Olefin hydrogenation, catalytic

Hydroformylation. Probably the best known catalytic carbonylation reaction is the hydroformylation, or 0x0 reaction, for producing aldehydes and alcohols from carbon monoxide, hydrogen, and olefins (eq. 9) (36). 

The catalysts with the simplest compositions are pure metals, and the metals that have the simplest and most uniform surface stmctures are single crystals. Researchers have done many experiments with metal single crystals in ultrahigh vacuum chambers so that unimpeded beams of particles and radiation can be used to probe them. These surface science experiments have led to fundamental understanding of the stmctures of simple adsorbed species, such as CO, H, and small hydrocarbons, and the mechanisms of their reactions (42) they indicate that catalytic activity is often sensitive to small changes in surface stmcture. For example, paraffin hydrogenolysis reactions take place rapidly on steps and kinks of platinum surfaces but only very slowly on flat planes however, hydrogenation of olefins takes place at approximately the same rate on each kind of surface site. 

A very significant recent development in the field of catalytic hydrogenation has been the discovery that certain transition metal coordination complexes catalyze the hydrogenation of olefinic and acetylenic bonds in homogeneous solution.Of these catalysts tris-(triphenylphosphine)-chloror-hodium (131) has been studied most extensively.The mechanism of the deuteration of olefins with this catalyst is indicated by the following scheme (131 -> 135) ... 

Rennard and Kokes (39) in their paper stated directly that their purpose was just to study the catalytic activity of palladium hydride in the hydrogenation of olefins, in this case ethylene and propylene. Kokes (39a) in his article recently published in Catalysis Reviews summarizes the results of studies on such catalytic systems. 

Scheme 6 Proposed mechanism for catalytic hydrogenation of olefin with 5...

CeDs solution (Scheme 7). Both t -arene complexes were also determined by the X-ray diffraction and showed no reaction to hydrogen and olefins. Therefore, it was considered that the formation of the t -arene complexes was a deactivation pathway in the catalytic hydrogenation. 

Khan, M. M., Ph.D. dissertation, Effects of Solvent and Surface Structure on Catalytic Hydrogenation of Olefins, Southern Illinois University at Carbondale, 1982, pp. 30-31. 

RuCl(PPh3 )3(alkyl) (90). Because of the fact that the orthometallated complex reacts with H2 to re-form HRuCl(PPh3)2, catalytic hydrogenation of olefins can result via such pathways, although product formation via reaction (11) is kinetically preferred (88). 

If R and R1 are not a methyl group, the process generates a chiral carbon center (C ). The overall catalytic addition of hydrogen to olefinic bonds generally is nearly always cis (7, p. 407) and to the olefinic face coordinated to the metal. This cis-endo-addition produces a chiral center(s) when one olefinic face is preferentially coordinated. 

Experiments with trichlorosilane-d, Cl3SiD, were most instructive about side reactions that can take place in the hypothetical catalytic olefin PtH(—S ) species during hydrosilation. Although trichlorosilane-d and methyldichlorosilane showed no exchange of deuterium and hydrogen at 100°C during many hours in the absence of a catalyst, traces... 

Kaneda et al. reported substrate-specific hydrogenation of olefins using the tri-ethoxybenzamide-terminated polypropylene imine) dendrimers (PPI) as nanoreactors encapsulating Pd nanoparticles (mean diameter 2-3 nm) [59]. The catalytic tests were performed in toluene at 30 °C under dihydrogen at atmospheric pressure (Table 9.3). The hydrogenation rates were seen to decrease with increasing generation of dendrimers, from G3 to G5. 

Table 9.12 Catalytic hydrogenation of olefins with Pd nanoparticles in a water-in-hexane microemulsion. (Reprinted with the permission of the American Chemical Society [79])...

Asymmetric catalytic reduction reactions represent one of the most efficient and convenient methods to prepare a wide range of enantiomerically pure compounds (i.e. a-amino acids can be prepared from a-enamides, alcohols from ketones and amines from oximes or imines). The chirality transfer can be accomplished by different types of chiral catalysts metallic catalysts are very efficient for the hydrogenation of olefins, some ketones and oximes, while nonmetallic catalysts provide a complementary method for ketone and oxime hydrogenation. 

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. 

Hydrogen.—The olefines cannot be hydrogenated with nascent hydrogen from any of the usual reducing agents. The reduction only succeeds catalytically with hydrogen in the presence of finely divided metals, such as nickel (Sabatier), palladium (Paal, Skita), or platinum (Fokin, Willstatter). Cf. the preparations on pp. 376 ff. 

The Hartree-Fock method was in any case the method of choice for the first quantitative calculations related to homogeneous catalysis. It was the method, for instance, on a study of the bonding between manganese and hydride in Mn-H, published in 1973 [28]. The first studies on single steps of catalytic cycles in the early 1980 s used the HF method [29]. And it was also the method applied in the first calculation of a full catalytic cycle, which was the hydrogenation of olefins with the Wilkinson catalyst in 1987 [30]. The limitations of the method were nevertheless soon noticed, and already in the late 1980 s, the importance of electron correlation was being recognized [31]. These approaches will be discussed in detail in the next section. 

Thus the two plausible catalytic cycles have been considered, one via an Ir dihydride complex A and the other via an IrH2(ri -H2) complex B (Fig. 3). The first is analogous to the well-established mechanism for rhodium diphosphine-catalyzed hydrogenation of olefins going through Ir(I) and Ir(III) intermediates [26-29]. 

Even in an excess of ligands capable of stabilizing low oxidation state transition metal ions in aqueous systems, one may often observe the reduction of the central ion of a catalyst complex to the metallic state. In many cases this leads to a loss of catalytic activity, however, in certain systems an active and selective catalyst mixture is formed. Such is the case when a solution of RhCU in water methanol = 1 1 is refluxed in the presence of three equivalents of TPPTS. Evaporation to dryness gives a brown solid which is an active catalyst for the hydrogenation of a wide range of olefins in aqueous solution or in two-phase reaction systems. This solid contains a mixture of Rh(I)-phosphine complexes, TPPTS oxide and colloidal rhodium. Patin and co-workers developed a preparative scale method for biphasic hydrogenation of olefins [61], some of the substrates and products are shown on Scheme 3.3. The reaction is strongly influenced by steric effects. 

W(CH3CN)(C0)3(TPPMS)2] was obtained in the reaction of TPPMS and [W(CH3CN)3(C0)3], and was used as catalyst in hydrogenation of benzene in water/heptane biphasic systems [164]. At 100 °C and 70 bar H2 the catalytic activity was found rather low (average TOP 1 h ). The same complex is also active in the hydrogenation of olefins (e.g. 1-hexene, 2,3-dimethyl- 1 -butene). 

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