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C-H bond activation of hydrocarbons by a tungsten allene complex Stephen H. K., Ng 2002

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C-H BOND A C T I V A T I O N OF H Y D R O C A R B O N S BY A TUNGSTEN A L L E N E C O M P L E X by STEPHEN H. K. N G B . S c , The University of British Columbia, 2000  A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE D E G R E E OF M A S T E R OF SCIENCE in THE F A C U L T Y OF G R A D U A T E STUDIES (Department of Chemistry)  We accept this thesis as conforming to the required standard  THE UNIVERSITY OF BRITISH C O L U M B I A July 2002 © Stephen H. K. Ng, 2002  U B C Rare Books and Special Collections - Thesis Authorisation Form  In p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t of the r e q u i r e m e n t s f o r an advanced degree at the U n i v e r s i t y of B r i t i s h Columbia, I agree t h a t the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and s t u d y . I f u r t h e r agree t h a t p e r m i s s i o n f o r e x t e n s i v e c o p y i n g of t h i s t h e s i s f o r s c h o l a r l y purposes may be g r a n t e d by the head of my department or by h i s or her r e p r e s e n t a t i v e s . I t i s u n d e r s t o o d t h a t c o p y i n g or p u b l i c a t i o n of t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l not be a l l o w e d w i t h o u t my w r i t t e n p e r m i s s i o n .  Department The U n i v e r s i t y of B r i t i s h Columbia Vancouver, Canada  Page 1 of 1  Abstract  Gentle thermolysis of the 18e alkyl-allyl complex, Cp*W(NO)(CH CMe )(ri 3  2  3  l,l-Me2C3H3) (1.1), generates a reactive 16e allene intermediate, Cp*W(NO)(ri H2C=C=CMe2) (A), by a first-order process with concomitant evolution of neopentane via hydrogen abstraction from the dimethylallyl ligand. Intermediate A has been structurally characterized as its PMe adduct, and is capable of effecting both single and 3  multiple intermolecular C-H bond activations of hydrocarbon solvents to form alkyl-allyl and allyl-hydrido complexes. The products of reactions of A with methyl-substituted arenes (i.e. sp C-H vs sp~ C-H) indicate an inherent preference for the activation of stronger arene C-H bonds, however steric effects are also relevant as indicated by the exclusive formation of benzylic C-H activation products in mesitylene. Thermolyses of 1.1 in alkane solvents generate products resulting from three successive C-H bond-activation reactions. Preliminary studies suggest that allyl-hydrido complexes are formed along with an organic product; for example, in cyclohexane, 1,1dimethylpropylcyclohexane results from coupling of a solvent molecule and a fragment derived from the precursor dimethylallyl ligand. The allyl-hydrido complexes have potential synthetic utility, since studies conducted on structurally and electronically related CpMo complexes show that they may be capable of ultimately producing homoallylic alcohols.  Table of Contents  Abstract  ii  Table of Contents  iii  List of Tables  viii  List of Figures  ix  List of Abbreviations  xi  Acknowledgements  xiii  CHAPTER ONE. Homogenous Intermolecular C-H Bond Activation Reactions of Hydrocarbons by Organometallic Species 1.1  Introduction  1.1.1  Synopsis of Organometallic C-H Bond-Activation Chemistry  1.1.2  Homogenous Intermolecular C-H Activations by Organometallic Complexes  1.2  1 2 2  4  1.1.2.1  Oxidative Addition  4  1.1.2.2  Sigma-bond Metathesis  5  1.1.2.3  Metalloradical Activation  6  1.1.2.4  1,2-Addition  7  The Legzdins C-H Bond-Activating Family of Compounds  9  1.2.1  Tungsten Acetylene System  9  1.2.2  Tungsten Alkylidene Systems  10  1.2.3  Molybdenum Alkylidene and Benzyne Systems  13  iv 1.3  The IdeaBehindCp*W(NO)(CH CMe3)(ri -l,l-Me2C3H3)(l.l)  15  1.4  The Scope of this Research Project and Format of this Thesis  19  1.5  Experimental Procedures  20  3  2  1.5.1  General Methods  20  1.5.2  N M R Assignments  22  1.5.3  Reagents  22  1.5.4  Synthesis of Cp*W(NO)(CH CMe )(ri -l,l-Me2C H3) (1.1)  23  :,  2  3  3  1.6 References and Notes  26  C H A P T E R T W O . Thermal Reactions of C p * W ( N O ) ( C H C M e ) ( r i - l , l - M e C 3 H ) 3  2  3  with Hydrocarbons: Scope of Single C - H Bond Activations  2  3  30  2.1  Introduction  31  2.2  Results and Discussion  32  2.2.1  A Serendipitous Discovery  32  2.2.2  Preliminary Studies on C-H Activation Potential Initiated by 1.1  33  2.2.2.1  Thermolysis of 1.1 in Benzene  33  2.2.2.2  Thermolysis of 1.1 in Tetramethylsilane  37  2.2.2.3  Thermolysis of 1.1 in Mesitylene  39  2.2.3  2.3  Thermolyses in Mono- and Di-Substituted Arenes  42  2.2.3.1  Thermolysis of 1.1 in Xylenes  43  2.2.3.2  Thermolysis of 1.1 in Toluene  48  2.2.3.3  Attempts to Independently Synthesize Complexes 2.4 - 2.15  50  Epilogue  51  2.4  Experimental Procedures  2.4.1  52  Preparative Thermolyses of 1.1 in Hydrocarbon Solvents: General Comments  52  2.4.2  Thermolysis of 1.1 in Benzene-^  53  2.4.3  Preparation of Cp*W(NO)(C H )(Ti -l,l-Me C3H ) (2.1)  53  2.4.4  Preparation of Cp*W(NO)(CH SiMe3Xri -l,l-Me2C3H3) (2.2)  54  2.4.5  Preparation of Cp*W(NO)(CH C H3-3,5-Me2)(ri -l,l-Me2C3H3) (2.3) 55  2.4.6  Reaction Products of Thermolyses of 1.1 in Toluene and  3  6  5  2  3  3  2  3  2  6  o, m, /^-Xylenes 2.4.7  56  Preparation of Cp*W(NO)(CH2C H4-4-Me)(ri -l ,1 - M e C H ) (2.4) 3  6  2  3  3  and Cp*W(NO)(C6H3-2,5-Me )(ri -l , l - M e C H ) (2.5)  57  3  2  2.4.8  2  3  3  Preparation of Cp*W(NO)(CH C H -3-Me)(r| -l,l-Me2C H ) (2.6), 3  2  6  4  3  3  Cp*W(NO)(C H -2,4-Me2)(ri -l,l-Me2C3H3) (2.7) and 3  6  3  Cp*W(NO)(C H -3,5-Me )(ri -l,l-Me2C3H3) (2.8)  58  3  6  2.4.9  3  2  Preparation of Cp*W(NO)(CH C H -2-Me)(r| -l , l - M e C H ) (2.9), 3  2  6  4  2  3  3  Cp*W(NO)(C H -2,3-Me )(Ti -l,l-Me2C3H ) (2.10) and 3  6  3  2  3  Cp*W(NO)(C H3-3,4-Me )(ri -l,1 .-Me C H ) (2.11) 3  6  2  2  3  3  58  2.4.10 Preparation of Cp*W(NO)(CH C H5)(ri -l,l-Me C H3) (2.12), 3  2  6  2  3  Cp*W(NO)(C H -2-Me)(ri -l,l-Me2C3H3) (2.13), 3  6  4  Cp*W(NO)(C H -3-Me)(r| -l,l-IVle C3H3) (2.14) and 3  6  4  2  Cp*W(NO)(C H -4-Me)(ri -l,l-Ivle C3H3) (2.15) 3  6  4  2  2.4.11 Independent Preparation of 2.12 via Metathesis  59 59  vi 2.4.12 Synthesis of Cp*W(NO)(r| -l,l-Me2C H3)(Cl) (2.16)  60  3  3  2.5  References and Notes  70  CHAPTER THREE. Mechanistic Investigations into the Thermal Chemistry of Cp*W(NO)(CH CMe3)(Tl -l,l-Me2C3H3)  73  3  2  3.1  Introduction  74  3.2  Results and Discussion  75  3.2.1  Kinetic Studies  75  3.2.2  Deuterium Labelling Studies  77  3.2.3  Independent Synthesis of a Possible Reactive Intermediate  79  3.2.4  Attempt to Couple the Reactive Species with 2,3-dimethyl-2-butene  83  3.2.5  Definitive Evidence for the Dimethylallene Reactive Intermediate  88  3.3  Epilogue  92  3.4  Experimental Procedures  94  3.4.1  Kinetic Studies and the Concurrent Preparation of Cp*W(NO)(C D ) 6  (T| -l, 1 -Me -allyWi) (2A-d . )  94  3  2  6a  5  c  3.4.2  Thermolysis of 2.1 in Benzene-df,  94  3.4.3  Synthesis of Cp*W(NO)(ri ^ram-H2C=CHC(Me)=CH2) (3.1)  95  3.4.4  Thermolysis of 3.1 in Benzene-Jfi  96  3.4.5  Preparation of Cp*W(NO)(rj -l,l ,2-Me3C H )(r| -3,3-Me2C3H3) (3.2) 96  3.4.6  Preparation of Cp*W(NO)(PMe )(ri -H2C=C=CMe2) (3.3)  3.5  4  3  1  3  References and Notes  2  3  2  97 99  CHAPTER FOUR. Multiple C-H Bond Activations of Hydrocarbons by Cp*W(NO)(n -H C=C=CMe ): Towards the Functionalization of Alkanes 2  2  2  102  4.1  Introduction  103  4.2  Results and Discussion  104  4.2.1  Thermolysis of 1.1 in Methylcyclohexane  104  4.2.2  Thermolysis of 1.1 in Cyclohexane  106  4.3  Potential Functionalization of Alkanes: Future Work  109  4.4  Epilogue  115  4.5  Experimental Procedures  116  4.5.1  Preparation of Cp*W(NO)(Ti -C Hi ,)(H) 4.1 and 4.2 and 3  7  Cp*W(NO)(r| -C6H9)(H) 4.3  116  3  4.5.2  Thermolysis of 1.1 in Cyclohexane in the presence of PMe  4.5.3  Preliminary Identification of Organic Products Generated during  117  3  Thermolysis of 1.1 in Cyclohexane  117  4.6 References and Notes  118  APPENDIX A: Solid-state Molecular Structure X-ray Crystallographic Data Refinement, and Structural Solution and Refinement Data for Compounds 2.1, 2.2, 2.3, 2.5, 3.2 and 3.3  121  APPENDIX B: Kinetic Data and Statistical Analysis Consulting Report  132  List of Tables  Table 2.1  Numbering Scheme, Yield and Analytical Data for Complexes 2.5 - 2.16  Table 2.2  M S and IR Characterization Data for Complexes 2.5 - 2.16  Table 2.3  N M R Characterization Data for Complexes 2.5 - 2.16  Table 3.1  Comparison of C { ' H } and ' H N M R Spectroscopic Resonances l3  of Complex 3.1 and CpMo(NO)(T] -/ran.v-2-methylbutadiene) 4  IX  List of Figures  Figure 1.1  The neopentyl-dimethylallyl complex Cp*W(NO)(CH CMe3)(ri -l,l-Me2C3H3) (1.1).  17  3  2  Figure 2.1  Solid state molecular structure of Cp*W(NO)(C H )(ri -l ,1 - M e C H ) 3  6  5  2  (2.1) with 50% probability thermal ellipsoids.  Figure 2.2  2D E X S Y N M R (CeDf,) plot showing exchange between unique  3  2  2  3  38  3  Solid state molecular structure of Cp*W(NO)(CH C H -3,5-Me ) 2  6  3  2  ( i f - l ,1 -Me C H3) (2.3) with 50% probability thermal ellipsoids. 2  Figure 2.5  3  41  Solid state molecular structure of Cp*W(NO)(C H3-2,5-Me ) 6  2  (r| -l,l-Me C3H ) (2.6) with 50% probability thermal ellipsoids. 3  2  Figure 3.1  36  Solid state molecular structure of Cp*W(NO)(CH SiMe )(ri -l ,1 Me C3H ) (2.2) with 50% probability thermal ellipsoids.  Figure 2.4  3  34  resonances of o- and w-hydrogens on the phenyl ligand of (2.1).  Figure 2.3  3  3  46  Kinetic data plot showing that the C-D bond activating ability of 1.1 is a first order process concurrent with the elimination of neopentane. 76  x  Figure 3.2  Identifying the synthesized diene as the trans isomer based on 80  characteristic NOE enhancements observed.  Figure 3.3  Solid state molecular structure of Cp*W(NO)(r| -l , l , 2 - M e C H ) 3  3  3  2  (Tl -3,3-Me C H ) (3.2) with 50% probability thermal ellipsoids. 1  2  Figure 3.4  3  3  87  Solid state molecular structure of Cp*W(NO)(PMe ) 3  (r| -H C=C=CMe ) (3.3) with 50% probability thermal ellipsoids. 89 2  2  Figure 3.5  2  Two extreme types of bonding proposed in monometallic allene complexes.  Figure 4.1  90  Hydride region of ' H N M R spectrum of cyclohexenyl-hydrido complex 4.3 in C6D . 6  108  XI  List of Abbreviations  The following abbreviations are employed in this Thesis. 0  degree (of angle or temperature)  d  a  the position once removed from a  D,d  reference point (i.e. a metal center)  A  heat  KO  integral at time t  e  electron  1(0)  initial integral  ee  enantiomeric excess  A  angstrom, 10"'° m  n  hapto, denotes ligand hapticity  anal.  analysis  Et 0  diethyl ether  atm  atmosphere(s)  g  gram  P  the position twice removed from a  Y  the position thrice removed from a  doublet or day(s)  2  reference point  2  H  reference point  br  broad (spectral)  h  hour(s)  'Bu  tert-butyl  'H  proton  Bzl  benzyl, C H C H  2  H  deuterium  °C  degrees Celsius  2  H { ' H } proton-decoupled H  2  6  5  , 3  C  carbon-13  ,3  C { ' H } proton-decoupled C  HMBC l 3  cal  calorie  calcd.  calculated  cm  2  heteronuclear multiple bond coherence  H M Q C heteronuclear multiple quantum coherence "  hv  irradiation  centimetre(s)  Hz  hertz (s" )  wavenumbers  Irrad.  irradiate  COSY  correlation spectroscopy  IR  infrared  Cp  r| -C H5, cyclopentadienyl  J  coupling constant  Cp*  r) -C Me , pentamethyl Cp  "i  n-bond J between atoms A and B  Cp'  Cp or Cp*  5  chemical shift in ppm  cm'  1  5  5  5  5  5  •'AB  1  observed rate constant kcal  kilocalorie(s)  K  degrees Kelvin  Oxl  L  litre(s)  31  LREI  low resolution electron impact  3I  P  2-Me-benzyl, CH C H -2-Me 2  6  4  phosphorous-31  P{'H} proton-decoupled P 31  LUMO lowest unoccupied molecular orbital  P  m  multiplet  p  para  m  meta  Ph  phenyl, C H  m/z  mass-to-charge ratio  ppm  parts per mi 11 i on  Me  methyl, C H  Pxyl  4-Me-benzyl, CH C H -4-Me  Mes  mesityl, CH C H -3,5-Me2  R  hydrocarbyl ligand  mg  milligram(s)  R , RI  residuals (statistics)  mL  millilitre(s)  s  singlet, strong (spectral) or secom  mmol  millimole(s)  selNOE selective NOE  mol  mole(s)  t  MS  mass spectrum  t,  Mxyl  3-Me-benzyl, CH C H -3-Me  T  temperature  NMR  nuclear magnetic resonance  TLC  thin-layer chromatography  NOE  nuclear Overhauser effect  THF  tetrahydrofuran  Npt  neopentyl, CH CMe  TMS  tetramethylsilane  v  stretching frequency  To!  tolyl, C H -Me  o  ortho  w  weak (spectral)  obs  obscured (spectral)  Xyl  dimethyl aryl ligand, C H -Me  3  2  3  6  +  2  2  4  6  2  3  ORTEP Oak Ridge Thermal Ellipsoid Plot  parent molecular ion  6  5  2  6  4  triplet or time /2  half-life  6  4  6  3  2  Acknowledgements  First and most importantly, I would like to thank my family who have supported me during my various endeavours over the past 25 years. Mom and Dad, thanks so much for being there for me when I needed you, and kudos to you two for being such great parents and keeping me out of trouble. To my big brother Dave, thanks for being my initial musical influence and not listening to garbage. My little sister Emily, thanks for allowing me to bug you to no end. Kate, thanks for keeping me amused with your foosball talents. To the newest addition to my family, my dear little Hannah, I know you can't read this right now, and you probably will never bother reading this Thesis, but thank you for brightening my days over the past 10 months or so. To the Big-Kahuna, a.k.a. Peter, my deepest thanks for taking me into your research group and letting me do my own thing around the lab. It has been a most enjoyable and satisfying experience. I appreciate the time you took to sit and chat with me when I had questions, worries, beefs and stories and 1 thank you for all your help and advice. Trevor, where do I start? You've been an amazing mentor, musical companion, lab partner and friend. I cannot begin to tell you how much fun you've made this whole research thing. Coffee breaks, hockey games, poking fun at people who have no business being made fun of... the list goes on. It has all been a huge part of my existence for the past two years of my life, and consequently I am greatly indebted to you.  xiv Big Swede, a.k.a Dr. Pamplin, thanks for all the help and advice you've given me during the final stretch of my degree. You have also been a vital part of my lab-sanity. Big thanks to you for ensuring that Trevor won nothing at golf. I must also express my gratitude to former members of the Legzdins group, namely Brett Sharp and Craig Adams, who showed me the ropes around the lab and addressed my teething-pain questions and concerns. Dr. Adams, thank you SO much for handing this project to me on a silver platter and acting as a consultant throughout the past two years. More thanks go out to you for putting up with me as a desk partner during those first eight months. Nick Burlinson, Liane Darge, Marietta Austria, Peter Borda, Brian Patrick, Marshall Lapawa, Bob Bau, Natalie Thompson and Judy Wrinskelle also deserve recognition for their invaluable assistance throughout the duration of this study. Last but not least, my thanks go out to Dennis Lefebvre who has given me a ride to and from the lab everyday in "l'autobus" and for being a constant source of laughter.  "Life moves pretty fast. If you don 7 stop and look around once in a while, you could miss it." Ferris Bueller  Chapter 1  Homogenous Reactions  Intermolecular  C-H  of Hydrocarbons  Bond-Activation  by Organometallic  Species  1.1 Introduction  2  1.2 The Legzdins C-H Bond-Activating Family of Compounds  9  1.3 The Idea Behind Cp*W(NO)(CH CMe3)(Tf-U-IVle2C3H3) (1.1)  15  1.4 The Scope of this Research Project and Format of this Thesis  19  1.5 Experimental Procedures  20  1.6 References and Notes  26  2  2 1.1 Introduction  The results of investigations performed on the thermal C-H bond-activating chemistry of a novel system is presented in this Thesis. To gain a better understanding of the significance of this discovery, it is essential to commence with a brief discussion regarding organom etal lie chemistry and the sub-field of C-H bond activation by transition metal complexes.  1.1.1 Synopsis of Organometallic C - H Bond-Activation Chemistry  Organometallic chemistry, in its most succinct definition, encompasses the study of complexes that contain at least one direct bond between a metal and a carbon atom. The inception of this scientific domain in 1760 with the preparation of "Cadet's fuming 1  liquid" has led to the development of a wide variety of new compounds, many of which play key roles in commercially important processes such as the polymerization of alkenes into polyethylene and polypropylene. The catalytic component of this reaction, active at 25 °C and 1 atm, is in stark contrast to the conditions required for thermal polymerization (200 °C and 1000 atm) and is just one example of the benefits reaped through the study of organometallics. That this dominion is effectively the link between the two broad fields 3  of organic and inorganic chemistry serves as a means of developing novel methods for tackling age-old problems. One such quandary is the activation of C-H bonds of hydrocarbons in a selective manner, followed by functionalization in an overall effort to  produce valuable materials starting from widely available and relatively inexpensive hydrocarbon feedstocks. The former transformation is the subject of interest in this 4  Thesis and involves the scission of a carbon-hydrogen (C-H) bond of a hydrocarbon substrate by an organometallic fragment. One of the ultimate goals is the activation of methane C-H bonds due to its large constituency in natural gas. Being the most simple, stable hydrocarbon subunit, it could 5  potentially be used as a building block to generate larger, more commercially useful products via breakage of its C-H links. Thus, one impetus for investigating the area of CH bond activation is the notoriously stable behaviour exhibited by alkanes, manifested by the low polarity of the C-H bond and the high bond energies of 90 - 110 kcal/mol.  6  Alkanes are not, however, completely unreactive as activation in the absence of metallic fragments has been known for quite some time. Thermal and photolytic reactions that require large amounts of energy are capable of cleaving C-H bonds, but do so in a typically non-selective manner, usually via free radical mechanisms.  7  Hence, there continues to be active research conducted in this field towards the discovery and evolution of metal-based systems that effect C-H bond activation of hydrocarbon substrates selectively and under relatively mild conditions.  4  1.1.2 Homogenous Intermolecular C-H Activations by Organometallic Complexes  Metal-mediated C-H bond activation using soluble organometallic compounds ordinarily occurs in one of four fashions, namely oxidative addition, o-bond metathesis, metalloradical activation, and 1,2-addition.  8  1.1.2.1 Oxidative Addition  Investigations involving the direct stoichiometric interaction of metal centers with C-H bonds provided the first essential pieces of data regarding the C-H activation process. Oxidative addition, the formal two-electron oxidation of the electronically unsaturated metal center via addition of R-H, leads to the formation of alkyl-hydrido complexes (eq. 1.1).  L M + R-H n  >• L M ^ n  H x —oxidation states  (1.1)  (x + 2)  As such, the metal center must fit certain criteria in order to be a viable host for oxidative addition. These criteria basically encompass the ability of the metal center to possess a d-electron configuration such that an (n+2) oxidation state exists and is accessible to accommodate the addition of 2e from the hydrocarbon C-H scission product' Typically, as a result of its coordinative unsaturation, the reactive intermediate  5  must be formed in situ via decomposition of a precursor species. One of the first examples of an organometallic species capable of effecting homogenous intermolecular oxidative addition to single C-H bonds involves the generation of the reactive intermediate, Cp*Ir'(PMe3) from its precursor Cp*Ir (PMe )H2 which is then able to m  3  activate C-H bonds of benzene, cyclohexane and neopentane (e.g. eq. 1.2).  9  (1.2)  1.1.2.2  Sigma-Bond Metathesis  Another common mechanism of C-H activation involves the exchange of alkyl groups R and R' of M-R and R ' - H (Scheme 1.1). The exchange process typically occurs at formally d° or f d° metal centers, " suggesting that an oxidative-addition type n  10  13  mechanism is not feasible because of the absence of an accessible (n+2) oxidation state.  Scheme 1.1 R'—-H ^  L M — R + R'-H n  L M n  R  L M—R' + R - H n  14  6  Mechanistic data collected for such systems provide evidence for a 2 + 2 o-bond 15  metathesis pathway containing a four-center transition state (Scheme 1.1). The large primary kinetic isotope effects (kn/ko ~ 3-6) support scission of the C-H linkage in the transition state. Additionally, kinetic studies showing first-order dependence on the concentrations of both metal complex and alkane substrate and negative entropies of activation are indicative of an associative mechanism and a highly ordered transition state. Analogous to Scheme 1.1, the metathesis of a metal-hydride and an alkane to reversibly yield the corresponding metal-alkyl and dihydrogen gas has also been established (e.g. eq. 1.3).  16,17  Me SU 3  O  Me Si-~ ° ^ Z r -  Me SU  3  3  -0^ Me Si^^Zr-H .^0 3  +^  \  o  •  Me Si3  +  +H  2  (1.3)  Me Sk 3  Me Si—°^Zr—/ 3  Me Si-'° 3  1.1.2.3 Metalloradical Activation  The exclusive activation of methane in benzene by paramagnetic substituted porphyrin Rh (II) complexes yield equimolar amounts of Rh-CH and Rh-H species.  1  3  Mechanistic studies conducted on (tetramesitylporphyrinato)rhodium(II) monomer,  7 (TMP)Rh' and (tetraxylylpotphyrinato)rhodium(II) dimer, [(TXP)Rh]2 provide evidence for a transition state involving a four-centered linear complex (Scheme 1.2).  