Syntheses, spectral and structural characterization of Ni(II) complexes of 4-amino-5-phenyl/3-pyridyl/thiophen-2H-1,2,4-triazole-3-thione

• Ni(II) complexes of 4-amino triazoles containing ethylenediamine (en) are reported.
• The bonding sites of ligands in the complexes are triazole and ethylenediamine nitrogen.
• Complexes contain extended hydrogen bonding which provide supramolecular framework.
• The structures of the complexes are stabilized by intermolecular and intramolecular hydrogen bonding.
• CHCl3 molecule is lost around 200 °C from complex 2 as shown by TGA.

New mixed ligand complexes [Ni(aptt)2(en)2] (1), [Ni(apytt)2(en)2]⋅CHCl3 (2) and [Ni(athtt)2(en)2] (3) with 4-amino-5-phenyl-2H-1,2,4-triazole-3-thione (Haptt), 4-amino-5-(pyridin-3-yl)-4,5-dihydro-3H-1,2,4-triazole-3-thione (Hapytt) and 4-amino-5-thiophen-2H-1,2,4-triazole-3-thione (Hathtt) have been prepared containing en as the secondary ligand. The metal complexes have been characterized with the aid of elemental analyses, IR, magnetic susceptibility and single crystal X-ray data. All the complexes are bonded through two nitrogen atoms of two triazole ligands and four nitrogens of two ethylenediamine and the resulting complexes have distorted octahedral geometry. The triazole ligands behave as uninegative monodentate, bonding through triazole nitrogen due to the hard character of the nickel(II). The complexes contain extended hydrogen bonding providing supramolecular framework. The course of the thermal degradation of complex 2 has been investigated by TG–DTA which suggest the loss of CHCl3 molecule around 200 °C and finally a residue of NiS is left behind.