MULTIPLE METAL-CARBON BONDS .14. PREPARATION OF ALKYLIDENETANTALUM COMPLEXES BY ALKYLIDENE TRANSFER FROM PHOSPHORANES - 1ST ETHYLIDENE COMPLEX AND HOW IT DECOMPOSES

The reaction of TaCp2(L)Me (L = PMe3 or PMe2Ph) with R3P=CHR′ (R = Me, Et, or Ph; R′ = H, Me, or Ph) gives L, R3P, and TaCp2(CHR′)Me in good yield. The ethylidene complex has properties much like other alkylidene complexes in this class, but most importantly, it does not rearrange to the known TaCp2(C2H4)Me complex under conditions where the latter is stable. Instead, it rearranges to TaCp2(propylene)H, possibly by migration of the alkyl to the alkylidene ligand followed by β-hydride elimination. © 1979.