Metals ruthenium

At one stage in our project we were surprised to learn that some workers had found difficulties in preparing the tetroxide from the dioxide, until we experienced the same trouble. This problem has now been resolved (3). Ruthenium dioxide is available commercially in both anhydrous and hydrated forms, the former being obtained by direct oxidation of ruthenium metal and the latter by a precipitation process. Only the hydrated form is oxidizable under the mild conditions (2,3) that we use and this form must be specified when purchasing the dioxide. It is noteworthy that the dioxide recovered from carbohydrate oxidations is always easily re-oxidized to the tetroxide. The stoichiometry has been determined of both the oxidation of the dioxide by periodate and reduction of the tetroxide which results on oxidation of an alcohol. 

Keywords Metathesis Alkenes Catalysis Ruthenium Metal carbene complexes... 

One other study of group 14 heteroallenes involving transition metals was reported in 1995. Jones et al. described the isolation of a ruthenium complex of a 1-silaallene (132—Scheme 32). The 1-silaallene also interacts with a hydrogen atom as well as the ruthenium metal center. Jones et al. describe this view... 

The precursor of ° Ru is ° Rh (tip, = 3 years). It is prepared by irradiating natural ruthenium metal with 20 MeV deuterons, " Ru (d, n) Rh. The target is then allowed to decay for several months to diminish the accompanying Rh activity. In a report on ° Ru Mossbauer spectroscopy [111], the authors reported on spectra of Ru metal, RuOa, and [Ru(NH3)4(HS03)2] at liquid helium temperature in standard transmission geometry using a Ge(Li) diode to detect the 127 keV y-rays. The absorber samples contained 1 g of ruthenium per cm. ... 

Since Chatt and Davidson13 observed the first clear example of simple oxidative addition of a C—H bond of naphthalene to a ruthenium metal center, Ru(dmpe)2 (dmpe = Me2PCH2CH2PMe2), hydrocarbon activation has been the subject of many transition metal studies.11 c Sometimes, the efforts in this field have ended in findings different from the initial objectives, which have been the starting point for the development of novel organometallic chemistry. 

Nakabayashi, M., M. Yamashita, and Y. Saito, Preparation of size-controlled ruthenium metal particles on carbon from hydro-carbonyl cluster complex. Chem. Lett., 1275-1278 (1994). 

Iglesia, E., Soled, S.L., and Fiato, R.A. 1992. Fischer-Tropsch synthesis on cobalt and ruthenium. Metal dispersion and support effects on reaction rate and selectivity. J. Catal. 137 212-24. 

No evidence of ruthenium metal formation was found in catalytic reactions until temperatures above about 265°C (at 340 atm) were reached. The presence of Ru metal in such runs could be easily characterized by its visual appearance on glass liners and by the formation of hydrocarbon products (J/1J) The actual catalyst involved in methyl and glycol acetate formation is therefore almost certainly a soluble ruthenium species. In addition, the observation of predominantly a mononuclear complex under reaction conditions in combination with a first-order reaction rate dependence on ruthenium concentration (e.g., see reactions 1 and 3 in Table I) strongly suggests that the catalytically active species is mononuclear. 

Ruthenium - the atomic number is 44 and the chemcial symbol is Ru. The name derives from the Latin ruthenia for the old name of Russia . It was discovered in a crude platinum ore by the Russian chemist Gottfried Wilhelm Osann in 1828. Osann thought that he had found three new metals in the sample, pluranium, ruthenium and polinium.He later withdrew his claim of discovery. In 1844 the Russian chemist Karl Karlovich Klaus was able to show that Osann s mistake was due to the impurity of the sample but Klaus was able to isolate the ruthenium metal and he retained Osann s original name of ruthenium. 

Subsequent thermal decomposition under vacuum or an inert atmosphere gives complex surface reactions and Ru(II) dicarbonyl species and ruthenium metal particles sized 1-1.5 nm form [92]. 

The reaction of 25 with Ic gives lactone 26, but the yield is only 40%. It was thought that the carbonyl oxygen should coordinate to the ruthenium metal to give... 

In traditional synthetic organic chemistry, the Wittig reaction plays an important role in carbon-carbon bond extension from the carbonyl group. CM is an attractive alternative for carbon-carbon extension from a terminal alkene. In fact, a pyrroh-dine ring of anthramycin derivative 55 has been constructed by RCM of 52, and the sidechain has been extended by CM of terminal alkene of 54 with ethyl acrylate. " In the CM, ruthenium carbene complex Ij, reported by Blechert, gives a good result since the ligand of the catalyst easily dissociated from the ruthenium metal at room temperature ... 

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). 

Dixneuf used [RuCl2(/>-cymene)]2 as a catalyst for the reaction of enyne 72a in the presence of imidazolium salt and CS2CO3 and obtained the enyne metathesis product 73a in a high yield. The enyne silyl ether 72b is converted under similar reaction conditions into r/i7ra-compound 73b which after the Tamao oxidation gives diol 74 (Scheme 28). In this reaction, V-heterocyclic carbene should be generated to coordinate to the ruthenium metal, but the actual species for this reaction is not well documented. 

Solutions of ruthenium carbonyl complexes in acetic acid solvent under 340 atm of 1 1 H2/CO are stable at temperatures up to about 265°C (166). Reactions at higher temperatures can lead to the precipitation of ruthenium metal and the formation of hydrocarbon products. Bradley has found that soluble ruthenium carbonyl complexes are unstable toward metallization at 271°C under 272 atm of 3 2 H2/CO [109 atm CO partial pressure (165)]. Solutions under these conditions form both methanol and alkanes, products of homogeneous and heterogeneous catalysis, respectively. Reactions followed with time exhibited an increasing rate of alkane formation corresponding to the decreasing concentration of soluble ruthenium and methanol formation rate. Nevertheless, solutions at temperatures as high as 290°C appear to be stable under 1300 atm of 3 2 H2/CO. 

Methane is the principal gas found with coal and oil deposits and is a major fuel and chemical used is the petrochemical industry. Slightly less than 20% of the worlds energy needs are supplied by natural gas. The United States get about 30% of its energy needs from natural gas. Methane can be synthesized industrially through several processes such as the Sabatier method, Fischer Tropsch process, and steam reforming. The Sabatier process, named for Frenchman Paul Sabatier (1854—1941), the 1912 Nobel Prize winner in chemistry from France, involves the reaction of carbon dioxide and hydrogen with a nickel or ruthenium metal catalyst C02 + 4H2 —> CH4 + 2H20. 

Ruthenium and osmium carbene complexes possess metal centers that are formally in the +2 oxidation state, have an electron count of 16 and are penta-coordinated. Ruthenium complexes exhibit a higher catalytic activity when an imidazole carbene ligand is coordinated to the ruthenium metal center (21). 

Scheme 20 A Ruthenium Metal Complex and the 17-Residue Peptides Which it Stabilizes 1771...

Chloro complexes of ruthenium(II) were found to hydrogenate maleic and fumaric adds to succinic add slowly at 60-80 °C and normal pressure of hydrogen. Non-activated alkenes lead to the production of ruthenium metal. The structures of the species involved are unknown. The mechanism involves coordination of the alkene followed by heterolytic cleavage of hydrogen, giving a ruthenium(II) hydride as the second step.41... 

A mixture of 14.6 g. (0.07 mole) of ruthenium trichloride and 2.4 g. (0.024 g. atom) of ruthenium metal (Note 4) is added, and the reaction mixture is heated and stirred under nitrogen for 80... 

Formation of the adduct chlorine trifluoride—ruthenium pentafluoride by reaction with ruthenium metal at ambient temperature is extremely violent. 

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