Synthesis and characterization of heteronuclear germanium(IV) lanthanide 1,3-diamino-2-propanoltetraacetates: Crystal and molecular structure of the [Ge(OH)(μ-Hpdta)(μ-OH) Ln(H2O)3] · 2H 2O complexes (Ln = Tb, Yb)

In the course of systematic studies, heteronuclear germanium lanthanide complexes based on 1,3-diamino-2-propanoltetraacetic acid (H5Hpdta) have been synthesized (Ln = Pr (I), Nd (II, the structure was described in [1]), Sm (III), Eu (IV), Gd (V), Tb (VI), Dy (VII), Ho (VIII), Er (IX), Tm (X), Yb (XI), Lu (XII)). Comparative analysis of their structure as a function of the lanthanide ion has been performed. The analysis is based on a combination of physicochemical data on complexes I–XII, including X-ray crystallographic data for two heteronuclear [Ge(OH)(μ-Hpdta)(μ-OH)Ln(H2O)3] · 2H2O complexes (Ln = Tb (VI) and Yb (XI). Isostructural crystals of VI and XI are monoclinic, Z = 4, space group P21/n, a = 9.340(4) and 9.3133(10) Å, b = 10.4839(14) and 10.4561(10) Å, c = 20.246(2) and 20.1222(10) Å, β = 95.12(3)° and 95.275(10)°, V = 1974.5(10) and 1951.2(3) A3, R1 = 0.0277 and 0.0241 for 4527 and 4751 reflections with I > 2σ(I). Crystals of VI and XI are composed of binuclear [Ge(OH)(μ-Hpdta)(μ-OH)Ln(H2O)3] molecules and crystal water molecules. The Ge and Ln atoms in VI and XI are linked by the bridging oxygen atom of the hydroxo group (Ge-O, 1.806(2) and 1.812(2) Å; Ln-O, 2.445(3) and 2.405(2) Å, respectively) and by the deprotonated oxygen atom of the isopropanol group of the Hpdta5-ligand (Ge-O, 1.865(2) and 1.864(2) Å; Ln-O, 2.302(2) and 2.255(2) Å in VI and XI, respectively). The coordination sphere of each of the Ge and Ln atoms involves one nitrogen atom (Ge-N, 2.097(3) and 2.096(3) Å; Ln-N, 2.670(3) and 2.628(3) Å in VI and XI, respectively) and two carboxyl oxygen atoms of four acetate arms of the completely deprotonated heptadentate Hpdta5− ligand (av. Ge-O, 1.922(3) and 1.920(3) Å; Ln-O, 2.349(2) and 2.298(2) Å in VI and XI, respectively). The coordination polyhedron of the Ge atom is completed to a distorted octahedron by the oxygen atom of the terminal hydroxo group (Ge-O, 1.811(2) Å in VI and 1.810(2) Å in XI), and the coordination polyhedron of the Ln atom is completed to an eight-vertex polyhedron by the oxygen atoms of three water molecules (av. Ln-O, 2.378(3) Å in VI and 2.342(3) Å in XI). In the crystals of VI and XI, complex molecules and crystal water molecules are combined by a system of hydrogen bonds into a three-dimensional framework.