………………………………………....14

1.5 Bond functions of the nitrido ligand: A, terminal; B, asymmetric linear bridge; C, symmetric linear bridge; D, bent bridge; E, T-shaped bridges ……………………………………………....16

1.6 MO diagram: π bonding of nitrido ligand in an octahedral ……………………....17

1.7 Orbital interactions between orbitals at different energy levels. A represents a nucleophilic ligand; B represents an electrophilic ligand ………………………………………………………………………..…….18

1.8 The “Chatt Cycle” for nitrogen fixation ………………………………….…….…22

1.9 Proposed reaction pathway of dinitrogen cleavage with Mo(NRAr′)3 ….…….…..23

2.1 Molecular orbitals showing interactions between the ring π-orbitals and d-orbitals on the iridium in compound 1b ……………………………...... …39

2.2 PCP ligands used for study: Al denotes the type of ligands with an aliphatic backbone and Ar denotes the type of ligands with an aromatic backbone …………………………………………………….….40

x 2.3 The relative Gibbs free energies (∆G298K) vs nuclear charge of P atom. Red corresponds to Aliphatic PCP Ligand and blue corresponds to Aromatic PCP Ligand ……………………………………………………..……...44

15 15 15 3.1 N-NMR spectrum of Cl(CH2)4C≡ N (B), p-Cl-(C6H4)C≡ N (C), 15 and o-F-(C6H4)C≡ N (D); byproducts of a scrambling reaction 15 with (t-BuO)3W≡N and MeC≡ N (A) …………………………………………...52

3.2 15N NMR spectrum of the reaction mixture between Me13C≡N, 15 t MeC≡ N and PhC≡N in the presence of a trace of (Bu O)3W≡N 15 recorded in d8-THF at 298 K, 50.6 MHz. The PhC≡ N signal shows enhancement due to 15N atom exchange and appears as a singlet due to lack of coupling to 1H or 13C whereas the MeC≡N 15N signal shows coupling to 1H, 3J1H–15N = 1.7 Hz and for Me13C≡15N coupling to 13C, 1J13C–15N = 17 Hz. The signal thus appears as a central 1 :3 :3 :1 quartet flanked by 13C satellites. The unsymmetrical nature of the 13C satellites arises from 12C/13C isotopic chemical shift perturbation.………….……………………………………………………....53

3.3 Eyring plot of ln(kobs/T) vs 1/T where y = - 6727x + 7.7142, R2 = 0.9937. The enthalpy parameters were calculated to be ∆H≠ = + 13.4(7) kcal mol-1 and ∆S≠ = -32(2) eu for the 15N isotope 15 13 exchange reaction between (t-BuO)3W≡ N and Me C≡N……………………....56

3.4 Free energy (at 298K) profiles for nitrogen exchange reaction

between (MeO)3W≡N and MeC≡N and structures of transition sates and intermediates with selected calculated structural parameters (Å) …….……...60

3.5 Free energy (at 298K) profiles for nitrogen exchange reaction

between (MeO)3Mo≡N and MeC≡N and structures of transition sates and intermediates with selected calculated structural parameters (Å) …………....61

4.1 Side and top (down the N-Cr bond) views of the crystal 16 t structure of ( BuO)3Cr≡N showing the C3v symmetry ……………………….…80

3 4.2 Orbital interaction diagram of a d -L3M fragment, where L is a simple σ donor ligand (left), with the N(p) orbitals (right). The L-M-L angle is ~110-116˚ for these molecules ……………………….……...82

xi 4.3 Molecular orbital energy diagram showing the interactions

between the six highest occupied π-type combinations of the (RO)3 fragment (middle) and M≡N 2σ and 1π orbitals with two different

energies relative to the (RO)3 orbitals, left and right, of the M≡N orbitals …………………………………………………….….……...84

4.4 He I photoelectron spectra of ROH and (RO)3M≡N (M = Cr, Mo, or W; R = tBu) ………………………………………….………...... 89

t 4.5 He I photoelectron spectra of ( BuO)3M≡N (M = Cr, Mo, or W) in the 8 to 11 eV range. The major features in the spectra are labeled a, b, and c. The onset30 of ionization is designated by a (*) …………………..….91

t 4.6 He II photoelectron spectra of ( BuO)3M≡N (M = Cr, Mo, or W). The data points are the He II spectra shown in comparison to the He I spectra (solid lines). The positions of the lowest energy ionizations with M≡N σ and π character are designated by a (*) ………….……..95

4.7 He I photoelectron spectra of (RO)3Mo≡N t i (Ra= Bu, Rb= Pr, Rc= CH3)2CF3C) ……………………………………….……...98

t i 4.8 He I photoelectron spectra of (RO)3Mo≡N, R= Bu(top), R= Pr(middle), 3 R= CF3(CH )2C (bottom) from 8.5 to 12 eV. The major ionization features in the spectra are labeled a, b, and c. The onset of ionization is designated by a (*) ……………………………………………………………..98

t i 4.9 He II photoelectron spectra of (RO)3Mo≡N (Ra= Bu, Rb= Pr, Rc= CH3)2CF3C). The data points are the He II spectra shown in comparison to the He I spectra (solid lines). The positions of the lowest energy ionizations with M≡N σ and π character are designated by a (*) …………………………………………………...……….…..99

t 4.10 Correlation diagram of the Kohn-Sham orbital energies of ( BuO)3M≡N……….103

4.11 Molecular orbital plots of 2a1, 3e, 2e, and 1e valance orbitals t (contour value = ±0.04) for ( BuO)3M≡N where M = Cr, Mo, and W. The orbital plots for molecules containing Cr and Mo are represented in the same set on the right because they look similar …………………………..105

xii 5.1 Structures of the optimized ditungstenazatetrahedrane complex from different view angles. For better view, the hydrogen atoms are omitted …………...…………………………………………………….…….123

5.2 Free energy (kcal/mol)) profiles for the ditungstunazatetrahedrane

(MeO)6W2(µ-NCMe)→ (MeO)3WCMe + (MeO)3WN……………………….…124

5.3 Structures of the optimized ditungstenazacyclobutadiene complex from different view angles. For better view, the hydrogen atoms are omitted……………………………………………………………………...... 129

5.4 Free energy (kcal/mol)) profiles for the ditungstunazacyclobutadiene

(MeO)6W2(µ-NCMe)→ (MeO)3WCMe + (MeO)3WN ……………………..…130

5.5 Free energy (kcal/mol)) profiles for the starting materials to the postulated intermediates: ditungstunazacyclobutadiene and

ditungstunazatetrahedrane. {(MeO)6W2 + MeCN → (MeO)6W2(µ-NCMe)} The red solid line is the pathway leading to the ditungstunazacyclobutadiene; The blue dash line is the pathway leading to the ditungstunazatetrahedrane. ……………………………………………………....134

5.6 Free energy (kcal/mol)) profiles for the metathesis reaction between

(MeO)6W2 and MeCN. (The solid line corresponds to the pathway for (MeO)6W2 + MeCN →(MeO)3WCMe + (MeO)3WN; the red dash line corresponds to the pathway for the formation of ditungstunazacyclobutadiene.) …………..………………………………………139

xiii

TABLE OF CONTENTS

Page Abstract…………………………………………………………………………………...ii

Dedication………………………………………………………………………………..v

Acknowledgements……………………………………………………………………...vi

Vita……………………………………………………………………………………...vii

List of Tables………………………………………………………………….………...ix

List of Figures…………………………………………………………………………...x

Chapters:

1 Introduction………………………………………………………………………....1 1.1 Transition Metal Complexes Containing Metal-Nitrogen Bonds………....….1 1.2 Transition Metal Amido Complexes………………………………...…….….1 1.3 Transition Metal Imido Complexes……………………………………...... 6 1.3.1 Imido Ligand as A Spectator Ligand……………………...... ….8 1.3.2 M=NR As a Reactive Site……………………………….………11 1.4 Transition Metal Nitrido Complexes………………………………..…….....14 1.4.1 Nitrogen Atom Transfer……………………………….………...19 1.4.2 Dinitrogen Activation…………………………………..…….....21 1.4.3 Metathesis Reactions of Triple Bonds……………………….….24 1.5 Statement of Research Purpose…………………………………...…….…...25 1.6 References…………………………………………………….…...………...27

2 Insights into ligand effects on the relative stability of the NH3 coordination iridium(I) complex and the hydrido amido iridium (III) complex…………………………………………………………………..………....33 2.1 Introduction……………………………………………………..….……...33 2.2 Computational Details………………………………………….………..35 2.3 Results and Discussion…………………………………………...……...... 36 xiv 2.4 Conclusions……………………………………………………………….45 2.5 References……………………………………………………….………..46

3 Metathesis of nitrogen atoms within triple bonds involving carbon, tungsten and molybdenum…………………………………………….………..….48 3.1 Introduction…………………………………………………..……..…….48 3.2 Results and Discussion…………………………………………….……..49 3.2.1 Mo≡N + W≡W → Mo≡W + W≡N………………….....49 3.2.2 Alkylidyne and Nitride Ligand Transfer Between Molybdenum and Tungsten……………………………...... 50 3.2.3 Estimation of Activation Parameters…………………...... ….54 3.2.4 Theoretical and Computational Considerations………………...57 3.3 Concluding Remarks……………………………………………………..64 3.4 Experimental……………………………………………………………..64 3.4.1 General Procedures……………………………………….....….64 3.4.2 Spectroscopic Methods…………………………………………65 3.4.3 Computational Methods…………………………………...……65 3.4.4 Synthesis and Reactions………………………………...….…...66 3.5 References…………………………………………………...……..…….74

4. Theoretical and spectroscopic investigations of the bonding and

reactivity of (RO)3M≡N molecules, where M = Cr, Mo and W…………………..78 4.1 Introduction………………………………………………………...…….78 4.2 Results and Discussion…………………………………………..………80 4.2.1 General Bonding Considerations. ………………………….....80 4.2.2 Photoelectron Spectroscopic Studies……………………....….87 4.2.3 Density Functional Studies……………………………..….….99 4.3 Conclusions……………………………………………………..…...….107 4.4 Experimental and Computational Procedures…………………...... ….109 4.5 References…………………………………………………..……..……114

5. Theoretical study of metathesis reactions involving metal-metal triple bond and carbon-nitrogen triple bond…………………………….….…….118 5.1 Introduction……………………………………………………..………118 5.2 Computational Details…………………………………………..………119 5.3 Results and Discussion…………………………………………..….…..120 5.3.1 The ditungstenazatetrahedrane complex………………..….…122 5.3.2 The ditungstenazacyclobutadiene complex………….……..…129 5.3.3 The formation of ditungstenazatetrahedrane and ditungstenazacyclobutadiene………………..………..…..133

xv 5.3.4 The overall reaction pathway for metathesis reaction (2)…….138 5.4 Conclusion…………………………………………..…………………..140 5.5 References……………………………………………………………….142

Appendices:

A. Calculated Cartesian coordinates for selected molecules in chapter 2……………..145

B. Calculated Cartesian coordinates in chapter 3……………………………………..164

C. Calculated Cartesian coordinates for molecules in chapter 4………………………173

D. Calculated Cartesian coordinates for reactants, stationary points, and products in chapter 5…………………………………………………………..185

Bibliography………………………………………………………………………...…229

xvi CHAPTER 1

INTRODUCTION

1.1 Transition Metal Complexes Containing Metal-Nitrogen Bonds.

Transition metal complexes containing metal-nitrogen bonds compose an important category in organometallic chemistry. These complexes have been implicated as reagents, reactive intermediates, or catalysts in a wide range of metal-mediated processes.1-5 Bonds between metal and nitrogen can be roughly divided into two classes

based on the ways in which nitrogen bounds to metal. In some cases, the ligands bound

to metal only through its long pair electrons. Bonds formed in this way are relatively

weak and so termed dative bond. In other instances, the ligands bound to metal through

covalent interaction between metal and nitrogen. Such ligands including amido (-NR2),

imido (=NR) and nitrido (≡N:) are of immense importance due to their reactivity and

applications.

1.2 Transition Metal Amido Complexes.

- Metal amides are compounds in which the NR2 ligand is attached to a metal. The

simplest case has the structural unit shown in I. The amido ligand is one of the most

1 prolific of ligands. Stable compounds are found for almost all elements ranging form

main group metal to transition metal including lanthanides.

LnMNR2

I

6 The first metal amide, Zn(NEt2)2, was reported by Frankland in 1856 , but the

transition metal amides were not discovered until the late 1950’s, excluding titanium

tetrakis (diphenyl amide) which was discovered in 1935 when Dermer and Fernelius7 reacted titanium tetrachloride with potassium diphenylamide. Since then metal amide complexes have been reported for almost all transition metals except some late transition metals.8 I the 1970’s, lanthanide amides began to appear9. More recently, low-valent late

transition metal amides are of wide interest due to their ability of catalytic

transformation.

By far a variety of synthetic routs to transition metal have been developed. One of

the most common methods is the transmetallation,10 namely the reactions of

transition-metal chlorides with lithium dialkylamides generally described in Equation 1.

LnM-Cl + Li-NR2 → LnM-NR2 + Li-Cl (1)

This synthetic procedure has been successfully employed to prepare a complete

series of first row transition-metal disilylamides and several lanthanide disilyamides by

11-15 using LiN(SiMe3)2. However reaction (1) is not always applicable to the synthesis of

2 low valent late transition-metal amides. In some cases, this reaction also leads to a

change in oxidation of metal. For example, the reaction of MoCl5 and LiNMe2 leads to the formation of Mo(NMe2)4 and Mo2(NMe2)6.

Another method to synthesis transition-metal amides is the reaction of

transition-metal halides with ammonia or amines to form metal amides.16-18 This

synthetic route has wide applications for the higher oxidation state halides of the early

transition metals. The main limitation is that the reaction rarely goes to completion and

the formation of amine complexes.

Transamination reactions (Equation 2) have also been applied to the synthesis of

transition-metal amides. In this type of reactions, amine with higher volatility is

eliminated. Therefore transamination reactions are limited in their application by amine

i volatility and steric factors. Reaction of Ti(NMe2)4 with excess HNPr2 gives

i Ti(NMe2)3NPr2 while reaction of Ti(NMe2)4 with 3 equivalent of HNPr2 produces

10 TiNMe2(NPr2)3.

LnMNR2 + HNR´2 → LnMNR´2 + HNR2 (2)

In addition, the direct oxidative addition of an N-H bond of ammonia or amine is

an important way to produce metal amides, as in Equation 3.

LnM + HNR2 → LnM(H)(NR2) (3)

Oxidative addition of N-H bond is more applicable to the synthesis of late transition

3 metal amides since the oxidative addition procedure generally requires electronic rich

low valent transition metal complexes. Many late transition-metal amides have been

synthesized through this method. It has been found that such reactions depend on the

relative N-H acidity, transition metal and the ancillary ligands of metal complexes.19

Another important fact is that the oxidative addition of an N-H bond to a low valent transition metal complex is potentially an important step in catalytic processes such as alkene hydroamination.20 Therefore systematic investigation of the factors influencing the oxidative addition reactions of N-H to transition metal centers is necessary to gain

insight into the transition-metal amides as intermediates in the catalytic cycles.

The reactivity of transition-metal amides generally depends on M-N bond polarity and bond strength. For a σ-bonded amido ligand there are three possible bonding interactions. The first has a structure (II) with a pyramidal nitrogen and approximately sp3 hybridization. The second structure (III) shows the trigonal planar nitrogen geometry

which illustrates the possibility of π bonding involving p lone pair donor of nitrogen and

d orbitals of the transition metal as well as approximately sp2 hybridization on nitrogen.

The amido can also behave as a bridging ligand shown in structure IV. A possible way to

avoid the formation of amido bridging moieties is the introduction of bulky substituents on nitrogen or other ancillary ligands.

4

R R R N LnM N N LnM R R R LnM MLn II III IV

The p-π/d-π interaction can either stabilize or destabilize the transition-metal

M-N complexes as indicated by Caulton.21 As shown in Figure 1.1, if the lone pair donor

on nitrogen interacts with an empty d orbital of metal center then the complex is stabilize.

On the other hand, if the lone pair donor interacts with a filled d orbital then the p-π/d-π

repulsion destabilizes the complex. Thus the amido ligand should bound more strongly to

high valent early transition metals which have vacant d orbitals than to low valent late

transition metals which have filled d orbitals.

5 π* π*

d p d

π π

Figure 1.1 π-interaction between p-π lone pair orbital on N and the empty and filled d orbitals of a transition metal.

1.3 Transition Metal Imido Complexes

Terminal transition metal Imido complexes which have the general formula

22 LnM(NR) was discovered in the late 1950’s. Since then, they have been the focus of considerable attention.23

The imido ligand can be described to bond to a transition-metal with one σ and either one or two π interactions. As shown in Figure 1.2, structure A shows a bent M-N-R linkage with a M=N double bond (one σ and one π). Nitrogen atom in this structure can be depicted as a sp2 hybridized nitrogen with the lone pair residing in a sp2 orbital.

M-N-R linkage in transition-metal imido complexes can also be linear, indicating a sp 6 hybridized nitrogen atom. In structure B, the M=N double bond is maintained and the

lone pair p orbital on nitrogen is mainly no-bonding possibly due to the mismatch of symmetry and energy between nitrogen p and available metal d orbitals. When symmetry allows and the energy level of the p and d orbitals are close, the lone pair will interact

with the empty metal d orbital, resulting in a triple bonded M≡N-R moiety shown in

structure C. It has been found that most of the linear imido complexes can be understood

in terms of M≡N-R structure.24 In general, when then M-N-R angle is greater than

155-160º the NR-2 ligand is normally considered as a linear six-electron donor with one σ

and two π interactions. Imido group are also known to be able to bridge two and even

three metal atoms. An important character of imido complexes is that their structures and

reactivity can be profoundly changed by modification of the substituent on N atom.

N LnM LnMN R LnM N R R A B C

Figure 1.2 Bonding modes for bent (A) and linear (B) or (C) imido complexes.

Transition-metal imido complexes have found wide applications in materials,

catalysts and nitrogen transfer reagents. The reactions can be divided into two types:

7 those in which the imido ligand acts as a supporting ligand and those where the M=NR

bond itself is the reactive site.24

1.3.1 Imido Ligand as A Spectator Ligand

One of the main applications of imido complexes is for catalytic reactions. In

most cases, the imido ligand itself does not react with the substrates but only functions as

a supporting or spectator ligand.

As a spectator ligand, the imido ligand has been used to develop well-defined olefin metathesis. Olefin metathesis has been one of the most fantastic discoveries in chemistry and become the standard synthetic reaction. Shrock, Chauvin, and Grubbs have won the Nobel Prize for their brilliant work in this area. It has been accepted that the olefin metathesis reaction proceeds through the formation and decomposition of a

metallacyclobutane intermediate.25 The procedure requires a transition metal complex

containing carbene ligand to facilitate the reaction.

Early olefin metathesis catalysts were typically prepared by the reaction of W(VI)

complexes (WCl6 or WOCl4) with alkylating agents such as alkyl aluminum, alkyl

lithium, and alkyl stannane.26 However, these early catalysts were not well characterized

and the oxidation state of the metal and the nature of the ligands were never determined.

Although many of these catalysts have been found to be very active, they are generally

the short-lived and tend to produce side products. They are also readily deactivated by

common Lewis base functional groups. As a consequence, the activity of this type of

8 catalysts can not be controlled in a rational manner. Therefore, development of

well-defined catalyst for olefin metathesis is of significant importance.

t t The five coordinate tungsten complex, ( BuO)4W=CH Bu, which was believed to

be a possible well-fefined catalyst for olefin metathesis, but the first attempt to prepare

t t this complex by the reaction between ( BuO)4WO and (PEt3)2TaCl3(CH Bu) resulted in

t t 27-28 t the formation of (PEt3)2W(O)Cl2(CH Bu) and ( BuO)4TaCl. (PEt3)2W(O)Cl2(CH Bu) was found to metathesize olefins very slowly. By addition a trace of Lewis acid such as

27 t AlCl3, the rate of metathesis was dramatically increased. (PEt3)2W(O)Cl2(CH Bu) is an

18 electrons compound, AlCl3 probably removes a chloride to generate an electron deficient complex which is active to olefin metathesis. However, the metathesis activity was limited since the alkylidene complexes other than the neopentylidene were not stable.29 One strategy to stabilize the alkylidene complexes is to introduce the sterically

bulky groups such as imido ligand in place of isoelectronic oxo ligands.

In 1982, Shrock and coworkers found a simple method to synthesize imido

alkylidene tungsten complex by transferring a proton from an amido nitrogen to an

alkylidyne carbon as shown in Equation 4.30

N NH PEt PEt3 3 70ºC t (4) Cl M CtBu Cl M CH Bu Toluene Et P Et3P Cl 3 Cl

9 The concern about this reaction is the involvement of phosphine ligands. Six years later an analogous transformation was found on dimethoxyethane complex,31 as shown in

t Figure 1.3. A four coordinated complex (R´O)2W(NR)(CH Bu) could be obtained by the treatment of 5 with bulky alkoxide lithium. The metal complexes of the general formula

[M(CHR)(NAr)(OR´)2] have been widely known as Schrock’s type catalysts, where M is

Mo or W. The reactivity of this type of catalysts can be tuned by modification the alkyl groups of alkoxides.32

tBu Cl Cl Cl MeO MeO Cl t t t 3 equiv W Bu W ClMg Bu Bu W tBu MeO Cl HCLDM Cl t OMe OMe Bu E 3 1 2 NHTMS

iPr iPr

iPr iPr iPr iPr i Pr i HN Pr 10 N 2 LiOR Cl Clt N MeO MeO Bu W tBu mol% tBu -DME W W Et N RO -2LiC Cl 3 Cl RO OMe OMe l 6 5 4

Figure 1.3 Synthesis of tungsten-based imido alkylidene complexes form alkyldyne complexes.

10 In addition, imido complexes have also found application in Ziegler-Natta olefin

polymerization. Olefin polymerization using single-site metallocenes is an important

subject in the polymer industry.33-35 Extensive work has been carried out to sudy

regio-/stereo-specificity and molecular weight control.34-37 It has been found that the

reaction chemistry of ansa-metallocenes often differs significantly from that of their

nonbridged analogues. Replacing the cyclopentadienide with isolobal ligand is a possible

approach to generate new alternative catalysts to metallocenes.38 As mentioned before,

imido ligand can be considered as a six-electron donor which bound to metal center

through one σ and two π bonds. The frontier orbitals of the imido ligand are somewhat

similar to those of cyclopentadienide ligand. Therefore, it is possible to use imido ligands

instead of cyclopentadienide ligands for new catalysts with the aim to tune both the

electronic and steric requirements of the metal center.

Much progress has been made in the development of imido-supported

non-metallocene ofefin polymerization catalyst during the past couple decades. Many

imido complexes in group 4-6 have been synthesized and tested for olefin polymerization.

The most active imido-supported olefin polymerization catalysts discovered so far are

predominantly titanium based complexes.39-40

1.3.2 M=NR As a Reactive Site

Another point of interest associated with M=NR is the reactivity of the unsaturated M=NR linkage itself. The reactivity of imido ligand varies with the nature

11 and oxidation state of the transition metal as well as the structure of the M-N-R linkage and the substituent R.41

A bent imido ligand has a feature of M=N double bond with the lone pair

electrons residing in one of the sp2 hybridied orbitals on nitrogen. Thus imido ligand with

a bent structure tends to be necleophilic and Lewis basic. In general, bent imido

complexes are found in complexes containing low valent tranisiton metal and other

multiply bonded ligands. When the imido ligand appears to be linear, the bond between

the metal center and nitrogen can be considered a triple bond in most cases. By formation

of an additional π bond through donating the p lone pair to the metal d orbital, the

electron density decreases on the nitrogen. Therefore, linear imido ligand is expected to

be electrophilic. For instances, this electrophilic reactivity has been observed for imido

complexes of chromium(IV),42 chromium(V)43 and tungsten(IV).44 However, not all

linear imido ligands exhibit electrophilic reactivity. For example, [Cp*Ir(NtBu)] which

has a linear terminal imido has been found to react with methyl iodide.45

With the active M=NR linkage, imido complexes have found the applications in

reactions such as E-H (E=H, C, and S) bond activation and amination of unsaturated

molecules.4 In E-H bond activation reactions, the group 4 imido complexes show the

greatest activity. Many titatium and zirconium imido complexes have been reported to

activate C-H bonds (from sp to sp3), H-H, and S-H bonds.46-49 For example the reactions

* of Cp2 Ti(NPh) with HC≡CR (R=Ph, SiMe3) and H2 produce the anilido-acetylide

12 * 46 * 48 complex Cp2 Ti(NHPh)(C≡CR) and hydride-amido complex Cp2 Ti(NHPh)(H)

* respectively. In contrast, the reaction of Cp2 Ti(NPh) with acetylene gives the

* 50 azametallacycle Cp2 Ti[N(Ph)CH=CH] as shown in V. The preference for acetylenic

C-H over [2+2] cycloaddition is probably due to steric interactions between the imide

and alkynl substituents. Not only do the imido titanium complexes undergo [2+2]

cycloadditon with alkynes and alkynes, they react with unsaturated substrates containing

C-E (E=N, O, P) multiple bonds.51-53

Ph Cp* N Ti CH2 Cp* C H2 V

Imido complex has also been implicated as an intermediate in hydroamination

reactions.54-56 A general method used to synthesize heterocycles is the catalytic

intramolecular hydroaminations of amines with unsaturated alkyl group.57-58 As shown in

Figure 1.4, reaction of amine with CpTiCl3 gives a imido titanium intermediate which

undergoes [2+2] cycloaddition between Ti=N and C≡C to form an azametallacycle.

Further treatment of the azametallacycle results in the desired herterocycle and initial titanium complex CpTiCl3.

13 Ti(Cp)Cl NH 2 N N Ti(Cp)Cl n CpTiCl3 n n C - 2 HCl C CC C C R R R + 2 HCl - CpTiCl3

N n C

Figure 1.4 Catalytic intramolecular hygroamination.

1.4 Transition Metal Nitrido Complexes

The first transition metal nitrido complex, “potassium osmiamate”, was

synthesized by Fritsche and Struve in 1847.59 The structure of its anion was initially

assigned as that shown in VI and it was not until 1901 that the presence of a nitride

ligand in this complex was recognized.60 The correct structure is shown in VII. The first

neutral mononuclear nitrido complex was reported in 1963 by Chatt and coworkers

whose structure is given in VIII.61 By far, mononuclear nitrido complexes are known for most of the first row transition metals and some of the second and third row metals.3

Most of the nitrido complexes favor high oxidation state metals with electron configurations in the range of d0 to d2.

14 N NO N

Os Cl PPh O Os O Re 3 - O O O Ph3P Cl

VI VII VIII

The application of nitrido ligands reflects the great stability of the metal nitrogen

triple bond. In 1966, Chatt recognized the inherent strength of the metal-nitrogen triple

bond as well as the ability of the nitrido group to offer stability to organotransition metal

62 species. He reported a series of arylrhenium nitride complexes, Re(N)Ar2(PR3)3 (where

R = alkyl). Later on, Belmonte and Shapley were also able to produce a series of ruthenium(VI) and osmium(VI) alkyl derivates by using the same stabilizing ability of

the nitrido ligand.63 Applications of nitido ligands have also been extended to

pharmaceuticals and electronic materials.64

Most nitrido complexes involve a terminal nitrido ligand which consists of one

M-N σ bond and two M-N π bonds as illustrated in Figure 1.5A. The lone pair of

electrons bestows weak basicity to the nitrido ligand. The strength of the basicity

depends on the metal and ancillary ligands of the complex. Under certain conditions, the

lone pair of electrons at the nitrido ligand is able to form a dative bond to the

transition-metal center of another complex. Thus asymmetrical M≡N-M bridges (Figure

1.5B) are formed. In some instances, symmetrical bridges (Figure 1.5C) are formed. In

this case the nitrogen p-π orbitals interact with d-π orbitals on both adjacent metals to

15 form two degenerate dπ-pπ-dπ orbitals. Apart form terminal nitrido ligand and linear

bridges, bent bridges (figure 1.5D) and T-shaped bridges (figure 1.5E) have also

appeared.65

M N M N M M N M

A B C

N M

MM MNM D E

Firure 1.5 Bond functions of the nitrido ligand: A, terminal; B, asymmetric linear bridge; C, symmetric linear bridge; D, bent bridge; E, T-shaped bridges.

The reactivity of the nitrido ligands depends on the nature of the transition metal, the oxidation state of the metal center, and the ancillary ligands of the complex. Like most multiply bonded ligands, the nitrido ligands have reactivity that ranges from electrophilic to nucleophilic. In general, the most electrophilic nitrido ligands are observed in complexes of high oxidation state early transition metals. Whereas low-valent late transition metals with π-acidic ancillary ligands exhibit nucleophilic nitrido ligands reactivity. 16

* σ * σ e2g * σ π*

nb t2g nb

p

Octahedral π Nitrogen Metal atom

Figure 1.6 MO diagram: π bonding of nitrido ligand in an octahedral.

The reactivity of the nitrido ligands can be rationalized by the nature of the frontier orbitals. For simplification the π bonding between nitrido and transition metal in an octahedral environment is given in Figure1.6. The π interaction of the ligand’s p orbitals with the metal’s d orbitals can be affected by the transition metal and the ancillary ligands. If the metal’s d orbitals is higher in energy than the ligand’s p orbitals, the pπ-dπ interaction results in a π* orbital which is mostly metal in character as shown in figure 1.7A. In this case, the nitride ligand is nucleophilic. On the toher hand, the ligand is predicted to be electrophilic when the π* is mostly ligand based as shown in figure 1.7B. Thus, nucleophilic nitrido ligand is typically for early transition metal 17 complexes in high oxidation state, while electrophilic nitrido ligand is expected for late transition metal complexes in low oxidation state. The above two situations are the two extreme cases on the two ends. Between the two extreme cases, the π* orbital contains both metal and ligand’s character when the ligand p orbital is close in energy to metal d orbital. In complexes of this type, the nitrido ligands exhibit both nucleophilic and electrophilic property.

π* π*

d p

π p d π

A B

Figure 1.7 Orbital interactions between orbitals at different energy levels. A represents a nucleophilic ligand; B represents an electrophilic ligand.

Transition-metal complexes with terminal nitride ligand have recently become of great interest not only for their ability to stabilize organotransition metal complexes but also for their potential role in nitrogen atom transfer, nitrogen fixation and catalytic processes. 18 1.4.1 Nitrogen Atom Transfer

Atom and group transfer reactions mediated by transition metal centers are

important in synthetic chemistry. One notable example of atom transfer occurs in the

cytochrome P-450 enzyme, where an iron porphyrin complex transfers an oxygen atom

from an iron oxo intermediate to a substrate. Atom transfer involving oxygen and sulfur has been identified an important class of reactions in biological chemistry.66 Nitrogen

atom transfer reactions are of interest due to the fact that nitrogen atom transfer is a key

intermediate step in the nitrogen fixation pathway and has the potential application in

amination.

The first example of complete inter-metallic nitrogen atom transfer was reported

in 1985, involving the reduction of (N)MnV(TTP) with CrII(TTP) in THF(Equation 5) in

which the nitrodomanganese(V) complex is formally reduced to manganese(II) upon the

transfer of the nitrogen atom, and forms the nitridochromium(V) complex.67 Woo and

coworkers have observed reversible nitrogen atom transfer reactions for

nitridomanganese porphyrin and salen complexes,68-69 as shown in Equation 6. Both of

the above reactions involve the transfer of three electrons. In addition to three-electron

nitrogen atom transfer, two-electron transfer has also been observed for both manganese

and chromium and complexes.68,70-71 As shown in Equation 7, nitrido and chloride

ligands exchange between the two complexes and the metal in nitrido complex is reduced by two units. The reversibility of the reaction depends on the metal and ancillary. For

19 example, the reaction between N≡MnV(OEP) and Cl-CrIII(TTP) is irreversible.72

(N)MnV(TTP) + CrII(TTP) MnII(TTP) + (N)CrV(TTP) (5)

(N)MnV(TTP) + MnII(OEP) MnII(TTP) + (N)MnV(OEP) (6)

V III III V N≡M (Ln) + Cl-M (L´n) Cl-M (Ln) + N≡M (L´n) (7) Where M = Mn or Cr, Ln and L´n = porphyrin or salen ligands

The nitrogen atom transfer can also be use to synthesize nitrdo complexes which

are difficult to obtain by common synthetic routes. In 2003, Bendix prepared a simple

2- nitrido complex, [Cr(N)Cl4] , by nitrogen atom transfer between CrCl3(THF)3 and

Mn(V)(N)(Salen).73 For the first row transition metals, most of the known nitrido

complexes contain polydentate ligands such as Schiff-bases, porphyrins, and salen. This

prevalence of polydentate arises from the harsh synthetic conditions which are not

2- compatible with monodentate ligands. The success in preparation of [Cr(N)Cl4] introduces an applicable procedure to the synthesis and isolation of the first row transition-metal nitrido complexes with monodentate ligands including phosphines, pyridines, thiocyanate, and amines.

Nitrogen atom transfer finds great utility in organic synthesis besides the preparation of metal compounds.74 It can serve as a nitrogen atom transfer reagent in the

preparation of specific nitrogen-containing organic compounds. For instance, Groves has

reported that high-valent nitridomanganese(V) complexes can be used for the

aziridination of cis-cyclooctene.75 This reaction was later extended to aziridination and

20 alkene amination by Carreira and coworkers.76

1.4.2 Dinitrogen Activation

Nitrogen which is an essential element in the biosphere of this planet composes

78% of the air. However this diatomic triple-bonded molecule is inert, which makes it

challenging to use as a feedstock. In nature, the nitrogen fixation is mainly through the

conversion of dinitrogen to ammonia by nitrogenase enzymes contained in bacteria.77-78

In industry, the Haber-Bosh process is used to produce over 100 million tons of ammonia annually.79 The reaction involved in the Haber-Bosh process is simple as shown in

Equation 8, but the realization of this reaction is extremely difficult due to kinetic

stability of N≡N triple bond.

N2 + 3H2 → 2NH3 (8)

The heterogeneous iron catalysts used in Haber-Bosh process requires high temperatures

(300-500°C) and pressures (500 atm). Recent development of the Ru catalyst allows

slightly milder operating conditions (70-105 atm, 350-470°C), it is still an

energetic-demand process.80 Therefore development of dinitrogen fixation systems under

mild conditions is of significant importance. Studies on the nitrogenase enzymes suggest

that transition metal plays an important role in dinitrogen activation. For decades,

enormous efforts have been made to develop the catalysts which are capable of

dinitrogen fixation under mild conditions. It has been postulated that a transition metal

nitride species plays an intermediate role by stabilizing the nitride ions formed by the 21 reductive cleavage of the N≡N bond during nitrogen fixation.81

One of the most mechanistically elaborated transition metal systems is reported by

Chatt as show in Figure 1.8 which is called “Chatt Cycle”.82 Two equivalent of ammonia were produced by a series of protonation and reduction of N2 coordinated to the Mo(0) complex. Similar process was reported later by Shrock employing Mo(III) complex with ligated ligand.83

N N

+H NH2 +N2 P Mo P L +e N NH3 P P P P P Mo P Mo L P L P P P +H +e +H +e NH2

NH2 N

P Mo P NH3 P Mo P L P L P P P

+H NH +e 3 +H NH N

P Mo P N P Mo P P L P L P P P +H Mo P +e +e P L P

Figure 1.8 The “Chatt Cycle” for nitrogen fixation.

22 Another important trend in dinitrogen activation is the dinitrogen cleavage by

high oxidation state metal centers. The first example of facile dinitrogen cleavage was

84 reported by Cummins et al with the complex Mo(NRAr′)3 [where R=C(CD3)2CH3]. The

reaction of Mo(NRAr′)3 with nitrogen under ambient conditions produces the

corresponding terminal nitride Mo(VI) complex, (Ar′RN)3Mo≡N. The conversion is

proposed to proceed through a dinuclear µ–N2 complex which subsequently cleaves the

N-N bond to form two equivalent of a terminal nitride as shown in Figure 1.9. In 1994,

Schrock and coworkers characterized a similar paramagnetic dinuclear dinitrogen Mo(III)

complex which substantiated the presence of 2.85

ArRN N NRAr ArRN Mo N Mo(NRAr) N NRAr 3 N2 1 atm Mo N ArRN Mo NRAr ArRN NHRAr -35 C NRAr Mo 1 NRAr ArRN NRAr 1-N2 2

N 30 C Mo NRAr t = 35 min ArRN 1/2 NRAr 3

Figure 1.9 Proposed reaction pathway of dinitrogen cleavage with Mo(NRAr′)3

23 1.4.3 Metathesis Reactions of Triple Bonds

Although the nitride complexes have been known for more than 150 years,

metathesis reaction involving M≡N bond has been only been reported very recently. In

t t 1982, Shrock reported “chop-chop” reactions: ( BuO)3W≡W( BuO)3 reacts with

t t acetylenes to give two equivalent corresponding alkylidynes; ( BuO)3W≡W( BuO)3 also reacts with nitriles to produce quantitatively alkylidyne complexes and nitride complexes.86 The later has become a useful method to generate group 6 metal (Mo and

W) nitrides. The nitride complexes, L3M≡N, where L = alkoxide and M = Mo or W, have been found by Chisholm87 to undergo nitrido ligand transfer reactions as illustrated in

Equation 9-11.

