Ruthenium oxygen containing

The increased stability of ruthenium carbene complexes towards oxygen-containing compounds might be because later transition metals, having more d-electrons, are softer and hence react better with soft bases, e.g. olefins. The early transition metals, on the other hand, having few d-electrons, are generally harder and react preferentially with hard bases, such as water or carbonyl compounds. 

An initial addition of a ruthenium-oxygen double bond to a a-C—H bond leads to an intermediate containing a carbon-ruthenium bond. This bond suffers a homolytic scission leading to a carbon radical, which is oxidized to a carbocation that provides a carbonyl group by deprotonation. 

Ruthenium-Catalysed Oxidation of Oxygen-Containing Compounds.297... 

Oxygen-containing Cl and C2 molecules can be efficiently synthesized from CO and H2 (syngas) using cobalt, rhodium, and ruthenium catalysts. Among these catalysts, ruthenium is very efficient and selectively provides products with less than C2 units [8,9] this is in contrast to the Rh and Co catalysts, which produce byproducts with more than C3 units (Eq. 11.2). 

Recyclable imidazolium-tagged ruthenium catalysts 89 and 90 have been developed to perform olefin RCM and CM in ILs [bmimJpF ] and [bmim][Tf2N]. A high level of recyclability combined with a high reactivity were obtained in the RCM of various di- or tri-substituted and/or oxygen-containing dienes (Scheme 1.53). Extremely low residual ruthenium levels were detected in the RCM products (average of 7.3 ppm per run). ... 

The chloride-, bromide-, and thiocyanate complexes of ruthenium(IIl) and osmium(IV) can be extracted from acid solutions by oxygen-containing solvents, also in the presence of TBP or amines [10,12-15]. Osmium has been separated from Ru after conversion into Osle and extraction with TO A [16]. From mixtures of thiocyanate complexes of Ru and Os, only the Os complex can be extracted into diethyl ether containing a small amount of peroxide [14]. Poljmrethane foam has also been used for separating Ru and Os as their thiocyanate complexes [17,18]. 

In this section we will discuss the role of surface modification to enhance electrocatalytic oxidation of methanol, one of the interesting components for fuel cell technology. Perhaps the most successful promoter of methanol electrooxidation is ruthenium. Pt/Ru catalysts appear to exhibit classical bifunctional behavior, whereas the Pt atoms dissociate methanol and the ruthenium atoms adsorb oxygen-containing species. Both platinmn and ruthenimn atoms are necessary for eomplete oxidation to occur at a significant rate. The bifunctional mechanism can account for a decrease in poisoning from methanol, as observed for Pt/Ru alloys. Indeed, CO oxidation has been attributed to a bifimctional mechanism that reduces the overpotential of this reaction by 0.1 V on the Pt/Ru surface. 

The general formula RuSe describes rathenium particles that are modified by a small amount of selenium the optimum activity is achieved for x 0.1. As obtained from anomalous small angle X-ray scattering (ASAXS) measurements, ruthenium forms almost spherical nanoparticles from which the selenium content is deposited onto the surface. The typical size of the rathenium particles is around 2.5 mn selenium forms small clusters on the surface with a diameter <0.6 nm. A mixing of the two components has not been observed. From extended X-ray absorption fine structure (EXAFS) analysis an oxygen-free selenium structure and oxygen-containing species on the uncovered rathenium surface... 

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