Sabrina Pietsch1, Ursula Paul1, Ian A Cade2, Michael J Ingleson3, Udo Radius4, Todd B Marder5. 1. Institut für Anorganische Chemie, Julius-Maximilians-Universität Würzburg, Am Hubland, 97074 Würzburg (Germany). 2. School of Chemistry, The University of Manchester, Manchester M13 9PL (UK). 3. School of Chemistry, The University of Manchester, Manchester M13 9PL (UK). michael.ingleson@manchester.ac.uk. 4. Institut für Anorganische Chemie, Julius-Maximilians-Universität Würzburg, Am Hubland, 97074 Würzburg (Germany). u.radius@uni-wuerzburg.de. 5. Institut für Anorganische Chemie, Julius-Maximilians-Universität Würzburg, Am Hubland, 97074 Würzburg (Germany). todd.marder@uni-wuerzburg.de.
Abstract
We report the isolation and detailed structural characterization, by solid-state and solution NMR spectroscopy, of the neutral mono- and bis-NHC adducts of bis(catecholato)diboron (B2 cat2 ). The bis-NHC adduct undergoes thermally induced rearrangement, forming a six-membered -B-C=N-C=C-N-heterocyclic ring via C-N bond cleavage and ring expansion of the NHC, whereas the mono-NHC adduct is stable. Bis(neopentylglycolato)diboron (B2 neop2 ) is much more reactive than B2 cat2 giving a ring expanded product at room temperature, demonstrating that ring expansion of NHCs can be a very facile process with significant implications for their use in catalysis.
We report the isolation and detailed structural characterization, by solid-state and solution NMR spectroscopy, of the neutral n class="Chemical">mono- and bis-NHC adducts of bis(catecholato)diboron (B2 cat2 ). The bis-NHC adduct undergoes thermally induced rearrangement, forming a six-membered -B-C=N-C=C-N-heterocyclic ring via C-N bond cleavage and ring expansion of the NHC, whereas the mono-NHC adduct is stable. Bis(neopentylglycolato)diboron (B2 neop2 ) is much more reactive than B2 cat2 giving a ring expanded product at room temperature, demonstrating that ring expansion of NHCs can be a very facile process with significant implications for their use in catalysis.
Authors: Laura Kuehn; Ludwig Zapf; Luis Werner; Martin Stang; Sabrina Würtemberger-Pietsch; Ivo Krummenacher; Holger Braunschweig; Emmanuel Lacôte; Todd B Marder; Udo Radius Journal: Chem Sci Date: 2022-06-07 Impact factor: 9.969
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