SYNTHESIS AND CHARACTERIZATION OF STERICALLY HINDERED ALKYLALUMINUM-PHOSPHORUS AND -ARSENIC COMPOUNDS - X-RAY CRYSTAL-STRUCTURES OF (ME3ECH2)(3)AL-CENTER-DOT-E'(SIME3)(3) (E = SI, E' = AS, E = C, E' = P, AS), (ME3SICH2)(2)(BR)AL-CENTER-DOT-P(SIME3)(3), AND [(ME3SICH2)(X)ALE(SIME3)(2)](2) (X = BR, E = P, AS, X = ME3SICH2, E = AS)

Reaction of (Me3SiCH2)(3)Al with E(SiMe3)(3) (E = P, As) in a 1:1 mole ratio affords the Lewis acid-base adducts (Me3SiCH2)(3)Al . P(SiMe3)( 3) (1) and (Me3SiCH2)(3)Al . As(SiMe3)(3) (2). Similarly, the 1:1 mole ratio reaction of (Me3CCH2)(3)Al with E(SiMe3)(3) (E = P, As) leads t o the isolation of (Me3CCH2)(3)Al . P(SiMe3)(3) (3) and (Me3CCH2)(3)Al . As(SiMe3)(3) (4). The adduct (Me3SiCH2)(2)(Br)Al . P(SiMe3)(3) (5) was obtained from the 1:1 mole ratio reaction of (Me3SiCH2)(2)AlBr wit h P(SiMe3)(3). The dimers [(Me3SiCH2)(Br)AlP(SiMe3)(2)](2) (6) and [(M e3SiCH2)(Br)AlAs(SiMe3)(2)](2) (7) were isolated as products of the li thium halide elimination reactions of (Me3SiCH2)AlBr2 (10) with LiE(Si Me3)(2) (E = P, As), while reaction of (Me3SiCH2)(2)AlBr with these sa me lithium pnictide salts leads to the isolation of [(Me3SiCH2)(2)AlP( SiMe3)(2)](2) (8) and [(Me3SiCH2)(2)AlAs(SiMe3)(2)](2) (9). Various ph ysical and spectroscopic data, including a variable-temperature NMR st udy of the dimeric compounds 6-9, are presented for the above compound s, as are the single-crystal X-ray structures of 2-7 and 9.