Several reactions between zinc(II) chloride and propanedioic acid were performed, with different molar ratios of reactants in selected solvents: acetone and acetonitrile. Three new compounds were prepared: In one a fully protonated acid is present, while in the other two a partially deprotonated state is present. [Zn(Hmal)2(OH2)2] (compound 1), K6Zn2(mal)4Cl2·2H2O (compound 2) and [ZnCl(Hmal)(3PyMeOH)] (compound 3) and their crystal structures were determined by means of single-crystal X-ray diffraction. In the structure of compound 1, two propanedioic acid anions were coordinated to the zinc central ion in a bidentate chelating manner, resulting in a formation of mononuclear neutral molecular species. In compound 2, the acidic anion was in a role of bridging ligand, that resulted in a formation of ring structures with zinc ions, into which potassium ions were incorporated, yielding a coordination polymer. The binding of the acidic anion to the central zinc atom in compound 3 was bidentate chelating and also bridging, which again led to the formation of a coordination polymer. In all three cases, the smaller units in the structure are linked by hydrogen bonds into a stable, three-dimensional structure.
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