Cyanide complexes of iron corrolates: Spin delocalization and autoreduction

Complex formation of (7,13-dimethyl-2,3,8,12,17,18-hexaethylcorrolato)iron chloride, [(7,13-Me2Et6C)FeCl], with cyanide ion in dimethylformamide, DMF-d(7), was studied by H-1 NMR spectroscopy. It is found that a bis-cyanide complex is formed initially, in which the electron configuration is a low-spin Fe(III) corrolate(2-.). This complex is not stable, and it is readily reduced with an excess of cyanide in the solution. The reduction occurs at the corrole ring instead of on the iron center giving the monocyanide complex of the low-spin Fe(III) corrole, [(7,13-Me2Et6C)FeCN](-). Thus, this is a case where an axial ligand serves as a reducing agent of the macrocycle and not of the metal.