Scheme 1.2  2(por)Rh-  (por)RhT llllllllll £  + CH  H \  4  H /  (por)Rh—CH  IIII11II j—| III III Ml  •Rh(por  3  + (por)Rh—H  H (por) = (TMP), (TXP)  1.1.2.4 1,2-Addition  Until quite recently, the identification of metal-alkylidenes that exhibit intermolecular C-H activation remained elusive. The proposed pathway involves the 14  addition of an alkane C-H bond across the metal-carbon double bond. The microscopic reverse reaction, the oc-hydrogen elimination of hydrocarbon, has been well documented, 20  1 S 21 23  as have many examples of intramolecular C-H activation. '' " '  At present there are  four reported systems that effect intermolecular C-H bond activation via generation of transient reactive alkylidene complexes from thermal decomposition of precursor bis(alkyl) species and one of these is given as an example in Scheme 1.3.  24-27  This method of C - H activation also includes the addition of a hydrocarbon C - H linkage across a metal-nitrogen " double bond resulting in the formation of a new 28  31  metal-carbon bond (Scheme 1.4).  Scheme 1.4  RN H  R  \ ^UZr-CH RN  H  A  H RN.  -CH  RN' H  3  R = tei^-Si  4  :Zr=NR  9  1.2 The Legzdins C - H Bond-Activating Family of Compounds  1.2.1 Tungsten Acetylene System  The alkyl-vinyl complex, Cp*W(NO)(CPh=CH )(CH SiMe3), has been 2  2  thoroughly studied and is capable of effecting dual C-H bond activation of alkane substrates under mild conditions (45 °C, 48 h) to yield metallocyclic-allyl complexes as a result of coupling between the vinyl ligand and the activated substrate (e.g. eq. 1.4).  32  (1.4)  Deuterium labelling studies in benzene-^ yield the C-D activated phenyl-vinyl analog with deuterium incorporation at the (3-position of the alkenyl ligand. This result implies the transient existence of a T| -acetylene complex that is responsible for the C-H 2  activating properties of the precursor alkyl-vinyl species. Further evidence for the generation of an intermediate acetylene is gained from the thermal reaction of Cp*W(NO)(CPh=CH )(CH SiMe ) in ethylacetate (Scheme 1.5). Attempts to trap the 33  2  2  3  proposed acetylene intermediate with trimethylphosphine have been unsuccessful.  10 Scheme 1.5  Mechanistic and kinetic studies show that the generation of the purported acetylene intermediate is rate-determining and that it is formed by elimination of tetramethylsilane from the precursor alkyl-vinyl complex. The reactive intermediate generated in situ is then capable of effecting C-H bond activations of methyl-substituted arenes to form mixtures of benzyl- and aryl-vinyl organometallic compounds.  1.2.2 Tungsten Alkylidene Systems  In 1997, members of the Legzdins research group reported the formation of a reactive neopentylidene species, Cp*W(NO)(=CHCMe3), upon thermal decomposition of Cp*W(NO)(CH CMe ) under moderate conditions (70 °C, 40-48 h). The generation of 2  3  2  the alkylidene species in situ leads to C-H activation of arene and alkane substrates (Scheme 1.6)  27  11 Scheme 1.6  Deuterium labelling studies show exclusive incorporation of deuterium into the synclinal position relative to the newly formed M-C(aryl) linkage. This stereoselectivity is consistent with a 1,2-addition mechanism across the M=C bond of a reactive alkylidene intermediate. Moreover, thermolysis of the precursor bis(neopentyl) species in neat PMe3 yields the base-stabilized adduct of the neopentilydene complex, namely Cp*W(NO)(PMe )(=CHCMe3). Mechanistic studies show that the bis(alkyl) complex 3  decomposes and eliminates neopentane in a first-order process with a rate constant of 4.6(1) x l O " s at 72 °C. 5  -1  34  Interestingly, the thermolysis of Cp*W(NO)(CH2CMe3)2 in methyl substituted arenes affords more than one product. '  34 35  The formation of benzylic C-H activated  products can subsequently eliminate neopentane to form a reactive benzylidene species, which has also been shown to activate C-H bonds (Scheme 1.7).  Surprisingly, the thermolysis of Cp*W(NO)(CH2CMe3)2 in cyclohexane in the presence of excess PMe3 yields two products, the aforementioned base-stabilized 27  neopentylidene complex, and a phosphine-trapped cyclohexene adduct (eq. 1.5).  The  formation of the latter complex indicates the sequential activation of two C-H bonds of cyclohexane.  13  1.2.2 Molybdenum Alkylidene and Benzyne Systems  Most recently, other members of the Legzdins group have reported the preparation of the molybdenum congener of the tungsten alkylidene species that is capable of effecting C-H activations of benzene and tetramethylsilane at roomtemperature in an analogous fashion. Remarkably, the thermolysis of 36  Cp*Mo(NO)(CH2CMe3)2 in benzene yields not only the anticipated neopentyl-phenyl species, but also a bis(phenyl) complex (eq. 1.6).  14 Trapping experiments utilizing pyridine generate two organometallic species, namely the pyridine adducts Cp*Mo(NO)(NC H5)(=CHCMe3), and 5  Cp*Mo(NO)(NC H5)(C H4) (eq. 1.7). 5  6  15  1.3 The Idea Behind Cp*W(NO)(CH CMe )(Tl -l,l-Me2C3H3) (1.1) 3  2  3  During the course of studies conducted on the reactivity of the tungsten neopentylidene system, an interesting result arose from one of the experiments. The thermolysis of Cp*W(NO)(CH2CMe3)2 in 2-methyl-2-butene results in the formation of a number of products as an exclusive result of C-H activation and the generation of a metallocyclic species comprised of two coupled substrate molecules, whose identity has 37  been confirmed by single-crystal x-ray diffraction analysis (eq. 1.8).  + other products (1.8)  The only viable rationale for the formation of this product involves the activation of one solvent molecule to give an intermediate neopentyl-allyl complex that subsequently eliminates another equivalent of neopentane to give a diene species that can then couple to a second molecule of the alkene to ultimately yield the product observed (Scheme 1.8).  16 Scheme 1.8  Consequently, the initial target was to synthesize a neopentyl-allyl complex that might thermally generate a diene intermediate via the elimination of neopentane. Presumably, if the diene is successfully formed in situ under thermal conditions in benzene-c/6 (for purposes of monitoring via ' H N M R spectroscopy), and i f it is indeed a reactive intermediate, then the thermolysis of the alkyl-allyl in 2-methyl-2-butene would result in a similar coupled product. Hence, the synthesis of the neopentyl-dimethylallyl complex, namely Cp*W(NO)(CH CMe3)(r|M,l-Me2C3H3) (1.1) which is the principal 2  precursor of the chemistry described in this Thesis, has been performed (Figure 1.1).  17  Figure 1.1 The neopentyl-dimethylallyl complex, C p * W ( N O ) ( C H C M e ) ( T i - l , l 3  2  3  M e C H ) (1.1) 2  3  3  The solution structure of 1.1. with the dimethylallyl terminus situated trans to the NO ligand as expected for this class of compound, has been established. The allyl 38  moiety of 1.1 also displays features indicative of a-n distortion as evinced by its C{'H} 13  N M R spectrum (CeDe) which exhibits a resonance at 101.7 ppm (allyl-CH) characteristic 3  2  of an sp -like carbon and a signal at 37.6 ppm (allyl-CH ) indicative of an sp -like 2  terminal carbon. The distortion observed for 1.1 is common for other transition-metal allyl complexes which display similar spectroscopic features. " 39  42  The endo conformation  adopted by the dimethylallyl ligand, as depicted in Figure 1.1, is supported by evidence from selective N O E N M R spectroscopic data.  43  For related 16e bis(alkyl) species, the presence of the 3e N O ligand results in strong backbonding interactions between the n* orbitals of the NO and the d and d xz  orbitals of the metal center. '  44 45  yz  This interaction results in the stabilization of the metal d-  orbitals involved relative to the non-bonding d L U M O , thereby rendering the metal xy  center Lewis acidic and prone to coordination by suitable Lewis bases. As an  intramolecular example, the dimethylallyl portion of 1.1 stabilizes the L U M O via the donor interaction, to afford an electronically saturated compound. The neopentyldimethylallyl complex can thus be described as an 18e complex as a result of the trihapticity of the allyl fragment.  19  1.4 The Scope of this Research Project and Format of this Thesis  Chapter 2 describes the synthesis and characterization of products obtained from the thermal reactions of 1.1 in various hydrocarbon solvents, and the thermodynamic product distributions acquired are discussed. The solid-state molecular structures of four of the compounds have been determined, and the metrical parameters are discussed with reference to solution structures established by N M R spectroscopic techniques. Chapter 3 discusses the mechanism of C-H activation initiated by the precursor neopentyl-dimethylallyl complex. Techniques utilized in the elucidation of the reactive intermediate are described, as are kinetic details. The solid-state molecular structures of two complexes arising from these studies are presented, as are the solution structures determined by means similar to those in Chapter 2. Chapter 4 describes the multiple C-H bond-activating ability initiated by 1.1 of alkane C-H linkages. This final chapter also discusses possibilities for future work in this area, some of which has already been initiated. This Thesis is formatted with Chapters 2 and 3 possessing five major Sections. If X is the Chapter number, then the Sections appear as X . l Introduction, X.2 Results and Discussion, X.3 Epilogue, X.4 Experimental Procedures, and X.5 References and Notes. Subsections of these categories are numbered using legal outlining procedures, e.g. X . 1.1, X . l . 2 , X.l.2.1, etc. All compounds discussed in each Chapter are catalogued numerically, e.g. in Chapter X , compounds appear as X . l , X.2, etc. Schemes, Tables, Figures and Equations are similarly sequenced. The standard experimental methodologies employed during the course of this research are described in detail in this Chapter, Section 1.5.1.  20 1.5 Experimental Procedures  1.5.1 General Methods  The following descriptions of methodologies employed throughout the course of this study apply to the entire thesis. All reactions and subsequent manipulations involving organometallic reagents were performed under anaerobic and anhydrous conditions either under high vacuum or an inert atmosphere of pre-purified argon or dinitrogen. Purification of inert gases was achieved by passing them first through a column containing MnO and then a column of activated 4 A molecular sieves. Conventional glovebox and vacuum-line Schlenk techniques were utilized throughout. The gloveboxes utilized were Innovative Technologies LabMaster 100 and MS-130 B G dual-station models equipped with freezers maintained at - 30 °C. Many reactions were performed in a thick-walled bomb, here defined as a glass vessel possessing a Kontes greaseless stopcock and a side-arm inlet for vacuum-line attachment. Small-scale reactions and N M R spectroscopic analyses were conducted in J. Young N M R tubes which were also equipped with a Kontes greaseless stopcock. All solvents were dried with appropriate drying agents under dinitrogen or argon atmospheres and distilled prior to use, or were directly transferred under vacuum from the appropriate drying agent. Hydrocarbon solvents, their deuterated analogues, diethyl ether and trimethylphosphine were dried and distilled from sodium or sodium/benzophenone ketyl. Tetrahydrofuran was distilled from molten potassium, and dichloromethane and chloroform were distilled from calcium hydride.  21  All IR samples were prepared as KBr pellets (~ 1 mg sample: ~ 100 mg KBr) and recorded on a B O M E M MB-100 FT-IR spectrometer unless otherwise noted. All N M R spectra were recorded at room temperature unless otherwise noted. ' H N M R spectra were recorded on Bruker AV-300 (300 MHz), Bruker AV-400 (400 MHz), or Bruker A M X 500 (500 MHz) instruments. H {'H} N M R spectra were recorded on a Bruker AMX-500 2  (77 MHz) instrument. C {'H} N M R spectra were recorded on Bruker AV-300 (75 1 3  MHz), Bruker AV-400 (100 MHz) or Bruker AMX-500 (125 MHz) instruments. A l l chemical shifts are reported in ppm, and all coupling constants are reported in Hz. N M R spectra were referenced to the residual protio-isotopomer present in a particular solvent. 2  H{'H}  N M R spectra ( C H ) are referenced to residual C H D (7.15 ppm) while 6  6  6  C{ H}  l3  5  l  N M R spectra are referenced to the natural abundance carbon signal of the solvent employed. P { ' H } N M R spectra are referenced to external H P 0 (85%) in C D (0.0 31  3  4  6  6  ppm). Where necessary, ' H - ' H COSY, ' H - ' H selNOE, ' H - C H M Q C and ' H - C H M B C 13  1 3  experiments were carried out to correlate and assign ' H and C signals. Low-resolution 1 3  mass spectra (EI, 70 eV) were recorded by the staff of the UBC Chemistry Mass Spectrometry Laboratory on a Kratos MS50 spectrometer utilizing the direct-insertion sample introduction method. Elemental analyses were performed by Mr. P. Borda at the Department of Chemistry at U B C and Ms. Pauline Maloney of Canadian Microanalytical Service Ltd. X-ray crystallographic data collection was performed by Dr. B . O. Patrick of the UBC X-ray Crystallographic Laboratory and Dr. R. Bau of the University of Southern California X-ray Crystallographic Laboratory.  22 1.5.2 N M R Assignments  The following format has been employed to help identify peaks in the N M R spectra: X X X ppm (multiplicity, coupling constant(s), relative number of atoms, ligandpart). Subscripts for specific portions of a ligand are as follows: syn, anti for syn and anticlinal methylene H atoms; o, m, p and ipso for positions on an aryl ring; aryl if the position is not known; s for H „, sy  a for H„„„ and c for H in allyl complexes. c  1.5.3 Reagents  The (CH2CMe3)2Mg'*(di°  xane  ) alkylating reagent and the  Cp*W(NO)(CH2CMe3)(Cl) complex were prepared according to published j  46,47  procedures. ' A modified version of the general synthetic method for dialkyl magnesium reagents was employed for the preparation of the dimethylallyl magnesium reagent. 3,3Dimethylallyl bromide (Fluka, 10 mL, 0.085 mol) was syringed into a 200-mL two-neck round bottom flask and diluted with Et20 (100 mL). In a glovebox, a 500-mL three-neck round bottom flask was charged with magnesium powder (4.2 g, 0.172 mol) and a magnetic stir-bar. The 500-mL flask was charged with Et20 (250 mL), and on a vacuumline, was fitted with a reflux condenser. Activation of the magnesium powder was accomplished via addition of sufficient dibromoethane (~ 1-2 mL) using a syringe. The suspension was allowed to reflux until all the added dibromoethane had reacted. The  23 suspension was then cooled in an ice bath to 0 °C, whereupon the ethereal bromide solution was added dropwise via a cannula over a 3-hour period. During this time, the contents of the flask were stirred rapidly, and the solution remained clear. Upon completion of the dropwise addition, the mixture was slowly warmed to room temperature. The transformation of the Grignard reagent into the bis(allyl)magnesium reagent was conducted in the usual manner for bis(alkyl) reagents. ( r ) - l , l 46  3  Me2C H3)2Mgx(dioxane) was isolated as a snow-white powder and titration with 0.1 M 3  HC1 afforded a titre of 127 g/mol (2.7 g, 50%).  1.5.4 Synthesis of Cp*W(NO)(CH CMe )(Ti -l,l-Me2C3H3) ( l . l ) 3  2  4 8  3  In a glovebox, a 400-mL Schlenk tube was charged with a magnetic stir bar and Cp*W(NO)(CH CMe )Cl (483 mg, 1.15 mmol). A 100-mL Schlenk tube was then 2  3  charged with a magnetic stir bar and the dimethylallyl magnesium reagent (147 mg, 1.16 mmol). On a vacuum-line, Et20 (200 mL) from a bomb was cannulated into the Schlenk tube containing the magnesium reagent with vigorous stirring to ensure dissolution. The resulting colourless solution was cooled to - 196 °C using a liquid N2 bath under a strong flow of Ar in an open system to prevent the introduction of air. Et20 (50 mL) was added in a similar fashion to the Schlenk tube containing the solid Cp*W(NO)(CH2CMe )Cl to 3  give a purple solution which was then cooled to - 60 °C with a Dry Ice/acetone bath. The resulting mixture was then cannulated dropwise into the 400-mL Schlenk tube (maintained at - 196 °C) at a slow enough rate that allowed the added solution to freeze  24 upon contact with the solidified ethereal solution. Sufficient E t 0 was added to the 1002  mL Schlenk tube and subsequently cannulated into the reaction flask to ensure complete transfer of Cp*W(NO)(CH CMe )Cl. The liquid N bath was replaced with a liquid 2  3  2  N /acetone bath at - 60 °C to slowly melt the ethereal contents. After being stirred for 5 2  minutes, the purple solution changed to a straw-yellow colour which then becomes a turbid orange solution after a further 10 minutes. The solution was stirred at - 60 °C for a total of 45 minutes, whereupon the contents were warmed to room temperature to ensure completion of reaction. The volume was reduced under vacuum to ~ 100 mL, and the turbid orange solution was filtered through an alumina (I) column ( 2 x 3 cm), which was rinsed with fresh E t 0 (2 x 10 mL), to give a clear bright orange filtrate. The volatiles 2  were then removed from the filtrate in vacuo to obtain an orange crystalline powder which was allowed to dry under high vacuum for 1 hour. Analysis of this solid by *H N M R spectroscopy revealed that complex 1.1 was the sole organometallic product. The analytically pure product was obtained as orange microcrystals (296 mg, 57 %) via crystallization from a THF/hexanes mixture (5 mL: 20 mL) at - 25 °C.  1.1: IR (cm ) 1546 (s, v ) . MS (LREI, m/z, probe temperature 150 °C) 489 [P , -1  +  N 0  184  W ] . ' H N M R (300 MHz, C D ) 5 0.67 (s, 3H, allyl Me), 1.02 (obs, l H , N p t C H ) , 6  6  2  1.02 (s, 3H, allyl Me), 1.42 (s, 9H, Npt CMe ), 1.42 (obs, I H , allyl CH ), 1.53 (s, 15H, 3  2  C Me ), 2.69 (m, I H , allyl CH ), 4.45 (m, 1H, allyl CH); ' H N M R (400 MHz, CD C1 ) 5  5  2  50.88 (d, V  H H  2  = 14.2, I H , Npt CH ), 0.99 (s, 3H, allyl Me), 1.02 (d, V 2  H H  2  = 14.2, I H , Npt  CH ), 1.06 (s, 9H, Npt CMe ), 1.24 (s, 3H, allyl Me), 1.61 (m, I H , allyl CH ), 1.82 (s, 2  3  2  15H, C Me ), 2.55 (m, I H , allyl CH ), 4.40 (m, I H , allyl CH). C{'H} N M R (75 MHz, 13  5  5  2  25 CD C1 ) 5 10.2 (C Me ), 19.5, 30.7 (allyl Me), 34.3 (Npt CMe ), 37.6 (allyl CH ), 39.9 2  2  5  5  3  2  (Npt CMe ), 40.7 (Npt CH ), 101.7 (allyl CH), 107.5 (C Me ), 147.8 (allyl C). S e l N O E 3  2  5  5  (400 MHz, C D ) 5 irrad. at 4.45, N O E at 1.02, irrad. at 0.67, N O E at 1.02, 1.42, 1.52 and 6  6  2.55. Anal. Calcd. for C oH NOW: C, 49.09; H , 7.21; N , 2.86. Found: C, 49.16; H , 7.03; 2  N.2.87.  35  26  1.6 References and Notes  (1) Elschenbroich, C ; Salzer, A. Organometallics; 2 ed.; V C H Publishers Inc.: New n d  York, 1992. (2) Seyferth, D. Organometallics 2001, 20, 1488. (3) Crab tree, R. H. The Organometallic Chemistry of the Transition Metals; 3 ed.; rd  Wiley and Sons: Toronto, 2001. (4) Crabtree, R. H. J. Chem. Soc, Dalton Trans. 2001, 2437. (5) Crabtree, R. H. Chem. Rev. 1995, 95, 987. (6) Crabtree, R. H. Chem. Rev. 1985, 85, 245. (7) Shilov, A. E.; Shul'pin, G. B. Activation and Catalytic Reactions of Saturated Hydrocarbons in the Presence of Metal Complexes; Kluwer Academic Publishers: Dordrecht, 2000; Vol.21. (8) Labinger, J. A.; Bercaw, J. E. Nature 2002, 417, 507. (9) Janowicz, A. H.; Bergman, R. G. J. Am. Chem. Soc. 1982, 104, 352. (10) Thompson, M . E.; Baxter, S. M . ; Bulls, A . R.; Burger, B. J.; Nolan, M . C ; Santarsiero, B. D.; Schaefer, W. P.; Bercaw, J. E. J. Am. Chem. Soc. 1987, 109, 203. (11) Watson, P. L. J. Am. Chem. Soc. 1983,105, 6491. (12) Rothwell, I. P. Acc. Chem. Res. 1988, 21, 153. (13) Sadow, A . D.; Tilley, T. D. J. Am. Chem. Soc. 2002, 124, 6814. (14) Arndsten, B. A.; Bergman, R. G.; Mobley, T. A.; Peterson, T. H. Acc. Chem. Res.  1995, 2S, 154.  27 (15) Hill, C. L., Ed. Activation and Functionalization of Alkanes; John Wiley and Sons: New York, 1989. (16) Vidal, V.; Theolier, A.; Thivolle-Cavat, J.; Basset, J. M . ; Corker, J. J. Am. Chem. Soc. 1996,118, 4595. (17) Niccolai, G. P.; Basset, J. M . Appl. Catal. A. 1996, 146, 145. (18) Sherry, A . E.; Wayland, B. B. J. Am. Chem. Soc. 1990, 112, 1259. (19) Wayland, B. B.; Ba, S.; Sherry, A . E. J. Am. Chem. Soc. 1991, 113, 5305. (20) Schrock, R. R. Acc. Chem. Res. 1979, 12, 98. (21) van Doom, J. A . ; van der Heijden, H.; Orpen, A . G. Organometallics 1994, 13, 4271. (22) McDade, C ; Green, J. C ; Bercaw, J. E. Organometallics 1982, 1, 1629. (23) Bulls, A. R.; Schaefer, W. P.; Serfas, M . ; Bercaw, J. E. Organometallics 1987, 6, 1219. (24) Coles, M . P.; Gibson, V. C ; Clegg, W.; Elsegood, M . R. J.; Porelli, P. A. J. Chem. Soc, Chem. Commun. 1996, 1963. (25) van der Heijden, H.; Hessen, B. J. Chem. Soc, Chem. Commun. 1995, 145. (26) Cheon, J.; Rogers, D. M . ; Girolami, G. S. J. Am. Chem. Soc. 1997, 119, 6804. (27) Tran, E.; Legzdins, P. J. Am. Chem. Soc. 1997, 119, 5071. (28) Bennett, J. L.; Wolczanski, P. T. J. Am. Chem, Soc. 1997, 119, 10696. (29) Schafer II, D. F.; Wolczanski, P. T. J. Am. Chem. Soc. 1998, 120, 4881. (30) Cummins, C. C ; Baxter, S. M . ; Wolczanski, P. T. J. Am. Chem. Soc. 1988, 110, 8731. (31) Walsh, P. J.; Hollander, F. J.; Bergman, R. G. J. Am. Chem. Soc. 1988,110, 8729.  