skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Mechanism for the homolytic cleavage of alkyl hydroperoxides by the manganese(III) dimer Mn{sup III}{sub 2}(2-OHsalpn){sub 2}

Abstract

The oxidation of Mn{sup III}{sub 2}(2-OHsalpn){sub 2}, 1 (2-OHsalpn = 1,3-bis(salicylideneamino)-2-propanol), with tert-butyl hydroperoxide was studied in organic media. A one-electron reaction occurs resulting in initial formation of the oxidized Mn{sup III}Mn{sup IV} (2-OHsalpn){sub 2}OH species 2 and a tert-butoxy radical. The Mn{sup III}Mn{sup IV}(2-OHsalpn){sub 2}OH complex can be readily protonated to yield Mn{sup III}Mn{sup IV} (2-OHsalpn){sub 2}{sup +}. Upon addition of excess tert-butyl hydroperoxide, singlet dioxygen is evolved in an exothermic reaction indicative of radical-induced disproportionation of the hydroperoxide. In the presence of a radical scavenger, the oxygen evolution is strongly attenuated. This system was observed to oxygenate cyclohexene to yield 2-cyclohexen-1-one, 2-cyclohexen-1-ol, and traces of cyclohexene oxide. Cumene is oxygenated to 2-phenyl-2-propanol and acetophenone, and cyclohexane is oxygenated to cyclohexanone and cyclohexanol. However, {sup 18}O-labeling experiments show that the oxygen in the products results exclusively from reactions with aerobic dioxygen and not from the tert-butyl hydroperoxide oxidant. These results indicate that oxygenation occurs by radical-initiated aerobic autoxidation and not via oxo transfer from a high-valent manganese oxo species. 2 was studied by UV-vis, IR, NMR, EXAFS, XANES, and EPR spectroscopies, which support the assignment of a dinuclear manganese (III/IV) terminal hydroxo structure. 2 was also formed by themore » direct reaction of Mn{sup III}Mn{sup IV}(2-OHsalpn){sub 2}{sup +} with OH{sup {minus}}, further supporting the description of 2 as having a terminal hydroxide ligand. The kinetics of its formation from 1 and tert-butyl hydroperoxide were examined and found to be first-order in peroxide.« less

Authors:
; ;  [1]
  1. Univ. of Michigan, Ann Arbor, MI (United States); and others
Publication Date:
OSTI Identifier:
476870
Resource Type:
Journal Article
Journal Name:
Inorganic Chemistry
Additional Journal Information:
Journal Volume: 35; Journal Issue: 12; Other Information: PBD: 5 Jun 1996
Country of Publication:
United States
Language:
English
Subject:
40 CHEMISTRY; MANGANESE COMPOUNDS; OXIDATION; PEROXIDES; REDUCTION; RADICALS; CHEMICAL REACTION YIELD; ABSORPTION SPECTROSCOPY; NUCLEAR MAGNETIC RESONANCE; X-RAY SPECTROSCOPY; ELECTRON SPIN RESONANCE; CHEMICAL REACTION KINETICS

Citation Formats

Caudle, M T, Riggs-Gelasco, P, and Gelasco, A K. Mechanism for the homolytic cleavage of alkyl hydroperoxides by the manganese(III) dimer Mn{sup III}{sub 2}(2-OHsalpn){sub 2}. United States: N. p., 1996. Web. doi:10.1021/ic951462u.
Caudle, M T, Riggs-Gelasco, P, & Gelasco, A K. Mechanism for the homolytic cleavage of alkyl hydroperoxides by the manganese(III) dimer Mn{sup III}{sub 2}(2-OHsalpn){sub 2}. United States. https://doi.org/10.1021/ic951462u
Caudle, M T, Riggs-Gelasco, P, and Gelasco, A K. Wed . "Mechanism for the homolytic cleavage of alkyl hydroperoxides by the manganese(III) dimer Mn{sup III}{sub 2}(2-OHsalpn){sub 2}". United States. https://doi.org/10.1021/ic951462u.
@article{osti_476870,
title = {Mechanism for the homolytic cleavage of alkyl hydroperoxides by the manganese(III) dimer Mn{sup III}{sub 2}(2-OHsalpn){sub 2}},
author = {Caudle, M T and Riggs-Gelasco, P and Gelasco, A K},
abstractNote = {The oxidation of Mn{sup III}{sub 2}(2-OHsalpn){sub 2}, 1 (2-OHsalpn = 1,3-bis(salicylideneamino)-2-propanol), with tert-butyl hydroperoxide was studied in organic media. A one-electron reaction occurs resulting in initial formation of the oxidized Mn{sup III}Mn{sup IV} (2-OHsalpn){sub 2}OH species 2 and a tert-butoxy radical. The Mn{sup III}Mn{sup IV}(2-OHsalpn){sub 2}OH complex can be readily protonated to yield Mn{sup III}Mn{sup IV} (2-OHsalpn){sub 2}{sup +}. Upon addition of excess tert-butyl hydroperoxide, singlet dioxygen is evolved in an exothermic reaction indicative of radical-induced disproportionation of the hydroperoxide. In the presence of a radical scavenger, the oxygen evolution is strongly attenuated. This system was observed to oxygenate cyclohexene to yield 2-cyclohexen-1-one, 2-cyclohexen-1-ol, and traces of cyclohexene oxide. Cumene is oxygenated to 2-phenyl-2-propanol and acetophenone, and cyclohexane is oxygenated to cyclohexanone and cyclohexanol. However, {sup 18}O-labeling experiments show that the oxygen in the products results exclusively from reactions with aerobic dioxygen and not from the tert-butyl hydroperoxide oxidant. These results indicate that oxygenation occurs by radical-initiated aerobic autoxidation and not via oxo transfer from a high-valent manganese oxo species. 2 was studied by UV-vis, IR, NMR, EXAFS, XANES, and EPR spectroscopies, which support the assignment of a dinuclear manganese (III/IV) terminal hydroxo structure. 2 was also formed by the direct reaction of Mn{sup III}Mn{sup IV}(2-OHsalpn){sub 2}{sup +} with OH{sup {minus}}, further supporting the description of 2 as having a terminal hydroxide ligand. The kinetics of its formation from 1 and tert-butyl hydroperoxide were examined and found to be first-order in peroxide.},
doi = {10.1021/ic951462u},
url = {https://www.osti.gov/biblio/476870}, journal = {Inorganic Chemistry},
number = 12,
volume = 35,
place = {United States},
year = {1996},
month = {6}
}