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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.) University of 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 this thesis as conforming to the required standard The University of B r i t i s h Columbia June 1968 In p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t o f the r e q u i r e m e n t s f o r an advanced degree a t the U n i v e r s i t y o f B r i t i s h Columbia, I ag r e e t h a t the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and Study. I f u r t h e r agree t h a t p e r m i s s i o n f o r e x t e n s i v e c o p y i n g o f t h i s t h e s i s f o r s c h o l a r l y p u rposes may be g r a n t e d by the Head o f my Department or by hits r e p r e s e n t a t i v e s . I t i s u n d e r s t o o d t h a t c o p y i n g or p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l not be a l l o w e d w i t h o u t my w r i t t e n p e r m i s s i o n . Department of The U n i v e r s i t y o f B r i t i s h Columbia Vancouver 8, Canada - i i -Abstract Although the organo hydride derivatives of boron and aluminum are well 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 to determine the re 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 of organo gallium hydride derivatives as compared with the s t a b i l i t i e s and reactions of the corresponding compounds of boron and aluminum. Various preparative routes to t h i s new class of gallium compounds have been investigated. These include the use of organo-mercury, organo-lithium and lithium hydride derivatives i n reactions with gallium hydride and gallium a l k y l compounds and t h e i r halogen substituted derivatives: Me3NGaH3 + HgR2 >- Me3NGaH2R + l/2Hg + 1/2H2 Me3NGaH2Cl + LiR y Me3NGaH2R + L i C l Me3NGaR2Cl + LiH • Me3NGaHR2 + L i C l A fourth preparative method involves disproportionation reactions between gallium hydride compounds and organo gallium compounds to y i e l d the mixed organo hydride derivatives. Alkyl-hydride disproportionation reactions were also examined using organo and hydride derivatives of different Group IIIB elements i n order to obtain a better understanding of the exchange process. Both infrared and proton NMR spectroscopy have been used extensively i n following the progress of these reactions and i n the characterization of the products. - i i i -Table of Contents Page I. T i t l e Page i I I . Abstract i i I I I . Table of Contents i i i IV. L i s t of Tables v i i V. L i s t of Figures v i i i VI. Acknowledgement i x VII. Introduction 1 VIII. Discussion and Results 10 A. Preparation of Trimethylamine Adducts of Organogallanes . 10 B. Properties of Trimethylamine Adducts of Organogallanes .. 20 (a) Physical 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 Different Group IIIB Hydride and Alkyls 41 - i v -Page IX. Experimental 50 A. Experimental Techniques 50 (a) Desiccation 50 (b) Grease 54 (c) Reaction-Filtration Apparatus 54 (d) Molecular Weight 58 (e) Spectroscopy 58 (£) Lithium Methyl Standardization 60 (g) Elemental Analysis 62 B. Preparative ' 64 (a) Preparation of Gallium T r i c h l o r i d e , GaCl 3 64 (b) Preparation of Lithium Gallium Hydride, LiGaH^ 66 (c) Preparation of Trimethylamine Gallane, Me3NGaH3 .... 67 (d) Preparation of Trimethylamine Trichlorogallane Me 3NGaCl 3 68 (e) Preparation of Trimethylamine Adducts of Monochloro-gallane, Me3NGaH2Cl, and Dichlorogallane, Me3NGaHCl2 69 (f) Preparation of Trimethylamine Adducts of Dichloro-monomethylgallane, Me3NGaMeCl2 and monochloro-dimethylgallane, Me3NGaMe2Cl 69 (g) Preparation of Trimethylamine Trimethylgallane, Me3NGaMe3 73 (h) Preparation of Trimethylamine Borane, Me3NBH3 73 (i) Preparation of Trimethylborane, Me3B 74 - V -Page (j) Preparation of Trimethylamine Trimethylborane, Me3NBMe3 7 6 (k) Preparation of Trimethylamine Trimethylalane, Me3NAlMe3 76 (1) Preparation of Trimethylamine Alane, Me 3NAlH 3 76 C. Reactions to Prepare Coordinated Organogallanes 77 (a) Reaction of Trimethylamine Gallane, Me3NGaH3, with Dimethyl Mercury, Me2Hg 77 (b) Reaction of Trimethylamine Adducts of Monochloro-dimethylgallane, Me3NGaMe2Cl, and Dichloromono-methylgallane, Me 3NGaCl 2 with Lithium Hydride LiH .. 77 (c) Reactions of Trimethylamine Adducts of Monochloro-gallane, Me3NGaH2Cl and Dichlorogallane, Me 3NHCl 2, with Lithium Methyl LiMe 78 (d) Equilibrium Reactions of Trimethylamine Gallane, Me3NGaH3 with Trimethylamine Trimethylgal1ane, Me 3NGaMe 3 79 D. Miscellaneous Reactions of Coordinated Gallanes 80 (a) Reaction of Trimethylamine Monomethy1gallane, Me3NGaH2Me with Ethylene, CH2CH2 80 (b) Reaction of Trimethylamine Monomethy1gallane, Me3NGaH2Me with Hydrogen Chloride,.HCl 81 (c) Reaction of Trimethylamine Gallane, Me3NGaH3 with Methanol, Me OH . 81 - v i -Page (d) Rearrangement Reaction Between Trimethylamine Alane, Me 3NAlH 3, and Trimethylamine Trimethylalane, Me3NAlMe3 82 (e) Rearrangement Reaction Between Trimethylamine Borane, Me3NBH3, and Trimethylamine Trimethylborane, Me3NBMe3 82 (f) Mixed Rearrangement Reactions Using Different Group IIIB Coordination Compounds 83 X. Bibliography . 85 - v i i -Lis t of 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 of "Me3NGaMeH2" i n Benzene 23 Table 4 Molar Ratios of "Me3NGaMe2H" i n Benzene 25 Table 5 NMR Data for "Me3NGaMe2H" and "Me3NGaMeH2" i n Cyclo-hexane and for "Me3NGaMe2D" and "Me3NGaMeD2" i n Benzene . 25 Table 6 Infrared Data for "Me3NGaMeH2", "Me3NGaMeD2" and "Me3NGaMe2H", "Me3NGaMe2D" 30 Table 7 Proton NMR Data for Me 3NAlMe 3_ nH n Species 40 Table 8 Molar Ratios of "Me3NAlMeH2" and "Me3NAlMe2H" i n Benzene 40 Table 9 NMR Data for Mixtures of Me3NBMe3 and Me3NBH3 i n C 5H 6 ... 41 Table 10 NMR Data of the Mixed Group IIIB Alkyls and Hydrides . 43 - v i i i -L i s t of Figures Page Figure 1 NMR Spectra of "Me3NGaMeH2" and "Me3NGaMe2H" 24 Figure 2 Infrared Spectra of "Me3NGaMeH2" and "Me3NGaMe2H" 29 Figure 3 NMR Spectra of Me3NGaH2OMe . 33 Figure 4 NMR spectra of "Me3NAlMe2H" and "Me3NAlMeH2" 39 Figure 5 NMR Spectra of Mixtures of Me3NBMe3 and Me3NBH3 42 Figure 6 NMR Spectra of Mixtures of Trimethylamine Adducts of Different Group IIIB Hydrides and Alkyls 44 Figure 7 Drying P i s t o l 51 Figure 8 Sublimer 52 Figure 9 Me3NGaH3 sublimer 53 Figure 10 Vacuum Line 55 Figure 11 Reaction-Filtration Apparatus 57 Figure 12 Molecular Weight Apparatus 59 Figure 13 Lithium Methyl Apparatus 61 Figure 14 Gallium Trichloride Apparatus 65 Figure 15 Apparatus for Reacting Me^Si and GaCl 3 71 Figure 16 Boron Trimethyl Apparatus 75 - i x -Acknowledgement I would l i k e to express my sincerest thanks to my research director Dr. Alan Storr, for his invaluable advice, guidance, and enlightening discussions throughout the course of this work. I am greatly indebted to Mr. S. Rak for the construction of much of the glass apparatus, to Mr. R. Burton, Miss C. B u r f i t t and Miss P. Watson for the NMR spectra, to Miss D. Johnson for the preparation of t h i s typescript and Miss J. Cowley for providing some of the diagrams. VII.Introduction Since the discovery of gallium i n 1875 (1) the knowledge of i t s chemist has increased steadily but only modestly i n comparison to i t s congeners, boron and aluminum. Quite recently, though, with the use of gallium i n the electronics industry, renewed emphasis i s being placed on the study of gallium. Reviews of gallium chemistry have appeared i n 1936 i n Gmelin (2), i n 1937 by Einecke (3), i n 1955 by P. de le Breteque (4) and more recently i n 1963 by N. N. Greenwood (5) and J. C. Hutter (6) and in 1966 by Sheka et al (7). In naming gallium hydride coordination compounds the GaH3 entity i s termed gallane and i s treated as the parent compound. Derivatives i n which the formal coordination number of gallium i s three, are named accordingly; e.g. GaHCl2 dichlorogallane, GaH2NMe2 dimethylaminogallane, GaMe3, trimethyl gallane. Addition compounds i n which the coordination of gallium i s four or greater are named thus; Et3PGaH3 triethylphosphine gallane, Me3NGaHCl2 trimethylamine dichlorogallane. Similar nomenclature i s applied to the analogous boron and aluminum compounds. The only exceptions to this nomen-clature are the well established names, such as lithium gallium hydride for the compound LiGaH^. One important char a c t e r i s t i c of Group IIIB compounds i s t h e i r electron deficiency, that i s , i n the t r i v a l e n t state one of the four o r b i t a l s (ns, n^x, n^y, n^z) available for bonding i s empty. This characteristic 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 to form dative bonds with strong electron donors. The energy change i s small i n going from planar sp 2 to tetrahedral sp 3 configurations i f electrons can be supplied to the vacant o r b i t a l s . This can be achieved by forming either multi-centred bridged bonds as i n the boron hydrides or donor-acceptor bonds such as the N —> Al dative bond i n Me 3NAlH 3. Coordination compounds of gallane, GaH3 and halogenogallanes, GaRs.n\y> with amines and phosphines have been investigated extensively over the past few years (8-12). The f i r s t adduct prepared and the most stable i s trimethylamine gallane, Me3NGaH3, which i s prepared at room temperature i n ether solution by the reaction: Me3NHCl + LiGaH^ y Me3NGaH3 + L i C l + H 2 2-1 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 to gallane than trimethylamine, the adduct Me2HNGaH3 slowly loses one mole of hydrogen to form the dimer [Me2NGaH2]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 to coordinate decreases i n the sequence; Me2HN > Me3N> C5H5N > Et 3N > <j>Me2N > <j>3N Trimethylphosphine, Me3P, has also been used as a ligand and i t s adduct strength i s almost equal to that of trimethylamine. This i s i n contrast to - 3 -the great i n s t a b i l i t y (10) of the aluminum.analogue Me3PA1H3 which can n o t \ be isolated. Other phosphine ligands form much less stable adducts with t h e ^ X gallane moiety, GaH3, and a 2:1 adduct with trimethylphosphine i s not observed, even at low temperatures (10). The sequence of ligand strengths i s ; Me2HN > Me3N > Me3P > Me2HP > Et 3P > 4>3P Arsine ligands form adducts with gallane but these are too unstable to isol a t e as are those formed with oxygen and sulphur ligands. Halogenogallane adducts with trimethylamine have been prepared by the following reactions; Me3NGaH3 + nHX »- Me3NGaH3_nXn + nH 2 where "n" = 1 or 2 and "X" = Cl or Br Me3NGaH3 + nMe3NHX • Me3NGaH3_nXn +*Me3N + *H2 where "n" = 1 and "X" = Cl or Br; "n" = 2 and "X" = C l . or by the reaction; nMe3NGaH3 + mMe3NGaX3 > m e ^ a t i ^ ^ 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 trimethyl-gallane with a l l the trimethyl derivatives of Group VB and dimethyl derivatives of Group VIB elements have been prepared by mixing trimethylgallane 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. For Group VIB an ir r e g u l a r sequence i s observed 0 > Se > S = Te. This sequence d i f f e r s from Group VIB ligand 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 trimethylgallane series i s thought to be influenced by d-orbital 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 related to the strength of the donor-acceptor bond (17); those of greatest bond strength i . e . greatest dissociation energy, have largest x values. L i t t l e work has been carried out on the chemistry of organogallanes and none has been reported on coordination compounds of the type DGaH3_nRn where "D" represents a Lewis base, i . e . Me3N, and "R" represents a simple a l k y l . 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 (Me2GaH)2 from the products obtained by cooling a mixture of Me3Ga and H 2 after i t had been subjected to a gas discharge at low pressure. Doubt (16) has been cast on this result by a l a t e r investigation and i t now appears that (Me2GaH)2 i s not prepared in this manner. A hydride species i s postulated by Eisch (18) as an intermediate i n the thermal decomposition of trii s o b u t y l g a l l a n e Bu3Ga 1 5 5 C ) Bu2GaH + Me2C=CH2 3Bu2GaH > 2Bu3Ga + GaH3 GaH3 > Ga + 3/2H2 4-1 4-2 4-3 - 5 -In the presence of olefins such as 1-decene, the diisobutylgallane formed as i n equation 4-1 adds rapidly to the o l e f i n . Bu2GaH + CH2=CH-C8H17 >• Bu 2GaC 1 0H 2 1 5-1 Eisch was also able to prepare (19) the uncoordinated hydride, diethylgallane, Et 2GaH, by the successful exchange reaction between a gallium halide and an aluminum hydride. The y i e l d of the desired product was low, but by the reaction he was able to prepare considerable quantities of the hydride. 