Synthesis, Structure and Hydrolysis Studies of Dimethyltris(Trimethylsilyl)Methylmetallanes of Aluminium and Gallium

The reactions of [(Me,Si),CLi. 2 thf] with Me,MCl (M = Al, Ga) afford the mixed trialkylmetallanes [(Me,%),- CAlMe,.thf] (1) and [(Me,Si),CGaMe,. thf] (2) in high yields. The coordinated THF molecule of compound 2 can be removed by sublimation in vacuo to yield the solvent-free product [(Me,%),- CGaMe,] (3). Hydrolysis of compound 2 with one equivalent of water at 0°C gives the trimeric hydroxide [f(Me,Si),- CGaMe(p-OH)),] (4), while the reaction with two equivalents of water at room tem perature yields the unusually stablc gallium hydroxide-water complex [{(Me,Si),- CGaMe(OH)(p-OH)MeGaC(SiMe,),} H20.2thf] (6). On heating, compound 6 is converted to the hydroxide [{(Me, si) 3 C} 4Ga4(P-O) z(P-OH)41 (5) 7 which has a heteroadamantane-like core. The hydrolysis of compound 1 with one equivalent of water at - 25 "C gives the dimeric hydroxide [{ (Me,Si),CAIMe( p OH)};2thf] (7), while the reaction with two equivalents of water results in the formation of the novei hydroxide [{(Me,Si),C~,Al.(p-O)2(~1-OH)41 (8)- which is isostructural to the gallium com pound 6 with the adamantane-like struc ture. The molecular structures of com pounds 1, 2, 4, 5.3THF, 6, 7 and 8.0.5THF have been determined by X-ray structure analysis. Compound 7 is the first structurally characterised alu minium hydroxide containing methyl groups, and 8 is the smallest structurally characterised galloxane hydroxide de scribed in literature