Grubbs catalysts are a series of transition metal carbene complexes used as catalysts for olefin metathesis. They are named after Robert H. Grubbs, the chemist who supervised their synthesis. Several generations of the catalyst have been developed. Grubbs catalysts tolerate many functional groups in the alkene substrates, are air-tolerant, and are compatible with a wide range of solvents. For these reasons, Grubbs catalysts have become popular in synthetic organic chemistry. Grubbs, together with Richard R. Schrock and Yves Chauvin, won the Nobel Prize in Chemistry in recognition of their contributions to the development of olefin metathesis. Grubbs catalysts are a series of transition metal carbene complexes used as catalysts for olefin metathesis. They are named after Robert H. Grubbs, the chemist who supervised their synthesis. Several generations of the catalyst have been developed. Grubbs catalysts tolerate many functional groups in the alkene substrates, are air-tolerant, and are compatible with a wide range of solvents. For these reasons, Grubbs catalysts have become popular in synthetic organic chemistry. Grubbs, together with Richard R. Schrock and Yves Chauvin, won the Nobel Prize in Chemistry in recognition of their contributions to the development of olefin metathesis. In the 1960s, ruthenium trichloride was found to catalyze olefin metathesis. Processes were commercialized based on these discoveries. These ill-defined but highly active homogeneous catalysts remain in industrial use. The first well-defined ruthenium catalyst was reported in 1992. It was prepared from RuCl2(PPh3)4 and diphenylcyclopropene. This initial ruthenium catalyst was followed in 1995 by what is now known as the first-generation Grubbs catalyst. It is synthesized from RuCl2(PPh3)3, phenyldiazomethane, and tricyclohexylphosphine in a one-pot synthesis.