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 . S iW9Nb3O40] are described. The water-soluble form of the Keggin-type tr isubstituted heteropolyanion, A-beta-SiW9Nb3O407-, of interest as a po lyoxoanion 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 s alt, [(eta(5)-C5Me5)Rh . SiW9Nb9O40](5-) was obtained in 21% yield as an analytically pure, homogeneous yellow-brown solid by the reaction o f [(eta(5)-C5Me5)Rh(CH3CN)(3)](2+) with the trisubstituted heteropolya nion SiW(9)Nb(3)O(40)7(-) in CH3CN-DMSO. These all-sodium salts have r equired their own novel preparations and purifications, and have never been derived directly from the known all-Bu4N+ salts of the correspon ding Keggin heteropolyanions. Compositional characterization was accom plished 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.