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

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 [XeF n ] 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.

Noncovalent Bonds through Sigma and Pi-Hole Located on the Same Molecule. Guiding Principles and Comparisons

“…Protein structures can also involve participation of π-hole bonds [ 97 , 98 ], as is also true of self-assembling systems [ 99 ]. As work has progressed, there has been recognition of π-holes as providing a means by which an aerogen bond (involving rare gas atoms) can form [ 100 , 101 , 102 , 103 , 104 ]. Other newly introduced types of σ/π- hole directed interactions are alkali and alkaline earth bond (e.g., beryllium bond, magnesium bond) in which atoms of 1st and 2nd groups contribute [ 105 , 106 , 107 , 108 , 109 ] or regium and spodium bonds which employ transition metals from 11th (regium [ 110 , 111 , 112 , 113 , 114 , 115 ]) or 12th (spodium [ 105 , 116 , 117 , 118 , 119 ]) groups of the periodic table.…”

Noble Gas Bonding Interactions Involving Xenon Oxides and Fluorides

“…The molecular electrostatic potential (MEP) surface of XeF 4 has been commented on above (see Figure 6 ). Figure 15 shows the MEP surfaces of XeF 2 and XeF 6 [ 88 ] that are worthy of mentioning, before the analysis of their X-ray structures. The MEP surface of XeF 2 shows a positive belt around the Xe atom and two symmetrically equivalent negative regions at the F atoms.…”

“…Noble gas or aerogen-bonding interactions were termed as such in 2015 [ 81 ], and afterward, several experimental [ 82 , 83 , 84 ] and theoretical [ 85 , 86 , 87 , 88 , 89 ] investigations have appeared in the literature describing and confirming their relevance in X-ray structures and also its interplay with other interactions. The purpose of this short review is to examine the recent research on NgB interactions, including theoretical and experimental investigations.…”

Noble-Gas Chemistry More than Half a Century after the First Report of the Noble-Gas Compound

“…Additional stimulation in the noble-gas research represents the discovery of noble gas (or aerogen) bonding [ 77 ]. It is a novel type of weak attractive noncovalent interaction [ 78 ]. According to IUPAC is defined as the attractive interaction between an electron rich atom or group of atoms and any element of Group-18 acting as electron acceptor [ 79 , 80 ].…”