Pentafluoroethylation of unactivated C(sp2)-X bonds (X = I, Br) using a storable, "ligandless" CuC2F5 reagent prepared by controlled self-condensation of ready available TMSCF3-derived CuCF3 has been developed. A thorough analysis by 19F NMR and ESI-MS revealed the nature of this reagent in solution. The operational simplicity and robustness of this system enables the efficient, late-stage incorporation of C2F5 units into a variety of (hetero)aryl and complex alkenyl halides such as glycals, nucleosides, and nucleobases.