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Tertiary phosphine complexes of zirconium(IV) and hafnium(IV) Carter, Alan 1985

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TERTIARY PHOSPHINE COMPLEXES OF ZIRCONIUM(IV) AND  HAFNIUM(IV)  by ALAN  CARTER  B.Sc.(Hons), Trent  A THESIS SUBMITTED  Polytechnic,  1982  IN PARTIAL FULFILLMENT OF  THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE  in  THE FACULTY OF GRADUATE STUDIES (Department of Chemistry)  We accept  this  t h e s i s as conforming  to the r e q u i r e d  standard  THE UNIVERSITY OF BRITISH ^OLtJRlftAJanuary 1985 © Alan Carter,  1985  In p r e s e n t i n g  t h i s t h e s i s i n p a r t i a l f u l f i l m e n t of  requirements f o r an advanced degree a t the  the  University  o f B r i t i s h Columbia, I agree t h a t the L i b r a r y s h a l l make it  f r e e l y a v a i l a b l e f o r reference  and  study.  I  further  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 copying 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 granted by the head o f  department o r by h i s o r her r e p r e s e n t a t i v e s .  my  It is  understood t h a t copying or 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  allowed without my  permission.  Department o f  QUvt'Av^ «rtJ/  The U n i v e r s i t y o f B r i t i s h Columbia 1956 Main Mall Vancouver, Canada V6T 1Y3  / R l "4  written  ii  ABSTRACT  The equivalent  t e t r a - h a l i d e s of z i r c o n i u m and hafnium were reacted of the p o t e n t i a l l y t r i d e n t a t e h y b r i d  ligand,  N(SiMe CH PR ) ~, 2  (R = Me, i - P r , t-Bu) to generate the c o r r e s p o n d i n g mono-ligand M C l { N ( S i M e C H P R ) ) , (M - Z r , H f ) . 3  the  2  2  2  2  2  data and the s i n g l e c r y s t a l X-ray  2  complexes  Based on the r e s u l t s obtained  2  solution spectroscopic  with one  from  diffraction  a n a l y s e s of H f C I { N ( S i M e C H P M e ) > and Z r C l { N ( S i M e C H P ( i - P r ) ) ) the 3  stereochemistries be m e r i d i o n a l displayed  of  2  2  2  3  2  2  3  2  2  2  2  2  i n s o l u t i o n , but both f a c i a l and m e r i d i o n a l  mono-ligand d e r i v a t i v e s  three e q u i v a l e n t s  served as u s e f u l s t a r t i n g m a t e r i a l s f o r  of MeMgCl to one e q u i v a l e n t  the t r i m e t h y l  geometries were  s t a t e dependent on the l i g a n d .  g e n e r a t i o n of z i r c o n i u m - and hafnium-carbon bonds.  generated  2  of a l l the MCI {N(SiMe C H P R ) ) complexes were found to  i n the s o l i d  The the  2  Thus the a d d i t i o n  of M C l { N ( S i M e C H P R ) } 3  2  complexes M ( C H ) { N ( S i M e C H P R ) } . 3  3  2  2  2  2  of MeMgCl was added to the mono-ligand complexes, an  inseparable  mixture of the monomethyl and dimethyl d e r i v a t i v e s was  the  solid  2  2  When two  equivalents  obtained.  2  The s t e r e o c h e m i s t r y o f H f ( C H ) { N ( S i M e C H P M e ) } i s f a c i a l i n 3  s t a t e but d i s p l a y s  3  2  2  2  2  unusual f l u x i o n a l behaviour i n s o l u t i o n .  This  behaviour i s observed f o r a l l the t r i m e t h y l d e r i v a t i v e s as a consequence of  the d i s s o c i a t i v e nature of the phosphine donors.  Several  rearrangement pathways f o r these compounds a r e d i s c u s s e d interpret  t h i s behaviour i n s o l u t i o n .  possible  i n an attempt to  iii  ACKNOWLEDGEMENTS  F i r s t l y , I would l i k e to thank, my s u p e r v i s o r , Dr. M i c h a e l F r y z u k , f o r h i s guidance MacNeil  throughout my two y e a r s h e r e .  Many thanks a l s o to Dr. Pat  f o r her h e l p d u r i n g the course of t h i s p r o j e c t .  Thanks a l s o to Dr.  A x e l Westerhaus f o r h i s s u p e r v i s i o n d u r i n g the e a r l y p a r t of t h i s work. F i n a l l y I would l i k e to thank my proof r e a d e r s , Dr. Ian B u t l e r , John Haynes and Dr. Pat MacNeil their  f o r the time and e f f o r t  l i b e r a l use of pen and p e n c i l ,  perseverence i n t y p i n g t h i s  and a l s o T i l l y  manuscript.  they put i n and  Schreinders for her  iv  To my Mother and F a t h e r  V  TABLE OF CONTENTS  Page  Abstract  i i  Acknowledgements  iv  Table of Contents  vl  List  of F i g u r e s  List  of Tables  List  of A b b r e v i a t i o n s  CHAPTER 1:  v l l viii ix  Introduction 1.1  1.2  Homoleptic A l k y l s of T i t a n i u m ( I V ) , and Hafnium(IV)  Zirconium(IV),  H e t e r o l e p t i c A l k y l s of T i t a n i u m ( I V ) , Z i r c o n i u m ( I V ) , and Hafnium(IV) 1.2.1  1.2.2  1.2.3  1.3  1  C y c l o p e n t a d i e n y l Complexes of T i t a n i u m ( I V ) , Z i r c o n i u m ( I V ) , and Hafnium(IV)  7  9  9  Phosphine Complexes of T i t a n i u m ( I V ) , Z i r c o n i u m ( I V ) , and Hafnium(IV)  12  Amide Complexes of T i t a n i u m ( I V ) , Z i r c o n i u m ( I V ) , and Hafnium(IV)  15  Design and S y n t h e s i s of a Hybrid Ligand  Multidentate 18  vi  Table  of Contents (contd)  CHAPTER 2.  Page  R e s u l t s and D i s c u s s i o n  23  2.1  P r e p a r a t i o n of L i N ( S i M e C H P R )  2.2  P r e p a r a t i o n and S t e r e o c h e m i s t r y o f MCl {N(SiMe CH PR ) }  2  3  2.3  2  2  2  2  2  23  2  24  2  P r e p a r a t i o n and S t e r e o c h e m i s t r y o f M(CH ) {N(SiMe CH PR ) } 3  CHAPTER 3.  Experimental  CHAPTER 4.  Summary  3  2  2  2  31  2  45 i  . .  50  Appendix  52  Bibliography  69  vii  LIST OF FIGURES  Fig.  1  R e p r e s e n t a t i o n of d-d o r b i t a l o v e r l a p i n a metal-phosphorus bond  12  R e p r e s e n t a t i o n of a phosphine cone angle 9  13  Fig.  2  Fig.  3a,3b, Bonding p o s s i b i l i t i e s a v a i l a b l e 3c amides  Fig. 4  Fig.  5a,5b  Page  to t r a n s i t i o n metal 15  R e p r e s e n t a t i o n of p-d o r b i t a l o v e r l a p i n a m e t a l n i t r o g e n bond  16  C o o r d i n a t i o n modes a v a i l a b l e to { N ( S i M e C H 2 P R ) * 2  *  2  2  0  Fig. 6  80 MHz *H NMR spectrum of mer-HfCI,{N(SiMe CH^Me ) ,}  Fig. 7  Proposed i s o m e r i s a t i o n of f a c - H f C l { N ( S i M e C H P M e ) ) to m e r - H f C l { N ( S i M e C H P M e ) }  27  S t r u c t u r e and numbering scheme o f H f C l { N ( S i M e C H P M e ) } (8a)  28  ?  3  3  Fig. 8  2  3  Fig. 9  2  10  Fig.  11  2  2  2  2  2  2  2  2  S t r u c t u r e and numbering scheme of Z r C l { N ( S i M e C H P ( i - P r ) ) } (9b) 3  Fig.  2  2  2  2  2  28  2  80MHz H NMR spectrum of mer-HfCI^{N(SiMe C H P ( t - B u ) ) } X  2  2  2  P { H } NMR spectrum f o l l o w i n g the r e a c t i o n between H f C l { N ( S i M e C H P ( i - P r ) ) } and two e q u i v a l e n t s of MeMgCl  31  26  0  2  30  1  3  2  2  2  2  33  Fig.  12  80MHz *H NMR spectrum of Hf (CH ) {N(SiMe ^ H ^ t - B u ) ) >  Fig.  13  V a r i a b l e - t e m p e r a t u r e *H and P { H } NMR s p e c t r a o f Hf(CH ) {N(SiMe CH P(t-Bu) ) }  37  S t r u c t u r e and numbering scheme f o r fac-Hf(CH ) {N(SiMe CH P(t-Bu) ) }  44  3  31  3  Fig.  14  3  3  2  3  3  2  2  2  2  2  2  36  1  2  2  2  viii  LIST OF TABLES  Page  Table 1  Bond lengths i n H f ( C H ) ( N ( S i M e C H P M e ) >  67  Table 2  Bond angles i n H f ( C H ) { N ( S i M e C H P M e ) )  68  3  3  3  3  2  2  2  2  2  2  2  2  ix  ABBREVIATIONS  Me i-Pr  methyl =  iso-propyl tertiary-butyl  t-Bu Ph  =  phenyl  sec  =  secondary  fac  facial  mer  =  meridional  e  =  electron  TBP  =  trigonal  BPR  =  Berry  A  =  Angstroms  mL  =  millilitres  °C  =  centigrade  s  =  singlet  d  2  doublet  bd  =  broad  t  =  triplet  m  =  multiplet  bipyramid  pseudorotation  doublet  m•p•=  melting point  I.R.  infra-red  1  CHAPTER 1  Introduction. There has been a growing development i n the chemistry group t r a n s i t i o n m e t a l s , with emphasis on the formation metal-hydrogen bonds. recognised process  with  still and  of metal-carbon and  The s y n t h e t i c p o t e n t i a l of such metal complexes was  the advent of Z i e g l e r - N a t t a c a t a l y s i s .  The Z i e g l e r - N a t t a  i s thought to i n v o l v e the i n t r a m o l e c u l a r m i g r a t i o n  group to an adjacent  coordinated  controversial. » la  b  3  R  of an a l k y l  o l e f i n , a l t h o u g h the a c t u a l mechanism i s  The o r i g i n a l Z i e g l e r - N a t t a process  E t A l i n the p o l y m e r i s a t i o n  M  of the e a r l y  of ethylene  ^  2  CH CH 2  polymer  TiCl^  (Scheme 1 ) .  M-CH CH R 2  utilised  e | j  '  m  M—H  2  Termination  Scheme 1  For  the metals on the l e f t  of the t r a n s i t i o n metal s e r i e s k >k and h i g h a b v  2  molecular weight be c a r r i e d  polymers are produced.  