No abstract

The amidinato compounds [GaMe,L] [L = RNCR'NR (R, R' = H, alkyl or aryl)], [GaMe(PhNCPhNPh),], [GaEt(PhNCMeNPh),] and [Ga(PhNCRNPh),] (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 [GaCl,{ RNCR'N(H)R)] (R = Ph or p-ClC,H,; R' = Me) and [GaC12(p-C1C,H,NCMeNC,H,C1-p)l 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,(PhNCPhNPh)] and [GaMe(PhNCPhNPh),] 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.* Non-SZ units employed: G = T, eV z 1.60 x 10 l 9 J.

Treatment of Ti c14 with carboxylic acids RC02H (R = C6F5, CH2CcF5, CH20C6F5) yields a series of titanium 0x0 compounds; the X-ray molecular structure of [TiO(02CC6F5)21 reveals an octameric unit and a unique 16-mem bered T i 8 0 8 ring, with two toluene molecules encapsulated above and below the ring in the molecular cavity.

Reaction of T1,( 7, 8-C2BgHll) with Et,NCS,AuBr, affords the known ion (1,2-C,B,Hl1),Au-, and also the novel 1 %electron species ( 1, 2-C,BgHll) Au (S,CNEtJ which is shown from X-ray data to have the 'slipped' structure previously found only in 20-or 21-electron systems; a similar structure is also deduced for the 18 electron compound (Ph,P),Pt( l,2-C2BQHll).

Reaction of N bCI, with aryl carboxylic acids yields the oxoniobium carboxylates [{N bCI,( O,CR)},O]