Metal-assisted transformation of N-benzoyldithiocarbazate to 5-phenyl-1,3,4-oxadiazole-2-thiol in the presence of ethylenediamine, and its first row transition metal complexes

The reaction of metal complexes of the type [M(HL)Cl] or [M(HL)2] [where M = Cu(II), Ni(II), Mn(II), Co(II) and Zn(II) and H2L = N-benzoyldithiocarbazate] with an excess of ethylenediamine (en) in CHCl3–MeOH medium leads to ring closure by desulfurisation to yield unique mixed-ligand complexes 1–4, [Cu(en)2](pot)2(pot = 5-phenyl-1,3,4-oxadiazole-2-thiol), [M(en)2(pot)2] [M = Ni(II), Mn(II)] and [Zn(en)(pot)2]. The metal complexes have been characterized by various physicochemical methods. The molecular structure of [Cu(en)2](pot)2 has been determined by a single crystal X-ray diffraction study. In the centrosymmetric unit of [Cu(en)2](pot)2, the metal ion has a square planar arrangement of four symmetry related N-atoms of two en groups and is ionically bonded to two pot anions. Weak interaction studies on the complex reveal the presence of a hydrogen-bonded network in the molecule involving non-coordinating donor atoms of the pot anion with en resulting in the formation of an extended three-dimensional network. The arrangement of the [Cu(en)2]2+ units, at a dihedral angle of 49.43° to pot−, provides a network of intermingled chains leading to a π–π stacked 3-dimensional framework.

Graphical abstractThe potassium salt of N-benzoyldithiocarbazate (H2L) generates 5-phenyl,1,3,4-oxadiazole-2-thiol(pot−) in an alkaline medium by an internal ring closer reaction via desulfurization. The molecular structure of [Cu(en)2](pot)2 has been determined by a single crystal X-ray diffraction study. Weak interaction studies on the complex reveal the presence of a hydrogen-bonded network in the molecule involving non-coordinating donor atoms of the pot anion with en, resulting in the formation of an extended three-dimensional network.Figure optionsDownload full-size imageDownload as PowerPoint slide