Synthesis and structural characterization of Ni(II) complexes containing a heterocyclic NO donor ligand

Five novel nickel(II) complexes have been successfully synthesized with a heterocyclic ligand, Opdac, [Ni(Opdac)2]Cl2 (1), [Ni(Opdac)2(CH3OH)2]Br2(CH3OH)2 (2), [Ni(Opdac)2]I2 (3), [Ni(Opdac)2NO3]NO3 (4) and [Ni(Opdac)2ClO4]ClO4 (5) where Opdac = 4-(1-H-1,3-benzimidazole-2-yl)-1,5-dimethyl-2-phenyl-1-2-dihydro-3-H-pyrazol-3-one. All the complexes were characterized by elemental analysis, molar conductivity, CHN analysis, magnetic susceptibility measurements, spectroscopic studies and TG/DTA methods. In all the complexes, Opdac acts as a bidentate ligand coordinating to Ni(II) ion via the benzimidazole imine nitrogen and the pyrazolone oxygen atoms. The complexes 1 and 3 have a tetrahedral geometry while 2, 4 and 5 have an octahedral geometry around the Ni(II) center.

Graphical abstractThe present investigation reports the synthesis of a series of nickel(II) complexes [Ni(Opdac)2]Cl2 (1), [Ni(Opdac)2(CH3OH)2]Br2(CH3OH)2 (2), [Ni(Opdac)2]I2 (3), [Ni(Opdac)2NO3]NO3 (4) and [Ni(Opdac)2ClO4]ClO4 (5) with the Schiff base ligand, 4-(1-H-1,3-benzimidazole-2-yl)-1,5-dimethyl-2-phenyl-1-2-dihydro-3-H-pyrazol-3-one (Opdac) and their characterization. In all the complexes, Opdac acts as neutral bidentate ligand forming six membered chelate ring around the central metal ion.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Ni(II) complexes of heterocyclic NO donor ligand. ► Synthesis, characterization and crystal structure. ► The complex 2 crystallizes in the monoclinic P21/c space group.