Toward Sustainable NHC‐Based Photosensitizers: Scalable Synthesis and Postfunctionalization of Fe, Co, and Mn Complexes

Iron‐NHC ( N ‐heterocyclic carbene) complexes hold strong promise as earth‐abundant alternatives to Ru‐ and Ir‐based photosensitizers, but their synthesis represents additional challenges. Here, we present a systematic study aimed at developing a robust, reproducible, and scalable protocol for the synthesis of [Fe(Brphtmeimb) 2 ] + that is suitable for researchers of all skill levels. By examining the effects of base, solvent, temperature, concentration, and iron source, we identified several previously overlooked parameters, including FeBr 2 solubility, temperature‐dependent precipitation, and solvent quality, that significantly impact reaction outcome. Optimization revealed that low‐temperature addition of LiHMDS and dilute reaction conditions (0.02 M) afford consistently improved yields. Further adjustment of ligand and base stoichiometry enabled reliable scale‐up, delivering the target complex in 64% yield on a 1 mmol scale. This practical procedure provides broad, dependable access to [Fe(Brphtmeimb) 2 ] + , facilitating its use across catalysis, materials chemistry, and related fields. Furthermore, we show postfunctionalization routes of [Fe(Brphtmeimb) 2 ] + via Suzuki‐type coupling and expand the reaction scope to include additional transition metals such as Mn(IV) and Co(III).