Ruthenium-TPPMS complex

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. 

Ru(II), Ru(I) and Ir(I) in an aqueous medium (90). Data for the different complexes are shown in Table II. The highest conversion is observed with the ruthenium(II) complexes, which correlates with the facility of Ru complexes to catalyze other hydrogen transfer reactions. The complex PdCl2(TPPMS)2 has been used as a two-phase aqueous-organic catalyst for the carbonylation of allylic chlorides (Eq. 30) 91). The reaction pro-... 

The use of water-soluble ligands was referred to previously for both ruthenium and rhodium complexes. As in the case of ruthenium complexes, the use of an aqueous biphasic system leads to a clear enhancement of selectivity towards the unsaturated alcohol [34]. Among the series of systems tested, the most convenient catalysts were obtained from mixtures of OsCl3 3H20 with TPPMS (or better still TPPTS) as they are easily prepared and provide reasonable activities and modest selectivities. As with their ruthenium and rhodium analogues, the main advantage is the ease of catalyst recycling with no loss of activity or selectivity. However, the ruthenium-based catalysts are far superior. 

Complexes of ruthenium, [HRu(CO)Cl(tppms)3] 2H20 and [HRu(CO) Cl(tppts)3], were reported to be catalysts for the same hydrogenation reaction (92). The metal complexes were not pure rather, they were used in the presence of the free sulfonated phosphanes and their respective oxides. 

Reduction of unsaturated substrates can also be performed by hydrogen transfer, usually from formate, catalyzed by rhodium and ruthenium complexes. Joo and co-workers have shown that RuCl2(tppms)2 [44] and RuCl2(PTA)4 [45,46] transforms aromatic as well as a, -unsaturated aldehydes to the corresponding aromatic or unsaturated alcohols, with a selectivity up to 98% in the latter case,... 

Water-soluble rhodium(I) complexes with TPPTS, TPPMS, and PTA ligands, such as [RhCl(TPPTS)3], are capable of hydrogenating aldehydes, although their catalytic activity is inferior to the ruthenium complexes discussed above [116]. In sharp contrast to the ruthenium(II)-based catalysts, in reactions of unsaturated al-... 

In line with the expected low reactivity of osmium(II) complexes [126], [OsC12(TPPMS)2], [OsH4(TPPMS)3], and [OsHC1(CO)(TPPMS)2], hydrogenated cinnamaldehyde at lower rates (and selectivities from 60 to 90%) than the analogous ruthenium(II) catalysts [127]. 

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). 

Ruthenium complexes of TPPTS and TPPMS [19-22] have been employed as catalysts or catalyst precursors for the hydrogenation of a,y unsaturated carbonyl compounds in biphasic systems [19-23aj c Section 2.4.2. Other ligands 7-13 are known and have been described [20, 23b, cj. 

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. 

Hydrosoluble iridium alkyl complexes may also be prepared by hydrolysis of alkynes and alkenes promoted by water-soluble precursors. The reaction with alkynes follows the well-known mechanism demonstrated by Bianchini et al. for ruthenium complexes.A reasonable mechanism, related to that of hydrolytic breakage, has been proposed by Chin etal. to account for the hydrolysis of ethene promoted by [Cp"lr(TPPMS)Cl2] 344 in the presence of silver salts in water. Scheme 37 describes the Chin s hydrolysis of alkynes, leading to [Cp Ir(TPPMS)(CO)(CH2R)] (69 R=Ph, Bz, Bu, />-Tol) via the aquo complex [Cp Ir(TPPMS)(OH2)OTf 345... 

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