palladium catalytic cycle

directory of Chem Help ASAP videos: https://www.chemhelpasap.com/youtube/ The transition metal in a coupling reaction participates in a catalytic cycle. In general, most coupling reactions use a palladium(II) salt as the catalyst. The first step is reduction of the palladium to palladium(0). Palladium(0) then reacts with the aryl halide through an oxidative addition, and the palladium metal is oxidized to palladium(II) to give R-Pd-X. This species reacts with the organometallic reagent to form R-Pd-R' in a transmetallation reaction. The palladium is still in the palladium(II) oxidation state. The intermediate is unstable. The palladium slips from between the two R-groups to form the biaryl product. This step also reforms the palladium(0) catalyst in what is called a reductive elimination.