Phosphinidene addition to conjugated allenes

Generating the transient electrophilic tungsten pentacarbonyl- phenylphosphinidene complex PhP=W(CO)₅ in the presence of 2,7-dimethyloc-ta-2,3,5,6-tetraene leads to the formation of a 3,4-di-substituted phosphole or a complexed phospholene, depending on the reaction conditions. The formation of the phospholene results from the reaction of PhP=W(CO)₅ with the diallene, while the formation of the phosphole arises from reaction with 3,4-diiso-propylidene-cyclobutene, which is formed in situ from the isomerization of the conjugated allene.