Generation and Reactivity of Methylphosphaketene in the Coordination Sphere of Tungsten

The [4 + 2] cycloadduct between the 1-methyl-2-keto-1,2-dihydrophosphinine pentacarbonyltungsten complex and dimethyl acetylenedicarboxylate can be used as a precursor for the methylphosphaketene tungsten complex under UV irradiation at room temperature. Under these conditions, the phosphaketene complex easily loses CO to give the methylphosphinidene complex. Highly reactive alcohols and primary alkylamines trap both the phosphaketene and the phosphinidene complexes. Less reactive phenol and bulky amines together with alkynes and conjugated dienes only trap the phosphinidene complex.