Stepwise synthesis of heterotrimetallic FeII/PdII/AuI coordination cages

The synthesis of heterotrimetallic molecular cages is reported. The assemblies contain three types of coordination compounds: FeII clathrochelate complexes, AuI3(pyrazolate)3 complexes, and [PdII(pyridine)4]2+ complexes. The cages were obtained in a stepwise fashion. A nanometer-sized metalloligand with three terminal 3-pyridyl donor groups was prepared by connection of three FeII clathrochelate complexes via a central Au3(pyrazolate)3 complex. A related strategy was employed for the synthesis of a ditopic N-donor ligand with two functionalized FeII clathrochelate complexes. Combining the tritopic ligand with Pd(CH3CN)42 resulted in the clean formation of a spherical PdII6FeII24AuI24 coordination cage with a diameter of ∼4.1 nm and a molecular weight of 21 kDa. The ditopic metalloligand was used for the construction of a PdII2FeII8AuI12 cage.