Design of bifunctional organometallic ‘electron reservoirs’: 35- to 38-electron sandwiches including the first stable, localized mixed valence complexes containing FeI

The new bimetallic complex (cpFe)(cp–cp)(FeC6Me6)+PF6–, (cp = C5H5)(2), synthesized from biferrocene and C6Me6, shows four oxidation states (FeIIIFeII)2+, (FeIIFeII)+, FeIIFeI, and (FeIIFe0)– reversibly connected by cyclic voltammetry; the first three are stable and can be isolated and Mossbauer spectroscopy was used to investigate the electronic structure of the localized mixed valence FeIIFeI.