SYNTHESIS AND PROPERTIES OF SOME GALLIUM AMIDINE COMPLEXES [GAX(Y)L(3-Y)] [X=ME, ET OR CL L=RNCR'NR (R,R'=H, ALKYL OR ARYL), Y=0-2] - CRYSTAL-STRUCTURES OF [GAME(2)(PHNCPHNPH)] AND [GAME-(PHNCPHNPH)(2)]

The amidinato compounds [GaMe(2)L] [L = RNCR'NR (R, R' = H, alkyl or a ryl)], [GaMe(PhNCPhNPh)(2)], [GaEt(PhNCMeNPh)(2)] and [Ga(PhNCRNPh)(3) ](R = Me or Ph) have been isolated from the reaction of the appropriat e gallium trialkyl with 1, 2 and 3 mol of amidine RNCR'N(H)R, respecti vely. The chloro derivatives [GaCl3 {RNCR'N(H)R}] (R = Ph or p-ClC6H4; R' = Me) and [GaCl2(p-ClC(6)H(4)NCMeNC(6)H(4)Cl-p)] have also been pr epared. The compounds have been fully characterised, and mass spectrom etric data indicate that the volatile dimethylgallium derivatives exis t as either monomers or dimers in the gas phase. X-Ray crystallographi c studies on [GaMe(2)(PhNCPhNPh)l and [GaMe(PhNCPhNPh)(2)] revealed mo nomeric structures and the presence of chelating amidinate ligands, wi th distorted tetrahedral and trigonal-bipyramidal co-ordination respec tively at the metal centres. Cleavage of the Ga-Me bond occurs on phot olysis in the. presence of a spin-trapping agent, and thermal decompos ition of the solids leads to the formation of gallium nitride.