Synthesis and spectroscopic identification of cobalt(III) complexes with 5-methyl-3-formylpyrazole-N( 4)-dipropylthiosemicarbazone (HMPzNPr2) : X-ray crystal structure of [Co(MPzNPr2h]N03.H20

Department of Chemistry University of Calcutta, 92, A. P. C. Road, Kolkata-700 009, India

l.U.C., Kolkata-700 098, India

Department of Chemistry, Howard University, 2400 Sixth Street N. W., Washington, DC 20059, U.S.A.

Manuscript received 7 January 2001

The coordination mode of the title ligand, IIMIzNPr₂ (synthesized for the first time and characterized by elemental analysis, mass, IR and ¹H NMR spectral parameters), is reported by solid state isolation and physicochemical identification of cobalt(III) complexes, [CoMPzNPr₂)₂ ] X.II₂O (X= Cl, Br, CIO₄, BF₄ and NO₃). Electronic spectral features of the diamagnetic Co¹¹¹ species classify them as six-coordinate distorted octahedral ones. IR spectra (4000-200 cm^-1) of the uncomplexed HMPzNPr₂ and its complexes have indicated a monodepr·otonatcd tridentate NNS function of the primary ligand molecule through the pyrazolyl (tertiary) ring nitrogen, azomcthine nitrogen and thiolato sulfur atom. ¹H NMR data (in d₆ DMSO at 300 MHz) for the free ligand and those of its Co¹¹¹ complexes are commensurate with the NNS tridcnticity of the monodeprotonated HMPzNPr₂ , as ascertained from down-field shift of the relevant protons adjacent to the bonding sites. X-Ray crystallography of [Co(MPzNPr₂)₂ ]NO₃ .H₂O (PI, triclinic) 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) A, respectively. The anion (NO₃¯ ) 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.