Preparation and characterization of an α-Keggin-type [SW12O40]2-complex

A divanadium-substituted derivative of 12-tungstosulfate(VI), [S(V2W10)O-40](4-) was prepared as the tetrabutylammonium (n-Bu4N+) salt by heating a 50 nM (M = mol dm(-3)) W(VI)-20 mM V(V)-0.5 M H2SO4-50% (v/v) CH3CN system at 70 degreesC for 24 h. The [S(V2W10)O-40](4-) anion Was transformed spontaneously into a monovanadium-substituted derivative, [S(VW11)O-40](3-) in a 70% (v/v) CH3CN-1.0 M HCl system at 70 degreesC. Oil the other hand, [SW12O40](2-) was precipitated as the n-Bu4N+ salt upon heating a 95% (v/v) CH3CN-0.5 M HCl system containing [S(V2W10)O-40](4-). The single-crystal X-ray structural analysis revealed that the structure consisted of an alpha-Keggin-type [SW12O40](2-) anion. The [SW12O40](2-) anion was characterized by IR and UV-vis spectroscopy, and voltammetry.