Use of EPR Spectroscopy to Unravel Reaction Mechanisms in (Catalytic) Bond Activation Reactions: Some Selected Examples

Abstract

Paramagnetic species are ubiquitous intermediates in many different reactions involving chemical bond activation and catalysis. Despite this fact, the use of electron paramagnetic resonance (EPR) spectroscopy for unraveling reaction mechanisms for homogeneous catalytic reactions has been rather limited. This overview article details several areas dealing with small molecule activation in the homogeneous medium where EPR spectroscopy is potentially useful and has sometimes been used. We will present various examples from the literature to show the usefulness of this method in studying the activation and possible fixation of small molecules such as H2, O2, and N2. Additionally, some examples related to nitridyl radicals and their relation with carbene radicals will also be discussed with a focus on their detection through EPR spectroscopy. We will present the usefulness and the limitations of this method by discussing selected examples from the literature. This is not meant to be a comprehensive review.