Formation constants of binary & ternary complexes of Cu (II) with substituted 1,2,4-triazoles & some O,O; O,N & N,N donors in aqueous medium

Abstract

The formation constants of 1 : 1 and 1 : 2 binary (Cu-A and Cu-A₂) and 1: 1 : 1 ternary (Cu-A-L) chelates [where A= 4-amino-5-mercapto-l,2,4-triazole (AMT) or 4-amino-5-mercapto- 3-methyl-l ,2,4-triazole (AMMT) and L= ethylenediamine (en); 1,10-phenanthroline (Phen); 2,2'-bipyridyl (Bipy), <em>o</em>-phenylenediamine (OPDA); glycine (Gly); <em>o</em>-aminophenol (<em>o</em>-AP); catechol (Cat); oxalic acid (Oxa) or thiodiacetic acid (TDA)] have been determined potentiometrically in aqueous medium. The ligands AMT and AMMT behave as primary ligands in presence of en, Gly, <em>o</em>-AP and Cat, while in presence of Phen, Bipy, NTA, IMDA and Oxa, they act as secondary ligands. They coordinate simultaneously in presence of OPDA and TDA. The overall stability constants, Log <em>&beta;</em><img src='http://www.niscair.res.in/jinfo/equation75.gif' border=0>_AL, are discussed in terms of the basicity of ligands, statistical aspects, electrostatic interaction, metal-ligand &pi;-interaction, denticity, nature of donor sites and stereochemical aspects.