Ruthenium dependence

In these compounds the cis-effect was observed which manifested itself in the weakening of the between nitrosyl group and ruthenium, depending on the amine electronodonor properties in cis-position to the coordinate HO-Ru-NO. The increase of amine electronodonor properties leads to displacement of electron atmosphere to ruthenium, diminshes its effective positive charge. This, in turn, stimulates the decrease of v in IR absorption spectrum,... 

Another example is the hydrogenation of the homoallylic eompound 4-methyl-3-cyclohexenyl ethyl ether to a mixture of 4-methylcyclohexyl ethyl ether and methylcyclohexane. The extent of hydrogenolysis depends on both the isomerizing and the hydrogenolyzing tendencies of the catalysts. With unsupported metals in ethanol, the percent hydrogenolysis decreased in the order palladium (62.6%), rhodium (23 6%), platinum (7.1%), iridium (3.9%), ruthenium (3.0%) (S3). 

The amount of coupled product was found to depend importantly on the catalytic metal a sequence for increased coupling to dicyclohexylamine was found to be Ru < Rh Pd Pt (59), a sequence that reflects one reason for the industrial preference for rhodium and ruthenium in hydrogenation of anilines. 

An excellent route to cyclohexylamines is by hydrogenation of the corresponding aniline over rhodium or ruthenium (17,18,19 2 36,63,64). Rhodium has proved especially useful in saturation of alkoxyanilines with minimal hydrogenolysis of the alkoxy function (45), The extent of hydrogenol ysis occurring in saturation of alkoxyanilines depends also on the solvent. Hydrogenolysis of p-methoxyaniline over Ru(OH)2 fell with alcohol solvent in the order methanol (35%) > ethanol (30%) > propanol (26%) > butanol (22%) > isopropanol (16%) > r-butanol (8%) (43). 

If saturation occurs first, the product will be relatively stable toward further reduction but if hydrogenolysis occurs first, the resulting olefin is readily reduced. This ratio depends greatly on substrate structure, the catalyst, and environment. Hydrogenolysis is best achieved over platinum, whereas palladium (77a,82a,122bJ62a), rhodium (I09a), or ruthenium (I0a,I09a) tend to favor olefin saturation. 

The behaviour of irradiated uranium has been studied mainly with respect to the release of fission products during oxidation at high temperatures The fission products most readily released to the gas phase are krypton, xenon, iodine, tellurium and ruthenium. The release can approach 80-100%. For ruthenium it is dependent upon the environment and only significant in the presence of oxygen to form volatile oxides of ruthenium. 

The composition of the mixed metal oxide may well vary over wide limits depending on the environment in which the anode will operate, with the precious metal composition of the mixed metal oxide coating adjusted to favour either oxygen or chlorine evolution by varying the relative proportions of iridium and ruthenium. For chlorine production RuOj-rich coatings are preferred, whilst for oxygen evolution IrOj-rich coatings are utilised. ... 

Almost every metal atom can be inserted into the center of the phthalocyanine ring. Although the chemistry of the central metal atom is sometimes influenced in an extended way by the phthalocyanine macrocycle (for example the preferred oxidation state of ruthenium is changed from + III to + II going from metal-free to ruthenium phthalocyanine) it is obvious that the chemistry of the coordinated metal of metal phthalocyanines cannot be generalized. The reactions of the central metal atom depend very much on the properties of the metal. 

The complexes of ruthenium and osmium in the same oxidation state are generally similar and are, therefore, treated together the structural (Table 1.3) and vibrational data (Table 1.4) have been set out in some detail to demonstrate halogen-dependent trends. 

The acceptance of a (new) catalytically mediated methodology by the target-directed synthetic community strongly depends on the availability, stability, and functional group tolerance of the respective catalysts. With the commercial availability of Grubbs5 benzylidene ruthenium catalyst A [13] and Schrock s even more active, yet highly air- and moisture-sensitive molybdenum catalyst B [14]... 

Although the actual reaction mechanism of hydrosilation is not very clear, it is very well established that the important variables include the catalyst type and concentration, structure of the olefinic compound, reaction temperature and the solvent. used 1,4, J). Chloroplatinic acid (H2PtCl6 6 H20) is the most frequently used catalyst, usually in the form of a solution in isopropyl alcohol mixed with a polar solvent, such as diglyme or tetrahydrofuran S2). Other catalysts include rhodium, palladium, ruthenium, nickel and cobalt complexes as well as various organic peroxides, UV and y radiation. The efficiency of the catalyst used usually depends on many factors, including ligands on the platinum, the type and nature of the silane (or siloxane) and the olefinic compound used. For example in the chloroplatinic acid catalyzed hydrosilation of olefinic compounds, the reactivity is often observed to be proportional to the electron density on the alkene. Steric hindrance usually decreases the rate of... 

