High stable sandwich-type polyoxometallates based on A-β-SiW9O3410-. Synthesis, chemical properties and characterization of [(A-β-SiW9O34)2(MOH2)3CO3]13− (M = Y3+ and Yb3+)

Highly hydrolytic and thermally stable sandwich-type polyoxometallates of [(A-β-SiW9O34)2(MOH2)3CO3]13− (M = Y3+ and Yb3+) have been synthesized and characterized by elemental analysis, IR, 13C and 29Si NMR, UV-Vis spectroscopy, TGA, DSC and single crystal structure analysis. The crystal structures of the complexes consist of two lacunary A-β-SiW9O3410- Keggin moieties which are linked by a (H2OMO)3C belt into an assembly of virtual C2 symmetry. Each M3+ ion adopts a mono-capped trigonal prismatic coordination. The hydrolytic and thermal stability conditions of the complexes and proving reasons for the retention of the isomeric form of the trilacunary A-β-SiW9O3410- ligand upon complexation are discussed.