A voltammetric study on the formation of V(V)- and V(IV)-substituted molybdophosphate(V) complexes in aqueous solution

Abstract The formation processes of V(V)- and V(IV)-substituted molybdophosphate complexes with the Keggin structure were studied by a combined redox and ion-transfer voltammetric study. There was a big difference in the formation processes between V(V)- and V(IV)-substituted mixed complexes in aqueous solution. The Mo(VI)+P(V)+V(IV) system produced a blue mixed complex in which the peripheral Mo atoms possessed the oxidation number of VI; only a mono-substituted complex was formed even in the presence of excess of V(IV). In the Mo(VI)+P(V)+V(V) system, on the other hand, evidence was obtained for the spontaneous transformation of a mono-substituted complex into mixed complexes with higher V(V) contents.

[1]  C. Hill,et al.  Role of Water in Polyoxometalate-Catalyzed Oxidations in Nonaqueous Media. Scope, Kinetics, and Mechanism of Oxidation of Thioether Mustard (HD) Analogs by tert-Butyl Hydroperoxide Catalyzed by H5PV2Mo10O40 , 1994 .

[2]  D. T. Lynch,et al.  Oxydehydrogenation of isobutyric acid with heteropolyacid catalysts: Experimental observations of deactivation , 1990 .

[3]  D. F. Boltz,et al.  Indirect ultraviolet spectrophotometric determination of vanadium utilizing molybdovanadophosphoric acid , 1968 .

[4]  M. Mellon,et al.  Colorimetric Determination of Phosphorus as Molybdivanadophosphoric Acid , 1944 .

[5]  M. Otake,et al.  Electron spin resonance studies of the reduced molybdovanadophosphoric heteropoly acids. I , 1973 .

[6]  M. Miwa,et al.  Metal-substitution of 12-Heteropolymolybdate with Iron Atoms , 1979 .

[7]  T. Osakai,et al.  Voltammetric study of the transfer of keggin-type heteropolyanions across the nitrobenzene/water interface , 1991 .

[8]  T. Osakai,et al.  Preparation and Properties of Heteropoly Molybdovanadate(V) Complexes , 1991 .

[9]  M. T. Pope,et al.  Models for heteropoly blues. Degrees of valence trapping in vanadium(IV)- and molybdenum(V)-substituted Keggin anions , 1975 .

[10]  E. Echigoya,et al.  12-Heteropolymolybdates as catalysts for vapor-phase oxidative dehydrogenation of isobutyric acid: 3. Molybdotungstophosphoric and molybdovanadophosphoric acids , 1984 .

[11]  T. Osakai,et al.  Synthesis and Characterization of Vanadium-Substituted Heteropoly Molybdosulfate(VI) Complexes , 1992 .

[12]  J. Grate,et al.  Multicomponent Polyanions. 46. Characterization of the Isomeric Keggin Decamolybdodivanadophosphate Ions In Aqueous Solution by 31P and 51V NMR , 1994 .

[13]  T. Osakai,et al.  Electrochemical Formation of 11-Molybdophosphate Anion at the Nitrobenzene/Water Interface and Its Applicability to the Determination of Orthophosphate Ion , 1991 .