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.