| Summary: | This work is focused on the complex interplay of geometry of I⋯X halogen bonds (HaB) and intermolecular interaction energy in two isomorphic cocrystals [CpFe(CO)<sub>2</sub>X] (C<sub>2</sub>I<sub>4</sub>) (X = Cl (<b>1</b>), Br (<b>2</b>)). Their IR-spectroscopic measurements in solid state and solution demonstrate the blue-shift of CO vibration bands, resulting from I⋯X HaB. The reluctance of their iodide congener [CpFe(CO)<sub>2</sub>I] to form the expected cocrystal [CpFe(CO)<sub>2</sub>I] (C<sub>2</sub>I<sub>4</sub>) is discussed in terms of different molecular electrostatic potential (MEP) of the surface of iodide ligands, as compared with chloride and bromide, which dictate a different angular geometry of HaB around the metal-I and metal-Br/Cl HaB acceptors. This study also suggests C<sub>2</sub>I<sub>4</sub> as a reliable HaB donor coformer for metal-halide HaB acceptors in the crystal engineering of hybrid metal–organic systems.
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