Imposing Latency in Ruthenium Sulfoxide-Chelated Benzylidenes: Expanding Opportunities for Thermal and Photoactivation in Olefin Metathesis

Herein we show the design and synthesis of an electron-rich, sulfoxide-chelated, ruthenium benzylidene. In contrast to previously reported sulfoxide-chelated ruthenium benzylidenes, this complex is more stable in a cis-dichloro conformation and is thus latent in typical olefin metathesis reactions. The complex was characterized by NMR, UV–vis, and X-ray spectroscopy, alongside density functional theory computations. The latent precatalyst could be activated thermally and, depending on the solvent, by UV–C or visible light. In addition, an original “thermo-chromatic” orthogonal sequence was developed, further improved by the use of a thioether chelated complex, where a divergent two-step synthesis can lead to a dihydrofuran or a dihydropyran depending only on the order by which the different stimuli, heat or light, are applied.