Controlled Generation of 9‐Boratriptycene by Lewis Adduct Dissociation: Accessing a Non‐Planar Triarylborane. (25th May 2020)

• Record Type: Journal Article
• Authors: Chardon, Aurélien; Osi, Arnaud; Mahaut, Damien; Doan, Thu‐Hong; Tumanov, Nikolay; Wouters, Johan; Fusaro, Luca; Champagne, Benoît; Berionni, Guillaume
• Is Part Of: Angewandte Chemie. Volume 132:Number 30(2020)
• Page Start: 12502
• Page End: 12506
• Publication Date: 2020-05-25
• Subjects: Lewis adducts -- non-planar boron Lewis acids -- triarylborane -- triptycene; Chemistry -- Periodicals; 540
• DOI: 10.1002/ange.202003119
• Languages: English
• ISSNs: 0044-8249

Abstract

Abstract: 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 p z orbital is one of the main reasons for its high Lewis acidity. Abstract : Breaking B–π conjugation : 9‐Boratriptycene is a bent and non‐conjugated triarylborane with an unprecedented geometrical shape, which confers a low reorganization energy and high Lewis acidity power.