Synthesis, Structure and Properties of Some 3d-Element Complexes with 2-[2-(Hydroxybenzylidene)-amino]-2-hydoxymethylpropane-1,3-diol

Abstract

2-[2-(Hydroxybenzylidene)-amino]-2-hydoxymethylpropane-1,3-diol (HL) reacts with cobalt, nickel, copper and zinc chlorides, bromides and acetates in water–ethanol solutions and gives MLX · nH2O and ML2 · nH2O complexes (M = Co, Ni, Cu, Zn; X = Cl, Br; n = 0–5). Single crystals of CuLBr were grown, and its crystal structure was determined by X-ray diffraction analysis. The crystals are tetragonal, a = 17.024(2), c = 8.720(2) A, space group P\(\bar 4\)21c, Z = 8, R1 = 0.0349. In the structure of this complex, the copper atom coordinates the deprotonated HL molecule. The coordination polyhedron of the central atom is an elongated tetragonal pyramid. Its base is built of the imine nitrogen atom, phenolic and alcoholic oxygen atoms, and bromine atom. The apex of the pyramid is occupied by the bromine atom of the adjacent complex connected with the initial complex by the plane of sliding reflection. Thus, the crystal contains infinite chains of complexes running along the c axis, the complexes being united by both bridging bromine atoms and O–H···O hydrogen bonds. The conclusions on the compositions and structures of the remaining compounds were made on the basis of elemental and combined thermal analyses, IR spectroscopy, and magnetic chemistry data. The copper halide complexes were found to have dimeric, and the other metal complexes monomeric, structures. In the synthesized complexes, the azomethine HL can function as a bidentate or tridentate ligand. The thermolysis of the coordination compounds proceeds through the stages of elimination of crystal water molecules (75–90°C) or inner-sphere water molecules (145–155°C) and complete thermal destruction (485–550°C).