Transition metal complexes with pyrazole based ligands, part 18: new binuclear Cu(I), Cu(II) and Co(II) complexes with 3,5-dimethyl-l-thiocarboxamide pyrazole: synthesis, structural and magnetic studies

摘要

Three new binuclear metal complexes of the formulas [(Cu2L2Cl4)-L-II] (1), [(Cu2L2Br2)-L-I] (2) and [(Co2L2Cl4)-L-II] (3) (L = 3,5-dimethyl-1-thiocarboxamide pyrazole) have been synthesized and characterized by chemical analysis, FT-IR spectroscopy, solution conductivity, solid state magnetic measurements and X-ray single crystal and variable temperature powder diffraction. Complex I forms doubly chloro-bridged dimers, with Cu(II) in distorted trigonal bipyramidal coordination with the apical positions occupied by chlorine atoms. Magnetic measurements indicate an antiferromagnetic interaction between the Cu(II) centres in the dimer, with the singlet-triplet exchange parameter of J = -19.40 cm(-1). Complex 2 forms doubly sulfur-bridged dimers, with Cu(I) in distorted tetrahedral coordination with apical positions occupied by bromine atoms. Complex 3 is a cobalt analogue of 1. It contains dinuclear units formed by five-coordinate high-spin Co(II) in a distorted trigonal bipyramidal environment. The magnetisation of 3 shows no significant departure from Curie-Weiss behaviour between room temperature and 5 K. All crystal structures are stabilized by two-dimensional hydrogen bonding networks between the carboxamide nitrogen donors and the terminal halide acceptors. (C) 2004 Elsevier B.V. All rights reserved.