Double Phosphaalkyne Insertion to a Tungsten Alkylidene: Formation of a Diphosphametallabicyclobutane

A unique diphosphametallabicyclobutane complex results from the reaction of the Schrock tungsten
neopentylidene with excess P⋮C-t-Bu, in contrast to
phosphaalkyne reaction products with similar molybdenum alkylidenes. A mechanistic rationalization for the
complex, which has been structurally characterized by
NMR spectroscopy and single-crystal X-ray analysis, is
postulated in terms of a ring-opening metathesis-like
mechanism.