Cerium(III) complexes with lacunary polyoxotungstates.: Synthesis and structural characterization of a novel heteropolyoxotungstate based on α-[SbW9O33]9- units

Several cerium(III) complexes with lacunary polyoxotungstates alpha-B-XW9O339- (X = As-III, Sb-III) and W5O186-, have been synthesized and characterized by single-crystal X-ray analysis, elemental analysis and IR spectroscopy. The X-ray analysis of Na-25[Ce(H2O)(5)As-4 W40O140] . 63H(2)O (1) reveals the framework of the well-known [As4W40O140](28-) anion with a {Ce(H2O)(5)}(3+) unit in the central site S1. The anion in (NH4)(19)[(SbW9O33)(4){WO2(H2O)}(2)Ce-3(H2O)(8)(Sb4O4)] . 48H(2)O (2) consists of a tetrahedral assembly of four alpha-B-(SbW9O339-)-W-III units connected by two additional six-coordinate tungsten atoms, three nine-coordinate monocapped square-antiprismatic cerium atoms and a Sb4O4 cluster. The Ce-III center in the [Ce(W5O18)(2)](9-) anion in Na-9[Ce(W5O18)] . NaCl . 30H(2)O (3) displays the square-antiprismatic environment observed in all complexes of the type [Ln(W5O18)(2)](n-).