Water-soluble ruthenium complex

Water-soluble ruthenium complexes RuHCl(tppts)3, RuCl2(tppts)3, RUH2 (tppts)3, or the rhodium complex RhCl(PTA)3, are also effective catalysts for the hydrogenation of the carbonyl function of aldehydes [16], carbohydrates [17], and keto acids [13], provided that the iodide salt Nal is added for ruthenium complexes. 

Ruthenium tetroxide was shown to oxidize PCBs in water [20], Water-soluble ruthenium complexes, such as [Ru(H20)2(DMS0)4]2+, are effective catalysts for the KHSO5 deep oxidation of a number of chloroaliphatics, of a-chlorinated al-kenes, polychlorobenzenes, and polychlorophenols. When the reactions are carried out in water in the presence of surfactant agents, degradation of the substrates is definitely faster. Aromatic substrates are mainly converted into HC1 and C02, polychlorophenols being more sensitive to oxidation than substituted benzenes [21]. Replacement of the DMSO- solvated ruthenium by RuPcS results in a definite improvement of the reaction course with hydrogen peroxide, since dismutation of... 

More recently, catalytic hydrogenations of alkenes by other catalysts in water have been explored. For example, water-soluble ruthenium complex RuCl2(TPPTS)3 has been used for the catalytic hydrogenation of unsaturated alkenes (and benzene). Hydrogenation of nonactivated alkenes catalyzed by water-soluble ruthenium carbonyl clusters was reported in a biphasic system. The tri-nuclear clusters undergo transformation during reaction but can be reused repeatedly without loss of activity. The organometallic aqua complex [Cp Ir (H20)3] " ... 

Several water-soluble ruthenium complexes, with P = TPPMS, TPPTS, or PTA ligands (cf. Section 2.2.3.2), catalyze the selective reduction of crotonaldehyde, 3-methyl-2-butenal (prenal), and trans-cinnamaldehyde to the corresponding unsaturated alcohols (Scheme 2) [33—36]. Chemical yields are often close to quantitative in reasonable times and the selectivity toward the aUyhc alcohol is very high (> 95%). The selectivity of the reactions is critically influenced by the pH of the aqueous phase [11] as well as by the H2 pressure [37]. The hydrogenation of propionaldehyde, catalyzed by Ru(II)/TPPTS complexes, was dramatically accelerated by the addition of inorganic salts [38], too. In sharp contrast to the Ru(II)-based catalysts, in hydrogenation of unsaturated aldehydes rhodium(I) complexes preferentially promote the reaction of the C=C double bond, although with incomplete selectivity [33, 39]. 

A water-soluble ruthenium complex, HRu(C0)Cl(TPPMs)3-2H20, was used for hydrogenation of olefins in the biphasic system decalin-water [155], Ruthenium catalyst immobilized on a hydrophilic microporous resin turned out to be more selective for partial hydrogenation of benzene to cyclohexene than the same catalyst immobilized on charcoal. 

The formation of P-hydroxyaldehydes from propargylic alcohols has also been observed in aqueous media in the presence of a catalytic amount of water-soluble ruthenium sulfophthalocyanine complex and the heterogeneous ruthenium hydroxyapatite catalyst [40]. 

Treatment of vinyl ether 165 with the water-soluble ruthenium allenylidene complex [(RuCl(/r-Cl)-(C=C=CPh2)(TPPMS)2)2]Na4 in CHCl3/water and CDC13/D20, respectively, afforded dioxepanes 166 and 167 (Scheme 45) <2003EJI1614> however, this method is of little synthetic interest. 

Hydrogenation of various unsaturated substrates has been carried out in water or in a two-phase system using preformed or in situ rhodium and ruthenium catalysts associated with water-soluble ligands. Complexes such as RhCl(PTA)3... 

Hydrodehalogenation of aliphatic or benzylic halides were catalyzed by water soluble ruthenium phosphine complexes in the presence of sodium formate as hydrogen donor [194], Hydroxycarbonylations could also be performed with high palladium catalyst activities in biphasic systems [195-197]. 

