57Fe Mossbauer Spectroscopy Studies of New Examples of Fully Averaged Mixed Valence Diiron and Iron/Ruthenium Compounds

Abstract We report that the Fe(II/III) compounds [(Cp*Fe)2L]·+ (L =pentalene and symmetric indacene) appear to be fully averaged mixed valent binuclear species on a Mossbauer spectroscopy time scale (∼100 ns) above 1.5K. This indicates essentially zero energy barrier to intramolecular electron transfer. In contrast, for L = asymmetric indacene trapped (discrete) Fe(II) and Fe(III) valence states are observed at ambient temperature. Finally the heterobinuclear complex [Cp*FeLCoCp*]n (L = pentalene) is similar to the homobinuclear Fe(II) analog for for n = 0, 1+ and similar to low spin FeIII) for the n = 2+ dication. The high degree of delocalization for the monocationic diiron and iron/ruthenium systems is attributed to the fused structure of the bridging ligands.