Metal-Assisted Synthesis of New and Highly Functionalized Diphosphines

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