13 13 L3W≡ CMe + L3Mo≡N L3W≡N + L3Mo≡ CMe (9)

15 15 L3W≡ N + L3Mo≡N L3W≡N + L3Mo≡ N (10)

L3Mo≡N + L3W≡WL3 L3W≡N + L3Mo≡WL3 (11)

The facility of nitrogen atom transfer as shown in Equation 9-11 initiates the

study of the potential for nitrogen atom exchange between metal nitrides and

t 15 organonitriles. The compound ( BuO)3W≡ N was shown to exchange its nitrogen atom

with that of acetonitrile (Equation 12) and further catalyze 15N scrambling with

benzonitrile88 (Equation 13). The similar reactions involving Mo analogue was only

observed when solution was heated up to 70°C. It has also been found that the reaction is

quite tolerant to steric factors and carbon-halogen bond as well as C=C bonds.

24 t 15 t 15 ( BuO)3W≡ N + MeC≡N (BuO)3W≡N + MeC≡ N (12)

H H

15 CN ((+)-Men-O)3W≡ C N (13) MeC15 H3CO H3CO

The reactivity of nitride toward metathesis reaction can be also extended to

alkynes.89-91 The conversion from alkylidyne to nitride upon the reaction between

t 92 RC≡W(O Bu)3 and PhCN has been observed by Schrock for more than two decades.

However, the first example of a conversion in the opposite direction was only reported by

89 Johnson very recently. It was found that N≡Mo(OC(CF3)2Me)3 undergoes metathesis

reaction with 3-hexyne at high temperature to give the corresponding propylidyne which

is a active catalyst for alkyne metathesis. The rate of this reaction increases when the

more highly fluorinated alkoxide ligands are involved. This discovery facilitates the

synthesis of the highly reactive catalysts for alkyne metathesis reactions.90-91

1.5 Statement of Research Purpose

The work in this thesis describes our computational studies employing the density

functional theory (DFT) on the oxidative addition of ammonia to iridium metal

complexes and the metathesis reactions of triple bonds involving the metal nitride

complexes. In chapter 2 we study the effects of ancillary ligand on the relative stability of

an ammonia iridium complex and its isomer, hydrido amido iridium complex to gain

insight into the N-H bond activation through direct cleavage by a transition metal 25 complex. In chapter 3 we study the nitrogen atom exchange between tungsten (or molybdenum) nitride and acetonitrile. The calculated reaction pathways show that the reactions proceed through a 2+2 cycloaddition and the reaction barriers are influenced by metal center. In chapter 4 we investigate the electronic structures of the molecules

(RO)3M≡N(M = Cr, Mo, W) with gas phase photoelectron spectroscopy and density functional calculations. The reactivity of this series of nitride complexes is sensitive to both metal center and the alkoxide ligands. In chapter 5 we perform a detailed computational study on the metathesis-like reaction between W≡W hexaalkoxides and acetonitrile which yields alkylidyne and nitride tungsten complexes to elucidate its mechanism.

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32 CHAPTER 2

INSIGHTS INTO LIGAND EFFECTS ON THE RELATIVE STABILITY OF THE NH3 COORDINATION IRIDIUM (I) COMPLEX AND THE HYDRIDO AMIDO IRIDIUM (III) COMPLEX

2.1 Introduction

Activation and cleavage of element-hydrogen bonds, E-H, where E = H, C, N and

O via oxidative addition to a transition metal complex is an important step of many

catalytic cycles. Hence, an understanding of the factors that influence the oxidative

addition and reductive elimination of H-E bonds is necessary to develop efficient

catalysts, and has attracted a lot of attention, especially for activation of dihydrogen and

alkanes.1-7 However, transition metal catalyzed reactions of ammonia by oxidative

addition or reductive elimination of H-N bonds are rare.8-10 The difficulties in activation

of the H-N bond of ammonia might be partially due to its strong Lewis base character,5 together with strong π-donating properties of the amide ligand.

The first example of the oxidative addition of ammonia to a mononuclear transition metal complex was reported by Casalnuovo and coworkers in 1987.8 The

iridium complex containing labile ethylene ligands, Ir(PEt3)2(C2H4)Cl, was reported to

33 insert the N-H bond of ammonia to form a very stable amide bridged dinuclear iridium

complex. The high stability of the amido bridge prohibits further reaction of the dimer.

Therefore, formation of the amido bridge should be avoided for a system to be suitable

for a catalytic cycle. The first terminal amido complex prepared by oxidative addition

of ammonia was not reported until 2005.11 Elegant work by Hartwig and coworkers

reported that an Ir(I) complex containing a PCP tridentate-pincer ligand cleaved the N-H

bond of ammonia readily at room temperature to form a hydrido amido Ir(III) complex.

They found that oxidative addition of ammonia can be achieved by switching from an

aromatic backbone to an aliphatic backbone of PCP ligand and this was attributed to the stronger electron donating ability of PCP ligand with aliphatic backbone than that of the

PCP ligand with aromatic backbone.

To achieve the oxidative addition of ammonia, a hydrido amido complex should

be favored over the isomeric ammonia coordination complex. The work herein, density

functional theory (DFT) calculations were used to study the effects of PCP ancillary

ligands on the relative stabilities of hydrido amido complexes and ammonia coordination

complexes. The geometries and energies of the four compounds 1a, 1b, 2a, and 2b 34 containing PCP ligands with t-butyl groups on P which are the same ligands used in

experiments were calculated. To evaluate the electronic and steric effects of the PCP

ligand, different substituents have been used to replace the tert-butyl group on

phosphorous atoms for each of the four compounds. An alternative method using charge

variation on P atoms to study the ligand effects is also reported.

2.2 Computational Details

All DFT calculations were performed using the Amsterdam Density Functional

(ADF) software package, version 2004.01, developed by Barends et al.12 and vectorized

by Ravenek.13 The numerical integration scheme used was developed by teVelde et

al.,14 and the geometry optimization procedure was based on the method of Versluis and

Ziegler.15 All geometry optimizations were carried out with no symmetry constraints

under the C1 point group by using the local exchange-correlation potential of Vosko et

al.16 and the non-local exchange and correlation corrections of Perdew and Wang

(PW91).17 All atoms were described using a triple-ζ Slater type orbital (STO) basis set

with one polarization function (TZP); the core was frozen at the 4f level for iridium, 1s for the second row atoms and 2p for the third row atoms. All atoms were corrected for scalar relativistic effects by using the Zeroth Order Regular Approximation (ZORA) method.18 All calculations utilized an INTEGRATION value of 7, geometries were converged to a gradient of 10-4 au/Å. The self-consistent field energy was converged to a value of 10-8. Frequencies were calculated by numerical differentiation of energy

35 gradients in slightly displaced geometries using double-sided displacements.19 Molecular

orbitals were visualized using molecular graphics package MOLEKEL.20

2.3 Results and Discussion

The geometries and energies of the four iridium compounds, 1a, 1b, 2a and 2b, which bear the same ligands used in the experiments, were calculated.11, 21 The purpose

was to evaluate the theoretical method chosen. The choice of the level of theory for this

work is mainly based on earlier work of this group.22-25 Where it was found that the

PW91/TZP described many transition metal complexes and actinide complexes fairly

well. Unfortunately, the iridium compounds were not among those calculated in these

studies. Therefore, it was necessary to evaluate the accuracy of this method for iridium

complexes. The selected geometrical parameters of these compounds are given in Table

2.1

36 C5 C2 C4 P1

C1 Ir NH3

P 1 C6 C3 C7 1a 1b 2a 2b Cal. Cal. Exp.21 Cal. Exp.11 Cal. Ir-H(1) 1.511 1.5131.51 Ir-N 1.980 2.209 2.215 1.973 1.999 2.202 Ir-C(1) 2.041 2.000 2.013 2.108 2.128 2.072 Ir-P(1) 2.325 2.269 2.261 2.332 2.298 2.284 Ir-P(2) 2.325 2.272 2.274 2.335 2.299 2.284 H(1)-Ir-N 141.9 142.4 139.4 H(1)-Ir-C(1) 62.5 65.866.80 N-Ir-C(1) 155.6 178.1 175.87 151.8 153.69 176.2 P(1)-Ir-P(2) 157.9 164.7 164.52 165.0 165.95 161.4 C(2)-P(1)-C(4) 106.5 103.7 104..4 107.0 105.37 104.9 C(4)-P(1)-C(5) 116.4 122.6 110.2 117.1 109.65 122.4 C(5)-P(1)-C(2) 103.6 102.4 102.5 102.4 101.91 102.7 C(3-P(2)-C(7) 106.5 102.9 102.7 106.4 105.85 104.9 C(7)-P(2)-C(6) 116.4 123.0 110.5 116.5 109.75 122.4 C(6)-P(2)-C(3) 103.6 102.7 102.6 103.2 101.54 102.7

Table 2.1 Selected bond lengths and bond angles of complexes 1a, 1b, 2a and 2b.

The calculated structures of 1b and 2a are close to experimental crystal structures except that the calculated bond angles C(7)-P(2)-C(6) deviate from the experimental

37 values by an average of 10º. This could be attributed to the crystal packing effects in

the solid state structures. For compound 2a, both the calculated and experimental

structures show that the H1, Ir, C1 and N atoms are in the same plane (the sum of the

angles H(1)-Ir-N, H(1)-Ir-C(1) and N-Ir-C(1) are 360.0 and 360.2 degree) and the

molecule exhibits a distorted trigonal bipyramidal structure. For compounds containing

the aromatic backbone PCP ligand, the ammonia coordinated compound (1b) is

calculated to be 0.60kcal/mol lower in energy than the hydrido amido compound (1a).

While for compounds containing the aliphatic backbone PCP ligand, the hydrido amido compound (2a) was calculated to be 2.95kcal/mol lower in energy than the ammonia coordinated compound (2b). Corrections for zero-point energies were not included for

the above calculations. Although the difference in zero-point energies for the ammonia

coordinated compound to hydrido amido compound could have significant impacts on

the absolute numbers of the relative energies, it would not affect the trend that the aliphatic backbone PCP ligand stabilizes the hydrido amido compound more than the aromatic PCP ligand does. This may be due to the stronger electron-donating ability of the aliphatic backbone than that of the aromatic backbone. As shown in Figure 2.1, in compound 1b there are molecular orbitals showing interaction between the ring

π-orbitals and d-orbitals on the iridium thus reducing the election density on the iridium.

While in coumpound 2b, there is no such π system on the aliphatic backbone ligand

available to interact with the d-orbitals on iridium. The calculated mulliken charges on

38 iridium are -0.0031 and -0.5015 for 1b and 2b respectively, which indicates that part of

the electron density on iridium is delocalized to the π system of the aromatic backbone

PCP ligand. These results are consistent with the experimental results.11, 21 Therefore, the level of theory chosen seems able to describe the system appropriately and was used in our further studies of the systems.

HOMO HOMO-6

Figure 2.1 Molecular orbitals showing interactions between the ring π-orbitals and d-orbitals on the iridium in compound 1b.

To systematically study the ligand affects on the relative stabilities of the

ammonia coordinated complexes versus the isomeric hydrido amido complexes, the

types of PCP ligands (figure 2.2) due to the rigidity of the PCP ligands were chosen, so

39 that they can be electronically modified for a specific property without changing the steric properties significantly.

PR2 PR2

PR2 PR2 Al Ar

Figure 2.2 PCP ligands used for study: Al denotes the type of ligands with an aliphatic backbone and Ar denotes the type of ligands with an aromatic backbone.

Aliphatic Aromatic

Ir-NH3 HIr-NH2 Ir-NH3 HIr-NH2

∆E ∆G298K ∆E ∆G298K ∆E ∆G298K ∆E ∆G298K H 0 0 3.69 1.95 0 0 8.86 7.10 Me 0 0 30.21 28.78 0 0 23.04 20.95 tBu 0 0 -2.95 — 0 0 0.60 —

Table 2.2 Relative energies and relative Gibbs free energies (298K) were given in kcal/mol. Ir-NH3 refers to ammonia coordinated compound while HIr-NH2 refers to hydrido amido compound.

40 The obvious way to modify the PCP ligands is to utilize different substituents R on

phosphorus atoms and three substituents (R=H, Me and tBu) were used for both Al and

Ar PCP ligands. The relative energies and Gibbs free energies (298K) in table 2.2 were defined with respect to ammonia coordinated compound.

Surprisingly, the relative energy is most positive when the substituent on the P atom is a methyl group not an H atom. In general, the methyl group substituted phosphine ligand is considered to be a stronger electron donating ligand than the non-substituted phosphine and thus the methyl substituted phosphorous ligand should stabilize the insertion compound relative to the ammonia complex. However, this is not the case for PCP ligands. It seems that the methyl group acts in an electron withdrawing role. To evaluate the electron-donating ability of the ligands with different substituents, we calculated model compounds with CO coordination to the metal fragments (LnIr), where Ln represents the aliphatic backbone PCP ligands. [Such

calculation has not been done for the aromatic backbone PCP ligand]. The stretching

frequency of the carbonyl is known to be a sensitive tool for determining the electronic

properties of the ligands Ln. Since frequency calculations are very expensive, we

calculated the frequency for complexes with H and methyl substituents only. The

computational results show the CO stretching frequency is lower for H (1961 cm-1) than for methyl (1978 cm-1), thus indicating that the ligand with methyl groups is a weaker electron donor than that with H atoms. Intuitively, this can be attributed to steric effects

41 since the size for different substituents are obviously different. By carefully comparing

the geometries of hydrido amido compounds for different substituents on the Al PCP

ligands, we found that the Ir-P bond length is the shortest when the substituents are

methyl groups (Ir-P bond length: 2.265, 2.255 and 2.332 Å for H, Me and tBu

respectively) but other parameters increase or decrease with the size of substituents.

The same phenomena were observed for ammonia coordinated complexes (Ir-P bond length: 2.245, 2.237 and 2.284 Å for H, Me and tBu respectively). One possible

explanation for this is that the ligand with methyl substituents is a better π acceptor than

the ligands with H or t-butyl substituents.

An alternative method was used to study the ligand effects introduced by different

substituents on the phosphorus atoms26 through varying the nuclear charge on the

phosphorus atoms of PCP ligand. Such variation in nuclear charge on phosphorus

atoms is equivalent to modifying the electronegativity of the phosphorus atoms and thus

modifying the electronic properties of the ligand. One advantage of this method is that

one can choose a small substituent and keep it consistent for all calculations and this

significantly reduces the computational cost. In this study, H atoms were used as the

substituents for both types of PCP ligands. The nuclear charge of phosphorus atom was

varied from 14.6 to 15.4 by 0.2 steps and the electronic energies and Gibbs free energies at 298K of hydride amido complexes and ammonia coordinated complexes were calculated for each nuclear charge of the phosphorus atoms. Again the relative electronic

42 energies and relative free energies were defined with respect to the ammonia coordinated compound. The relative free energies plotted against the nuclear charge of phosphorus atom are shown in Figure 2.3.

As shown in Figure 2.3, the relative free energies decrease with the nuclear charge of the phosphorus atoms for both aliphatic and aromatic backbone PCP ligands.

Decreasing the nuclear charge of an atom is equivalent to decreasing the electronegativity of the atom thus increasing the electron releasing ability of the atom.

Therefore, the PCP ligands with less nuclear charge on the phosphorus atoms are stronger electron donors. The figure shows a straight trend that increasing the electron donating ability favors the hydrido amido complexes over the ammonia coordination complexes. At each nuclear charge, we can also see that the relative free energy is always higher for aromatic backbone PCP ligands than for aliphatic backbone PCP ligands. Although the negative relative free energy can be approached by decreasing the nuclear charge on the phosphorus atoms for both types of PCP ligand, the aromatic backbone PCP ligand requires a smaller phosphorus nuclear charge than the aliphatic backbone PCP ligand does. In other words, it is harder for an aromatic backbone PCP ligand to favor the insertion over coordination. To achieve such a goal, substituents with better electron donating ability are required for aromatic backbone PCP ligand.

This is consistent with the experiment result that the insertion compound is favored by the aliphatic backbone PCP ligand with t-butyl substituents and the coordination

43 compound is favored by the aromatic backbone PCP ligand with t-butyl substituents.

20

15

10

Aliphatic Aromatic (Kcal/mol) 298K

G 5 ∆

0 15.4 15.2 15 14.8 14.6

-5 Nuclear charge

Figure 2.3 The relative Gibbs free energies (∆G298K) vs nuclear charge of P atom. Red corresponds to Aliphatic PCP Ligand and blue corresponds to Aromatic PCP Ligand.

44 2.4 Conclusions

The study of the subsituent effects has shown that the oxidative addition of ammonia by an iridium complex to form a hydrido amido complex can be achieved by increasing the electron donating ability of the PCP ligand since the ligand with a better electron donating ability stabilizes the insertion compound relative to the coordination compound. Of course, instead of modifying the substituents on the phosphorous atom

of the PCP ligands, we can also modify the backbone of the PCP ligand. One typical

example is to use the aliphatic backbone instead of the aromatic backbone. The nuclear

charge variation method can also be applied to the backbone modification of PCP ligand.

45 2.5 References

(1) E. L. Muetterties, Chem. Soc. Rev. 1983, 12, 283.

(2) R. G. Bergman, Science 1984, 223, 902.

(3) R. H. Crabtree, Chem. Rev. 1985, 85, 245.

(4) D. M. Roundhill, Chem. Rev. 1992, 92, 1.

(5) D. G. Musaev, K. Morokma, J. Am. Chem. Soc. 1995, 117, 799.

(6) K. K. Jespersen, M. Czerw, K. Zhu, B. Singh, M. Kanzelberger, N. Darji, P. D. Achord, K. B. Renkema, A. S. Goldman, J. Am. Chem. Soc. 2002, 124, 10797.

(7) A. C. Sykes, P. White, M. Brookhart, Organometallics 2006, 25, 1664.

(8) A. L. Casalnuovo, J. C. Calabese, D. Milstein, Inorg. Chem. 1987, 26, 973.

(9) S. Park, D. M. Roundhill, A. L. Rheingold, Inorg. Chem. 1987, 26, 3972.

(10) G. L. Hillhouse, J. E. Bercaw, J. Am. Chem. Soc. 1984, 106, 5472.

(11) J. Zhao, A. S. Goldman, J. F. Hartwig, Science, 2005, 307, 1080.

(12) (a) E.J. Baerends, D.E. Ellis, P. Ros, Chem. Phys. 1973, 2, 41. (b) E.J. Baerends, P. Ros, Chem. Phys. 1973, 2, 52. (c) G. teVelde, E.J. Baerends, J. Comput. Phys. 1992, 99, 84. (d) C.G. Fonseca, O. Visser, J.G. Snijders, G. teVelde, E.J. Baerends, in Methods and Techniques in Computational Chemistry, METECC-95, ed. E. Clementi and G. Corongiu, STEF, Cagliara, Italy, 1995, pg. 305.

(13) W. Ravenek, in Algorithms and Applications on Vector and Parallel Computers, ed. H.J.J. teRiele, T.J. Dekker and H.A. van deHorst, Elsevier, Amsterdam, 1987.

(14) P.M. Boerrigter, G. teVelde, E.J. Baerends, Int. J. Quantum Chem. 1998, 87.

(15) L. Verslius, T. Ziegler, J. Chem. Phys. 1998, 88, 322.

(16) H. Vosko, L. Wilk, M. Nusair, Can. J. Phys. 1980, 58, 1200.

46 (17) P. Perdew, Phys. Rev. B. 1992, 46, 6671.

(18) E. VanLenthe, A.E. Ehlers, E.J. Baerends, J. Chem. Phys. 1999, 110, 8943.

(19) (a) L. Fan, T. Ziegler, J. Chem. Phys. 1992, 96, 9005. (b) L. Fan, T. Ziegler, J.Am. Chem. Soc. 1992, 114, 10890.

(20) P. Flükiger, H. P. Lüthi, S. Portmann, J. Weber, Swiss Center for Scientific Computing, Manno (Switzerland), 2000.

(21) M. Kanzeleberger, X. Zhang, T. J. Emge, A. S. Goldman, J. Zhao, C. Incarvito, J. F. Hartwig, J. Am. Chem. Soc. 2003, 125, 13644.

(22) M. L. Drummond, Ph.D. Dissertation, The Ohio State University, 2005.

(23) E. J. Palmer, Ph.D. Dissertation, The Ohio State University, 2005.

(24) C. M. Brett, Ph.D. Dissertation, The Ohio State University, 2005.

(25) J. L. Sonnenberg, Ph.D. Dissertation, The Ohio State University, 2005.

(26) B. F. Gherman, C. J. Cramer, Inorg. Chem. 2004, 43, 7281.

47 CHAPTER 3

METATHESIS OF NITROGEN ATOMS WITHIN TRIPLE BONDS INVOLVING CARBON, TUNGSTEN AND MOLYBDENUM

Reproduced with permission from Inorganic Chemistry, 2008, 47, 5377-5385. Copyright 2008 American Chemical Society

3.1 Introduction

The evolution of olefin metathesis involving transition metal alkylidenes is one of

the most fascinating and preparatively useful stories in chemistry.1 Not long after the

initial industrial discovery of olefin metathesis, Pennella, Banks and Bailey2 disclosed a

seemingly even more miraculous tale of triple bond metathesis involving alkynes. In

1975, Katz and McGinnis3 addressed the mechanism of olefin metathesis involving metal

carbene intermediates, and proposed that alkyne metathesis proceeded via a similar mechanism involving the 2+2 cycloaddition of C≡C and M≡C bonds to give a planar metallacyclobutadiene intermediate. This was soon thereafter demonstrated by the elegant work of Schrock and coworkers4 involving the reactions between trialkoxy

tungsten alkylidynes and alkynes. This reaction too has entered into the tool kit of

organic reagents.5 We describe here our findings of the metathesis reaction involving

48 metal-nitrogen and carbon-nitrogen triple bonds where the metals are either tungsten or

molybdenum. A preliminary report on this work appeared in 20036 and subsequently

related work was reported by Johnson in 2005.7,8

3.2 Results and Discussion

3.2.1 Mo≡N + W≡W → Mo≡W + W≡N

t 9 t t 10 The reaction between (Bu O)3Mo≡N and (Bu O)3W≡W(OBu )3 proceeds quite rapidly in hydrocarbon solutions to give the mixed metal MoW triply bonded complex

t t 11 t MoW(OBu )6 with the formation of (Bu O)3W≡N. The compound MoW(OBu )6 can

readily be identified in the mass spectrum by the presence of the molecular ion which shows the distinct isotopic distribution predicted for a MoW containing species. It is also seen in the 1H NMR spectrum where two But singlets are observed as expected for each

of the three alkoxide ligands bound to each metal. However, it has not been possible to

isolate this heteronuclear MM’ bonded compound because this compound reacts further

t t t with (Bu O)3Mo≡N with the ultimate formation of Mo2(OBu )6 and (Bu O)3W≡N. The

t t t compounds Mo2(OBu )6, MoW(OBu )6 and W2(OBu )6 show similar solubilities and

almost certainly co-crystallize. The driving force for this reaction rests with the favorable

redox reaction involving the two metals: Mo(VI) + W(III) → Mo(III) + W(VI) and almost certainly proceeds by way of an activated trinuclear cluster involving a triply bridging nitride. Structural precedent for this exists in the form of the tetranuclear cluster

49 i 12 13 13 Mo4(µ3-N)2(OPr )12 and in related M3(µ3-O)(OR)10 , MoW2(µ3-O)(OR)10 and W3(µ3-

14 P)(OR)9 clusters.

3.2.2 Alkylidyne and Nitride Ligand Transfer Between Molybdenum and Tungsten

Although the triple bonds between the metals Mo and W and carbon and nitrogen

are estimated to be ~120-155 kcal/mol15, 16 they are kinetically labile and readily

transferable between metal centers as shown in the reactions 1, 2, and 3 below, where L =

ButO.

13 13 L3W≡ CMe + L3Mo≡CPh L3W≡CPh + L3Mo≡ CMe (1)

13 13 L3W≡ CMe + L3Mo≡N L3W≡N + L3Mo≡ CMe (2)

15 15 L3W≡ N + L3Mo≡N L3W≡N + L3Mo≡ N (3)

These reactions can be monitored by NMR spectroscopy in solvents such as toluene-d8.

The presence of 183W, I=1/2 which occurs in ~15% natural abundance aids in the

13 15 1 detection of C and N nuclei by the presence of J183W satellites.

These observations led us to interrogate the metathesis reactions involving M≡N and

C≡N described below.

W≡N* + RC≡N W≡N + RC≡N*

t 15 t The compound (Bu O)3W≡ N is readily prepared from the reaction between W2(OBu )6

15 and labeled acetonitrile CH3C≡ N and if this reaction is carried out in a hydrocarbon

solvent the tungsten nitride is formed as a finely divided microcrystalline product.17 The

t compound (Bu O)3W≡N is only sparingly soluble in solvents such as toluene and in the 50 solid-state exists as an infinite polymeric chain involving the connectivity

(→W≡N→W≡N→).11 Because of the poor solubility in hydrocarbons our studies of N atom exchange were carried out in the more polar and coordinating solvent THF. The

t molybdenum analogue (Bu O)3Mo≡N adopts an analogous structure in the solid state but

is somewhat more soluble in hydrocarbon solvents because of the weaker donor strength

of the less polar Mo≡N bond.

15 t 15 The reaction between MeC≡ N and (Bu O)3W≡N in THF-d8 was followed by N

NMR. The signal at δ~248 ppm decreased in intensity as the signal due to

t 15 (Bu O)3W≡ N grew in intensity at δ~732 ppm. A similar reaction was carried out

t employing (Bu O)3Mo≡N in THF-d8 but no reaction was observed at room temperature.

However, heating the solution to 70 °C did bring about a similar reaction with the

t 15 formation of (Bu O)3Mo≡ N.

The tungsten nitride complex was then used as a catalyst for the N atom exchange

as shown in eq. 4. The reactions were again monitored by 15N NMR spectroscopy.

Cat. MeC≡15N + RC≡N MeC≡N + RC≡15N (4)

A broad range of nitriles was chosen to both test the generality of the N atom exchange

t and also to test the tolerance of (Bu O)3W≡N toward various functional groups. For the

groups where R = ortho and para-C6H4F, -C6H4Cl, (CH2)4Cl, Me3C, Ph, PhCH2, Ph2CH,

Ph3C and –CH=CH-CN scrambling of the label was observed. The reaction is quite tolerant to steric factors and carbon-halogen bonds as well as C=C bonds. Rather

51 interestingly the ortho-fluorophenyl nitrile showed 15N-19F coupling with its signal at δ

271.7 appearing as a doublet. See Figure 3.1. At this point it is worth noting that

Johnson has recently demonstrated that alkynes will react with fluorinated alkoxide

molybdenum and tungsten nitrides to yield the respective alkylidynes and nitriles.8

15 15 15 Figure 3.1 N-NMR spectrum of Cl(CH2)4C≡ N (B), p-Cl-(C6H4)C≡ N (C), and o-F- 15 15 (C6H4)C≡ N (D); byproducts of a scrambling reaction with (t-BuO)3W≡N and MeC≡ N (A).

In order to establish that in reaction 4 the metathesis involved solely nitrogen

atom exchange and not a cyano group exchange, we also examined the reaction between 52 Me13C≡N, MeC≡15N and PhC≡N. As shown in Figure 3.2 the exchange catalyzed by

t (Bu O)3W≡N involved exclusively W≡N and C≡N metathesis.

Figure 3.2 15N NMR spectrum of the reaction mixture between Me13C≡N, MeC≡15N and t PhC≡N in the presence of a trace of (Bu O)3W≡N recorded in d8-THF at 298 K, 50.6 MHz. The PhC≡15N signal shows enhancement due to 15N atom exchange and appears as a singlet due to lack of coupling to 1H or 13C whereas the MeC≡N 15N signal shows coupling to 1H, 3J1H–15N = 1.7 Hz and for Me13C≡15N coupling to 13C, 1J13C–15N = 17 Hz. The signal thus appears as a central 1 :3 :3 :1 quartet flanked by 13C satellites. The unsymmetrical nature of the 13C satellites arises from 12C/13C isotopic chemical shift perturbation.

53 The exchange reactions noted above do not occur in pyridine-d5 which is a good

donor to tungsten and presumably blocks coordination of the weaker nitrile donor. Also

t 18 the siloxide bridged dimeric compound [(Bu Me2SiO)3W≡N]2 does not react with

MeC≡15N.

19 The chiral menthoxide complexes, both [(+)-men-O]3W≡N and [(-)-men-

19 15 O]3W≡N were prepared and shown to catalyze exchange of N between MeC≡ N and the bulky enantiomerically pure (S)-2-(6-methoxy, 2-napthyl)-propionitrile (See eq. 5).

This raises the possibility of enantio-selective N atom exchange but we have not investigated this further at this time.

H H ((+)-Men-O)3W(N) CN C15N

MeC15N H3CO H3CO (5)

3.2.3 Estimation of Activation Parameters.

The atom exchange reaction proceeds at convenient rates under ambient conditions to allow its study by a variety of conventional techniques. However, the specifics of the system proved problematic. For example, the limited solubility and the

t high air-sensitivity of (Bu O)3W≡N made following the course of the reaction by react-IR

unreliable. Similarly, mass spectrometry was complicated by relative intensities of RCN+ and RCNH+ ions due to experimental conditions and 15N NMR required too long

acquisition times. We finally resorted to the use of 13C NMR spectroscopy to follow the 54 13 t 15 13 13 reaction between Me C≡N and (Bu O)3W≡ N. The C signal for Me C≡N appears as a

singlet at δ 116.96 ppm and upon 15N atom exchange coupling to 15N, I=1/2 leads to a

doublet at 117.01 and 116.77 ppm. The line –shape analysis program in XWIN-NMR

makes it possible to extrapolate relative concentrations of Me13C≡N and Me13C≡15N with

t 15 time and hence obtain data for kinetics. By keeping the concentration of (Bu O)3W≡ N

constant and varying the concentration of nitrile, it was determined that the reaction is

first order in nitrile. (See experimental.) A variable temperature study (20-50℃)

following the decay of Me13C≡N allowed for the production of the Eyring plot shown in

Figure 3.3. Based on this an estimation of the activation parameters can be made: ∆H≠ =

+13.4(7) kcal/mol and ∆S≠ = -32(2) eu.

55 -12.5 0.00305 0.0031 0.00315 0.0032 0.00325 0.0033 0.00335 0.0034 0.00345

-13

-13.5

-14 ln(kobs/T)

-14.5

-15

-15.5 1/T

2 Figure 3.3 Eyring plot of ln(kobs/T) vs 1/T where y = - 6727x + 7.7142, R = 0.9937. The enthalpy parameters were calculated to be ∆H≠ = + 13.4(7) kcal mol-1 and ∆S≠ = -32(2) 15 15 13 eu for the N isotope exchange reaction between (t-BuO)3W≡ N and Me C≡N.

Although the alkyne metathesis reaction has been well explored in terms of its

synthetic utility and reaction pathway, to our knowledge the kinetics and activation

parameters have only been determined for a related reaction involving the exchange of alkyne units and the metallacyclobutadiene complex, (DIPP)3W(C3R3), where R = Et, and

n 20 Pr and DIPP = 2,6-diisopropylphenoxide, with 3-hexyne-d10 (See eq. 6).

56 (DIPP)3W(C3R3) + R’C≡CR’ → (DIPP)3W(C3RR’2) + RC≡CR (6) n Where R = Et, Pr . R’ = CD2CD3

For R = Et, a variable temperature study led to the determination of ∆H≠ = +26.1(4)

kcal/mol and ∆S≠ = +15.2(15) eu while for P = Prn, ∆H≠ = +25.4(5) kcal/mol and ∆S≠ =

+16.3(16) eu.20 The reaction was also shown to be the 1st order in tungsten and

independent of 3-hexyne-d10 in the concentration range studied. Thus the activation parameters reported by Schrock pertain to a rate limiting elimination of RCCR from the metallacyclobutadiene whereas in our study the parameters most likely reflect an associative 2+2 reaction. Qualitatively, we can see that this is reflected in the positive entropy of activation for reaction 6 and the negative ∆S≠ value for the N atom metathesis reaction.

3.2.4 Theoretical and Computational Considerations

Following the initial theoretical considerations of Bursten21 in 1983 considerable

attention has been given to the relative stabilities and bonding in metallacyclobutadiene

and metallatetrahedrane complexes and their role in the alkyne metathesis reaction.22-24

This work has led up to the most recent 2006 publication25 dealing with the total reaction

pathway for alkyne metathesis by molybdenum and tungsten (RO)3M≡CMe complexes as

determined by density functional theory employing B3LYP and the effective core

potentials of Hay and Walt with a double-ζ valence basis set including one f polarization

function for Mo and W atoms.

57 We have employed density functional theory using exchange and gradient-

corrected correlation functional PW91 to investigate the reaction pathway leading to the nitrogen atom metathesis reactions described above. Two kinds of basis set systems, BS-

I (LanL2DZ basis sets augmented by a f polarization function for metal atoms and the 6-

31G* basis sets for non-metal atoms) and BS-II (SDD basis sets for metal atoms and cc-

pVTZ basis sets for non-metal atoms), were used to study the potential energy surfaces of

the metathesis reactions between (MeO)3M≡N (where M=W, Mo) and MeC≡N. The

reaction pathways found by employing a larger basis set system, BS-II, are similar to

those found by using BS-I. For both basis set systems, the same number of stationary

points with similar structures on the reaction pathway was found for each reaction. The

slightly higher activation free energies obtained by using BS-II than by using BS-I is

mainly due to the lack of f polarization function for metal atoms in BS-II. This is evident

by comparing the activation free energies for reaction between (MeO)3W≡N and MeC≡N

obtained from BS-I, BS-II, BS-III (LanL2DZ for metal atoms and 6-31G* for non-metal

atoms) and BS-IV (SDD for metal atoms and 6-31G* for non-metal atoms). The

activation free energy is defined by the difference of free energies between the high lying

transition structure (TS1A) and the starting materials. The calculated activation free

energies from BS-I to BS-IV are 25.9, 31.7, 29.4 and 29.3kcal/mol respectively. The

almost same values based on BS-III and BS-IV indicate that the different effective core potentials seem to have no effect on the activation free energy for this calculation.

58 Employment of an f function brings down the energy by about 3.5kcal/mol, while

employment of triple basis sets cc-pVTZ for non-metal atoms slightly increases the

activation free energy but does not have a significant effect on the reaction pathway. The

calculated activation free energy by using BS-I is closest to the experimental value.

Based on the above facts, we presented our results calculated by using BS-I.

The calculated free energy profiles for the nitrogen atom exchange reaction

between (MeO)3M≡N and and MeC≡N and structures of transition sates and

intermediates with selected calculated structural parameters (Å) for W and Mo using BS-I

are shown in Figure 3.4 and 3.5 respectively.

59

Figure 3.4 Free energy (at 298K) profiles for nitrogen exchange reaction between

(MeO)3W≡N and MeC≡N and structures of transition sates and intermediates with selected calculated structural parameters (Å).

60

Figure 3.5 Free energy (at 298K) profiles for nitrogen exchange reaction between

(MeO)3Mo≡N and MeC≡N and structures of transition sates and intermediates with selected calculated structural parameters (Å).

61 The overall reaction between (MeO)3W≡N and MeC≡N involves nitrogen

exchange and a conformation change. The nitrogen exchange is endothermic (∆G = 4.6

kcal/mol, which is principally caused by the presence of the different conformations of

(MeO)3W≡N in RA and PA′). In this step, two transition states, Ts1A and Ts2A, are located. The higher lying transition stateTs1A connects minima Int1A and Int2A. The intermediate Int2A is transformed to another intermediate Int3A through transition state

Ts2A. However, we shall not overemphasize the existence of intermediate Int2A and

Ts2A since the barrier for transformation from Int2A to Int3A is only about 0.6kcal/mol and the analogous intermediate and transition state were not found in the reaction

pathway involving the molybdenum analogue. Dissociation of Int1A and Int3A, leading

to formation of separate tungsten nitride and acetonitrile, can occur without barriers. The

Int1A has a free energy of 3.3 kcal/mol, which is essentially caused by the loss of entropy

associated with the interaction between (MeO)3W≡N and MeC≡N. The higher free

energy of Int3A than that of PA′ is also caused by such a loss of entropy. As can be seen

in Figure 3.4, different conformations of (MeO)3W≡N are present in the product of

nitrogen exchange step, PA′, and the reactant, RA. The conformer A′ in PA′ is calculated

to be higher in free energy than conformer A in RA by 4.6kcal/mol, which accounts for

the difference of the free energies between RA and PA′. A′ can be readily transformed into the more stable conformer A by crossing an energy barrier of about 3kcal/mol. The

similar metathesis pathway was calculated for reaction between the (MeO)3Mo≡N and

62 MeC≡N except that neither analog of Int2A nor analog of TS2A was found in this

pathway. The transition state Ts1B connects minima Int1B and Int2B which further

dissociates to form (MeO)3Mo≡N and MeC≡N. Similar conformation transfer from B′ to

B was also observed.

