Synthesis and Characterisation of Polyoxotungstate Compounds With Complex Copper and Cobalt Cations

Salts of the heteropolytungstates [PW11 M(H2O)O39]5-, M=Cu, Co, Mn, with the following complex cations were prepared: [Cu(LL)2(H2O)]2+, [Cu(LL)3]2+, LL= 1,10-phenantroline (phen), 2,2′-bipyridine (bipy), [Cu(phen)2Cl]+, [Co(bipy)2(CO3)]+, and [Co(phen)3]2+, Compounds with [SiW11 M(H2O)O39]6-, M=Cu, Co, Mn, and the cations [Co(LL)2(H2O)]2+, and [Co(bipy)2(CO3)]+ were also prepared. Synthesis was carried out in aqueous or nitromethane solutions. The compounds were characterised b y elemental and thermal analysis and spectroscopic techniques. Spectroscopic properties and the thermal stability of the polyanions in these compounds could thus be compared with those of simpler salts. BET surface areas were determined. Except for salts of [Cu(bipy)3]2+, the compounds decompose on heating at temperature above 200°C, the exact temperature depending on the cation. Some are stable up to 300°C. For salts of the [Cu(LL)2(H2O)]2+ cations, more detailed thermal studies were performed, based on the infra red spectra of the decomposition products obtained at several temperatures.