Cobalt(II) and copper(II) complexes of (2-thiophene)-(5,6-diphenyl-[1,2,4]-triazin-3-yl)hydrazone

Author： El-Dissouky Ali Al-Fulij Othman Kandil Samir S.

ISSN： 0095-8972

Source： Journal of Coordination Chemistry, Vol.57, Iss.7, 2004-05, pp. : 605-614

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Abstract

New complexes having the formulae [L₂CoX₂] and [LCuCl₂], [LCuCl] and [LCu](ClO₄)₂ where L = (2-thiophene)-(5,6-diphenyl-[1,2,4]-triazin-3-yl)hydrazone TDPTH; X = Cl, OAc or ClO₄ have been synthesized and characterized on the basis of elemental analyses, conductance, magnetic moments and infrared, electronic and ESR spectral data. The IR spectra indicate that TDPTH is a neutral bidentate ligand, coordinating via a triazine-N and azomethine-N in [L₂CoX₂] and [LCuCl₂] with the thiophene-S not coordinated but is tridentate in [LCuCl] and [LCu](ClO₄)₂ through the same two nitrogen atoms and thiophene-S. The magnetic moment and electronic spectral data suggest a distorted octahedral structure for Co(II) complexes, a dimeric square pyramidal geometry for [LCuCl₂] through chloride bridges and a dimeric diamagnetic, four-coordinate copper in [LCu](ClO₄)₂ through thiophene-S bridges. The X-band ESR spectra of Co(II) complexes, in the solid state, are rhombic with three g values consistent with a high-spin distorted octahedral structure. The X-band ESR spectrum of the powdered sample of both [LCuCl₂]·2H₂O and [LCu](ClO₄)₂ at room temperature and at 77 K showed only one broad signal due to ΔM_s = ± 1 transition and a weak signal due to the forbidden ΔM_s = ± 2 transition, indicating an antiferromagnetic interaction between copper(II) centers whereas [LCuCl] is ESR silent, indicating a monovalent copper ion in this complex.