Synthesis of the Prototypical Cyclic Metallocene Triad: Mixed-Valence Properties of [(FeCp)3(trindenyl)] Isomers**

Mixed-valence compounds, which have at least two redox sites in different oxidation states linked by a bridging ligand that promotes electron transfer from one site to the other, are excellent benchmarks for the study of intramolecular electron transfer (1). Transition metal complexes that display multielectron redox chemistry are therefore attracting much interest due to their potential applications in molecular materials for catalysis and electronics (2). In particular, compounds containing multiple ferrocene (Fc) units are suitable models since these units display versatile organic chemistry and a well-defined redox behavior (3-5). Although there have been many reports of biferrocenyl complexes,(1c, 3, 5) experimental (6) and theoretical (7) studies on oligoferrocene systems are relatively scarce despite their potential to highlight those factors that influence the mechanistic pathway of intercomponent electron transfer.