Bismuth(III)-Containing Heteropolytungstates [Bi(XW11O39)2]n- (X = Si, Ge, n=13; X = P, n=11) and [Bi(P2W17O61)2]17-

We report on the synthesis and structural characterization of four bismuth(III)-containing sandwich-type heteropolytungstates with Bi in 8-coordination. The three isostructural Keggin-type ions [Bi(alpha-XW11O39)(2)](n-) {X = Si (1), Ge (2), n = 13; X = P (3), n = 11} and the Wells-Dawson-type ion [Bi(alpha(2)-P2W17O61)(2)](17-) (4) were prepared via simple one-pot synthetic procedures in aqueous medium. The novel polyanions comprise a Bi3+ ion linking two monolacunary {XW11} or {X2W17} units in a sandwich-type fashion. The Bi3+ ion is coordinated by four oxygens of each monolacunary POM unit, resulting in 8-coordination with square-antiprismatic geometry. Such a coordination mode is rare for Bi3+.