Metastable states associated with a change in the metal–metal bonding network of (MoV)6 polyoxoanions: a DFT study of [(Mo2VO4)3(μ6-CO3)(μ-CO3)3(μ-OH)3]5−

Abstract

DFT calculations carried out on the recently characterized cluster ion [(Mo₂^VO₄)₃(μ₆-CO₃)(μ-CO₃)₃(μ-OH)₃]⁵⁻ (1) confirm the existence of three Mo–Mo bonds localized across the oxo ligands, with a strong alternation of the Mo–Mo distances (2.63/3.71 Å). The possibility of stabilizing a different organization of the metal–metal bond network is then investigated. A local energy minimum with high relative energy (+2.12 eV) is associated with the displacement of three metal–metal bonds across the hydroxo/carbonate bridging ligands. The six Mo–Mo distances are then equalized in the range 3.1/3.3 Å. The dimeric structure of 1 tied up by a network of six hydrogen bonds suggests the idea of a concerted displacement of the six protons along the H-bond pathways. Two equilibrium positions differing by the location of the Mo–Mo bonds are again characterized for this hypothetic isomer of 1. The most stable of these states (+1.43 eV with respect to the ground state of 1) is now associated with a network of relatively short Mo–Mo bonds (3.01 Å) localized across the carbonate ligands.