Are Ar₃SbCl₂ Species Lewis Acidic? Exploration of the Concept and Pnictogen Bond Catalysis Using a Geometrically Constrained Example

Abstract

As part of our investigations into the Lewis acidic behavior of antimony derivatives, we have decided to study the properties of 5-phenyl-5,5dichloro-λ 5 -dibenzostibole (1), a dichlorostiborane with an antimony atom confined to a five-membered heterocycle. Our work shows that the resulting geometrical constraints elevate the Lewis acidity of the antimony atom, as confirmed by the crystal structure of 1-THF and the solution study of the interaction of 1 with Ph 3 PO. The enhanced Lewis acidic properties of 1, which exceed those of simple dichlorostiboranes such as Ph 3 SbCl 2 , also become manifest in pnictogen bonding catalysis experiments involving the reductions of imines with Hantzsch ester. The influence of geometrical constraints in the chemistry of this compound is also supported by a computational activation strain analysis as well as by an energy decomposition analysis of a model Me 3 PO adduct.

Binding, Sensing, And Transporting Anions with Pnictogen Bonds: The Case of Organoantimony Lewis Acids

“…In addition to demonstrating the importance of catecholate perchlorination, compound 27 may also benefit from its bicyclic structure. The integration of two antimony-fused five membered rings most likely accentuates the geometrical constraints imposed on the ground state structure, boosting its Lewis acidity …”

“…The integration of two antimony-fused five membered rings most likely accentuates the geometrical constraints imposed on the ground state structure, boosting its Lewis acidity. 54 …”

Exploring the Effects of Se Basicity on a Te···Se Interaction Supported by a Rigid Indazolium Backbone

“…This focus started predominantly with halogen bonds − and progressively worked its way to the left of the periodic table, extending to chalcogen bonds, pnictogen bonds, and even tetrel bonds . With their use of empty σ*-orbitals, these compounds have challenged the notion that the interactions they form are purely “non-covalent.” While the Gabbaı̈ lab has a strong tradition with pnictogen-based Lewis acids, − welike othershave become enamored with the neighboring chalcogens. − …”

Solution Studies of a Water-Stable, Trivalent Antimony Pnictogen Bonding Anion Receptor with High Binding Affinities for CN–, OCN–, and OAc–

“…Anion binding and recognition, an important subfield of host–guest interactions, is used to direct crystal engineering and molecular templating, , for selective sensing of anions , and for metal-free catalysis in organic synthesis. , Pnictogens have played an important role in anion binding in the +5 oxidation state. − This is largely due to the high Lewis acidity of the electron-deficient central pnictogen. Pnictogens in the +3 oxidation state are typically viewed as Lewis bases due to the presence of a lone pair. − The heaviest pnictogens are amphoteric in the +3 oxidation state, and by carefully choosing the chemical environment of the pnictogen, the scales can be tipped toward Lewis acidity allowing for anion binding mediated by pnictogens in the +3 oxidation state. − Figure depicts some of the examples where trivalent pnictogens have been purposefully used for anion binding.…”