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Coordination compounds of alkyl gallium hydrides Wiebe, Victor Graham 1968

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COORDINATION COMPOUNDS OF ALKYL GALLIUM HYDRIDES  by  VICTOR GRAHAM WIEBE B.Sc. (Hons.) U n i v e r s i t y o f B r i t i s h Columbia 1966  A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE  In The Department of Chemistry  We accept t h i s t h e s i s as conforming t o the required standard  The U n i v e r s i t y of B r i t i s h June 1968  Columbia  In p r e s e n t i n g  for  this  thesis  in partial  an a d v a n c e d d e g r e e a t t h e U n i v e r s i t y o f B r i t i s h C o l u m b i a ,  that  the L i b r a r y  Study.  thesis  shall  I further  make i t f r e e l y  agree that  f o r s c h o l a r l y p u r p o s e s may  publication  of this  w i t h o u t my w r i t t e n  thesis  Department of Columbia  I agree  for reference  for extensive  and  copying of  this  be g r a n t e d b y t h e Head o f my  It i s understood  for financial  permission.  The U n i v e r s i t y o f B r i t i s h V a n c o u v e r 8, Canada  available  permission  D e p a r t m e n t o r b y hits r e p r e s e n t a t i v e s .  or  f u l f i l m e n t of the requirements  gain  shall  that  n o t be  copying  allowed  - i i -  Abstract Although the organo hydride d e r i v a t i v e s o f boron and aluminum are w e l l c h a r a c t e r i z e d ^ l i t t l e work has been reported on the corresponding gallium systems.  The present study was i n i t i a t e d t o determine the r e l a t i v e s t a b i l i t i e s  and r e a c t i v i t y o f organo gallium hydride d e r i v a t i v e s as compared with the s t a b i l i t i e s and reactions o f the corresponding compounds o f boron and aluminum. Various preparative routes t o t h i s new class o f gallium compounds have been i n v e s t i g a t e d .  These include the use o f organo-mercury, organo-lithium  and l i t h i u m hydride d e r i v a t i v e s i n reactions with gallium hydride and gallium a l k y l compounds and t h e i r halogen s u b s t i t u t e d d e r i v a t i v e s :  Me NGaH + HgR 3  3  2  >-  Me NGaH R + l/2Hg + 1/2H 3  2  2  Me NGaH Cl + LiR  y Me NGaH R + L i C l  Me NGaR Cl + LiH  • Me NGaHR + L i C l  3  3  2  2  3  3  2  2  A fourth preparative method involves d i s p r o p o r t i o n a t i o n reactions between gallium hydride compounds and organo gallium compounds to y i e l d the mixed organo hydride d e r i v a t i v e s .  Alkyl-hydride disproportionation reactions  were also examined using organo and hydride d e r i v a t i v e s o f d i f f e r e n t Group IIIB elements i n order t o obtain a b e t t e r understanding o f the exchange process. Both i n f r a r e d and proton NMR spectroscopy have been used extensively i n f o l l o w i n g the progress o f these reactions and i n the c h a r a c t e r i z a t i o n o f the products.  - iii Table of Contents Page I. II. III.  T i t l e Page Abstract  i i i  Table of Contents  i i i  IV.  L i s t of Tables  vii  V.  L i s t of Figures  viii  VI.  Acknowledgement  ix  VII. VIII.  Introduction  1  Discussion and Results  10  A.  Preparation of Trimethylamine Adducts of Organogallanes .  10  B.  Properties of Trimethylamine Adducts of Organogallanes ..  20  (a)  P h y s i c a l Properties  20  (b)  NMR Data  21  (c)  Infrared Data  28  C.  Reaction of Trimethylamine Adducts of Organogallanes ....  31  (a)  With HCI  31  (b)  With Ethylene  32  (c)  With Methanol  32  D.  Mechanisms of Exchange  35  E.  Exchange Reactions Involving Other Group IIIB Elements ..  38  (a)  Aluminum Alkyl-Hydride Exchange  38  (b)  Boron Alkyl-Hydride Exchange  41  (c)  Mixing Trimethylamine Adducts of D i f f e r e n t Group IIIB Hydride and A l k y l s  41  - iv Page IX.  Experimental A.  B.  50  Experimental  Techniques  50  (a)  Desiccation  50  (b)  Grease  54  (c)  R e a c t i o n - F i l t r a t i o n Apparatus  54  (d)  Molecular Weight  58  (e)  Spectroscopy  58  (£)  Lithium Methyl Standardization  60  (g)  Elemental Analysis  62  Preparative  '  64  (a)  Preparation o f Gallium T r i c h l o r i d e , GaCl  (b)  Preparation o f Lithium Gallium Hydride, LiGaH^  (c)  Preparation o f Trimethylamine Gallane, Me NGaH  (d)  Preparation o f Trimethylamine T r i c h l o r o g a l l a n e  3  Me NGaCl 3  (e)  64  3  66 3  ....  68  3  Preparation o f Trimethylamine Adducts o f Monochlorogallane, Me NGaH Cl, and Dichlorogallane, Me NGaHCl 3  (f)  67  2  3  2  69  Preparation o f Trimethylamine Adducts o f Dichloromonomethylgallane, Me NGaMeCl2 and monochloro3  dimethylgallane, Me NGaMe Cl 3  (g)  69  2  Preparation o f Trimethylamine Trimethylgallane, Me NGaMe 3  73  3  (h)  Preparation o f Trimethylamine Borane, Me NBH  (i)  Preparation of Trimethylborane,  3  Me B 3  3  73 74  - V -  Page (j)  Preparation of Trimethylamine Me NBMe 3  (k)  7 6 3  Preparation o f Trimethylamine Trimethylalane, Me NAlMe 3  (1) C.  Trimethylborane,  76  3  Preparation o f Trimethylamine Alane, Me NAlH 3  76  3  Reactions t o Prepare Coordinated Organogallanes (a)  77  Reaction o f Trimethylamine Gallane, Me NGaH , with 3  3  Dimethyl Mercury, Me Hg  77  2  (b)  Reaction o f Trimethylamine Adducts o f Monochlorodimethylgallane, Me NGaMe Cl, and Dichloromono3  2  methylgallane, Me NGaCl with Lithium Hydride L i H .. 3  (c)  2  77  Reactions of Trimethylamine Adducts o f Monochlorogallane, Me NGaH Cl and Dichlorogallane, Me NHCl , 3  2  3  2  with Lithium Methyl LiMe (d)  78  E q u i l i b r i u m Reactions o f Trimethylamine Gallane, Me NGaH with Trimethylamine Trimethylgal1ane, 3  3  MeNGaMe 3  D.  79  3  Miscellaneous Reactions o f Coordinated Gallanes (a)  Reaction o f Trimethylamine Monomethy1gallane, Me NGaH Me with Ethylene, CH CH 3  (b)  80  2  2  80  2  Reaction of Trimethylamine Monomethy1gallane, Me NGaH Me with Hydrogen Chloride,.HCl 3  (c)  81  2  Reaction o f Trimethylamine Gallane, Me NGaH with 3  Methanol, Me OH  .  3  81  - vi Page (d)  Rearrangement Reaction Between Trimethylamine  Alane,  Me NAlH , and Trimethylamine Trimethylalane, 3  3  Me NAlMe 3  (e)  Rearrangement Reaction Between Trimethylamine Borane, Me NBH , and Trimethylamine 3  3  Me NBMe 3  (f)  82  3  Trimethylborane, 82  3  Mixed Rearrangement Reactions Using D i f f e r e n t Group IIIB Coordination Compounds  X.  Bibliography  83 .  85  - vii L i s t o f Tables Page Table 1  Proton NMR Data i n Cyclohexane Solvent  22  Table 2  Proton NMR Data i n Benzene Solvent  22  Table 3  Molar Ratios o f "Me NGaMeH " i n Benzene  23  Table 4  Molar Ratios o f "Me NGaMe H" i n Benzene  25  Table 5  NMR Data f o r  3  2  3  2  "Me NGaMe H" and "Me NGaMeH " i n Cyclo3  2  3  2  hexane and f o r "Me NGaMe D" and "Me NGaMeD " i n Benzene . 3  Table 6  2  3  2  25  Infrared Data f o r "Me NGaMeH ", "Me NGaMeD " and 3  2  3  2  "Me NGaMe H", "Me NGaMe D" 3  2  3  30  2  Table 7  Proton NMR Data f o r Me NAlMe _ H  Table 8  Molar Ratios o f "Me NAlMeH " and "Me NAlMe H" i n Benzene  40  Table 9  NMR Data f o r Mixtures o f Me NBMe and Me NBH i n C H  41  Table 10  NMR Data o f the Mixed Group IIIB A l k y l s and Hydrides  3  3  3  n  n  2  Species 3  3  3  40 2  3  3  5  6  ... .  43  - viii L i s t o f Figures Page Figure 1  NMR Spectra o f "Me NGaMeH " and "Me NGaMe H"  Figure 2  Infrared Spectra of "Me NGaMeH " and "Me NGaMe H"  29  Figure 3  NMR Spectra o f Me NGaH OMe  33  Figure 4  NMR spectra o f "Me NAlMe H" and "Me NAlMeH "  Figure 5  NMR Spectra o f Mixtures o f Me NBMe and Me NBH  Figure 6  NMR Spectra o f Mixtures o f Trimethylamine Adducts o f  3  2  3  3  3  24  2  2  3  2  .  2  3  2  3  3  39  2  3  3  3  42  D i f f e r e n t Group IIIB Hydrides and A l k y l s  44  Figure 7  Drying P i s t o l  51  Figure 8  Sublimer  52  Figure 9  Me NGaH sublimer 3  53  3  Figure 10 Vacuum Line  55  Figure 11 R e a c t i o n - F i l t r a t i o n Apparatus  57  Figure 12 Molecular Weight Apparatus  59  Figure 13 Lithium Methyl Apparatus  61  Figure 14 Gallium T r i c h l o r i d e Apparatus  65  Figure 15 Apparatus f o r Reacting Me^Si and GaCl Figure 16 Boron Trimethyl Apparatus  3  71 75  - ix -  Acknowledgement I would l i k e t o express my s i n c e r e s t thanks t o my research d i r e c t o r Dr. Alan S t o r r , f o r h i s invaluable advice, guidance, and enlightening discussions throughout the course of t h i s work. I am g r e a t l y indebted t o Mr. S. Rak f o r the construction o f much of the glass apparatus, t o Mr. R. Burton, Miss C. B u r f i t t and Miss P. Watson f o r the NMR spectra, t o Miss D. Johnson f o r the preparation of t h i s t y p e s c r i p t and Miss J . Cowley f o r providing some of the diagrams.  VII.Introduction Since the discovery o f gallium i n 1875 (1) the knowledge o f i t s chemist has increased s t e a d i l y but only modestly i n comparison t o i t s congeners, boron and aluminum.  Quite r e c e n t l y , though, with the use o f gallium i n the  e l e c t r o n i c s i n d u s t r y , renewed emphasis i s being placed on the study o f gallium.  Reviews o f gallium chemistry have appeared i n 1936 i n Gmelin (2),  i n 1937 by Einecke (3), i n 1955 by P. de l e Breteque (4) and more recently i n 1963 by N. N. Greenwood (5) and J . C. Hutter (6) and i n 1966 by Sheka et a l (7). In naming gallium hydride coordination compounds the GaH3 e n t i t y i s termed gallane and i s t r e a t e d as the parent compound.  Derivatives i n which  the formal coordination number o f gallium i s three, are named accordingly; e.g. GaHCl gallane.  2  d i c h l o r o g a l l a n e , GaH NMe dimethylaminogallane, GaMe3, t r i m e t h y l 2  2  Addition compounds i n which the coordination o f gallium i s four or  greater are named thus; Et PGaH3 triethylphosphine gallane, Me3NGaHCl 3  trimethylamine  dichlorogallane.  2  S i m i l a r nomenclature i s applied t o the  analogous boron and aluminum compounds.  The only exceptions t o t h i s nomen-  clature are the w e l l established names, such as l i t h i u m gallium hydride f o r the compound LiGaH^. One important c h a r a c t e r i s t i c o f Group IIIB compounds i s t h e i r electron d e f i c i e n c y , that i s , i n the t r i v a l e n t state one o f the four o r b i t a l s (ns, n^x, n^y, n^z)  a v a i l a b l e f o r bonding i s empty.  This c h a r a c t e r i s t i c i s  - 2 exemplified by the dimeric and polymeric nature of a great many of these compounds, and by t h e i r a b i l i t y t o form dative bonds with strong e l e c t r o n donors. sp  3  The energy change i s small i n going from planar s p  2  to tetrahedral  configurations i f electrons can be supplied to the vacant o r b i t a l s .  This can be achieved by forming e i t h e r multi-centred bridged bonds as i n the boron hydrides or donor-acceptor bonds such as the N —> A l dative bond i n Me NAlH . 3  3  Coordination compounds o f gallane, GaH and halogenogallanes, 3  GaRs. \y> n  with amines and phosphines have been i n v e s t i g a t e d extensively over the past few years (8-12). The f i r s t adduct prepared and the most stable i s trimethylamine gallane, Me NGaH , which i s prepared at room temperature i n 3  3  ether s o l u t i o n by the r e a c t i o n :  y Me NGaH + L i C l + H  Me NHCl + LiGaH^ 3  3  3  2-1  2  A 2:1 adduct can also be prepared by adding more amine gas to the compound, but t h i s 2:1 adduct decomposes at -21°C.  Though dimethylamine i s a stronger  donor t o gallane than trimethylamine, the adduct Me2HNGaH slowly loses 3  one mole of hydrogen t o form the dimer [Me NGaH ]2. 2  2  Other amine ligands have  been used with gallane but t h e i r adduct strengths are considerably weaker and t h e i r a b i l i t y t o coordinate decreases i n the sequence;  Me HN > Me N> C H N > E t N > <j>MeN 2  3  5  5  3  2  > <j>N 3  Trimethylphosphine, Me P, has also been used as a ligand and i t s adduct 3  strength i s almost equal t o that of trimethylamine.  This i s i n contrast to  - 3the great i n s t a b i l i t y (10) of the aluminum.analogue Me3PA1H which can n o t \ 3  be i s o l a t e d .  Other phosphine ligands form much less s t a b l e adducts with t h e ^ X  gallane moiety, GaH , and a 2:1 adduct with trimethylphosphine i s not 3  observed, even at low temperatures (10).  The sequence o f l i g a n d strengths  is; Me HN > Me N > Me P > Me HP > E t P > 4>P 2  3  3  2  3  3  Arsine ligands form adducts with gallane but these are too unstable to i s o l a t e as are those formed with oxygen and sulphur ligands. Halogenogallane  adducts with trimethylamine have been prepared by the  following r e a c t i o n s ;  Me NGaH 3  3  + nHX  »- Me NGaH _ X 3  3  n  n  + nH  2  where "n" = 1 or 2 and "X" = C l or Br Me NGaH 3  3  + nMe NHX  • Me3NGaH3_ X +*Me N + *H  3  n  n  3  2  where "n" = 1 and "X" = C l or Br; "n" = 2 and "X" = C l . or by the r e a c t i o n ; nMe NGaH + mMe NGaX 3  3  3  3  >me^ati^^  where "n" + "m" = 3, "X" = C l , Br or I and "n" = 1, or 2 with C l .  The coordination chemistry of some of the simpler a l k y l gallanes have also been thoroughly studied (13,14).  Coordination compounds of t r i m e t h y l -  gallane with a l l the t r i m e t h y l d e r i v a t i v e s of Group VB and dimethyl d e r i v a t i v e s of Group VIB elements have been prepared by mixing t r i m e t h y l g a l l a n e with the appropriate ligand.  The strength of the donor-acceptor bond i n compounds  _ 4 formed with Group VB ligands decreases i n the sequence N > P > As > Sb. Group VIB an i r r e g u l a r sequence i s observed  0 > Se > S = Te.  For  This  sequence d i f f e r s from Group VIB l i g a n d strengths with trimethylalane where a regular decrease i n ligand strength down the Group i s observed.  The  i r r e g u l a r i t y i n the t r i m e t h y l g a l l a n e s e r i e s i s thought t o be influenced by d - o r b i t a l p a r t i c i p a t i o n i n bonding.  The chemical s h i f t of Ga-Me i n the  trimethylgallane adducts can be r e l a t e d to the strength of the donor-acceptor bond (17); those of greatest bond strength i . e . greatest d i s s o c i a t i o n energy, have largest x values. L i t t l e work has been c a r r i e d out on the chemistry of organogallanes  and  none has been reported on coordination compounds of the type DGaH3_ R where n  n  "D" represents a Lewis base, i . e . Me N, and "R" represents a simple a l k y l . 3  group e.g.  Me, or Et. The e a r l i e s t report of an organogallane was by  V/iberg (15) who reported the i s o l a t i o n of (Me GaH) 2  obtained by c o o l i n g a mixture of Me Ga and H 3  a gas discharge at low pressure.  2  2  from the products  a f t e r i t had been subjected to  Doubt (16) has been cast on t h i s r e s u l t  by a l a t e r i n v e s t i g a t i o n and i t now appears that (Me GaH) 2  2  i s not prepared  i n t h i s manner. A hydride species i s postulated by Eisch (18) as an intermediate i n the thermal decomposition  Bu Ga  of t r i i s o b u t y l g a l l a n e  1 5 5  C  3  ) Bu GaH + Me C=CH 2  3Bu GaH  > 2Bu Ga + GaH  2  GaH  2  3  3  3  > Ga + 3/2H  2  2  4-1 4-2 4-3  - 5In the presence of o l e f i n s such as 1-decene, the d i i s o b u t y l g a l l a n e formed as i n equation 4-1 adds r a p i d l y to the o l e f i n .  