Synthesis of Cobaltocenes Bearing 4‑(2,6-Dimethylpyridin-1-ium-4-yl)phenyl Moiety and Their Stoichiometric and Catalytic Reactivity toward Ammonia Formation

Novel cobaltocenium compounds bearing a 4-(2,6-dimethylpyridin-4-yl)phenyl group are designed and synthesized for the use of proton-coupled electron transfer (PCET) reagents. Reduction and protonation of these compounds afford the corresponding cobaltocenes bearing a 4-(2,6-dimethylpyridin-1-ium-4-yl)phenyl moiety with bond dissociation free energies (BDFEs) of 34.4–43.0 kcal/mol. A superstoichiometric amount of ammonia is formed from the catalytic reduction of dinitrogen with these cobaltocenes in the presence of a molybdenum-nitride complex under ambient reaction conditions.