Formation of Metallacyclic Iron Carbene Complexes via C−O Coupling between the Two Ligands of Bis(carbamoyl) Intermediates

The bis(carbamoyl)iron complexes Fe[C(O)NR2]2(CO)4, prepared either by reaction of carbamoyl anions [Fe(C(O)NR2)(CO)4]- with 0.5 equiv of oxalyl chloride or by alkoxy/amine exchange from Fe(CO2Me)2(CO)4, undergo, even at low temperature, a rapid carbon−oxygen coupling of their two carbamoyl ligands to afford, after decarbonylation, stable metallacyclic carbenes of the general A mechanism of the reaction is proposed.