Synthesis and characterization of tris(trimethylsilyl)methyl halide derivatives of aluminum:: Potential precursors for low-valent aluminum compounds.: Crystal structures of [{(Me3Si)3CAlF2}3], [(Me3Si)3CAlX2•THF] (X = Cl, Br, I), and [{(THF)2K(Me3Si)3CAlF2(μ-F)F2AlC(SiMe3)3}2]

The novel bulky alkylaluminum dihalogenides [(Me3Si)(3)CAlX2 . THF] (X = F, 1; X = Cl, 4; X = Br, 5; X = I, 6) and dialkylaluminum halogenides [(Me3Si)(3)CAl(Me)X . THF] (X = Cl, 8; X = Br, 9; X = I, 10) have been prepared by reaction of the mixed trialkylalane [(Me3Si)(3)CAlMe2 . THF] with Me3SnX (X = F, Cl) and X-2 (X = Br, I) in a 2:1 and 1:1 molar ratio, respectively. The coordinated THF molecule of compound 1 can be removed by heating in vacuo to yield the trimeric solvent-free organoaluminium diflouride [{(Me3Si)(3)CAlF2}(3)] (2). Compound 2 shows no cocatalytic activity with group 4 metallocenes for ethylene polymerization. Reaction of [(Me3Si)(3)CAlF2 . THF] (1) with potassium fluoride gave the unusual coordination compound [C{(THF)(2)K(Me3Si)(3)CAlF2(mu-F)F2AlC(SiMe3)(3)}(2)] (3). The molecular structures of compounds 2-6 have been determined by X-ray structure analysis. Compound 2 is the first structurally characterized organoaluminum difluoride, and 6 is the first structurally characterized organoaluminum diiodide.