Hydrothermal synthesis and structural characterization of two inorganic-organic composite sandwich-type tungstogermanates

Two new inorganic-organic hybrid polyoxotungstates [enH(2)][C8N4H22](3)H-2[Co-4(enH)(2)(GeW9O34)(2)] center dot 6H(2)O (1) and [Co(en)(3)](2)H-6[Co-4(enH)(2)(GeW9O34)(2)] center dot 14H(2)O (2) (en = ethylene-diamine) have been synthesized by hydrothermal methods and characterized by IR, TG, XRD, XPS, elemental analysis, and single-crystal X-ray analysis. The polyoxoanion frameworks of the two compounds consist of two classical tetra-Co sandwiched polyoxoanions [Co-4(H2O)(2)(GeW9O34)(2)] in which two organic ligands substitute two water molecules. The tetra-Co clusters in 1 and 2 exhibit the familiar structural type of a beta-junction at the sites of metal incorporation. Compound 1 is of interest owing to its C8N4H20 ligands resulting from the reaggregation of triethylenetetramine which occurs under 160 degrees C.