The electrophilic phosphinidene complex PhPW(CO)5 reacts with bis(imine) 5, possessing a single carbon spacer, to give the C−N insertion product 6. B3LYP/6-31G* calculations indicate that this process occurs by way of a 2,3-sigmatropic shift from the initially formed phosphane ylide. The alternative, 1,3-dipolar cycloaddition, followed by ring-opening of the bicyclic structure, can be ruled out since both steps are