EFFECT OF STERIC HINDRANCE ON KINETIC AND EQUILIBRIUM DATA FOR SUBSTITUTION-REACTIONS OF DIAQUA(N-SUBSTITUTED ETHYLENEDIAMINE)PALLADIUM(II) WITH CHLORIDE IN AQUEOUS-SOLUTION

Kinetic and thermodynamic data are reported for the complex formation reactions: Pd(R4en)(H2O)2(2+) Cl- reversible k1 Pd(R4en)(H2O)Cl+ +H2O and Pd(R4en)(H2O)Cl+ +Cl- reversible k2 Pd(R4en)-Cl2+H2O, as a function of steric hindrance for R = Me and Et. The reported rate constants for these reactions decrease drastically on increasing the steric hindrance. These findings along with strongly negative DELTA-S] values support the operation of an associative reaction mechanism. Values for the complex formation and acid-dissociation constants are reported, from which speciation plots are constructed. All the results are discussed in reference to the corresponding data for the unsubstituted en system and the cis-Pt(NH3)2(H2O)2(2+) species.