out homogeneously employing  a l l y l ) as the c a t a l y s t , o r d e r of magnitude l e s s The important  2  3  3  5  also  - Z r , Hf : ( r ) - C H ) = 3  3  5  a l t h o u g h the r e a c t i v i t y of these systems i s an than that of the Z i e g l e r - N a t t a type  reagents i n o r g a n i c and  i n o r g a n i c c h e m i s t r y was  ( T I - C H ) Z r ( H ) C l with o l e f i n s 5  2  have subsequently  organometallic chemistry.  of the h y d r o z i r c o n a t i o n r e a c t i o n , 5  M( TI -C H ) ^ ( M  a l k y l s of the group IVb metals  synthetic u t i l i t y  5  E t h y l e n e p o l y m e r i s a t i o n can  3  demonstrated  catalysts. proven  to be  Their  w i t h the d i s c o v e r y  which i n v o l v e s the r e a c t i o n of  (Scheme 2 ) .  CsHi8  17  Scheme 2  The  o r g a n o m e t a l l i c complex 2 can be converted  to a v a r i e t y of o r g a n i c  products upon r e a c t i o n with a s u i t a b l e e l e c t r o p h i l e . ** The  e a r l y development of  t r a n s i t i o n metal  s e r i e s was  were i n t r i n s i c a l l y  unstable.  o-hydrocarbyl c h e m i s t r y throughout  hampered by the m i s c o n c e p t i o n I n v e s t i g a t i o n s which sought  nature of t r a n s i t i o n metal a l k y l decomposition  that metal  the alkyls  to a s c e r t a i n  pathways gave, as a  the  3  consequence, i n v a l u a b l e and  isolation.  information  regarding  their  successful  preparation  There a r e s e v e r a l decomposition pathways a v a i l a b l e to  t r a n s i t i o n metal a l k y l s . y-elimination, reductive  They a r e most commonly r e f e r r e d to as or-, fj- and e l i m i n a t i o n , and homolysis (eqns. 1, 2, 3, 4, and  5 respectively).  a-Elimination  H M-CHjjCHgR r ' ^ 1  M=CHCH R 2  (l)  p-Elimination  H M-CH CH R 2  2  ^  M  CHR 1| CH  ( 2 )  2  y-Elimination  MCCH^CH.R  ^M()CH  2  CHR Reductive  Elimination  M " N  2  •  XZ  <*>  4  Homolysis  M— R  Intramolecular  ^  M* + R*  ^  (5)  p-hydrogen a b s t r a c t i o n i n v o l v e s the m i g r a t i o n of a  p-hydrogen from a h y d r o c a r b y l  group to the metal c e n t r e .  s p e c i e s formed d u r i n g t h i s process may c o o r d i n a t i o n sphere.  The  be e l i m i n a t e d or remain i n the  bond b r e a k i n g  by t h i s route are  phenomena i n o r g a n i c s y n t h e s i s (e.g. h y d r o f o r m y l a t i o n ,  decomposition  E n e r g e t i c a l l y t h i s process  pathway.  The  the h y d r o c a r b y l group has unsaturated;  a  p r o b a b i l i t y of p-hydrogen;  illustrated  i s the most  important  facile  b) the metal i s c o o r d i n a t i v e l y These e f f e c t s  sequence of a s e r i e s of t i t a n i u m  below (Scheme 3 ) .  T i ( E t ) « T i ( M e ) <Ti(CH CMe ) < T i ( C H S i M e ) 4  both  h y d r o s i l a t i o n , and  c) the metal c e n t r e i s s t e r i c a l l y unhindered.  alkyls,  i n fact  p - e l i m i n a t i o n i n c r e a s e s when a)  are e x e m p l i f i e d i n the f o l l o w i n g s t a b i l i t y homoleptic  unsaturated  p - e l i m i n a t i o n pathway i s r e v e r s i b l e ;  metal-carbon bond making and  hydroboration).  The  lt  2  3  4  2  3  4  Scheme 3 * Homoleptic r e f e r s to compounds c o n t a i n i n g o n l y one type of l i g a n d w i t h the g e n e r a l formula MR (M = t r a n s i t i o n m e t a l , R » h y d r o c a r b y l group) i n c o n t r a s t to h e t e r o l e p t i c which i s a term used to d e s c r i b e complexes c o n t a i n i n g s e v e r a l d i f f e r e n t types of l i g a n d s . X  5  The  complex, T i C E t ) ^ , which i s extremely s u s c e p t i b l e  to ^ - e l i m i n a t i o n , has  not been i s o l a t e d , w h i l e i n c o n t r a s t , T i ( C H S i M e ) ^ which c o n t a i n s the 2  sterically  bulky - C H S i M e 2  s t a b l e to temperatures  3  3  l i g a n d , has no B-hydrogens and i s subsequently  approaching  80°C.  P y r o l y s i s s t u d i e s have a l s o shown  the homoleptic a l k y l s MR^ (M = Z r , Hf, R = M e S i C H - , Me CCH -, Me SnCH -) 3  decompose v i a r e d u c t i v e e l i m i n a t i o n r a t h e r The  2  than  3  2  ^-abstraction.  3  2  5  process o f c r e l i m i n a t i o n proceeds with the m i g r a t i o n of a  p r o t o n from the orcarbon of an a l k y l group  to the metal c e n t r e to generate  an a l k y l i d e n e - h y d r i d e i n t e r m e d i a t e or p r o d u c t . example was r e p o r t e d i n 1974  6  3  3  2  Ta(CH CMe ) 2  3  5  documented  (eqn. 6 ) .  Ta(CH CMe ) C 1 + 2 L i C H C M e 2  The f i r s t  2  3  —+  [ I n t e r m e d i a t e ] —->•  —•*• (CH CMe ) Ta=CHCMe + CMe^ + 2 L i C l 2  3  3  (6)  3  B  C  The n e o p e n t y l l i g a n d s on B a r e s t e r i c a l l y  too demanding, t h e r e f o r e ,  subsequently a proton on one of the n e o p e n t y l groups  i s a b s t r a c t e d by a  second n e o p e n t y l l i g a n d w i t h the ensuing e l i m i n a t i o n of neopentane. a l t e r n a t e mechanism has s i n c e been proposed which suggests  LiCH CMe 2  m e t a l l a t e s one of the protons on T a ( C H C M e ) ^ C l to generate 2  (CHCMe )Cl}~Li  +  indicate  ct-elimination i s f a c i l i t a t e d  3  that  which e l i m i n a t e s L i C l  3  to g i v e product C. by the removal  d e n s i t y from the a l k y l C-H bond to the metal c e n t r e .  7  An 3  {Ta(CH CMe ) ~  Recent  2  3  3  studies  of e l e c t r o n  6  The mentioned  Y~ H- i e  m  n a t i o n  decomposition  a c t i v a t i o n energy,  pathway i s the l e a s t documented of the  pathways.  afore-  I t i s a process which has a h i g h  a t t r i b u t a b l e to the s t e r i c requirements of the  reaction. Reductive e l i m i n a t i o n p r o v i d e s a route f o r the cleavage of m e t a l carbon, and metal-hydrogen stable oxidation process w i t h i n prominent involves  bonds.  states d i f f e r i n g  the e a r l y group  f o r the l a t e r  8  a  Per  Et^P  infrequent  t r a n s i t i o n metal c h e m i s t r y , becoming more Reductive e l i m i n a t i o n  of e i t h e r an a l k y l / h y d r i d e  ^  Pd(PEt ) 3  or an  usually  alkyl/alkyl  uncommon decomposition initially  pathway.  The  IVb  Me  2  (7)  However t h i s i d e a was  f o r t h e i r main group  o c c u r r e n c e of t h i s process  l a r g e t r a n s i t i o n metal-carbon  d i s p e l l e d w i t h the t a b u l a t i o n of  bond f o r c e c o n s t a n t s f o r T i M e C l  to those found  +  t r a n s i t i o n metal a l k y l s i s an  infrequent  a t t r i b u t e d to the r e l a t i v e l y  bond s t r e n g t h .  2  Me  Homolytic cleavage f o r the group  metal-carbon  I t i s an  having  (eqn. 7 ) .  Et P 3 ^  was  to those metals  by two u n i t s .  t r a n s i t i o n metals.  c i s - o r i e n t a t e d groups  combination  I t i s confined  3  and TiMe^ which were s i m i l a r  c o u n t e r p a r t s ( c . f . MeSnCl,).  In f a c t ,  7  horaolysis has now been I m p l i c a t e d i n the decomposition of a few t i t a n i u m and o r g a n o z i r c o n i u m compounds  9  (eqns. 8, 9 ) .  ( C H C H ) Zr-CH Ph — - • ( C H C H ) Z r * + 6  5  2  3  2  6  5  2  5  2  3  2  6  5  2  *CH Ph  3  (C H CH ) Zr-CH Ph — ( C H C H ) ZrCH 6  organo-  3  (8)  2  2  +  *Ph  (9)  A r e l a t i o n s h i p between the v a r i o u s modes of decomposition and the s t a b i l i t y of a metal a l k y l complex cannot be g i v e n ;  however, the f o l l o w i n g  sequence i s g e n e r a l l y the most a c c u r a t e and w i d e l y a c c e p t e d  PhCH  > Me SiCH  2  3  2  > Me CCH 3  2  1 0  stability  (Scheme 4 ) .  > Ph > M e » E t > S e c - a l k y l  Scheme 4  1.1  Homoleptic  A l k y l s of T i t a n i u m ( I V ) , Z i r c o n i u m ( I V ) , and  Homoleptic r e a c t i n g an a l k y l halide.  a l k y l s of the group  IVb metals are g e n e r a l l y prepared by  l i t h i u m or G r i g n a r d reagent w i t h a t r a n s i t i o n  metal  The c o o r d i n a t i o n number of the metal with r e s p e c t to the number of  a l k y l s u b s t i t u e n t s , can be i n f l u e n c e d by r e g u l a t i n g group  Hafnium(IV).  (Scheme 5 ) .  the s i z e of the a l k y l  8  3LiR  4LiR  MCI  [MR ]^ 4  -[MCIR ] 3  4  M = Hf,Zr  M = Hf Zr ;  R=fTH(SiMe ^]  R =CH CMe 2  CH SiMe 2  3  3  3  Scheme 5  The bulky b i s ( t r i m e t h y l s i l y l m e t h y l ) l i g a n d about  the metal c e n t r e , f a i l i n g  Zr and H f for  1 1  .  