title: Solvent effects on the conversion of dicopper(II) micro-eta(2):eta(2)-peroxo to bis-micro-oxo dicopper(III) complexes: direct probing of the solvent interaction.
abstract: A new tridentate ligand, PYAN, is employed to investigate solvent influences for dioxygen reactivity with [Cu(PYAN)(MeCN)]B(C(6)F(5))(4) (1). Stopped-flow kinetic studies confirm that the adducts [[u(II)(PYAN)]2)(O(2))][B(C(6)F(5))(4)](2) (2(Peroxo)) and [[u(III)(PYAN)]2)(O)(2)][B(C(6)F(5))(4)](2) (2(Oxo)) are in rapid equilibrium. Thermodynamic parameters for the equilibrium between 2(Peroxo) and 2(Oxo) re as follows: THF, deltaH degrees approximately -15.7 kJ/mol, deltaS degrees approximately -83 J/K.mol; acetone, deltaH degrees approximately -15.8 kJ/mol, deltaS degrees approximately -76 J/K.mol. UV-visible absorption and resonance Raman spectroscopic signatures demonstrate that the equilibrium is highly solvent dependent; the mixture is mostly 2(Peroxo) in CH(2)Cl(2), but there are significantly increasing quantities of 2(Oxo) along the series methylene chloride --> diethyl ether --> acetone --> tetrahydrofuran (THF). Copper(II)-N(eq) stretches (239, 243, 244, and 246 cm(-)(1) in CH(2)Cl(2), Et(2)O, acetone, and THF, respectively) are identified for 2(Peroxo), but they are not seen in 2(Oxo), revealing for the first time direct evidence for solvent coordination in the more open 2(Peroxo) structure.
authors.affiliation: Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland 21218, USA.
authors.forename: Hong-Chang
authors.initials: HC
authors.lastname: Liang
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Henson
authors.forename: Lanying Q
authors.initials: LQ
authors.lastname: Hatcher
authors.forename: Michael A
authors.initials: MA
authors.lastname: Vance
authors.forename: Christiana Xin
authors.initials: CX
authors.lastname: Zhang
authors.forename: David
authors.initials: D
authors.lastname: Lahti
authors.forename: Susan
authors.initials: S
authors.lastname: Kaderli
authors.forename: Roger D
authors.initials: RD
authors.lastname: Sommer
authors.forename: Arnold L
authors.initials: AL
authors.lastname: Rheingold
authors.forename: Andreas D
authors.initials: AD
authors.lastname: Zuberbühler
authors.forename: Edward I
authors.initials: EI
authors.lastname: Solomon
authors.forename: Kenneth D
authors.initials: KD
authors.lastname: Karlin
mesh_terms: D003300:Copper / Q000737:chemistry*; D018360:Crystallography, X-Ray; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry*; D010100:Oxygen / Q000737:chemistry*; D012997:Solvents; D013059:Spectrum Analysis, Raman / Q000379:methods
chemical_list: D009942:Organometallic Compounds; D012997:Solvents; D003300:Copper; D010100:Oxygen