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Organohelium Compounds: Structures, Stabilities and Chemical Bonding Analyses
Author(s) -
Fourré Isabelle,
Alvarez Elsa,
Chaquin Patrick
Publication year - 2014
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.201300932
Subject(s) - chemistry , molecule , metastability , electron localization function , hydrogen bond , covalent bond , crystallography , chemical bond , atoms in molecules , computational chemistry , electron , organic chemistry , physics , quantum mechanics
This paper deals with the possibility of forming short and relatively strong carbon–helium bonds in small typical organic molecules through substitution of one or several H atoms by He + . A structural and energetics study (based on high‐level calculations) of this unusual bonding, as well as a topological characterization of the resulting cations, is undertaken. Stable species generally requires substitution of about half of the hydrogen atoms for formation. Under these conditions, the number of such species appears to be potentially unlimited. “True” CHe bonds exhibit equilibrium distances ranging from 1.327 (C 2 H 2 He 2 2+ ) to 1.129 Å (He 2 CO 2+ ). The energies of neutral He releasing range from approximately 5 kcal mol −1 [He 2 CO 2+ , ( Z )‐C 2 H 2 He 2 2+ ] to 25 kcal mol −1 (C 2 HHe 3 3+ ), but remain most frequently around 10 kcal mol −1 . However, most of He + ‐substituted hydrocarbons are metastable with respect to CC cleavage, except derivatives of ethene. Atoms in molecules (AIM) and electron localization function (ELF) topological descriptors classify the CHe bond as a weak charge‐shift interaction [S. Shaik, D. Danovich, B. Silvi, D. L. Lauvergnat, P. C. Hiberty, Chem. Eur. J. 2005, 11, 6358–6371 ] in agreement with a recent publication by Rzepa [S. H. Rzepa, Nat. Chem. 2010, 2, 390–393 ]. He 2 CO 2+ is the only investigated compound that presents a CHe bonding ELF basin, which indicates a non‐negligible covalent contribution to the bond. Other modifications in the electronic structure, such as the breaking of the triple bond in ethyne derivatives or the loss of aromaticity in C 6 H 3 He 3 3+ , are also nicely revealed by the ELF topology.