Catalytic Reduction of Dinitrogen via Hydroboration
Shun Suginome, Atsushi Okochi, Taiji Nakamura, Asuka Konomi, Hiromasa Tanaka, Kazunari Yoshizawa, Yoshiaki Nishibayashi
Abstract
The conversion of dinitrogen (N 2 ) into ammonia (NH 3 ) or other nitrogenous compounds under mild conditions remains highly desirable, given the extremely harsh conditions required by the typically employed Haber–Bosch process, which reacts N 2 with dihydrogen (H 2 ) to produce NH 3 . However, the catalytic conversion of N 2 using H 2 or related compounds containing H–E bonds (where E represents a general element) as reductants under mild conditions has remained elusive. Herein, we report the catalytic reduction of N 2 via hydroboration, wherein N 2 (1 atm) reacts with catecholborane in the presence of molybdenum–nitride complexes bearing PCP-type pincer ligands as catalysts at 60 °C, yielding up to 32 equiv of borylamines based on the molybdenum atom. The catalytic reaction proceeds through three successive 1,2-additions of hydroborane to the molybdenum–nitrogen bond, disproportionation of the molybdenum–hydride complex, and regeneration of the molybdenum–nitride complex via cleavage of the nitrogen–nitrogen triple bond. The catalytic reduction of N 2 with a “H 2 equivalent” under mild reaction conditions represents a notable advance toward the development of ideal nitrogen fixation systems.