Abstract

Ramesh Pangunoori and Kashi Ram

The formation constants of 1:1 & 1:2 binary M-A and M-A2 and 1:1:1 ternary metal complexes M-A-L or M-L'-A, where A= N-Phosphonomethyl iminodiacetic acid (PMI), L = Glycine (Gly) an β-Alanine (Ala), L' = 2,2-Bipyridyl (Bipy), 5-Sulphosalicylic acid (SSA), 1,10-1 henanthroine (Phen), Oxalic acid (Oxa) and Iminodiacetic acid (ida) and M = Co(ll), Nli(ll) and Cu(ll) have been evaluated potentiometrically in aqueousmedium at 30° C and at 0.10 M (KNOa) ionic strength. Theligand PMI behaves as a primary llgand in the presence of N,0 donors, i.e., Gly and Ala while in the presence of O.O and N<N donors, viz., Bipy, SSA, Phen, Oxa and ida, it acts as a secondary ligand. The stepwise and overalM .1,1:2 and 1:1:1 formation constants, log K1 (log K2), log K,2, log β2, log K1 T,the difference in stability constants of 1:1 secondary metal complexes and 1:1:1 ternary systems (ΔlogK), the percentage of relative stabilisation ( [% R.S. ) values and percentage of distribution of various species have been determined and discussed in terms of basicity of ligands, statistical aspects, electrostatic interaction, metal-ligand pi-interaction, denticity, nature of donor sites and stereochemical aspects.

N-Phosphqnomethyl; Donors; Aqueous

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