A new binuclear germanium(IV) and copper(II) complex with 1,3-diamino-2-propanoltetraacetic acid: Crystal and molecular structure of [(H2O)(OH)Ge(μ-Hpdta)Cu(H2O)] • 3H2O

A heteronuclear germanium(IV) and copper(II) complex with 1,3-diamino-2-propanoltetraacetic acid (H5Hpdta) has been synthesized for the first time. The compound has been characterized by elemental analysis, X-ray diffraction, thermogravimetry, and IR spectroscopy. The structure of the complex [(H2O)(OH)Ge(μ-Hpdta)Cu(H2O)] · 3H2O (I) has been determined by single-crystal X-ray diffraction. The crystals of I are monoclinic, a = 1 5.327(4) Å, b = 11.626(3) Å, c =21.058(3) Å, β = 96.35(2)°, V = 3729.2(2) Å3, Z = 8, space group C2/c, R1 = 0.0551 on 3090 reflections with I > 2σ(I). The structural units of the crystal of I are binuclear complex molecules [(H2O)(OH)Ge(μ-Hpdta)Cu(H2O)] and crystal water molecules. The germanium and copper atoms are linked by the bridging oxygen atom of the deprotonated isopropanol group of the Hpdta5− ligand (Ge-O, 1.843(3) Å; Cu-O, 2.221(3) Å). The coordination spheres of the Ge and Cu atoms contain each one nitrogen atom (Ge-N, 2.090(4) Å; Cu-N, 2.000(4) Å) and two carboxyl oxygen atoms from four acetate arms of the heptadentate Hpdta5− ligand (av. Ge-O, 1.909(3) Å; Cu-O, 1.948(3) Å). The coordination polyhedron of the Ge atom is completed to a distorted octahedron by the oxygen atoms of the terminal hydroxy group (Ge-O, 1.786(3) Å) and a water molecule (Ge-O, 1.904(3)Å). The coordination polyhedron of the copper atom is completed to a prolate tetragonal pyramid (4 + 1) by the oxygen atom of a water molecule in the equatorial position (Cu-O, 1.955(4) Å) and the bridging O(11) atom (Hpdta5−) in the apical position. Binuclear molecules are linked pairwise in a head-to-head manner via double Cu-O(2) bridges to form the centrosymmetric tetranuclear supramolecule {[(H2O)(OH)Ge(μ-Hpdta)Cu(H2O)]}2. The coordination of the Cu atom is completed by the weak Cu-O(2A) contact (3.303 Å) to an asymmetrically elongated tetragonal bipyramid (4 + 1 +1). In the crystal, the complex molecules and crystal water molecules are combined by a system of hydrogen bonds into a three-dimensional framework.