Triel Bonds, π-Hole-π-Electrons Interactions in Complexes of Boron and Aluminium Trihalides and Trihydrides with Acetylene and Ethylene.

Sławomir Grabowski

doi:10.3390/molecules200611297

Abstract

MP2/aug-cc-pVTZ calculations were performed on complexes of aluminium and boron trihydrides and trihalides with acetylene and ethylene. These complexes are linked through triel bonds where the triel center (B or Al) is characterized by the Lewis acid properties through its π-hole region while π-electrons of C2H2 or C2H4 molecule play the role of the Lewis base. Some of these interactions possess characteristics of covalent bonds, i.e., the Al-π-electrons links as well as the interaction in the BH3-C2H2 complex. The triel-π-electrons interactions are classified sometimes as the 3c-2e bonds. In the case of boron trihydrides, these interactions are often the preliminary stages of the hydroboration reaction. The Quantum Theory of “Atoms in Molecules” as well as the Natural Bond Orbitals approach are applied here to characterize the π-hole-π-electrons interactions.

Highlights

The hydrogen bond seems to be the most often analyzed Lewis acid-Lewis base interaction since its key role in numerous chemical, physical and biochemical processes is well known [1,2]
One can mention Groups 14–17 elements interacting as the Lewis acid centers with Lewis bases; such interactions are named as tetrel [14,15,16,17,18], pnicogen [19,20,21,22], chalcogen [23,24,25,26] and halogen bonds [27,28], respectively
It may mean that the hydroboration reaction takes place here and that the stable BH3-C2H4 complex linked by the triel bond does not exist

Summary

Introduction

The hydrogen bond seems to be the most often analyzed Lewis acid-Lewis base interaction since its key role in numerous chemical, physical and biochemical processes is well known [1,2]. It often may be considered as the preliminary stage of the proton transfer process [3] and it is often the main factor responsible for the arrangement of molecules in crystal structures [1,2,4]. Often those centers have the dual character since they act simultaneously as the Lewis acid and as the Lewis base

Objectives

Results

Conclusion