2Et 3Ga + GaCl 3 • 3Et 2GaCl 5-2 Et 2GaCl + Et 2AlH + KC1 • Et 2GaH + K [ E t 2 A l C l 2 ] 5-3 Diethylgallane was found to add very readily to olefins to form unsymmetrical organogallanes but these readily disproportionated to 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 of a few compounds of the form GaH2R and GaHR2 as well as the preparation of an unstable polymeric (GaH 3) x (20). The compounds of the form GaH2R prepared are GaH2Cl (11) and GaH2NMe2, GaH2PMe2 (12) and these are dimeric as expected. Compounds of the form GaHR2 have been prepared by Schmidbaur et al (21,22) who were able to prepare GaHCl 2 and GaHBr2, dimers, i n good y i e l d from trimethylsilane and the appropriate halide. The Ga-H bond of these compounds i s found to readily 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 derivatives of the preceding members of Group IIIB are well characterized. Uncoordinated a l k y l boranes have been known since 1935 when Schlesinger and coworkers investigated the reaction of boron t r i a l k y l s with diborane (24-27). 2R3B + B 2H 6 >- 2R2BHBH2R 6-1 4R3B + B 2H 6 >• 3R2BHBHR2 6-2 "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 th 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 st a r t i n g materials (28-31). y 3LiBH\ + BC1 3 + 2Me3B • 3Me2B2h\ + 3LiCl 6-3 Li A l h \ + 4Pr 2BCl > 2Pr"B 2H 2 + L i A l C l 4 6-4 2NaBH[+ + 2CH2=CHBr • 2NaBr + Et 2B 2h\ 6-5 Uncoordinated organoboranes are usually dimers with hydrogen bridges preferred over a l k y l or ary l bridges. They are readily oxidized and very readily add under mild conditions to a l l types of a l i p h a t i c and aromatic olefins and with dienes and acetylene hydrocarbons. - 7 -Uncoordinated a l k y l aluminum hydrides have also been synthesized by a variety of methods (32-34). E t 2 A l C l + NaH h e X a " 6 > NaCl + Et 2AlH 7-1 Me 3Al + excess H 2 discharge' ( M e3 A 12 H3^n + (Me 2AlH) n 7-2 LiAl.H^ + Me3M • Me 2AlH + LiMH3Me 7-3 where "M" = B, A l , Ga A more general method involves the direct o l e f i n and hydrogen reaction with aluminum metal. RC=CH2 + H 2 + Al >- R2A1H 7-4 Thermal decomposition of higher t r i a l k y l s has also produced hydride species (35). i ?nn°r E t 2 A l Bu > Et 2AlH + CH2=CHC2H5 7-5 Organo alanes readily add across the double bond of 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 organoalanes tend to disproportionate to form symmetric organoalanes. Exchange of al k y l groups of organoalanes occurs-, very rapidly i n non-polar solvents but exchange i s slowed down i n polar solvents (36). Coordination compounds of organo boron hydrides and organo aluminum hydrides are well characterized. Thus organo-boron hydrides of the form B R 3 n Hn f w ^ e r e " n" = 0» 1> 2, 3) react with amines to 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 2Hi tR 2 + 2NR3 y 2R3NBH2R 8-1 [R3NH]X + LiBH3R • R3NBH2R + LiX + H2 8-2 where "X" = halogen. R.NBR* + H9 • RqNBHRp + R'H 8-3 0 d z pressure d 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-)3 with LiAlH^ in the presence of amines. (RBO)3 + 3NR3 ^ 0 ^ 3 5 ^ ' 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. Me3NAlEt2Cl + LiH E t 2 ° > Me3NAlEt2H + LiCl 8-5 - 9 -M e 3 N A l E t C l 2 + 2LiH 2 > Me 3NAlEtH 2 + 2 L i C l 9-1 B. Me 3NAlH 3 + R 2Hg h e x a n e , Me 3NAlR 2H + H 2 + Hg 9-2 Me 3NAlH 3 + l/2R 2Hg h e x a n e , Me 3NAlRH 2 + 1/2H2 + l/2Hg 9-3 C. 2Me 3NAlR 3 + Me 3NAlH 3 -> 3Me 3NAlR 2H 9-4 Me 3NAlR 3 + 2Me 3NAlH 3 >- 3Me 3NAlRH 2 9-5 D. Me 3NAlH 3 + L i R • Me 3NAlRH 2 + LiH 9-6 (Side r e a c t i o n : Me 3NAlH 3 + LiH • L i A l H ^ + Me3N) 9-7 E. L i A l H 4 + R 2A1C1 i ? ^ ' > 2Me 3NAlRH 2 + L i C l 9-8 The r e a c t i v i t y o f the Al-C and Al-H bonds i s g r e a t l y reduced i n forming 1:1 adducts and t h i s may be u t i l i z e d i n preparing h i t h e r t o > unpreparable h i g h l y l a b i l e organo aluminum compounds (43). The R 3A1 moiety i s a stronger acceptor than the R 3B moiety, and the organo aluminum forms 1:1 donor-adduct complexes with most Group VB and VIB l i g a n d s . The str e n g t h o f the l i g a n d - A l bond decreases r e g u l a r l y down a group and with Group VB l i g a n d forming stronger bonds than Group VIB l i g a n d s . The present i n v e s t i g a t i o n was i n i t i a t e d to determine the r e l a t i v e s t a b i l i t i e s of organogallane 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 o f the corresponding w e l l known boron and aluminum compounds. In a d d i t i o n i t was hoped that the study would f u r t h e r expand our knowledge o f the coordina-t i o n chemistry of 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 having an organo group attached to the g a l l i u m on the acceptor p r o p e r t i e s o f the gallane 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 alkylgallanes (19) suggested that the most profitable l i n e of approach to the desired compounds would be v i a substitution reactions involving introduction of organo groups into coordinated gallium compounds. Several methods of synthesis were attempted. The f i r s t synthetic route involved the reaction of trimethylamine gallane with organomercury compounds, both ether and benzene being used as solvents. 2Me3NGaH3 + Me2Hg • 2Me3NGaMeH2 + Hg + H 2 10-1 At room temperature or below, no product was formed, even after one day. The only reaction occurring was the decomposition of the starting material, trimethylamine gallane. Me3NGaH3 • Me3N + Ga + 3/2H2 10-2 At higher temperatures a def i n i t e product according to equation 10-1 did result. It was found that this reaction occurs more favorably under - 11 -refluxing 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 reaction. A higher temperature, such as i n refluxing benzene rather than diethyl 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 Me3NGaH3 s t a r t i n g material and the trimethylamine monomethylgallane, Me3NGaMeH2, product. The presence of f i n e l y divided gallium metal, from the decomposition of Me3NGaH3, see equation 10-2, i n the reaction system probably catalyses further decomposition of the product into hydrogen, methane and trimethylamine gases and gallium metal. This type of autocatalytic decomposition has been noted i n a number of gallium systems (18,45). The analogous reaction i n aluminum chemistry gave quite high yields of trimethylamine organoalanes (40,41,46). 2 Me 3NA1H3 + nHgR2 »- 2Me 3NAlR nH 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 for this 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 elimination of a hydride ion 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, exhibit f a r less a b i l i t y to form five-coordinate configurations. The only established molecule of this type i s (Me 3N) 2GaH 3 which dissociates to the tetra-coordinated compound above -21°C (9). The aluminum anaiogue of t h i s compound (Me 3N) 2AlH 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 Me3NGaH3 i s s l i g h t l y unstable at this temperature, decomposition occurred. At lower temperatures where Me3NGaH3 i s stable and there i s a p o s s i b i l i t y of gallium penta-coordinating no reaction was observed, possibly because the Hg-alkyl bond i s then thermo-chemically stable to e l e c t r o p h i l i c attack. This i s indicated i n the aluminum reaction,(see equation li-^,where elevated temperatures and refluxing solvents, usually cyclohexane, were needed to ensure complete reaction. At higher temperatures Me3NGaH3 could possibly dissociate, and the GaH3 moiety then react. Another important consideration i s the difference i n electronegativity between gallium and aluminum. Aluminum has an electronegativity,^Allred-Rochow), of 1.47 and since the electronegativity of hydrogen i s 2.1, the Al-H bond i s considerably polarized with the hydrogen more strongly attract-ing the bond-forming electrons giving i t a 6 - charge and giving the aluminum atom a substantial 6+ charge. Thus, the aluminum i s provided with a strong driving force for the e l e c t r o p h i l i c attack and for easy loss of hydride ion. Gallium,on the other hand, has an electronegativity, Allred-Rochow, of 1.82, rendering the Ga-H bond far less polar and thus decreasing both, the driving force for 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 definite reaction takes place, as indicated by the equation 10-1, rather than mere decomposition of the s t a r t i n g material was evidenced by the proton NMR spectrum of the product which showed three peaks at T = 10.12, 10.21, 10.28 (T_- = 2.84 p.p.m.), closely resembling the Ga-Me absorption peaks observed i n products obtained by alternate routes. In addition the - 13 -infrared spectrum of the product i n benzene solution showed two bands at 1840, 1780 cm * i n the Ga-H stretching frequency region indicating the presence of several species. Small droplets of mercury metal were observed in the residue i n the reaction flask giving further evidence of reaction. However, the low yields of organogallane products obtained by this method turned our attention to alternative routes. The second synthetic route involved the lithium hydride reduction of trimethylamine adducts of organogallium halides; Me3NGaMe2Cl + LiH y Me3NGaMe2H + L i C l 13-1 Me3NGaMeCl2 + 2 LiH > Me3NGaMeH2 + 2LiCl 13-2 The trimethylamine monomethyldichlorogallane can readily be prepared by the following routes. Me \ Me^Si + GaCl 3 y [Me 3Si GaCl 2] y Cl Me 3SiCl + MeGaCl2 13-3 Me3N + MeGaCl2 • Me3NGaMeCl2 13-4 The reaction 13-3, reported by Schmidbaur. and coworkers (21,22,47) proceeds smoothly without solvent at 40°C to y i e l d trimethylchlorosilane, Me 3SiCl, b o i l i n g point 57.9°C (48) and monomethyldichlorogallane, MeGaCl2, melting point 75-76°C, i n high y i e l d . The v o l a t i l e components Me 3SiCl and excess Mei+Si were pumped o f f at 0°C to leave the desired product^MeGaCl 2 j a - 14 -white s o l i d which analysed for CI = 46.2% and Ga = 42.6%; theoretical 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 MeGaCl2 i n concentrated acid (69). The gallium was analysed as the precipitate GaMe [CgHeNO^. An excess of trimethylamine was then added to the s o l i d monomethyldichlorogallane and the mixture held at 0°C for some hours after which the excess amine was removed to leave a white s o l i d Me3NGaMeCl2 i n the flask. Alternative routes to t h i s l a t t e r compound involve reaction of hydrogen chloride with trimethylgallane i n ether followed by amine addition, Me3Ga + 2HC1 E t 2 ° > MeGaCl2 + 2CH.1+ 14-1 MeGaCl2 + Me3N E t 2 ° > Me3NGaMeCl2 14-2 or equilibrium reaction between trimethylamine trichlorogallane and trimethylamine trimethylgallane. 2Me3NGaCl3 + Me3NGaMe3 > 3Me3NGaMeCl2 14-3 A l l the above reactions proceed i n high y i e l d . An NMR spectrum of the compound Me3NGaMeCl2 showed two peaks, one at T = 8.36 corresponding to Me-N resonance and a second peak of one-third the integrated intensity at x = 9.92 for the Ga-Me resonance. The preparation of trimethylamine dimethylmonochlorogallane (49,50), Me3NGaMe2Cl, involved the reaction of stoichiometric amounts of hydrogen - 15 -chloride and trimethylgallane i n ether, followed by amine addition, or the u t i l i z a t i o n of the equilibrium reaction Me3Ga + HCI * Me2GaCl + CH^ 15-1 Me2GaCl + Me3N * Me3NGaMe2Cl 15-2 2Me3NGaMe3 + Me3NGaCl3 3Me3NGaMe2Cl 15-3 The f i n a l reduction of these trimethylamine adducts of chloromethyl-gallane was carried out by adding the LiH i n ether at -20°C, followed by a period of two hours at room temperature. The reaction mixture was f i l t e r e d and the ether removed at low temperature to 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 monomethyl-dichlorogallane with two moles of lithium hydride,, gave an NMR spectrum with two peaks, attributed to Ga-Me at x = 9.99, 10.14. The l a t t e r corresponds to Ga-Me i n Me3NGaMeH2 and the former may be either due to Ga-Me in the partly reduced species Me3NGaMeClH or to Ga-Me i n LiGaMeX2H, this l a t t e r species being formed by the reaction LiH + Me3NGaMeX2 LiGaMeX2H + Me3N 15-4 where X = H or Cl. 