Ruthenium Ru catalyst

Hydrogenation of olefinic unsaturation using ruthenium (Ru) catalyst is well known. It has been widely used for NBR hydrogenation. Various complexes of Ru has been developed as a practical alternative of Rh complexes since the cost of Ru is one-thirtieth of Rh. However, they are slightly inferior in activity and selectivity when compared with Rh catalyst. 

Tested platinum (Pt), palladium (Pd), and ruthenium (Ru) catalysts Initial rate measurements made for hexadecane and diesel fuel... 

In spite of its versatility, metathesis could not, until lately, be developed to its full synthetic potential because the traditional catalysts were ill-suited for application being relatively short-hved and susceptible to air, moisture, or side reactions. Schrock was the first to develop an entire family of tungsten-alkylidene and, more importantly, molybdenum-alkylidene complexes with very high activity and selectivity in olefin metathesis. Further on, Grubbs discovered ruthenium (Ru) catalysts which up to now are among the most tolerant of functional groups initiators. ... 

New molybdenum and ruthenium (Ru) catalysts 1-5 (Figure 2), which combine high catalytic activity with fairly good stability, however, have revolutionized the field. As a result, recent decades have seen a burgeoning of interest in the olefin metathesis, as witnessed by a rapidly growing number of elegant applications. Using this tool, chemists can now efficiently... 

This reaction is performed industrially using the Haber Bosch process over iron (Fe) or ruthenium (Ru) catalysts at high temperatures (>400 °C) and high pressures (>100 bar). Using state-of-the-art surface science and theoretical techniques, the detailed reaction mechanism has been elucidated and a complete potential energy surface (PES) on terrace and step sites of Ru is shown in Figure 1.10. 

The goal of Haber s research was to find a catalyst to synthesize ammonia at a reasonable rate without going to very high temperatures. These days two different catalysts are used. One consists of a mixture of iron, potassium oxide. K20, and aluminum oxide. Al203. The other, which uses finely divided ruthenium, Ru. metal on a graphite surface, is less susceptible to poisoning by impurities. Reaction takes place at 450°C and a pressure of 200 to 600 atm. The ammonia... 

Since ruthenium and rhodium are neighboring elements in the periodic table, a closer comparison of the properties of ruthenium-copper and rhodium-copper clusters is of interest (17). When we compare EXAFS results on rhodium-copper and ruthenium-copper catalysts in which the Cu/Rh and Cu/Ru atomic ratios are both equal to one, we find some differences which can be related to the differences in miscibility of copper with ruthenium and rhodium. The extent of concentration of copper at the surface appears to be lower for the rhodium-copper clusters than for the ruthenium-copper clusters, as evidenced by the fact that rhodium exhibits a greater tendency than ruthenium to be coordinated to copper atoms in such clusters. The rhodium-copper clusters presumably contain some of the copper atoms in the interior of the clusters. 

Despite the numerous reports concerning NHC-Ru olefin metathesis initiators, a complex incorporating a carbene that has only one exocyclic substituent adjacent to the carbenic centre was not reported until 2008. Studies by Grubbs and co-workers led to the development of ruthenium-based catalysts bearing such carbene ligands, in this case incorporating thiazole-2-ylidenes [63] (Fig. 3.19). 

Supported (alumina, silica) Ru catalysts The Mossbauer data show that RuCl3 (l-3)H20 reacts chemically when supported onto alumina, but does not when impregnated on a silica support. The study further shows that a supported ruthenium catalyst converts quantitatively into RUO2 upon calcination, and that the reduction of a supported ruthenium catalyst converts all of the ruthenium into the metallic state... 

The feasibility of carbon-supported nickel-based catalysts as the alternative to the platinum catalyst is studied in this chapter. Carbon-supported nickel (Ni/C, 10 wt-metal% [12]), ruthenium (Ru/C, 10 wt-metal% [12]), and nickel-ruthenium composite (Ni-Ru/C, 10 wt-metal%, mixed molar ratio of Ni/Ru 0.25,1,4, 8, and 16 [12]) catalysts were prepared similarly by the impregnation method. Granular powders of the activated carbon without the base pretreatment were stirred with the NiCl2, RuC13, and NiCl2-RuCl3 aqueous solutions at room temperature for 24 h, respectively. Reduction and washing were carried out in the same way as done for the Pt/C catalyst. Finally, these nickel-based catalysts were evacuated at 70°C for 10 h. 

