Ruthenium homogeneous catalysis

In this paper we disclose the syngas homologation of carboxylic acids via ruthenium homogeneous catalysis. This novel homologation reaction involves treatment of lower MW carboxylic acids with synthesis gas (C0/H2) in the presence of soluble ruthenium species, e.g., Ru02, Ru3(C0)12, H4Ru4(C0)12, coupled with iodide-containing promoters such as HI or an alkyl iodide (1). 

Catalytic hydrogenation of tnfluoroacetic acid gives tnfluoroethanol in high yield [73], but higherperfluorocarboxybc acids and their anhydndes are reduced much more slowly over rhodium, iridium, platinum, or ruthenium catalysts [7J 74] (equation 61) Homogeneous catalysis efficiently produces tnfluoroethanol from tnfluoroacetate esters [75] (equation 61)... 

J. Halpem Developments in homogeneous catalysis [using ruthenium complexes], pp. 146-162 (65). 

Cabeza, J.A., in Braunstein, P., Oro, L.A., Raithby, P.R. (Eds.), Homogeneous Catalysis with Ruthenium Carbonyl Cluster Complexes Metal Clusters in Chemistry, Vol. 2. Wiley-VCH GmbH, Weinheim,... 

Several copper, silver, ruthenium, rhodium, and cobalt compounds (e.g., Ru-Cl3 aq, [RuC h(l)ipy) (bipy=2,2 -bipyridine), RhCl3 aq, fotx(dimelbylglyoxima-to)cobalt derivatives (cobaloximes), etc.) have been found to catalyze hydrogenations in aqueous solutions [9]. Although important for the early research into homogeneous catalysis, these catalysts did not gain synthetic significance. 

The cost of the catalysts represents a major hurdle on the road to the industrial application of homogeneous catalysis, and in particular for the production of fine chemicals [1, 2], This is particularly true for chiral catalysts that are based on expensive metals, such as rhodium, iridium, ruthenium and palladium, and on chiral ligands that are prepared by lengthy total syntheses, which often makes them more expensive than the metals. In spite of this, the number of large-scale applications for these catalysts is growing. Clearly, these can only be economic if the substrate catalyst ratio (SCR) can be very high, often between 103 and 105. 

Promising applications for metal-NHC compounds in materials science and medicinal chemistry are based on the strong metal-carbon bond and the high donor capability of the NHC. The most extensive investigations have been carried out in the field of homogeneous catalysis. Here, NHCs have to be considered as typical directing or innocent spectator ligands, best comparable to trialkylphosphines. The recent successful applications of NHCs in ruthenium-catalyzed olefin metathesis... 

In the methanol synthesis, a fast hydrogenation of the adsorbed formaldehyde would overcome arguments invoking any thermodynamic limitation to its formation. Formaldehyde adsorbed through both the oxygen and the carbon ends has been characterized in homogeneous catalysis (43), on oxide surfaces (44) and more recently on ruthenium metal (45). 

Hydrogen addition to multiple bonds is catalyzed by certain complex metal salts in solution. This may be described as homogeneous catalysis and, compared to heterogeneous catalysis, is a relatively new development in the area of hydrogenation reactions. Rhodium and ruthenium salts appear to be generally useful catalysts ... 

Heterometal alkoxide precursors, for ceramics, 12, 60-61 Heterometal chalcogenides, synthesis, 12, 62 Heterometal cubanes, as metal-organic precursor, 12, 39 Heterometallic alkenes, with platinum, 8, 639 Heterometallic alkynes, with platinum, models, 8, 650 Heterometallic clusters as heterogeneous catalyst precursors, 12, 767 in homogeneous catalysis, 12, 761 with Ni—M and Ni-C cr-bonded complexes, 8, 115 Heterometallic complexes with arene chromium carbonyls, 5, 259 bridged chromium isonitriles, 5, 274 with cyclopentadienyl hydride niobium moieties, 5, 72 with ruthenium—osmium, overview, 6, 1045—1116 with tungsten carbonyls, 5, 702 Heterometallic dimers, palladium complexes, 8, 210 Heterometallic iron-containing compounds cluster compounds, 6, 331 dinuclear compounds, 6, 319 overview, 6, 319-352... 

Keywords Homogeneous catalysis Ruthenium complexes Organosilicon compounds Organic synthesis... 

Carbohydrate oxidations are generally performed with dioxygen in the presence of heterogeneous catalysts, such as Pd/C or Pt/C [230]. An example of homogeneous catalysis is the ruthenium-catalyzed oxidative cleavage of protected mannitol with hypochlorite (Fig. 4.77) [231]. 

We have already alluded to the diversity of oxidation states, the dominance of oxo chemistry and the cluster carbonyls. Brief mention should be made too of the tendency of osmium (shared also by ruthenium and, to some extent, rhodium and iridium) to form polymeric species, often with oxo, nitrido or carboxylato bridges. Although it does have some activity in homogeneous catalysis (e.g. of m-hydroxylation, hydroxyamination or animation of alkenes, see p. 558, and occasionally for isomerization or hydrogenation of alkenes, see p. 571), osmium complexes are perhaps too substitution-inert for homogeneous catalysis to become a major feature of the chemistry of the element. The spectroscopic properties of some of the substituted heterocyclic nitrogen-donor complexes may yet make osmium an important element for photodissociation energy research. 

It is mostly complexes of ruthenium and rhodium that have been used to conduct hydrogenation reactions in ionic liquids and little attention has so far been paid to modifying the employed catalysts to improve their performance in the ionic environment. The majority of the catalysts used are identical to those employed in conventional homogeneous catalysis conducted in molecular solvents like, for example, RhCl(PPh3)3 and RuCl2(PPh3)3. 

G Braca, C. Sbrana, G. Valentmi, C- Andrich and G. Gregorio Carbonytation and Homologation of Methanol, Methyl Ethers and Esters in the presence of Ruthenium Catalysis (Fundamental Research in Homogeneous Catalysis v. 3. ed.. M. Tsutsui), pp. 221 238. Plenum Prevs (1979). 

Homogeneous Catalysis P-donor Ligands Palladium Organometallic Chemistry Rhodium Organometallic Chemistry Ruthenium Organometallic Chemistry. 

Asymmetric Synthesis by Homogeneous Catalysis Coordination Chemistry History Coordination Organometallic Chemistry Principles Dihydrogen Complexes Related Sigma Complexes Electron Transfer in Coordination Compounds Electron Transfer Reactions Theory Heterogeneous Catalysis by Metals Hydride Complexes of the Transition Metals Euminescence Luminescence Behavior Photochemistry of Organotransition Metal Compounds Photochemistry of Transition Metal Complexes Ruthenium Organometallic Chemistry. 

Metal complex chemistry, homogeneous catalysis and phosphane chemistry have always been strongly connected, since phosphanes constitute one of the most important families of ligands. The catalytic addition of P(III)-H or P(IV)-H to unsaturated compounds (alkene, alkyne) offers an access to new phosphines with a good control of the regio- and stereoselectivity [98]. Hydrophosphination of terminal nonfunctional alkynes has already been reported with lanthanides [99, 100], or palladium and nickel catalysts [101]. Ruthenium catalysts have made possible the hydrophosphination of functional alkynes, thereby opening the way to the direct synthesis of bidentate ligands (Scheme 8.35) [102]. 

Homogeneous catalysis by some 7 ruthenium and rhodium com- (8) plexes... 

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