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 readily sublimed. The area under the peaks suggests that only about 25% of the product exists as Me3NGaMeH2. The infrared • spectrum of the reduced" species showed - 16 -two bands i n the Ga-H st r e t c h i n g frequency range at 1880 cm * and 1830 cm The reduction of trimethylamine dimethylmonochlorogallane with l i t h i u m hydride produced a product which i n benzene s o l u t i o n showed a Ga-Me NMR resonance peak at T = 10.20 corresponding to the p o s i t i o n obtained f o r Me3NGaMe2H prepared by other methods and s i g n i f i c a n t l y higher than the Ga-Me resonance i n Me3NGaMe2Cl which appeared at x = 10.11. In both of the above reductions, that i s using the mono- and dichloro-gallanes, the y i e l d of trimethylamine methyl gallanes was very low and the products were always ..contamin-ated with chloride which was d i f f i c u l t or impossible to remove. Reactions at higher temperatures or f o r longer periods of time only r e s u l t e d i n the decomposition of the products. Reactions using excess LiH gave none of the expected product^ p o s s i b l y only the lithium compounds, LiGaMe2XH and LiGaMeX 2H, where X i s Cl or H, (see equation 15-4), would be formed. Analogous aluminum reactions gave s i m i l a r r e s u l t s (41). Thus reacting Me 3NAlEt 2Cl with LiH f o r nine hours i n r e f l u x i n g ether resulted i n only one-h a l f of the chloride being reduced to the hydride Me3NAlEt 2H. Times of up to 24 hours were used i n attempting the LiH reduction of Me3NAlEtCl 2 to Me3NAlEtH 2, but only p a r t i a l conversion was observed. The Me3NAlMe2Cl compound i n contrast to the ethyl compound did not react at a l l with LiH i n r e f l u x i n g ether, and neither d i d Me3NAlMeCl 2. Although t h i s second method of preparation was superior to the dimethyl mercury route, subsequent methods led to higher y i e l d s . Thus a more advantageous synthesis involved the reaction of lit h i u m methyl with halogenogallanes (11). Me 3NGaH 2Cl + LiMe * Me3NGaMeH2 + L i C l 16-1 Me3NGaHCl2 + 2LiMe * Me3NGaMe2H + 2LiCl 17-1 When stoichiometric amounts of trimethylamine monochlorogallane and lithium methyl were mixed i n ether, lithium chloride was precipitated. After f i l t r a t i o n and removal of solvent at low temperature, the product Me3NGaMeH2 could be sublimed to give a high y i e l d of a chloride-free material. The infrared and NMR spectra of this compound, with other physical data were collected and are discussed l a t e r . The NMR spectrum showed a peak at x = 8.18 assigned to Me-N resonance, and also three peaks corresponding to Ga-Me resonance at x = 10.09, 10.18, 10.24 which compare favorably to the spectra of Me3NGaH2Me samples prepared by other routes. S i m i l a r l y when two molar equivalents of lithium methyl were reacted with one molar equivalent of trimethylamine dichloromonomethylgallane i n l i k e manner, the compound Me3NGaMe2H was produced, which could be sublimed as a nearly pure product, though a trace of chloride was always present. The infrared and NMR spectra of t h i s compound were also recorded. The NMR spectrum contained a peak at x = 8.20 assigned to Me-N resonance, and also for Ga-Me resonance indicated three peaks at x = 10.10, 10.18, 10.25 which compare favorably to the spectra of Me3NGaMe2H samples prepared by other methods. In addition there was a very small peak at x = 10.04 which was probably due to the Ga-Me of the Me3NGaMeHCl species. This same chloro species was postulated as a side product from the preparations using Me3NGaMeCl2 and LiH, giving a peak at x = 10.02 and was s i m i l a r l y d i f f i c u l t to remove by sublimation. These chlorogallane compounds react very s i m i l a r l y to th e i r aluminum analogues (40,51) where at room temperature, i n either benzene or ether solvent, lithium methyl reacted very rapidly with trialkylamine - 18 -chloroalkylalanes, as indicated below, i n equation 18-1, to produce t r i a l k y l -nRLi + R'oNAlCl H 3 > nLiCl + R%NA1R H 18-1 3 n 3-n 3 n 3-n 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 to produce an alkylated alane adduct, LiMe + Me 3NAlH 3 »- LiH + Me3NAlMeH2 18-2 but a side reaction LiH + Me 3NAlH 3 >- LiAlH^ + Me3N 18-3 made i t d i f f i c u l t to control the stoichiometry of the desired reaction and the y i e l d of Me3NAlMeH2 was low. This side reaction seems to be a standard reaction with Group IIIB alkyls (52) where a stronger nucleophile such as LiH, Me2NH, or CaH2 replaces a weaker nucleophile such as Me3N. When a s i m i l a r reaction was attempted, using lithium methyl with trimethylamine gallane, none of the desired product Me3NGaMeH2 was produced. The reaction probably proceeded f i r s t by alkylation of the gallane followed by lithium hydride replacement of trimethylamine. LiMe + Me3NGaH3 LiH + Me3NGaMeH2 * LiH + Me 3NGaMeH2 •> LiGaMeH3 + Me3N 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 dissolved i n benzene was recorded. This gave several peaks, a singlet at x = 9.92 assigned to Ga-Me i n LiGaMeH3 and a t r i p l e t and quartet centred at x = 9.2 and 6.9 respectively which are assigned to ether coordinated to the LiGaMeH3 molecule. On prolonged pumping of the white solidjLiGaMeH 3,at room temperature a l l the ether could be removed and LiGaMeH3 now seemed to be only partly soluble i n benzene. Possibly the LiGaMeH3 had polymerized, some graying was also observed indicating that the lithium compound was decomposing. Lithium gallium hydride, LiGaH l + 7is also postulated to have ether coordinated to i t (55) and decomposes at room temperature i n ether solution or when the ether solvent i s removed. No Me-N resonance was observed i n the NMR spectra. This system was not i n v e s t i -gated further, because i t seemed not to lead to the desired organogallane amine adducts. The f i n a l method employed for synthesising trimethylamine adducts of organogallanes was the highly successful route involving the equilibrium reaction between trimethylamine gallane and trimethylamine trimethylgal1ane. Me3NGaH3 + 2Me3NGaMe3 y 3Me3NGaMe2H 19-1 2Me3NGaH3 + Me3NGaMe3 > 3Me3NGaMeH2 19-2 Again the products can be p u r i f i e d by sublimation, but i n this method the starting materials are both extremely pure and there are no side products. Infrared and NMR spectra were collected on the products and compare favourably to those obtained from compounds prepared by alternative routes. - 20 -The aluminum analogues were prepared i n the very same manner by mixing 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 subliming 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 Reactions of Trimethylamine Adducts of Organogallanes (a) P h y s i c a l P r o p e r t i e s The trimethylamine organogallanes appear at very low temperatures to be n i c e white s o l i d s but at room temperatures they appear as waxes or o i l s . Me3NGaMe£H was placed i n a sublimer and sublimed o n t o the c o l d f i n g e r cooled to -78°C. Then t h i s c o l d f i n g e r was allowed to s l o w l y warm up and i t s temperature noted. At about -6°C some of the m a t e r i a l on the c o l d f i n g e r began t o melt but the melting p o i n t was riot sharp c o n t i n u i n g ' u n t i l about 20°C at which temperature a l l the compound was l i q u i d . M e 3 N G a M e H 2 was l i k e w i s e sublimed onto the c o l d f i n g e r and warmed up. At 4°C some of the M e 3 N G a M e H 2 began to melt and at about 25°C a l l of the compound had melted i n t o a very viscous o i l . When some Me3NGaMeH2 was placed i n a c a p i l l a r y tube and sealed o f f under n i t r o g e n , the compound again showed a melting p o i n t range of 4 t o 20°C. At room temperature, about 18°C, i f the two phases are mechanically separated, the NMR s p e c t r a of both phases are very s i m i l a r i n d i c a t i n g that the two phases are of s i m i l a r composition. The long melting range may i n d i c a t e that there i s . a change occuring i n which the s o l i d was polymerized and on m e l t i n g , becomes monomeric. This type of behaviour was observed f o r compounds o f the type Me2NGaMe2 (62). The molecular weights of Me3NGaMe2H and Me3NGaMeH2 were both determined 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 molecular weight of Me3NGaMe2H was found to be 172 i n a 0.0341 molal s o l u t i o n , t h i s compares to the t h e o r e t i c a l - 21 -molecular weight for a monomer of 160, to give the degree of association as 1.08. The molecular weight of Me3NGaMeH2 was found to be 175 : in a 0.0423 m solution. This compares to the theoretic molecular weight of the monomer of 146 gms mole ^ and gives a degree of association of 1.20. It seems as i f these compounds are primarily monomers but there i s no doubt some association probably through dipole-dipole interactions rather than bridged dimers. With s i m i l a r aluminum compounds (40,41) the degree of association for Me3NAlMeH2 i s 1.95 and for Me3NAlMe2H i s 1.34. Substituting a better bridging ligand such as chloride i n place of methyl i n the aluminum compounds results i n an irreg u l a r effect on the degree of association, Me 3NAlH 3 and Me 3NAlH 2Cl show degrees of association of 1.43 and 1.32 respectively, whereas bridging a b i l i t y i s i n the sequence Cl > H > Me. Neither dipole-dipole interactions nor bridged dimers have been generally accepted to explain the association of Group IIIB coordination compounds and there i s s t i l l a good deal of controversy (53) because the real nature of the bonding forces effecting the compounds are l i t t l e understood and therefore no predictions 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 internal standard, cyclohexane x „ I7 =8.54 and benzene x~ „ =2.84. Cyclohexane i C 6 H 1 2 C 6 H 6 has the advantage that a l l proton peaks i n this solvent are 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 to solvent interaction are very small and benzene has the advantage that i t s resonance peak appears at low enough f i e l d to be free from interference with any other proton peaks i n the samples. Most samples were run at a concentration of about 0.5 M to 1 M. Table 1 Proton NMR Data i n Cyclohexane Solvent Species Me-N (T) Ga-Me (T) Me3NGaMe3 7.72 10.57 Me3NGaMe2H 7.63 10.51 Me3NGaMeH2 7.61 10.42 Me3NGaMeCl2 7.66 10.27 Table 2 Proton NMR Data i n Benzene Solvent Species Me-N (T) Ga-Me (T) Me 3NGaMe 3 8.34 --> 8.10(sat.) 10.22 -Me3NGaMe2H 8.22 10.17 Me3NGaMeH2 8.10 10.08 Me 3NGaH3 8.02 -- • Me3NGaMe2Cl 8.31 10.11 Me3NGaMeCl2 8.36 9.92 Me 3NGaCl 3 8.19 --GaMe3 -- 10.15 MeGaCl2 -- 9.90a Me3NGaHMeCl 8.20 10.03 Me3NGaMeD2 8.10 10.09 Me3NGaMe2D 8.20 10.17 Me3NGaH2OMe 8.12 6.65b S chmi db aur ref. 47 gives Ga-Me x = 9.20 i n This i s for Ga-OMe. The proton NMR spectra of Me3NGaMe2H and Me3NGaMeH2 both show, at the same p o s i t i o n s , three d i s t i n c t signals with d i f f e r e n t areas under the three peaks f o r the two "compounds", see figure 1. It seems probable therefore that an equilibrium i s established i n so l u t i o n and that a l l four possible species are present. Me3NGaMe3 Me3NGaMe2H 1 - e ' Me3NGaMeH2 Me3NGaH3 Quotation marks are put around those formula or compounds whose stoichiometry corresponds to the formula but i n so l u t i o n a l l four compounds as l i s t e d above e x i s t together to make up t h i s correct stoichiometry. For "Me3NGaMeH2" i n benzene the three Ga-Me signals appear at T = 10.24, 10.17, 10.09 and a Me-N peak at x = 8.10. The signals are assigned as i s i n Table 3 below. The r a t i o of molar concentrations and the percentage of each compound i n s o l u t i o n are also l i s t e d . Table 3 Molar Ratios of "Me^NGaMeH^" i n Benzene Species Ga-Me (x) Peak Area Molar % of Each r a t i o Ratio Me3NGaMe3 10.24 1 1 ' 3.1% Me3NGaMe2H 10.17 4.85 7.0 22.9 Me3NGaMeH2 10.09 5.00 15.0 47.0 Me3NGaH3 -- -- 8.6 27.0 )• a l l present together i n so l u t i o n . - 24 -»'Me3NGaMeH2" 0 , 1 1 -1 . . : 1 1 , 1 , , , 1 3 *» 5 6 f 8 cj io il 'A Chemical Sh i f t x(ppm) > "Me3NGaMe2H'* 0 I • ; 1 — I \ j — — , , , - I 1 1 I 1 — I -3 ^ 5 6 7 % Chemical Shift x (ppm) >• FIGURE 1 NMR Spectra of "Me3NGaMeH2" and "Me3NGaMe2H" at 60 Mc/sec. - 25 -Sim i l a r l y for the compound "Me3NGaMe2H" i n benzene the following data were obtained. Table 4 Molar Ratios of "Me3NGaMe2H" i n Benzene Species Ga-Me (x) Peak Area r a t i o Molar Ratio % of Each Me 3NGaMe 3Me3NGaMe2H Me 3NGaMeH2 Me3NGaH3 -10.22 10.16 10.07 1.6 5.16 1 2.1 6.1 3.95 1 16.0 46.4 30.0 7.6 Sim i l a r l y three Ga-Me signals were observed for each of the compounds "Me3NGaMeH2" and "Me3NGaMe2H" i n cyclohexane solution and for the deuterated compounds "Me3NGaMeD2" and "Me3NGaMe2D" i n benzene solution. These' are l i s t e d and the different NMR signals assigned i n Table 5. Table 5 NMR Data for "Me3NGaMe2H" and "Me3NGaMeH2" i n Cyclohexane and for "Me3NGaMe2D" and "Me3NGaMeD2" i n Benzene "Me 3NGaMe2H" i n C 6H 1 2 "Me 3NGaMeH2" i n C 6H 1 2 Species Ga-Me % of Each Species Ga-Me ("0 % of Each Me 3NGaMe3 10.57 27.0% Me 3NGaMe 3 10.57 8. . 