The transition state Ts1A was calculated to be higher in free energy than the

starting materials by 25.9 kcal/mol (about 12 kcal/mol in enthalpy). This calculated free

energy barrier for the nitrogen atom exchange reaction between (MeO)3W≡N and

MeC≡N is in good agreement with the experimental observations. While for reaction

involving (MeO)3Mo≡N and MeC≡N the transition state Ts1B was calculated to be

higher in free energy than the starting materials by 39.2 kcal/mol which is about 13

kcal/mol higher than for the tungsten ananogue. This result is also consistent with the

t experimental observation that nitrogen atom exchange between (Bu O)3Mo≡N and

MeC≡N only occurs at elevated temperatures.

The calculated pathways leading to N atom metathesis and alkyne metathesis bear

the similarity that reactions proceed through 2+2 cycloaddition but there exist differences between them. In both types of metathesis reactions, the ring-closing step is the rate determining step. However, no metal-alkyne adduct can be located along the pathway for alkyne metathesis and this was attributed to the fact that the d0 metal center can not

stabilize an alkyne complex by back donation. Metal-nitrile complexes (i.e. Int1A and

Int1B) were found along the reaction coordinates for the N atom exchange reactions and

63 the formation of metal-nitrile complexes is probably due to the dipole-dipole interactions and weak van der Waals interactions between the metal nitride fragment and nitrile since the distance between the two fragments is fairly large and both fragments are almost unperturbed. DFT may have problem handling with such interactions and higher level of theoretical considerations might be needed to study these weakly associated complexes.

3.3 Concluding Remarks

The facility of nitrogen atom metathesis described herein together with the recent report by Johnson et al7,8 on the metathesis involving molybdenum nitrogen triple bonds

and alkynes to form molybdenum-alkylidynes and organic nitriles shows the kinetic

lability of these strong M≡N bonds. If these reactions can be coupled to the Cummins26-

29 reductive cleavage of N≡N by Mo(NR2)3 compounds then a relative simple and

inexpensive route to 15N labeled organic compounds will be achieved. Interestingly, the

t 30 compound ( BuO)3CrN does not appear to entertain this type of chemistry though in

t reactions with M2(O Bu)6 redox chemistry is observed with the formation of the blue

t 31 t volatile compound Cr(O Bu)4 along with the compounds ( BuO)3MN as identified by their molecular ions in the mass spectrometer.

3.4 Experimental

3.4.1 General Procedures

All operations were carried out under an inert atmosphere of argon with dry and deoxygenated solvents using standard Schlenk-line and dry box procedures. All

64 chemicals were purchased from commercial sources and were used as received unless

duly noted. Aromatic and aliphatic hydrocarbon solvents were dried over either sodium

or potassium and THF and diethylether were distilled from sodium/benzophenone.

CH3CN was dried over CaH2 and distilled prior to use. All distilled solvents were stored

over 4Å molecular sieves. The nitriles employed in the N atom exchange reactions were

stored over 4Å sieves and were subjected to three freeze/thaw degas cycles prior to use.

Deuterated solvents and 13C/15N labeled isotopically enriched compounds were obtained from Cambridge Isotope Laboratories, Inc. and were similarly dried and degassed prior to

use.

3.4.2 Spectroscopic Methods

1H, 19F, 13C{1H}, 15N NMR spectra were recorded on Brucker Avance 400 and

500 MHz spectrometers. IR spectra were recorded on a Perkin-Elmer GX FT-IR

spectrophotometer as KBr pellets. Mass spectra were recorded on a Kratos MS25 RFA

double focusing magnetic sector mass spectrometer as positive ions.

3.4.3 Computational Methods

All calculations were performed using density functional theory as implemented

in the Guassian 03 suite of programs.34 The PW91PW9135 [Perdew and Wang’s 1991

exchange and gradient-corrected correlation functional] density functional were used for all calculations. Two types of basis set systems, BS-I and BS-II were used for potential

energy surface calculations. In BS-I, the LanL2DZ36 basis sets augmented by an f

65 polarization function (ζ(f)=0.823, W; ζ(f)=1.043, Mo ) 37 were used for transition metal

atoms and the 6-31G* basis sets38 were used for all other non-metal atoms in the model

compounds. In BS-II, the SDD basis sets39 were used for transition metal atoms and cc-

pVTZ basis sets40 were used for all other non-metal atoms. Two other basis set systems,

BS-III (LanL2DZ for metal atoms and 6-31G* for non-metal atoms) and BS-IV (SDD for

metal atoms and 6-31G* for non-metal atoms), were also used for activation energy

calculations to assess the influences of different effective core potential and the f

polarization functions. All the structures were fully optimized. Frequency calculations

were also performed to confirm that all the stationary points were minima or transition

states (no imaginary frequency for minimum and one imaginary frequency for transition

state). Intrinsic reaction coordinates (IRC)41 calculations were carried out on transition states to confirm these structures are indeed connecting two minima. The discussed energies are relative Gibbs free energies (∆G298K). The relative enthalpies (∆H298K)

are also provided for reference. All the relative energies were defined with respect to the

starting materials.

3.4.4 Synthesis and Reactions

t 10 19 19 The compounds W2(OR)6, where R = OBu , (+)-menthyl and (-)-menthyl ,

32 t 30 were prepared by alcoholysis reactions involving W2(NMe2). (Bu O)3CrN,

t 9 t 33 (Bu O)3MoN and (Bu O)3MoCPh were prepared according to literature procedures.

66 15 Synthesis of (O-t-Bu)3W N. W2(O-t-Bu)6 (1.00 g, 1.24 mmol) was dissolved

in hexane (250 mL) with rapid stirring. A hexane solution (10 mL) containing MeC15N

( 0.4 g, 9.5 mmol) was added to the dark red solution with rapid stirring. Immediately after addition of the acetonitrile, the color changed to dark amber and a brown precipitate

15 was formed. The brown precipitate [(O-t-Bu)3W N] was collected over an air-

sensitive filter frit, washed with three 10 mL portions of hexane, and dried in vacuo (500

1 15 mg, 96 % yield). H-NMR (500 MHz, d8-THF): = 1.49 (s, 9H, OC(CH3)3). N-NMR

183 15 (500 MHz, d8-THF): = 732 ppm [(s), J( W- N) 54 Hz]. IR (KBr plates, Nujol mull):

934 cm-1 (W15N); the 1020 cm-1 band attributed to (WN) for the unlabelled derivative was absent.

Synthesis of [(+)-Men-O]3WN. [(+)-Men-O]3WC -Et (500 mg, 0.72 mmol)

was dissolved in hexane (150 mL) with rapid stirring. Benzonitrile (1 mL) was added via

a gas tight syringe to the stirring hexane solution. The vessel was placed under vacuum,

sealed and stirred for 24 hours. After stirring, the volume was reduced to ca 2 mL of

hexane. Acetonitrile (5 mL) was added and a brown jelly-like solid was formed. The

solid was titurtated (15 minutes) until a brown powder formed. The brown solid was

filtered, washed with acetonitrile five times, and dried in vacuo (389 mg, 81% yield). 1H-

NMR (500 MHz, C6D6): = 4.77 (m, 1H); 2.91 (d, 1 H); 2.54 (m, 1H); 1.82 (d, 2H);

1.58 (qt, 2H); 1.34 (d, 3H); 1.19 and 1.15 (d of d, 8H) 1.0 (m, 1H). 13C-NMR (500 MHz,

67 C6D6): = 88.41, 51.59, 45.49, 35.12, 32.28, 25.87, 23.23, 23.13, 21.59, 16.45. IR

(KBr plates, Nujol mull): 1023 cm-1 (WN).

Synthesis of [(-)-Men-O]3WN. [(-)-Men-O]3WC -Et (750 mg, 1.09 mmol)

was dissolved in hexane (150 mL) with rapid stirring. Benzonitrile (1 mL) was added via

a gas tight syringe to the stirring hexane solution. The vessel was placed under vacuum,

sealed and stirred for 24 hours. After stirring, the volume was reduced to 2 mL of hexane.

Acetonitrile (5 mL) was added and a brown jelly-like solid formed. The solid was

titurtated (15 minutes) until a brown powder formed. The brown solid was filtered,

washed with acetonitrile five times, and dried in vacuo (512 mg, 72 % yield). 1H-NMR

(500 MHz, C6D6): = 4.77 (m, 1H); 2.91 (d, 1 H); 2.54 (m, 1H); 1.82 (d, 2H); 1.58 (qt,

2H); 1.34 (d, 3H); 1.19 and 1.15 (d of d, 8H) 1.0 (m, 1H). 13C-NMR (500 MHz,

C6D6): = 88.41, 51.59, 45.49, 35.12, 32.28, 25.87, 23.23, 23.13, 21.59, 16.45. IR

(KBr plates, Nujol mull): 1021cm-1 (WN).

t t t Reaction of ( BuO)3Mo≡N with W2(O Bu)6. W2(O Bu)6 (0.25 g) and hexanes

t (10 mL) were added to a Schlenk flask and allowed to stir. Separately ( BuO)3Mo≡N

(0.20 g) and hexanes (10 mL) were added to a second Schlenk flask and allowed to stir.

t t The ( BuO)3Mo≡N solution was added to the W2(O Bu)6 solution via cannula. The

mixture was left to stir at room temperature overnight. A white precipitate formed and

t the solution was filtered. The white solid was identified as (Bu O)3WN by NMR and

68 mass spectrometry. The filtrate was concentrated and yielded a red microcrystalline solid.

t + t + By mass spectrometry the ions Mo2(OBu )6 and MoW(OBu )6 were identified.

t t t Reaction of ( BuO)3Cr≡N with Mo2(O Bu)6. ( BuO)3Cr≡N (0.057 g, 0.2 mmol) was added with hexanes (10 mL) to a Schlenk flask and allowed to stir. Separately,

t Mo2(O Bu)6 (0.126 g, 0.2 mmol) was added with hexanes (10 mL) to a Schlenk flask and allowed to stir. Both flasks were placed in a dry ice/acetone bath and were allowed to stir

t for 1 h until the solution had cooled to -78 ºC. The ( BuO)3Cr≡N solution was slowly (15

t min) added via cannula to the Mo2(O Bu)6 solution. The mixture was kept at -78 ºC and

was allowed to stir for 2 h. The solvent was removed in vacuo. As the flask slowly

warmed a blueish-green liquied formed around the stopper of the flask. The blueish-

t green volatile compound was identified as Cr(O Bu)4 by comparison of the infrared

t 1 spectrum with that of known Cr(O Bu)4. H NMR of reaction mixture (C6D6 solvent,

t C6D5H reference, ppm): δ 1.59 (b.s.), δ 1.57 (s), δ 1.55 (s), δ 1.48 (s, ( BuO)3Mo≡N).

t + The mass spectrum of the dried reaction product showed the ( BuO)3Mo≡N) ion.

t t t Reaction of ( BuO)3Cr≡N with W2(O Bu)6. ( BuO)3Cr≡N (0.063 g, 0.22 mmol)

was added with hexanes (10 mL) to a Schlenk flask and allowed to stir. Separately,

t W2(O Bu)6 (0.177 g, 0.22 mmol) was added with hexanes (10 mL) to a Schlenk flask and

allowed to stir. Both flasks were place in a dry ice/acetone bath and were allowed to stir

t for 1 h until the solutions had cooled to -78 ºC. The ( BuO)3Cr≡N solution was slowly

t (15 min) added via cannula to the W2(O Bu)6 solution. The mixture was kept at -78 ºC

69 and was allowed to stir for 2 h. The solvent was removed in vacuo. As the flask slowly

warmed a blueish-green liquid formed around the stopper of the flask. The blueish-green

t volatile compound was identified as Cr(O Bu)4 by comparison of the infrared spectrum

t 31 1 with that of known Cr(O Bu)4. H NMR of reaction mixture (C7D8 solvent, C7D7H

t reference, ppm): δ 3.42 (s), δ 2.1 (s), δ 1.59 (s, ( BuO)3W≡N), δ 1.48 (s), δ 1.45 (s). The

t mass spectrum of the dried reaction product has the correct peak range for ( BuO)3W≡N).

t 15 t t 15 Reaction of ( BuO)3W≡ N with ( BuO)3Mo≡N. ( BuO)3W≡ N (0.0209 g, 0.05

t mmol) and ( BuO)3Mo≡N (0.0165 g, 0.05 mmol) were added to a NMR tube and allowed

1 to react in d8-THF at room temperature for 1 week. The H NMR spectrum of reaction

mixture shows no change from starting materials. The 15H NMR spectrum of reaction

t 15 mixture (d8-THF solvent, d7-THF reference, ppm): δ 828.8 (s, ( BuO)3W≡ N), δ 731.8

t 15 ( BuO)3W≡ N). Mass spectral analysis of the reaction products verifies the presence of

t 15 ( BuO)3Mo≡ N.

t t t Reaction of ( BuO)3W≡CMe with ( BuO)3Mo≡N. (BuO)3W≡CMe (0.0215 g,

0.05 mmol) was made in an NMR tube according to a previously reported method.

t ( BuO)3Mo≡N (0.0165 g, 0.05 mmol) was added to the tube and allowed to react at room

1 temperature for 1 week. H NMR of reaction mixture (C6D6 solvent, C6D5H reference,

t t ppm): δ 3.57 (s, 3, JHW = 7.2 HZ, ( BuO)3W≡CMe), δ 2.58 (s, 3, ( BuO)3Mo≡CMe), δ

t t 1.48 (s, 27, ( BuO)3Mo≡N), δ 1.46 (s), δ 1.44 (s, 27, ( BuO)3W≡CMe), δ 1.44 (s), δ 1.42

70 13 1 (s). C{ H} NMR (C6D6 solvent, C6D5H reference, ppm): δ 333.1 (s), δ 279.6 (s, 1,

t t ( BuO)3Mo≡CMe), δ 254.1 (s, 1, JCW = 306.5 HZ, ( BuO)3W≡CMe).

t t t Reaction of ( BuO)3W≡CMe with ( BuO)3Mo≡CPh. ( BuO)3W≡CMe (0.0054 g,

0.0125 mmol) was made in an NMR tube according to a previously reported method.

t ( BuO)3Mo≡CPh (0.0051 g, 0.0125 mmol) was added to the tube and allowed to react at

1 room temperature for 1 week. H NMR of reaction mixture (C6D6 solvent, C6D5H

t t reference, ppm): δ 7.49 (d, 2, ( BuO)3Mo≡CPh), δ 7.33 (d, 2, ( BuO)3W≡CPh), δ 7.23 (t,

t t t 2, ( BuO)3W≡CPh), δ 7.09 (t, 2, ( BuO)3Mo≡CPh), δ 6.87 (t, 1, ( BuO)3Mo≡CPh), δ 6.82

t t (t, 1, ( BuO)3W≡CPh), δ 3.57 (s, 3, JHW = 7.2 HZ, ( BuO)3W≡CMe), δ 2.58 (s, 3,

t t ( BuO)3Mo≡CMe), δ 1.49 (s, 27, ( BuO)3Mo≡CPh), δ 1.48 (s), δ 1.44 (s, 27,

t t 13 1 ( BuO)3W≡CMe), δ 1.42 (s, 27, ( BuO)3W≡CPh). C{ H} NMR of reaction mixture

(C6D6 solvent, C6D5H reference, ppm): δ 333.1 (s), δ 307.8 (s), δ 279.8 (s, 1,

t t ( BuO)3Mo≡CPh), δ 254.1 (s, 1, JCW = 306.5 HZ, ( BuO)3W≡CMe).

t i t t i Reaction of ( BuO)3W≡C Pr with ( BuO)3Mo≡N. (BuO)3W≡C Pr (0.0229 g,

t 0.05 mmol) and ( BuO)3Mo≡N (0.0165 g, 0.05 mmol) were added to a NMR tube and

1 allowed to react at room temperature for 1 week. H NMR of reaction mixture (C6D6

t i solvent, C6D5H reference, ppm): δ 4.05 (sept, 1, JHW = 6.85 HZ, ( BuO)3W≡C Pr), δ 3.11

t i t t i (sept, 1, ( BuO)3Mo≡C Pr), δ 1.48 (s, 27, ( BuO)3Mo≡N), δ 1.47 (s, 27, ( BuO)3Mo≡C Pr),

t i t t i δ 1.46 (s, 27, ( BuO)3W≡C Pr), δ 1.45 (s, 27, ( BuO)3W≡N), δ 1.24 (d, 6, ( BuO)3W≡C Pr),

t i δ 1.16 (d, 6, ( BuO)3Mo≡C Pr).

71 Preparation of samples for the determination of kinetics. All samples were

prepared in a NMR tube equipped with a J. Young® adapter. For all runs a stock solution

13 of Me CN in d8-THF was prepared by weighing 48.5 mg in a 5 mL volumetric flask to produce a 0.231 M solution. For the determination of the enthalpy parameters 890 µL of

15 d8-THF was added to 11.3 mg of (O-t-Bu)3W N via a gas tight syringe and transferred to

the NMR tube. Addition of 110 µL of the stock solution with a gas tight syringe followed.

Preparation occurred immediately before NMR spectra were collected. In this instance,

catalyst and nitrile concentration remained constant throughout the temperature range (50

C, 40 C, 35 C, 21 C). In each case the same was heated in the probe and once

the overnight run finished the sample was removed and placed in respective temperature

oil bath for the time.. In the case of the determination of the reaction order in nitrile, the

amount of catalyst remained the same while the amount of stock solution was changed

accordingly to desired ratio ([cat:nitrile] = 1:1, 1:0.5, 1:2).

The nitrile cleavage reaction involving Me13CN was monitored by 13C{1H} NMR spectroscopy. The parameters used were as follows: number of scans (NS = 15), number of data points (TD = 65 536), receiver gain (RG = 2896) and relaxation time (D1 = 75 s).

The deconvolution of 13C NMR spectra was done using XWIN-NMR version 3.5 PL6.

13 The T1 relaxation times for acetonitrile (15.2 s) C signals were measured at 298 K. The

Ernst equation (1) [where t1= T1 relaxation time, pw 90 = 90 pulse width, at =

acquistion time and d1 = delay time between pulses]. NMR probe temperatures were

72 calibrated with a sample of ethylene glycol and van Greet’s equation was used to

determine the optimal pulse widths for the delay time used in NMR experiments.

Calculation of the kinetics and activation parameters. The absolute concentration of catalyst in solution was determined by a proton integration of the O-t-Bu

resonance (s, 1.49 ppm) versus the Me13C N methyl resonance (d, 1.95 J=10.7 Hz). The

cleavage and atom exchange was measured by following the disappearance of a singlet at

115.9 ppm (Me13C N) and the appearance of a doublet at 115.95 and 115.82 ppm(Me13C 15N). The lorentizan deconvulation of 13C spectra was performed using

XWIN-NMR 3.5 PL6. All of the cleavage and atom exchanges reactions were of the type

A + B C + D where the rate law was determined (Equation 2) where = [A] – [A]eq.

By plotting ln[( /( (1-1/K) + [A]e + [B]e + (1/K)([C]e +[D]e))] vs time the slope is

inserted into Equation 2 to solve for kobs. The enthalpy parameters were calculated by

≠ ≠ plotting ln(kobs/T) vs (1/T) where the slope = - H /R and the intercept = ( S /R) + 23.8.

The order of nitrile was determined by doubling the concentration of the nitrile compared

to a constant catalyst concentration.

73 3.5 References

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75 (31) Alyea, E. C.; Basi, J. S.; Bradley, D. C. J. Chem. Soc. A. 1971, 772.

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77 CHAPTER 4

THEORETICAL AND SPECTROSCOPIC INVESTIGATIONS OF THE BONDING

AND REACTIVITY OF (RO)3M≡N MOLECULES, WHERE M = CR, MO AND W

Reproduced with permission from Inorganic Chemistry, 2009, 48, 828-837. Copyright 2009 American Chemical Society

4.1 Introduction Spurred by the discovery of metal-alkylidyne complexes that are active as catalysts for alkyne metathesis reactions, the interest in compounds containing metal-heteroatom multiple bonds has increased rapidly in the last twenty years.1-6

Transition metal-organic and transition metal-heteroatom multiple bonds are functional groups with diverse reactivities, ranging from stabilization of metals in high oxidation states to serving as the center of reactivity in a molecule.5 Some common reactions

involving the metal-heteroatom bond include atom or group transfer reactions and

metathesis reactions.7-11 The reactivity of metal-heteroatom molecules is greatly

influenced by the metal, the electron configuration of the metal, and the particular set of attendant ligands.

78 In traversing the transition elements from group 4 to group 10, one finds that the

electronegativity increases and that with increasing dn electron count one encounters what

has been described as an “OXO Wall” after which multiple bonding is not favored. Also

early transition metal terminal oxo groups are considered nucleophilic while for the later

elements in their high oxidation states they have been considered electrophilic. To a less

extent the same considerations have been applied to the terminal metal-nitride ligand.

Nucleophilic nitrides of the early transition elements are often subject to hydrolysis

yielding ammonia while the nitrides of high valent group VII~VIII elements have been

shown to react with tertiary phosphine, carbanions, dienes and thiolates.12-15

In this work we examine the electronic structure of a series of tris-alkoxide group

6 transition metal-nitrido molecules. The effect of the metal on the electronic structure is

t observed in ( BuO)3M≡N where M is Cr, Mo, or W, and the effect of substitutions on the

t i alkoxides is observed in the series of molecules (RO)3Mo≡N where R is Bu, Pr, or

16-18 CF3Me2C. The combination of gas phase UV photoelectron spectroscopy and

calculations employing density functional theory provide insight into the nature of the

frontier molecular orbitals in the series of compounds and the electron distribution within

the M≡N bond. A comparison is also made with simple organic nitriles.

79

Figure 4.1 Side and top (down the N-Cr bond) views of the crystal structure16 of t ( BuO)3Cr≡N showing the C3v symmetry.

4.2 Results and Discussion

4.2.1 General Bonding Considerations.

Unlike dinitrogen and organic nitriles, the multiple bonds to nitrogen in

metal-nitrido molecules involve metal d orbitals, which are also involved in interactions

with the attendant ligands. As a first step in considering the metal interactions with the

alkoxides, the oxygen donors simply serve to determine the relative ordering of the d

orbitals. The effect of the σ donor orbitals of the alkoxides on the d orbitals is shown on

the left side of Figure 4.2 for a typical (RO)3M fragment. The ligand σ donor orbitals

form a1 and e symmetry combinations, as illustrated in 1 below for the oxygen p orbitals

directed at the metal. The ligand e symmetry orbitals in 1 mix with the two sets of metal e

symmetry orbitals, the dx2-y2, dxy and dxz, dyz. The resulting upper e orbitals on the left of

Figure 4.2 are the antibonding counterparts of M-L σ bonds. At the trigonal N≡M–O

80 16, 17, 24 angle of ~101-108˚ for these alkoxides these orbitals are primarily dx2-y2, dxy in

character with smaller amounts of dxz, dyz. The lower e orbitals on the left of Figure 4.1

are mostly nonbonding and primarily dxz, dyz in character. The ligand a1 combination in 1

mixes with the metal dz2 orbital to destabilize the predominantly dz2 orbital. The resultant

order of the predominantly metal fragment orbitals is then: dxz, dyz ≤dz2 < dx2-y2, dxy which is the same as the crystal field splitting of d orbitals for the trigonal angles of these alkoxides.

A qualitative representation of the interaction of these L3M fragment orbitals with

the nitrogen p orbitals is shown in the middle of Figure 4.2. The HOMO is designated

with the label 2σ, and the SHOMO is label 1π. The 1π orbital is formed primarily from interaction of the N pπ orbitals with the predominantly metal dxz,dyz orbitals, and further

mixing with the predominantly metal dx2-y2, dxy orbitals is ignored in the diagram. This

order of 2σ above 1π is partly a consequence of the N(2s) contributions to this M≡N σ

orbital, similar to the description of the bonding in HCN and CH3CN. From ADF

calculations, the N(2s) contributions to the highest occupied orbital of σ symmetry of

these molecules is on the order of 30%.19 An additional reason for the destabilization of

the 2σ relative to the 1π is the contribution from the ligand a1 orbital shown on the left of 81 Figure 4.2. For the purposes of the present work, the splitting of the 2σ and 1π orbitals

from these interactions is small, particularly in comparison to effects of the oxygen π

donor orbitals discussed next. As one additional contrast to nitrogen triple bonds in

organic nitriles, the lowest unoccupied molecular orbitals are the predominantly metal

dx2-y2 and dxy orbitals labeled 1δ rather than the C-N π* orbitals of organic nitriles.

3 Figure 4.2 Orbital interaction diagram of a d -L3M fragment, where L is a simple σ donor ligand (left), with the N(p) orbitals (right). The L-M-L angle is ~110-116˚ for these molecules.

Alkoxide π-donor effects. Discussion of the effects of the oxygen π donor orbitals

on the electronic structure could be continued in terms of the interaction of the (RO)3M fragment with a nitrogen atom. However, as will be seen, the effects of the oxygen π donor orbitals are much more significant than a simple perturbation of the character and

82 relative energy of the predominantly metal d orbitals. An alternative approach is to view

the system in terms of (RO)3 and M≡N fragments. This approach separates the alkoxide ligand framework (the constant in the system) from the variable M≡N framework. Hence, it allows ready analysis of the effects of M substitution on the electronic structure of the system. Conversely, for the (RO)3 Mo≡N molecules where the alkoxide is varied, the

constant Mo≡N framework is separated from the alkoxide framework so that the effects

of alkoxide substitution on the electronic structure can be effectively probed.

For simplicity, the oxygen p orbitals that are π with respect to the metal are

separated into two groups: those parallel to the M≡N framework and those perpendicular

are shown in 2. The a1 (׀׀)to the M≡N framework. The parallel combinations a1 and e

combination has (׀׀)combination has reasonable overlap with the M≡N σ orbital, and the e

reasonable overlap with the M≡N π orbitals. The perpendicular ligand combinations a2 and e(┴) shown in 3 will interact much less significantly with the M≡N orbitals. In fact,

by symmetry the a2 combination does not interact with the M≡N orbitals at all. The

a2) follows from the> (׀׀)relative ordering of the six oxygen pπ combinations (a1

combinations, being of the (׀׀)nodal and overlap properties of the orbitals. The e(┴) and e

same symmetry, may further mix and split with each other. Most important, it should be

83 noted that the a2 orbital is completely antibonding and is the most destabilized of the

combinations.

Figure 4.3 Molecular orbital energy diagram showing the interactions between the six highest occupied π-type combinations of the (RO)3 fragment (middle) and M≡N 2σ and 1π orbitals with two different energies relative to the (RO)3 orbitals, left and right, of the M≡N orbitals.

A qualitative molecular orbital diagram illustrating the interactions of the (RO)3

π-type combinations with the M≡N orbitals is presented in Figure 4.3. The diagram

presents two possibilities with regards to the relative energies of the M≡N fragment

orbitals and the ligand orbitals. On the right of the diagram the relative energies and

interactions of the M≡N orbitals with the alkoxide orbitals are such that the 2a1 and 3e

84 orbitals become the highest occupied. On the left of the diagram the M≡N orbitals are more stable and the alkoxide a2 orbital becomes the highest occupied. Depending on the particular transition metal, the actual electronic structure of the (RO)3M≡N molecules

may correspond to either description. The relative ordering and character of the orbitals is

the subject of the present photoelectron and computational studies. Regardless of the

orbitals form bonding and antibonding (׀׀)relative energies, the ligand a1 and e

combinations with the M≡N σ and π orbitals, respectively. Hence, the definitions of

localized M≡N σ and π orbitals are no longer valid because of significant orbital mixing

with the strong π donor ligand orbitals. We will label the occupied valence molecular

orbitals of the (RO)3M≡N molecules according to the designations given in Figure 4.3.

Note that the top cluster, the 2a1, 3e, a2, and 2e, are all either antibonding between the

M≡N orbitals and the oxygen donor orbitals or antibonding between the oxygen donor

orbitals themselves (the a2). In contrast, the lower set of orbitals, the 1e and 2a1, are bonding both within the M≡N orbitals and between M≡N orbitals and the oxygen donor orbitals. An energy gap between the antibonding and bonding sets is expected.

The orbital interaction diagram, Figure 4.3, assumes that the relative energies of the ligand symmetry combinations remain constant as the metal is changed. However, as the metal-oxygen distances decrease (M=W ≈ Mo > Cr), the distances between the oxygen atoms also decrease and the intramolecular interactions between the oxygen atoms increase. The spread of the ligand symmetry orbitals will be greatest for the

85 (RO)3Cr≡N molecule because the bonding or antibonding nature of each particular

symmetry orbital becomes more important as the overlap between the oxygen p orbitals

increases. With this in mind, the ligand a2 combination will be least stable for the

distances between the oxygen atoms in the Cr molecule and more stable for the distances

in the Mo and W molecules.

Electronegativity Consideration. Some trends in the orbital stabilities and

characters may be anticipated from the relative electronegativity of the atoms. For

instance, in the cases of HC≡N, and CH3C≡N, the N atom is more electronegative than the C atom, so the highest occupied σ and π orbitals are polarized towards N, but

otherwise correspond directly to the 2σg and 1πu orbitals of N2. Simply put, both

hydrogen cyanide and acetonitrile are better σ donors than N2. The lower electronegativities of the metal atoms would by themselves suggest similar polarizations in the transition metal-nitrido molecules, but the effects of the attendant ligand on the metal must also be taken into account. The electronegativities of the transition metals decrease as a group is descended: Cr(VI)=3.37, Mo(VI)=2.20, and W(VI)=1.67.20

Therefore, the description of the Cr molecule would be expected to lie to the left of the descriptions of the Mo and W molecules in the interactions depicted in Figure 4.2. Based on these considerations, ionizations containing substantial M≡N σ and π character should decrease in energy as M = Cr > Mo > W. The M≡N polarity as well as the N atom basicity should increase as the group is descended (M = Cr < Mo < W).

86 The orbital framework developed thus far is sufficient for discussion of the

photoelectron spectra. The description to this stage has not included the full set of atomic

functions or the effects of mixing the oxygen p orbitals with the alkyl σ framework.

These interactions, which will be discussed in the computational section following

analysis of the photoelectron spectra, have lesser influence on the relative energies,

bonding, and polarity of the orbitals that make up the metal-nitride triple bond in these

tris-alkoxide complexes.

4.2.2 Photoelectron Spectroscopic Studies

Just as in the studies of triple bonds to nitrogen in simpler molecules,

photoelectron spectroscopy helps to quantify the nature of the orbital interactions and the

trends in energies in metal-nitrides discussed in the previous section. The He I

t photoelectron spectra of the ( BuO)3M≡N (M=Cr, Mo, or W) molecules in the 8.5 to 15.0

eV ionization energy range are presented in Figure 4.4. For comparison the spectrum of

tBuOH is included. The tBuOH spectrum provides a benchmark for understanding the

t contribution of the alkoxide ligands to the ( BuO)3M≡N spectra. The alcohol spectrum

consists of three distinct regions in the 10 to 15 eV range. Band A at 10.22 eV derives from the oxygen p orbital (lone pair) that is perpendicular to the C-O-H plane, and band

B derives from the oxygen p orbital (long pair) that is in the C-O-H plane, bisecting the

C-O-H angle. Both are strongly mixed with the C-C and C-H σ bonds of the t-butyl group,

and the in-plane orbital is additionally mixed with the O-H σ bond. The different mixings,

87 particularly with the O-H bond, account for the different energies of the ionizations. The

mixing in band B is more bonding in nature than the mixing in band A, as evidenced by

the width of the ionization band. Band C can be assigned to the O-C(σ), C-C(σ), as well

as the C-H(σ) ionizations.

The ionizations of the alcohol are related to those of the alkoxides by removing

the hydroxyl proton from the alcohol and placing the resulting alkoxide on the metal. In a

stepwise process, removal of the proton produces an alkoxide with three-fold symmetry

(C3v), and the oxygen-based ionization that was in band B, which was stabilized by

overlap with the H(1s) function, becomes degenerate with band A in an e symmetry pair

that is predominantly the oxygen px and py orbitals (assuming the z axis is along the

three-fold symmetry axis). The loss of stabilization provided by the proton in comparison

to the metal destabilizes all of the alkoxide ionizations relative to the alcohol. Judging by

the shift of band C from the alcohol to the alkoxide spectra, the predominantly oxygen px and py ionizations will be about 10 eV before overlap interactions with the M≡N and

neighboring ligand orbitals in the molecule. These interactions produce the spread of

ionizations from 8.5 to 11.5 eV in the spectra of the tris-alkoxide metal-nitride molecules.

The spread of 3 eV indicates substantial interaction.

88

Figure 4.4 He I photoelectron spectra of ROH and (RO)3M≡N (M = Cr, Mo, or W; R = tBu)

Metal Substitution. One of the most helpful means of assigning ionizations is to

look at a series of molecules with the same ligand set but different transition metals, because ionizations from metal-based orbitals will shift as the metal is changed. Looking at the spectra of the transition metal nitrides, the spectra can once again be separated into

89 three separate regions: A+A*(8.5-10.5eV), B(10.5 to 11.5 eV), and C(11.5 to 15.0 eV).

Region C is essentially the same as M is changed, implying the region is dominated by

ionizations from ligand-based orbitals. The region contains the C-C(σ), C-H(σ), as well

as the C-O(σ) and perhaps M-O(σ) ionizations on the low energy side of the region. Not

surprisingly, this region closely matches the corresponding region of tBuOH, with some

broadening on the leading edge. Band B is fairly consistent as M is changed, once again

implying dominant ligand character. However, subtle changes are apparent in the spectra

that signal the presence of ionizations from orbitals containing some metal character. Not

surprisingly, the leading bands (A+A*) of the spectra show the largest changes, implying

that this region contains the ionizations from the orbitals that contain the most metal character.

(RO) M≡N ROH 3 Cr Mo W 8.5 – 10.0 eV (A) 0.09 0.13 0.21 0.18 10.0 – 10.5 eV (A*) 0.065 10.5 – 14.5 eV (B+C) 0.91 0.80 0.77 0.82

Table 4.1 Relative areas of the He I spectra regions (A, A*, B+C) of tBuOH and t ( BuO)3M≡N relative to the total area (A+A*+B+C).

It is useful to compare the relative areas of the ionization bands of the Cr, Mo,

and W analogs, shown in Table 4.1. This is particularly helpful in showing that the 90 t ionization feature labeled A* in the ( BuO)3Cr≡N spectrum shifts into band A in the spectra of the Mo and W compounds, because the relative area of combined A*+A agrees

t well with the relative areas of band A for ( BuO)3M≡N (M = Mo or W). In terns of the molecular orbital model shown in Figure 3.3, band A contains the ionizations with antibonding character that form the first cluster of molecular orbitals (2a1, 3e, a2, and 2e), while band B contains the ionizations with bonding combinations of the M≡N σ and π with the ligand a1 and e (1a1 and 1e).

t Figure 4.5 He I photoelectron spectra of ( BuO)3M≡N (M = Cr, Mo, or W) in the 8 to 11 eV range. The major features in the spectra are labeled a, b, and c. The onset30 of ionization is designated by a (*).

91 Focusing on the region containing the first cluster of ionizations, photoelectron

spectra were recollected in the 8.5 to 10.5 eV region, Figure 4.5, so that a more detailed

analysis of the ionization features could be obtained. The ionization energies of the

t prominent features of the ( BuO)3M≡N spectra are given in Table 4.2. The experimental trend for the onset of ionization21 is W < Cr < Mo. For ionizations from similar orbitals

containing metal character, the expected trend of ionization energy is W < Mo < Cr.

Further evidence of this unexpected trend is obtained from the positions of the first band

of each molecule, where the experimental trend in ionization energies follows as Cr < W

< Mo. The observation that the Cr analog does not fall in line with the Mo and W systems

leads to the proposition that the first spectral feature of the Cr molecule is not due to

ionization of an orbital containing Cr≡N σ and/or π character. From the molecular orbital

t considerations shown in Figure 4.3, the first ionization of ( BuO)3Cr≡N more than likely corresponds to ionization of the a2 ligand combination.

(RO)3M≡N Ionization Energy (eV) M R (*)30 a b c IP(calc.) 9.43 Cr (CH ) C 8.77 9.03 10.20 8.42 3 3 9.57 Mo (CH3)3C 8.89 9.279.58 9.96 8.54 9.39 10.03 W (CH ) C 8.75 9.21 8.46 3 3 9.71 10.16 Mo (CH3)2HC 9.10 9.48 9.85 10.26 8.76 Mo CF3(CH3)2C 9.73 10.36 10.36 10.91 9.45

Table 4.2 Prominent features in the He I photoelectron spectra, and the calculated lowest ionization potentials (IP) by ADF2007.01. See Figure 4.4 for definitions of peaks. 92 As mentioned before, this orbital is completely antibonding between the oxygen

atoms and shorter distances between the oxygen atoms will lead to a less stable orbital

and lower ionization energy. On the other hand, since the first spectral features of the Mo

and W analogs do follow the expected trend for metal-based ionizations, it is likely that

the first ionization features of these molecules are due to ionization of orbitals containing

some M≡N σ and/or π character, specifically the 2a1 and 3e orbitals in Figure 4.3. The

ligand a2 orbital, being completely non-bonding with respect to the metal, should be

stabilized as one moves from Cr to Mo to W. Therefore, the ionization from the a2 orbital more than likely occurs under b for the Mo analog and under b or c for the W analog.

