A highly bent triarylborane, 9‐boratriptycene, was generated in solution by selective protodeboronation of the corresponding tetra‐aryl boron ate complex with the strong Brønsted acid HNTf2. The iptycene core confers enhanced Lewis acidity to 9‐boratriptycene, making it unique in terms of structure and reactivity. We studied the stereoelectronic properties of 9‐boratriptycene by quantifying its association with small N‐ and O‐centered Lewis bases, as well as with sterically hindered phosphines. The resultant Lewis adducts exhibited unique structural, spectroscopic, and photophysical properties. Beyond the high pyramidalization of the 9‐boratriptycene scaffold and its low reorganization energy upon Lewis base coordination, quantum chemical calculations revealed that the absence of π donation from the triptycene aryl rings to the boron vacant pz orbital is one of the main reasons for its high Lewis acidity.

Three synthetic methods towards semi‐planar triarylboranes with two aryl rings connected by a methylene bridge have been developed. The fine‐tuning of their stereoelectronic properties and Lewis acidities was achieved by introducing fluorine, methyl, methoxy, n‐butyl and phenyl groups either at their exocyclic or bridged aryl rings. X‐ray diffraction analysis and quantum‐chemical calculations provided quantitative information on the structural distortion experienced by the near planar hydro‐boraanthracene skeleton during the association with Lewis bases such as NH3 and F−. Though the methylene bridge between the ortho‐positions of two aryl rings of triarylboranes decreased the Gibbs free energies of complexation with small Lewis bases by less than 5 kJ mol−1 relative to the classical Lewis acid BAr3, the steric shielding of the CH2 bridge is sufficient to avoid the formation of Lewis adducts with larger Lewis bases such as triarylphosphines. A newly synthesized spirocyclic amino‐borane with a long intramolecular B−N bond that could be dissociated under thermal process, UV‐irradiation, or acidic conditions might be a potential candidate in Lewis pairs catalysis.

We developed two synthetic strategies towards triptycene‐derived bulky boranes, boronates, and boron ate‐complexes. Starting from borylated or brominated anthracenes and using a Br/Li exchange and [4+2] cycloaddition reaction with in‐situ generated benzyne, we produced a series of triptycene boronates and borates with various boron substituents in positions 1 and 9, such as BPin, Bneo, BF3K and B(Mes)2. Single‐crystal X‐ray diffraction analysis and UV‐Vis/photoluminescence measurements provided quantitative information on the effect of the triptycene scaffold on the photophysical and electronic properties of the obtained compounds.

Die planare Geometrie trivalenter Bor‐Lewis‐Säuren kann durch den Einbau eines Boratoms am Rand des Triptycengerüsts überwunden werden. G. Berionni und Mitarbeiter beschreiben in ihrer Zuschrift auf S. 12502 die Herstellung von 9‐Boratriptycen, einem Triarylboran mit ungewöhnlicher Struktur und hoher Lewis‐Acidität. Diese Eigenschaften werden durch die sehr niedrige Reorganisationsenergie des Triptycen‐Kerns und die Abwesenheit einer Konjugation der B‐Atomorbitale mit den orthogonal angeordneten Arylringen verursacht.