Light-Driven Hydrodefluorination of Electron-Rich Aryl Fluorides by an Anionic Rhodium-Gallium Photoredox Catalyst

James T. Moore, Michael J. Dorantes, Zihan Pengmei, Timothy M. Schwartz, Jacob Schaffner, Samantha L. Apps, Carlo A. Gaggioli, Ujjal Das, Laura Gagliardi, David A. Blank, Connie C. Lu

Research output: Contribution to journalArticlepeer-review

10 Scopus citations

Abstract

An anionic Rh−Ga complex catalyzed the hydrodefluorination of challenging C−F bonds in electron-rich aryl fluorides and trifluoromethylarenes when irradiated with violet light in the presence of H2, a stoichiometric alkoxide base, and a crown-ether additive. Based on theoretical calculations, the lowest unoccupied molecular orbital (LUMO), which is delocalized across both the Rh and Ga atoms, becomes singly occupied upon excitation, thereby poising the Rh−Ga complex for photoinduced single-electron transfer (SET). Stoichiometric and control reactions support that the C−F activation is mediated by the excited anionic Rh−Ga complex. After SET, the proposed neutral Rh0 intermediate was detected by EPR spectroscopy, which matched the spectrum of an independently synthesized sample. Deuterium-labeling studies corroborate the generation of aryl radicals during catalysis and their subsequent hydrogen-atom abstraction from the THF solvent to generate the hydrodefluorinated arene products. Altogether, the combined experimental and theoretical data support an unconventional bimetallic excitation that achieves the activation of strong C−F bonds and uses H2 and base as the terminal reductant.

Original languageEnglish (US)
Article numbere202205575
JournalAngewandte Chemie - International Edition
Volume61
Issue number42
DOIs
StatePublished - Oct 17 2022

Bibliographical note

Funding Information:
This material is based upon work supported by the National Science Foundation under Grant Nos. 2102095 and 2054723. We thank Dr. Andrew Healy, Prof. Aaron Massari, Connor Reilly, and Dr. Victor Young, Jr. for experimental assistance. TMS, UD, and CCL gratefully acknowledge Prof. Alexander Filippou for providing access to facilities and additional resources.

Publisher Copyright:
© 2022 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.

Keywords

  • Gallium
  • Heterobimetallic
  • Hydrodefluorination
  • Photoredox Catalysis
  • Rhodium

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