Silaborates with an unprecedented cluster geometry

The reaction of o-silaborane with a series of carbanions is presented. Addu cts of o-silaborane were prepared in reaction with Grignard reagents (RMgBr R = Me, Ph, benzyl, allyl, vinyl, and ethinyl) (3a-f). The salts were isol ated in high yield and characterized by elemental analyses and NMR spectros copy. In the case of the benzylide adduct the structure in the solid state was determined by X-ray single-crystal structure analysis. Ab initio calcul ations were carried out on the methylide derivative [Me3Si2B10H10](-), and results of the geometry optimizations together with calculated NMR chemical shifts are discussed. The first substitution reaction at a silicon vertex of the o-silaborane skeleton is presented with the synthesis of [MeSiPhSiB1 0H10], which is characterized by X-ray crystal structure analysis.