3% Me 3NGaMe2H 10.51 45.4 Me3NGaMe2H 10.51 27. .5 Me 3NGaMeH2 10.42 23.6 Me3NGaMeH2 10.42 35. .0 Me 3NGaH3 — 4.0 Me 3NGaH3 — 29. .2 "Me3NGaMe2D" i n C 6H 6 "Me3NGaMeD2" i n C 6H 6 Species Ga-Me (x) % of Each Species Ga-Me CO % of Each Me3NGaMe3 Me 3NGaMe2D Me 3NGaMeD2 Me 3NGaD 310.29 10.22 10.16 16.8% 40.9 34.1 8.2 Me 3NGaMe 3Me 3NGaMe2D Me3NGaMeD2 Me3NGaD3 10.26 10.22 10.13 1.7% 13.6 44.3 40.4 - 26 -These same set of three Ga-Me peaks were found i n a l l the compounds of the form "Me3NGaMe2H" and "Me3NGaMeH2" prepared by a l l four experimental procedures. The compounds which were sublimed 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 the same as those obtained by mixing the reagents Me3NGaMe3 and Me3NGaH3 together i n benzene. Mixing these 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 . at r a t i o s o f 1:2, 1:1, 2:1 et c . gave the same three peak p o s i t i o n s but j u s t d i f f e r e n t area r a t i o s . The percentages o f each species present i n s o l u t i o n must be taken as only approximate, f o r small amounts o f i m p u r i t i e s such as Me3N, or g a l l i u m metal, from decomposing Me3NGaH3 could g r e a t l y a f f e c t the conc e n t r a t i o n s , and v a r i a t i o n s as great as f i v e percent i n the amount o f each species present i n s o l u t i o n have been observed f o r the same "compound". Temperature would a l s o have a marked e f f e c t on the percentages of the species present, though t h i s was not i n v e s t i g a t e d . Heating the s o l u t i o n s might lead t o a time averaged s i g n a l f o r the p r e d i c t e d products i . e . Me3NGaH2Me or Me3NGaMe2H but low thermal s t a b i l i t y o f the species precludes such work. The e q u i l i b r i u m between the fou r compounds i n s o l u t i o n does not seem to be time dependent f o r two NMR s p e c t r a were obtained from the same sample one month apart and there 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 of the peaks. A v a r i a t i o n of the solvents i . e . benzene or cyclohexane, seems to have l i t t l e e f f e c t on the percentage o f each species i n solution," compare Tables 3, 4 and 5. The percentage o f that species i n s o l u t i o n which compares to the s t o i c h i o m e t r y o f the "compound" prepared i . e . Me3NGaMe2H present i n a s o l u t i o n o f "Me3NGaMe2H" and Me3NGaMeH2 present i n a s o l u t i o n o f "Me3NGaMeH2" i s always the greatest. The percentage o f each species i s only approximate, thus no solvent e f f e c t i s evidenced i n the two s o l u t i o n used. I f a strong - 27 -donor solvent such as an ether were used then there may be a change i n the peak r a t i o s caused by the solvent p a r t l y r e p l a c i n g amine from some o f the spe c i e s , but t h i s has yet t o be i n v e s t i g a t e d . The approximate Ga-Me peak separations were 5 cps at 60 Mc/sec and about 8 cps at 100 Mc/sec, thus showing the s i g n a l s a r i s e from three d i f f e r e n t species and not from s p i n - s p i n coupling. 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 the Me-N resonance. From Table 2 i t i s seen that the trimethylamine 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 the compounds "Me3NGaMe2H" and "Me3NGaMeH2" a l l trimethylamine groups must be exchanging very r a p i d l y , and the peak p o s i t i o n s seem t o be i n the average p o s i t i o n between the extremes of Me3NGaMe3 and Me3NGaH3. The NMR spectrum of a neat sample o f "Me3NGaMe2H" was obtained. Using TMS i n benzene as an e x t e r n a l standard the f o l l o w i n g peaks, assigned as Ga-Me resonances, were observed, area under the peak i s i n brackets, x = 9.92 [1], 10.02 [1.1], 10.10 [1.7], 10.18 [6.5], 10.26 [7.9]. At the probe temperature of 30°C the compound "Me3NGaMe2H" e x i s t s as a viscous o i l . I t i s p l a u s i b l e t o assign the peaks at x = 10.26, 10.18, 10.10 to the^compounds Me3NGaMe3, Me3NGaMe2H and Me3NGaMeH2 r e s p e c t i v e l y , f o r these three peaks roughly 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 the compound "Me3NGaMe2H" i n benzene, see Table 5. The peaks at x = 9.92 and 10.02 could be assigned t o b r i d g i n g methyl groups i n dimeric or polymeric species. Such downfield s h i f t s have been observed f o r the b r i d g i n g methyl groups of ( A l M e 3 ) 2 (54). A l t e r n a t i v e l y these peaks could be assigned to methyl groups of species showing strong 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 to Me-N indicating that a l l the amine groups are exchanging rapidly even i n the neat l i q u i d . The proton NMR of the chlorinated compounds Me3NGaMe2Cl and Me3NGaMeCl2 i n benzene show only a single resonance for Ga-Me at room temperature. Presumably the higher ef f i c i e n c y of chlorine as a bridging group, over methyl or hydrogen (61), leads to a stable dimer or a s p e c i f i c single compound or very rapid exchange. (c) Infrared Data The infrared absorption spectra of the compounds "Me3NGaMeH2", "Me3NGaMe2H" and t h e i r deuterated analogues "Me3NGaMeD2" and "Me3NGaMe2D" were recorded i n benzene solution between 400 cm ^  and 4000 cm \ see Figure 2. These compounds have a vapour pressure of about 2 mm of Hg and the gas phase infrared spectra of some were recorded. Assignments of bands can be made on the bases of the well established structures (11, 55) of the adducts of GaH X , where X i s halogen and n i s 0, 1, 2, 3 (11). A l l bands 3-n n 6 not assigned to coordinated trimethylamine or carbon-hydrogen vibrations are l i s t e d i n Table 6 below. From Table 6 i t i s seen that the vibration frequency of Ga-H decrease by a factor of about / T i . e . 1.41 when going to the deuterated species as i s expected from the reduced mass effect. The infrared data of trimethylamine organogallanes generally support the NMR res u l t s . The Ga-H stretching frequencies observed for "Me3NGaMe2H" and "Me3NGaMeH2" are broader bands than those observed for Me3NGaH3 (11) and a shoulder at lower frequency i s observed which i s not found i n the spectrum of Me3NGaH3. These differences could be attributed to the presence of p a r t l y methylated gallane species i n solution. The gas phase of the - 29 -Wavenumber (cm ) FIGURE 2 Infrared Spectra of "Me3NGaMeH2" and "Me3NGaMe2H" i n C 5H 6 - 30 -Table 6 Infrared Data for "Me3NGaMeH2", "Me3NGaMeD2" and "Me3NGaMe2H","Me3NGaMe2D" "Me3NGaMeH2" "Me3NGaMeD2" vH/vD Assignment (55) 1845(vs),1815(vs) 1760(sh) 745(vs) 707(s) 685(s,b) 488(s),495(sh) 1313(vs) 1.41; 1.38 jantisym., sym. Ga-H stretch 1270(sh) 1.39 538(s) 1.37 antisym. Ga-H deformation 490(m) 1.44 sym. Ga-H deformation 680(w,b) -- Ga-C 470(m) -- , Ga-N stretch "Me3NGaMe2H" "Me3NGaMe2D" vH/vD Assignment (55) 1840(vs) 1760(sh) 745(s) 695 (s)? 690(sh) 485(m),495(sh) }l295(vs) 538(s) 490(w) 690(s,b) 475(m) 1.42 1.36 1.42 } antisym., sym. Ga-H stretch antisym. Ga-H deformation sym. Ga-H deformation Ga-G Ga-N stretch where vs; very strong; s strong; m medium; w weak; sh shoulder; b broad; units are i n cm compounds "Me3NGaMe2H" and "Me3NGaMeH2" give infrared spectra that are very s i m i l a r to that of pure Me3NGaH3 (8). The infrared spectrum i n the region between 630 cm * and 720 cm i s characterized by strong benzene solvent absorbance so the assignment of bands i n t h i s region, Ga-H symmetric deforma-tion and Ga-C vibrations, are only tentative. - 31 -C. Reaction of Trimethylamine Organogallanes (a) With HCl The compound "Me3NGaMeH2" i n benzene solution reacted readily at below room temperature with one mole of hydrogen chloride to liberate one mole of gas which was shown by i t s infrared spectrum to be mostly hydrogen with a trace of methane, and to form the compounds "Me3NGaHClMe". A second mole of HCl gas reacted as easily as the f i r s t with the compound "Me3NGaMeH2", and a second mole of gas was evolved which again was mostly hydrogen but now contained about 10% methane. The reaction of trimethylamine gallane with HCl gas to give hydrogen and trimethylamine chlorogallane has been examined previously (11) and proceeds smoothly i n solution or neat. It seems reasonable then that hydrogen can be evolved from trimethylamine adducts of organogal1ane. It seems that some methane i s also evolved as evidenced i n the infrared spectrum. This could be explained by the fact that the "Me3NGaMeH2" compound equilibrates i n solution to form some Me3NGaMe2H and Me3NGaMe3 which could then react with HCl to give o f f methane gas, as indicated i n the equations below. HCl + Me3NGaMe3 • Me3NGaMe2Cl + CH^ 31-1 HCl + Me3NGaMe2Cl > Me3NGaMeCl2 + Ctik 31-2 The etherate of GaMe3 reacts under mild conditions with HCl gas,(see experimental section), to liberate methane; t h u s i t seems l i k e l y that Me3NGaMe3 would also react with HCl. In the reaction of a trimethyl-amine organogallane with HCl elimination of a proton i s s l i g h t l y preferred - 32 -to that of a methyl group, for the amount of methane liberated i s less than that expected on the bases of the percentage of Me3NGaMe3 and Me3NGaMe2H in solution as calculated from the NMR data, see Table 3 . (b) With Ethylene Ethylene gas was condensed onto a benzene solution of "Me3NGaMeH2" and after several hours at room temperature no hydrogallation or any other reaction occurred. The ethylene gas was pumped o f f and i d e n t i f i e d and the NMR and infrared spectra of the benzene solution indicated that the star t i n g material was unchanged. Schmidbaur and coworkers ( 2 1 , 2 2 ) and Eisch ( 1 8 , 1 9 ) have shown that uncoordinated gallanes of the type X2GaH, where X i s C l , Br or Et, hydro-gallate a large variety of double and t r i p l e bonds at low or moderate temperatures. No hydrogallation reaction with a coordinated gallane has been reported and attempts usually resulted i n the decomposition of 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 solution or neat, at about 0°C, with methanol. One mole of Me3NGaH3 w i l l react with one, two, or three moles of methanol to liberate one, two, or three moles of hydrogen respectively. The NMR spectrum of the clear benzene solution which f i r s t results from the reaction shows two peaks, one at x = 8 . 1 2 ( x „ u = L 6 H 6 2 . 