Sulfonamide mit heterocyclischen Substituenten als Extraktionsmittel für Kupfer(II)

Sulfonamides with Heterocyclic Substituents as Extractants for Copper(II) With 2-picolylbenzenesulfonamide (N2NHO₂SC₆H₅) as a model of the technical extractant LIX 34, the influence of functional variations on the extraction of copper(II) is studied and estimated by a comparison of the pH_1/2 values. The relation pH_1/2～–σ_p is observed for extractants with substituents in p-position of the benzene ring. Turning to 2-pyridylethylbenzenesulfonamide, which forms six-membered rings, an increase of pH_1/2 is observed. But no direct comparison is possible with 2-pyridylbenzenesulfonamide as the copper(II) complexes are dimeric having a structure analogous to copper(II) acetate. The substitution of the methylene group by an SO₂–(PSA? H) or an NH-residue (PTSH? H) is connected with an with an increase of pH_1/2 in the first case, but a decrease of pH_1/2 in the second one (7,2₅ and 2,7₀). The application of PTSH? H as an extractant for copper(II) is confined by a slow redox reaction with this ion. π-electron delocalization within the chelate rings, which are derived from sulfonylhydrazones of heterocyclic ketones, is a factor which, in general, improves the extraction properties. There is a strong differentiation of PH_1/2 (APSH? H 1,4; BBSH? H 6,9). An increase of the tetrahedral distortion of the chromophore CuN₄, as it is indicated by ESR, measurements, is connected with a decrease of pH_1/2. The benzenesulfonyl group influences the copper(II) extraction by bidentate nitrogen containing ligands in a twofold may: The protonation of the pyridyl and also that of other heterocyclic residues is rendered more difficult, but NH-acidity is increased. Some of the new extractants (APSH? H, BPSH? H) are as active as LIX reagents.