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

• Published in: Journal of the American Chemical Society 2021-09, Vol.143 (38), p.15556-15561
• Main Authors: 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
• Format: Article
• Language: English
• Subjects: Benzaldehydes - chemistry; Coordination Complexes - chemistry; Ferric Compounds - chemistry; Kinetics; Ligands; Molecular Structure; Oxidation-Reduction; Oxygen - chemistry; Sulfides - chemistry
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/jacs.1c03358

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.