3-(4-Pyridyl)-2,4-pentanedione - a bridge between coordinative, halogen, and hydrogen bonds

3-(4-Pyridyl)-2,4-pentanedionate, an established ditopic ligand for metal complexes, offers additional interaction modes which may be exploited for crystal engineering: we have assembled structures in which halogen bonds coexist with coordinative and hydrogen bonds. An adduct of the neutral 3-(4-pyridyl)-2,4-pentanedione to tetrafluorodiiodobenzene proves the suitability of the pyridine N as a nucleophile in halogen bonds. This feature is preserved in Fe and Al complexes of the substituted acetylacetonate. For the latter, an experimental charge density based on high resolution diffraction data gives insight into the halogen bonds.