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Hafnium complexes stabilized by a macrocyclic ligand Corkin, James R. 2000

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Hafnium Complexes Stabilized by a Macrocyclic Ligand by  James R. Corkin B.Sc. (Hon.), University of British Columbia, 1997  A thesis submitted in partial fulfillment of the requirement for the degree of  MASTER 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 April 2000 © James R. Corkin, 2000  UBC  Special Collections - Thesis Authorisation Form  Page 1 of 1  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 o f t h e requirements f o r an advanced degree a t t h e U n i v e r s i t y o f B r i t i s h Columbia, I agree t h a t t h e 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 study. 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 o f 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 t h e head o f my department o r by h i s o r h e r 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 copying o r p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l gain 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 o f  C  \)9> Vfi \ S  The U n i v e r s i t y o f B r i t i s h Columbia Vancouver, Canada Date  Rpr.l 1 7 / a O O Q  http://www.library.ubc.ca/spcoll/thesauth.html  4/11/00  ii  ABSTRACT The goal of this thesis is to investigate the chemistry of hafnium complexes of the macrocyclic ligand, PhP(CHSiMe2NSiMe2CH2)2PPh ([P N ]). The hafnium dichloride, 2  2  2  [P2N2]HfCl2 (1) is used as a starting material for all other compounds synthesized. 1 is isostructural with its zirconium analogue, [P N ]ZrCl , but does not exhibit identical 2  2  2  chemistry. While reaction of [P2N ]ZrCl with 2 equivalents of CgK under N resulted in 2  2  2  formation of a zirconium dinitrogen compound, the same is not true for the hafnium analogue. Instead, the major product of the reaction of 1 with 2 equivalents of C«K is a hafnium dimer, {[P N ]Hf}2 (2). 2  [P N2]HfI 2  2  (3) is synthesized  2  via the reaction  of 1 with  excess  trimethylsilyliodide. Evidence will be presented that ([P N ]Hf)2(u.- r| :ri -N2) (4) is the 2  2  2  2  major product of the reaction between 3 and 2 equivalents of CgK under dinitrogen, while {[P2N]Hf}2 (2) and [P N2]Hf(C H ) (5) appear to be minor products. 2  2  7  8  Reaction of 1 with 2 equivalents of MeMgCl results in the formation of  [P2N2]HfMe2 (6). The zirconium analogue of 6 reacts with toluene under an atmosphere of Ff to give [P2N ]Zr(CvH8), but this is not true for 6. Instead, reaction of 6 under H2 2  2  results in the formation of a hafnium tetrahydride, {[P2N2]Hf}2(n-H)4 (7). A  metathesis  reaction of one equivalent of 1 with one equivalent of  Mg(C4H )(THF) results in formation of [P2N ]Hf(C4H ) (8). Unlike most mononuclear 6  2  2  6  [P2N2] compounds, this compound exhibits 2 inequivalent phosphorus atoms evidenced by an A B doublet pattern in the ^Pj !!} N M R spectrum. 1  TABLE OF CONTENTS ABSTRACT  ii  TABLE OF CONTENTS  iii  LIST O F T A B L E S  vi  LIST O F F I G U R E S  vii  LIST O F A B B R E V I A T I O N S  ix  ACKNOWLEDGEMENTS  xiii  DEDICATION  xiv  CHAPTER 1  G E N E R A L INTRODUCTION  1.1  Comparison of Hafnium and Zirconium  1  1.2  Introduction to Dinitrogen  5  1.3  Nitrogen Fixation  7  1.4  Transition Metal Dinitrogen Complexes  9  1.5  Ligands and Dinitrogen Complexes from the Fryzuk Group  13  1.6  The Scope of this Thesis  19  1.7  References  20  CHAPTER 2  TOWARDS A NEW HAFNIUM DINITROGEN C O M P L E X  2.1  Introduction to [P2N2] Zirconium Complexes  2.2  Synthesis and Characterization of [P N ]HfCl2(l)  26  2.3  Preliminary Attempts to Form a Hafnium Dinitrogen Complex .  31  2.4  Synthesis and Characterization of [P N ]Hfl2 (3)  36  2  2  2  2  25  iv 2.5  Synthesis and N M R Characterization of  38  {[P N ]Hf} ((a-Ti :Ti -N ) (4) 2  2  2  2  2  2  2.6  Further Characterization of {[P N ]Hf} (|a-ri :ri -N ) (4)  2.7  Preliminary Reactivity Studies on {[P N ]Hf} (uvn :r| -N ) (4).  45  2.8  Summary  47  2.9  References  48  CHAPTER 3  2  2  2  2  2  2  43  2  2  2  2  2  2  ORGANOMETALLIC AND HYDRIDE COMPLEXES OF HAFNIUM  3.1  Transition Metal Hydrides  3.2  Synthesis and Characterization of [P N ]HfMe (6)  54  3.3  Attempted Synthesis of [P N ]Hf(C H ) (5)  57  3.4  Synthesis and Characterization of {[P N ]Hf} (>H)4 (7)  59  3.5  Synthesis and Characterization of [P N ]Hf(C4H ) (8)  61  3.6  Summary  63  3.7  References  64  CHAPTER 4  50 2  2  2  7  2  2  8  2  2  2  2  2  6  EXPERIMENTAL PROCEDURES  4.1  General Procedures  66  4.2  Reagents and Starting Materials  66  4.3  Analytical Methods  67  4.4  Hydrazine Analysis  67  V  4.5  4.6  Synthesis of New Compounds  68  4.5.1  [P N ]HfCl2 (1)  68  4.5.2  {[P N ]Hf} (2)  69  4.5.3  [P N ]HfI (3)  70  4.5.4  {[P N ]Hf} (p.-n :ri -N ) (4)  70  4.5.5  [P N ]HfMe (6)  71  4.5.6  {[P N ]Hf} {u-H } (7)  71  4.5.7  [P N ]Hf(C H ) (8)  72  2  2  2  2  2  2  2  2  2  2  2  2  2  2  2  2  2  2  2  2  2  2  4  4  6  References  73  FUTURE PROSPECTS  74  APPENDIX A.1  X-ray Crystallographic Analysis of [P N ]HfCl (1)  76  A.2  X-ray Crystallographic Analysis of [P N ]HfMe (6)  80  2  2  2  2  2  2  vi  LIST OF T A B L E S  Table 1.1  Properties of Hafnium and Zirconium which  2  Differ Significantly Table 1.2  Reduction Potentials for Zirconium/Hafnium Analogues  4  Table 1.3  Summary of the Differences in Chemical Properties between Nitrogen and Phosphorus  13  Table 2.1  A Comparison of Selected Bond Lengths (A) and Angles (deg) in [P N ]MC1 M=Zr, H f  29  2  Table 2.2  2  2  The results of a study of the reaction of [P N ]HfCl (1) with 2 equivalents of CgK under 1 atm N in toluene  33  The results of a study of the reaction of [P N ]HfI (3) with 2 equivalents of CsK under 1 atm N in toluene  38  The results of a study of the reaction of [P N ]HJI (3) with 2 equivalents of CgK under 4 atm N in toluene  41  2  2  2  2  Table 2.3  2  2  2  2  Table 2.4  2  2  2  2  Table 3.1  Selected Bond Lengths (A) and Angles (deg) in [P N ]HfMe (6). 57 2  2  2  vii  LIST OF FIGURES  Figure 1.1  The only crystallographically characterized hafnium(III) metallocene compound.  4  Figure 1.2  A representation of the molecular orbitals of dinitrogen and their relative energies.  6  Figure 1.3  The structural model of the FeMo cofactor site determined by single crystal X-ray crystallography.  9  Figure 1.4  The binding modes of dinitrogen in mononuclear and dinuclear transition metal compounds.  10  Figure 1.5  The only known hafnium dinitrogen complex, {Cp* Hf(N )} (it-'n :ri -N ).  11  Three weakly activated dinitrogen complexes  12  1  2  Figure 1.6  2  1  2  2  with type D bonding (mononuclear side-on). Figure 1.7  A pictorial representation of [N(SiMe CH PR ) ]" ([PNP])  14  Figure 1.8  The route to formation of ([PNP]ZrCl) (n -r| :'n -N )  15  Figure 1.9  A n orbital interaction diagram for the bonding molecular orbitals of side-on and edge-on bridging of the dinitrogen ligand between two ML4 fragments.  16  Figure 1.10  The route to formation of [P N ]Li (l,4-dioxane)  18  Figure 2.1  Some of the reactions of [P N ]ZrCl which have relevance to this thesis.  25  Figure 2.2  A n ORTEP diagram of [P N ]HfCl (1) showing the solid  28  1  2  2  2  2  2  2  2  2  2  2  2  2  2  2  2  2  2  2  state molecular structure. Figure 2.3  The H and ^ P ^ H } N M R spectra of [P N ]HfCl (1)  29  Figure 2.4  The process by which equilibration of [P N ] silyl methyls is believed to take place. The ' H and ^ P ^ H ) N M R spectra of {[P N ]Hf} (2)  30  Figure 2.5  ]  2  2  2  2  2  2  2  2  32  viii  Figure 2.6  The P { ' H } N M R spectrum of [P N ]HfCl (1) + 2 CgK under 1 atm N after 25 hours.  33  Figure 2.7  The H and " P l / H } N M R spectra of [P N ]HfI (3)  37  Figure 2.8  The ^ P ^ H } N M R spectrum of the reaction between [P N ]HfI (3) and 2 equivalents of CgK under 1 atm N after 25 hours.  39  The P { ' H } N M R spectrum of the reaction between [P N ]Hfl (3) and 2 equivalents of C K under 4 atm N after 8 days.  40  31  2  2  2  2  J  2  2  2  2  2  2  2  Figure 2.9  31  2  2  2  8  2  Figure 2.10  The silyl methyl region of the ' H N M R spectrum for the products from the reaction of 3 with 2 equivalents of CgK in toluene for 8 days.  41  Figure 2.11  The phenyl region of H N M R spectrum for the products from the reaction of 3 with 2 equivalents of CgK in toluene for 8 Days.  42  Figure 2.12  Selected E.I. Mass Spectrometry data for ([P N ]Hf) N  Figure 2.13  Theoretical isotope distribution pattern for E.I. Mass Spectrometry analysis of ([P N ]Hf) N as determined by Isotope Pattern Calculator™ v. 1.6.6.  44  Figure 2.14  The ^ and P { ' H } N M R spectra for the reaction shown in Equation 2.5.  46  Figure 3.1  Useful organic functional groups derived  51  !  2  2  2  2  2  2  44  2  2  31  from acylzirconium compounds. Figure 3.2  The H and P { H } N M R spectra of [P N ]HfMe (6).  Figure 3.3  A n ORTEP Diagram showing the solid state molecular structure of [P N ]HfMe (6). The ' H and P { ' H } N M R spectra for the attempted synthesis of [P N ]Hf(C Hg).  l  31  2  2  Figure 3.4  55  1  2  2  2  56  2  58  3I  2  2  7  Figure 3.5  The P { H } and HNMR  4  61  Figure 3.6  The H and P { ' H } N M R spectra of [P N ]Hf(C4H ) (8)  63  31  l  1  l  spectra for {[P N ]Hf} (^-H) (7). ... 2  2  2  31  2  2  6  LIST OF A B B R E V I A T I O N S  H  proton  'H{ P}  observe proton while decoupling phosphorus  H or D  deuterium  P{ H}  observe phosphorus while decoupling proton  31  31  1  A  angstrom, 10" m 10  A45  8  absorbance at 458 nm wavelength of light  Anal.  analysis  atm  atmosphere  AU  atomic units  br.  broad  Bz  benzyl group, (-CH C6H )  Calcd.  calculated  cis  cisoidal  cat.  catalyst  2  5  cm"  wave number  Cp  cyclopentadienyl group, [C5H5]"  Cp  penta(methyl)cyclopentadienyl group, [CsMes]  d  doublet  deg  degrees  DME  1,2-dimethoxyethane, (CHsO^CyHU  d"  number of d electrons  dd  doublet of doublets coupling pattern  1  E.I.  electron impact  Enz.  enzyme  eq.  equivalent(s)  etc.  etcetera  fac  facial  g  grams  HOMO  highest occupied molecular orbital  Hz  Hertz, seconds"  I  nuclear spin quantum number, or iodine  IR  infrared  J -B  n-bond coupling constant between A and B atoms  K  degrees Kelvin  kJ  kiloJoule  LUMO  lowest unoccupied molecular orbital  M  central metal atom, or molar  m  multiplet  n  A  M  +  1  parent ion  Me  methyl group, - C H  mg  milligram(s)  MHz  megaHertz  mL  millilitre  mm  millimetre  mmol  millimole  3  m-Ph  meta-hydrogen in phenyl ring  MO  molecular orbital  m  spin orientation quantum number  s  OEPG  octaethylporphyrinogen  NMR  nuclear magnetic resonance  [PNP]  [N(SiMe CH PR2)2] "  [P N ]  [PhP(CH SiMe NSiMe CH2)2PPh] "  o-Ph  ortho-hydrogen in phenyl ring  Ph  phenyl group, -C6H5  P-Ph  phenyl group of [P2N2] phosphine  /?-Ph  para-hydrogen in phenyl ring  ppm  parts per million  'Pr  isopropyl group  R  alkyl substituent  RT  room temperature  S  total spin quantum number  s  singlet or seconds  t  triplet  trans  transoidal  THF  tetrahydrofuran,  w 1/2  base width at half height  5  chemical shift, or a molecular orbital with 2 nodal pi  2  r|  x  2  1  2  2  2  2  x = hapticity  2  2  C4H8O  [i-X  bridging X-ligand  71  molecular orbital with 1 nodal plane  %  percent  %T  percent transmittance  o  molecular orbital with no nodal planes  °  degrees  °C  degrees Celsius  xiii  ACKNOWLEDGEMENTS  First, I must thank my supervisor, Dr. Mike Fryzuk. His guidance and support have been invaluable, particularly his editing of this thesis.  His patience during the  writing of this thesis has been nothing short of remarkable. To all of the members of the Fryzuk lab in general, thanks for the memories and forbearance. To Mike Shaver, for bringing laughter to the lab, to Mike Petrella, for his support, on the court and off, to Bruce McKay, for help with the hydrazine analysis and the use of his desk, to Lara Morello, for letting me deluge her with questions before her comprehensive, to Chris Kozak and Fran Kerton, for their help and general knowledge of chemistry, to Chris Carmichael, for letting me kick him off the PC so much, and especially to Sam Johnson, for answering my many questions with many more questions. I greatly appreciate the help of the U B C Department of Chemistry support staff, in particular Dr. Brian Patrick (X-ray crystallography), Brian Ditchburn (glassblowing), Peter Borda (elemental analysis), Marietta Austria and Liane Darge (NMR spectroscopy). Thanks also to all the people in stores for being so helpful when I was in desperate search of chemicals and equipment. Finally, a very special thanks to Teresa Jackson for always being there.  xiv  To my parents  1  CHAPTER 1 INTRODUCTION  1.1  Comparison of Hafnium and Zirconium  The chemistry of hafnium is extremely similar to that of zirconium, more so than that of any other pair of elements. 1> The primary reason for this parallelism is the effect 2  known as the lanthanide contraction, which accounts for the similarity in size between second and third row transition metals and can be rationalized as follows. There are four common types of orbitals: s,p,d, and f.  Of these, f orbitals are the most diffuse and  therefore the least penetrating. For this reason, f electrons do not shield valence electrons effectively in comparison with electrons in other orbitals.