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Selective Alcohol Oxidation by a Copper TEMPO Catalyst: Mechanistic Insights by Simultaneously Coupled Operando EPR/UV‐Vis/ATR‐IR Spectroscopy
Author(s) -
Rabeah Jabor,
Bentrup Ursula,
Stößer Reinhard,
Brückner Angelika
Publication year - 2015
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.201504813
Subject(s) - electron paramagnetic resonance , copper , catalysis , chemistry , benzyl alcohol , alcohol , redox , photochemistry , alcohol oxidation , spectroscopy , infrared spectroscopy , ultraviolet visible spectroscopy , electron transfer , inorganic chemistry , organic chemistry , nuclear magnetic resonance , physics , quantum mechanics
The first coupled operando EPR/UV‐Vis/ATR‐IR spectroscopy setup for mechanistic studies of gas‐liquid phase reactions is presented and exemplarily applied to the well‐known copper/TEMPO‐catalyzed (TEMPO=(2,2,6,6‐tetramethylpiperidin‐1‐yl)oxyl) oxidation of benzyl alcohol. In contrast to previous proposals, no direct redox reaction between TEMPO and Cu I /Cu II has been detected. Instead, the role of TEMPO is postulated to be the stabilization of a (bpy)(NMI)Cu II ‐O 2 ⋅− ‐TEMPO (bpy=2,2′‐bipyridine, NMI= N ‐methylimidazole) intermediate formed by electron transfer from Cu I to molecular O 2 .