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

Abstract Eight new compounds ofα-M a H b P 2 W 18−n (NbO 2 ) n O 62−n ·xH 2 O] types(M-K + ,Me 4 N + ,Et 4 N + or Bu 4 n N + ; n = 1, a+b =7; n = 3, a+b = 9) were synthesized from vacant heteropoly tungstate precursorsα 2 -[P 2 W 17 O 61 ] 10− and α-[P 2 W 15 O 56 ] 12− . The products were characterized by IR and UV, X-ray photoelectron spectra, polarography, cyclic voltammetry and 31 P NMR spectra. The IR and UV spectra confirm that these new compounds possess the Dawson structure. (NbO 2 ) ligands show an additional band at ca 870 cm −1 in the IR spectra. The polarographic results indicated that there was a polarographic reduction potential of O 2 2− at ca −0.3 V, and 31 P NMR spectra showed a sharp two-line spectrum for each anion,α 2 -[P 2 W 17 (NbO 2 )O 61 ] 7− ; −7.99 and −10.21 ppm; α-[P 2 W 15 (NbO 2 ) 3 O 59 ] 9− ; −6.69 and −10.83 ppm.