^  Therefore, the valence  electrons of elements with f electrons are held more closely to the nucleus. However, this f electron effect is not sufficient by itself to explain the lanthanide contraction, somewhere between 10 and 30% of the effect can be contributed to relativistic effects,^ which will be discussed below. The effects of the lanthanide contraction are observed most strongly when comparing zirconium to hafnium. The result is that the radii of hafnium ions and atoms are nearly identical to those of zirconium. The M  4 +  ionic radius is 0.74 A for zirconium  versus 0.75 A for hafnium. The covalent radius is estimated at 1.45 A for zirconium versus 1.44 A for hafnium J  Nearly every organometallic compound of hafnium for  which X-ray crystal data are available is isostructural with its zirconium analogue, with  Chapter 1 References begin on page 20  2  metal-ligand distances approximately 0.01 A to 0.02 A shorter for hafnium. ^  It should  be noted that hafnium-ligand bonds are generally 5 to 10% stronger than their zirconium counterparts irrespective of the nature of the ligandA? jhe slightly smaller covalent radius may play a small part in this increased bond strength but it certainly does not completely account for it. In truth, the reason for this is not well understood, but the empirical evidence is unassailable. Only three bulk properties of these two metals are significantly different: density, neutron-absorbing abilities, and transition temperatures such as melting point and boiling point.^ These are summarized in Table 1.1. None of these three properties appears to have an effect on the reactivity of these two metals and are included only for completeness and to emphasize the similarity between hafnium and zirconium.  Table 1.1  Properties of Hafnium and Zirconium which Differ Significantly  Density  Neutron  (gem" )  Absorptivity  Zirconium  6.51  Hafnium  13.28  3  Melting Point (°C)  Boiling Point (°C)  Very Low  1857  4200  600x higher  2222  4450  One notable exception to the chemical similarity between hafnium and zirconium is their reduction potentials. Interestingly, it is this difference in reduction potential that allows zirconium to be separated from hafnium. 8,9  Chapter 1 References begin on page 20  A n explanation for this difference  3  arises from an examination of the previously mentioned relativistic effects. For electrons in atoms or molecules, the velocity of the electron, v, will increase with increasing atomic number, Z. Thus, relativistic effects are more noticeable for heavier elements.  As v  increases, the relativistic rest mass of the electron, m, will increase and the relativistic average radius for s and p electrons will decrease. This results in a relativistic contraction of s and p orbitals. Since d and f orbitals are not as penetrating as s and p orbitals they will not be contracted. In fact, d and f orbitals will expand due to increased screening by the contracted s and p orbitals. ^  In addition, d and f orbitals are energetically  destabilized due to this indirect effect. 1 M 2 In the case of zirconium/hafnium, the larger atomic number for hafnium leads to more contracted s and p shells and more diffuse and destabilized f and d orbitals. The contraction of the s and p shells explains the relativistic contribution to the lanthanide contraction mentioned earlier.  The relativistic destabilization of the d orbitals on  hafnium provides a theoretical explanation for the difficulty in reducing hafnium compared with zirconium. This destabilization discourages electron addition and thus makes reduction of hafnium more arduous. 13, 14 Due to the paucity of even partially, characterized hafnium(III) compounds, 7, 15 comparison of reduction potentials with zirconium is difficult.  a  However, Table 2.1  shows those compounds for which the reduction potentials of both a zirconium and hafnium analogue have been measured.  The important fact to note is the increase in  reduction potential in going from zirconium to hafnium, supporting the supposition that hafnium is more difficult to reduce than zirconium.  Chapter 1 References begin on page 20  4  Table 1.2  Reduction Potentials for Zirconium/Hafnium Analogues  Complex or Reaction  M  4  ^  +  Reduction Potential (V)  M  MCl {r| -C5H3(SiMe3)2}2 5  2  MC1 " 2  6  a  Reference  4  Hafnium  Zirconium  -1.70  -1.55  16  -1.87  -1.55  17  -3.1  -2.53  13  Reduction potentials are measured versus the saturated calomel electrode  Another aspect of hafnium chemistry that demonstrates the difficulty in reducing hafnium(IV) is the almost complete lack of stable hafnium(III) compounds.  Unlike  titanium, for which an oxidation state of +3 is fairly common, zirconium(III) chemistry is comparatively rare hafnium(III)  5  and hafnium(III) chemistry is virtually non-existent.  metallocene,  characterized.^ A literature  shown in Figure  1.1,  has  search did not reveal the  Only one  been crystallographically existence  of any  other  crystallographically characterized hafnium(III) compounds.  Me3C Me C 3  ^" X  H  f  M63  _ , CMe  Figure 1.1  ?  The only crystallographically characterized hafnium(III) compound.  Chapter 1 References begin on page 20  metallocene  5  For a variety of reasons, the chemistry of hafnium is not considered very fashionable, at least in comparison with that of zirconium. 18 Besides the similarity of hafnium to zirconium, obtaining highly pure hafnium starting materials can be arduous because of the difficulty in separating it from zirconium. 15  In addition, despite the  incredible similarity between the two elements, many of the practical applications of zirconium chemistry are less efficient when extended to hafnium chemistry.  For  example while certain zirconocenes have been shown to be fairly active polymerization catalysts, 19-21  n  o  highly active hafnium polymerization catalyst is yet known. As a  result of these factors, the chemistry of hafnium is much less studied than that of zirconium.  1.2  I n t r o d u c t i o n to D i n i t r o g e n  A major portion of this thesis deals with the activation of dinitrogen. As such, some background material is presented below. Dinitrogen comprises 78 percent of our atmosphere;  22  however, unlike other small molecules such as C O 2 , O2, etc., which play  an important role in metabolism, N2 does not. This seems surprising at first, because one would anticipate that such a ubiquitous and simple molecule would serve some function in such a complex lifeform as a human being. Furthermore, although N2 is isoelectronic with carbon monoxide, its reactivity is nowhere near as extensive as that of CO.  A  discussion of the bonding scheme of the N2 molecule may shed some light on this situation. Figure 1.2 shows the molecular orbital scheme of dinitrogen, as derived from  Chapter 1 References begin on page 20  6  Description  Schematic  o  17i antibonding g  N  N  Degenerate pair in  Energy  Number of Electrons  -7 eV  xy and xz planes  O  (LUMO)  NCZ^N  3<j weakly bonding (HOMO) g  l 7 r bonding Degenerate pair in xy and xz planes  -15.58 eV  g  N  ON  N  N(  2a  u  antibonding  2a bonding g  Figure 1.2  -17.1 eV  -18.7 eV  -35.5 eV (Estimated)  A representation of the molecular orbitals of dinitrogen and their relative energies.  photoelectron spectra^,24 d m  theoretical calculations.25,26  j h e are two aspects of e r  this molecular orbital diagram that are worthy of discussion. First, the H O M O - L U M O gap of N is very large (0.6 eV larger than that of carbon monoxide). Second, the H O M O 2  energy is comparatively very low, meaning the large gap is at precisely the energy range  Chapter 1 References begin on page 20  7 in which other molecules have frontier orbitals available for chemical reactions.27 These two features help to explain why dinitrogen is so unreactive compared with carbon monoxide. Of course, the lack of a dipole moment also contributes to N ' s rather inert 2  nature.  1.3  Nitrogen Fixation  Despite its apparent inertness, nitrogen is an essential element in biological systems.  It is present in many reduced forms in the molecules that form the building  blocks of life: amino acids, nucleotides, etc. The abundance of nitrogen in the earth's solid crust is only 0.002% by mass.28 At one time, the only source of fixated nitrogen was from these scarce minerals (e.g. saltpeter (KNO3), and Chile saltpeter (NaNOa)) or from living sources. When land is extensively cultivated, fixed nitrogen is removed at a rate greater than that at which it can be naturally replenished. This requires that nitrogencontaining compounds be added to the soil as fertilizers, the most common of which is ammonia. In industry, the system discovered by Haber and made industrially feasible by Bosch dominates the nitrogen fixation landscape. The Haber process converts mixtures of dihydrogen and dinitrogen to ammonia using a heterogeneous iron catalyst and is shown in Equation 1.1.29  FG est N (g) + 3 H (g) 2  •  2  > 450 °C > 270 atm.  Chapter 1 References begin on page 20  2 NH (g) 3  1.1  8  The ammonia produced may then be used as a fertilizer or converted into other nitrogen containing compounds, which may be used in explosives, plastics, fibers and industrial chemicals. Unfortunately, this process requires a large amount of energy to produce the high temperatures and pressures necessary. Recently, a ruthenium on graphite catalyst has been developed which allows for slightly milder conditions (70-105 atm, 350-470 °C), but this has not yet seen widespread use and is still under development.30 Nature, though, has no problems whatsoever fixing dinitrogen under ambient temperature and pressure.  There are many bacteria that fix dinitrogen using enzymes  known as nitrogenases.29 The commonly accepted reaction is shown in Equation 1.2.  N + 8H + 8e~+16MgATP 2  +  E  " " Z  » 2NH + H + 16MgADP + 16HP0 " 3  2  4  1.2  2  It has long been known that the active site of many nitrogenase enzymes contains the transition metals iron and molybdenum. Recently, single-crystal X-ray analyses for FeMo proteins of Clostridium pasteurianum^^^  and Azotobacter vinelandii^'^  2  have  produced a model which contains cuboidal Fe S3 and Fe3MoS3 units bridged by three 4  sulfides as shown in Figure 1.3. While it is still not clear exactly how dinitrogen binds to this site, the six central Fe atoms are coordinatively unsaturated, possibly providing an N  2  coordination site. Also, nitrogenases have been discovered which contain vanadium-* 6,37 or iron atoms-^ in place of molybdenum. These discoveries indicate that many different transition metals may facilitate nitrogen fixation.  Chapter 1 References begin on page 20  9  OOCCH  STT—Fe^ —S(Cys)—Fe^-  ; Fe'  S-—Fe^  Figure 1.3  1.4  Fe—;S -S-  "Fe  /  2  C—CH CH COO" / 2  2  s—Mo-—0C0  ^Fe—-s  N(His)  The structural model of the FeMo cofactor site determined by single crystal X-ray crystallography.  Transition Metal Dinitrogen Complexes  For some time now, the creation of a catalytic nitrogen fixation cycle that takes place near room temperature and at low pressures has been considered one of the "holy grails" of chemistry. The presence of transition metals in nitrogenase and their use as catalysts in the Haber process have naturally led to an investigation of transition metal dinitrogen complexes. Allen and Senoff reported the first major breakthrough in this field in 1965 when they published their now famous paper-* 8 wherein they detailed the formation of [Ru(NH3)sN2]X2 where X = Br", I", BF4" and PF ". This compound is 6  mononuclear and the bonding of dinitrogen is end-on, which is by far the most common mode of bonding in dinitrogen compounds.27,39,40 Figure 1.4 details the possible modes of coordination in transition metal dinitrogen compounds.  Type A bonding is most often seen in 18-electron complexes  with strong field ligands such as phosphines.27,39,40 Their N - N bond distances appear to be almost universally the same, around 1.12 A, no matter the nature of the metal or co-  Chapter I References begin on page 20  10  ligands, while free N has an N - N bond distance of 1.0975 A . > > 27  39  40  2  Thus, the  dinitrogen ligand in the majority of these complexes is considered to be weakly activated. Crystallographically characterized complexes of type B have yet to been found. Such a binding mode has been proposed to occur as an intermediate in the end to end rotation of an r[ -N l  ligand in a rhenium complex, (n -C Me )Re(CO) (N2). 5  2  5  5  41  2  The zirconium  complex [Cp2Zr(CHSiMe3)(N2)] was suggested to contain an n - N ligand on the basis 2  2  of EPR and IR data,  2  4  2  but details are still uncertain.  As well, an excited state of an  osmium complex has been very recently shown to exhibit type B bonding using the photocrystallographic technique where a complex is excited while mounted on a diffractometer  4 3  N M N Side-on Mononuclear (B)  End-on Mononuclear (A)  N M  N^=N  M  M  M, N  End-on Dinuclear (C)  Side-on Dinuclear (D)  X  M N  v  .M  End-on Side-on Dinuclear (E)  Figure 1.4  The binding modes of dinitrogen in mononuclear and dinuclear transition metal compounds.  Chapter 1 References begin on page 20  11  Type C is also fairly common and observed in transition metal dinitrogen metal complexes that span the periodic table.27,3 9  j  n  e  o n  i  v  k  hafnium dinitrogen  n o w n  complex^ exhibits both type C and type A bonding. The route to the formation of this complex is shown in Figure 1.5. Cp*  Cp*  \/  2Cp* Hfl 2  Na/K, N  N  2  2  DME (-41 ° C )  N  %  III  N  \ V \ I  Hf  /\  Cp* F i g u r e 1.5  Cp*  The only known hafnium dinitrogen complex, {Cp 2Hf(N2)}2(|-i-  Although no molecular structure has been determined, the complex is believed to be isostructural with the zirconium analogue for which a molecular structure has been determined employing single crystal X-ray crystallography.45,46 Very careful control of reaction conditions was necessary to isolate any hafnium dinitrogen compound.  