Halogenase-mimicking selective chlorination of unactivated C–H bonds by a Fe-complex

Abstract

In this study, we report a selective aliphatic C–H bond chlorination mediated by Fe-bTAML (bTAML: biuret-modified tetraamido macrocyclic ligand) using sodium hypochlorite as the chlorine source. The reaction predominantly yields chlorinated products over hydroxylated ones across various unactivated C–H bonds in acetonitrile–water medium. The formation of rearranged chlorinated products in norcarane and the absence of stereo-retention in cis-dimethylcyclohexane suggests the involvement of a long-lived, cage-escaped carbon radical intermediate. UV-Vis and EPR spectroscopic analyses confirm the presence of [Fe^V(O)–(NO₂)bTAML]⁻ (2) as the reactive intermediate. The 3°:2° selectivity in hydrocarbons, kinetic isotope effect (KIE), and detailed kinetic studies indicate hydrogen atom abstraction (HAA) by [Fe^V(O)–(NO₂)bTAML]⁻ (2) as the rate-determining step.