Determination of Spin Inversion Probability, H-Tunneling Correction, and Regioselectivity in the Two-State Reactivity of Nonheme Iron(IV)-Oxo Complexes

Yoon Hye Kwon; Binh Khanh Mai; Yong-Min Lee; Sunder N Dhuri; Debasish Mandal; Kyung-Bin Cho; Yongho Kim; Sason Shaik; Wonwoo Nam

doi:10.1021/acs.jpclett.5b00527

Determination of Spin Inversion Probability, H-Tunneling Correction, and Regioselectivity in the Two-State Reactivity of Nonheme Iron(IV)-Oxo Complexes

J Phys Chem Lett. 2015 Apr 16;6(8):1472-6. doi: 10.1021/acs.jpclett.5b00527. Epub 2015 Apr 6.

Authors

Yoon Hye Kwon¹, Binh Khanh Mai², Yong-Min Lee¹, Sunder N Dhuri^{1

3}, Debasish Mandal⁴, Kyung-Bin Cho¹, Yongho Kim², Sason Shaik⁴, Wonwoo Nam¹

Affiliations

¹ †Department of Chemistry and Nano Science, Ewha Womans University, Seoul 120-750, Korea.
² ‡Department of Applied Chemistry and Institute of Natural Sciences, Kyung Hee University, Gyeonggi-do 446-701, Korea.
³ ¶Department of Chemistry, Goa University, Goa 403 206, India.
⁴ §Institute of Chemistry and the Lise Meitner-Minerva Center for Computational Quantum Chemistry, The Hebrew University of Jerusalem, 91904 Jerusalem, Israel.

PMID: 26263154
DOI: 10.1021/acs.jpclett.5b00527

Abstract

We show by experiments that nonheme Fe(IV)O species react with cyclohexene to yield selective hydrogen atom transfer (HAT) reactions with virtually no C═C epoxidation. Straightforward DFT calculations reveal, however, that C═C epoxidation on the S = 2 state possesses a low-energy barrier and should contribute substantially to the oxidation of cyclohexene by the nonheme Fe(IV)O species. By modeling the selectivity of this two-site reactivity, we show that an interplay of tunneling and spin inversion probability (SIP) reverses the apparent barriers and prefers exclusive S = 1 HAT over mixed HAT and C═C epoxidation on S = 2. The model enables us to derive a SIP value by combining experimental and theoretical results.

Keywords: density functional theory; kinetic isotope effect; spin inversion; tunneling; two-state reactivity.