Phosphinidene addition to conjugated allenes

Generating the transient electrophilic tungsten pentacarbonyl-phenylphosphinidene complex PhPW(CO)5 in the presence of 2,7-dimethylocta-2,3,5,6-tetraene leads to the formation of a 3,4-disubstituted phosphole or a complexed phospholene, depending on the reaction conditions. The formation of the phospholene results from the reaction of PhPW(CO)5 with the diallene, while the formation of the phosphole arises from reaction with 3,4-diisopropylidene-cyclobutene, which is formed in situ from the isomerization of the conjugated allene.