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

Abstract

A series of new 3d-metal complexes based on 2-amino-3-(1-methylbenzimidazol-2-yl)-4(5H)-ketothiophen (HL 1) and 2-amino-3-(2-benzothiazolyl)-4(5H)-ketothiophen (HL 2) were synthesized. Compounds of the general formulas [ML 2] and [M(HL 1) 2Cl 2] (where M = Co 2+, Ni 2+, Zn 2+, Cu 2+) were prepared by the reaction of the above mentioned ligands with the corresponding acetate (for [ML 2]) or chloride (for [M(HL 1) 2Cl 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 HL 1, complexes with the neutral form of HL 2 cannot be obtained under the same conditions. All the complexes were studied by spectroscopic methods and X-ray crystallography (for [CuL 1 2] · H 2O). 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.