Triazenide-supported [Cu 4 S] structural mimics of Cu Z that mediate N 2 O disproportionation rather than reduction.

As part of the nitrogen cycle, environmental nitrous oxide (N 2 O) undergoes the N 2 O reduction reaction (N 2 ORR) catalyzed by nitrous oxide reductase, a metalloenzyme whose catalytic active site is a tetranuclear copper-sulfide cluster (Cu Z ). On the other hand, heterogeneous Cu catalysts on oxide supports are known to mediate decomposition of N 2 O (deN 2 O) by disproportionation. In this study, a Cu Z model system supported by triazenide ligands is characterized by X-ray crystallography, NMR and EPR spectroscopies, and electronic structure calculations. Although the triazenide-ligated Cu 4 (μ 4 -S) clusters are closely related to previous formamidinate derivatives, which differ only in replacement of a remote N atom for a CH group, divergent reactivity with N 2 O is observed. Whereas the formamidinate-ligated clusters were previously shown to mediate single-turnover N 2 ORR, the triazenide-ligated clusters are found to mediate deN 2 O, behavior that was previously unknown to natural or synthetic copper-sulfide clusters. The reaction pathway for deN 2 O by this model system, including previously unidentified transition state models for N 2 O activation in N-O cleavage and O-O coupling steps, are included. The divergent reactivity of these two related but subtly different systems point to key factors influencing behavior of Cu-based catalysts for N 2 ORR ( i.e. , Cu Z ) and deN 2 O ( e.g. , CuO/CeO 2 ).