Boron: The Fifth Element

0453279 - ÚOCHB 2016 RIV CH eng M - Monography Chapter
Sedlák, Robert - Fanfrlík, Jindřich - Pecina, Adam - Hnyk, Drahomír - Hobza, Pavel - Lepšík, Martin
Noncovalent Interactions of Heteroboranes.
Boron: The Fifth Element. Cham: Springer International Publishing, 2015 - (Hnyk, D.; McKee, M.), s. 219-239. Challenges and Advances in Computational Chemistry and Physics, 20. ISBN 978-3-319-22281-3
Institutional support: RVO:61388963 ; RVO:61388980
Keywords : sigma-hole bonding * boron clusters * quantum chemistry
Subject RIV: CF - Physical ; Theoretical Chemistry

This chapter deals with noncovalent interactions between heteroboranes and their various molecular partners. The physical essence of noncovalent interactions is first discussed in general. Subsequently, the bonding of boron clusters is discussed based on their unusual electron distribution, especially around the heteroatoms or the exo-substituents. The bare (i.e. not linked to hydrogen) heteroatoms within the cage bear prevailingly a partial positive charge. This results in an opposite direction of the compound dipole moments (as proved experimentally), contrary to what would be expected from the electronegativity concept. The anisotropic distribution of the electron density around the heteroatoms gives rise to the so-called sigma-holes, regions of positive electrostatic potential (ESP). This can be viewed as a driving force for noncovalent interactions with, e.g. organic aromatics or Lewis bases. Examples of sigma-hole bonding of heteroboranes incorporated in the cluster cages are chalcogen or pnictogen bonding. Exo-substituents can also be centers of sigma-hole bonding, in this case halogen bonding. Sigma-holes can be tuned, e.g. by other exo-substituents or by the point of attachment to the cage. Apart from the sigma-hole bonding, the hydride character of the terminal hydrogens of the heteroboranes is responsible for forming unique dihydrogen H center dot center dot center dot H bonds. The choices of optimal computational protocols to study the crucial energy terms contributing to these interactions are reviewed.
Permanent Link: http://hdl.handle.net/11104/0254176