Preparation and Reactivity of Anionic Iron Sandwich Complex Bearing π-Phenol Ligand Acting as Proton-Coupled Electron Transfer Reagent

A neutral Fe(II) sandwich complex bearing a π-phenol ligand with a trifluoroborate substituent [Cp*Fe(η(6)-2-(t)Bu-6-BF(3)-C(6)H(3)OH)] is designed and prepared, which affords the corresponding anionic Fe(I) sandwich complex [Cp*Fe(η(6)-2-(t)Bu-6-BF(3)-C(6)H(3)OH)](-) with an effective O-H bond dissociation free energy at 40.7 kcal/mol in tetrahydrofuran on treatment with KC(8). The anionic complex acts as a proton-coupled electron transfer reagent for the reduction of organic substrates such as acetophenone and anthracene, whereas the reaction with a Mo(IV) nitride complex leads to the stoichiometric formation of ammonia.