This then leaves band c to be tentatively assigned to the ionization of the other e combination, labeled 2e in Figure 4.3. The spectrum of the W complex gives evidence of spin-orbit splitting in this ionization as expected for this assignment.

He II Spectra. To provide additional evidence of the position of ionizations that contain M≡N σ and π character, the photoelectron spectra were recollected using a He II photon source. Experimental cross-sections for ionizations from molecules roughly follow the trends predicted by the Gelius model, where molecular cross sections are treated as the sum of the atomic cross sections of the atoms that contribute to the molecular orbital character.22 Yeh and Landau have performed calculations to predict the

cross-sectional behavior of the atomic elements.22 The calculated valence atomic He

II/He I ionization cross-section ratios for the atoms in these molecules are H(0.153); C2p

93 (0.306); N2p (0.4); O2p (0.639); F2p (0.905); Cr3d (0.925); Mo4d (0.323); and W5d

(0.322). Although ionizations from Mo and W-based orbitals are predicted to drop in

intensity when He II is used as the photon source, experimentally they are known to gain

in intensity under He II radiation.23 The calculated cross-sections do not account for the

Super-Koster Kronig transitions that occur for second and third row transition metals;

these processes increase the intensity of ionizations from orbitals containing metal

character.23 Thus in comparing He II spectra with He I spectra, ionizations with metal

character are expected to grow with respect to those with oxygen and nitrogen character,

which in turn are expected to grow with respect those with carbon and hydrogen character.

The He II ionization intensities of the (RO)3M≡N analogs in the 8 to 15 eV region are

compared to the He I ionization intensities in Figure 4.6. The ionizations in the 8.5 to

11.5 eV region (bands A, A* and B grow in intensity relative to band C under He II

radiation, consistent with substantial oxygen, metal, and nitrogen character in regions A

and B substantial C-C σ and C-H σ character in region C. Not surprisingly, the ionization between 8.0 and 10.5 eV (bands A and A*) show the most growth in intensity when He II

is used as the photon source, indicating the most metal character in the ionizations of this

region.

94

t Figure 4.6 He II photoelectron spectra of ( BuO)3M≡N (M = Cr, Mo, or W). The data points are the He II spectra shown in comparison to the He I spectra (solid lines). The positions of the lowest energy ionizations with M≡N σ and π character are designated by a (*).

t Looking more closely at the ( BuO)3Cr≡N spectra, the most growth under He II radiation occurs around 9.5 eV (the high end of band A designated by *); therefore, the ionizations with Cr≡N σ and π character must occur in this region of the spectrum. This does not correspond to the first ionization feature of the Cr spectra. Based on this data, the first ionization does not correspond to ionization of a Cr-containing orbital, consistent with assignment of the first ionization of the Cr compound to the a2 ligand combination.

95 Looking at the 8.5 to 11.5 eV region of the Mo molecule, the most growth occurs in the

beginning of band A under He II radiation. A similar conclusion is reached when looking

at the spectra of the W molecule, although the intensity changes are not as pronounced.

Spin-orbit coupling when orbitals are close in energy and contain W character will

increase the mixing between orbitals and diminish the intensity effects. Nonetheless, the

assignment of M≡N σ and π character to the first ionization feature of the Mo and W spectra is supported by the He II data analysis. Although the positions of the ionization containing the most metal character are identified in the He II spectral analysis, the overall growth in the region points toward extensive mixing between the M≡N orbitals and the alkoxide framework.

Ligand Substitution. Another useful technique for assigning ionizations in photoelectron spectroscopy is to study a series of molecules with varying ancillary ligands attached to the same transition metal center. In this particular instance, we have studied the (RO)3Mo≡N molecules where R = C(CH3)3, CH(CH3)3, or CCF3(CH3)2. This allows one to study the effects of alkoxide substitution on the electronic structure of the transition metal nitrides. The general layout of the spectra from 8.0 to 15.0 eV is unaffected by alkoxide substitution; the spectra still consist of three distinct regions: A, B, and C (see Figure 4.7). The spectral features all shift in accordance with the expected donor capacity of the alkoxide ligand: -OC(CH3)3 > -OCH(CH3)2> -OCCF3(CH3)2. In general, the shifts correlate well with the shift of the lone pair ionizations of the free

96 alcohols, where (CH3)3COH = 10.22eV, (CH3)2HCOH = 10.36 eV, and (CH3)2(CF3)COH

= 11.11 eV. Although the overall layout of the spectra does not change as the alkoxide donor identity is changed, subtle changes are present in ionization band A, shown in

Figure 4.8. The prominent ionization features in band A are labeled a, b, and c, and, as seen in Table 4.2, these features shift in accordance with the overall donor ability of the

t alkoxide ligand. The cross-sectional changes seen in the ( BuO)3Mo≡N He II spectrum

are also seen in the He II spectra of the substituted alkoxide molecules (see Figure 4.9).

The leading edge of band A grows substantially with respect to the rest of the spectrum

for all of the substituted molybdenum nitrides. Hence, changing the alkoxide donor group

serves only to shift the overall ionization energies in the spectra and the ionizations from

the M≡N σ and π remaining the first ionizations of the molybdenum-nitride molecules.

97

t i Figure 4.7 He I photoelectron spectra of (RO)3Mo≡N (Ra= Bu, Rb= Pr, Rc= CH3)2CF3C).

t i Figure 4.8 He I photoelectron spectra of (RO)3Mo≡N, R= Bu(top), R= Pr(middle), R= 3 CF3(CH )2C (bottom) from 8.5 to 12 eV. The major ionization features in the spectra are labeled a, b, and c. The onset of ionization is designated by a (*). 98

t i Figure 4.9 He II photoelectron spectra of (RO)3Mo≡N (Ra= Bu, Rb= Pr, Rc= CH3)2CF3C). The data points are the He II spectra shown in comparison to the He I spectra (solid lines). The positions of the lowest energy ionizations with M≡N σ and π character are designated by a (*).

4.2.3 Density Functional Studies

t First, the gas phase geometries of the ( BuO)3M≡N molecules, where M = Cr, Mo

and W, were calculated by employing density functional theory as implemented by

ADF2007.01. Computational details are given in the experimental section. The calculated

bond distances and angles for the C3v symmetric (CO)3M≡N cores are given in Table 4.3 where a comparison is made with their observed solid-state molecular structures.16,17,24

Whereas the solid-state structure for M = Mo and W contain an infinite chain involving

99 (M≡N→M≡N→)∞ interactions with very long dative N→M bond distance > 2.5 Å, the

chromium containing molecule is discrete and thus might be expected to more closely represent the calculated gas phase structure. In comparing the experimental and calculated we note first the relative good agreement and then that the maximum deviations are seen for tungsten where the calculated W≡N distance is 1.715 Å and the observed is 1.740 Å. The observed lengthening of the W≡N bond in the solid-state structure may well rest with its strong dative bond.

Cr Mo W (tBuO) M≡N 3 Exp. Calc. Exp. Calc. Exp. Calc. M-N (Å) 1.538 1.549 1.661 1.680 1.740 1.715 M-O (Å) 1.739 1.765 1.882 1.904 1.872 1.910 O-C (Å) 1.442 1.452 1.452 1.462 1.475 1.467 C-C(Å) (avg.) 1.499 1.530 1.522 1.529 1.526 1.528 N-M-O (°) 108.2 109.1 103.3 107.4 101.6 107.3 M-O-C (°) 137.4 133.9 135.1 134.2 136.6 134.2 O-C-C (°) (avg.) 106.9 107.7 108.1 107.6 108.6 107.5 O O (Å) 2.86 2.890 3.17 3.146 3.18 3.159

Table 4.3 Comparison of the ADF2007.01 optimized geometrical parameters with the t crystal structure parameters for ( BuO)3M≡N.

The calculated orbital energies of the highest six occupied frontier orbitals for

each of the metal containing nitrides are given in Table 4.4 The HOMOs, which are

underlined in Table 4.4, follow the expected trend and indicate that for M = Cr, the

HOMO is indeed an alkoxide oxygen pπ combination of a2 symmetry. We also note the 100 calculations predict a significant energy gap between the HOMO-4 and HOMO-5 orbitals

of ~1.0 eV. Thus of the six occupied frontier orbitals there is a set of four (a2, 2a1, 3e, 2e) above two (1e, 1a1). The principal atomic orbital contribution of these frontier orbitals is

given in Table 4.5.

Label Orbital Makeup Cr Mo W

a2 OR (a2) -6.21 -6.44 -6.53 2a1 M≡N σ – OR (a1) -6.59 -6.32 -6.27 3e M≡N π and OR (e) -6.54 -6.60 -6.40 2e M≡N π and OR (e) -7.07 -6.87 -6.83 M≡N π and OR (e) 1e -7.80 -7.86 -7.82 and M(dxy, dx2-y2) 1a1 M≡N σ + OR (a1) -8.00 -7.95 -7.80

Table 4.4 The calculated orbital energies (in eV) of the highest six occupied orbitals for t ( BuO)3M≡N.

In looking at the data shown in Table 4.5, one is struck by orbital mixing in what

might formally constitute the metal-nitrogen triple bond as represented by the valence

bond description M≡N. Only the a2 orbital is in a sense easily described as ligand based lone pair combination. The principal features of the M≡N σ component arise from 2a1 and 1a1 where it can be seen that for M=W 2a1 has a dominant contribution while for

M=Cr it is the more stabilized 1a1 orbital. The M≡N π orbitals are seen to be extensively

mixed with alkoxide ligand orbitals. The M≡N π bonding orbitals have e symmetry and

as can be seen from Table 4.5 the entries for chromium and molybdenum are similar and 101

Cr Mo W a2 76% O p 74% O p 73% O p 17% C p 18% C p 19% C p

2a1 3% N s 3% N s 6% N s 37% N p 42% N p 53% N p 4% Cr dz2 6% Mo dz2 10% W dz2 34% O p 32% O p 18% O p 15% C p 8% C p 4% C p 3e 7% N p 8% N p 43% N p 7% Cr dxz,dyz 5% Mo dxz,dyz 19% W dxz,dyz 2% W p 56% O p 57% O p 20% O p 17% C p 18% C p 6% C p 2e 32% N p 37% N p 9% N p 11% Cr dxz,dyz 12% Mo dxz,dyz 2% W dxz,dyz 3% Cr dxy,dx2-y2 1% Mo dxy,dx2-y2 5% Cr p 4% Mo p 2% W p 25% O p 26% O p 56% O p 12% C p 11% C p 15% C p 1e 12% N p 9% N p 5% N p 12% Cr dxy,dx2-y2 10% Mo dxy,dx2-y2 9% W dxy,dx2-y2 11% Cr dxz,dyz 9% Mo dxz,dyz 6% W dxz,dyz 10% O p 10% O p 15% O p 36% C p 40% C p 44% C p 12% H s 13% H s 14% H s

1a1 3% N s 3% N s 2% N s 23% N p 17% N p 10% N p 26% Cr dz2 20% Mo dz2 15% W dz2 2% Cr p 3% Mp p 2% W p 6% O p 10% O p 19% O p 26% C p 31% C p 34% C p 8% H s 8% H s 12% H s

t Table 4.5 Calculated primary orbital characters for ( BuO)3M≡N.

quite different from those for tungsten. For M=Cr and Mo, the metal dxz, dyz contribution is largely split between the 1e and 2e orbitals with the latter having the greater N 2p(π)

102 character. For M=W, the 3e orbital carries the major contribution of metal dxz, dyz and N pπ orbitals. Despite the similarity in the frontier orbital atomic compositions for M=Cr and Mo, the relative energies of the orbitals are different. For M=Cr, the order is a2>3e>2a1; for M=Mo, 2a1>a2>3e and for M=W, 2a1>3e>a2 and these are depicted in

Figure 4.10. It is also particularly interesting to note the closeness in energy for

t ( BuO)3W≡N of the W≡N σ/lone pair with that of the W≡N π bonding MO.

t Figure 4.10 Correlation diagram of the Kohn-Sham orbital energies of ( BuO)3M≡N.

103 A pictorial representation of the native of the key frontier orbitals is given in

Figure 4.11. From these views the 2a1 orbital for M=W is somewhat more extended toward the vacant site while the corresponding orbital for M=Cr is more delocalized.

Although the change is subtle, it likely contributes to the observation that the t ( BuO)3W≡N molecules are associated in the solid-state while the chromium analogue exists as a monomer. Also in Figure 4.11 the principal W≡N π bonding orbital is clearly seen to be the 3e orbital while for M=Cr, the π bonding is less obvious but is comprised of in parts of the 1e and 2e orbitals.

104 t t ( BuO)3W≡N ( BuO)3M≡N (M=Cr,Mo)

2a1 2a1

3e 3e

2e 2e

1e 1e

Figure 4.11 Molecular orbital plots of 2a1, 3e, 2e, and 1e valance orbitals (contour value t = ±0.04) for ( BuO)3M≡N where M = Cr, Mo, and W. The orbital plots for molecules containing Cr and Mo are represented in the same set on the right because they look similar.

The calculated lowest ionization energies are given in Table 4.2 along with a comparison with the experimental values. In all cases the calculated ionization energies are smaller than the experimental but differ by less than 1 eV. The calculated values

105 correlated well with the experimental results with regard to changing the metal

Cr

(CH3)2HCO < (CF3)(CH3)2CO. The orbital origin of ionization is calculated to be for

M=Cr, a2; for M=Mo, 2a1, and for M=W, 3e. Thus, for tungsten we see an example of

where Koopmans’ theorem breaks down as it does indeed for N2. [Although strictly

speaking Koopmans’ theorem applies to Hartree-Fock orbital eigenvalues and not directly

t to Kohn-Sham orbital energies.] For ( BuO)3W≡N we have the ground state

2 4 2 t + 2 2 3 configuration ···a2 (3e) (2a1) and for [( BuO)3W≡N] , ···a2 (2a1) (3e) . For N2 in its

2 4 + 4 1 ground state the order is ···(2σg) (1π) and for N2 , ···(1π) (2σg) . The calculated

ionization energies for the W≡N 2a1 and 3e orbitals for M=W are 8.60 and 8.46 eV, respectively.

The calculations also produce a number of other interesting comparisons within this series. The results of Mulliken charges on the metal, nitrogen and oxygen atoms are compared in Table 4.6 along with the molecules’ dipole moments and M≡N bond

dissociation energies. It is clearly seen that the effective positive charge on the metal and

the negative charge on nitrogen increases down the series of the group 6 elements. This

results in a change of sign of the dipole moment but only for M=W is the sign negative

because of the influence of the negative charges on the oxygen atoms. The reversed sign

of the dipole moment for tungsten is the only example where the simple bond polarity of

the metal-nitride bond, Mδ+-Nδ- is seen to determine the overall direction of the dipole. In

106 the case of ((CF3)(CH3)2CO)3Mo≡N the large positive dipole arises from the position of the three CF3 group in an anti-configuration with respect to the W≡N bond.

t (BuO)3M≡N (RO)3Mo≡N

Cr Mo W (CH3)2HC CF3(CH3)2C M +1.51 +1.95 +2.00 +1.89 +1.97 N -0.53 -0.63 -0.66 -0.60 -0.60 O -0.67 -0.75 -0.77 -0.75 -0.75 µ(debye) 0.569 0.129 -0.417 -0.108 5.488 BDE(kcal/mol) 127.2 163.6 181.3 162.8 162.1

Table 4.6 Mulliken charges, molecular dipole moment (µ) and M≡N bond dissociation

energies (BDE) calculated by ADF2007.01 for (RO)3M≡N.

The M≡N stretching frequencies were also calculated and these followed the trend

observed experimentally: Cr>Mo~W though the calculated and experimental values

differed significantly. Experimental (calculated) frequencies in cm-1: M=Cr, 1037(1110);

M=Mo, 1020(1045); M=W, 1010(1048). Rather interestingly the experimental to

calculated values of δ15N (relative to 15NH3) were in close agreement: M=Mo, 828(822);

t M=W, 732(735). The calculated value of ( BuO)3Cr≡N was 935 ppm.

4.3 Conclusions

From the experimental and computational studies reported herein, the bonding in the molecules (RO)3M≡N can be understood in terms of extensions of the multiple

bonding in N≡N and CH3C≡N. However, unlike N2 and CH3CN, the present study

107 indicates the importance of the alkoxide donors to the electronic structure. Because of

extensive mixing with the oxygen orbitals, the 2a1 orbital of the tungsten and

molybdenum analogs, which contains substantial N(2pz) character, contains little metal

dz2 character and is largely non-bonding. Therefore, this orbital is capable of donating

electrons with little cost to the stability of the molecule. This explains the formation of

the linear chains of the Mo and W molecules in the solid state with only small structural

changes in the molecules. The HOMO of the chromium molecules is the

highest-occupied alkoxide a2 orbital because of the strong antibonding character between

the oxygen atoms and the smaller metal atom that serves to provide short Cr-O and O-O

distances. Therefore, the chromium molecule is easier to oxidize than would be

anticipated in comparison to the molybdenum and tungsten molecules.

Both the charge distribution of the molecules and the N atom basicity are

directly dependent on the identity of M. The polarization of the M≡N bond increases as

M=Cr

Because the 2a1 orbital of the Cr molecules is not the HOMO and the N atom is less basic in the Cr molecule than in the Mo and W molecules, the Cr molecule has less tendency to form linear chains in the solid state.

The substitutions on the alkoxide donor ligands studied here have little affect on the electronic structure of the (RO)3Mo≡N molecules other than shifting all of the ionization energies together, again pointing to the extensive delocalization of the

108 molecular orbitals. The orbital compositions and relative orbital positions are not

substantially changed because all of the orbitals are shifted similarly in accordance with

the overall donor ability of the alkoxide ligand.

The reactivity of the transition metal nitrides, analogous to that of the organic

nitriles, is not particularly surprising in light of this understanding of the electronic

structure and bonding. The W≡N molecule not only has the greatest charge dipole

(Mδ+-Nδ-) but also the greatest N-atom basicity. The M≡N bond strength increases as

M=CrMo>>

Cr. This underscores the importance of not relating thermodynamics of bonds to their kinetic lability.

4.4 Experimental and Computational Procedures

General Methods. All manipulations were carried out using an argon (Ar) or dinitrogen (N2) atmosphere and standard air and moisture sensitive techniques in a

Vacuum Atmospheres Glovebox or Schlenk line. Solvents were distilled from CaH2 or

Na/Benzophenone ketyl, purged of oxygen with either Ar or N2 and stored over 4 Å

sieves. All reagents were purchased from Aldrich unless otherwise stated and used

without further purification. tert-Butanol was vacuum distilled from CaSO4.

Fluoroalcohols (Lancaster Synthesis) were distilled under Ar and stored over 4 Å sieves.

Molybdenum pentachloride (Strem Chemicals) was used as purchased. Lithium, sodium

109 or potassium alkoxide and fluoroalkoxide salts were prepared using a reported method25.

Molybdenum tetrachloride-bisacetonitrile (MoCl4(CH3CN)2) was prepared via a reported

26,27 t t method. The compounds ( BuO)3MN, where M = Cr, Mo, W, and M2(O Bu)6 (where

M = Mo and W) were prepared via reported syntheses.16,18,28,29 The molybdenum nitrido

alkoxides and fluoroalkoxides were prepared via modification of a reported synthesis.17

Spectroscopic methods. Proton (1H) and fluorine (19F) NMR were carried out on

a Varian Gemini 2000 spectrometer operating at a 300 MHZ proton and 282 MHZ fluorine

NMR Larmor frequencies. Infrared (IR) Spectra were taken as KBr pellets on a Nicolet

510P FT-IR spectrophotometer using OMNI E. S. P. software. Mass spectra were taken on a Kratos MS 80 high resolution mass spectrometer using Negative Ion CI with methane (CH4) as reagent gas. A Kratos MS 25 RFA double focusing magnetic sector

mass spectrometer was also used to record the missed metal spectrum. A positive ion EI

source with a trap current of 100 µA at a temp of 225 °C at 52 eV. A 3kV analyzer was

used with a resolution of 2000 using the 5% peak height definition. The scanning rate

was 5 sec/decade with a mass range of 1100 to 275. A third party (MSS) data system was

used.

Photoelectron spectra. The photoelectron spectra were recorded using an

instrument that features a 36 cm radius, 8 cm gap McPherson hemispherical analyzer with custom-designed sample cells, detection system, and control electonics.30 The excitation source was a quartz lamp with the ability, depending on operating conditions,

110 to produce He Iα (21.218 eV) or He IIα (40.814 eV) photons. The ionization energy scale

2 2 was calibrated by using the E1/2 ionization of methyl iodide (9.538 eV). The argon P3/2 ionization was also used as an internal calibration lock for the energy scale during He I and He II data collection runs. Resolution (measured as full-width-at-half-maximum of

2 the argon P3/2 ionization) was 0.016-0.024 eV during He I data collection. Assuming a

linear dependence of analyzer intensity to the kinetic energy of the electrons within the

energy range of these experiments, all data were intensity corrected with the

experimentally-determined analyzer sensitivity function.

Because discharge sources are not monochromatic31, each spectrum was

corrected for the presence of ionizations from other source lines. The He I spectra were

corrected for ionizations from the He Iβ line (1.957 eV) higher in energy with 3% of the

intensity of ionizations from the He Iα line. He II spectra were similarly corrected for

ionizations from the He IIβ line (7.568 eV higher in energy and 12% of the intensity of

the He IIα line.)

The samples sublimed cleanly with no detectable evidence of decomposition

products in the gas phase or as solid residue. The sublimation ranges (°C at ~10-4 Torr)

t t t for each molecule were ( BuO)3Cr≡N, -4 to 20; ( BuO)3Mo≡N, 38 to 57; ( BuO)3W≡N, 58

i to 78; ( PrO)3Mo≡N, 42 to 75; (Me2CF3CO)3Mo≡N, 28 to 61. The temperatures were

measured using a “K” type thermocouple attached directly to the ionization cell through a

vacuum feedthrough.

111 Data Analysis. In the figures of the photoelectron spectra, the vertical length of

each data mark represents the experimental variance of that point.32 The ionization bands

are represented analytically with the best fit of asymmetric Gaussian Peaks. Due to the

extensive overlap of many ionization features, the individual peaks used to obtain an

analytical representation of a band do not necessarily represent separate ion states. The

number of peaks used was the minimum necessary to get an analytical representation of

the He I spectrum. For fitting the He II spectra, the peak positions and half-widths were

fixed to those of the He I fit, and only the relative intensities were allowed to vary.

The confidence limits for the relative integrated peak areas are ±5%. The

primary source of uncertainty is the determination of the baseline. The baseline is caused

by electron scattering and is taken to be linear over the small energy range of these

spectra. The fitting procedures used to fit the spectra have been described in more detail

elsewhere.32

Computational Details. All DFT calculations were performed using the

Amsterdam Density Functional (ADF) software package, version 2007.01,33 developed

by Baerends and co-workers.34 The numerical integration scheme used was developed by

teVelde et al.,35 and the geometry optimization procedure was based on the method of

36 Versluis and Ziegler. All geometry optimizations were carried out under C3v symmetry

by using the local exchange-correlation potential of Vosko et al.37 and the non-local exchange and correlation corrections of Perdew and Wang (PW91).38 All atoms were

112 described using a triple-ζ Slater type orbital (STO) basis set with one polarization

function (TZP); the core was frozen at the 2p, 3d and 4f level for chromium,

molybdenum and tungsten, and 1s for the second row atoms. All atoms were corrected

for scalar relativistic effects by using the Zeroth Order Regular Approximation (ZORA)

method.39 All calculations utilized an INTEGRATION value of 6, geometries were

converged to a gradient of 10-3 au/Å. The self-consistent field energy was converged to a value of 10-6. Frequencies were calculated by numerical differentiation of energy

gradients in slightly displaced geometries using double-sided displacements.40 Molecular

orbitals were visualized with the molecular graphics package MOLEKEL, a free utility

from the Swiss Center for Scientific Computing41. The plots were created with an

isosurface value of ±0.04.

113 4.5 References.

(1) Caulton, K. G,; Chisholm, M. H.; Doherty, S.; Folting, K. Organometallics 1995, 14, 2585.

(2) Blau, R. J.; Chisholm, M. H.; Eichorn, B. W.; Huffman, J. C.; Kramer, K. S.; Lobkowsky, E. B.; Streib, W. E. Organometallics 1995, 14, 1855.

(3) Baxter, D. V.; Chisholm, M. H.; Distasi, V. F.; Haubrick, S. T. Chemistry of Materials 1995, 7, 84.

(4) Chisholm, M. H.; Foltingstreib, K.; Tiedtke, D. B.; Lemoigno, F.; Eisenstein, O. Angew Chem Int Edit 1995, 34, 110.

(5) Mayer, J. M.; Nugent, W. A. Metal-Ligand Multiple Bonds: the Chemistry of Transition Metal Complexes Containing Oxo, Nitrido, Imido, Alkylidene, or Alkylidyne Ligands; John Wiley & Sons: New York, 1988.

(6) Wang, X.; Andrews, L.; Lindh, R.; Veryazov, V.; Roos, B. O. J. Phys. Chem. A 2008, 112, 8030.

(7) (a) Burroughs, B. A.; Bursten, B. E.; Chen, S.; Chisholm, M. H.; Kidwell, A. R. Inorg. Chem. 2008, 47, 5377. (b) Chisholm, M. H.; Delbridge, E. E.; Kidwell, A. R.; Quinlan, K. R. Chem. Commun. 2003, 126.

(8) (a) Geyer, A. M.; Wiedner, E. S.; Gary, J. B.; Gdula, R. L.; Kuhlmann, N. C.; Johnson, M. J. A.; Dunietz, B. D.; Kampf, J. W. J. Am. Chem. Soc. 2008, 130, 8984. (b) Gdula, R. L.; Johnson, M. J. A. J. Am. Chem. Soc. 2006, 128, 9614. (c) Gdula, R. L.; Johnson, M. J. A.; Ockwig, N. W. Inorg. Chem. 2005, 44, 9140.

(9) Cherry, J.-P. F.; Johnson, A. R.; Baraldo, L. M.; Tsai, Y.-C.; Cummins, C. C.; Kryatov, S. V.; Rybak-Akimova,E. V.; Capps, K. B.; Hoff, C. D.; Harr, C. M.; Nolan, S. P. J. Am. Chem. Soc. 2001, 123, 7271

(10) Bendix, J. J. Am. Chem. Soc. 2003, 125, 13348.

(11) Woo, K. L.; Goll, G. J.; Czapla, D. J.; Hays, A. J. J. Am. Chem. Soc. 1991, 113, 8478.

114 (12) (a) Wong, T.-W.; Lau, T.-C.; Wong, W.-T. Inorg. Chem. 1999, 38, 6181. (b) Chiu, S.-M.; Wong, T.-W.; Man, W.-T.; Wong, W.-T.; Peng, S.-M.; Lau, T.-C. J. Am. Chem. Soc. 2001, 123, 12720. (c) Chan, P.-M.; Yu, W.-Y.; Che, C.-M.; Cheung, K.-K. J. Chem. Soc. Dalton Trans. 1998, 3183.

(13) Crevier, T.J.; Bennett, B.K.; Soper, J.D.; Bowman, J.A.; Dehestani, A.; Hrovat, D.A.; Lovell, S.; Kaminsky, W.; Mayer, J.M. J. Am. Chem. Soc. 2001, 123, 1059.

(14) Maestri, A.G.; Cherry, K.S.; Toboni, J.J.; Brown, S.N. J. Am. Chem. Soc. 2001, 123, 7459.

(15) Huynh, M.V.; White, P.S.; Meyer, T.J. J. Am. Chem. Soc. 2001, 123, 9170.

(16) Chui, H. T.; Chen, Y. P.; Chuang, S. H.; Jen, J. S.; Lee, G. H.; Peng, S. M. Chem. Commun. 1996, 139.

(17) Chan, D. M. T.; Chisholm, M. H.; Folting, K.; Huffman, J. C.; Marchant, N. S. Inorg. Chem. 1986, 25, 4170.

(18) Schrock, R. R.; Listemann, M. L.; Sturgeoff, L. G. J. Am. Chem. Soc. 1982, 104, 4291.

(19) All % characters are from ADF2007.01 geometry optimizations.

(20) Sanderson, R. T. Simple Inorganic Substances; Krieger: Malabar, FL, 1989.

(21) Onset of ionization (*) = ionization energy at which the amplitude is 10% of the maximum amplitude of the lowest energy Gaussian peaks used to fit each spectrum.

(22) Yeh, J.J.; Lindau, I. Atomic Data and Nuclear Data Tables 1985, 32, 1.

(23) Green, J. C. Acc. Chem. Res. 1994, 27, 131.

(24) Chisholm, M. H.; Hoffman, D. M.; Huffman, J. C. Inorg. Chem. 1983, 22, 2903.

(25) Samuels, J. A.; Lobkovsky, E. B.; Folting, K.; Huffman, J. C.; Zwanziger, J. W.; Caulton, K. G. J. Am. Chem. Soc. 1993, 115, 5093.

(26) Dilworth, J. R.; Richards, R. L. Inorg. Synth. 1980. 20. 119.

115 (27) Allen, E. A.; Brisdon, B. J.; Fowles, G. W. A. J. Chem. Soc. 1964, 4531.

(28) Chisholm, M. H.; Cotton, F. A.; Murillo, C. A.; Reichert, W. W. Inorg. Chem. 1977, 16, 1801.

(29) Akiyama, M.; Chisholm, M. H.; Cotton, F. A.; Extine, M. W.; Haitko, D. A.; Little, D.; Fanwick, P. E. Inorg. Chem. 1979, 18, 2266.

(30) Lichtenberger, D. L.; Kellogg, G. E.; Kristofzski, J. G.; Page, D.; Turner, S.; Klinger, G.; Lorenzen, J. Rev. Sci. Instrum. 1986, 57, 2366.

(31) Turner, D. W.; Baker, C.; Baker, A. D.; Brundle, C. R. Molecular Photoelectron Spectroscopy; Wiley-Interscience: New York, 1970.

(32) Lichtenberger, D. L.; Copenhaver, A. S. J. Electron. Spectrosc. Relate. Phenom. 1990, 50, 335.

(33) ADF2007.01; SCM, Theoretical Chemistry, Vrije Universiteit: Amsterdam, The Netherlands; http://www.scm.com.

(34) (a) Baerends, E. J.; Ellis, D. E.; Ros, P. Chem. Phys. 1973, 2, 41. (b) te Velde, G.; Baerends, E. J. J. Comput. Phys. 1992, 99, 84. (c) Fonseca Guerra, C.; Snijders, J. G.; te Velde, G.; Baerends, E. J. Theor. Chim. Acc. 1998, 99, 391. (d) Bickelhaupt, F. M.; Baerends, E. J. ReV. Comput. Chem. 2000, 15, 1. (e) te Velde, G.; Bickelhaupt, F. M.; Fonseca Guerra, C.; van Gisbergen, S. J. A.; Baerends, E. J.; Snijders, J. G.; Ziegler, T. J. Comput. Chem. 2001, 22, 931.

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116 (41) (a) MOLEKEL4.3: P. Flükiger, H. P. Lüthi, S. Portmann, J.Weber, Swiss Center for Scientific Computing, Manno, Switzerland,2000–2002; (b) S. Portmann, H. P. Lüthi, Chimia 2000, 54,766.

117 CHAPTER 5

THEORETICAL STUDY OF METATHESIS REACTIONS INVOLVING METAL-METAL TRIPLE BOND AND CARBON-NITROGEN TRIPLE BOND

5.1 Introduction

The metathesis of triple bonds is one of the most impressive synthetic

methodologies in organometallic chemistry.1-4 Of particular interest are the dimetal

hexaalkoxide complexes M2(OR)6 (M =Mo, W) which react with small organic

molecules containing C≡E (E = C, N, O) moiety leading to cleavage of the C≡E bond or

to a reduction of its bond order.5 The most remarkable reactions of this type are the

mutual scission of M-M and C-E (E = C, N) triple bonds, the ‘chop-chop’ reactions

(Equation 1 and 2), which were first noted by Schrock in 1982.6

t t W2(O Bu)6 + RC≡CR 2( BuO)3W≡CR (1)

t t t W2(O Bu)6 + RC≡N (BuO)3W≡CR + ( BuO)3W≡N (2)

A wide variety of alkynes have been found to undergo the metathesis reactions with the ditungsten hexaalkoxides to give tungsten alkylidyne complexes which are active towards alkyne metathesis.5-8 Both Experimental and theoretical studies on reaction (1) show that

this reaction may begin with the coordination of the alkyne to the ditungsten alkoxide

118 2 leading to the formation of an alkyne adduct [(RO)6W2(µ,η -C2R´2)] which has a

8-11 tetrahedrane-like core W2C2.

Similarly the reaction of ditungsten alkoxide with nitriles gives quantitatively tungsten alkylidynes and nitrides as shown in Equation 2.6 This reaction has become a useful method to synthesize tungsten and molybdenum nitrides. Interestingly, when

t M2(O Bu)6 (M = W, Mo) reacts with dimethylcyanamide (Me2NCN), metathesis was observed for tungsten while 1:1 adduct formation occured for molybdenum.12-14 The observation of the nitrile adduct of dimolybdenum alkoxide sheds some light on the

t elucidation of the reaction pathways of the metathesis between W2(O Bu)6 and RCN.

However, the detailed reaction pathway remains unclear. In this chapter we report computational studies employing density functional theory (DFT) aimed at elucidating the mechanism of this reaction.

5.2 Computational Details

All calculations were performed using density functional theory as implemented in the Guassian 03 suite of programs.15 The PW91PW9116-20 [Perdew and Wang’s 1991 exchange and gradient-corrected correlation functional] density functional were used for all calculations. The LanL2DZ21-23 was used for transition metal atoms and the 6-31G* basis sets24-28 were used for all other non-metal atoms in the model compounds. All the structures were fully optimized without symmetry constrained. Frequency calculations were also performed to confirm that all the stationary points were minima or transition

119 states (no imaginary frequency for minimum and one imaginary frequency for transition

state). Intrinsic reaction coordinates (IRC)29-30 calculations were carried out on transition

states to confirm these structures are indeed connecting two minima. The discussed

energies are relative Gibbs free energies (∆G298K). All the relative energies were defined

with respect to the starting materials.

5.3 Results and Discussion

Although crystallography is rarely a reliable method for the elucidation of

31 t 13 reaction pathways, we believed that the structure of [( BuCH2O)6Mo2(µ-NCNMe2)] provided some insight into the mechanism of reaction (2). In this adduct the Me2NCN is

bound to both metal centers with C-N bond of the cyano group oriented in the same plane

as Mo-Mo bond and thus gives a planar core Mo2CN as shown in I. An analogue

[(RO)6W2(µ-CNR2)] has been therefore assumed as a possible intermediate in the

metathesis reaction (2). This adduct will be referred as a ditungstenazacyclobutadiene

complex later. Another possible intermediate has been postulated as the nitrile adduct

with a pseudo tetrahedral W2CN core (II). Such adducts which will be referred as

ditungstenazatetrahedrane complexes later have been observed for several ditungsten

32-33 systems but not directly for the M2(OR)6 species.

120 R

C N

MM I II

We study the geometry and energies of the two possible intermediates first and then the possibility for the conversion from the intermediates to alkylidyne and nitride.

We also perform an examination of the formation of the two possible intermediate from the starting materials. Finally, we analyze the whole reaction pathway for the metathesis reaction between ditungsten hexaalkoxides and nitriles. In these studies we employ methoxide rather than tert-butoxide ligands to reduce the computational time.

121 5.3.1 The ditungstenazatetrahedrane complex

The optimized structure of the ditungstenazatetrahedrane complex, as shown in

Figure 5.1, contains two bridged methoxide ligands. The acetonitrile is bonded to both

metal centers with C-N bond perpendicular to the W-W bond resulting in a

tetrahedral-like W2NC core where the C-N bond distance is calculated to be 1.434 Å and

W-W bond distance 2.572 Å. It is also interesting to note that nitrogen is bounded to the metal centers equally and so is the carbon. The distances from nitrogen to metal centers are calculated to be 2.073 Å which is very close to the distances from carbon to the metal centers (2.061 Å). In this respect, the ditungstenazatetrahedrane complex closely

t 2 8 resembles the adduct [( BuCH2O)6W2(py)(µ,η -C2Et2)]. The tetrahedral geometry of the

W2NC core of the ditungstenazatetrahedrane complex is similar to that of the W2C2 core

2 of [(NpO)6W2(py)(µ,η -C2Et2)]. In contrast, the bond distances of the W2NC core and the

2 C-C≡N angle in [(MeO)6W2(µ,η -MeCN)] are quite different from those in a similar

2 ditungsten nitrile adduct W2Cl4(µ,η -MeCN)(µ-dppm)2] which also contains a tetrahedral

32 W2NC core. These parameters in the latter are as follows: C-N=1.303 Å, W-W=2.499 Å,

W-N=2.103/2.101 Å, W-C=2.114/2.096 Å, C-C-N=116.4º.

122

Figure 5.1 Structures of the optimized ditungstenazatetrahedrane complex from different view angles. For better view, the hydrogen atoms are omitted.

