Tetrel Bonds with π-Electrons Acting as Lewis Bases-Theoretical Results and Experimental Evidences.

Sławomir Grabowski

doi:10.3390/molecules23051183

Abstract

MP2/aug-cc-pVTZ calculations were carried out for the ZFH3-B complexes (Z = C, Si, Ge, Sn and Pb; B = C2H2, C2H4, C6H6 and C5H5-; relativistic effects were taken into account for Ge, Sn and Pb elements). These calculations are supported by other approaches; the decomposition of the energy of interaction, Quantum Theory of Atoms in Molecules (QTAIM) and Natural Bond Orbital (NBO) method. The results show that tetrel bonds with π-electrons as Lewis bases are classified as Z···C links between single centers (C is an atom of the π-electron system) or as Z···π interactions where F‒Z bond is directed to the mid-point (or nearly so) of the CC bond of the Lewis base. The analogous systems with Z···C/π interactions were found in the Cambridge Structural Database (CSD). It was found that the strength of interaction increases with the increase of the atomic number of the tetrel element and that for heavier tetrel elements the ZFH3 tetrahedral structure is more deformed towards the structure with the planar ZH3 fragment. The results of calculations show that the tetrel bond is sometimes accompanied by the Z-H···C hydrogen bond or even sometimes the ZFH3-B complexes are linked only by the hydrogen bond interaction.

Highlights

The tetrel bond is a Lewis acid—Lewis base interaction that may play an important role in some chemical and biological processes [1]; for example, it may be considered as a preliminary stage of the SN 2 reaction [2]
The σ-hole is usually located in this case in the elongation of the covalent bond to the tetrel centre and it is often characterized by the positive electrostatic potential (EP) [3,4]
In spite of the fact that the term “tetrel bond” appeared recently [6] and this interaction was classified as the σ-hole bond in the last decade [3,4,5] it was analyzed in earlier studies

Summary

Introduction

The tetrel bond is a Lewis acid—Lewis base interaction that may play an important role in some chemical and biological processes [1]; for example, it may be considered as a preliminary stage of the SN 2 reaction [2] This interaction was classified as the σ-hole bond by Politzer and coworkers since it may be defined as an interaction between the 14th Group element acting as the Lewis acid centre through its σ-hole and a region that is rich of the electron density by a lone electron pair, π-electron system etc. The σ-hole is usually located in this case in the elongation of the covalent bond to the tetrel centre and it is often characterized by the positive electrostatic potential (EP) [3,4] It seems that first time the tetrel bond was analyzed in terms of the σ-hole concept in the SiF4 complexes with amines [5]. In spite of the fact that the term “tetrel bond” appeared recently [6] and this interaction was classified as the σ-hole bond in the last decade [3,4,5] it was analyzed in earlier studies.

Objectives

Discussion

Conclusion