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

Abstract The heteropolyanion [Ce 4 (OH) 2 (H 2 O) 9 (P 2 W 16 O 59 ) 2 ] 14– ( 1 ) has been isolated as a potassium salt, in ∼40 % yield, from a neutral solution formed by reaction of a suspension of K 12 H 2 P 2 W 12 O 48 ·24 H 2 O in 1 M LiCl with Na 2 WO 4 and Ce(NO 3 ) 3 . Single crystal X-ray analysis of K 12 H 2 [Ce 4 (OH 2 ) 9 (OH) 2 (P 2 W 16 O 59 ) 2 ]·48 H 2 O (monoclinic, space group C 2 , a =28.198 0(2) A, b =12.205 80(10) A, c =23.238 00(10) A, α =114.879 0(10)°; 17 164 independent reflections; R 1 =0.057 6) reveals an anion of C 2 v virtual symmetry in which four Ce 3+ cations are sandwiched between two novel divacant lacunary derivatives of the Wells–Dawson anion, α-[P 2 W 18 O 62 ] 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 μ 3 -OH(Ce 3 ), one μ 2 -H 2 O(Ce 2 ) and four μ 3 -O(W,Ce 2 ). The heteropolyanion is stable in aqueous solution and yields well resolved 31 P ( δ =+4.0 ppm) and 183 W NMR spectra (8 lines of equal intensity, δ =+296 to −188 ppm) that are consistent with the solid state structure. © 2000 Academie des sciences / Editions scientifiques et medicales Elsevier SAS polyoxometalates / lanthanides / tungsten / NMR / crystallography