Ruthenium determination

Ross filter method, 108, 109 Rowland grating, concave, 121 Rubidium, determination by x-ray emission spectrography, 328 Ruthenium, determination by x-ray emission spectrography, 328... 

Instrumental Neutron Activation Analysis (INAA) was applied to the determination of the platinum metals as part of a study of their uptake, accumulation and toxicity in plants. Long irradiations are described for iridium, osmium and ruthenium determinations in specially grown plant materials. An interference in the determination of platinum in plant matrices by this method is reported also. Short irradiations, utilising thermal and epithermal fluxes are investigated for rhodium and palladium determinations, with further studies using cyclic activation analysis. 

Selenium, bis(diethyldithiocarbamato)-stereochemistry, 60 Selenium, bis(dithiofurancarbamato)-stereochemistry, 60 Selenium(II) complexes bis(dithiochelate), 60 Selenocyanate complexes linkage isomers, 186 Selenonium ions, trifluoro-stereochemistry, 37 Self-exchange reactions, 333 electron transfer rate constants, 347-353, 366 rate constants calculation, 348 rate constants, 362 Semicarbazide, 1,4-diphenylthio-ruthenium determination, 546 Semi-glycinecresol red metallochromic indicator, 557 Semi-xylenol orange metallochromic indicator, 557 Seven-coordinate compounds stereochemistry, 69-83 Sidgwick, Nevil Vincent, 16 Silicon, tris(acetylacetone)-configuration, 195... 

Radioruthenium enters plants because of direct contamination however, it is usually concentrated in certain water plants, so that its determination is significant, particularly in regions where radioactive waste materials are stored in the sea. Ruthenium determination can be carried out by a simple and direct y-ray spectrometric method. When it satisfies the other conditions, this procedure is rapid and economical. It is difficult to distinguish ° Ru and ° "Ru because of their closely spaced y-lines. 

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. 

A considerable number of EDTA complexes of ruthenium have been synthesized [130-132] there has been interest in their catalytic potential while several compounds have had their structures determined. Synthetic routes relating to these compounds are shown in Figure 1.50. 

The mechanistic investigations presented in this section have stimulated research directed to the development of advanced ruthenium precatalysts for olefin metathesis. It was pointed out by Grubbs et al. that the utility of a catalyst is determined by the ratio of catalysis to the rate of decomposition [31]. The decomposition of ruthenium methylidene complexes, which attribute to approximately 95% of the turnover, proceeds monomolecularly, which explains the commonly observed problem that slowly reacting substrates require high catalyst loadings [31]. This problem has been addressed by the development of a novel class of ruthenium precatalysts, the so-called second-generation catalysts. 

In summary, the order of reactivity for the most commonly used ruthenium-based metathesis catalysts was found to be 56d>56c>9=7. This order of reactivity is based on IR thermography [39], determination of relative rate constants for the test reaction 58—>59 (Eq. 8) [40], and determination of turnover numbers for the self metathesis of methyl-10-undecenoate [43]. 

The palladium and platinum metals also form carbonyl compounds. Of the expected compounds Pd(CO)4, Pt(CO)4, Ru(CO)5, Os (CO) 5, Mo-(CO)e, and W(CO)6 only Mo(CO)e has been prepared, although some unsaturated ruthenium carbonyls have been prepared. The compounds Pd(CO)2Cl2, Pt(CO)2Cl2, K[PtCOCl3], etc., show the stability of the four dsp2 bonds. It would be interesting to determine whether or not each CO is bonded to two metal atoms in compounds such as [Pt(CO)Cl2]2, whose structure is predicted to be... 

The structures of two group 14 heteroallenes that are complexed to other atoms have been determined—a ruthenium complex of a 1-silaallene (132a) and a... 

The complex 65 was synthesized by reaction of the imidazolinium salt with the precursor ruthenium complex 67 (catalytically inactive) in the presence of silver carbonate (Scheme 42). The complex being air-stable and stable on silicagel was isolated in 52% yield after chromatography. The diastereomeric and enantiomeric purity of 65 was determined by HPLC analysis and found to be above 98% (de and ee). The molecular structure was determined by X-ray analysis and showed the unusual twist geometry of this complex. 

C19-0138. A chemist wanted to determine E ° for the Ru /Ru reduction reaction. The chemist had all the equipment needed to make potential measurements, but the only chemicals available were R11CI3, a piece of ruthenium wire, CuSOq, copper wire, and water. Describe and sketch a cell that the chemist could set up to determine this E°. Show how the measured voltage would be related to ° of the half-reaction. If the cell has a measured voltage of 1.44 V, with the ruthenium wire being negative, determine E ° for Ru / Ru. 

In the following we consider nitrogen atoms adsorbed on a ruthenium surface that is not completely flat but has an atomic step for each one hundred terrace atoms in a specific direction. The nitrogen atoms bond stronger to the steps than to the terrace sites by 20 kj mok. The vibrational contributions of the adsorbed atoms can be assumed to be equal for the two types of sites. (Is that a good assumption ) Determine how the coverage of the step sites varies with terrace coverage. 

Because of- the similarity in the backscattering properties of platinum and iridium, we were not able to distinguish between neighboring platinum and iridium atoms in the analysis of the EXAFS associated with either component of platinum-iridium alloys or clusters. In this respect, the situation is very different from that for systems like ruthenium-copper, osmium-copper, or rhodium-copper. Therefore, we concentrated on the determination of interatomic distances. To obtain accurate values of interatomic distances, it is necessary to have precise information on phase shifts. For the platinum-iridium system, there is no problem in this regard, since the phase shifts of platinum and iridium are not very different. Hence the uncertainty in the phase shift of a platinum-iridium atom pair is very small. 

These conclusions from the infrared reflectance spectra recorded with Pt and Pt-Ru bulk alloys were confirmed in electrocatalysis studies on small bimetallic particles dispersed on high surface area carbon powders.Concerning the structure of bimetallic Pt-Ru particles, in situ Extended X-Ray Absorption Fine Structure (EXAFS>XANES experiments showed that the particle is a true alloy. For practical application, it is very important to determine the optimum composition of the R-Ru alloys. Even if there are still some discrepancies, several recent studies have concluded that an optimum composition about 15 to 20 at.% in ruthenium gives the best results for the oxidation of methanol. This composition is different from that for the oxidation of dissolved CO (about 50 at.% Ru), confirming a different spatial distribution of the adsorbed species. 

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