Substitution Reaction of Some Lead(II) Polyamine-N-polyacetate Complexes with Cobalt(II) Ions

Abstract

Kinetics of the substitution reactions of lead (II) complexes of ethylenediaminetetraacetate (edta), N-(2-hydroxyethy)ethylenediamine-N, N', N'-triacetate (edtaoh), 1, 2-cyclohexanediaminetetraacetate (cydta), and diethylenetriamine-N, N, N', N", N"-pentaacetate (dtpa) with cobalt (II) ions has been studied in the pH range 2.6∼4.9, at an ionic strength of 0.1, in the presence of excess lead (II) ions ( (0.04∼2.0) × 10^-4 mol.dm^-8), and at 20°C. The reverse reactions have been kinetically studied in the presence of excess cobalt (II) ions ((0.1∼2.0) × 10^-4 mol. dm^-8) in a similar way to the above study.
The initial rate equations for the forward and reverse reactions have been obtained from the measurement of change in absorbance in the region 240∼250 nm. The rate constants for the formation of CoHX^(n-s)- where X^n- represents the ligand groups, K_CoHX, were estimated; the values of K_CoHX were 1.2 × 10⁷, 1.4 × 10⁷ and 4.3 × 10⁷ mol^-1 dms². sec^-1 for edta, edtaoh and cydta, respectively.