Zero-order desorption occurs if the rate of desorption does not depend on the adsorption coverage, as seen with relatively large silver islands on a ruthenium surface (Fig. 7.7), where the Ag atoms desorb from the edges of the island. As the 0" term in Eq. (12) vanishes, the curves exhibit a clearly recognizable exponential shape on the leading side. Such situations are rare. 

Figure 7.8. The compensation effect in the desorption ofAg from a ruthenium surface activation energy and pre-exponential factor depend in the same way on coverage. The...

Reduction of acetophenone by PrOH/H has been studied with the ruthenium complexes [Ru(H)(ri2-BH )(CO)L(NHC)], (L = NHC, PPh3, NHC = IMes, IPr, SIPr). The activity of the system is dependent on the nature of the NHC and requires the presence of both PrOH and H, implying that transfer and direct hydrogenation mechanisms may be operating in parallel [15]. 

A kinetic study of the hydrodefluorination of C F H in the presence of EtjSiH indicated a first-order dependence on both [fluoroarene] and [ruthenium precursor] and a zero-order dependence on the concentration of alkylsilane, implying that the rate-limiting step in the catalytic cycle involves activation of the fluoroarene. The regioselectivity for hydrodefluorination of partially fluorinated substrates such as CgFjH has been accounted for by an initial C-H bond activation as shown in the... 

The development of highly efficient methanol fnel cells depends on a nnmber of scientific aspects (1) the development of more highly active catalysts for methanol oxidation at temperatnres not over 60 to 70°C (desirable in cells without ruthenium, which is in short supply) (2) the development of selective catalysts for the oxygen electrode (i.e., of catalysts insensitive to the presence of methanol) and (3) the development of new membrane materials having a lower methanol permeability. 

An example for a non-structure-sensitive reaction is provided by Davis et al. [102], who investigated the liquid-phase hydrogenation of glucose over carbon and silica based ruthenium catalysts with particle sizes between 1.1 and 2.4 run. Depending on catalyst loading which was between 0.56 wt.% and 5 wt.%, dispersion decreased from 91% to 43%. At the same time, TOFs varied only insignificantly in a range between 0.21 1/s and 0.32 1/s. 

The most widely used method for adding the elements of hydrogen to carbon-carbon double bonds is catalytic hydrogenation. Except for very sterically hindered alkenes, this reaction usually proceeds rapidly and cleanly. The most common catalysts are various forms of transition metals, particularly platinum, palladium, rhodium, ruthenium, and nickel. Both the metals as finely dispersed solids or adsorbed on inert supports such as carbon or alumina (heterogeneous catalysts) and certain soluble complexes of these metals (homogeneous catalysts) exhibit catalytic activity. Depending upon conditions and catalyst, other functional groups are also subject to reduction under these conditions. 

We report here studies on a polymer fi1m which is formed by the thermal polymerization of a monomeric complex tris(5,5 -bis[(3-acrylvl-l-propoxy)carbonyll-2,2 -bipyridine)ruthenium(11) as its tosylate salt,I (4). Polymer films formed from I (poly-I) are insoluble in all solvents tested and possess extremely good chemical and electrochemical stability. Depending on the formal oxidation state of the ruthenium sites in poly-I the material can either act as a redox conductor or as an electronic (ohmic) conductor having a specific conductivity which is semiconductorlike in magnitude. 

Physical properties of binary or ternary Ru/Ir based mixed oxides with valve metal additions is still a field which deserves further research. The complexity of this matter has been demonstrated by Triggs [49] on (Ru,Ti)Ox who has shown, using XPS and other techniques (UPS, Mossbauer, Absorption, Conductivity), that Ru in TiOz (Ti rich phase) adopts different valence states depending on the environment. Possible donors or acceptors are compensated by Ru in the respective valence state. Trivalent donors are compensated by Ru5+, pentavalent acceptors will be compensated by Ru3+ or even Ru2+. In pure TiOz ruthenium adopts the tetravalent state. The surface composition of the titanium rich phase (2% Ru) was found to be identical to the nominal composition. 

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