ZINC(II), CADMIUM(II) AND MERCURY(II) COMPLEXES OF MACROCYCLIC LIGANDS DERIVED FROM 2,6-DIACETYLPYRIDINE

Abstract

A novel series of complexes, of the type [M(DAPCH)X₂(M=Zn(II), Cd(II) or Hg(II); DAPCH =planar pentadentate ligand derived from 2,6-diacetylpyridine and carbohydrazide, X=Cl, Br, I, NO₃, CH₃COO) have been synthesized and characterized by elemental analyses, conductance measurements and infrared spectral data. The ligand DAPCH appears to behave as a pentadentate ligand, having coordination sites at one pyridine nitrogen, two azomethine nitrogen and two amide oxygen atoms. Possible structures are proposed for these complexes. All the complexes contain terminal hydrazinic nitrogen atoms with an unshared electron pair and may take part in nucleophilic condensations. Therefore, the reactions of these complexes (X=Cl, Br, NO₃) with 2,6-diacetylpyridine have also been studied viz., 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 DAPCH and 2,6-diacetylpyridine; X=Cl, Br, NO₃) have been isolated by carrying out the reactions by different methods. The infrared spectra of these cyclic products are reported.