title: One- and two-electron reduced 1,2-diketone ligands in [Zn(II)(L*)2(Et2O)], [Co(II)(L*)2(Et2O)], and Na2(Et2O)4[Co(II)(LRed)2].
abstract: The reaction of 1,2-diketone bis(2,6-diisopropylphenyl)glyoxal (L(Ox)) with ZnCl(2) or CoCl(2) (ratio 2:1) in dry diethyl ether with 2 equiv of sodium (per transition-metal ion) afforded the neutral complexes [Zn(II)(L(*))(2)(Et(2)O)] (1) and [Co(II)(L(*))(2)(Et(2)O)] (2), which were characterized by X-ray crystallography, magnetochemistry, IR, electron paramagnetic resonance, and UV-vis spectroscopy. When 4 equiv of sodium were added, complex Na(2)(Et(2)O)(4)[Co(II)(L(Red))(2)] (4) was isolated, which included some crystals of a minor (<2%) product Na(Et(2)O)(2)[Co(III)(L(Red))(2)] (3). (L(*))(-) represents the pi-radical monoanion of the 1,2-diketone, and (L(Red))(2-) is its enediolate(2-) analogue. The electronic structures of 1, 2, and 4 have been elucidated by spectroscopy, and results are corroborated by broken-symmetry density functional theory calculations using the B3LYP functional. 1 possesses an S = 0 ground state with an excited triplet state that is 130 cm(-1) higher in energy; 2 and 4 have an S = 1/2 ground state. These complexes corroborate the notion that acyclic 1,2-diketones are redox noninnocent ligands.
authors.affiliation: Max-Planck-Institut für Bioanorganische Chemie, Stiftstrasse 34-36, D-45470 Mülheim an der Ruhr, Germany.
authors.forename: Geoffrey H
authors.initials: GH
authors.lastname: Spikes
authors.forename: Carsten
authors.initials: C
authors.lastname: Milsmann
authors.forename: Eckhard
authors.initials: E
authors.lastname: Bill
authors.forename: Thomas
authors.initials: T
authors.lastname: Weyhermüller
authors.forename: Karl
authors.initials: K
authors.lastname: Wieghardt
mesh_terms: D002712:Chlorides / Q000737:chemistry; D003035:Cobalt / Q000737:chemistry; D018360:Crystallography, X-Ray / Q000379:methods; D006037:Glyoxal / Q000031:analogs & derivatives* / Q000737:chemistry; D007097:Imines / Q000737:chemistry; D007659:Ketones / Q000737:chemistry*; D008024:Ligands; D008958:Models, Molecular; D008968:Molecular Conformation; D015394:Molecular Structure; D010783:Photometry / Q000379:methods; D013053:Spectrophotometry / Q000379:methods; D017967:Zinc Compounds / Q000737:chemistry
chemical_list: D002712:Chlorides; D007097:Imines; D007659:Ketones; D008024:Ligands; D017967:Zinc Compounds; C525944:bis(2,6-diisopropylphenyl)glyoxal; D003035:Cobalt; D006037:Glyoxal; C016837:zinc chloride; C018021:cobaltous chloride