Comment on “Speciation of Aqueous Palladium(II) Chloride Solutions Using Optical Spectroscopies” by C. D. Tait, D. R. Janecky, and P. S. Z. Rogers

Direct experimental evidence, statistical models, and linear free energy relationships indicate that mixed-ligand complex formation is an important aspect of Pd hydrolysis in natural solutions. Within the normal pH range of seawater the dominant hydrolyzed species of Pd(II) is PdCl3OH−2. Comparisons of Pd(II) and Pt(II) chemistry indicate that the equilibrium characteristics of the two metals are quite similar, with Pt(II) forming stronger complexes than Pd(II). Formulations of the solution chemical behavior of metals such as Pd(II) should be viewed in the context of typical stepwise complexation behavior, statistically predicted complexation relationships, and the behavior of chemical analogs such as Pt(II)