Tetrameric complexes of germanium(IV) and cobalt(II), Nickel(II), or Zinc(II) with 1,3-Diamino-2-propanol-tetraacertic acid: crystal and molecular structures of [(OH)2Ge2(μ-Hpdta)2Zn2(H2O)4] · 12H2O

Abstract

Heteronuclear germanium(IV) and Zn(II) (Co(II), Ni(II)) complexes with 1,3-diamino-2-propanol-tetraacetic acid (H5Hpdta) were synthesized. The compounds were characterized by elemental analysis, thermogravimetry, and IR spectroscopy. X-ray diffraction analysis of the crystals of [(OH)2Ge2(μ-Hpdta)2Zn2(H2O)4] · 12H2O (I) was performed. The crystals are tetragonal, a = 15.2022(9)A, c = 20.932(3) A, V = 4837.5(7) A3, Z = 4, space group P43, R1 = 0.0449 over 11399 reflections with I > 2σ(I). The structural units of the crystal are tetrametric complex molecules [(OH)2Ge2(μ-Hpdta)2Zn2(H2O)4] and water molecules of crystallization. The tetramer is composed of two similar neutral dimeric molecules [(OH)Ge(μ-Hpdta)Zn(H2O)2]. The germanium and zinc atoms in the dimer are linked by the bridging oxygen atom of the deprotonated isopropanol group of the Hpdta5− ligand (average Ge-O, 1.844(2)A; Zn-O, 2.192(3)A). The coordination sphere of the Ge and Zn atoms contains also one nitrogen atom (average Ge-N, 2.074(4)A; Zn-N, 2.156(3)A), four oxygen atoms belonging to four acetate branches of the octadentate Hpdta5− ligands including two carboxyl O atoms for each Ge atom (average Ge-O, 1.912(3)A) and two carbonyl O atoms for each Zn (average Zn-O, 2.065(3)A). The coordination polyhedron of each Ge atom is completed to a distorted octahedron by the oxygen atom of the terminal hydroxy group (average Ge-O, 1.772(2)A) and the carboxyl oxygen atom of the bridging acetate branch (average Ge-O, 1.926(3)A) coordinated through carbonyl oxygen to Zn atom (average Zn-O, 2.148(3)A) of the second dimeric molecule. The distorted octahedron around each Zn atom is completed by oxygens of two water molecules at substantially different distances (average Zn-O, 1.984(3) and 2.100(3)A). The structural units are combined by O-H…O hydrogen bonds to form a framework.