Novel Mononuclear and Binuclear Zinc(II), Cadmium(II) and Mercury(II) Complexes of Macrocyclic Ligands

Abstract

A novel series of complexes of the type [M(DAPTH)X₂] (M = Zn(II), Ca(II) or Hg(II); DAPTH = pentadentate ligand derived from 2,6-diacetylpyridine and thiocarbohydrazide, X = Cl, Br, CH₃COO), have been synthesized and characterized by elemental analyses, electrical conductance measurements and infrared spectral data. The ligand DAPTH is found to behave as a pentadentate ligand having coordination sites at the pyridine nitrogen, two azomethine nitrogens and two thioamide sulphur atoms. Tentative structures have been proposed for these complexes. All of these complexes contain terminal hydrazinic nitrogen atoms with an unshared electron pair and may take part in nucleophilic condensations. Therefore, the reactions of these complexes with 2,6-diacetylpyridine have also been studied which cause ring closure and formation of macrocyclic ligand complexes. Two types of cyclic products, viz. mononuclear [M(L«)X₂] and binuclear [M₂(L«)X₄] (M = Zn(II), Cd(II) or Hg(II); L« = macrocyclic ligand derived from DAPTH and 2,6-diacetylpyridine; X = Cl, Br or CH₃COO) have been isolated by carrying out the reactions by different methods. The infrared spectra of these cyclic products are reported.