title: A Comparison of the Selectivity of Extraction of [PtCl6](2-) by Mono-, Bi-, and Tripodal Receptors That Address Its Outer Coordination Sphere.
abstract: Extraction and binding studies of [PtCl6](2-) are reported for 24 mono-, bi-, and tripodal extractants containing tris(2-aminoethyl)amine (TREN) or tris(3-aminopropyl)amine (TRPN) scaffolds. These reagents are designed to recognize the outer coordination sphere of [PtCl6](2-) and to show selectivity over chloride anion under acidic conditions. Extraction from 0.6 M HCl involves protonation of the N-center in tertiary amines containing one, two, or three urea, amide, or sulfonamide hydrogen-bond donors to set up the following equilibrium: 2L(org) + 2H(+) + [PtCl6](2-) ⇌ [(LH)2PtCl6](org). All reagents show higher Pt loading than trioctylamine, which was used as a positive control to represent commercial trialkylamine reagents. The loading of [PtCl6](2-) depends on the number of pendant amides in the extractant and follows the order tripodal > bipodal > monopodal, with urea-containing extractants outperforming amide and sulfonamide analogues. A different series of reagents in which one, two, or three of the alkyl groups in tris-2-ethylhexylamine are replaced by 3-N'-hexylpropanamide groups all show a comparably high affinity for [PtCl6](2-) and high selectivity over chloride anion in extractions from aqueous acidic solutions. (1)H NMR titration of three extractants [LH·Cl] with [(Oct4N)2PtCl6] in CDCl3 provides evidence for high selectivity for [PtCl6](2-) over chloride for tri- and bipodal extractants, which show higher binding constants than a monopodal analogue.
authors.affiliation: School of Chemistry, University of Nottingham , Nottingham, NG7 2RD, U.K.
authors.forename: Rebecca J
authors.initials: RJ
authors.lastname: Warr
authors.affiliation: School of Chemistry, University of Nottingham , Nottingham, NG7 2RD, U.K.
authors.forename: Katherine J
authors.initials: KJ
authors.lastname: Bell
authors.affiliation: School of Chemistry, University of Nottingham , Nottingham, NG7 2RD, U.K.
authors.forename: Anastasia
authors.initials: A
authors.lastname: Gadzhieva
authors.affiliation: School of Chemistry, University of Nottingham , Nottingham, NG7 2RD, U.K.
authors.forename: Rafel
authors.initials: R
authors.lastname: Cabot
authors.affiliation: EaStCHEM School of Chemistry, University of Edinburgh , Edinburgh, EH9 3FJ, U.K.
authors.forename: Ross J
authors.initials: RJ
authors.lastname: Ellis
authors.affiliation: EaStCHEM School of Chemistry, University of Edinburgh , Edinburgh, EH9 3FJ, U.K.
authors.forename: Jy
authors.initials: J
authors.lastname: Chartres
authors.affiliation: EaStCHEM School of Chemistry, University of Edinburgh , Edinburgh, EH9 3FJ, U.K.
authors.forename: David K
authors.initials: DK
authors.lastname: Henderson
authors.affiliation: School of Chemistry, University of Nottingham , Nottingham, NG7 2RD, U.K.
authors.forename: Eleni
authors.initials: E
authors.lastname: Lykourina
authors.affiliation: EaStCHEM School of Chemistry, University of Edinburgh , Edinburgh, EH9 3FJ, U.K.
authors.forename: A Matthew
authors.initials: AM
authors.lastname: Wilson
authors.affiliation: EaStCHEM School of Chemistry, University of Edinburgh , Edinburgh, EH9 3FJ, U.K.
authors.forename: Jason B
authors.initials: JB
authors.lastname: Love
authors.affiliation: EaStCHEM School of Chemistry, University of Edinburgh , Edinburgh, EH9 3FJ, U.K.
authors.forename: Peter A
authors.initials: PA
authors.lastname: Tasker
authors.affiliation: School of Chemistry, University of Nottingham , Nottingham, NG7 2RD, U.K.|School of Chemistry, University of Manchester , Manchester, M13 9PL, U.K.
authors.forename: Martin
authors.initials: M
authors.lastname: Schröder