Cleavage of Polarized P-P Bonds in N-Heterocyclic Diphosphines in Reactions with Metal Olefin Complexes

A CC-saturated N-heterocyclic diphosphine was prepared and reacted with W(CO)(4)(cod) in acetonitrile to give a mixture of two complexes arising from insertion of an acetonitrile molecule or a metal dicarbonyl fragment, respectively, into the P-P bond of the starting material. Cleavage of P-P bonds was likewise observed upon treating a diphosphine with metal olefin complexes; these reactions proceeded either by metal insertion to give phosphenium-phospholide complexes or via metathesis with formation of a P-chloro N-heterocyclic phosphine (NHP) and transfer of a phospholyl unit to the metal. The newly formed complexes were characterized by spectroscopic data and in several cases by single-crystal X-ray diffraction studies, and mechanistic explanations for the observed product diversity are proposed.