Estimation of the dissolved structures and condensation reactivities of mononuclear molybdenum(VI) species in solution using the UV-vis absorption spectra and molecular orbital calculation DV-X alpha

The dissolved structures of the mononuclear molybdate species, MoO42-, HMoO4-, and H2MoO4, in aqueous solution were estimated by optimizing their structure models so that their UV-vis absorption spectra were well reproduced by the DV-X alpha molecular orbital calculation. In this paper it is proposed that the former two species are tetrahedral ions, and the last is a distorted octahedral species. Using the values of the bond order obtained by a Mulliken population analysis the reason why the dimolybdate anion Mo2O72- does not exist, in contrast with the presence of the well-known dichromate anion Cr2O72-, has been explained. The key species which plays an important role in condensation reactions of molybdate system is not the HMoO4- ion, but the H2MoO4 With very weak Mo-OH bonds.