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

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The coordination mode of the title ligand, HMPzNPr 2 (synthesized for the first time and characterized by elemental analysis, mass, IR and 1 H NMR spectral parameters), is reported by solid state isolation and physicochemical identification of cobalt(III) complexes, [Co(MPzNPr 2 ) 2 ]X.H 2 O (X = Cl, Br, ClO 4 , BF 4 and NO 3 ). Electronic spectral features of the diamagnetic Co I I I 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. 1 H NMR data (in d 6 DMSO at 300 MHz) for the free ligand and those of its Co I I I 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 ]NO 3 .H 2 O (P1, triclinic) has authenticated a CoN 4 S 2 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 he 1.894(4), 1.956(4) and 2.214(2) A, respectively. The anion (NO - 3 ) is II-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.