Ruthenium -complexes

Ruthenium complexes also catalyze the oxidation of triphenylphosphine to triphenylphosphine oxide [76,79,81,119]. Among the catalytically active mthenium complexes are [Ru(NCSXCO)(NO)(PPh3)2] and [Ru(NCS) 0)(PPh3)2(02)] which have been found to catalyze this reaction at 50-80 in xylene solution [76,79]. These two complexes are related through the equilibrium reaction shown by equation (69). 

ITie actual catalytic cycle is reported to involve reaction of the dioxygen complex with triphenylphosphine followed by a slow oxygen atom transfer reaction to give a 

The individual steps in the mechanism proposed for the ruthenium catalyzed oxidation of triphenylphosphine are similar to those of the platinum catalyzed reaction. However, the stoichiometry of one step and the relative rates of several other steps appear to be somewhat different. The observed rate laws are quite different from those of the platimun complex. The rate equations for the proposed mechanism are shovm in equation (71) for the dioxygen complex and equation (72) for the carbonyl complex (RuOj = [Ru(NCSXN0XPPh3)j(02)] RuCO = [Ru(NCSXCOXNOXPPh3)2]). 

Analysis of the data on the basis of these equations yields ki = 1.26 x 10 and K2= 1.63 x 10 1 mol . In contrast to the observations of Halpem and coworkers who found that the rate of triphenylphosphine oxidation catalyzed by [Pt(02)(PPh3)2] depended linearly on [PPha], the above two rate equations require that the reciprocal of the rate depends on [PhaP] .  

Cenini, Fusi and Capparella [119] found that [RuCl2(PPh3)3] is an effective 

The potential of ruthenium complexes has been extensively explored along with fundamental studies on their interactions with molecules of biological interest [27—30]. The most studied series are structurally related to cisplatin and, in principle, ruthenium offers the exploitable property of access to two oxidation states, Ru(II) and (III), which differ in their rates of substitution the higher oxidation state is more inert and allows the possibility of introduction of a relatively inert and thus inactive complex which could be activated by reduction in vivo. This is of particular relevance with respect to the hypoxic or oxygen-deficient areas of tumours which occur at distances from the vascular system as a result of the enhanced respiration of rapidly growing cells (see Chapter 8). The potential for activation of Ru(III) complexes by reduction in this environment has been succintly reviewed [28]. 

Further, the existence of a number of stable radioisotopes of ruthenium holds promise for development of agents for organ imaging, and it should be remembered that ruthenium will possess some properties similar to those of technetium, whose complexes have been used for some considerable time for this purpose. In this respect, Clarke [28] has pointed out that considerable information on distribution of radioruthenium in animals has been accumulated because it is a major product in nuclear reactor waste. 

The systematic studies on ruthenium complexes have involved antitumour and mutagenesis assays, tissue distribution studies and detailed 

Data from Ref. 27 for P388 leukemia. Counteranions omitted for sake of clarity. 

In contrast to the situation with copper-based catalysts, 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 1995. In the early work, the square pyramidal ruthenium (II) halide 146 was used in combination with a cocatalyst (usually aluminum isopropoxide). 

There has been substantial work on catalyst development with the aim of finding more active catalysts and catalysts appropriate for different monomers and reaction media, The complexes 149-151 (Table 9.6) appear to be some of the more active catalysts. 

Ishida et al. also used [Ru(bpy)3]2+ as the photosensitizer and [Ru(bpy)2(CO)2]2+ as the cocatalyst to produce CO and formate in a water/dimethylformamide (DMF) mixture with l-benzyl-l,4-dihydronicotinamide (BNAA) as the sacrificial reductant 

In aqueous solution, [Ru(bpy)3]2+ was used as the photosensitizer and methyl viologen as the electron mediator, with TEOA or EDTA as the sacrificial reductant 

The ability of these polycarboxylate [182-185] compounds to scavenge NO is ideal for their application to various biological systems, as alleviators of some of the diseases which are the consequences of high NO toxicity [176, 186, 187]. Some of these compounds have been shown to preferentially inhibit iNOS [178, 183, 188] rather than cNOS. Employing an NO scavenger rather than an NOS inhibitor eliminates enzyme specificity [183]. The Ru-NO bond is extremely stable and remains intact 

In each metallocene unit, the cyclopentadienyl rings are parallel and staggered with respect to each other, the rings are twisted at 17.7°, thereby relieving the steric repulsions of the hydrogen atoms in the bridging methylene groups [87]. 

