Tris(ortho-carboranyl)borane: An Isolable, Halogen-Free, Lewis Superacid

Manjur O Akram; John R Tidwell; Jason L Dutton; Caleb D Martin

doi:10.1002/anie.202212073

Tris(ortho-carboranyl)borane: An Isolable, Halogen-Free, Lewis Superacid

Angew Chem Int Ed Engl. 2022 Nov 14;61(46):e202212073. doi: 10.1002/anie.202212073. Epub 2022 Oct 17.

Authors

Manjur O Akram¹, John R Tidwell¹, Jason L Dutton², Caleb D Martin¹

Affiliations

¹ Department of Chemistry and Biochemistry, Baylor University, One Bear Place #97348, Waco, TX 76798, USA.
² Department of Biochemistry and Chemistry, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria, 3086, Australia.

Abstract

The synthesis of tris(ortho-carboranyl)borane (BoCb₃ ), a single site neutral Lewis superacid, in one pot from commercially available materials is achieved. The high fluoride ion affinity (FIA) confirms its classification as a Lewis superacid and the Gutmann-Beckett method as well as adducts with Lewis bases indicate stronger Lewis acidity over the widely used fluorinated aryl boranes. The electron withdrawing effect of ortho-carborane and lack of pi-delocalization of the LUMO rationalize the unusually high Lewis acidity. Catalytic studies indicate that BoCb₃ is a superior catalyst for promoting C-F bond functionalization reactions than tris(pentafluorophenyl)borane [B(C₆ F₅ )₃ ].

Keywords: Boranes; Boron; Carboranes; Fluoride Ion Affinity; Lewis Acids.

Abstract

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