A l l the group  precludes f o u r - c o o r d i n a t i o n  to d i s p l a c e a l l the c h l o r i d e l i g a n d s  IVb homoleptic a l k y l s a r e a i r s e n s i t i v e ;  example, z i r c o n i u m t e t r a b e n z y l takes up two moles of  among other p r o d u c t s , b e n z y l a l c o h o l and benzaldehyde The group  to generate,  after  hydrolysis.  IVb metal a l k y l s u s u a l l y generate RH upon h y d r o l y s i s ;  sensitivity  from  to m o i s t u r e i s of the g e n e r a l order T i < Zr  <Hf.  1  their From  2  c a l c u l a t e d heats of f o r m a t i o n and metal-carbon bond e n e r g i e s , * the thermal 3  s t a b i l i t y of the a l k y l s  f o l l o w s the same t r e n d , w i t h the c o r r e s p o n d i n g  metal-carbon bond e n e r g i e s d e c r e a s i n g i n the sequence The  thermal decomposition of the t e t r a - a l k y l s  Q ^ P h X ^ H ^ e >CH^CMe^.  [MR^] o f t e n produces  alkanes  and a reduced metal s p e c i e s , however, even s u b t l e changes i n the nature of the  h y d r o c a r b y l group can i n f l u e n c e the decomposition products (Scheme 6 ) .  9  H R=CH CMe 2  CH SiMe  [ZrRj  RR + RH «•  3  2  3  R =CH SnMe 2  RR + RH CgH +C H +  6  2  6  R = CH Ph 2  Scheme 6  1.2  H e t e r o l e p t l c a l k y l s of T l t a n l u m ( I V ) , Z l r c o n l u m ( I V ) Three c a t e g o r i e s w i l l  and  Hafnlum(IV).  be reviewed: 1) d e r i v a t i v e s c o n t a i n i n g c y c l o -  p e n t a d i e n y l groups, 2) complexes u t i l i s i n g  phosphine l i g a n d s , 3)  systems  c o n t a i n i n g n i t r o g e n donors.  1.2.1  C y c l o p e n t a d i e n y l complexes of T i t a n i u m ( I V ) ,  Zirconium(IV),  and  Hafnium(IV). There are few Hf.  The  earliest  examples of mono-cyclopentadienyl  r e p o r t e d d e r i v a t i v e s have the g e n e r a l  {ZrCl R_ ( n - C c H r ) } (n • 1,2) n J—n 5  3  3  thermally unstable; are formed.  The  complexes of Zr  (R - n e o p e n t y l ) .  7  and  formula  These complexes are  however, i n the presence of PMe , i s o l a b l e compounds  bis-cyclopentadienyl derivatives:  (M • T i , Z r , H f ) , l , are f a r more numerous.  3  ( T I - C H ) jMR 5  5  5  2  (  R  *  M e  )  10  .R Mr"  The b i s - c y c l o p e n t a d i e n y l  complexes a r e commonly prepared from the a p p r o p r i -  ate m e t a l l o c e n e d i c h l o r i d e and a s u i t a b l e a l k y l l i t h i u m or G r i g n a r d reagent (eqn. 10).  ( n - C H ) 2MC1 + 2RLi —•*• ( n -C H ) jMRj + 2 L i C l 5  5  5  5  2  5  5  (10)  The products are u s u a l l y monomeric, c o l o u r l e s s , c r y s t a l l i n e s o l i d s which may be p u r i f i e d by s u b l i m a t i o n . reactive  The metal-carbon  towards p r o t i c media, forming metal-oxygenated  eliminating  5  5  In c o n t r a s t 2  d e r i v a t i v e s and  an alkane (eqn. 11).  ( n -C H ) ZrMe + ROH — +  towards 0  bonds are extremely  5  2  2  ( n -C H ) Zr(0R)Me + 5  5  5  2  Me  (11)  to t h e i r homoleptic c o u n t e r p a r t s they are r e l a t i v e l y u n r e a c t i v e and C 0 » The* --hetaroleptic complexes a l s o e x h i b i t a g r e a t e r degree 2  of thermal s t a b i l i t y . -70°C, w h i l e C p Z r M e 2  2  For example, Z r M e  4  decomposes a t temperatures  sublimes between 100-110°C at 10"*• mm Hg.  The  above  11  s t a b i l i t y of these systems i s i n part  attributed  l i g a n d , which i s not only s t e r i c a l l y demanding  to the  cyclopentadienyl  but s u b s t i t u t i o n a l ^  inert.  The i n s e r t i o n of CO i n t o the metal-carbon bonds of z i r c o n o c e n e and hafnocene d i a l k y l d e r i v a t i v e s t i o n (eqn. 12). ^  1 5 >  1  has r e c e n t l y  undergone e x h a u s t i v e  investiga-  6  ( n ^ C H )2MR 5  5  5  2  + CO — +  ( n - C H ) ^(COIOR  (12)  5  5  5  M *= Zr, Hf R = Me, CH Ph 2  The r e a c t i o n with CO generates considered  2.  to be a u n i n e g a t i v e f o u r - e l e c t r o n  an 18 e l e c t r o n zirconium  n—acyls,  complex.  The a c y l group may be donor l i g a n d which r e s u l t s i n  I s o l a t i o n has so f a r o n l y been p o s s i b l e  derivatives.  2  f o r the  12  1.2.2  Phosphine  Complexes o f T l t a n l u m ( I V ) , Z i r c o n i u m ( I V ) , and  Hafnium(IV). Phosphine  complexes of the e a r l y group  Many of the known phosphine phosphine  donor  t r a n s i t i o n metals are r a r e .  complexes d i s p l a y s u b s t a n t i a l l a b i l i t y when the  i s c o o r d i n a t e d to metals which have  d e n s i t y , such as Z r ( I V ) or H f ( I V ) .  no d e l e c t r o n  One p o s s i b l e e x p l a n a t i o n f o r t h i s  behaviour i s found by r e f e r e n c e to the two b a s i c i n t e r a c t i o n s b e l i e v e d to be i n v o l v e d  i n a phosphorus-metal  bond, namely, a d o n a t i o n from the lone  p a i r of e l e c t r o n s on the phosphorus % backdonation from f u l l  atom i n t o an empty metal d o r b i t a l and  or p a r t l y f u l l d - o r b i t a l s on the metal to low  energy vacant d - o r b i t a l s on phosphorus  ( F i g . 1).  dir-dir bacxdonation Metal—c d orbital Phosphorus d orbital F i g u r e 1.  R e p r e s e n t a t i o n of d-d o r b i t a l o v e r l a p i n a metal-phosphorus bond.  The extent of du-du i n t e r a c t i o n i s dependent of  on two f a c t o r s : a) the degree  d - o r b i t a l o v e r l a p , and b) the e l e c t r o n d e n s i t y a t the metal c e n t r e  a v a i l a b l e f o r backdonation, which  i s presumably  small i n a formally  13  d° metal complex.  However, a l a r g e du-d-jt i n t e r a c t i o n does not  necessarily  generate a n o n - l a b i l e phosphine complex.  I n v e s t i g a t i o n s on  of a s e r i e s of Ni(0)  a v a r i e t y of phosphine donors  complexes c o n t a i n i n g  concluded that i t i s the e l e c t r o n i c character complex. ' 1 8  according  1 9  the  s i z e of the phosphine donors r a t h e r  that p r i n c i p a l l y determines the  stability  than  stability  of  their the  A l a r g e number of phosphine l i g a n d s have been ranked  to cone angle ( F i g . 2 ) , (the angle subtended by a cone i n a  Ni-PR, fragment).  Figure  2.  Representation  of a phosphine cone a n g l e ,  E a r l y t r a n s i t i o n metal phosphine c h e m i s t r y i s s t i l l for  example, there  zirconium  are o n l y a few  reported  i n which the metal i s i n a +4  complex has  in i t s infancy,  phosphine d e r i v a t i v e s of  oxidation  j u s t r e c e n t l y been d e s c r i b e d .  9.  2 0  The  state.  One  particular  reaction involved  the  14  c a r b o n y l a t i o n of C p Z r ( C l ) C H P P h 2  interaolecular  2  proton  to generate product B v i a  2  an  t r a n s f e r pathway (Scheme 7 ) .  ,PPh CH PPh 2  2 C  p  ZrCICH PPh 2  2  CO  2  CH PPh 3  2  Scheme 7  The  l a b i l i t y of the phosphine donor was  unsuccessful  also displayed during  attempts to induce i n t r a m o l e c u l a r  the  proton-abstraction  s e r i e s of neopentyl phosphine complexes o f ^ Z r ( I V )  7  (eqn.  in a  13). (13)  Z r ( C H C M e ) Cl (}pHe ) 2  3  Only one  2  2  + PMe ~^ 2  3  2  s i g n a l was  3  present  ZrCl  i n the  3 1  P  2  &He  )( PMe ) ( C H C M e ) 2  3  NMR  3  2  when PMe  3  was  3  added  PMe  1 2 +  to  Z r C l ( C H C M e ) ( P M e ) , which suggested the phosphine l i g a n d s were 2  2  3  2  3  exchanging r a p i d l y on  2  the NMR  time s c a l e  38  (eqn.  13).  3  15  1.2.3  Amide C o m p l e x e s o f T i t a n i u m ( I V ) , Z i r c o n i u m ( I V ) , and A metal  coordinated  amide i s a compound w h i c h  to a metal  (R = a l k y l ,  aryl  relatively  s m a l l number o f p h o s p h i n e  transition  m e t a l s , a wide v a r i e t y  characterised. transition  There  or s i l y l )  3b,  3c.  In contrast  possibilities  illustrated  to  the  f o r the e a r l y  group  available  to  b e l o w ( F i g . 3 a , 3b,  3c).  M  3b  3a  N—3a,  .  M  R  Figure  1  units  o f amide d e r i v a t i v e s h a v e b e e n  These are  Kl  R-  2  o r more NR"^  complexes i s o l a t e d  are s e v e r a l bonding  metal amides.  c o n t a i n s one  Hafnium(IV).  Bonding  M  possibilities  available  to t r a n s i t i o n  metal  amides  A m e t a l amide c a n a d o p t mode o f h y b r i d i s a t i o n unit  b e t w e e n two  i n v o l v e s a p^-du to  explain  units  found  metal  a p y r a m i d a l c o n f i g u r a t i o n w i t h an a p p r o x i m a t e  o f t h e n i t r o g e n atom ( 3 a ) , o r s e r v e as a centres (3b).  