A new mixed-valent dicopper complex 5 was generated from ligand exchange by dissolving a bis­(CH3CN) precursor 3 in acetone. Introduction of a water molecule in place of an acetonitrile ligand was evidenced by base titration and the presence of a remaining coordinated CH3CN by IR, 19F NMR, and theoretical methods. The proposed structure (CH3CN–Cu–(SR)–Cu–OH2) was successfully DFT-optimized and the calculated parameters are in agreement with the experimental data. 5 has a unique temperature-dependence EPR behavior, with a localized valence from 10 to 120 K that undergoes delocalized at room temperature. The electrochemical signatures are in the line of the other aquo parent 2 and sensibly different from the rest of the series. Similar to the case of 2, 5 was finally capable of single turnover N2O reduction at room temperature. N2 was detected by GC-MS, and the redox character was confirmed by EPR and ESI-MS. Kinetic data indicate a reaction rate order close to 1 and a rate 10 times faster compared to 2. 5 is thus the second example of that kind and highlights not only the main role of the Cu–OH2 motif, but also that the adjacent Cu-X partner (X = OTf– in 2 and CH3CN in 5) is a new actor in the casting to establish structure/activity correlations.