Catalytic Reduction of Dinitrogen via Hydroboration

Conversion of dinitrogen (N2) into ammonia (NH3) or other nitrogenous compounds under mild conditions is highly desired, considering the extremely harsh conditions for the Haber-Bosch process to react N2 with dihydrogen (H2). However, catalytic conversion of N2 using H2 or its analogues having H–E bonds (E represents any element) as a re-ductant under mild conditions has been elusive. Herein, we report the first catalytic reduction of N2 via hydrobora-tion, where N2 (1 atm) is reacted with catecholborane in the presence of molybdenum–nitride complexes bearing PCP-type pincer ligands as catalysts at 60 °C to afford up to 32 equiv of borylamines based on the molybdenum atom. The catalytic reaction proceeds through three successive 1,2-addition of hydroborane to molybdenum–nitrogen bond, disproportionation of molybdenum–hydride complex, and regeneration of molybdenum–nitride complex via cleav-age of nitrogen–nitrogen triple bond. Catalytic reduction of N2 with “H2 equivalent” under mild reaction conditions marks a substantial advancement in developing ideal nitrogen fixation systems.