Structure-defining interactions in the salt cocrystals of [(Me₅C₅)₂Fe]⁺I₃⁻–XC₆H₄OH (X = Cl, I): weak noncovalent vs. strong ionic bonding

In the cocrystalline salts [(Me₅C₅)₂Fe]⁺I₃⁻/(4-XC₆H₄OH) (X = Cl, I), the directionality of X⋯I−I₂ halogen bonds is a significant packing factor notwithstanding their relatively low energies (∼10 kcal mol⁻¹), as compared to the fivefold stronger ionic bonding between [(Me₅C₅)₂Fe⁺] and [I₃]⁻ (∼50 kcal mol⁻¹). This adds significant details to the structural landscape of [(Me₅C₅)₂Fe⁺]I₃ and offers an illustrative example of the stronger structure-defining effect of halogen bonding over the hydrogen one.