8 4 p.p.m.) corresponding to 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 reaction product slowly evolves trimethylamine. The trimethylamine ligand i s also evolved from the product mixture on removal of solvent. In both - 33 -(a) 4 5 6 Chemical S h i f t 7 t(Ppm) II 'Z. (b) / 2 3 5 6 7 S <* Chemical S h i f t x(ppm) • FIGURE 3 NMR Spectra of Me3NGaH2OMe at 60 Mc/sec. (a) Immediately a f t e r p r e p a r a t i o n (b) A f t e r removal o f solvent 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 results which i s now only partly soluble i n benzene. The NMR spectrum of th i s p a r t l y soluble species i s quite complex. The Me3N peak decreases i n intensity and two broad peaks appear at x = 8.6 and x = 9.1. These could be attributed to Me-N resonance but th i s i s uncertain. The peak assigned to Ga-OMe at x = 6.65 also decreases i n intensity 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 result of spin-spin coupling, (see Figure 3). The infrared spectra of these products, except the product from reaction with three molar equivalents of methanol, a l l show a complex Ga-H stretching region i n the range 1910 cm * to 1825 cm * with the centre of the band s h i f t i n g from approximately 1850 cm ^ to 1900 cm ^  with loss of amine. The exact nature of the reaction of methanol with Me3NGaH3 i s only partly understood. It i s known that alcohol reacts with trimethylgallium to form dimethylgallium alkoxides, [Me2GaOR]2 (56). These compounds form very weak adducts with trimethylamine, except where R = Me i n which case no adduct forms. It i s argued that the -OR group acts as a stronger electron donor than trimethylamine. The reaction of Me3NGaH3 with methanol probably proceeds thus; Me3NGaH3 + Me OH • Me3NGaH2OMe + H 2 34-1 H 2 / \ 2MeqNGaH90Me >- MeO OMe + 2Mec,N 34-2 Ga H 2 - 35 -nMe3NGaH2OMe 0 Me H 2 ,Ga VI Me / H 2 Ga + nMe3N 35-1 -1 n Dimers, trimers or polymers could be formed by reactions 34-2 and 35-1 Indeed some insoluble material, presumably polymeric, was obtained from the reactions i n addition to the soluble compounds. These methoxy derivatives would cert a i n l y be a new class of gallanes and t h e i r preparation, structure and properties warrant further study. D. Mechanism of Exchange From the NMR, infrared and experimental data there i s strong evidence that the four compounds of the type Me3NGaMenH3_n where n = 0, 1, 2, 3 co-exist i n solution. The intermediate that gives r i s e to these species i n solution must presumably be reached by a bridged gallium species: Me Me3N Me • Ga \ .Ga-H Me \ X N -NMec H \ H N This bridged intermediate can then dissociate along the dashed l i n e , then reform and redissociate so as to produce a l l four different species. A number of exchange reactions of Group IIIB a l k y l addition 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 - 3 6 -found that a p p l i e s t o a l l or t o a large number of these a l k y l or Lewis base exchanges. The NMR s p e c t r a of the trimethylamine organogallanes i n d i c a t e that a l l amines are e q u i v a l e n t , that i s , they must be exchanging very r a p i d l y . The bridged s t r u c t u r e shown above could lose both i t s amine ligands to form the more s t a b l e four-coordinate g a l l i u m dimer species w i t h the amine ligands 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 . A l t e r n a t i v e l y , i n s o l u t i o n , the amine l i g a n d could f i r s t d i s s o c i a t e from the monomeric gall a n e and then be free i n s o l u t i o n . The gallane species would now be three-coordinate and could e a s i l y become four-coordinate by d i m e r i z a t i o n . Me N \ Me H X \ Me H \ H \ \ This dimer could then d i s s o c i a t e to again form three-coordinate gallane species which then recombines with amine l i g a n d s . . Amine exchange could a l s o occur by some m o d i f i c a t i o n of these two routes as i s observed w i t h aluminum a l k y l exchange. Exchange between a l k y l aluminum adducts of the type Me 3NAlMe 3 and Me 3NAlMe 2X, where X i s a halogen, occurs by two competing mechanisms (59). The f i r s t i s through a bridged 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 to the bridged gallane shown above. The second i s through a bridged dimer i n which one aluminum atom i s f i v e - c o o r d i n a t e and the other i s four-coordinate. Me N N Me /Me \ X \ / MdN » A 1 \ A l Me' N X ' \ NMe \ - 37 -This four-coordinate part i s obtained from a three-coordinate aluminum of the type AlMe3 o r AlMe 2X from which the trimethylamine ligand has dissociated. It must be remembered that "Me3NGaMeH2n does not hydrogallate o l e f i n s so, i n the gallium case, the existence of an uncoordinated GaH 3 species seems u n l i k e l y . NMR studies with trimethylamine trimethylgallane (54) have shown that i n the presence of excess amine a bimolecular exchange takes place as indicated i n equation 37-1, * * Me3N + Me3NGaMe3 > Me3N + Me3NGaMe3 37-1 but i n the presence of excess trimethylgallane a d i s s o c i a t i o n of the adduct i s the rate c o n t r o l l i n g step. Me3NGaMe3 Me3N + GaMe3 37-2 Possibly both these types of exchange are occurring i n solutions of trimethyl-amine organogallanes. No exchange studies have previously been reported i n v o l v i n g hydride-alkyl exchange i n Group IIIB compounds. In summary, i t seems that the compounds "Me3NGaMeH2M and "Me3NGaMe2H" roughly p a r a l l e l , i n properties and reactions, the chemistry of Me3NGaH3 and Me3NGaMe3. The thermal s t a b i l i t y of "Me3NGaMe2H" and "Me3NGaMeH2" i s s i m i l a r to that of Me3NGaH3 and greater than that of the uncoordinated gallanes (20,21). However the boron and aluminum analogues possess much higher thermal s t a b i l i t y . - 38 -E. Exchange Reactions Involving Other Group IIIB Elements (a) Aluminum Alkyl-Hydride Exchange Because of the unusual behaviour of trimethylamine adducts of organo-gallane i n solution a re-examination of trimethylamine adducts of organo-alanes was i n order. Peters and coworkers (41) prepared the compounds "Me3NAlMeH2" and "Me3NAlMe2H" by mixing the appropriate amounts of Me3NAlMe3 and Me 3NAlH 3 i n ether and then removing the solvent. Some of the properties of these compounds are l i s t e d below. "Me3NAlMe2H": m.p. 33-35°C, b.p. (1 mm Hg) 42-43°C, degree of association i n C 6H 1 2 i s 1.34, v Al-H 1750 cm"1, NMR i n C f iH 1 2 (x„ „ = 8.54) Me-N x = 7.59, C 6 H 1 2 — Al-Me x = 10.81, 10.86. "Me3NAlMeH2": m.p. -35°C, b.p. (1 mm Hg) 25-26°C, degree of association i n C 6H 1 2 i s 1.95, v Al-H 1750 cm NMR i n C BH 1 2 (rn „ =8.54) Me-N x = 7.52, L 6 H 1 2 — Al-Me x = 10.88, 10.78. The NMR doublet above 10 Thas been explained i n terms of a dimer with alternative methyl or hydrogen bridges. A re-examination of this NMR work led to the spectra shown i n Figure 4. The NMR data are 1-i's.ted i n the follow-ing table. - 39 -"Me3NAlMeH2" o- 5 <r 7 Chemical Sh i f t x(ppm) -"Me3NAlMe2H" '0 n Chemical Shift x (ppm) »-FIGURE £ NMR Spectra of "Me3NAlMeH2" and "Me3NAlMe2H" at 60 Mc/sec. 40 Table 7 Proton NMR Data for MeqNAlMe„ H Species s 3-n n r Species C 6H 6 Solvent C 6H 1 2 Solvent Me3NAlMe3 »'Me3NAlMe2H" "Me3NAlMeH2" Me 3NAlH 3 Me-N ( x ) 8.31 8.26 8.06 7.94 Me-Al ( x ) Me-N ( x ) Me-Al ( x ) 10.58 10.45, 10.51, 10.56 10.47, 10.53, 10.58 7.61 7.62 7.61 7.71 10.92 10.81, 10.87, 10.92 10.80, 10.87, 10.92 An examination of these samples with a Varian HA-100 spectrometer showed the Me-Al peaks to 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 to the trimethylamine methylgallane spectra previously discussed and this leads to the assumption that an analogous set of aluminum compounds s i m i l a r to gallium compounds are exi s t i n g together i n solution, thus the following assignments are made. Table 8 Molar Ratios of "Me3NAlMeH2" and "Me3NAlMe 2H" i n Benzene "Me3NAlMeH2" Species Ga-Me ( x ) Peak Area Molar % of Each Ratio Ratio Me3NAlMe3 10.58 7 1 4.3 Me3NAlMe2H 10.53 24 5.1 21.9 Me3NAlMeH2 10.47 21 9 38.4 Me 3NAlH 3 -- 8.3 35.4 "Me3NAlMe2H" Species Ga-Me ( x ) Peak Area Molar Ratio Ratio % of Each Me 3NAlMe 3 10.56 29 1 29.3 Me3NAlMe2H 10.51 25 1.3 38.3 Me3NAlMeH2 10.45 7 0.72 21.2 Me3NAlH3 -- 0.38 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 of equilibrium products i n solution, an examina-tion of the analogous boron systems was made to see i f t h i s exchange i s characteristic of a l l Group IIIB elements. The compounds Me3NBMe3 and Me3NBH3 were mixed i n a 1:2 and 2:1 molar r a t i o i n benzene but no exchange was observed of either 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 for Mixtures of Me3NBMe 3 and Me 3NBH3 i n C 6H 6 Species Me-N (x) B-Me (x) B-H (x) J„ B_ H c p s Me3NBH3 7.81 -- 7.89 99 "Me3NBH2Me" 7.91, 8.16 10.05 7.82 98 "Me3NBHMe2" 7.96, 8.19 10.00 7.76 99 Me 3NBMe 3 8.24 9.99 The B^ H interactions were not observed. 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 interactions rather than any a l k y l or amine exchange. (c) Mixing Trimethylamine Adducts of Different Group IIIB Hydrides  and Alkyls A large number of exchange reactions using 1:1 molar ratios of reagents were attempted, i n benzene solution, of the type indicated by the following general equation - 42 -Me3NBMe3 + 2Me3 0 NBH3 V 1 1 1' » • -1 1 1 , , , , , , 1 2 3 4 j e 7 S 9 io i) Chemical Shift x(ppm) >• 2Me3NBMe3 + Me3NBH3 0 Chemical Sh i f t T(ppm) FIGURE 5 NMR Spectra of Mixtures of Me3NBMe3 and Me3NBH3 i n C 6 H 6 j 60 Mc/sec - 43 -Me3NMR3 + Me3NM'R3' =—»• Me^MR^R' 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 of trimethylamine or methyl groups takes place i s also indicated i n the table as are the NMR data of the individual reagents. Table 10 NMR Data of the Mixed Group IIIB Alkyls and Hydrides Reagents N-Me M-Me Me3NMR3 + Me3NM'RJ Exchange M-N-Me M»-•N-Me Exchange . M-Me M'--Me a) Me3NBH3 + Me3NAlMe3 NO 7.97 8. .24 NO -. 10 .59 b) Me3NBH3 + Me3NGaMe3 NO 7.99 8. ,29 NO -• 10 .29 c) Me 3NAlH 3 + Me3NGaMe3 YES 8. 11 YES 10 .47? 10 .11 10 .51 10 .17 10 .57 10 .25 d) Me3NBMe3 + Me 3NAlH 3 NO 8.01 8. ,17 YES 9 .94 10 .49 10 .54 10 .60 e) Me 3NBMe 3 + Me3NGaH3 YES 8. 12 NO -• 10 .04 f) Me3NAlMe3 + Me3NGaH3 YES 8. 17 NO 10 .60 g) Me3NBMe3 + Me3NAlMe3 YES 8. 22 NO 10 .04 10 .63 h) Me3NBMe3 + Me3NGaMe3 YES 8. 11 NO 9 .97 10 .28 i ) Me3NGaMe3 + Me3NAlMe3 YES 8. 30 NO 10 .28 io .59 j) Me 3NBMe 3 8. 24 9 .99 k) Me3NAlMe3 8. 31 10 .58 1) Me 3NGaMe 3 8. 34 10 .22 m) Me3NBH3 7. 81 -• n) Me 3NAlH 3 7. 94 -• o) Me3NGaH3 8. 02 — • The solvent was used as an internal standard i . e . TC6 H6 84 p .p .m - 44 -(a) Me3NBH3 + Me3NAlMe3 Chemical Shift x(ppm) »-(b) Me3NBH3 + 0 Me3NGaMe3 1 1 l , , ^ 1 , 1 1 1 1 1 1 < o i z . 3 « v s 6 ? S < f / o / i ' A Chemical Sh i f t x (ppm) > (c) Me 3NAlH 3 + Me3NGaMe3 0 1 ill 4 X 1 2 ^ > r . * — — i * 5 6 7 % 1 Chemical Shift x(ppm) > FIGURE 6 NMR Spectra of, Mixed Trimethylamine Adducts of Different Group IIIB Hydrides and Alkyls at 60 Mc/seo. - 45 -(d) Me3NBMe3 + Me 3NAlH 3 1 r ' ' 1 1 1 1 r ! - J , H ^ , 1 1 2 . 3 4 5 fe ? <8 ^ ;o )) (a. Chemical Shift x(ppm) >• (e) Me3NBMe3 + 0 Me3NGaH3 \ t- - T — 1 . 1 j 1 1 • • Chemical Sh i f t x (ppm) >• (f) Me3NAlMe3 0 + Me3NGaH3 1 1 ' '——I L 1 1 1 — 1 1 — i — "I T   , , , , , : , a - 3 i- s- 6 . i % 9 io I, ix Chejnical S h i f t x(ppm) • FIGURE 6^  (Continued) - 46 -(g) Me3NBMe3 + 0 Me3NAlMe3 1 L 1 • ' I I c 71 1 1 1 1 1 Chemical Sh i f t x(ppm) > (h) Me3NBMe3 + Me3NGaMe3 1 t o < x 3 4 » 4 1 s q i o li Chemical Shift x(ppm) »-(i) Me3NAlMe3 + Me3NGaMe3r-T : l 1 ; 1 i * ^-i r 3 4 S 6 7 ? ^ 10 11 Chemical Sh i f t x(ppm) > FIGURE 6 (Continued) - 47 -An examination of Table 10 indicates that no general mechanism or pr i n c i p a l can be invoked to explain a l l the results and as mentioned e a r l i e r the mechanisms of 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 spite of the uncertainties, some observa-tions and crude conclusions can be arrived 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 (as i s postulated f o r the alkyl-hydride exchange i n the trimethylamine adducts of organogallanes and organoalanes (59)), then those metals which five-coordinate or compounds which can readily lose t h e i r Lewis base adduct should show an exchange occurring. This i s born out with the compound Me3NBMe3, which i s i t s e l f largely dissociated into Me3N gas and BMe3 at room temperature. The exchange reactions with t h i s moiety a l l show Me3N exchange and with Me 3NAlH 3 show alkyl-hydride exchange. Of the three Group IIIB elements used, aluminum has the greatest tendency for five-coordination, thus,almost a l l the reactions involving Me3NAlMe3 and Me 3NAlH 3 show Me3N exchange. From the NMR spectra, two of the reactions indicate alkyl-hydride exchange. The f i r s t , that between Me 3NAlH 3 and Me3NGaMe3 to produce gallane compounds which have Ga-Me signals at x = 10.11, 10.17, 10.25, corresponding to Me3NGaMeH2, Me3NGaMe2H and some st a r t i n g material Me3NGaMe3 as well as possibly some Me3NGaH3, a l l of which are i n equilibrium i n solution. In additionjthe alane compounds produced give signals at x - 10.51, 10.57 corresponding to Me3NAlMe2H and Me3NAlMe3. 