Open AccessCombined Theoretical and Experimental Investigation of Lewis Acid-Carbonyl Interactions for Metathesis
Author(s) -
Tanmay Malakar,
Carly S. Hanson,
James J. Devery,
Paul M. Zimmerman
Publication year - 2021
Publication title -
acs catalysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.898
H-Index - 198
ISSN - 2155-5435
DOI - 10.1021/acscatal.0c05277
Subject(s) - chemistry , lewis acids and bases , benzaldehyde , catalysis , infrared spectroscopy , acetone , titration , computational chemistry , photochemistry , organic chemistry
The coordination of a carbonyl to a Lewis acid represents the first step in a wide range of catalytic transformations. In many reactions it is necessary for the Lewis acid to discriminate between starting material and product, and as a result, how these structures behave in solution must be characterized. Herein, we report the application of computational modeling to calculate properties of the solution interactions of acetone and benzaldehyde with FeCl 3 . Using these chemical models, we can predict spectral features in the carbonyl region of infrared (IR) spectroscopy. These simulated spectra are then directly compared to experimental spectra generated via titration-IR. We observe good agreement between theory and experiment, in that, between 0 and 1 equiv carbonyl with respect to FeCl 3 , a pairwise interaction dominates the spectra. When >1 equiv carbonyl is present, our theoretical model predicts two possible structures composed of 4:1 carbonyl to FeCl 3 , for acetone as well as benzaldehyde. When these predicted spectra are compared with titration-IR data, both structures contribute to the observed solution interactions. These findings suggest that the resting state of FeCl 3 -catalyzed carbonyl-based reactions employing simple substrates starts as a Lewis pair, but this structure is gradually consumed and becomes a highly ligated, catalytically less active Fe-centered complex as the reaction proceeds. An analytical model is proposed to quantify catalyst inhibition due to equilibrium between 1:1 and 4:1 carbonyl:Fe complexes.