Valence Localization at a Bio-inspired Mixed-Valent {Cu 2 S} 2+ Motif upon Solvation in Acetonitrile: Effect on Nitrous Oxide Reductase (N 2 Or) Activity

International audience; We demonstrate, based on experimental and theoretical evidence, that the isolated [2(CH3CN)2]2+ complex prepared in CH3CN and containing a mixed‐valent {Cu2II,IS} core evolves towards a new [2(CH3CN)3]2+ species upon solvation in CH3CN. Unlike its type III structural analogue [2(H2O)(OTf)]+ active toward N2O reduction, this new type I compound is inactive. This outcome opens new perspectives for a rational for N2O activation using bio‐inspired Cu/S complexes, especially on the role of the valence localization/delocalization and the Cu−Cu bond on the reactivity.