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Late-Metal-Catalyzed Hydrogenation and Hydrometallation Pd, Pt, Rh

One of the first metal-catalyzed reactions learned by organic chemistry students is the Pd-catalyzed hydrogenation of alkenes and alkynes. The reaction is stereo- [Pg.283]

Consider the reaction of 2,3-dimethyl-2-butene with H2 catalyzed by Pd/C. Two new C-H bonds are made, and a C=C 7r bond breaks. The fact that the addition is stereospecifically syn suggests that an insertion reaction is occurring. The Pd metal is in the (0) oxidation state (i.e., d10), so it can react with H2 by an oxidative addition to give two Pd-H bonds. At this point Pd is in the (II) oxidation state. Coordination and insertion of the alkene into one of the Pd-H bonds gives Pd-C and C-H bonds. Finally, reductive elimination gives the product and regenerates Pd°, which begins the catalytic cycle anew. [Pg.284]

Note that curved arrows are typically not used to show electron flow in each mechanistic step. However, the catalytic cycle is explicitly drawn, and every step is one of the typical reactions of metals. [Pg.284]

Every late-metal hydrogenation catalyst, whether homogeneous or heterogeneous, probably uses exactly the same catalytic cycle, although some catalysts, particularly sterically encumbered ones such as Wilkinson s catalyst, require that ligand dissociation or substitution occur before the catalytic cycle gets underway. In the case of metals supported on solids such as activated C, silica, and alumina, the support may participate in the reaction in ways that need not concern you here. [Pg.284]

Formic acid and 1,4-cyclohexadiene are sometimes used as alternative H2 sources in hydrogenation and hydrogenolysis reactions. Protonation of Pd(0) by [Pg.284]


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And metal catalyzed

Hydrogen catalyzed

Hydrogen metal catalyzed

Hydrogen, and metal

Hydrogenation, catalyzed

Hydrometalation

Hydrometalations

Hydrometallation

Hydrometallation metallation

Hydrometallation, metal-catalyzed

Hydrometallization

Pd and Pt

Pd hydrogenation

Pd metal

Pd-catalyzed hydrogenation

Pt-metallization

Rh-catalyzed hydrogenation

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