2-ALKYLIDENEPHOSPHIRANES

Three stable alkylidenephosphiranes have been synthesized from the add ition of the terminal phosphinidene complex Ph-P-W(CO)5 to allene, 1,1 -dimethylallene, and tetramethylallene. Isopropylidenephosphirane 16b was characterized by a single-crystal X-ray structure determination. D emetalation of its W(CO)5 group provides the uncamplexed compound. The addition reaction with tetramethylallene also yields vinylphosphirane epimers, which rearrange to phospholene 20. Ab initio MP2/6-31G stru ctures and energies are presented for the parent uncomplexed methylene phosphirane and its dimethyl derivatives.