A New Mode of Chemical Reactivity for Metal-Free Hydrogen Activation by Lewis Acidic Boranes

Bennett, Elliot, Lawrence, Elliot, Blagg, Robin, Mullen, Anna, Macmillan, Fraser, Ehlers, Andreas, Scott, Daniel, Sapsford, Joshua, Ashley, Andrew, Wildgoose, Gregory and Slootweg, Chris (2019) A New Mode of Chemical Reactivity for Metal-Free Hydrogen Activation by Lewis Acidic Boranes. Angewandte Chemie International Edition, 58 (25). pp. 8362-8366. ISSN 1433-7851

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Abstract

We herein explore whether tris(aryl)borane Lewis acids are capable of cleaving H2 outside of the usual Lewis acid/base chemistry described by the concept of “frustrated Lewis pairs” (FLPs). Instead of a Lewis base we use a chemical reductant to generate stable radical anions of two highly‐hindered boranes: tris(3,5‐dinitromesityl)borane and tris(mesityl)borane. NMR spectroscopic characterization reveals that the corresponding borane radical anions activate (cleave) dihydrogen, whilst EPR spectroscopic characterization, supported by computational analysis, reveals the intermediates along the hydrogen activation pathway for the first time. This radical–based, redox pathway involves homolytic cleavage of H2, in contrast to conventional models of FLP chemistry which invoke a heterolytic cleavage pathway. This represents a new mode of chemical reactivity for hydrogen activation by borane Lewis acids.

Item Type: Article
Faculty \ School: Faculty of Science > School of Chemistry
Faculty of Medicine and Health Sciences > Norwich Medical School
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Depositing User: LivePure Connector
Date Deposited: 16 Apr 2019 14:30
Last Modified: 01 Apr 2020 00:39
URI: https://ueaeprints.uea.ac.uk/id/eprint/70601
DOI: 10.1002/anie.201900861

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