Searching for the Hidden Hydrides: The Competition between Alkene Isomerization and Metathesis with Grubbs Catalysts

Although Grubbs metathesis catalysts have enabled syntheses of a range of molecules, alkene isomerization, a known and problematic side reaction, is poorly understood. Several mechanisms which have been advanced to account for isomerization were studied by using electronic structure calculations. The pathway catalyzed by a ruthenium hydride emerged as the most facile process by a significant margin. For the first time, we have obtained experimental evidence for the presence of this species in a metathesis-active system.