Olefins homogeneous hydrogenation

In view of these observations it is not surprising that there occur a wide variety of catalytic reactions, particularly involving hydrocarbons. For example, the isomerization of olefins, homogeneous hydrogenations, group substitution in the vicinity of double bonds, and polymerization reactions are all catalyzed by transition metal complexes. 

Chiral ligands for homogeneous hydrogenation of olefins and ketones... 

In benzene or similar solvents, tris(triphenylphosphine)halogenorhodium(I) complexes, RhX[P(C6H5)3]3, are extremely efficient catalysts for the homogeneous hydrogenation of nonconjugated olefins and acetylenes at ambient temperature and pressures of 1 atmosphere (6). Functional groups (keto-, nitro-, ester, and so on) are not reduced under these conditions. 

The homogeneous hydrogenation of soybean oil methyl ester Olefin disproportionation... 

The efficiency of Crabtree s catalyst as a catalyst for small molecule hydrogenation has been known for many years. Unlike many homogeneous hydrogenation catalysts, Crabtree s catalyst is able to reduce hindered olefins at favourable rates.7 It has never been reported as a catalyst for the hydrogenation of rubber except for its use in the hydrogenation of bulk PBD.8 This paper describes the first use of Crabtree s catalyst in the hydrogenation NBR. Kinetic data are presented and analyzed to understand the underlying chemistry. 

J. A. Osborne, F. J. Jardine, J. F. Young, G. Wilkinson, The Preparation and Properties of Tris(triphenylphosphi-ne)halogenorhodium(I) and some Reactions thereof including Catalytic Homogeneous Hydrogenation of Olefins and Acetylenes and their Derivatives, J. Client Soc A. 1966,1711-1732. 

The reaction of an olefin with hydrogen may be analogous to the related homogeneous reaction (44, 46). The olefin may form a n complex with a single center and combine with hydrogen in the sequence shown in Fig. 22A. Besides the reverse of the preceding sequence, an alternative... 

Young, J. F. Osborn, J. A. Jardine, F. A. Wilkinson, G. Flydride intermediates in homogeneous hydrogenation reactions of olefins and acety-... 

Figure 9.1 General scheme for the homogeneous hydrogenation of olefins.

In principle, the mechanism of homogeneous hydrogenation, in the chiral as well as in the achiral case, can follow two pathways (Figure 9.5). These involve either dihydrogen addition, followed by olefin association ( hydride route , as described in detail for Wilkinson s catalyst, vide supra) or initial association of the olefin to the rhodium center, which is then followed by dihydrogen addition ( unsaturate route ). As a rule of thumb, the hydride route is typical for neutral, Wilkinson-type catalysts whereas the catalytic mechanism for cationic complexes containing diphosphine chelate ligands seems to be dominated by the unsaturate route [1]. 

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