A Singlet Phosphinidene Stable at Room Temperature

We report the synthesis of a phosphorus analog of carbenes, namely a phosphinidene, that is stable for weeks in the solid state at room temperature. This compound, a (phosphino) phosphinidene, was prepared by irradiation-induced elimination of carbon monoxide from the corresponding (phosphino) phosphaketene. Because of the electronic properties of the substituent, this compound features a PP multiple bond, similarly to stable singlet aminocarbenes, which feature a nitrogen-carbon double bond. It undergoes a [2 + 1] cycloaddition with an electron-poor alkene and a [1 + 1] coupling reaction with isonitriles. We also show that, without steric protection, singlet phosphinidenes dimerize to give the corresponding diphosphenes.