Carbocation-Coupled Electron Transfer: An α-Ferrocenylmethylium as a Masked Primary Alkyl Radical

Despite the extensive development of proton-coupled electron transfer (PCET), carbocation-coupled electron transfer (CCCET), which formally transfers a carbon-centered radical, remains significantly less explored. Here, we disclose that a redox-active permethylated α-ferrocenylmethylium, [(C₅Me₅)(C₅Me₄CH₂)Fe][BArF₄] (ArF = C₆F₅), can act as a masked primary alkyl radical through CCCET. It undergoes a series of transformations, including coupling with stable radicals, addition to unsaturated double bonds, and C-H activation of heterocycles. These transformations are difficult to achieve using redox-inert carbocations, thus emphasizing the importance of the redox-active ferrocenyl group in the structure. This study not only expands the scope of CCCET but also provides a novel and efficient strategy for the construction of C-X (X = C, O, etc.) bonds via radical pathways.