The coupling of coordinated isocyanide with a fragment diphosphinocarb
ene in the complexes fac-[Mn(CO)(3)(CNR){(PPh2)(2)Cl}] (3a, R = Ph; 3b
, R = Bu-t) leads to the formation of 4a,b, which contain the new kete
nimines [(PPh2)C=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-im
ino-2, 3-dihydroindole ligand.