Synthesis and spectroscopic characterisation of cobalt(III) complexes with S-benzyl dithiocarbazate of 5-methyl-3-formyl pyrazole (HMPzSB): X-ray crystal structure of [Co(MPzSB)(2)]Cl

The coordination mode of the title ligand, HMPzSB (synthesized for the first time and characterised by elemental analysis, mass, IR and PMR spectral parameters), is reported by solid state isolation and physicochemical identification of cobalt (III) complexes, [Co(MPzSB)(2)]X (X = Cl, ClO4 and BF4). Electronic spectral features of these diamagnetic Co-III species classify them as six-coordinate distorted octahedral ones. IR spectra (4000-200 cm(-1)) of HMPzSB and its complexes are indicative of an uninegative tridentate NNS function of the title ligand through the Pyrazolyl (N-2) nitrogen, azomethine nitrogen and thiolato sulphur atom. H-1-NMR data (in d(6)-DMSO at 300 MHz) of the uncomplexed ligand and its Co-III species are commensurate with the tridenticity (NNS) of the deprotonated form of HMPzSB. X-ray crystallographic studies of [Co(MPzSB)(2)]Cl has authenticated that the geometry of the species is distorted octahedral, as envisaged, with the two deprotonated primary ligand systems (MPzSB(-)). The Co-N (azomethine) and Co-N (pyrazolyl) bond lengths are 1.898(4) & 1.954(5) Angstrom and 1.903(4) & 1.916(5) Angstrom in ligand A & B, respectively where as that of Co-S (thiolato) is 2.217(2) and 2.255(2) Angstrom in the two ligands. The extended planarity of the dithiocarbazate moiety and the pyrazolyl ring of the primary ligand system are maintained because of the ligation phenomenon to Co-III. (C) 1997 Elsevier Science Ltd.