Carboranes as Lewis Acids: Tetrel Bonding in CB11H11 Carbonium Ylide

Maxime Ferrer,José Elguero,Josep M. Oliva-Enrich,Ibon Alkorta

doi:10.3390/cryst11040391

Maxime Ferrer, José Elguero + Show 2 more

Open Access

https://doi.org/10.3390/cryst11040391

Copy DOI

Abstract

High-level quantum-chemical computations (G4MP2) are carried out in the study of complexes featuring tetrel bonding between the carbon atom in the carbenoid CB11H11—obtained by hydride removal in the C-H bond of the known closo-monocarbadodecaborate anion CB11H12(−) and acting as Lewis acid (LA)—and Lewis bases (LB) of different type; the electron donor groups in the tetrel bond feature carbon, nitrogen, oxygen, fluorine, silicon, phosphorus, sulfur, and chlorine atomic centres in neutral molecules as well as anions H(−), OH(−), and F(−). The empty radial 2pr vacant orbital on the carbon centre in CB11H11, which corresponds to the LUMO, acts as a Lewis acid or electron attractor, as shown by the molecular electrostatic potential (MEP) and electron localization function (ELF). The thermochemistry and topological analysis of the complexes {CB11H11:LB} are comprehensively analysed and classified according to shared or closed-shell interactions. ELF analysis shows that the tetrel C⋯X bond ranges from very polarised bonds, as in H11B11C:F(−) to very weak interactions as in H11B11C⋯FH and H11B11C⋯O=C=O.

Highlights

High-level quantum-chemical computations (G4MP2) are carried out in the study of complexes featuring tetrel bonding between the carbon atom in the carbenoid CB11 H11 —obtained by hydride removal in the C-H bond of the known closo-monocarbadodecaborate anion CB11 H12 (−)
The loss of H(−) in the C-H leads to a structure with C5v symmetry—with a geometrical change which involves a considerable flattening of the CB5 pentagonal pyramid with expansion of the corresponding B5 pentagon, since there is an increase of the B-B bond distance of ∆ = +0.022 Å
The results presented in this work show that by means of quantum-chemical computations we should expect the formation of tetrel complexes between the icosahedral carbonium ylide CB11 H11 —derived from extraction of H(−) in the known anion CB11 H12 (−) —and a set of simple molecules and anions

Summary

Introduction

High-level quantum-chemical computations (G4MP2) are carried out in the study of complexes featuring tetrel bonding between the carbon atom in the carbenoid CB11 H11 —obtained by hydride removal in the C-H bond of the known closo-monocarbadodecaborate anion CB11 H12 (−). The very stable B12 H12 (2−) dianion and its neutral dicarbon counterparts ortho-(1,2C2 B10 H12 ), meta-(1,7-C2 B10 H12 ), and para-carborane (1,12-C2 B10 H12 ) are icosahedral systems that are closely related to elemental boron. Their isoelectronic analogue, closomonocarbadodecaborate anion CB11 H12 (−) , first prepared in 1967 [1] and further with other synthesis methods [2,3], is resistant to cage degradation, and many derivatives have been synthesized as described in the literature [4]. Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations

Objectives

Results

Discussion

Conclusion