SYNTHESIS, STRUCTURE AND ESR-SPECTRUM OF THE TRICLINIC AND MONOCLINICFORMS OF HYDRATED K-8[MO-8(V-IV)V4O40]

The triclinic K-8[Mo-8(V-IV)V4O40]. 10H(2)O (I) and monoclinic K-8[Mo- 8(V-IV) V4O40]. 9H(2)O (II) have been prepared from molybdenum(VI)-oxi de and ammonium vanadate in aqueous solution by adding potassium hydro xide and their structures characterized by ESR spectra and X-ray struc ture analysis. The structure of the same [Mo-8(V-IV)V4O40](8-) anion i n both compounds is based on a central VO4 tetrahedron surrounded by a puckered ring of eight edge-sharing MoO6 octahedra, with four VO4 tet rahedra filling the gaps between the pairs of octahedra. The ESR spect ra of both compounds clearly indicate that one vanadium atom is in the +4 oxidation state. In the crystal structure molybdovanadate anions a re interconnected by K+ ions and water molecules.