The calculated free energy of the ditungstenazatetrahedrane complex is about 10.0 kcal/mol higher than that of the separated (MeO)6W2 and MeCN. To determine if this

adduct is indeed an intermediate in the metathesis-like reaction, we examined the

possibility of obtaining the tungsten alkylidyne and tungsten nitride from this adduct. The

calculated reaction pathway for the conversion from the ditungstenazatetrahedrane

complex to alkoxide bridged alkylidyne and nitride is given in Figure 5.2. The free energies and selected bond lengths of the transition states and intermediates along the reaction pathway are given in Table 5.1 and their structures are shown in V1 to V19.

123

Figure 5.2 Free energy (kcal/mol)) profiles for the ditungstunazatetrahedrane

(MeO)6W2(µ-NCMe)→ (MeO)3WCMe + (MeO)3WN

The overall reaction pathway calculated for the conversion from ditungstenaza-

tetrahedrane complex (V1) to metathesis products involves a series of transition states

and minima. The highest lying transition state V2 is calculated to be 18.7 kcal/mol higher in free energy than the starting reagents, (MeO)6W2 and MeCN. In the structure of V2, the C-N axis is rotated approximately 45º to the W-W axis. The imaginary frequency for

V2 corresponds to the twisting of C-N axis away and back to its perpendicular position relative to W-W axis. In the forward direction, V2 connects to a minimum V3 and in the

backward direction, V2 connects to V1. The second highest lying transition state V10 is

124 only about 1 kcal/mol lower in energy than v2. The imaginary frequency of V10 shows a

C-N stretch indicating a cleavage of C-N bond involved.

The transition state V10 connects, in the forward direction, to a minimum (V11) in which there is no longer either a C-N bond or a W-W bond and the distances for C to N and W to W are 2.953 Å and 2.949 Å, respectively. However, the tungsten alkylidyne is not completely formed in V11 since the C-W distance is somewhat longer than an alkylidyne C-W distance and the C-C-W angle is 160º. The minimum V11 is about 9 kcal/mol lower in energy than V1. Through a few low lying transition states (V12, V14,

V16, V18) which are all below the V1 in energy, V11 is transformed into an tungsten alkylidyne and tungsten nitride adduct (V19) in which the metal centers are bridged by two methoxide ligands and the nitride and alkylidyne group are anti to each other. This adduct is calculated to be about 3 kcal/mol lower in free energy than the separated tungsten alkylidyne and tungsten nitride.

V1 V2 V3

125

V4 V5 V6

V7 V8 V9

V10 V11 V12

V13 V14 V15

V16 V17 V18

126

V19

In the backward direction, the transition state V10 connects the minimum V9 whose structure is similar to that of V3 except for the orientation of some methoxide groups. Three transition states (V4, V6, V8) are located between V3 and V9. These transition states and the minima to which they connect are close in energy within a range of 4 kcal/mol. Two observations may explain the small change in energy: the imaginary frequency for each of the three transition states shows only methoxide ligand rotation which has a small barrier; the bond distances of the W2CN core barely change.

Although the reaction pathway for the conversion from ditungstenazatetrahedral

to tungsten alkylidyne and nitride is complicated, only two high lying transition states V2

and V10 are kinetically significant, as others occur at much lower energy. The former

corresponds to the twisting of C-N bond and the later the cleavage of the C-N bond and

W-W bond.

127

∆G298K W-W C-N W1-C W2-C W1-N W2-N V1 10.0 2.572 1.435 2.061 2.061 2.073 2.073

V2 18.6 2.539 1.445 1.990 2.176 2.449 1.913 V3 11.0 2.601 1.418 1.997 2.293 2.895 1.843 V4 11.5 2.612 1.416 2.002 2.291 2.929 1.837 V5 10.9 2.618 1.411 2.010 2.291 2.947 1.834 V6 12.2 2.641 1.422 2.005 2.317 2.957 1.815 V7 10.0 2.633 1.413 2.012 2.323 2.949 1.822 V8 11.0 2.649 1.418 2.004 2.362 2.946 1.816 V9 8.3 2.628 1.417 2.000 2.346 2.925 1.822 V10 17.6 2.658 1.802 1.919 2.254 3.288 1.750 V11 0.9 2.949 2.953 1.808 2.481 4.020 1.696 V12 1.7 2.940 2.937 1.809 2.476 4.016 1.697 V13 0.3 2.931 2.950 1.802 2.561 3.966 1.700 V14 3.8 2.980 3.130 1.795 2.664 4.011 1.699 V15 1.1 3.050 3.217 1.782 2.905 3.965 1.701 V16 1.8 3.345 4.241 1.769 3.600 4.424 1.702 V17 -1.7 3.564 5.444 1.766 4.298 4.873 1.702 V18 1.4 3.645 6.339 1.767 4.906 5.017 1.701 V19 -7.2 3.635 6.697 1.779 5.156 5.044 1.698

Table 5.1 Free energies (kcal/mol) and selected bond distance (Å) for intermediates and transition states on the pathway from ditungstenazatetrahedrane to tungsten alkylidyne and nitride.

128 5.3.2 The ditungstenazacyclobutadiene complex

The calculated ditungstenazacyclobutadiene is given in Figure 5.3. The

acetonitrile bridges the two tungsten atoms and the C-N bond lies in the same plane as the

W-W bond. The nitrogen is bound to both metal centers while the carbon is only bound to one metal center. There are five terminal methoxide ligands with two of them binding to the tungsten atom that is bound to both nitrogen and carbon and the rest binding to the other tungsten atom. The sixth methoxide ligand is a bridging ligand which binds to the tungsten atom with three terminal alkoxide ligands more strongly (W-O = 2.000 Å) than to the one with two terminal alkoxide ligands (W-O = 2.324Å). In this structure, the C-N

distance has lengthened by 0.196 Å from 1.171 Å (the C-N distance in free MeCN) to

1.367 Å. The increase of the C-N distance is similar to that of the molybdenum analogues

seen in the solid-state structures.13-14

Figure 5.3 Structures of the optimized ditungstenazacyclobutadiene complex from different view angles. For better view, the hydrogen atoms are omitted

129 The ditungstenazacyclobutadiene is calculated to be 2.9 kcal/mol higher in free energy than the starting materials, which is about 7 kcal/mol lower than the ditungsten- azatetrahedrane. We further examine the possibility for the conversion from the ditungstenazacyclobutadiene to tungsten alkylidyne and nitride. The calculated reaction coordinate is given in Figure 5.4. The free energies and selected bond lengths of the transition states and intermediates along the reaction pathway are given in Table 5.2 and their structures are shown in P1 to P9.

18.7 P6

9.0 P2

2.7 P4 P1 2.9 P3 -1.8 1.6 P8 P5 P9 -2.0 -2.0

P7 -6.7

Figure 5.4 Free energy (kcal/mol)) profiles for the ditungstunazacyclobutadiene

(MeO)6W2(µ-NCMe)→ (MeO)3WCMe + (MeO)3WN

130

P1 P2 P3

P4 P5 P6

P7 P8 P9

The overall reaction pathway for ditungstenazacycloazabutadiene is less complicated. The highest lying transition state P6 is 18.7 kcal/mol higher in energy than the starting reagents. In this structure, both the C-N bond and the W-W are significantly lengthened. Indeed, the C-N distance of 2.016 Å indicates that the C-N bond is cleaved.

The imaginary frequency for P6 moves MeC and N groups apart and together leading to the cleavage and the formation of the C-N bond and the W-W bond.

131 The minimum P7 which is connected to the transition state P6 in the forward

direction is calculated to be 6.7 kcal/mol lower in free energy than the starting reagents.

In this structure, both of the C-N and W-W bond are cleaved with distances of 3.039 and

3.265 Å respectively. The tungsten alkylidyne and tungsten nitride are almost formed since the calculated distances of the W-C and W-N bond (1.768 and 1.741 Å respectively) are only slightly longer than those in the free alkylidyne and nitride. Also a near linear

C-C-W bond angle is observed with a value of 179º. Although the minimum P7 is about

2.7 kcal/mol lower in free energy than the separated tungsten alkylidyne and nitride, such a dimer has not been observed in experiments. This might be due to the formation of the nitride polymer and alkylidyne dimer is more energetically favorable.14

The transition state P6 connects, in the backward direction, to a minimum (P5)

which is calculated to be 2 kcal/mol lower in free energy than the starting reagents. In P5,

the C-N axis remains almost in the same plane as the W-W axis with the nitrogen and

their bond distances are 1.364 and 2.653 Å respectively. In going form P1 to P5, the main

change in the structure is the orientation of the methoxide ligands, especially for the

position of the bridged methoxide ligands. In P1, the bridged methoxide group is in the same plane as the W2CN core while in P5, the bridged methoxide ligand rotates out of the

plane by 52º.

The transformation of the ditungstenazacyclotadiene into the metathesis products,

tungsten alkylidyne and nitride begins with the rearrangement of the methoxide ligand.

132 This rearrangement slightly perturbs the W2CN core and thus leads to a molecular

geometry which facilitates the following step, the cleavage of the C-N and W-W bonds.

The rate-determining step is the cleavage step with a barrier of 18.6 kcal/mol.

∆G298K W-W C-N W1-C W2-C W1-N W2-N

P1 2.9 2.554 1.367 1.948 3.312 1.970 2.081

P2 9.0 2.662 1.365 1.922 3.267 1.998 2.020

P3 1.6 2.602 1.331 1.951 3.236 2.032 2.041

P4 2.7 2.626 1.345 1.939 3.205 2.043 1.996

P5 -2.0 2.653 1.364 1.929 3.108 2.158 1.921

P6 18.7 2.782 2.016 1.800 3.472 2.293 1.788

P7 -6.7 3.265 3.039 1.768 4.094 2.134 1.741

P8 1.8 3.671 3.002 1.775 4.388 2.206 1.710

P9 -2.0 2.999 3.903 1.772 4.573 2.206 1.707

Table 5.2 Free energies (kcal/mol) and selected bond distance (Å) for intermediates and transition states on the pathway from ditungstenazacyclobutadiene to tungsten alkylidyne and nitride.

5.3.3 The formation of ditungstenazatetrahedrane and ditungstenazacyclo- butadiene

The calculated reaction pathways for the reactions from the ditungstenazatetra-

hedrane and ditungstenazacyclobutadiene to tungsten alkylidyne and nitride show both of

133 them can be readily cleaved to give quantitatively tungsten alkylidyne and nitride, but to

confirme if they are indeed the intermediates for the reaction between W2(MeO)6 and

MeCN, we consider the possibility for the formation of these two postulated intermediates from the starting reagents, W2(MeO)6 and MeCN , in this section.

The calculated reaction pathways for the formation of the ditungstenazacyclo- butadiene and ditungstenazatetrahedrane from the starting reagents are given in Figure

5.5 and the structures of the transition states and intermediates are shown in F1 to F5, C6

to C11 and T6 to T19.

Figure 5.5 Free energy (kcal/mol)) profiles for the starting materials to the postulated

intermediates: ditungstunazacyclobutadiene and ditungstunazatetrahedrane. {(MeO)6W2 + MeCN → (MeO)6W2(µ-NCMe)} The red solid line is the pathway leading to the ditungstunazacyclobutadiene; The blue dash line is the pathway leading to the ditungstunazatetrahedrane.

134 As shown in Figure 5.5, there is a common part in the reaction pathways for the

formation of the ditungstenazacyclobutadiene and ditungstenazatetrahedrane. This is the

beginning part of both reaction pathways (from R to F5). First the MeCN coordinates to

one of the tungsten atoms in the W2(OMe)6 to give an adduct (F1). In F1, the MeCN binds to tungsten atom through its lone pair donor on nitrogen and lies perpendicular to the W-W axis. Moving forward from F1, the MeCN tilts towards the other tungsten center to form a minimum (F3) containing a cyclobutadiene-like core W2CN. This transformation involves a transition state (F2) whose energy is calculated to be 16.6 kcal/mol higher than the starting reagents. Another transition state (F4), about 5 kcal/mol higher than F5, is required to connect the minimum F3 and F5. The difference between

F3 and F5 is that one of the methoxide ligand bridges the tungsten atoms in F5, but no bridging methoxide ligand is observed in F3.

From the minimum F5, two distinct pathways evolve for accounting for the formation of the ditungstenazacyclobutadiene and ditungstenazatetrahedrane. When F5 crosses the transition state C6, the reaction leads to the formation of ditungstenaza- cyclobutadiene. On the other hand, the reaction will result in the formation of ditungstenazatetrahedrane if F5 crosses the transition state T6.

The pathway leading to the formation of the ditungstenazacyclobutadiene is straightforward and facile from the minimum F5. In going from F5 to C11, three transition states with low barriers are found and their imaginary frequencies show that

135 these transformations only involve the rotation of the methoxide ligands. In contrast, the

pathway leading to the formation of the ditungstenazatetrahedrane is much more

complicated and energetically unfavorable. The highest lying transition state (T10) on the

pathway between F5 and T19 is calculated to be 24.2 kcal/mol higher in free energy than

the starting reagents. This transition state corresponds to the transformation from a planar

W2CN to a structure where the C-N rotates to 30º relative to the W-W axis. Another

transition state T18 which is significantly higher in energy than the rest is 18.6 kcal/mol higher in free energy than the starting regents. T18 is a transition state transforming the

W2CN where the C-N rotates to 30º relative to the W-W axis to a tetrahedral-like W2CN.

F1 F2 F3

F4 F5 T6

136

T7 T8 T9

T10 T11 T12

T13 T14 T15

T16 T17 T18

137

T19

C6 C7 C8

C9 C10 C11

5.3.4 The overall reaction pathway for metathesis reaction (2)

We now consider the overall reaction pathway for the metathesis reaction between

W2(OMe)6 and MeCN. It has been found that the formation of the possible intermediate,

ditungstenazacyclobutadiene, is more energetically favored over the formation of the

ditungstenazatetrahedrane. The ditungstenazacyclobutadiene is 7 kcal/mol more stable

than the ditungstenazatetrahedrane. The formation of the latter needs to overcome a 138 barrier of 24.2 kcal/mol which is approximately 8 kcal/mol higher than that required for the former. In addition, the conversions from these two postulated intermediates to metathesis products have similar barriers. The metathesis reaction between W2(OMe)6 and MeCN is therefore more likely to proceed through the formation and cleavage the ditungsten of a ditungstenazacyclobutadiene intermediate.

Figure 5.6 Free energy (kcal/mol)) profiles for the metathesis reaction between

(MeO)6W2 and MeCN. (The solid line corresponds to the pathway for (MeO)6W2 + MeCN →(MeO)3WCMe + (MeO)3WN; the red dash line corresponds to the pathway for the formation of ditungstunazacyclobutadiene.)

139 The overall reaction pathway for the metathesis reaction is given in Figure 5.6.

The reaction begins with the coordination of acetonitrile to W2(OMe)6 to give an adduct

with a planar cyclobutadiene-like W2CN core. Before the scission of the C-N and W-W

bond in this adduct, a series of rearrangements of the position of the methoxide group are

necessary. The rate-determining step is the cleavage step. It is also interesting to note that

the ditungstenazacyclobutadiene structurally similar to the molybdenum analogue characterized in experiment is not among the stationary points found on the overall pathway. Such a structure can be, however, readily obtained from the minimum (C7) on the pathway. The minima C7 is identical to the minimum P5 located on the pathway for the conversion from the ditungstenazacyclobutadiene to metathesis products. In the backward direction from P5, the ditungstenazacyclobutadiene is formed.

5.4 Conclusion

DFT has been applied to study the metathesis reaction between W2(OMe)6 and

MeCN. The reaction begins with the coordination of acetonitrile to W2(OMe)6 to give an

adduct with a planar cyclobutadiene-like W2CN core and is then followed by the cleavage

of the C-N and W-W bond in this adduct to give tungsten alkylidyne and tungsten nitride.

The rate-determining step is the cleavage step. The ditungstenazacyclobutadiene

t intermediate, which is structurally related to ( BuO)6Mo2(NCNMe2), can also be readily

obtained from the starting reagents. This structure is calculated to be thermodynamically

unfavorable relative to the metathesis products and thus no such analogue for tungsten is

140 observed experimentally. For reaction between Mo2(OMe)6 and MeCN, the formation of

molybdenum alkylidyne and nitride is calculated to be slightly thermodynamically

unfavorable by about 2 kcal/mol higher in free energy relative to the starting reagents.

The acetonitrile adduct (MeO)6Mo2(NCMe) that is structurally related to

t ( BuO)6Mo2(NCNMe2), namely a dimolybdenumcyclobutadiene is calculated to be 10

kcal/mol above the starting materials. However, when dimethylcyanamide is substituted

for acetonitrile, the adduct (MeO)6Mo2(NCNMe2) is calculated to be about 4 kcal/mol

lower in free energy than the starting reagents. This is consistent with the observation that

t 34 R2NCN reversibly binds to Mo2(O Bu)6 in toluene-d8 solutions (R = Me, Et).

141 5.5 References

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(2) Bunz, U. H. F. Acc. Chem. Res. 2001, 34, 998.

(3) Chisholm, M. H.; Delbridge, E. E.; Kidwell, A. R.; Quinlan, K. R. Chem. Comm. 2003, 126.

(4) Geyer, A. M.; Wiedner, E. S.; Gary, J. B.; Gdula, R. L.; Kuhlmann, N. C,; Johnson, M. J. A.; Dunietz, B. D.; Kampf, J. W. J. Am. Chem. Soc. 2008, 130, 8984.

(5) Chisholm, M. H.; J. Chem. Soc., Dalton Trans. 1996, 1781.

(6) Schrock, R. R.; Listemann, M. L.; Strugeoff, L. G. J. Am. Chem. Soc. 1982, 104, 4291.

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144 APPENDIX A

CALCULATED CARTESIAN COORDINATES FOR SELECTED MOLECULES IN CHAPTER 2

Supporting Ligands Used in Chapter 1:

PR2

PR2

Al (R = H, Me, tBu)

PR2

PR2

Ar (R = H, Me, tBu) 145

(Al)Ir(H)NH2 R=H C -0.117560 0.084189 -2.529540 H 0.470033 0.023450 -3.453586 H -0.843012 0.904806 -2.634021 C 0.729790 0.276277 -1.266667 H 1.542504 -0.468259 -1.255181 H 1.207954 1.271395 -1.294271 C -0.121657 0.126977 0.000000 H -0.855831 0.953702 0.000000 C 0.729790 0.276277 1.266667 H 1.207954 1.271395 1.294271 H 1.542504 -0.468259 1.255181 C -0.117560 0.084189 2.529540 H 0.470033 0.023450 3.453586 H -0.843012 0.904806 2.634021 P -1.103490 -1.459645 -2.239944 P -1.103490 -1.459645 2.239944 Ir -1.411153 -1.590226 0.000000 N -3.346069 -2.086093 0.000000 H -3.907992 -2.253916 0.828905 H -3.907992 -2.253916 -0.828905 H 0.072954 -2.180831 0.000000 H -0.325295 -2.469642 2.877711 H -2.118666 -1.387983 3.246387 H -2.118666 -1.387983 -3.246387 H -0.325295 -2.469642 -2.877711

(Al)Ir(H)NH2 R=Me C -0.068292 -0.001282 -2.499843 H 0.472136 -0.155358 -3.442876 H -0.652892 0.926342 -2.585046 C 0.827250 0.052284 -1.263773 H 1.522725 -0.798882 -1.254369 H 1.449834 0.962070 -1.281016 C -0.018005 0.035642 0.000000 H -0.633199 0.945001 0.000000 C 0.827250 0.052284 1.263773 H 1.449834 0.962070 1.281016

146 H 1.522725 -0.798882 1.254369 C -0.068292 -0.001282 2.499843 H 0.472136 -0.155358 3.442876 H -0.652892 0.926342 2.585046 P -1.243120 -1.386990 -2.234757 P -1.243120 -1.386990 2.234757 Ir -1.539192 -1.446927 0.000000 N -3.528130 -1.490574 0.000000 H -4.111059 -1.484074 0.826333 H -4.111059 -1.484074 -0.826333 H -0.191205 -2.256111 0.000000 C -0.330424 -2.800912 2.922478 H -0.204079 -2.623304 4.001880 H -0.866153 -3.739551 2.746147 H 0.650789 -2.863357 2.438217 C -2.577562 -1.0848523.418344 H -2.097893 -0.927195 4.400512 H -3.145093 -0.193764 3.126366 H -3.262359 -1.940647 3.467787 C -2.577562 -1.084852 -3.418344 H -2.097893 -0.927195 -4.400512 H -3.262359 -1.940647 -3.467787 H -3.145093 -0.193764 -3.126366 C -0.330424 -2.800912 -2.922478 H -0.866153 -3.739551 -2.746147 H -0.204079 -2.623304 -4.001880 H 0.650789 -2.863357 -2.438217

t (Al)Ir(H)NH2 R=Bu C -0.003073 -0.000409 -2.545102 H 0.978196 -0.250057 -2.963719 H -0.534289 0.581210 -3.310751 C 0.129017 0.740766 -1.223209 H 0.907437 1.518835 -1.304080 H -0.810476 1.278936 -1.027050 C 0.414833 -0.145203 0.000000 C 0.129017 0.740766 1.223209 H -0.810476 1.278936 1.027050 H 0.907437 1.518835 1.304080

147 C -0.003073 -0.000409 2.545102 H 0.978196 -0.250057 2.963719 H -0.534289 0.581210 3.310751 P -0.883263 -1.591644 -2.277036 P -0.883263 -1.591644 2.277036 Ir -0.586683 -1.999620 0.000000 H 1.462983 -0.453643 0.000000 N -0.591300 -3.972666 0.000000 H -0.719914 -4.538676 -0.821864 H -0.719914 -4.538676 0.821864 H -1.506207 -0.798110 0.000000 C -2.762808 -1.267425 -2.629872 C -3.564410 -2.395600 -1.958266 C -3.112706 0.063066 -1.942226 C -3.209294 -1.127331 -4.101312 H -3.394754 -3.366697 -2.438293 H -3.313455 -2.495235 -0.899331 H -4.638849 -2.169820 -2.032372 H -2.639503 0.920468 -2.435592 H -4.202549 0.209144 -2.003929 H -2.844371 0.077669 -0.882315 H -4.288712 -0.890424 -4.081429 H -2.708527 -0.296131 -4.630249 H -3.100059 -2.051369 -4.694517 C 0.022467 -2.757079 -3.449675 C 1.372053 -3.006665 -2.748195 C -0.777657 -4.054573 -3.577809 C 0.300186 -2.194802 -4.854472 H 1.962714 -2.083081 -2.701762 H 1.255200 -3.373816 -1.723866 H 1.955372 -3.735210 -3.324646 H -1.733119 -3.868861 -4.085000 H -0.211283 -4.782557 -4.176966 H -0.998743 -4.519341 -2.608455 H 0.871067 -2.951378 -5.417911 H -0.624336 -1.980444 -5.419988 H 0.914580 -1.278276 -4.831403 C -2.762808 -1.267425 2.629872 C -3.112706 0.063066 1.942226 C -3.564410 -2.395600 1.958266

148 C -3.209294 -1.127331 4.101312 H -2.639503 0.920468 2.435592 H -2.844371 0.077669 0.882315 H -4.202549 0.209144 2.003929 H -3.394754 -3.366697 2.438293 H -4.638849 -2.169820 2.032372 H -3.313455 -2.495235 0.899331 H -4.288712 -0.890424 4.081429 H -3.100059 -2.051369 4.694517 H -2.708527 -0.296131 4.630249 C 0.022467 -2.7570793.449675 C -0.777657 -4.054573 3.577809 C 1.372053 -3.006665 2.748195 C 0.300186 -2.194802 4.854472 H -1.733119 -3.868861 4.085000 H -0.998743 -4.519341 2.608455 H -0.211283 -4.782557 4.176966 H 1.962714 -2.083081 2.701762 H 1.955372 -3.735210 3.324646 H 1.255200 -3.373816 1.723866 H 0.871067 -2.951378 5.417911 H 0.914580 -1.278276 4.831403 H -0.624336 -1.980444 5.419988

(Al)IrNH3 R=H C 0.021140 -0.014334 0.014429 H 1.120634 -0.032530 0.053406 H -0.314030 1.029547 -0.009508 C -0.573981 -0.844719 1.151868 H -0.186669 -0.488226 2.122608 H -1.666607 -0.698175 1.173969 C -0.250779 -2.336487 0.960858 C -0.839859 -3.141843 2.132882 H -1.933588 -3.005418 2.168089 H -0.442872 -2.768008 3.093114 C -0.524228 -4.629052 1.978642 H 0.556796 -4.810577 2.076176 H -1.056668 -5.281742 2.681392 P -0.492942 -0.940589 -1.501876

149 P -0.987333 -4.979315 0.222765 Ir -0.567999 -3.121277 -0.967512 H -0.081349 -3.443078 -3.681959 H -0.256287 -4.938793 -3.041015 H -1.583863 -4.027536 -3.366574 N -0.626430 -3.987863 -3.012675 H 0.851082 -2.420123 1.064847 H -1.742347 -0.313772 -1.809610 H 0.225825 -0.262959 -2.544854 H -2.363717 -5.347066 0.361179 H -0.534648 -6.329895 0.038038

(Al)IrNH3 R=Me C -0.001298 -0.000970 -2.489565 H 1.088869 -0.081426 -2.604197 H -0.419999 0.408665 -3.418943 C -0.350702 0.774860 -1.235018 H 0.156550 1.753319 -1.216464 H -1.426958 0.994387 -1.204877 C 0.036041 -0.030312 0.000000 C -0.350702 0.774860 1.235018 H -1.426958 0.994387 1.204877 H 0.156550 1.753319 1.216464 C -0.001298 -0.000970 2.489565 H 1.088869 -0.081426 2.604197 H -0.419999 0.408665 3.418943 P -0.699976 -1.664142 -2.201729 P -0.699976 -1.664142 2.201729 Ir -0.579365 -2.040629 0.000000 H -0.202719 -4.731411 0.000000 H -1.590773 -4.512773 0.816694 H -1.590773 -4.512773 -0.816694 N -1.070651 -4.201558 0.000000 H 1.131602 -0.094613 0.000000 C -2.426609 -1.376811 -2.714447 H -2.401052 -1.118397 -3.785094 H -3.058535 -2.255590 -2.549921 H -2.840643 -0.540536 -2.141956

150 C 0.010767 -2.664053 -3.526419 H -0.451959 -3.656313 -3.597630 H -0.171491 -2.080005 -4.451313 H 1.087171 -2.780419 -3.354088 C -2.426609 -1.376811 2.714447 H -3.058535 -2.255590 2.549921 H -2.401052 -1.118397 3.785094 H -2.840643 -0.540536 2.141956 C 0.010767 -2.664053 3.526419 H -0.171491 -2.080005 4.451313 H -0.451959 -3.656313 3.597630 H 1.087171 -2.780419 3.354088

(Al)IrNH3 R=tBu C 0.006973 -0.012426 -2.494643 H 0.530383 -0.263349 -3.422557 H -0.376257 1.007522 -2.607182 C 0.860353 -0.110918 -1.237389 H 1.452070 -1.033128 -1.236903 H 1.580526 0.723369 -1.194240 C -0.020738 -0.083122 0.000000 H -0.497582 0.899625 0.000000 C 0.860353 -0.110918 1.237389 H 1.580526 0.723369 1.194240 H 1.452070 -1.033128 1.236903 C 0.006973 -0.012426 2.494643 H 0.530383 -0.263349 3.422557 H -0.376257 1.007522 2.607182 P -1.413434 -1.151684 -2.254437 P -1.413434 -1.151684 2.254437 Ir -1.531002 -1.501357 0.000000 H -2.942784 -3.708149 -0.820112 H -2.942784 -3.708149 0.820112 H -4.002383 -2.793460 0.000000 N -3.034320 -3.110898 0.000000 C -2.960744 -0.116892 -2.718591 C -4.187191 -0.846339 -2.143080 C -2.834769 1.175778 -1.889509 C -3.162549 0.263153 -4.190399

151 H -4.306605 -1.863574 -2.534793 H -4.098501 -0.886674 -1.049955 H -5.099603 -0.281940 -2.382919 H -2.095129 1.876063 -2.286575 H -3.807086 1.687742 -1.886211 H -2.575461 0.946824 -0.856069 H -4.026957 0.946325 -4.255207 H -2.290107 0.804358 -4.597467 H -3.374808 -0.600768 -4.841701 C -0.883900 -2.695392 -3.238602 C 0.183839 -3.330576 -2.312889 C -2.077154 -3.647332 -3.377093 C -0.256138 -2.466611 -4.630316 H 1.102954 -2.736319 -2.304113 H -0.163923 -3.400595 -1.272761 H 0.443391 -4.333610 -2.675332 H -2.906301 -3.183076 -3.929490 H -1.764398 -4.550033 -3.924844 H -2.455126 -3.996823 -2.402164 H -0.001375 -3.454536 -5.053124 H -0.939312 -1.960811 -5.338320 H 0.689118 -1.895386 -4.582349 C -2.960744 -0.116892 2.718591 C -2.834769 1.175778 1.889509 C -4.187191 -0.846339 2.143080 C -3.162549 0.263153 4.190399 H -2.095129 1.876063 2.286575 H -2.575461 0.946824 0.856069 H -3.807086 1.687742 1.886211 H -4.306605 -1.863574 2.534793 H -5.099603 -0.281940 2.382919 H -4.098501 -0.886674 1.049955 H -4.026957 0.946325 4.255207 H -3.374808 -0.600768 4.841701 H -2.290107 0.804358 4.597467 C -0.883900 -2.695392 3.238602 C -2.077154 -3.647332 3.377093 C 0.183839 -3.330576 2.312889 C -0.256138 -2.466611 4.630316 H -2.906301 -3.183076 3.929490

152 H -2.455126 -3.996823 2.402164 H -1.764398 -4.550033 3.924844 H 1.102954 -2.736319 2.304113 H 0.443391 -4.333610 2.675332 H -0.163923 -3.400595 1.272761 H -0.001375 -3.454536 5.053124 H 0.689118 -1.895386 4.582349 H -0.939312 -1.960811 5.338320

(Al)IrCO R=H C -0.139084 0.212251 2.530038 H 0.432959 0.236263 3.465371 H -0.957486 0.943826 2.603185 C 0.697730 0.465831 1.272231 H 1.065436 1.507013 1.280873 H 1.589948 -0.180567 1.292915 C -0.123976 0.187178 0.000696 C 0.697923 0.465883 -1.270768 H 1.589979 -0.180656 -1.291456 H 1.065736 1.506962 -1.279107 C -0.138801 0.212756 -2.528721 H -0.956721 0.944835 -2.602084 H 0.433477 0.236437 -3.463922 P -0.922887 -1.437754 -2.239535 H -1.925746 -1.538407 -3.249181 H 0.005637 -2.338450 -2.841623 P -0.921973 -1.438709 2.240427 H 0.008069 -2.338790 2.841092 H -1.923823 -1.541100 3.250908 Ir -1.242280 -1.662017 0.000432 H -0.956616 0.921702 0.000647 C -2.297978 -3.244026 -0.000053 O -2.940856 -4.217416 -0.000536

(Al)IrCO R=Me C -0.170611 1.682718 2.519569 H 0.340912 2.005358 3.436400 H -1.253553 1.801459 2.666550

153 C 0.287250 2.401616 1.255563 H -0.029641 3.456894 1.276701 H 1.386137 2.418537 1.215883 C -0.250372 1.707279 -0.000093 C 0.287329 2.401417 -1.255837 H 1.386306 2.418260 -1.216010 H -0.029470 3.456656 -1.277135 C -0.170316 1.682373 -2.519801 H -1.253176 1.801307 -2.667172 H 0.341559 2.004702 -3.436543 P 0.176997 -0.086440 -2.213665 P 0.177178 -0.086076 2.213741 Ir -0.122687 -0.434386 0.000057 H -1.346048 1.837280 -0.000079 C -0.005052 -2.301273 -0.000116 O 0.163855 -3.454007 -0.000432 C -0.609916 -0.991593 3.565674 H -0.321615 -2.049337 3.548658 H -0.257811 -0.502680 4.491738 H -1.700376 -0.921684 3.484336 C 1.957844 -0.193728 2.601434 H 2.075063 0.057643 3.665802 H 2.338944 -1.201730 2.406419 H 2.520759 0.517233 1.988133 C -0.610205 -0.991594 -3.565772 H -0.257428 -0.502852 -4.491666 H -0.322666 -2.049532 -3.548726 H -1.700637 -0.920888 -3.484831 C 1.957672 -0.194724 -2.601094 H 2.338265 -1.202968 -2.406312 H 2.075228 0.056894 -3.665356 H 2.520833 0.515763 -1.987481

(Al)IrCO R=tBu C -0.233325 1.701988 2.546867 H 0.319016 2.100367 3.407500 H -1.295541 1.713143 2.821438 C -0.010598 2.475735 1.250154 H -0.558959 3.431371 1.285783

154 H 1.047216 2.743203 1.153785 C -0.413899 1.683347 0.003080 C 0.009093 2.478454 -1.235760 H 1.069518 2.731608 -1.129911 H -0.527106 3.440947 -1.270533 C -0.214147 1.713194 -2.537633 H -1.275489 1.732562 -2.815043 H 0.343365 2.112567 -3.394276 P 0.214019 -0.055880 -2.269835 P 0.206093 -0.063801 2.272941 Ir 0.043743 -0.365548 0.000681 H -1.510587 1.624164 -0.006081 C 0.231922 -2.221839 -0.003331 O 0.301322 -3.383488 -0.007406 C -1.104762 -1.051366 3.218512 C -0.670403 -2.519376 3.324078 C -1.448571 -0.496075 4.611645 C -2.360195 -0.955939 2.318614 H -0.443887 -2.960430 2.346462 H 0.208629 -2.629551 3.974619 H -1.490829 -3.103949 3.769062 H -1.849419 0.532310 4.571806 H -2.239791 -1.130260 5.046196 H -0.589663 -0.512442 5.306821 H -3.184785 -1.500320 2.799445 H -2.690248 0.081878 2.177088 H -2.187400 -1.386044 1.324704 C 2.058134 -0.235152 2.716267 C 2.599158 -1.555969 2.140275 C 2.750973 0.905147 1.944903 C 2.407385 -0.108201 4.205671 H 2.085877 -2.438427 2.538208 H 2.509727 -1.571967 1.049459 H 3.665923 -1.641832 2.394602 H 2.540833 1.888652 2.375917 H 3.838230 0.748404 1.981156 H 2.449147 0.910267 0.894003 H 3.506771 -0.114649 4.299438 H 2.052122 0.840083 4.647658 H 2.024913 -0.946146 4.812525

155 C -1.101650 -1.035596 -3.216741 C -1.448292 -0.470852 -4.605400 C -0.668035 -2.503128 -3.331837 C -2.354357 -0.944516 -2.312393 H -1.844349 0.559187 -4.558135 H -0.592128 -0.487349 -5.304116 H -2.244197 -1.098684 -5.040512 H -0.449231 -2.952259 -2.356258 H -1.486018 -3.083030 -3.787263 H 0.215404 -2.609114 -3.977054 H -3.180590 -1.487240 -2.792074 H -2.176993 -1.377678 -1.320717 H -2.684086 0.092831 -2.165403 C 2.063706 -0.234168 -2.721567 C 2.766104 0.923178 -1.985907 C 2.611355 -1.540195 -2.118770 C 2.400175 -0.141766 -4.216788 H 2.542249 1.898395 -2.429175 H 2.491908 0.946138 -0.927653 H 3.853037 0.769808 -2.045533 H 2.077126 -2.431262 -2.466452 H 3.667749 -1.646242 -2.406680 H 2.561413 -1.515801 -1.025271 H 3.498719 -0.134966 -4.318761 H 2.025441 -1.001254 -4.797577 H 2.026747 0.789045 -4.680415

(Ar)Ir(H)NH2 R=H C 0.000176 -0.000494 -1.203798 C 1.400327 0.009016 -1.213193 C 2.134359 0.037384 0.000000 C 1.400327 0.009016 1.213193 C 0.000176 -0.000494 1.203798 C -0.706844 0.010182 0.000000 H -0.543806 -0.018213 -2.151288 H -0.543806 -0.018213 2.151288 H -1.795729 0.013497 0.000000 C 2.134458 -0.089878 2.534913 H 2.107993 -1.125096 2.906472

156 H 1.712154 0.549849 3.318999 C 2.134458 -0.089878 -2.534913 H 2.107993 -1.125096 -2.906472 H 1.712154 0.549849 -3.318999 Ir 4.201714 0.104951 0.000000 H 3.716061 1.619263 0.000000 P 3.918622 0.291679 2.239206 H 4.112988 1.575445 2.818111 H 4.582275 -0.457416 3.257546 P 3.918622 0.291679 -2.239206 H 4.582275 -0.457416 -3.257546 H 4.112988 1.575445 -2.818111 N 5.855102 -1.009403 0.000000 H 6.362266 -1.305644 -0.828813 H 6.362266 -1.305644 0.828813

