Speciation of Molybdenum(VI) in Chloride Media at Elevated Mo Concentrations

[Image: see text] Speciation of Mo(VI) in chloride media (0.5–11 M HCl) at elevated Mo concentrations (0.1–300 mM Mo) was investigated using UV spectroscopy. In addition to five major monomeric species, H(2)MoO(4), H(3)MoO(4)(+), H(3)MoO(4)Cl, MoO(2)Cl(2), and MoO(2)Cl(3)(–), chemometric analysis of UV spectra suggests the presence of three cationic dinuclear species that predominate in solutions of 1–4.5 M HCl at >20 mM Mo concentrations. Thermodynamic values and molar absorptivity spectra were calculated from UV spectrophotometric data using refined numerical methods. The stability constants determined for three Mo dimers are log β = 3.53 ± 0.05 (H(2)Mo(2)O(5)(2+)), log β = 3.60 ± 0.04 (H(3)Mo(2)O(5)(3+)), and log β = 2.91 ± 0.03 (H(3)Mo(2)O(6)Cl(2+)).