Synthesis and study of the structure of new 3d-metal coordination compounds with substituted 2-amino-4(5H)-ketothiophens

A series of new 3d-metal complexes based on 2-amino-3-(1-methylbenzimidazol-2-yl)-4(5H)-ketothiophen (HL1) and 2-amino-3-(2-benzothiazolyl)-4(5H)-ketothiophen (HL2) Were synthesized. Compounds of the general formulas [ML2] and [M(HL1)(2)Cl-2] (where M = Co2+, Ni2+, Zn2+, Cu2+) were prepared by the reaction of the above mentioned ligands with the corresponding acetate (for [ML2]) or chloride (for [M(HL1)(2)Cl-2]) salts in a methanol or a methanol-chloroform medium. The choice of the anion in the initial metal salt, as well as the selection of the ligand, is crucial for obtaining coordination compounds with a neutral or deprotonated form of the 2-amino-4(5H)-ketothiophens. Thus, in contrast to HL1, complexes with the neutral form of HL2 cannot be obtained under the same conditions. All the complexes were studied by spectroscopic methods and X-ray crystallography (for [CuL21] center dot H2O). The coordination polyhedron of the copper atom is formed by four nitrogen atoms from two ligand anions and the geometry of the coordination sphere is intermediate between tetrahedral and square-planar. (C) 2008 Elsevier Ltd. All rights reserved.