Synergistic effects of CH3CO2H and Ca2+ on C–H bond activation by MnO4−. Issue 39 (29th September 2022)

• Record Type: Journal Article
• Authors: Shi, Huatian; Cheng, Lin; Pan, Yi; Mak, Chi-Keung; Lau, Kai-Chung; Lau, Tai-Chu
• Is Part Of: Chemical science. Volume 13:Issue 39(2022)
• Page Start: 11600
• Page End: 11606
• Publication Date: 2022-09-29
• Subjects: Chemistry -- Periodicals; 540.5
• DOI: 10.1039/d2sc03089f
• Languages: English
• ISSNs: 2041-6520

Abstract

Abstract : The activation of metal-oxo species with Lewis acids is of current interest. Abstract : The activation of metal-oxo species with Lewis acids is of current interest. In this work, the effects of a weak Brønsted acid such as CH3 CO2 H and a weak Lewis acid such as Ca 2+ on C–H bond activation by KMnO4 have been investigated. Although MnO4 − is rather non-basic (p K a of MnO3 (OH) = −2.25), it can be activated by AcOH or Ca 2+ to oxidize cyclohexane at room temperature to give cyclohexanone as the major product. A synergistic effect occurs when both AcOH and Ca 2+ are present; the relative rates for the oxidation of cyclohexane by MnO4 − /AcOH, MnO4 − /Ca 2+ and MnO4 − /AcOH/Ca 2+ are 1 : 73 : 198. DFT calculations show that in the active intermediate of MnO4 − /AcOH/Ca 2+, MnO4 − is H-bonded to 3 AcOH molecules, while Ca 2+ is bonded to 3 AcOH molecules as well as to an oxo ligand of MnO4 − . Our results also suggest that these synergistic activating effects of a weak Brønsted acid and a weak Lewis acid should be applicable to a variety of metal-oxo species.