The crystal structure of the somewhat related complex (CsH5)Fe[C5H4-C(0)-CsHJRu(C5H5) has been reported [88], but its redox properties are unknown. 

Complex Ferrocene-centered oxidation E° V Ruthenocene-centered oxidation Solvent Reference 

On complex formation, oxidation of the ruthenium center seems to become easier, while that of the ferrocene moiety becomes more diffcult. 

The X-ray structure of the somewhat similar complex [(jj -C5H5)Fe()/ -C5H4)]Ru(PMe3)2(C5Me5) has been reported [95]. 

Ag/AgCl reference electrode (reproduced by permission of the Chemical Society of Japan). 

3-bis(4-methyl-2-pyridylimino)isoindoline (4-MeLH), catalyzes the oxidation of MeOH, EtOH, 1-butanol, 2-butanol and cyclohexanol at 60-75 C and 1 atm of 0 [22]. The primary products are aldehydes (acetals) 

Cinnamyl alcohol (1) and allylic alcohols of the terpenoid series, the essential oils of flowers, used as flavors and fragrances (geraniol, 2 nerol, 3 prenol, 4 carveol, 5 -ionol, 6) can be oxidized to the corresponding unsaturated carbonyl compounds in the presence of hydrated in 1,2-dichloroethane (1 atm 0, 70 °C) [23]. 

The medium is heterogeneous. Good yields of the product aldehydes require the addition of 2,6-di-t-butyl-p-cresol to prevent their further oxidation. 

Allyl alcohol is oxidized to acrolein and its epoxy derivative by 0 in the presence of P Cl in aqueous solution [26]. Ru(III)EDTA 

Copper phenanthroline complexes catalyze the oxidation of methanol 

A relatively new type of stationary phase is based on sodium magnesium silicates, in which metal atoms have been replaced by an optically active tris(l,10-phen-anthrohne)rufhenium(II) complex [19]. These stationary phases (Ceramosphere by Shiseido see Table 2) have a high loading capacity due to their large specific surface area and are used at temperatures of 50 °C or higher in the polar normal-phase mode. For optimization of the separation the methanol content can be varied, and in order to shorten retention times the temperature can be increased. 

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Ruthenium complexes have been used in the hydrocarbonylation of simple esters to produce the corresponding homologous esters (50). The hydrocarbonylation affects the alkyl moiety rather than the carboxylate group ... 

X-ray crystallography, 3, 623 Ruscodibenzofuran synthesis, 4, 698, 709 Ruthenacyclobutane, 3-cyano-synthesis, 1, 667 Ruthenium complexes with pyridines, 2, 124 triazenido, 5, 675 Rutin... 

Cj Hydroformation of CO with high-molecular weight olefins on either a cobalt or ruthenium complex bound to polymers. 

Imidazole is characterized mainly by the T) (N) coordination mode, where N is the nitrogen atom of the pyridine type. The rare coordination modes are T) - (jt-) realized in the ruthenium complexes, I-ti (C,N)- in organoruthenium and organoosmium chemistry. Imidazolium salts and stable 1,3-disubsti-tuted imidazol-2-ylidenes give a vast group of mono-, bis-, and tris-carbene complexes characterized by stability and prominent catalytic activity. Benzimidazole follows the same trends. Biimidazoles and bibenzimidazoles are ligands as the neutral molecules, mono- and dianions. A variety of the coordination situations is, therefore, broad, but there are practically no deviations from the expected classical trends for the mono-, di-, and polynuclear A -complexes. 

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