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 ligands (with one ambidentate donor site), 3,5-dimethyl-1-(N-methyl/ethyl)thiocarbamylpyrazole (HL1 for N-methyl, HL2 for N-ethyl) have been synthesized and characterized by elemental analyses. IR, UV-Vis and H-1 NMR spectral studies. 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) has a distorted octahedral structure with the ambidentate ligands coordinated to the Co(III) ion as uninegative bidentate chelating agents via the pyrazole ring nitrogen (tertiary) and the thiocarbamyl iminyl nitrogen atoms. The distortion from the regular octahedral geometry is ascribed to the stereochemical limitations imposed by the planar bidentate ligands. (C) 2000 Elsevier Science B.V. All rights reserved.