Abstract
The second-order Møller–Plesset perturbation theory calculations with the aug-cc-pVTZ basis set were performed on complexes of triel species: BCl3, BH3, AlCl3, and AlH3 acting as Lewis acids through the B or Al centre with Lewis base units: NCH, N2, NH3, and Cl− anion. These complexes are linked by triel bonds: B/Al⋅⋅⋅N or B/Al⋅⋅⋅Cl. The Quantum Theory of ´Atoms in Molecules´ approach, Natural Bond Orbital method, and the decomposition of energy of interaction were applied to characterise the latter links. The majority of complexes are connected through strong interactions possessing features of covalent bonds and characterised by short intermolecular distances, often below 2 Å. The BCl3⋅⋅⋅N2 complex is linked by a weak interaction corresponding to the B⋅⋅⋅N distance of ~3 Å. For the BCl3⋅⋅⋅NCH complex, two configurations corresponding to local energetic minima are observed, one characterised by a short B⋅⋅⋅N distance and a strong interaction and another one characterised by a longer B⋅⋅⋅N distance and a weak triel bond. The tetrahedral triel structure is observed for complexes linked by strong triel bonds, while, for complexes connected by weak interactions, the structure is close to the trigonal pyramid, particularly observed for the BCl3⋅⋅⋅N2 complex.
Highlights
The number of experimental and theoretical studies concerning inter- and intramolecular interactions increased rapidly in recent years [1,2,3,4,5,6,7]
For the BCl3 ···NCH complex, two configurations corresponding to local energetic minima are observed, one characterised by a short B···N distance and a strong interaction and another one characterised by a longer B···N distance and a weak triel bond
The tetrahedral triel structure is observed for complexes linked by strong triel bonds, while, for complexes connected by weak interactions, the structure is close to the trigonal pyramid, observed for the
Summary
The number of experimental and theoretical studies concerning inter- and intramolecular interactions increased rapidly in recent years [1,2,3,4,5,6,7]. In the above-mentioned centres, the depletion of the electron charge may be observed on their edges in directions of their bonds with other atoms. These sites are just named as σ-holes; the above-described electron charge outflow is often sufficient to lead to the positive electrostatic potential (EP) at the σ-holes and, to their Lewis acid properties. It may be confusing that the centres described here play a role of Lewis acids since the majority of them are electronegative atoms Some of these centres may be characterised by π-holes that are regions of the depletion of the electron charge and, often of the positive electrostatic potential.
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