Novel large heteropolymetalate complexes formed from Ni(II) and cryptate [As4W40O14028-—Synthesis and structure characterization

The heteropolytungstate (NH4)20[Na2(H2O)2Ni(H2O)5{Ni(H2O)}2As4W40O140] · 61H2O is obtained by the reaction of Na27[NaAs4W40O140] · 60H2O with NiCl2 · 6H2O and NH4Cl in pH≈4.0. 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, α = 78.010(2)°, β = 82.145(2)δ, γ = 74.385(2)°, V = 8.978(2) nm3, triclinic crystal system, space group: P1, Z = 2, R1 = 0.0512, and wR2 = 0.0684(I >2σ). The four S2 sites of the big cyclic ligand [As4W40O140]28- are occupied by two Na+ and two Ni2+ respectively, and each site supplies four Od 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 [As4W40O140]28- and connects with one Od, and its coordination number is six.