Multifunctional Photocatalysts Based on Half-Sandwich Cyclometalated Ir(III) Complexes with π-Extended Ligands

Photocatalysis has emerged as a powerful strategy in synthetic organic chemistry to avoid harsh conditions and toxic oxidants. Herein, we report the photocatalytic activity of half-sandwich Ir(III) complexes in different transformations. For the first time, Cp*Ir(III) complexes were applied in photooxidative coupling reactions of amines, without any additives, achieving quantitative imine formation, and in thioether photooxidation reactions, reaching high chemoselectivity for sulfoxide formation. Furthermore, exceptional activity was observed in photodehydrogenation of N-heterocyclic substrates. Reactions proceeded under mild conditions, including room temperature and an ambient air or oxygen atmosphere, with considerably low catalyst loadings (0.005-0.25 mol %). Complex 1, bearing the π-extended C^∧N pbpn ligand, was also active even in aqueous media (MeCN/H₂O 1:1) and under sunlight, reaching full conversion within hours. Mechanistic studies indicated the involvement of reactive oxygen species, such as singlet oxygen (¹O₂) and superoxide anion radical (O₂^•-), operating via both energy and electron transfer pathways. These findings establish this Cp*Ir(III) complex as an efficient, versatile, and sustainable photocatalyst, constituting one of the first examples of half-sandwich Ir complexes employed in diverse photooxidative organic reactions.