Selective Alcohol Oxidation by a Copper TEMPO Catalyst: Mechanistic Insights by Simultaneously Coupled Operando EPR/UV‐Vis/ATR‐IR Spectroscopy

Abstract

Abstract 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 .