(Ar)Ir(H)NH2 R=Me C 0.130941 0.082181 -1.206746 C 1.530314 -0.004498 -1.215462 C 2.242867 -0.029189 0.000000 C 1.530314 -0.004498 1.215462 C 0.130941 0.082181 1.206746 C -0.572691 0.146696 0.000000 H -0.410839 0.097307 -2.156222 H -0.410839 0.097307 2.156222 H -1.659586 0.225043 0.000000 C 2.281284 -0.181115 2.515283 H 2.186707 -1.219863 2.862892 H 1.923322 0.463763 3.326585 C 2.281284 -0.181115 -2.515283 H 2.186707 -1.219863 -2.862892 H 1.923322 0.463763 -3.326585 Ir 4.294728 -0.118418 0.000000 H 3.924613 1.404905 0.000000 P 4.069054 0.114347 2.229900 P 4.069054 0.114347 -2.229900 N 5.764809 -1.458599 0.000000 C 4.299353 1.822626 -2.815981 H 5.320463 2.167112 -2.622857

157 H 4.082484 1.856805 -3.893202 H 3.602398 2.472288 -2.275182 C 4.907117 -0.904034 -3.471927 H 4.440619 -0.683869 -4.447078 H 5.976878 -0.660261 -3.503929 H 4.794707 -1.967190 -3.229502 C 4.299353 1.822626 2.815981 H 4.082484 1.856805 3.893202 H 5.320463 2.167112 2.622857 H 3.602398 2.472288 2.275182 C 4.907117 -0.904034 3.471927 H 5.976878 -0.660261 3.503929 H 4.440619 -0.683869 4.447078 H 4.794707 -1.967190 3.229502 H 6.233952 -1.809379 -0.826475 H 6.233952 -1.809379 0.826475

t (Ar)Ir(H)NH2 R=Bu C 0.039540 -0.198738 1.207952 C 1.422757 0.057402 1.209982 C 2.125715 0.238330 0.000000 C 1.422757 0.057402 -1.209982 C 0.039540 -0.198738 -1.207952 C -0.662063 -0.326727 0.000000 H -0.479270 -0.349749 2.160827 H -0.479270 -0.349749 -2.160827 H -1.727664 -0.564999 0.000000 C 2.166825 0.079914 -2.528260 H 2.027345 1.033825 -3.049766 H 1.813165 -0.692473 -3.220621 C 2.166825 0.079914 2.528260 H 2.027345 1.033825 3.049766 H 1.813165 -0.692473 3.220621 P 3.976354 -0.112002 2.269191 P 3.976354 -0.112002 -2.269191 Ir 4.163425 0.357687 0.000000 H 3.544643 -1.020707 0.000000 N 5.916500 1.278402 0.000000 H 6.487911 1.403260 0.821845

158 H 6.487911 1.403260 -0.821845 C 4.728374 1.151138 3.445520 C 6.241325 0.902497 3.516503 C 4.416797 2.507197 2.785927 C 4.148286 1.161236 4.869919 H 6.453324 -0.015378 4.081969 H 6.707667 0.788270 2.529012 H 6.734528 1.739224 4.033459 H 3.335406 2.689435 2.768321 H 4.876252 3.311711 3.373745 H 4.773573 2.568578 1.754530 H 4.659717 1.953440 5.441365 H 3.070656 1.397928 4.885785 H 4.306733 0.208894 5.405782 C 4.387931 -1.972584 2.623667 C 3.305600 -2.804359 1.921568 C 5.750477 -2.2908351.983823 C 4.400591 -2.425387 4.099821 H 2.309145 -2.656985 2.353813 H 3.244713 -2.608098 0.849179 H 3.562556 -3.868435 2.041368 H 6.578773 -1.792243 2.501371 H 5.928555 -3.375485 2.042297 H 5.784132 -2.001341 0.929431 H 4.593520 -3.513431 4.091353 H 5.202358 -1.967974 4.704541 H 3.431180 -2.277912 4.608910 C 4.728374 1.151138 -3.445520 C 4.416797 2.507197 -2.785927 C 6.241325 0.902497 -3.516503 C 4.148286 1.161236 -4.869919 H 3.335406 2.689435 -2.768321 H 4.773573 2.568578 -1.754530 H 4.876252 3.311711 -3.373745 H 6.453324 -0.015378 -4.081969 H 6.734528 1.739224 -4.033459 H 6.707667 0.788270 -2.529012 H 4.659717 1.953440 -5.441365 H 4.306733 0.208894 -5.405782 H 3.070656 1.397928 -4.885785

159 C 4.387931 -1.972584 -2.623667 C 5.750477 -2.290835 -1.983823 C 3.305600 -2.804359 -1.921568 C 4.400591 -2.425387 -4.099821 H 6.578773 -1.792243 -2.501371 H 5.784132 -2.001341 -0.929431 H 5.928555 -3.375485 -2.042297 H 2.309145 -2.656985 -2.353813 H 3.562556 -3.868435 -2.041368 H 3.244713 -2.608098 -0.849179 H 4.593520 -3.513431 -4.091353 H 3.431180 -2.277912 -4.608910 H 5.202358 -1.967974 -4.704541

(Ar)IrNH3 R=H C 0.000262 -0.002371 -1.202509 C 1.401138 0.005214 -1.209038 C 2.155459 0.052078 0.000000 C 1.401138 0.005214 1.209038 C 0.000262 -0.002371 1.202509 C -0.710791 0.010642 0.000000 H -0.540788 -0.023230 -2.152799 H -0.540788 -0.023230 2.152799 H -1.800118 0.011988 0.000000 C 2.130892 -0.099377 2.526920 H 2.223580 -1.150843 2.837068 H 1.653824 0.449271 3.346940 C 2.130892 -0.099377 -2.526920 H 2.223580 -1.150843 -2.837068 H 1.653824 0.449271 -3.346940 P 3.843453 0.490410 -2.204842 P 3.843453 0.490410 2.204842 Ir 4.181428 0.250786 0.000000 N 6.396440 0.328654 0.000000 H 6.804437 -0.128035 0.817175 H 6.804437 -0.128035 -0.817175 H 6.734965 1.293194 0.000000 H 3.823042 1.832483 2.684796 H 4.574387 -0.036278 3.318569

160 H 3.823042 1.832483 -2.684796 H 4.574387 -0.036278 -3.318569

(Ar)IrNH3 R=Me C -0.000433 -0.007295 -1.204502 C 1.403660 0.001449 -1.205912 C 2.144634 0.032852 0.000000 C 1.403660 0.001449 1.205912 C -0.000433 -0.007295 1.204502 C -0.712684 0.004670 0.000000 H -0.539351 -0.008851 -2.156991 H -0.539351 -0.008851 2.156991 H -1.803746 0.014786 0.000000 C 2.161170 -0.034384 2.506222 H 2.336471 -1.066212 2.838498 H 1.663289 0.498147 3.325276 C 2.161170 -0.034384 -2.506222 H 2.336471 -1.066212 -2.838498 H 1.663289 0.498147 -3.325276 Ir 4.159641 0.364366 0.000000 P 3.773159 0.738748 2.159432 P 3.773159 0.738748 -2.159432 C 3.325737 2.503684 -2.331859 H 4.144049 3.163417 -2.031888 H 3.058660 2.686849 -3.381787 H 2.463998 2.704838 -1.688307 C 4.791428 0.418922 -3.619754 H 4.146588 0.653072 -4.490137 H 5.677364 1.069220 -3.623753 H 5.109398 -0.630527 -3.646548 C 3.325737 2.503684 2.331859 H 3.058660 2.686849 3.381787 H 4.144049 3.163417 2.031888 H 2.463998 2.704838 1.688307 C 4.791428 0.418922 3.619754 H 5.677364 1.069220 3.623753 H 4.146588 0.653072 4.490137 H 5.109398 -0.630527 3.646548 H 6.794714 0.285609 -0.819051

161 H 6.582119 1.674662 0.000000 H 6.794714 0.285609 0.819051 N 6.338454 0.684579 0.000000

t (Ar)IrNH3 R=Bu C 0.009577 0.181919 1.205960 C 1.408842 0.040840 1.203049 C 2.142791 -0.016382 0.000000 C 1.408842 0.040840 -1.203049 C 0.009577 0.181919 -1.205960 C -0.704214 0.265872 0.000000 H -0.522034 0.236993 2.164553 H -0.522034 0.236993 -2.164553 H -1.789741 0.387976 0.000000 C 2.136629 -0.084124 -2.513952 H 1.744146 0.562989 -3.303746 H 2.058681 -1.103870 -2.901939 C 2.136629 -0.084124 2.513952 H 1.744146 0.562989 3.303746 H 2.058681 -1.103870 2.901939 P 3.904692 0.257662 2.248890 P 3.904692 0.257662 -2.248890 Ir 4.141086 0.070957 0.000000 C 4.089990 2.094294 2.746279 C 5.446004 2.597323 2.229113 C 3.010094 2.809966 1.917161 C 3.901232 2.459794 4.226485 H 6.296452 2.061197 2.672378 H 5.484680 2.518763 1.134701 H 5.561063 3.661113 2.485166 H 1.993110 2.574238 2.242856 H 3.154656 3.894753 2.010783 H 3.085070 2.538833 0.865017 H 3.929536 3.560843 4.306651 H 2.920582 2.138498 4.622020 H 4.695775 2.064461 4.883149 C 4.739909 -1.147648 3.206415 C 4.499667 -2.367340 2.288058 C 6.246710 -0.877658 3.309511

162 C 4.164681 -1.457520 4.599121 H 3.433405 -2.590549 2.176574 H 4.886635 -2.195757 1.276427 H 4.985784 -3.250958 2.721364 H 6.452903 0.023172 3.906541 H 6.745172 -1.727315 3.802368 H 6.712949 -0.761991 2.320382 H 4.720840 -2.311052 5.021369 H 4.266291 -0.612729 5.303324 H 3.103606 -1.756945 4.561100 C 4.089990 2.094294 -2.746279 C 3.010094 2.809966 -1.917161 C 5.446004 2.597323 -2.229113 C 3.901232 2.459794 -4.226485 H 1.993110 2.574238 -2.242856 H 3.085070 2.538833 -0.865017 H 3.154656 3.894753 -2.010783 H 6.296452 2.061197 -2.672378 H 5.561063 3.661113 -2.485166 H 5.484680 2.518763 -1.134701 H 3.929536 3.560843 -4.306651 H 4.695775 2.064461 -4.883149 H 2.920582 2.138498 -4.622020 C 4.739909 -1.147648 -3.206415 C 6.246710 -0.877658 -3.309511 C 4.499667 -2.367340 -2.288058 C 4.164681 -1.457520 -4.599121 H 6.452903 0.023172 -3.906541 H 6.712949 -0.761991 -2.320382 H 6.745172 -1.727315 -3.802368 H 3.433405 -2.590549 -2.176574 H 4.985784 -3.250958 -2.721364 H 4.886635 -2.195757 -1.276427 H 4.720840 -2.311052 -5.021369 H 3.103606 -1.756945 -4.561100 H 4.266291 -0.612729 -5.303324 N 6.343514 0.241098 0.000000 H 6.685064 0.750586 -0.814747 H 6.685064 0.750586 0.814747 H 6.836884 -0.652043 0.000000

163

APPENDIX B

CALCULATED CARTESIAN COORDINATES IN CHAPTER 3

(MeO)3WN W 0.000158 -0.000703 -0.069258 N 0.001110 -0.000414 1.615016 O -0.085099 1.809095 -0.556939 O -1.525354 -0.978438 -0.556445 O 1.610604 -0.831067 -0.557220 C 2.680555 -1.383619 0.204012 H 2.790370 -2.449685 -0.055543 H 3.613456 -0.856280 -0.055931 H 2.481515 -1.280445 1.284307 C -0.139280 3.012731 0.203582 H -0.123949 2.790386 1.284180 H 0.727387 3.641315 -0.060475 H -1.064053 3.555885 -0.052783 C -2.543348 -1.623165 0.203930 H -3.519948 -1.187432 -0.064977 H -2.551252 -2.696736 -0.047705 H -2.361733 -1.494473 1.284597

MeCN C 0.000000 0.000000 -1.182685 H 0.000000 1.031900 -1.567583 H 0.893651 -0.515950 -1.567583 H -0.893651 -0.515950 -1.567583 C 0.000000 0.000000 0.276783 N 0.000000 0.000000 1.448308 164

Int1A W -0.613763 0.000022 -0.159029 O -0.066921 -1.562122 -1.029880 O -0.067605 1.562893 -1.029012 O -2.445579 -0.000535 0.242950 C 3.489993 0.000053 0.447675 N 3.532041 0.000802 -0.724377 N 0.175665 -0.000166 1.332604 C 0.908248 2.562368 -0.745743 H 1.148231 2.573516 0.331050 H 1.821963 2.346204 -1.321443 H 0.501912 3.541075 -1.048620 C 3.392935 -0.000890 1.902165 H 3.881914 0.891812 2.322705 H 2.321804 0.001078 2.176431 H 3.877963 -0.896455 2.321195 C 0.909321 -2.561404 -0.747320 H 1.822890 -2.344588 -1.323013 H 1.149443 -2.573111 0.329437 H 0.503296 -3.540080 -1.050715 C -3.170526 -0.000882 1.469645 H -2.481628 -0.001017 2.331489 H -3.811188 0.895824 1.505749 H -3.811031 -0.897716 1.505323

Int2A W 0.206000 -0.116638 -0.126031 O 0.913300 1.575801 0.412564 O -0.102143 -1.872979 0.492893 O 1.954151 -0.498128 -0.671406 C -1.903796 0.491892 -0.236923 N -0.986457 0.183520 -1.435665 N -1.445842 0.428120 0.970511 C -1.205218 -2.569335 1.037857 H -1.792937 -1.890541 1.682848 H -1.852766 -2.943087 0.224772 H -0.833631 -3.421889 1.628823 C -3.298255 0.838555 -0.671938

165 H -3.924695 1.046292 0.206021 H -3.262442 1.715502 -1.337213 H -3.714211 0.003502 -1.257286 C 0.392067 2.692738 1.105220 H 0.055936 3.456426 0.380911 H -0.468479 2.391036 1.729088 H 1.184539 3.125600 1.738734 C 3.260870 -0.192930 -0.225142 H 3.568076 -0.893839 0.570053 H 3.954922 -0.283703 -1.075264 H 3.271294 0.841398 0.164035

Int3A W 0.581212 -0.000016 0.088391 O 0.204563 -1.546732 -0.890629 O 0.204198 1.547259 -0.889548 O 2.318901 -0.000089 0.855622 C -3.525205 0.000378 -0.016935 N -0.460027 -0.000790 1.413385 N -3.342622 0.001847 -1.175552 C -0.798903 2.557637 -0.796998 H -1.611632 2.319924 -1.500987 H -1.204504 2.606513 0.227457 H -0.343740 3.524366 -1.066333 C -3.705424 -0.001760 1.429440 H -2.703864 -0.001995 1.898060 H -4.262543 0.891904 1.751539 H -4.261699 -0.896879 1.748942 C -0.798706 -2.557002 -0.798806 H -1.203916 -2.606931 0.225759 H -1.611669 -2.318351 -1.502214 H -0.343877 -3.523542 -1.069380 C 3.482923 -0.000038 0.023435 H 3.244989 -0.000175 -1.059605 H 4.080801 0.898415 0.248215 H 4.081092 -0.898253 0.248405

166

Ts1A W 0.232453 -0.146176 -0.054050 O 0.942778 1.631700 -0.255932 O -0.277674 -1.980560 -0.096206 O 2.028134 -0.688614 -0.219334 C -1.787355 0.561333 0.037638 N -1.324411 0.313162 -1.180210 N -0.950099 0.369047 1.247645 C -1.511036 -2.637682 0.047991 H -1.984695 -2.350524 1.008001 H -2.186731 -2.344593 -0.779404 H -1.359958 -3.729140 0.024294 C -3.174436 1.067167 0.320458 H -3.674434 0.372979 1.013471 H -3.106231 2.042352 0.826946 H -3.740931 1.158536 -0.615231 C 0.332772 2.884444 -0.070828 H -0.420552 3.054273 -0.865287 H -0.181995 2.918251 0.911015 H 1.090988 3.683355 -0.121708 C 3.184646 -0.230058 0.464040 H 3.144451 -0.486254 1.537759 H 4.064464 -0.715344 0.013692 H 3.262228 0.866267 0.350103

Ts2A W -0.231904 -0.099827 0.093839 O -0.811441 1.628433 -0.479357 O 0.044332 -1.855929 -0.568853 O -1.976753 -0.447832 0.679962 C 2.032902 0.443765 -0.022157 N 0.828670 0.083165 1.463317 N 1.508121 0.376777 -1.127901 C 1.166568 -2.697714 -0.725394 H 1.849670 -2.285949 -1.490507 H 1.715193 -2.802287 0.229445 H 0.820840 -3.691670 -1.054218 C 3.300195 0.711324 0.691590

167 H 3.578404 -0.166537 1.292636 H 4.089686 0.942937 -0.039357 H 3.160363 1.552808 1.385706 C -0.191902 2.869854 -0.735309 H 0.254725 3.283805 0.188256 H 0.601529 2.756792 -1.495989 H -0.950916 3.575676 -1.112303 C -3.245655 -0.195497 0.103733 H -3.467467 -0.933584 -0.687519 H -4.011805 -0.274245 0.891218 H -3.258590 0.822093 -0.328149

A' W 0.000001 0.010481 0.101793 N 0.000038 -0.726791 1.612956 O 1.555618 -0.594541 -0.752698 O -0.000075 1.865467 0.506361 O -1.555568 -0.594673 -0.752693 C -2.603384 -1.467147 -0.333418 H -3.555908 -0.912309 -0.346298 H -2.670353 -2.308313 -1.042856 H -2.405946 -1.848160 0.682562 C 2.603507 -1.466928 -0.333424 H 2.406097 -1.847964 0.682552 H 2.670553 -2.308083 -1.042868 H 3.555983 -0.912007 -0.346295 C -0.000138 2.866932 -0.514323 H -0.897788 3.495764 -0.394436 H 0.897696 3.495567 -0.394762 H -0.000375 2.450278 -1.541732

Ts-A' W 0.000911 -0.025797 0.048256 N 0.513471 0.181973 1.640866 O 0.051959 1.692630 -0.688681 O -1.684520 -0.841552 0.116452 O 1.311673 -1.120612 -0.722528 C 2.485830 -1.722028 -0.181471

168 H 2.394744 -2.818029 -0.260254 H 3.356471 -1.392736 -0.772424 H 2.617206 -1.431389 0.874517 C 0.418307 2.959696 -0.144393 H 0.695577 2.857067 0.918131 H 1.269872 3.359257 -0.719160 H -0.435902 3.648887 -0.246388 C -3.035276 -0.969342 -0.250710 H -3.262557 -0.402300 -1.171873 H -3.259272 -2.035088 -0.427194 H -3.683928 -0.604225 0.565112

(MeO)3MoN Mo -0.000187 -0.000275 -0.092891 N 0.000068 0.001093 1.566949 O 0.243546 1.810226 -0.587727 O -1.689909 -0.694933 -0.586307 O 1.445941 -1.116659 -0.586307 C 2.384273 -1.841499 0.194417 H 2.306639 -2.915093 -0.050988 H 3.403419 -1.495870 -0.052027 H 2.199872 -1.698102 1.274497 C 0.405220 2.983805 0.194357 H 0.376180 2.749708 1.273892 H 1.373437 3.453074 -0.053047 H -0.403807 3.694704 -0.048480 C -2.788452 -1.140840 0.194525 H -3.680456 -0.542853 -0.061595 H -2.993711 -2.199749 -0.040963 H -2.577052 -1.039772 1.274429

Int1B Mo 0.782591 -0.000177 -0.214068 O 0.232777 1.578334 -1.089082 O 0.236757 -1.578250 -1.092767 O 2.629398 0.000486 0.194945 C -3.341492 0.002345 0.445242 N -3.377237 0.011815 -0.726664

169 N -0.000132 -0.002452 1.254298 C -0.755976 -2.547090 -0.783685 H -0.977376 -2.553355 0.298655 H -1.679267 -2.314992 -1.339581 H -0.383066 -3.539623 -1.088565 C -3.262567 -0.010609 1.901211 H -3.750784 -0.910910 2.306168 H -2.198846 -0.008306 2.196427 H -3.759615 0.877073 2.322878 C -0.758063 2.547739 -0.775521 H -1.680869 2.321155 -1.334395 H -0.981473 2.547491 0.306376 H -0.382151 3.541256 -1.073354 C 3.322644 0.002402 1.434781 H 2.619817 -0.004523 2.286951 H 3.969969 -0.890053 1.487171 H 3.957671 0.903403 1.491750

Int2B Mo 0.739231 0.000006 0.120290 O 0.387062 -1.564137 -0.872083 O 0.387078 1.564249 -0.871937 O 2.476178 -0.000239 0.922996 C -3.396277 0.000004 -0.019304 N -0.314000 -0.000109 1.405316 N -3.184919 0.000114 -1.172753 C -0.631131 2.552548 -0.774128 H -1.438645 2.313584 -1.485340 H -1.047946 2.589420 0.247780 H -0.193210 3.532286 -1.029078 C -3.621607 -0.000120 1.421148 H -4.188613 0.894024 1.723952 H -4.188572 -0.894350 1.723778 H -2.640916 -0.000149 1.928064 C -0.631209 -2.552383 -0.774358 H -1.047921 -2.589408 0.247589 H -1.438778 -2.313226 -1.485438 H -0.193385 -3.532104 -1.029531 C 3.616929 0.000014 0.065600

170 H 3.355059 0.002175 -1.012810 H 4.223336 0.897832 0.274228 H 4.221546 -0.899725 0.271138

TsB Mo 0.309836 -0.162776 -0.138647 O 0.952651 1.672620 -0.224977 O -0.162786 -2.030756 -0.119087 O 2.122186 -0.632942 -0.378612 C -1.750908 0.470325 -0.054292 N -1.282178 0.266192 -1.263730 N -0.886097 0.279475 1.160134 C -1.337249 -2.676990 0.282273 H -1.724724 -2.224043 1.220091 H -2.112494 -2.565592 -0.502949 H -1.146188 -3.752228 0.441063 C -3.151304 0.913992 0.262927 H -3.618717 0.179896 0.937612 H -3.114871 1.875934 0.797574 H -3.731176 1.012067 -0.664394 C 0.318120 2.854079 0.175601 H -0.426520 3.158034 -0.588301 H -0.218634 2.698221 1.136390 H 1.056894 3.666773 0.287078 C 3.175649 -0.303036 0.510590 H 3.001940 -0.716065 1.521727 H 4.106437 -0.734613 0.108543 H 3.270637 0.796953 0.572723

Ts-B' Mo 0.024354 -0.062221 0.054164 N 0.461913 0.252242 1.626928 O -0.423326 1.623677 -0.660437 O -1.382192 -1.337576 0.100867 O 1.591600 -0.773172 -0.721795 C 2.869695 -1.015289 -0.148238 H 3.094599 -2.093791 -0.210148 H 3.630759 -0.459381 -0.722274

171 H 2.894596 -0.691984 0.907590 C -0.389257 2.926084 -0.089097 H -0.078655 2.884300 0.969677 H 0.319625 3.549873 -0.659616 H -1.394681 3.373905 -0.163683 C -2.752647 -1.459982 -0.207233 H -3.059583 -0.774682 -1.019841 H -2.948583 -2.496446 -0.533214 H -3.369730 -1.252502 0.686450

B' Mo -0.000007 0.011457 0.140588 N -0.000161 -0.731436 1.622333 O 1.572001 -0.578259 -0.730459 O 0.000289 1.876730 0.563060 O -1.572175 -0.577768 -0.730500 C -2.610084 -1.449417 -0.301259 H -3.566094 -0.898351 -0.298706 H -2.688258 -2.291227 -1.010444 H -2.406735 -1.838577 0.711868 C 2.609574 -1.450316 -0.301233 H 2.406078 -1.839410 0.711890 H 2.687420 -2.292150 -1.010426 H 3.565797 -0.899621 -0.298677 C 0.000566 2.835357 -0.493173 H -0.897876 3.469652 -0.402955 H 0.898445 3.470284 -0.401828 H 0.001387 2.378887 -1.504573

172 APPENDIX C

CALCULATED CARTESIAN COORDINATES FOR MOLECULES IN CHAPTER 4

t ( BuO)3CrN Cr 0.000000 0.000000 0.142516 N 0.000000 0.000000 -1.406651 O 1.668282 0.000000 0.718769 O -0.834141 -1.444774 0.718769 O -0.834141 1.444774 0.718769 C -1.480656 2.564571 0.057394 C 2.961312 0.000000 0.057394 C -1.480656 -2.564571 0.057394 C -1.991722 3.449764 1.199162 H -1.155264 3.782387 1.826914 H -2.502616 4.334657 0.795910 H -2.698011 2.891682 1.826914 C -2.638071 2.043585 -0.794809 H -2.261786 1.383614 -1.586214 H -3.346901 1.483120 -0.171867 H -3.171903 2.881363 -1.263809 C -0.450760 3.306429 -0.794809 H -0.909383 4.187630 -1.263809 H 0.389031 3.640062 -0.171867 H -0.067351 2.650571 -1.586214 C -0.450760 -3.306429 -0.794809 H -0.067351 -2.650571 -1.586214 H 0.389031 -3.640062 -0.171867 H -0.909383 -4.187630 -1.263809 C -1.991722 -3.449764 1.199162 H -2.698011 -2.891682 1.826914 173 H -2.502616 -4.334657 0.795910 H -1.155264 -3.782387 1.826914 C -2.638071 -2.043585 -0.794809 H -3.171903 -2.881363 -1.263809 H -3.346901 -1.483120 -0.171867 H -2.261786 -1.383614 -1.586214 C 3.088832 -1.262845 -0.794809 H 2.957870 -2.156942 -0.171867 H 2.329138 -1.266958 -1.586214 H 4.081285 -1.306267 -1.263809 C 3.088832 1.262845 -0.794809 H 2.957870 2.156942 -0.171867 H 4.081285 1.306267 -1.263809 H 2.329138 1.266958 -1.586214 C 3.983444 0.000000 1.199162 H 5.005231 0.000000 0.795910 H 3.853275 0.890705 1.826914 H 3.853275 -0.890705 1.826914

t ( BuO)3MoN Mo 0.000000 0.000000 0.161963 N 0.000000 0.000000 -1.517669 O 0.908237 -1.573113 0.732535 O -1.816474 0.000000 0.732535 O 0.908237 1.573113 0.732535 C 1.551075 2.686541 0.037300 C 1.551075 -2.686541 0.037300 C -3.102150 0.000000 0.037300 C 2.077162 3.597750 1.148495 H 2.793107 3.055894 1.779829 H 2.582333 4.472732 0.717009 H 1.249929 3.946848 1.779829 C 0.508435 3.404413 -0.818463 H 0.115433 2.729636 -1.589648 H -0.322522 3.754960 -0.192608 H 0.958255 4.274159 -1.316579 C 2.694090 2.142524 -0.818463 H 3.222403 2.966953 -1.316579 H 3.413152 1.598168 -0.192608

174 H 2.306217 1.464786 -1.589648 C -3.202526 1.261888 -0.818463 H -3.090630 2.156792 -0.192608 H -2.421650 1.264850 -1.589648 H -4.180658 1.307206 -1.316579 C -3.202526 -1.261888 -0.818463 H -3.090630 -2.156792 -0.192608 H -4.180658 -1.307206 -1.316579 H -2.421650 -1.264850 -1.589648 C -4.154323 0.000000 1.148495 H -5.164666 0.000000 0.717009 H -4.043035 -0.890954 1.779829 H -4.043035 0.890954 1.779829 C 0.508435 -3.404413 -0.818463 H -0.322522 -3.754960 -0.192608 H 0.115433 -2.729636 -1.589648 H 0.958255 -4.274159 -1.316579 C 2.694090 -2.142524 -0.818463 H 3.413152 -1.598168 -0.192608 H 3.222403 -2.966953 -1.316579 H 2.306217 -1.464786 -1.589648 C 2.077162 -3.597750 1.148495 H 2.582333 -4.472732 0.717009 H 2.793107 -3.055894 1.779829 H 1.249929 -3.946848 1.779829

t ( BuO)3WN W 0.000000 0.000000 0.140993 N 0.000000 0.000000 -1.573612 O 0.911903 -1.579462 0.709283 O -1.823806 0.000000 0.709283 O 0.911903 1.579462 0.709283 C 1.556867 2.696573 0.009633 C 1.556867 -2.696573 0.009633 C -3.113735 0.000000 0.009633 C 2.082609 3.607185 1.120007 H 2.799254 3.066291 1.751529 H 2.587586 4.481831 0.687950 H 1.255859 3.957371 1.751529

175 C 0.511509 3.408362 -0.845915 H 0.116809 2.725884 -1.609424 H -0.316830 3.764232 -0.219441 H 0.959905 4.274269 -1.351896 C 2.695973 2.147161 -0.845915 H 3.221673 2.968437 -1.351896 H 3.418335 1.607733 -0.219441 H 2.302280 1.464101 -1.609424 C -3.207483 1.261201 -0.845915 H -3.101505 2.156499 -0.219441 H -2.419089 1.261783 -1.609424 H -4.181578 1.305833 -1.351896 C -3.207483 -1.261201 -0.845915 H -3.101505 -2.156499 -0.219441 H -4.181578 -1.305833 -1.351896 H -2.419089 -1.261783 -1.609424 C -4.165218 0.000000 1.120007 H -5.175173 0.000000 0.687950 H -4.055113 -0.891080 1.751529 H -4.055113 0.891080 1.751529 C 0.511509 -3.408362 -0.845915 H -0.316830 -3.764232 -0.219441 H 0.116809 -2.725884 -1.609424 H 0.959905 -4.274269 -1.351896 C 2.695973 -2.147161 -0.845915 H 3.418335 -1.607733 -0.219441 H 3.221673 -2.968437 -1.351896 H 2.302280 -1.464101 -1.609424 C 2.082609 -3.607185 1.120007 H 2.587586 -4.481831 0.687950 H 2.799254 -3.066291 1.751529 H 1.255859 -3.957371 1.751529

i ( PrO)3MoN Mo 0.000000 0.000000 -0.023293 N 0.000000 0.000000 1.652468 O -1.831423 0.000000 -0.539811 O 0.915712 -1.586059 -0.539811 O 0.915712 1.586059 -0.539811

176 C 1.517387 2.628192 0.263043 C -3.034775 0.000000 0.263043 C 1.517387 -2.628192 0.263043 C 0.806102 3.937884 -0.047457 H 0.906952 4.183328 -1.113349 H -0.261594 3.864123 0.193683 H 1.239286 4.757058 0.542288 C 3.007257 2.667047 -0.047457 H 3.500090 3.451782 0.542288 H 3.477225 1.705514 0.193683 H 3.169392 2.877108 -1.113349 C 0.806102 -3.937884 -0.047457 H -0.261594 -3.864123 0.193683 H 0.906952 -4.183328 -1.113349 H 1.239286 -4.757058 0.542288 C 3.007257 -2.667047 -0.047457 H 3.477225 -1.705514 0.193683 H 3.500090 -3.451782 0.542288 H 3.169392 -2.877108 -1.113349 C -3.813359 1.270838 -0.047457 H -3.215632 2.158608 0.193683 H -4.076344 1.306220 -1.113349 H -4.739376 1.305276 0.542288 C -3.813359 -1.270838 -0.047457 H -3.215632 -2.158608 0.193683 H -4.739376 -1.305276 0.542288 H -4.076344 -1.306220 -1.113349 H 1.365411 2.364961 1.322575 H 1.365411 -2.364961 1.322575 H -2.730822 0.000000 1.322575

(Me2CF3CO)3MoN Mo 0.000000 0.000000 0.262954 N 0.000000 0.000000 1.938252 O -0.914286 -1.583590 -0.281152 O 1.828572 0.000000 -0.281152 O -0.914286 1.583590 -0.281152 C -1.540887 2.668895 0.430246 C -1.540887 -2.668895 0.430246

177 C 3.081774 0.000000 0.430246 C -2.073053 3.590633 -0.697567 C -0.511612 3.422181 1.270017 H -0.137289 2.750121 2.051892 H 0.324661 3.758083 0.647112 H -0.970560 4.294025 1.751113 C -2.707890 2.154160 1.270017 H -3.233455 2.987542 1.751113 H -3.416926 1.597877 0.647112 H -2.313030 1.493957 2.051892 C 3.219502 1.268022 1.270017 H 3.092265 2.160207 0.647112 H 2.450319 1.256164 2.051892 H 4.204014 1.306483 1.751113 C 3.219502 -1.268022 1.270017 H 3.092265 -2.160207 0.647112 H 4.204014 -1.306483 1.751113 H 2.450319 -1.256164 2.051892 C 4.146105 0.000000 -0.697567 C -0.511612 -3.422181 1.270017 H 0.324661 -3.758083 0.647112 H -0.137289 -2.750121 2.051892 H -0.970560 -4.294025 1.751113 C -2.707890 -2.154160 1.270017 H -3.416926 -1.597877 0.647112 H -3.233455 -2.987542 1.751113 H -2.313030 -1.493957 2.051892 C -2.073053 -3.590633 -0.697567 F -2.703312 4.682273 -0.168522 F -1.075434 4.051086 -1.495255 F -2.970626 2.956896 -1.495255 F -2.703312 -4.682273 -0.168522 F -2.970626 -2.956896 -1.495255 F -1.075434 -4.051086 -1.495255 F 5.406623 0.000000 -0.168522 F 4.046060 -1.094190 -1.495255 F 4.046060 1.094190 -1.495255

178

t + [( BuO)3CrN] Cr 0.000000 0.000000 0.119148 N 0.000000 0.000000 -1.420220 O 1.676644 0.000000 0.705588 O -0.838322 -1.452016 0.705588 O -0.838322 1.452016 0.705588 C -1.488799 2.578676 0.085187 C 2.977599 0.000000 0.085187 C -1.488799 -2.578676 0.085187 C -1.996713 3.458409 1.222523 H -1.165109 3.800108 1.850838 H -2.504599 4.338092 0.807502 H -2.708435 2.909068 1.850838 C -2.640697 2.046036 -0.795082 H -2.255929 1.405461 -1.596205 H -3.351149 1.485902 -0.175687 H -3.155488 2.903799 -1.244631 C -0.451571 3.309928 -0.795082 H -0.937020 4.184633 -1.244631 H 0.388746 3.645132 -0.175687 H -0.089201 2.656422 -1.596205 C -0.451571 -3.309928 -0.795082 H -0.089201 -2.656422 -1.596205 H 0.388746 -3.645132 -0.175687 H -0.937020 -4.184633 -1.244631 C -1.996713 -3.458409 1.222523 H -2.708435 -2.909068 1.850838 H -2.504599 -4.338092 0.807502 H -1.165109 -3.800108 1.850838 C -2.640697 -2.046036 -0.795082 H -3.155488 -2.903799 -1.244631 H -3.351149 -1.485902 -0.175687 H -2.255929 -1.405461 -1.596205 C 3.092267 -1.263893 -0.795082 H 2.962404 -2.159229 -0.175687 H 2.345129 -1.250961 -1.596205 H 4.092508 -1.280833 -1.244631 C 3.092267 1.263893 -0.795082 H 2.962404 2.159229 -0.175687

179 H 4.092508 1.280833 -1.244631 H 2.345129 1.250961 -1.596205 C 3.993427 0.000000 1.222523 H 5.009197 0.000000 0.807502 H 3.873544 0.891040 1.850838 H 3.873544 -0.891040 1.850838

t + [( BuO)3MoN] Mo 0.000000 0.000000 0.137914 N 0.000000 0.000000 -1.536269 O 0.901801 -1.561966 0.687057 O -1.803603 0.000000 0.687057 O 0.901801 1.561966 0.687057 C 1.556384 2.695736 0.038271 C 1.556384 -2.695736 0.038271 C -3.112768 0.000000 0.038271 C 2.063979 3.574917 1.204878 H 2.774895 3.016296 1.823800 H 2.569285 4.450132 0.777021 H 1.224741 3.911277 1.823800 C 0.517581 3.443425 -0.793638 H 0.143970 2.804115 -1.604743 H -0.324080 3.769219 -0.170494 H 0.978576 4.332748 -1.241279 C 2.723303 2.169951 -0.793638 H 3.262982 3.013846 -1.241279 H 3.426279 1.603948 -0.170494 H 2.356450 1.526739 -1.604743 C -3.240884 1.273475 -0.793638 H -3.102199 2.165271 -0.170494 H -2.500420 1.277376 -1.604743 H -4.241558 1.318902 -1.241279 C -3.240884 -1.273475 -0.793638 H -3.102199 -2.165271 -0.170494 H -4.241558 -1.318902 -1.241279 H -2.500420 -1.277376 -1.604743 C -4.127959 0.000000 1.204878 H -5.138570 0.000000 0.777021 H -3.999636 -0.894981 1.823800

