Pb(II) coordination and synergistic ion-exchange extraction by combinations of sulfonamide chelates and 2,2'-bipyridine.

The disulfonamide ligands 1,2-C(6)H(4)(NH(2)SO(2)C(6)H(5))(2) (1) and 1,2-C(6)H(4)(NH(2)SO(2)C(6)H(4)-p-Bu(t))(2) (2), which are readily available in good yields from o-phenylenediamine and the corresponding sulfonyl chlorides, efficiently extract Pb(II) from water into 1,2-dichloroethane when used in synergistic combinations with 2,2'-bipyridine via an ion-exchange mechanism. The extraction was shown to proceed via the formation of a ternary Pb-sulfamido-2,2'-bipyridine complex. The X-ray crystal structure of the binary Pb-sulfamido complex 3 shows a coordination polymer with a stereochemically active lone pair on Pb formed by S=O-Pb axial coordination.