Selective functionalization of C(sp³)–H bonds: Catalytic chlorination and bromination by Ironᴵᴵᴵ-acacen-halide under ambient condition

The oxidative catalytic halogenations of the C(sp³)–H bond of alkanes promoted by Feᴵᴵᴵ(acacen)Cl (1ᴵᴵᴵ-Cl) and Feᴵᴵᴵ(acacen)Br (1ᴵᴵᴵ-Br) in the presence of trifluoroacetic acid (TFA) were investigated. Four major steps were involved: (i) formation of [Feᵛ(acacen)(oxo)X] species (X = Cl or Br), (ii) hydrogen-atom transfer, (iii) halogen atom rebound, and (iv) regeneration of 1ᴵᴵᴵ-Cl or 1ᴵᴵᴵ-Br. TFA played a significant role in (i) forming the high-valent iron-oxo intermediate and (ii) generating the reaction selectivity. Copyright © 2022 The Royal Society of Chemistry.