Perfluorinated arenes (benzene(F) derivatives, diphenyl(F), naphthalene(F)) were converted into X-perfluoroarenes (X = Br, I) via the developed one-pot protocol based on [Fe(acetylacetonate)(3)]-assisted C-F functionalization. The syntheses proceed under mild conditions and employ readily available perfluorinated arenes, which are treated with EtMgBr followed by addition of X-2/[Fe(acetylacetonate)(3)] (0.8 mol %); yields range from good to moderate. The sigma-hole donor properties of the obtained mono-and di-X-perfluoroarenes and the significance of these species for halogen-bonding-based crystal engineering was illustrated in a series of postsynthetic experiments, all supported by density functional theory (DFT) energy calculations, molecular electrostatic potential (MEP) surface analysis, and the quantum theory of atoms in molecules (QTAIM). These include (i) a solid-state X-ray diffraction study of X-perfluoroarene self-association (dimerization) via iodine sigma-hole.electron belt interactions (three X-ray structures) and (ii) verification of X-perfluoroarene s-hole donor abilities by their interactions with iodides acting as external s-hole acceptors (five X-ray structures); a Hirshfeld surface analysis was performed for all eight structures.