Hydrothermal synthesis and structural characterization of three inorganic–organic composite sandwich-type phosphotungstates

Three inorganic–organic composite sandwich-type phosphotungstates [Ni(tepa)(H2O)]4H2[Ni4(H2O)2(α-B-PW9O34)2]·8H2O (1), (enH2)3[Ni2(H2O)10][Ni4(H2O)2(α-B-PW9O34)2]·en·8H2O (2) and (enH2)10[Mn4(H2O)2(α-B-PW9O34)2]2·20H2O (3) (tepa=tetraethylenepentamine and en=ethylenediamine) have been synthesized by the hydrothermal reaction of the trivacant Keggin polyoxoanion [α-A-PW9O34]9− with Ni2+ or Mn2+ ions in the presence of tepa or en and structurally characterized by IR spectra, elemental analysis, thermogravimetric analysis and variable temperature magnetic susceptibility. X-ray crystallographic analyses indicate that they all contain the classical tetra-M sandwiched polyoxoanions [M4(H2O)2(α-B-PW9O34)2]10− (M=Ni2+ or Mn2+) and nickel-organoamine cations or organoamine cations work as the charge balance ions. The tetra-M clusters in 1, 2 and 3 exhibit the familiar structural type of a β-junction at the sites of metal incorporation. The study of magnetic property of 1 is indicative of a typical ferromagnetic coupling between Ni2+ cations.