The first sandwich-type heteropolytungstates consisting of trivacant gallium(III)-substituted Keggin fragments

The new polyoxotungstates (NH4)(5)Na-9[Cu-4(H2O)(2)(GaW9-O-34)(2)](.)22H(2)O (1) and (NH4)(14)[Zn-4(H2O)(2)(GaW9O34)(2)](.)37H(2)O (2) were synthesized in aqueous solution and characterized by IR and Raman spectroscopy, energy dispersive X-ray fluorescence and single-crystal X-ray analysis. Compounds 1 and 2 contain the trivacant alpha-B-(GaW9O34)(11-) Keggin fragment, which is structurally characterized for the first time. The lacunary (GaW9O34)(11-) structure exhibits a centered Ga-[1] atom, which is bound to four oxygen atoms and thus achieves a tetrahedral coordination sphere. The synthesis of 1-2 enlarges the class of sandwich-type polyoxoanions and enables the syntheses of a new series of gallium(III)-substituted polyoxotungstates. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005).