Formation and Stabilities of Binary and Ternary Complexes of Transition Metal Ions Containing 4-Amino-5-Mercapto-3-N-Propyl-1,2,4-Triazole and Other Ligands in Solution

S. Mohan Rao, N. J. P. Subhashini and Shivaraj*

Department of Chemistry, Osmania University, Hyderabad-500 007 (India)

A pH-metric study of binary MA, MA2 and ternary MAL complex formation where M = Co(ll), Ni(ll), Cu(ll) and Zn(II); A = 4-amino-5-mercapto-1,2,4-triazole and 4-ammo-5-mercapto-3-n-propyl-1,2,4-triazole and L = glycine(gly), phenylalanine(phe ala), salicylic acid(sa), catechol(cat), ethylene-diamine(en) and 1,10-phenanthroline(phen) has been carried out in aqueous medium at 30+1° C and 0.1 M ionic strength. All metal ions were formed 1:1 and 1:2 binary complexes and 1:1:1 ternary complexes. The thermodynamic parameters DH, DG and DS have been calculated with known equations and discussed. The relative stabilities of the ternary complexes are quantitatively expressed in terms of the statistical parameter, D logK. The results were discussed in the light of the basicity of ligands, statistical aspects, electrostatic interactions, metal-ligand interactions, denticity, nature of donor sites and stereochemical aspects. The concentration profiles have indicated the favourability of the formation of binary and ternary complexes in general as reflected in the D log K values.

AMT; AMET; Binary Complexes; Ternary Complexes