Synthesis of molybdovanadates coordinated by oxalato ligands. The crystal structure of K-6 [Mo6V2O24 (C2O4)(2)] center dot 6H (2) O

摘要: The oxalato complex of a polyoxomolybdovanadate, K-6[Mo6V2O24(C2O4)(2)] . 6H(2)O has been obtained by reaction of potassium molybdate, ammonium vanadate and tartaric or ascorbic acid. Such conversion of dicarboxylate into oxalate ions indicates the catalytic role of molybdenum. Complexes of analogous composition also were obtained in the reactions of MoO3, V2O5 and potassium oxalate, or M2CO3 (M = Rb, Cs) and oxalic acid. The centrosymmetrical molybdovanadate anion [Mo6V2O24(C2O4)(2)](6-) consists of six MoO6 and two VO6 edge-sharing octahedra to give the gamma-[Mo6O26](4-) structure. All complexes were characterized by powder and single crystal X-ray analyses, ESR and IR spectra and TG and DSC measurements.