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

The reactions of [(Me 3 Si) 3 CLi2thf] with Me 2 MCl (M = Al, Ga) afford the mixed trialkylmetallanes [(Me 3 Si) 3 ‐CAlMe 2 ·thf] ( 1 ) and [(Me 3 Si) 3 CGaMe 2 ·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 3 Si) 3 ‐CGaMe 2 ] ( 3 ). Hydrolysis of compound 2 with one equivalent of water at 0°C gives the trimeric hydroxide [{(Me 3 Si) 3 CGaMe(μ‐OH)} 3 ] ( 4 ), while the reaction with two equivalents of water at room temperature yields the unusually stable gallium hydroxide‐water complex [{(Me 3 Si) 3 CGaMe(OH)(μ‐OH)MeGaC(SiMe 3 ) 3 ) H 2 O·2thf] ( 6 ). On heating, compound 6 is converted to the hydroxide [{(Me 3 Si) 3 C} 4 Ga 4 (μ‐O) 2 (μ ‐OH) 4 ] ( 5 ), which has a heteroadamantane‐like core. The hydrolysis of compound 1 with one equivalent of water at − 25°C gives the dimeric hydroxide [{(Me 3 Si) 3 CAlMe(μ‐OH)} 2 ·2thf] ( 7 ), while the reaction with two equivalents of water results in the formation of the novel hydroxide [{(Me 3 Si) 3 C} 4 Al 4 (μ‐O) 2 (μ‐OH) 4 ] ( 8 ), which is isostructural to the gallium compound 6 with the adamantane‐like structure. The molecular structures of compounds 1, 2, 4, 5 ·3THF, 6, 7 and 8 ·0.5 THF have been determined by X‐ray structure analysis. Compound 7 is the first structurally characterised aluminium hydroxide containing methyl groups, and 8 is the smallest structurally characterised galloxane hydroxide described in literature.