Ruthenium oxides

L. Ruthenia, Russia) Berzelius and Osann in 1827 examined the residues left after dissolving crude platinum from the Ural mountains in aqua regia. While Berzelius found no unusual metals, Osann thought he found three new metals, one of which he named ruthenium. In 1844 Klaus, generally recognized as the discoverer, showed that Osann s ruthenium oxide was very impure and that it contained a new metal. Klaus obtained 6 g of ruthenium from the portion of crude platinum that is insoluble in aqua regia. 

Ion implantation has also been used for the creation of novel catalyticaHy active materials. Ruthenium oxide is used as an electrode for chlorine production because of its superior corrosion resistance. Platinum was implanted in mthenium oxide and the performance of the catalyst tested with respect to the oxidation of formic acid and methanol (fuel ceU reactions) (131). The implantation of platinum produced of which a catalyticaHy active electrode, the performance of which is superior to both pure and smooth platinum. It also has good long-term stabiHty. The most interesting finding, however, is the complete inactivity of the electrode for the methanol oxidation. 

Carbon nanotubes mixed with ruthenium oxide powder, and immersed in a liquid electrolyte, have been shown by a Chinese research group to function as supercapacilors with much larger capacitance per unit volume than is normally accessible (Ma et al. 2000). 

Hydrogenation of 19-nor-A -3-keto steroids also gives 5a- and 5 -product mixtures under the usual conditions but with ruthenium oxide at high pressures only the 5j8-isomer is formed.The presence of a 4-methyl group on a A -3-keto steroid increases the amount of a attack as compared to the parent enone. ... 

A solution of 20 g of estradiol in 500 ml of ethanol containing 1 ml of 40 % sodium hydroxide is hydrogenated over 5 g of ruthenium oxide or 3-5 g of 5% ruthenium-on-charcoal at 65° and 1500 psi. After filtration and evaporation, the residue is recrystallized to give 80% of 5a, 10a-estrane-3j9, 17 -diol. °... 

Ruthenium-ozyd, n. (any) ruthenium oxide, esp. the sesquioxide, ruthenium(III) oxide, -oxydul, n. ruthenium monoxide, ruthenium-(II) oxide, -saure, /. ruthenic acid, -ver-bindung, /. ruthenium compound. 

The extent of coupling is also influenced by the solvent. In the hydrogenation of aniline over ruthenium oxide, coupling decreased with solvent in the order methanol > ethanol > isopropanol > t-butanol. The rate was also lower in the lower alcohols, probably owing to the inhibiting effect of greater concentrations of ammonia (44). Carboxylic acid solvents increase the amount of coupling (42). 

High-valent ruthenium oxides (e. g., Ru04) are powerful oxidants and react readily with olefins, mostly resulting in cleavage of the double bond [132]. If reactions are performed with very short reaction times (0.5 min.) at 0 °C it is possible to control the reactivity better and thereby to obtain ds-diols. On the other hand, the use of less reactive, low-valent ruthenium complexes in combination with various terminal oxidants for the preparation of epoxides from simple olefins has been described [133]. In the more successful earlier cases, ruthenium porphyrins were used as catalysts, especially in combination with N-oxides as terminal oxidants [134, 135, 136]. Two examples are shown in Scheme 6.20, terminal olefins being oxidized in the presence of catalytic amounts of Ru-porphyrins 25 and 26 with the sterically hindered 2,6-dichloropyridine N-oxide (2,6-DCPNO) as oxidant. The use... 

Tungsten halides, 3, 974, 984, 988 synthesis, 3,974 Tungsten hexaalkoxides physical properties, 2,347 Tungsten oxide ruthenium oxide support... 

Recently, we have shown that the combination of barium tetratitanate, BaTi40g and sodium hexatitanate, NagTigOis, with ruthenium oxides leads to active photocatalysts for water decomposition[1,2]. The unique feature of these photocatalysts is that no reduction of the titanates is required to be activated this is intrinsically different from conventional photocatalysts using TIO2 which are often heat-treated in a reducing atmosphere. Such different photocatalytic characteristics suggest that efficiency for the separation of photoexcited charges (a pair of electrons and holes) which is the most important step in photocatalysis is... 

Because of the considerable corrosivity of chlorine toward most metals, anodic chlorine evolution can only be realized for a few electrode materials. In industry, graphite had been used primarily for this purposes in the past. Some oxide materials, manganese dioxide for instance, are stable as well. At present the titanium-ruthenium oxide anodes (DSA see Chapter 28) are commonly used. 

Detailed studies have been performed on pseudocapacitors with layers of hydrated ruthenium oxide, RuOj- HjO. Protons relatively readily undergo intercalation and deintercalation in this material ... 

The total capacity of a ruthenium oxide electrode [the usual double-layer capacity plus the pseudocapacity of reaction (21.4)] is rather high (i.e., several hundred F/g), even more than at the electrodes of carbon double-layer capacitors. The maximum working voltage of ruthenium oxide pseudocapacitors is about 1.4 V. 

A wider application of ruthenium oxide capacitors is hindered by the high cost of ruthenium oxide. Attempts have been reported, therefore, to substitute ruthenium oxide with other, cheaper materials capable of intercalation and deintercalation of hydrogen and/or other ions. Promising results with pseudocapacities of about 100 F/g have been obtained with the mixed oxides of ruthenium and vanadium and also with mixed oxides on the basis of manganese oxide. 

The layer of titanium and ruthenium oxides usually is applied to a titanium substrate pyrolytically, by thermal decomposition (at a temperature of about 450°C) of an aqueous or alcoholic solution of the chlorides or of complex compounds of titanium and rathenium. The optimum layer composition corresponds to 25 to 30 atom % of ruthenium. The layer contains some quantity of chlorine its composition can be written as Ruq 2sTio 750(2- c)Cl r At this deposition temperature and Ru-Ti ratio, the layer is a poorly ordered solid solution of the dioxides of ruthenium and titanium. Chlorine is completely eliminated from the layer when this is formed at higher temperatures (up to 800°C), and the solid solution decomposes into two independent phases of titanium dioxide and ruthenium dioxide no longer exhibiting the unique catalytic properties. 

Sugimoto W, Saida T, Takasu Y. 2006. Co-catalytic effect of nanostructured ruthenium oxide towards electro-oxidation of methanol and carbon monoxide. Electrochem Commun 8 411-415. 

Oxidation States of Ruthenium Oxide and Ru-Based Electrodes. 95... 

For Cl2 or 02 evolution the stability of ruthenium based electrodes is not sufficient on a technical scale. Therefore the possibility of stabilizing the ruthenium oxide without losing too much of its outstanding catalytic performance was investigated by many groups. For the Cl2 process, mixed oxides with valve metals like Ti or Ta were found to exhibit enhanced stability (see Section 3.1), while in the case of the 02 evolution process in solid polymer electrolyte cells for H2 production a mixed Ru/Ir oxide proved to be the best candidate [68, 80]. 

Rare, shiny, and lightest metal of the platinum group. Hardens platinum and palladium. The presence of 0.1 % of ruthenium in titanium improves its resistance to corrosion 100-fold. The spectacular catalytic properties of ruthenium are used on industrial scales (hydrogenations, sometimes enan-tioselective, and metathesis). Titanium electrodes coated with ruthenium oxide are applied in chlorine-alkaline electrolysis. Suitable for corrosion-resistant contacts and surgical instruments. 

Long JW, Swider KE, Merzbacher Cl, Rolison DR. Voltammetric characterization of ruthenium oxide-based aerogels and other Ru02 solids The nature of capacitance in nanostructured materials. Langmuir 1999 15(3) 780-5. 

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