Importance of Nonclassical σ-Hole Interactions for the Reactivity λ3-Iodane Complexes

Key for the observed reactivity lambda(3)-iodanes, powerful reagents for the selective transfer of functional groups to nucleophiles, are the properties of the 3-center-4-electron bond involving the iodine atom and the two linearly arranged ligands. This bond is also involved in the formation of the initial complex between the lambda(3)-iodane and a nucleophile, which can be a solvent molecule or a reactant. The bonding in such complexes can be described by means of sigma-hole interactions. In halogen compounds, sigma-hole interaction was identified as a force in, crystal packing or in the formation of supramolecular chains. More recently, sigma-hole interactions were also shown to affect the reactivity of the iodine-based-hypervalent reagents. Relative to their monovalent counterparts, where the sigma-hole is located on the extension of the sigma-bond, in the hypervalent species our DFT calculations, re-veal the formation of a nonclassical sigma-hole region with one or even two maxima. This observation calculations. The SAPT analysis shows that the sigma-hole bond between the lambda(3)-iodane and the nucleophile is not necessarily of purely electrostatic nature but may also contain a significant covalent component. This covalent component may facilitate chemical transformation of the compound by means of reductive elimination or other mechanisms and is therefore an indicator for its reactivity. Here, we also show that the shape, location, and strength of the sigma-holes can be tuned by the choice of ligands and measures such as Bronsted activation of the iodane reagent. At the limit, the tuning transforms the nonclassical sigma-hole regions into coordination sites, which allows us to control how a nucleophile will bind and react with the iodane.