Synthesis, structure and ESR spectrum of the triclinic and monoclinic forms of hydrated K 8[Mo 8(V IV)V 4O 40

Abstract

The triclinic K 8[Mo 8(V IV)V 4O 40]·10H 2O ( I) and monoclinic K 8[Mo 8(V IV) V 4O 40]·9 2O ( II) have been prepared from molybdenum(VI)-oxide and ammonium vanadate in aqueous solution by adding potassium hydroxide and their structures characterized by ESR spectra and X-ray structure analysis. The structure of the same [Mo 8(V IV)V 4O 40] 8− anion in both compounds is based on a central VO 4 tetrahedron surrounded by a puckered ring of eight edge-sharing MoO 6 octahedra, with four VO 4 tetrahedra filling the gaps between the pairs of octahedra. The ESR spectra of both compounds clearly indicate that one vanadium atom is in the +4 oxidation state. In the crystal structurek molybdovanadate anions are interconnected by K + ions and water molecules.