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Methylene Bridging Effect on the Structures, Lewis Acidities and Optical Properties of Semi‐planar Triarylboranes
Author(s) -
Doan ThuHong,
Chardon Aurélien,
Osi Arnaud,
Mahaut Damien,
Tumanov Nikolay,
Wouters Johan,
Champagne Benoît,
Berionni Guillaume
Publication year - 2021
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.202003319
Subject(s) - lewis acids and bases , chemistry , methylene bridge , borane , steric effects , adduct , methylene , intramolecular force , aryl , crystallography , ether , polymer chemistry , medicinal chemistry , stereochemistry , catalysis , organic chemistry , alkyl
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 NH 3 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 BAr 3 , the steric shielding of the CH 2 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.