Water-soluble ruthenium vinylidene and allenylidene complexes were also synthetized in the reaction of [ RuC12(TPPMS)2 2] and phenylacetylene or diphenylpropargyl alcohol [29], The mononuclear Ru-vinylidene complex [RuCl2 C=C(H)Ph (TPPMS)2] and the dinuclear Ru-allylidene derivative [ RuCl( x-Cl)(C=C=CPh2)(TPPMS)2 2] both catalyzed the cross-olefin metathesis of cyclopentene with methyl acrylate to give polyunsaturated esters under mild conditions (Scheme 7.10). 

With the work by Grubbs et al. [27] and Herrmann et al. [28], the use of ruthenium carbene complexes as homogeneous catalysts for the ROMP (Ring-Opening Metathesis Polymerization) of olefins was estabhshed (see Section 2.4.4.3). The development of catalysts that can catalyze hving polymerization in water was an important goal to achieve, especially for applications in biomedicine. In this context, two water-soluble ruthenium carbene complexes (3 and 4) have been reported that act as initiators for the living polymerization of water-soluble monomers in a quick and quantitative manner [29]. 

RUO4 was shown to oxidize PCBs in water [21]. Water-soluble Ru complexes, such as [Ru(H20)2(dmso)4], were effective catalysts for the KHSO5 oxidation of a number of polychlorobenzenes and polychlorophenols, mainly converted into HCl and CO2 [22]. Replacement of the dmso- solvated ruthenium by RuPcS resulted... 

When conducting the ROMP of norbornene or cyclooctadiene in miniemulsions [82], two approaches were followed (i) addition of a catalyst solution to a miniemulsion of the monomer and (ii) addition of the monomer to a miniemulsion of Grubbs catalyst in water. With the first approach it was possible to synthesize stable latexes with a high conversion, whereas for the second approach particles of >400 nm were created, without coagulum, but with 100% conversion. Subsequently, a water-soluble ruthenium carbene complex [poly(ethylene oxide)-based catalyst] was prepared and used in the direct miniemulsion ROMP of norbornene [83], whereby particles of 200-250 nm were produced. The catalytic polymerization of norbornene in direct miniemulsion was also carried out in the presence of an oil-soluble catalyst generated in situ, or with a water-soluble catalyst [84] the reaction was faster when using the oil-soluble catalyst. Helical-substituted polyacetylene could be efficiently polymerized in direct miniemulsion to yield a latex with particles that ranged between 60 and 400 nm in size, and which displayed an intense circular dichroism [85] that increased as the particle size decreased. The films were prepared from dried miniemulsion latexes that had been mixed with poly(vinyl alcohol) (PVA) in order to conserve the optical activity. 

Olefin metathesis reaction that reorganizes carbon-carbon double bonds provides fundamentally new strategies for natural product synthesis and polymer chemistry. Hilvert and coworkers built up an artificial metalloenzyme by covalently tethering a Grubbs-Hoveyda-type Ru complex to a protein scaffold [78]. An /V-heterocyclic carbene (NHC) ligand, which has been reported as a suitable ligand for a number of water-soluble ruthenium-based metathesis catalysts, was derivatized with an electrophilic bromoacetamide. The Ru carbene complex (27 in Figure 10.16) was then attached by site-selective alkylation of the cysteine... 

Single-wall carbon nanotubes (SWCNTs) are likewise promising as active components in organic and hybrid solar cells. A model has been prepared by linking through peptidic bonds a water-soluble ruthenium(II) tris(bi-pyridyl) complex. The resulting Ru-SWCNTs, also soluble in water, was photoactive with the delayed formation of Rubipy3 ... 

As discussed above for ferrocene derivatives, small water-soluble ruthenium and osmium complexes are good candidates for redox enzyme catalysis mediation for their reversible (II/III) behavior and relative stabiKty in the two-oxidation state in water. The alteration of the aromatic rings is a means of tuning of the redox potential/structure characteristics of the complexes, which is important for efficient redox enzyme mediation [75, 76]. Table 1 gives the redox potentials in acetonitrile of a series of neutral osmium(II) dichloride complexes with different substituted ligands [77]. 

---