Two Hexa-Ni-Substituted AsW9O34 Clusters Functionalized by Organic Ligands

Abstract

Hydrothermal reactions of trilacunary precursor A-α-AsW9O34 9− polyoxoanions and nickel ions in the presence of ethylenediamine (en = ethylenediamine) led to two new hexa-Ni-substituted Keggin-type tungstoarsenates [Ni6(μ 3-OH)3(en)3(H2O)6(B-α-AsW9O34)]·6H2O (1) and [Ni6(μ 3-OH)3(en)3(H2O)6(B-α-AsW9O34)]·10H2O (2), which have been characterized by elemental analyses, IR spectra, powder X-ray diffraction, thermogravimetric analyses and single-crystal X-ray diffraction. Crystal data for 1: hexagonal, R3c, a = b = 20.4379(5) A, c = 21.5062(6) A, β = 120o, V = 7779.8 (3) A3 and Z = 6; for 2: momoclinic, P21/c, a = 13.4200(3) A, b = 19.1428(5) A, c = 22.8845(9) A, β = 112.403(3)o, V = 5435.2(3) A3 and Z = 4. Structural analyses reveal that the [Ni6(μ 3-OH)3(B-α-AsW9O34)] clusters in 1 and 2 are covalently functionalized by neutral en ligands, in which two similar {Ni6(μ 3-OH)3(en)3(H2O)6}9+ cores have been observed by our lab. Notably, 1 and 2 represent the highest number of substituted transition metal ions in all known lacunary Keggin-type polyoxotungstoarsenate monomers.