Department of Chemistry, Université de Sherbrooke, Centre in Green Chemistry and Catalysis, J1K 2R1, Sherbrooke, Québec, Canada.
Fakultät für Chemie und Biochemie, Organische Chemie I, Ruhr-Universität Bochum, Universitätsstraße 150, 44801, Bochum, Germany.
Chemphyschem. 2023 Jan 3;24(1):e202200634. doi: 10.1002/cphc.202200634. Epub 2022 Oct 5.
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.
环状二芳基碘鎓化合物，如碘鎓衍生物，近年来越来越多地被用作非共价路易斯酸。与非环状体系相比，它们对亲核取代更为稳定，路易斯酸性也更强。本文通过量子化学计算和能量分解分析，对这种更高的路易斯酸性进行了分析和解释。其关键起源是碘轨道能级和杂化的变化，导致更有利的静电相互作用和更好的电荷转移。这两者似乎都以相似的方式贡献，而氢键以及与芳环的空间排斥作用最多只起次要作用。与碘鎓相比，卤化碘鎓（溴鎓和氯鎓）的路易斯酸性较弱，卤素越轻，这主要是基于不利的电荷转移相互作用。
