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Switchover of the Mechanism between Electron Transfer and Hydrogen‐Atom Transfer for a Protonated Manganese(IV)–Oxo Complex by Changing Only the Reaction Temperature
Author(s) -
Jung Jieun,
Kim Surin,
Lee YongMin,
Nam Wonwoo,
Fukuzumi Shunichi
Publication year - 2016
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.201602460
Subject(s) - chemistry , kinetic isotope effect , switchover , mesitylene , manganese , triflic acid , hydrogen atom , protonation , electron transfer , deuterium , reaction mechanism , photochemistry , computational chemistry , catalysis , atomic physics , organic chemistry , physics , ion , alkyl , electrical engineering , engineering
Hydroxylation of mesitylene by a nonheme manganese(IV)–oxo complex, [(N4Py)Mn IV (O)] 2+ ( 1 ), proceeds via one‐step hydrogen‐atom transfer (HAT) with a large deuterium kinetic isotope effect (KIE) of 3.2(3) at 293 K. In contrast, the same reaction with a triflic acid‐bound manganese(IV)‐oxo complex, [(N4Py)Mn IV (O)] 2+ ‐(HOTf) 2 ( 2 ), proceeds via electron transfer (ET) with no KIE at 293 K. Interestingly, when the reaction temperature is lowered to less than 263 K in the reaction of 2 , however, the mechanism changes again from ET to HAT with a large KIE of 2.9(3). Such a switchover of the reaction mechanism from ET to HAT is shown to occur by changing only temperature in the boundary region between ET and HAT pathways when the driving force of ET from toluene derivatives to 2 is around −0.5 eV. The present results provide a valuable and general guide to predict a switchover of the reaction mechanism from ET to the others, including HAT.