Ligand-centered oxidation in a diiron s-indacene complex

The reaction of 1,3,5,7 tetra-tert-butyl-s-indacene (Ic') with [Fe-2(CO)(9) ] gives the bimetallic complex [{Fe(CO)(3)}(2)Ic'], 1, where the two Fe(CO) (3) fragments are coordinated to the same face of the Ic' ligand. The cycli c voltammogram of 1 displays two quasi-reversible molecular oxidation waves and an irreversible molecular reduction wave. 1 can be chemically oxidized to its monocation with silver tetrafluoroborate. Comparison of the crystal structures of 1 and [{Fe(CO)(3)}(2)Ic'](+)[BF4](-). CH2Cl2, 2, shows littl e change in bond lengths on oxidation. Although, at first glance, 2 may app ear to be an Fe-0/Fe-I mixed-valence compound, Mossbauer and EPR spectrosco py suggest that that the ionized electron originates from a largely indacen e-based orbital. The structural and spectroscopic features of 1 and 2 have been rationalized by density functional calculations and compared to those of related systems.