Preparation and characterization of new peroxyniobium-containing phosphotungstates with dawson structures

Eight new compounds ofα-MaHbP2W18−n(NbO2)nO62−n·xH2O] types(M-K+,Me4N+,Et4N+or Bu4nN+; n = 1, a+b =7; n = 3, a+b = 9) were synthesized from vacant heteropoly tungstate precursorsα2-[P2W17O61]10− and α-[P2W15O56]12−. The products were characterized by IR and UV, X-ray photoelectron spectra, polarography, cyclic voltammetry and31P NMR spectra. The IR and UV spectra confirm that these new compounds possess the Dawson structure. (NbO2) ligands show an additional band atca 870 cm−1 in the IR spectra. The polarographic results indicated that there was a polarographic reduction potential of O22− atca −0.3 V, and31P NMR spectra showed a sharp two-line spectrum for each anion,α2-[P2W17(NbO2)O61]7−; −7.99 and −10.21 ppm; α-[P2W15(NbO2)3O59]9−; −6.69 and −10.83 ppm.