Mixed ligand Co(II), Ni(II) and Cu(II) complexes containing terephthalato ligands. Crystal structures of diaqua(2,2 '-dipyridylamine)(terephthalato)metal(II) trihydrates (metal = cobalt or nickel)

A series of nine ternary Co(II), Ni(II) and Cu(II) complexes with some arom atic diamines and dianion of terephthalic acid (tpht) have been synthesized and characterized by elemental analysis, magnetic susceptibility measureme nts, IR and diffuse-reflectance spectroscopy. All compounds were obtained a s microcrystalline solids, stable in air and insoluble in common solvents. Two of them, [M(tpht)(dipya)(H2O)(2)]. 3H(2)O [M = Co(II), Ni(II); dipya = 2,2'-dipyridylamine], were obtained as single crystals and their crystal st ructures have been determined by X-ray structure analysis. Both structures consist of discrete [M(tpht)(dipya)(H2O)(2)](2+) complex units with two H2O molecules in the trans position. Three additional H2O molecules together w ith coordinated H2O and O atoms from COO groups make a three-dimensional ne twork of hydrogen bonds. Terephthalato ligands are coordinated by only one COO group, which acts as a chelating ligand. Central metal ions are in a di storted octahedral environment. Based on the above-mentioned analysis and k nown crystal structures, the possible structures and geometry of the comple xes are discussed. All Co(II) and Ni(II) complexes are pseudooctahedral and mononuclear, with only one of the tpht COO groups coordinated in a chelate mode. Cu(II) complexes have probably distorted octahedral geometry with br idging role of tpht ions and monodentate or strongly asymmetric coordinatio n of COO groups. (C) 2000 Elsevier Science Ltd. All rights reserved.