Only  when sodium/potassium alloy was used as the reducing agent, dimethoxyethane as the solvent and a hafnium iodide as the starting material, did the researchers isolate appreciable amounts of the dinitrogen compound. Attempts to prepare this compound using other reducing agents, solvents, and hafnium halides often resulted in a change of solution color to the appropriate color but it was not possible to isolate any dinitrogen complex in appreciable quantity. In contrast, the zirconium analogue was produced from Cp^ZrCb, not Cp*2ZrI , choice of solvent and reducing agent did not prove to be vital, 2  Chapter 1 References begin on page 20  12  and yields of the zirconium dinitrogen compound were higher. The zirconium analogue has a bridging N with an N - N bond distance of 1.182(5) A and terminal N ' s with N - N 2  2  bond distances of 1.116(8) A and 1.114(7) A, indicating a low level of activation of the dinitrogen ligands.45,46  Presumably, this also holds true for the hafnium dinitrogen  compound. Examples of type D dinitrogen bonding are rare in comparison with types A and C.  A nickel-lithium complex, [{(C H5Li)3Ni} N -2(C H ) 0] , has been isolated in 6  2  2  2  5  2  2  which the dinitrogen molecule is bound side-on with an unusually long N - N bond length of 1.35 A.47 As well, two samarium complexes,48,49  a n c  j  a  u r a  n i u m complex^ have  been reported to exhibit this mode of bonding and are shown in Figure 1.6. (THF) Li(OEPG) 2  F i g u r e 1.6  Cp*  Cp*  R  R  Three dinitrogen complexes with type D bonding.  In contrast to the nickel-lithium compound and the samarium complex on the left of Figure 1.6, the N - N bond length in the latter two complexes is comparable with free dinitrogen (1.09 A). Examples of type D bonding from this laboratory will be discussed below. A tantalum complex, {[NPN]TaH} N ([NPN] = PhP(CH SiMe NPh) ), which 2  2  2  2  2  exhibits the very rare type E bonding^ has recently been synthesized in the Fryzuk lab. 1  Chapter 1 References begin on page 20  13  1.5  Ligands and Dinitrogen Complexes from the Fryzuk Group  Ligands with a nitrogen donor atom are well known, as are ligands with a phosphorus donor atom. However, despite sharing the same group in the periodic table, nitrogen and phosphorus are certainly not identical in their chemical behaviour. Some differences between the chemistries of nitrogen and phosphorus are summarized in Table 1.3  Table 1.3 .  Summary of the Differences in Chemical Properties between Nitrogen and Phosphorus ^ 5  Nitrogen  Phosphorus  Very strong pn-pn bonds  Weak pn-pn bonds  Example: N  Example: P 4  2  pn-dn bonding is rare  Weak to moderate but important d7c-p7r and d%-d% bonding  No valence expansion  Valence expansion  Example: N F  Example: P F  3  5  It is the second property listed in Table 1.3 that has the most importance when considering ligands of each element.  The inability of nitrogen to act as an electron  density acceptor makes nitrogen ligands more suitable for electropositive transition metals and high oxidation states. Phosphorus ligands, on the other hand, are more suited to late metals and low oxidation states where electron density is available for backbonding. A particularly useful aspect of phosphine donors in ligands is the ability to 31  utilize  P N M R spectroscopy; the phosphorus-31 nucleus (1=1/2) is 100% abundant and  Chapter I References begin on page 20  14  possesses reasonable sensitivity (6.6% that of 'H) for spectroscopic study.53 Chemical shift values span a wide range (>600 ppm) and thus provide general information regarding coordination of a phosphine to a metal center. Spin coupling to other nuclei is quite sensitive to the stereochemistry of a complex and may supply a more detailed analysis of the coordination sphere. 'Hybrid' ligands have been designed which combine phosphine and amide donors. Thefirstsuch ligand created in the Fryzuk lab was named [PNP] and is shown in Figure 1.7.  Me  RP  Me  2  M  2  2  PR  2  R = Me, Ph, Pr , Bu* 1  F i g u r e 1.7  A pictorial representation of [N(SiMe CH PR2)2]" ([PNP]). 1  2  2  As an anionic, formal six-electron donor, the [PNP] ligand is somewhat comparable to the isoelectronic Cp ligand.  Due to the presence of both amide and  phosphine donors in one chelating array, [PNP] forms complexes with both early and late transition metals. 54-60  As  w e  \ ^ j j possible to change the chemical properties of the t  s  ligand by altering the substituents on the phosphines.^l Of particular interest to this thesis is the formation of ([PNP]ZrCl)2(u-r| :r| -N2) 2  from a zirconium(IV) trichloride starting material as shown in Figure 1.8.62  Chapter 1 References begin on page 20  2  15  Me  F i g u r e 1.8  2  The route to formation of ([PNP]ZrCl) (u^r| :r| -N2). 2  2  2  The N - N bond distance of 1.548(7) A in this complex is the longest discovered to date and is much longer than that observed for the N - N single bond of hydrazine, 1.46 A. This side-on bridging mode can be rationalized using qualitative molecular orbital arguments as presented in the literature^ and briefly summarized below. Different M O schemes can be generated for end-on and side-on bridging modes of the N ligand 2  between two M L 4 fragments. Three d orbitals on each metal (dxy,d z and d ) which point X  yz  between the ligands on each of the M L 4 fragments and the N unit are available for n or 5 2  bonding.63 in the case of end-on bridging, two % molecular orbitals are generated. In the side-on case, one % orbital and one 8 orbital are generated. illustrated in Figure 1.9.  Chapter 1 References begin on page 20  These two cases are  16  End-on Bonding  F i g u r e 1.9  Side-on Bonding  A n orbital interaction diagram for the bonding molecular orbitals of sideon and edge-on bridging of the dinitrogen ligand between two M L fragments. 4  In general, end-on bridging is a more favourable coordination mode because § orbitals are intrinsically less stabilized than % orbitals. The reason for this is that overlap for 5 orbitals should be less than that for n orbitals in analogy to metal-metal quadruple bond arguments.64 So the question arises, why does side-on bridging arise at all? In the case of ([PNP]ZrCl)2(n-ri :r| -N2), it is believed that the amide donor is held by the 2  2  phosphine ligands in such a conformation that it overlaps with the appropriate d orbital to form a % bond. This prevents that particular metal d orbital from n bonding with the N unit, thus forcing the side on bridging conformation. 62  Interestingly, i f one of the  chlorides in the starting material is replaced with a Cp ligand, the bonding mode of dinitrogen changes to end-on and the bond length decreases to 1.301(3) A. It appears that  Chapter 1 References begin on page 20  2  17  this is due to % overlap between the Cp ligand and the d orbital that would be used for 8 overlap with the N2 unit. Clearly, the choice of ancillary ligands plays an important role in determining the availability of certain orbitals which, in turn, determines which bonding mode is lower in energy.  Attempts have been made to form a [PNP] hafnium  dinitrogen complex in a similar manner but they were unsuccessful. While [PNP] has proven to be an extremely versatile ligand, and much fascinating chemistry has been reported,54-58,60,65  o  n  e m a  j  o r  'pitfall' proved to be the dissociation  of the phosphine donors from the metal. This dissociation of the phosphine donors led to uncontrolled reactivity, particularly for the early transition metals.56,61 j circumvent  this  problem,  an  [PhP(CHSiMe2NSiMe2CH2)2PPh]" ([P N ]) 2  2  2  2  anionic was designed  na  n  attempt to  macrocyclic using  lithium  ligand, as a  template.66 The synthesis of [P2N2] is shown in Figure 1.10 in a form slightly modified from that presented in the literature. The amide ligands will form strong bonds with the early transition metals and the macrocylic ligand design holds the phosphines more firmly in place than the previous chelating ligand, [PNP]. As well, conversion from a chelating ligand to a macrocyclic ligand allows for further stabilization of complexes due to the macrocyclic effect. 67  Chapter 1 References begin on page 20  18  2 LiPHPh Me /Si^  Me Si  2  Me Si.  Et 0  2  r  2  O C 0  CI  CI  -2LiCI  Me  2  Ph-PH  N H  2  ^ HP—Ph  4 "BuLi CI  k  H Si Me  -N. 2  .  CI  Et 0  J  0°C  2  Si Me  - 4 BuH n  2  -2LiCI  Me SL S'-  2  N  Ph—PSi Me  Me .Si  2  f 2  R-Ph Si Me  0  Me .Si  <-x> 2  R-Ph  Ph—P-  N  Si 2  Me Si  2  S  Si  Me,  Men  S=Et Q 2  Figure 1.10  The route to formation of [P2N2]Li2(l,4-dioxane).  The [ P N ] ligand has been used in the preparation of many metal complexes.68-75 J^Q 2  2  most relevant metal complexes for this thesis are those of zirconium, which will be discussed in the following chapter.  Chapter 1 References begin on page 20  19  1.6  The Scope of this Thesis  The objective of this thesis is to explore the chemistry that arises when the [P2N2] macrocyclic ligand is bound to the group 4 metal, hafnium.  As detailed in the  introduction to each of the following two chapters, the incorporation of [P2N2] onto zirconium led to some novel and intriguing chemistry. Due to the similarity between zirconium and hafnium it was hoped that much of this zirconium chemistry might be duplicated or perhaps expanded upon with hafnium. The work presented in Chapter 2 focuses on the synthesis and characterization of a new hafnium dinitrogen complex. Likely due to the difficulty in reducing hafnium, in comparison with zirconium, this synthesis was not as straightforward as originally hoped. The molecular structure of [P2N2]HfCl2 is also presented.  Further investigation into  organometallic hafnium complexes has been explored and is discussed in Chapter 3 along with a new hafnium hydride. Again, while some of the chemistry for hafnium is very similar to that of zirconium, there are appreciable differences in the synthetic routes to some of these complexes.  Chapter 1 References begin on page 20  20  1.6  References  1) Cotton, F. A . ; Wilkinson, G. Advanced Inorganic Chemistry; 5 ed.; John Wiley & Sons: New York, 1988, pp 778. 2) Ibid., pp 957. 3) Greenwood, N . N . ; Earnshaw, A. Chemistry of the Elements; 2 ed.; Reed Educational and Professional Publishing Ltd, 1997, pp 1232. 4) Laerdahl, J. K.; KFaegri, J. J. Chem. Phys. 1998, 109, 10806. 5) Cardin, D. J.; Lappert, M . F.; Raston, C. L . Chemistry of Organo-Zirconium and Hafnium Compounds; 1st ed.; Ellis Horwood Limited: West Sussex, 1986, pp 18. 6) Lappert, M . F.; Patil, D. S.; Pedley, J. B. J. Chem. Soc, Chem. Commun. 1975, 830. 7) Wayne, A . K . ; Bella, S. D.; Gulino, A.; Lanza, G.; Fragala, I. L . ; Stern, C. L.; Marks, T. J. J. Am. Chem. Soc. 1999, 121, 355. 8) Larsen, E. M . ; Moyer, J. W.; Gil-Arnao, F.; Camp, M . J. Inorg. Chem. 1974, 13, 574. 9) Katabua, M . ; Rolland, P.; Mamantov, G.; Hulett, L. Inorg. Chem. 1982, 21, 3569. 10) Banna, M.S.J. Chem. Educ. 1985, 62, 197. 1 l)Pyykko, P.; Desclaux, J. P. Acc. Chem. Res. 1979,12, 276. 12) Pitzer, K . S. Acc. Chem. Res. 1979,12, 271. 13) Heath, G. A.; Moock, K . A.; Sharp, D. W.; Yellowlees, L . J. J. Chem. Soc, Chem. Commun. 1985, 1503. 14) Pyykko, P. J. Chem. Educ. 1988, 88, 563. 15) Cardin, D. J.; Lappert, M . F.; Raston, C. L . Chemistry of Organo-Zirconium and Hafnium Compounds; 1 ed.; Ellis Horwood Limited: West Sussex, 1986, pp 24.  Chapter 1 References begin on page 20  21  16) Shriver, D. F.; Atkins, P.; Langford, C. Ff. Inorganic Chemistry, 2 ed.; W.H. Freeman and Company: New York, 1994. 17) Cardin, D. J.; Lappert, M . F.; Raston, C. L . Chemistry of Organo-Zirconium and Hafnium Compounds, 1 ed.; Ellis Horwood Limited: West Sussex, 1986, pp 270. 18) Ibid., pp 19. 19) Brintzinger, H . H . ; Fischer, D.; Mulhaupt, R.; Rieger, B.; Waymouth, R. M . Angew. Chem. Int. Ed. (English) 1995, 34, 1143. 20) Hoveyda, A. H.; Morken, J. P. Angew. Chem. Int. Ed. (English) 1996, 35, 1262. 21) Piers, W. E. Chem., Eur. J. 1998, 4, 13. 22) Petrucci, R. H . General Chemistry: Principles and Modern Applications; 5 ed.; Macmillan Publishing Company: New York, 1989, pp 188. 23) Al-Joboury, M . I.; May, D. P.; Turner, D. W. J. Am. Chem. Soc. 1965, 616. 24) Turner, D. W.; May, D. P. J. Chem. Phys. 1966, 45, 471. 25) Mulliken, R. S. Can. J. Chem. 1958, 36, 10. 26) Caulton, K . G.; Dekock, R. L.; Fenske, R. F. J. Am. Chem. Soc. 1970, 92, 515. 27) Sellman, D. Angew. Chem. Int. Ed. (English) 1974,13, 639. 28) Petrucci, R. H . General Chemistry: Principles and Modern Applications; 5 ed.; Macmillan Publishing Company: New York, 1989, pp 504. 29) Jennings, A. R. Catalytic Ammonia Synthesis: Fundamentals and Practices; Plenum Press, 1991; Vol. 1. 30) Chem. Eng. (New York) 1993, March 19. 31) Woo, J. K.; Woo, D.; Rees, D. C. Biochemistry 1993, 32, 7104.  Chapter 1 References begin on page 20  22  32) Chem, J.; Christiansen, J.; Campobasso, N . ; Bolin, J. T.; Tittsworth, R. C ; Hales, B. I ; Rehr, J. J.; Cramer, S. P. Angew. Chem. Int. Ed. (English) 1993, 32, 1592. 33) Chan, M . K.; Jongsun, K.; Rees, D. C. Science 1993, 260, 792. 34) Kim, J.; Rees, D. C. Nature 1992, 360, 553. 35) Kim, J.; Rees, D. C. Science 1992, 257, 1677. 36) Eady, R. R.; Leigh, G. J. J. Chem. Soc, Dalton. Trans. 1994, 2739. 37) Robson, R. L.; Eady, R. R.; Richardson, T. H.; Miller, R. W.; Hawkins, M . ; Postgate, J. R. Nature 1986, 322, 388. 