Ruthenium, catalyst

As catalysts, ruthenium- or molybdenum-alkylidene complexes are often employed, e.g. commercially available compounds of type 7. Various catalysts have been developed for special applications. " ... 

More synthetic interest is generated by the potentially very useful hydration of dienes. As shown on Scheme 9.6, methylethylketone (MEK) can be produced from the relatively cheap and easily available 1,3-butadiene with combined catalysis by an acid and a transition metal catalyst. Ruthenium complexes of several N-N chelating Hgands (mostly of the phenanthroline and bipyridine type) were found active for this transformation in the presence of Bronsted acids with weakly coordinating anions, typically p-toluenesulfonic acid, TsOH [18,19]. In favourable cases 90 % yield of MEK, based on butadiene, could be obtained. 

Asymmetric Olefin Metathesis Using Ruthenium Catalysts Ruthenium catalysts for asymmetric synthesis have also been developed (Figure 6.3). 

Catalyst deactivation during consecutive lactose and xylose hydrogenation batches over Mo promoted sponge nickel (Activated Metals) and Ru(5%)/C (Johnson Matthey) catalysts were studied. Deactivation over sponge nickel occurred faster than on Ru/C in both cases. Product selectivities were high (between 97 and 100%) over both catalysts. However, related to the amount of active metal on the catalyst, ruthenium had a substantially higher catalytic activity compared to nickel. 

Isoalkanes can also be synthesized by using two-component catalyst systems composed of a Fischer-Tropsch catalyst and an acidic catalyst. Ruthenium-exchanged alkali zeolites288 289 and a hybrid catalyst290 (a mixture of RuNaY zeolite and sulfated zirconia) allow enhanced isoalkane production. On the latter catalyst 91% isobutane in the C4 fraction and 83% isopentane in the C5 fraction were produced. The shift of selectivity toward the formation of isoalkanes is attributed to the secondary, acid-catalyzed transformations on the acidic catalyst component of primary olefinic (Fischer-Tropsch) products. 

Ring-closing metathesis is well suited for the preparation of five- or six-membered heterocycles, and has also been successfully used to prepare tetrahydropyridines on insoluble supports (Entries 1 and 2, Table 15.23). Because metathesis catalysts (ruthenium or molybdenum carbene complexes) are electrophilic, reactions should be conducted with acylated amines to avoid poisoning of the catalyst. 

A model manure solution was prepared based on 10% glucose (as a carbohydrate hydrolysate model) with the various mineral components. The model solution was processed with three different catalyst formulations for comparison. The two nickel catalysts, ruthenium stabilized and copper stabilized (4), exhibited no effects from the contaminants, while the ruthenium showed reduced activity similar to that already noted. 

The hydroformylation of alkenes to give linear aldehydes constitutes the most important homogeneously catalyzed process in industry today [51]. The hydroformylation of propene is especially important for the production of n-bu-tyraldehyde, which is used as a starting material for the manufacture of butanol and 2-ethylhexanol. Catalysts based on cobalt and rhodium have been the most intensively studied for the hydroformylation of alkenes, because they are industrially important catalysts. While ruthenium complexes have also been reported to be active catalysts, ruthenium offers few advantages over cobalt or... 

Catalyst Ruthenium loading (wt.%) Average particle size (A) Turnover number (sec-1 x 103, 280"C)... 

Bis(ruthenium dichloride-S-BINAP)-triethylamine catalyst Ruthenium, bis[[1,1l-binaphthalene]-2,2 -diylbis[diphenylphosphine]-P,P ]di-p-chlorodichloro(N,N-diethylethanamine)di- (114717-51-0), 77, 3... 

Noble metal catalysts. Ruthenium and other noble metals are also active, and while the active alkylidene species remained for a long time elusive,... 

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