title: Structural insights into the coordination and extraction of Pb(II) by disulfonamide ligands derived from o-phenylenediamine.
abstract: The o-phenylenediamine-derived disulfonamide ligands 1 and 2 complex and efficiently extract Pb(II) from water into 1,2-dichloroethane via ion-exchange, in combination with 2,2'-bipyridine (97.5% and 95.0%, respectively, for 1:1 ligand-to-Pb ratios). The corresponding Pb(II)-sulfonamido binary complexes of ligands 1 and 2 (3 and 4, respectively), and ternary complexes with 2,2'-bipyridine (5 and 6, respectively), were isolated and characterized. (1)H NMR spectra of the organic phases after extraction show the formation of ternary Pb-sulfonamido-bipy complexes. X-ray characterization of 3, 4, and the ternary complex 5 consistently demonstrates four primary coordination sites and a stereochemically active lone pair on Pb. The X-ray structure of 3 shows a pseudo trigonal bipyramidal configuration on Pb, with the lone pair occupying one of the equatorial sites, and the formation of an unusual "hemidirected" coordination polymer via axial S=O-Pb coordination. The same axial S=O-Pb coordination pattern with two DMSO molecules is observed in the structure of 4.[2(CH(3))(2)SO)], thus rationalizing the high solubility of the binary complexes in strongly coordinating solvents. In contrast, the X-ray structure of the ternary complex 5 reveals a distorted four-coordinate configuration with only weak S=O-Pb coordination leading to dimer formation, thus explaining its higher solubility in weakly coordinating solvents. FT-IR spectroscopy confirms the X-ray data, since the ligand nu(S)(=)(O) stretching frequencies shift to lower values in the binary Pb(II)-sulfonamido complexes and are again altered upon formation of the ternary Pb(II)-sulfonamido-bipy complexes, as would be expected for 2,2'-bipy complexation and hindered S=O-Pb coordination.
authors.affiliation: Department of Chemistry and Biochemistry, Florida International University, Miami, 33199, USA.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Alvarado
authors.forename: Jay M
authors.initials: JM
authors.lastname: Rosenberg
authors.forename: Aileen
authors.initials: A
authors.lastname: Andreu
authors.forename: Jeffrey C
authors.initials: JC
authors.lastname: Bryan
authors.forename: Wei-Zhong
authors.initials: WZ
authors.lastname: Chen
authors.forename: Tong
authors.initials: T
authors.lastname: Ren
authors.forename: Konstantinos
authors.initials: K
authors.lastname: Kavallieratos
mesh_terms: D007854:Lead / Q000032:analysis / Q000737:chemistry*; D008024:Ligands; D015394:Molecular Structure; D010655:Phenylenediamines / Q000737:chemistry*; D012997:Solvents / Q000737:chemistry; D013449:Sulfonamides / Q000737:chemistry*
chemical_list: D008024:Ligands; D010655:Phenylenediamines; D012997:Solvents; D013449:Sulfonamides; D007854:Lead