Synthesis and structure of binuclear compounds of copper(I) with [(3,5-dimethylpyrazole-1-carbothioyl)-amino]-carboxylic esters

Abstract

New coordination compounds of copper(I) have been synthesized: [Cu₂L ¹₂ Cl₂] (I) and [Cu₂(HL²)₂Br₂] (II), where L¹ is methyl 3-[(3,5-dimethyl-pyrazole-1-carbothioyl)-amino]-propionate, and HL² is ethyl [(3,5-dimethyl-pyrazole-1-carbothioyl)-amino]-acetate. X-ray diffraction analysis showed that the crystal structures of these compounds are built from binuclear molecules. The L¹ and HL² molecules perform the bridging tridentate cyclic function, which results in a closure of two five-membered chelate cycles CuN₂SC and metallocycle Cu₂S₂. Each Cu atom coordinates the N atom of the pyrazole ring, the halogen atom (Cl in I and Br in II), and two S atoms, thus forming a distorted tetrahedron. The Cu₂S₂ metallocycles, the CuN₂SC chelate cycles, and the pyrazole rings are flat. Both CuN₂SC chelate cycles are almost perpendicular to the Cu₂S₂ metallocycle and form a chair conformation. Redox reactions in CuCl₂·2H₂O-L¹-ethanol and CuBr₂-HL²-ethanol systems were examined by EPR spectroscopy.