Cover Picture: Soluble Heteropolyniobates from the Bottom of Group IA (Angew. Chem. Int. Ed. 52/2011)



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Polyoxoniobates (PONb) differ from nearly all other polyanionic clusters in their unusual solubility behavior. In their Communication on page 12 514 ff., M. Nyman and co-workers show that the Cs salts of PONb are the most soluble and the Li salts the least. The opposite trend holds for other polyoxometalates and anionic clusters, owing to factors such as the strong inner-sphere complexation ability of large alkali-metal ions. The excellent solubility of the Rb and Cs heteropolyniobates offers a unique system for aqueous ion-association studies.