Synthesis and characterization of two tris-chelate complexes of cobalt(III) with 3,5-dimethyl-1-(N-methyl/ethyl) thiocarbamyl-pyrazole (HL1, HL2) - biologically important bidentate ligands with one ambidentate donor site

Cobalt(III) complexes, of two potentially pyrazole-derived bidentate ligand s (with one ambidentate donor site), 3,5-dimethyl-1-(N-methyl/ethyl)thiocar bamylpyrazole (HL1 for N-methyl, HL2 for N-ethyl) have been synthesized and characterized by elemental analyses. IR, UV-Vis and H-1 NMR spectral studi es. The structure of Co(L-2)(3) has been determined by single-crystal X-ray diffraction studies. The complex (triclinic, space group P (1) over bar) h as a distorted octahedral structure with the ambidentate ligands coordinate d to the Co(III) ion as uninegative bidentate chelating agents via the pyra zole ring nitrogen (tertiary) and the thiocarbamyl iminyl nitrogen atoms. T he distortion from the regular octahedral geometry is ascribed to the stere ochemical limitations imposed by the planar bidentate ligands. (C) 2000 Els evier Science B.V. All rights reserved.