Cationic ruthenium complexes of the type [Cp Ru(MeCN)3]PF6 have been shown to provide unique selectivities for inter- and intramolecular reactions that are difficult to reconcile with previously proposed mechanistic routes.29-31 These observations led to a computational study and a new mechanistic proposal based on concerted oxidative addition and alkyne insertion to a stable ruthenacyclopropene intermediate.32 This proposal seems to best explain the unique selectivities. A similar mechanism in the context of C-H activation has recently been proposed from a computational study of a related ruthenium(ll) catalyst.33... 

The Elsevier system has since been shown to carry out several ester hydrogenations that were previously deemed impossible [114]. The hydrogenation of dimethyl phfhalate to phfhalide with ruthenium cluster catalysts has already been discussed (Table 15.15, Entry 4). The application of [Ru(acac)3] and triphos -this time with a 20-fold excess of Et3N as additive - delivers good yields of phthalide. However, the use of isopropanol (I PA) as solvent and 24% HBF4 allows further hydrogenation to 1,2,-bis-hydroxylmethyl benzene for the first time. Both of these reactions were carried out under milder conditions (100°C, 85 bar H2, 16 h) than those reported previously. 

Ruthenium (Ru), rhodium (Rh), and cobalt (Co) form the most active and versatile catalysts, with a prevalence for Ru effective catalysts have been reported also for other metals such as Ni, Pd, Pt, Cr, W, Mo, Mn, Nb, and Ta, some of which, however, are selective for the partial reduction of polynuclear aromatics. 

A range of other terminal alkenes has been hydrogenated with ruthenium-diphosphine catalysts. The first set of substrates (Fig. 30.7 Table 30.5) was hydrogenated with Ru-BINAP in dichloromethane (DCM) at 30°C. Products of double bond migration were also detected [5]. 

The asymmetric synthesis of allenes via enantioselective hydrogenation of ketones with ruthenium(II) catalyst was reported by Malacria and co-workers (Scheme 4.11) [15, 16]. The ketone 46 was hydrogenated in the presence of iPrOH, KOH and 5 mol% of a chiral ruthenium catalyst, prepared from [(p-cymene) RuC12]2 and (S,S)-TsDPEN (2 equiv./Ru), to afford 47 in 75% yield with 95% ee. The alcohol 47 was converted into the corresponding chiral allene 48 (>95% ee) by the reaction of the corresponding mesylate with MeCu(CN)MgBr. A phosphine oxide derivative of the allenediyne 48 was proved to be a substrate for a cobalt-mediated [2 + 2+ 2] cycloaddition. 

Ruthenium/carbon catalysts have also been promoted by the addition of Fe. Bron et al. reported the addition of Fe to a preformed Ru/C catalyst via adsorption of Fe complexes, followed by heat treatment. They found an increase in oxygen reduction activity of three to five times over unmodified Ru/C. It was suggested that the surfaces of Ru particles were covered with FeN,Cy sites. As discussed previously, the Pd alloys have shown significant MeOH tolerance toward oxygen reduction and appear to have activities closest to that of Ft. 

For a review of asymmetric Mo-catalyzed metathesis, see Catalytic Asymmetric Olefin Metathesis, A. H. Hoveyda, R. R. ScHROCK, Chem. Eur. J. 2001, 7, 945-950 for reports on chiral Ru-based complexes, see (b) Enantioselective Ruthenium-Catalyzed Ring-Qosing Metathesis, T.J. Sei-DERS, D.W. Ward, R.H. Grubbs, Org. Lett. 2001, 3, 3225-3228 (c) A Recyclable Chiral Ru Catalyst for Enantioselective Olefin Metathesis. Efficient Catalytic Asymmetric Ring-Opening/Cross Metathesis In Air, J. J. Van Veldhuizen, S. B. 

Alumina-supported Ru catalysts derived from supported ruthenium carbonyls have been reported to be effective for carbon dioxide methanation, showing higher activity than other catalysts prepared from RUCI3. The catalytic activity depended on the nuclearity of the carbonyl precursor [111]. 

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