28 (32) Debad, J. D.; Legzdins, P.; Lumb, S. A.; Batchelor, R. J.; Einstein, F. W. B. J . Am. Chem. Soc. 1995, 117, 3288. (33) Debad, J. D.; Legzdins, P.; Lumb, S. A.; Rettig, S. J.; Batchelor, R. J.; Einstein, F. W. B. Organometallics 1999,18, 3414. (34) Adams, C. S.; Legzdins, P.; Tran, E. J. Am. Chem. Soc. 2001, 123, 612. (35) Adams, C. S.; Legzdins, P.; Tran, E. Organometallics 2002, 21, 1474. (36) Wada, K.; Pamplin, C. B.; Legzdins, P. J. Am. Chem. Soc. 2002, 124, published on web 24 July 2002. (37) Tran, E. Development of Tungsten Alkylidene Complexes for Activation of Hydrocarbons: Synthesis, Selectivities, and Mechanisms. Ph.D. Thesis, University of British Columbia, Vancouver, BC, December 2001. (38) Faller, J. W.; DiVerdi, M . J.; John, J. A. Tetrahedron Lett. 1991, 32, 1271. (39) Ipaktschi, J.; Mirzaei, F.; Demuth-Eberle, G. J.; Beck, J.; Serafin, M . Organometallics 1997, 16, 3965. (40) Frohnapfel, D. S.; White, P. S.; Templeton, J. L. Organometallics 1997,16, 3737. (41) Villanueva, L. A.; Ward, Y. D.; Lachicotte, R.; Liebeskind, L. S. Organometallics 1996,75,4190. (42) Adams, R. D.; Chodosh, D. F.; Faller, J. W.; Rosan, A . M . J. Am. Chem. Soc. 1979, 101, 2570. (43) Direct evidence for endo- vs exo-allyl conformations using selective N O E N M R spectroscopy is sometimes not available, and logical inferences must be made to ascertain the solution structure. For example, irradiation of the signal due to the central allyl H atom leading to an NOE enhancement of the Cp* methyl H atoms signal is direct  29 evidence for an exo configuration. However, its absence, and hence the implication of an endo configuration, must be confirmed by irradiation of the trans Me group signal that should exhibit an N O E enhancement of the Cp* ring signal. (44) Legzdins, P.; Rettig, S. J.; Sanchez, L. J.; Bursten, B. E.; Gatter, M . J. J. Am. Chem. Soc. 1985, 107, 1411. (45) Bursten, B. E.; Cayton, R. H . Organometallics 1987, 6, 2004. (46) Dryden, N . H.; Legzdins, P.; Trotter, J.; Yee, V. C. Organometallics 1991, 10, 2857. (47) Debad, J. D.; Legzdins, P.; Batchelor, R. J.; Einstein, F. W. B. Organometallics 1993, 12, 2094. (48) Adams, C.S. C-H Activation of Hydrocarbons by Tungsten Alkylidene and Related Complexes. Ph.D. Thesis, University of British Columbia, Vancouver, BC, October 2001.  30  Chapter 2 Thermal Reactions ofCp*W(NO)(CH CMe )(rf-l,l-Me C H ) 2  3  2  3  3  with Hydrocarbons: Scope of Single C-H Bond Activations  2.1 Introduction  31  2.2 Results and Discussion  32  2.3 Epilogue  51  2.4 Experimental Procedures  52  2.5 References and Notes  70  31  2.1 Introduction  As described in Chapter One, the preparation of Cp*W(NO)(CH CMe3)(ri -l,l3  2  Me2C3H3) (1.1) was an effort to identify the intermediate involved in the coupling reaction that occurs when the well-studied bis(neopentyl) species, Cp*W(NO)(CH CMe3) , " is thermolysed in 2-methyl-2-butene. 1  2  3  2  The unexpected result observed from the thermal reaction of 1.1 in benzene, namely the formation of an aryl containing organometallic product, encouraged the pursuit of further studies. Presumably, C-H bond activation via some as yet unidentified pathway led to the incorporation of a phenyl group. Reactions were thus performed to assess the breadth of the reactivity of 1.1 towards different hydrocarbon solvents. This Chapter expands upon the observations mentioned above and provides detailed information pertaining to the scope of the single C-H bond activations initiated by 1.1 under suitable thermolytic conditions. When more than one type of C-H bond is present in a substrate (e.g. sp C-H vs sp C-H), the formation of more than one 2  3  organometallic product is observed. The product ratios reflect the thermodynamic distribution of activations initiated by 1.1 for different classes of C-H bonds.  32 2.2 Results and Discussion  2.2.1 A Serendipitous Discovery  The formation of Cp*W(NO)(C D )(ri -l,l-Me2-allyl-t/i) (2.W ) as a result of 3  6  5  6  apparent C-D bond activation upon thermolysis of 1.1 in benzene-^ was an unexpected result. Instead of resonances attributable to the formation of the putative cw-diene intermediate, signals resulting from a dimethylallyl-containing organometallic species are detectable in the ' H N M R spectrum. C{'H} N M R data (CeDe) include signals near the 13  solvent peak (8 128.0) assignable to the aryl carbon atoms. These data constitute the first indication of an aryl ligand as no resonances are observed for the deuterated-phenyl ligand in the ' H N M R data initially acquired. Further analysis, including the acquisition of D N M R spectroscopic data (CgHr,), which reveal resonances in the aryl region, and 2  mass spectral data consistent with the supposed formulation, permits the identification of the final product as 2.1-d6. This discovery marks the identification of a fourth Legzdins precursor " that is 4  6  capable of effecting C-D bond activation of benzene-tig. The thermal reactivity of 1.1 in a variety of different hydrocarbon solvents was then examined in order to elucidate the scope of the C-H bond activations initiated by the neopentyl-dimethylallyl complex.  33 2.2.2 Preliminary Studies on C - H Activation Potential Initiated by 1.1  7  2.2.2.1 Thermolysis of 1.1 in Benzene  The first obvious substrate to test the C - H activating ability, given the result seen from its deuterated analog, is protio-benzene (eq. 2.1). As expected, the yellow crystalline product from the thermolysis of 1.1 in benzene exhibits N M R spectral features identical to that of the deuterated species, plus resonances in the aryl region in its *H N M R spectrum (CeDt) which correspond to those seen in the D { H } N M R spectrum 2  1  (CeHe) for complex 2.1-^6- A single-crystal X-ray crystallographic analysis has been 8  performed to confirm the identity of the final organometallic product, Cp*W(NO)(C H )(ri -l,l-Me2C3H3) (2.1), and its ORTEP diagram is shown in Figure 3  6  5  2.1 which shows complex 2.1 to possess an 18e, three-legged piano-stool structure.  +  CMe  4  (2.1)  2.1  The solid-state molecular structure of 2.1 exhibits features characteristic of o-K distortion of the dimethylallyl moiety. This feature is manifested as a longer C(7)-C(8) and shorter C(8)-C(9) bond (1.439(6) and 1.365(5) A respectively), suggestive of more respective  34  Figure 2.1 Solid-state molecular structure of Cp*W(NO)(C H )(ri -l,l-Me2C3H3) (2.1) 3  6  5  with 50 % probability thermal ellipsoids shown. Selected interatomic distances (A) and angles (deg): W(l)-N(l) = 1.762(3), W(l)-C(7) = 2.218(4), W(l)-C(8) = 2.363(4), W ( l ) C(9) = 2.768(4), W( 1 )-C( 1) = 2.186(3), N(l)-0(1) = 1.224(4), C(7)-C(8) = 1.439(6), C(8)-C(9) = 1.365(5), W(l)-N(l)-0(1) = 169.5(3), W(l)-C(l)-C(6) = 121.4(2), C(7)C(8)-C(9) = 124.8(4), W( 1 )-C(7)-C(8) = 77.3(2), C(8)-C(9)-C( 10) = 124.3(4), C(10> C(9)-C(ll) = 113.5(3)  35 single- and double-bond character. Solution N M R data also support this diagnosis as 9  evinced by its ^ C ^ F i } N M R spectrum (CeDg) which exhibits a resonance at 95.3 ppm (allyl-CH) characteristic of an sp -like carbon and a signal at 37.6 ppm (allyl-CH2) 2  indicative of an sp -like terminal carbon. Other transition-metal allyl complexes display 3  similar spectroscopic and solid-state metrical features that are consistent with distortions of this type. " Conversely, a T|'-dimethylallyl complex exhibits spectroscopic features 10  13  indicative of the loss of the trihapticity of the allyl fragment (see Section 3.2.4). Also evident from the ORTEP diagram of complex 2.1 is the expected orientation of the dimethylallyl ligand, with the most substituted carbon atom of the three-carbon allyl backbone situated trans to the NO ligand. This orientation can be explained by the electronic asymmetry at the tungsten center resulting from different acceptor characteristics of the NO and aryl ligand. Furthermore, the substituted allyl ligand is 14  also rotated away from the idealized exo orientation to maximize the ^-interaction between the non-bonding orbital of the allyl ligand and the metal center.  15  The exo conformation adopted by the dimethylallyl ligand in the solid state is consistent with its apparent solution structure, based on selective N O E N M R spectroscopic data. This is in contrast to the endo configuration observed in solution for 16  complex 1.1. Theoretical calculations performed on similar asymmetric-allyl transitionmetal complexes reveal that there is a minimal energy difference between the idealized endo and exo conformers, thus suggesting that the two different orientations observed 15  for complexes 1.1 and 2.1 are sterically influenced. As noted previously, the phenyl hydrogen and carbon atoms all exhibit unique 17  resonances in both spectra ('H and C { ' H } in CtDe), similar to that observed for aryl I3  36  ligands in similar complexes, and is rationalized as a result of slow rotation about the 18  W - C bond of the phenyl ligand on the N M R timescale. E X S Y N M R data confirms the rotation about the W - C bond, as exchange is observed between the two resonances for the weto-hydrogens and the two resonances for the or//?o-hydrogens (see Figure 2.2).  Figure 2.2 2D E X S Y N M R  (CeDe)  plot showing exchange between unique resonances of  o- and w-hydrogens on the phenyl ligand of complex 2.1  37  2.2.2.2 Thermolysis of 1.1 in Tetramethylsilane  Another prototypical hydrocarbon solvent commonly used in the Legzdins research group for C-H activation experiments is tetramethylsilane, due to the exclusive presence of primary sp C-H bonds. Thermolysis of the 18e complex 1.1 in TMS at 50 °C 3  for 6 hours results in the quantitative formation (as determined by H N M R spectroscopy) !  of the 18e alkyl-allyl complex, Cp*W(NO)(CH SiMe3)(Ti -l ,l-Me C H3) (2.2) (eq. 2.2). 3  2  2  +  3  CMe  4  (2.2)  2.2  Complex 2.2 is thermally stable in TMS, and the known bis(alkyl) complex, 19  Cp* W(NO)(CH2SiMe3)2, is not formed on prolonged reaction times. A single-crystal X ray crystallographic analysis has been performed on 2.2, and the resulting ORTEP 20  diagram is shown in Figure 2.3. The most striking feature of the solid-state molecular structure of 2.2 is the endo configuration adopted by the dimethylallyl ligand. Again, this is consistent with its solution structure as determined by selective N O E N M R spectroscopic data and is possibly due to the steric congestion the molecule experiences 16  between the methyls on the allyl ligand and the rapidly rotating methyls of the trimethylsilylmethyl group.  38  Figure 2.3 Solid-state molecular structure of Cp*W(NO)(CH SiMe )(ri -l,l-Me C H ) 3  2  3  2  3  3  (2.2) with 50 % probability thermal ellipsoids shown. Selected interatomic distances (A) and angles (deg): W(l)-N(l) = 1.760(5), W(l)-C(l 1) = 2.182(6), W(l)-C(12) = 2.433(6), W( 1 )-C( 13) = 2.874(6), W( 1 )-C( 16) = 2.217(6), C( 11 )-C( 12) = 1.46( 1), C( 12)-C( 13) = 1.348(9), N( 1 )-0(l) = 1.237(7), W( 1 )-N(l )-0(I) = 170.7(5), C( 11 )-C( 12)-C(l3) = 124.9(7), W(l)-C(l 1)-C(12) = 81.2(4), C(12)-C(13)-C(14) = 125.6(7), C(14)-C(13)C(15) = 113.5(7)  39 Not surprisingly, the N M R spectroscopic features of 2.2 parallel those of 1.1, excluding the resonances observed for the alkyl group where obvious differences arise from the substitution of a silicon atom for a carbon atom. Likewise, the IR stretching frequencies observed for the nitrosyl group differ by only 6 wavenumbers (1555 and 1549 cm" for 1.1 and 2.2, respectively). The nitrosyl ligands of related compounds 1  21  display metrical and spectroscopic parameters comparable to those of complex 2.2.  2.2.2.3 Thermolysis of 1.1 in Mesitylene  The thermal reaction of 1.1 in mesitylene results in the exclusive formation of Cp*W(NO)(CH C6H3-3,5-Me )(ri -l,l-Me2C3H3) (2.3) (eq. 2.3). A single-crystal X-ray 2  2  2  crystallographic analysis has been performed, and the ORTEP diagram is shown in 22  Figure 2.4.  (2.3)  2.3 The ' H N M R spectrum (C^De) of 2.3 exhibits features indicative of fast rotation about the W(l)-C(l 1) bond on the N M R timescale, namely the sharp singlet observed for both methyl groups (8 2.38) and the resonance attributable to both ort/?o-hydrogens on  40 the aryl ring (8 7.38). Presumably, the steric congestion present in the phenyl-allyl complex 2.1 is alleviated by the extra C(l 1)-C(12) bond of the benzyl moiety, similar to that seen for related complexes. ; Again, as in the previously discussed complex 2.2, the 2  23  solid-state molecular structure contains an exo-allyl conformation which is consistent with the solution structure as determined by selective N O E N M R spectroscopic evidence.  16  In many respects, complex 2.3 is very similar to the previously studied benzylmesityl complex, Cp*W(NO)(CH C6H5)(CH2C H3-3,5-Me2). This similarity is due to 2  2  6  the r] -bonding mode that the mesityl group adopts, which can be viewed as an extreme 2  form of an r| -allyl moiety based on several criteria " suggested for such complexes 3  23  26  (Scheme 2.1). For example, the tungsten-allyl carbon bond lengths (W(l)-C(20) = 2.187(5) and W(l)-C(21) = 2.391(5) A) displayed by 2.3, parallel those of the benzylmesityl complex (W-C(l) = 2.181(4) and W-C(2) = 2.391(4) A respectively). As such, the comparison of spectroscopic and structural characteristics exhibited by both complexes is pertinent.  41  Figure 2.4 Solid-state molecular structure of Cp*W(NO)(CH2C H3-3,5-Me2)(ri -l,l3  6  MesCjHb) (2.3) with 50 % probability thermal ellipsoids shown. Selected interatomic distances (A) and angles (deg): W(l)-N(l) = 1.753(4), W(l)-C(20) = 2.187(5), W ( l ) C(21) = 2.391 (5), W( 1 )-C(22) = 2.961 (5), W(l)-C( 11) = 2.239(4), N( 1 )-0(l) = 1.240(5), C(20)-C(21) = 1.454(8), C(21)-C(22) - 1.365(6), C ( l 1)-C(12) = 1.493(6), W(l)-N(l)0(1) = 171.1(4), W(l)-C(20)-C(21) = 79.3(3), W(l)-C(l 1)-C(12) = 120.5(3), C(20)C(21)-C(22) = 125.5(5), C(21)-C(22)-C(24) = 123.5(4), C(23)-C(22)-C(24) = 115.2(4)  42 The W(l)-C(l 1)-C(12) bond angle of 120.5(3) of 2.3 is similar to that observed 0  for the benzyl-mesityl complex (W-C(3)-C(4) = 120.1(3) °). The deviation from ideal sp  3  hybridization (109.5 °) can be attributed to the relief it brings from steric congestion with the bulky pentamethylcyclopentadienyl ligand. Given that complex 1.1 has been shown to effect bond activation of aryl sp C - H linkages (as evinced by the analogous reaction in benzene), the fact that there is exclusive formation of the benzylic C-H activation product when 1.1 is heated in mesitylene is not all that surprising. For aryl C-H activation, the transition-state of an intermediate 7X-arene 2  complex is presumably higher in energy than that of the cj-sp C-H complex formed 3  during benzylic C-H activation, as a result of adverse steric interactions imposed by the aryl methyl substituents (vide infra).  2.2.3 Thermolyses in Mono- and Di-Substituted Arenes  The thermal reactions of 1.1 in methyl-substituted arenes generate a reactive intermediate that may react with stronger arene C-H bonds (110 kcal/mol) or weaker benzylic C-H bonds (96-102 kcal/mol). It is of importance to understand the 27  selectivities exhibited by transition metal complexes for preferential activation of one type of C-H bond over another. The industrial and catalytic implications are such that it 28  is necessary to ascertain the kinetic selectivities of these potentially important compounds.  29  is addressed.  In this study, however, the issue of thermodynamic distribution of products  43 2.2.3.1 Thermolysis of 1.1 in Xylenes  The thermal reaction of 1.1 in p-xylene results in the formation of two organometallic products in > 95% overall yield as determined by crude ' H N M R spectroscopy (CeD^) of the final reaction mixture (eq. 2.4). The product generated upon activation of a benzylic sp C-H bond of p-xylene, 3  namely Cp*W(NO)(CH2C H4-4-Me)(ri -l,l-Me2C3H3) (2.4), and that from the activation 3  6  of an aryl sp C-H bond, namely Cp*W(NO)(C H3-2,5-Me )(r| -l,l-Me2C3H3) (2.5), are 2  3  6  2  formed in an approximate 1:3 respective ratio, which is preserved even after three times the normal reaction time. Statistically, you would expect a 3:2 ratio of benzylic vs aryl activated products due to the availability of the sp and sp C-H bonds on a molecule of 3  2  /^-xylene. Thus, the proportions displayed mark the thermodynamic distribution of the products generated at 50 °C, indicative of a tendency to activate aryl C-H bonds in preference to the benzylic ones.  (2.4)  26%  74%  44 The preferential generation of the aryl-activated species over that of benzylic is a trend commonly seen in many C-H activating transition-metal complexes. The most prevalent rationalization for this selectivity, which is in stark contrast to that observed for mechanisms involving radical species, are the thermodynamics of the bond-breaking 30  and bond-forming involved. Although the bond-dissociation energy for sp C-H bond scission is greater than that of sp C-H bonds, the resulting metal-carbon interaction is 3  stronger for M-C(sp ) than M-C(sp ) z  J  ' '  Another common rationale is the ease of  formation of 7T-arene complexes as opposed to rj-methylarene complexes which lead to the respective aryl and benzylic activated species. ' '  2 28 34  Both organometallic compounds formed during the reaction are completely separable to permit full characterization of each. Of interest is the '.H N M R resonance observed for the ort/zo-hydrogen of the major product, 2.5, in C^Df, (8 6.12) which is a common spectral feature found for ortho H atoms of other hydrocarbyl complexes containing methyl-substituted aryl ligands. '  2 18  A single-crystal X-ray crystallographic analysis has been performed on complex 35  2.5, and its ORTEP diagram is displayed in Figure 2.5. As expected, the solid-state structure of 2.5 is similar to that of 2.1, although most interestingly, the W(l)-C(16)C(17) bond angle (126.3(4)°) deviates from the anticipated value of 120°. This appears to be a general feature found in the solid-state molecular structures of other transition-metal nitrosyl complexes containing o-methylated aryl ligands ' and can be rationalized by 2 24  relief of steric hindrance between the omethyl group and the W(l)-C(16) linkage. These other compounds are also observed to be thermally unstable and undergo decomposition by (3-H elimination, which is a manifestation of the distorted W(l)-C(l 6)-C(17) bond  45 angle, placing the (3-H of the aryl ligand near the metal-centered L U M O . However, it 2  appears that the presence of the dimethylallyl moiety may stabilize 2.5 as the electronically saturated 18e compound, much like the r| -vinyl species in related 2  complexes.  36  The thermolyses of 1.1 in m- and o-xylene yield similar findings. The thermal reaction with w-xylene yields three products, namely Cp*W(NO)(CH2C6H4-3-Me)(r| 3  l , l - M e C H ) (2.6), Cp*W(NO)(C H -2,4-Me )(ri -l,l-Me2C H ) (2.7) and 3  2  3  3  6  3  2  Cp*W(NO)(C H -3,5-Me )(Ti -l,l-Me C H ) (2.8) (eq. 2.5). 3  6  3  2  2  3  3  3  3  46  Figure 2.5 Solid-state molecular structure of Cp*W(NO)(C H3-2,5-Me )(Ti -l,l3  6  2  N/^CiHi) (2.5) with 50 % probability thermal ellipsoids shown. Selected interatomic distances (A) and angles (deg): W(l)-N(l) = 1.762(5), W(l)-C(l 1) = 2.235(6), W(l)C(12) = 2.363(6), W(l)-C(13) = 2.776(6), W(l)-C(16) = 2.205(6), C(l 1 )-C( 12) = 1.438(9), C(12)-C(13)= 1.371(9), N(l)-0(1 )= 1.232(7), W(l)-N(l)-0(1) = 168.6(5), W( 1 )-C( 16)-C( 17) = 126.3(4), C( 11 )-C( 12)-C( 13) = 124.5(6), W( 1 )-C( 11 )-C( 12) = 76.7(4), C(12)-C(13)-C(14) = 124.6(6), C(14)-C(13)-C(15) = 113.8(6)  47 Not surprisingly, the product ratio obtained is comparable to that for the benzylic and aryl activated species of complexes 2.4 and 2.5. Notably, within the two aryl C-H activated species, 2.8 is over two times more prevalent than 2.7 even though statistically, there should be twice the amount of 2.7 over 2.8. This distribution can be attributed to steric factors that favour the possible formation of 7i-arene complexes as far removed as possible from the methyl substituents to yield a final product with the methyls meta to the W-C(aryl) linkage, and again is an indication of the thermodynamically favoured product ratio. The thermal reaction of 1.1 with o-xylene generates three organometallic products, namely Cp*W(NO)(CH C6rLr2-Me)(iiM J - M e C H ) (2.9), 2  2  3  3  Cp*W(NO)(C H3-2,3-Me2)(n -l,l-Me2C H3) (2.10) and Cp*W(NO)(C H3-3,4-Me )(ri 3  6  3  3  6  2  l , l - M e C H ) (2.11) (eq. 2.6). 2  3  3  (2.6)  2.11 48%  48 The most striking difference between the product ratio observed is the markedly decreased proportion of the benzylic C-H activated species. Interestingly, the observed trend of decreasing proportions of benzylic activation in different xylene solvents (para > meta > ortho) is analogous to that seen for other related complexes. This feature is 2  perhaps a manifestation of steric hindrance imposed by the adjacent methyl group, subsequently increasing the preference for the formation of the aryl-activated complexes.  2.2.3.2 Thermolysis of 1.1 in Toluene  The thermolysis of 1.1 in toluene leads to the generation of all four products of CH activation, specifically Cp*W(NO)(CH C H )(ri -l,l-Me2C3H3) (2.12), 3  2  6  5  Cp*W(NO)(C H -2-MeXri -l,l-Me2C3H3) (2.13), Cp*W(NO)(C H -3-MeXri -l,l3  6  3  4  6  4  M e C H ) (2.14) and Cp*W(NOXC H -4-Me)(r| -l,l-Me2C3H3) (2.15) (eq. 2.7). 3  2  3  3  6  4  Complexes 2.12 - 2.15 were characterized as a mixture, and thus many of the resonances expected for each individual compound were not discernable due to overlapping signals, despite extensive use of a multitude of advanced NMR spectroscopic techniques. Again, the product ratio observed for complexes 2.12 - 2.15 reflects the thermodynamic distributions for benzylic and aryl C-H bond activations initiated by 1.1 under thermal conditions. This notion is supported by the similar proportion of aryhbenzyl species compared to the ratios observed for products from activation of C-H bonds of m- and p- xylene, and that now statistically there are more sites for formation of the W-C(aryl) linkages with toluene.  49  Similar to the spectroscopic features exhibited by the mesityl-dimethylallyl complex (2.3), the ' H N M R spectrum (CeDe) of 2.12 displays elements indicative of fast rotation about the W-C bond on the N M R timescale, namely the sharp resonances observed for all of the aryl C-H moieties and the equivalent signals attributable to the mand o-aryl C-H linkages (8 7.32 and 7.71, respectively).  50 2.2.3.3 Attempts to Independently Synthesize Complexes 2.4 - 2.15  Since more than one organometallic species was anticipated from the reactions of 1.1 in methyl-substituted arenes, Cp*W(NO)(ri -l,l-Me2C3H3)(Cl) (2.16), has been 3  synthesized with the goal of independently preparing the predicted products, as judged by crude ' H N M R spectroscopic data of the final reaction mixtures. Relevant hydrocarbyl metatheses of 2.16 with suitable Grignard reagents have been attempted but, led to the formation of intractable products (eq. 2.8). Other techniques are utilized to isolate the products formed for characterization purposes and these are described in Section 2.4.  •>-  2.16  intractable products  (2.8)  51 2.3 Epilogue  The studies discussed in this Chapter have elucidated the scope of single C-H bond activations via thermal reactions of 1.1 in the chosen hydrocarbon solvents. In addition, the thermodynamic preference for aryl activations over benzylic are evident in the product distributions observed for the thermolyses with p- and m-xylene and toluene. Similar reactions conducted with o-xylene and mesitylene yield product ratios that are suggestive of steric hindrance of benzylic and aryl C-H activation, respectively. Aside from the exclusive formation of 2.3 from reaction of 1.1 in mesitylene, all other thermolyses performed yield products resulting from the activations of all C-H bonds found in the substrate. That there appears to be no evidence for the formation of the bis(trimethylsilylmethyl), benzyl-aryl or the bis(mesityl) species upon reaction of 1.1 in tetramethylsilane, toluene, and mesitylene respectively, indicates that the dimethylallyl ligand is not prone to elimination from the metal's coordination sphere to form the reactive alkylidene and benzylidene species which are known to have C-H activating abilities.  1,2  52  2.4 Experimental Procedures  2.4.1 Preparative Thermolyses of 1.1 in Hydrocarbon Solvents: General Comments  Unless otherwise noted, the following general procedure was used to prepare new compounds via thermolysis of 1.1: a 30 mL bomb was charged with the reported amount of 1.1, a magnetic stir bar, and sufficient solvent to yield an approximately 10 % (w/w) orange solution. The solvent was either directly pipetted into the reaction vessel from a storage bomb inside a glovebox, or vacuum transferred onto the orange microcrystals on a vacuum line. The sealed bomb was then heated at 50 °C for a period of 6 hours in a V W R Scientific Products Circulating Bath 1160A. During this time, the appearance of the reaction mixture either remained unchanged (deep-orange) or it lightened to an orange-yellow colour. Alternatively, it darkened to a brown colour, whereupon further steps were necessary to extract and isolate the analytically pure organometallic products. The reaction bomb was removed from the bath, and the reaction was quenched by placing the bomb under a flow of cold water, or dipping into a cold bath. The volatiles were removed in vacuo, and the resulting residue was dried under high vacuum for a suitable period of time. It was then dissolved in CeD6, and the crude ' H N M R spectral data were obtained to determine the number of principal organometallic products present, and the ratios in which they were formed. Average product ratios were determined via multiple integrations of like signals in the ' H N M R spectrum of the final reaction mixture. The N M R solvent was then removed, and the residue was redissolved in the reported solvent or solvent mixtures for recrystallization of the products. The solutions were then  53 concentrated to the point of incipient crystallization and cooled for a suitable amount of time at - 30 °C, to obtain the organometallic products as crystals. The reported yields are not optimized.  2.4.2 Thermolysis of 1.1 in Benzene-dfo  Complexes 2.1-df, -c were prepared by the thermolysis of 1.1 (10 mg, 0.02 mmol) a  in benzene-^- Yellow crystals of complexes l.X-d^ were obtained via crystallization of the residue from 4:1 Et 0/hexanes. 2  2.l-d . : M S (LREi, m/z, probe temperature 120 °C) 501 [P , +  6a  l84  c  W]. 'H NMR  (400 MHz, C D ) 5 0.82 (s, 3H, allyl Me), 1.51 (s, 15H, C M e ) , 1.62 (br s, 3H allyl Me), 6  6  5  5  1.73 (brm, I H , allyl CH ), 2.48 (br m, IH, allyl CH ), 3.52 (br m, I H , allyl CH). H{'H} 2  2  2  N M R (61 MHz, C H ) 5 0.78 (allyl Me-di), 1.61 (allyl Me-rf,), 3.52 (allyl CD), 6.60-8.4 6  6  (Ph D)  2.4.3 Preparation of C p * W ( N O ) ( C H ) ( r | - l , l - M e C H 3 ) (2.1) 3  6  5  3  2  Complex 2.1, first prepared by Craig Adams, was formed during the thermolysis 17  of 1.1 (48 mg, 0.10 mmol) in benzene. Complex 2.1 was isolated as yellow microcrystals by recrystallization of the residue from 4:1 Et 0/hexanes (34 mg, 70 %). 2  2.1: IR (cm" ) 1562 (s, v o). M S (LREI, m/z, probe temperature 150 °C) 495 [P , 1  +  N  184  W ] . H N M R ( 3 0 0 MHz, C D ) 5 0.82 (s, 3H, allyl Me), 1.51 (s, 15H, C Me ), 1.62 (br 1  6  6  5  5  s, 3H, allyl Me), 1.74 (br m, 1H, allyl C H ) , 2.49 (br m, 1H, allyl CH ), 3.54 (br m, 1H, 2  allyl CH), 6.64 (br d, 1H, Ph H ), onho  H ), meta  8.39 (d, J 3  H H  2  7.08 (t, V  = 6.7, 1H, Ph H ); ortho  H  H  - 7.1, 1H, Ph W ), 7.30 (m, 2H, Ph para  ' H N M R (400 MHz, CDC1 ) 5 0.87 (s, 3H, allyl 3  Me), 1.51 (br s, 3H, allyl Me), 1.76 (s, I5H, C Me ), 1.90 (br m, 1H, allyl CH ), 2.42 (br 5  5  2  m, 1H, allyl CH ), 3.73 (br m, 1H, allyl CH), 6.68 (br d, 1H, Ph H ), 2  7.1, 1H, Ph Hpara), 7.12 (q, V 13  6.93 (t, V H = H  onho  H  H  = 7.0, 2H, Ph H ), meta  C{'H} N M R (75 MHz, CDCI3) 5 10.4  (C5A&5),  7.86 (d, VHH = 6.4, 1H, Ph  H ). ortho  21.8, 29.4 (allyl Me), 37.6 (allyl C H ) , 2  95.3 (allyl CH), 107.6 (C Me ), 123.4 (Ph C ), 126.8, 127.9 (Ph C ), 139.6, 141.9 5  (Ph C ), ortho  5  para  meta  148.5 (allyl C), 168.8 (Ph C ^ ) . Sel N O E (400 MHz, C D ) 8 irrad. at 3.54, 6  6  NOE at 0.82, 1.51 and 1.74, irrad. at 0.82, N O E at 1.51, 1.63, 3.54, 6.64, 8.39. Anal. Calcd. for C i H N O W : C, 50.92; H , 5.90; N , 2.83. Found: C, 50.61; H, 5.95; N , 2.92. 2  29  2.4.4 Preparation of Cp*W(NO)(CH SiMe )(Tl -i,l-Me C3H ) (2.2) 3  2  3  2  3  Complex 2.2 was prepared via thermolysis of 1.1 (75 mg, 0.15 mmol) in tetramethylsilane. The reaction mixture was then cooled overnight in a freezer (- 30 °C) to obtain orange needles of 2.2 (47 mg, 61 %)  55 2.2: IR (cm" ) 1549 (s, v ) . MS (LRE1, m/z, probe temperature 80 °C) 505 [ P , 1  +  N 0  1 8 4  W ] . ' H N M R (400 MHz, C D ) 8 -0.78 (d, VHH = 14.09, 1H, SiCH ), -0.59 (d, J  =  2  6  6  2  m  14.09, I H , SiCH ), 0.45 (s, 9H, Si.Me ), 0.61 (s, 3H, allyl Me ), 1.12 (s, 3H, allyl Me), 2  3  1.18 (m, I H , allyl CH ), 1.51 (s, 15H, C Me ), 2.55 (m, 1H, allyl CH ), 4.43 (m, I H , allyl 2  CH).  13  5  5  2  C{'H} N M R (125 MHz, C D ) 5 2.01 (SiCH ), 4.34 (SiMe ), 10.2 (C Me ), 19.6, 6  6  2  3  5  5  28.9 (allyl Me), 39.3 (allyl CH ), 101.9 (allyl CH), 106.9 ( C M e ) . Sel NOE (400 MHz, 2  5  5  C D ) Sirrad. at 0.61, NOE at-0.78, 0.45, 1.12, 1.18, 1.51 and 2.55. Anal. Calcd. for 6  6  C i H N O S i W : C, 45.15; H, 6.98; N , 2.77. Found: C, 45.37; H, 6.92; N , 2.90. 9  35  2.4.5 Preparation of Cp*W(NO)(CH2C6H3-3,5-Me )(ri -l,l-Me2C3H ) (2.3) 3  2  3  Complex 2.3 was prepared by the thermolysis of 1.1 (79 mg, 0.16 mmol) in mesitylene. The volume was reduced to 2 mL, and hexanes (10 mL) were added via a syringe. Cooling of the mixture resulted in the crystallization of 2.3 as orange microcrystals (57 mg, 66 %).  2.3: IR (cm" ) 1533 (s, v ) . MS (LREI, m/z, probe temperature 120 °C) 537 [P , 1  +  N 0  1 8 4  W ] . ' H N M R (400 MHz, C D ) 5 1.08 (s, 3H, allyl Me), 1.17 (s, 3H, allyl Me), 1.46 (s, 6  6  15H, C Me ), 1.52 (obs, I H , allyl CH ), 1.79 (d, V ™ = 9.46, I H , Mes C H ) , 2.38 (s, 6H, 5  5  2  Mes Me ), 2.45 (m, I H , allyl CH ), 2.80 (d, V 2  2  2  H H  = 9.46, 1H, Mes C H ) , 3.58 (s, I H , allyl 2  CH), 6.72 (s, I H , Mes U ), 7.38 (s, 2H, Mes H ). pam  ortho  C{ H}  ]3  l  N M R (125 MHz, C D ) 5 6  9.88 (C M? ), 20.63 (allyl Me), 22.03 (Mes Me ), 27.65 (allyl Me), 28.23 (allyl CH ), 5  5  2  2  6  56 39.69 (Mes CH ), 98.86 (allyl CH), 106.49 (C Me ), 125.24 (Mesp-CU), 128.70 (Mes o2  5  5  C H ) , 152.4 (allyl C), 136.5, 169.2 (C d- Sel NOE (400 MHz, C D ) 5 irrad. at 3.58, aiy  6  6  N O E at 1.08, 1.52, 2.45, irrad. at 1.08, N O E at 1.17, 1.46, 1.79, 2.80, 3.58 and 7.38. Anal. Calcd. for  C24H35NOW:  C, 53.64; H, 6.56; N , 2.61. Found: C, 53.80; H, 6.61; N ,  2.75.  2.4.6 Reaction Products of Thermolyses of 1.1 in Toluene and o, /n,/>-XyIenes  Thermolysis of 1.1 in toluene and xylene solvents yielded final reaction mixtures with multiple organometallic products due to activation of different C-H bonds present in the hydrocarbons. For the various reaction mixtures, the residues remaining after the reaction solvent had been removed were triturated with pentane ( 3 x 1 0 mL) to alleviate the oily appearance. Solid product was isolated via crystallization from hexanes. It was then possible to separate the benzylic C-H activated product from the aryl C-H activated species via two possible methods: a. Preparative thin-layer chromatography on an alumina (I) plate (20 x 20 x 0.15 cm) b. Column chromatography through an alumina (1) column (0.5 x 3 cm) The former separation technique was utilized once for the products from reaction of 1.1 in p-xy\ene and this is discussed in Section 2.4.7. The latter technique was employed for the remainder of the product separations. The products isolated via crystallization were dissolved in a 1:5 Et 0/hexanes solvent mix and eluted through the column described 2  57 above which was pre-wetted with the eluting solvent. A yellow eluate resulted which upon concentration and cooling to - 30 °C overnight yielded solely the aryl C-H activated products. Eluting the column with 1:4 Et 0/hexanes gave a solution consisting of small 2  amounts of both aryl and benzylic C-H activated species. Stripping the alumina column with E t 0 yielded an orange solution which upon addition of hexanes, and then 2  subsequent concentration and cooling to - 30 °C overnight yielded solely the benzylic CH activated product.  2.4.7 Preparation of Cp*W(NO)(CH C H -4-Me)(Tl -i,l-Me C3H3) (2.4) and 3  2  6  4  2  Cp*W(NO)(C H -2,5-Me )(ri -l,l-Me C3H3) (2.5) 3  6  3  2  2  Complexes 2.4 - 2.5 were formed via the thermolysis of 1.1 (292 mg, 0.60 mmol) in /^-xylene. The resulting residue following removal of solvent was an orange/yellow oil. The solid products obtained after work-up as outlined in Section 2.4.6 were dissolved in a minimal amount of THF and applied to a preparative-TLC plate using a syringe (26 gauge), leaving a 10 mm thick orange/yellow band. The plate was left to sit for 30 minutes to allow evaporation of the THF solvent. The plate was then loaded into a development chamber charged with E t 0 (200 mL) and sealed to minimise solvent loss 2  and ensure maximum vapour saturation. After 70 minutes of development, the plate was removed from the chamber and allowed to dry. No clear separation was evident, but a definite region was visible where the band was lighter in colour. The alumina above this region was scraped off and stripped of any organometallic product with THF and subsequently filtered thru a Celite plug to obtain a yellow solution that upon  58 recrystallization from 1:4 Et 0/hexanes yielded yellow needles of complex 2.5 (53 mg, 2  17 %). The alumina below the lighter region was treated in a similar fashion to obtain orange needles of complex 2.4 (24 mg, 8 %).  2.4.8 Preparation of Cp*W(NO)(CH C H4-3-IVIe)(r| -l,l-Me2C3H3) (2.6), 3  2  6  Cp*W(NO)(C H3-2,4-Me )(ri -l,l-lvIe2C3H3) (2.7) and Cp*W(NO)(C H -3,53  6  2  6  3  Me )(T| -l,l-Me2C3H3) (2.8) 3  2  Complexes 2.6 - 2.8 were prepared via the thermolysis of 1.1 (100 mg, 0.20 mmol) in m-xylene. The resulting residue following removal of solvent was an orange/yellow oil. Subsequent work-up and separation of products as outlined in Section 2.4.6 afforded complex 2.6 as orange blocks (15 mg, 14 %) and a mixture of complexes 2.7 and 2.8 as orange/yellow microcrystals (40 mg, 37 %).  2.4.9 Preparation of Cp*W(NO)(CH2C6H -2-Me)(ri -l,l-!VIe2C3H3) (2.9), 3  4  Cp*W(NO)(C6H -2,3-Me )(r| -l,l-Me C3H3) 3  3  2  2  (2.10) and Cp*W(NO)(C H -3,46  3  Me )(r) -l,l-Me C3H3) (2.11) 3  2  2  Complexes 2.9 - 2.11 were formed by the thermolysis of 1.1 (205 mg, 0.42 mmol) in o-xylene. The resulting residue following removal of solvent was an orange/yellow oil. Subsequent work-up and separation of products as outlined in Section 2.4.6 afforded complex 2.9 as orange microcrystals (21 mg, 10 %) and a mixture of complexes 2.10 and 2.11 as orange/yellow microcrystals (56 mg, 26 %).  59 2.4.10 Preparation of Cp*W(NO)(CH2C H5)(if-l,l-Me C H ) (2.12), 6  2  3  3  Cp*W(NO)(C H -2-Me)(T| -l,l-Me2C H ) (2.13), Cp*W(NO)(C H -3-Me)(Ti -l,l3  6  3  4  3  3  6  4  Me C H ) (2.14) and Cp*W(NO)(C H -4-Me)(TV -l,l-Me2C H3) (2.15) 3  2  3  3  6  4  3  Complexes 2.12 - 2.15 were prepared via the thermolysis of 1.1 (200 mg, 0.41 mmol) in toluene. After the 6 hour reaction period, the resulting solution was a dark orange/brown colour which yielded a brown oil upon solvent removal under vacuum. Subsequent work-up and separation of products as outlined in Section 2.4.7 afforded complex 2.12 and a mixture of complexes 2.13 - 2.15 as orange/yellow blocks (156 mg, 75 %). Complex 2.12 was independently synthesized via metathesis for characterization purposes (see Section 2.4.11).  2.4.11 Independent Preparation of 2.12 via Metathesis  Complex 2.12 was prepared by a method similar to the procedure published for Cp*W(NO)(CH C H5)(CH CMe3). In the glovebox, a 100-mL Schlenk tube was 1  2  6  2  charged with a magnetic stir bar and (l,l-Me2C3H3)2Mgx(dioxane) (103 mg, 0.53 mmol). A 200-mL Schlenk tube was then charged with a stir bar and Cp*W(NO)(CH C H )(Cl) 2  6  5  (250 mg, 0.53 mmol). On a vacuum line, THF (80 mL) was vacuum transferred into the Schlenk tube containing the organometallic halide and into the Schlenk tube with the magnesium reagent (10 mL). The two resulting solutions were then mixed at - 78 °C over a period of 5 minutes via a cannula, whereupon the initial deep-red colour of the solution changed to orange/yellow after being stirred at - 78 °C for 10 minutes. The resulting  60 solution was then warmed to 0 °C and allowed to react for 1 hour. The solvent was then removed at 0 °C over a period of 30 minutes. The product was extracted from the residue with C H 2 C I 2 ( 3 x 1 0 mL) and filtered through an alumina (I) plug ( 2 x 3 cm) supported on a frit to yield a yolk-orange solution. The CH C1 was removed under vacuum, and the 2  2  residue was dissolved in a 2:1 Et 0/hexanes mix, which afforded complex 2.12 as yellow 2  and orange blocks after subsequent concentration to its incipient crystallization point and cooling to - 30 °C for 2 hours (138 mg, 52 %).  61 Table 2.1 Numbering Scheme, Yield and Analytical Data for Complexes 2.4 - 2.15 Cmpd  Colour  No.  (yield, % )  C  H  N  Cp*W(NO)(CH C H -4-Me)(r| l,l-Me C H )  2.4  orange (8)  52.78 (52.66)  6.36 (6.26)  2.68 (2.75)  Cp*W(NO)(Cr,H 2,5-Me )(n. l,l-Me C H )  2.5  yellow (17)  52.78 (52.67)  6.36 (6.26)  2.68 (2.66)  Cp*W(NO)(CH C H4-3-lVIe)(Ti l,l-Me C H )  2.6  orange (14)  52.78 (52.76)  6.36 (6.20)  2.68 (2.71)  Cp*W(NO)(C H -2,4-Me )(Tl l,l-Me C H )  2.7  yellow (37)  52.78 (52.54)  6.36 (6.43)"  2.68 (2.83)*  Cp*W(NO)(C H -3,5-Me )(Tl l,l-Me C H )  2.8  b  b  b  b  Cp*W(NO)(CH C H -2-Me)(Ti l,l-Me C H )  2.9  orange (10)  52.78 (53.02)  6.36 (6.36)  2.68 (2.92)  Cp*W(NO)(C H -2,3-Me )(n. l,l-Me C H3)  2.10  yellow (26)  52.78 (52.93)  6.36 (6.37)  Cp*W(NO)(C H -3,4-Me )(Tl l,l-Me C H )  2.11  c  c  c  c  Cp*W(NO)(CH C H )(Tl -l,lMe C H )  2.12  orange (52)  51.88 (51.95)  6.13 (6.25)  2.75 (2.86)  Cp*W(NO)(C6H -2-Me)(ri -l,lMe C H )  2.13  yellow (75)''  51.88 (51.84/  6.13 (6.49/  2.75 (2.85/  Cp* W(NO)(C H -3-Me)(ri -l ,1Me C H )  2.14  d  d  d  d  Cp*W(NO)(C H -4-Me)(ri -l,lMe C H )  2.15  d  d  d  d  Complex  3  2  2  3  fi  4  3  3  r  2  3  2  3  3  2  2  3  6  3  3  6  2  3  3  2  3  3  3  2  3  3  6  4  3  3  6  2  3  2  3  2  3  3  2  3  (i  5  3  3  4  2  3  3  3  6  2  3  4  3  3  c  2.68 (2.61)  c  3  6  2  c  3  2  3  c  3  6  2  A  3  2  2  A  3  6  2  Anal. Calcd. % (Found %) a  4  3  a: isolated yield, b: characterized as a mixture of 2.7 - 2.8, c: characterized as a mixture of 2.10 2.11. d: characterized as a mixture of 2.13 - 2.15  62 Table 2.2 M S and IR Characterization Data for Complexes 2.4 - 2.15 Compound  MS  Probe temperature  No.  ( L R E I , m/z)  (°C)  2.4  523  120  1553  2.5  523  120  1567  2.6  523  120  1560  2.7-2.8*  523  120  1552  523  150  1552  2.10-2.11"  523  150  1552  2.12  509  120  1552*  2.13-2.15"  509  120  1561  2.9  .  IR (v  K B r , cm" ) 1  N O )  a: characterized as a mixture, b: Nujol mull recorded on ATI Mattson-Genesis FTIR  63 Table 2.3 N M R Characterization Data for Complexes 2.4 - 2.15 Compound  'H N M R  no.  (C D ) 8  2.4°  6  T3  C {IH} N M R (C D ) 5  6  6  1.07 (s, 3H, allyl Me)  9.7 (CsMes)  1.15 (s, 3H, allyl Me)  20.5 (allyl Me)  1.46 (s, 15H,C Me )  21.0 (Pxyl Me)  5  5  1.46 (obs, 1H, allyl C H )  27.4 (allyl Me)  2  1.80 (m, I H , J 2  H H  = 11.6, Bzl C H ) 2  2.26 (s, 3H, Pxyl Me)  35.2 (Bzl C H ) 2  39.6 (allyl C H ) 2  2.43 (m, I H , allyl C H )  98.3 (allyl CH)  2  2.77 (m, I H , V H = 11.6, Bzl C H )  106.3 (C Me )  3.56 (m, IH allyl CH)  124.8 (Pxyl p-CH)  7.13 (obs , 2H, Pxyl m-CH)  128.0 (obs Pxyl o-CH)  7.62 (d, 2H, V  130.4 (Pxyl m-CM)  H  2  H H  = 7.6, Pxyl o-CH)  5  5  149.8 (allyl C)  2.5*  6  0.80 (s, 3H, allyl Me)  10.2 (C Me )  1.54 (2, 15H, C M e )  21.0 (Xyl Me)  1.74 (s, 3H, allyl Me)  22.6 (allyl Me)  s  5  5  5  1.79 (m, 1H, allyl C H )  27.6 (Xyl Me)  2.18 (s, 3H, X y l Me)  28.6 (allyl Me)  2  2.50 (m, 1H, allyl C H )  39.6 (allyl C H )  2.80 (s, 3H, X y l Me)  96.1 (allyl CH)  3.70 (m, IH, allyl CH)  107.3 (CsMes)  6.12 (s, I H , X y l o-CH)  124.8 (Xyl CH)  6.77 (d, I H , V  H H  = 7.4, X y l C H )  130.4 ( X y l C H )  7.25 (d, I H , V  H H  = 7.4, X y l C H )  140.4 (Xyl o-CH)  2  2  148.0 (allyl C) 170.3  (Xyl Cipso)  64 Table 2.3 N M R Characterization Data for Complexes 2.4 - 2.15 Compound  'HNMR  no.  (C D ) 5  2.6°  6  1.06  l 3  (C D ) 5 6  6  5  22.0 (Mxyl Me)  1.45 (s, 15H,C Me )  27.5 (allyl Me)  5  27.8 (Mxyl CH )  1.53 (m, I H , allyl CH )  2  2  JHH=  2  11.4, Mxyl CH ) 2  39.6 (allyl CH ) 2  2.38 (s, 3H, Mxyl Me)  98.2 (allyl CH)  2.46 (m, 1H, allyl CH )  106.3 (C Me )  2  2.81 (d, I H , V  a,c  5  1.11 (s, 3H, allyl Me)  1.79 (d, IH,  H H  6  9.7 (C Me )  (s, 3H, allyl Me)  5  2J  C {IH} N M R  5  = 11.4, Mxyl CH ) 2  5  124.0 (Mxyl CH)  3.54 (m, IH, allyl CH)  128.0 (obs Mxyl CH)  6.89 (d, IH, VHH = 7.3, Mxyl CH)  128.0 (obs Mxyl CH)  7.27 (t, 1 H , V H H = 7.5, Mxyl CH)  131,4 (Mxyl CH)  7.54 (d, 1 H , V  136.5 (MxylC)  H H  = 7.8, Mxyl CH)  7.58 (s, IH, Mxyl o-CH)  153.0 (allyl C)  0.81 (s, 3H, allyl Me)  10.3 (CsAfes)  1.54 (s, 1 5 H , C M e )  21.2 (Xyl Me)  1.74 (s, 3H, allyl Me)  23.0 (allyl Me)  s  5  1.78 (m, IH, allyl CH )  28.4 (Xyl Me)  2.28 (s, 3H, X y l Me)  28.7 (allyl Me)  2  2.49 (m, IH, allyl CH )  39.7 (Xyl Me)  2.82 (s, 3H, Xyl Me)  96.0 (allyl CH)  3.71 (m, IH, allyl CH)  107.0 (C Me )  6.22 (d, 1 H , J  H H  = 7.4, X y l CH)  124.7 (Xyl CH)  6.82 (d, IH, J  H H  = 7.4, Xyl CH)  131.7 (Xyl CH)  2  2  2  7.15 (obs, 1H, X y l CH)  5  5  139.3 (Xyl CH)  65 Table 2.3 N M R Characterization Data for Complexes 2.4 - 2.15 Compound  1  no. 2.8  ax  H NMR  l 3  (C D ) 8  (C D ) 8 6  6  6  0.86 (s, 3H, allyl Me)  10.3 (C Me )  1.55 (s, 15H, C Me )  21.4 (Xyl Me)  1.65 (bs, 3H, allyl Me)  21.6 (Xyl Me)  1.77 (m, 1H, allyl C H )  21.9 (allyl Me)  2.28 (s, 3H, X y l Me)  29.3 (allyl Me)  2.34 (s, 3H, Xyl Me)  37.4 (allyl C H )  5  5  5  2  5  2  2.50 (m, 1H, allyl CH )  95.6 (allyl CH)  3.56 (bm, 1H, allyl CH)  107.3 (C Me )  6.30 (bs, 1H, X y l CH)  125.6 (Xyl CH)  6.71 (s, 1H, X y l CH)  138.3 (XylCH)  8.04 (s, 1H, X y l C H )  140.0 (XylCH)  2  2.9*  C {1H} N M R  5  5  0.81 (m, 1H, allyl C H )  9.7 (C Me )  1.20 (s, 3H, allyl Me)  20.3 (allyl Me)  1.27 (s, 3H, allyl Me)  21.5 (Oxyl Me)  1.49 (s, 15H, C Me )  26.9 (allyl Me)  2  5  5  5  2.04 (m, 1H, allyl CH )  5  26.9 (Bzl CH )  2  2  2.19 (d, 1 H , J H H = 10.7, B z l C H )  103.2 (allyl CH)  2.36 (d, 1 H , J H H = 10.7, Bzl CH )  106.5 (C Me )  2.45 (s, 3H, Oxyl Me)  125.1 (Oxyl CH)  3.98 (m, 1H, allyl CH)  125.8 (Oxyl CH)  7.05 (m, 1H, Oxyl CH)  129.0 (Oxyl CH)  7.10 (obs 1H, Oxyl CH)  130.1 (OxylCH)  2  2  2  2  7.10 (obs, 1H, Oxyl CH) 7.23 (d, 1H, J H H = 7.0, OxylCH) 3  5  5  6  66 Table 2.3 N M R Characterization Data for Complexes 2.4 - 2.15 Compound  H NMR  no.  (C D ) 8  2.10  6  13  C {IH} N M R (C D ) 8  6  6  0.85 (s, 3H, allyl Me)  10.3 (CsMes)  1.55 (s, 15H, C Me )  19.6 (Xyl Me)  1.59 (s, 3H, allyl Me)  19.8 (Xyl Me)  5  5  1.76 (obs, 1H, allyl C H )  24.7 (allyl Me)  2.21 (br s,6H, 2 Xyl Me)  28.4 (allyl Me)  2.50 (m, 1H, allyl CH )  37.4 (allyl CH )  3.56 (brm, 1H, allyl CH)  95.9 (allyl CH)  6.45 (br s, 2H, 2 X y l CH)  106.9 (C Me )  7.07 (d, 1H,  128.8 (XylCH)  2  2  2  VHH  = 7.4, Xyl CH)  5  5  137.8 (Xyl CH) 141.7 (Xyl CH)  2.11 a,d  0.88 (s, 3H, allyl Me)  10.3 (CsMe )  1.55 (s, 15H, Q M e )  19.5 (Xyl Me)  1.65 (br s, 3H, allyl Me)  19.8 (Xyl Me)  1.76 (obs, 1H, allyl C H )  21.8 (allyl Me)  2.18 (s, 3H, X y l Me)  29.4 (allyl Me)  2.27 (s, 3H, Xyl Me)  37.3 (allyl C H )  s  5  2  2  2.50 (m, 1H, allyl CH )  95.8 (allyl CH)  3.56 (br s, 1H, allyl CH)  106.9 (C Me )  7.13 (obs, 1H, X y l CH)  130.2 (Xyl CH)  8.17 (obs, 1H, Xyl CH)  140.2 (Xyl CH)  8.19 (s, 1H, Xyl CH)  143.7 (Xyl CH)  2  s  5  6  67  Table 2.3 N M R Characterization Data for Complexes 2.4 - 2.15 Compound  'H NMR  no.  (C D ) 5  2.12"  a.e  2A3  6  , 3  C {1H} N M R (C D ) 5  6  6  1.04  (s, 3 H , allyl Me)  9.7 (C Me )  1.14  (s, 3 H , allyl Me)  2 0 . 5 (allyl Me)  1.43  (s, 1 5 H , C M e )  2 7 . 5 (allyl Me)  1.55  (br s, 1 H , allyl C H )  1.78  (d,  2.46  (m, 1 H , allyl C H )  2.81  (d,  3.52  (m, 1 H , allyl C H )  7.03  (t,  7.32  (t, 2 H , V H H = 7 . 4 , aryl m - C H )  1 3 0 . 4 (aryl o - C H )  7.71  (d, 2 H , V H H = 7 . 4 , aryl o - C H )  1 5 3 . 4 (allyl C )  2.26  (s,  10.2(C Me )  3.55  (brm, 1 H , allyl C H )  21.7  6.47  (br s,  9 5 . 8 (allyl C H )  6.88  (d,  7.25  (t,  8.21  (d, 1 H , V H = 7 . 1 , T o l C H )  5  5  5  27.8  2  1H, J 2  H  H = H . 5 , Bzl  CH ) 2  2  1H,  3H,  3  H  H =  1 1 . 