Electrophilic functionalization of N2 moieties in metal dinitrogen complexes typically initiates the catalytic synthesis of N-containing molecules directly from N2. Despite intensive research in the last six decades, how to efficiently and even quantitatively convert N2 into diazenido and hydrazido species still poses a great challenge. In this regard, systematic and comprehensive investigations to elucidate the reaction intricacies are of profound significance. Herein, we report a kinetic dissection on the first and second electrophilic functionalization steps of a new Cr0–N2 system with HOTf, MeOTf, and Me3SiOTf. All reactions pass through fleeting diazenido intermediates and furnish long-lived final hydrazido products, and both steps are quantitative conversions at low temperatures. All of the second-order reaction rates of the first and second transformations were determined as well as the lifetimes of the intervening diazenido species. Based on these findings, we succeeded in large-scale and near-quantitative preparation of all hydrazido species.

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Multimetallic nitride species, especially those containing biologically related iron or molybdenum, are fundamentally important to understand the nitrogen reduction process catalysed by FeMo‐nitrogenase. However, until now, there remains no report about the construction of structurally well‐defined FeMo heteronuclear nitrido complex and its reactivity toward ammonia formation. Herein, a novel thiolate‐bridged FeIIMoVI complex featuring a bent Fe−N≡Mo fragment is synthesized and structurally characterized, which can be easily protonated to form a μ‐imido complex. Subsequently, through the proton‐coupled electron transfer (PCET) process, this imido species can smoothly convert into the μ‐amido complex, which can further undergo reductive protonation to afford the FeMo complex containing an ammine ligand. Overall, we present the first well‐defined {Fe(μ‐S)2Mo} platform that can give a panoramic picture for the late stage (N3−→NH2−→NH2−→NH3) of biological nitrogen reduction by the heterometallic cooperativity.