Photocatalytic C-H activation and the subtle role of chlorine radical complexation in reactivity.
Science
; 372(6544): 847-852, 2021 05 21.
Article
em En
| MEDLINE
| ID: mdl-34016778
ABSTRACT
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, -OCH3 or -OCCl2CH3] was disclosed. The system was reportedly capable of alkane activation by alkoxy radicals (ROâ¢) 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 (Clâ¢) generation as the rate-limiting step. Density functional theory calculations support the formation of [Clâ¢][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.
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Idioma:
En
Revista:
Science
Ano de publicação:
2021
Tipo de documento:
Article
País de afiliação:
Estados Unidos