Bu GaH + CH =CH-C H 2  2  8  17  >• B u G a C H 2  10  5-1  21  Eisch was also able t o prepare (19) the uncoordinated hydride, d i e t h y l g a l l a n e , Et GaH, by the successful exchange reaction between a 2  gallium h a l i d e and an aluminum hydride.  The y i e l d o f the desired product  was low, but by the reaction he was able to prepare considerable q u a n t i t i e s of the hydride.  2Et Ga + GaCl 3  • 3Et GaCl  3  Et GaCl + E t A l H + KC1 2  5-2  2  • Et GaH + K [ E t A l C l ]  2  2  2  5-3  2  Diethylgallane was found to add very r e a d i l y to o l e f i n s to form unsymmetrical organogallanes but these r e a d i l y disproportionated t o form symmetrical organo-gallium compounds. The only other s i g n i f i c a n t preparations of uncoordinated gallanes have been the preparations o f a few compounds o f the form GaH R and GaHR as 2  2  w e l l as the preparation o f an unstable polymeric ( G a H ) (20). The compounds 3  x  of the form GaH R prepared are GaH Cl (11) and GaH NMe , GaH PMe (12) and 2  2  these are dimeric as expected. prepared by Schmidbaur  2  2  2  2  Compounds o f the form GaHR have been 2  et a l (21,22) who were able t o prepare GaHCl and 2  GaHBr , dimers, i n good y i e l d from t r i m e t h y l s i l a n e and the appropriate 2  halide.  The Ga-H bond o f these compounds i s found to r e a d i l y hydrogallate  a great many unsaturated organic groups (23). Almost a l l the uncoordinated  - 6 gallanes are d i f f i c u l t to prepare pure and are found to be much less stable than the corresponding alanes. In contrast to the sparsely known organogallanes, the organohydride d e r i v a t i v e s of the preceding members of Group IIIB are w e l l characterized. Uncoordinated a l k y l boranes have been known since 1935 when Schlesinger and coworkers i n v e s t i g a t e d the r e a c t i o n of boron t r i a l k y l s with diborane (24-27). 2R B + B H  6  >- 2R BHBH R  6-1  4R B + B H  6  >• 3R BHBHR  6-2  3  2  3  2  2  2  2  2  "R" = Me, Et, Pr A l l f i v e of the possible mono to t e t r a a l k y l boranes have been prepared by t h i s manner. More modern preparative methods to t h i s type of compound u t i l i z e the complex metal hydrides as s t a r t i n g materials (28-31). y  3LiBH\ + BC1  3  + 2Me B  • 3Me B h\ + 3 L i C l  3  2  L i A l h \ + 4Pr BCl  > 2Pr"B H  2  2  2NaBH + 2CH =CHBr [+  •  2  Uncoordinated organoboranes  6-3  2  2  + LiAlCl  2NaBr + E t B h \ 2  2  4  6-4 6-5  are u s u a l l y dimers with hydrogen bridges  p r e f e r r e d over a l k y l or a r y l bridges.  They are r e a d i l y oxidized and very  r e a d i l y add under mild conditions to a l l types of a l i p h a t i c and aromatic o l e f i n s and with dienes and acetylene hydrocarbons.  - 7Uncoordinated a l k y l aluminum hydrides have also been synthesized by a v a r i e t y o f methods (32-34).  E t A l C l + NaH  h e X a  2  Me Al + excess H 3  2  "  > NaCl + E t A l H  6  7-1  2  discharge'  LiAl.H^ + Me M  (Me  3 2 3^n A1  H  (Me AlH)  +  2  n  • Me AlH + LiMH Me  3  2  7-2 7-3  3  where "M" = B, A l , Ga  A more general method involves the d i r e c t o l e f i n and hydrogen r e a c t i o n with aluminum metal.  RC=CH + H 2  2  + Al  >- R A1H  7-4  2  Thermal decomposition o f higher t r i a l k y l s has also produced hydride species (35). i E t A l Bu 2  ?nn°r > E t A l H + CH =CHC H 2  2  2  7-5  5  Organo alanes r e a d i l y add across the double bond o f 1-olefins but with much greater d i f f i c u l t y across 2- or higher o l e f i n s .  Mixed  tend to disproportionate to form symmetric organoalanes. groups of organoalanes  organoalanes  Exchange o f a l k y l  occurs-, very r a p i d l y i n non-polar solvents but  exchange i s slowed down i n p o l a r solvents (36). Coordination compounds of organo boron hydrides and organo aluminum hydrides are w e l l characterized. Thus organo-boron hydrides of the form B R  3  n n f ^ H  w  e r e  " " n  =  0» 1> 2, 3) react with amines t o form 1:1 amine boranes.  - 8 A large number of these 1:1 addition compounds with cyclic and acyclic, primary, secondary and tertiary amines have been reported (37).  B Hi R 2  t  y 2R NBH R  + 2NR  2  3  3  [R NH]X + LiBH R 3  8-1  2  • R NBH R + LiX + H  3  3  2  8-2  2  where "X" = halogen. R.NBR* + H 0  d  • RqNBHRp + R'H  9  pressure  z  d  8-3  z  Amine organoboranes have also been synthesized by other procedures. Hawthorne (38,39) demonstrated that amine monoalkylboranes could be obtained in good yield by the reaction of B-trialkyl boroxines (-BR-0-) with 3  LiAlH^ in the presence of amines.  (RBO) + 3NR 3  3  ^0^35^  '  3  R  B  H  2  N  R  3  8-4  Highly pure amine-organoboranes are thermally and hydrolytically more stable than the uncoordinated species.  They have found use as reagents in  some specific reactions because of their reactivity towards some carbonyls in aldehydes and ketones and towards mercaptans (44).. Alkyl aluminum hydride amine complexes have been investigated and characterized by several groups of workers in recent years (40-42). The synthetic methods employed are listed below:  A.  Me NAlEt Cl + LiH 3  2  E t 2  ° > Me NAlEt H + LiCl 3  2  8-5  - 9 -  Me NAlEtCl 3  B.  Me NAlH  3  + R Hg  Me NAlH  3  + l/2R Hg  3  3  C.  2Me NAlR 3  1:1  h  e  3  x  a  n  3  h  e  x  a  n  3  + Me NAlH  3  3  3  + 2Me NAlH  Me NAlH  3  + LiR  3  2  , Me NAlRH  e  2  3  + 2LiCl  2  , Me NAlR H + H  e  2  3  3  > Me NAlEtH  2  Me NAlR 3  D.  + 2LiH  2  2  + Hg  + 1/2H  2  9-1 9-2 + l/2Hg  2  9-3  -> 3Me NAlR H  9-4  >- 3Me NAlRH  9-5  3  2  3  • Me NAlRH 3  2  + LiH  2  (Side r e a c t i o n :  Me NAlH  E.  LiAlH  i ? ^ ' > 2Me NAlRH  The  r e a c t i v i t y o f the A l - C and A l - H bonds i s g r e a t l y reduced i n f o r m i n g  adducts  4  + R A1C1 2  3  3  + LiH  9-6  3  • L i A l H ^ + Me N)  9-7  3  2  + LiCl  9-8  and t h i s may be u t i l i z e d i n p r e p a r i n g h i t h e r t o > u n p r e p a r a b l e  h i g h l y l a b i l e organo aluminum compounds ( 4 3 ) . The  R A1 3  moiety i s a s t r o n g e r a c c e p t o r than the R B 3  organo aluminum forms 1:1 ligands.  The s t r e n g t h  moiety, and the  donor-adduct complexes w i t h most Group VB and  VIB  o f t h e l i g a n d - A l bond decreases r e g u l a r l y down a  group and w i t h Group VB l i g a n d f o r m i n g s t r o n g e r bonds t h a n Group VIB The p r e s e n t i n v e s t i g a t i o n was  i n i t i a t e d t o determine  ligands.  the r e l a t i v e  s t a b i l i t i e s o f o r g a n o g a l l a n e d e r i v a t i v e s as compared w i t h the s t a b i l i t i e s t h e c o r r e s p o n d i n g w e l l known boron and aluminum compounds.  of  In a d d i t i o n i t  was hoped t h a t the s t u d y would f u r t h e r expand our knowledge o f t h e c o o r d i n a t i o n c h e m i s t r y o f g a l l i u m compounds, and i n p a r t i c u l a r , would demonstrate the e f f e c t o f h a v i n g an organo group a t t a c h e d t o the g a l l i u m on the a c c e p t o r properties  o f the g a l l a n e moiety, GaH . 3  VIII.  Discussion and Results  A. Trimethylamine Adducts of Organogallanes The low thermal s t a b i l i t y of the known uncoordinated a l k y l g a l l a n e s (19) suggested that the most p r o f i t a b l e l i n e of approach t o the desired compounds would be v i a s u b s t i t u t i o n reactions i n v o l v i n g i n t r o d u c t i o n of organo groups i n t o coordinated gallium compounds.  Several methods of synthesis were  attempted. The f i r s t s y n t h e t i c route involved the r e a c t i o n of trimethylamine gallane with organomercury compounds, both ether and benzene being used as solvents.  2Me NGaH + Me Hg 3  3  2  • 2Me NGaMeH + Hg + H 3  2  2  10-1  At room temperature or below, no product was formed, even a f t e r one day. The only reaction occurring was the decomposition of the s t a r t i n g m a t e r i a l , trimethylamine  gallane.  Me NGaH 3  3  •  Me N + Ga + 3/2H 3  2  10-2  At higher temperatures a d e f i n i t e product according t o equation 10-1 did r e s u l t .  I t was found that t h i s r e a c t i o n occurs more favorably under  - 11 r e f l u x i n g conditions when the hydrogen generated was allowed to escape, rather than i n a sealed Carius tube where the excess pressure would tend to stop or even reverse the r e a c t i o n .  A higher temperature, such as i n  r e f l u x i n g benzene rather than d i e t h y l ether, gave a higher y i e l d , though even under these conditions the y i e l d of product was low due to the thermal i n s t a b i l i t y of both the Me NGaH s t a r t i n g material and the trimethylamine 3  3  monomethylgallane, Me NGaMeH , product. 3  2  The presence of f i n e l y divided  gallium metal, from the decomposition of Me NGaH , see equation 10-2, i n the 3  3  reaction system probably catalyses f u r t h e r decomposition of the product i n t o hydrogen, methane and trimethylamine gases and gallium metal.  This type o f  a u t o c a t a l y t i c decomposition has been noted i n a number of gallium systems (18,45).  The analogous r e a c t i o n i n aluminum chemistry gave quite high  y i e l d s of trimethylamine organoalanes  2 Me NA1H + nHgR 3  3  2  (40,41,46).  »- 2Me NAlR H _ 3  n  3  n  + nH  2  + nHg  11-1  where n = 1, 2, 3 and R = a l k y l or a r y l .  The mechanism proposed f o r t h i s reaction (40) i s e l e c t r o p h i l i c attack of the aluminum on to the a l k y l with the aluminum now being five-coordinate.  This  i s then followed by cleavage of the mercury a l k y l bond and e l i m i n a t i o n o f a hydride i o n which i s picked up by the mercury to form an a l k y l mercury hydride which subsequently decomposes to mercury metal and hydrogen gas. Gallium compounds,on the other hand, e x h i b i t f a r less a b i l i t y to form five-coordinate configurations.  The only established molecule of t h i s type  i s (Me N) GaH which d i s s o c i a t e s to the tetra-coordinated compound above 3  -21°C  2  3  (9). The aluminum anaiogue o f t h i s compound (Me N) AlH 3  2  3  i s a monomeric  - 12 s o l i d with a melting point of 90°C (46).  Thus, since gallium i s unable to  penta-coordinate at room temperature and because Me NGaH i s s l i g h t l y 3  3  unstable at t h i s temperature, decomposition occurred. At lower temperatures where Me NGaH i s stable and there i s a p o s s i b i l i t y of gallium penta3  3  coordinating no reaction was observed, p o s s i b l y because the Hg-alkyl bond i s then thermo-chemically s t a b l e to e l e c t r o p h i l i c attack.  This i s i n d i c a t e d  i n the aluminum reaction,(see equation li-^,where elevated temperatures and r e f l u x i n g solvents, u s u a l l y cyclohexane, were needed to ensure complete reaction.  At higher temperatures Me NGaH could p o s s i b l y d i s s o c i a t e , and 3  3  the GaH moiety then react. 3  Another important consideration i s the difference i n e l e c t r o n e g a t i v i t y between gallium and aluminum. Rochow), of 1.47  Aluminum has an e l e c t r o n e g a t i v i t y , ^ A l l r e d -  and since the e l e c t r o n e g a t i v i t y of hydrogen i s 2.1,  the  Al-H bond i s considerably p o l a r i z e d with the hydrogen more strongly a t t r a c t ing the bond-forming electrons g i v i n g i t a 6 - charge and g i v i n g the aluminum atom a s u b s t a n t i a l 6+ charge.  Thus, the aluminum i s provided with a strong  d r i v i n g force f o r the e l e c t r o p h i l i c attack and f o r easy loss of hydride i o n . Gallium,on the other hand, has an e l e c t r o n e g a t i v i t y , Allred-Rochow, of 1.82,  rendering the Ga-H  bond f a r less p o l a r and thus decreasing both, the  d r i v i n g force f o r e l e c t r o p h i l i c attack and the a b i l i t y to  lose a hydride  ion. That a d e f i n i t e r e a c t i o n takes place, as i n d i c a t e d by the equation rather than mere the proton NMR 10.21, 10.28  10-1,  decomposition of the s t a r t i n g material was evidenced by  spectrum of the product which showed three peaks at T = 10.12, (T_-  = 2.84 p.p.m.), c l o s e l y resembling the Ga-Me absorption  peaks observed i n products obtained by alternate routes.  In addition the  - 13 i n f r a r e d spectrum o f the product i n benzene s o l u t i o n showed two bands at 1840, 1780 cm * i n the Ga-H s t r e t c h i n g frequency region i n d i c a t i n g the presence o f several species. Small droplets of mercury metal were observed i n the residue i n the reaction f l a s k giving further evidence o f r e a c t i o n . However, the low y i e l d s o f organogallane products obtained by t h i s method turned our a t t e n t i o n to a l t e r n a t i v e routes. The second synthetic route involved the l i t h i u m hydride reduction o f trimethylamine adducts o f organogallium h a l i d e s ;  y Me NGaMe H + L i C l  Me NGaMe Cl + LiH 3  2  3  Me NGaMeCl + 2 LiH 3  13-1  2  > Me NGaMeH + 2 L i C l  2  3  13-2  2  The trimethylamine monomethyldichlorogallane can r e a d i l y be prepared by the f o l l o w i n g routes.  Me^Si + GaCl  y  3  [Me Si  Me \  3  y  GaCl ] 2  Cl Me SiCl + MeGaCl 3  Me N + MeGaCl 3  2  • Me NGaMeCl 3  2  13-3 13-4  2  The reaction 13-3, reported by Schmidbaur. and coworkers (21,22,47) proceeds smoothly without solvent at 40°C t o y i e l d  trimethylchlorosilane,  M e S i C l , b o i l i n g point 57.9°C (48) and monomethyldichlorogallane, MeGaCl , 3  melting point 75-76°C, i n high y i e l d .  2  The v o l a t i l e components Me SiCl and 3  excess Mei+Si were pumped o f f at 0°C to leave the desired product^MeGaCl  2j  a  - 14 white s o l i d which analysed f o r CI = 46.2% and Ga = 42.6%; t h e o r e t i c a l CI = 46.6% and Ga = 44.8%.  The methyl group on the gallium atom could not be  removed by hydrolysing with water, although presumably i t could be removed by b o i l i n g MeGaCl  i n concentrated acid (69). The gallium was analysed as  2  the p r e c i p i t a t e GaMe [CgHeNO^.  An excess o f trimethylamine was then added  to the s o l i d monomethyldichlorogallane  and the mixture held at 0°C f o r some  hours a f t e r which the excess amine was removed to leave a white s o l i d Me NGaMeCl i n the f l a s k . 3  2  A l t e r n a t i v e routes to t h i s l a t t e r compound involve r e a c t i o n of hydrogen chloride with t r i m e t h y l g a l l a n e i n ether followed by amine a d d i t i o n ,  Me Ga + 2HC1  E t 2  MeGaCl + Me N  E t 2  3  2  ° > MeGaCl + 2CH.1+  14-1  ° > Me NGaMeCl  14-2  2  3  3  2  or e q u i l i b r i u m r e a c t i o n between trimethylamine t r i c h l o r o g a l l a n e and trimethylamine t r i m e t h y l g a l l a n e .  2Me NGaCl + Me NGaMe 3  3  3  3  > 3Me NGaMeCl  A l l the above reactions proceed i n high y i e l d .  