Evidence of AlII Radical Addition to Benzene

Debdeep Mandal; T Ilgin Demirer; Tetiana Sergeieva; Bernd Morgenstern; Haakon T A Wiedemann; Christopher W M Kay; Diego M Andrada

doi:10.1002/anie.202217184

Evidence of Al^II Radical Addition to Benzene

Angew Chem Int Ed Engl. 2023 Mar 20;62(13):e202217184. doi: 10.1002/anie.202217184. Epub 2023 Feb 17.

Authors

Debdeep Mandal¹, T Ilgin Demirer¹, Tetiana Sergeieva¹, Bernd Morgenstern¹, Haakon T A Wiedemann², Christopher W M Kay^{2

3}, Diego M Andrada¹

Affiliations

¹ General and Inorganic Chemistry Department, University of Saarland, Campus C4.1, 66123, Saarbrücken, Germany.
² Physical Chemistry Department, University of Saarland, Campus B2.2, 66123, Saarbrücken, Germany.
³ London Centre for Nanotechnology, University College London, 17-19 Gordon Street, London, WC1H 0AH, UK.

PMID: 36594569
DOI: 10.1002/anie.202217184

Abstract

Electrophilic Al^III species have long dominated the aluminum reactivity towards arenes. Recently, nucleophilic low-valent Al^I aluminyl anions have showcased oxidative additions towards arenes C-C and/or C-H bonds. Herein, we communicate compelling evidence of an Al^II radical addition reaction to the benzene ring. The electron reduction of a ligand stabilized precursor with KC₈ in benzene furnishes a double addition to the benzene ring instead of a C-H bond activation, producing the corresponding cyclohexa-1,3(orl,4)-dienes as Birch-type reduction product. X-ray crystallographic analysis, EPR spectroscopy, and DFT results suggest this reactivity proceeds through a stable Al^II radical intermediate, whose stability is a consequence of a rigid scaffold in combination with strong steric protection.

Keywords: Aluminum; EPR Spectroscopy; Low-Valent Compounds; Radicals; Structure Elucidation.

Abstract

Grants and funding