Valence Localization at a Bio‐inspired Mixed‐Valent {Cu2S}2+ Motif upon Solvation in Acetonitrile: Effect on Nitrous Oxide Reductase (N2Or) Activity

: We demonstrate, based on experimental and theoretical evidence, that the isolated [2(CH3 CN)2 ]2+ complex prepared in CH3 CN and containing a mixed-valent {Cu2II,I S} core evolves towards a new [2(CH3 CN)3 ]2+ species upon solvation in CH3 CN. Unlike its type III structural analogue [2(H2 O)(OTf)]+ active toward N2 O reduction, this new type I compound is inactive. This outcome opens new perspectives for a rational for N2 O activation using bio-inspired Cu/S complexes, especially on the role of the valence localization/delocalization and the Cu-Cu bond on the reactivity.