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. 2023 Jan 3;24(1):e202200634.
doi: 10.1002/cphc.202200634. Epub 2022 Oct 5.

A Quantum-chemical Analysis on the Lewis Acidity of Diarylhalonium Ions

Raphaël Robidas  1 , Dominik L Reinhard  2 , Stefan M Huber  2 , Claude Y Legault  1
Affiliations

A Quantum-chemical Analysis on the Lewis Acidity of Diarylhalonium Ions

Raphaël Robidas et al. Chemphyschem. .

Abstract

Cyclic diaryliodonium compounds like iodolium derivatives have increasingly found use as noncovalent Lewis acids in the last years. They are more stable toward nucleophilic substitution 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; energy decomposition analysis; halogen bonding; hypervalent iodine; iodonium.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Prototypical diphenyliodonium and cyclic halonium ions.
Figure 2
Figure 2
Common yet incorrect representation of the iodine(III) lone pairs compared to a electronically sound representation.
Figure 3
Figure 3
a) s‐type and b) p‐type lone pair orbitals calculated with the NBO method for ion 1.
Figure 4
Figure 4
Optimized structures of: a) 1 and 2; b) 1 and 2 bromide adducts.
Figure 5
Figure 5
Energy levels (in a. u.) of the s‐type and p‐type LP orbitals of ion 1 as a function of the C−I−C angle.
Figure 6
Figure 6
σ‐holes of ions 1 (left) and 2 (right); most positive potential in blue.
Figure 7
Figure 7
SAPT(DFT) analysis of a scan of the H−I−C1−C2 dihedral angle in model 5⋅Br.
Figure 8
Figure 8
SAPT Analysis of Br⋅⋅⋅halolium interactions in 2⋅Br, 3⋅Br, and 4⋅Br adducts.
Figure 9
Figure 9
NBO charges of selected atoms in 2, 3, 4 and 2⋅Br, 3⋅Br, 4⋅Br.
See this image and copyright information in PMC

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