Thermodynamical study on the formation of some mixed ligand complexes of non-transition metal ions in solution I. The formation and the stability of some Pb(II) mixed ligand complexes

Abstract

The stability constants of the binary complexes of type PbB, PbB2, and the mixed ligand complexes of type PbAB have been studied by potentiometric pH titration technique at ionic strength I = 0.10 (KNO3) and at temperature 15, 25, 35 and 45°C respectively, where A = 2,2′-bipyridyl (bipy) or 1,10-phenanthroline (phen); B = malonate (mal), succinate (suc), or anthranilate (anth). The equalibrium constants ΔlogK,1 ΔΔG, ΔΔH, and ΔΔS of the reaction PbA + PbB = PbAB + Pb2+ have been calculated. The results show that the discriminating effects2 between the primary ligand (bipy or phen) and the secondary ligand (mal, suc or anth) in those non-transition metal mixed ligand complexes are also evident, and as a measurement of this effect, ΔΔH is more appropriate than ΔlogK. The possible reasons which lead to these results have been discussed.