Geometrically Constrained Organoboron Species as Lewis Superacids and Organic Superbases

Abstract This report unveils an advancement in the formation of a Lewis superacid (LSA) and an organic superbase by the geometrical deformation of an organoboron species towards a T‐shaped geometry. The boron dication [ 2 ] 2+ supported by an amido diphosphine pincer ligand features both a large fluoride ion affinity (FIA>SbF 5 ) and hydride ion affinity (HIA>B(C 6 F 5 ) 3 ), which qualifies it as both a hard and soft LSA. The unusual Lewis acidic properties of [ 2 ] 2+ are further showcased by its ability to abstract hydride and fluoride from Et 3 SiH and AgSbF 6 respectively, and effectively catalyze the hydrodefluorination, defluorination/arylation, as well as reduction of carbonyl compounds. One and two‐electron reduction of [ 2 ] 2+ affords stable boron radical cation [ 2 ]⋅ + and borylene 2 , respectively. The former species has an extremely high spin density of 0.798 e at the boron atom, whereas the latter compound has been demonstrated to be a strong organic base (calcd. p K BH + (MeCN)=47.4) by both theoretical and experimental assessment. Overall, these results demonstrate the strong ability of geometric constraining to empower the central boron atom.