PHOSPHINIDENETANTALUM(V) COMPLEXES OF THE TYPE [(N3N)TA=PR] AS PHOSPHA-WITTIG REAGENTS (R = PH, CY, TBU, N3N = (ME3SINCCH2CH2)3N)

A smooth reaction with aldehydes yielding phosphaalkenes and the oxotantalum complex [(N3N)Ta = O] is reported for the phosphinidine complexes mentioned in the title, which have a nucleophilic phosphorus atom. The crystal structure of [(N3N)-Ta = PR] (1, R = cyclohexyl) shows that the reactive Ta = PR unit is stabilized by its location within a pocket afforded by the SiMe3 substituents of the (N3N) ligand.