Ruthenium complexes butadiene

More synthetic interest is generated by the potentially very useful hydration of dienes. As shown on Scheme 9.6, methylethylketone (MEK) can be produced from the relatively cheap and easily available 1,3-butadiene with combined catalysis by an acid and a transition metal catalyst. Ruthenium complexes of several N-N chelating Hgands (mostly of the phenanthroline and bipyridine type) were found active for this transformation in the presence of Bronsted acids with weakly coordinating anions, typically p-toluenesulfonic acid, TsOH [18,19]. In favourable cases 90 % yield of MEK, based on butadiene, could be obtained. 

The 1,5 cyclooctadiene complex [Cp Ru(jj rf--C Yiu) (CO)]OTf was isolated upon treatment of Cp Ru(j)" -butadiene)X (X = Cl, Br) with butadiene, AgOTf, and CO. A similar [4-1-4] cycloaddition (a thermally forbidden reaction see Woodward-Hoffmann Rules)) is observed when Cp Ru(isoprene)Cl is treated with iso-prene, AgOTf, and CO. Likewise, the reaction of 1,3-pentadiene with Cp Ru( ) -l,3-pentadiene)Cl results in linear dimerization to form [Cp Ru(4-methyl-(l,3-jj 6-8-j) )-nonadienediyl)]OTf. These types of dimerization occur with both stoichiometric and catalytic amounts of the ruthenium complex. ... 

The complex functions as the most suitable source of the tricarbonylruthe-nium unit in syntheses of tricarbonyl(7-diene)ruthenium complexes. Derivatives of 1,3-cyclohexadiene, 1,3-cycloheptadiene, cycloheptatriene, cyclooc-tatetraene, 2,4,6-cycloheptatrien-l-one, bicyclo[3.2. l]octa-2,6-diene, bicyclo-[3.2. l]octa-2,4-diene, and butadiene have been prepared by displacement of 1,5-cyclooctadiene. 

Enantiomerically pure ruthenium complexes [CpRuLL (CH2=Cll2)]PF6 17, where LL is (S,S)-Chiraphos or (-)-Diop, catalyze the cyclocondensation of benzaldehyde (2 a) with ( )-l-methoxy-3-trimethylsilyloxy-l,3-butadiene (16. Danishefsky s diene), albeit with low optical yields of 25% and 16% ee (18 as a major isomer), respectively39. 

Conjugated dienes can be selectively hydrated to ketones in the presence of cationic ruthenium complexes with bipyridyl ligands. The role of ruthenium is to catalyze the isomerization of allylic alcohols formed by the addition of water to diene. This method allows one to convert butadiene to methyl ethyl ketone in high yield [187]. Hydration of triple bonds is one of the oldest catalytic processes of organic chemistry. Though this reaction has no industrial value, it can serve as a tool of fine organic synthesis. The hydration can be catalyzed by rhodium salts under phase-transfer conditions [188]. The more exotic process of the hydrolysis of phenylacetylene to toluene and carbon monoxide catalyzed by ruthenium complex should also be mentioned [189] ... 

The ruthenium catalyst generated in situ from H2Ru(CO)(PPh3)3, (S)-SEGPHOS and the TADDOL-derived phosphoric acid (169) promoted butadiene hydrohydroxyalkylation to form enantiomerically enriched products (168) (Scheme 61). Match/mismatch effects between the chiral ligand and the chiral TADDOL-phosphate counterion have been described. For the first time, single-crystal X-ray diffraction data for a ruthenium complex modified by a chiral phosphate counterion has been reported. ... 

Nitrile rubber polymers, having lower molecular weight have been prepared by metathesis of nitrile butadiene rubber with ruthenium indenylidene complexes [65]. 

The trinuclear pentahydride complex [Cp Ru]3(/w-H)3(/x3-H)2 (105) in Scheme 26 consists of ruthenium centers tightly bound by bridging hydrides. Treatment of the pentahydride complex with excess butadiene in THF results in a trinuclear 1-methyl-1,3-dimetalloallyl complex [Cp"Ru]3(H)4[/x3- ] -C(Me)CHCH] (106). This interaction shows the cooperation of all three ruthenium centers as either coordination sites or activation sites. Similar results are found by treating (105) with isoprene. Treatment of (105) with five equivalents of cyclopentadiene results in bond cleavage of the cyclopentadiene to form a dark purple crystalline solid [Cp Ru(/u.-H)]3[/x3- j4-C(Me)=CHCH=CH] (107). In this complex, two of the ruthenium centers act as a coordination site, while the third is an activation... 

