Interaction of Molybdophosphates with Palladium(II) Salts in Aqueous Solution
Russian Journal of Inorganic Chemistry
, E-ISSN: 1531-8613
Boreskov Institute of Catalysis SB RAS
UV-Vis spectroscopy and P-31 NMR spectroscopy were used to study the interaction of H3PMo12O40 with H2PdCl4 or PdSO4 in aqueous solution at pH 3.0-4.5 and the ratio [Pd(II)] : [H3PMo12O40] = 1:1. Palladium(II) remains in solution in the form of intensely colored hydroxo species and does not change the structure of the newly formed unsaturated heteropolymolybdates PMo11O397- and PMo9O349- as shown by NMR data. Heteropoly compounds precipitated from tetrabutylammonium (TBA) or cesium salts were characterized using IR spectroscopy, differential dissolution (DD), and elemental analysis. It was found that the composition of a compound was affected by not only formation conditions in the solution but also the precipitant cation. In the absence of Pd(II), TBA(+) precipitated a salt of PMo11 heteropoly anion (HPA); Cs+ precipitated a salt of PMo9 HPA from the same solutions. DD analysis identified the Cs salts precipitated in the presence of Pd(II) as complexes PMo9 and PMo9Pd. The conclusion was drawn that Pd(II) interacted with unsaturated heteropolymolybdates more weakly than with their analogues PW11O397- and PW9O349-. This weak interaction can consist of the adsorption of Pd(II) species on negatively charged HPAs.