Ruthenium complexes acetylene

Other transition-metals have also been used. For example, Trost183 reported that heating a 1 1 mixture of 1-octene and 1-octyne in DMF-water (3 1) at 100°C with a ruthenium complex for 2 h generated a 1 1 mixture of two products corresponding to the addition of the alkene to the acetylene (Eq. 3.47). The presence of a normally reactive enolate does not interfere with the reaction. 

Ru-vinylidene complexes can be easily prepared by reaction of low-valent ruthenium complexes with terminal acetylenes. Treatment of the Ru(ii) complex 117 with phenylacetylene gave the Ru(iv)-vinylidene complex 118 in 88% yield (Scheme 41 ).60 The reaction of 118 with C02 in the presence of Et3N afforded selectively the Ru-carboxylate complex 120, probably via the terminal alkynide intermediate 119. 

The regioselective anti-Markovnikov addition of benzoic acid to phenyl-acetylene has also been carried out with success at 111 °C in the presence of ruthenium complexes containing a tris(pyrazolyl)borate (Tp) ligand [RuCl(Tp)(cod), RuCl(Tp)(pyridine), RuCl(Tp)(N,N,Ar,AT-tetramethylethyl-enediamine )] with a stereoselectivity in favour of the (E)-enol ester isomer [22]. The o-enynyl complex Ru(Tp)[PhC=C(Ph)C=CPh](PMe/-Pr2) (C) efficiently catalyses the regioselective cyclization of a,cu-alkynoic acids to give en-docyclic enol lactones [23] (Eq. 2). 

The activation of terminal alkynes and propargylic alcohols by appropriate ruthenium complexes provides general and easy access to ruthenium vinyli-dene and allenylidene intermediates. These cumulenic systems offer a variety of possibilities in catalysis for selective transformations of acetylenic deriva-... 

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)]. 

RuCl2(PMe3)(C6Me6) and RuCl2(PMe3)(p-cymene) appear to be much more efficient catalysts than other mononuclear ruthenium complexes, or Ru3(CO)12, for a variety of secondary amines and terminal alkynes, such as diethylamine, morpholine, piperidine, and pyrrolidine (65,201), except for acetylene itself (202,203). The regioselective addition to the terminal carbon suggests that that the reaction proceeds via an arene ruthenium vinyl-idene intermediate that has been characterized (66) (Section II,A,3,d). 

AUcynylchalcogenato ruthenium complexes react with zirconocene to give rise to heterobimetallic early-late dissymmetrically bridged complexes of family (76) (equation 39). In those specific complexes, the two metal centers are linked by /u.-chalcogenido and /x-a, jr-alkynyl moieties. The acetylenic bridge is unsymmetrical because the terminal carbon of alkynyl is ct-bonded to ruthenium, while zirconium interacts with both alkynyl carbons in a side-on fashion. 

For the intermolecular hydroacylation of olefins and acetylenes, ruthenium complexes - as well as rhodium complexes - are effective [60-64]. In 1980, Miller reported the first example of an intermolecular hydroacylation of aldehydes with olefins to give ketones, during their studies of the mechanism of the rhodium-catalyzed intramolecular cydization of 4-pentenal using ethylene-saturated chloroform as the solvent [60]. A similar example of the hydroacylation of aldehydes with olefins using ruthenium catalyst is shown in Eq. 9.43. When the reaction of propionaldehyde with ethylene was conducted in the presence of RuCl2(PPh3)3 as the catalyst without... 

Since CO2 and R2NH give carbamic acid and its salts, this reaction is an extension of the addition of carboxylic acids [151] to terminal acetylenes to give enol ester catalyzed by ruthenium complexes (Eqs. 11.84 and 11.85). 

Dixneuf suggested that this reaction proceeds via the nucleophilic attack of a carbamate anion to the ruthenium vinylidene intermediate generated by the reaction of ruthenium complexes with terminal acetylene. The details of this reaction are discussed in Chapter 8. 

Various vinylsilanes, olefins or acetylenes insert into the ortho C-H bond of aromatic ketones in the presence of catalytic amount of ruthenium complexes in high yields [21,22], The C-H bond cleavage reaction of aromatic ketones also involves orthometallation which is promoted by prerequisite coordination of the carbonyl group to ruthenium (Scheme 14.9) [21], This type of reaction has a wide generality for aromatic and alkenyl ketones with a variety of alkenes. 

Supported platinum, rhodium, and ruthenium complex catalysts have been used extensively in the reaction of trisubstituted silanes with acetylene in the gas phase, predominantly in a continuous-flow apparatus. Formation of a polymer layer on the surface after immobilization of the platinum complex has protected the catalyst against leaching in long-term hydrosilylation tests [91]. 

In order to further explore the reactivity of the homobimetallic ruthenium complexes, the reaction of 4 with terminal alkynes was investigated. Thus, when phenylacetylene or ferf-butylacetylene was added to a solution of complex 4 in CH2CI2 or benzene, the rapid and quantitative formation of the corresponding rathenium- vinylidene complexes, 8 and 9, respectively, was observed (13). The formation of 8 and 9 can be rationalised by the displacement of the ethylene ligand by the respective acetylene followed by an alkyne-to-vinylidene transformation. 

Acetylenic compounds form adducts with acrylic acid derivatives, catalysed by a ruthenium complex with 1,5-cyclooctadiene (cod) and 1,3,5-cyclooctatriene (cot), as shown in reaction 10. ... 

Aryne complexes of late transition metals are very reactive towards both nucleophiles (amines, alcohols, water) and electrophiles (iodine). They also undergo insertion reactions with CO, alkenes and alkynes,but while the behaviour of ruthenium complexes is somewhat similar to that of titanium or zirconium complexes, the reactivity of nickel complexes is rather different [6,8]. Examples of these reactions that are particularly interesting for the purposes of this chapter are shown in Schemes 8 and 9. Ruthenium complex 33 undergoes insertion of a molecule of benzonitrile,benzaldehyde or di(p-tolyl)acetylene to yield met-allacycles 40,41 and 42, respectively (Scheme 8). Further insertion of a second unsaturated molecule into these metallacycles has not been observed [25,27]. 

Compounds having carbon-carbon double bond such as alkenes and allylalco-hol, add to acetylene compounds in the presence of ruthenium complexes. For example, as shown in eq. (16.28), alkene adds with 1,2-addition to alkyne without... 

The first examples of linear co-dimerization of acetylenes with buta-l,3-diene have been reported. Aliphatic terminal acetylenes (196) react with buta-1,3-diene in the presence of a catalytic amount of an appropriate ruthenium complex at 60-80 C to give almost quantitative yields of E-conjugated enynes (197). ... 

Also, ruthenium complex 44 reacted with alkynes yielding 45, which underwent migratory insertion of the NHC ligand into the Ru alkylidene yielding 46 (Scheme 3.16). ° Trzeciak and co-workers demonstrated that [(NHC)Ru(p-cymene)Cl2] was able to polymerize phenyl acetylene, and that the resulting product was terminated by the imidazolium ion, likely via the same... 

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