Two new multi-cobalt-containing heteropolyoxotungstates

Two new multi-cobalt-containing polyoxotungstates K4Na6Co2(H2O)12{Co(H2O)4[Co2(H2O)10Co4(H2O)2(B-α-SiW9O34)2]2} · 40H2O (1) and K10Na2[Co4(H2O)2(GeW9O34)2] · 20H2O (2) have been obtained by the routine synthetic reactions in aqueous solution. The polyoxoanion framework of 1 consists of two sandwich-type polyoxoanions [Co4(H2O)2(B-α-SiW9O34)2]12− connected together by a [CoO2(H2O)4] cluster to constitute the sandwich dimer, and then, four isolated Co(H2O)5 cations coordinate to the dimer through four μ2-O atoms. The polyoxoanion 2 is isomorphic to the sandwich-type polyoxoanion [Co4(H2O)2(B-α-SiW9O34)2]12− in 1. The magnetic property of compound 1 has been studied by measuring its magnetic susceptibility in the temperature range 2.0–300.0 K, indicating the existence of intramolecular ferromagnetic Co–Co interactions, and, the electrochemical properties of 1 and 2 are detected in the pH 4 buffer solution.