Syntheses and characterization of the heptasodium salt of the Keggin-type triniobium-substituted polyoxoanion SiW9Nb3O407- and the all-sodium salt of the polyoxoanion-supported organometallic complex [(eta(5)-C5Me5)Rh center dot SiW9Nb3O40](5-)

The preparations of A-beta Na7SiW9Nb3O40 and Na-5[(eta(5)-C5Me5)Rh . SiW9Nb3O40] are described. The water-soluble form of the Keggin-type trisubstituted heteropolyanion, A-beta-SiW9Nb3O407-, of interest as a polyoxoanion support for organometallic complexes, was isolated in pure form in 61% yield as its heptasodium salt with 16 waters of hydration. The polyoxoanion-supported organometallic complex as its all-sodium salt, [(eta(5)-C5Me5)Rh . SiW9Nb9O40](5-) was obtained in 21% yield as an analytically pure, homogeneous yellow-brown solid by the reaction of [(eta(5)-C5Me5)Rh(CH3CN)(3)](2+) with the trisubstituted heteropolyanion SiW(9)Nb(3)O(40)7(-) in CH3CN-DMSO. These all-sodium salts have required their own novel preparations and purifications, and have never been derived directly from the known all-Bu4N+ salts of the corresponding Keggin heteropolyanions. Compositional characterization was accomplished by complete elemental analyses, TG/DTA, and FT-IR. Structural characterization in solution was achieved by combination of H-1, C-13 and W-183 NMR spectroscopies.