text: In the 1960s and 1970s various groups reported the ring-opening polymerization of norbornene catalyzed by hydrated trichlorides of ruthenium and other late transition metals in polar, protic solvents. This prompted Robert H. Grubbs and coworkers to search for well-defined, functional group tolerant catalysts based on ruthenium. The Grubbs group successfully polymerized the 7-oxo norbornene derivative using ruthenium trichloride, osmium trichloride as well as tungsten alkylidenes. They identified a Ru(II) carbene as an effective metal center and in 1992 published the first well-defined, ruthenium-based olefin metathesis catalyst, (PPh)ClRu=CHCH=CPh:
  The corresponding tricyclohexylphosphine complex (PCy)ClRu=CHCH=CPh was also shown to be active. This work culminated in the now commercially available 1st generation Grubbs catalyst.