A Mononuclear Non-heme Iron(III)–Peroxo Complex with an Unprecedented High O–O Stretch and Electrophilic Reactivity

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 with an Unprecedented High O–O Stretch and Electrophilic Reactivity

2021

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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