5 , Bzl  J H = 7.4, H  CH )  Tol  2  arylp-CH)  C H )  1H, VHH = 7.1,TO1 C H ) 1H, VHH = 7.1,TO1 C H ) H  (bzl  CH ) 2  3 9 . 8 (allyl C H ) 2  106.4 (C Me ) 5  5  123.1 (aryl/7-CH)  Tol Me)  1H,  5  9 7 . 9 (allyl C H )  2  1 H , J  6  1 2 7 . 7 (aryl m-CH)  5  5  (Tol Me)  106.9 (C Me ) 5  5  124.8  (Tol  128.0  (obs, Tol  139.5  (Tol  C H )  141.2  (Tol  C H )  C H ) C H )  68 Table 2.3 N M R Characterization Data for Complexes 2.4 - 2.15 Compound  'H NMR  no.  (C D )5 6  2.14°'  e  l 3  C {IH} N M R (C D )8  6  6  2.35 (s, 3H, Tol Me)  10.2 (CsMe )  3.55 (br m, I H , allyl CH)  21.9 (Tol Me)  6.47 (br s, I H , Tol CH)  95.8 (allyl CH)  6.94 (d, I H , VHK = 6.6, Tol CH)  106.9 (C Me )  7.16 (obs, l H . T o l C H )  123.5 (Tol CH)  8.24 (s, IH, Tol CH)  126.9 (Tol CH)  6  5  5  5  137.2 (Tol CH) 143.1 (Tol CH)  2.15  fl,e  2.28 (s, 3H, Tol Me)  10.2 (C M? )  3.55 (brm, I H , allyl CH)  21.5 (Tol Me)  6.58 (br s, I H , Tol CH)  95.8 (allyl CH)  7.08 (d, I H , VHH = 6.6, Tol CH)  106.9 (C Me )  7.16 (obs, IH, Tol CH)  128.0 (obs Tol CH)  8.31  (d, I H , J H = 7.1, Tol CH) 3  H  5  5  5  129.6  (Tol  5  CH)  140.1 (TolCH) 142.4 (Tol CH)  a: 'H NMR (400 MHz); C {'H} NMR (100 MHz) b: 'H NMR (500 MHz); C {*H} NMR (125 MHz) 13  13  c: characterized as a mixture of 2.7 - 2.8 d: characterized as a mixture of 2.10 - 2.11 e: characterized as a mixture of 2.13 - 2.15  2.4.12 Synthesis of C p * W ( N O ) ( r | - l , l - M e 2 C H ) ( C l ) (2.16) 3  3  3  In a glovebox, a 100-mL Schlenk tube with a magnetic stir bar was charged with Cp*W(NO)Cl (203 mg, 48 mmol) while another Schlenk was charged with ( r | - l , l 3  2  Me2C3H3)2Mg.xdioxane (66 mg, 52 mmol). On a vacuum line, sufficient THF was added to both Schlenk tubes to dissolve the contents and give a turquoise coloured solution of Cp*W(NO)Cl and a clear, colourless solution of the magnesium reagent. The former 2  solution was chilled to - 78 °C with a liquid N2/acetone bath, and the latter solution was solidified via cooling to - 196 °C with a liquid N2 bath. The two components were added together via cannulation at a rate which allowed the solution to freeze upon contact with the solid. The reaction vessel was then warmed and maintained at - 78 °C for 2 hours while the melted THF solution was stirred, and changed in appearance from a clear turquoise to a turbid orange solution. The volatiles were removed in vacuo, and the resulting orange/brown solid was dissolved in 1:4 Et20/hexanes and eluted through an alumina (I) column (0.5 x 1 cm) with E t 0 . Subsequent concentration and cooling of the 2  filtrate afforded orange microcrystals of complex 2.16 (20 mg, 9 %).  2.16: IR (era" ) 1578 (s, v o). M S (LREI, m/z, probe temperature 120 °C) 453 [P , 1  +  N  m  W ] , 423 [P - NO]. H N M R (500 MHz, C D ) 5 1.55 (s, 3H, allyl Me), 1.57 (s, 15H, +  !  6  6  CsMe ), 1.68 (bs, I H , allyl CH ), 1.95 (bs, 3H, allyl Me), 2.48 (bs, I H , allyl CH ), 3.57 5  2  (bs, I H , allyl CH). C{ H} u  l  2  N M R (125 MHz, C D ) 5 9.97 (C Me ), 21.37 (allyl Me), 6  6  5  s  29.97 (allyl Me), 39.31 (allyl CH ), 96.24 (allyl CH), 108.46 (C Me ). Anal. Calcd. for 2  5  5  C5H24CINOW: C, 39.71; H , 5.33; N , 3.09. Found: C, 40.03; H, 5.43; N , 3.03  70  2.5 References and Notes  (1) Adams, C. S.; Legzdins, P.; Tran, E. J. Am. Chem. Soc. 2001, 123, 612. (2) Adams, C. S.; Legzdins, P.; Tran, E. Organometallics 2002, 21, 1474. (3) Adams, C. S.; Legzdins, P.; McNeil, W. S. Organometallics 2001, 20, 4931. (4) Tran, E.; Legzdins, P. J. Am. Chem. Soc. 1997, 119, 5071. (5) Debad, J. D.; Legzdins, P.; Lumb, S. A.; Batchelor, R. J.; Einstein, F. W. B. Am. Chem. Soc. 1995, 117, 3288. (6) Legzdins, P.; Martin, J. T.; Einstein, F. W. B.; Jones, R. H. J. Am. Chem. Soc. 1987,(5,1826. (7) Ng, S. H . K.; Adams, C. S.; Legzdins, P. J. Am. Chem. Soc. 2002, 124, published on web 23 July 2002. (8) Crystal data for 2.1: monoclinic, space group P2Jc, a = 12.8869(3) A , b = 9.0219(3) A, c = 16.7835(7) A, /3 = 92.439(2) °,V=\949.6(1)  A , Z = 4, R, = 0.038, wR 3  2  = 0.066, and GOFOF ) = 1.07 for 4484 reflections and 229 variables. 2  (9) Bent, H. A . Chem. Rev. 1961, 61, 275. (10) Ipaktschi, J.; Mirzaei, F.; Demuth-Eberle, G. J.; Beck, J.; Serafin, M . Organometallics 1997, 16, 3965. (11) Frohnapfel, D. S.; White, P. S.; Templeton, J. L. Organometallics 1997,16, 3131. (12) Villanueva, L. A.; Ward, Y . D.; Lachicotte, R.; Liebeskind, L. S. Organometallics 1996, 75,4190. (13) Adams, R. D.; Chodosh, D. F.; Faller, J. W.; Rosan, A . M . J. Am. Chem. Soc. 1979, 707,2570.  71 (14) Faller, J. W.; DiVerdi, M . J.; John, J. A. Tetrahedron Lett. 1991, 32, 1271. (15) Schilling, B. E. R.; Hoffman, R.; Faller, J. W. J. Am. Chem. Soc. 1979, 101, 592. (16) Direct evidence for endo- vs exo-allyl conformations using selective N O E N M R spectroscopy is sometimes not available, and logical inferences must be made to ascertain the solution structure. For example, irradiation of the signal due to the central allyl H atom leading to an N O E enhancement of the Cp* methyl H atoms signal is direct evidence for an exo configuration. However, its absence, and hence the implication of an endo configuration, must be confirmed by irradiation of the trans Me group signal that should exhibit an N O E enhancement of the Cp* ring signal. (17) Adams, C S . C-H Activation of Hydrocarbons by Tungsten Alkylidene and Related Complexes. Ph.D. Thesis, University of British Columbia, Vancouver, B C , October 2001. (18) Debad, J. D.; Legzdins, P.; Batchelor, R. J.; Einstein, F. W. B. Organometallics 1993, 12, 2094. (19) Bau, R.; Mason, S. A.; Patrick, B. O.; Adams, C. S.; Sharp, W. B.; Legzdins, P. Organometallics 2001, 20, 4492. (20) Crystal data for 2.2: monoclinic, space group C2/c, a = 15.3944(6) A , b = 8.4977(3) A , c = 32.326(1) A , /3 = 90.753(3) °, V = 4228.4(3) A , Z = 8, R, = 0.053, wR 3  2  = 0.0107, and GOF(7^) = 1.60 for 4410 reflections and 221 variables. (21) Legzdins, P.; Rettig, S. J.; Sanchez, L. Organometallics 1988, 7, 2394. (22) Crystal data for 2.3: monoclinic, space group Pbca, a = 14.2207(7)  k,b-  15.9939(7) A , c - 19.5926(9) A , V - 4456.2(3) A , Z = 8, /?/ = 0.063, wR = 0.082, and 3  2  GO¥(F ) = 0.80 for 5645 reflections and 264 variables. 2  72 (23) Legzdins, P.; Jones, R. H.; Phillips, E. C ; Yee, V. C ; Trotter, J.; Einstein, F. W. B. Organometallics 1991, 10, 986. (24) Dryden, N . H.; Legzdins, P.; Trotter, J.; Yee, V. C. Organometallics 1991, 10, 2857. (25) Cotton, F. A.; LaPrade, M . D. J. Am. Chem. Soc. 1968, 90, 5418. (26) Carmona, E.; Marin, J. M . ; Paneque, M . ; Poveda, M . L. Organometallics 1987, 6, 1757. (27) Castelhano, A. L ; Griller, D. J. Am. Chem. Soc. 1982, 104, 3655. (28) Jones, W. D.; Feher, F. J. Acc. Chem. Res. 1989, 22, 91. (29) Jones, W. D.; Hessell, E. T. J. Am. Chem. Soc. 1993, 115, 554. (30) Pryor, W. A.; Tang, F. Y.; Tang, R. H.; Church, D. F. J. Am. Chem. Soc. 1982, 104, 2885 and references cited therein. (31) Johansson, L.; Ryan, O. B.; Romming, C ; Tilset, M . J. Am. Chem. Soc: 2001, 123, 6579. (32) Bryndza, H. E.; Fong, L. K.; Paciello, R. A.; Tam, W.; Bercaw, J. E. J. Am. Chem. Soc. 1987, 109, 1444. (33) Jones, W. D.; Feher, F. J. J. Am. Chem. Soc. 1984, 106, 1650. (34) Debad, J. D.; Legzdins, P.; Lumb, S. A.; Rettig, S. J.; Batchelor, R. J.; Einstein, F. W. B. Organometallics 1999, 18, 3414. (35) Crystal data for 2.5: monoclinic, space group R-3, a — 21.258(5) A, b = 21.258(5) A, c = 21.258(5) A, p = 118.048(4) °,V= 3447.2(14) A , Z=6,R,= 3  0.0495, wR =  0.1134, and GOT^F ) = 1.083 for 5208 reflections and 258 variables. 2  (36) Legzdins, P.; Smith, K. M . ; Rettig, S. J. Can. J. Chem. 2001, 79, 502.  2  73  Chapter 3  Mechanistic Investigations into the Thermal Chemistry of Cp*W(NO)(CH CMe )(r} -l,l-Me C H ) 3  2  3  2  3  3  3.1 Introduction  74  3.2 Results and Discussion  75  3.3 Epilogue  92  3.4 Experimental Procedures  94  3.5 References and Notes  99  74 3.1 Introduction  The primary purpose of the earlier work carried out during the course of this research project was to identify the C-H activation products resulting from thermal reactions of 1.1 in several representative hydrocarbon solvents, namely protio-benzene, tetramethylsilane, mesitylene, xylenes, and toluene. Preliminary research performed by C. S. Adams' had already ascertained that 1.1 is easily synthesized using methods similar to that employed for the well-studied Cp*W(NO)(CH CMe3)(CH C6H5), and that it reacts with benzene under thermal 2  2  conditions. The serendipitous discovery of the C-H bond-activating chemistry initiated by 1.1 towards benzene provided a convenient starting point for our mechanistic investigations. Thus, "H N M R kinetic studies in deuterio-benzene were utilized to establish suitable thermolytic temperatures and reaction times that were used throughout the course of this study. Further mechanistic insight was obtained by several different methods that were employed to ascertain the identity of the reactive intermediate involved in the C-H bond activating chemistry of 1.1 under thermal conditions. This Chapter provides full details of the investigations briefly mentioned above, studies to identify fully the organometallic products formed during the mechanistic studies, and the route taken to confirm the formation of the reactive intermediate from gentle heating of 1.1.  75  3.2 Results and Discussion  3.2.1 Kinetic Studies  The observed clean conversion of 1.1 to 2.1 during the reaction with benzene prompted a study of the reaction kinetics. The reaction of 1.1 with benzene-^ at 50 °C for 250 minutes (~ 4 Vi half-lives) has provided kinetic data that enables the standardization of suitable thermolytic conditions that were employed in these studies. 1.1 decomposes by a first-order process with a rate constant of 2.2(1) x 10" s" (R = 4  1  2  0.999) that eliminates neopentane to generate several new organometallic complexes, namely Cp*W(NO)(C D )(ri -l,l-Me CCDCH ) ( 2 . W ) , Cp*W(NO)(C D )(ri -l,l3  6  5  3  2  2  6a  6  5  Me(CH D)C H ) (2A-d ) and Cp*W(NO)(C6D )(ri -l,l-(CH D)MeC H ) ( 2 . W ) 3  2  3  3  6h  5  2  3  3  6c  which are deuterated variants of the already characterized phenyl-dimethylallyl complex 2.1 (eq. 3.1, Figure 3.1).  1.1  (3.1)  2.1-tf'6a f  65%  2.1-d6c  2.1-d,'6b  r  35%  f  The rate constant calculated for the reaction in C6D under the conditions utilized 6  is consistent with data collected in similar systems that exhibit rate-limiting dissociation of hydrocarbon via hydrogen abstraction from an ancillary ligand. The half-life of 53 minutes at 50 °C prompted the use of a 6 hour reaction period to ensure > 99 % generation of the reactive intermediate responsible for the C-H bond activating chemistry of 1.1 under thermal conditions.  time (s)  Figure 3.1 Kinetic data plot showing that the C-D bond activating ability of 1.1 is a first order process concurrent with the elimination of neopentane (see Appendix B for data)  77  3.2.2 Deuterium Labelling Studies  Complexes 2.1-d6a-c have been identified using H N M R and ' H N M R 2  spectroscopic data which also afford the product ratios given in eq. 3.1. Deuterium 3  incorporation into the dimethylallyl ligand of the final product as shown initially suggests three potential reactive intermediates (an allene, a c/s-diene, and a ^ram'-diene complex) generated via hydrogen abstraction from the dimethylallyl ligand to form a transitionstate entity that eventually eliminates neopentane. The activation of a C-D bond could then proceed via the microscopic reverse to yield the final phenyl-allyl complex. Scheme 3.1 depicts a potential pathway by which the C-D bond activation could occur through the proposed reactive dimethylallene intermediate. Similar pathways can be drawn for CD bond activation via the suggested cw-diene and trans-diene reactive intermediates. It should be noted that the H N M R spectrum (C(,H.6) shows no incorporation of deuterium 2  into the Cp* ring, thereby eliminating the possibility of a C-H activation pathway via oxidative addition of a tucked in Cp*-methyl C-H bond.  4  Preliminary analysis of the product ratios for complexes 2.1-d6a-c indicates the incorporation of 1.12 atoms of deuterium into the allyl ligand of the final product, which is quite surprising, given that similar studies conducted on other Legzdins C-H activating complexes clearly indicate mono-inclusion of deuterium. This observation suggests that 2  more than simple hydrogen-for-deuterium substitution is occurring during the C-D activation of benzene-t/rv For example, it is plausible that a portion of the final products included more than one atom of deuterium substituting hydrogens in the dimethylallyl moiety.  78  Scheme 3.1  As a result, it was initially proposed that the phenyl-allyl complex formed in this reaction could potentially eliminate benzene-c/sH in an analogous fashion to that of neopentane and activate another molecule of benzene-c/6, via a pathway that generated one of the other proposed reactive intermediates discussed in this section, but at a slow enough rate such that only a small portion could perform the second activation under the thermolytic conditions utilized. This corresponding rate would be understandably slower 2  3  due to the stronger bond energy exhibited by metal-(sp -carbon) vs metal-(sp -carbon) linkages, as in the case of 1.1.  The thermolysis of 2.1 in benzene-afe results in the re-isolation of starting product, as determined by ' H and D N M R spectroscopic data which show no evidence for 2  deuterium incorporation in the spectral window employed, thereby substantiating the irreversibility of the C-D activation in question. Presumably, if the phenyl complex was capable of activating a C-D bond of deuterio-benzene under these conditions, the organometallic product from such a reaction would have deuterium signals in the aryl region and at the chemical shifts corresponding to the allyl C H 3 groups and central allyl hydrogen. Rigorous statistical analysis subsequently performed on the spectroscopic data 3  suggests that the activation of deuterio-benzene results in the incorporation of only one atom of deuterium into the dimethylallyl ligand of 2.1-fifea-c (1.12 + 0.14), thereby indicating that the reaction occurs stoichiometrically and providing further evidence that supports the thermal stability of complexes 2.1-ofea-c in benzene-fife-  3.2.3 Independent Synthesis of a Possible Reactive Intermediate  In a further effort to identify the reactive intermediate, a process of elimination has been employed. Specifically, one of the possible intermediates has been synthesized and thermolyzed in benzene to test the thermal stability and the C-D bond activation potential. In this study, one of the proposed r| -diene intermediates has been synthesized 4  and fully characterized before testing. A n X-ray analysis was attempted on the product in an effort to conclusively identify the solid-state stereochemistry of the diene moiety, but  unfortunately the crystals grown were extremely disordered. Selective N O E N M R spectroscopy experiments identify the prepared product as the ?rara-2-methybutadiene complex (3.1), as evinced by observed NOE enhancements of the resonances attributed to synclinal hydrogens on both of the C H 2 groups when irradiating the Me resonance. This observation is only possible if the diene ligand exists in the trans form (see Figure 3.2)  NOE enhancement not observed  \ VV^  >  H4  !  H 2  -  ^c J I  I  H  H CT II  H*  C  H * ^ i H* H*  2  I Me  HT  H  trans  CIS  3.1 H* = hydrogen corresponding to resonance irradiated H = hydrogen corresponding to resonance with expected NOE enhancement  Figure 3.2 Identifying the synthesized diene as the trans isomer based on characteristic N O E enhancements observed.  Thermolysis of complex 3.1 in benzene-^ leads to no reaction, and isolation of the originally synthesized complex. This result, in conjunction with the apparent formation of Cp*W(NO)(C D )(r| -l,l-(CH2D)MeC3H3) 2 . W 3  6  5  6 c  from the presumed  trans-diene reactive intermediate in the initial mechanistic study, suggests the existence of a possible mechanism by which the two methyl substituents on the dimethylallyl  81  ligand can exchange. This would account for the possible generation of complex 2.1-dec from its sister-c/s-equivalent,  2.1-6?6b-  On the N M R timescale at room temperature, E X S Y  N M R spectroscopic data exhibit cross peaks attributable to rapid exchange of the methyl groups of the allyl ligand, thereby suggesting the potential for a mechanism as shown in Scheme 3.2. This proposed pathway hinges on the ability of a-n distorted r| -allyl 3  fragments to break the 2e bond, rotate about the remaining single bonds to exchange the terminal allyl substituents, and revert back to the original endo or exo configuration.  58  Scheme 3.2  The spectroscopic properties of complex 3.1 exhibit features similar to those of related molybdenum species that have been structurally characterized. The closest  82 resemblance to compound 3.1 is the previously reported isostructural CpMo(NO)(r| 4  ?m/7.s -2-methylbutadiene) complex. Unlike the molybdenum congener, the tungsten ,  9  diene exists only as one isomer with the methyl substituent anti to the Cp* ring. Presumably, this is the result of steric crowding in the syn conformer between the pentamethylcyclopentadienyl ring and the methyl group that does not exist for the less sterically hindered cyclopentadienyl molybdenum analogue.  H NMR (C D ) S  C{ H} NMR (C D ) 5  13  1  6  Assignment  Hi  H  Complex 3.1  3.15  2.35  1.11  0.95  CpMo Analogue  2.88  3.35  2.37  1.94  H  2  3  H  4  1  6  6  Me  Ci  c  3.29  2.05  50.4  80.3  3.45  1.53  50.5  79.7  H  5  c  2  6  c  Me  103.9  55.2  18.5  115.8  55.3  18.1  3  4  Table 3.1 Comparison of C{'H} and ' H NMR spectroscopic resonances of 13  complex 3.1 and CpMo(NO)(r) -^rara'-2-methylbutadiene) (see Figure 3.2 for numbering 4  scheme)  As expected with related complexes such as these, the chemical shifts exhibited by each hydrogen and carbon atom within the /ram-2-methylbutadiene framework are extremely similar. The geminal coupling observed in complex 3.1 and the Mo analogue for Hi and H? (2.8 and 4.2 Hz respectively) as well as for H 4 and H 5 (3.8 and 3.1 Hz respectively) are alike, as is the vicinal coupling between H i and H (13.9 and 14.4 Hz 3  respectively) and the four-bond coupling observed between H 3 and H 4 (1.0 and 0.8 Hz respectively).  83 The analytical and spectroscopic evidence obtained for complex 3.1 is consistent with its formulation as an 18e, "three-legged piano-stool" molecular structure, with the diene ligand attached to the metal centre in a twisted transoidal fashion, much like the structurally characterized CpMo(r) -^ra^i-2,5-dimethyl-2,4-hexadiene). 4  10  3.2.4 Attempt to Couple the Reactive Species with 2,3-dimethyl-2-butene  One method of elucidating the intermediate is to employ a reagent capable of undergoing a coupling reaction upon coordination to the metal centre. Characterization of the product can often result in the suggestion of the bonding nature of the intermediate based on the observed C-C bond formation in the final species. The reaction of 2,3-dimethyl-2-butene with the acetylene intermediate previously mentioned in Section 1.2.1 for the alkyl-vinyl complex affords ar| -allyl cyclic complex 3  as a result of dual C-H bond activation and reductive coupling (Scheme 3.3)."  Scheme 3.3  ON  /  — S i —  y  -  Q  X - Me Si 4  ON  W.  84  Although the final allyl product does not implicate a reactive acetylene intermediate, the thermal reaction of 1.1 with 2,3-dimethyl-2-butene might form an organometallic complex, as a coupled product, which would implicate one of the proposed intermediates as being the species responsible for the C-H bond activating chemistry of 1.1 under mild conditions (Scheme 3.4).  Scheme 3.4  The rationale for the potential formation of the compounds illustrated in Scheme 3.4 is the result of other coupling reactions seen in organometallic chemistry. There have been numerous examples of C-C bond formation observed with the central carbon of the allene backbone to give metallocyclic-vinyl and allyl products. " The formation of 12  15  85 these complexes upon reaction with the substituted alkene could effectively lead to the identity of the reactive species. Upon thermolysis of 1.1 in 2,3-dimethyl-2-butene, the initial pale orange solution changes to a bright orange-red hue, and the product isolated from the reaction mixture as red blocks has been characterized by extensive N M R spectroscopic techniques and analytical methods. However, the data from the initial analytical studies do not provide enough evidence to distinguish the final product. A single-crystal X-ray crystallographic analysis has been performed to ascertain the connectivity of the organometallic 16  complex, and its ORTEP diagram is shown in Figure 3.3.  1.1  (3.2)  3.2  The formation of this alternate allyl complex from the activation of a methyl C-H bond of 2,3-dimethyl-2-butene leaves the dimethylallyl moiety o-bound in the solid state (eq. 3.2). This feature is evident from the orientation of the dimethylallyl group and the C(ll)-C(12) and C(12)-C(13) bond lengths of 1.500(6) and 1.342(7) A respectively, each typical of C-C single- and double- bond character, respectively. One last indication of the loss of its previous r| coordination is the W(l)-C(ll)-C(12) bond angle of 113.3(3)°, 3  which is much more obtuse towards ideal sp character than previously observed angles 3  ranging from 77.3 - 81.2°. Perhaps the most notable feature of the ' H N M R spectrum of 3.2 in C(X>6 is the significant downfield shift of the signal for the P-hydrogen of the r) -allyl fragment (5 1  5.82) from its typical values (8 3.54 - 4.43), indicative of the loss of metal-to-ligand electron density transfer that existed in the r) -allyl fragment. The exclusively o-bound 3  dimethylallyl ligand in the solid state is also manifested by solution N M R spectroscopy as the distinguishable triplet of the central hydrogen resonance. This feature demonstrates the inability of the dimethylallyl fragment to undergo the r\ to V dynamic processes 3  evident in other compounds (see Section 3.2.3).  