title: Hydroxo-bridged dicopper(II,III) and -(III,III) complexes: models for putative intermediates in oxidation catalysis.
abstract: A macrocyclic ligand (L(4-)) comprising two pyridine(dicarboxamide) donors was used to target reactive copper species relevant to proposed intermediates in catalytic hydrocarbon oxidations by particulate methane monooxygenase and heterogeneous zeolite systems. Treatment of LH4 with base and Cu(OAc)2·H2O yielded (Me4N)2[L2Cu4(μ4-O)] (1) or (Me4N)[LCu2(μ-OH)] (2), depending on conditions. Complex 2 was found to undergo two reversible 1-electron oxidations via cyclic voltammetry and low-temperature chemical reactions. On the basis of spectroscopy and theory, the oxidation products were identified as novel hydroxo-bridged mixed-valent Cu(II)Cu(III) and symmetric Cu(III)2 species, respectively, that provide the first precedence for such moieties as oxidation catalysis intermediates.
authors.affiliation: Department of Chemistry, Center for Metals in Biocatalysis, Chemical Theory Center, and Minnesota Supercomputing Institute, University of Minnesota , 207 Pleasant Street SE, Minneapolis, Minnesota 55455, United States.
authors.forename: Mohammad Reza
authors.initials: MR
authors.lastname: Halvagar
authors.forename: Pavlo V
authors.initials: PV
authors.lastname: Solntsev
authors.forename: Hyeongtaek
authors.initials: H
authors.lastname: Lim
authors.forename: Britt
authors.initials: B
authors.lastname: Hedman
authors.forename: Keith O
authors.initials: KO
authors.lastname: Hodgson
authors.forename: Edward I
authors.initials: EI
authors.lastname: Solomon
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Cramer
authors.forename: William B
authors.initials: WB
authors.lastname: Tolman
mesh_terms: D002384:Catalysis; D003300:Copper / Q000737:chemistry* / Q000378:metabolism; D006878:Hydroxides / Q000737:chemistry* / Q000378:metabolism; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry* / Q000378:metabolism; D010084:Oxidation-Reduction; D010105:Oxygenases / Q000737:chemistry* / Q000378:metabolism; D017641:Zeolites / Q000737:chemistry*
chemical_list: D006878:Hydroxides; D009942:Organometallic Compounds; D017641:Zeolites; D003300:Copper; D010105:Oxygenases; C021555:methane monooxygenase