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. 2025 Apr 7;64(15):e202422190.
doi: 10.1002/anie.202422190. Epub 2025 Mar 2.

Abstraction of Hydride from Alkanes and Dihydrogen by the Perfluorotrityl Cation

Derek W Leong  1 , Achyut R Gogoi  1 , Tapas Maity  1 , Chun-I Lee  1 , Nattamai Bhuvanesh  1 , Osvaldo Gutierrez  1 , Oleg V Ozerov  1
Affiliations

Abstraction of Hydride from Alkanes and Dihydrogen by the Perfluorotrityl Cation

Derek W Leong et al. Angew Chem Int Ed Engl. .

Abstract

Lewis acids play a central role in a large variety of chemical transformations. The reactivity of the strongest Lewis acids is typically studied in the context of affinity towards hard bases, such as fluoride or oxygenous species. Carbocations can be viewed as soft Lewis acids, possessing significant affinity for softer bases, such as hydride. This work presents the ambient-temperature isolation of salts of the perfluorotrityl cation ((C6F5)3C+ or F15Tr+) in combination with halogenated carborane anions. The F15Tr+ cation exhibits remarkable hydride affinity, illustrated by the observation of hydride abstraction from dihydrogen, and of the rapid abstraction of hydride from -CH2-groups in alkanes. Theoretical studies support the favorability of hydride abstraction from dihydrogen, and indicate that the hydride abstraction from alkanes proceeds via a concerted hydride transfer process that is sensitive to steric effects.

Keywords: Carbocation; Carborane; Hydride abstraction; Silylium.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
The parent trityl cation Tr+ , selected literature examples of fluorinated trityls, and the fluorinated trityl salts prepared and studied in this work.
Figure 2
Figure 2
Synthesis of F15Tr+ salts and POV‐Ray rendition of the ORTEP (50 % probability ellipsoids) of F15Tr[Cl11]. Selected bond lengths (Å) and angles (°): C1−C2: 1.445(4); C1−C8: 1.445(4); C1−C14: 1.447(4); C2−C1−C8: 119.7(2); C8−C1−C14: 120.0(2); C14−C1−C2: 120.3(2).
Figure 3
Figure 3
Hydride abstraction reactions F15Tr+ alkanes, tetraethylsilane, and dihydrogen.
Figure 4
Figure 4
Equatorial vs axial hydride abstraction from cyclohexane by F15Tr+ calculated at the UB3LYP‐D3/6‐311+g(d,p)‐CPCM(Chlorobenzene) level of theory. Gibbs energies and enthalpies are in kcal/mol, and the C−H distances (in red) given for the TS geometries are in Å.
Figure 5
Figure 5
Top: Gibbs energies and enthalpies (in parentheses), in kcal/mol, for the abstraction of hydride from H2 by F15Tr[C6F5S‐CB11Cl11] calculated at the UB3LYP‐D3/6‐311+g(d,p)‐CPCM(Chlorobenzene) level of theory. Bottom: Typical heterolytic splitting of H2 by a borane/phosphine frustrated Lewis pair.
See this image and copyright information in PMC

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