Metal-Assisted Synthesis of New and Highly Functionalized Diphosphines

The coupling of coordinated isocyanide with a fragment diphosphinocarbene in the complexes fac-[Mn(CO)₃(CNR){(PPh₂)₂CI}] (3a, R = Ph; 3b, R = ^tBu) leads to the formation of 4a,b, which contain the new ketenimines [(PPh₂)₂CCNR] (5a,b). The N-phenylketenimine in 4a undergoes a [4 + 1] cycloaddition by treatment with phenyl isocyanide to give 6, a neutral complex containing a unique 2-(diphosphinomethylidene)-3-imino-2,3-dihydroindole ligand.