Metastable states associated with a change in the metal–metal bonding network of (Mo^V)₆polyoxoanions: a DFT study of [(Mo₂^VO₄)₃(μ₆-CO₃)(μ-CO₃)₃(μ-OH)₃]⁵⁻

Abstract

DFT calculations carried out on the recently characterized cluster ion [(Mo 2 V O 4 ) 3 (µ 6 -CO 3 )(µ-CO 3 ) 3 (µ-OH) 3 ] 5Ϫ (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 (ϩ2.12 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 (ϩ1.43 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.