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

Bennett, Elliot L ORCID: 0000-0003-3798-4296, Lawrence, Elliot J, Blagg, Robin J, Mullen, Anna S, MacMillan, Fraser, Ehlers, Andreas W, Scott, Daniel J, Sapsford, Joshua S, Ashley, Andrew E, Wildgoose, Gregory G
et al (show 1 more authors) (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.

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We herein explore whether tris(aryl)borane Lewis acids are capable of cleaving H<sub>2</sub> 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. This radical-based, redox pathway involves the homolytic cleavage of H<sub>2</sub> , 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
Uncontrolled Keywords: boranes, dihydrogen, electron paramagnetic resonance, Lewis acids, radicals
Depositing User: Symplectic Admin
Date Deposited: 14 May 2019 15:48
Last Modified: 19 Jan 2023 00:45
DOI: 10.1002/anie.201900861
Open Access URL: https://doi.org/10.1002/anie.201900861
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URI: https://livrepository.liverpool.ac.uk/id/eprint/3041299