PALLADIUM(II) COMPLEXES OF N-SULFONYLAMINO ACIDS .3. TERNARY ADDUCTS WITH 2,2'-BIPYRIDINE

The equilibria involved in the formation of ternary adducts of Pd2+ wi th N-sulfonylamino acids (H,L) and 2,2'-bipyridine were investigated t hrough d.c. polarography, H-1 NMR and electronic spectroscopy in aqueo us solution starting from strongly acidic conditions. The formation of the ternary species appears to proceed through the initial binding of the heteroaromatic base to Pd2+ followed. at higher pH values. by lig ation of one amino acid dianion. The pK(NH) value of the latter. rangi ng from 3.2 to 4.7 for the different amino acids, is unchanged or slig htly higher compared to that observed in the formation of the [PdL(2)] (2-) species from the precursor [PdL] in the binary Pd2+-L(2-) systems . A comparison is made with the corresponding ternary complexes of Cu2 +, Cd2+ and Zn2+.