Cationic Triarylchlorostibonium Lewis Acids

Omar Coughlin; Tobias Krämer; Sophie L Benjamin

doi:10.1021/acs.organomet.2c00426

Cationic Triarylchlorostibonium Lewis Acids

Organometallics. 2023 Feb 20;42(5):339-346. doi: 10.1021/acs.organomet.2c00426. eCollection 2023 Mar 13.

Authors

Omar Coughlin¹, Tobias Krämer², Sophie L Benjamin¹

Affiliations

¹ Department of Chemistry, Nottingham Trent University, Clifton Lane, Nottingham NG11 8NS, U.K.
² Department of Chemistry, Maynooth University, Maynooth, Co. Kildare W23 F2H6, Ireland.

Abstract

Organopnictogen cations show promise as powerful, tunable main-group Lewis acid catalysts. The synthesis, solid-state structures, and reactivity of a series of weakly coordinated triarylchlorostibonium salts [Ar₃SbCl][B(C₆F₅)₄] (Ar = Ph, 3-FC₆H₄, 4-FC₆H₄, 3,5-F₂C₆H₃, 2,4,6-F₃C₆H₂) are reported. The cation in each adopts a tetrahedral coordination environment of antimony, with near complete separation from the anion. Structural, computational, and reactivity studies reveal that the Lewis acidity of [Ar₃SbCl]⁺ generally increases with increased fluorination of the Ar substituents, with a secondary quenching effect from para fluorination. [Ar₃SbCl]⁺ is reduced to Ar₃Sb in the presence of Et₃SiH, and the mechanism of this reaction has been modeled computationally. Preliminary studies demonstrate that they are useful catalysts for the dimerization of 1,1-diphenylethylene and the Friedel-Crafts alkylation of benzene.