Triphenylphosphine Photorelease and Induction of Catalytic Activity from Ruthenium-Arene Complexes Bearing a Photoswitchable <i>o</i>‑Tosylamide Azobenzene Ligand

The reactivity of cationic arene ruthenium complexes bearing a photoswitchable o-tosylamide azobenzene ligand toward various phosphorus nucleophiles was investigated. The resulting phosphine-ruthenium complexes containing an azobenzene ligand were isolated as the Z isomer. Under appropriate reaction conditions, quantitative triphenylphosphine photorelease from the complex was achieved through Z → E isomerization of the ligand. This process was applied to the photoinitiation of the catalytic aza-Morita–Baylis–Hillman reaction.