Controlled Generation of 9‐Boratriptycene by Lewis Adduct Dissociation: Accessing a Non‐Planar Triarylborane
Aurélien Chardon, Arnaud Osi, Damien Mahaut, Thu‐Hong Doan, Nikolay Tumanov, Johan Wouters, Luca Fusaro, Benoı̂t Champagne, Guillaume Berionni
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 HNTf 2 . 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.