Iodine(III)‐Based Halogen Bond Donors: Properties and Applications

Abstract

Halogen bonding, the non‐covalent interaction of Lewis bases with an electron‐deficient region of halogen substituents, received increased attention recently. Consequently, the design and evaluation of numerous halogen‐containing species as halogen bond donors have been subject to intense research. More recently, organoiodine compounds at the iodine(III) state have been receiving growing attention in the field. Due to their electronic and structural properties, they provide access to unique binding modes. For this reason, our groups have been involved in the development of such compounds, in the quantification of their halogen bonding strength (through the evaluation of their Lewis acidities), as well as in the evaluation of their activities as catalysts in several model reactions. This account will describe these contributions.

Evaluation of Halogenopyridinium Cations as Halogen Bond Donors

“…This can lead to much higher positive charges on the halogen atoms, making them very strong halogen bond donors. 40 , 41 …”

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

“…[15] In the following years, attention shifted to dibenzo[b,d]iodolium ions such as 2, which feature a central five-membered ring (Figure 1). [12,[16][17][18] These variants have been described as more stable toward reductive elimination compared to diaryliodonium salts, which should make them particularly suitable for catalysis, and a rationalization based on a trigonal-bipyramidal arrangement of the lone pairs and bonds around iodine has been proposed. [19] Figure 1.…”

Computational investigation of cyclic substituted iodine(III) halogen bond donors

“…Iodine(III) compounds have emerged as powerful halogen bond donors. 1 Most of these compounds are diaryliodonium salts, either cyclic or acyclic. The aryl moieties can be functionalized to optimize the properties of these halogen bond donors for specific applications.…”

“…In particular, the Lewis acidity of a small set of acyclic diaryliodonium salts has been first determined by NMR using the Gutmann-Beckett method, 2 then, using different titration methods, an extended set of iodine(III) compounds was investigated. 3 Cyclic diaryliodonium salts have been mostly studied using isothermal calorimetry (ITC) [4][5][6] as well as by 1 H NMR titrations. 5 In particular, cyclic diaryliodonium salts have been shown to possess Lewis acidities that can rival those of dicationic bidentate iodine(I) halogen bond donors.…”