3  2  14-3  An NMR spectrum o f the  compound Me NGaMeCl showed two peaks, one at T = 8.36 corresponding t o 3  2  Me-N resonance and a second peak of one-third the integrated i n t e n s i t y at x = 9.92 f o r the Ga-Me resonance. The preparation o f trimethylamine dimethylmonochlorogallane  (49,50),  Me NGaMe Cl, involved the r e a c t i o n o f s t o i c h i o m e t r i c amounts of hydrogen 3  2  - 15 chloride and trimethylgallane i n ether, followed by amine a d d i t i o n , o r the u t i l i z a t i o n o f the e q u i l i b r i u m reaction  Me Ga + HCI  *  Me GaCl + CH^  15-1  Me GaCl + Me N  *  Me NGaMe Cl  15-2  3Me NGaMe Cl  15-3  3  2  3  2Me NGaMe + Me NGaCl 3  3  3  2  3  2  3  3  2  The f i n a l reduction o f these trimethylamine adducts o f chloromethylgallane was c a r r i e d out by adding the LiH i n ether at -20°C, followed by a period o f two hours at room temperature.  The reaction mixture was f i l t e r e d  and the ether removed at low temperature t o leave a white s o l i d which was then p u r i f i e d by sublimation. The product i n benzene, from the reaction of trimethylamine monomethyldichlorogallane with two moles o f l i t h i u m hydride,, gave an NMR spectrum with two peaks, a t t r i b u t e d t o Ga-Me at x = 9.99, 10.14.  The l a t t e r corresponds  to Ga-Me i n Me NGaMeH and the former may be e i t h e r due t o Ga-Me i n the 3  2  p a r t l y reduced species Me NGaMeClH or to Ga-Me i n LiGaMeX H, t h i s l a t t e r 3  2  species being formed by the r e a c t i o n  LiH + Me NGaMeX 3  2  LiGaMeX H + Me N 2  3  15-4  where X = H or C l . The former p o s s i b i l i t y seems most l i k e l y as the material could be r e a d i l y sublimed.  The area under the peaks suggests that only about 25% o f the  product e x i s t s as Me NGaMeH . 3  2  The i n f r a r e d • spectrum o f the reduced" species showed  - 16 two bands i n the Ga-H s t r e t c h i n g frequency range a t 1880 cm * and 1830 cm The r e d u c t i o n o f t r i m e t h y l a m i n e dimethylmonochlorogallane h y d r i d e produced  with  lithium  a product which i n benzene s o l u t i o n showed a Ga-Me NMR  peak at T = 10.20 c o r r e s p o n d i n g t o t h e p o s i t i o n o b t a i n e d f o r  resonance  Me3NGaMe H p r e p a r e d by o t h e r methods and s i g n i f i c a n t l y h i g h e r than t h e Ga-Me 2  resonance  i n Me3NGaMe2Cl which appeared  at x  = 10.11.  In both o f t h e above  r e d u c t i o n s , t h a t i s u s i n g t h e mono- and d i c h l o r o - g a l l a n e s , t h e y i e l d o f t r i m e t h y l a m i n e methyl g a l l a n e s was v e r y low and t h e p r o d u c t s were always ..contamina t e d w i t h c h l o r i d e which was d i f f i c u l t o r i m p o s s i b l e t o remove. at h i g h e r temperatures decomposition  Reactions  o r f o r l o n g e r p e r i o d s o f time o n l y r e s u l t e d i n t h e  o f the products.  R e a c t i o n s u s i n g excess  L i H gave none o f t h e  expected p r o d u c t ^ p o s s i b l y o n l y t h e l i t h i u m compounds, LiGaMe XH and 2  15-4), would be formed.  LiGaMeX H, where X i s C l o r H, (see e q u a t i o n 2  Analogous aluminum r e a c t i o n s gave s i m i l a r r e s u l t s  (41).  Thus r e a c t i n g  M e N A l E t C l w i t h L i H f o r n i n e hours i n r e f l u x i n g e t h e r r e s u l t e d i n o n l y one3  2  h a l f o f t h e c h l o r i d e b e i n g reduced t o t h e h y d r i d e Me3NAlEt H. 2  to 24 hours were used i n attempting Me3NAlEtH , b u t o n l y p a r t i a l 2  Times o f up  the L i H r e d u c t i o n o f M e 3 N A l E t C l t o 2  c o n v e r s i o n was observed.  The Me3NAlMe Cl 2  compound i n c o n t r a s t t o t h e e t h y l compound d i d not r e a c t at a l l w i t h L i H i n r e f l u x i n g e t h e r , and n e i t h e r d i d Me3NAlMeCl . 2  Although  t h i s second method o f p r e p a r a t i o n was s u p e r i o r t o t h e dimethyl  mercury r o u t e , subsequent methods l e d t o h i g h e r y i e l d s .  Thus a more advantageous s y n t h e s i s i n v o l v e d t h e r e a c t i o n o f l i t h i u m methyl with h a l o g e n o g a l l a n e s (11).  Me NGaH Cl + LiMe 3  2  *  Me NGaMeH 3  2  + LiCl  16-1  Me NGaHCl + 2LiMe 3  2  *  Me NGaMe H + 2 L i C l 3  17-1  2  When s t o i c h i o m e t r i c amounts o f trimethylamine monochlorogallane and l i t h i u m methyl were mixed i n ether, l i t h i u m c h l o r i d e was p r e c i p i t a t e d . A f t e r f i l t r a t i o n and removal o f solvent at low temperature, the product Me NGaMeH could be sublimed to give a high y i e l d of a c h l o r i d e - f r e e m a t e r i a l . 3  2  The i n f r a r e d and NMR spectra o f t h i s compound, with other p h y s i c a l data were c o l l e c t e d and are discussed l a t e r . 8.18  The NMR spectrum showed a peak at x =  assigned to Me-N resonance, and also three peaks corresponding t o  Ga-Me resonance at x = 10.09, 10.18, 10.24 which compare favorably to the spectra o f Me NGaH Me samples prepared by other routes. 3  2  S i m i l a r l y when two  molar equivalents o f l i t h i u m methyl were reacted with one molar equivalent of trimethylamine dichloromonomethylgallane  i n l i k e manner, the compound  Me NGaMe H was produced, which could be sublimed as a nearly pure product, 3  2  though a trace o f c h l o r i d e was always present. of t h i s compound were also recorded.  The i n f r a r e d and NMR spectra  The NMR spectrum contained a peak at  x = 8.20 assigned t o Me-N resonance, and also f o r Ga-Me resonance i n d i c a t e d three peaks at x = 10.10, 10.18, 10.25 which compare favorably t o the spectra of Me NGaMe H samples prepared by other methods. 3  2  In a d d i t i o n there was a  very small peak at x = 10.04 which was probably due to the Ga-Me o f the Me NGaMeHCl species. 3  This same chloro species was postulated as a side  product from the preparations using Me NGaMeCl and LiH, g i v i n g a peak at 3  2  x = 10.02 and was s i m i l a r l y d i f f i c u l t t o remove by sublimation. These chlorogallane compounds react very s i m i l a r l y t o t h e i r aluminum analogues (40,51) where at room temperature, i n e i t h e r benzene or ether solvent, l i t h i u m methyl reacted very r a p i d l y with t r i a l k y l a m i n e  - 18 c h l o r o a l k y l a l a n e s , as i n d i c a t e d below, i n equation 18-1, t o produce t r i a l k y l -  nRLi + R ' o N A l C l H n 3-n  > n L i C l + R%NA1R H n 3-n  3  3  18-1  3  where n = 1, 2, 3, R = a l k y l or a r y l , and R' = Me or Et.  amine organoalanes.  Lithium a l k y l also reacts with trimethylamine alane t o  produce an a l k y l a t e d alane adduct,  LiMe + Me NAlH 3  3  »- LiH + Me NAlMeH  3  >- L i A l H ^ + Me N  3  18-2  2  but a side r e a c t i o n LiH + Me NAlH 3  18-3  3  made i t d i f f i c u l t t o c o n t r o l the stoichiometry o f the desired r e a c t i o n and the y i e l d o f Me NAlMeH was low. This side r e a c t i o n seems to be a standard 3  2  r e a c t i o n with Group IIIB a l k y l s (52) where a stronger nucleophile such as LiH,  Me NH, or CaH replaces a weaker nucleophile such as Me N. 2  2  3  When a s i m i l a r r e a c t i o n was attempted, using l i t h i u m methyl with trimethylamine gallane, none of the desired product Me NGaMeH was produced. 3  2  The r e a c t i o n probably proceeded f i r s t by a l k y l a t i o n o f the gallane followed by l i t h i u m hydride replacement o f trimethylamine.  LiMe + Me NGaH 3  3  LiH + Me NGaMeH 3  2  *  LiH + Me NGaMeH 3  2  •> LiGaMeH + Me N 3  3  18-4 18-5  - 19 The ether solvent was removed at low temperature  and the NMR spectrum  of the white s o l i d d i s s o l v e d i n benzene was recorded.  This gave several  peaks, a s i n g l e t at x = 9.92 assigned t o Ga-Me i n LiGaMeH and a t r i p l e t and 3  quartet centred at x = 9.2 and 6.9 r e s p e c t i v e l y which are assigned t o ether coordinated to the LiGaMeH3 molecule. solidjLiGaMeH ,at room temperature 3  On prolonged pumping o f the white  a l l the ether could be removed and  LiGaMeH now seemed t o be only p a r t l y soluble i n benzene. 3  P o s s i b l y the  LiGaMeH had polymerized, some graying was also observed i n d i c a t i n g that 3  the l i t h i u m compound was decomposing. Lithium g a l l i u m hydride, LiGaH is l+7  also postulated t o have ether coordinated t o i t (55) and decomposes at room temperature  i n ether s o l u t i o n or when the ether solvent i s removed.  Me-N resonance was observed i n the NMR spectra.  No  This system was not i n v e s t i -  gated f u r t h e r , because i t seemed not t o lead t o the desired organogallane amine adducts. The f i n a l method employed f o r s y n t h e s i s i n g trimethylamine adducts o f organogallanes was the h i g h l y successful route i n v o l v i n g the e q u i l i b r i u m reaction between trimethylamine gallane and trimethylamine trimethylgal1ane.  Me NGaH + 2Me NGaMe  3  y 3Me NGaMe H  19-1  2Me NGaH + Me NGaMe  3  > 3Me NGaMeH  19-2  3  3  3  3  3  3  3  3  2  2  Again the products can be p u r i f i e d by sublimation, but i n t h i s method the s t a r t i n g materials are both extremely pure and there are no side products. Infrared and NMR spectra were c o l l e c t e d on the products and compare favourably t o those obtained from compounds prepared by a l t e r n a t i v e routes.  - 20 -  The aluminum analogues were p r e p a r e d i n the v e r y same manner by m i x i n g s t o i c h i o m e t r i c q u a n t i t i e s o f Me3NAlMe3 and Me3NAlH  3  and d i s t i l l i n g  or  s u b l i m i n g o f f , i n q u a t i t a t i v e y i e l d , the a l k y l a l a n e amine complex.  B.  P r o p e r t i e s and R e a c t i o n s o f T r i m e t h y l a m i n e Adducts o f O r g a n o g a l l a n e s (a)  Physical  Properties  The t r i m e t h y l a m i n e o r g a n o g a l l a n e s appear at v e r y low temperatures t o be n i c e w h i t e s o l i d s but at room temperatures they appear as waxes o r o i l s . Me3NGaMe£H was p l a c e d i n a s u b l i m e r and s u b l i m e d o n t o t h e c o l d f i n g e r c o o l e d t o -78°C. Then t h i s c o l d f i n g e r was i t s temperature n o t e d . At about -6°C  a l l o w e d t o s l o w l y warm up  some o f t h e m a t e r i a l on the c o l d  began t o melt but the m e l t i n g p o i n t was riot sharp 20°C at which temperature a l l the compound was  continuing liquid.  l i k e w i s e s u b l i m e d onto the c o l d f i n g e r and warmed up. Me NGaMeH 3  2  ' until  Me NGaMeH2 3  finger  about was  At 4°C some o f the  began t o melt and a t about 25°C a l l o f the compound had  i n t o a very viscous o i l .  and  melted  When some M e 3 N G a M e H 2 was p l a c e d i n a c a p i l l a r y  tube  and s e a l e d o f f under n i t r o g e n , the compound a g a i n showed a m e l t i n g p o i n t range o f 4 t o 20°C.  At room t e m p e r a t u r e , about 18°C,  i f the two phases are  m e c h a n i c a l l y s e p a r a t e d , the NMR s p e c t r a o f b o t h phases are v e r y s i m i l a r i n d i c a t i n g t h a t t h e two phases are o f s i m i l a r c o m p o s i t i o n . range may  The l o n g m e l t i n g  i n d i c a t e t h a t t h e r e i s . a change o c c u r i n g i n which the s o l i d  p o l y m e r i z e d and on m e l t i n g , becomes monomeric.  was  T h i s t y p e o f b e h a v i o u r was  observed f o r compounds o f the type M e 2 N G a M e 2 ( 6 2 ) . The m o l e c u l a r w e i g h t s o f Me NGaMe2H and Me3NGaMeH2 were b o t h determined 3  c r y o s c o p i c a l l y i n benzene s o l u t i o n .  The m o l e c u l a r weight o f Me NGaMe H was 3  2  found t o be 172 i n a 0.0341 m o l a l s o l u t i o n , t h i s compares t o the t h e o r e t i c a l  - 21 molecular weight f o r a monomer o f 160, to give the degree o f association as 1.08.  The molecular weight of Me3NGaMeH was found to be 175 : 2  i n a 0.0423 m s o l u t i o n .  This compares to the t h e o r e t i c molecular weight o f  the monomer of 146 gms mole ^ and gives a degree o f association of  1.20.  I t seems as i f these compounds are p r i m a r i l y monomers but there i s no doubt some association probably through dipole-dipole i n t e r a c t i o n s rather than bridged dimers.  With s i m i l a r aluminum compounds (40,41) the degree o f  a s s o c i a t i o n f o r Me NAlMeH i s 1.95 and f o r Me3NAlMe H i s 1.34. 3  2  Substituting  2  a b e t t e r b r i d g i n g ligand such as chloride i n place of methyl i n the aluminum compounds r e s u l t s i n an i r r e g u l a r e f f e c t on the degree o f a s s o c i a t i o n , Me NAlH and Me NAlH Cl show degrees of a s s o c i a t i o n o f 1.43 3  3  3  2  and 1.32  r e s p e c t i v e l y , whereas bridging a b i l i t y i s i n the sequence Cl > H > Me. Neither dipole-dipole i n t e r a c t i o n s nor bridged dimers have been generally accepted to explain the a s s o c i a t i o n of Group IIIB coordination compounds and there i s s t i l l a good deal o f controversy  (53) because the r e a l nature of the  bonding forces e f f e c t i n g the compounds are l i t t l e understood and  therefore  no p r e d i c t i o n s can be made about the degree of association i n other Group IIIB coordination compounds. (b)  NMR Data  Proton NMR data.were obtained using both cyclohexane and benzene as solvents.  In both solvents the solvent peak was taken as the i n t e r n a l  standard, cyclohexane x „ i  C  I7  =8.54 and benzene x~ „ =2.84.  6 12 H  C  6 6 H  has the advantage that a l l proton peaks i n t h i s solvent are  Cyclohexane concentration  independent, but i t has the disadvantage that the solvent peak at x = 8.54 often obscures the Me-N peak which appears at about x = 8. Benzene solutions on the other hand show a concentration  dependence at higher  concentrations.  - 22 Fortunately at low concentrations, around 0.1 M to 1 M, the s h i f t s observed due t o solvent i n t e r a c t i o n are very small and benzene has the advantage that i t s resonance peak appears at low enough f i e l d t o be free from i n t e r f e r e n c e with any other proton peaks i n the samples.  Most samples were run at a  concentration o f about 0.5 M t o 1 M. Table 1 Proton NMR Data i n Cyclohexane Species  Me-N (T)  Me NGaMe Me NGaMe H Me NGaMeH Me NGaMeCl  7.72 7.63 7.61 7.66  3  3  3  2  3  2  3  2  Solvent  Ga-Me ( T ) 10.57 10.51 10.42 10.27  Table 2 Proton NMR Data i n Benzene Solvent Species  Me-N (T)  MeNGaMe Me NGaMe H Me NGaMeH MeNGaH Me NGaMe Cl Me NGaMeCl Me NGaCl GaMe MeGaCl Me NGaHMeCl Me NGaMeD Me NGaMe D Me NGaH OMe 3  3  3  2  3  2  3  3  3  2  3  2  3  3  3  2  3  3  2  3  3  2  2  8.34 --> 8.10(sat.) 8.22 8.10 8.02 8.31 8.36 8.19 ---  8.20 8.10 8.20 8.12  Ga-Me ( T ) 10.22 10.17 10.08 -- •  10.11 9.92 --  10.15 9.90 10.03 10.09 10.17 6.65  a  b  S chmi db aur r e f . 47 gives Ga-Me x = 9.20 i n This i s f o r Ga-OMe.  The  p r o t o n NMR s p e c t r a o f Me3NGaMe2H and Me3NGaMeH both show, at t h e 2  same p o s i t i o n s , t h r e e d i s t i n c t  signals with d i f f e r e n t  peaks f o r the two "compounds", see f i g u r e 1.  