38) Allen, A. D.; Senoff, C. V. J. Chem. Soc, Chem. Commun. 1965, 621. 39) Hidai, M . ; Yasushi, M . Chem. Rev. 1995, 95, 1115. 40) Chatt, J.; Dilworth, J. R.; Richards, R. L . Chem. Rev. 1978, 78, 589. 41) Cusanelli, A.; Sutton, D. J. Chem. Soc, Chem. Commun. 1989, 1719. 42) Jeffery, J.; Lappert, M . F.; Riley, P. I. J. Organomet. Chem. 1979, 181, 25. 43) Fomitchev, D. V.; Bagley, K. A.; Coppens, P. J. Am. Chem. Soc. 2000,122, 532 44) Roddick, D. M . ; Fryzuk, M . D.; Seidler, P. F.; Hillhouse, G. L.; Bercaw, J. E. Organometallics 1985, 4, 97. 45) Manriquez, J. M . ; Bercaw, J. E. J. Am. Chem. Soc. 1974, 96, 6229. 46) Manriquez, J. M . ; Sanner, R. D.; Marsh, R. E.; Bercaw, J. E. J. Am. Chem. Soc. 1976, 98, 8351. 47) Jonas, K. Angew. Chem. Int. Ed. (English) 1973,12, 997. 48) Evans, W: J.; Ulibarri, T. A.; Ziller, J. W. J. Am. Chem. Soc. 1988,110, 6877. 49) Jubb, J.; Gambarotta, S. J. J. Am. Chem. Soc. 1994,114, 4411. 50) Roussel, P.; Scott, P. J. Am. Chem. Soc. 1998, 120, 1070.  Chapter 1 References begin on page 20  23  51) Fryzuk, M . D.; Johnson, S. A.; Rettig, S. J. J. Am. Chem. Soc. 1998, 120, 11024. 52) Cotton, F. A.; Wilkinson, G. Advanced Inorganic Chemistry; 5 ed.; John Wiley & Sons: New York, 1988, pp 384. 53) Abraham, R. J.; Fisher, J.; Lotus, P. Introduction to NMR Spectroscopy; John Wiley & Sons: New York, 1988, pp 4. 54) Fryzuk, M . D.; Macneil, P. A . ; Rettig, S. J.; Secco, A . S.; Trotter, J. Organometallics 1982, 1, 918.  55) Fryzuk, M . D.; Rettig, S. J.; Westerhaus, A . ; Williams, H . D. Inorg. Chem. 1985, 24, 4316. 56) Fryzuk, M . D ; Carter, A.; Westerhaus, A. Inorg. Chem. 1985, 24, 642. 57) Fryzuk, M . D.; Joshi, K . Organometallics 1989, 8, 722. 58) Fryzuk, M . D.; Mylvaganam, M ; Zawarotko, M . J.; MacGillivray, L . R. J. Am. Chem. Soc. 1993, 115, 10360. 59) Fryzuk,  M . D.; Mylvaganam,  Organometallics  M . ; Zawarotko,  M . J.; MacGillivray, L . R.  1996, 15, 1134.  60) Fryzuk, M . D.; Leznoff, D. B.; Ma, S. F.; S.J.Rettig; V . G . Young, J. Organometallics 1998,77,2313. 61) Fryzuk, M . D.; Carter, A . Organometallics  1 9 9 2 , 1 1 , 469.  62) Fryzuk, M . D.; Haddad, T. S.; Murugesapilla, M . ; McConville, D. H . ; Rettig, S. J. J. Am. Chem. Soc. 1993,115, 2782.  63) Albright, T. A.; Burdett, J. K . ; Whangbo, M . H . Orbital Interactions in Chemistry; Wiley-Interscience: New York, 1985.  Chapter 1 References begin on page 20  24  64) Cotton, F. A.; Wilkinson, G. Advanced Inorganic Chemistry; 5 ed.; John Wiley & Sons: New York, 1988, pp 1087. 65) Fryzuk, M . D.; Mylvaganam, M . ; Zawarotko, M . J.; MacGillivray,  L. R.  Organometallics 1996, 15, 1134. 66) Fryzuk, M . D.; Love, J. B.; Rettig, S. J. J. Chem. Soc, Chem. Commun. 1996, 2783. 67) Cotton, F. A . ; Wilkinson, G. Advanced Inorganic Chemistry; 5 ed.; John Wiley & Sons: New York, 1988, pp 47. 68) Bowdridge, M . R. Niobium Phosphine Macrocyclic Complexes; U B C : Vancouver, 1998, pp 80. 69) Fryzuk, M . D.; Love, J. B.; Rettig, S. J.; Young, V . G. Science 1997, 275, 1445. 70) Fryzuk, M . D.; Love, J. B.; Rettig, S. J. J. Am. Chem. Soc. 1997,119, 9071. 71) Fryzuk, M . D.; Giesbrecht, G. R.; Rettig, S. J. Inorg. Chem. 1998, 37, 6928. 72) Fryzuk, M . D.; Love, J. B.; Rettig, S. J. Organometallics 1998,17, 846. 73) Fryzuk, M . D.; Johnson, S. A.; Rettig, S. J. Organometallics 1999, 18, 4059. 74) Jafarpour, L . New Ligands: Design and Coordination Chemistry with the Transition Metals andLanthanides; U B C : Vancouver, 1999. 75) Leznoff, D. B. Paramagnetic Organometallic Complexes; U B C : Vancouver, 1997, pp 318.  Chapter 1 References begin on page 20  25  CHAPTER 2 TOWARDS A NEW HAFNIUM DINITROGEN COMPLEX  2.1  Introduction to [P2N2] Zirconium Complexes  The inspiration for the hafnium chemistry which appears in this thesis arose from some very interesting reactions of [P N ]ZrCl2 (A). As such a brief discussion of this 2  2  zirconium chemistry is in order. A series of reactions arising from [P N ]ZrCl is shown 2  2  2  in Figure 2.1.  C  Figure 2.1  Some of the reactions of [P N ]ZrCl which have relevance to this thesis.  Chapter 2 References begin on page 48  2  2  2  26  Previous work from the Fryzuk lab has shown that reduction of [P2N2]ZrCl2 (A) under N2 results in the formation of a dinuclear zirconium dinitrogen complex, {[P N ]Zr} (u-n :r| -N ) (B). Similar to the [PNP] complex shown in Figure 1.8, this 2  2  2  2  1  2  2  complex, also contains dinitrogen coordinated in a side-on mode.  The X-ray crystal  structure of this compound indicated an N - N bond length of 1.43 A . Also shown in Figure 2.1 is an unprecedented reaction whereby the dinitrogen complex reacts with H to 2  form {[P N ]Zr} (u-Ti -N2HXu-Fl) (C), which has an N - H bond and a bridging hydride. 2  2  2  1  2  Moreover, under an argon atmosphere, reduction of A yields the zirconium dimer, {[P2N2]Zr} (D).2 The phenyl groups coordinated to zirconium in this compound are 2  'activated', that is, they the metal center has donated electron density to the phenyl rings and they have lost their aromaticity. Evidence of this is supplied both in the X-ray crystal structure and in the H N M R spectrum. !  The goal of this chapter is to detail attempts to extend the chemistry shown in Figure 2.1 by altering the metal center from zirconium to hafnium. The first step towards completion of this goal was to synthesize the hafnium analogue of A.  2.2  Synthesis and Characterization of [P N ]HfCl2 2  2  Reaction of the TFIF adduct of hafnium(I V) tetrachloride with one equivalent of [P N ]Li (l,4-dioxane) resulted in the formation of [P N2]HfCl (1). 2  2  2  2  2  The optimum  conditions for this reaction occurred when a suspension of starting materials was refluxed in toluene overnight at approximately 120 °C. This resulted in isolation of diamagnetic 1, as a white solid, in excellent yields; this is shown below in Equation 2.1. The reaction  Chapter 2 References begin on page 48  27  also takes place in THF at room temperature but the yields are lower. Whether this is due to the lower temperature or the change in solvent is uncertain.  .1  [P N ]HfCl2 (1) 2  Complex  1 was characterized by  J  H and  microanalysis and X-ray crystal structure analysis.  3I  2  P{ H} 1  N M R spectroscopy,  Crystals of 1 suitable for X-ray  diffraction were grown from a saturated D M E solution. A n ORTEP diagram of 1 is shown in Figure 2.2. The solid state molecular structure of 1 is best described as distorted octahedral. N(l), N(2), Cl(l) and Cl(2) can be described as forming a square plane with a combined equatorial angle of 360.1°.  P(l) and P(2) can then be described as adopting axial  positions with a P(l)-Hf(l)-P(2) angle of 153.76(3)° which is drawn back from the optimum 180° due to the constraints of the macrocyclic ligand framework. The small  Chapter 2 References begin on page 48  28  cavity size of the [P2N2] ligand forces the metal to sit atop the ligand, which places the two chlorides cis to each other.  Si(3)  F i g u r e 2.2  A n ORTEP diagram of [P2N2]F£fCl2 (1) showing the solid state molecular structure. The silyl methyl groups have been omitted; only the ipso carbons of the phosphorus phenyl groups are shown.  The [P2N2] framework is distorted, adopting a C2 twist in the solid state. This feature has been observed in many [P2N] and [PNP] c o m p l e x e s . T h e solid state 3  2  structure of 1 is nearly identical to that of its zirconium analogue, [P N ]ZrCl2 (A), and 2  2  Table 2.1 below shows a comparison of selected bond lengths and angles for the two compounds. As with the zirconium analogue, the Hf-N, -P and -CI bond lengths are not unusual and compare with those of other Group 4 amido and phosphine complexes.4>9-12  Chapter 2 References begin on page 48  29  Table 2.1  A Comparison of Selected Bond Lengths (A) and Angles (deg) in [P N ]MC1 M=Zr, H f 2  2  2  M=Hf  M=Zr  2.136(4) N(l)-M(l)-N(2)  96.6(1)  96.8(2)  2.134(3)  2.125(4) P(l)-M(l)-P(2)  153.76(3)  152.52(6)  M(l)-P(l)  2.684(1)  2.694(2) C1(1)-M(1)-C1(2)  83.32(4)  82.57(7)  M(l)-P(2)  2.673(1)  2.707(2) N(1)-M(1)-C1(2)  90.88(9)  89.5(1)  M(1)-C1(1)  2.461(1)  2.455(2) N(2)-M(1)-C1(1)  89.22(9)  91.3(1)  M(1)-C1(2)  2.461(1)  2.448(2)  Bond Lengths  M=Hf  M=Zr  M(l)-N(l)  2.125(3)  M(l)-N(2)  Bond Angles  P{ H} 1  —i—i—i—i—i—i—i—i—i—i i i 8.0  Figure 2.3  7.6  (ppm)  7.2  iiiiii  i  2.0  1.0 (ppm)  0.0  The H and P{ ri} N M R spectra of [P N ]HfCl (1). The two regions of the ^ N M R spectrum are not shown on the same scale. l  3l  l  Chapter 2 References begin on page 48  2  2  2  30  As part of an ongoing theme of this thesis, a comparison with the zirconium analogue of this compound is in order. Figure 2.3 shows the *H and P { ' H } N M R 31  spectra of [P N ]HfCl 2  2  2  (1).  The  31  P { H } N M R spectrum of 1 shows a singlet 1  resonancewhich is shifted 8.5 ppm downfield from that of the zirconium analogue. The ' H N M R spectrum is virtually identical to that of the zirconium analogue with slight displacements of each characteristic signal. The solid state molecular structure of 1 does not appear to hold in solution. The solution structure is more compatible with a C  2 v  symmetry. Only 2 resonances due to silyl methyl protons are observed reflecting the "top and bottom" asymmetry of 1. If the C symmetry of the solid state held in solution, one 2  would expect to observe 4 silyl methyl resonances. It seems, therefore, that the [P N ] 2  2  framework is quite flexible in solution and undergoes a "rocking" motion centered at the trigonal silyl amide groups as shown in Figure 2.4. CI ci 1  Figure 2.4  -  The process by which equilibration of [P N ] silyl methyls is believed to take place. Silyl methyl groups are omitted for clarity.  Chapter 2 References begin on page 48  2  2  31  2.3  P r e l i m i n a r y A t t e m p t s to F o r m a H a f n i u m D i n i t r o g e n C o m p l e x  Despite the knowledge that reduction of hafnium is not as easy as reduction of zirconium, it was still believed that attempting to synthesize a hafnium dinitrogen complex would be a worthy endeavor. The first attempt followed a procedure identical to the one that formed the zirconium dinitrogen complex, involving reduction of the starting chloride complex with 2 equivalents of potassium graphite 1 but the results were not as expected. Instead of the desired dinitrogen complex, the major product, as indicated by 31  P { ' H } N M R spectroscopy, was a hafnium dimer, {[P N ]Hf} (2), with coordination of 2  2  2  the activated phenyl rings on one phosphorus to the other metal atom as shown in Equation 2.2.  CI c i  V  Hf  P  C K 8  4 atm N  2  8 Days Toluene  2.2  Silyl methyl groups omitted for clarity  2  Chapter 2 References begin on page 48  32  shown in Figure 2.1, this compound also has a zirconium analogue,  As  {[P N ]Zr} (D), which is the major product when [P N ]ZrCl (A) is reduced with CgK 2  2  2  2  2  2  in the absence of N , for example under Ar or vacuum.2. Complex D was first noticed as 2  an impurity in the reaction that produces {[P N ]Zr} (u.-ri -N ) (B). For the zirconium 2  2  2  2  2  system, under N , the dimer was a fairly minor impurity. Unfortunately, when the metal 2  center is changed to hafnium, the dimer appears to be the major product of this reaction, at least under these conditions. Figure 2.5 shows the *H and P { H } N M R spectra of 31  1  {[P N ]Hf} (2). 2  2  2  r~si^N- "n Si  s i  ± - s.. U sSi  P  7  N-Si-J {[P N ]Hf} (2) 2  31  p {  1 j  2  2  1  H  SiMe  H  2  C D H 6  L^JJ (ppm) F i g u r e 2.5  Activated  Ph  5  0  (ppm)  31  2  A timed reaction of [P N ]HfJCl 2  2  4  i i r  The U and P { ' H } N M R spectra of {[P N ]Hf} l  Ring CH AAxV  -i—i—i—i—i  10  15  5  2  2  2  2  (2).  (1) with 2 equivalents of CgK under 1  atmosphere of nitrogen was undertaken in order to carefully monitor the reaction by 31  P { H } N M R spectroscopy. The results are shown below in Table 2.2 and Figure 2.6 ]  indicates the signals listed in Table 2.2.  Chapter 2 References begin on page 48  33  Table 2.2  The results of a study of the reaction of [PN2]HfCl2 (1) with 2 equivalents of CgK under 1 atm N in toluene 2  2  Others  Compound  [P N ]HfCl2 (1)  {[P N2]Hf} (2)  P Shift (ppm)  -5.8 (s)  11.7(m), 1.9(m)  8.6 (s)  -8.2 (s)  % after 1 Hour"  89%  8.5%  1.8%  0.0%  4 Hours  52%  38%  6.8%  1.6%  8 Hours  20%  63%  12%  3.3%  25 Hours  0%  80%  16%  3.3%  4 Days  0%  80%  17%  2.9%  31  2  2  2  2  a  Spin system appears to be A A ' B B ' . Percentages of each compound determined from integration of their P { H } N M R signals. a  b  31  1  P{ H}  31  1  {[P N ]Hf}2(2) 2  2  [P N ]HfCI (1) 2  2  2  Postulated [P N ]Hf(C H ) (5) 2  2  7  8  Postulated {[P N ]Hf} (n-Ti :r, -N2) (4) 2  "i—  1  r  ~ l — I — I  6  10  ~i—1—i—1 2  2  2  2  2  r  (ppm) Figure 2.6 The P { H } N M R spectrum of [P N ]HfCl2 (1) + 2 CgK under 1 atm N after 25 hours. * indicates unknown. 31  1  2  Chapter 2 References begin on page 48  2  2  34  While this experiment was not particularly enlightening, there are two features that are worthy of discussion. First, the reaction that produces the dimer, 2, is much faster than initially anticipated, appearing to be complete after only 25 hours. Secondly, the signals at 8.6 ppm and -8.2 ppm are intriguing.  From a comparison with the  chemical shifts in analogous zirconium compounds, it can be speculated that the signal at 8.6 ppm is due to a toluene complex, 5, while the signal at -8.2 ppm is due to a dinitrogen complex. The formation of the toluene complex, 5, is interesting because once again, as with the dimer, much more is formed for hafnium than is observed for zirconium in the analogous reaction. In the case of zirconium, formation of the toluene complex in this reaction is practically negligible.  