A ligand-centered review on structure, synthesis, and significance of diiron coordination complexes

Diiron coordination complexes represent a structurally diverse and functionally rich class of coordination compounds, carrying significant importance in catalysis and material design due to their capability to possess variable oxidation states and spin states. The development of these complexes has attracted considerable attention due to their structural similarity to the active sites of metalloenzymes and their roles in redox catalysis, small molecule activation, and photochemical reactions. Bridging ligands are essential for improving electronic communication and magnetic interactions among iron centers, and they also act as functional analogs of metalloenzymes such as hydrogenases and ribonucleotide reductases. This review focuses on the synthesis of dinuclear iron complexes utilizing various bridging ligands, including oxo, carboxylate, thiolate, and phosphine, which enhance metal-metal interactions and cooperative reactivity. Key synthetic approaches include controlled stoichiometric reactions involving iron precursors and polydentate ligands, sequential metalation methods, and ligand exchange conducted under inert or photochemical conditions.