Latent, Yet Highly Active Photoswitchable Olefin Metathesis Precatalysts Bearing Cyclic Alkyl Amino Carbene (CAAC)/Phosphite Ligands

The ligand shell that surrounds an active metal center has a paramount effect on its reactivity and properties. In this work, the photoswitchable nature of phosphite olefin metathesis precatalysts and the robustness of cyclic alkyl amino carbene (CAAC) ligands are combined. Also, the synthesis, characterization, and photoactivity of two ruthenium indenylidene complexes bearing a CAAC/phosphite ligand system are reported. Exposure to 405 nm light efficiently activates the precatalysts and promotes a wide range of olefin metathesis reactions. Moreover, the catalysts display formidable latency at ambient temperatures, even with the highly reactive dicyclopentadiene and its derivatives, allowing the preparation of stable monomer-catalyst formulations with a long pot life. In addition, the chemoselectivity of CAAC catalysts is preserved, preventing olefin migration reactions at elevated temperatures and allowing efficient recycling for multiple reaction cycles under air.