Xenon Derivatives as Aerogen Bond-Donating Catalysts for Organic Transformations: A Theoretical Study on the Metaphorical “Spherical Cow in a Vacuum” Provides Insights into Noncovalent Organocatalysis

Computations
indicate that cationic and noncharged xenon derivatives
should exhibit higher catalytic activity than their iodine-based noncovalent
organocatalytic congeners. Perfluorophenyl xenonium­(II) is expected
to demonstrate the best balance between catalytic activity and chemical
stability for use in organocatalysis. Comparing its catalytic activity
with that of isoelectronic perfluoroiodobenzene indicates that the
high catalytic activity of cationic noncovalent organocatalysts is
predominantly attributed to the electrostatic interactions with the
reaction substrates, which cause the polarization of ligated species
during the reaction progress. In contrast, the electron transfer and
covalent contributions to the bonding between the catalyst and substrate
have negligible effects. The dominant effect of electrostatic interactions
results in a strong negative correlation between the calculated Gibbs
free energies of activation for the modeled reactions and the highest
potentials of the σ-holes on the central atoms of the catalysts.
No such correlation is observed for noncharged catalysts.