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Open AccessArticle

Thermodynamic Hydricity of Small Borane Clusters and Polyhedral closo-Boranes

1
A. N. Nesmeyanov Institute of Organoelement Compounds and Russian Academy of Sciences (INEOS RAS), 28 Vavilova St, 119991 Moscow, Russia
2
Faculty of Chemistry, M.V. Lomonosov Moscow State University, 1/3 Leninskiye Gory, 119991 Moscow, Russia
*
Authors to whom correspondence should be addressed.
Dedicated to Professor Bohumil Štibr (1940-2020), who unfortunately passed away before he could reach the age of 80, in the recognition of his outstanding contributions to boron chemistry.
Academic Editors: Igor B. Sivaev, Narayan S. Hosmane and Bohumír Grűner
Molecules 2020, 25(12), 2920; https://doi.org/10.3390/molecules25122920
Received: 6 June 2020 / Revised: 21 June 2020 / Accepted: 23 June 2020 / Published: 25 June 2020
Thermodynamic hydricity (HDAMeCN) determined as Gibbs free energy (ΔG°[H]) of the H detachment reaction in acetonitrile (MeCN) was assessed for 144 small borane clusters (up to 5 boron atoms), polyhedral closo-boranes dianions [BnHn]2−, and their lithium salts Li2[BnHn] (n = 5–17) by DFT method [M06/6-311++G(d,p)] taking into account non-specific solvent effect (SMD model). Thermodynamic hydricity values of diborane B2H6 (HDAMeCN = 82.1 kcal/mol) and its dianion [B2H6]2− (HDAMeCN = 40.9 kcal/mol for Li2[B2H6]) can be selected as border points for the range of borane clusters’ reactivity. Borane clusters with HDAMeCN below 41 kcal/mol are strong hydride donors capable of reducing CO2 (HDAMeCN = 44 kcal/mol for HCO2), whereas those with HDAMeCN over 82 kcal/mol, predominately neutral boranes, are weak hydride donors and less prone to hydride transfer than to proton transfer (e.g., B2H6, B4H10, B5H11, etc.). The HDAMeCN values of closo-boranes are found to directly depend on the coordination number of the boron atom from which hydride detachment and stabilization of quasi-borinium cation takes place. In general, the larger the coordination number (CN) of a boron atom, the lower the value of HDAMeCN. View Full-Text
Keywords: polyhedral boranes; borane clusters; borohydrides; Lewis acidity; hydride donating ability; DFT calculations polyhedral boranes; borane clusters; borohydrides; Lewis acidity; hydride donating ability; DFT calculations
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MDPI and ACS Style

Golub, I.E.; Filippov, O.A.; Kulikova, V.A.; Belkova, N.V.; Epstein, L.M.; Shubina, E.S. Thermodynamic Hydricity of Small Borane Clusters and Polyhedral closo-Boranes. Molecules 2020, 25, 2920.

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