Formation of calcium-carbon bonds from a Lewis acid-base reaction of calcium bis[bis-(trimethylsilyl)amide] and tris(trimethylsilyl-methyl)alane

Treatment of calcium bis[bis(trimethylsilyl)amide] with two equivalents of tris (trimethylsilylmethyl) alane yields (Me3SiCH2)(2)Al-N(SiMe3)(2) (1) an d the dimer [(Me3Si)(2)N-Ca(mu-CH2SiMe3)(2)Al(CH2SiMe3)2](2) (2). The five- coordinate bridging carbon atoms show Ca-C bond lengths of 264 and 268 pm. A similar reaction with calcium bis[bis(trimethylsilyl)phosphanide] gives t he dimer [(Me3SiCH2)(2)Al-P(SiMe3)(2)](2) (3) with crystallographic C2 symm etry. A calcium-containing species is not isolable, however, in the presenc e of DME - ether cleavage reactions and the formation of the centrosymmetri c dimer [(Me3SiCH2)(2)Al-OCH2CH2OMe](2) (4) are observed. The central moiet y is an Al2O2 cycle with fivefold coordinated aluminium centers.