Covalent and Non-covalent Noble Gas Bonding Interactions in XeFn Derivatives (n = 2–6): A Combined Theoretical and ICSD Analysis

Rosa M Gomila,Antonio Frontera

doi:10.3389/fchem.2020.00395

Abstract

A noble gas bond (also known in the literature as aerogen bond) can be defined as the attractive interaction between any element of group-18 acting as a Lewis acid and any electron rich atom of group of atoms, thus following the IUPAC recommendation available for similar π,σ-hole interactions involving elements of groups 17 (halogens) and 16 (chalcogens). A significant difference between noble gas bonding (NgB) and halogen (HaB) or chalcogen (ChB) bonding is that whilst the former is scarcely found in the literature, HaB and ChB are very common and their applications in important fields like catalysis, biochemistry or crystal engineering have exponentially grown in the last decade. This article combines theory and experiment to highlight the importance of non-covalent NgBs in the solid state of several xenon fluorides [XeFn]m+ were the central oxidation state of Xe varies from +2 to +6 and the number of fluorine atoms varies from n = 2 to 6. The compounds with an odd number of fluorine atoms (n = 3 and 5) are cationic (m = 1). The Inorganic Crystal Structural Database (ICSD) strongly evidences the relevance of NgBs in the solid state structures of xenon derivatives. The ability of Xe compounds to participate in π,σ-hole interactions has been studied using different types of electron donors (Lewis bases and anions) using DFT calculations (PBE1PBE-D3/def2-TZVP) and the molecular electrostatic potential (MEP) surfaces.

Highlights

The starting point of the noble gas chemistry was in 1962 with the discovery of XePtF6 and XeF2 compounds by Bartlett (1962) and Zirin groups (Chernick et al, 1962), respectively
X-ray Crystal Structure The Inorganic Crystal Structural Database (ICSD) has been inspected manually to investigate the ability of xenon difluoride to participate in noble gas bonding (NgB)
It can be observed that all X-ray structures present Xe···F contacts with distances that are clearly longer than Rcov and shorter than Rvdw suggesting the non-covalent nature of these NgBs

Summary

Introduction

The starting point of the noble gas chemistry was in 1962 with the discovery of XePtF6 and XeF2 compounds by Bartlett (1962) and Zirin groups (Chernick et al, 1962), respectively This discovery opened a new field of research that has grown in the last two decades due to the improvements in the experimental techniques and instrumentation to carry out reactions and measurements in extreme conditions (Haner and Schrobilgen, 2015; Grandinetti, 2018). Another interesting step in this field was the synthesis in 2000 by Seidel and Seppelt of the first compound having a noble gas–noble metal bond [AuXe4]2+ (Seidel and Seppelt, 2000). The final aim is to control the molecular recognition process precisely to be able to build selective molecular receptors, sensors, supramolecular catalysts, polymers, etc

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Results

Conclusion