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 − I 2 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.