interaction  the r e l a t i v e l y  The  in addition  s h o r t M-N  third to a  possibility, a component was  bond d i s t a n c e s and  i n s e v e r a l of these complexes  (Fig. 4).  sp  3  bridging  3c, put  which forward  the p l a n a r R NM 2  16  F i g u r e 4.  The  Representation  of p-d  o r b i t a l overlap  i n a metal-nitrogen  pu-dn component of the bonding i n v o l v e s the i n t e r a c t i o n of the  p a i r of e l e c t r o n s on the n i t r o g e n atom w i t h the m e t a l .  Zr(IV)  and  partly f u l l rc-electron  in contrast  to the  l a t i o n and  energy vacant d - o r b i t a l s on  t h e r e f o r e form s t a b l e amide  l a t e r group t r a n s i t i o n metals which have  or f u l l d - o r b i t a l s and  as a consequence behave as  poor  acceptors.  Both homoleptic and There are  lone  H f ( I V ) , which have vacant d - o r b i t a l s , can accept pit  e l e c t r o n d e n s i t y from a n i t r o g e n donor and derivatives,  low  bond  two  h e t e r o l e p t i c t r a n s i t i o n metal amides are known.  common procedures employed i n t h e i r p r e p a r a t i o n :  transamination.  The  transmetal-  former i n v o l v e s the a d d i t i o n of a l i t h i u m  17  amide to the a p p r o p r i a t e metal h a l i d e g e n e r a l l y used  to prepare homoleptic  4 L i ( N M e ) + MCl^  (eqn. 1 4 ) . T h i s i s the method amides.  2 2  * M(NMe ) ^ + 4 L i C l  2  (14)  2  M - T i , Z r , Hf.  The  p r e p a r a t i o n of h e t e r o l e p t i c  amides can be accomplished  by t r a n s -  a m i n a t i o n (eqn. 15), a process which i n v o l v e s the exchange of one amide f o r another a t the metal c e n t r e .  The more v o l a t i l e  amine i s u s u a l l y  displaced.  Zr(NMe ) 2  4  + 2HN(i-Pr)  2  — * Zr(NMe ) (N( i - P r ) . ) + 2HNMe 2  2  2  2  2  (15)  The use of b u l k y amido l i g a n d s a l l o w s the i s o l a t i o n of complexes having low c o o r d i n a t i o n numbers, f o r example, T i {N( (SiMe ) ) ^ 3  The homoleptic amides M ( N R ) 2  thermally protic  stable;  l 4  compared to T i ( N M e ) . 2  1+  however, they are r e a d i l y h y d r o l y s e d and r e a c t w i t h  s o l v e n t s to generate  the metal a l k o x i d e  2  a d d i t i o n of l i t h i u m  hafnium  3  (M - T i , Z r , Hf, R - a l k y l ) are  Z r ( N R ) ^ + 4R0H — — » Z r ( O R )  The  2  l 4  2 3  (eqn. 1 6 ) .  + 4R NH 2  (16)  or sodium ( h e x a m e t h y l d i s i l y l ) a m i d e to z i r c o n i u m o r  t e t r a c h l o r i d e generates  the h y d r o c a r b o n - s o l u b l e compounds  18  M C 1  4-n  { N ( S i M e  3>2>  (  n  n  " ' > X  2  (  e  c  l n  1 7  >'  n L i { N ( S i M e ) } + MCl^ 3  24 25. '  • M C l _ {N(SiMe ) > + n L i C l  2  4  n  3  2  n  (17)  The t r i s - a m i d o d e r i v a t i v e s , M C I { N ( S i M e ) ) , are a i r s t a b l e , i n c o n t r a s t to 3  2  3  the b i s - d e r i v a t i v e s , M C l ( N ( S i M e ) > , which are s l i g h t l y a i r and moisture 2  sensitive.  3  2  2  The a d d i t i o n of methyl l i t h i u m  c o r r e s p o n d i n g m e t a l - a l k y l amides (eqn.  MCl {N(SiMe ) } 2  3  2  2  silylamide  1.3  18).  + 2MeLi — * M ( M e ) { N ( S i M e ) )  The d i - a l k y l metal amides are u n r e a c t i v e also k i n e t i c a l l y  to these complexes g i v e s the  2  3  towards 0  2  2  2  + 2LiCl  and m o i s t u r e .  i n e r t , a p r o p e r t y which i s a t t r i b u t a b l e  (18)  They a r e  to the l a r g e  l i g a n d s which tend to preclude r e a c t i v i t y at the metal c e n t r e .  Design and S y n t h e t i c U t i l i t y of a Hybrid M u l t i d e n t a t e  Ligand.  The concept of l i g a n d d e s i g n has been a prominent f e a t u r e i n the development of t r a n s i t i o n metal c h e m i s t r y . electronic  1 7  By c o n t r o l l i n g  the s t e r i c and  environment about the metal c e n t r e i t i s p o s s i b l e to i n f l u e n c e  the s t a b i l i t y and r e a c t i v i t y of the complex.  The d i f f i c u l t y  i n isolating  19  and s u c c e s s f u l l y c h a r a c t e r i s i n g  phosphine complexes  has been overcome by d e v e l o p i n g a l i g a n d  of the group IVb metals  system which c o n t a i n s both  phosphine donors and an amide donor i n a c h e l a t i n g  array,  3.  :PR.  3  The l i g a n d , 3, may  formally  be regarded as a u n i n e g a t i v e 6e donor, or a  u n i n e g a t i v e Ae donor s i m i l a r i n n a t u r e to the a l l y l upon the tendency of the l i g a n d manner ( F i g s . 5a, 5b)  group C H ~ , depending 3  5  to c o o r d i n a t e i n a b i d e n t a t e or  respectively.  tridentate  20  Me Me Me  ,Me  Me Me Me  Me  Si" V"  Ml"*  PR  RP 2  +M<  5a  PR  2  5b  Figures  5a and 5b.  Coordination  modes a v a i l a b l e to [ N C S i M e j C H j P I ^ ) ] ~ *  Initial  i n v e s t i g a t i o n s which u t i l i s e d  2  this ligand  i n conjunction  with  metals from the l a t e r groups of the t r a n s i t i o n metal s e r i e s : N i , Pd, Pt gave a range of r e a c t i v e t r a n s i t i o n metal c h l o r o  d e r i v a t i v e s , 4.  PPh2 Me si z  NMe-) Si  -M-  CI  26 27 '  21  Coordination  of the l i g a n d  to z i r c o n i u m and hafnium was a l s o  successful,  g e n e r a t i n g b i s - l i g a n d d e r i v a t i v e s of the formula MCI {N(SiMe CH PR2)2 ^ 2» 2  5 >  2  2  28» 29  5  These d e r i v a t i v e s d i s p l a y e d  l i m i t e d r e a c t i v i t y , a r e s u l t a t t r i b u t e d to  s t e r i c crowding at the metal c e n t r e .  Addition  of excess H f C l  produced a hafnium t e t r a c h l o r i d e adduct of e m p i r i c a l Hf Cl {N(SIMe CH PMe ) }, 2  7  useful  2  2  2  2  6.  4  to 5^  formula  T h i s d e r i v a t i v e was found to be p a r t i c u l a r l y  i n generating hydride d e r i v a t i v e s .  However, 6 was  i n s o l u b l e and i t s c h e m i c a l nature was p o o r l y  relatively  characterised.  22  6  T h i s t h e s i s examines the f o r m a t i o n and s t e r e o c h e m i s t r y of the monoligand  derivatives, MCI {N(SiMe CH PR ) } 3  2  2  2  2  a  n  d  explores t h e i r  r e a c t i v i t y with p a r t i c u l a r emphasis on the f o r m a t i o n of bonds•  chemical  metal-carbon  23  CHAPTER 2  2.1  S y n t h e s i s o f LlN(SlMe C H P R ) . ?  ?  2  ?  The a d d i t i o n of N H ( S i M e C H C 1 ) 2  THF  generates 2  2  2  2  Me  N H  derivatives  (eqn. 1 9 ) .  Me,  Me  N Li  3LIPR,  CI  CI  to three e q u i v a l e n t s of L i P R i n  2  the c o r r e s p o n d i n g lithium-amido-phosphine  LiN(SiMe CH PR ) 2  2  R,P  +HPR + 2 L i C l  (19)  2  PR,  R=Me l * R=i-Pr 7b* a  R=t-Bu 7c  The  products a r e c o l o u r l e s s , c r y s t a l l i n e ,  a i r and moisture  sensitive  s o l i d s , which a r e s o l u b l e i n a v a r i e t y of o r g a n i c s o l v e n t s . purified  by f r a c t i o n a l  crystallisation  from hexanes a t -30°C.  They a r e In  a d d i t i o n , 7c o c c l u d e s a s m a l l amount of THF from the r e a c t i o n mixture which  The compounds 7a and 7b were o r i g i n a l l y  prepared by Dr. A x e l Westerhaus  24  cannot be removed by r e c r y s t a l l l s a t i o n t h e r e f o r e used as a THF  2.2  from d i f f e r e n t  solvate.  P r e p a r a t i o n and s t e r e o c h e m i s t r y o f MCI {N(SiMe ?  The a d d i t i o n of L i N ( S i M e C H P R ) 2  a p p r o p r i a t e metal mono-ligand  s o l v e n t s , and I t I s  2  2  (R - Me,  2  ;  C H 2 ^ *  i - P r , t-Bu) to the  t e t r a c h l o r i d e MCl^ (M - Z r , Hf) generates the  d e r i v a t i v e s M C I { N ( S i M e C H P R ) ) (eqns. 20, 21). 3  2  2  2  2  5 days L i N ( S i M e C H P M e ) + MCl^ 2  2  2  * MCI {N(SiMe CH jPMe ) ) + L i C l  2  3  2  2  2  (20)  M - Hf, 8a* M - Z r , 9a* 1 day L i N ( S i M e C H P R ) + MCl^ 2  *  2  2  2  MCI {N(SiMe C H P R ) ) + L i C l 3  2  2  2  2  M  R  Hf  i-Pr  8b*  Hf  t-Bu  8c  Zr  i-Pr  9b*  Zr  t-Bu  9c  (21)  The compounds $a, 8J>, 9ja and 9J> were o r i g i n a l l y prepared by Dr. A. U e s t e r h a u s . The X-ray c r y s t a l s t r u c t u r e s of 8a and 9b were o b t a i n e d from samples a l s o prepared by Dr. Westerhaus. ^ 7  25  Initially,  oily  monitoring  this reaction  derivative  5, was  reaction  products and by  poor y i e l d s of 8a were o b t a i n e d ; 3 1  P { H } NMR  formed f i r s t  1  established  that  which then underwent a  with excess H f C l ^ to generate 6 (eqn.  the  however,  bis-ligand  conproportionation  22).  (22)  5  6  In an attempt to o p t i m i s e the refined  to i n c l u d e  dilution. bulkier  The  y i e l d s of 8a  longer r e a c t i o n  reaction  of  phosphine s a l t s 7b  (R = Me),  times and  colourless,  (R = i - P r ) , and  7c  (R = t-Bu)  soluble  solvents.  (eqn.  moisture s e n s i t i v e s o l i d s , which are are  the  21),  i n good y i e l d s .  from hexane/toluene at -30°C.  i n hexanes or d i e t h y l e t h e r but  was  solution  z i r c o n i u m or hafnium t e t r a c h l o r i d e with  products c r y s t a l l i s e a i r and  procedure  higher reactant  proceeds d i r e c t l y to g i v e the mono-ligand d e r i v a t i v e s The  the  only  readily soluble  They  are  slightly  i n aromatic  26  S t e r e o c h e m i s t r y of the mono l i g a n d The  derivatives.  proton NMR of 8a (R = Me) d i s p l a y s one resonance f o r the s i l y l  methyl protons ( S i C H ) , and two " f i l l e d - i n " d o u b l e t s  f o r the methylene  3  (PCH ) and methyl (PCH ) protons ( F i g . 6 ) . 2  3  PMe  SiMe  ppm  Figure  6.  80MHz, H NMR spectrum of m e r - H f C I { N ( S i M e C H P M e ) > X  3  2  2  2  2  The  X-ray c r y s t a l l o g r a p h i c a n a l y s i s of 8a (R = Me) s u r p r i s i n g l y showed  the  ligand  i s bound i n a f a c i a l  orientation.  proton NMR data which i n f e r s a m e r i d i o n a l phosphine l i g a n d , a s c r i b a b l e  This  silylmethyl  methylene ( P C H ) , and methyl (PCH ) p r o t o n s . 2  orientated  species  i s i n c o n s i s t e n t with the  mode of l i g a t i o n  to the e q u i v a l e n t  If a static,  3  that  f o r the amido(SiCH ), 3  facially  e x i s t s i n s o l u t i o n then two d i s s i m i l a r environments f o r  In a m e r i d i o n a l geometry, the methyl protons can be d e s c r i b e d as b e l o n g i n g to an A A XX' s p i n system which reduces to an A X s p i n system when JyyJ i s l a r g e . T h i s generates a v i r t u a l t r i p l e t f o r the A p r o t o n s . ^0 I f however ^xx'^AX'' ^ i H - * - i - ' doublet i s observed r a t h e r than the v i r t u a l t r i p l e t one might have expected to see from trans-disposed phosphines. 2  2  i|  a  e £  n  2  27  the aforementioned groups would be g e n e r a t e d . inconsistency  an  i s o m e r i s a t i o n of the  To account  for  f a c i a l l y orientated  this  l i g a n d i s thought  * to take place  i n s o l u t i o n to generate the m e r i d i o n a l l y bound analog  (Fig.  7).  Figure  7.  Proposed i s o m e r i s a t i o n of fac-HfCI,{N(SiMe CH PMe ) } to m e r - H f C l { N ( S i M e C H P M e ) } i n s o l u t i o n . 2  3  2  2  2  2  2  2  2  F l u x i o n a l processes i n v o l v i n g fac-mer i n t e r c o n v e r s i o n s have been d i s m i s s e d on the b a s i s of P {-^H} v a r i a b l e - t e m p e r a t u r e NMR experiments on 8a, which d i s p l a y s o n l y one s i g n a l down to -90°C. 3 1  28  CIS)  C(3)  F i g u r e 8.  S t r u c t u r e and numbering scheme of H f C I { N ( S i M e C H P M e ) ) 3  2  2  2  2  (8a).  F i g u r e 9.  S t r u c t u r e and numbering scheme of Z r C l { N ( S i M e C H P ( i - P r ) ) ) 3  (9b).  2  2  2  2  29  I n c r e a s i n g the s i z e of the a l k y l group on the phosphorus donor induces dramatic  s t e r e o c h e m i c a l changes i n the molecule.  g r a p h i c a n a l y s i s of 9b (R = i - P r ) shows the l i g a n d  The c r y s t a l l o -  to be bound i n a  m e r i d i o n a l o r i e n t a t i o n ( F i g . 9 ) , w i t h i r r e g u l a r o c t a h e d r a l geometry. is  i n c o n t r a s t to 8a i n which the l i g a n d  i s bound f a c i a l l y ,  (This  see F i g . 8 ) .  One p o s s i b l e reason f o r t h i s g e o m e t r i c a l m o d i f i c a t i o n would be the minimisation of ligand-ligand phosphine groups.  To i n t e r p r e t  the proton NMR i s d i f f i c u l t signals. geometry;  r e p u l s i o n s between the b u l k i e r  the s t e r e o c h e m i s t r y of 9b (R • i - P r ) from  owing to the m u l t i p l i c i t y o f the i s o - p r o p y l  In s o l u t i o n 9b (R = i - P r ) appears o n l y one type of s i l y l m e t h y l  (R = Me);  a singlet  to r e t a i n i t s m e r i d i o n a l  s i g n a l i s observed  A much simpler s p e c t r a l p a t t e r n i s observed analog 8c (R = t-Bu)  iso-propyl  with the b u l k i e r  ( F i g . 10), which i s s i m i l a r f o r the s i l y l m e t h y l protons  " f i l l e d - i n " d o u b l e t s f o r both  down to -90°C.  the t e r t i a r y - b u t y l  tertiary-butyl  to t h a t d e s c r i b e d f o r 8a (SiCH ) 3  together with  ( P C ( C H ) ) and methylene 3  3  (PCH ) groups are present i n the proton NMR which i s once again c o n s i s t e n t 2  w i t h a m e r i d i o n a l geometry.  In f a c t  i t i s b e l i e v e d a l l the mono-ligand  d e r i v a t i v e s MC1 {N(SiMe CH PR ) >; 8 and 9 (R = Me, i - P r , t-Bu, M - Z r , 3  Hf) e x i s t  2  2  2  2  i n a m e r i d i o n a l conformation  i n solution.  30  F i g u r e 10.  80MHz *H NMR  spectrum of  mer-HfCI {N(SiMe CH P(t-Bu) ) > 3  2  2  2  2  31  2.3  The p r e p a r a t i o n and s t e r e o c h e m i s t r y o f M(CH ) {N(SiMe C H P R ) ) 3  3  2  2  2  2  The a d d i t i o n of t h r e e e q u i v a l e n t s of MeMgCl i n THF to an e t h e r s o l u t i o n of the mono-ligand  complexes M C I { N ( S i M e C H P R ) > 3  2  2  2  2  8_ and 9 (R =  Me, i - P r , t-Bu, M = Z r , Hf) generates the c o r r e s p o n d i n g t r i m e t h y l d e r i v a t i v e s M ( C H ) { N ( S i M e C H P R ) ) (eqn. 2 3 ) . 3  3  2  2  2  2  M C l { N ( S i M e C H P R ) } + 3MeMgCl — - * M(CH ) {N(SiMe C H P R ) ) + 3 M g C l 3  2  2  2  2  3  3  2  M  R  Hf Hf Hf Zr Zr Zr  Me i-Pr t-Bu Me i-Pr t-Bu  2  2  2  10a 10b 10c Ua* Ub 11c  These compounds are c o l o u r l e s s , moisture s e n s i t i v e , c r y s t a l l i n e which are u n s t a b l e at room temperature  2  solids,  and r a p i d l y decompose i n a i r . The  thermal s t a b i l i t y of these complexes decreases i n the order t-Bu > i - P r > Me and Hf > Z r . Although the t e r t i a r y - b u t y l phosphine more b a s i c  donors  are s l i g h t l y  than the i s o p r o p y l or methyl a n a l o g s , the e l e c t r o n i c  influences  which c o n t r i b u t e to the s t a b i l i t y of the t r i - a l k y l d e r i v a t i v e s i s presumably  minimal when compared to the s t e r i c  11a was o n l y observed  effects.  i n the proton NMR and was not i s o l a t e d .  32  The  analogous r e a c t i o n  to the t r i m e t h y l  preparation,  using  2 moles  of MeMgCl to generate the d i m e t h y l d e r i v a t i v e s M(CH ) C1 {N(SiMe CH jPRj) > 3  (eqn.  24) was u n s u c c e s s f u l .  the mono-ligand d e r i v a t i v e s  2  2  The a d d i t i o n of two e q u i v a l e n t s  o f t h e i r p h y s i c a l or chemical  3  2  2  2  Y  -»•  2  Hf(Me ) C l { N ( S i M e C H P R ) ) } 2  2  2  2  not be  properties.  H f C l { N ( S i M e C H P R ) } + 2MeMgCl  x  o f MeMgCl to  8a (R - Me) and 8b (R • i - P r ) generated a  mixture of both the mono- and d i - a l k y l products which could separated on the b a s i s  2  x-0, y=3 x=l,  (24)  y=2  x=2, y=l  The  addition  of two e q u i v a l e n t s  i s o l a t i o n of the t r i m e t h y l  of MeMgCl to 8c (R - t-Bu) r e s u l t e d  i n the  d e r i v a t i v e 10c (R - t-Bu) and s t a r t i n g  material. Monitoring MeMgCl by  3 1  the r e a c t i o n of 8b (R • i - P r ) with 2 e q u i v a l e n t s  P { H } NMR i n d i c a t e d 1  formed w i t h i n  that  the t r i m e t h y l  derivative  3 minutes ( F i g . 1 1 ) . Two a d d i t i o n a l s i n g l e t  is initially  resonances  b e g i n to appear c o n c u r r e n t with the disappearence of the t r i m e t h y l resonance.  The two new peaks correspond  to the mono- and d i - a l k y l  d e r i v a t i v e s H f ( C H ) C 1 { N ( S i M e C H P ( i - P r ) ) ) and Hf(CH ) C1{N(SiMeg3  2  2  2  2  2  3  2  of  then  33  CH P(t-Pr) ) ) . 2  of  2  The c h e m i c a l s h i f t s of these d e r i v a t i v e s l i e between those  2  the t r i m e t h y l complex and s t a r t i n g  material.  L = N(SiMe CH PR ) 2  2  2  t = 3 min  LHfMeCU LHfMe,CI  30  20  W  f  M  e  3  10  P Pm  To"  30  "7b~  t =  30 min  t=  1h  ~o  P Pm  ppm Figure  11.  To  JO  To"  P NMR spectrum f o l l o w i n g the r e a c t i o n between H f C l { N ( S i M e C H 2 P ( i - P r ) ) > and two e q u i v a l e n t s of MeMgCl. 3 1  3  2  2  2  34  Presumably the f o r m a t i o n  o f these  products  occurs v i a a c o n p r o p o r t i o n a t i o n  r e a c t i o n between the t r i m e t h y l s p e c i e s 10b (R • i - P r ) and s t a r t i n g m a t e r i a l 8b (R - i - P r ) (eqn. 25, scheme 8 ) .  