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 aryl)], [GaMe(PhNCPhNPh)(2)], [GaEt(PhNCMeNPh)(2)] and [Ga(PhNCRNPh)(3)](R = Me or Ph) have been isolated from the reaction of the appropriate gallium trialkyl with 1, 2 and 3 mol of amidine RNCR'N(H)R, respectively. 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 prepared. The compounds have been fully characterised, and mass spectrometric data indicate that the volatile dimethylgallium derivatives exist as either monomers or dimers in the gas phase. X-Ray crystallographic studies on [GaMe(2)(PhNCPhNPh)l and [GaMe(PhNCPhNPh)(2)] revealed monomeric structures and the presence of chelating amidinate ligands, with distorted tetrahedral and trigonal-bipyramidal co-ordination respectively at the metal centres. Cleavage of the Ga-Me bond occurs on photolysis in the. presence of a spin-trapping agent, and thermal decomposition of the solids leads to the formation of gallium nitride.