Synthesis and characterization of sterically hindered alkylaluminum-phosphorus and -arsenic compounds.: X-ray crystal structures of (Me3ECH2)3Al•E′(SiMe3)3 (E = Si, E′ = As; E = C, E′ = P, As), (Me3SiCH2)2(Br)Al•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 to 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 with P(SiMe3)(3). The dimers [(Me3SiCH2)(Br)AlP(SiMe3)(2)](2) (6) and [(Me3SiCH2)(Br)AlAs(SiMe3)(2)](2) (7) were isolated as products of the lithium halide elimination reactions of (Me3SiCH2)AlBr2 (10) with LiE(SiMe3)(2) (E = P, As), while reaction of (Me3SiCH2)(2)AlBr with these same lithium pnictide salts leads to the isolation of [(Me3SiCH2)(2)AlP(SiMe3)(2)](2) (8) and [(Me3SiCH2)(2)AlAs(SiMe3)(2)](2) (9). Various physical and spectroscopic data, including a variable-temperature NMR study of the dimeric compounds 6-9, are presented for the above compounds, as are the single-crystal X-ray structures of 2-7 and 9.