In fact, characterization of the  zirconium toluene complex came from a completely different [P2N2]ZrMe2,  reaction between  hydrogen and toluene,^ which will be described in greater detail in Chapter  3 While the signal assigned to the dinitrogen complex is very small, it is an encouraging sign, as it indicates that modification of this procedure may provide a route to {[P N ]Hf}2(n-ri :r| -N ) (4). Equation 2.3 summarizes the compounds that appear to 2  2  2  2  2  have formed at the end of this reaction as determined from P{ H} N M R spectroscopy. 31  1  One disappointing aspect of this experiment was the color of the solution produced. While the majority of zirconium dinitrogen complexes exhibit an intense deep blue or blue-green color in solution, the solution in this case was a dark brown which matches the color of {[P N ]Zr} (D) not { ^ ^ Z r H u - r i ' . - n - ^ ) (B). 2  2  2  2  As these reaction conditions proved to be unsuccessful in forming any appreciable quantity of the desired hafnium dinitrogen compound, the first modification to the  Chapter 2 References begin on page 48  35  CI  CI  V Hf  l\ Si  N^-Si-—I 1  Silyl methyl g r o u p s omitted for clarity  2C K 1 atm N 8  2  4 Days Toluene  Hf  Hf-  /\  N  2.3 N  \ /  U s i N-si—I  N-Si-ft  L_ >N^siJ S  2  4  80 %  3.3 %  -Hf^  U r -sU s  N  5  16 %  synthetic plan was to change the reducing agent. Sodium-potassium alloy (Na/K) was used to prepare the only known hafnium dinitrogen compound, and so Na/K was the logical alternative.  Unfortunately, using either toluene or D M E as solvents, an  intractable gray paste was formed from which no N M R data were interpretable and attempts to grow crystals were also unsuccessful.  Chapter 2 References begin on page 48  36  2.4  Synthesis and Characterization of [P N2]HfI (3) 2  As  previously described, the  (Cp*2Hf(N2)}2(u.-N2),  2  only known hafnium dinitrogen complex,  was prepared from a diiodide complex after attempts to use a  dichloride complex as a starting material were unsuccessful. Thus, it seemed reasonable to investigate the effects of a change in the precursor to be reduced.  Reaction of a  toluene solution of [ P 2 N ] H f C i 2 (1) with a slight excess of trimethylsilyliodide resulted in 2  formation of [P2N2]HfI (3) as shown in Equation 2.4. 2  In this case, there is no analogous zirconium compound with which to compare complex 3. Assuming an analogous structure for the diiodide as was found for the dichloride, one would expect little change in the N M R spectra upon replacement of chloride with iodide, and to a degree this is observed. The P { H } N M R signal is still a singlet resonance and 31  Chapter 2 References begin on page 48  1  37  the change in chemical shift from that of 2 is 0.4 ppm downfield.  In the ' H N M R  spectrum of the diiodide complex, the two silyl methyl signals are now separated by 0.3 ppm while for the dichloride complex the separation is less than 0.05 ppm. The P { H } 31  1  and H N M R spectra are shown below in Figure 2.7. !  31  P{ H} 1  I I  V J  —Si  I—S>'N [P N ]Hfl (3) 2  111111111111111111111111111111111  -5  -6  -7  2  2  -8  (ppm)  ]  SMe?  H m,p-Ph  o-Ph  C D H 6  5  Ring C H ^AM\  8.0  7.6  7.2  1.0  2.0  0.0  (ppm)  (ppm)  F i g u r e 2.7  2  AAAA\  The H and P { H ) N M R spectra of [P N ]Hfl2 (3). The two regions of the N M R spectrum are not shown on the same scale. X  31  1  2  2  To date, only a partially solved X-ray crystal structure is available for 3, as all crystals grown have exhibited twinning and refinement proved impossible. For this reason, an ORTEP diagram is unavailable; however, the X-ray crystal data available do show the  Chapter 2 References begin on page 48  38  connectivity of the molecule is that postulated from the ' H and P { H } N M R data and 3I  1  shown in Figure 2.7.  2.5  S y n t h e s i s a n d N M R C h a r a c t e r i z a t i o n o f { [ P N ] H f } 2 ( u - r | : r i - N 2 ) (4) 2  2  2  2  Reaction of [P N ]HfI (3) with 2 equivalents of CsK under 1 atmosphere of 2  2  2  dinitrogen produced a mixture of products and a solution with an intense blue color, a color characteristic of the {[P N2]Zr}((j,-ri :ri -N2) analogue. 2  These products, their  2  2  tentative  assignments,  and their percentages  as determined  by  31  P{'H} N M R  spectroscopy are summarized in Table 2.3.  T a b l e 2.3  The results of a study of the reaction of [P2N2]Fffl2 (3) with 2 equivalents of CgK under 1 atm N2 in toluene  [P N ]Hfl2  Compound  2  2  (3) 31  {[P2N ]Hf}  [P N ]Hf(C H )  {[P N2]Hf} (!a-N2)  (2)  (5)  (4)  2  2  2  2  7  8  2  2  8.6 (s)  -8.2 (s)  0%  0%  % after 1 Hour"  100%  11.7(m), 1.9(m) 0%  4 Hours  77%  9.2%  8.4%  5.7%  8 Hours  55%  21%  14%  9.4%  25 Hours  31%  26%  21%  20%  72 Hours  4.6%  33%  32%  29%  -5.4 (s)  P Shift (ppm)  a  Spin system appears to be A A ' B B ' . Percentages of each compound determined from integration of their P { H } N M R signals. a  31  1  Chapter 2 References begin on page 48  39  Figure 2.8 shows the P { H } N M R spectrum after 25 hours for the reaction of 31  1  [PN2]Hfl2 (3) with 2 equivalents of CgK under 1 atmosphere of nitrogen. In comparison 2  with Figure 2.6, the signal at 8.6 and the signal at -8.2 ppm have increased in size (and integration sum) rather dramatically while the signals for the dimer, 2, have decreased. The P{ F£} N M R chemical shift of the speculated dinitrogen complex combined with 31  1  the intense blue color was an excellent indication of dinitrogen complex formation, but it remained uncertain that the signal at -8.2 ppm was due to a dinitrogen complex.  P{ H} 1  Postulated  [P N ]Hfl (3) 2  2  2  -i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—  15  10  5  0  -5  -10  (ppm)  Figure 2.8  The P { H } N M R spectrum of the reaction between [P N ]Hfl2 (3) and 2 equivalents of CgK under 1 atm N2 after 25 hours. 31  1  Chapter 2 References begin on page 48  2  2  40  In an attempt to increase the yield of the dinitrogen complex, 4, the reaction was repeated in a sealed reactor, under 4 atmospheres of dinitrogen for a period of 8 days. With these changes in reaction conditions, the signal at -8.2 ppm became the major signal. The large increase in integration size of this signal, when the only change to the reaction is to increase the N pressure, is further evidence that it can be assigned to a 2  dinitrogen complex.  Unfortunately, a higher percentage of starting material remains  when compared to the same reaction using 1 atm of N , and the other impurities are still 2  present although in smaller amounts as shown in Figure 2.9 and listed in Table 2.4.  31  Postulated  P{ H}  {[P N ]Hf} (u-T :Ti -N ) (4)  1  2  2  2  1  2  2  2  Postulated [P N ]Hf(C H ) (5) 2  2  "I 14  F i g u r e 2.9  7  8  12 1  10 1  1  8 1  1  6 1  1  4 1  1  2  0  1(ppm) <~  -2  -4  ~l I I  -6 1 -81  -10r  The P { ' H } N M R Spectrum of the reaction between [P N ]HfI (3) and 2 equivalents of CgK under 4 atm N after 8 days. 31  2  2  Chapter 2 References begin on page 48  2  2  41  The results of a study of the reaction of [P N2]HfI of C g K under 4 atm N in toluene  T a b l e 2.4  2  (3)  2  with 2 equivalents  2  Compound J 1  [P N ]Hfl 2  P Shift (ppm)  2  2  {[P N ]Hf} 2  2  3  2  -5.4 (s)  11.7(m), 1.9(m) 16%  2  [P N ]Hf(C H ) 5 8.6 (s)  {[P N ]Hf} (u-N ) 4 -8.2 (s)  13%  52%  2  2  7  8  2  2  2  2  a  % after 8 Days under 4 atm N  19%  2  Previous work from the Fryzuk laboratory has shown that at room temperature the ' H N M R spectrum for the analogous zirconium dinitrogen compound, {[P N ]Zr} (u,2  2  2  r| :r| -N ) (B) has the following characteristics. The phenyl region has a fairly broad 2  2  2  1 1  I  0.8  I  1 1 1 1  0.7  | i i l n i i i l | l l l l i i i i i | i i i i i i i i i |  0.6  0.5  0.4  0.3  I  0.2  2  {[P N ]Hf}  3  [P N ]Hfl  4  {[P N ]Hf} (u-Ti :r| -N )  5  [P N ]Hf(C H )  2  2  2  2  2  2  2  2  I  0.1  2  | l i i  -0.0  2  2  2  M  7  i i i i |  -0.1  2  2  8  I  i [ l i i i i i i l l | l i  -0.2 -0.3  (ppm)  F i g u r e 2.10  The silyl methyl region of the N M R spectrum for the products from the reaction of [P N ]HfI (3) with 2 equivalents of C K in toluene for 8 days. 2  2  Chapter 2 References begin on page 48  2  8  42  signal at 8.1 ppm assigned to the o-Ph proton, while the m-Ph and p-Ph protons are sharper at 6.9 ppm. The methylene region shows a characteristic multiplet. The silyl methyl region shows one sharp resonance at 0.4 ppm and a broad resonance at 0.2 ppm. At low temperatures (eg. -80°C) 4 silyl methyl resonances can be clearly seen, while at high temperatures, the broad signal becomes much sharper giving two sharp signals in total for the silyl methyl region. Figure 2.10 shows the silyl methyl region of the H ]  N M R spectrum for the products from the reaction of 3 with 2 equivalents of CgK in  i  i  8.2  F i g u r e 2.11  i  i  8.0  2  {[P N ]Hf}2  3  [P N ]Hfl  4  {[P N ]Hf} (n-T :T -N )  5  [P N ]Hf(C H )  2  2  2  2  2  i  2  i  7.8  2  ,  2  2  2  1  7  i  2  1  2  4  2  8  i  i  7.6 (ppm)  i  7.4  i  1  7.2  1  1  7.0  1  1—  6.8  The phenyl region of the ' H N M R spectrum for the products from the reaction of 3 with 2 equivalents of CgK in toluene for 8 Days. A l l unmarked signals are indeterminable due to overlap.  Chapter 2 References begin on page 48  43  toluene for eight days. Compounds 2 and 3 have been previously isolated so their silyl 4 and 5 were assigned by  methyl signatures could be unambiguously assigned.  comparing this ' H N M R spectrum with the ' H N M R spectra for the analogous zirconium complexes. Inspection of this H N M R spectrum reveals that the broad resonance seen l  for {[P2N ]Zr} (p.-r| :ri -N2) ( B ) at 0.2 ppm seems to be missing. It is possible that it is 2  2  2  2  either buried under the impurity signals or broadened to a greater extent than observed for the zirconium analogue. The phenyl region of the ' H N M R spectrum is shown in Figure 2.11 where, once again, assignment of the product signals was done first by assigning previously isolated compounds 2 and 3 and then by comparison with the zirconium analogues. The three lowest field resonances in Figure 2.11 are due to the o-Ph protons for each of the marked compounds.  The m/p-Ph proton assignments are naturally more tentative due to  extensive overlap. The methylene region of this H N M R spectrum is extremely J  complicated due to signal overlap among the 4 products. Attempts to isolate 4 have been unsuccessful to this point. Each of the reaction components appears to have very similar solubilities in all solvents used.  2.6  F u r t h e r C h a r a c t e r i z a t i o n o f { [ P N ] H i 7 ( u - T i : r | - N 2 ) (4) 2  2  2  2  2  Further evidence for the formation of 4 comes from E.I. mass spectrometry data. Shown in Figure 2.12 is a portion of the E.I. mass spectrum. Figure 2.13 shows the theoretical mass spectrometry signature one would expect from 4. This signature was created using Isotope™ v. 1.6.6, a program designed specifically to model mass  Chapter 2 References begin on page 48  44  spectrometry signatures.  The theoretical signature is a near exact match for the  experimental one shown in Figure 2.12.  In Figure 2.12, signatures for {[P N ]Hf}2N 2  2  where a single nitrogen molecule has been stripped from the parent compound and for {[P N ]Hf} (2), can also be seen and are labeled. 2  2  2  ([P N ]Hf) N 2  100 , 55  c o  2  2  2  80 60 40  ([P N ]Hf) N 2  20  ([P N ]Hf) 2  1350  2  2  2  2  1400  1450  M/z F i g u r e 2.12  Selected E.I. mass spectrometry data for ([P N ]Hf) N 2  2  2  2  100 80 -I  t  60  |  40  J  20 0 1445  1446 1447  1448  1449  1450  1451  1452  1453  1454  1455 1456  1457  M/z  F i g u r e 2.13  Theoretical isotope distribution pattern for E.I. mass spectrometry analysis of ([P N ]Hf) N as determined by Isotope Pattern Calculator™ v. 1.6.6. 2  2  2  2  Chapter 2 References begin on page 48  45  Not shown here, but also observed in the E.I. mass spectrum, are the signatures for [P N2]Hf(C7H8) (5) and for [P N ]HfI and [P N ]Hf. Interestingly, no signature is 2  2  2  2  2  observed for [P N ]HfI (3), likely due to the weakness of the Hf-I bond. 2  2  2  To confirm the presence of a dinitrogen compound in the products from the reaction of [P N ]HfI (3) with 2 equivalents of C g K , the mixture of products was 2  2  2  degraded with H C 1 and the resultant products analyzed to detect hydrazine according to literature procedure. 1  Hydrazine was detected, confirming the presence of a dinitrogen  3  compound, however it was not possible to determine the percent of hydrazine formed per moi of {[P N ]Hf} (n-r| :ri -N ) (4), due to the inability to isolate 4. 2  2  2.7  2  2  2  2  P r e l i m i n a r y R e a c t i v i t y S t u d y o n {[P N ]Hf}2(n-Ti :r| -N ) (4) 2  2  2  2  2  As discussed in the introduction to this chapter, the zirconium analogue of 4 shows unprecedented reactivity with H , forming a compound with a bridging hydride 2  and an N - H moiety as opposed to simply eliminating N . While to this point it has not 2  been possible to isolate 4, the mixture of products, which includes 4, was reacted with H as shown in Equation 2.5. Figure 2.14 shows the P{ H} and *H N M R spectra for this 31  1  reaction. 