Triphenylphosphine Photorelease and Induction of Catalytic Activity from Ruthenium-Arene Complexes Bearing a Photoswitchable o-Tosylamide Azobenzene Ligand

The reactivity of cationic arene ruthenium complexes bearing photoswitchable o-tosylamide azobenzene ligand towards various phosphorus nucleophiles was investigated. The resulting phosphine-ruthenium complexes containing 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 photo-initiation of catalytic aza Morita-Baylis-Hillman reaction.