The Interplay between Various σ- and π-Hole Interactions of Trigonal Boron and Trigonal Pyramidal Arsenic Triiodides

Jindřich Fanfrlík,Pavel Hobza,Zdeňka Růžičková,Aleš Růžička,Petr Švec,Drahomír Hnyk

doi:10.3390/cryst7070225

Abstract

Boron and arsenic triiodides (BI3 and AsI3, respectively) are similar molecules that differ mainly in their geometries. BI3 is a planar trigonal molecule with D3h symmetry, while AsI3 exhibits a trigonal pyramidal shape with C3v symmetry. Consequently, the As atom of the AsI3 molecule has three σ-holes, whereas the B atom of the BI3 molecule has two symmetrical π-holes. Additionally, there are σ-holes on the iodine atoms in the molecules studied. In the first step, we have studied σ-hole and π-hole interactions in the known monocrystals of BI3 and AsI3. Quantum mechanical calculations have revealed that the crystal packing of BI3 is dominated by π-hole interactions. In the case of AsI3, the overall contribution of dihalogen bonding is comparable to that of pnictogen bonding. Additionally, we have prepared the [Na(THF)6]+[I(AsI3)6]−(AsI3)2 complex, which can be described as the inverse coordination compound where the iodine anion is the center of the aggregate surrounded by six AsI3 molecules in the close octahedral environment and adjacent two molecules in remote distances. This complex is, besides expected dihalogen and pnictogen bonds, also stabilized by systematically attractive dispersion interactions.

Highlights

The σ-hole and π-hole are regions with a positive electrostatic potential (ESP) surface along the extension of a covalent σ-bond and in the direction perpendicular to the σ-bond framework, respectively
We We have studied the the interplay between σ- and π-hole interactions in the known solid state have studied interplay between σ- and π-hole interactions in the known solid state structures of 3 and AsI3 as well as in the newly reported [Na(THF)6]+[I(AsI
LastThe onelast canone be described as the inverse coordination compound where the iodine anion is the can be described as the inverse coordination compound where the iodine anion is center the center of the aggregate

Summary

Introduction

The σ-hole and π-hole are regions with a positive electrostatic potential (ESP) surface along the extension of a covalent σ-bond and in the direction perpendicular to the σ-bond framework, respectively. These areas with a positive ESP surface enable a counterintuitive noncovalent interaction, at which a partially negatively charged atom interacts with an electron-rich region [1,2]. The best known and most extensively studied is the σ-hole on halogen (X) atoms, where the respective interactions are called X-bonds [3] This concept has been extended to chalcogens, pnictogens (Pn), and tetrels [4]. The more positive the Vmax , the stronger the respective interaction [5]

Methods

Results

Conclusion