SYNTHESIS AND CRYSTAL-STRUCTURE OF LI2[(ME3SICH2)3AL-CH2-AL(CH2SIME3)3] - A DILITHIOMETHANE DERIVATIVE

Reaction of (trimethylsilyl)methyllithium with the methylene-bridged aluminium tetrachloride Cl2Al-CH2-AlCl2 yields dilithium methylenebis[tris(trimethylsilylmethyl)aluminate] (2) as the only isolable product. All attempts for preparing the tetraalkyl analogue have been unsuccessful. The crystal structure of 2 exhibits a hexacoordinated central carbon atom with short Li-C distances. Both lithium atoms and the methylene hydrogens of the Al-CH2-Al unit are almost coplanar. The discussion of the structure and properties leads to the attractive description of 2 as an adduct of tris(trimethylsilylmethyl)aluminium to dilithiomethane CH2Li2.