Unraveling N–O Cleavage and N–H Bond Formation for NO Reduction to NH 3 at a Bimetallic Fe–Mo Site

Reductive transformation of nitric oxide (NO) by heme proteins is critical for dissimilatory nitrate reduction to ammonium, a microbial nitrogen-conserving process. This study reports the complete reduction of bound NO to NH 3 on a bimetallic FeMo platform through a protonation-hydride reduction strategy. Protonation of the μ-NO group generated a μ-NOH intermediate, which, upon reaction with HBpin, underwent simultaneous N–O bond cleavage and N–H bond formation to give a μ-NH imide. Subsequent transformations among nitride, imide, and amide were achieved via deprotonation/protonation and the additions of hydride, hydrogen atoms, and H 2 provide molecular-level mechanistic insight into ammonia synthesis and nitrogenous-species interconversion.