The functionalization of methane, ethane, and other alkanes derived from fossil fuels is a central goal in the chemical enterprise. Recently, a photocatalytic system comprising [CeIVCl5(OR)]2−[CeIV, cerium(IV); OR, –OCH3or –OCCl2CH3] was disclosed. The system was reportedly capable of alkane activation by alkoxy radicals (RO•) formed by CeIV–OR bond photolysis. In this work, we present evidence that the reported carbon-hydrogen (C–H) activation of alkanes is instead mediated by the photocatalyst [NEt4]2[CeCl6] (NEt4+, tetraethylammonium), and RO• are not intermediates. Spectroscopic analyses and kinetics were investigated for C–H activation to identify chlorine radical (Cl•) generation as the rate-limiting step. Density functional theory calculations support the formation of [Cl•][alcohol] adducts when alcohols are present, which can manifest a masked RO• character. This result serves as an important cautionary note for interpretation of radical trapping experiments.
- Award ID(s):
- 1902509
- Publication Date:
- NSF-PAR ID:
- 10230250
- Journal Name:
- Science
- Volume:
- 372
- Issue:
- 6544
- Page Range or eLocation-ID:
- p. 847-852
- ISSN:
- 0036-8075
- Publisher:
- American Association for the Advancement of Science (AAAS)
- Sponsoring Org:
- National Science Foundation
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