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(η6-2-tBu-6-BF3-C6H3OH)] is designed and prepared, which affords the corresponding anionic Fe(I) sandwich complex [Cp*Fe(η6-2-tBu-6-BF3-C6H3OH)]- with an effective O-H bond dissociation free energy at 40.7 kcal/mol in tetrahydrofuran on treatment with KC8. 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.