Novel large heteropolymetalate complexes formed from Ni(II) and cryptate [As4W40O140]28- -: Synthesis and structure characterization

The heteropolytungstate (NH4)20[Na-2(H2O)(2)Ni(H2O)(5){Ni(H2O)}(2)AS(4)W(40)O(140)] . 61H(2)O is obtained by the reaction of Na-27[NaAS(4)M(40)O(140)] . 60H(2)O with NiCl2 . 6H(2)O and NH4Cl in pHapproximate to4.0. The structure and chemical composition are determined by X-ray diffraction analysis and element analysis. The crystal data and main structure refinement are: a = 1.33135(18) nm, b = 1.9722(3) nm, c = 3.6430(5) nm, alpha = 78.010(2)degrees, beta = 82.145(2)degrees, gamma = 74.385(2)degrees, V = 8.978(2) nm(3), triclinic crystal system, space group: P (1) over bar, Z = 2, R1 = 0.0512, and wR2 = 0.0684(l > 2sigma). The four S2 sites of the big cyclic ligand [AS(4)W(40)O(140)](28-) are occupied by two Na+ and two Ni2+ respectively, and each site supplies four O-d coordinating to metal ion. The coordination number of Ni2+ is six, and that of two Na+ is five and six respectively. The third Ni2+ locates outside the cyclic [AS(4)W(40)O(140)](28-) and connects with one Od, and its coordination number is six.