SYNTHESIS AND CHARACTERIZATION OF TRIS(TRIMETHYLSILYL)METHYL HALIDE DERIVATIVES OF ALUMINUM - POTENTIAL PRECURSORS FOR LOW-VALENT ALUMINUM COMPOUNDS - CRYSTAL-STRUCTURES OF [((ME3SI)(3)CALF2)(3)], [(ME3SI)(3)CALX2-CENTER-DOT-THF] (X = CL, BR, I), AND (THF)(2)K(ME3SI)(3)CALF2(MU-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 halogenid es [(Me3Si)(3)CAl(Me)X . THF] (X = Cl, 8; X = Br, 9; X = I, 10) have b een 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 mo lar ratio, respectively. The coordinated THF molecule of compound 1 ca n be removed by heating in vacuo to yield the trimeric solvent-free or ganoaluminium diflouride [{(Me3Si)(3)CAlF2}(3)] (2). Compound 2 shows no cocatalytic activity with group 4 metallocenes for ethylene polymer ization. Reaction of [(Me3Si)(3)CAlF2 . THF] (1) with potassium fluori de gave the unusual coordination compound (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 fi rst structurally characterized organoaluminum difluoride, and 6 is the first structurally characterized organoaluminum diiodide.