areas under t h e t h r e e  I t seems p r o b a b l e t h e r e f o r e  t h a t an e q u i l i b r i u m i s e s t a b l i s h e d i n s o l u t i o n and t h a t a l l f o u r p o s s i b l e species are present.  Me NGaMe3 Me NGaMe H Me NGaMeH Me NGaH 3  3  1 - e  '  2  3  )•  a l l present together i n s o l u t i o n .  2  3  3  Q u o t a t i o n marks a r e put around those formula o r compounds whose s t o i c h i o m e t r y corresponds as l i s t e d  t o t h e formula but i n s o l u t i o n a l l f o u r compounds  above e x i s t t o g e t h e r t o make up t h i s c o r r e c t s t o i c h i o m e t r y .  For "Me3NGaMeH " i n benzene the t h r e e Ga-Me s i g n a l s appear a t T = 10.24, 2  10.17, 10.09 and a Me-N peak a t x = 8.10. T a b l e 3 below.  The s i g n a l s are a s s i g n e d as i s i n  The r a t i o o f molar c o n c e n t r a t i o n s and t h e percentage o f  each compound i n s o l u t i o n are a l s o l i s t e d .  Table 3 Molar R a t i o s o f "Me^NGaMeH^" i n Benzene  Species  Ga-Me (x)  Peak Area ratio  Me NGaMe Me NGaMe H Me NGaMeH Me NGaH  10.24 10.17 10.09 --  1 4.85 5.00 --  3  3  3  2  3  3  2  3  Molar Ratio 1 ' 7.0 15.0 8.6  % o f Each  3.1% 22.9 47.0 27.0  - 24 -  »'Me NGaMeH2" 3  0,  -1  .  3  .  *»  :  5  Chemical S h i f t  1 1  1  1  6  f  x(ppm)  ,1  ,  ,  ,  8  cj  io  il  >  "Me NGaMe H'* 3  2  0 •  ;  1  —- II  \1  j1  3  ^  5  — — , I  6  Chemical S h i f t  ,1  — ,I -  7  %  x (ppm)  I  >•  FIGURE 1 NMR Spectra o f "Me NGaMeH " and "Me NGaMe H" at 60 Mc/sec. 3  2  3  2  1  'A  - 25 S i m i l a r l y f o r the compound "Me NGaMe H" i n benzene the f o l l o w i n g data 3  2  were obtained. Table 4 Molar Ratios o f "Me3NGaMe H" i n Benzene 2  Species  Ga-Me (x)  Me NGaMe Me NGaMe H Me NGaMeH Me NGaH -  10.22 10.16 10.07  3  3  3  2  3  2  3  Peak Area ratio  % o f Each  Molar Ratio  1.6 5.16 1  16.0 46.4 30.0 7.6  2.1 6.1 3.95 1  3  S i m i l a r l y three Ga-Me signals were observed f o r each o f the compounds "Me NGaMeH " and "Me NGaMe H" i n cyclohexane s o l u t i o n and f o r the deuterated 3  2  3  2  compounds "Me NGaMeD " and "Me NGaMe D" i n benzene s o l u t i o n . 3  2  3  2  These' are  l i s t e d and the d i f f e r e n t NMR signals assigned i n Table 5. Table 5 NMR Data f o r "Me NGaMe H" and "Me NGaMeH " i n Cyclohexane "Me NGaMe D" and "Me NGaMeD " i n Benzene 3  2  3  "Me NGaMe H" i n C H 3  2  Species Me NGaMe Me NGaMe H Me NGaMeH Me NGaH 3  3  3  2  3  2  3  6  Me NGaMe Me NGaMe D Me NGaMeD Me NGaD 3  3  3  2  3  3  2  3  and f o r  2  "Me NGaMeH " i n C H 3  1 2  2  6  1 2  % o f Each  Species  Ga-Me ("0  % o f Each  10.57 10.51 10.42  27.0% 45.4 23.6 4.0  Me NGaMe Me NGaMe H Me NGaMeH Me NGaH  10.57 10.51 10.42  8.. 3% 27..5 35..0 29..2  —  "Me NGaMe D" i n C H Species  2  3  Ga-Me  3  3  3  2  2  6  3  3  3  2  3  3  2  —  3  "Me NGaMeD " i n C H 3  6  Ga-Me (x)  % o f Each  10.29 10.22 10.16  16.8% 40.9 34.1 8.2  Species  2  Ga-Me  6  6  % o f Each  CO  Me NGaMe Me NGaMe D Me NGaMeD Me NGaD 3  3  3  2  3  3  2  3  10.26 10.22 10.13  1.7% 13.6 44.3 40.4  - 26 These same s e t o f t h r e e Ga-Me peaks were found i n a l l t h e compounds o f the form "Me3NGaMe2H" and "Me3NGaMeH " p r e p a r e d by a l l f o u r e x p e r i m e n t a l 2  procedures.  The compounds which were s u b l i m e d and then d i s s o l v e d i n benzene  gave s p e c t r a e x a c t l y t h e same as t h o s e o b t a i n e d by m i x i n g t h e reagents Me NGaMe3 and Me3NGaH t o g e t h e r i n benzene. 3  3  M i x i n g t h e s e l a t t e r two compounds  i n benzene i n d i f f e r e n t molar r a t i o s i . e . a t r a t i o s o f 1:2, 1:1, 2:1 e t c . gave the same t h r e e peak p o s i t i o n s b u t j u s t d i f f e r e n t a r e a r a t i o s . The p e r c e n t a g e s o f each s p e c i e s p r e s e n t i n s o l u t i o n must be t a k e n as o n l y approximate, f o r s m a l l amounts o f i m p u r i t i e s such as Me3N, o r g a l l i u m m e t a l , from decomposing Me3NGaH3 c o u l d g r e a t l y a f f e c t t h e c o n c e n t r a t i o n s , and v a r i a t i o n s as g r e a t as f i v e p e r c e n t i n t h e amount o f each s p e c i e s p r e s e n t i n s o l u t i o n have been observed f o r t h e same "compound".  Temperature would  a l s o have a marked e f f e c t on t h e p e r c e n t a g e s o f t h e s p e c i e s p r e s e n t , though t h i s was n o t i n v e s t i g a t e d .  H e a t i n g t h e s o l u t i o n s might l e a d t o a time  averaged s i g n a l f o r t h e p r e d i c t e d p r o d u c t s i . e . Me NGaH2Me o r Me3NGaMe2H 3  but low t h e r m a l s t a b i l i t y o f t h e s p e c i e s p r e c l u d e s such work.  The e q u i l i b r i u m  between t h e f o u r compounds i n s o l u t i o n does n o t seem t o be time dependent f o r two NMR s p e c t r a were o b t a i n e d from t h e same sample one month a p a r t and t h e r e were no d i f f e r e n c e s i n i n t e n s i t y o r p o s i t i o n o f any o f t h e peaks. A v a r i a t i o n o f t h e s o l v e n t s i . e . benzene o r c y c l o h e x a n e , seems t o have l i t t l e e f f e c t on t h e p e r c e n t a g e o f each s p e c i e s i n s o l u t i o n , " compare Tables 3, 4 and 5.  The p e r c e n t a g e o f t h a t s p e c i e s i n s o l u t i o n which compares t o  t h e s t o i c h i o m e t r y o f t h e "compound" p r e p a r e d i . e . Me NGaMe H p r e s e n t i n a 3  s o l u t i o n o f "Me NGaMe H" and Me NGaMeH 3  2  i s always t h e g r e a t e s t .  3  2  2  p r e s e n t i n a s o l u t i o n o f "Me NGaMeH "  The p e r c e n t a g e o f each s p e c i e s i s o n l y  thus no s o l v e n t e f f e c t i s e v i d e n c e d i n t h e two s o l u t i o n used.  3  2  approximate, I f a strong  - 27 -  donor s o l v e n t such as an e t h e r were used then t h e r e may be a change i n t h e peak r a t i o s caused by t h e s o l v e n t p a r t l y r e p l a c i n g amine from some o f t h e s p e c i e s , b u t t h i s has y e t t o be i n v e s t i g a t e d . The approximate Ga-Me peak s e p a r a t i o n s were 5 cps a t 60 Mc/sec and about 8 cps a t 100 Mc/sec, thus showing t h e s i g n a l s a r i s e from t h r e e d i f f e r e n t s p e c i e s and n o t from s p i n - s p i n c o u p l i n g . I t i s i n t e r e s t i n g t o note that i n a l l the s p e c t r a run only a s i n g l e sharp peak was observed f o r t h e Me-N resonance.  From T a b l e 2 i t i s seen  t h a t t h e t r i m e t h y l a m i n e group i s i n d i f f e r e n t e l e c t r o n i c environments i n d i f f e r e n t compounds. Thus i n s o l u t i o n s o f t h e compounds "Me3NGaMe2H" and "Me3NGaMeH " a l l t r i m e t h y l a m i n e groups must be exchanging v e r y r a p i d l y , 2  and t h e peak p o s i t i o n s seem t o be i n t h e average p o s i t i o n between t h e extremes o f Me3NGaMe3 and Me3NGaH . 3  The NMR s p e c t r u m o f a n e a t sample o f "Me3NGaMe2H" was o b t a i n e d .  Using  TMS i n benzene as an e x t e r n a l s t a n d a r d t h e f o l l o w i n g p e a k s , a s s i g n e d as Ga-Me r e s o n a n c e s , were o b s e r v e d , a r e a under t h e peak i s i n b r a c k e t s , x [1], 10.02 [1.1], 10.10 [1.7], 10.18 [6.5], 10.26 [7.9].  = 9.92  At t h e probe  t e m p e r a t u r e o f 30°C t h e compound "Me3NGaMe2H" e x i s t s as a v i s c o u s o i l .  It  i s p l a u s i b l e t o a s s i g n t h e peaks a t x = 10.26, 10.18, 10.10 t o the^compounds Me NGaMe , Me NGaMe H and Me NGaMeH 3  3  3  2  3  2  r e s p e c t i v e l y , f o r t h e s e t h r e e peaks  r o u g h l y p a r a l l e l , i n i n t e n s i t y and p o s i t i o n those found f o r t h e compound "Me NGaMe H" i n benzene, see Table 5. 3  2  The peaks a t x = 9.92 and 10.02  c o u l d be a s s i g n e d t o b r i d g i n g methyl groups i n d i m e r i c o r p o l y m e r i c s p e c i e s . Such d o w n f i e l d s h i f t s have been o b s e r v e d f o r t h e b r i d g i n g methyl groups o f (AlMe ) 3  2  (54). A l t e r n a t i v e l y t h e s e peaks c o u l d be a s s i g n e d t o methyl groups  o f s p e c i e s showing s t r o n g d i p o l e - d i p o l e i n t e r a c t i o n .  There i s a s i n g l e  - 28 peak at x = 7.29 corresponding t o Me-N i n d i c a t i n g that a l l the amine groups are exchanging r a p i d l y even i n the neat l i q u i d . The proton NMR of the chlorinated compounds Me NGaMe2Cl and Me NGaMeCl 3  3  2  i n benzene show only a s i n g l e resonance f o r Ga-Me at room temperature. Presumably the higher e f f i c i e n c y o f chlorine as a b r i d g i n g group, over methyl or hydrogen (61), leads t o a stable dimer or a s p e c i f i c s i n g l e compound or very r a p i d exchange. (c)  Infrared Data  The i n f r a r e d absorption spectra of the compounds "Me NGaMeH ", 3  2  "Me NGaMe H" and t h e i r deuterated analogues "Me NGaMeD " and "Me NGaMe D" 3  2  3  2  3  2  were recorded i n benzene s o l u t i o n between 400 cm ^ and 4000 cm \ see Figure 2. These compounds have a vapour pressure o f about 2 mm o f Hg and the gas phase i n f r a r e d spectra of some were recorded.  Assignments o f bands  can be made on the bases o f the w e l l established structures (11, 55) of the adducts o f GaH  X , where X i s halogen and n i s 0, 1, 2, 3 (11). A l l bands -n n 6  3  not assigned t o coordinated trimethylamine or carbon-hydrogen are  l i s t e d i n Table 6 below.  vibrations  From Table 6 i t i s seen that the v i b r a t i o n  frequency o f Ga-H decrease by a f a c t o r o f about / T i . e . 1.41 when going t o the  deuterated species as i s expected from the reduced mass e f f e c t . The i n f r a r e d data o f trimethylamine organogallanes generally support  the NMR r e s u l t s .  The Ga-H s t r e t c h i n g frequencies observed f o r "Me NGaMe H" 3  2  and "Me NGaMeH " are broader bands than those observed f o r Me NGaH (11) 3  2  3  3  and a shoulder at lower frequency i s observed which i s not found i n the spectrum o f Me NGaH . 3  3  These differences could be a t t r i b u t e d to the presence  of p a r t l y methylated gallane species i n s o l u t i o n .  The gas phase o f the  - 29 -  Wavenumber (cm ) FIGURE 2 Infrared Spectra of "Me NGaMeH " and "Me NGaMe2H" i n C H 3  2  3  5  6  - 30 Table 6 Infrared Data f o r "Me NGaMeH ", "Me NGaMeD " and "Me NGaMe H","Me NGaMe D" 3  "Me NGaMeH " 3  3  "Me NGaMeD "  2  3  1845(vs),1815(vs) 1760(sh) 745(vs) 707(s) 685(s,b) 488(s),495(sh)  2  1313(vs) 1270(sh) 538(s) 490(m) 680(w,b) 470(m)  "Me NGaMe H" 3  2  1840(vs) 1760(sh) 745(s) 695 (s)? 690(sh) 485(m),495(sh)  vH/vD  2  vH/vD  }l295(vs)  1.42  538(s) 490(w) 690(s,b) 475(m)  1.36 1.42  3  3  2  3  2  Assignment (55)  1.41; 1.38 jantisym., sym. Ga-H s t r e t c h 1.39 1.37 antisym. Ga-H deformation 1.44 sym. Ga-H deformation -Ga-C -, Ga-N s t r e t c h  "Me NGaMe D"  2  2  Assignment (55) antisym., sym. Ga-H s t r e t c h  }  antisym. Ga-H deformation sym. Ga-H deformation Ga-G Ga-N s t r e t c h  where v s ; very strong; s strong; m medium; w weak; sh shoulder; b broad; u n i t s are i n cm  compounds "Me NGaMe H" and "Me NGaMeH " give i n f r a r e d spectra that are very 3  2  3  2  s i m i l a r t o that o f pure Me NGaH (8). 3  between 630 cm * and 720 cm  3  The i n f r a r e d spectrum i n the region  i s characterized by strong benzene solvent  absorbance so the assignment of bands i n t h i s region, Ga-H symmetric deformat i o n and Ga-C v i b r a t i o n s , are only t e n t a t i v e .  - 31 C.  Reaction of Trimethylamine Organogallanes (a)  With HCl  The compound "Me3NGaMeH " i n benzene s o l u t i o n reacted r e a d i l y at 2  below room temperature with one mole o f hydrogen c h l o r i d e to l i b e r a t e one mole o f gas which was shown by i t s i n f r a r e d spectrum to be mostly hydrogen with a trace o f methane, and t o form the compounds "Me NGaHClMe". 3  A second mole o f HCl gas reacted as e a s i l y as the f i r s t with the compound "Me NGaMeH ", and a second mole o f gas was evolved which again 3  2  was mostly hydrogen but now contained about 10% methane. The r e a c t i o n o f trimethylamine gallane with HCl gas to give hydrogen and trimethylamine chlorogallane has been examined p r e v i o u s l y (11) and proceeds smoothly i n s o l u t i o n or neat.  I t seems reasonable then that  hydrogen can be evolved from trimethylamine adducts o f organogal1ane. I t seems that some methane i s also evolved as evidenced i n the i n f r a r e d spectrum.  This could be explained by the fact that the "Me NGaMeH " 3  2  compound e q u i l i b r a t e s i n s o l u t i o n t o form some Me NGaMe H and Me NGaMe 3  2  3  3  which could then react with HCl t o give o f f methane gas, as i n d i c a t e d i n the equations below.  HCl + Me NGaMe 3  3  HCl + Me NGaMe Cl 3  2  •  Me NGaMe Cl + CH^  31-1  >  Me NGaMeCl  31-2  3  3  2  2  +  Cti  k  The etherate o f GaMe reacts under mild conditions with HCl gas,(see 3  experimental section), t o l i b e r a t e methane; t h u s i t seems l i k e l y that Me NGaMe would also react with HCl. 3  3  In the r e a c t i o n o f a t r i m e t h y l -  amine organogallane with HCl e l i m i n a t i o n o f a proton i s s l i g h t l y preferred  -  32  -  to that o f a methyl group, f o r the amount o f methane l i b e r a t e d i s less than that expected on the bases of the percentage of Me NGaMe and Me NGaMe H 3  3  3  2  i n s o l u t i o n as c a l c u l a t e d from the NMR data, see Table 3 . (b)  With Ethylene  Ethylene gas was condensed onto a benzene s o l u t i o n o f "Me NGaMeH " and 3  2  a f t e r several hours at room temperature no h y d r o g a l l a t i o n or any other r e a c t i o n occurred. The ethylene gas was pumped o f f and i d e n t i f i e d and the NMR and i n f r a r e d spectra o f the benzene s o l u t i o n i n d i c a t e d that the s t a r t i n g material was unchanged. Schmidbaur and coworkers  and Eisch  (21,22)  (18,19)  have shown that  uncoordinated gallanes o f the type X GaH, where X i s C l , Br o r E t , hydro2  g a l l a t e a large v a r i e t y o f double and t r i p l e bonds at low or moderate temperatures.  No h y d r o g a l l a t i o n r e a c t i o n with a coordinated gallane has  been reported and attempts u s u a l l y r e s u l t e d i n the decomposition o f the amine-gallane s t a r t i n g material ( 5 5 ) . (c)  With Methanol  Trimethylamine gallane w i l l react i n benzene or ether s o l u t i o n or neat, at about 0°C, with methanol.  One mole o f Me NGaH w i l l react with one, 3  3  two, or three moles o f methanol t o l i b e r a t e one, two, o r three moles o f hydrogen r e s p e c t i v e l y .  The NMR spectrum of the c l e a r benzene s o l u t i o n which  f i r s t r e s u l t s from the reaction shows two peaks, one at x = 8 . 1 2 ( x „ L  2.84  =  u  6 6 H  p.p.m.) corresponding t o Me-N resonance, and a second peak at x = 6 . 6 5  which i s assigned to the Ga-OMe resonance.  At room temperature the neat  r e a c t i o n product slowly evolves trimethylamine.  