Formation and structural characterization of a diiron aminoalkylidene complex with N-cyano substituent

The reaction of the isocyanide complex [Fe2Cp2(CO)3(CNMe)], 1Me, with BrCN (1.2 eq.), in acetonitrile at 60 °C, led to the low-yield isolation, after work-up, of the unprecedented N-methylcyanamido-(cyano)alkylidene complex [Fe2Cp2(CO)3{μ-C(CN)N(CN)Me}], 3. The synthesis of 3 represents an uncommon example of Csingle bondC bond forming cyanylation reaction taking place at a metal complex despite competitive oxidative addition pathways; it proceeded with the presumable, intermediate formation of a N-methylcyanamido-alkylidyne precursor readily undergoing CN– addition, and was accompanied by the production of minor amounts of [Fe2Cp2(CO)4] and monoiron(II) piano-stool compounds. Compound 3 was fully characterized by single crystal X-ray diffraction, elemental analysis, IR and NMR spectroscopy. The reaction of [Fe2Cp2(CO)4] with cyanogen bromide, under conditions resembling those employed for 1Me/BrCN, afforded a mixture of [FeCpBr(CO)2] and [FeCp(CN)(CO)2].