3-(4-pyridyl)-acetylacetone--a fully featured substituted pyridine and a flexible linker for complex materials

3-(4-Pyridyl)-acetylacetone (HacacPy) acts as a pyridine-type ligand towards CdX2 (X = Cl, Br, I). Chain polymers with six-coordinated metal cations are obtained from CdCl2 and with alternating five- and six-coordinated Cd centers from CdBr2. In either case, the formation of these compounds does not depend on the precise stoichiometry. In contrast, two different reaction products form with the heavier congener CdI2, namely a ligand-rich molecular complex CdI2(HacacPy)2 and a ligand-deficient one-dimensional polymer [CdI2(HacacPy)](1)(∞). Interconversion between these two iodo derivatives is possible via thermal degradation and mechanochemical synthesis. The acetylacetone moiety in HacacPy may be deprotonated and chelated to Fe(III), and the resulting complex Fe(acacPy)3 reacts analogously to a bridging polypyridine ligand towards the same Cd halides as the molecule HacacPy itself. With CdCl2 and CdBr2, isomorphous chain polymers are obtained in which the Cd cations adopt distorted octahedral coordination and one of the peripheric pyridyl groups remains uncoordinated. With CdI2, the iron complex acts as a mu3Fe(acacPy)3 bridge between tetrahedral Cd centers and gives rise to a ladder structure.