CI L - W l .+ LMCH.  LM  •LMCH+ LMCI  ML  1  1  3  CH (25)  L = N(SiMe CH PR ) 2  L HfCl  2  3  + 2MeMgCl  -»•-| L HfMe  3  + -j L H f C l + 2 M g C l 3  2  conproportionation L HfMe CI x y (x - 1,2,3) Scheme 8  35  For 8c (R - t-Bu), prevent  s t e r i c r e p u l s i o n between the t e r t i a r y - b u t y l groups may  the b r i d g i n g c o n p r o p o r t i o n a t i o n  exchange.  step, which p r e c l u d e s  methyl-halide  T h i s would account f o r the i s o l a t i o n of s t a r t i n g m a t e r i a l i n the  r e a c t i o n of 8c (R - t-Bu) w i t h 2 e q u i v a l e n t s of MeMgCl.  An e q u i l i b r i u m i s  e v e n t u a l l y e s t a b l i s h e d between the monomethyl and d i m e t h y l s t a r t i n g m a t e r i a l ( a s demonstrated by the f a c t  d e r i v a t i v e s and  that a f t e r m o n i t o r i n g the  r e a c t i o n over a p e r i o d of 24 h i n the P { H } NMR, the c o n c e n t r a t i o n s , of 3 1  all  1  s p e c i e s i n s o l u t i o n remain c o n s t a n t ) .  p r o p o s a l of m e t h y l - h a l i d e  exchange, the r e a c t i o n of 8b (R • i - P r ) and 10b  (R = i - P r ) was monitored by corresponding belonging  3 1  P { H } NMR. 1  The  W i t h i n minutes the s i n g l e t  to 10b (R = i - P r ) disappeared  to the monomethyl and d i m e t h y l  methyl-halide  To f u r t h e r i n v e s t i g a t e the  and two new resonances  analogs  appear, which i n d i c a t e d  exchange was t a k i n g p l a c e .  proton NMR s p e c t r a f o r a l l the t r i m e t h y l d e r i v a t i v e s show one  type of s i l y l m e t h y l  ( S i C H ) , phosphine (PR )» and methylene (PCH ) p r o t o n 3  2  2  environment ( F i g . 1 2 ) . One anomaly, however, i s the presence of o n l y one triplet  resonance f o r the methyl groups a t t a c h e d  to the metal c e n t r e .  36 *CCH, SiCH,  HtCH  3  -CH,  1 p pm  F i g u r e 12.  If  80MHz *H NMR spectrum of  one assumes a r i g i d  H f ( C H ) { N ( S i M e C H , P ( t - B u ) ,/) , } 3  3  2  o c t a h e d r a l geometry  2  2  J  around the metal t h e r e  should be two s i g n a l s generated by the methyl p r o t o n s .  One s i g n a l f o r the  methyl group t r a n s to the amide and one f o r the two methyl groups c i s to the  amide donor.  The v a r i a b l e - t e m p e r a t u r e  p r o v i d e s a p o s s i b l e answer to t h i s dilemma d i s p l a y s one s i g n a l at room  3 1  P { H } NMR of 10c (R = t-Bu)  ( F i g . 1 3 ) . 10c (R = t-Bu)  temperature (as one might p r e d i c t  phosphorus n u c l e i i n e q u i v a l e n t e n v i r o n m e n t s ) . -70°C and f i n a l l y , One  :  on c o o l i n g  f o r two  T h i s s i g n a l broadens a t  to -90°C, two resonances appear.  p o s s i b l e i n t e r p r e t a t i o n of the v a r i a b l e - t e m p e r a t u r e NMR d a t a  r e q u i r e s a process whereby one of the phosphine donors d i s s o c i a t e s from the metal to generate a f i v e c o o r d i n a t e i n t e r m e d i a t e . r e c o o r d i n a t i o n o f the phosphine donor.  T h i s i s then f o l l o w e d by  I t would appear that the c o o r d i -  nated and u n c o o r d i n a t e d phosphorus n u c l e i a r e only d i s t i n g u i s h a b l e i n  37  e 13.  V a r i a b l e - t e m p e r a t u r e *H and P { H ) NMR Hf ( C H ) { N ( S i M e C H P ( t - B u ) ) >. 3 1  3  3  2  2  2  2  1  of  38  the  31  P { H } NMR spectrum a t low temperature when the process o f 1  association/dissociation exchange  i s slowed down or stopped.  r a t e of the phosphorus  In other words, the  n u c l e i between the two environments a t room  temperature i s f a s t i n comparison to the frequency d i f f e r e n c e two s i g n a l s , and as a consequence, resonance peak.  between the  the two s i g n a l s merge to form one  The process i s s a i d  to be f a s t on the NMR time  scale.  To pursue the i d e a of phosphine d i s s o c i a t i o n , AlMe, was added s o l u t i o n of 10c (R = t-Bu) i n an attempt to prevent r e c o o r d i n a t i o n phosphine donor by g e n e r a t i n g  the c o r r e s p o n d i n g phosphorus/AlMe  12.  12  3  3 8  to a  of the adduct,  39  Monitoring upfield  this  reaction  i n the  after  the a d d i t i o n of e x c e s s A l M e .  1  light  of the f a c t  T h i s was  3  o r 8c (R = t - B u ) ; the c o n t e n t i o n  species  P { H } NMR  spectrum, there  o f a p p r o x i m a t e l y 4ppm i n t h e peak, p o s i t i o n o f 10c  shift  dissociate  3 1  that  t h e r e was  the t r i c h l o r o  formed  aluminium, i s accompanied  AlMe  3  and 8a (R =  d e r i v a t i v e s , which i s i n accordance  I t i s , however,  i s ' 12J .  (R=t-Bu)  an e n c o u r a g i n g r e s u l t , i n  no r e a c t i o n b e t w e e n  t h a t the phosphine donors  in solution.  i s an  Normally adduct by a d o w n f i e l d  i n these complexes  do  extremely u n l i k e l y  that  formation involving shift  Me)  with  not the  new  phosphorus  i n the phosphorus  and  peak  39 position.  F u r t h e r m o r e , one  competition occurring  between  cannot r u l e out the p o s s i b i l i t y t h e two L e w i s a c i d  aluminium f o r the phosphine donors To e x p l a i n NMR  spectrum  rather  f o r the methyl groups  attached  the idea of phosphine d i s s o c i a t i o n , rearrangement  pathways  available  p e n t a c o o r d i n a t e s p e c i e s would one  o f t h e p h o s p h i n e arms One  groups  c e n t r e s of hafnium  than simple adduct  t h e o b s e r v a t i o n o f o n l y one  of  triplet  formation.  resonance i n the  to the m e t a l c e n t r e  one must e x a m i n e  and  the  *H  utilising  possible  to p e n t a c o o r d i n a t e complexes  be g e n e r a t e d i n t h e t r i m e t h y l  31*32 (  complexes  a  If  dissociates).  p o s s i b l e mechanism r e q u i r e s  t o be a r r a n g e d t e t r a h e d r a l l y ,  the n i t r o g e n donor  and  three  (a requirement which i s not  methyl  40  u n r e a l i s t i c based on the c r y s t a l l o g r a p h i c data obtained with  the phosphorus donors c o o r d i n a t e d  faces of the t e t r a h e d r o n .  f o r 10a (R » Me))  to the metal through two  dissimilar  I f one c o n s i d e r s the n i t r o g e n atom to p l a y the  r o l e of p i v o t , each phosphorus donor i s d i s s o c i a t e d i n t u r n and r o t a t e d through 120°, whereupon different  r e c o o r d i n a t i o n to the metal takes  face of the t e t r a h e d r o n .  p l a c e through a  A f t e r a complete 360° r o t a t i o n of the  c h e l a t i n g phosphine a l l the methyl groups w i l l have occupied  equivalent  p o s i t i o n s (Scheme 9 ) .  Me Scheme 9  The Berry p s e u d o r o t a t i o n m e c h a n i s m  33  i n v o l v e s the p a i r w i s e  of a p i c a l and e q u a t o r i a l l i g a n d s i n p e n t a c o o r d i n a t e  TBP complexes.  exchange In the  scheme shown below (Scheme 10), E' i s a p i v o t and does not p a r t i c i p a t e i n any p o s i t i o n a l  exchange.  41  Scheme 10 T h i s mechanism i s demonstrated below i s an attempt to account f o r the behaviour of the methyl groups i n the M(CH ) { N ( S i M e C H P R ) ) 3  3  2  2  2  c  o  m  2  P  l  e  x  e  s  (Scheme 11). (For  c l a r i t y , only the c o o r d i n a t e d arms of the c h e l a t i n g  amido-phosphine  l i g a n d are shown).  Scheme 11  On moving from s t r u c t u r e A to s t r u c t u r e B (Scheme 11) one proceeds through two c o n s e c u t i v e BPR's each s t r u c t u r e generated by permutation of the four ligands  p r e c e d i n g i t w i t h CI and C3 a c t i n g as p i v o t s .  structures  A and B i t has been shown 1 ( C H ) = 2 ( C H ) , 3 ( C H ) = 1 ( C H ) , 3  2(CH )=3(CH ). 3  In comparing  3  3  3  3  42  A further involving  possible  mechanism to account f o r i s o r a e r i s a t i o n s  TBP complexes i s known as t u r n s t i l e r o t a t i o n ,  ( T R ) . The  3 2  mechanism corresponds to an i n t e r n a l r o t a t i o n of one a p i c a l and one equatorial  ligand  r o t a t i n g as a p a i r versus the o p p o s i t e l y  three remaining l i g a n d s  rotating  t r i o of  (Scheme 12).  4  5  Scheme 12  Once again by m a n i p u l a t i o n of the M(CH ) {N(SiMe C H P R ) ) d e r i v a t i v e s t o 3  3  2  2  2  2  accommodate two s u c c e s s i v e TR's one generates e q u i v a l e n t (Scheme 13).  methyl groups  43  Scheme 13  Comparing  s t r u c t u r e s C and D, Once a g a i n i t has been shown 3 ( C H ) « 1 ( C H ) , 3  2(CH )-1(CH ), 3  3  2(CH )-3(CH ).  