title: Synthetic, structural, electrochemical and solvent extraction studies of neutral trinuclear Co(II), Ni(II), Cu(II) and Zn(II) metallocycles and tetrahedral tetranuclear Fe(III) species incorporating 1,4-aryl-linked bis-beta-diketonato ligands.
abstract: Uncharged complexes, formulated as trimeric metallocycles of type [M3(L(1))3(Py)6] (where M = cobalt(II), nickel(II) and zinc(II) and L(1) is the doubly deprotonated form of a 1,4-phenylene linked bis-beta-diketone ligand of type 1,4-bis(RC(O)CH2C(O))C6H4 (R = t-Bu)) have been synthesised, adding to related, previously reported complexes of these metals with L(1) (R = Ph) and copper(ii) with L(1) (R = Me, Et, Pr, t-Bu, Ph). New lipophilic ligand derivatives with R = hexyl, octyl or nonyl were also prepared for use in solvent extraction experiments. The X-ray structures of H2L(1) (R = t-Bu) and of its trinuclear (triangular) nickel(II) complex [Ni3(L(1))3(Py)6].3.5Py (R = t-Bu) are also presented. Electrochemical studies of H2L(1), [Co3(L(1))3(Py)6], [Ni3(L(1))3(Py)6], [Cu3(L(1))3], [Zn3(L(1))3(Py)6] and [Fe4(L(1))6] (all with R = t-Bu) show that oxidative processes for the complexes are predominantly irreversible, but several examples of quasireversible behaviour also occur and support the assignment of an anodic process, seen between +1.0 and +1.6 V, as involving metal-centred oxidations. The reduction behaviour for the respective metal complexes is not simple, being irreversible in most cases. Solvent extraction studies (water/chloroform) involving the systematic variation of the metal, bis-beta-diketone and heterocyclic base concentrations have been performed for cobalt(II) and zinc(II) using a radiotracer technique in order to probe the stoichiometries of the respective extracted species. Significant extraction synergism was observed when 4-ethylpyridine was also present with the bis-beta-diketone ligand in the chloroform phase. Competitive extraction studies demonstrated a clear uptake preference for copper(II) over cobalt(II), nickel(II), zinc(II) and cadmium(II).
authors.affiliation: Centre for Heavy Metals Research, School of Chemistry, University of Sydney, NSW 2006, Australia.
authors.forename: Jack K
authors.initials: JK
authors.lastname: Clegg
authors.forename: David J
authors.initials: DJ
authors.lastname: Bray
authors.forename: Kerstin
authors.initials: K
authors.lastname: Gloe
authors.forename: Karsten
authors.initials: K
authors.lastname: Gloe
authors.forename: Katrina A
authors.initials: KA
authors.lastname: Jolliffe
authors.forename: Geoffrey A
authors.initials: GA
authors.lastname: Lawrance
authors.forename: Leonard F
authors.initials: LF
authors.lastname: Lindoy
authors.forename: George V
authors.initials: GV
authors.lastname: Meehan
authors.forename: Marco
authors.initials: M
authors.lastname: Wenzel
mesh_terms: D018360:Crystallography, X-Ray; D003500:Cyclization; D004563:Electrochemistry; D007659:Ketones / Q000138:chemical synthesis* / Q000737:chemistry; D008024:Ligands; D019216:Metals, Heavy / Q000737:chemistry*; D008958:Models, Molecular; D015394:Molecular Structure; D010084:Oxidation-Reduction; D011725:Pyridines / Q000737:chemistry; D012997:Solvents / Q000737:chemistry*
chemical_list: D007659:Ketones; D008024:Ligands; D019216:Metals, Heavy; D011725:Pyridines; D012997:Solvents; C023666:pyridine