Mixed-ligand complexes of palladium(II). Part 2. Diaqua(ethylenediamine) palladium(II) complexes of L-asparagine and L-glutamine
Abstract
The reactions of [Pd(en)(OH2)2]2+(en = ethylenediamine) with L-asparagine monohydrate and L-glutamine in 0.5 mol dm–3 K[NO3] have been studied by potentiometric titrations. The results obtained can be explained by equilibria (i) and (ii) where L–= H2NCOCH2CH(NH2)CO2– or H2NCOCH2CH2CH(NH2)CO2–, and log K1 and [Pd(en)(OH)2]2++ L–[graphic omitted][Pd(en)L]+(i), [Pd(en)L]+[graphic omitted][Pd(en)L′]+ H+(ii) pKa′ are 10.46 and 6.46 for asparagine and 10.76 and 9.03 for glutamine respectively. The mode of co-ordination of the two ligands in their protonated and deprotonated complexes is discussed on the basis of these parameters.