Crystal Structure of Zinc(II) Hydrated Trinuclear Complex with Monoprotonated Ethylenediaminetetraacetate Anion(3-), [Zn3(HEdta)2(H2O)6]

The crystal structure of the [Zn3(HEdta)2(H2O)6] complex (I) is determined by X-ray diffraction analysis. The crystals are orthorhombic, a = 14.780 A, b = 29.699 A, c = 7.032 A, Z = 4, and space group Pna21. The structural units of crystals I are trinuclear linear molecules, in which the peripheral atoms Zn(1) and Zn(2) each coordinate two N atoms and three O atoms of the HEdta3- ligand and the O(w) atom of the H2O molecule, whereas the central Zn(3) atom coordinates four O(w) atoms of the H2O molecules and two terminal O atoms of the two HEdta3- ligands. The HEdta3- ligand fulfills a hexadentate chelating-bridging function. The bond lengths are as follows: Zn-O(HEdta), 2.006(4)-2.123(4) A; Zn-N, 2.214(6) and 2.128(5) A; and Zn-O(w), 2.006(6)-2.225(5) A. In structure I, there is a specific contact formed by hydrogen bonds, owing to which the distance between the central atoms of individual molecules appears to be shorter than that in covalently bonded complexes