87  Figure 3.3 Solid-state molecular structure of Cp*W(NO)(TvM,l,2-Me C3H )(Tl -3,31  3  r v ^ C i H i ) (3.2)  2  with 50 % probability thermal ellipsoids shown. Selected interatomic  distances (A) and angles (deg): W(l)-C(l 1) = 2.236(5), C ( l 1)-C(12) = 1.500(6), C(12)C(13) = 1.342(7), W(l)-C(21) = 2.219(5), W(l)-C(16) = 2.403(5), W(l)-C(17) = 2.696(5), C(21)-C(16)= 1.438(7), C(16)-C(17)= 1.375(7), N(l)-0(1) = 1.221(5), C(17)C( 16)-C(21) = 119.9 (5), C( 11 )-C( 12)-C( 13) = 130.3(5), W( 1 )-C( 11 )-C( 12) = 113.3(3), W( 1 )-N( 1 )-0( 1) = 170.9(4), C(l4)-C( 13)-C( 15) = 114.4(4), W(l)-C(21 )-C( 16) = 79.0(3)  88 3.2.5 Definitive Evidence for the Dimethylallene Reactive Intermediate  Common trapping experiments involve the use of a suitable Lewis base that can stabilize the reactive electronically unsaturated metal centre, effectively taking a "snapshot" of the connectivity that the reactive species exhibits at the time of coordination. The thermal reaction of 1.1 in neat trimethylphosphine yields the base-stabilized adduct of the dimethylallene complex, namely Cp*W(NO)(PMe )(r| -H2C=C=CMe2) (3.3) (Scheme 2  3  3.5). Initially characterized by N M R spectroscopic data, suitable single crystals were eventually grown and analyzed by X-ray diffraction. Figure 3.4 shows the ORTEP 17  diagram of the trimethylphosphine adduct and presents its selected bond lengths and angles. This structure confirms the identity of the reactive intermediate responsible for the C-H bond activating chemistry of 1.1 as the r) -dimethylallene complex.  Scheme 3.5  89  Figure 3.4 Solid-state molecular structure of Cp*W(NO)(PMe )(r| -H2C=C=CMe2) (3.3) 2  3  with 50 % probability thermal ellipsoids shown. Selected interatomic distances (A) and angles (deg): W(l)-N(l) = 1.795(4), W(l)-C(l 1) = 2.205(4), W(l)-C(12) = 2.148(5), W(1)-P(T) = 2.4660(12), N(l)-0(1) = 1.224(5), C ( l 1)-C(12) = 1.436(7), C(12)-C(13) = 1.324(7), W(l )-N( 1 )-0(I) = 175.0(4), N( 1 )-W(l)-C( 11) = 91.00( 18), C( 12)-W( 1 )-C(l 1) = 38.49(18), C(l 1)-C(12)-C(13) = 134.0(5), C(12)-C(13)-C(14) = 121.8(5), C(12)-C(13)C(15) = 124.3(5)  90 A major topic of discussion with regards to transition-metal allene complexes is the uncertainty of the exact bonding mode of the cumulated diene ligand; whether they should be described as metallacyclopropane derivatives via two o-bonds from the carbon backbone to the metal (X), or as 7i-complexes to the metal centre (Y) (see Figure 3.5).  M;  18,19  c  I  M--il  C  (X)  (Y)  Figure 3.5 Two extreme types of bonding proposed in monometallic allene complexes  In other monometallic allene complexes, the allene fragment behaves similiarly to an olefm-like ligand. As such, the dual-component bonding interaction originally 20  proposed by Dewar, Chart and Duncanson remains the paramount approach to 21  22  describing the interaction of an alkene with a transition metal,  and thus likewise the  interaction of an allene with a metal. Whether a complex exhibits more attributes of nadduct or metallacyclopropane character is dependant on the relative extents of metal-toligand and ligand-to-metal electron-density transfer.  24  The most striking feature of the solid-state molecular structure of 3.3 is the nonlinear nature of the allene framework, C(l 1)-C(12)-C(13), which has also been documented for other r| -allene complexes. ' ' ' 2  14 15 18 19,25  " The established angle of 30  134.0(5) is among the most acute found for acyclic allene complexes and is a 0  31  manifestation of the considerable back-donation of electron density from the metal to the  91  alkene n* orbitals, probably as a result of the increased contribution from the trimethylphosphine ligand. In addition, this large back-donation results in the increased 32  difference in the coordinated C=C bond length (1.436(7) A) versus that of the uncoordinated C=C (1.324(7) A). The elongation of C(l 1)-C(12) suggests a decrease in the bond order from formally two towards one. This proposal is further supported by evidence gathered from ' H and C { ' H } N M R spectroscopic data. The large upfield l3  shifts observed for the methylene carbon (5 7.7) and hydrogen (5 0.67, 1.97) signals are consistent with considerable sp character of the terminal carbon. This upfield shift is 3  33  also evident for the central carbon atom signal (5 165.7), while the remaining assignable resonances are relatively unchanged from free dimethylallene. In the solid-state molecular structures of other r) -allene transition-metal 2  complexes, the distance from the metal to the bound terminal carbon of the allene backbone is normally 0.05 - 0.19 A greater than the distance from the metal to the central carbon, akin to the metrical parameters exhibited by 3.3 (W(l)-C(l 1) = 2.205(4) A, W(l)-C(12) = 2.148(5) A). This has been rationalized by the ability of the two orthogonal n* -orbitals of the central carbon atom to overlap with a filled d orbital of the metal, '  20 34  and the higher electron density resulting from that interaction.  19  92 3.3 Epilogue  This appears to be the first definitive demonstration of the C-H bond activating ability of a transition-metal allene complex, but not the first example exhibited by an allyl-alkyl organometallic compound. Bergman and McGhee reported the C-H activation of benzene-^ by an (r| -allyl)(alkyl)iridium complex. Based on deuterium labelling 3  35  studies, an allene intermediate was proposed, but they were unable to conclusively identify the reactive species. The first-order rate constant determined for the thermolysis of 1.1 in benzene-^ (2.2(1) x 10" s" ) is consistent with the rate-determining step being the intramolecular 4  1  generation of A via elimination of neopentane (formed through hydrogen abstraction from the dimethylallyl ligand). The synthesis and characterization of the r| -/ram -diene complex, 3.1, reveals 4  ,  spectroscopic data remarkably similar to that of the CpMo congener. Presumably 3.1 adopts the twisted transoidal diene ligand attachment to the metal centre observed for other related complexes. Thermolysis of the diene compound in benzene-^e for 6 hours at 50 °C revealed its stability under those conditions and ruled it out as a potential reactive intermediate of the C-H activating species formed via hydrogen abstraction and subsequent ejection of neopentane from the metal's coordination sphere. The formation of a new allyl complex, namely 3.2, from the thermolysis of 1.1 in 2,3-dimethyl-2-butene, opens a new study on C-H activation by alkyl-allyl complexes. Presumably, due to the absence of the central hydrogen on the r\ fragment, the formation 3  93  of an allene complex is impossible. However, perhaps this will open a new route to the formation of diene complexes that may possess C - H activating character.  94  3.4 Experimental Procedures  3.4.1 Kinetic Studies and the Concurrent Preparation of  Cp*W(NO)(C D )(Ty -l,l3  6  5  Me -allyl-d,) (2. W . ) 2  6a  c  A J. Young N M R tube was charged with 1.1. (1.0 mg, 0.020 mmol), benzene-^ (0.8 mL) and an inert internal standard, hexamethyldisilane (1 mg, 0.007 mmol), and the contents were mixed thoroughly. The thermolysis was monitored by 'H N M R spectroscopy at 323.0 K, with the number of scans set to one. The loss of starting material vs time was determined by the integration of the neopentyl C M e signal vs the 3  hexamethyldisilane signal, except for the t = 0 value which was extrapolated from the plot of starting material loss vs time. The first-order rate constant for the decomposition of 1.1 was determined by the plot of ln(I(t)/I(0)) vs time. After 4.5 h, the sample was removed from the probe, and the crystalline product 2.1-fifea-c was analyzed by N M R and MS spectroscopic techniques.  3.4.2 Thermolysis of 2.1 in Benzene-<4  A thermolysis of the protio-phenyl complex, 2.1 (10 mg, mmol), was performed in benzene-fife (1 mL) for 6 h at 50 °C to test its thermal stability. After the reaction time, 'H N M R spectroscopic data (CeDe) suggested that no reaction had occurred as the resonances observed exactly matched those of the starting complex. D N M R 2  95 spectroscopic data (CgHe) showed no deuterium signals within the spectral window employed.  3.4.3 Synthesis of Cp*W(NO)(V-'rans-H C=CHC(Me)=CH ) (3.1) 2  2  Preparation of the r| -frvms-diene tungsten complex was performed using a 4  modified version of the previously published procedure, using isoprene as the trapping agent. Previous research in the Legzdins group showed that the likelihood of forming 36  the c/s-isomer was unlikely, as similar diene complexes that had been prepared would spontaneously isomerise to the thermodynamically more favoured trans form. ' 9  10,37  In a  thick-walled bomb, Cp*W(NO)(CH SiMe )2 (401 mg, 0.77 mmol) was dissolved in 2  3  pentane (60 mL), and isoprene (3 mL, 30 mmol) was syringed into the reaction vessel. The resulting mixture was frozen using a liquid N2 bath, and H2 gas (14 psig) was then introduced. The contents were allowed to warm up and react overnight while being stirred. After 16 hours, the final mixture was concentrated and cooled to obtain yellow crystals of 3.1 (20 mg, 6 %).  3.1: IR (Nujol, cm" ) 1560 (w, v o ) . MS (LREI, m/z, probe temperature 120 °C) 1  N  417 [P , +  184  W ] . ' H N M R (400 MHz, C D ) 5 0.95 (dd, V 6  6  H H  = 3.91, % H = 0.98, 1H,  C=CH ), 1.11 (m, 1H, CH), 1.64 (s, 15H, C Me ), 2.05 (s, 3H, CMe), 2.35 (m, 1H, 2  5  CH=C# ), 3.15 (dd, J 2  2  5  = 4.16, V H = 13.94, 1H, CH=C// ), 3.29 (d, J 2  H H  H  2  C=CH ). C{'H} N M R (125 MHz, C D ) 5 10.2 (C Me ), 13  2  6  6  5  5  m  - 3.67, 1H,  18.5 (CMe), 50.4 (CH=CH ), 2  96 55.2 (C=CH ), 80.3 (CH), 103.9 (C(Me)=CH ), 110.2 (C Me ). S e l N O E (400 MHz, 2  2  5  5  C D ) 8 irrad. at 2.05, N O E at 3.15 and 3.29, irrad. at 1.64, N O E at 0.95, 1.11, 2.35 and 6  6  3.29. Anal. Calcd. for C i H N O W : C, 43.18; H, 5.56; N , 3.36. Found: C, 43.26; H , 5.39; 5  2 3  N , 3.34.  3.4.4 Thermolysis of 3.1 in Benzene-dfe  A thermolysis of complex 3.1 was performed in benzene-fife at 50 °C for 6 h to test its thermal stability. After the reaction time, H N M R spectroscopic data (CeD^,) ]  suggested that no reaction had occurred as the resonances observed exactly matched those of the starting complex.  3.4.5 Preparation of Cp*W(NO)(ri -l,l,2-Me3C3H )(Tl -3,3-Me2C H3) (3.2) 3  l  2  3  Complex 3.2 was prepared by the thermolysis of 1.1 (66 mg, 0.13 mmol) in 2,3dimethyl-2-butene. The resulting residue was a bright orange/red oil which was triturated with hexanes ( 2 x 1 0 mL) to obtain red specks among the oil upon removal of the hexanes under high vacuum. The residue was dissolved in E t 0 and eluted through an 2  alumina (I) column (0.5 x 3 cm). The solvent was then removed from the eluate, and orange blocks of 3.2 were isolated by recrystallization of the residue from pentane (26 mg, 38 %)  97 3.2: IR(cm"') 1577 (s, v ) . MS (LRE1, m/z, probe temperature 120 °C) 501 [P , +  N 0  184  W ] . ' H N M R (400 MHz, C D ) 5 0.70 (s, 3H, T| -allyl Me), 1.07 (d, 3  6  6  2  = 4.6, IH, T |  JHH  3  -  allyl CH ), 1.33 (s, 3H, r| -allyl Me), 1.56 (obs, I H , r)'-allyl CH ), 1.59 (s, 15H, C Me ), 3  2  2  5  5  1.96 (s, 3H, ri -allyl Me), 1.97 (obs, I H , r| -allyl CH ), 1.98 (s, 3H, V -allyl Me), 2.19 (s, 1  1  2  3H, r| -allyl CMe), 2.48 (d, 3  2  J H H  = 4.6, I H , Tj -allyl CH ), 5.82 (t, V 2  = 7.3, I H , r| -allyl 1  3  H H  CH. C{ U) N M R (100 MHz, C D ) 5 9.9 (C Me ), 18.6 (ri'-allyl Me), 18.6 (n'-allyl n  x  6  6  5  5  CH ), 22.6 (if-allyl Me), 22.6 (r| -allyl Me), 22.8 (ri -allyl Me), 26.0 (V-allyl Me), 44.8 3  3  2  (r| -allyl CH ), 106.9 (C Me ), 133.3 (r)'-allyl-CH). Sel N O E (400 MHz, C D ) 5 irrad. at 3  2  5  5  6  6  1.59, N O E at 0.70 and 1.07. Anal. Calcd. for C i H N O W : C, 50.31; H , 7.04; N , 2.79. 2  35  Found: C, 50.58; H , 7.20; N , 2.89.  3.4.6 Preparation of Cp*W(NO)(PMe )(r| -H2C=C=CMe ) (3.3) 2  3  2  Complex 3.3 was prepared by the thermolysis of 1.1 (67 mg, 0.14 mmol) in neat trimethylphosphine. The resulting residue was triturated with hexanes ( 2 x 1 0 ml) and the solvent was removed. The product was allowed dried for 1 hour under high vacuum, whereupon hexane extracts of the residue were transferred to the top of an alumina (I) column (0.5 x 3 cm), and eluted with E t 0 to obtain a yellow solution. The solvent was 2  once again removed from the eluate and the final residue was recrystallized from a 3:1 pentane/Et 0 solvent mix to obtain complex 3.3 as yellow blocks (16 mg, 24 %). 2  3.3: IR (cm" ) 1541 (s, v ) . MS (LREI, m/z, probe temperature 120 °C) 493 [P , 1  +  N 0  184  W ] . H N M R (400 MHz, C D ) 5 0.67 (d, J !  2  6  6  = 7.31, 1H, allene C H ) , 1.27 (d, J p = 2  H H  2  H  8.8, 9H, PMe ), 1.67 (s, 15H, C M e ) , 1.78 (s, 3H, allene Me), 1.97 (br s, 1H, allene 3  5  5  C H ) , 2.44 (s, 3H, allene Me). C { ' H } NMR(100 MHz, C D ) 5 7.7 (allene CH ), 10.4 13  2  6  6  2  ( C M e ) , 17.3 (d, J p = 31, PMe ), 25.9 (allene Me), 31.9 (allene Me), 104.6 (C Me ), 2  5  5  C  3  5  5  165.7 (=C=CH ). P {'H} N M R (121 MHz, C D ) 8 -21.4 (s, VPW = 345, PMe ). Sel 3 1  2  6  6  3  NOE (400 MHz, C D ) 8 irrad. at 0.67, N O E at 1.67, 1.97 and 2.44, irrad. at 1.78, N O E 6  6  at 1.27 and 2.44. Anal. Calcd. for C i H N O P W : C , 43.83; H,6.54; N , 2.84. Found: C , 8  43.65; H, 6.53; N , 2.97.  32  99 3.5 References and Notes  (1) Adams, C.S. C-H Activation of Hydrocarbons by Tungsten Alkylidene and Related Complexes. Ph.D. Thesis, University of British Columbia, Vancouver, BC, October 2001. (2) Adams, C. S.; Legzdins, P.; Tran, E. J. Am. Chem. Soc. 2001, 123, 612. (3) The method utilized in the statistical analysis of integral data for the quantitative incorporation of deuterium was provided by Natalie Thompson of the U B C Department of Mathematics. Her consultation report as well as a the raw integral data collected is included in Appendix B. (4) Schock, L. E.; Brock, C. P.; Marks, T. J. Organometallics 1987, 6, 232. (5) Becconsall, J. K.; Job, B. E.; O'Brien, S. J. Chem. Soc. A 1967, 423. (6) Benn, R.; Rufinska, A.; Schroth, G. J. Organomet. Chem. 1981, 217, 91. (7) Thompson, M . E.; Baxter, S. M . ; Bulls, A. R.; Burger, B. J.; Nolan, M . C ; Santarsiero, B. D.; Schaefer, W. P.; Bercaw, J. E. J. Am. Chem. Soc. 1987, 109, 203. (8) Abrams, M . B.; Yoder, J. C ; Loeber, C ; Day, M . W.; Bercaw, J. E. Organometallics 1999, 18, 1389. (9) Christensen, N . J.; Hunter, A . D.; Legzdins, P. Organometallics 1989, 8, 930. (10) Hunter, A. D.; Legzdins, P.; Nurse, C. R. J. Am. Chem. Soc. 1985, 107, 1791. (11) Debad, J. D.; Legzdins, P.; Lumb, S. A.; Rettig, S. J.; Batchelor, R. J.; Einstein, F. W. B. Organometallics 1999, 18, 3414. (12) Yin, J.; Jones, W. M . Tetrahedron 1995, 51, 4395.  100 (13) Doxsee, K. M . ; Juliette, J. J. J.; Zientara, K.; Nieckarz, G. J. Am. Chem. Soc. 1994, 7/5,2147. (14) Choi, J. C ; Sarai, S.; Koizumi, T.; Osakada, K.; Yamamoto, T. Organometallics 1998, 77, 2037. (15) Lee, L ; Wu, I. Y.; Lin, Y . C ; Lee, G. H.; Wang, Y. Organometallics 1994, 13, 2521. (16) Crystal data for 3.2: monoclinic, space group P2\/n, a = 9.1734(7) A, b 16.9621(11) A, c = 13.2647(10) A, p = 95.201(4) °, V = 2055.5(3) A , Z = 4,7?/ = 0.0378, 3  wR = 0.0748, and GOF(F ) = 0.983 for 4496 reflections and 247 variables. 2  2  (17) Crystal data for 3.3: monoclinic, space group P2\/c, a — 9.1458(5) A, b 13.6500(7) A, c = 15.9576(9) A, B = 98.724(3) °,V=l969.10(18)  A , Z = 4, 7?/ = 0.0358, 3  wR = 0.0667, and GO¥(F ) = 0.946 for 4135 reflections and 217 variables. 2  2  (18) Okamoto, K.; Kai, Y.; Yasuoka, N . ; Kasai, N . J. Organomet. Chem. 1974, 65, 427. (19) Racanelli, P.; Pantini, G.; Immirzi, A.; Allegra, G.; Porri, L. Chem. Commun.  1969, 361. (20) Bowden, F. L ; Giles, R. Coord. Chem. Rev. 1976, 20, 81. (21) Dewar, M . J. S. Bull. Soc. Chim. Fr. 1951, 18, C71. (22) Chart, J.; Duncanson, L. A. J. Chem. Soc. 1953, 2939. (23) Albright, T. A.; Hoffman, R.; Thibeault, J. C ; Thorn, D. L. J. Am. Chem. Soc. 1979,101, 3801. (24) Greaves, E. O.; Lock, C. J . L ; Maitlis, P. M . Can. J. Chem. 1968, 46, 3879.  101 (25) Binger, P.; Langhauser, F.; Wedeman, P.; Gabor, B.; Mynott, R.; Kruger, C. Chem. Ber. 1994, 127, 39. (26) Clark, H . C ; Dymarski, M . J.; Payne, N . C. J. Organomet. Chem. 1979, 165, 117. (27) Lentz, D.; Willemsen, S. Organometallics 1999, 18, 3962. (28) Werner, H.; Schneider, D.; Schulz, M.J. Organomet. Chem. 1993, 451, 175. (29) Pu, J.; Peng, T.-S.; Arif, A . M . ; Gladysz, J. A . Organometallics 1992, 11, 3232. (30) Yasuoka, N . ; Morita, M . ; Kai, Y . ; Kasai, N . J. Organomet. Chem. 1975, 90, 111. (31) Yin, J.; Abboud, K. A.; Jones, W. M . J. Am. Chem. Soc. 1993, 115, 3810. (32) The exceptionally strong 7l-donor ability of the related Cp*W(NO)(PPh ) 3  fragment has been documented, see: Burkey, D. J.; Debad, J. D.; Legzdins, P. J. Am. Chem. Soc. 1997, 119, 1139. (33) Gibson, V. C ; Parkin, G.; Bercaw, J. E. Organometallics 1991, 10, 220. (34) Hewitt, T. G.; De Boer, J. J. J. Chem. Soc. A. 1971, 817. (35) McGhee, W. D.; Bergman, R. G. J. Am. Chem. Soc. 1988, 110, 4246. (36) Debad, J. D.; Legzdins, P.; Young, M . A. J. Am. Chem. Soc. 1993, 115, 2051. (37) Hunter, A . D.; Legzdins, P.; Nurse, C. R.; Einstein, F. W. B.; Willis, A . C ; Bursten, B. E.; Gatter, M. J. J. Am. Chem. Soc. 1986, 108, 3843.  102  Chapter 4 Multiple  C-H Bond Activations  Cp*W(NO)(rf-H C-C-CMe2): 2  of Hydrocarbons  by  Towards Functionalization  of  Alkanes  4.1 Introduction  103  4.2 Results and Discussion  104  4.3 Potential Functionalization of Alkanes: Future Work  109  4.4 Epilogue  115  4.5 Experimental Procedures  116  4.6 References and Notes  118  103  4.1  Introduction  Chapters 2 and 3 describe the C-H activation reactions of Cp*W(NO)(r| 2  H2C=C=CMe2) (A) with tetramethylsilane, benzene, benzene-^, and various methylsubstituted arenes to yield their respective hydrocarbyl-dimethylallyl complexes. Some of these reactions permit the elucidation of the thermodynamic distribution of products, based on the different C-H bond environments found on the hydrocarbon in question (e.g. sp aryl C-H bond vs sp benzylic C-H bond). However, the question of thermodynamic 2  3  distributions for different types of sp hybridized C-H bonds (e.g. primary vs secondary 3  vs tertiary) has yet to be addressed. As mentioned in Chapter 1, alkanes constitute a large proportion of the worlds' hydrocarbon feedstocks, and thus the ultimate goal is to convert these abundant, relatively inexpensive, and inert substrates into more desirable materials of commercial value. The first step towards the functionalization of these alkane substrates is the C-H activation process that opens the doors for incorporation of new functional groups that are of potential synthetic utility. In this context, this Chapter seeks to elucidate the organometallic products formed during reactions of A with saturated alkane solvents such as methylcyclohexane and cyclohexane, and provide some preliminary discussion pertaining to the thermodynamic distribution of the final products generated. In addition, pertinent discussion is presented regarding potential alkane functionalization processes based on the C-H bond-activating chemistry exhibited by the tungsten-allene complex.  104 4.2 Results and Discussion  4.2.1 Thermolysis of 1.1 in Methylcyclohexane  Given the similarity in C-H activating chemistry initiated by the well-studied bis(neopentyl) complex, namely Cp*W(NO)(CH2CMe3)2,'~ it is not unreasonable to 3  anticipate the generation of similar organometallic species upon thermolysis of 1.1 in alkyl-substituted cyclic alkanes. Consistently, two principal products are formed in the reaction between the tungsten-allene reactive intermediate (A) and methylcyclohexane, namely the two isomeric species, Cp*W(NO)(r) -C7Hii)(H) (4.1 and 4.2) (eq. 4.1). 3  Compounds 4.1 and 4.2 are identical to the principal organometallic species isolated from the reactions of the intermediate neopentylidene and benzylidene species (Cp*W(NO)(=CHCMe ) and Cp*W(NO)(=CHC H ), respectively) described in Section 3  6  5  1.2.2 with methylcyclohexane. The major product in all three cases, 4.1, is formed in  105 greater than 90 % yield as indicated by H N M R spectroscopy and exhibits an exocyclic 1  endo-rf-aUyl linkage with the terminal CH.2 group cis to the nitrosyl ligand. Analogous to the dimethylallyl moiety of the majority of complexes characterized and presented in this Thesis, the C{'H} N M R spectrum of complex 4.1 (C6D ) exhibits a high-field signal 13  6  assignable to the terminal allyl-carbon cis to the NO group that is indicative of sp -like 3  character (5 41.3), and low-field resonances for the remaining two carbons of the allyl backbone, suggestive of sp -like character (5 80.0 C H , 121.1 C). These spectroscopic 2  features are consistent with the familiar o-n distortions observed for allyl-nitrosyl complexes due to the 7i-accepting nature of the NO ligand in solution and in the solid state. " The previously determined solid-state molecular structure of 4.1 also reveals 4  7  evidence for the distortion seen in solution. The minor product, 4.2, has been identified 2  as an isomer of 4.1, with the allyl CH2 group found trans to the N O ligand, as shown in eq. 4.1. N O E spectroscopic techniques were unable to decisively distinguish between the possible exo or endo configurations for the exocyclic-allyl species. However, as with 4.1, the steric bulk of the methylcyclohexenyl group in an exo conformer with the large Cp* ring is highly unfavoured. Thus, it is fair to assume that 4.2 also adopts an endo configuration. There is also evidence for the interconversion of 4.1 and 4.2 based on spinsaturation transfer observed between the resonances attributable to the allyl C H atoms of both complexes in NOE experiments, possibly via rotation about the W-C linkage of an ri -allyl intermediate. Therefore, the product ratio observed reflects the thermodynamic 1  distribution of complexes 4.1 and 4.2 generated at 50°C (~ 49:1 respectively). The corresponding alkylidene reactions performed at an elevated temperature (70 °C) yield a ratio of ~ 9:1, which further supports the notion that 4.1 is the thermodynamically  106 preferred conformation for the two possible isomers. The apparent exclusive formation of exocyclic r| -allyl complexes vs the endocyclic species suggests that A preferentially 3  activates the thermodynamically stronger primary C - H bonds, much like other metalbased alkane activation systems.  