Synthesis and spectroscopic identification of cobalt(III) complexes with 5-methyl-3-formylpyrazole-N(4)-dipropylthiosemicarbazone (HMPzNPr2):: X-ray crystal structure of [Co(MPzNPr2)2]NO3.H2O

The coordination mode of the title ligand, HMPzNPr(2) (synthesized for the first time and characterized by elemental analysis, mass, IR and H-1 NMR spectral parameters), is reported by solid state isolation and physicochemical identification of cobalt(III) complexes, [Co(MPzNPr(2))(2)]X.H2O (X = Cl, Br, CIO4, BF4 and NO3). Electronic spectral features of the diamagnetic Co-III species classify them as six-coordinate distorted octahedral ones. IR spectra (4000-200 cm(-1)) of the uncomplexed HMPzNPr(2) and its complexes have indicated a monodeprotonated tridentate NNS function of the primary ligand molecule through the pyrazolyl (tertiary) ring nitrogen, azomethine nitrogen and thiolato sulfur atom. H-1 NMR data (in d(6) DMSO at 300 MHz) for the free ligand and those of its Co-III complexes are commensurate with the NNS tridenticity of the monodeprotonated HMPzNPr(2), as ascertained from down-field shift of the relevant protons adjacent to the bonding sites. X-Ray crystallography of [Co(MPzNPr(2))(2)]NO3.H2O (P (1) over bar, trielinic) has authenticated a CoN4S2 octahedral coordination with severe distortion as evidenced from selected bond parameters; the average Co-N (azomethine), Co-N (pyrazolyl) and Co-S (thiolato) bond lengths are found to be 1.894(4), 1.956(4) and 2.214(2) Angstrom, respectively. The anion (NOD is H-bonded with the imino-proton of the pyrazolyl ring of one primary ligand molecule and at the same time the associated water molecule is also H-bonded with the nitrate ion.