Four-Electron Oxidation of Phenols to p-Benzoquinone Imines by a (Salen)ruthenium(VI) Nitrido Complex.
Proton-coupled electron-transfer reactions of phenols have received considerable attention because of their fundamental interest and their relevance to many biological processes. Here we describe a remarkable four-electron oxidation of phenols by a (salen)ruthenium(VI) complex in the presence of pyridine in CH3OH to afford (salen)ruthenium(II) p-benzoquinone imine complexes. Mechanistic studies indicate that this reaction occurs in two phases. The first phase is proposed to be a two-electron transfer process that involves electrophilic attack by Ru≡N at the phenol aromatic ring, followed by proton shift to generate a Ru(IV) p-hydroxyanilido intermediate. In the second phase the intermediate undergoes intramolecular two-electron transfer, followed by rapid deprotonation to give the Ru(II) p-benzoquinone imine product.
Department of Biology and Chemistry and Institute of Molecular Functional Materials, City University of Hong Kong , Tat Chee Avenue, Hong Kong, China.
Jianhui
J
Xie
Department of Biology and Chemistry and Institute of Molecular Functional Materials, City University of Hong Kong , Tat Chee Avenue, Hong Kong, China.
Wai-Lun
WL
Man
Department of Biology and Chemistry and Institute of Molecular Functional Materials, City University of Hong Kong , Tat Chee Avenue, Hong Kong, China.
Chun-Yuen
CY
Wong
Department of Chemistry and State Key Laboratory of Synthetic Chemistry, The University of Hong Kong , Pokfulam Road, Hong Kong, China.
Xiaoyong
X
Chang
Department of Chemistry and State Key Laboratory of Synthetic Chemistry, The University of Hong Kong , Pokfulam Road, Hong Kong, China.
Chi-Ming
CM
Che
Department of Biology and Chemistry and Institute of Molecular Functional Materials, City University of Hong Kong , Tat Chee Avenue, Hong Kong, China.
Tai-Chu
TC
Lau