8  4.2.2 Thermolysis of 1.1 in Cyclohexane  9  Reaction o f A with cyclohexane leads to the generation of a cyclohexenyl-hydrido complex, namely Cp*W(NO)(r) -C6H9)(H) (4.3) (eq. 4.2). This transformation constitutes 3  a novel mode of multiple C - H activations of cyclohexane, a relatively inert solvent that has frequently been used to study the C - H activations of other hydrocarbons. " 10  A  12  4.3  For comparison, the well-studied bis(alkyl) species such as Cp*W(NO)(CH2CMe3)2 react with cyclohexane in a completely different manner. Their thermolyses in the presence of an excess of trimethylphosphine in cyclohexane at 70 °C  107 for 40 hours result in the formation of two base-stabilized complexes, namely the alkylidene and the cyclohexene adducts. However, in the absence of a suitable Lewis 1  base, only decomposition occurs to afford intractable products, presumably due to the elevated temperatures employed. The thermal reaction of 1.1 in cyclohexane in the presence of excess trimethylphosphine results in the exclusive generation of the basestabilized allene adduct. These reactivity differences suggest that new avenues of alkane activation chemistry may well be accessible through alkyl-allyl complexes such as 1.1. The solution N M R spectroscopic data show that the nitrosyl ligand also effects o7t distortion on the cyclohexenyl fragment as seen in other allyl structures. The "C{ H} N M R spectrum of 4.3 (CeD ) displays a resonance at low field corresponding to the s p 6  like terminal allyl-carbon cis to the N O ligand (8 93.2), and high-field sp -like resonances 2  for the central and remaining terminal allyl-carbon atoms (8 61.8, 73.4). Furthermore, no signals attributable to any other isomers are present. Presumably, the formation of the endo species is, as in the case of 4.1 and 4.2, highly unfavourable due to inevitable steric interactions between the cyclohexenyl fragment and the Cp* ring. A single-crystal X-ray crystallographic analysis has been performed on 4.3, confirming the connectivity as shown in eq. 4.2. Unfortunately, the quality of the diffraction data collected precludes any meaningful discussion of the metrical parameters of 4.3 and, in addition, the hydride could not be conclusively located. However, the ' H N M R spectrum of 4.3 (CeDe) displays a distinctive hydride resonance (8 -0.57, JWH 132) (Figure 4.1), and the IR spectrum (KBr pellet) exhibits a VWH stretching frequency at 12  1898 cm" , thereby confirming the proposed formulation of 4.3.  I  i  -0.30  i  i  i  ]  i  i  i  -0.40  i  i  -0.50  i  i  i  i  i  -0.60 ppm  i  i  i  i  j  -0.70  i  i  i  i  |  -0.80  Figure 4.1 Hydride region of ' H N M R spectrum of cyclohexenyl-hydrido complex 4.3 in C D . ( 6  6  183  W I = 7 [14.4%], J 2  W H  = 131.7 Hz, 5 = -0.57 ppm)  109  4.3 Potential Functionalization of Alkanes: Future Work  The formation of new organometallic species as a consequence of successive C-H bond-activation reactions of alkane substrates is an extremely interesting feature, although it is not unique to these systems. For example, Crabtree and Baudry showed that cyclopentane reacts with lr and Re systems to form cyclopentadienyl-containing species as a result of multiple hydrogen loss. However, an alkene must be added as a hydrogen acceptor for the reactions to proceed (Scheme 4.1).  13-16  Seemayer reported the  multiple C-H bond activation of cyclohexane by early-transition metal cations (Sc , T i +  and V ) , to give T| -benzene species. However, this transformation has little practical +  6  17  implications since it is performed in the gas phase. Intramolecular multiple C-H bond activations have also been observed, but are less useful for purposes of direct alkanefunctionalization.  18-21  Scheme 4.1  +  +  CH CH CMe3 3  2  CH CH CMe3 3  2  +  110 The potential for functionalization of hydrocarbons using the tungsten-allene system is most evident in the cases of the formation of Cp*W(NOXr| -2,3,3-Me3C3H X r|'-3,33  2  Me2C3H3) (3.2), 4.1, and 4.3 from thermal reactions of 1.1 in 2,3-dimethyl-2-butene, methylcyclohexane and cyclohexane, respectively. In these instances, new allyl complexes are formed from the hydrocarbon substrate, and are thus potentially suitable reagents for organic syntheses based on the research conducted on CpMo(NO)(allyl) fragments. ' " 5 6,22  28  That the Cp*W and CpMo fragments possess comparable structural and  electronic features suggests the metal-allyl species mentioned above (3.2, 4.1 - 4.3) may exhibit similar reactivity to form organic products. " 29  32  The selectivity exhibited by CpMo(NO)(X)(r| -allyl) (X = halide) complexes for 3  the generation of homoallylic alcohols is due to the electronic asymmetry arising from variations in acceptor properties of the nitrosyl and halide ligands (eq. 4.3). '  23 33  (R)  ee > 90% (S)  The G-7T, distortions common to metal-allyl-nitrosyl complexes permit the allyl ligand to adopt an r\ configuration with the bond retained being between the metal center l  and the terminal allyl-carbon cis to the NO ligand." This effectively opens up a Lewis acidic site at the metal center where an aldehyde could bind and generate a chair-like 33  transition state for the coupling of the two organic fragments to occur (Scheme 4.2).  Ill  Scheme 4.2  r| -r| 3  ON  M  o  / X  ,  1  >•  ^  ON  M  /\ X  (R)  H  "  PhCHO  OH Ph  ON'  Mo —  MeOH  ee > 90% (S)  Ph H  The generation of similar homoallylic alcohols may be plausible by applying this known reaction to the Cp*W(NO)(allyl)(hydrido) systems. It is known that transitionmetal hydride complexes can be converted to the corresponding halide species by dissolution in halogenated organic solvents such as dichloromethane, whereupon 34  analogous a-n distortions can lead to the opening of a coordination site for an aldehyde to bind, and undergo the same reactivity to yield the desired organic product. Scheme 4.3 illustrates a possible reaction pathway to generate homoallylic alcohols starting from the cyclohexenyl-hydrido complex (4.3). A similar reaction pathway could be drawn for the analogous reaction with the exocyclic r| -allyl methylcyclohexenyl-hydrido complex. 3  112  Scheme 4.3  All of the work presented thus far concerns the characterization of the final organometallic species present in the reaction mixtures. However, the issue of organic products generated during the thermolyses requires thorough investigation, and could potentially yield some interesting results. In this regard, studies are required to identify the non-organometallic species synthesized concurrently with the compounds discussed in this Thesis. Preliminary data collected from the thermolysis of 1.1 in cyclohexane yield an interesting result. As well as the generation of 4.3, GC-MS data suggest that the coupled  113 organic product, 1,1-dimethylpropylcyclohexane, is also present in the final reaction mixture. This product is possibly formed as a result of coupling between a coordinated cyclohexenyl group and an alkyl fragment derived from the precursor dimethylallyl ligand (Scheme 4.4).  Scheme 4.4  [ W*] = Cp*W(NO)  In the reaction pathway proposed in Scheme 4.4, initial single C - H bond activation of cyclohexane affords the allyl-alkyl product (B), which can undergo double  114 (3-H elimination to generate an alternative alkyl-allyl (C). The allyl moiety could then switch to a T|' binding mode, providing an accessible double bond that subsequently couples with the alkyl group much like the tungsten-acetylene system to give an alkene 35  complex (D). Complex D can then activate a second molecule of cyclohexane and subsequent P-H elimination can lead to the ejection of the purported 1,1dimethylpropylcyclohexane from the metal's coordination sphere, leaving a cyclohexene adduct (E) that P-H eliminates to yield the final cyclohexenyl-hydrido complex, 4.3. Preliminary experiments have been initiated in an effort to further elucidate the scope of alkane C-H bond-activation chemistry exhibited by A . The H N M R spectrum of !  the crude residue from the thermolysis of 1.1 in pentane reveals the generation of multiple organometallic species, as evinced by a plethora of resonances attributable to hydride ligands.  115  4.4 Epilogue  Reaction of A with methylcyclohexane gives an indication of the selectivity for different sp C-H bonds. The formation of the exocyclic allyl species and the absence of 3  evidence for any endocyclic isomer suggests the preference of A to activate primary C-H bonds, a common feature observed for other metal-based alkane C-H activating complexes. The generation of allyl-hydrido organometallic species as a consequence of multiple C-H bond activations of saturated alkane substrates by A is a result of great interest. Given the rigorous studies that have been conducted on the structurally and electronically similar CpMo(NO)(allyl)(X) (X = halide) species, the potential reactivity of the hydrido complexes to ultimately yield homoallylic alcohols of synthetic use in organic chemistry opens new avenues of research regarding the functionalization of alkanes using the precursor neopentyl-dimethylallyl complex. The apparent generation of the coupled organic product from the thermal reaction of 1.1 with cyclohexane is also bound to spark much interest in the chemical community as another means of functionalizing saturated alkanes by the same precursor species. As such, there is still much work to be performed on this diverse system that is, to our knowledge, the first reported C-H activating system that has been confirmed to involve a reactive allene intermediate.  116  4.5 Experimental Procedures  4.5.1 Preparation of Cp*W(NO)(ri -C7H,,)(H) (4.1 and 4.2) and Cp*W(NO)(rf3  C H )(H) (4.3) 6  9  Complexes 4.1 and 4.2 were formed via the thermolysis of 1.1 (80 mg, 0.16 mmol) in methylcyclohexane and complex 4.3 was formed via thermolysis of 1.1 (50 mg, 0.10 mmol) in cyclohexane The reaction mixtures at the end of the 6-hour period were a dark orange/brown colour, and the residues formed upon removal of the solvent were brown oils. The residues were triturated with hexanes ( 2 x 1 0 mL) which were dried under high vacuum for approximately 1 hour to obtain mixtures of dark specks interspersed in brown oils, which were then redissolved in a 1:3 Et20/hexanes solvent mixture and eluted through an alumina (I) column (0.5 x 3 cm) to afford yellow solutions. The solvent was once again removed, and the final residues were recrystallized from 3:1 pentane/Et20 solvent mixes to obtain complexes 4.1 and 4.2 as yellow microcrystals (3.5 mg, 5 %), and complex 4.3 as yellow blocks (14 mg, 32 %). Complexes 4.1 and 4.2 were identified by comparison of their H N M R resonances to those previously reported. ]  2  4.3: IR (cm" ) 1568 (s, v o ) , 1898 (m, V H). M S (LREI, m/z, probe temperature 1  N  120 °C) 431 [P , +  184  W  W ] . H N M R (500 MHz, C D ) 5 -0.57 (s, VWH = 132, IH, WH), 1  6  6  1.16 (m, IH, cyclohexenyl C H ) , 1.42 (m, IH, cyclohexenyl C H ) , 1.69 (s, 15H, a  2  a  2  C Me ), 2.46 (m, IH, cyclohexenyl C H ) , 2.58 (m, I H , cyclohexenyl C H ) , 2.62 (m, 5  5  b  2  b  2  2H, cyclohexenyl C H ), 2.75 (m, 1H, allyl C H), 3.59 (m, I H , allyl C H), 5.30 (m, I H , C  2  X  y  allyl C H). C{'H} N M R (125 MHz, C D ) 5 10.4 (C Me ), 19.9 (cyclohexenyl C H ) , 13  Z  6  6  5  5  a  2  117 26.6 (cyclohexenyl C H ), 28.7 (cyclohexenyl C H ), 61.8 (allyl C H ), 73.4 (allyl C H), C  2  b  2  y  2  Z  93.2 (allyl C H ), 103.9 (C Me ). Anal. Calcd. for C i H N O S i W : C, 44.56; H, 5.84; N , X  2  5  5  6  25  3.25. Found: C, 44.40; H, 5.76; N , 3.24.  4.5.2 Thermolysis of 1.1 in Cyclohexane in the Presence of Excess PMe3  Complex 3.3 was formed via thermolysis of 1.1 (26 mg, 0.05mmol) in cyclohexane and trimethylphosphine (0.2 mL, 1.93 mmol). The volatiles were removed in vacuo, and the resulting residue was worked-up as described in Section 3.4.6.  4.5.3 Preliminary Identification of Organic Products generated during Thermolysis of 1.1 in Cyclohexane  The thermal reaction of 1.1 in cyclohexane was conducted as described in Section 4.5.2, except that the volatiles were removed in vacuo and collected in a GC bomb. A blank reaction of neat cyclohexane was also performed, and its volatiles were also collected in a GC bomb in an identical fashion. Both sets of volatiles were analysed via GC-MS, and their spectra were subtracted to obtain a spectrum devoid of peaks attributable to inherent products from the heating of cyclohexane. Preliminary analysis suggests the presence of 1,1-dimethylpropylcyclohexane. Organic volatiles analysis was performed using an Agilent 6890 Series gas chromatograph with an HP-5 M S column coupled to an Agilent 5973 Network mass-selective detector.  118 4.6 References and Notes  (1) Tran, K ; Legzdins, P. J. Am. Chem. Soc. 1997, 119, 5071. (2) Adams, C. S.; Legzdins, P.; Tran, E. J. Am. Chem. Soc. 2001, 123, 612. (3) Adams, C. S.; Legzdins, P.; Tran, E. Organometallics 2002, 21, 1474. (4) Schilling, B. E. R.; Hoffman, R.; Faller, J. W. J. Am. Chem. Soc. 1979, 101, 592. (5) Adams, R. D.; Chodosh, D. F.; Faller, J. W.; Rosan, A. M . J. Am. Chem. Soc. 1979, 707,2570. (6) Faller, J. W.; Nguyen, J. T.; Ellis, W.; Mazzieri, M . R. Organometallics 1993, 72, 1434. (7) Ipaktschi, J.; Mirzaei, F.; Demuth-Eberle, G. J.; Beck, J.; Serafin, M . Organometallics 1997, 16, 3965. (8) Arndsten, B. A.; Bergman, R. G.; Mobley, T. A.; Peterson, T. H.Acc. Chem. Res.  1995, 28, 154. (9) Ng, S. H. K.; Adams, C. S.; Legzdins, P. J. Am. Chem. Soc. 2002,124, published on web 23 July 2002. (10) McGhee, W. D.; Bergman, R. G../. Am. Chem. Soc. 1988, 110, 4246. (11) Cummins, C. C ; Baxter, S. M . ; Wolczanski, P. T. J. Am. Chem. Soc. 1988, 110, 8731. (12) Schaller, C. P.; Cummins, C. C ; Wolczanski, P. T. J. Am. Chem. Soc. 1996, 775, 591. (13) Crabtree, R. H.; Mihelcic, J. M . ; Quirk, J. M . J. Am. Chem. Soc. 1979,101, 7738.  119 (14) Crabtree, R. H.; Mellea, M . F.; Mihelcic, J. M . ; Quirk, J. M . J. Am. Chem. Soc.  1982, 104, 107. (15) Crabtree, R. H.; Demou, P. C ; Eden, D.; Mihelcic, J. M . ; Parnell, C. A.; Quirk, J. M . ; Morris, G. E. J. Am. Chem. Soc. 1982,104, 6994. (16) Baudry, D.; Ephritikine, M . ; Felkin, H. J. Chem. Soc, Chem. Commun. 1980, 1243. (17) Seemeyer, K.; Schroder, D.; Kempf, M . ; Lettau, O.; Muller, J.; Schwarz, H. Organometallics 1995, 14, 4465. (18) Prinz, M . ; Grosche, M . ; Herdtweck, E.; Herrmann, W. A . Organometallics 2000, 19, 1692. (19) Kickham, J. E.; Guerin, F.; Stewart, J. C ; Stephan, D. W. Angew. Chem. Int. Ed. 2000, 39, 3263. (20) Kickham, J. E.; Guerin, F.; Stewart, J. C ; Urbanska, E.; Stephan, D. W. Organometallics 2001, 20, 1175. (21) Stephan, D. W. Can. J. Chem. 2002, 80, 125. (22) Faller, J. W.; Linebarrier, D. L. Organometallics 1990, 9, 3182. (23) Faller, J. W.; DiVerdi, M . J.; John, J. A. Tetrahedron Lett. 1991, 32, 1271. (24) Faller, J. W.; Murray, D. L.; White, D. L.; Chao, K. H . Organometallics 1983, 2, 400. (25) Faller, J. W.; Chao, K. H. J. Am. Chem. Soc. 1983,105, 3893. (26) Faller, J. W.; Mazzieri, M . R. J. Organomet. Chem. 1990, 383, 161. (27) Vanarsdale, W. E.; Winter, R. E. K.; Kochi, J. K. J. Organomet. Chem. 1985, 296, 31.  120 (28) Vanarsdale, W. E.; Winter, R. E. K.; Kochi, J. K. Organometallics  1986, 5, 645.  (29) Legzdins, P.; Veltheer, J. E. Acc. Chem. Res. 1993, 26, 41. (30) Poli, R ; Smith, K. M . Organometallics  2000, 19, 2858.  (31) Bursten, B. E.; Cayton, R. H. Organometallics  1987, 6, 2004.  (32) Legzdins, P.; Rettig, S. J.; Sanchez, L. J.; Bursten, B. E.; Gatter, M . J. Chem. Soc. 1985,  Am.  107, 1411.  (33) Faller, J. W.; Linebarrier, D. L. J. Am. Chem. Soc. 1989, 111, 1937. (34) Crabtree, R. H. The Organometallic  Chemistry of the Transition Metals; 3  rd  ed.;  Wiley and Sons: Toronto, 2001. (35) Debad, J. D.; Legzdins, P.; Lumb, S. A.; Rettig, S. J.; Batchelor, R. J.; Einstein, F. W. B. Organometallics  1999,  18, 3414.  APPENDIX A Solid-state Molecular Structure X-ray Crystallographic Data Refinement, and Structural Solution and Refinement Data for Compounds 2.1, 2.2, 2.3, 2.5, 3.2 and 3.3  122 Table A l Data Refinement, and Structural Solution and Refinement Data for Compounds 2.1, 2.2 and 2.3 Crystal Data Empirical formula  2.1  2.2  C21H29NOW  Ci H NOWSi  C24H35NOW  Crystal Habit, color  Prism, yellow  Platelet, orange  Block, orange  Crystal size (mm)  0.30 x 0.20 x 0.20  0.30x0.15 x 0.08  0.40x0.30x0.15  Crystal system  Monoclinic  Monoclinic  Orthorhombic  Space group  P2,/C  C2/c  Pbca  Volume (A )  1949.6(1)  4228.4(3)  4456.2(3)  12.8869(3)  15.3944(6)  14.2207(7)  b(A)  9.0219(3)  8.4977(3)  15.9939(7)  c(A)  16.7835(7)  32.326(1)  19.5926(9)  <x(°) PO  90  90  90  92.439(2)  90.753(3)  90  Y(°) Z Density (calculated) (Mg/m )  90  90  90  4  8  8  1.687  1.500  1.602  Absorption coefficient (cm" )  59.39  54.73  52.03  Fooo  976.00  1904.00  2144.00  3  a  (A)  9  2.3 35  3  1  123  Table A l Data Refinement, and Structural Solution and Refinement Data for Compounds 2.1, 2.2 and 2.3 (cont'd) Crystal Data Formula weight (g/mol)  2.1  2.2  2.3  495.32  477.34  537.40  Radiation  M o K a , 0.71069 A  M o K a , 0.71069 A  M o K a , 0.71069 A  20max  57.5  55.9  55.7  Measured Reflections: Total  13123  12879  41082  Measured Reflections: Unique  4484  4410  5645  Structure Solution Method  Direct  Direct  Direct  Refinement  Full-matrix leastsquares  Full-matrix leastsquares  Full-matrix leastsquares  No. Observations  4264  4156  5120  No. Variables Final R Indices  229  221  264  RI =0.038, wR2 0.066  RI = 0.036, wR2 0.071  RI =0.031, wR2 0.038  Goodness-of-fit on  1.07  1.60  0.80  Largest diff. peak and hole (e' A" )  1.08 and-1.64  2.01 and-1.75  3.30 and -2.01  O  Structure Solution and Refinement  3  3  a  R ] on F = Z | (|F | - |F |) | / Z |F |; wR2 = = [ ( Z ( F 0  C  0  (w ( |F | - |F | ) ) / degrees of freedom ] . 2  Q  C  l/2  2 0  -F  2 c  f)  / Z w(F  2 0  ) ] ; w = [ c V ]"'; 2  l / 2  b  GOF = [ Z  124 Table A2 Data Refinement, and Structural Solution and Refinement Data for Compounds 2.5, 3.2 and 3.3 Crystal Data Empirical formula  2.5  3.2  3.3  C23H33NOW  C21H35NOW  C18H32NOPW  Crystal Habit, color  Brick, orange  Prism, yellow  Chip, yellow  Crystal size (mm)  0.11 x 0.09x0.04  0.45 x 0.35 x 0.20  0.25 x 0.20x0.10  Crystal system  Rhombohedral  Monoclinic  Monoclinic  Space group  R-3  P2i/n  P2,/c  Volume (A )  3447.2(14)  2055.5(3)  1969.10(18)  (A)  21.258(5)  9.1734(7)  9.1458(5)  b(A)  21.258(5)  16.9621(11)  13.6500(7)  c(A)  21.258(5)  13.2647(10)  15.9576(9)  a(°)  118.048(4)  90  90  PO  118.048(4)  95.201(4)  98.724(3)  Y(°) Z Density (calculated) (Mg/m )  118.048(4)  90  90  6  4  4  1.513  1.62  1.664  Absorption coefficient (cm" )  50.37  58.05  59.50  Fooo  1560  1000  976  3  a  3  1  125  Table A2 Data Refinement, and Structural Solution and Refinement Data for Compounds 2.5, 3.2 and 3.3 (cont'd) Crystal Data Formula weight (g/mol)  2.5  3.2  3.3  523.35  501.35  493.27  Radiation  M o K a , 0.71073 A  M o K a , 0.71069 A  M o K a , 0.71069 A  20max ( ° )  55.06  55.74  55.74  Measured Reflections: Total  20952  4496  18136  Measured Reflections: Unique  5208  4496  4135  Structure Solution Method  Direct  Direct  Direct  Refinement  Full-matrix leastsquares  Full-matrix leastsquares  Full-matrix least squares  No. Observations  5208  4496  4135  No. Variables Final R Indices  258  247  217  RI =0.0413, wR2 = 0.098  RI = 0.031 l , w R 2 = 0.073  RI =0.0281, wR2 = 0.065  1.083  0.985  0.947  0.222 and -0.866  0.169 and-1.460  0.154 and-2.497  Structure Solution and Refinement  3  Goodness-of-fit on p  2b  Largest diff. peak and hole (e" A" ) 3  a  R l on F = £ | (|F | - |F |) | / S |F |; wR2 = = [ (Z (F 0  C  0  (w (|F | - |F | f) / degrees of freedom ] . 