2  {[P N ]Hf}  3  [ 2N ]Hfl  2  p  2  2  2  2  4  a  t  m  H  2  • 4 5  {[P2N ]Hf} (H-ri :r, -N ) 2  2  2  2  [P N ]Hf(C H ) 2  2  7  8  Chapter 2 References begin on page 48  2  H e x a n e s  2.5  2  46  Figure 2.14  The *H and P { H } N M R spectra for the reaction shown in Equation 2.5. 31  !  The P { H } N M R spectrum shows a mixture of products with the two major 31  1  signals labeled. The signal at 8.6 ppm is assigned to one of the starting materials in the reaction, [P N2]Hf(C7H8) (5). The signal at -10.0 ppm has been very tentatively assigned 2  as {[P2N ]Hf} ((i-ri -N2H)(|j,-H). 2  2  2  The 'Ff N M R spectrum is too complicated to assign  any of the normal signature signals for [P N ] but one interesting signal to note is that at 2  2  5.65 ppm. This signal is broad and in the general region where N - H signals are observed.  Chapter 2 References begin on page 48  47  The N-H signal for the zirconium analogue is observed at 5.53 ppm, extremely close to this signal. This reaction also provides further evidence that the P { H ) signal at -8.2 is due 31  1  to {[P N ]Hf} (n-'n :ri -N ) (4) while the signal at 8.6 ppm is due to [P N ]Hf(C H ) (5). 2  2  2  2  2  2  2  2  7  8  A look back at Figure 2.9 reveals the presence of four compounds. The signals assigned to {[P N ]Hf} (2) and [P N ]HfI (3) are unambiguous because these two compounds 2  2  2  2  2  2  have been previously isolated. The signals at 8.6 ppm and -8.2 ppm are tentatively assigned to 5 and 4 respectively.  Figure 2.14 reveals that following reaction of this  mixture of compounds with H , only the signal at 8.6 ppm remains unchanged. As well, 2  the 'Fl NMR spectrum reveals the presence of activated phenyl signals that are assigned to 5 confirming that this compound has not changed under these conditions. Thus, it seems reasonable to assign the signal at 8.6 ppm to the toluene complex, 5, and by process of elimination the signal at -8.2 ppm is due to 4. As well, 4 is expected to react with H while 5 is not, which is what is observed if the P { H } signals are assigned as 31  1  2  outlined above.  2.8  Summary  The hafnium chemistry presented in this chapter is, in many ways, very similar to the zirconium chemistry discussed in the introduction to the chapter. The X-ray crystal structure of [P N ]HfCl (1) is isostructural with that of its zirconium analogue which is 2  2  2  as expected. However, it is at this point that the chemistry of the two metals begins to show some subtle and not so subtle differences.  Chapter 2 References begin on page 48  It was not possible to synthesize a  48  hafnium dinitrogen compound in any appreciable amount from [P N ]HfCl2 (1), instead a 2  hafnium dimer, {[P N ]Hf} (2) was the major product. 2  2  2  2  However, alteration of the  hafnium starting material from a chloride complex to an iodide complex did result in the formation of a hafnium dinitrogen complex, {[P N ]Hf} (|it-ri :'n -N ) (4), as shown by 2  2  2  2  2  2  N M R spectroscopy, E.I. mass spectrometry, and hydrazine analysis. Unfortunately, at this point in time, it has not been possible to either isolate compound 4 or grow X-ray quality crystals. However, as best can be determined, this is only the second hafnium dinitrogen compound reported. Finally, the observation of an N - H signal in the H N M R !  spectrum for the reaction of 4 with H is a promising sign. 2  2.9  References  1) Fryzuk, M . D.; Love, J. B.; Rettig, S. I ; Young, V. G. Science 1997, 275, 1445. 2) Fryzuk, M . D.; Love, J. B., Unpublished results. 3)Fryzuk, M . D.; Johnson, S. A.; Rettig, S. J. Organometallics 1999,18, 4059. 4) Fryzuk, M . D.; Love, J. B.; Rettig, S. J. Organometallics 1998, 17, 846. 5) Fryzuk, M . D.; Leznoff, D. B.; Ma, S. F.; S.J.Rettig; V . G . Young, J. Organometallics  1998, 17, 2313. 6) Fryzuk, M . D.; Mylvaganam, M . ; Zawarotko, M . J.; MacGillivray, L. R. J. Am. Chem. Soc. 1993, 115, 10360. 7) Fryzuk, M . D.; Haddad, T. S.; Murugesapilla, M . ; McConville, D. H . ; Rettig, S. J. J. Am. Chem. Soc. 1993,115, 2782.  Chapter 2 References begin on page 48  49  8) Fryzuk, M . D.; Macneil, P. A.; Rettig, S. J.; Secco, A. S.; Trotter, J. Organometallics  1982, 1, 918. 9) Black, D. G.; Swenson, D. C ; Jordan, R. F. Organometallics 1995,12, 3539. 10) Fryzuk, M . D.; Carter, A. Organometallics 1992, 11, 469. 1 l)Fryzuk, M . D.; Haddad, T. S.; Berg, D. J. Coord. Chem. Rev. 1990, 99, 137. 12) Brand, H ; Arnold, J. Organometallics 1993, 12, 3655. 13) Watt, G. W.; Chrisp, J. D. Analytical Chemistry 1952, 24, 2006.  Chapter 2 References begin on page 48  50  CHAPTER 3 ORGANOMETALLIC AND HYDRIDE COMPLEXES OF HAFNIUM Transition Metal Hydrides  3.1  There is much current interest in the development of transition metal complexes as reagents for organic synthesis. 1 Transition metal hydrides constitute one important class of compounds currently under study.  They are utilized in both catalytic and  2-4  stoichiometric processes.^ One process which employs a transition metal hydride is the process known as hydrozirconation. Hydrozirconation employs zirconium hydrides to form zirconium-carbon bonds by inserting an alkene or an alkyne into a zirconiumhydrogen bond. Many organometallic compounds of zirconium have been formed in this manner  and  this process  also finds uses in organic  synthesis. 6  As well,  dihydridozirconocene will catalytically hydrogenate alkenes under an atmosphere of H as shown in Equation 3.1.  \  7  /  ^C = C^  {ZrH (t -C H ) } 2  +  2 H  2  1  5  5  2  |  n  ^  2  2  HC  | CH  3.1  Figure 3.1 shows some of the reactions of zirconium compounds that ultimately form useful organic functional groups.  Chapter 3 References begin on page 64  9  51  R-CH=CH, Cp Zr(H)CI  Hydrozirconation  2  R-CH -CH -ZrCp CI 2  2  2  CO 2571.5 atm  R-CH -CH -C-ZrCp CI 2  2  NaOH  HCI/H,0  H 0 2  Electrophilic abstraction  R  CH  2  CH  Figure 3.1  2  —  C  H  2  2  2  R-CH -CH -C-OH 2  Br /MeOH  2  R-CH -CH -C-OMe 2  2  Useful organic functional groups derived from acylzirconium compounds.  Hafnium hydrides are less studied than their zirconium counterparts and hydrohafnation is virtually unknown in organic synthesis.  One study did show that  hydrohafnation is more sensitive to steric effects than hydrozirconation. 10,11 There are two typical methods for preparing early transition metal hydrides. The first involves the use of a reducing agent and a hydride source to replace an anionic halide ligand.  A n example where L1AIH4 performs both functions  Equation 3.2.  Chapter 3 References begin on page 64  12  is shown in  52  Li[AIH ] 4  [{Cp ZrCI(0)}]  1  2  / [{Cp ZrH } ] 2  2  2  3.2  2  The second hydride preparation method entails hydrogenolysis of an organometallic compound with H2 gas. A n example is shown in Equation 3.3 where temperatures of 80 °C and pressures of 60 atm are required. 13  (n  -C H R) MMe 5  4  2  1  2  2CH/  / [{(n -C H R) MH } ] 5  2  5  4  2  2  2  3.3  M = Z r o r Hf R = H , M e , P r , B u , P h C H , or P h M e C H i  For  [P2N2]  t  2  metal complexes, both methods have been previously employed successfully  in the Fryzuk lab. {[P2N2]Ta} (p:-H)4 was prepared using a tandem hydrogenolysis 2  reduction sequence 14 as shown in Equation 3.4. Me,  =  Me  -TaC  5 H, -6 MeH  3.4 I  SLN^  S i  7  Silyl methyl groups omitted for clarity H.H| Hi H  p  Si-|\ \ - S i N —Si—J  Chapter 3 References begin on page 64  53  On the other hand, {[P N2]Zr}2(|a-H) was p r e p a r e d 2  4  15  from [ P N ] Z r C l using K C as a 2  2  2  8  reducing agent under 4 atmospheres o f H as shown in Equation 3.5. 2  CI  CI  4 H  V  4C K 8  TOV ~| V—S>NVl i_J S  2  O I Si-& S  Silyl methyl groups omitted for clarity  Toluene -4 MeH  3.5  /^s>N -r H s  K  Si-'A rU S ktr J ^ S J""l J s  ol  Interestingly, it does not appear to be possible to form a zirconium hydride from [P2N2]ZrMe2. resulted  15  When this reaction was attempted, an unexpected toluene complex  as shown in Equation 3.6. Me Me 4 atm H  V  2  Toluene/THF  -Zr. Si--&  -2 MeH  3.6  Silyl methyl groups omitted for clarity  UsrN^ _j s i  Chapter 3 References begin on page 64  54  To the best of our knowledge, this reaction is unprecedented.  In the absence of  H.2, no reaction takes place, indicating the likely presence of a hydride intermediate but this has not been experimentally confirmed. The question also arose as to whether or not this reaction was specific only to toluene, or i f other aromatic organometallic compounds could be made. Unfortunately,  [P2N2]ZrMe2  is extremely thermally and light sensitive.  As such, it is difficult to prepare in sufficient quantities to use in subsequent reactions. It is a well established precedent that certain organometallic hafnium(IV) compounds are more thermally stable than their zirconium analogues. 16-19 As well, the use of hafnium analogues can facilitate investigation of intermediates in cases where this proves difficult for zirconium compounds.20-22 jhe first step in investigating the hafnium chemistry of the  3.2  [P2N2]  ligand was to prepare the hafnium compound,  Synthesis and Characterization of [P N ]HfMe 2  CI  2  2  [P2N2]HfMe2 (6).  (6)  CI  6  Chapter 3 References begin on page 64  55  The synthesis of [P2N ]HfMe (6) was accomplished by the metathesis reaction of 2  2  [P N ]HfCl (1) with two equivalents of the Grignard reagent, MeMgCl as shown in 2  2  2  Equation 3.7.  Compound 6 was characterized by H and P { H } N M R spectroscopy, 31  l  1  elemental analysis and X-ray crystal structure analysis.  —i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—r 8.0 7.5 7.0 6.5  — i — i — i — i — i — i — i — i — i — i — i — i — i — i — [ — 1.2 0.8 0.4 0.0  (PPm)  F i g u r e 3.2  (ppm)  The ' H and P { H } N M R spectra of [P N ]HfMe (6). The two regions of the *H N M R spectrum are not shown on the same scale. 31  !  2  2  2  Figure 3.2 shows the ' H and P { ' H } N M R spectra of 6. In a manner similar to 31  most other mononuclear group 4 metal [P N ] complexes known, the dimethyl compound 2  adopts C  2 v  2  symmetry in solution at ambient temperature as evidenced by N M R  spectroscopy. As expected, the methyl protons are coupled to two equivalent phosphorus  Chapter 3 References begin on page 64  56  nuclei, and appear as a triplet at 0.65 ppm. Unlike the case of the zirconium analogue, their signal is not masked by the  [P2N2]  ligand methylene protons, but is clearly visible.  Interestingly, while it was not possible to grow crystals of the zirconium analogue of this compound, crystals of the hafnium analogue were grown easily from slow evaporation of a D M E solution. A n ORTEP diagram of complex 6 is shown in Figure 3.3.  C(3)  Figure 3.3  A n ORTEP diagram showing the solid state molecular structure of [P2N ]HfMe 2  2  (6).  The substitution of methyl groups for chloride moieties when going from 1 to 6 has resulted in a substantial structural change. The geometry around the metal center is now best described as trigonal prismatic with the two trigonal planes described by: N ( l ) , P(l), and C(25); and N(2), P(2), and C(26). The methyl carbons are not located in a  Chapter 3 References begin on page 64  57  square plane with the amido nitrogens, but are rotated out of this plane. As well, the phosphine and amide "bite angles", P(l)-Hf-P(2) and N(l)-Hf-N(2), have both changed considerably. The phosphine bite angle has decreased from 153.76(3)° to 135.79(3) ° while the amide bite angle has increased from 96.6(1) ° to 113.2(1) °. Table 3.1 shows selected bond distances and angles for complex 6. The Hf-C, - N and -P bond distances are once again, not unusual and compare with those of other Group 4 methyl complexes. 16,23  T a b l e 3.1  Selected Bond Lengths ( A ) and Angles (deg) in [P N2]HfMe (6) 2  Bond Lengths  Bond Angles  Hf(l)-N(l)  2.147(3)  N(l)-Hf(l)-N(2)  113.5(1)  Hf(l)-N(2)  2.149(3)  P(l)-Hf(l)-P(2)  135.79(3)  Hf(l)-P(l)  2.781(1)  C(25)-Hf(l)-C(26)  82.0(2)  Hf(l)-P(2)  2.783(1)  N(l)-Hf(l)-C(25)  97.2(2)  Hf(l)-C(25)  2.263(1)  N(2)-Hf(l)-C(25)  134.6(2)  Hf(l)-C(26)  2.277(1)  3.3  2  A t t e m p t e d S y n t h e s i s o f [ P N ] H f ( C H ) (5) 2  2  7  8  Having prepared [P N ]HfMe (6), the subsequent aim was the synthesis of a 2  2  2  toluene complex, [P N ]Hf(C H ) (5), using methods similar to those which produced 2  2  7  8  [P N ]Zr(C H ). 2  2  7  8  Chapter 3 References begin on page 64  P o s t u l a t e d Hydride S i g n a l  2 Major Products  31 P{ H} 1  6 (Starting Material) N o P e a k at 8.6  F i g u r e 3.4  T h e ' H and ^ P l ' H } [ P N ] H f ( C H ) (5). 2  2  7  8  Chapter 3 References begin on page 64  N M R spectra f o r the attempted  synthesis  59  A reactor containing [P N2]HfMe (6), in a mixture of toluene and THF, was sealed under 2  2  4 atmospheres of H . The H and P { H } N M R spectra of the results of this reaction are l  2  shown in Figure 3.4.  31  1  If formation of 5 had resulted, as expected, the P { H } N M R 31  1  spectrum would exhibit a signal at 8.6 ppm as observed in the spectrum for the hafnium dinitrogen reaction.  As well, the H N M R spectra of  [P N ]Zr(C H ) has signals  !  2  2  7  8  between 2 and 4 ppm which are attributed to activation of the toluene ring. One would expect to see similar signals for the hafnium analogue in the  !  H N M R spectrum.  However, neither of these features is observed in the N M R spectra shown in Figure 3.4. Integration of the P { H } N M R spectrum indicates 2 major products; the sharp signal at 31  !  4.9 ppm and the broad lump centered at -2.9 ppm.  As well, a small amount of the  starting material, 6, is present. The *H N M R spectrum indicates a multiplet centered at 10.7 ppm which looks identical to that for the hydride in {[P N ]Zr} (u.