New Platinum Superoxo Complex. Kiselev Yu.M., Pankratov D.A., Shundrin L.A., Kiseleva I.N. //Russian Journal of Inorganic Chemistry. 1996. V. 41. № 12. P. 1963-1966
Products of oxidation of Pt(IV) hexahydroxo complexes with ozone in alkali media have been studied with physicochemical methods (electron spectroscopy, EPR, and cyclic voltammetry). The oxidation product is pink at alkali concentration in solution higher than 5 mol/l. The pink complex represents previously undescribed platinum superoxo complex with a bridging O2- group.
Our previous study concerned the possibility of preparing platinum compounds in unusually high oxidation states from alka1ine solutions under the action of ozone. In that study, we detected a blue platinum superoxo complex of binuclear structure with the O2- bridging group. The bridge structure of this complex was supported by ESR, and the complex was show to form only at rather low alkalinity. At higher alkali concentrations (cOH- > 5 mol/l), a similar reaction results in a pale pink complex containing oxidizer.
Solutions of the pink platinum complex have been obtained with ozonization of Pt(OH)62- solutions in KOH under ambient conditions. The alkali concentration was 5÷20 mol/l, and the overall content of platinum was (1.5÷6.0)·10-3 mol/l. Chemical analysis of solutions for platinum was performed by the techniques described in work (variants of iodometric titration with visual or potentiometric detection of the equivalence point). The conditions at which the pink compound is isolated into the solid phase have not been found (the variable factors: inorganic cation of different size, inorganic anion, temperature, concentrations of components).
The obtained results suggest that the pink compound formed by the reaction of O3 with Pt(OH)62- in highly alkaline medium is a binuclear hydroxo complex with a bridging superoxo group, structurally similar to analogous cobalt compounds.