The trimethylamine ligand  i s also evolved from the product mixture on removal of solvent.  In both  - 33 -  (a)  5  4  Chemical  6 Shift  7  II  'Z.  t(Ppm)  (b)  /  2  3  5  6  Chemical S h i f t  7 x(ppm)  S  <*  •  FIGURE 3 NMR S p e c t r a o f Me NGaH OMe a t 60 Mc/sec. 3  (a) (b)  2  Immediately a f t e r p r e p a r a t i o n A f t e r removal o f s o l v e n t and r e d i s s o l v i n g  i n benzene  •z  -  34  -  cases a white s o l i d r e s u l t s which i s now only p a r t l y soluble i n benzene. The NMR spectrum of t h i s p a r t l y soluble species i s quite complex.  The Me N 3  peak decreases i n i n t e n s i t y and two broad peaks appear at x = 8.6 and x = 9.1.  These could be a t t r i b u t e d t o Me-N resonance but t h i s i s uncertain.  The peak assigned to Ga-OMe at x = 6.65 also decreases i n i n t e n s i t y and two other quite intense peaks at x = 6.57 and x = 6.71 appear which are f i e l d dependent and not the r e s u l t of spin-spin coupling, (see Figure 3). The i n f r a r e d spectra o f these products, except the product from r e a c t i o n with three molar equivalents of methanol, a l l show a complex Ga-H s t r e t c h i n g region i n the range 1910 cm * t o 1825 cm * with the centre o f the band s h i f t i n g from approximately  1850 cm ^ t o 1900 cm ^ with loss o f amine.  The exact nature of the r e a c t i o n of methanol with Me NGaH i s only 3  p a r t l y understood.  3  I t i s known that alcohol reacts with t r i m e t h y l g a l l i u m  to form dimethylgallium alkoxides, [Me GaOR] (56). 2  These compounds form  2  very weak adducts with trimethylamine, except where R = Me i n which case no adduct forms.  I t i s argued that the -OR group acts as a stronger e l e c t r o n  donor than trimethylamine.  The r e a c t i o n of Me NGaH with methanol probably 3  3  proceeds thus;  Me NGaH + Me OH 3  3  • Me NGaH OMe + H 3  2  H 2MeqNGaH 0Me 9  2  34-1  2  / >- MeO  \ OMe + 2Mec,N Ga H 2  34-2  - 35 -  H ,Ga 2  nMe NGaH OMe 3  2  0 Me  H Ga / 2  VI  + nMe N 3  35-1  Me - n 1  Dimers, trimers or polymers could be formed by reactions 34-2 and 35-1 Indeed some i n s o l u b l e m a t e r i a l , presumably polymeric, was obtained from the reactions i n a d d i t i o n t o the soluble compounds.  These methoxy d e r i v a t i v e s  would c e r t a i n l y be a new class of gallanes and t h e i r preparation, s t r u c t u r e and properties warrant f u r t h e r study.  D.  Mechanism of Exchange From the NMR, i n f r a r e d and experimental data there i s strong evidence  that the four compounds of the type Me NGaMe H _ where n = 0, 1, 2, 3 3  co-exist i n s o l u t i o n .  n  3  n  The intermediate that gives r i s e to these species  i n s o l u t i o n must presumably be reached by a bridged g a l l i u m species:  Me Me N  Me • Ga  3  Me  H  \ .Ga-  \ HX \N H  -NMec  N  This bridged intermediate can then d i s s o c i a t e along the dashed l i n e , then reform and r e d i s s o c i a t e so as to produce a l l four d i f f e r e n t species. A number o f exchange reactions of Group IIIB a l k y l a d d i t i o n compounds have been reported i n the l i t e r a t u r e (57,58,59) but no general mechanism has been  -  -  36  found t h a t a p p l i e s t o a l l o r t o a l a r g e number o f t h e s e a l k y l o r Lewis base exchanges.  The  NMR  s p e c t r a o f the t r i m e t h y l a m i n e  organogallanes  indicate  t h a t a l l amines are e q u i v a l e n t , t h a t i s , t h e y must be exchanging v e r y rapidly.  The b r i d g e d s t r u c t u r e shown above c o u l d l o s e b o t h i t s amine  l i g a n d s t o form the more s t a b l e f o u r - c o o r d i n a t e  g a l l i u m dimer s p e c i e s  the amine l i g a n d s r e c o o r d i n a t i n g as the dimer d i s s o c i a t e s .  with  Alternatively,  i n s o l u t i o n , the amine l i g a n d c o u l d f i r s t d i s s o c i a t e from the monomeric g a l l a n e and t h e n be f r e e i n s o l u t i o n . three-coordinate  The  g a l l a n e s p e c i e s would now  be  and c o u l d e a s i l y become f o u r - c o o r d i n a t e by d i m e r i z a t i o n .  Me  Me  N  \  X  Me  H  \  H  \  H  \  \  T h i s dimer c o u l d then d i s s o c i a t e t o a g a i n form t h r e e - c o o r d i n a t e  gallane  s p e c i e s which then recombines w i t h amine l i g a n d s . . Amine exchange c o u l d a l s o o c c u r by some m o d i f i c a t i o n o f t h e s e two r o u t e s as i s observed w i t h aluminum a l k y l exchange. Me NAlMe 3  3  Exchange between a l k y l aluminum adducts o f the t y p e  and Me NAlMe X, where X i s a h a l o g e n , occurs by two 3  mechanisms (59).  2  The  competing  f i r s t i s t h r o u g h a b r i d g e d dimer i n which the  two  aluminum atoms are f i v e - c o o r d i n a t e s i m i l a r t o the b r i d g e d g a l l a n e shown above.  The  second i s through a b r i d g e d dimer i n which one  f i v e - c o o r d i n a t e and the o t h e r i s f o u r - c o o r d i n a t e . Me MdN  Me  N N  \  »A1  Me'  X  \ N  X'  /Me  \  Al  \  / N  \  Me  aluminum atom i s  - 37 -  This  four-coordinate  the type AlMe3  o  r  part i s obtained  AlMe X 2  I t must be remembered  from a t h r e e - c o o r d i n a t e  aluminum o f  from which t h e t r i m e t h y l a m i n e l i g a n d has d i s s o c i a t e d .  t h a t "Me3NGaMeH2 does not h y d r o g a l l a t e n  i n t h e g a l l i u m case, the e x i s t e n c e  o f an u n c o o r d i n a t e d GaH  3  o l e f i n s so,  species  seems  unlikely. NMR s t u d i e s w i t h t r i m e t h y l a m i n e t r i m e t h y l g a l l a n e i n the presence o f excess amine a b i m o l e c u l a r  (54) have shown t h a t  exchange takes p l a c e as  i n d i c a t e d i n e q u a t i o n 37-1,  * Me N + Me NGaMe 3  but  3  * Me N + Me NGaMe  >  3  3  3  i n t h e presence o f excess t r i m e t h y l g a l l a n e  i s the rate c o n t r o l l i n g  37-1  3  a d i s s o c i a t i o n o f t h e adduct  step.  Me NGaMe 3  Me N + GaMe  3  3  37-2  3  P o s s i b l y b o t h these types o f exchange are o c c u r r i n g i n s o l u t i o n s o f t r i m e t h y l amine o r g a n o g a l l a n e s .  No exchange s t u d i e s have p r e v i o u s l y been  i n v o l v i n g h y d r i d e - a l k y l exchange i n Group IIIB  compounds.  In summary, i t seems t h a t t h e compounds "Me NGaMeH2  and "Me NGaMe2H"  M  3  roughly  parallel,  Me NGaMe . 3  3  i n properties  3  gallanes higher  (20,21).  thermal  3  3  and r e a c t i o n s , t h e chemistry o f Me NGaH and  The thermal s t a b i l i t y  s i m i l a r t o t h a t o f Me NGaH  reported  3  3  o f "Me NGaMe H" and "Me NGaMeH " i s 3  2  3  2  and g r e a t e r than t h a t o f t h e u n c o o r d i n a t e d  However t h e boron and aluminum analogues possess much  stability.  - 38 E.  Exchange Reactions Involving Other Group IIIB Elements (a)  Aluminum Alkyl-Hydride Exchange  Because o f the unusual behaviour of trimethylamine adducts o f organogallane i n s o l u t i o n a re-examination o f trimethylamine adducts o f organoalanes was i n order.  Peters and coworkers  (41) prepared the compounds  "Me NAlMeH " and "Me NAlMe H" by mixing the appropriate amounts o f Me NAlMe 3  2  3  2  3  and Me NAlH i n ether and then removing the solvent. 3  3  Some o f the properties  3  of these compounds are l i s t e d below.  "Me NAlMe H": 3  2  m.p. 33-35°C, b.p. (1 mm Hg) 42-43°C, degree o f association i n C H 6  NMR i n C H fi  12  i s 1.34, v Al-H 1750 cm" , 1  1 2  (x„ „ C  = 8.54) Me-N x = 7.59,  6 12  —  H  Al-Me x = 10.81, 10.86. "Me NAlMeH ": 3  2  m.p. -35°C, b.p. (1 mm Hg) 25-26°C, degree o f association i n C H 6  NMR i n C H B  1 2  (r „ n  L  1 2  6 12 H  i s 1.95, v Al-H 1750 cm =8.54) Me-N x = 7.52, —  Al-Me x = 10.88, 10.78.  The NMR doublet above 10 Thas been explained i n terms o f a dimer with a l t e r n a t i v e methyl or hydrogen bridges. led t o the spectra shown i n Figure 4. ing t a b l e .  A re-examination o f t h i s NMR work The NMR data are 1-i's.ted i  n  the follow-  - 39 -  "Me NAlMeH " 3  2  o-  5  Chemical S h i f t  <r  7  x(ppm) -  "Me NAlMe H" 3  2  '0  Chemical S h i f t  x (ppm)  »-  FIGURE £  NMR Spectra o f "Me NAlMeH " and "Me NAlMe H" at 60 Mc/sec. 3  2  3  2  n  40 Table 7 Proton NMR Data f o r MeqNAlMe„ H Species 3-n n s  Species  C H 6  Me-N Me NAlMe »'Me NAlMe H" "Me NAlMeH " Me NAlH 3  2  3  2  3  3  Solvent  6  C H 6  Me-Al ( x )  (x)  8.31 8.26 8.06 7.94  3  3  r  Me-N  10.58 10.45, 10.51, 10.56 10.47, 10.53, 10.58  1 2  Solvent Me-Al ( x )  (x)  7.61 7.62 7.61 7.71  10.92 10.81, 10.87, 10.92 10.80, 10.87, 10.92  An examination o f these samples with a Varian HA-100 spectrometer showed the Me-Al peaks t o be f i e l d dependent as were the Me-Ga peaks. These trimethylamine methylalane spectra show a remarkable s i m i l a r i t y t o the trimethylamine methylgallane spectra p r e v i o u s l y discussed and t h i s leads to the assumption that an analogous set o f aluminum compounds s i m i l a r to gallium compounds are e x i s t i n g together i n s o l u t i o n , thus the f o l l o w i n g assignments  are made. Table 8  Molar Ratios of "Me NAlMeH " and "Me NAlMe H" i n Benzene 3  2  3  2  "Me NAlMeH " 3  2  Species Me NAlMe Me NAlMe H Me NAlMeH Me NAlH 3  3  3  2  3  2  3  Ga-Me ( x )  Peak Area Ratio  Molar Ratio  10.58 10.53 10.47  7 24 21  1 5.1 9 8.3  --  3  % o f Each 4.3 21.9 38.4 35.4  "Me NAlMe H" 3  2  Species Me NAlMe Me NAlMe H Me NAlMeH Me NAlH 3  3  3  2  3  3  2  3  Ga-Me ( x )  Peak Area Ratio  10.56 10.51 10.45  29 25 7 --  Molar Ratio 1 1.3 0.72 0.38  % o f Each 29.3 38.3 21.2 11.2  - 41 (b)  Boron Alkyl-Hydride Exchange  On the bases that the trimethylamine adducts of organogallanes and organoalanes y i e l d a series o f e q u i l i b r i u m products i n s o l u t i o n , an examinat i o n o f the analogous boron systems was made to see i f t h i s exchange i s c h a r a c t e r i s t i c o f a l l Group IIIB elements.  The compounds Me NBMe and 3  3  Me NBH were mixed i n a 1:2 and 2:1 molar r a t i o i n benzene but no exchange 3  3  was observed o f e i t h e r the trimethylamine groups or methyl groups on the boron, as indicated by the NMR spectra, Figure 5. The NMR data i s summarized i n Table 9. Table 9 NMR Data f o r Mixtures o f Me NBMe and Me NBH i n C H 3  3  3  Species  Me-N (x)  B-Me (x)  B-H (x)  Me NBH "Me NBH Me" "Me NBHMe " Me NBMe  7.81 7.91, 8.16 7.96, 8.19 8.24  -10.05 10.00 9.99  7.89 7.82 7.76  3  3  3  2  3  3  The  3  2  3  B^H i n t e r a c t i o n s were not observed.  6  6  J„ _ B  H  c p s  99 98 99  The s l i g h t s h i f t i n the Me-N  and B-Me peaks i n the above compounds i s probably due to dipole-dipole i n t e r a c t i o n s rather than any a l k y l or amine exchange. (c)  Mixing Trimethylamine Adducts o f D i f f e r e n t Group IIIB Hydrides and A l k y l s  A large number o f exchange reactions using 1:1 molar r a t i o s of reagents were attempted, i n benzene s o l u t i o n , o f the type i n d i c a t e d by the f o l l o w i n g general equation  - 42 -  Me NBMe + 2Me NBH 3  3  3  3  0 V  1'  »  •  -1  2  1  1  ,  ,  3  4  j  e  Chemical S h i f t  2Me NBMe + Me NBH 3  3  3  11  , 7  S  x(ppm)  ,  ,  9  io  ,  i)  >•  3  0 T(ppm)  Chemical S h i f t  FIGURE 5 NMR Spectra o f Mixtures o f Me NBMe and Me NBH i n C H 3  3  3  3  6  6 j  60 Mc/sec  1  - 43 Me NMR + Me NM'R ' 3  3  3  =—»• Me^MR^R'  3  3 / 2  + Me^M'R^R'  3/2  where M and M* = B, A l , Ga; R and R' = Me, H  Figure 6 gives the NMR spectra obtained from the above reactions.  The NMR  data are gathered i n Table 10 below and whether exchange o f trimethylamine or methyl groups takes place i s also indicated i n the table as are the NMR data o f the i n d i v i d u a l reagents.  Table 10 NMR Data o f the Mixed Group IIIB A l k y l s and Hydrides Reagents Exchange  Me NMR + Me NM'RJ 3  3  3  N-Me M-Me M-N-Me M»-•N-Me Exchange . M-Me M'--Me  a) Me NBH + Me NAlMe b) Me NBH + Me NGaMe c) Me NAlH + Me NGaMe  NO NO YES  7.97 7.99  d) Me NBMe + Me NAlH  NO  8.01  3  3  3  3  3  3  3  3  3  3  3  3  3  3  3  3  MeNBMe + Me NGaH Me NAlMe + Me NGaH Me NBMe + Me NAlMe Me NBMe + Me NGaMe Me NGaMe + Me NAlMe MeNBMe Me NAlMe MeNGaMe Me NBH Me NAlH o) Me NGaH  e) f) g) h) i) j) k) 1) m) n)  3  3  3  3  3  3  3  3  3  3  3  3  3  3  3  3  3  3  3  3  3  3  3  3  3  3  3  3  3  3  3  3  YES YES YES YES YES  8.11  8..24 8.,29  NO NO YES  8.,17  YES  8.12 8.17 8.22 8.11 8.30 8.24 8.31 8.34 7.81 7.94 8.02  The solvent was used as an i n t e r n a l standard i . e .  NO NO NO NO NO  10 .59 10 .29 -• 10 .47? 10 .11 10 .51 10 .17 10 .57 10 .25 9.94 10 .49 10 .54 10 .60 10 .04 -• 10 .60 10 .04 10 .63 9 .97 10 .28 10 .28 io .59 9 .99 10 .58 10 .22 -.  -•  -• — •  T  C6 6 H  84 p .p .m  - 44 -  (a)  Me NBH + Me NAlMe 3  3  3  3  Chemical S h i f t  (b)  l  »-  Me NBH + Me NGaMe 3  3  3  ,  i  (c)  ^  ,  z  .  3  1  0  o  x(ppm)  3  1  «  v  ,  s  1  1  6  Chemical S h i f t  ?  1  S  1  <  x (ppm)  f  >  1  /  o  1  /  1  i  '  <  A  Me NAlH + Me NGaMe 3  3  3  3  01 ill 4 X  1  2  ^  >  *  r 5  Chemical S h i f t  .  6  *  — —  i  7  x(ppm)  %  >  1  FIGURE 6 NMR Spectra of, Mixed Trimethylamine Adducts of Different and A l k y l s at 60 Mc/seo.  Group IIIB Hydrides  - 45 -  (d)  Me NBMe 3  1  + Me NAlH  3  3  r  ' '  2 . 3  1  3  1  1  1  4  5  fe  1  Chemical S h i f t  Me NBMe + Me NGaH  (e)  3  3  3  ,  r!-J  ?  x(ppm)  H  ^  <8  -T—  (f)  1  3  j Chemical S h i f t 1  Me NAlMe + Me NGaH 3  3  1  1  •  •  x (ppm)  >•  ,1  — ,i —  3  0 1  '  '——I "I  L  a - 3  (a.  \ .  3  1  ,  ))  >•  0 t-  ^  ;o  T1  11  11  i-  s-  —  ,1  6  .  i  Chejnical S h i f t x(ppm) FIGURE 6^ (Continued)  %  •  1  ,  ,  9  io  :  ,  I,  ix  - 46 -  (g)  Me NBMe + Me NAlMe 3  3  3  3  0 •  '  I  71  c  I  Chemical S h i f t  (h)  1  1  x(ppm)  L 1  1  >  Me NBMe + Me NGaMe 3  3  3  x  <  3  t  3  »  4  4  Chemical S h i f t  (i)  1  1  1 o  1  Me NAlMe 3  3  1  q  s  x(ppm)  io  li  »-  + Me NGaMe 3  T  3  3r  : 4  l  S  Chemical S h i f t  1  6  ;  1  7  x(ppm)  FIGURE 6 (Continued)  *  i  ^  ?  >  ^-i 10  r  11  - 47 An examination o f Table 10 i n d i c a t e s that no general mechanism or p r i n c i p a l can be invoked t o explain a l l the r e s u l t s and as mentioned e a r l i e r the mechanisms o f exchange reactions between Group IIIB t r i a l k y l s or t h e i r adducts are l i t t l e understood.  In s p i t e o f the u n c e r t a i n t i e s , some observa-  t i o n s and crude conclusions can be a r r i v e d at. I f a bridged dimer i s formed as an intermediate i n which one or both metal atoms are five-coordinate and one metal may be four-coordinate postulated f o r the a l k y l - h y d r i d e exchange i n the trimethylamine  (as i s  adducts o f  organogallanes and organoalanes (59)), then those metals which five-coordinate or compounds which can r e a d i l y lose t h e i r Lewis base adduct should show an exchange occurring.  