INTERACTION OF DL-PENICILLAMINE WITH DI-M- HYDROXOBIS(1,10-PHENANTHROLINE)DIPALLADIUM(II) ION IN AQUEOUS SOLUTION: KINETICS AND MECHANISM

Kinetics of interaction between DL-penicillamine with the di-µ-hydroxobis(1,10-phenanthroline) dipalladium(II) ion complex has been studied spectrophotometrically as a function of [Pd2(1,10-phen)2(OH)2] 2+ concentration, where 1,10-phen = 1, 10-phenanthroline, [DL-penicillamine], pH and temperature. The reaction has been monitored at the λmax 240 nm. of the substituted complex, where the spectral difference between the reactant and product is maximum. The reaction rate increases with an increase in DL-penicillamine concentration and it shows a linear dependence on the concentration of DL-penicillamine. The second order rate constants 10 2 k2 values are 69.99, 87.46, 133.93 and 159.19-dm 3 mol -1 s -1 at 20, 25, 30 and 35 0 C respectively have been calculated from the slope of k(obs) versus [DL-penicillamine] plot. From the experimental findings an associative mechanism for the substitution reaction is proposed. The activation parameters (∆H ≠ =45.39 ± 1.4 KJ/mol -1 , ∆S ≠ = -93.41 ± 2.3 JK -1 mol -1 )