Abstract: The stability constants of the binary complexes Pd(CA)⁺ and the ternary complexes Pd(Phen)(CA)⁺ have been determined by potentiometric pH titration.The stability difference among the ternary mixed-ligand complexes has been discussed.The experimental results indicate the existence of intramolecular aromatic ring stacking interactions in the ternary mixed-ligand complexes Pd (Phen)(PheCA)⁺.The extent of stacking depends on the number of methylene groups between the phenyl moiety and the coordinated carboxylate groups.The best fit stacking is reached with 2-phenylacetate and 3-phenylpropionate.

Key words: palladium(Ⅱ), mixed-ligand complex, aromatic ring stacking, stability constant