Synthesis and characterization of novel Wells-Dawson-type mono vanadium(V)-substituted tungsto-polyoxometalate isomers: 1- and 4-[S2VW17O62](5-).
Two vanadium(V)-substituted tungsto-polyoxometalate isomers, 1- and 4-[S2VW17O62](5-), were prepared as their tetra-alkyl ammonium salts from a W(VI)-H2SO4-V(V) reaction mixture in aqueous CH3CN solution. X-ray crystallographic structural analysis revealed that both isomers have a Wells-Dawson-type structure with a higher occupancy of vanadium at polar sites and belt sites for 1- and 4-[S2VW17O62](5-), respectively. The isomers were also characterized by elemental analysis, infrared, Raman, UV-vis, and (51)V NMR spectroscopies as well as voltammetry, and the data obtained were compared with that derived from [S2W18O62](4-). Significantly, the reversible potentials for the vanadium(V/IV) couple for both 1- and 4-[S2VW17O62](5-) in CH3CN (0.1 M n-Bu4NPF6) are considerably more positive than the tungstate reduction process exhibited by the [S2W18O62](4-) framework, implying that the presence of vanadium should be useful in catalytic reactions. The one-electron-reduced [S2V(IV)W17O62](6-) forms of both isomers were prepared in solution by controlled potential bulk electrolysis and characterized by voltammetry and EPR spectroscopy.
Department of Applied Science, Faculty of Science, Kochi University , Kochi 780-8520, Japan.
Tadaharu
T
Ueda
Miho
M
Ohnishi
Motoo
M
Shiro
Jun-ichi
J
Nambu
Toshiaki
T
Yonemura
John F
JF
Boas
Alan M
AM
Bond
D056831:Coordination Complexes / Q000737:chemistry*; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D017973:Tungsten Compounds / Q000737:chemistry*; D014639:Vanadium / Q000737:chemistry*; D000099294:Polyoxometalates
D056831:Coordination Complexes; D017973:Tungsten Compounds; D014639:Vanadium; C102296:polyoxometalate I; D000099294:Polyoxometalates