Hydrolytic species of the ion cis-diaqua(ethylenediamine) palladium (II) complex and of cis-dichloro (ethylenediamine) palladium (II): Fitting its equilibrium models in aqueous media with or without chloride ion

Article abstract of DOI:10.1016/S0020-1693(96)05105-5

Thermodynamic data for equilibria involved in the overall hydrolytic process of the cis-[Pd(en) (H₂O)₂]²⁺ complex in the presence or absence of chloride ion are reported. All expected hydrolytic species are taken into account to calculate their formation constants and to fit the equilibrium model. The formation constants (log β_pqr) of aqua and/or hydroxo complexes were obtained from E(H⁺) data of alkalimetric titrations of cis-[Pd(en)(H₂O)₂] (ClO₄)₂ solutions. The log β_pqr values of chloro-containing complexes were obtained from E(H⁺) and E(Cl^-) data pairs, taking into account the above log β data as fixed values. All formation constants were fitted by SUPERQUAD calculations: log β_pqr for cis-aqua-hydroxo (pqr= 10-1, -6.68 (10)), di-μ-hydroxo (20-2, -7.758(4)), cis-dihydroxo (10-2, -14.523(4)), cis-dichloro (120, 5.24(1)), cis-chloro-aqua (110, 3.18(1)) and cis-chloro-hydroxo (11-1, -3.75(4)) species for I=0.15 mol dm^-3 in NaClO₄ and t=37°C. This constant set allows good simulation of experimental titration curves and is used to obtain a variety of species distribution diagrams.