[Fp*Fc][PF₆]: A remarkable non-symmetric dinuclear cation in a very stable mixed-valent state

We report herein dicarbonyl(pentamethylcyclopentadienyl)(ferroceniumyl)iron hexafluorophosphate, which contains a dimetallic cation with a remarkably stable mixed-valent (MV) structure and unexpected redox features. The electronic structure of this compound is discussed in the light of the existing Hush model, which suggests an unusually strong electronic coupling between the two iron centers, despite the non-symmetric environment of the metallic centers. End-to-end charge delocalization is not the main contributor to the extra-large stability of this MV complex, which originates from electronic effects other than the energetic difference between the two MV redox isomers (ΔG⁰). This open-shell derivative has also been briefly tested as a catalyst in the reductive etherification of aldehydes by hydrosilanes.