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 first synthesized them. There are two generations of the catalyst, as shown on the right. In contrast to other olefin metathesis catalysts, Grubbs' catalysts tolerate other functional groups in the alkene, are air-tolerant and are compatible with a wide range of solvents. For these reasons, Grubbs' catalysts have become popular in synthetic organic chemistry.