Redox Properties of the Chini Clusters [Pt3(CO)6]n2– (n = 1–7) in Solution: A Hybrid DFT Study. Application to their Oxidation by O2

Abstract

The Chini clusters (Pt3(CO)6)n2– display fascinating size-dependent redox properties. These redox properties are poorly described by ordinary density functional theory (DFT) calculations. In particular, the functionals PBE, B3LYP, and MPW1K yield very poor values of the reduction potentials of the couples (Pt3(CO)6)n–/(Pt3(CO)6)n2– in solution, suggesting that the clusters resist oxidation by O2 in contradiction to the experimental evidence. We propose an original hybrid DFT method, using PBE for the metal and MPW1K for the CO ligands, which yields much more realistic values of the reduction potentials. As an application we show that the growth of the Chini clusters subsequent to their oxidation is due to a transfer of the neutral Pt3(CO)6 unit from the oxidized to a nonoxidized cluster.