An [FeIII34] Molecular Metal Oxide

The dissolution of anhydrous iron bromide in a mixture of pyridine and acetonitrile, in the presence of an organic amine, results in the formation of an [Fe34] metal oxide molecule, structurally characterised by alternate layers of tetrahedral and octahedral FeIII ions connected by oxide and hydroxide ions. The outer shell of the complex is capped by a combination of pyridine molecules and bromide ions. Magnetic data, measured at temperatures as low as 0.4 K and fields up to 35 T, reveal competing antiferromagnetic exchange interactions; DFT calculations showing that the magnitudes of the coupling constants are highly dependent on both the Fe‐O‐Fe angles and Fe−O distances. The simplicity of the synthetic methodology, and the structural similarity between [Fe34], bulk iron oxides, previous FeIII–oxo cages, and polyoxometalates (POMs), hints that much larger molecular FeIII oxides can be made. Fe Maiden: Ein molekulares [Fe34]‐Metalloxid besteht aus einem [Fe4]‐Tetraeder, das in einem gekappten [Fe18]‐Tetraeder verkapselt ist, auf dessen Flächen sich vier [Fe3]‐Dreiecke anordnen. Die Struktur enthält abwechselnde Schichten von tetraedrischen und oktaedrischen Fe‐Ionen, die über Oxid‐ und Hydroxidanionen verknüpft sind.