This i s born out with the compound Me NBMe , which i s 3  3  i t s e l f l a r g e l y d i s s o c i a t e d i n t o Me N gas and BMe at room temperature. The 3  3  exchange reactions with t h i s moiety a l l show Me N exchange and with Me NAlH 3  show alkyl-hydride exchange.  3  3  Of the three Group IIIB elements used, aluminum  has the greatest tendency f o r f i v e - c o o r d i n a t i o n , thus,almost a l l the reactions i n v o l v i n g Me NAlMe and Me NAlH show Me N exchange. 3  3  3  3  3  From the NMR spectra, two o f the reactions i n d i c a t e alkyl-hydride exchange. The f i r s t , that between Me NAlH 3  3  and Me NGaMe t o produce gallane compounds 3  3  which have Ga-Me s i g n a l s at x = 10.11, 10.17, 10.25, corresponding to Me NGaMeH , Me NGaMe H and some s t a r t i n g material Me NGaMe as w e l l as 3  2  3  2  3  3  p o s s i b l y some Me NGaH , a l l of which are i n e q u i l i b r i u m i n s o l u t i o n . In 3  3  a d d i t i o n j t h e alane compounds produced give s i g n a l s at x - 10.51, 10.57 corresponding t o Me NAlMe H and Me NAlMe . 3  2  3  3  There i s a shoulder at x = 10.47  on the NMR peak at x = 10.51, and so we can surmise that the compound Me NAlMeH i s also present, and. maybe some s t a r t i n g material Me NAlH . The 3  2  NMR spectrum shows no change over a two week period.  3  3  Thus i t seems that the  - 48 two sets o f exchange reactions o f trimethylamine adducts of organoalanes and organogallanes are e x i s t i n g together i n s o l u t i o n .  I t i s a great puzzle why  the compounds Me NAlMe and Me NGaH don't exchange a l k y l groups s i n c e , as 3  3  3  3  postulated above, these two species e x i s t at a steady concentration i n the products o f exchange between Me NAlH and Me NGaMe . 3  3  3  3  The second r e a c t i o n showing a l k y l exchange i s between Me NBMe and 3  3  Me3N"AlH, to produce alane compounds g i v i n g signals at T = 10.49, 10.54, 10.60 3  corresponding t o Me NAlMeH , Me NAlMe2H, and Me NAlMe , and boron compounds . 3  2  3  3  3  g i v i n g a s i g n a l at x = 9.95 which i s about 13 ,cps i n width at h a l f peak height.  Since there are methyl groups t r a n s f e r r e d t o the alanes there should  also be hydride groups t r a n s f e r r e d t o the boron atom.  Thus the broad peak at  x = 9.95 probably represents s e v e r a l compounds o f the type Me NBMeH , 3  Me NBMe H and p o s s i b l y some s t a r t i n g material Me NBMe . 3  2  3  Spin-spin coupling  3  of the methyl protons with the "^B nucleus, along with quadrupole probably causes the loss o f d e t a i l from t h i s peak. also unchanged over a period o f time.  2  broadening  This NMR spectrum i s  Again i t i s p u z z ^ l i n g why the compounds  Me NBH and Me NAlMe do not show methyl-hydride exchange. 3  3  3  3  The BH moiety i s a stronger Lewis a c i d than BMe and i t s tendency t o 3  3  d i s s o c i a t e from trimethylamine i s much less than BMe .  Boron i s not known  3  to have a coordination number greater than four, and therefore any Lewis base adduct o f a t r i s u b s t i t u t e d boron atom must d i s s o c i a t e before a bridged dimer i n v o l v i n g boron can be formed.  Thus, i n the NMR spectra i t i s  observed that a l l s o l u t i o n s containing Me NBH show no Me N exchange, and i n 3  3  3  the exchange between Me NBMe and Me NAlH where i t i s postulated that 3  3  3  3  formation o f species o f the type Me NBMe H and Me NBMeH and p o s s i b l y Me NBH 3  2  3  2  3  3  occurred, i t i s seen that there are two NMR signals f o r Me N, i n d i c a t i n g that 3  - 49 there is restricted amine exchange here as well. In conclusion i t seems that a great deal of more work must be done, particularly on reaction kinetics, in order to understand the exchange of ligands in alkyl and hydride compound of the Group IIIB elements.  VII.  A.  Experimental  Experimental Techniques (a)  Desiccation  A l l gases were dried f i r s t by f r a c t i o n a t i n g under high vacuum through a trap at -20°C, to remove large amounts of water, and then condensed at -196°C i n t o one limb o f a drying p i s t o l , see Figure 7, packed with a mixture of glass-wool and phosphorus pentoxide. the phosphorus pentoxide by a l t e r n a t e l y other limb.  The gas i s passed through  • cooling one limb and then the  The d r i e d gases are then stored at less than one atmosphere i n  large glass bulbs attached to the vacuum l i n e . A l l solvents were d r i e d and r e d i s t i l l e d before use; d i e t h y l ether over l i t h i u m hydride, n-butyl ether over molten sodium, benzene and cyclohexane over molten potassium.  Methanol was d i s t i l l e d from a mixture of magnesium  turnings and iodine. S o l i d components were p u r i f i e d by sublimation, e i t h e r by vacuum bulbto-bulb sublimation o r as with trimethylamine hydrochloride, sublimed to the cooled c e n t r a l f i n g e r of the apparatus shown i n Figure 8.  Trimethylamine  gallane was sublimed under dynamic vacuum from the f l a s k t o the large v e r t i c a l tube, marked as A, o f the apparatus, which was cooled to -80°C, shown i n Figure 9.  FIGURE 7_ Drying P i s t o l  FIGURE 8 Sublimer  - 54 A l l glassware was washed with acetone, oven d r i e d , evacuated and f i l l e d with n i t r o g e n before use.  A l l nitrogen used was Canada L i q u i d A i r "L"  grade, p u r i f i e d nitrogen. The hydride and a l k y l d e r i v a t i v e s , because o f t h e i r r e l a t i v e i n s t a b i l i t y and extreme r e a c t i v i t y with oxygen o r water vapour were a l l prepared and handled i n e i t h e r a high-vacuum system or a nitrogen f i l l e d dry box.  The  high vacuum system developed f o r the work i s shown i n Figure 10. A doublestage rotary o i l pump (Welch S c i e n t i f i c Co.) and an e l e c t r i c a l l y heated s i n g l e stage mercury d i f f u s i o n pump were used to obtain a vacuum o f greater than 10 ^ mm o f Hg. The dry box (Kewaunee S c i e n t i f i c Equipment) had a s p e c i a l ante-chamber that could be evacuated by a double-stage rotary o i l pump and then f i l l e d with dry n i t r o g e n t o ensure the p u r i t y o f the atmosphere i n the box. dry  The  box i s also connected to a c i r c u l a t i n g pump which c i r c u l a t e s the box's  atmosphere through a drying t r a i n containing molecular sieve (Fisher type 5A) and a copper furnace t o remove any oxygen. (b)  Grease  Apiezon "N" grease was used i n the summer and Apiezon "L" i n the winter on a l l j o i n t s unless otherwise stated.  On apparatus that was warmed above  room temperature Apiezon "T" grease was used.  The p r i n c i p a l thought behind  the design and use o f any apparatus i n the research was to have a few greased j o i n t s as p o s s i b l e . (c)  R e a c t i o n - F i l t r a t i o n Apparatus  The apparatus shown i n Figure 11 found extensive use i n our work. The apparatus i s evacuated f i l l e d with dry nitrogen, and the reactants are placed i n f l a s k A. A d d i t i o n a l reagents may be added during the course o f a reaction  to manometer  f0 5=^  FIGURE 10  Vacuum Line, Part A  from P a r t A  Vacuum L i n e , P a r t B  - 58 by r o t a t i n g the dumper tube _B, the reaction mixture i s s t i r r e d by a magnetic bar C.  The products, i f gaseous may be removed by a Topler pump through  one o f the stopcocks, or i f i n s o l u t i o n can be f i l t e r e d through the s i n t e r e d d i s c J2 (medium porosity) by cooling or evacuating the r e c e i v e r f l a s k E_. (d)  Molecular Weights  Molecular weights were determined by the cryoscopic method.  In the  dry box an accurately known weight of pure compound was dissolved i n a weighed sample o f pure benzene (about 15 ml).  The benzene s o l u t i o n was  poured i n t o the molecular weight apparatus, see Figure 12, and removed from the dry box.  A slow stream of pure nitrogen was flushed through the  apparatus as i t was cooled i n an i c e bath.  The f r e e z i n g point o f the  s o l u t i o n was recorded and compared with that o f pure benzene solvent and with standard solutions o f biphenyl i n benzene solvent. The f o l l o w i n g empirical formula was used t o c a l c u l a t e the molecular weights.  molecular weight =  [K^jXfweight o f sample (gms)] [weights of benzene solvent (gms)]X [change i n temperature (°C)]  = f r e e z i n g point depression constant  (e)  5.10°C per molal.'  Spectroscopy  Infrared spectroscopy was used throughout t h i s work f o r semi-quantitat i v e analysis and f o r s t r u c t u r a l .determination o f compounds.  Infrared  spectra were recorded on the f o l l o w i n g Perkin-Elmer instruments; 137, NaCl range 4000 - 650 cm , 137, KBr, range 800 - 400 cm , 457 range 4000 -1  -1  250 cm , 21 range 4000 - 550 cm . -1  -1  The observable range f o r both l i q u i d  and gas samples was between 4000 and 400 cm ^ because KBr windows were used.  - 59 -  rogen  FIGURE  12  Molecular Weight Apparatus  - 60 For gaseous or v o l a t i l e samples a 10 cnugas c e l l was used with KBr windows.  For l i q u i d or s o l u t i o n samples a 0.05 cm f i x e d path length s o l u t i o n  c e l l with KBr windows was used and a variable-thickness c e l l f i l l e d with pure solvents (usually benzene) was placed i n the reference beam t o compensate f o r solvent absorption.  Because o f the i n s t a b i l i t y o f most o f the  gallium hydride adducts prepared, a l l i n f r a r e d s o l u t i o n c e l l s were loaded i n the dry box and a spectrum run as r a p i d l y as p o s s i b l e . As with i n f r a r e d spectroscopy, nuclear magnetic resonance spectroscopy, NMR, was used as a t o o l t o i n v e s t i g a t e reactions and f o r s t r u c t u r a l determination.  The instruments used were a Varian A-60 and J e l c o C-60 both  operating with a radiofrequency o f 60 megacycles per second and a Varian HA-100 which operates at a radiofrequency o f 100 megacycles per second. Most samples were run i n benzene s o l u t i o n with a concentration o f about 0.1 M t o 1 M.  The benzene proton s i g n a l was used as an i n t e r n a l standard  and was defined as T = 2.840 p.p.m.  Tetramethylsilane, TMS, was used as  an external standard on several samples and i s defined as  = 10.000 p.p.m.  The NMR sample tubes were s p e c i a l l y f i t t e d with a flame-seal c o n s t r i c t i o n and a B-10 q u i c k - f i t cone so that the samples could be loaded and sealed under an atmosphere o f nitrogen.  As with the i n f r a r e d samples, the NMR  spectra were run as r a p i d l y as p o s s i b l e since steady decomposition  at room  temperature often impeded prolonged i n v e s t i g a t i o n . (f)  Lithium Methyl Standardization  On standing ether s o l u t i o n s o f l i t h i u m methyl slowly decompose (35), and consequently  these s o l u t i o n s were standardized j u s t before use.  The  apparatus i n Figure 13 was used f o r the standardization. In a t y p i c a l standardization 5.0 ml o f the l i t h i u m methyl ether s o l u t i o n  61 -  BS12  FIGURE 13  Lithium Methyl Apparatus  - 62 was added to the apparatus i n the glove box.  The apparatus was then removed  from the glove box, the ether s o l u t i o n frozen i n l i q u i d nitrogen, the apparatus evacuated and then attached to the gas burette which was completely f u l l o f concentrated s u l f u r i c acid.  A mixture of 70% p-dioxane and 30%  water was slowly added from the top r e s e r v o i r hydrolysing the l i t h i u m methyl and f o r c i n g a l l the methane gas i n t o the gas burette.  The gas  burette was removed and shaken several times to remove traces of ether and then the volume of gas measured, and the r e s u l t s averaged.  t h i s procedure was repeated several times  Volume of gas was 71.6 ml at 19°C thus molarity  was 0.598 M. (g) i)  Elemental Analysis Active Hydrogen:  Active hydrogen was measured by p l a c i n g a small weighed\ amount of compound i n a round bottom f l a s k i n the dry box,, attaching a stopcock adaptor and evacuating on the vacuum l i n e .  A small volume of degassed,  d i l u t e aqueous HN0 s o l u t i o n was then condensed onto the s o l i d at -196°C. 3  The mixture was allowed to reach room temperature and l e f t to react f o r about one hour with s t i r r i n g .  Me NGaHX + H 3  2  +  • Me N + G a 3  The volume of hydrogen gas, non-condensable  +3  + 2X  _  + H  2  62-1  at -196°C, was then measured  II  using a Topler pump.  The amount of active hydrogen i n the compound was then  calculated. This aqueous s o l u t i o n was made up to a known volume and aliquots were used i n the determination of chloride and gallium as i n d i c a t e d below.  - 63 ii)  Chloride  A measured aliquot of the s o l u t i o n prepared above was made s l i g h t l y a c i d i c with d i l u t e n i t r i c a c i d , then a s l i g h t excess of aqueous s i l v e r n i t r a t e s o l u t i o n was added, whereupon s i l v e r chloride i s p r e c i p i t a t e d .  The  p r e c i p i t a t e was then heated t o 80°C and s t i r r e d vigorously to coagulate the i n i t i a l l y c o l l o i d a l p r e c i p i t a t e .  The p r e c i p i t a t e was c o l l e c t e d i n a  f i l t e r i n g c r u c i b l e , washed with very d i l u t e n i t r i c acid and dried at 120°C. The p r e c i p i t a t e was weighed as AgCl which contains 24.74% chlorine by weight. iii)  Gallium  A measured aliquot of the s o l u t i o n prepared i n section ( i ) was measured out i n t o a beaker.  The s o l u t i o n was f i r s t made meutral with d i l u t e ammonia  s o l u t i o n , then was made s l i g h t l y a c i d i c , pH 5-7, with d i l u t e aqueous HCl. The s o l u t i o n was then heated to 80°C and a s l i g h t excess of a 5% s o l u t i o n of 8-hydroxyquinoline i n g l a c i a l a c e t i c acid was added followed by an aqueous s o l u t i o n o f saturated ammonium acetate u n t i l p r e c i p i t a t i o n of Ga(CgH NO) 6  complete.  3  is  A f t e r d i g e s t i o n at 80°C f o r one hour, the yellow p r e c i p i t a t e was  c o l l e c t e d i n a f i l t r a t i o n c r u c i b l e and the p r e c i p i t a t e washed, f i r s t with hot, then cold water.  The p r e c i p i t a t e was then dried at 120°C and weighed,  and i t s gallium content c a l c u l a t e d from the formula Ga(CgH NO) 6  13.89% gallium by weight.  3  which i s  This method has been found to give accurate  determinations f o r a minimum concentration of 10 mg o f gallium i n 50 ml of s o l u t i o n . I f the gallium compound had a methyl ligand attached to i t then t h i s ligand was not removed under mild hydrolysing  conditions  such as i n d i l u t e  HN0 s o l u t i o n s , and gallium was p r e c i p i t a t e d as GaMe(CgHgN0)2 which contains 3  18.78% gallium.  I f the gallium compound had two or more methyl  ligands  - 64 attached to i t then these were also often not removed under mild hydrolysing conditions.  Attempts to p r e c i p i t a t e gallium as a 8-hydroxyquinoline  complex  were not too successful f o r the complexes formed tended to be c o l l o i d s and d i f f i c u l t to f i l t e r o f f .  