A metal–amide dependent, catalytic C–H functionalisation of triphenylphosphonium methylide

We report the [Y{N(SiMe sub(3)) sub(2)} sub(3)] catalysed dehydrocoupling of triphenylphosphonium methylide with phenylsilane to form the silylated ylide Ph sub(3)PCHSiH sub(2)Ph. Attempts to catalyse this reaction with the related group 2 hexamethyldisilazide base [Ca{N(SiMe sub(3)) sub(2)} sub(2)] led to the catalytic formation of the phosphine Ph sub(2)PCHSiH sub(2)Ph along with Ph sub(2)PMe in low selectivity, while group 1 bases [M{N(SiMe sub(3)) sub(2)}] (M = Li, Na, K) proved ineffective for both transformations. The stoichiometric reactions of Ph sub(3)PCH sub(2) with [M{N(SiMe sub(3)) sub(2)} sub(n)] have been investigated and allowed the isolation and characterisation of a cyclometallated phosphonium methylide complex of yttrium.