Mixed-ligand complexes of palladium(II). Part 1. Diaqua(ethylenediamine) palladium(II) complexes of glycylglycine and glycinamide

Abstract

Potentiometric titrations of diaqua(ethylenediamine)palladium(II) with glycylglycine and glycinamide in 0.1 mol dm^–3 K[NO₃] have been carried out. The results are consistent with the equilibria (i) and (ii) where en = NH₂CH₂CH₂NH₂, Gly-GlyO = NH₂CH₂CONHCH₂CO₂^–, and Gly(NH₂)= NH₂CH₂CONH₂ log K₁ and pK_a′ are 9.60 and 3.76 for Gly-GlyO^– and 8.64 and 2.47 for Gly(NH₂). [Pd(en)(OH₂)₂]²⁺+ Gly-GlyO^– [graphic omitted] [Pd(en)(Gly-GlyO)]+ [graphic omitted] [Pd(en)(Gly-GlyO)′]+ H⁺(i), [Pd(en)(OH₂)₂]²⁺+ Gly(NH₂) [graphic omitted] [Pd(en){Gly(NH₂)}]²⁺ [graphic omitted] [Pd(en){Gly(NH₂)}′]⁺+ H⁺(ii)