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

摘要

The heteropolytungstates #alpha#, #beta#-K_aH_bXW_9M_3O_37(H_2O)_3·nH_2O (X = Si, Ge; M = Al, Ga, In, a + b = 7) are reported. All their ~183W NMR spectra consist of two lines with an intensity ratio 2:1, as expected for the _3v structure of trisubstitued A#alpha#, A#beta#-Keggin anions. They have characteristic patterns of ~183W NMR chemical shifts: #delta#_(belt w) > #delta#_(cap w_), #DELTA# = #delta#_belt - #delta#_cap > 0 and #DELTA#_(x 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.