Cation effect on formation of preyssler-type 30-tungsto-5-phosphate: enhanced Yield of Na-encapsulated derivative and direct synthesis of Ca- and Bi-encapsulated derivatives

Abstract

The effect of cations in a reaction mixture for the preparation of the Preyssler-Jeannin-Pope type 30-tungsto-5-phosphate [P5W30O110Na]14– is investigated. Reaction of phosphate and tungstate with a P/W ratio of ca. 3.9 in an acidic aqueous solution without cations selectively leads to the Dawson-type 18-tungsto-2-phosphate, [P2W18O62]6–. Amongst all the alkali cations, only Na+ allows formation of the Preyssler-type polyanion [P5W30O110Na]14–, with an encapsulated Na+ ion, and the product yield can be improved by increasing Na+ amount. The presence of Li+ ions instead results in the Dawson-type polyanion [P2W18O62]6–, whereas K+, Rb+, and Cs+ selectively result in the Keggin-type polyanion [PW12O40]3–. An improved synthetic procedure for the Na+-encapsulated Preyssler-ion leading to a higher isolated yield is presented. Furthermore, addition of Ca2+ and Bi3+ compounds allows formation of the Ca2+- and Bi3+-encapsulated Preyssler-type polyanions, [P5W30O110Ca]13– and [P5W30O110Bi]12–, respectively. Furthermore, single-crystal XRD structure of the Bi3+-encapsulated Preyssler-type polyanions, [P5W30O110Bi]12–, is presented for the first time.