Synthesis, Crystal Structure And Characterization Of Polyoxotungstates Containing Transition Metal

In this paper, four unreported novel compounds, which are based on the building units of sandwich-type polyanions [α-B-BiW₉O³³]^9- and the classical [α-SiW12O40]4-, have been synthesized by conventional and hydrothermally methods with transition metals. Two kinds of nitrogen contained ligand: triethanolamine and 1, 2-diaminobenzene, as organic composition have been utilized. These compounds have been structurally characterized by elemental analyses, IR, TG and single crystal X-ray diffractions. The magnetic properties of compound 1 have been studied.1. Three sandwich-type derivatives have been synthesized and structurally characterized:Na₈[(C₆H₁₅O₃N)H]₂[(X(H₂O)₃)₂(X_0.5(W_0.5O))₂(β-B-BiW₉ O₃₃)₂]·nH₂O (X=Mn^II, Co^II, Ni^II;C₆H₁₅O₃N = triethanolamine) (1-3)Three new sandwich-type polyoxotungstates (1-3) have been synthesized in good yield using an in-situ conventional solution synthesis method by reaction in aqueous media below 80°C. Compounds 1-3 represent the firstβ-B-BiW₉ sandwich-type polyoxometalates with triethanolamine cations structurally. All the three compounds have the same building unit of [(X(H₂O)₃)₂(X_0.5W_0.5O)₂(β-B-BiW₉O₃₃)₂)]^10-. The adjacent units from 1 or 2 are joined by Na+ cations in different ways to construct 1D chains or 2D sheets. Then a 3D supramolecular structure is further formed by hydrogen bond interactions among water molecules and protonated triethanolamine cations. Meanwhile only compound 3 shows a 0D structure. The magnetic properties of 1 indicate dominant paramagnetic interactions.2. A new polyoxometalate compound on the base of Keggin type polyoxoanion cluster decorated by Cu-1, 2-diaminobenzene coordination ion has been hydrothermally synthesized and structurally characterized:[Cu(C₆H₆N₂)₂]₂[α-SiW₁₂O₄₀]·H₂O (4)We obtained a 2D organic-inorganic hybrid material of compound 4 by hydrothermally synthesized. The classical Keggin type polyoxometalte H₄SiW₁₂O₄₀·20H₂O has been used as the starting material. Study found that in compound 4, the copper complexes, respectively from two different Keggin anions through the terminal oxygen and bridging oxygen covalent bond to form a two-dimensitonal coordination polymer layered structure. This has been reported in the literature rarely.