title: A Ruthenium(III)-Oxyl Complex Bearing Strong Radical Character.
abstract: Proton-coupled electron-transfer oxidation of a RuII-OH2complex, having an N-heterocyclic carbene ligand, gives a RuIII-O.species, which has an electronically equivalent structure of the RuIV=O species, in an acidic aqueous solution. The RuIII-O.complex was characterized by spectroscopic methods and DFT calculations. The oxidation state of the Ru center was shown to be close to +3; the Ru-O bond showed a lower-energy Raman scattering at 732 cm-1and the Ru-O bond length was estimated to be 1.77(1) Å. The RuIII-O.complex exhibits high reactivity in substrate oxidation under catalytic conditions; particularly, benzaldehyde and the derivatives are oxidized to the corresponding benzoic acid through C-H abstraction from the formyl group by the RuIII-O.complex bearing a strong radical character as the active species.
authors.affiliation: Department of Chemistry, Faculty of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennoudai, Tsukuba, Ibaraki, 305-8571, Japan.
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Shimoyama
authors.affiliation: Department of Chemistry, Faculty of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennoudai, Tsukuba, Ibaraki, 305-8571, Japan.
authors.forename: Tomoya
authors.initials: T
authors.lastname: Ishizuka
authors.affiliation: Department of Chemistry, Faculty of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennoudai, Tsukuba, Ibaraki, 305-8571, Japan.
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Kotani
authors.affiliation: Institute for Materials Chemistry and Engineering, Kyushu University, Motooka, Nishi-Ku, Fukuoka, 819-0395, Japan.
authors.forename: Yoshihito
authors.initials: Y
authors.lastname: Shiota
authors.affiliation: Institute for Materials Chemistry and Engineering, Kyushu University, Motooka, Nishi-Ku, Fukuoka, 819-0395, Japan.
authors.forename: Kazunari
authors.initials: K
authors.lastname: Yoshizawa
authors.affiliation: Picobiology Institute, Graduate School of Life Science, University of Hyogo, RSC-UH Leading Program Center, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo, 679-5148, Japan.
authors.forename: Kaoru
authors.initials: K
authors.lastname: Mieda
authors.affiliation: Picobiology Institute, Graduate School of Life Science, University of Hyogo, RSC-UH Leading Program Center, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo, 679-5148, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Ogura
authors.affiliation: Kyushu Synchrotron Light Research Center, 8-7 Yayoigaoka, Tosu, Saga, 841-0005, Japan.
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Okajima
authors.affiliation: Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba, Ibaraki, 305-0801, Japan.
authors.forename: Shunsuke
authors.initials: S
authors.lastname: Nozawa
authors.affiliation: Department of Chemistry, Faculty of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennoudai, Tsukuba, Ibaraki, 305-8571, Japan. kojima@chem.tsukuba.ac.jp.
authors.forename: Takahiko
authors.initials: T
authors.lastname: Kojima
keywords: N-heterocyclic carbenes; catalysis; oxyl radicals; ruthenium; substrate oxidation