title: Cation and anion selectivity of zwitterionic salicylaldoxime metal salt extractants.
abstract: 3-Dialkylaminomethyl substituted salicylaldoximes are efficient metal salt extractants, and, in contrast to related "salen"-based reagents, are sufficiently stable to acid hydrolysis to allow commercial application in base metal recovery. Crystal structures show that metal salts are bound by a zwitterionic form of the reagents, with copper(II) nitrate, tetrafluoroborate and trifluoroacetate forming [Cu()(2)X(2)] assemblies in a tritopic arrangement with a trans-disposition of the anions outwith the coordination sphere. Copper(II) chloride, bromide and zinc(II) chloride form 1:1 assemblies, [Cu()X(2)], with the halides in the inner coordination sphere of the metal, leading to high chloride selectivity and very good mass transport efficiencies of CuCl(2). Introduction of the anion-binding sites into the salicylaldoxime extractants changes their cation selectivities; the ligands co-extract small amounts of Fe(III) along with Cu(II) from mixed metal aqueous feed solutions, an issue which will need to be addressed prior to industrial application.
authors.affiliation: School of Chemistry, University of Edinburgh, Edinburgh, UKEH9 3JJ.
authors.forename: Ross S
authors.initials: RS
authors.lastname: Forgan
authors.forename: James E
authors.initials: JE
authors.lastname: Davidson
authors.forename: Francesca P A
authors.initials: FP
authors.lastname: Fabbiani
authors.forename: Stuart G
authors.initials: SG
authors.lastname: Galbraith
authors.forename: David K
authors.initials: DK
authors.lastname: Henderson
authors.forename: Stephen A
authors.initials: SA
authors.lastname: Moggach
authors.forename: Simon
authors.initials: S
authors.lastname: Parsons
authors.forename: Peter A
authors.initials: PA
authors.lastname: Tasker
authors.forename: Fraser J
authors.initials: FJ
authors.lastname: White
mesh_terms: D000838:Anions / Q000737:chemistry; D002412:Cations / Q000737:chemistry; D003300:Copper / Q000737:chemistry*; D007501:Iron / Q000737:chemistry*; D008024:Ligands; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D010091:Oximes / Q000737:chemistry*; D012492:Salts / Q000138:chemical synthesis / Q000737:chemistry; D015032:Zinc / Q000737:chemistry*
chemical_list: D000838:Anions; D002412:Cations; D008024:Ligands; D009942:Organometallic Compounds; D010091:Oximes; D012492:Salts; C005704:salicylaldoxime; D003300:Copper; D007501:Iron; D015032:Zinc