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Abstract This study presents a mechanism of ammonia oxidation catalyzed by Ru II (NH 3 )PF 6 2 ( Ru =Ru(tpy)(dmabpy)) complexes. All intermediates, including the elusive Ru III (NH 2 ) 2+ and Ru IV (NH) 2+ , were detected, with several intermediates characterized spectroscopically. The catalytic cycle follows multiple reaction pathways branching at the key intermediates Ru III (NH 2 ) 2+ and Ru II (N 2 H 4 ) 2+ . The competition between the pathways is influenced by ammonia concentration and the local proton concentration generated during electrooxidation at the anode. In the N−N bond‐forming steps, dimerization of Ru III (NH 2 ) 2+ and nucleophilic attack of Ru IV (NH) 2+ by ammonia compete, while in the subsequent Ru II (N 2 H 4 ) 2+ oxidation, direct oxidation competes with proton‐catalyzed disproportionation. These findings provide molecular‐level insights into the catalytic cycle and offer guidance for developing more efficient ruthenium‐based ammonia oxidation catalysts.
Yuan et al. (Thu,) studied this question.