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

We demonstrate, based on experimental and theoretical evidence, that the isolated [2(CH 3 CN) 2 ] 2+ complex prepared in CH 3 CN and containing a mixed‐valent {Cu 2 II,I S} core evolves towards a new [2(CH 3 CN) 3 ] 2+ species upon solvation in CH 3 CN. Unlike its type III structural analogue [2(H 2 O)(OTf)] + active toward N 2 O reduction, this new type I compound is inactive. This outcome opens new perspectives for a rational for N 2 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.