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Earth‐abundant metal‐catalyzed oxidative conversion of ammonia into dinitrogen is a promising process to utilize ammonia as a transportation fuel. Herein, we report the manganese‐catalyzed ammonia oxidation under chemical or electrochemical conditions using a manganese complex bearing (1S,2S)‐N,N′‐bis(3,5‐di‐tert‐butylsalicylidene)‐1,2‐cyclohexanediamine. Under chemical conditions using oxidant, up to 17.1 equivalents of N2 per catalyst are generated. Also, mechanistic studies by stoichiometric reactions reveal that a nucleophilic attack of ammonia on manganese nitrogenous species occurs to form a nitrogen–nitrogen bond leading to dinitrogen. Moreover, we conduct density functional theory (DFT) calculations to confirm the plausible reaction mechanism. In addition, this reaction system is applicable under electrochemical conditions. The catalytic reaction proceeds with 96 % faradaic efficiency (FE) in bulk electrolysis to give up to 6.56 equivalents of N2 per catalyst. [ABSTRACT FROM AUTHOR]

The direct formation of ammonia from molecular dinitrogen under mild reaction conditions was achieved by using new cobalt dinitrogen complexes bearing an anionic PNP-type pincer ligand. Up to 15.9 equivalents of ammonia were produced based on the amount of catalyst together with 1.0 equivalent of hydrazine (17.9 equiv of fixed nitrogen atoms). [ABSTRACT FROM AUTHOR]

Keywords: ammonia oxidation; dinitrogen; electrochemical oxidation; heterogeneous catalysis; transition metal complexes EN ammonia oxidation dinitrogen electrochemical oxidation heterogeneous catalysis transition metal complexes 1498 1498 1 11/30/21 20211101 NES 211101 B The Cover Feature shows b manganese-catalyzed ammonia oxidation, which is currently attracting attention because of its potential applications to direct ammonia fuel cells. Ammonia oxidation, dinitrogen, electrochemical oxidation, heterogeneous catalysis, transition metal complexes Furthermore, mechanistic studies, including density functional theory (DFT) calculations, reveal that nucleophilic attack of ammonia on manganese imide complexes occurs to form a nitrogen-nitrogen bond leading to dinitrogen. [Extracted from the article]

Until 2015, well-defined transition metal complexes capable of catalyzing nitrogen reduction into ammonia or silylamines were limited to molybdenum and iron complexes, which are relevant to biological nitrogen fixation. In the last five years, other transition metal complexes not related to nitrogenases have been reported to exhibit catalytic activity toward nitrogen fixation under mild reaction conditions. This review article describes the historical background and recent advances on the conversion of dinitrogen into ammonia or silylamines catalyzed by transition metal complexes other than vanadium, molybdenum, and iron complexes. [Display omitted] • Summary of the nitrogen fixation catalyzed by metal complexes except for Mo, Fe, V. • Ti, Re, Ru, Os, and Co complexes are active for catalytic NH 3 formation. • Ti, Cr, W, Mn, Re, Co, Rh, Ir, Ni, and U complexes catalyze dinitrogen silylation. [ABSTRACT FROM AUTHOR]