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A Frustrated and Confused Lewis Pair
Author(s) -
McQuilken Alison C.,
Dao Quang Minh,
Cardenas Allan Jay P.,
Bertke Jeffery A.,
Grimme Stefan,
Warren Timothy H.
Publication year - 2016
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.201608968
Subject(s) - frustrated lewis pair , hydroboration , borane , chemistry , boranes , lewis acids and bases , adduct , isocyanate , covalent bond , stereochemistry , nuclear magnetic resonance spectroscopy , polymer chemistry , substrate (aquarium) , organic chemistry , catalysis , boron , polyurethane , oceanography , geology
We report a new class of frustrated Lewis pairs (FLPs) by the hydroboration of bulky isocyanates iPr2 ArNCO ( iPr2 Ar=2,6‐ i Pr 2 C 6 H 3 ) and Ph2tBu ArNCO ( Ph2tBu Ar=2,6‐Ph 2 ‐4‐ t BuC 6 H 2 ) with Piers’ borane (HB(C 6 F 5 ) 2 ). While hydroboration of smaller isocyanates such as iPr2 ArNCO leads to isocyanate—N/B FLP adducts, hydroboration of the bulkier Ph2tBu ArNCO allows isolation of the substrate‐free aminoborane with a short, covalent N−B bond. This confused FLP reversibly binds unsaturated substrates such as isocyanates and isocyanides, suggesting the intermediacy of a “normal” FLP along the reaction pathway, supported by high‐level DFT studies and variable‐temperature NMR spectroscopy. These results underscore the possibility of FLP behavior in systems that possess no obvious frustrated Lewis acid–base interaction.