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The elusive active species in nickel(ii)-mediated oxidations of hydrocarbons by peracids: a NiII-oxyl species, an aroyloxy radical, or a NiII-peracid complex?
- Title
- The elusive active species in nickel(ii)-mediated oxidations of hydrocarbons by peracids: a NiII-oxyl species, an aroyloxy radical, or a NiII-peracid complex?
- Authors
- Wu Z.; Sun D.; Lee Y.-M.; Zhao Y.; Nam W.; Wang Y.
- Ewha Authors
- 남원우; 이용민
- SCOPUS Author ID
- 남원우; 이용민
- Issue Date
- 2023
- Journal Title
- Dalton Transactions
- ISSN
- 1477-9226
- Citation
- Dalton Transactions vol. 52, no. 25, pp. 8676 - 8684
- Publisher
- Royal Society of Chemistry
- Indexed
- SCIE; SCOPUS
- Document Type
- Article
- Abstract
- Nonheme nickel(ii)-mediated oxidations of hydrocarbons by meta-chloroperbenzoic acid (mCPBA) show promising activity and selectivity; however, the active species and the reaction mechanism of these reactions are still elusive after decades of efforts. Herein, a novel free radical chain mechanism of the Ni(ii)-mediated oxidation of cyclohexane by mCPBA is investigated using density functional theory calculations. In this study, we rule out the involvement of a long speculated NiII-oxyl species. Instead, an aroyloxy radical (mCBA˙) and a NiIII-hydroxyl species formed by a rate-limiting O-O homolysis of a NiII-mCPBA complex are active species in the C-H bond activation to form a carbon-centered radical R˙, where mCBA˙ is more robust than the NiIII-hydroxyl species. The nascent R˙ radical either reacts with mCPBA to form a hydroxylated product and a mCBA˙ radical to propagate the radical chain or reacts with the solvent dichloromethane to form a chlorinated product. In addition, the NiII-mCPBA complex is found for the first time to be a robust oxidant in hydroxylation of cyclohexane, with an activation energy of 13.4 kcal mol−1. These mechanistic findings support the free radical chain mechanism and enrich the mechanistic knowledge of metal-peracid oxidation systems containing transition metals after group 8 in periodic table of elements. © 2023 The Royal Society of Chemistry.
- DOI
- 10.1039/d3dt01276j
- Appears in Collections:
- 자연과학대학 > 화학·나노과학전공 > Journal papers
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