Electron Delocalization from the Fullerene Attachment to the Diiron Core within the Active-Site Mimics of [FeFe]Hydrogenase

Attachment of the redox-active C<sub>60</sub>(H)­PPh<sub>2</sub> group modulates the electronic structure of the Fe<sub>2</sub> core in [(μ-bdt)­Fe<sub>2</sub>(CO)<sub>5</sub>(C<sub>60</sub>(H)­PPh<sub>2</sub>)]. The neutral complex is characterized by X-ray crystallography, IR, NMR spectroscopy, and cyclic voltammetry. When it is reduced by one electron, the spectroscopic and density functional theory results indicate that the Fe<sub>2</sub> core is partially spin-populated. In the doubly reduced species, extensive electron communication occurs between the reduced fullerene unit and the Fe<sub>2</sub> centers as displayed in the spin-density plot. The results suggest that the [4Fe4S] cluster within the H cluster provides an essential role in terms of the electronic factor.