Gravimetric determinations  of g a l l i u m i n these  l a t t e r compounds was d i f f i c u l t and the r e s u l t s poor.  Wade and coworkers  (69) have proposed a method of analysing these compounds, by t i t r a t i n g with EDTA a f t e r the removal of organic ligands by b o i l i n g the sample f o r several hours i n concentrated h y d r o c h l o r i c a c i d .  B.  Preparative (a)  Preparation of Gallium T r i c h l o r i d e (63) GaCl  3  Gallium t r i c h l o r i d e was prepared by d i r e c t combination of the elements. Pure c h l o r i n e gas (Matheson Ltd.) was d r i e d by passing through  concentrated  s u l p h u r i c a c i d i n a bubbler and was then passed i n t o the a l l glass apparatus shown i n Figure 14.  The gallium metal, about 15 gms,  ( A l f a Inorganics  Inc.)  placed i n A soon melted on warming with a bunsen burner, and reacted with the c h l o r i n e , f i r s t to give a colourless l i q u i d , gallium t e t r a c h l o r o g a l l a t e (64), G a C l i 2  (melting point 170.5°C (65)).  t  l i q u i d G a C l i disappeared 2  On adding more chlorine t h i s  and the l i q u i d gallium burned with a grey-white  t  flame g i v i n g a v o l a t i l e white s o l i d , gallium t r i c h l o r i d e GaCl3, (melting point 79°C).  A  2Ga(l) + 2 C l ( g ) 2  (Ga )(GaCl ")(l) + Cl (g) +  4  2  (Ga )(GaCli  )  +  A  t  •> G a C l 2  6  64-1 64-2  FIGURE 14 Gallium T r i c h l o r i d e Apparatus  - 66 The rate of flow o f chlorine gas and rate of heating the molten gallium were adjusted so that most o f the v o l a t i l e GaCl was deposited i n the cooled 3  r e c e i v e r boat C.  A f t e r a l l the gallium had reacted ( e s s e n t i a l l y 100%),  any sublimate i n A was driven i n t o £ by warming and then flame s e a l i n g the c o n s t r i c t i o n at B^. The apparatus was then evacuated and flame sealed at F_. The crude h a l i d e was then resublimed into the ampoules E_ and then these were sealed at t h e i r c o n s t r i c t i o n s .  The gallium t r i c h l o r i d e was found to remain  stable i n d e f i n i t e l y when stored t h i s way. (b)  Preparation o f Lithium Gallium hydride (66), LiGaH^  4LiH + GaClo  ^ § > LiGaH room Temp.  6  u  + 3LiCl  66-1  H  An ampoule of G a C l , was weighed and broken open i n the dry box and 3  placed i n a c o n i c a l f l a s k .  The gallium t r i c h l o r i d e was then dissolved i n  d i e t h y l ether and the ampoule washed several times to ensure q u a n t i t a t i v e removal o f GaCl . 3  determined.  The empty ampoule was reweighed and the weight o f GaCl  The ethereal s o l u t i o n o f GaCl  3  3  and a l l the washings were now  added t o the nitrogen f i l l e d r e a c t i o n - f i l t r a t i o n apparatus (see Figure 11) and the s o l u t i o n brought up t o about 150 ml. From the weight o f GaCl  3  c a l c u l a t e d , (8.59 gms; 48.8 mmoles) the weight  of about 16 molar equivalents o f f i n e l y ground l i t h i u m hydride (7.45 gms; 938 mmoles) ( A l f a Inorganics Inc.), enough f o r a f o u r - f o l d excess, was weighed out under nitrogen i n t o the dumper tube. The r e a c t i o n f l a s k was cooled to -50°C i n an acetone-solid C0  2  bath  and the dumper tube rotated upwards to permit the slow addition o f LiH to the r e a c t i o n f l a s k over a period o f about t h i r t y minutes.  A bubbler was  - 67 attached to the apparatus so that the r e a c t i o n could be c a r r i e d out under a constant pressure of one atmosphere o f nitrogen.  The coolant was allowed  to warm up t o room temperature and the mixture was s t i r r e d f o r about f i f t y hours to ensure complete r e a c t i o n . The r e s u l t i n g r e a c t i o n mixture was f i l t e r e d through the glass s i n t e r e d d i s c and a c l e a r c o l o u r l e s s f i l t r a t e r e s u l t e d . This f i l t r a t e was then transf e r r e d , i n the dry box, to a c o n i c a l f l a s k f i t t e d with a break s e a l and an extended neck which was flame sealed f o r storage.  The LiGaH^ ether s o l u t i o n  was observed to be i n d e f i n i t e l y s t a b l e i f stored i n a l l glass ampoules under a nitrogen atmosphere and cooled below 0°C. Lithium g a l l i u m deuteride, LiGaD^, was prepared and stored i n exactly the same manner as LiGaH , only l i t h i u m deuteride, LiD, ( A l f a Inorganics 4  Inc.) was s u b s t i t u t e d i n the preparation f o r l i t h i u m hydride. (c)  Preparation of Trimethylamine  LiGaHi, + MeoNHCl  ^  3  Gallane (9), Me3NGaH-3  •  room temp.  MeoNGaHo + L i C l 0  3  .  + H  ?  67-1  *  A known amount o f l i t h i u m g a l l i u m hydride (2.38 gms; 29.4 mmoles) i n ether s o l u t i o n was placed i n the r e a c t i o n - f i l t r a t i o n apparatus, see Figure 11.  S l i g h t l y less than the s t o i c h i o m e t r i c amount of trimethylamine hydro-  c h l o r i d e , Me NHCl, (2.644 gms; 27.6 mmoles) ( A l f a Inorganics Inc.) d r i e d 3  and p u r i f i e d by sublimation, was placed i n the dumper tube o f the r e a c t i o n vessel which contained a nitrogen atmosphere. The ether s o l u t i o n o f LiGaH^ was f i r s t cooled to -50°C i n a dry-ice cooled acetone bath, as the trimethylamine hydrochloride was added over a period of about 10 minutes.  Then the s o l u t i o n was allowed to warm up to  - 68 room temperature and s t i r r e d f o r about four hours to ensure complete r e a c t i o n . The s o l u t i o n was next f i l t e r e d through the glass s i n t e r . and the r e c e i v e r f l a s k containing the c l e a r ether s o l u t i o n was attached t o the s u b l i mation apparatus, see Figure 9.  This apparatus was attached to the vacuum  l i n e and the ether was pumped o f f at -50°C.  When most o f the ether was  removed, the residue was allowed t o warm up t o room temperature while the large bulb part of the sublimation apparatus was immersed i n an acetones o l i d C0 slush bath. 2  The pure trimethylamine gallane was vacuum sublimed  as long n e e d l e - l i k e c r y s t a l s i n t o the cooled r e c e i v e r .  The o v e r a l l y i e l d  i n going from g a l l i u m t r i c h l o r i d e t o trimethylamine gallane was about 60%. The deuterated compound, trimethylamine t r i d e u t e r o g a l l a n e , Me NGaD 3  3  was prepared i n the same manner only l i t h i u m gallium deuteride was s u b s t i t u t e d f o r l i t h i u m i g a l l i u m hydride. (d)  Preparation o f Trimethylamine T r i c h l o r o g a l l a n e , Me NGaCl 3  Me N + GaCl 3  >- Me NGaCl  3  3  3  68-1  3  An ampoule containing 5.318 gms (30.2 mmoles) of GaCl  3  was broken open  i n the glove box and placed i n a c o n i c a l f l a s k f i t t e d with a stopcock adaptor.  The f l a s k was removed from the dry box and evacuated on the  vacuum l i n e . GaCl  3  A very large excess of Me N was then condensed on.tothe 3  at l i q u i d nitrogen temperature and then the mixture was slowly warmed  up t o 0°C and kept at t h i s temperature f o r four hours.  The excess Me N  i s then pumped o f f at -20°C and a white s o l i d o f Me NGaCl 3  which was then examined by NMR and i n f r a r e d spectroscopy.  3  3  i s l e f t behind The y i e l d i s  e s s e n t i a l l y 100% and the compound can be stored i n d e f i n i t e l y i n the dry box.  - 69 (e)  Preparation of Trimethylamine Adducts of Monochlorogallane, Me NGaH Cl, and Dichlorogallane, Me NGaHCl2 (11) 3  2  2  Me NGaH + HCl  *  Me NGaH Cl + H  Me NGaH + 2HC1  *  Me NGaHCl + 2H  3  3  3  3  3  2  3  69-1  2  2  69-2  2  Trimethylamine monochlorogallane, Me NGaH Cl was prepared by weighing 3  2  out 0.2414 gms (1.83 mmoles) o f Me NGaH , i n t o a c o n i c a l f l a s k f i t t e d with 3  3  a stopcock adaptor and then evacuating the f l a s k on the vacuum l i n e .  41.9  ml at NTP (1.83 mmoles) o f HCl gas was condensed i n t o the conical at l i q u i d nitrogen temperature and then the f l a s k was allowed t o warm up t o room temperature.  A f t e r about two hours the f l a s k was frozen i n l i q u i d nitrogen  and the noncondensable  gas, hydrogen, pumped o f f with a Topler pump.  of gas 42.1 ml at NTP (1.84 mmoles).  Yield  The product Me NGaH Cl, could be 3  2  sublimed under a dynamic vacuum at room temperature t o a cold f i n g e r o f a sublimer cooled t o -78°C and c o l l e c t e d as a white s o l i d . The trimethylamine d i c h l o r o g a l l a n e , Me NGaHCl was s i m i l a r l y obtained 3  2  from the product of trimethylamine gallane (0.1608 gms; 1.22 mmoles) and HCl gas (56.0 ml at NTP, 2.44 moles).  The hydrogen evolved was measured  by the Topler pump as 55.8 ml at NTP.  The product i s a white  involatile  s o l i d , only s l i g h t l y soluble i n benzene. (f)  Preparation o f Trimethylamine Adducts o f Dichloromonomethylgallane Me NGaMeCl 3  (22,  2  and Monochlorodimethylgallane, Me NGaMe Cl Method I 3  2  47, 68) :  Me^Si + GaCl  40°C 3  ~* Me SiCl + 'MeGaCl 3  2  69-3  - 70 Me N + MeGaCl 3  0°C 2  *  Me NGaMeCl 3  70-1  2  In the dry box an ampoule o f GaCl was weighed, broken open and placed 3  i n the apparatus as shown i n Figure 15.  The G a C l was then sublimed i n t o 3  the r e a c t i o n vessel by warming the outside o f the tube and c o o l i n g the r e a c t i o n vessel i n acetone-solid C0 slush bath, and the c o n s t r i c t i o n flame 2  sealed.  The empty ampoule was then reweighed and the amount o f GaCl  determined (5.60 gms; 31.7 mmoles).  3  Excess t e t r a m e t h y l s i l a n e , Me^Si, (3.44  gms; 39.0 mmoles) was condensed onto the G a C l 40°C and allowed to react f o r two hours.  3  and the mixture warmed up t o  The reaction vessel was then  cooled to 0°C and the v o l a t i l e components, excess Mei Si and M e S i C l , were +  3  pumped o f f and the desired product methyldichlorogallane,  MeGaCl , as a white 2  s o l i d , stable under nitrogen at room temperature was l e f t i n the f l a s k . On the vacuum l i n e an excess o f Me N gas (1.17 1 at NTP; 50.9 mmoles) 3  was then condensed onto the s o l i d MeGaCl and the mixture held at 0°C f o r 2  several hours a f t e r which the excess Me N was pumped o f f , leaving a white 3  solid.  The product was then examined by i n f r a r e d and NMR spectroscopy. The  y i e l d i n going from GaCl  3  to Me NGaMeCl i s quite high. 3  2  Only the d i c h l o r o  gallium species i s prepared by t h i s method. Method I I  Me Ga + 2HC1 3  Me N + MeGaCl 3  Et20 + MeGaCl + 2CH\ room temp. 2  0°C  * Me NGaMeCl 3  2  2  70-2 70-3  An ampoule containing GaMe (0.199 gms; 1.73 mmoles) was broken open 3  i n the dry box and d i s s o l v e d i n about 25 ml of d i e t h y l ether i n a c o n i c a l  - 72 f l a s k f i t t e d with a stopcock adaptor.  The f l a s k was removed from the dry  box, attached t o the vacuum l i n e and HCl gas (77.5 ml at NTP; 3.46 mmoles) was condensed i n t o the f l a s k .  The f l a s k was warmed up to room temperature  and kept at t h i s temperature f o r about onejhour before being frozen i n l i q u i d nitrogen and the v o l i t i l e components, CH^, ( i d e n t i f i e d by i t s i n f r a r e d spectrum) pumped o f f through a Topler pump.  Y i e l d of gas 76.9 ml at NTP.  Into t h i s ether s o l u t i o n o f MeGaCl was then condensed excess Me N 2  3  and allowed t o react at room temperature f o r two hours.  The unreacted Me N 3  and ether solvent were then removed at -20°C to leave a white powder behind who's spectra compares favorably with the i n f r a r e d and NMR s p e c t r a o f Me NGaMeCl 3  prepared by other methods.  Me Ga + HCl  -^r > Me GaCl + CH room temp. ?  z  Me N + Me GaCl 3  72-1  E  q  3  -  2  U  H  • Me NGaMe Cl 3  72-2  2  Using one mole o f HCl (37.7 ml at NTP; 1.73 mmoles) with one mole o f Me Ga (0.198 gms; 1.73 mmoles) and condensing on excess Me N, the compound 3  3  Me NGaMe Cl was e a s i l y prepared by a method analogous t o that f o r the 3  2  preparation o f Me NGaMeCl . 3  The y i e l d of these reactions was high.  2  Method I I I  Me NGaMeo + 2Me NGaCl room temp. 3  3  3  3  3  3  3  3  3  To prepare the Me NGaMeCl 3  3  2  2  72-3  > 3Me NGaMe Cl  72-4  3  3  2Me NGaMe + Me NGaCl 3  ^ 3Me NGaMeCl  3  3  3  3  z  3  room temp.  3  compound: , Me NGaCl 3  2  z  3  (0.349 gms; 1.48 mmoles)  2  - 73 and Me NGaMe 3  (0.129 gms; 0.74 mmoles) were weighed out i n the dry box,  3  dissolved i n ether and put i n t o a conical f l a s k f i t t e d with a stopcock adaptor.  This f l a s k was removed from the dry box, attached t o the vacuum  l i n e and the solvent removed at -20°C leaving a white powder behind which analysed by i n f r a r e d and NMR spectroscopy as Me NGaMeCl23  Me NGaMe Cl was prepared i n the same manner only using 0.159 gms (0.68 3  2  mmoles) o f Me NGaCl 3  (g)  3  and 0.233 gms, (1.34 mmoles) of Me NGaMe . 3  3  Preparation o f Trimethylamine Trimethylgallane, Me NGaMe 3  Me N + GaMe 3  • Me NGaMe  3  3  3  73-1  3  An ampoule o f GaMe containing 2.16 gms (18.8 mmoles), prepared i n the 3  laboratory, was broken open i n the glove box and placed i n a c o n i c a l f l a s k f i t t e d w i t h a stopcock adaptor.  On the vacuum l i n e Me N gas, about ten times 3  excess, was condensed onto the GaMe and allowed to react f o r about two 3  hours at 0°C. The excess Me N was then pumped o f f at -20°C and a white 3  sblidy  s l i g h t l y s t i c k y , was l e f t behind.  The pure Me NGaMe could be stored 3  3  i n d e f i n i t e l y i n a n i t r o g e n f i l l e d f l a s k at room temperature. (h)  Preparation o f Trimethylamine Borane, Me NBH 3  LiBHi, + Me NHCl 3  H  3  —>- Me NBH + L i C l room temp. 3  i  3  2  3  + H  2  73-2  z  Trimethylamine borane was prepared by a procedure s i m i l a r t o that f o r the preparation o f Me NGaH , 3  3  The differences being, l i t h i u m borohydride,  LiBH^, was used i n place o f LiGaH^, and the e n t i r e r e a c t i o n was c a r r i e d out at room temperature, i f the Me NHCl was added below room temperature no 3  - 74 r e a c t i o n was observed. (i)  Preparation of Trimethylborane (67), Me3B,  CH Br + Mg 3  3MeMgBr + BF 3  n-butyl ether *MeMgBr 70°C  74-1  n-butyl ether •>• BMe 3 + 3MgBrF 70°C  74-2  In the three-necked f l a s k o f the apparatus shown i n Figure 16 a Grignard, MeMgBr, was prepared i n the f o l l o w i n g manner.  Clean magnesium  turnings, (7.20 gms; 0.292- mmoles) (B § A L t d . ) , 100 ml of dry n-butyl ether, and a few c r y s t a l s o f iodine were added to the f l a s k and the e n t i r e apparatus was purged with nitrogen.  Then 16.5 ml (0.302 moles (BDH Ltd.)  of methyl bromide dissolved i n 50 ml of n-butyl ether was added very slowly so that the reaction mixture was kept at a temperature o f 50°C.  The  mixture was vigorously s t i r r e d f o r about s i x hours, the magnesium was a l l consumed and the s o l u t i o n turned black.  