Assembly of High-Spin [Fe-3] Clusters by Ligand-Based Multielectron Reduction

The hexanuclear [Na12Fe6(tris-cyclo-salophen)(2)(THF)(14)], 1-THF, and the trinuclear [Na6Fe3(tris-cyclo-salophen)(py)(9)], 1-py, Fe(II) clusters can be easily assembled in one step from the ligand-based reduction of the [FeII(salophen)(THF)] complex. These complexes consist of triangular cores where three Fe(II) ions are held together, within range of bonding interaction, by the hexa-amide, hexaphenolate macrocyclic ligand tris-cyclo-salophen(12-). The tris-cyclo-salophen(12-) ligand is perfectly suited for binding three Fe(II) centers at short distances, allowing for strong magnetic coupling between the Fe(II) centers. The macrocyclic ligand is generated by the reductive coupling of the imino groups of three salophen ligands, resulting in three new C-C bonds. The six electrons stored in the ligand become available for the reduction of carbon dioxide with selective formation of carbonate.