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 Me3NAlMeH2 i s also present, and. maybe some st a r t i n g material Me 3NAlH 3. The NMR spectrum shows no change over a two week period. Thus i t seems that the - 48 -two sets of exchange reactions of trimethylamine adducts of organoalanes and organogallanes are existing together i n solution. It i s a great puzzle why the compounds Me3NAlMe3 and Me3NGaH3 don't exchange a l k y l groups since, as postulated above, these two species exist at a steady concentration i n the products of exchange between Me 3NAlH 3 and Me3NGaMe3. The second reaction showing a l k y l exchange i s between Me3NBMe3 and Me3N"AlH,3to produce alane compounds giving signals at T = 10.49, 10.54, 10.60 corresponding to Me3NAlMeH2, Me3NAlMe2H, and Me3NAlMe3, and boron compounds . giving a signal 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 transferred to the alanes there should also be hydride groups transferred to the boron atom. Thus the broad peak at x = 9.95 probably represents several compounds of the type Me3NBMeH2, Me3NBMe2H and possibly some starting material Me3NBMe3. Spin-spin coupling of the methyl protons with the "^ B nucleus, along with quadrupole broadening probably causes the loss of d e t a i l from t h i s peak. This NMR spectrum i s also unchanged over a period of time. Again i t i s puzz^ling why the compounds Me3NBH3 and Me3NAlMe3 do not show methyl-hydride exchange. The BH3 moiety i s a stronger Lewis acid than BMe3 and i t s tendency to dissociate from trimethylamine i s much less than BMe3. Boron i s not known to have a coordination number greater than four, and therefore any Lewis base adduct of a t r i s u b s t i t u t e d boron atom must dissociate before a bridged dimer involving boron can be formed. Thus, i n the NMR spectra i t i s observed that a l l solutions containing Me3NBH3 show no Me3N exchange, and i n the exchange between Me3NBMe3 and Me 3NAlH 3 where i t i s postulated that formation of species of the type Me3NBMe2H and Me3NBMeH2 and possibly Me3NBH3 occurred, i t i s seen that there are two NMR signals for Me3N, indicating that - 49 -there is restricted amine exchange here as well. In conclusion it 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. Experimental A. Experimental Techniques (a) Desiccation A l l gases were dried f i r s t by fractionating under high vacuum through a trap at -20°C, to remove large amounts of water, and then condensed at -196°C into one limb of a drying p i s t o l , see Figure 7, packed with a mixture of glass-wool and phosphorus pentoxide. The gas i s passed through the phosphorus pentoxide by alternately • cooling one limb and then the other limb. The dried 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 dried and r e d i s t i l l e d before use; diethyl ether over lith 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. Solid components were p u r i f i e d by sublimation, either by vacuum bulb-to-bulb sublimation or as with trimethylamine hydrochloride, sublimed to the cooled central finger of the apparatus shown i n Figure 8. Trimethylamine gallane was sublimed under dynamic vacuum from the flask to the large v e r t i c a l tube, marked as A, of 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 dried, evacuated and f i l l e d with nitrogen before use. A l l nitrogen used was Canada Liquid A i r "L" grade, p u r i f i e d nitrogen. The hydride and al k y l derivatives, because of 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 or water vapour were a l l prepared and handled i n either a high-vacuum system or a nitrogen f i l l e d dry box. The high vacuum system developed for the work i s shown i n Figure 10. A double-stage 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 single stage mercury diffusion pump were used to obtain a vacuum of greater than 10 ^  mm of Hg. The dry box (Kewaunee S c i e n t i f i c Equipment) had a special 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 nitrogen to ensure the purity of the atmosphere i n the box. The dry box i s also connected to a c i r c u l a t i n g pump which circulates the box's atmosphere through a drying t r a i n containing molecular sieve (Fisher type 5A) and a copper furnace to 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 pr i n c i p a l thought behind the design and use of any apparatus i n the research was to have a few greased joints as possible. (c) Reaction-Filtration 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 flask A. Additional reagents may be added during the course of a reaction 5=^  to manometer f0 FIGURE 10 Vacuum Line, Part A from Part A Vacuum Line, Part B - 58 -by rotating 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 of the stopcocks, or i f i n solution can be f i l t e r e d through the sintered disc J2 (medium porosity) by cooling or evacuating the receiver flask 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 of pure benzene (about 15 ml). The benzene solution was poured into 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 ice bath. The freezing point of the solution was recorded and compared with that of pure benzene solvent and with standard solutions of biphenyl i n benzene solvent. The following empirical formula was used to calculate the molecular weights. [K^jXfweight of sample (gms)] molecular weight = [weights of benzene solvent (gms)]X [change i n temperature (°C)] = freezing point depression constant 5.10°C per molal.' (e) Spectroscopy Infrared spectroscopy was used throughout this work for semi-quantita-t i v e analysis and for structural .determination of compounds. Infrared spectra were recorded on the following Perkin-Elmer instruments; 137, NaCl range 4000 - 650 cm - 1, 137, KBr, range 800 - 400 cm - 1, 457 range 4000 -250 cm - 1, 21 range 4000 - 550 cm - 1. The observable range for both l i q u i d and gas samples was between 4000 and 400 cm ^  because KBr windows were used. - 59 -rogen F I G U R E 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 solution samples a 0.05 cm fixed path length solution 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 to compensate for solvent absorption. Because of the i n s t a b i l i t y of most of the gallium hydride adducts prepared, a l l infrared solution c e l l s were loaded i n the dry box and a spectrum run as rapidly as possible. As with infrared spectroscopy, nuclear magnetic resonance spectroscopy, NMR, was used as a tool to investigate reactions and for structural determination. The instruments used were a Varian A-60 and Jelco C-60 both operating with a radiofrequency of 60 megacycles per second and a Varian HA-100 which operates at a radiofrequency of 100 megacycles per second. Most samples were run i n benzene solution with a concentration of about 0.1 M to 1 M. The benzene proton signal was used as an internal 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 constriction 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 of nitrogen. As with the infrared samples, the NMR spectra were run as rapidly as possible since steady decomposition at room temperature often impeded prolonged investigation. (f) Lithium Methyl Standardization On standing ether solutions of lithium methyl slowly decompose (35), and consequently these solutions were standardized just before use. The apparatus i n Figure 13 was used for the standardization. In a t y p i c a l standardization 5.0 ml of the lithium methyl ether solution 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 solution 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 of 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 reservoir hydrolysing the lithium methyl and forcing a l l the methane gas into the gas burette. The gas burette was removed and shaken several times to remove traces of ether and then the volume of gas measured, this procedure was repeated several times and the results averaged. Volume of gas was 71.6 ml at 19°C thus molarity was 0.598 M. (g) Elemental Analysis i ) Active Hydrogen: Active hydrogen was measured by placing a small weighed\ amount of compound i n a round bottom flask i n the dry box,, attaching a stopcock adaptor and evacuating on the vacuum l i n e . A small volume of degassed, di l u t e aqueous HN03 solution was then condensed onto the s o l i d at -196°C. The mixture was allowed to reach room temperature and l e f t to react for about one hour with s t i r r i n g . Me3NGaHX2 + H + • Me3N + Ga + 3 + 2X_ + H 2 62-1 The volume of hydrogen gas, non-condensable 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 solution was made up to a known volume and aliquots were used i n the determination of chloride and gallium as indicated below. - 63 -i i ) Chloride A measured aliquot of the solution 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 acid, then a s l i g h t excess of aqueous s i l v e r n i t r a t e solution was added, whereupon s i l v e r chloride i s precipitated. The precipitate was then heated to 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 ipitate. The precipitate was collected i n a f i l t e r i n g crucible, washed with very dilu t e n i t r i c acid and dried at 120°C. The precipitate was weighed as AgCl which contains 24.74% chlorine by weight. i i i ) Gallium A measured aliquot of the solution prepared i n section (i) was measured out into a beaker. The solution was f i r s t made meutral with d i l u t e ammonia solution, 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 solution was then heated to 80°C and a s l i g h t excess of a 5% solution of 8-hydroxyquinoline i n g l a c i a l acetic acid was added followed by an aqueous solution of saturated ammonium acetate u n t i l p r e c i p i t a t i o n of Ga(CgH6NO)3 i s complete. After digestion at 80°C for one hour, the yellow precipitate was collected i n a f i l t r a t i o n crucible and the precipitate washed, f i r s t with hot, then cold water. The precipitate was then dried at 120°C and weighed, and i t s gallium content calculated from the formula Ga(CgH6NO)3 which i s 13.89% gallium by weight. This method has been found to give accurate determinations for a minimum concentration of 10 mg of gallium i n 50 ml of solution. I f the gallium compound had a methyl ligand attached to i t then this ligand was not removed under mild hydrolysing conditions such as i n dilute HN03 solutions, and gallium was precipitated as GaMe(CgHgN0)2 which contains 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 precipitate gallium as a 8-hydroxyquinoline complex were not too successful for the complexes formed tended to be colloids and d i f f i c u l t to f i l t e r off. Gravimetric determinations of gallium i n these l a t t e r compounds was d i f f i c u l t and the results 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 after the removal of organic ligands by b o i l i n g the sample for several hours i n concentrated hydrochloric acid. B. Preparative (a) Preparation of Gallium Trichloride (63) GaCl 3 Gallium t r i c h l o r i d e was prepared by direct combination of the elements. Pure chlorine gas (Matheson Ltd.) was dried by passing through concentrated sulphuric acid i n a bubbler and was then passed into the a l l glass apparatus shown i n Figure 14. The gallium metal, about 15 gms, (Alfa Inorganics Inc.) placed i n A soon melted on warming with a bunsen burner, and reacted with the chlorine, f i r s t to give a colourless l i q u i d , gallium tetrachlorogallate (64), Ga 2Cli t (melting point 170.5°C (65)). On adding more chlorine t h i s l i q u i d Ga 2Cli t disappeared and the l i q u i d gallium burned with a grey-white flame giving 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). 