Phosphine complexes ruthenium

The bidentate phosphine complexes were among the earliest ruthenium phosphine complexes to be made [85] often displacement is a convenient route ... 

The homo- and cross-addition of alkenes catalyzed by a transition-metal provided another economical way of forming C-C bonds.155 These reactions are carried out by using nickel, palladium, or ruthenium phosphine complexes to yield vinylarenes and some can occur in aqueous media. By using carbohydrate-derived ligands, asymmetric hydrovinylations can be carried out in aqueous conditions.156... 

Rate data have appeared (161) for the hydrodimerization of acrylonitrile to adiponitrile, which is catalyzed by various ruthenium-phosphine complexes (/, p. 101). 

Scheme 14.3 Proposed relationship between different ruthenium-phosphine complexes. The anion has been omitted and is PF4 throughout.

Together with Schrock s molybdenum-imido compound 50 ° the ruthenium-phosphine complexes 51 and especially 52 developed by Grubbs " proved to be an outstanding achievement in the development of molecular catalysts for olefin metathesis reactions (Scheme 10). 

From a practical standpoint, it is of interest to devise a one-step synthesis of the catalyst. Since both reactions 2 and 3 are ligand substitution reactions, it is quite conceivable that both steps can be carried out at the same time. When we reacted [Ru(COD)Cl2]n with BINAP and sodium acetate in acetic acid, we indeed obtained Ru(BINAP)(OAc)2 in good yields (70-80%). Interestingly, when the reaction was carried out in the absence of sodium acetate, no Ru(BINAP)(OAe)2 was obtained. The product was a mixture of chloro-ruthenium-BINAP complexes. A 3ip NMR study revealed that the mixture contained a major species (3) (31P [ H] (CDCI3) Pi=70.9 ppm P2=58.3 ppm J = 52.5 Hz) which accounted for more than 50% of the ruthenium-phosphine complexes (Figure 2). These complexes appeared to be different from previously characterized and published Ru(BINAP) species (12,13). More interestingly, these mixed complexes were found to catalyze the asymmetric hydrogenation of 2-(6 -methoxy-2 -naphthyl)acrylic acid with excellent rates and enantioselectivities. 

Many ruthenium complexes have been tested in the silylative coupling reaction. In the synthetic procedure the absence of by-products of the homocoupling of vinylsilanes is required so an excess of the olefin has usually been used. However, the screening tests performed at the 1 1 ratio of styrene and phenyldimethylvinylsilane with a variety of ruthenium catalysts have shown that pentacoordinated monocarbonyl bisphosphine complexes appear to be the most active and selective catalysts of which RuHCl(CO)(PCy3)2 has shown high catalytic activity under conditions of catalyst loadings as low as 0.05 mol % [55]. Cuprous salts (chloride, bromide) have recently been reported to be very successful co-catalysts of ruthenium phosphine complexes, markedly increasing the rate and selectivities of all ruthenium phosphine complexes [54]. 

In the presence of [RuC12(CO)3]2 as a catalyst, frans-bis(vinylsilyl)ethenes are exclusively formed but [(cyclooctadiene)RhX]2 (where X is Cl or OSiMe3) catalyzes mostly the formation of gem-dimeric products. Ruthenium phosphine complexes give both products [119] the gem products subsequently undergo intramolecular ring closure to yield cyclotetrasiloxane [ 120], cyclotetrasilazane and cyclohexacarbosilanes [117], respectively. 

Consiglio and Morandini and co-workers (67) have investigated the stereochemistry involved in the addition of acetylenes to chiral ruthenium complexes. Reaction of propyne with the separated epimer of the chiral ruthenium phosphine complex 34 at room temperature results in the chemo- and stereospecific formation of the respective propylidene complex 64. An X-ray structure of the product (64) proves that the reaction proceeds with retention of configuration at the ruthenium center. The identical reaction utilizing the epimer with the opposite configuration at ruthenium (35) also proceeded with retention of configuration at the metal center, proving that the stereospecificity of the reaction in not under thermodynamic control [Eq. (62)]. 