The two traps were then immersed  i n an acetone-solid C O 2 slush bath and 6.1 gms  (0.090 moles) (Matheson  Co.)  of boron t r i f l u o r i d e , BF , measured out i n a c a l i b r a t e d gas bulb and 3  condensed i n t o 50 ml of n-butyl ether was added dropwise over a 4 hour period from the dropping funnel i n t o the Grignard s o l u t i o n .  The mixture  was then warmed to 70°C, a slow stream of nitrogen bubbled through and the system maintained t h i s way f o r an a d d i t i o n a l two hours, allowing the product to condense i n t o the cold traps. The traps were removed from the rest of the apparatus and attached to the vacuum l i n e .  The BMe3 was p u r i f i e d by f r a c t i o n a t i o n on the vacuum l i n e  and stored i n a large gas bulb.  The y i e l d was low.  Boron Trimethyl Apparatus  - 76 (j)  Preparation o f Trimethylamine Trimethylborane, Me3NBMe3  Me N + BMe 3  > MeNBMe  3  3  76-1  3  A sample o f BMe was measured out i n a gas bulb (2.61 cm of Hg i n 3  3.19-1 volume at 23°C) (4.92 mmoles) and condensed i n t o a c o n c i a l f l a s k attached to the vacuum l i n e .  A s l i g h t excess of Me N (2.80 cm o f Hg i n a 3  3.19 1 volume at 23°C) (5.08 mmoles) was condensed onto the BMe and allowed 3  to react and warm up t o room temperature.  The excess Me N was then pumped 3  o f f at -20°C and a white s o l i d o f Me NBMe remained which was stored under 3  3  a nitrogen atmosphere at room temperature. (K)  The y i e l d was 100%.  Preparation of Trimethylamine Trimethylalane, Me3NAlMe3  Me N + AlMe 3  > Me NAlMe  3  3  76-2  3  Trimethylamine trimethylalane, Me NAlMe3, was prepared by a procedure 3  s i m i l a r to that used to prepare Me3NGaMe3, The difference i n the procedure was that trimethylaluminum ( A l f a Inorganics Inc.) was used i n place o f GaMe  3  and only a s l i g h t excess of Me N gas was used. 3  (1)  Preparation of Trimethylamine alane, Me3NAlH3  LiAHt, + MeoNHCl H  3  > Me^NAlHq + L i C l + H room temp.  3  d  9  76-3  z  Trimethylamine alane Me NAlH , was prepared and p u r i f i e d i n the same 3  3  way as Me NGaH , only L i A l H ^ ( A l f a Inorganics Inc.) was used i n place o f 3  LiGaH^.  3  Care was taken to avoid the formation o f the bis-amine adduct which  i s quite s t a b l e , by using excess LiAlH^.  - 77 C.  Reactions to Prepare Coordinated Organogallanes (a)  Reaction of Trimethylamine Gallane, Me3NGaH3 with Dimethyl Mercury Me Hg 2  2Me NGaH + Me Hg 3  3  2  • 2Me NGaH Me + H 3  In a t y p i c a l reaction 0.373 gms  2  2  + Hg  77-1  (2.85 mmoles) o f Me NGaH and 0.338 gms 3  3  (1.47 mmoles) of Me Hg ( A l f a Inorganics Inc.) were mixed i n a conical f l a s k 2  with 50 ml o f benzene i n the dry box.  The c o n i c a l was removed from the dry  box, f i t t e d with a r e f l u x condenser and flushed with a slow stream o f nitrogen while the benzene s o l u t i o n was refluxed.  A f t e r 75 minutes graying of the  s o l u t i o n was observed and the reaction was stopped. then capped and the s o l u t i o n f i l t e r e d i n the dry box.  The conical f l a s k was Then the c o n i c a l f l a s k  was f i t t e d with a stopcock adaptor and the s o l u t i o n was concentrated by removing most o f the benzene at -20°C by pumping i t o f f on the vacuum l i n e . The s o l u t i o n was then examined by i n f r a r e d and NMR spectroscopy to be c e r t a i n a d e f i n i t e product does e x i s t . (b)  Reaction of Trimethylamine Adducts of Monochlorodimethylgallane, Me NGaMe Cl, and Dichloromonomethylgallane Me3NGaMeCl , with 3  2  2  Lithium Hydride, LiH.  Me NGaMeCl + 2LiH  E t 2  Me NGaMe Cl + LiH  E t 2  3  2  3  2  ° > Me NGaMeH + 2 L i C l  77-2  ° > Me NGaMe H + L i C l  77-3  3  3  2  2  Trimethylamine dichloromonomethylgallane, Me NGaMeCl 3  2  (0.178 gms;  - 78 0.919 mmoles) was weighed out, dissolved i n ether and placed i n the r e a c t i o n f i l t r a t i o n apparatus, see Figure 11. Excess LiH (0.032 gms; 4.0 mmoles) placed i n the dumper tube was slowly added at -20°C and the r e a c t i o n mixture s t i r r e d f o r a p e r i o d of two hours at room temperature.  The r e a c t i o n mixture  was then f i l t e r e d and the ether removed at -40°C leaving a paste or o i l  like  material behind, which was then examined by i n f r a r e d and NMR spectroscopy t o confirm that a d e f i n i t e product d i d form. Trimethylamine monochlorodimethylgallane, Me NGaMe2Cl, (0.271 gms; 3  1.26 mmoles) was reacted with 0.0274 gms (3.42 mmoles) o f LiH i n a s i m i l a r manner.  Again a paste or o i l l i k e material r e s u l t e d from the r e a c t i o n  which was then analysed by i n f r a r e d and NMR spectroscopy.  The y i e l d from  these reactions was quite low. (c)  Reaction of Trimethylamine Adducts of Monochlorogallane, Me3NGaH Cl, 2  and Dichlorogallane, Me3NGaHCl , with Lithium Methyl, LiMe 2  MeoNGaHoCl + LiMe 3  MeoNGaHClo + 2LiMe 3  > MeoNGaH Me + L i C l ?  room temp.  z  z  § room temp  3  >  MeoNGaHMe + 2 L i C l 2  3  78-1  z  78-2  z  A quantity of Me NGaH Cl (0.369 gms; 2.21 mmoles) was weighed out i n 3  2  the dry box and d i s s o l v e d i n 30 ml o f ether i n a c o n i c a l f l a s k .  Lithium  methyl i n ether s o l u t i o n (3.51 ml of 0.63 M; 2.21 mmoles) was also added t o this flask.  The f l a s k was allowed to stand f o r several hours at room tempera-  ture and then, the white p r e c i p i t a t e that formed was f i l t e r e d o f f and the c l e a r s o l u t i o n put i n t o a d i f f e r e n t f l a s k .  I t was then f i t t e d with a stopcock  adaptor, removed from the dry box attached t o the vacuum l i n e and the ether  - 79 pumped o f f at -70°C.  An o i l remained i n the f l a s k and when analysed by  i n f r a r e d and NMR compared favorably t o Me NGaH Me prepared by other routes. 3  In an analogous manner Me NGaHCl 3  2  (0.247 gms; 1.23 mmoles) and LiMe  2  (1.3 ml of 1.89 M; 2.46 mmoles) were mixed together i n ether s o l u t i o n , f i l t e r e d and then the solvent removed t o y i e l d a s t i c k y o i l product.  The  i n f r a r e d and NMR analysis i n d i c a t e s that some Me NGaHMe was formed. 3  (d)  2  E q u i l i b r i u m Reactions o f Trimethylamine Gallane Me NGaH with 3  Trimethylamine Trimethylgallane, Me NGaMe 3  3  3  1) E t 0 2  2 Me NGaH + Me NGaMe ' — £ »• 3Me NGaH Me . room temp. ^ 3  3  3  3  3  3  3  3  0  79-1  2  0  1) E t 0 2  Me NGaH + 2 Me oNGaMe 3 3 3  3  3  ^ ^ • 3Me NGaHMe room temp. ^  3  3  3  79-2  2  0  These methylgallane species are prepared by mixing the two reagents i n a s u i t a b l e solvent at room temperature i n the glove box.  For monomethyl-  gallane trimethylamine adduct, Me NGaH Me, a t y p i c a l preparation was mixing 3  2  0.398 gms (2.30 mmoles) o f Me NGaMe and 0.608 gms (4.60 mmoles) o f Me NGaH 3  i n benzene.  3  3  3  For trimethylamine dimethylgallane, Me NGaHMe 0.612 gms 3  2  (3.51 mmoles) o f Me NGaMe and 0.232 gms (1.76 mmoles) o f Me NGaH were mixed 3  i n benzene.  3  3  3  The solutions were then examined by NMR and i n f r a r e d spectroscopy.  To prepare a solvent o f free pure compound d i e t h y l .ether was a b e t t e r solvent t o use.  In these cases, the ether solutions were placed i n a conical  f l a s k f i t t e d with a stopcock adaptor, attached t o the vacuum l i n e and the ether removed at -40°C leaving the product as an o i l o r past l i k e substance. The deuterated analogs; trimethylamine  monomethylbideuterogallane,  Me NGaD Me, and trimethylamine dimethyldeuterogallane, Me NGaDMe , are 3  2  3  2  -  prepared i n the same manner,  0.126  80  -  gms  (0.938  mmoles) o f Me3NGaD3 was weighed  out and dissolved i n a benzene s o l u t i o n containing  gms  0.0815  mmoles)  (0.469  o f Me NGaMe3, t o prepare the Me3NGaD2Me compound. To prepare the Me NGaDMe2 3  3  compound,  0.0512  gms  mmoles) o f Me NGaD and  (0.379  3  o f Me3NGaMe3 were mixed i n benzene s o l u t i o n .  3  gms  0.132  (0.758  mmoles)  The i n f r a r e d and NMR data were  c o l l e c t e d on these compounds.  D.  Miscellaneous Reactions o f Coordinated Gallanes (a)  Reaction o f Trimethylamine Monomethylgallane, Me NGaH2Me with 3  Ethylene.,  CH =CH  M e o5 N G a Hz o M e  Me NGaH Me 3  2  (0.562  2  2  + 2CHo = zC H z  gms;  3.85  ?  benzene—  room temp.  y  n3  M e  N  G  a  M  e  z  E  t  80-1  n  mmoles) was dissolved i n benzene i n the  dry box, placed i n a c o n i c a l f l a s k f i t t e d with a stopcock adaptor and then the f l a s k was attached to the vacuum l i n e .  Ethylene gas  ml a t NTP;  (172.5  7 . 7 0 mmoles) was condensed onto the benzene s o l u t i o n o f Me NGaH Me at l i q u i d 3  2  nitrogen temperatures and then the s o l u t i o n was allowed t o warm up t o room temperature and magnetically s t i r r e d . A f t e r seven hours a t room temperature some graying o f the s o l u t i o n was observed but the manometer o f the vacuum l i n e showed l i t t l e gas uptake. An NMR spectrum o f the v o l a t i l e components c o l l e c t e d i n a NMR tube connected to the vacuum l i n e was obtained and an i n f r a r e d and NMR spectra o f the benzene s o l u t i o n were also recorded.  - 81 (b)  Reaction of Trimethylamine Monomethylgallane Me NGaH Me with 3  2  Hydrogen Chloride, HCl  benzene  Me NGaH Me + HCl 3  * Me NGaHClMe + H  2  81-1  +- Me NGaMeCl + H  2  81-2  3  2  benzene  Me NGaHClMe + HCl 3  3  2  A benzene s o l u t i o n of Me NGaH Me (0.242 gms; 1.66 mmoles) was made up 3  2  i n a c o n i c a l f l a s k i n the dry box.  The f l a s k was f i t t e d with a stopcock  adaptor, cooled to -196°C and evacuated on the vacuum l i n e .  The HCl gas  (37.2 ml at NTP; 1.66 mmoles) was condensed i n t o the benzene s o l u t i o n and the mixture allowed t o warm up to room temperature f o r about two hours, then the s o l u t i o n was frozen down again.  The non-condensable gas was removed v i a  a Topler pump, y i e l d o f gas 35.4 ml at NTP.  Infrared and NMR spectra of the  gas l i b e r a t e d and of the benzene s o l u t i o n were recorded. A second p o r t i o n of HCl gas (36.9 ml at NTP; 1.65 mmoles) was condensed i n t o the above s o l u t i o n i n the same manner as the f i r s t .  The non-condensable  gas was removed by a Topler pump and i t s i n f r a r e d spectrum obtained, also the i n f r a r e d and NMR spectra of benzene s o l u t i o n were obtained.  The benzene  solvent was then removed at 0°C on the vacuum l i n e and a white s o l i d was l e f t i n the f l a s k . (c)  Reaction of Trimethylamine Gallane, Me NGaH , with Methanol, MeOH 3  Me NGaH + nMeOH 3  3  3  benzene room temp.  81-3  n  where "n" = 1, 2, 3  In a t y p i c a l reaction 0.101 gms (0.77 mmoles) o f Me NGaH was weighed 3  3  - 82 out and dissolved i n about 15 ml of benzene i n a conical f l a s k f i t t e d with a stopcock adaptor. 0.0486 gms  This f l a s k was then evacuated on the vacuum l i n e and  (1.52 mmoles) of MeOH was condensed onto the benzene s o l u t i o n .  A f t e r r e a c t i n g the reagents f o r two hours at room temperature the f l a s k was frozen i n l i q u i d nitrogen and the non-condensable and measured with a Topler pump.  gas, hydrogen, pumped o f f  Y i e l d of gas 31.5 ml at NTP.  A white  s o l i d remained i n the f l a s k on removal of benzene at low temperature. (d)  Rearrangement Reaction Between Trimethylamine Alane, Me3NAlH , 3  and Trimethylamine Trimethylalane, Me NAlMe 3  2MenNAlH. + MeoNAlMeo i  o  MeoNAlHo  o  t  =^ • 3Me NAlH Me room temp 3  6  i  b  e  n  z  e  n  e h  z  3MeoNAlHMe  room temp  82-1  ?  3  a  + 2Me q N A l M e o  o  3  3  82-2  9  z  Trimethylamine monomethylalane, Me NAlH Me, was prepared by mixing 3  Me NAlH 3  3  2  (0.0699 gms; 0.785 mmoles) and Me NAlMe 3  i n 2 ml of pure benzene i n the dry box.  (0.0516 gms; 0.395 mmoles)  3  Trimethylamine dimethylalane,  Me NAlHMe , was prepared s i m i l a r l y by mixing Me NAlH 3  2  3  mmoles) and Me NAlMe 3  (0.0263 gms; 0.296  3  (0.0773 gms; 0.592 mmoles) i n 3 ml of benzene.  3  Infrared and NMR spectra were recorded of a l l the products and the spectra compared to the l i t e r a t u r e r e s u l t s (41). (e)  Rearrangement Reaction Between Trimethylamine Borane, Me NBH 3  Trimethylamine Trimethylborane,  2MeoNBH + MeoNBMeo o o A 6 q  q  and  Me3NBMe3  b e n z e n e  q  MeoNBHo + 2Me NBMe o o A O  3  >- "Me NBHoMe" 3  room temp  3  benzene ^ "MeqNBHMeo" room temp 3  82-3  z  z  82-4  - 83 In a t y p i c a l preparation 0.0700 gms (1.01 mmoles) o f Me NBH and 0.0561 3  3  gms (0.506 mmoles) o f Me NBMe were mixed together i n a few mis o f benzene 3  3  i n the dry box to prepare the compound trimethylamine monomethylborane, Me NBH Me. 3  To prepare trimethylamine dimethylborane, Me NBHMe , 0.121 gms  2  3  2  (1.09 mmoles) o f Me N(BtMe and 0.0375 gms (0.545 mmoles) o f Me NBH were 3  3  3  s i m i l a r l y mixed together i n a few mis o f benzene.  3  Infrared and NMR spectra  were recorded on a l l the s o l u t i o n s . (f)  Mixed Rearrangement Reactions Using D i f f e r e n t Group IIIB Coordination Compounds  A number o f rearrangement reactions were attempted with d i f f e r e n t Group IIIB hydrido-and alkyl-trimethylamine adducts. prepared i n the same manner.  A l l r e a c t i o n mixtures were  The s o l i d hydride compounds were weighed out  i n a small beaker i n the dry box and a c a l c u l a t e d volume o f a standard benzene s o l u t i o n o f one o f the t r i a l k y l trimethylamine adduct, to make a one t o one molar mixture, was syringed i n t o the beaker containing the known weight o f hydride or c a l c u l a t e d volumes o f the standard solutions o f the t r i a l k y l compounds were mixed together i n a beaker.  The resultant solutions  were then examined by i n f r a r e d and NMR spectroscopy.  The f o l l o w i n g gives a  l i s t o f the reactions attempted and q u a n t i t i e s of reagents used.  Me NAB + Me NA'B ' 3  3  .  3  3  3  1  • "Me NAB , B' 3  5  3/2  3/2  " + "MeoNA'B . B' . "  where A, or A' = B, A l , Ga; and B or B = Me or H. 1  d  3/2  3/2  - 84 -  Me NAB 3  3  quantity  Me NA'B'  quantity  0.58 ml of 0.490 M (0.282 mmoles)  Me NGaMe  2.0 ml of 0.141 M (0.282 mmoles)  0.80 ml of 0.490 M (0.394 mmoles)  Me NAlMe  0.72 ml o f 0.197 M (0.141 mmoles)  Me NGaMe  1.0 ml o f 0.141 M (0.141 mmoles) 0.0126 gms (0.141 mmoles)  3  3  1  Me NBMe  2  Me NBMe  3  Me NAlMe  4  Me NGaMe  1.0 ml of 0.141 M (0.141 mmoles)  Me NAlH  3  5  Me NAlMe  1 ml of 0.197 M (0.197 mmoles)  Me NGaH  3  6  Me NAlMe  1 ml o f 0.197 M (0.197 mmoles)  Me NGaD  7  Me NBMe  1 ml of 0.490 M (0.490 mmoles)  Me NAlH  3  8  Me NBMe  1 ml o f 0.490 M (0.490 mmoles)  Me NGaH  3  9  Me NAlMe  1 ml o f 0.197 M (0.197 mmoles)  Me NBH  3  10  Me NGaMe  1 ml of 0.141 M (0.141 mmoles)  Me NBH  3  3  3  3  3  3  3  3  3  3  3  3  3  3  3  3  3  3  3  3  3  3  3  3  3  3  3  3  3  3  3  3  3  3  3  2.0 ml of 0.197 M (0.394 mmoles)  0.0258 gms (0.197 mmoles) 0.0264 gms (0.197 mmoles) 0.0436 gms (0.490 mmoles) 0.0642 gms (0.490 mmoles) 0.0143 gms (0.197 mmoles) 0.0103 gms (0.141 mmoles)  - 85 X. 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