2Ga(l) + 2Cl 2(g) A (Ga +)(GaCli t ) 64-1 (Ga +)(GaCl 4")(l) + Cl 2(g) A •> Ga 2Cl 6 64-2 FIGURE 14 Gallium Trichloride Apparatus - 66 -The rate of flow of chlorine gas and rate of heating the molten gallium were adjusted so that most of the v o l a t i l e GaCl 3 was deposited i n the cooled receiver boat C. After a l l the gallium had reacted (essentially 100%), any sublimate i n A was driven into £ by warming and then flame sealing the constriction at B^. The apparatus was then evacuated and flame sealed at F_. The crude halide was then resublimed into the ampoules E_ and then these were sealed at t h e i r constrictions. 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 of Lithium Gallium hydride (66), LiGaH^ 4LiH + GaClo ^ § > LiGaH u + 3LiCl 66-1 6 room Temp. H An ampoule of GaCl 3, was weighed and broken open i n the dry box and placed i n a conical flask. The gallium t r i c h l o r i d e was then dissolved in diethyl ether and the ampoule washed several times to ensure quantitative removal of GaCl 3. The empty ampoule was reweighed and the weight of GaCl 3 determined. The ethereal solution of GaCl 3 and a l l the washings were now added to 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 solution brought up to about 150 ml. From the weight of GaCl 3 calculated, (8.59 gms; 48.8 mmoles) the weight of about 16 molar equivalents of f i n e l y ground lithium hydride (7.45 gms; 938 mmoles) (Alfa Inorganics Inc.), enough for a four-fold excess, was weighed out under nitrogen into the dumper tube. The reaction flask was cooled to -50°C i n an acetone-solid C0 2 bath and the dumper tube rotated upwards to permit the slow addition of LiH to the reaction flask over a period of about t h i r t y minutes. A bubbler was - 67 -attached to the apparatus so that the reaction could be carried out under a constant pressure of one atmosphere of nitrogen. The coolant was allowed to warm up to room temperature and the mixture was s t i r r e d for about f i f t y hours to ensure complete reaction. The resulting reaction mixture was f i l t e r e d through the glass sintered disc and a clear colourless f i l t r a t e resulted. This f i l t r a t e was then trans-ferred, i n the dry box, to a conical flask f i t t e d with a break seal and an extended neck which was flame sealed for storage. The LiGaH^ ether solution was observed to be i n d e f i n i t e l y stable i f stored i n a l l glass ampoules under a nitrogen atmosphere and cooled below 0°C. Lithium gallium deuteride, LiGaD^, was prepared and stored i n exactly the same manner as LiGaH 4, only lithium deuteride, LiD, (Alfa Inorganics Inc.) was substituted i n the preparation for lithium hydride. (c) Preparation of Trimethylamine Gallane (9), Me3NGaH-3 LiGaHi, + MeoNHCl • MeoNGaHo + L i C l + H ? 67-1 ^ 3 room temp. 0 3 . * A known amount of lithium gallium hydride (2.38 gms; 29.4 mmoles) i n ether solution 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 stoichiometric amount of trimethylamine hydro-chloride, Me3NHCl, (2.644 gms; 27.6 mmoles) (Alfa Inorganics Inc.) dried and p u r i f i e d by sublimation, was placed i n the dumper tube of the reaction vessel which contained a nitrogen atmosphere. The ether solution of 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 solution 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 reaction. The solution was next f i l t e r e d through the glass s i n t e r . and the receiver flask containing the clear ether solution was attached to the s u b l i -mation apparatus, see Figure 9. This apparatus was attached to the vacuum li n e and the ether was pumped o f f at -50°C. When most of the ether was removed, the residue was allowed to warm up to room temperature while the large bulb part of the sublimation apparatus was immersed i n an acetone-s o l i d C0 2 slush bath. The pure trimethylamine gallane was vacuum sublimed as long needle-like crystals into the cooled receiver. The overall y i e l d i n going from gallium t r i c h l o r i d e to trimethylamine gallane was about 60%. The deuterated compound, trimethylamine trideuterogallane, Me3NGaD3 was prepared i n the same manner only lit h i u m gallium deuteride was substituted for lithium igallium hydride. (d) Preparation of Trimethylamine Trichlorogallane, Me3NGaCl3 Me3N + GaCl 3 >- Me3NGaCl3 68-1 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 conical flask f i t t e d with a stopcock adaptor. The flask was removed from the dry box and evacuated on the vacuum l i n e . A very large excess of Me3N was then condensed on.tothe GaCl 3 at l i q u i d nitrogen temperature and then the mixture was slowly warmed up to 0°C and kept at th i s temperature for four hours. The excess Me3N i s then pumped o f f at -20°C and a white s o l i d of Me3NGaCl3 i s l e f t behind which was then examined by NMR and infrared spectroscopy. The y i e l d i s esse 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, Me3NGaH2Cl, and Dichlorogallane, Me2NGaHCl2 (11) Me3NGaH3 + HCl * Me3NGaH2Cl + H 2 69-1 Me3NGaH3 + 2HC1 * Me3NGaHCl2 + 2H 2 69-2 Trimethylamine monochlorogallane, Me3NGaH2Cl was prepared by weighing out 0.2414 gms (1.83 mmoles) of Me3NGaH3, into a conical flask f i t t e d with a stopcock adaptor and then evacuating the flask on the vacuum l i n e . 41.9 ml at NTP (1.83 mmoles) of HCl gas was condensed into the conical at l i q u i d nitrogen temperature and then the flask was allowed to warm up to room temperature. After about two hours the flask was frozen i n l i q u i d nitrogen and the noncondensable gas, hydrogen, pumped o f f with a Topler pump. Yi e l d of gas 42.1 ml at NTP (1.84 mmoles). The product Me3NGaH2Cl, could be sublimed under a dynamic vacuum at room temperature to a cold finger of a sublimer cooled to -78°C and collected as a white s o l i d . The trimethylamine dichlorogallane, Me3NGaHCl2 was s i m i l a r l y obtained 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 i n v o l a t i l e s o l i d , only s l i g h t l y soluble i n benzene. (f) Preparation of Trimethylamine Adducts of Dichloromonomethylgallane Me3NGaMeCl2 and Monochlorodimethylgallane, Me3NGaMe2Cl Method I (22, 47, 68) : Me^Si + GaCl 3 40°C ~* Me 3SiCl + 'MeGaCl2 69-3 - 70 -Me 3N + MeGaCl2 0°C * Me3NGaMeCl2 70-1 In the dry box an ampoule of GaCl 3 was weighed, broken open and placed i n the apparatus as shown i n Figure 15. The GaCl 3 was then sublimed into the reaction vessel by warming the outside of the tube and cooling the reaction vessel i n acetone-solid C0 2 slush bath, and the constriction flame sealed. The empty ampoule was then reweighed and the amount of GaCl 3 determined (5.60 gms; 31.7 mmoles). Excess tetramethylsilane, Me^Si, (3.44 gms; 39.0 mmoles) was condensed onto the GaCl 3 and the mixture warmed up to 40°C and allowed to react for two hours. The reaction vessel was then cooled to 0°C and the v o l a t i l e components, excess Mei+Si and Me 3SiCl, were pumped o f f and the desired product methyldichlorogallane, MeGaCl2, as a white s o l i d , stable under nitrogen at room temperature was l e f t i n the flask. On the vacuum l i n e an excess of Me3N gas (1.17 1 at NTP; 50.9 mmoles) was then condensed onto the s o l i d MeGaCl2 and the mixture held at 0°C for several hours after which the excess Me3N was pumped o f f , leaving a white s o l i d . The product was then examined by infrared and NMR spectroscopy. The y i e l d i n going from GaCl 3 to Me3NGaMeCl2 i s quite high. Only the dichloro gallium species i s prepared by this method. Method II Me3Ga + 2HC1 Et20 + MeGaCl2 + 2CH\ 70-2 room temp. Me3N + MeGaCl2 0°C * Me3NGaMeCl2 70-3 An ampoule containing GaMe3 (0.199 gms; 1.73 mmoles) was broken open i n the dry box and dissolved i n about 25 ml of diethyl ether i n a conical - 72 -flask f i t t e d with a stopcock adaptor. The flask was removed from the dry box, attached to the vacuum l i n e and HCl gas (77.5 ml at NTP; 3.46 mmoles) was condensed into the flask. The flask was warmed up to room temperature and kept at th i s temperature for 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 infrared spectrum) pumped o f f through a Topler pump. Yie l d of gas 76.9 ml at NTP. Into t h i s ether solution of MeGaCl2 was then condensed excess Me3N and allowed to react at room temperature f o r two hours. The unreacted Me3N and ether solvent were then removed at -20°C to leave a white powder behind who's spectra compares favorably with the infrared and NMR spectra of Me3NGaMeCl2 prepared by other methods. MeqGa + HCl E - ^ r > Me?GaCl + CHU 72-1 3 room temp. z H Me3N + Me2GaCl - • Me3NGaMe2Cl 72-2 Using one mole of HCl (37.7 ml at NTP; 1.73 mmoles) with one mole of Me3Ga (0.198 gms; 1.73 mmoles) and condensing on excess Me3N, the compound Me3NGaMe2Cl was e a s i l y prepared by a method analogous to that for the preparation of Me3NGaMeCl2. The y i e l d of these reactions was high. Method I I I Me3NGaMeo + 2Me3NGaCl3 ^ 3Me3NGaMeCl2 72-3 3 3 3 3 room temp. 3 z 2Me3NGaMe3 + Me3NGaCl3 > 3Me3NGaMe2Cl 72-4 3 3 3 3 room temp. 3 z To prepare the Me3NGaMeCl2 compound: , Me3NGaCl3 (0.349 gms; 1.48 mmoles) - 73 -and Me3NGaMe3 (0.129 gms; 0.74 mmoles) were weighed out i n the dry box, dissolved i n ether and put into a conical flask f i t t e d with a stopcock adaptor. This flask was removed from the dry box, attached to the vacuum li n e and the solvent removed at -20°C leaving a white powder behind which analysed by infrared and NMR spectroscopy as Me3NGaMeCl2-Me3NGaMe2Cl was prepared i n the same manner only using 0.159 gms (0.68 mmoles) of Me 3NGaCl 3 and 0.233 gms, (1.34 mmoles) of Me3NGaMe3. (g) Preparation of Trimethylamine Trimethylgallane, Me3NGaMe3 Me3N + GaMe3 • Me3NGaMe3 73-1 An ampoule of GaMe3 containing 2.16 gms (18.8 mmoles), prepared i n the laboratory, was broken open i n the glove box and placed i n a conical flask f i t t e d with a stopcock adaptor. On the vacuum l i n e Me3N gas, about ten times excess, was condensed onto the GaMe3 and allowed to react for about two hours at 0°C. The excess Me3N was then pumped o f f at -20°C and a white sblidy s l i g h t l y s t i c k y , was l e f t behind. The pure Me3NGaMe3 could be stored i n d e f i n i t e l y i n a nitrogen f i l l e d flask at room temperature. (h) Preparation of Trimethylamine Borane, Me3NBH3 LiBHi, + Me3NHCl —>- Me3NBH3 + L i C l + H 2 73-2 H 3 room temp. i 2 z Trimethylamine borane was prepared by a procedure si m i l a r to that for the preparation of Me3NGaH3, The differences being, lithium borohydride, LiBH^, was used i n place of LiGaH^, and the entire reaction was carried out at room temperature, i f the Me3NHCl was added below room temperature no - 74 -reaction was observed. (i) Preparation of Trimethylborane (67), Me3B, CH3Br + Mg n-butyl ether *MeMgBr 74-1 70°C 3MeMgBr + BF3- n-butyl ether •>• BMe 3 + 3MgBrF 74-2 70°C In the three-necked flask of the apparatus shown i n Figure 16 a Grignard, MeMgBr, was prepared i n the following manner. Clean magnesium turnings, (7.20 gms; 0.292- mmoles) (B § A Ltd.), 100 ml of dry n-butyl ether, and a few crystals of iodine were added to the flask and the entire 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 of 50°C. The mixture was vigorously s t i r r e d for about s i x hours, the magnesium was a l l consumed and the solution 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 3, measured out i n a calibrated gas bulb and condensed into 50 ml of n-butyl ether was added dropwise over a 4 hour period from the dropping funnel into the Grignard solution. The mixture was then warmed to 70°C, a slow stream of nitrogen bubbled through and the system maintained this way for an additional two hours, allowing the product to condense into 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 fractionation 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 of Trimethylamine Trimethylborane, Me3NBMe3 Me 3N + BMe3 > Me 3NBMe 3 76-1 A sample of BMe3 was measured out i n a gas bulb (2.61 cm of Hg i n 3.19-1 volume at 23°C) (4.92 mmoles) and condensed into a concial flask attached