title: Proton-Induced, Reversible Interconversion of a μ-1,2-Peroxo and a μ-1,1-Hydroperoxo Dicopper(II) Complex.
abstract: The μ-1,2-peroxo dicopper(II) complex (2) of a compartmental bis(tetradentate) pyrazolate-based ligand is shown to convert, upon protonation, to the corresponding μ-1,1-hydroperoxo dicopper(II) complex (3). The transformation is cleanly reversed with base, and an apparent pK(a) = 22.2 ± 0.3 for the Cu2OOH unit in MeCN has been determined. The unprecedented stability of 3 (t(1/2) = 9 h in nitrile solvents at room temperature, giving the hydroxo-bridged dicopper complex) has allowed for its structural characterization by X-ray diffraction. While the O-O bond length (1.462(3) Å) barely changes upon protonation from 2 to 3, the O-O stretching frequency is much higher in the hydroperoxo complex 3 (860 cm(-1)). 3 mediates 2e(-) oxo transfer to the nucleophilic substrate PPh3 but is not activated for H-atom abstraction.
authors.affiliation: Institut für Anorganische Chemie, Georg-August-Universität Göttingen, Tammannstraße 4, 37077 Göttingen, Germany.
authors.forename: Nicole
authors.initials: N
authors.lastname: Kindermann
authors.affiliation: Institut für Anorganische Chemie, Georg-August-Universität Göttingen, Tammannstraße 4, 37077 Göttingen, Germany.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Dechert
authors.affiliation: Institut für Anorganische Chemie, Georg-August-Universität Göttingen, Tammannstraße 4, 37077 Göttingen, Germany.
authors.forename: Serhiy
authors.initials: S
authors.lastname: Demeshko
authors.affiliation: Institut für Anorganische Chemie, Georg-August-Universität Göttingen, Tammannstraße 4, 37077 Göttingen, Germany.
authors.forename: Franc
authors.initials: F
authors.lastname: Meyer
mesh_terms: D056831:Coordination Complexes / Q000737:chemistry*; D003300:Copper / Q000737:chemistry*; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D010100:Oxygen / Q000737:chemistry; D010545:Peroxides / Q000737:chemistry*; D011522:Protons
chemical_list: D056831:Coordination Complexes; D010545:Peroxides; D011522:Protons; D003300:Copper; D010100:Oxygen