3  3  3  There Is at the p r e s e n t time no evidence to support a l l or any of the  p r e c e d i n g mechanisms.  rearrangement  They are shown only to i l l u s t r a t e  pathways a v a i l a b l e to the t r i m e t h y l  The s o l i d  complexes.  s t a t e s t r u c t u r e of 10a ( F i g . 14) shows the l i g a n d i s  bound i n a f a c i a l mode as p r e v i o u s l y encountered f o r the d e r i v a t i v e 8a (R - Me). geometry.  the p o s s i b l e  trichloro  There are l a r g e d e v i a t i o n s from an o c t a h e d r a l  The C(5)-Hf-N bond angle i s 136° 1";  approximately 44° out of a t r a n s o r i e n t a t i o n .  the n i t r o g e n atom  lying  The n i t r o g e n atom and  three  carbon atoms of the methyl groups appear to be arranged i n the form of a pseudo-tetrahedron.  Although the C(4)-Hf-N angle of 113° and  C(3)-Hf-N  44 angle of 102° show s l i g h t  d e v i a t i o n s from the expected  t e t r a h e d r a l angle  of 109°, the C(5)-Hf-N o f 136° i s much too l a r g e f o r a r e g u l a r  Figure  14.  tetrahedron.  S t r u c t u r e and numbering scheme f o r fac-Hf(CH ) {N(SiMe CH PMe ) }. 3  The  Hf-P bond l e n g t h s , ranging  l a r g e r than the corresponding derivatives.  3  2  2  2  2  from 2.761 to 2.806 A,are 0.055 to 0.070' bond l e n g t h s  found f o r the t r i c h l o r o  T h i s may t e n t a t i v e l y be a t t r i b u t e d to an i n c r e a s e i n  3 7  e l e c t r o n d e n s i t y a t the metal c e n t r e when the more e l e c t r o n e g a t i v e c h l o r i d e atoms are r e p l a c e d r e g i o n on s o l i d provide  by the l e s s e l e c t r o n e g a t i v e methyl groups.  samples ( C s l d i s k ) of the t r i m e t h y l d e r i v a t i v e s d i d not  any d e f i n i t i v e  information  on t h e i r  Bolid-state  band assignments were made by comparison to previous given f o r metal-nitrogen frequencies ^ 2  2 5  The f a r IR  .  structures. A l l  literature  and metal-halogen l . R . s t r e t c h i n g  values  45  CHAPTER 3  EXPERIMENTAL  General Information. performed glovebox  under p r e p u r i f i e d equipped  Schlenk-type  prior  The compounds  to u s e .  s t a t e d ) were  n i t r o g e n i n a vacuum atmospheres HE-553-2  with a M0-40-2H p u r i f i c a t i o n system  glassware.  were sublimed HP(t-Bu)  A l l m a n i p u l a t i o n s ( u n l e s s otherwise  or i n standard  Z r C l ^ ( A l d r i c h ) and H f C ^ ( A l f a )  The secondary  phosphines,  HPMe » H P ( i - P r ) 2  were prepared a c c o r d i n g to l i t e r a t u r e p r o c e d u r e s .  2  3 4  '  3 5  '  3 6  2  and  The  l i t h i u m amide d e r i v a t i v e s 7a and 7b and the mono-ligand complexes 8a, 8b, 9a, 9b were o r i g i n a l l y prepared by Dr. A.  Westerhaus.  n i t r o g e n , and halogen a n a l y s e s were performed Department.  S o l v e n t s were d r i e d , d i s t i l l e d  procedures.  Crystal  of t h i s department. instruments depending  s t r u c t u r e a n a l y s e s were performed  by standard  by Dr. S.J. R e t t i g  *H NMR s p e c t r a were r u n on one of the f o l l o w i n g upon the c o m p l e x i t y of the p a r t i c u l a r  o b t a i n e d at 32.442 MHz on the WP-80;  Infrared  Carbon, hydrogen,  by Mr. P. Borda of t h i s  and degassed  Bruker WP-80, V a r i a n XL-100, o r Bruker WH-400.  referenced  37  to e x t e r n a l P(OMe)  3  all  3 1  3 1  P { H } NMR s p e c t r a were 1  P chemical s h i f t s were  s e t a t 141.00 ppm r e l a t i v e  s p e c t r a were run on a N i c o l e t  spectrum:  to 85% HjPO^.  5D-X F.T. i n s t r u m e n t .  Deuterated  benzene (CgDg) and d e u t e r a t e d t o l u e n e (C Dg) were o b t a i n e d from 7  Chemical  Aldrich  Company, d r i e d over a c t i v a t e d 4A m o l e c u l a r s i e v e s and vacuum  transferred  prior  to u s e .  46  P r e p a r a t i o n of LiN{SiMe CH P ( t - B u ) ) 2  To a c o l d  2  2  (-78°C) t o l u e n e s l u r r y  ( = 3 0 mL) of L i P ( t - B u )  46 mmol), prepared by s t i r r i n g n-BuLi and H P ( t - B u ) THF  to t h i s s o l u t i o n was added  dropwise.  After allowing  2  through a medium-porosity  3 1  of s t i c k y white c r y s t a l s .  = 12Hz); P C H S i ,  X  2  P { H } ( C D , ppm): +18.2(s). 6  a n a l y t i c a l l y pure samples  P r e p a r a t i o n of  H NMR ( C D , ppm): 6  3  toluene (150 mL).  2  - 1Hz).  material.  2  2  2  2  2  2  (4.0 g, 5.7 mmol) i n t o l u e n e  The r e a c t i o n mixture was s t i r r e d  a t room temperature f o r  through C e l i t e , and the t o l u e n e removed under vacuum. from minimum toluene/hexanes and c o o l i n g to  -30°C gave white n e e d l e s : y i e l d  (filled  p  dropwise to a s l u r r y of H f C l ^ (2.18 g, 5.79 mmol) i n  r e s i d u e was r e c r y s t a l l i s e d  3  1.10 ( b r d.  3  HfCI {N(SiMe CH P(t-Bu) ) )  (30 mL) was added  3  3  3  of t h i s  2  PC(CH ) ,  PC(CH ) ,  = 8.2 Hz); S i C H , 0.34 ( d , . \ j  A s o l u t i o n of L i N ( S i M e C H P ( t - B u ) )  1 day, f i l t e r e d  and reduced  So f a r we have been unable to o b t a i n  1  6  p  frit  C o o l i n g to -30°C a f f o r d e d a 60% 6  0.56 ( d , J  2  (3.53 g 15.3 mmol)  2  the r e s i d u e was e x t r a c t e d w i t h  i n volume u n t i l c r y s t a l l i s a t i o n began. yield  2  the s o l u t i o n to warm to room temperature, the  hexanes (3 x 100 mL), f i l t e r e d  p  f o r 6 days, was added  neat H N ( S i M e C H C 1 )  v o l a t i l e s were removed under vacuum;  J  (7.0 g,  (100 mL) and the r e s u l t i n g y e l l o w s o l u t i o n allowed to warm s l o w l y to  -15°C;  3  2  2  5.24 g ( 8 1 % ) .  1.30 ( " f i l l e d - i n ' d o u b l e t , | J 3  i n doublet, | J 2  p  + \j | p  X  H NMR ( C D , ppm): 6  fi  + J | = 13.2 Hz); P C H S i , 1.07 5  p  p  2  - 10.5 Hz); S i C H , 0.47 ( s ) . 3  3 1  P{ H} 1  The  47  ( C D , ppm); +38.5 ( s ) . 6  Anal. Calcd. for C 2 5 2 H  6  7.14; m.p.  C 1  2  N, 1.91; CI, 14.50.  3  H f  ^2  S i  2  :  C  »  3 6  *  !  0 2  H  »  Found: C, 35.86; H, 7.19; N, 1.85; C I , 14.30.  249-251°C. IR ( C s l , c m ) : Hf-N, 398;  Hf-Cl,  - 1  296.  P r e p a r a t i o n of Z r C l {N(SiMe ^ ^ ( t ^ B u ) ) ) 3  2  2  The i d e n t i c a l c o n d i t i o n s d e s c r i b e d above f o r the hafnium d e r i v a t i v e were used to prepare the z i r c o n i u m complex. ppm): P C ( C H ) , 1.26 3  (filled  3  C f i H e d - i r f doublet  1.08  ( C D , ppm) +33.85 ( s ) . 6  6  8.11; N, 2.17; m.p.  | J  + \j |  2  p  p  Anal.  C I , 16.45.  234-236°C.  i n doublet  | J  Y i e l d : 85%. *H NMR +  3  p  5  J |  Calcd. for C  2 2  H  5 2  &  2  S i C H , 0.50  (s).  3  3 1  P{ H} 1  C l N P S i Z r : C, 40.88; 3  2  Found: C, 41.16; H, 8.30;  IR ( C s l , c m ) :  6  = 13.5 Hz); P C H S i ,  p  - 10.1 Hz);  (C D ,  2  H,  N, 2.13; C I , 16.21.  Zr-N, 399; Z r - C l , 325. 304.  - 1  P r e p a r a t i o n of H f ( C H ) { N ( S i M e C H P ( t - B u ) ) ) 3  To a s t i r r e d  3  2  2  3  2  1.1M  The r e s u l t i n g mixture was s t i r r e d  filtered  0.48  3  ( s ) ; HfCH , 0.87 3  2  2  2  f o r three hours whereupon  the E t 0 was 2  The s o l i d was e x t r a c t e d with hexanes (15 mL),  through a f i n e - p o r o s i t y f r i t ,  P C ( C H ) , 1.12  2  i n THF, 6.1 mmol) was added dropwise.  minimum hexanes at -30°C f o r one day. ppm):  2  s o l u t i o n of H f C l { N ( S i M e C H P ( t - B u ) ) ) (1.5 g, 2.1  mmol) i n E t 0 , MeMgCl (5.58 mL,  removed under vacuum.  2  (d, J 3  p  (t, J  and allowed to r e c r y s t a l i s e from Yield  65% (0.9 g ) .  - 11.2Hz); PCH , 0.78 2  3  p  = 1.2Hz).  31  (d, J 2  P{ H} (CgD ): 1  6  p  *H NMR  (C D ,  - 6.1Hz);  +20.88 ( s ) .  g  6  SiCH , 3  Anal.  48  Calcd. f o r C 9.14;  2 5  H  6 1  HfP Si N: 2  2  C, 44.66; H, 9.14; N, 2.08.  Found C, 44.46; H,  N, 1.88, IR ( C s l , cm"* ); Hf-N 502,481. 1  P r e p a r a t i o n of H f ( C H ) { N ( S i M e C H P ( i - P r ) ) ) 3  3  2  2  2  2  The analogous c o n d i t i o n s d e s c r i b e d d e r i v a t i v e were used.  Yield  above f o r the t e r t i a r y - b u t y l  70%. *H NMR ( C D , ppm): S i C H , 0.41 ( s ) ; 6  6  PCH , 0.89 ( d , J - 6.3Hz); HfCH , 0.74 ( t , J 2  3  2  p  (m); C  2 1  H  3  3  p  = 3.5Hz); PCH(CH ), 1.13 3  PCH(CH ) 1.94 (m). P { H } ( C D , ppm): +2.4 ( s ) . A n a l . C a l c d . f o r 3 1  1  3  5 3  6  6  H f N P S i : C, 40.92; H, 8.67; N, 2.27.  2.39.  2  Found C, 41.03; H, 8.65; N,  2  IR ( C s l , c m ) :  Hf-N 488, 457.  - 1  P r e p a r a t i o n of Hf ( C H ) {N(SiMe CH PMe ) ) . 3  3  2  2  2  2  The i d e n t i c a l c o n d i t i o n s d e s c r i b e d d e r i v a t i v e were used. 4.5Hz); P C H 6.7Hz).  