Substitution of aqua ligands from cis-[Pt(en)(H2O)2](ClO4)2 and cis-[Pt(dmen)(H2O)2](ClO4)2 (en = ethylenediamine, dmen = N N′-dimethyl ethylenediamine) by glycine in aqueous medium—a kinetic and mechanistic approach



The kinetics of the interaction of glycine with cis-[Pt(en)(H2O)2](ClO4)2 and cis-[Pt(dmen)(H2O)2](ClO4)2 (en = ethylenediamine, dmen = N,N′-dimethylethylene-diamine) have been studied spectrophotometrically as a function of [substrate complex], [glycine], and temperature at a particular pH (4.0) where the substrate complex exists predominantly as the diaqua species and glycine as the zwitterion. The reaction was found to proceed through two consecutive steps. The first step involves the ligand-assisted anation, while the second step involves chelation when the second aqua ligand is displaced. Rate constants have been evaluated using the Weyh and Hamm method. Activation parameters for both steps have also been calculated using the Eyring equation. The low enthalpy of activation and large negative values of entropy of activation indicate an associative mode of activation for both steps. © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 37: 489–495, 2005