Surface‐like NO_x Reduction at an Atomically‐Precise Tricopper Cluster

The combustion of nitrogen-containing fuels and increasing use of nitrogen-rich fertilizers is accumulating NO_x pollutants in the environment. Copper is an attractive catalyst material for reductive NO_x remediation, yet ambiguity persists regarding the elementary bond-making and bond-breaking steps occurring at the catalyst interface. Starting from a molecular tricuprous μ₃-oxo complex (1), an unusually reduced and highly reactive surface-like cluster (2) has been prepared. Characterization data and electronic structure calculations are consistent with 2 featuring σ-aromaticity that primes the tricopper core for two-electron chemistry. Cluster 2 mediates catalytic reductive coupling of NO to N₂, proceeding through N₂O, via sequential oxygen atom transfer steps. Stoichiometric reduction of NO₃ ^- and NO₂ ^- is also disclosed, mapping the complete denitrification cycle at an atomically-precise molecular cluster.