First 12-tungstovanadate Keggin compound: synthesis and crystal structure of [Me4N]7[VW12O40]·15H2O

Abstract

The hydrothermal reaction of Na₂WO₄·2H₂O with finely powdered vanadium metal and tetramethylammonium chloride at 160 °C gave an orange solution which yielded the 12-tungstovanadate Keggin compound [Me₄N]₇[VW₁₂O₄₀]·15H₂O 1. This novel compound has been characterized by the IR, UV-VIS and EPR spectroscopic methods, manganometric titration, and single crystal structure analysis. The crystal structure consists of discrete tetramethylammonium cations, lattice water molecules, and anions of the mixed-valence species [VW₁₂O₄₀]^7–. The anion cluster contains tungsten addenda atoms and a {V^IVO₄} group at its center which is responsible for the overall tetrahedral symmetry of the near spherical polyanion.