Further examples include homo-, co- and terpolymers of manganese carbonyl, iron carbonyl or cyclopentadienyl, and ruthenium-phosphine complexes [31, 59, 60]. 

In place of carbon monoxide, isocyanides are often used as the isoelectronic compound. In 1986, Jones et al. reported that the low-valent ruthenium phosphine complex catalyzed intramolecular insertion of isocyanide into the sp3 C-H bond under thermal conditions (Eq. 33) [60,61 ]. Their finding provided a new route for synthesis of indole. An interesting feature of their reaction is that C-H bond cleavage occurs even in the presence of an excess of the trapping ligand, i.e., isocyanide. 

Ru(Tp)(PPh3)(MeCN)2]PFg has been employed as catalyst to produce l-iodo-2-naphthol in DMF and 2-iodobenzo[d]oxepin in benzene from l-(2/-iodoethynylphenyl)-2-propyloxirane. The solvent-dependent chemoselectivity has been ascribed to a solution equilibrium between ruthenium-Tt-iodoalkyne and ruthenium-2-iodovinylidene intermediates.66 The same ruthenium phosphine complex has been efficiently employed as catalyst in the nucleophilic addition of water, alcohols, aniline, acetylacetone, pyrroles, and dimethyl malonate to unfunctionalized enediynes that yielded functionalized benzene products in good yields (Fig. 8.6).67 [Ru(Tp)-(PPh3)(MeCN)2]PFg has been also found very active in catalytic benzannulation of l-phenyl-2-ethynylbenzenes in dichloroethane to afford phenanthrene.68... 

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]. 

The present interest in asymmetric catalysis was demonstrated by awarding Nobel prizes to three winners W. S. Knowles (USA) for elaboration of rhodium complex catalysts effective in asymmetric synthesis of anti-Parkinson medicine, R. Noyori (Japan) for elaboration of a new catalytic system based on chiral ruthenium-phosphine complex catalysts that are very effective in hydrogenation reactions, and B. Sharpless (USA) for elaboration of epoxidation and other reactions under the action of chiral titanium complexes. 

Stimulating results achieved in hydrogenation of C=C double bonds with phosphinerhodium complexes led to the application of these compounds for the catalytic reduction of C=0 and C=N double bonds. The present review summarizes the results in this area reported up until now. To give a more complete picture of the subject, some reports on iridium and ruthenium phosphine complex catalysts have been included as well. 

Since the researcher normally looks to the chemistry of soluble complexes in designing polymer-bound catalysts, it is notable that some areas that have proven fruitful in homogeneous catalysis have been omitted from investigations using polymer-bound catalysts. One of these areas concerns the reactions of arenes. Benzene, for example, may be hydrogenated with homogeneous cobalt phosphite and ruthenium phosphine complexes, but the corresponding supported versions are not reported. Aryl halides may be carboxylated in the presence of a soluble palladium catalyst ... 

Pentadienyl (L) ligand rotation has been studied by P- H NMR spectroscopy for the ruthenium-phosphine complexes [(L)RuCl(PR3)2] (7). The pentadienyl ligand rotates with respect to the RUCIP2 framework exchanging the two phosphines as well as the two sides of the ligand (Scheme 4). 

Monophosphines can be used as promoters, but the promoting effect is small. Chelating diphosphines have a much higher promoting efficiency. if) Phosphine-substituted trinuclear clusters can be used as catalyst precursors, but conversions are lower than when Ru3(CO)i2 and the phosphine are added separately [154]. Conversely, the use of preformed mononuclear ruthenium-phosphine complexes affords the best results [178, 180]. The role of mononuclear species as the active catalysts is strongly implied and has also been confirmed by a detailed mechanistic study (see Chapter 6). 

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