Synthesis, structure of polymeric cobalt-containing heteropolytungstates and their applications in oxidation catalysis

The new polymeric compounds (Me4N)(2)Na-2[Na2Co2H2W12O42(H2O)(12)].16H(2)O (1) and Na-3 [NaCo3H2W12O42(H2O)(16)].22H(2)O (2) have been synthesized by reaction of sodium tungstate, and cobalt(II) nitrate. In these crystal structures the paratungstate-B units act as hexa- and octadentate ligands, respectively. Both crystal structures have been determined from single-crystal X-ray diffraction: they consist of paratungstate-B units which are linked to each other by Co-oxygen and Na-oxygen polyhedra. In the case of 1 this connection leads to layers of [Na2Co2H2W12O42(H2O)(12)](n)(4n-), 2 represents a three-dimensional polymeric structure consisting of anionic [NaCo3H2W12O42(H2O)(16)](n)(3n-) units. Crystal data for 1: monoclinic, space group C2/m, a = 20.295(4), b = 15.466(3), c = 13.204(3) Angstrom, beta = 121.04(3)degrees. Crystal data for 2: triclinic, space group P1,a = 12.288(2), b= 13.028(3), c= 14.894(3) Angstrom, alpha = 107.50(3)degrees, beta=99.30(3)degrees, gamma=111.82(3)degrees. The catalytic properties of both compounds for the oxidation of alcohols with H2O2 were studied. (C) 1997 Elsevier Science S.A.