Synthesis, structure and spectroscopic characterization of Ni(II), Co(II), Cu(II) and Zn(II) complexes with saccharinate and pyrazole

Four mononuclear mixed-ligand complexes of Co(II), Ni(II), Cu(II) and Zn(II), with saccharin (sac) and pyrazole (Hpz) were synthesized and characterized on the basis of elemental analysis, FT-IR spectroscopy, magnetic susceptibility, thermal analysis data and X-ray diffraction. The [Co(sac)(2)(HPZ)(2)(H2O)2] (1) and [Ni(sac)(2)(Hpz)(2)(H2O)(2)] (2) had similar molecular structures but distinct monoclinic crystal structure types (space group P2(1)/n for 1 and P2(1)/c for 2); the members of each pair of ligands were mutually trans. The saccharinate ligands were N-coordinated. The copper complex showed the same coordination environment as the Co and Ni complexes but crystallizes in the triclinic space group P! and presented pseudo-Jahn-Teller distortion along the O(w)-Cu-O(w) bonds. The [Zn(sac)(2)(pz)(2)] complex was tetrahedrally coordinated and crystallized in the monoclinic space group C2/c. Thermal decomposition of the complexes in a nitrogen atmosphere resulted in removal of the water molecules and pyrazole ligands at relatively low temperature and formation of stable metal saccharinates as intermediates, which also decomposed at higher temperatures, about 300 degrees C. (c) 2007 Elsevier Ltd. All rights reserved.