A Four-Oxidation-State Family of Coordinated Carbon: The First Isolable and Crystallographically Characterized Triradical [M]−C4−[M]3+

The deep blue complex [Cp*(dippe)Fe(μ-C4)Fe(dippe)Cp*]3+[PF6]-3 (43+[PF6]-3) was prepared by a cascade of three successive one-electron oxidations of the neutral complex Cp*(dippe)Fe(μ-C4)Fe(dippe)Cp* (4). This unprecedented trication was characterized by X-ray methods, and its triradical structure was established on the basis of Mossbauer, near-IR, and ESR spectroscopy.