A Mononuclear Non-heme Iron(III)–Peroxo Complex with an Unprecedented High O–O Stretch and Electrophilic Reactivity
2021
Zhu, Wenjuan | Jang, Semin | Xiong, Jin | Ezhov, Roman | Li, Xiao-Xi | Kim, Taeyeon | Seo, Mi Sook | Lee, Yong-Min | Pushkar, Yulia | Sarangi, Ritimukta | Guo, Yisong | Nam, Wonwoo
A mononuclear non-heme iron(III)–peroxo complex, [Fe(III)(O₂)(13-TMC)]⁺ (1), was synthesized and characterized spectroscopically; the characterization with electron paramagnetic resonance, Mössbauer, X-ray absorption, and resonance Raman spectroscopies and mass spectrometry supported a high-spin S = ⁵/₂ Fe(III) species binding an O₂ unit. A notable observation was an unusually high νO–O at ∼1000 cm–¹ for the peroxo ligand. With regard to reactivity, 1 showed electrophilic reactivity in H atom abstraction (HAA) and O atom transfer (OAT) reactions. In the HAT reaction, a kinetic isotope effect (KIE) value of 5.8 was obtained in the oxidation of 9,10-dihydroanthracene. In the OAT reaction, a negative ρ value of −0.61 in the Hammett plot was determined in the oxidation of p-X-substituted thioanisoles. Another interesting observation was the electrophilic reactivity of 1 in the oxidation of benzaldehyde derivatives, such as a negative ρ value of −0.77 in the Hammett plot and a KIE value of 2.2. To the best of our knowledge, the present study reports the first example of a mononuclear non-heme iron(III)–peroxo complex with an unusually high νO–O value and unprecedented electrophilic reactivity in oxidation reactions.
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