180 H -3.999636 0.894981 1.823800 C 0.517581 -3.443425 -0.793638 H -0.324080 -3.769219 -0.170494 H 0.143970 -2.804115 -1.604743 H 0.978576 -4.332748 -1.241279 C 2.723303 -2.169951 -0.793638 H 3.426279 -1.603948 -0.170494 H 3.262982 -3.013846 -1.241279 H 2.356450 -1.526739 -1.604743 C 2.063979 -3.574917 1.204878 H 2.569285 -4.450132 0.777021 H 2.774895 -3.016296 1.823800 H 1.224741 -3.911277 1.823800

t + [( BuO)3WN] W 0.000000 0.000000 0.073802 N 0.000000 0.000000 -1.641626 O 0.895779 -1.551535 0.652895 O -1.791558 0.000000 0.652895 O 0.895779 1.551535 0.652895 C 1.571891 2.722595 0.063463 C 1.571891 -2.722595 0.063463 C -3.143781 0.000000 0.063463 C 2.052169 3.554461 1.265638 H 2.750366 2.974781 1.880238 H 2.567316 4.446722 0.888059 H 1.201053 3.869278 1.880238 C 0.543998 3.486743 -0.764054 H 0.184494 2.869096 -1.597757 H -0.307610 3.795795 -0.145699 H 1.010043 4.389393 -1.179290 C 2.747609 2.214487 -0.764054 H 3.296304 3.069419 -1.179290 H 3.441060 1.631499 -0.145699 H 2.392463 1.594325 -1.597757 C -3.291607 1.272256 -0.764054 H -3.133449 2.164295 -0.145699 H -2.576957 1.274771 -1.597757 H -4.306347 1.319973 -1.179290

181 C -3.291607 -1.272256 -0.764054 H -3.133449 -2.164295 -0.145699 H -4.306347 -1.319973 -1.179290 H -2.576957 -1.274771 -1.597757 C -4.104338 0.000000 1.265638 H -5.134632 0.000000 0.888059 H -3.951419 -0.894497 1.880238 H -3.951419 0.894497 1.880238 C 0.543998 -3.486743 -0.764054 H -0.307610 -3.795795 -0.145699 H 0.184494 -2.869096 -1.597757 H 1.010043 -4.389393 -1.179290 C 2.747609 -2.214487 -0.764054 H 3.441060 -1.631499 -0.145699 H 3.296304 -3.069419 -1.179290 H 2.392463 -1.594325 -1.597757 C 2.052169 -3.554461 1.265638 H 2.567316 -4.446722 0.888059 H 2.750366 -2.974781 1.880238 H 1.201053 -3.869278 1.880238

i + [( PrO)3MoN] Mo 0.000000 0.000000 0.093654 N 0.000000 0.000000 1.768996 O -1.803039 0.000000 -0.446615 O 0.901520 -1.561478 -0.446615 O 0.901520 1.561478 -0.446615 C 1.554517 2.692503 0.169905 C -3.109034 0.000000 0.169905 C 1.554517 -2.692503 0.169905 C 0.806070 3.963416 -0.200319 H 0.869654 4.138138 -1.282945 H -0.249824 3.903283 0.088296 H 1.259686 4.816594 0.318597 C 3.029384 2.679785 -0.200319 H 3.541450 3.499217 0.318597 H 3.505254 1.735288 0.088296 H 3.148906 2.822211 -1.282945 C 0.806070 -3.963416 -0.200319

182 H -0.249824 -3.903283 0.088296 H 0.869654 -4.138138 -1.282945 H 1.259686 -4.816594 0.318597 C 3.029384 -2.679785 -0.200319 H 3.505254 -1.735288 0.088296 H 3.541450 -3.499217 0.318597 H 3.148906 -2.822211 -1.282945 C -3.835454 1.283631 -0.200319 H -3.255430 2.167995 0.088296 H -4.018560 1.315927 -1.282945 H -4.801136 1.317377 0.318597 C -3.835454 -1.283631 -0.200319 H -3.255430 -2.167995 0.088296 H -4.801136 -1.317377 0.318597 H -4.018560 -1.315927 -1.282945 H 1.456986 2.523575 1.263358 H 1.456986 -2.523575 1.263358 H -2.913973 0.000000 1.263358

+ [(Me2CF3CO)3MoN] Mo 0.000000 0.000000 0.348858 N 0.000000 0.000000 2.019437 O -0.907197 -1.571312 -0.185291 O 1.814394 0.000000 -0.185291 O -0.907197 1.571312 -0.185291 C -1.551232 2.686813 0.451794 C -1.551232 -2.686813 0.451794 C 3.102465 0.000000 0.451794 C -2.057580 3.563833 -0.766131 C -0.538142 3.489822 1.261570 H -0.189850 2.873293 2.100655 H 0.315673 3.790902 0.645330 H -1.016151 4.388839 1.667412 C -2.753203 2.210955 1.261570 H -3.292770 3.074432 1.667412 H -3.440854 1.622070 0.645330 H -2.393420 1.601062 2.100655 C 3.291345 1.278866 1.261570 H 3.125181 2.168832 0.645330

183 H 2.583270 1.272231 2.100655 H 4.308922 1.314407 1.667412 C 3.291345 -1.278866 1.261570 H 3.125181 -2.168832 0.645330 H 4.308922 -1.314407 1.667412 H 2.583270 -1.272231 2.100655 C 4.115160 0.000000 -0.766131 C -0.538142 -3.489822 1.261570 H 0.315673 -3.790902 0.645330 H -0.189850 -2.873293 2.100655 H -1.016151 -4.388839 1.667412 C -2.753203 -2.210955 1.261570 H -3.440854 -1.622070 0.645330 H -3.292770 -3.074432 1.667412 H -2.393420 -1.601062 2.100655 C -2.057580 -3.563833 -0.766131 F -2.690112 4.659410 -0.289558 F -1.025454 3.965301 -1.536715 F -2.921324 2.870720 -1.536715 F -2.690112 -4.659410 -0.289558 F -2.921324 -2.870720 -1.536715 F -1.025454 -3.965301 -1.536715 F 5.380223 0.000000 -0.289558 F 3.946778 -1.094581 -1.536715 F 3.946778 1.094581 -1.536715

184 APPENDIX D

CALCULATED CARTESIAN COORDINATES FOR REACTANTS, STATIONARY POINTS, AND PRODUCTS IN CHAPTER 5

MeCN C 0.000000 0.000000 -1.182558 H 0.000000 1.031670 -1.567566 H 0.893452 -0.515835 -1.567566 H -0.893452 -0.515835 -1.567566 C 0.000000 0.000000 0.276768 N 0.000000 0.000000 1.448205

185 W2(OMe)6 W 1.170548 0.009984 0.020459 W -1.170326 -0.009859 -0.020614 O 1.672467 1.591869 -0.911332 O 1.699371 -1.588950 -0.866219 O 1.635088 0.039506 1.866035 O -1.699561 1.591061 0.861644 O -1.634878 -0.044593 -1.865837 O -1.672310 -1.589086 0.915279 C -1.017372 -2.664259 1.569806 H -1.356500 -2.710216 2.619670 H -1.290396 -3.612413 1.073968 H 0.080851 -2.547901 1.548589 C -0.951217 -0.057039 -3.109350 H -1.262813 -0.946136 -3.685288 H -1.225753 0.844495 -3.684911 H 0.144598 -0.079476 -2.972740 C -1.065609 2.696755 1.485750 H -1.386528 3.627900 0.986437 H -1.376746 2.744378 2.544200 H 0.035155 2.619941 1.435374 C 1.064119 -2.697222 -1.484385 H 1.365111 -3.624362 -0.965541 H -0.036419 -2.607340 -1.455034 H 1.393825 -2.764258 -2.536131 C 0.950710 0.056095 3.109072 H 1.242888 -0.831948 3.696777 H 1.244202 0.958910 3.673100 H -0.145279 0.055063 2.971919 C 1.017581 2.664856 -1.569415 H -0.081275 2.560306 -1.528352 H 1.308784 3.616331 -1.090590 H 1.339219 2.693857 -2.625392

186

F1 W -1.191804 -0.227844 -0.055979 W 1.153230 -0.162463 0.092286 O 1.671358 0.146563 1.929322 O 1.827675 0.135212 -1.712896 O -1.604352 -0.821752 1.734575 O 1.473864 -2.075728 0.112526 O -1.584613 -1.524339 -1.379507 O -1.681831 1.586795 -0.510984 N 1.046802 1.998017 0.065277 C 0.908397 3.158788 -0.008416 C -3.053562 1.877718 -0.781088 H -3.403766 2.667864 -0.092851 H -3.153128 2.240216 -1.819564 H -3.721624 0.999672 -0.662632 C 0.715683 4.596969 -0.089130 H 1.335135 5.114508 0.660947 H 1.003223 4.960982 -1.088292 H -0.342163 4.851047 0.084808 C 1.284578 0.757427 -2.853160 H 1.956964 0.589645 -3.714777 H 0.281822 0.358304 -3.102137 H 1.184862 1.851734 -2.704343 C 1.021293 0.670082 3.069304 H 0.058598 0.160297 3.244318 H 1.676412 0.535007 3.948992 H 0.831215 1.755355 2.946894 C -2.959682 -1.152749 2.047439 H -3.034539 -2.237535 2.237049 H -3.260510 -0.609475 2.960274 H -3.677620 -0.893965 1.240696 C -0.820458 -2.481925 -2.119330 H -1.485175 -3.325247 -2.372125 H -0.456630 -2.020428 -3.053050 H 0.039090 -2.830765 -1.526209 C 2.803381 -2.553628 0.283078 H 2.783831 -3.656856 0.314649 H 3.457285 -2.239762 -0.554809 H 3.238999 -2.184090 1.232102

187 F2 W -1.024514 -0.460906 -0.000041 W 1.257801 0.217014 -0.000057 O 1.815343 0.844655 1.731419 O 1.815255 0.845110 -1.731384 O -1.584426 0.009572 1.809494 O 2.301633 -1.399495 -0.000232 O -1.213470 -2.333229 -0.000138 O -1.584530 0.009930 -1.809449 N -0.120784 1.862613 0.000163 C -1.109195 2.521841 0.000423 C -2.865175 -0.442812 -2.244416 H -3.178713 0.162413 -3.113272 H -2.821515 -1.504713 -2.548382 H -3.647135 -0.343349 -1.462003 C -2.242156 3.429596 0.000526 H -2.865674 3.258740 0.893818 H -1.909793 4.482411 0.001562 H -2.864633 3.260156 -0.893763 C 1.156385 1.460951 -2.827025 H 1.772312 1.307826 -3.730485 H 0.154093 1.033211 -2.984298 H 1.064831 2.550346 -2.653601 C 1.156513 1.460265 2.827212 H 0.154612 1.031811 2.985023 H 1.772978 1.307834 3.730421 H 1.064017 2.549547 2.653572 C -2.864970 -0.443447 2.244501 H -2.821826 -1.506158 2.545718 H -3.177236 0.159788 3.115191 H -3.647567 -0.341380 1.463068 C -0.287779 -3.425263 -0.000389 H -0.475033 -4.040168 0.896203 H -0.474712 -4.039522 -0.897493 H 0.750855 -3.063447 -0.000090 C 3.725481 -1.380524 0.000212 H 4.095557 -2.419881 0.000053 H 4.112176 -0.865621 -0.899708 H 4.111584 -0.866078 0.900645

188 F3 W 1.014671 -0.034452 0.112375 W -1.460890 0.182637 -0.115500 O -2.367078 -0.331272 1.478251 O -2.109565 -0.379284 -1.811146 O 1.113608 0.056334 2.055049 O -1.567544 2.042198 -0.139983 O 2.177946 1.519700 0.143702 O 1.428074 -0.141951 -1.809995 N -0.449287 -1.613685 0.004560 C 0.729332 -2.090619 0.143834 C 2.661239 -0.631633 -2.304951 H 3.527749 -0.251623 -1.727027 H 2.687416 -1.738643 -2.271649 H 2.784516 -0.317207 -3.356756 C 1.192840 -3.501704 0.273275 H 1.626277 -3.665262 1.274931 H 0.362224 -4.210502 0.125049 H 1.988853 -3.718740 -0.457287 C -1.562012 -1.253172 -2.798729 H -2.206219 -1.196384 -3.691198 H -0.533014 -0.953018 -3.050123 H -1.558198 -2.289024 -2.417299 C -1.975143 -1.174394 2.561594 H -0.993662 -0.867204 2.956207 H -2.743516 -1.092214 3.347678 H -1.919100 -2.221693 2.217157 C 2.299340 0.011340 2.823980 H 2.977216 0.831422 2.519193 H 2.044976 0.134527 3.891152 H 2.835123 -0.951466 2.702612 C 2.702182 2.374405 -0.846513 H 2.371459 3.413246 -0.658054 H 3.807706 2.359709 -0.817607 H 2.361316 2.071935 -1.854027 C -1.037980 3.277542 0.298303 H 0.048359 3.183258 0.456249 H -1.243033 4.044143 -0.466752 H -1.523591 3.568419 1.245032

189 F4 W -1.146191 -0.064122 0.034474 W 1.460929 0.066148 -0.255549 O 2.611429 -0.958330 0.860543 O 2.192079 1.747347 -0.697212 O -0.445868 -1.911878 0.308372 O 1.488511 -0.802047 -1.924781 O -2.643877 -0.967322 -0.791307 O -1.701539 1.605858 -0.768841 N 0.431964 0.662297 1.270936 C -0.796964 0.607857 1.831117 C -2.235395 2.827827 -0.310880 H -3.197465 3.036185 -0.814057 H -2.392970 2.819113 0.784784 H -1.540092 3.651513 -0.558100 C -1.147487 0.956639 3.239354 H -0.598731 0.315255 3.953162 H -0.877219 2.003001 3.467274 H -2.225693 0.829375 3.416300 C 1.824086 3.075323 -0.329629 H 2.742143 3.630934 -0.076372 H 1.330365 3.564882 -1.185553 H 1.142260 3.065129 0.536849 C 2.408188 -1.523615 2.148080 H 1.767505 -2.418434 2.076248 H 3.392291 -1.809530 2.554996 H 1.927274 -0.787664 2.816820 C -1.053198 -2.964473 1.035447 H -2.101989 -3.092801 0.704440 H -0.505476 -3.906546 0.853683 H -1.050519 -2.758666 2.124100 C -3.936281 -0.479160 -1.090737 H -4.411521 -1.146280 -1.830826 H -4.574821 -0.453305 -0.187509 H -3.877805 0.542187 -1.512482 C 0.767186 -1.760903 -2.677140 H -0.042116 -1.263545 -3.238211 H 1.463192 -2.237008 -3.387323 H 0.330358 -2.515807 -2.003093

190 F5 W -1.283377 -0.049513 -0.048571 W 1.376215 0.030383 -0.234055 O 2.702950 -0.568280 1.003458 O 2.079117 1.613819 -1.013662 O 0.057633 -1.634265 0.321010 O 1.589040 -0.956952 -1.846653 O -2.562403 -1.384039 -0.528018 O -1.951128 1.450141 -1.004311 N 0.319303 0.842529 1.148867 C -0.938712 0.728499 1.678634 C -2.332242 2.786922 -0.740255 H -3.352491 2.956939 -1.126346 H -2.308368 3.002148 0.343294 H -1.644467 3.474624 -1.262553 C -1.358374 1.203711 3.031345 H -0.808934 0.668272 3.827174 H -1.141192 2.279650 3.155723 H -2.435846 1.043862 3.187252 C 1.930715 2.978134 -0.660565 H 2.908527 3.375424 -0.336141 H 1.597234 3.545679 -1.546211 H 1.197583 3.094144 0.159066 C 2.758077 -0.723231 2.409075 H 2.619979 -1.781961 2.690075 H 3.754628 -0.397287 2.753605 H 1.979620 -0.108933 2.896999 C 0.064150 -2.504601 1.444936 H -0.864809 -3.101020 1.435872 H 0.931265 -3.185499 1.381344 H 0.113472 -1.938932 2.393612 C -3.971151 -1.379093 -0.339310 H -4.401205 -2.232591 -0.889832 H -4.229966 -1.484763 0.729320 H -4.419706 -0.444738 -0.724900 C 1.063082 -2.116143 -2.454405 H 0.298650 -1.834987 -3.200578 H 1.883174 -2.646656 -2.968147 H 0.602759 -2.773992 -1.697711

191 C6 W -1.275646 -0.014385 -0.103269 W 1.378731 0.036896 -0.111632 O 2.624650 -1.272508 0.497038 O 2.116555 1.755258 0.270336 O 0.011999 -1.514957 -0.766755 O 1.682087 0.346949 -1.974470 O -2.533806 -0.730160 -1.353474 O -1.909331 1.774933 0.010901 N 0.253851 -0.146962 1.444068 C -1.042820 -0.415429 1.770841 C -2.356689 2.681380 1.000544 H -3.363142 3.047887 0.732600 H -2.393107 2.201104 1.995022 H -1.672591 3.547104 1.040934 C -1.541133 -0.815747 3.120730 H -1.056514 -1.750033 3.457974 H -1.309377 -0.039875 3.872255 H -2.629987 -0.973854 3.106952 C 1.906457 2.626012 1.370933 H 2.866884 2.780864 1.892871 H 1.547935 3.601872 0.999855 H 1.170069 2.201869 2.077490 C 2.544203 -2.352301 1.409602 H 2.317220 -3.293331 0.878985 H 3.523063 -2.457162 1.907569 H 1.760917 -2.158641 2.164811 C -0.056073 -2.930795 -0.805836 H -0.983189 -3.222339 -1.328677 H 0.811840 -3.327769 -1.359371 H -0.069202 -3.361612 0.212687 C -3.944963 -0.819729 -1.207847 H -4.373076 -1.171221 -2.161669 H -4.220398 -1.537061 -0.414018 H -4.382121 0.166824 -0.964518 C 1.571573 1.498676 -2.785635 H 1.924084 2.395842 -2.243227 H 2.184481 1.352359 -3.691287 H 0.520396 1.651628 -3.091634

192 C7 W -1.288600 -0.048609 -0.035719 W 1.364177 0.000198 -0.036735 O 2.626985 -0.726061 1.191588 O 2.095657 1.616756 -0.756565 O 0.069513 -1.670453 0.365690 O 1.655247 -0.827804 -1.751116 O -2.426349 -1.396150 -0.767570 O -1.954288 1.467035 -0.953944 N 0.207466 0.669676 1.343481 C -1.093622 0.649542 1.751697 C -2.376948 2.783599 -0.652108 H -3.378249 2.951676 -1.085058 H -2.414789 2.949534 0.439434 H -1.675400 3.505269 -1.105840 C -1.604565 1.038051 3.098236 H -1.150224 0.405602 3.882477 H -1.347392 2.086363 3.333956 H -2.697857 0.925114 3.150757 C 1.924210 2.958422 -0.325537 H 2.903873 3.363428 -0.016633 H 1.543559 3.566656 -1.164914 H 1.221386 3.020584 0.525338 C 2.427142 -1.312257 2.468753 H 1.904835 -2.278921 2.370788 H 3.413436 -1.473149 2.933808 H 1.816724 -0.642368 3.100883 C 0.113160 -2.935140 -0.288546 H -0.885255 -3.397819 -0.245699 H 0.425704 -2.815903 -1.340539 H 0.846409 -3.575546 0.231152 C -3.827950 -1.571259 -0.610773 H -4.156105 -2.381173 -1.283854 H -4.078820 -1.852665 0.427188 H -4.375832 -0.647476 -0.873905 C 1.679535 -0.287488 -3.060436 H 2.077504 0.743067 -3.053672 H 2.321025 -0.926708 -3.691276 H 0.660601 -0.278260 -3.489541

193 T6 W -1.292587 0.079346 -0.087402 W 1.349390 -0.008975 -0.136098 O 2.579163 -1.281517 0.582777 O 2.071917 1.735653 0.127289 O -0.071549 -1.544848 -0.742716 O 1.680022 0.153738 -2.008879 O -2.579370 -0.471943 -1.360397 O -1.773922 1.906038 0.117185 N 0.217605 -0.161994 1.431694 C -1.075299 -0.404936 1.772303 C -2.199721 2.786793 1.135819 H -3.187546 3.202548 0.868731 H -2.274382 2.267497 2.108566 H -1.484210 3.623222 1.227017 C -1.583995 -0.793818 3.121532 H -1.154115 -1.760008 3.443020 H -1.299021 -0.043467 3.880521 H -2.680291 -0.886624 3.116129 C 1.816848 2.697280 1.139605 H 1.130967 2.293853 1.906321 H 2.774090 2.975932 1.613313 H 1.373343 3.599120 0.683432 C 2.562320 -2.208083 1.652236 H 1.752919 -1.960897 2.363143 H 2.417053 -3.233891 1.270738 H 3.536422 -2.160561 2.168447 C -0.099331 -2.898584 -0.311555 H -0.066845 -2.977306 0.791665 H -1.029545 -3.373742 -0.669974 H 0.763386 -3.439472 -0.738537 C -3.589944 -1.395724 -1.677292 H -4.244041 -0.959479 -2.451997 H -3.147770 -2.325066 -2.079647 H -4.205708 -1.643710 -0.793231 C 1.673887 1.245137 -2.907764 H 2.004515 2.171917 -2.403483 H 2.357433 1.016202 -3.743110 H 0.657978 1.395098 -3.315284

194 T7 W -1.323935 0.011173 -0.044744 W 1.311556 0.012883 -0.126962 O 2.594068 -1.037089 0.824512 O 1.973161 1.791863 -0.292838 O -0.076624 -1.674839 -0.338734 O 1.612258 -0.264843 -1.996170 O -2.676124 -0.946873 -0.980350 O -1.875184 1.805791 -0.322686 N 0.221572 0.190469 1.468460 C -1.062013 0.007356 1.871066 C -2.287563 2.931802 0.424216 H -3.320718 3.198482 0.139928 H -2.251121 2.725048 1.509309 H -1.630662 3.789611 0.196070 C -1.571588 -0.048437 3.273527 H -1.122544 -0.894472 3.824635 H -1.309900 0.873118 3.823669 H -2.664996 -0.166933 3.287683 C 1.727139 2.945268 0.497811 H 1.059414 2.708406 1.345652 H 2.689523 3.324622 0.882858 H 1.266415 3.726411 -0.131196 C 2.615824 -1.723908 2.061296 H 1.815028 -1.347652 2.723969 H 2.484271 -2.808817 1.904512 H 3.598150 -1.554830 2.534545 C -0.085144 -2.882157 0.416395 H -0.026963 -2.680077 1.501481 H -1.021984 -3.429577 0.211395 H 0.771697 -3.509476 0.115050 C -2.629539 -1.916010 -2.018099 H -1.601130 -2.288686 -2.165670 H -3.293400 -2.757620 -1.755384 H -2.993630 -1.462975 -2.956725 C 1.586875 0.610369 -3.107298 H 1.922108 1.623852 -2.820101 H 2.255627 0.207729 -3.887183 H 0.563434 0.672664 -3.520850

195 T8 W -1.347715 -0.005229 -0.013668 W 1.234897 -0.076955 -0.110758 O 2.410098 -0.489736 1.373288 O 2.465481 1.128078 -0.943614 O -0.100244 -1.338366 1.030580 O 1.238932 -1.355118 -1.541115 O -2.672877 -1.387894 0.059991 O -2.130082 0.914188 -1.484464 N 0.165468 1.299791 0.788326 C -1.088517 1.483951 1.224995 C -3.323351 1.654006 -1.670186 H -4.200002 0.997277 -1.519104 H -3.382651 2.498319 -0.958596 H -3.347861 2.050752 -2.698981 C -1.600527 2.569115 2.111061 H -1.056562 2.584253 3.071690 H -1.458383 3.556257 1.635756 H -2.672198 2.431280 2.315476 C 2.214115 2.389716 -1.550838 H 1.382463 2.904070 -1.036367 H 3.128141 3.003739 -1.488663 H 1.947478 2.252643 -2.613344 C 3.320788 0.425764 1.969361 H 2.772856 1.164674 2.583588 H 4.001229 -0.145915 2.622907 H 3.912172 0.966448 1.207854 C -0.004583 -1.719676 2.398700 H 0.163923 -0.837939 3.041041 H -0.949113 -2.208205 2.692534 H 0.835096 -2.420368 2.529567 C -2.543754 -2.792597 -0.102187 H -1.507754 -3.124058 0.087127 H -3.222681 -3.300244 0.605039 H -2.831733 -3.077873 -1.130296 C 2.362828 -1.755910 -2.319241 H 3.066665 -0.915917 -2.465612 H 2.895122 -2.584763 -1.819276 H 2.001642 -2.106776 -3.300431

196 T9 W -1.438883 0.005928 -0.038986 W 1.223376 -0.042906 -0.055157 O 2.391684 -1.316459 0.804255 O 2.547053 1.322330 -0.315462 O -0.226253 -1.621930 0.394652 O 1.006922 -0.464688 -1.934945 O -2.855609 -1.202087 -0.458427 O -1.886851 1.502602 -1.125070 N 0.144865 0.852653 1.210937 C -1.177605 0.862733 1.648989 C -2.102570 2.889969 -0.975974 H -3.076979 3.154816 -1.422860 H -2.098520 3.182965 0.089767 H -1.312595 3.449737 -1.508213 C -1.632985 1.450147 2.942627 H -1.161119 0.936487 3.799265 H -1.358369 2.518146 3.011028 H -2.724883 1.361593 3.042216 C 2.412639 2.734618 -0.254927 H 1.606667 3.015456 0.448387 H 3.368058 3.172190 0.080854 H 2.172869 3.136708 -1.255556 C 3.570757 -0.978443 1.535754 H 3.318441 -0.782957 2.593511 H 4.253525 -1.843463 1.491584 H 4.075439 -0.090737 1.115281 C -0.199057 -2.438458 1.565529 H -0.144648 -1.814754 2.475831 H -1.120245 -3.044137 1.596226 H 0.683336 -3.095237 1.524681 C -2.793681 -2.432234 -1.173419 H -1.772022 -2.851929 -1.160819 H -3.489353 -3.150342 -0.706985 H -3.107135 -2.267475 -2.219343 C 2.181906 -0.701391 -2.722688 H 2.937686 0.089995 -2.564505 H 2.631747 -1.679674 -2.472855 H 1.879629 -0.709425 -3.782836

197 T10 W 1.294081 -0.079922 -0.093275 W -1.352773 0.039598 -0.060018 O -2.642017 1.470720 -0.334148 O -2.427163 -1.587424 -0.049184 O 0.013528 1.559468 -0.579896 O -0.140995 -0.938220 -1.397435 O 2.880500 0.912668 -0.421688 O 2.210794 -1.782297 -0.231652 N -0.547581 0.048453 1.593559 C 0.819561 0.157762 1.802672 C 3.479893 -2.118689 0.303262 H 4.212745 -1.311361 0.114000 H 3.411356 -2.285661 1.394961 H 3.838332 -3.047908 -0.172582 C 1.412652 0.341914 3.163568 H 0.925153 1.185111 3.685779 H 1.267143 -0.558270 3.788747 H 2.493492 0.540680 3.100828 C -3.203845 -2.134246 1.003497 H -2.600675 -2.221934 1.926485 H -4.088953 -1.505901 1.225342 H -3.558309 -3.137529 0.709329 C -4.011782 1.336710 0.035800 H -4.144154 1.484490 1.124117 H -4.584691 2.118836 -0.491625 H -4.427124 0.350864 -0.244683 C -0.099768 2.976306 -0.513311 H 0.256464 3.339620 0.467356 H 0.497046 3.444248 -1.314314 H -1.160991 3.242400 -0.637414 C 3.146477 2.284842 -0.690316 H 2.723096 2.577088 -1.666145 H 2.726025 2.933067 0.096483 H 4.240330 2.417493 -0.724671 C -0.244441 -2.239856 -2.029312 H -1.140039 -2.741375 -1.636664 H -0.326481 -2.083618 -3.115280 H 0.666841 -2.803368 -1.784450

198 P1 W -1.317386 -0.207665 -0.000035 W 1.223095 0.055547 -0.000016 N -0.296594 1.477695 0.000266 C -1.645201 1.712218 0.000358 O -1.835278 -1.016582 1.654072 C -2.990266 -0.720745 2.432854 O -1.835330 -1.015819 -1.654490 C -2.990330 -0.719543 -2.433092 O 0.403879 -1.769862 -0.000496 C 0.937528 -3.095212 -0.000328 O 2.836499 -1.054781 -0.000136 C 4.122569 -0.466487 -0.000054 O 1.866340 0.827196 1.621008 C 1.280470 1.740996 2.538945 O 1.866343 0.827770 -1.620761 C 1.280285 1.741656 -2.538498 C -2.280872 3.062003 0.000769 H -1.968338 3.639749 0.889471 H -1.968323 3.640300 -0.887570 H -3.378272 2.985699 0.000737 H -3.677722 -1.583179 -2.414064 H -3.677617 -1.584405 2.413410 H 2.035872 -3.054445 -0.001036 H 4.880818 -1.268603 -0.000174 H 0.699002 1.190375 3.298795 H -2.678895 -0.542439 -3.477328 H -3.526087 0.174506 -2.064226 H 0.698191 1.191163 -3.297965 H 0.619800 2.459493 -2.023542 H 2.096411 2.286108 -3.042580 H 4.269816 0.162984 -0.899558 H 4.269823 0.162712 0.899639 H 2.096669 2.285811 3.042518 H 0.619444 2.458534 2.024262 H -2.678809 -0.544150 3.477170 H -3.526080 0.173464 2.064458 H 0.571071 -3.617027 -0.899883 H 0.572258 -3.616428 0.900060

199 P2 W -1.404175 -0.105767 -0.190475 W 1.244755 0.011731 0.043051 N -0.243625 0.468626 1.330683 C -1.573468 0.679403 1.555634 O -2.065208 -1.873860 -0.328368 C -3.267745 -2.437691 0.186087 O -1.923514 0.996805 -1.642384 C -2.930268 1.990096 -1.795978 O 0.817832 -1.666343 -0.889182 C 1.726224 -2.505991 -1.599688 O 2.822228 -0.130380 -1.083759 C 3.974827 0.677807 -0.990557 O 2.224875 -0.549286 1.580727 C 1.822723 -0.936180 2.884330 O 1.438272 1.884216 -0.388671 C 0.653837 3.030962 -0.119685 C -2.212614 1.181399 2.804143 H -1.929199 0.553664 3.668152 H -1.879204 2.211374 3.025268 H -3.309253 1.183095 2.714977 H -3.717963 1.611971 -2.469884 H -3.924070 -2.721266 -0.654388 H 2.577612 -2.807825 -0.964821 H 4.681477 0.387912 -1.787211 H 1.571567 -2.011503 2.898090 H -2.478322 2.887856 -2.251374 H -3.382976 2.266194 -0.827302 H 0.026124 3.271372 -0.996216 H 0.004794 2.898233 0.764051 H 1.335417 3.880026 0.064350 H 3.710707 1.745380 -1.106076 H 4.469392 0.540883 -0.008281 H 2.666813 -0.756522 3.571135 H 0.942683 -0.355753 3.211973 H -3.015461 -3.344959 0.760585 H -3.809362 -1.735766 0.845651 H 2.125431 -1.993482 -2.489719 H 1.159210 -3.400708 -1.907029

200 P3 W 1.447060 -0.080745 -0.156447 W -1.137217 -0.023240 0.144006 N 0.115790 1.362273 -0.678743 C 1.373151 1.696440 -0.958207 O 2.067179 -1.440610 -1.306630 C 1.536067 -2.759807 -1.516742 O 2.205599 -0.288948 1.564401 C 3.486554 0.098431 2.061898 O -1.376564 -1.203567 -1.404963 C -2.581262 -1.909618 -1.640379 O -1.543140 -1.536835 1.224958 C -1.685269 -1.782076 2.611519 O -2.572723 1.072376 -0.590044 C -2.592451 1.755757 -1.826125 O -1.332567 0.954390 1.815283 C -1.346353 2.351552 1.995004 C 1.910103 2.951196 -1.554051 H 1.443909 3.140998 -2.536741 H 1.681119 3.816373 -0.906288 H 2.999899 2.890920 -1.687991 H 4.175347 -0.762787 2.021349 H 1.827495 -3.422691 -0.684229 H -3.445227 -1.216658 -1.647088 H -0.848154 -2.411240 2.959078 H -2.499623 1.044333 -2.669347 H 3.369117 0.413141 3.111835 H 3.920235 0.933984 1.484863 H -1.446967 2.582487 3.069719 H -0.420618 2.819323 1.605514 H -2.205036 2.788035 1.448748 H -1.688528 -0.826687 3.163435 H -2.633122 -2.320523 2.783166 H -3.547864 2.300929 -1.913828 H -1.751023 2.471439 -1.887632 H 0.439301 -2.720148 -1.600301 H 1.970834 -3.146453 -2.452396 H -2.745134 -2.655506 -0.838053 H -2.520405 -2.425974 -2.613548

201 P4 W 1.360935 0.087485 -0.146677 W -1.249604 -0.135309 0.023470 N 0.141808 -0.311749 1.443318 C 1.431568 -0.128284 1.778585 O 2.007279 1.593673 -1.078080 C 2.220090 2.973985 -0.847516 O 2.127099 -1.411106 -0.986467 C 3.369999 -2.077733 -0.760654 O -0.848015 1.831048 0.112928 C -1.611318 2.849103 -0.506710 O -2.035987 0.252842 -1.679037 C -2.459583 -0.523200 -2.783182 O -2.549803 0.020832 1.427387 C -2.415690 0.529215 2.739871 O -1.486204 -1.992408 -0.435047 C -0.794144 -3.169279 -0.074174 C 2.046932 -0.145585 3.135793 H 1.536380 0.570525 3.803949 H 1.950597 -1.147176 3.591760 H 3.115090 0.113308 3.089686 H 4.192805 -1.520527 -1.240554 H 2.547716 3.438357 -1.792111 H -1.744764 2.637610 -1.583445 H -1.845148 -0.274242 -3.666106 H -2.163548 1.605261 2.706369 H 3.304231 -3.079752 -1.214756 H 3.577740 -2.179916 0.317980 H -0.222056 -3.552540 -0.937898 H -0.097714 -2.987912 0.765662 H -1.528402 -3.936833 0.229301 H -2.367192 -1.599910 -2.558126 H -3.513231 -0.281260 -3.008625 H -3.373208 0.392065 3.269724 H -1.611416 -0.001822 3.280748 H 1.284317 3.450069 -0.512747 H 3.001398 3.127923 -0.082016 H -1.099762 3.820429 -0.382271 H -2.617089 2.919181 -0.047960

202 P5 W -1.288600 -0.048609 -0.035719 W 1.364177 0.000198 -0.036735 O 2.626985 -0.726061 1.191588 O 2.095657 1.616756 -0.756565 O 0.069513 -1.670453 0.365690 O 1.655247 -0.827804 -1.751116 O -2.426349 -1.396150 -0.767570 O -1.954288 1.467035 -0.953944 N 0.207466 0.669676 1.343481 C -1.093622 0.649542 1.751697 C -2.376948 2.783599 -0.652108 H -3.378249 2.951676 -1.085058 H -2.414789 2.949534 0.439434 H -1.675400 3.505269 -1.105840 C -1.604565 1.038051 3.098236 H -1.150224 0.405602 3.882477 H -1.347392 2.086363 3.333956 H -2.697857 0.925114 3.150757 C 1.924210 2.958422 -0.325537 H 2.903873 3.363428 -0.016633 H 1.543559 3.566656 -1.164914 H 1.221386 3.020584 0.525338 C 2.427142 -1.312257 2.468753 H 1.904835 -2.278921 2.370788 H 3.413436 -1.473149 2.933808 H 1.816724 -0.642368 3.100883 C 0.113160 -2.935140 -0.288546 H -0.885255 -3.397819 -0.245699 H 0.425704 -2.815903 -1.340539 H 0.846409 -3.575546 0.231152 C -3.827950 -1.571259 -0.610773 H -4.156105 -2.381173 -1.283854 H -4.078820 -1.852665 0.427188 H -4.375832 -0.647476 -0.873905 C 1.679535 -0.287488 -3.060436 H 2.077504 0.743067 -3.053672 H 2.321025 -0.926708 -3.691276 H 0.660601 -0.278260 -3.489541

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204 P7 W -1.492031 0.162612 -0.201421 W 1.756551 -0.045220 0.047136 N 0.438691 1.070223 -0.177409 C -2.056802 0.462136 1.446953 O -2.591894 -1.281119 -0.827975 C -3.730049 -1.929755 -0.294833 O -2.257447 1.584735 -1.199260 C -2.919071 2.791374 -0.872483 O 2.310515 -0.903783 -1.568674 C 1.635513 -1.142901 -2.794639 O 0.061585 -1.358434 -0.105018 C 0.000195 -2.765682 0.061976 O 1.935242 -0.767640 1.802036 C 1.045686 -0.982634 2.888569 O 3.214863 1.152141 0.161625 C 3.315182 2.555709 -0.005125 C -2.538204 0.737494 2.819550 H -1.811616 0.393316 3.579245 H -2.699830 1.817855 2.986358 H -3.494866 0.224425 3.027875 H -3.723630 2.972240 -1.606813 H -4.630338 -1.613208 -0.852924 H 1.521667 -0.203497 -3.363236 H 0.049898 -3.043022 1.130887 H 0.004398 -1.066353 2.535032 H -2.201972 3.630005 -0.924711 H -3.348548 2.745497 0.143234 H 3.929459 2.773390 -0.895722 H 2.310338 2.999529 -0.128542 H 3.810152 2.989472 0.880044 H -0.945203 -3.136396 -0.364595 H 0.849056 -3.236924 -0.464842 H 1.340599 -1.909663 3.408576 H 1.121036 -0.137648 3.595156 H -3.622140 -3.024415 -0.408425 H -3.869109 -1.688086 0.773582 H 0.635916 -1.572042 -2.603944 H 2.231773 -1.854713 -3.388925

