Ruthenium studies

For the binary hdide/nitrile complexes of ruthenium studied here, it is clear that none of these models is sufficient replacement of each chloride by benzonitrile stabilizes the ruthenium orbitals to the eatest degree (0.6 eV), affects die 7t-donor levels of the remaining coordinated chlorides to a smaller extent (0.4 eV overall mean), and lowers the nitrile n-acceptor orbitals still less (0.3 eV). This may be compared with theoretical estimates of 0.25 to 0.5eV for halide/halide interactions in cis -[RuX2(NH3>4]+ (X = Cl- or Br). 

Ruthenium—Titanium Oxides. The x-ray diffractioa studies of mthenium—titanium oxide coatiags show that the coatiag components are preseat as the metal dioxides, each ia the mtile form as weU as ia soHd solutioa with each other (13). The developmeat of the crystal stmcture begias to occur at a bake temperature of about 400°C. By foUowiag the diffractioa line for the mtile stmcture, an iacrease ia crystallinity can be seen as temperatures are iacreased to the 600—700°C range. Above these temperatures, the peak begias to separate iato two separate peaks, iadicative of phase separatioa iato iadividual mtile oxides, oae rich ia mthenium and one rich ia titanium. 

A typical SSIMS spectrum of an organic molecule adsorbed on a surface is that of thiophene on ruthenium at 95 K, shown in Eig. 3.14 (from the study of Cocco and Tatarchuk [3.28]). Exposure was 0.5 Langmuir only (i.e. 5 x 10 torr s = 37 Pa s), and the principal positive ion peaks are those from ruthenium, consisting of a series of seven isotopic peaks around 102 amu. Ruthenium-thiophene complex fragments are, however, found at ca. 186 and 160 amu each has the same complicated isotopic pattern, indicating that interaction between the metal and the thiophene occurred even at 95 K. In addition, thiophene and protonated thiophene peaks are observed at 84 and 85 amu, respectively, with the implication that no dissociation of the thiophene had occurred. The smaller masses are those of hydrocarbon fragments of different chain length. 

SSIMS has also been used to study the adsorption of propene on ruthenium [3.29], the decomposition of ammonia on silicon [3.30], and the decomposition of methane thiol on nickel [3.31]. 

The first example of homogeneous transition metal catalysis in an ionic liquid was the platinum-catalyzed hydroformylation of ethene in tetraethylammonium trichlorostannate (mp. 78 °C), described by Parshall in 1972 (Scheme 5.2-1, a)) [1]. In 1987, Knifton reported the ruthenium- and cobalt-catalyzed hydroformylation of internal and terminal alkenes in molten [Bu4P]Br, a salt that falls under the now accepted definition for an ionic liquid (see Scheme 5.2-1, b)) [2]. The first applications of room-temperature ionic liquids in homogeneous transition metal catalysis were described in 1990 by Chauvin et al. and by Wilkes et ak. Wilkes et al. used weekly acidic chloroaluminate melts and studied ethylene polymerization in them with Ziegler-Natta catalysts (Scheme 5.2-1, c)) [3]. Chauvin s group dissolved nickel catalysts in weakly acidic chloroaluminate melts and investigated the resulting ionic catalyst solutions for the dimerization of propene (Scheme 5.2-1, d)) [4]. 

An example of a stereoselective hydrogenation in ionic liquids was recently successfully demonstrated by Drie en-H6lscher et al. On the basis of investigations into the biphasic water/n-heptane system [51], the ruthenium-catalyzed hydrogenation of sorbic acid to cis-3-hexenoic acid in the [BMIM][PFg]/MTBE system was studied [52], as shown in Scheme 5.2-8. 

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. 

Tris(2,2 -bipyridine)ruthenium(II) complex (Ru(bpy)3+) has been most commonly employed as a chromophore in the studies of photoinduced ET. Electrostatic effects on the quenching of the emission from the Ru(II) complex covalently bound to polyeletrolytes have been studied by several groups [79-82]. 

The pentammine aqua ion [Ru(NH3)j(H20)]2+, best made by zinc amalgam reduction and aquation of [Ru(NH3)5C1]2+, undergoes extensively studied substitution reactions first order in both the ruthenium complex and the incoming ligand (e.g. NH3, py) and is a convenient source of other... 

Porphyrin complexes have been the most intensively studied macrocyclic complexes of these metals [129]. They are formed in a wide range of oxidation states (II-VI) and they are, therefore, treated together under this heading, though most of the chemistry for ruthenium lies in the II-IV states. Octaethylporphyrin (OEP) complexes are typical. 

The carboxylates complexes of osmium have been studied less than the ruthenium analogues [173],... 

The first catalytic study of Reaction 1 was published in 1902 by Sabatier and Senderens (1) who reported that nickel was an excellent catalyst. Since that time, the active catalysts were identified as the transition elements with unfilled 3d, 4d, and 5d orbitals iron, cobalt, nickel, ruthenium, rhenium, palladium, osmium, indium, and platinum, as well as some elements that can assume these configurations (e.g., silver). These are discussed later. For practical operation of this process,... 

Catalysts. The methanation of CO and C02 is catalyzed by metals of Group VIII, by molybdenum (Group VI), and by silver (Group I). These catalysts were identified by Fischer, Tropsch, and Dilthey (18) who studied the methanation properties of various metals at temperatures up to 800°C. They found that methanation activity varied with the metal as follows ruthenium > iridium > rhodium > nickel > cobalt > osmium > platinum > iron > molybdenum > palladium > silver. 

Other Metals. Ruthenium was studied by the Bureau of Mines... 

In contrast to the situation with copper-based catalysis, most studies on ruthenium-based catalysts have made use of preformed metal complexes. The first reports of ruthenium-mediated polymerization by Sawamoto and coworkers appeared in I995.26 In the early work, the square pyramidal ruthenium (II) halide 146 was used in combination with a cocatalyst (usually aluminum isopropoxide). 

The ruthenium analogue of 47 Ru(ri5-C5Ph5)(CO)2Br (48) is also available, when Fe(CO)5 is replaced by Ru3(CO)12 [68]. A wide range of substitution products were obtained through replacement of both carbonyl and bromide ligand against two-electron ligands L such as phosphines, phosphites, and ethylene. Electrochemistry of these derivatives were studied in some detail. 

A synthetically useful reaction has been reported between alkaline bromine water and dimethyl sulphoxide118, the product being the perbromosulphone (equation 36). A kinetic study of the oxidation of dimethyl sulphoxide by bromate ions, catalysed by ruthenium(III) salts, has also been published but no yield data are available119. 

The search for even more active and recyclable ruthenium-based metathesis catalysts has recently led to the development of phosphine-free complexes by combining the concept of ligation with N-heterocyclic carbenes and benzyli-denes bearing a coordinating isopropoxy ligand. The latter was exemplified for Hoveyda s monophosphine complex 13 in Scheme 5 [12]. Pioneering studies in this field have been conducted by the groups of Hoveyda [49a] and Blechert [49b], who described the phosphine-free precatalyst 71a. Compound 71a is prepared either from 56d [49a] or from 13 [49b], as illustrated in Scheme 16. 

The moments of complexes containing NO offer a puzzling problem. The diamagnetism of compounds of iron and ruthenium suggests that Feiv and RuIV form a double bond with NO, making seven bonds in all, which woud lead to /t = 0. But this structure cannot be applied to [Co(NH3)6-NO]Cl2, which has a moment corresponding to a triplet state. Further study of such complexes is needed. 

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