A quantum-chemical analysis on the Lewis acidity of diaryl-halonium ions

06 April 2022, Version 1
This content is a preprint and has not undergone peer review at the time of posting.

Abstract

Cyclic diaryliodonium compounds like iodolium derivatives have increasingly found use as noncovalent Lewis acids in the last years. They are more stable than acyclic systems and are markedly more Lewis acidic. Herein, this higher Lewis acidity is analyzed and explained via quantum-chemical calculations and energy decomposition analyses. Its key origin is the change in energy levels and hybridization of iodine’s orbitals, leading to both more favorable electrostatic interaction and better charge transfer. Both of the latter seem to contribute in similar fashion, while hydrogen bonding as well as steric repulsion with the phenyl rings play at best a minor role. In comparison to iodolium, bromolium and chlorolium are less Lewis acidic the lighter the halogen, which is predominantly based on less favorable charge-transfer interactions.

Keywords

Lewis acids
hypervalent iodine
halogen bonding
energy decomposition analyses
iodonium

Supplementary materials

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