205 P8 W -1.617602 0.151557 -0.190289 W 2.037560 -0.120833 0.021383 N 0.521573 0.667392 -0.034575 C -2.050791 0.471860 1.500690 O -3.196403 -0.643005 -0.926491 C -4.528722 -0.737146 -0.465278 O -1.738350 1.860433 -1.070187 C -1.641736 3.188048 -0.606919 O 2.297582 -1.077737 -1.574570 C 1.460056 -1.455624 -2.673380 O -0.645319 -1.621070 -0.286468 C -1.206328 -2.837084 0.167213 O 2.071887 -1.141465 1.597566 C 1.088572 -1.483391 2.578329 O 3.333345 1.237983 0.128692 C 3.218313 2.661475 0.156484 C -2.424418 0.728480 2.910731 H -1.522370 0.837805 3.542819 H -3.013558 1.657094 3.024556 H -3.020720 -0.097592 3.340701 H -2.078362 3.868570 -1.360222 H -5.155291 0.010368 -0.986125 H 1.321054 -0.592131 -3.344417 H -1.371452 -2.828906 1.263759 H 0.127629 -0.993364 2.353134 H -0.579699 3.466615 -0.461836 H -2.171573 3.317290 0.354439 H 3.771967 3.075073 -0.701928 H 2.160926 2.970104 0.104354 H 3.671487 3.032233 1.090113 H -2.182613 -3.032758 -0.317770 H -0.519742 -3.670240 -0.076029 H 0.957817 -2.577026 2.573863 H 1.464537 -1.166649 3.564768 H -4.928274 -1.741708 -0.694433 H -4.591047 -0.557600 0.623207 H 0.488093 -1.799864 -2.287921 H 1.971671 -2.263429 -3.219527

206 P9 W 1.727018 0.023285 -0.198308 W -2.171410 0.011852 -0.005512 N -0.465373 0.034226 0.048170 C 2.137980 -0.062414 1.523050 O 3.409623 -0.011987 -1.110866 C 4.711622 -0.391927 -0.727055 O 1.285256 -1.837228 -0.665574 C 0.927184 -2.917389 0.160772 O -2.677811 1.711293 -0.625560 C -1.927254 2.850144 -1.072610 O 1.383951 1.918503 -0.545367 C 1.614492 3.069214 0.234942 O -2.713829 -0.340172 1.765593 C -1.977359 -0.562197 2.971704 O -2.637174 -1.346345 -1.217792 C -1.881366 -2.229215 -2.058786 C 2.540849 -0.142802 2.945566 H 1.660481 -0.067241 3.612443 H 3.045038 -1.098085 3.181237 H 3.228975 0.675080 3.228006 H 1.054482 -3.866678 -0.393842 H 4.861575 -1.473516 -0.907241 H -2.292865 3.127032 -2.074246 H 1.690208 2.823572 1.310156 H -0.892933 -0.515361 2.779327 H -0.136985 -2.849009 0.474204 H 1.546870 -2.951507 1.076561 H -2.145284 -2.014897 -3.106778 H -0.799542 -2.090408 -1.899520 H -2.171430 -3.264759 -1.819468 H 2.557663 3.557118 -0.078683 H 0.794282 3.801759 0.094033 H -2.263948 0.209343 3.704412 H -2.246417 -1.553940 3.369623 H 5.449778 0.165104 -1.331936 H 4.891938 -0.184719 0.344141 H -0.851364 2.613971 -1.108230 H -2.114932 3.684431 -0.377696

207 V1 W -1.285843 0.004804 0.110185 W 1.285771 0.005069 0.110467 O 2.590503 1.338904 -0.237307 O 2.470301 -1.479249 -0.066897 O -0.000382 1.267041 1.352710 O -0.000149 -1.111403 1.356400 O -2.591057 1.337973 -0.238245 O -2.469856 -1.479976 -0.067308 N 0.000083 0.929618 -1.227290 C 0.000105 -0.491641 -1.422301 C -2.351117 -2.837497 -0.433519 H -3.305320 -3.348989 -0.221156 H -2.129255 -2.932942 -1.511598 H -1.544970 -3.329731 0.142352 C 0.000267 -1.200340 -2.739931 H -0.890974 -0.920050 -3.330549 H 0.891838 -0.920374 -3.330206 H 0.000021 -2.295875 -2.619881 C 2.353354 -2.836288 -0.435381 H 2.130724 -2.930220 -1.513423 H 3.308494 -3.346707 -0.224649 H 1.548445 -3.330746 0.140312 C 2.628032 2.531039 -1.004194 H 1.711997 2.615258 -1.613862 H 2.722619 3.404192 -0.335033 H 3.513724 2.496492 -1.661509 C -0.000607 2.689650 1.260464 H -0.899171 3.078093 1.771104 H 0.897566 3.078411 1.771555 H -0.000408 3.035880 0.213385 C -2.628709 2.530135 -1.005110 H -2.724862 3.403133 -0.335978 H -1.712057 2.615154 -1.613739 H -3.513569 2.494836 -1.663499 C -0.000312 -1.252189 2.778799 H 0.900403 -1.813746 3.077711 H -0.000562 -0.259482 3.256178 H -0.900898 -1.814084 3.077463

208 V2 W -1.332022 -0.103460 -0.062013 W 1.205602 -0.016547 -0.021903 O 2.581926 -1.335234 -0.352130 O 2.487524 1.375315 0.336473 O -0.064736 -1.221386 -1.305758 O -0.040963 1.289772 -1.192884 O -2.482426 -1.515844 0.487097 O -2.698212 1.193610 -0.243127 N 0.398408 -0.794149 1.528026 C -0.259114 0.492489 1.504378 C -2.703375 2.587462 -0.533562 H -3.390301 2.770152 -1.376668 H -3.082381 3.126396 0.351287 H -1.693249 2.948121 -0.785663 C -0.363247 1.388760 2.698883 H -1.011789 0.939857 3.473314 H 0.633178 1.540355 3.151526 H -0.779812 2.372791 2.431662 C 2.235477 2.733925 0.662708 H 2.257834 2.874015 1.758415 H 3.025887 3.360798 0.214525 H 1.251360 3.059537 0.279688 C 3.861204 -1.414856 0.268444 H 3.777045 -1.955767 1.227962 H 4.543566 -1.975271 -0.393789 H 4.275149 -0.407847 0.457923 C 0.052728 -2.649684 -1.389948 H -0.890374 -3.055258 -1.791070 H 0.881865 -2.882680 -2.074436 H 0.266790 -3.091918 -0.403680 C -2.217590 -2.644275 1.317917 H -2.427887 -3.567307 0.750801 H -1.171823 -2.634136 1.673291 H -2.898844 -2.602169 2.184208 C 0.109438 1.362854 -2.612359 H 1.033975 1.918664 -2.847310 H 0.158753 0.359347 -3.069641 H -0.750732 1.912005 -3.034925

209 V3 W -1.332029 -0.022202 -0.275963 W 1.223743 -0.099670 0.202851 O 2.632678 -1.328425 -0.279202 O 2.459610 1.369321 0.474353 O 0.031528 -1.461944 -0.970702 O 0.244618 1.040065 -1.300922 O -2.653170 -1.331136 0.119668 O -2.414676 1.513334 -0.563498 N 0.550850 -0.535399 1.862102 C -0.591754 0.248326 1.558771 C -2.079647 2.895572 -0.572076 H -2.938806 3.464782 -0.961896 H -1.846466 3.239672 0.451490 H -1.195736 3.066411 -1.210524 C -1.158616 1.116963 2.660615 H -1.521542 0.485124 3.490828 H -0.368009 1.769580 3.071821 H -1.994385 1.742332 2.310289 C 2.139858 2.748396 0.549094 H 1.942731 3.036142 1.599487 H 2.998393 3.338008 0.182318 H 1.250198 2.996225 -0.059507 C 4.023524 -1.163961 0.000513 H 4.310766 -1.843927 0.821385 H 4.598704 -1.440361 -0.900654 H 4.259131 -0.124867 0.287036 C -0.031109 -2.886685 -0.889748 H -0.715153 -3.269948 -1.664715 H 0.987360 -3.267352 -1.063262 H -0.373946 -3.214607 0.105895 C -2.955403 -2.221867 1.178936 H -2.816944 -3.265209 0.844415 H -2.310291 -2.033234 2.054300 H -4.012967 -2.088371 1.465841 C 0.574224 0.829437 -2.681630 H 1.544610 1.309531 -2.889885 H 0.633102 -0.246148 -2.921839 H -0.204714 1.305671 -3.301628

210 V4 W -1.335785 -0.037140 -0.274284 W 1.224564 -0.084687 0.242734 O 2.625378 -1.343210 -0.190749 O 2.473821 1.388509 0.389360 O 0.005542 -1.541747 -0.738273 O 0.261142 0.936457 -1.357966 O -2.712933 -1.270292 0.174329 O -2.393197 1.497881 -0.649488 N 0.561326 -0.355677 1.934749 C -0.607167 0.346184 1.551113 C -2.049009 2.873802 -0.732390 H -2.918216 3.434169 -1.113106 H -1.770827 3.262318 0.263879 H -1.190889 3.008876 -1.413385 C -1.233608 1.263360 2.581287 H -1.593116 0.671506 3.441851 H -0.477507 1.969825 2.967322 H -2.083581 1.831737 2.173394 C 2.160964 2.771011 0.362748 H 1.943989 3.130570 1.386784 H 3.030530 3.329610 -0.025801 H 1.285167 2.980476 -0.279352 C 4.025948 -1.156557 0.013392 H 4.357688 -1.792402 0.852652 H 4.561458 -1.474207 -0.898887 H 4.265933 -0.102915 0.235546 C 0.020884 -2.945441 -0.970997 H -0.486717 -3.175430 -1.922784 H 1.075142 -3.259046 -1.022269 H -0.482974 -3.479565 -0.148484 C -2.963250 -2.181119 1.230201 H -2.686478 -3.206125 0.924745 H -2.390212 -1.908491 2.133105 H -4.042622 -2.168965 1.459835 C 0.603676 0.611109 -2.710383 H 1.563201 1.093778 -2.959563 H 0.695394 -0.480231 -2.854000 H -0.182943 1.004591 -3.377510

211 V5 W -1.338209 -0.057530 -0.273857 W 1.216868 -0.065974 0.298259 O 2.610912 -1.341022 -0.119782 O 2.459183 1.416428 0.339500 O -0.051023 -1.641539 -0.441555 O 0.296908 0.774924 -1.414264 O -2.774864 -1.203162 0.217210 O -2.345900 1.468627 -0.796467 N 0.535224 -0.178158 1.997520 C -0.637394 0.458775 1.538055 C -1.985287 2.831828 -0.952998 H -2.858680 3.389566 -1.328630 H -1.662762 3.262419 0.012560 H -1.152733 2.922952 -1.672435 C -1.306321 1.441397 2.479375 H -1.681231 0.910335 3.372177 H -0.572425 2.187899 2.831156 H -2.152738 1.963019 2.006540 C 2.150559 2.790029 0.174148 H 1.904901 3.243952 1.153090 H 3.032180 3.309757 -0.240205 H 1.293522 2.936911 -0.509562 C 4.019454 -1.135858 -0.027031 H 4.422838 -1.755136 0.792947 H 4.490321 -1.459924 -0.972636 H 4.262432 -0.076163 0.160993 C 0.100471 -2.929513 -1.029281 H -0.263624 -2.929138 -2.071046 H 1.171325 -3.185124 -1.006978 H -0.473918 -3.670864 -0.449393 C -2.929528 -2.134684 1.276284 H -2.134803 -2.900938 1.245184 H -2.877082 -1.618092 2.250521 H -3.910579 -2.627398 1.174185 C 0.673918 0.339823 -2.725049 H 1.604984 0.854413 -3.015050 H 0.840833 -0.750947 -2.766320 H -0.127077 0.614046 -3.433628

212 V6 W 1.372537 -0.073228 0.234711 W -1.230333 -0.024716 -0.212248 O -2.565066 -1.397252 0.060988 O -2.412716 1.462399 0.141397 O 0.129835 -1.696161 -0.060320 O -0.223115 0.284996 1.613401 O 2.850115 -0.964832 -0.557426 O 2.309275 1.320201 1.139856 N -0.640889 0.306508 -1.897118 C 0.584889 0.811133 -1.383797 C 1.867365 2.600758 1.562137 H 2.690864 3.104675 2.094622 H 1.562713 3.214619 0.694333 H 0.999882 2.497555 2.238226 C 1.198385 1.978871 -2.132560 H 1.499379 1.662003 -3.147319 H 0.463300 2.794666 -2.253084 H 2.086348 2.376192 -1.616881 C -2.568803 2.678629 -0.560523 H -2.525421 2.512789 -1.654539 H -3.542244 3.127389 -0.296445 H -1.770955 3.395754 -0.285844 C -3.979781 -1.227922 0.003396 H -4.360981 -1.606208 -0.961508 H -4.438801 -1.819719 0.814824 H -4.264766 -0.167332 0.116060 C 0.013105 -3.068526 0.300124 H 0.636479 -3.295269 1.182419 H -1.044690 -3.287278 0.517922 H 0.346635 -3.696681 -0.543447 C 2.998762 -1.687791 -1.767866 H 2.430617 -2.634094 -1.727967 H 2.629262 -1.092202 -2.620754 H 4.067358 -1.919185 -1.911812 C -0.517962 -0.456414 2.800330 H -1.413304 -0.022001 3.274210 H -0.708287 -1.521398 2.581431 H 0.337402 -0.369192 3.492493

213 V7 W -1.388396 0.055257 0.233680 W 1.205452 0.001020 -0.216893 O 2.531172 1.393201 0.044959 O 2.328579 -1.520357 0.180042 O -0.156080 1.673589 -0.069929 O 0.210058 -0.311525 1.617144 O -2.860461 0.954678 -0.560380 O -2.331876 -1.327295 1.136104 N 0.605484 -0.343069 -1.902222 C -0.612518 -0.843107 -1.390492 C -1.901612 -2.594285 1.612699 H -2.705435 -3.035667 2.224180 H -1.675311 -3.266381 0.765583 H -0.988756 -2.478671 2.222986 C -1.234573 -2.019596 -2.116748 H -1.517726 -1.724996 -3.143050 H -0.508182 -2.847132 -2.204002 H -2.133931 -2.392217 -1.602209 C 3.248158 -2.133040 -0.711282 H 2.717959 -2.537284 -1.593533 H 4.012043 -1.414438 -1.067254 H 3.760767 -2.956830 -0.185792 C 3.931015 1.224073 0.232709 H 4.454825 1.206252 -0.740706 H 4.313759 2.082641 0.811883 H 4.161541 0.291956 0.779573 C -0.044113 3.060288 0.227997 H -0.334963 3.649059 -0.658617 H -0.703699 3.330598 1.070440 H 1.005179 3.282294 0.480586 C -3.017618 1.643907 -1.789353 H -2.470862 2.603307 -1.767882 H -2.629859 1.036776 -2.625733 H -4.090108 1.849103 -1.943982 C 0.491925 0.452067 2.792624 H 1.388309 0.032978 3.278604 H 0.674599 1.515216 2.556917 H -0.365811 0.370218 3.482870

214 V8 W 1.391234 -0.041723 0.227941 W -1.223611 -0.056894 -0.198483 O -2.537948 -1.415442 0.217737 O -2.321558 1.518569 0.022140 O 0.148004 -1.704730 0.106966 O -0.188932 0.431669 1.537637 O 2.862318 -1.054969 -0.416386 O 2.358275 1.447291 0.929305 N -0.631262 0.048125 -1.912294 C 0.630146 0.565208 -1.523552 C 2.010070 2.811203 1.095798 H 2.834033 3.330255 1.613361 H 1.838184 3.290401 0.114916 H 1.087690 2.908417 1.696671 C 1.270611 1.567845 -2.463714 H 1.427980 1.109448 -3.456359 H 0.611278 2.442238 -2.611473 H 2.241460 1.924056 -2.084153 C -3.202770 2.096395 -0.928460 H -2.659466 2.343437 -1.859353 H -4.031131 1.407300 -1.183165 H -3.634388 3.018695 -0.503438 C -3.948431 -1.219150 0.203131 H -4.333825 -1.179076 -0.832630 H -4.420699 -2.076665 0.712105 H -4.236145 -0.289406 0.727071 C 0.010153 -2.888263 0.881253 H 0.945600 -3.470613 0.822193 H -0.201872 -2.650962 1.939455 H -0.827259 -3.479161 0.479301 C 2.970583 -1.946542 -1.515343 H 2.258412 -2.783070 -1.406706 H 2.746531 -1.418259 -2.458673 H 3.998584 -2.344070 -1.547474 C -0.489653 0.561814 2.921345 H -1.282235 1.317209 3.048901 H -0.832833 -0.399877 3.340975 H 0.419270 0.890249 3.452694

215 V9 W -1.373166 -0.075481 -0.240152 W 1.221127 -0.103172 0.179187 O 2.570529 -1.419546 -0.248504 O 2.261260 1.523535 0.033087 O -0.137903 -1.722708 -0.301506 O 0.238389 0.384487 -1.608952 O -2.833253 -1.153520 0.337274 O -2.347577 1.449679 -0.828448 N 0.621211 -0.110730 1.899645 C -0.610370 0.481081 1.523477 C -2.230303 2.860012 -0.755066 H -3.200380 3.275823 -0.431333 H -1.446025 3.165702 -0.039874 H -1.992330 3.275377 -1.749687 C -1.212101 1.472956 2.500268 H -1.403469 0.976471 3.467945 H -0.510406 2.303977 2.695943 H -2.160252 1.893884 2.131367 C 3.152394 2.067635 0.995224 H 2.615595 2.296358 1.934462 H 3.973378 1.363088 1.229409 H 3.592398 2.996512 0.593131 C 3.974591 -1.194673 -0.318146 H 4.436116 -1.308939 0.679936 H 4.416425 -1.950256 -0.990511 H 4.212258 -0.188848 -0.709764 C 0.011083 -2.807303 -1.211841 H -0.933590 -3.375245 -1.256406 H 0.266151 -2.431183 -2.217933 H 0.826532 -3.454060 -0.854311 C -2.918261 -2.102663 1.389235 H -2.173386 -2.905829 1.248723 H -2.727333 -1.615826 2.361974 H -3.930411 -2.540316 1.388153 C 0.429760 1.574882 -2.382678 H 0.623087 2.446180 -1.736419 H 1.297383 1.421697 -3.044238 H -0.471679 1.743847 -2.993050

216 V10 W 1.368429 -0.019521 0.119158 W -1.275975 -0.044384 -0.146260 O -2.568368 -1.347729 0.461379 O -2.189333 1.541990 0.398888 O 0.079211 -1.708725 0.035361 O 0.119991 0.340324 1.684959 O 2.741291 -1.132612 -0.571544 O 2.482822 1.428573 0.667742 N -1.232004 0.139054 -1.886093 C 0.447014 0.617981 -1.439248 C 2.214344 2.817915 0.758856 H 3.139140 3.342990 1.050302 H 1.857516 3.211398 -0.210224 H 1.435597 3.007066 1.519875 C 0.852697 1.360521 -2.677996 H 0.847196 0.697517 -3.559828 H 0.158616 2.191765 -2.890798 H 1.870538 1.769389 -2.555147 C -2.872152 2.533058 -0.350199 H -2.656678 2.433041 -1.429355 H -3.960916 2.442216 -0.185647 H -2.552535 3.530149 -0.000543 C -3.939603 -1.318358 0.084457 H -4.057887 -1.455062 -1.006132 H -4.461203 -2.141567 0.601335 H -4.410677 -0.360858 0.376769 C -0.049882 -2.791982 0.949779 H 0.907498 -3.339791 0.996097 H -0.318673 -2.435083 1.959455 H -0.847614 -3.463261 0.596084 C 2.781948 -2.216231 -1.486181 H 1.852697 -2.807496 -1.426082 H 2.894196 -1.830649 -2.514455 H 3.647580 -2.855546 -1.245497 C 0.471635 0.314210 3.063909 H -0.364431 0.735463 3.645672 H 0.663573 -0.716381 3.414815 H 1.378018 0.922973 3.236911

217 V11 W 1.463248 -0.115688 0.078196 W -1.471040 0.095378 -0.122192 O -2.669593 -1.081253 0.783820 O -1.928786 1.804062 0.568384 O -0.082650 -1.547912 -0.301739 O 0.326886 0.069964 1.706246 O 2.578286 -1.268591 -0.956876 O 2.901637 0.855128 0.837390 N -2.141098 0.179525 -1.678238 C 0.633065 0.995322 -1.081620 C 3.484948 2.139715 0.747353 H 4.490175 2.053885 0.298136 H 2.864227 2.812280 0.130546 H 3.588664 2.567989 1.759058 C 0.437800 1.908179 -2.235923 H -0.140347 1.409587 -3.031771 H -0.116251 2.819513 -1.949880 H 1.416613 2.219496 -2.643344 C -2.598332 2.902361 -0.026378 H -2.915368 2.660098 -1.056781 H -3.483245 3.153283 0.584347 H -1.925708 3.778329 -0.035827 C -3.831597 -1.740527 0.303674 H -4.042110 -1.458010 -0.742880 H -3.687940 -2.834027 0.368544 H -4.688133 -1.464074 0.942945 C -0.190376 -2.715287 0.516224 H 0.756214 -3.280495 0.452235 H -0.400151 -2.456513 1.568160 H -1.011002 -3.343908 0.135040 C 2.376527 -1.946745 -2.187018 H 1.363226 -2.382976 -2.217730 H 2.487338 -1.243436 -3.030831 H 3.130096 -2.746392 -2.282133 C 0.743110 -0.192706 3.039061 H -0.088405 0.058489 3.717902 H 1.007646 -1.256956 3.191613 H 1.621633 0.427012 3.295978

218 V12 W 1.462228 -0.122506 0.087097 W -1.462943 0.075998 -0.134934 O -2.666219 -1.035700 0.844943 O -1.919536 1.829770 0.434443 O -0.069850 -1.583202 -0.190337 O 0.295087 0.131659 1.690472 O 2.620345 -1.323083 -0.834753 O 2.848959 0.948866 0.809787 N -2.132607 0.050887 -1.694316 C 0.636384 0.879588 -1.172473 C 3.376043 2.249677 0.633009 H 4.400687 2.175047 0.228189 H 2.749633 2.837825 -0.059584 H 3.421693 2.764103 1.608264 C 0.444541 1.689533 -2.402098 H -0.138338 1.125187 -3.149080 H -0.106153 2.624581 -2.197231 H 1.423521 1.959220 -2.837865 C -2.589339 2.882171 -0.238410 H -2.903871 2.566479 -1.249420 H -3.475829 3.175212 0.350938 H -1.917408 3.755903 -0.309508 C -3.828923 -1.720268 0.403884 H -4.034046 -1.505707 -0.659803 H -3.690406 -2.807853 0.540478 H -4.686851 -1.399509 1.020287 C -0.171526 -2.672864 0.730167 H 0.753968 -3.272180 0.669456 H -0.314965 -2.311545 1.763049 H -1.029672 -3.302345 0.446797 C 2.459718 -2.096592 -2.014377 H 1.462605 -2.569691 -2.023224 H 2.556757 -1.453087 -2.905947 H 3.241844 -2.873388 -2.041300 C 0.683646 0.273183 3.047897 H -0.145054 0.749678 3.597640 H 0.892720 -0.709287 3.512365 H 1.586740 0.903680 3.133668

219 V13 W -1.470433 -0.148689 -0.134768 W 1.443622 0.016998 0.138022 O 2.726346 -0.915709 -0.915131 O 1.857035 1.851645 -0.156098 O 0.064588 -1.603503 -0.110353 O -0.236923 0.299775 -1.700099 O -2.625142 -1.509949 0.533031 O -2.807015 1.040075 -0.756868 N 2.038090 -0.213210 1.713668 C -0.744948 0.670371 1.297034 C -3.297819 2.325509 -0.425699 H -4.385746 2.259879 -0.252321 H -2.802801 2.716311 0.480056 H -3.118789 3.017637 -1.266767 C -0.521186 1.335202 2.603844 H 0.102542 0.700919 3.255569 H -0.000422 2.302782 2.493489 H -1.487900 1.522777 3.104789 C 2.477145 2.808398 0.688262 H 2.742206 2.360271 1.662273 H 3.390058 3.182464 0.192659 H 1.791476 3.660945 0.840306 C 3.891347 -1.618003 -0.505495 H 4.030424 -1.543103 0.587404 H 3.799664 -2.679607 -0.795780 H 4.765999 -1.189193 -1.024515 C 0.184054 -2.549038 -1.184558 H -0.739990 -3.151188 -1.217942 H 0.333918 -2.034771 -2.147163 H 1.042288 -3.206386 -0.976991 C -2.524112 -2.403097 1.630595 H -1.557213 -2.934802 1.593730 H -2.588515 -1.849462 2.583379 H -3.348905 -3.132558 1.573800 C -0.315410 1.509219 -2.452845 H 0.341156 1.402618 -3.333019 H -1.349617 1.689909 -2.794538 H 0.031994 2.372071 -1.857543

220 V14 W 1.485870 0.148977 -0.203080 W -1.474798 -0.001574 0.100368 O -2.805136 0.707828 -1.054640 O -1.834304 -1.873837 0.099655 O -0.129917 1.505599 -0.342061 O 0.257098 -0.532810 -1.684902 O 2.520726 1.631789 0.421161 O 2.924020 -0.954985 -0.738118 N -2.071918 0.451358 1.625139 C 0.832030 -0.658546 1.260171 C 3.522369 -2.169627 -0.326622 H 4.565408 -1.972716 -0.023656 H 2.971083 -2.614369 0.519697 H 3.531613 -2.879148 -1.171594 C 0.572783 -1.337823 2.551977 H -0.118976 -0.742772 3.172434 H 0.116458 -2.333055 2.408617 H 1.515726 -1.474931 3.111167 C -2.475745 -2.699512 1.057414 H -2.733240 -2.125024 1.964994 H -3.397022 -3.112640 0.610046 H -1.813158 -3.543062 1.321362 C -4.014686 1.381979 -0.735881 H -4.113668 1.510290 0.356703 H -4.020684 2.368203 -1.231554 H -4.864307 0.792179 -1.121193 C -0.266057 2.889495 -0.623798 H 0.734079 3.322992 -0.783497 H -0.877928 3.025474 -1.531495 H -0.755835 3.394388 0.227107 C 2.592674 2.368208 1.628525 H 1.851545 3.187474 1.621171 H 2.394422 1.720408 2.499613 H 3.600577 2.809055 1.717197 C 0.335823 -1.873542 -2.166935 H -0.391989 -1.982736 -2.988883 H 1.348723 -2.085547 -2.554508 H 0.086235 -2.604285 -1.376900

221 V15 W 1.505378 0.107040 -0.260250 W -1.530483 0.035176 0.023501 O -2.983381 0.470784 -1.106034 O -1.791122 -1.811935 0.429186 O -0.178188 1.470945 -0.597962 O 0.116937 -0.735193 -1.519637 O 2.587537 1.650438 0.025187 O 2.841664 -1.144224 -0.755869 N -1.990125 0.754087 1.495022 C 1.004470 -0.415081 1.368618 C 3.417261 -2.295742 -0.164399 H 4.514567 -2.178335 -0.145463 H 3.043636 -2.441732 0.863719 H 3.172129 -3.183868 -0.772611 C 0.717956 -0.837471 2.758302 H -0.161162 -0.293618 3.146904 H 0.500575 -1.918687 2.821992 H 1.576148 -0.626984 3.421163 C -2.288075 -2.433730 1.602531 H -2.507027 -1.683897 2.383674 H -3.213056 -2.981958 1.350413 H -1.546890 -3.160271 1.980673 C -4.187586 1.171446 -0.821321 H -4.186262 1.536956 0.220808 H -4.279103 2.021034 -1.519074 H -5.042984 0.492350 -0.978408 C -0.190486 2.792823 -0.038055 H 0.678654 3.343863 -0.428453 H -1.118050 3.292060 -0.359197 H -0.162163 2.754541 1.063639 C 3.018528 2.406790 1.142938 H 2.741214 3.466885 1.006871 H 2.569328 2.028131 2.077031 H 4.118561 2.342967 1.214231 C 0.154240 -2.120196 -1.874213 H -0.631334 -2.297617 -2.627637 H 1.137341 -2.367359 -2.310028 H -0.040891 -2.766608 -1.001397

222 V16 W 1.601924 0.093001 -0.263170 W -1.729719 0.074401 0.029992 O -3.026779 0.266690 -1.323285 O -1.835847 -1.694470 0.720053 O -0.213345 1.389961 -0.255846 O 0.030721 -0.820212 -1.235095 O 2.587084 1.728655 -0.136599 O 2.883298 -1.029533 -1.101836 N -2.444115 0.912895 1.326880 C 1.548122 -0.517239 1.396484 C 3.719009 -2.083399 -0.656290 H 4.774129 -1.797848 -0.812635 H 3.551135 -2.296988 0.413420 H 3.513460 -2.991304 -1.250383 C 1.467566 -1.060545 2.772530 H 0.647114 -0.581755 3.337244 H 1.274894 -2.148867 2.771562 H 2.401012 -0.888012 3.338316 C -2.405055 -2.151363 1.940313 H -2.801786 -1.302848 2.525322 H -3.220258 -2.859600 1.711714 H -1.632162 -2.679909 2.524809 C -4.305918 0.894063 -1.292077 H -4.467431 1.389519 -0.319139 H -4.353781 1.634946 -2.107235 H -5.083268 0.129690 -1.458488 C -0.181866 2.681055 0.382991 H 0.631613 3.261129 -0.075663 H -1.146815 3.180944 0.220116 H -0.006797 2.566728 1.464400 C 3.238167 2.422190 0.912714 H 2.842147 3.451480 0.986453 H 3.098418 1.906929 1.878799 H 4.317439 2.484807 0.686378 C 0.039862 -2.221058 -1.521616 H -0.847800 -2.458513 -2.132115 H 0.950202 -2.472611 -2.091249 H 0.003771 -2.816944 -0.593991

223 V17 W 1.661171 0.003878 -0.218118 W -1.891693 0.122820 0.030306 O -2.640741 -0.276471 -1.658641 O -2.211607 -1.247352 1.295089 O -0.231081 1.216290 0.151682 O 0.010834 -1.113916 -0.637754 O 2.438767 1.723882 -0.550358 O 2.804452 -1.106607 -1.250432 N -2.959678 1.328079 0.582702 C 2.138474 -0.379459 1.437983 C 3.895367 -1.953835 -0.935973 H 4.829098 -1.501422 -1.314820 H 3.980351 -2.104118 0.154230 H 3.755364 -2.928895 -1.434809 C 2.512958 -0.752383 2.822321 H 1.677661 -0.561602 3.520767 H 2.765194 -1.825327 2.903718 H 3.384445 -0.178328 3.186447 C -3.125684 -1.284787 2.387553 H -3.665236 -0.325608 2.473418 H -3.844172 -2.105788 2.224832 H -2.562309 -1.483589 3.314655 C -3.804201 0.251650 -2.289833 H -4.262601 1.035726 -1.662307 H -3.516478 0.671916 -3.267844 H -4.524782 -0.567424 -2.452602 C -0.141315 2.579532 0.614177 H 0.371321 3.175721 -0.154563 H -1.158443 2.956253 0.793031 H 0.446451 2.598344 1.545681 C 3.275082 2.598675 0.183228 H 2.810551 3.600101 0.246645 H 3.458136 2.216428 1.202642 H 4.240914 2.701900 -0.343122 C -0.025748 -2.539034 -0.583285 H -0.963315 -2.886965 -1.049684 H 0.828566 -2.956557 -1.143061 H 0.011006 -2.891758 0.462181

224 V18 W -1.682051 -0.000689 0.097138 W 1.958990 0.121550 -0.006676 O 2.294338 -0.730979 1.647379 O 2.513524 -0.908826 -1.500637 O 0.374219 1.292199 -0.102983 O -0.067335 -1.162282 -0.188229 O -2.283320 1.824849 0.118516 O -2.386937 -0.705971 1.702045 N 3.154117 1.332093 -0.002926 C -2.746216 -0.691359 -1.132148 C -3.506066 -1.520670 2.014704 H -4.268634 -0.911390 2.530747 H -3.941082 -1.957008 1.100091 H -3.180110 -2.327220 2.693730 C -3.622953 -1.232890 -2.198453 H -3.523900 -2.330209 -2.288714 H -4.688276 -1.017217 -1.997031 H -3.379720 -0.799653 -3.185329 C 3.644049 -0.739870 -2.351056 H 4.202804 0.171380 -2.075200 H 4.299385 -1.622410 -2.256490 H 3.296688 -0.665788 -3.395316 C 3.291185 -0.461072 2.629355 H 3.904096 0.407182 2.331011 H 2.793608 -0.257465 3.592224 H 3.932062 -1.351723 2.741621 C 0.386621 2.735215 -0.145308 H -0.243711 3.119307 0.668229 H 1.425068 3.082839 -0.044534 H -0.035654 3.064173 -1.107574 C -3.314313 2.513315 -0.560707 H -2.890275 3.365573 -1.124104 H -3.849546 1.847301 -1.260652 H -4.033412 2.913502 0.177185 C -0.081866 -2.494489 -0.702506 H 0.933410 -2.758132 -1.039989 H -0.401928 -3.197530 0.086163 H -0.781793 -2.564918 -1.551773

225 V19 W -1.687334 0.000007 -0.007903 W 1.946074 0.000009 -0.110931 O 2.316823 1.579875 0.868679 O 2.316778 -1.579980 0.868502 O 0.400499 0.000112 -1.291632 O -0.169168 -0.000064 1.225532 O -1.992763 -1.585353 -1.020256 O -1.992791 1.585490 -1.020057 N 3.199752 0.000057 -1.256285 C -3.060190 -0.000077 1.123611 C -3.020458 2.563140 -0.981380 H -3.549951 2.574457 -1.950690 H -3.741520 2.349959 -0.173506 H -2.569104 3.557561 -0.817731 C -4.198823 -0.000142 2.073541 H -4.186462 0.890532 2.728443 H -5.169001 -0.001193 1.542959 H -4.185259 -0.889832 2.729757 C 3.368641 -2.528242 0.713239 H 4.019989 -2.251811 -0.133946 H 3.960696 -2.561642 1.643584 H 2.927895 -3.523834 0.536889 C 3.368697 2.528140 0.713510 H 4.020044 2.251783 -0.133700 H 2.927963 3.523754 0.537255 H 3.960748 2.561444 1.643861 C 0.344844 0.000166 -2.725726 H -0.203346 0.899273 -3.048055 H 1.366900 0.000407 -3.134751 H -0.202950 -0.899145 -3.048158 C -3.020388 -2.563051 -0.981664 H -2.568972 -3.557485 -0.818266 H -3.741364 -2.350065 -0.173661 H -3.549989 -2.574195 -1.950916 C -0.097279 -0.000190 2.651877 H 0.452116 -0.898729 2.979120 H 0.452160 0.898265 2.979277 H -1.110918 -0.000198 3.081748

226 (MeO)3WCMe W -0.000258 0.000037 -0.248707 O 1.500502 -1.040565 -0.768057 O 0.150642 1.820952 -0.764658 O -1.653107 -0.778365 -0.765332 C 0.001260 -0.001682 1.519958 C -2.775316 -1.308819 -0.077486 H -2.641328 -1.234856 1.014956 H -3.680362 -0.750801 -0.374639 H -2.907503 -2.367885 -0.359843 C 0.252721 3.057783 -0.076384 H 0.236958 2.905511 1.016047 H 1.194676 3.556841 -0.363546 H -0.591372 3.706674 -0.368347 C 2.522205 -1.746492 -0.081231 H 3.505394 -1.338656 -0.374167 H 2.399168 -1.657039 1.011334 H 2.484345 -2.811721 -0.368722 C 0.003115 -0.003359 3.003124 H 0.927477 0.446523 3.408568 H -0.848302 0.571022 3.411031 H -0.068264 -1.029088 3.408092

(MeO)3WN W 0.000000 -0.000162 -0.072554 N -0.000038 -0.000005 1.619745 O 1.627772 -0.829696 -0.562716 O -0.095864 1.824221 -0.562790 O -1.532482 -0.994720 -0.562866 C -2.532077 -1.646586 0.215700 H -3.516818 -1.221651 -0.040967 H -2.532991 -2.721070 -0.032633 H -2.337862 -1.513339 1.293504 C 2.693023 -1.368126 0.215504 H 2.478299 -1.272064 1.293390 H 2.822349 -2.431748 -0.045518 H 3.622217 -0.826733 -0.028817

227 C -0.160528 3.016064 0.215446 H 0.703212 3.653652 -0.036752 H -1.087549 3.557093 -0.037734 H -0.148536 2.781364 1.293380

228 BIBLIOGRAPHY

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