Singlet (Phosphino)phosphinidenes are Electrophilic

A room-temperature stable (phosphino)phosphinidene reacts with carbon monoxide, stable singlet carbenes, including the poor pi-accepting imidazol-2-ylidene, and phosphines giving rise to the corresponding phosphaketene, phosphinidene-carbene and phosphinidene-phosphine adducts, respectively. Whereas the electronic ground-state calculations indicate a PP multiple bond character in which the terminal phosphorus is negatively charged, the observed reactivity clearly indicates that (phosphino)phosphinidenes are electrophilic as expected for an electron-deficient species. This is further demonstrated by competition experiments as well as by the results of Fukui function calculations.