-H) . Thus, it 2  2  2  4  seemed that it may be possible to form a hafnium hydride using a variation of the reaction shown in Figure 3.4. In fact, the formation of {[P N ]Hf} (u.-H)4 by hydrogenation of 6 2  2  2  required only a small change in the synthetic plan.  3.4  S y n t h e s i s a n d C h a r a c t e r i z a t i o n o f {[P N ]Hf}2(M--H)4 (7) 2  2  By changing solvents from a toluene/THF mixture to neat benzene, the formation of {[P N ]Hf} (u.-H)4 (7) was possible as depicted in Equation 3.8. Complex 7 is 2  2  2  sparingly soluble in benzene and crashes out of solution as yellow microcrystals, making separation from the parent compound a fairly simple matter.  Chapter 3 References begin on page 64  60  The ^ P ^ H } and ' H N M R spectra are shown in Figure 3.5.  In this case, the  change in the chemical shift of the phosphorus nuclei is more drastic than in other  [P2N2]  compounds when switching from {[P2N2]Zr} (p.-H) to its hafnium analogue. The signal 2  4  is observed at 4.4 ppm, 10.3 ppm downfteld from the zirconium analogue signal, which is at -5.9 ppm. As well, the hydride quintet has moved downfteld 4.25 ppm from 5.0 ppm to 9.25 ppm. The other characteristic signals in the ' H N M R spectrum have not changed appreciably.  Chapter 3 References begin on page 64  61  T  1  1  1  1  1  9.0  1  1  1  1  1  8.5  1  1  1  1  1  8.0  1  1  1  1  1  I  7.5  '  1  1.2  1  1  1  3.5  1  1  1  0.4  (PPm)  F i g u r e 3.5  1  0.8  1  1  1  -  0.0  (ppm)  The P{ H} and H N M R spectra for {[P N ]Hf} (^-H) (7). * Indicates impurity or solvent. 3l  l  :  2  2  2  4  S y n t h e s i s a n d C h a r a c t e r i z a t i o n o f [ P N ] H f ( C H ) (8) 2  2  4  6  Can other chemistry of [P N ]ZrCl be extended to hafnium analogues? Again, a 2  2  2  metathesis reaction of one equivalent of [P N ]FffCl 2  2  2  (1) with one equivalent of  Mg(C4Ff6)(THF) results in the formation of [P N ]Hf(C4H6) (8) in good yield as shown 2  in Equation 3.9.  Chapter 3 References begin on page 64  2  2  62  CI CI  V Hf  Mg(C H )(THF) 4  si^ IN— -'^ L-sT ^Si-J N SI  6  2  THF 18 Hours  N  3.9  Silyl methyl groups omitted for clarity  _^ Hf •7-Si  P  |N .  U ^ S i ^ N ^•Si  J  Si-7\  Complex 8 was characterized by ' H and P { H } N M R spectroscopy and 31  1  elemental analysis. The P { H } and *H N M R spectra are shown in Figure 3.6. For this 31  1  compound, the P { H } N M R spectrum shows an AJ3 doublet pattern for non-equivalent 31  1  phosphorus nuclei centered at 0 ppm with a large P-P coupling constant of 78.2 Hz. This coupling pattern is identical to that observed in the zirconium analogue. The *H N M R spectrum indicates that the solid state C twist observed in so many [P N ] compounds, is 2  2  2  maintained in solution at room temperature, in contrast to most [P N ] compounds where 2  C  2 v  2  symmetry is observed in solution. One silyl methyl resonance is quite broad, and  broadened features are also observed in other characteristic signals.  Chapter 3 References begin on page 64  63  31  P{ H} 1  H„  T  r ^!rV i s i  S i  x  [P N ]Hf(C H ) (8) 2  "I—I—I  1—I—I—1 1—|  1 1—I  1—|  10  2  4  6  1—I—I—I—|—I—i—I—I—|—!~  -10  0  (ppm)  1  H  SiMe,  C D H 6  5  m,p-Ph o-Ph  1  i  1  1  1  1  i  Ring C H  1  1  1  1  i  8.0  1  1  1  ' i  1  1  1  1  i  1  7.0  1  1  1  i  6.0  1  i  i  i  |  i  i  i  i  |  i  i  2.0  (ppm)  F i g u r e 3.6  i  i  2  |i i i  H  i  |  i  i  i  i |  1.0  i  i i  0.0  (ppm)  The ' H and ?{ H) N M R spectra of P a ^ H f r c O k ) (8). The two regions of the H N M R spectrum are not shown on the same scale. 3l  l  l  3.6  Summary  As with the chemistry presented in Chapter 2, the hafnium chemistry presented in this chapter begins with a new hafnium compound,  [P2N2]HfMe2 (6),  which is assumed  to be isostructural with its zirconium analogue. Once again it is at this point that the chemistry of the two metals begins to diverge. It was hoped that a hafnium toluene  Chapter 3 References begin on page 64  64  complex could be generated and its reaction pathway studied to elucidate features of the zirconium analogue, but this proved unfeasible.  Instead, a new hafnium hydride  compound, {[P2N2]Hf}2(u,-H)4 (7), has been prepared and characterized.  Finally, a  butadiene complex of hafnium, [P2N2]Hf(C4He) (8), has also been prepared and characterized.  3.7  References  1) Spessard, G. O.; Miessler, G. L . Organometallic Chemistry; Corey, P. F., Ed.; PrenticeHall, Inc.: New Jersey, 1997, pp 377. 2) Pearson, R. G. Chem. Rev. 1985, 85, 41. 3) Moore, D. S.; Robinson, S. D. Chem. Soc. Rev. 1983, 415452. 4) Hlatky, G. G.; Crabtree, R. H . Coord. Chem. Rev. 1985, 65, 1. 5) Collman, J. P.; Hegedus, L. S. Principles and Applications of Organotransition Metal Chemistry; 1st ed.; Kelly, A . , Ed.; University Science Books: M i l l Valley, California, 1980, pp 60. 6) Cardin, D. J.; Lappert, M . F.; Raston, C. L . Chemistry of Organo-Zirconium and Hafnium Compounds; 1st ed.; Ellis Horwood Limited: West Sussex, 1986, pp 24. 7)Wailes, P. C ; Weigold, H.; Bell, A . P. J. Organomet. Chem. 1972, 43, C32. 8) Negishi, E.; Takahashi, T. Aldrichimica Acta 1985, /<5, 31. 9) Spessard, G. O.; Miessler, G. L. Organometallic Chemistry; Corey, P. F., Ed.; PrenticeHall, Inc.: New Jersey, 1997, pp 408.  Chapter 3 References begin on page 64  65  10) Cardin, D. J.; Lappert, M . F.; Raston, C. L. Chemistry of Organo-Zirconium and Hafnium Compounds, 1 ed.; Ellis Horwood Limited: West Sussex, 1986, pp 401. 11) Tolstikov, G. A.; Miftakov, M . S.; Valeev, F. A. Izv. Akad. Nauk SSSR, Ser. Khim. 1979, 2576. 12) Kautzner, B.; Wailes, P. C ; Weigold, H . J. Chem. Soc, Chem. Commun. 1969, 1105. 13) Couturier, S.; Gautheron, B.J. Organomet. Chem. 1978, 157, C61. 14) Fryzuk, M . D.; Johnson, S. A ; Rettig, S. J. J. Am. Chem. Soc. 1998,120, 11024. 15) Fryzuk, M . D.; Love, J. B., Unpublished results. 16) Fryzuk, M . D.; Carter, A. Organometallics 1992, 11, 469. 17) Helmut, G. A ; Sanzo, F. P. D.; Rausch, M . D.; Uden, P. C. J. Organomet. Chem. 1976,  107, 257.  18) Razuvaev, G. A . ; Vyshinskaya, L. I.; Mar'in, V . P. Dokl. Akad. Nauk SSSR 1975, 225, 827. 19) Razuvaev, G. A . ; Mar'in, V . P.; Drushkov, O. N . ; Vyshinskaya, L. I. J. Organomet. Chem. 1982,231, 125. 20) Bercaw, J. E.; Moss, J. R. Organometallics 1992, 11, 639. 21) Roddick, D. M . ; Bercaw, J. E. Chem. Ber. 1989, 122, 1579. 22) Roddick, D. M . ; Fryzuk, M . D.; Seidler, P. F.; Hillhouse, G. L . ; Bercaw, J. E. Organometallics 1985, 4, 97. 23) Fryzuk, M . D.; Haddad, T. S.; Berg, D. J. Coord. Chem. Rev. 1990, 99, 137.  Chapter 3 References begin on page 64  66  CHAPTER 4 Experimental Procedures  4.1  General Procedures  A l l manipulations were performed under prepurified nitrogen in a Vacuum Atmospheres HE-553-2 workstation equipped with an MO-40-2H purification system or using Schlenk-type glassware.  The term "reactor" refers to a cylindrical, thick-walled  Pyrex vessel equipped with a 5 mm (or 10 mm, for larger bombs) Kontes Teflon needle valve and a ground glass joint for attachment to a vacuum line. These "reactors" allow pressures as high as 4 atm to be maintained inside the tube.  4.2  Reagents and Starting Materials  THF was predried by refluxing over CaH for at least 24 hours and dried by 2  refluxing over sodium benzophenone ketyl, followed by distillation under argon. Toluene and hexanes were purchased in anhydrous form from Aldrich, sparged with N2, and deoxygenated by filtration through columns containing alumina and Q-5 catalyst under a positive pressure of N2.I Benzene, diethyl ether, and dimethoxyethane were also refluxed over sodium benzophenone ketyl and distilled under argon. Deuterated THF (C+DgO) and deuterated benzene (C^De) were refluxed under vacuum with sodium potassium amalgam (Na/K), vacuum transferred to a clean vessel and "freeze-pumpthawed" three times prior to use.  Chapter 4 References begin on page 73  67  The  following  HfCl (THF) )2 4  compounds  were  [syn-P N ]Li (dioxane),  2  2  2  3  2  prepared C K , 4  8  and  by  published  procedures:  Mg(C4H )(THF) . 6  2  Me SiI, 3  MeMgCl, BzMgCl, and H were used as received. Diatomaceous earth (Celite) was dried 2  overnight at 170 ° C before being taken inside the glovebox for use.  4.3  Analytical Methods  *H and  31  P { H } N M R spectroscopy were performed on a Bruker AMX-500 1  instrument (500.135 M H z and 202.458 MHz) or a Bruker AC-200 machine (200.132 M H z and 81.015 MHz). and  31  *H N M R spectra were referenced to internal C D H (7.15 ppm) 6  P { H } N M R spectra were referenced to external P(OMe ) 1  3  3  5  (141.0 ppm, with  respect to 85% H P 0 at 0.00 ppm). 3  4  C, H and N microanalyses were performed by Mr. P. Borda of this department. The X-ray crystal structures were determined at U B C Crystallographic Services in this department by Dr. B . Patrick. The crystals were loaded in a small glass vial and covered with paratone oil in the glovebox to prevent decomposition. Details of the structure determinations are given in the Appendices.  4.4  Hydrazine Analysis  Hydrazine was analyzed according to the procedure published by Watt and Chrisp.  5  The products from the reaction of [P N ]HfI (3) with 2 equivalents of C g K 2  2  2  were weighed into a 200 mL Schlenk tube (0.280g) and dissolved in 50 mL of E t 0 . 10 2  Chapter 4 References begin on page 73  68  mL of 2.0 M HC1 in Et20 was added to this solution. The solution immediately lost its blue color and a white precipitate formed. The clear solution and white precipitate were stirred for 1 hour and the solvents removed in vacuo. The flask was exposed to the air, extracted into 100 mL of H2O and filtered into a 500 mL volumetric flask which was filled with 1.0 M HC1. A 2.0 mL aliquot of this solution was added to 20 mL of a color developer (p-dimethylaminobenzaldehyde, 4.0 g; ethanol, 200 mL; 1.0 M HC1, 20 mL) and diluted to 25.0 mL with 1.0 M HC1. Absorbance readings of the sample were taken within 10 minutes.  The spectrometer was set to 100% transmittance using a blank  solution consisting of 1.0 M HC1. Absorbance readings of 0.33, 0.34 and 0.33 A U were obtained at  4.5  A458.  Synthesis o f N e w C o m p o u n d s  4.5.1  [P N ]HfCI 2  2  2  (1)  Li (dioxane)[P N ] (6.83 g, 10.8 mmol) and HfCl (THF) (5.00 g, 10.8 mmol) 2  2  2  were each weighed into a thick walled reactor.  4  2  Addition of 150 mL toluene to this  intimate mixture resulted in a cloudy white solution. The reactor was sealed and the mixture was refluxed for 18 hours at 120 °C. The solvents were then removed in vacuo, the off white residue extracted into toluene (2 x 50 mL) and filtered through Celite. The filtrate was evaporated to dryness and the residue washed with hexanes (2 x 10 mL) yielding 7.25 g, 86 % of 1 as a white powder. The product was crystallized by the slow evaporation of a D M E solution.  Chapter 4 References begin on page 73  69  Anal. Calcd. For C IL2Cl HfN P Si : C, 36.85; H , 5.41; N , 3.58. Found: C, 37.04; H , 24  2  2  2  4  5.48; N , 3.56. *H N M R ( C D , 25 °C, 500.135 MHz) 5 7.87 (m, 4H, o-H phenyl), 7.05 (m, 6H, m/p-H 6  6  phenyl), 1.41 ( A B X m, 4H, C H ring), 1.32 ( A B X m , 4H, C H ring), 0.38 (s, 12H, SiMe 2  2  2  ring), 0.34 (s, 12H, SiMe ring). P { H } ( C D , 25 °C, 202.458 M H z ) 5 -5.8 (s) 31  1  2  4.5.2  6  { [ P N ] H f ) (2) 2  [P N ]HfCl 2  6  2  2  2  (1) (0.73g, 0.93  2  mmol) and C K (0.25g, 1.86 mmol) were each 8  weighed into a 200 mL thick-walled reactor, to which 50 mL of toluene was added, all in the glovebox. The reactor was removed from the glovebox and cooled to -198 °C in a liquid nitrogen bath while under a flow of N .  After 30 minutes, the reactor was sealed  2  and allowed to warm to room temperature. The reaction mixture was stirred for 8 days and filtered through Celite. Toluene was removed in vacuo and the residues dissolved in hexanes and filtered. The hexanes solution was left in a -40 °C freezer overnight where 2 crashed out of solution as a yellow brown powder. Yield: 0.22g, 32.2%. Note: further studies showed that it does not matter what type of atmosphere (N , Ar, or near vacuum) is inside the reactor. 2  Anal. Calcd. For C 8H 4Hf N4P Si8: C, 40.52; H , 5.95; N , 3.95. Found: C, 40.39; H , 4  8  2  4  5.97; N , 3.75. ' H N M R ( C D , 25 °C, 200.132 MHz) 6 7.40 (m, 4H, o-H phenyl), 7.10 (m, 6H, m/p-H 6  6  phenyl), 4.19 (m, 8H, m/p-H activated phenyl), 3.39 (m, 4H, o-H activated phenyl), 1.49 ( A B X m, 8H, C H ring), 1.15 ( A B X m, 8H, C H ring), 0.52 (s, 12H, SiMe ring), 0.50 (s, 2  Chapter 4 References begin on page 73  2  2  70  12H, SiMe ring), 0.31 (s, 12H, SiMe ring), 0.04 (s, 12H, SiMe ring). 2  2  2  31  P{'H} (C D , 6  6  25 °C, 81.015 MHz) 5 11.7 (m, 2P), 1.9 (m, 2P)  4.5.3  [P N ]HfI (3) 2  2  2  10.0 mL (70 mmol, -10 equivalents) of MesSil was added to a stirred solution of [P N ]HfCl (1) (5.21g, 6.66 mmol) in 80 mL of toluene at -78 °C. The reactor was 2  2  2  sealed and the solution stirred for 18 hours, during which time the solution acquired a very pale yellow-green color. Toluene was removed in vacuo and the residues washed with hexanes ( 2 x 1 0 mL) yielding 2.8g, 88 % of 3 as a very pale green powder. Anal. Calcd. For C H 4 I H f N P S i : C, 29.87; H , 4.39; N , 2.90. Found: C, 30.02; H , 24  2  2  2  2  4  4.43; N , 2.89. ' H N M R ( C D , 25 °C, 200.132 MHz) 5 7.92 (m, 4H, o-H phenyl), 7.05 (m, 6H, m/p-H 6  6  phenyl), 1.58 ( A B X m, 4H, C H ring), 1.27 (AJ3X m, 4H, C H ring), 0.48 (s, 12H, SiMe 2  ring), 0.39 (s, 12H, SiMe ring).  