A Ruthenium(III)–Oxyl Complex Bearing Strong Radical Character
Yoshihiro Shimoyama, Tomoya Ishizuka, Hiroaki Kotani, Yoshihito Shiota,
Kazunari Yoshizawa, Kaoru Mieda, Takashi Ogura, Toshihiro Okajima, Shunsuke Nozawa, and
Takahiko Kojima*
Abstract
Proton-coupled electron-transfer oxidation of a RuII OH2 complex, having an N-heterocyclic carbene ligand, gives a RuIII OC species, which has an electronically equivalent structure of the RuIV=O species, in an acidic aqueous solution. The RuIII OC 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 1 and the Ru O bond length was estimated to be 1.77(1) . The RuIII OC 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 OC complex bearing a strong radical character as the active species.
DOI: 10.1002/anie.201607861
Yoshihiro Shimoyama, Tomoya Ishizuka, Hiroaki Kotani, Yoshihito Shiota,
Kazunari Yoshizawa, Kaoru Mieda, Takashi Ogura, Toshihiro Okajima, Shunsuke Nozawa, and
Takahiko Kojima*
Abstract
Proton-coupled electron-transfer oxidation of a RuII OH2 complex, having an N-heterocyclic carbene ligand, gives a RuIII OC species, which has an electronically equivalent structure of the RuIV=O species, in an acidic aqueous solution. The RuIII OC 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 1 and the Ru O bond length was estimated to be 1.77(1) . The RuIII OC 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 OC complex bearing a strong radical character as the active species.
DOI: 10.1002/anie.201607861
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