Catalytic Ammonia Oxidation to Dinitrogen by a Nickel Complex

Abstract We report a nickel complex for catalytic oxidation of ammonia to dinitrogen under ambient conditions. Using the aryloxyl radical 2,4,6‐tri‐ tert ‐butylphenoxyl ( t Bu 3 ArO⋅) as a H atom acceptor to cleave the N−H bond of a coordinated NH 3 ligand up to 56 equiv of N 2 per Ni center can be generated. Employing the N ‐oxyl radical 2,2,6,6‐(tetramethylpiperidin‐1‐yl)oxyl (TEMPO⋅) as the H‐atom acceptor, up to 15 equiv of N 2 per Ni center are formed. A bridging Ni‐hydrazine product identified by isotopic nitrogen ( 15 N) studies and supported by computational models indicates the N−N bond forming step occurs by bimetallic homocoupling of two paramagnetic [Ni]−NH 2 fragments. Ni‐mediated hydrazine disproportionation to N 2 and NH 3 completes the catalytic cycle.