2  31  2  4.5.4  2  P { H } ( C D , 25 °C, 81.015 MHz) 5 -5.4 (s) 1  6  6  {[P N ]H02(u-r| .Ti -N ) (4) 2  2  2  2  2  C K (0.33g, 3.32 mmol) and [P N ]HfI 8  2  2  2  (3) (1.21g, 1.26 mmol) were each  weighed into a 200 mL thick-walled reactor, to which 50 mL of toluene was added, all in the glovebox. The reactor was removed from the glovebox and cooled to -198 °C in a liquid nitrogen bath while under a flow of N . After 30 minutes, the reactor was sealed 2  and allowed to warm to room temperature. The solution was stirred for 16 hours and a blue-purple color was observed.  The reactor was then allowed to stir vigorously for  another 7 days. The solution was then filtered through Celite and evaporated to dryness.  Chapter 4 References begin on page 73  71  Washing with a minimal amount of hexanes (2 x 10 mL) yielded 0.85 g of a dark solid. 31  P { H } N M R indicates the composition of this solid to be approximately 52% 4, 19% 3, 1  16% 2, and 13% 5. Mass spec. (E.I.): M  4.5.5  [P N ]HfMe 2  2  2  +  1450.  (6)  To a solution of [P N ]HfCl (1) (3.02 g, 3.86 mmol) in THF was added 3.0 M 2  2  2  MeMgCl in THF (2.57 mL, 7.77 mmol) at 0 °C. The solution was warmed to room temperature and stirred for l h after which the solvents were evaporated in vacuo. The off white residue was extracted into toluene (2 x 20 mL) and filtered through celite. The filtrate was evaporated to dryness and the residue washed with hexanes (2 x 10 mL) yielding 2.24 g, 77 % of 6 as a white powder. The product was crystallized by the slow evaporation of a D M E solution. Anal. Calcd. For C H H f N P S i : C, 42.12; H , 6.53; N , 3.78. Found: C, 42.14; H , 6.52; 26  48  2  2  4  N , 3.74. ' H N M R ( C D , 25 °C, 500.135 MHz) 5 7.62 (m, 4H, o-H phenyl), 7.07 (m, 6H, m/p-H. 6  6  phenyl), 1.03 (m, 8H, C H ring), 0.72 (t, 6H, Zr-CH ), 0.22 (s, 12H, SiMe ring), 0.20 (s, 2  3  2  12H, SiMe ring). ^ P ^ H } ( C D , 25 °C, 202.458 MHz) 5 -9.6 (s) 2  4.5.6  6  6  { [ P N ] H f } { u - H } (7) 2  2  2  4  50 mL of C H 6 was added to 1.02g (1.3 mmol) of [P N ]HfMe (6) in a reactor 2  6  which was sealed.  2  2  The reactor was "freeze-pump-thawed" three times to remove all  gases. H was introduced to the reactor which was cooled to -198 °C. After the solvent 2  had thawed but prior to warming to room temperature, the reactor was shaken to promote  Chapter 4 References begin on page 73  72  dissolution of H2 in the solution.  The reactor was left overnight during which time a  microcrystalline yellow solid precipitated.  Removal of solvent by filtration resulted in  0.345 g, 37.2% of 7. Anal. Calcd. For C H H f N P S i : C, 40.41; H , 6.22; N , 3.93. Found: C, 40.56; H , 6.21; 48  88  2  2  4  N , 3.76. ' H N M R ( C D , 25 °C, 500.135 MHz) 5 9.25 (m, 4H, Hf-H), 7.19 (m, 8H, o-H phenyl), 6  6  7.12 (m, 12H, m/p-H phenyl), 0.83 (m, 16H, C H ring), 0.04 (s, 24H, SiMe ring), -0.03 2  (s, 24H, SiMe ring).  31  2  P { H } ( C D , 25 °C, 202.458 MHz) 5 4.4 (s) 1  6  6  [ P N ] H f ( C H 6 ) (8)  4.5.7  To  2  2  an  2  4  intimate  mixture  of  [P N ]HfCl 2  2  (1) (1.42g,  2  1.8  mmol)  and  Mg(C4H6)(THF) was added 15 mL of THF at 0 °C. When warmed to room temperature, 2  the solution took on a deep red color.  The solution was stirred overnight and THF  removed in vacuo. The residues were dissolved in 15 mL of hexanes and the solution placed in the freezer at a temperature of - 40 °C. Overnight, a red powder precipitated giving 0.90 g, 6 5 % of 8. Anal. Calcd. For C H 4 H f N P S i : C, 43.93; H , 6.32; N , 3.66. Found: C, 43.72; H , 6.28; 28  8  2  2  4  N , 3.66. [  H N M R ( C D , 25 °C, 200.132 MHz) 5 7.62 (m, 4H, o-H phenyl), 7.08 (m, 6H, m/p-H 6  6  phenyl), 6.03 (dd, 2H,  meso-H), 2.18 (dd, 2H, C A syn-H), 0.61 (dd, 2H, C A  anti-H), 1.14 ( A B X m, 4H, C H ring), 1.12 ( A B X m, 4H, C H ring), 0.38 (s, 12H, SiMe 2  2  2  ring), 0.22 (s, 12H, SiMe ring). ^ { ' H J N M R ( C D , 25 °C, 80.015 MHz) 5 4.7 and 2  4.8 (d, J 2  P P  = 78.2Hz)  Chapter 4 References begin on page 73  6  6  4.6  References  1) Pangborn, A . B . ; Giardello, M . A . ; Grubbs, R. H . ; Rosen, R. K . ; Timmers, F. Oganometallics 1996, 15, 1518. 2) Manzer, L . E. Inorg. Chem. 1982, 21, 135. 3) Fryzuk, M . D.; Love, J. B.; Rettig, S. J. J. Chem. Soc., Chem. Commun. 1996, 2783. 4) Bergbreiter, D. E.; Killough, J. M . J. Am. Chem. Soc. 1978, 100, 2126. 5) Watt, G. W.; Chrisp, J. D. Analytical Chemistry 1952, 24, 2006.  Chapter 4 References begin on page 73  74  FUTURE PROSPECTS A wide range of chemistry has been demonstrated for the new hafnium [P2N2] complexes presented in this thesis, but there is need for further research within this area. In general, many of the systems presented are in need of further physical characterization, while the synthesis of new products is always a worthy goal. Further work is certainly needed in terms of characterization of {[P2N2]HT}(u.2  r| :r| -N2) and perhaps alteration of the synthetic plan to improve yields and/or decrease 2  2  impurity production. If this compound can be isolated, there are many possibilities for further reactivity. Theoretical studies have indicated that a {[P2N2]M}2((X-TI -HNNH)(|LI2  H)  2  complex may be accessible. 1 Perhaps the greater thermal stability of hafnium  complexes compared with zirconium complexes may allow synthesis of this compound. [P2N ]HfCi2 (1) has proven to be a useful starting material for many of the 2  compounds presented in this thesis.  While the synthesis of [P2N2]HfMe (2) and its 2  ability to form a hydride complex where the zirconium analogue did not was of interest, further work is necessary to determine why this compound differs in reactivity so drastically from the zirconium analogue. As well, many other alkyl systems of hafnium may be synthesized as only the methyl derivative has been examined to this point. Of particular interest is the reactivity of [P2N2]HfCi2 with LiCH.2SiMe3. Recent work from the Fryzuk laboratory with the analogous niobium(IV) complex, [P2N2]NbCl2 has shown that these reaction [P N2]Nb=CHSiMe3.2 2  conditions can produce  niobium alkylidenes, for  example  Perhaps this reaction could be extended to generate a rare  example of a hafnium alkylidene. Finally the need for X-ray crystal structures can not be  75  overemphasized. It would be of great interest to compare the bonding of many of these hafnium compounds with their zirconium analogues.  References  1) Basch, H . ; Musaev, D. G.; Morokuma, K . ; Fryzuk, M . D.; Love, J. B.; Seidel, W. W.; Albinati, A . ; Koetzle, T. F.; Klooster, W. T.; Mason, S. A . ; Eckert, J. J. Am. Chem. Soc. 1999, 121, 523. 2) Fryzuk, M . D.; Kozak, C.K., Unpublished results.  76  APPENDIX A.1 X-ray Crystallographic Analysis of [P N ]HfCl (1) 2  A.1.1  2  2  Crystal Data  Empirical Formula  C 4H42N2Cl2HfP Si4  Formula Weight  782.29  Crystal Color, Habit  clear, chip  Crystal Dimensions  0.15  Crystal System  orthorhombic  Lattice Type  Primitive  Lattice Parameters  a = 9.3152(8) A  2  b=  2  x 0.15 x 0.15 mm  16.5962(5) A  c = 21.3811(7) A V = 3305.5(2) A  Space Group  P 2 i 2 i 2 i (#19)  Z value  4  Dca/c  1.572 g/cm  Fooo  1568.00  H(MoKa)  35.71  A.l.2  3  3  cm"  1  Intensity Measurements  Diffractometer  Rigaku/ADSC C C D  Radiation  MoKct (A, = 0.71069 A) Graphite monochromated  Detector Aperture  94 mm x 94 mm  Data Images  464 exposures @ 35.0 seconds  77  cp oscillation Range (x = 0)  0.0-190.0°  © oscillation Range (x = 90.0)  -19.0-23.0°  Detector Position  40.62 mm  Detector Swing Angle  -5.55° 55.8°  No. of Reflections Measured  Total: 28469 Unique: 3999 (R,„, = 0.066)  Corrections  Lorentz-polarization Absorption (trans, factors: 0.7796- 1.0000)  A . 1.3 Structure Solution and R( Structure Solution  Patterson Methods (DIRDIF92 P A T T Y )  Refinement  Full-matrix least-squares  Function Minimized  Sco(jFo | - |Fc 1 )  Least Squares Weights  co = l/[a (Fo )]  p-factor  0.0000  Anomalous Dispersion  A l l non-hydrogen atoms  No. Observations (I>0.00o(I))  6846  No. Variables  316  Reflection/Parameter Ratio  21.66  Residuals (on F , all data): R; Rw  0.036; 0.055  Goodness of Fit Indicator  0.51  Max Shift/Error in Final Cycle  0.00  No. Observations (I>3a(I))  5913  2  2  2  2  2  2  Residuals (on F, I>3a(I)): R; Rw  0.020; 0.025  Maximum peak in Final Diff. Map  0.68  elk  Minimum peak in Final Diff. Map  -1.10  e/A  Table A . l :  Atom  1  3  Atomic Coordinates and B,  X  y  z  B  e g  Hf(l)  0.08378(2)  0.97608(1)  0.16637  0.890(4)  Cl(l)  -0.1402(2)  0.94810(10)  0.10928(9)  2.77(3)  Cl(2)  0.0421(2)  0.84100(10)  0.21020(10)  3.97(5)  P(l)  -0.031(10)  1.08273(8)  0.24618(7)  1.10(3)  P(2)  0.2891(2)  0.92249(9)  0.08962(7)  1.38(3)  Si(l)  0.2845(2)  1.06481(9)  0.27779(7)  1.19(3)  Si(2)  0.4049(2)  0.91470(10)  0.22206(7)  1.69(3)  Si(3)  0.2511(2)  1.10590(10)  0.06974(8)  1.72(3)  Si(4)  -0.0373(2)  1.15670(10)  0.11763(8)  1.62(3)  N(l)  0.2724(5)  0.9895(3)  0.2213(2)  1.21(8)  N(2)  0.1025(5)  1.0873(3)  0.1169(2)  1.39(8)  C(l)  0.1310(6)  1.1375(3)  0.2661(3)  1.21(9)  C(2)  0.4056(7)  0.8657(3)  0.1413(3)  1.8(1)  C(3)  0.3793(6)  1.0166(4)  0.0711(3)  2.3(1)  C(4)  -0.1363(6)  1.1472(4)  0.1955(3)  1.7(1)  C(5)  0.4503(6)  1.1290(4)  0.2742(3)  2.4(1)  C(6)  0.2705(7)  1.0193(4)  0.3573(3)  2.3(1)  C(7)  0.3787(8)  0.8358(4)  0.2832(3)  2.9  C(8)  0.5897(8)  0.9541(5)  0.2343(4)  3.6  C(9)  0.1921(9)  1.1226(5)  -0.0131(3)  3.4  C(10)  0.3649(8)  1.1929(4)  0.0946(4)  2.8  C(ll)  -0.1725(8)  1.1444(4)  0.0533(3)  2.8  C(12)  0.0260(8)  1.2639(4)  0.1142(3)  2.6  C(13)  -0.1222(5)  1.0671(4)  0.3204(2)  1.4  C(14)  -0.1755(6)  1.1332(4)  0.3539(3)  2.1  C(15)  -0.2378(7)  1.1212(5)  0.4124(3)  2.9  C(16)  -0.2492(9)  1.0448(5)  0.4370(3)  3.4  C(17)  -0.1970(8)  0.9799(6)  0.4043(3)  3.4  C(18)  -0.1333(7)  0.9908(4)  0.3454(3)  2.3  C(19)  0.2695(6)  0.8646(3)  0.0184(3)  1.5  C(20)  0.3915(6)  0.8336(4)  -0.0127(3)  2.0  C(21)  0.3749(7)  0.7831(4)  -0.0635(3)  2.1  C(22)  0.2399(7)  0.7645(4)  -0.0857(3)  2.0  C(23)  0.1195(7)  0.7964(4)  -0.0571(3)  2.3  C(24)  0.1341(6)  0.8465(4)  -0.0049(3)  1.9  APPENDIX A.2 X-ray Crystallographic Analysis of [P N ]HfMe2 (6) 2  A.2.1  2  Crystal Data  Empirical Formula  C 6H48HfN P Si  Formula Weight  741.46  Crystal Color, Habit  clear, block  Crystal Dimensions  0.30 x 0.30 x 0.10 mm  Crystal System  monoclinic  Lattice Type  Primitive  Lattice Parameters  a = 11.3209(7) A b = 10.8041(3) A  2  2  2  4  c = 28.1451(9) A  V = 3441.6(2) A Space Group  P2i/n (#14)  Z value  4  D /  1.431 g/cm  ca  C  Fooo  1504.00  p.(MoKa)  32.75 cm"  A.2.2  3  3  1  Intensity Measurements  Diffractometer  Rigaku/ADSC CCD  Radiation  M o K a ( X = 0.71069 A) Graphite monochromated  Detector Aperture  94 mm x 94 mm  81  Data Images  772 exposures @ 16.0 seconds  (j) oscillation Range (% = 0) Q oscillation Range (% = 90.0) Detector Position Detector Swing Angle  0.0-189.9° -19.0-23.0°  40.47(1) mm -5.52(1)° 55.8°  No. of Reflections Measured  Total: 23903 Unique: 7571 ( R = 0.041) mr  Corrections  Lorentz-polarization Absorption (trans, factors: 0.6526-  1.0000)  A.2.3 Structure Solution and R< Structure Solution  Direct Methods (SIR97)  Refinement  Full-matrix least-squares  Function Minimized  IQ(|FO |-|FC |)  Least Squares Weights  ffl = l/[a (Fo )]  p-factor  0.0000  Anomalous Dispersion  A l l non-hydrogen atoms  No. Observations (I>0.00a(I))  7219  No. Variables  316  Reflection/Parameter Ratio  22.84  Residuals (on F , all data): R; Rw  0.048; 0.107  Goodness of Fit Indicator  1.47  Max Shift/Error in Final Cycle  0.06  No. Observations (I>3a(I))  6957  2  2  2  2  2  2  Residuals (on F, I>3o(I)): R; Rw  0.036; 0.063  Maximum peak in Final Diff. Map  1.35  Minimum peak in Final Diff. Map  -1.37 eVA  Table A . 2 :  Atom  elk  3  3  A t o m i c C o o r d i n a t e s a n d B,  X  y  z  B  eq  Hf(l)  0.65750(1)  0.23340(1)  0.65160(5)  1.428(4)  P(l)  0.50370(1)  0.03890(9)  0.63100(4)  1.93(2)  P(2)  0.74380(9)  0.43630(9)  0.60230(3)  1.56(2)  Si(l)  0.38980(1)  0.28500(1)  0.59870(5)  2.14(2)  Si(2)  0.73980(1)  -0.03330(1)  0.60430(5)  2.23(2)  Si(3)  0.79260(1)  0.19670(1)  0.54750(4)  1.87(2)  Si(4)  0.51990(1)  0.50130(1)  0.64240(5)  2.51(3)  N(l)  0.51010(3)  0.34560(3)  0.62890(1)  1.78(7)  N(2)  0.73090(3)  0.12540(3)  0.59540(1)  1.92(7)  C(l)  0.42520(4)  0.11840(4)  0.58290(1)  2.36(9)  C(2)  0.58270(4)  -0.09030(4)  0.60400(2)  2.45(9)  C(3)  0.73360(3)  0.36020(4)  0.54440(1)  1.91(8)  C(4)  0.63670(4)  0.56280(4)  0.60220(2)  3.0(1)  C(5)  0.36070(6)  0.36310(6)  0.53980(2)  4.6(1)  C(6)  0.25150(5)  .29060(6)  0.63280(3)  4.1(1)  C(7)  0.80190(5)  -0.06790(5)  0.66420(2)  4.1(1)  C(8)  0.82610(5)  -0.12370(5)  0.56060(3)  4.9(2)  C(9)  0.74710(5)  0.12780(5)  0.48850(2)  3.9(1)  C(10)  0.95660(5)  0.20020(5)  0.55270(2)  3.5(1)  C(ll)  0.57740(6)  0.52430(6)  0.70410(2)  4.7(1)  C(12)  0.38170(6)  0.59320(5)  0.63480(3)  4.9(2)  C(13)  0.39430(4)  -0.03090(4)  0.66870(2)  2.44(9)  C(14)  0.27350(4)  -0.02800(5)  0.65940(2)  3.5(1)  C(15)  0.19700(5)  -0.08220(7)  0.69140(2)  4.8(2)  C(16)  0.23790(6)  -0.14090(7)  0.73160(2)  4.9(2)  C(17)  0.35790(5)  -0.14420(7)  0.74110(2)  4.8(2)  C(18)  0.43600(4)  -0.08990(5)  0.70970(2)  3.4(1)  C(19)  0.88480(3)  0.51510(4)  0.60590(1)  1.76(8)  C(20)  0.95490(4)  0.53830(5)  0.56660(2)  2.8(1)  C(21)  1.05610(5)  0.60970(5)  0.57160(2)  3.4(1)  C(22)  1.08800(4)  0.66040(5)  0.61520(2)  2.7(1)  C(23)  1.02030(5)  0.63620(5)  0.65420(2)  3.3(1)  C(24)  0.92130(4)  0.56220(5)  0.64960(2)  3.2(1)  C(25)  0.59360(5)  0.19070(5)  0.72540(2)  3.5(1)  C(26)  0.83120(5)  0.26530(5)  0.69210(2)  3.6(1)  

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