Kinetic study of iron (III)-catalyzed reactions via near-IR spectroscopy

Studying Fe(III)-catalyzed reactions by NMR poses challenges due to the paramagnetic nature of Fe(III) species. Consequently, spin-independent methods for studying iron(III)-catalyzed processes are of significant interest to the iron catalysis community. This work introduces, for the first time, mechanistic insights into two Fe(III)-catalyzed organic reactions using near-IR spectroscopy, which enables the determination of rate constants and the analysis of reaction intermediates. Time-resolved near-IR spectroscopy allows monitoring the formation and disappearance of functional groups, providing data that can be processed similarly to NMR or UV-vis spectroscopy for kinetic studies. Using this approach, rate constants for a Fe(III)-catalyzed Meyer-Schuster rearrangement and Michael additions were determined. Furthermore, near-IR spectra of a mixture of stoichiometric amounts of catalyst and reagent revealed spectral shifts associated with catalyst-substrate interactions, allowing the identification of the part of the substrate activated by the catalyst.