to the vacuum l i n e . A s l i g h t excess of Me3N (2.80 cm of Hg i n a 3.19 1 volume at 23°C) (5.08 mmoles) was condensed onto the BMe3 and allowed to react and warm up to room temperature. The excess Me3N was then pumped off at -20°C and a white s o l i d of Me3NBMe3 remained which was stored under a nitrogen atmosphere at room temperature. The y i e l d was 100%. (K) Preparation of Trimethylamine Trimethylalane, Me3NAlMe3 Me3N + AlMe 3 > Me3NAlMe3 76-2 Trimethylamine trimethylalane, Me3NAlMe3, was prepared by a procedure s i m i l a r to that used to prepare Me3NGaMe3, The difference i n the procedure was that trimethylaluminum (Alfa Inorganics Inc.) was used i n place of GaMe3 and only a s l i g h t excess of Me3N gas was used. (1) Preparation of Trimethylamine alane, Me3NAlH3 LiAHt, + MeoNHCl > Me^NAlHq + L i C l + H 9 76-3 H 3 room temp. 3 d z Trimethylamine alane Me 3NAlH 3, was prepared and p u r i f i e d i n the same way as Me3NGaH3, only LiAlH^ (Alfa Inorganics Inc.) was used i n place of LiGaH^. Care was taken to avoid the formation of the bis-amine adduct which i s quite stable, by using excess LiAlH^. - 77 -C. Reactions to Prepare Coordinated Organogallanes (a) Reaction of Trimethylamine Gallane, Me3NGaH3 with Dimethyl Mercury  Me2Hg 2Me3NGaH3 + Me2Hg • 2Me3NGaH2Me + H 2 + Hg 77-1 In a t y p i c a l reaction 0.373 gms (2.85 mmoles) of Me3NGaH3 and 0.338 gms (1.47 mmoles) of Me2Hg (Alfa Inorganics Inc.) were mixed i n a conical flask with 50 ml of benzene i n the dry box. The conical 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 of nitrogen while the benzene solution was refluxed. After 75 minutes graying of the solution was observed and the reaction was stopped. The conical flask was then capped and the solution f i l t e r e d i n the dry box. Then the conical flask was f i t t e d with a stopcock adaptor and the solution was concentrated by removing most of the benzene at -20°C by pumping i t o f f on the vacuum l i n e . The solution was then examined by infrared and NMR spectroscopy to be certain a definite product does ex i s t . (b) Reaction of Trimethylamine Adducts of Monochlorodimethylgallane,  Me3NGaMe2Cl, and Dichloromonomethylgallane Me3NGaMeCl2, with  Lithium Hydride, LiH. Me3NGaMeCl2 + 2LiH E t 2 ° > Me3NGaMeH2 + 2LiCl 77-2 Me3NGaMe2Cl + LiH E t 2 ° > Me3NGaMe2H + L i C l 77-3 Trimethylamine dichloromonomethylgallane, Me3NGaMeCl2 (0.178 gms; - 78 -0.919 mmoles) was weighed out, dissolved i n ether and placed i n the reaction-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 reaction mixture s t i r r e d for a period of two hours at room temperature. The reaction 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 l i k e material behind, which was then examined by infrared and NMR spectroscopy to confirm that a definite product did form. Trimethylamine monochlorodimethylgallane, Me3NGaMe2Cl, (0.271 gms; 1.26 mmoles) was reacted with 0.0274 gms (3.42 mmoles) of LiH i n a si m i l a r manner. Again a paste or o i l l i k e material resulted from the reaction which was then analysed by infrared and NMR spectroscopy. The y i e l d from these reactions was quite low. (c) Reaction of Trimethylamine Adducts of Monochlorogallane, Me3NGaH2Cl,  and Dichlorogallane, Me3NGaHCl2, with Lithium Methyl, LiMe MeoNGaHoCl + LiMe > MeoNGaH?Me + L i C l 78-1 3 z room temp. 3 z MeoNGaHClo + 2LiMe § > MeoNGaHMe2 + 2LiCl 78-2 3 z room temp 3 z A quantity of Me3NGaH2Cl (0.369 gms; 2.21 mmoles) was weighed out i n the dry box and dissolved i n 30 ml of ether i n a conical flask. Lithium methyl i n ether solution (3.51 ml of 0.63 M; 2.21 mmoles) was also added to this flask. The flask was allowed to stand for several hours at room tempera-ture and then, the white precipitate that formed was f i l t e r e d o f f and the clear solution put into a different flask. It was then f i t t e d with a stopcock adaptor, removed from the dry box attached to the vacuum li n e and the ether - 79 -pumped o f f at -70°C. An o i l remained i n the flask and when analysed by infrared and NMR compared favorably to Me3NGaH2Me prepared by other routes. In an analogous manner Me3NGaHCl2 (0.247 gms; 1.23 mmoles) and LiMe (1.3 ml of 1.89 M; 2.46 mmoles) were mixed together i n ether solution, f i l t e r e d and then the solvent removed to y i e l d a sticky o i l product. The infrared and NMR analysis indicates that some Me3NGaHMe2 was formed. (d) Equilibrium Reactions of Trimethylamine Gallane Me3NGaH3 with  Trimethylamine Trimethylgallane, Me3NGaMe3 1) Et 20 2 Me 3NGaH3 + Me 3NGaMe 3 ' — £ »• 3Me3NGaH2Me 79-1 . 3 3 3 0 room temp. 0 ^ 1) Et 20 Me 3NGaH3 + 2 Me oNGaMe 3 ^ ^ • 3Me 3NGaHMe2 79-2 3 3 3 3 room temp. 0 ^ These methylgallane species are prepared by mixing the two reagents i n a suitable solvent at room temperature i n the glove box. For monomethyl-gallane trimethylamine adduct, Me3NGaH2Me, a ty p i c a l preparation was mixing 0.398 gms (2.30 mmoles) of Me3NGaMe3 and 0.608 gms (4.60 mmoles) of Me3NGaH3 i n benzene. For trimethylamine dimethylgallane, Me3NGaHMe2 0.612 gms (3.51 mmoles) of Me3NGaMe3 and 0.232 gms (1.76 mmoles) of Me3NGaH3 were mixed in benzene. The solutions were then examined by NMR and infrared spectroscopy. To prepare a solvent of free pure compound diethyl .ether was a better solvent to use. In these cases, the ether solutions were placed i n a conical flask f i t t e d with a stopcock adaptor, attached to the vacuum li n e and the ether removed at -40°C leaving the product as an o i l or past l i k e substance. The deuterated analogs; trimethylamine monomethylbideuterogallane, Me3NGaD2Me, and trimethylamine dimethyldeuterogallane, Me3NGaDMe2, are - 80 -prepared i n the same manner, 0 . 1 2 6 gms ( 0 . 9 3 8 mmoles) of Me3NGaD3 was weighed out and dissolved i n a benzene solution containing 0 . 0 8 1 5 gms ( 0 . 4 6 9 mmoles) of Me3NGaMe3, to prepare the Me3NGaD2Me compound. To prepare the Me3NGaDMe2 compound, 0 . 0 5 1 2 gms ( 0 . 3 7 9 mmoles) of Me3NGaD3 and 0 . 1 3 2 gms ( 0 . 7 5 8 mmoles) of Me3NGaMe3 were mixed i n benzene solution. The infrared and NMR data were collected on these compounds. D. Miscellaneous Reactions of Coordinated Gallanes (a) Reaction o f Trimethylamine Monomethylgallane, Me3NGaH2Me with  Ethylene., C H 2 = C H 2 MeoNGaHoMe + 2CHo = C H ? benzene— y n M e N G a M e E t n 80-1 5 z z z room temp. 3 z Me3NGaH2Me ( 0 . 5 6 2 gms; 3 . 8 5 mmoles) was dissolved i n benzene i n the dry box, placed i n a conical flask f i t t e d with a stopcock adaptor and then the flask was attached to the vacuum l i n e . Ethylene gas ( 1 7 2 . 5 ml at NTP; 7 . 7 0 mmoles) was condensed onto the benzene solution o f Me3NGaH2Me at l i q u i d nitrogen temperatures and then the solution was allowed to warm up to room temperature and magnetically s t i r r e d . After seven hours at room temperature some graying o f the solution was observed but the manometer of the vacuum l i n e showed l i t t l e gas uptake. An NMR spectrum of the v o l a t i l e components collected i n a NMR tube connected to the vacuum l i n e was obtained and an infrared and NMR spectra of the benzene solution were also recorded. - 81 -(b) Reaction of Trimethylamine Monomethylgallane Me3NGaH2Me with Hydrogen Chloride, HCl Me3NGaH2Me + HCl benzene * Me3NGaHClMe + H 2 81-1 Me3NGaHClMe + HCl benzene +- Me3NGaMeCl2 + H 2 81-2 A benzene solution of Me3NGaH2Me (0.242 gms; 1.66 mmoles) was made up i n a conical flask i n the dry box. The flask 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 into the benzene solution and the mixture allowed to warm up to room temperature for about two hours, then the solution was frozen down again. The non-condensable gas was removed v i a a Topler pump, y i e l d of gas 35.4 ml at NTP. Infrared and NMR spectra of the gas liberated and of the benzene solution were recorded. A second portion of HCl gas (36.9 ml at NTP; 1.65 mmoles) was condensed into the above solution 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 infrared spectrum obtained, also the infrared and NMR spectra of benzene solution 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 flask. (c) Reaction of Trimethylamine Gallane, Me3NGaH3, with Methanol, MeOH Me3NGaH3 + nMeOH benzene 81-3 room temp. n where "n" = 1, 2, 3 In a t y p i c a l reaction 0.101 gms (0.77 mmoles) of Me3NGaH3 was weighed - 82 -out and dissolved i n about 15 ml of benzene i n a conical flask f i t t e d with a stopcock adaptor. This flask was then evacuated on the vacuum l i n e and 0.0486 gms (1.52 mmoles) of MeOH was condensed onto the benzene solution. After reacting the reagents for two hours at room temperature the flask was frozen i n l i q u i d nitrogen and the non-condensable gas, hydrogen, pumped o f f and measured with a Topler pump. Yie l d of gas 31.5 ml at NTP. A white s o l i d remained i n the flask on removal of benzene at low temperature. (d) Rearrangement Reaction Between Trimethylamine Alane, Me3NAlH3,  and Trimethylamine Trimethylalane, Me3NAlMe3 2MenNAlH. + MeoNAlMeo =^ • 3Me3NAlH?Me 82-1 i o t a room temp 3 z M e o N A l H o + 2Me q N A l M e o b e n z e n e h 3MeoNAlHMe 9 o o 6 i room temp 3 z 82-2 Trimethylamine monomethylalane, Me3NAlH2Me, was prepared by mixing Me 3NAlH 3 (0.0699 gms; 0.785 mmoles) and Me3NAlMe3 (0.0516 gms; 0.395 mmoles) i n 2 ml of pure benzene i n the dry box. Trimethylamine dimethylalane, Me3NAlHMe2, was prepared s i m i l a r l y by mixing Me 3NAlH 3 (0.0263 gms; 0.296 mmoles) and Me3NAlMe3 (0.0773 gms; 0.592 mmoles) i n 3 ml of benzene. 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 results (41). (e) Rearrangement Reaction Between Trimethylamine Borane, Me3NBH3 and  Trimethylamine Trimethylborane, Me3NBMe3 2MeoNBHq + MeoNBMeo b e n z e n e >- "Me3NBHoMe" 82-3 o o A 6 room temp 3 z MeoNBHo + 2MeqNBMeq benzene ^ "MeqNBHMeo" 82-4 o o A O room temp 3 z - 83 -In a t y p i c a l preparation 0.0700 gms (1.01 mmoles) of Me3NBH3 and 0.0561 gms (0.506 mmoles) of Me3NBMe3 were mixed together i n a few mis of benzene i n the dry box to prepare the compound trimethylamine monomethylborane, Me3NBH2Me. To prepare trimethylamine dimethylborane, Me3NBHMe2, 0.121 gms (1.09 mmoles) of Me3N(BtMe3 and 0.0375 gms (0.545 mmoles) of Me3NBH3 were s i m i l a r l y mixed together i n a few mis of benzene. Infrared and NMR spectra were recorded on a l l the solutions. (f) Mixed Rearrangement Reactions Using Different Group IIIB  Coordination Compounds A number of rearrangement reactions were attempted with different Group IIIB hydrido-and alkyl-trimethylamine adducts. A l l reaction mixtures were prepared i n the same manner. The s o l i d hydride compounds were weighed out i n a small beaker i n the dry box and a calculated volume of a standard benzene solution of one of the t r i a l k y l trimethylamine adduct, to make a one to one molar mixture, was syringed into the beaker containing the known weight of hydride or calculated volumes of the standard solutions of the t r i a l k y l compounds were mixed together i n a beaker. The resultant solutions were then examined by infrared and NMR spectroscopy. The following gives a l i s t of the reactions attempted and quantities of reagents used. Me3NAB3 + Me3NA'B3' • "Me3NAB , B' " + "MeoNA'B . B' . " . 3 1 5 3/2 3/2 d 3/2 3/2 where A, or A' = B, A l , Ga; and B or B1 = Me or H. - 84 -Me3NAB3 q u a n t i t y Me3NA'B'3 q u a n t i t y 1 Me3NBMe3 2 Me3NBMe3 3 Me3NAlMe3 4 Me3NGaMe3 5 Me3NAlMe3 6 Me3NAlMe3 7 Me3NBMe3 8 Me3NBMe3 9 Me3NAlMe3 10 Me3NGaMe3 0.58 ml of 0.490 M (0.282 mmoles) 0.80 ml of 0.490 M (0.394 mmoles) 0.72 ml of 0.197 M (0.141 mmoles) 1.0 ml of 0.141 M (0.141 mmoles) 1 ml of 0.197 M (0.197 mmoles) 1 ml of 0.197 M (0.197 mmoles) 1 ml of 0.490 M (0.490 mmoles) 1 ml of 0.490 M (0.490 mmoles) 1 ml of 0.197 M (0.197 mmoles) 1 ml of 0.141 M (0.141 mmoles) Me3NGaMe3 Me3NAlMe3 Me3NGaMe3 Me3NAlH3 Me3NGaH3 Me3NGaD3 Me3NAlH3 Me3NGaH3 Me3NBH3 Me3NBH3 2.0 ml of 0.141 M (0.282 mmoles) 2.0 ml of 0.197 M (0.394 mmoles) 1.0 ml of 0.141 M (0.141 mmoles) 0.0126 gms (0.141 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. Bibliography 1. 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