Mixed-ligand complexes of palladium(II). Part 3. Diaqua(ethylene-diamine) palladium(II) complexes of L-amino-acids

Abstract

The reactions of [Pd(en)(OH₂)₂]²⁺(en = ethylenediamine) with the amino-acids glycine, L-alanine, sarcosine, NN-dimethylglycine, L-leucine, L-phenylalanine, L- proline, L-tryptophan, L-methionine, and S-methyl-L-cysteine have been studied by potentiometric titrations. For L-methionine and S-methyl-L-cysteine, equilibria (i) and (ii)[Pd(en)(OH₂)₂]²⁺+ L–[graphics omitted] [Pd(en)L]⁺+ 2H₂O (i), [Pd(en)(OH₂)₂]²⁺+ HL[graphics omitted] [Pd(en)(HL)]²⁺+ 2H₂O (ii) hold in solution, where L^–= MeS[CH₂]_nCH(NH₂)CO₂^–(n= 1 or 2). For the remaining amino-acids only equilibrium (i) is significant.