3 1  Yield  0.67 ( d , J 2  2  P{ H} (C D , 1  6  6  above f o r the t e r t i a r y b u t y l  73%. H NMR ( C D , ppm): PCH , 0.96 ( d , J X  2  5  6  3  = 8Hz); S i C H , 0.20 ( s ) ; HfCH , 0.47 ( t , J 3  p  3  ppm): -17.3 ( s ) .  C, 30.98; H, 7.39 N, 2.77.  3  Anal. Calcd. f o r C  1 3  H  3 ?  p  p  =  HfNP Si : 2  2  Found: C, 30.78; H, 7.32; N, 2.80. IR ( C s l ,  c m ) : Hf-N 450,445. - 1  P r e p a r a t i o n of Z r ( C H ) { N ( S i M e C H P ( t - B u ) ) ) . 3  3  2  2  2  2  MeMgCl, (4.2 mL, 1.1M i n THF, 4.6 mmol), was added to a s t i r r e d solution  of Z r C l { N ( S i M e C H P ( t - B u ) ) } (1.0 g. 1.5 mmol) i n Et 0 (25 mL).  The r e s u l t i n g  3  solution  2  2  was l e f t  2  2  to s t i r  2  f o r f i v e minutes a f t e r which  =  49  time the E t 0 was removed under vacuum and the remaining s o l i d  extracted  2  with hexanes (20 mL) and f i l t e r e d f o r one day generated  through a f i n e  spiky c r y s t a l s .  S i C H , 0.45 ( s ) , PCH , 0.73 ( d , J 2  3  Hz); for C  2  Yield  frit.  Cooling  70%. *H NMR ( C D , ppm): g  6  - 6 Hz); P C ( C H ) , 1.03 ( d . J - 11 3  p  3  p  Z r C H , 1.07 ( t , 1 H z ) . P { H } ( C D , ppm): +20.35 ( s ) . 3 1  H  6 1  Anal.  1  3  2 5  to -30°C  7  8  Calcd.  N P S i Z r : C, 51.22; H, 10.51; N, 2.39. Found: C. 51.34; H, 2  2  10.45; N, 2.49.  IR ( C s l , c m ) .  Zr-N 505, 476.  - 1  P r e p a r a t i o n of Z r ( C H ) { N ( S i M e C H P ( i - P r ) ) > . 3  3  2  2  2  The i d e n t i c a l c o n d i t i o n s d e s c r i b e d zirconium  2  above f o r the analogous  t e r t i a r y b u t y l d e r i v a t i v e were used.  Yield  67%. *H NMR  (CgDg,  ppm): S i C H , 0.37 ( s ) ; PCH , 0.84 ( d , J = 13.8 Hz); Z r C H , 0.9 ( t , J 2  3  3.8 Hz); PCH(CH ), 3  (s).  3  2  p  1.17 (m); PCH(CH ), 2 1  H  5 3  3 1  -  1  6  fi  N P S i Z r : C, 47.68; H, 10.10; N, 2.65. 2  p  2.04 (m). P { H } ( C D , ppm): +8.7  3  Anal. Calcd. f o r C  3  2  C, 47.63; H, 10.13; N, 2.80. IR ( C s l , c m ) : - 1  Found:  Zr-N 432, 419.  P r e p a r a t i o n of Z r ( C H ) {N(SiMe C H P M e ) } 3  3  2  2  2  2  The i d e n t i c a l c o n d i t i o n s d e s c r i b e d tertiary-butyl  d e r i v a t i v e were used.  f o r the analogous z i r c o n i u m  However,  a t the present  not been able to i s o l a t e an a n a l y t i c a l l y pure p r o d u c t .  time we have  50  CHAPTER 4  Summary  A s e r i e s of mono-amido' phosphine d e r i v a t i v e s of z i r c o n i u m hafnium of the formula M C I { N ( S i M e C H P R ) } were prepared. 3  2  2  2  The  2  and single  c r y s t a l X-ray d i f f r a c t i o n a n a l y s i s of H f C l { N ( S i M e C H P M e ) ) i n d i c a t e s 3  that the molecule  2  i s f a c i a l , which, i n accordance  2  2  w i t h the  2  NMR  s p e c t r o s c o p i c d a t a , i s o m e r i s e s to a m e r i d i o n a l geometry i n s o l u t i o n . c o n t r a s t , i n both the s o l i d  s t a t e and  solution,  i s m e r i d i o n a l , a geometry which i s adopted derivatives i n solution. minimize and  ZrCl {N(SiMe CH P(i-Pr) ) > 3  2  2  2  3  2  Presumably t h i s s t e r e o c h e m i s t r y i s adopted  the s t r a i n generated  2  by a l l the M C I { N ( S i M e C H P R ) >  the non-bonding r e p u l s i o n s between the PR  to reduce  In  2  groups on the  upon the p l a n a r S i - N - S i  2  2  2  to  ligand  u n i t , which i s  l e s s when the phosphine l i g a n d s are t r a n s d i s p o s e d . These mono-ligand d e r i v a t i v e s were used  as s t a r t i n g m a t e r i a l s f o r  the f o r m a t i o n of the t r i m e t h y l complexes, M(CH ) {N(SiMe-^CH^R^ 3  Hf, R » Me,  i - P r , t-Bu)  3  i n a d d i t i o n to the analogous  d i m e t h y l complexes which were i s o l a t e d as a m i x t u r e .  2  (M = Z r .  monomethyl and The  g e n e r a t i o n of  the  monomethyl and d i m e t h y l products a r i s e v i a a c o n p r o p o r t i o n r e a c t i o n between the c o r r e s p o n d i n g  t r i - a l k y l complex and  s t a r t i n g m a t e r i a l , which  f a c i l i t a t e s a l k y l - h a l i d e exchange between the two metal c e n t r e s i n these derivatives.  The  NMR  d a t a i n d i c a t e s the t r i m e t h y l complexes are  in solution.  T h i s behaviour  fluxional  i s b e l i e v e d to occur as a consequence of the  51  d i s s o c i a t i v e nature of the phosphine donors of the c h e l a t i n g l i g a n d . S e v e r a l p o s s i b l e mechanisms which u t i l i s e  the i d e a of phosphine  d i s s o c i a t i o n were c o n s i d e r e d i n an attempt to e x p l a i n the e q u i v a l e n c e the methyl groups a t t a c h e d to the metal  c e n t r e i n the  ^  NMR.  mechanism r e q u i r e s the t r i m e t h y l complexes to move towards a  The  of  first  facial  o r i e n t a t i o n which would not o n l y i n c r e a s e the s t r a i n on the p l a n a r S i - N - S i u n i t but a l s o l e a d to an i n c r e a s e i n the non-bonding r e p u l s i o n s between the phosphine groups.  For these reasons  I would tend to favour the  Berry  p s e u d o r o t a t i o n or t u r n s t i l e mechanisms, because i n both mechanisms the c h e l a t i n g l i g a n d does not have to a t t a i n a f a c i a l  conformation.  52  APPENDIX  PCCH,  Si  1  P pm 80 MHz  *H NMR of L i N ( S i M e C H P ( t - B u ) ) 2  2  2  2  54 a  E S C "IB  6E'. -tC  Z2+  'B*  BSC  BE  I B B 'OE  IZT'CZ  F.T.-I.R. of H f ( C H ) { N ( S i M e C H P ( i - P r ) ) } 3  3  2  2  2  2  rSt't:  55  SiCH,  POM.  HfCH'  -CH  J  I 5  ppm  80 MHz  I  2  I  I  0  I  *H NMR of H f ( C H ) ( N ( S i M e C H P M e ) ) 3  3  2  2  2  2  56  F.T.-I.R. of H f ( C H ) { N ( S i M e C H P M e ) } 3  3  2  2  2  2  57  PCCH,  SiCH,  HfCH  3  1  ppm 80 MHz  *H NMR of H f ( C H ) { N ( S i M e C H ( t - B u ) ) ) 3  3  2  2  2  2  58  *I  OBX'M  ^BtE6  BEO£ Y  BOBO *E  C H I 't  1 3 N y n I MSNVMJ.X  F.T.-I.R. of H f ( C H ) { N ( S i M f i C H P ( t - B u ) ) } 3  3  2  2  2  2  "O  60  Z S E *CB  TOB-BS  O E » *»C  F.T.-I.R. of  000*06  6 » S '6*  B63*l»  2r(CH ) {N(SiMe CH (t-Bu) ) ) 3  3  2  2  2  2  I r e 'BE  61  -PCCH  SiCH,  3  0  1# ppm 80 MHz  *H NMR of Z r C l { N ( S i M e C H P ( t - B u ) ) ) 3  2  2  2  2  F.T.-I.R. of  ZrCl {N(SiMeJCHJPCt-Bu) ) } 3  2  2  63  SiCH PCCH  3  3  1  ppm *H NMR o f H f C l { N ( S i M e C H ( t - B u ) ) } 3  2  2  2  2  64  o •  OBiM2  ZBS  81  BBC *BT  B B ! "IT  CUB  'B  Z*LC'%  13NVJ.1 I H S N V U I X  F.T.-I.R. o f H f C l { N ( S i M e C H ( t - B u ) ) > 3  2  2  2  2  1££.S'Z  0  SiCH,  o o  ZrCH, N  IS  1 PCHCH,  CO if  ro O r  HI  •0  CH-  H  v '  to  PCHCH,  TV 2  ppm  0  66  F.T.-I.R. of  Zr(OT ) {N(Site CH P(i-Pr) ) } 3  3  2  2  2  2  67  Table 1  Bond l e n g t h s (A) with estimated standard d e v i a t i o n s i n parentheses of  Hf(CH ) {N(SiMe CH PMe ) }  Bond  Length(A)  Hf - P ( l ) Hf -P(2) Hf -N Hf -C(3) Hf -C(4) Hf -C(5) P(l)-C(l) P(D-C(6) P(D-C(7) P(2)-C(2)  2.761(2) 2.806(2) 2.156(4) 2.272(7) 2.246(7) 2.243(8) 1.803(7) 1.821(8) 1.835(8) 1.811(7)  3  3  2  2  2  2  Bond  P(2)-C(8) P(2)-C(9) Si(l)-N Si(l)-C(l) Si(l)-C(10) Si(l)-C(ll) Si(2)-N Si(2)-C(2) Si(2)-C(12) Si(2)-C(l3)  Length( A)  1.836(8) 1.827(8) 1.735(5) 1.884(6) 1.851(8) 1.869(8) 1.739(5) 1.892(7) 1.869(7) 1.870(7)  68 Table 2  Bond angles (deg) with estimated standard d e v i a t i o n s i n parentheses of Bonds  P ( l ) -Hf P ( l ) -Hf P ( l ) -Hf P ( l ) -Hf P ( l ) -Hf P(2) -Hf P(2) -Hf P(2) -Hf P(2) -Hf N -Hf N -Hf N -Hf C(3)-Hf C(3)-Hf C(A)-Hf Hf - P ( D Hf - P ( D Hf - P ( D C ( l ) -PCD C(l)-P(D C(6) - P ( D Hf -P(2)  -P(2) -N -C(3) -C(4) -C(5) -N -C(3) -C(4) -C(5) -C(3) -C(4) -C(5) -C(4) -C(5) -C(5) -C(l) -C(6) -C(7) -C(6) -C(7) -C(7) -C(2)  Hf(CH ) {N(SiMe CH PMe ) ) 3  3  Angle(deg)  115.32(6) 79.60(13) 162.6(2) 80.0(2) 78.3(2) 73.62(11) 80.8(2) 162.4(2) 83.2(2) 113.0(3) 102.4(2) 136.8(3) 85.3(3) 98.1(3) 109.6(3) 100.3(2) 117.2(3) 123.0(3) 104.4(4) 107.4(4) 102.7(5) 99.8(2)  2  2  2  2  Bonds  Hf -P(2)-C(8) Hf -P(2)-C(9) C(2)-P(2)-C(8) C(2)-P(2)-C(9) C(8)-P(2)-C(9) N -Si(l)-C(l) N -Si(l)-C(10) N -Si(l)-C(ll) C(l)-Si(l)-C(10) C(l)-Si(l)-C(ll) C(10)-Si(l)-C(ll) N -Si(2)-C(2) N -Si(2)-C(12) N -Si(2)-C(13) C(2)-Si(2)-C(12) C(2)-Si(2)-C(13) C(12)-Si(2.)-C(13) Hf -N -Si(l) Hf -N -Si(2) Si(l)-N -Si(2) P(l)-C(l)-Si(l) P(2)-C(2)-Si(2)  Angle(deg)  115.8(3) 127.3(2) 103.3(3) 105.4(3) 102.3(4) 110.0(3) 114.3(3) 112.2(4) 105.8(4) 105.6(3) 108.4(5) 108.3(3) 112.0(3) 114.5(3) 107.7(4) 106.0(3) 107.9(4) 122.9(2) 118.2(3) 117.3(3) 109.6(3) 108.3(3)  69  Bibliography  la.  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