When butadiene is treated with RuCls in 2-methoxyethanol at 100°C, yellow-brown crystals of composition (C4H8)3RuCl2 are obtained 381). Crystal structural analysis has identified 381, 382] the complex as (2,6,10-dodecatriene-l,12-diyl)dichlororuthenium (146), analogous to the nickel complex (194) suggested 608) as the catalytic intermediate in the nickel-catalyzed cyclic trimerization of butadiene. In this complex, the ruthenium atom has a trigonal-bipyramidal configuration with the... 

Catalysts from Group VIII metals have given unsatisfactory results. In the polymerization of butadiene with soluble cobalt catalysts tritium is not incorporated when dry active methanol is employed [115], although it is combined when it has not been specially dried [117, 118]. Alkoxyl groups have been found when using dry alcohol [115, 119] but the reaction is apparently slow and not suited to quantitative work [119]. Side reactions result in the incorporation of tritium into the polymer other than by termination of active chains [118], probably from the addition of hydrogen chloride produced by reaction of the alcohol with the aluminium diethyl chloride [108], Complexes of nickel, rhodium and ruthenium will polymerize butadiene in alcohol solution [7, 120], and with these it has not been possible to determine active site concentrations directly. 

Poly(l,4-butadiene) segments prepared by the ruthenium-mediated ROMP of 1,5-cyclooctadiene can be incorporated into the ABA-type block copolymers with styrene (B-106) and MMA (B-107).397 The synthetic method is based on the copper-catalyzed radical polymerizations of styrene and MMA from the telechelic poly(butadiene) obtained by a bifunctional chain-transfer agent such as bis(allyl chloride) or bis-(2-bromopropionate) during the ROMP process. A more direct route to similar block copolymers is based on the use of a ruthenium carbene complex with a C—Br bond such as Ru-13 as described above.67 The complex induced simultaneous or tandem block copolymerizations of MMA and 1,5-cyclooctadiene to give B-108, which can be hydrogenated into B-109, in one pot, catalyzed by the ruthenium residue from Ru-13. 

Third, n-allyl complexes are formed by palladium and cobalt analogous complexes of nickel and platinum are less stable, while ruthenium, rhodium, and iridium are not yet known to form them. In catalytic reactions the deuteration of cyclic paraffins over palladium has provided definite evidence for the existence of rr-bonded multiply unsaturated intermediates, while 7r-allylic species probably participate in the hydrogenation of 1,3-butadiene over palladium and cobalt, and of 1,2-cyclo-decadiene and 1,2-cyclononadiene over palladium. Here negative evidence is valuable platinum, for example does not form 7T-allylic complexes readily and the hydrogenation of 1,3-butadiene using platinum does not require the postulate that 7r-allylic intermediates are involved. Since both fields here are fairly well studied it is unlikely that this use of negative evidence will lead to contradiction in the light of future work. 

Ruthenium dihydride complexes catalyze coupling reactions of acetylenes with dienes [149], The reaction of 1-octyne with 1.3-butadiene catalyzed by RuH2(PBu-j. affords 2- dodecen-5-yne (eq (44)). A similar coupling reaction is also catalyzed b RuCl(CH.)(QH,2)[165j. 

We had established in previous catalytic reactions involving complex 24 that this precatalyst was activated by the removal of the cod (1,5-cyclooctadiene) from the ruthenium by its reaction with the alkyne substrate via a [2 + 2 + 2] cydization as illustrated in Equation 1.64 [57]. Thus, not only does this reaction constitute an activation of the Ru complex 24 by reacting off the cod, it also serves as a novel atom economic reaction in its own right. Both internal and terminal alkynes participate. The overall atom economy of this process is outstanding since cod itself is simply available by the nickel-catalyzed dimerization of butadiene. Thus, the tricyclic product is available by the simple addition to two molecules of butadiene and an alkyne with anything else only needed catalytically. 

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