Synthesis,W-183 NMR spectroscopic characterization and properties of trisubstituted heteropolytungstates containing Group 3A elements

摘要

The heteropolytungstates alpha,beta -KaHbXW9M3O37(H2O)(3).n H2O (X = Si,Ge; M = Al, Ga, In, a + b = 7) are reported. All their W-183 NMR spectra consist of two lines with an intensity ratio 2:1, as expected for the C-3r structure of trisubstituted A alpha, A beta -Keggin anions. They have characteristic patterns of W-183 NMR chemical shifts: delta (belt) (W) > delta (cap) (W), Delta = delta (belt) - delta (cap) > 0 and Delta (alpha) (isomer) > Delta (beta) isomer. In addition, the chemical shifts of tungstosilicates shift 15 +/- 5 ppm upfield with respect to tungstogermanates, probably resulting from the different ionic radii of silicon and germanium. (C) 2001 Elsevier Science Ltd. All rights reserved. [References: 19]