A large heteropolytungstotetracerate(III) based on a new divacant lacunary derivative of the Wells-Dawson tungstophosphate anion☆

The heteropolyanion [Ce-4(OH)(2)(H2O)(9)(P2W16O59)(2)](14-) (1) has been isolated as a potassium salt, in similar to 40 % yield from a neutral solution formed by reaction of a suspension of K12H2P2W12O48. 24 H2O in 1 M LiCl with Na2WO4 and Ce(NO3)(3). Single crystal X-ray analysis of K12H2[Ce-4(OH2)(9)(OH2(P2W16O59)(2)]. 48 H2O (monoclinic, space group C-2, a = 28.138 0(2) Angstrom, b = 12.205 80(10) Angstrom, c = 23.233 00(10) Angstrom, alpha = 114.879 0(10)degrees; 17 164 independent reflections; R-1 = 0.057 6) reveals an anion of C-2t, virtual symmetry in which four Ce3+ cations are sandwiched between two novel divacant lacunary derivatives of the Wells-Dawson anion, alpha-[P2W18O62](6-). The lacunary anions (of C-s symmetry) have adjacent metal atom vacancies on both sides of the equator of the Wells-Dawson structure. The four cerium(III) centers (two 9- and two 10-coordinate) are linked by two mu(3)-OR(Ce-3), one mu(2)-H2O(Ce-2) and four mu(3)-O(W,Ce-2). The heteropolyanion is stable in aqueous solution and yields well resolved P-31 (delta = + 4.0 ppm) and W-183 NMR spectra (8 lines of equal intensity, delta = + 296 to - 188 ppm) that are consistent with the solid state structure. (C) 2000 Academic des sciences / Editions scientifiques et medicales Elsevier SAS