1/2  0  C  2 0  - F f) / X w(F 2  c  z 0  w = [ &¥ * ]"'; 0  b  GOF = [ X  126 Table A 3 Bond Distances (A) in the Solid-State Molecular Structure Determined for 2.1 W(1)N(1) 1.762(3) W(1)C(1) 2.186(3) W(I)C(7) 2.218(4) W(1)C(8) 2.363(4) W(1)C( 12) 2.306(3) W ( I ) C ( 13) 2.398(3) W(1)C( 14) 2.430(3) W(1)C(15) 2.389(3) W(1)C(16) 2.306(3) 0(1)N(1) 1.224(4) C(1)C(2) 1.406(5)  C(1)C(6) 1.397(4) C(2) C(3) 1.383(5) C(3) C(4) 1.375(6) C(4) C(5) 1.368(7) C(5) C(6) 1.401(5) C(7) C(8) 1.439(6) C(7) H(6) 1.06(4) C(7) H(7) 0.91(4) C(8) C(9) 1.365(5) C(8) H(8) 1.00(5) C(9) C( 10) 1.495(5)  C(9) C ( l l ) 1.500(5) C(12) C(13) 1.411(6) C(12) C(16) 1.408(6) C(12) C(17) 1.513(6) C(13)C(I4) 1.409(7) C(13)C(18) 1.510(6) C(14) C(15) 1.403(5) C(14) C(I9) 1.501(5) C(15)C(16) 1.405(5) C(15)C(20) 1.489(6) C(16) C(21) 1.502(5)  Table A4 Bond Angles (°) in the Solid-State Molecular Structure Determined for 2.1 N(l) W ( l ) C ( l ) 93.3(1) N(l) W ( l ) C(7)92.1(2) N(l) W ( l ) C(8) 104.6(1) N ( l ) W ( l ) C(12) 95.4(1) N ( l ) W ( l ) C(13) 127.7(1) N(1)W(1) C(14) 149.5(1) N(l) W ( l ) C(15) 121.7(1) N(1)W(1) C(16) 92.3(1) C ( l ) W ( l ) C(7) 130.1(1) C ( l ) W ( l ) C(8) 94.7(1) C ( l ) W ( l ) C(12) 133.1(1) C(1)W(1) C(13) 129.6(1) C ( l ) W ( l ) C(14) 95.8(1) C ( l ) W ( l ) C(15) 78.5(1) C ( l ) W ( l ) C(16) 98.2(1) C(7) W ( l ) C(8) 36.4(2) C(7) W ( l ) C(12) 95.5(1) C(7) W ( l ) C(13) 81.8(1) C(7) W ( l ) C(14) 103.8(2) C(7) W ( l ) C(15) 136.5(1) C(7)W(1) C(16) 131.1(1) C(8)W(1) C(12) 127.0(1) C(8) W ( l ) C(13) 100.5(1) C(8) W ( l ) C(14) 103.6(1) C(8) W ( l ) C(15) 133.4(1) C(8) W ( l ) C(16) 158.1(1) C(12)W(1) C(13) 34.8(2) C(12) W ( l ) C(14) 57.8(1) C(12) W ( l ) C(15) 57.8(1) C(12) W ( l ) C(16) 35.6(1)  C(13)W(1) C(14) 33.9(2) C(13)W(1) C(15) 56.4(1) C(13) W ( l ) C(16) 57.8(1) C(14) W ( l ) C(l 5) 33.8(1) C(14)W(1) C(16) 57.6(1) C(15) W ( l ) C(I6) 34.8(1) W(1)N(1) O ( l ) 169.5(3) W(1)C(1) C(2) 123.0(2) W(1)C(1) C(6) 121.4(2) C(2)C(1) C(6) 115.5(3) C(1)C(2) C(3) 122.5(3) C(2) C(3) C(4) 120.3(4) C(3)C(4) C(5) 119.3(4) C(4)C(5) C(6) 120.4(4) C(1)C(6) C(5) 121.9(4) W(I)C(7) C(8) 77.3(2) W(1)C(7) H(6) 110(3) W(1)C(7) H(7) 120(3) C(8)C(7) H(6) 113(2) C(8)C(7) H(7) 116(3) H(6)C(7) H(7) 115(4) W(1)C(8) C(7) 66.3(2) W(1)C(8) C(9) 92.0(2) W(1)C(8) H(8) 106(3) C(7)C(8) C(9) 124.8(4) C(7) C(8) H(8) 117(3) C(9) C(8) H(8) 118(3) W(I)C(12) C(l 3) 76.1(2) W(1)C(12) C(16) 72.2(2) W(1)C(12) C(17) 121.1(3)  C(13)C(12) C(16) 107.6(3) C(I3)C(12) C(17) 127.1(5) C(16)C(12) C(17) 125.2(5) W(1)C(13) C ( l 2) 69.0(2) W(1)C(13) C(14) 74.3(2) W(1)C(13) C(18) 128.8(3) C(12)C(I3) C(14) 108.6(3) C(12)C(13) C(18) 126.7(5) C(14)C(I3) C(18) 124.3(5) W(I)C(14) C(13) 71.8(2) W(1)C(14) C(15) 71.5(2) W(1)C(14) C(19) 128.1(3) C(13)C(14) C(15) 107.1(3) C(13)C(14) C(19) 123.8(5) C(15)C(14) C(19) 128.7(5) W(1)C(15) C(14) 74.7(2) W(1)C(15) C(16) 69.4(2) W(1)C(15) C(20) 129.5(3) C(14)C(15) C(16) 109.0(3) C(14)C(15) C(20) 125.7(5) C(16)C(15) C(20) 124.6(5) W(1)C(16) C(l 2) 72.2(2) W(1)C(16) C(15) 75.9(2) W(1)C(16) C(21) 121.7(2) C(12) C(16)C(15) 107.7(3) C(12)C(16) C(21) 126.9(5) C(15)C(16) C(21) 125.2(5)  127  Table A5 Bond Distances (A) in the Solid-State Molecular Structure Determined for 2.2 W ( 1 ) N ( 1 ) 1.760(5)  S i ( l ) C ( 1 7 ) 1.877(9)  C(3) C(8) 1.50(1)  W ( 1 ) C ( 1)2.460(6)  S i ( l ) C ( 1 8 ) 1.885(9)  C(4) C(5) 1.427(9)  W ( 1 ) C ( 2 ) 2.355(6)  S i ( l ) C ( 1 9 ) 1.857(9)  C ( 4 ) C ( 9 ) 1.51(1)  W ( 1 ) C ( 3 ) 2.324(6)  0 ( 1 ) N ( 1 ) 1.237(7)  C ( 5 ) C ( 1 0 ) 1.51(1)  W ( 1 ) C ( 4 ) 2.354(7)  C ( 1 ) C ( 2 ) 1.430(9)  C ( l 1 ) C ( 1 2 ) 1.46(1)  W ( 1 ) C ( 5 ) 2.458(6)  C ( 1 ) C ( 5 ) 1.396(9)  C ( 1 1 ) H ( 1 I B ) 0.98(7)  W(1)C(11)2.182(6)  C ( 1 ) C ( 6 ) 1.50(1)  C ( 1 1 ) H ( 1 1 A ) 1.03(7)  W ( 1 ) C ( 1 2 ) 2.433(6)  C ( 2 ) C ( 3 ) 1.41(1)  C(12) C ( l 3) 1.348(9)  W ( 1 ) C ( 1 6 ) 2.217(6)  C(2) C(7) 1.49(1)  C(13) C ( l 4) 1.49(1)  S i ( l ) C ( 1 6 ) 1.858(7)  C ( 3 ) C ( 4 ) 1.40(1)  C(13) C ( 1 5 ) 1.49(1)  Table A 6 Bond Angles (°) in the Solid-State Molecular Structure Determined for 2.2 C ( l ) 141.3(2)  C(5) W ( l ) C ( l 1)85.4(2)  C ( 4 ) C ( 3 ) C(8) 124.9(9)  C(2) 107.0(3)  C(5)W(1)  C ( I 2 ) 110.3(2)  W ( 1 ) C ( 4 ) C(3) 71.4(4)  C(3) 88.4(2)  C(5) W ( l ) C(16) 115.2(2)  W ( 1 ) C ( 4 ) C(5) 76.8(4)  C(4) 106.1(3)  C ( U ) W ( l ) C ( l 2) 36.4(2)  W ( 1 ) C ( 4 ) C(9) 125.6(5)  C(5) 140.4(2)  C ( l l ) W ( l ) C(16) 129.2(2)  C(3) C(4) C(5) 107.8(6)  C ( l 1)92.1(3)  C(12) W ( l ) C ( 16) 93.7(2)  C ( 3 ) C ( 4 ) C(9) 126.8(8)  C(12) 89.0(2)  C ( 1 6 ) S i ( l ) C(17) 108.9(3)  C ( 5 ) C ( 4 ) C(9) 124.6(8)  C(16) 96.7(2)  C ( 1 6 ) S i ( l ) C ( I 8 ) 109.7(4)  W ( 1 ) C ( 5 ) C ( l ) 73.6(4)  C(2) 34.5(2)  C ( 1 6 ) S i ( l ) C(19) 115.7(3)  W ( 1 ) C ( 5 ) C ( 4 ) 68.8(4)  C(3) 57.2(2)  C ( 1 7 ) S i ( l ) C ( I 8 ) 108.2(5)  W(1)C(5)  C(4) 56.7(2)  C ( 1 7 ) S i ( l ) C(19) 106.6(3)  C ( 1 ) C ( 5 ) C(4) 108.3(6)  C(5) 33.0(2)  C(18) S i ( l ) C(19) 107.4(4)  C ( 1 ) C ( 5 ) C(10) 125.7(7)  C ( l l ) 116.2(2)  W ( l ) N ( l ) O ( l ) 170.7(5)  W(1)C(11)  C ( 12) 81.2(4)  C(12) 129.5(2)  W ( 1 ) C ( 1 ) C(2) 68.7(3)  W(1)C(11)  H ( 1 1 B ) 112(4)  C(16) 85.6(2)  W ( 1 ) C ( 1 ) C(5) 73.4(3)  W ( 1 ) C ( U ) H ( l I A ) 118(4)  C(3) 35.1(3)  W ( 1 ) C ( 1 ) C(6) 126.3(5)  C(12)C(11)  H ( 1 1 B ) 114(4)  C(4) 57.9(2)  C ( 2 ) C ( 1 ) C(5) 107.8(6)  C(12)C(11)  H ( l 1A) 120(4)  C(5) 56.6(2)  C ( 2 ) C ( 1 ) C ( 6 ) 124.3(7)  H ( l I B ) C ( l 1) H ( 1 1 A ) 109(6)  C ( l l ) 138.9(2)  C ( 5 ) C ( 1 ) C ( 6 ) 127.8(7)  W(1)C(12)  C ( l 1)62.4(3)  C(12) 164.0(2)  W(1)C(2)  W(1)C(12)  C ( 13) 94.6(4)  C(16) 85.2(2)  W ( 1 ) C ( 2 ) C ( 3 ) 71.2(4)  W(1)C(12)  H(12) 101(4)  C(4) 34.9(3)  W ( 1 ) C ( 2 ) C(7) 126.7(5)  C ( l 1 ) C ( 1 2 ) C ( 1 3 ) 124.9(7)  C(5) 57.1(2)  C ( 1 ) C ( 2 ) C(3) 107.8(6)  C ( l 1 ) C ( 1 2 ) H(12) 116(4)  C ( l l ) 113.0(3)  C ( 1 ) C ( 2 ) C(7) 125.2(8)  C(13)C(12)  H(12) 117(4)  C(12) 149.1(3)  C ( 3 ) C ( 2 ) C(7) 1.26.0(8)  C(12)C(13)  C ( 1 4 ) 125.6(7)  C(16) 117.2(3)  W ( 1 ) C ( 3 ) C(2) 73.7(4)  C(12)C(13)  C ( 1 5 ) 120.1(7)  C(5) 34.4(2)  W ( 1 ) C ( 3 ) C ( 4 ) 73.7(4)  C(14)C(13)  C ( l 1)82.1(3)  W ( 1 ) C ( 3 ) C ( 8 ) 121.6(5)  W(1)C(16)  C(12) 117.8(3)  C ( 2 ) C ( 3 ) C(4) 108.3(6)  C(16) 140.7(3)  C ( 2 ) C ( 3 ) C(8) 126.6(9)  C ( 1)76.8(4)  C(10) 130.2(5)  C ( 1 5 ) 113.5(7) S i ( l ) 118.3(3)  128 Table A 7 Bond Distances (A) in the Solid-State Molecular Structure Determined for 2.3 W(1)N(1) 1.753(4) W(1)C(1) 2.438(4) W(1)C(2) 2.390(4) W(1)C(3) 2.323(4) W(1)C(4) 2.324(5) W(1)C(5) 2.419(4) W(1)C(11)2.239(4) W(1)C(20) 2.187(5) W(1)C(21) 2.391(5) 0(1)N(1) 1.240(5) C(1)C(2) 1.439(6) C(1)C(5) 1.414(6) C(1)C(6) 1.497(7)  C(2) C(3) 1.413(7) C(2) C(7) 1.498(6) C(3) C(4) 1.427(6) C(3)C(8) 1.501(7) C(4) C(5) 1.441(6) C(4) C(9) 1.502(7) C(5) C(10) 1.501(6) C(11)C(I2) 1.493(6) C(11)H(16) 0.92(6) C(l 1) H(l 7) 0.96(5) C(12) C(13) 1.392(7) C(12) C(17) 1.402(7) C(13)C(I4) 1.393(7)  C(14) C(14) C(I5) C(16) C(16) C(20) C(20) C(20) C(21) C(21) C(22) C(22)  C(15) C(18) C(16) C(17) C(19) C(21) H(27) H(28) C(22) H(29) C(23) C(24)  1.399(8) 1.520(8) 1.375(8) 1.394(7) 1.508(8) 1.454(8) 0.95(6) 0.94(7) 1.365(6) 1.02(5) 1.491(7) 1.502(7)  Table A 8 Bond Angles (°) in the Solid-State Molecular Structure Determined for 2.3 N(l) W ( l ) C ( l ) 149.4(2) N(l) W ( l ) C(2) 1 16.1(2) N(1)W(1) C(3) 92.3(2) N(l) W ( l ) C(4) 102.8(2) N ( l ) W ( l ) C(5) 137.4(2) N(1)W(1) C ( l 1)93.6(2) N(1)W(1) C(20) 94.3(2) N(1)W(1) C(21) 108.4(2) C ( l ) W ( l ) C(2) 34.7(1) C ( l ) W ( l ) C(3) 58.0(2) C(1)W(1) C(4) 58.1(2) C(1)W(1) C(5) 33.9(2) C ( l ) W ( l ) C ( l l ) 109.6(2) C(1)W(1) C(20) 88.4(2) C(1)W(1) C(21)91.7(2) C(2)W(1) C(3) 34.9(2) C(2)W(1) C(4) 58.5(2) C(2)W(1) C(5) 57.2(1) C(2)W(1) C ( l l ) 141.2(2) C(2)W(1) C(20) 79.4(2) C(2)W(1) C(21) 102.7(2) C(3)W(1) C(4) 35.8(2) C(3) W ( l ) C(5) 58.3(2) C(3) W ( l ) C ( l l ) 127.5(2) C(3) W ( l ) C(20) 106.5(2) C(3) W ( l ) C(21) 136.7(2) C(4)W(1) C(5) 35.3(2) C(4) W ( l ) C ( l 1)92.4(2) C(4)W(1) C(20) 137.9(2) C(4) W ( l ) C(21) 148.5(2) C(5)W(1) C ( l 1)84.0(2) C(5)W(1) C(20) 121.7(2) C(5) W ( l ) C(2I) 114.0(2) C(11)W(1) C(20) 125.0(2)  C(11)W(1) C(21)89.7(2) C(20) W ( l ) C(21)36.7(2) W(1)N(1) O(l) 171.1(4) W(1)C(1) C(2) 70.9(2) W(1)C(1) C(5) 72.3(2) W(1)C(1) C(6) 124.9(3) C(2)C(1) C(5) 107.7(4) C(2)C(1) C(6) 127.3(4) C(5)C(I) C(6) 124.9(4) W(1)C(2) C ( l ) 74.5(2) W(1)C(2) C(3) 70.0(2) W(1)C(2) C(7) 128.6(3) C(1)C(2) C(3) 108.2(4) C(1)C(2) C(7) 125.3(4) C(3)C(2) C(7) 125.8(4) W(1)C(3) C(2) 75.2(3) W(1)C(3) C(4) 72.2(3) W(1)C(3) C(8) 123.6(3) C(2)C(3) C(4) 108.5(4) C(2)C(3) C(8) 126.6(4) C(4)C(3) C(8) 124.6(5) W(1)C(4) C(3) 72.1(3) W(1)C(4) C(5) 75.9(3) W(1)C(4) C(9) 128.2(3) C(3)C(4) C(5) 107.3(4) C(3)C(4) C(9) 124.3(4) C(5)C(4) C(9) 126.9(4) W(1)C(5) C ( l ) 73.8(3) W(1)C(5) C(4) 68.8(2) W(1)C(5) C(10) 128.4(3) C(1)C(5) C(4) 108.3(4) C(1).C(5) C(10) 124.6(4) C(4)C(5) C(10) 126.8(4) W(1)C(11) C(12) 120.5(3)  W(1)C(11) H(16) 111(3) H(I6)C(11) H(I7) 100(4) C(11)C(12) C(13) 121.5(4) C(11)C(12) C(17) 120.9(4) C(13)C(12) C(17) 117.5(4) C(12)C(13) C(14) 121.9(5) C(13)C(14) C(15) 118.7(5) C(13)C(14) C(18) 120.1(5) C(15)C(14) C(18) 121.3(5) C(14)C(15) C(16) 121.1(5) C(15)C(16) C(17) 119.2(5) C(15)C(16) C(19) 120.3(5) C(17)C(16) C(19) 120.5(5) C(12)C(17) C(16) 121.7(5) W(1)C(20) C(21)79.3(3) W(I)C(20) H(27) 114(4) W(I)C(20) H(28) 124(5) C(21)C(20) H(27) 110(4) C(21)C(20) H(28) 113(4) H(27)C(20) H(28) 112(5) W(1)C(21) C(20) 64.0(3) W(1)C(21) C(22) 100.5(3) W(I)C(21) H(29) 105(3) C(20)C(21) C(22) 125.5(5) C(20)C(21) H(29) 118(3) C(22)C(21) H(29) 116(3) C(2I)C(22) C(23) 120.8(5) C(2I)C(22) C(24) 123.5(4) C(23)C(22) C(24) 115.2(4) W(1)C(11) H(17) 102(3) C(12)C(11) H(16) 111(3) C(12)C(11) H(17) 109(3)  129 Table A 9 Bond Distances (A) in the Solid-State Molecular Structure Determined for 2.5 Wl Nl 1.762(5) WI Cl6 2.205(6) Wl CM 2.235(6) Wl C3 2.320(6) Wl C2 2.346(7) Wl C12 2.363(6) Wl C4 2.376(6) Wl Cl 2.435(6) Wl C5 2.456(6) Ol Nl 1.232(7) Cl C5 1.415(9) Cl C2 1.446(9)  Cl C6 1.504(9) C2 C3 1.431(9) C2 C7 1.496(9) C3 C4 1.423(9) C3 C8 1.502(9) C4 C5 1.439(9) C4 C9 1.497(9) C5 CIO 1.485(8) Cl 1 CI2 1.438(9) Cll HI 1A 0.979(7) Cll HI IB 0.980(8) C12 C13 1.371(9)  C12 H12 C13 C15 CI3 C14 C16 C17 C16C21 C17C18 C17C22 C18C19 C19 C20 C20C21 C20 C23  0.978(10) 1.499(9) 1.509(9) 1.411(9) 1.422(9) 1.406(9) 1.509(9) 1.381(9) 1.372(9) 1.401(8) 1.524(9)  Table A I 0 Bond Angles (°) in the Solid-State Molecular Structure Determined for 2.5 Nl Wl C16 98.3(2) Nl Wl C l l 89.1(2) C16 Wl C l l 130.9(2) Nl Wl C3 88.6(2) CI6 Wl C3 110.6(2) Cl 1 Wl C3 118.1(2) Nl Wl C2 100.5(2) C16 Wl C2 139.9(2) Cl 1 Wl C2 84.5(2) C3 Wl C2 35.7(2) Nl Wl C12 104.3(2) C16 Wl C12 95.6(2) Cl 1 Wl CI2 36.3(2) C3 Wl C12 149.0(2) C2 Wl C12 113.3(2) Nl Wl C4 112.4(2) C16 Wl C4 81.3(2) Cl 1 Wl C4 139.6(2) C3 Wl C4 35.3(2) C2 Wl C4 58.8(2) C12 Wl C4 143.2(2) Nl Wl Cl 135.4(2) C16 Wl Cl 119.8(2) Cl 1 Wl Cl 83.0(2) C3 Wl Cl 58.2(2) C2 Wl Cl 35.2(2) C12 Wl Cl 94.8(2) C4 Wl Cl 57.4(2) Nl Wl C5 145.4(2) C16 Wl C5 87.6(2) Cl I Wl C5 112.6(2) C3 Wl C5 57.8(2)  C2 Wl C5 57.8(2) C12 Wl C5 109.0(2) C4 Wl C5 34.6(2) Cl Wl C5 33.6(2) Ol Nl Wl 168.6(5) C5 Cl C2 108.4(6) C5 Cl C6 125.1(6) C2 Cl C6 126.3(6) C5 Cl Wl 74.0(4) C2 Cl Wl 69.1(3) C6C1 Wl 127.0(4) C3 C2 Cl 107.0(6) C3 C2C7 125.4(6) Cl C2 C7 127.4(6) C3 C2 Wl 71.1(3) Cl C2 Wl 75.8(4) C7 C2 Wl 123.0(4) C4C3C2 108.7(6) C4 C3 C8 126.6(6) C2 C3C8 124.5(6) C4C3 Wl 74.5(3) C2 C3 Wl 73.2(3) C8C3 Wl 122.1(4) C3C4C5 107.7(6) C3 C4 C9 125.9(6) C5 C4 C9 125.9(6) C3 C4 Wl 70.2(3) C5 C4 Wl 75.8(3) C9C4 Wl 126.1(4) Cl C5 C4 108.1(5) Cl C5 C10 125.4(6) C4C5 CIO 125.8(6)  Cl C5 Wl 72.4(3) C4 C5 Wl 69.7(3) C10C5 Wl 131.1(4) C12 Cl 1 Wl 76.7(4) C12C11 H11A 122(4) Wl C l l H11A 116(5) C12 C l l HUB 110(5) Wl Cl 1 HI IB 112(5) HI 1A Cl 1 HUB 114(6) C13C12C11 124.5(6) C13 C12 Wl 92.2(4) Cll C12 Wl 67.0(3) C13 C12 H12 118(4) Cl 1 C12 H12 117(4) Wl C12H12 106(4) C12 C13 C15 119.8(6) C12 C13 C14 124.6(6) C15 C13 C14 113.8(6) C17CI6C21 116.1(6) C17C16W1 126.3(4) C21 C16W1 117.3(4) CI8C17C16 119.8(6) C18C17C22 117.5(6) C16 C17C22 122.7(6) C19C18C17 122.1(6) C20C19C18 120.0(6) C19C20C21 118.7(6) C19C20C23 121.9(6) C2I C20C23 119.4(6) C20C21 C16 123.3(6)  130  Table A l l Bond Distances (A) in the Solid-State Molecular Structure Determined for 3.2 Wl Nl 1.761(4) Wl C21 2.219(5) Wl C l l 2.236(5) Wl C2 2.313(5) Wl C l 2.319(5) Wl Cl6 2.403(5) Wl C3 2.405(4) Wl C5 2.420(5) Wl C4 2.468(5) Ol Nl 1.220(5) Cl C5 1.419(7) Cl C2 1.423(7)  Cl C7 1.492(7) C2 C3 1.427(7) C2 C8 1.506(7) C3 C4 1.423(6) C3 C9 1.507(6) C4 C5 1.429(7) C4CI0 1.509(7) C5 C6 1.496(7) Cl 1 C12 1.500(6) Cl 1 H2 1.05(6) Cl I H3 0.92(6) C12 C13 1.342(7)  C12 HI 0.88(5) C13 C14 1.495(7) C13 C15 1.503(7) C16 C17 1.376(7) C16C21 1.438(7) C16C20 1.508(7) C17C18 1.500(7) C17C19 1.504(8) C21 H4 0.96(6) C21 H5 1.04(7)  Table A12 Bond Angles (°) in the Solid-State Molecular Structure Determined for 3.2 Nl Wl C21 92.7(2) Nl Wl Cl 1 89.7(2) C21 Wl C l l 129.54(19) Nl Wl C2 94.45(18) C21 Wl C2 135.0(2) Cl 1 Wl C2 94.88(18) Nl Wl C l 90.61(19) C2I Wl C l 99.89(19) Cl 1 Wl C l 130.49(18) C2 Wl C l 35.79(17) Nl Wl C16 86.86(18) C21 Wl C16 35.98(19) C l l Wl C16 94.05(18) C2 Wl C16 170.99(18) Cl Wl C16 135.40(18) Nl Wl C3 127.35(18) C21 Wl C3 130.7(2) Cl 1 Wl C3 83.32(18) C2 Wl C3 35.14(16) Cl Wl C3 58.20(17) C16 Wl C3 145.54(17) Nl Wl C5 119.59(19) C21 Wl C5 79.73(19) C l l Wl C5 139.49(18) C2 Wl C5 58.29(18) Cl Wl C5 34.77(17) C16 Wl C5 113.43(17) C3 Wl C5 57.03(17) Nl Wl C4 147.72(18) C2I Wl C4 96.78(19) C l l Wl C4 107.19(18) C2 Wl C4 57.68(17)  Cl Wl C4 57.40(17) C16 Wl C4 118.11(16) C3 Wl C4 33.93(15) C5 Wl C4 33.98(16) Ol Nl Wl 170.9(4) C5 Cl C2 108.5(4) C5 Cl C7 126.0(5) C2 C l C7 125.3(5) C5 Cl Wl 76.5(3) C2 Cl Wl 71.9(3) C7 Cl Wl 121.0(4) Cl C2 C3 107.5(4) C l C2 C8 125.0(5) C3 C2 C8 126.5(5) Cl C2 WI 72.3(3) C3 C2 Wl 75.9(3) C8C2 Wl 126.5(4) C4 C3 C2 108.3(4) C4 C3 C9 124.1(4) C2 C3 C9 126.9(5) C4C3 Wl 75.5(3) C2 C3 Wl 68.9(3) C9C3 Wl 128.8(4) C3 C4 C5 107.7(4) C3C4C10 124.8(4) C5 C4 C10 126.6(5) C3 C4 Wl 70.6(3) C5 C4 Wl 71.2(3) C10C4W1 131.8(4) Cl C5 C4 107.9(4) Cl C5 C6 124.5(5) C4 C5 C6 127.1(5)  Cl C5 Wl 68.7(3) C4 C5 Wl 74.9(3) C6 C5 Wl 128.3(3) C12C11 Wl 113.3(3) C12 Cl I H2 105(3) Wl Cl 1 H2 103(3) C12 Cl I H3 112(4) Wl Cl I H3 115(4) H2 Cl 1 H3 108(5) C13CI2C11 130.3(5) C13C12H1 116(3) Cl 1 C12 HI 114(3) C12 C13 C14 121.4(5) C12 C13 C15 124.1(4) C14C13C15 114.4(4) C17C16C21 119.9(5) C17C16C20 121.2(5) C21 C16C20 118.8(5) C17C16 Wl 86.5(3) C2I CI6 Wl 65.0(3) C20CI6W1 115.1(3) C16C17C18 124.3(5) C16C17CI9 121.7(5) C18C17C19 111.1(5) C16C21 Wl 79.0(3) C16C21 H4 125(4) W1 C21 H4 109(3) C16C21 H5 113(4) Wl C21 H5 112(3) H4 C21 H5 113(5)  131 Table A13 Bond Distances (A) in the Solid-State Molecular Structure Determined for 3.3 Wl NI 1.795(4) Wl C12 2.149(5) Wl C l l 2.205(4) Wl C4 2.339(5) Wl C3 2.356(5) Wl C5 2.365(5) Wl C2 2.405(4) Wl C l 2.416(4) Wl PI 2.4660(12) PI C18 1.826(5)  PI C16 1.826(5) PI C17 1.826(5) C6C1 1.509(6) C10C5 1.505(6) C9 C4 1.496(7) C5 C l 1.419(6) C5 C4 1.429(7) C14C13 1.517(7) C15 C13 1.502(7) NI OI 1.224(5)  Cl I C12 1.437(7) Cl I HI 0.91(5) Cl I H2 1.12(6) C13 C12 1.324(7) C7 C2 1.495(6) C2C1 1.412(6) C2 C3 1.442(6) C4 C3 1.438(7) C8C3 1.501(6)  Table A14 Bond Angles (°) in the Solid-State Molecular Structure Determined for 3.3 N l W l C12 108.62(18) NI W l C l l 90.99(18) C12 W l C l l 38.50(18) N l Wl C4 95.98(17) C12 Wl C4 142.06(17) C l l Wl C4 115.53(18) N l Wl C3 110.16(16) C12 Wl C3 140.97(17) Cl 1 Wl C3 143.42(18) C4 Wl C3 35.68(16) Nl Wl C5 116.03(17) C12 Wl C5 106.73(17) C l l Wl C5 85.31(18) C4 Wl C5 35.37(16) C3 Wl C5 58.84(16) Nl Wl C2 145.14(16) C12 Wl C2 105.72(16) C l l W l C2 120.35(17) C4 W l C2 58.42(16) C3 Wl C2 35.25(15) C5 Wl C2 57.67(16) Nl Wl C l 150.43(17) C12 Wl C l 89.19(16) Cl 1 W l C l 88.84(17) C4 Wl C l 57.98(16) C3 Wl C l 57.96(15) C5 W l C l 34.52(16) C2 Wl C l 34.05(15) N l Wl PI 80.87(13)  C12 Wl PI 85.84(13) C l l W l PI 117.14(14) C4 Wl PI 127.27(12) C3 Wl PI 96.04(12) C5 Wl PI 152.70(12) C2 Wl PI 95.94(11) Cl W l PI 124.97(12) C18P1 C16 101.5(3) C18PI C17 99.5(3) C16P1 C17 102.9(3) CI8P1 Wl 110.4(2) C16P1 W l 113.90(17) C17 PI W l 125.32(18) Cl C5 C4 108.1(4) Cl C5 C10 126.1(4) C4 C5 C10 125.0(5) C l C5 W l 74.7(3) C4 C5 Wl 71.3(3) C10C5 W l 127.9(3) 01 Nl Wl 175.0(4) C12 C l 1 W l 68.6(3) C12C11 HI 122(3) Wl C l 1 HI 120(3) C12 C l 1 H2 120(3) Wl C l l H2 112(3) HI C l l H2 109(4) C12 CI3 C15 124.3(5) C12 C13 C14 121.8(5) CI5 C13 C14 113.9(5)  Cl C2 C3 108.3(4) C l C2C7 125.6(4) C3 C2 C7 125.7(4) Cl C2 Wl 73.4(3) C3 C2 Wl 70.5(3) C7C2 W l 127.8(3) C5 C4C3 107.9(4) C5 C4 C9 126.2(5) C3 C4 C9 125.7(4) C5 C4 Wl 73.3(3) C3 C4 Wl 72.8(3) C9C4W1 123.1(4) C13C12C1I 134.0(5) C13C12W1 149.2(4) Cl 1 C12 Wl 72.9(3) C2 C l C5 108.7(4) C2 C l C6 125.1(4) C5 C l C6 126.1(4) C2 C l W l 72.5(3) C5 C l W l 70.8(3) C6C1 W l 125.4(3) C4 C3 C2 107.0(4) C4 C3C8 125.7(4) C2 C3 C8 126.7(4) C4 C3 Wl 71.5(3) C2C3 Wl 74.2(2) C8C3W1 126.4(3)  APPENDIX B Kinetic Data and Statistical Analysis Consulting Report  Table A15 Kinetic Data: Integral of Npt CMe3 signal vs internal standard signal 1  H NMR spectrum (C^D^) showing decomposition of 1.1  Time (s)  Integral  Ln (I(t)/I(0))  0  1.257862  0  312  1.176471  -0.06689  612  1.111111  -0.12405  912  1.010101  -0.21936  1212  0.943396  -0.28768  1512  0.884956  -0.35163  1812  0.813008  -0.43643  2112  0.775194  -0.48406  2412  0.714286  -0.56589  3012  0.628931  -0.69315  3612  0.534759  -0.85535  4212  0.480769  -0.96178  4812  0.421941  -1.0923  5412  0.363636  -1.24101  6012  0.314465  -1.38629  7212  0.245098  -1.63551  8412  0.194932  -1.86452  9612  0.151057  -2.11951  10812  0.112233  -2.41659  12012  0.088183  -2.65775  13212  0.069204  -2.90011  15012  0.049652  -3.23212  134  Significance Testing of Carbon-Hydrogen Bond in an Organometallic Complex Natalie Thompson STAT 551 PROJECT, 2002  1 Introduction  The following describes a method to determine the hydrogen loss in an organometallic complex; and it describes how to determine the relative proportion of times the loss comes from the central allyl instead of from the allyl Me's.  The dimethylallyl ligand (allyl) is combined with benzene (CeHe) as the control group. And then the dimethylallyl ligand is combined with deuterated benzene (CeD^). Deuterium (D) is essentially the same as hydrogen (H) but it is not detected by N M R Spectroscopy. As such, the benzene and d-benzene (deuterated benzene) will undergo the same reactions with the allyl, but when CeD6 combines with the allyl instead of a CeH  6  hydrogen the 6 D molecules will be undetected.  The benzene or deuterated benzene bond to either the central allyl or the allyl Me by dropping one of their hydrogen or deuterium molecules, respectively. This loss will herein be referred to as the hydrogen loss. The presence of a single hydrogen loss would indicate a particular molecular structure as the outcome of the reaction with benzene. The total loss of greater than one hydrogen atom would imply a more complicated outcome.  135 There were five repetitions of each of the two reactions. The hydrogen mass was recorded at four locations of the molecular structure. These are labeled central allyl H, term allyl H , allyl Me 1, and allyl Me 2. Both allyl Me's are structurally indiscernible from each and are thus combined as one outcome. And the term allyl H is used to calibrate the N M R Spectroscopy (NMRS).  In the control group, the number of hydrogen molecules is known. The deuterium group will reveal where and how many hydrogen molecules originated from the benzene. The questions addressed in this paper are the following: •  How to test the hypothesis that only one hydrogen is replaced by benzene in the reaction.  •  How to determine the relative frequency of times the hydrogen loss occurs at the central allyl instead of from one of the two allyl Me's.  2 Analysis  The number of hydrogen atoms is known for the control group. As such, due to the relative error in the N M R S rescale the results for the five repetitions so that the average of the trials is equal to the known expected hydrogen mass.  For the central allyl obtain the average before scaling. Since the expected mass for this group is one, this average is the also the scale for this group. Divide the mass for each  136 trial for the central allyl by this scale. The average of the scaled masses will be 1. Use this scale for the deuterium trials for the central allyl group. Obtain the average for this group.  For the M e l group the known expected mass is 3. Obtain the average of the masses for the trial for the un-scaled readings. Divide the average mass by 3 to obtain the scale factor. Then divide the mass for each trial for the Me Group by this scale factor. The average of the scaled masses will be 3. Apply this scale factor to each of the trials for Me 1 for the deuterium trials as well.  Follow the same scaling procedure for Me 2 as was carried out for Me 1, in the last paragraph.  Sum the central, Me 1 and Me 2 mass for each of the ten trials, label them x j to X5 for c  C  the control group and xid to xsa for the deuterium group. Compare the means of the two groups with a paired t-test using the following estimates for the expected values and the standard deviations. (I = [Z , (x )]+5 5  i=  c  \ii=  [E  5 i =  ic  i  (x )]+5 id  G = [ Z i(x -u. ) 5  c  i=  lc  c  2  •4] 1/2  Cd- [ E i=i(x -|!d) •4] 1/2 5  id  137 The standard deviation for the difference of the means 5= jic-M-d is: — r~ 2 , _ 2 l/2 n  a - [a  c  + Od ] .  A confidence interval for the overall hydrogen loss is: 5 ± U,aJ2 * O.  Under the assumption that only one hydrogen molecule is lost, the following describes a method to determine the relative frequency of hydrogen molecules lost from the central allyl instead of from either the Me 1 or Me 2 locations.  Take the average of the scaled masses for the central allyl for the control group and the deuterium group. Label these, n and ITd respectively. Let the difference of the two be c  m = ric-rid.  This is the proportion of times the hydrogen is lost from the central allyl. In order to obtain a confidence interval for this proportion, use the following as an estimate for standard deviation: x = [x +Xd ]' , where x and Xd are the standard deviations for n and rid respectively. x 2  2  /2  c  c  c  c  and Xd are obtained using a similar equation used to calculate o , replacing the xi with the c  c  individual masses for each trial at the central allyl, and using the appropriate mean.  A confidence interval for the proportion of times the hydrogen loss occurs at the central allyl is: 03 ± U,oJ2 * T.  138  3. Discussion  It is easiest to calculate the standard deviation for the net hydrogen mass loss, 8, by first combining the masses for the central, Me 1 and Me 2 since it avoids the cumbersome and possibly impossible calculation of the correlation between the masses of different locations on the same molecule.  The proportion of times the hydrogen loss occurs at the central allyl can be obtained directly without rescaling since it was shown that only one hydrogen loss occurred in the reaction. If more or less hydrogen was lost, the loss from the central allyl would need to be divided by this amount, to get the proportion.  1 139 Table A16  Deuterium incorporation ' H NMR integral data: Control Cp*W(NO)(C H )(Ti -l,l-Me2C3H3) (2.1) 3  6  5  Central allyl H  Allyl Mel  Allyl Me2  Terminal allyl H  1.0700  3.0431  3.7851  1.0000  0.9922  2.9677  3.6561  1.0000  1.0539  2.9566  3.6249  1.00.00  1.0201  2.9819  3.6763  1.0000  1.0049  2.9386  3.5610  1.0000  Table A17  Deuterium incorporation ' H NMR integral data: Experimental Cp*W(NO)(C D )(Ti -l,l-Me -allyl-rf ) (2A-d ) 3  6  5  2  1  6  Central allyl H  Allyl Mel  Allyl Me2  Terminal allyl H  0.3600  2.6633  3.5217  1.0000  0.3679  2.6743  3.4541  1.0000  0.3508  2.5945  3.6116  1.0000  0.3581  2.6096  3.4118  1.0000  0.3589  2.6140  3.5607  1.0000  

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