Ruthenium Allenylidenes and Indenylidenes as Catalysts in Alkene Metathesis

Malacea, Raluca; Dixneuf, Pierre H.

doi:10.1002/9783527622870.ch8

Cited by 4 publications

(4 citation statements)

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“…Thus, while nucleophiles add selectively to C γ or C α , electrophiles are generally inclined to attack the β-position of the polycarbon chain . This peculiar and easily controlled reactivity has been largely used to promote both catalytic reactions and selective stoichiometric structural elaborations of the allenylidene moiety, which have found application in several areas of synthetic organic chemistry and materials science.…”

Section: Introductionmentioning

confidence: 99%

Electron-Poor Rhenium Allenylidenes and Their Reactivity toward Phosphines: A Combined Experimental and Theoretical Study

et al. 2011

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The reaction of 1-(phenyl)-1-(p-nitrophenyl)-2-propyn-1-ol with the Re(I) precursor [(triphos)(CO)2Re(OTf)] in dichloromethane at 0 °C afforded the cationic allenylidene complex [(triphos)(CO)2Re{CCC(C6H5)(p-C6H4NO2)}]+ (3) as a dark burgundy red triflate salt after solvent evaporation. The reaction of 3 with 1.2 equiv of the phosphine PMePh2 at −40 °C led first to the γ-phosphonioalkynyl complex [(triphos)(CO)2Re{CCCPh(p-C6H4NO2)(PMePh2)}]+ (5) (observed as a pair of distinct rotamers, 5a,b) and then, on slow increase of the temperature to 0 °C, to the α-phosphonioallenyl complex [(triphos)(CO)2Re{C(PMePh2)CCPh(p-C6H4NO2)}]+ (6). On the other hand, the reaction of 3 with the more nucleophilic PMe3 at −60 °C led to its complete transformation into a compound, suggested to be the α-phosphonioallenyl derivative [(triphos)(CO)2Re{C(PMe3)CC(C6H5)(p-C6H4NO2)}]+ (7). To study the effect due to the strongly electron withdrawing p-nitrophenyl substituent on the allenylidene geometry, electronic structure, and reactivity with phosphines, we performed theoretical calculations on 3 and other hypothetical p-nitro-substituted allenylidenes as well as on the products and plausible intermediates of its reaction with PMe3 and PMePh2. Finally, theoretical methods were applied to shed light on the nature of the two rotamers observed for the γ-phosphonioalkynyl complex 5.

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Section: Introductionmentioning

confidence: 99%

Electron-Poor Rhenium Allenylidenes and Their Reactivity toward Phosphines: A Combined Experimental and Theoretical Study

et al. 2011

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“…The parent systems 6 are classic ruthenium precursors for which phosphine dissociation gives entry to a rich catalytic and coordination chemistry, including high-yield routes to catalytically important ,, alkylidene, allenylidene, and vinylidene derivatives. The utility of the catecholate analogue Ru(η 1 ,η 1 - O,O′ -O 2 C 6 H 4 )(PPh 3 ) 3 8 (Scheme b) is limited in comparison, this complex resisting, for example, transformation into vinylidene or benzylidene derivatives .…”

Section: Resultsmentioning

confidence: 99%

“…Soft Lewis acids based on BINO complexes of the late transition metals have the potential to further expand this rich area of opportunity. Advances in group 10-BINO chemistry, particularly by the Gagné group, are notable in this context. , Despite the enormous scope of ruthenium catalysis, , however, Ru derivatives are very recent. The first example, 18-electron Ru(( R )-BINO)( p -cymene) 1 , was reported by Yao, Li, and co-workers in 2008, while our group recently described Ru–BINO catalysts relevant to asymmetric olefin metathesis ( 2 , 3 ; Chart ) .…”

Section: Introductionmentioning

confidence: 94%

A Reactive Ru–Binaphtholate Building Block with Self-Tuning Hapticity

et al. 2011

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A versatile Ru-BINO building block is reported, which offers a straightforward entry point into the chemistry of atropisomeric binaphtholate complexes of ruthenium. Reaction of RuCl(2)(PPh(3))(3)6a with Tl(2)((S)-BINO) affords Ru((S)-BINO)(PPh(3))(2)7 as a mixture of isomers: in 7', the BINO ligand is bound via η(3)-CCO,η(1)-O' donors, and in symmetrical 7″, via η(3)-CCO,η(3)-O'C'C' interactions. The bis(enolate) BINO bonding mode in the latter, not previously observed for any metal, underscores the remarkable geometric and electronic flexibility of the binaphtholate moiety. The BINO ligand proves able to stabilize complexes containing as few as two, and as many as four, additional ligands in 7 and its derivatives, enabling a synthetic versatility that contrasts with that of the superficially similar o-catecholate complex Ru(o-cat)(PPh(3))(3). As with the important achiral Ru precursor 6a, complex 7 undergoes facile transformation into a range of products under mild conditions, including acetonitrile, pyridine, and vinylidene derivatives. Single-crystal X-ray structures are reported for three of these complexes: Ru(η(3),η(3)-(S)-BINO)(PPh(3))(2)7″, Ru(η(3),η(1)-(S)-BINO)(PPh(3))(2)(MeCN) 9, and Ru(η(3),η(1)-(S)-BINO)(PPh(3))(py)(2)11. (13)C{(1)H} NMR signatures are proposed for new and known BINO coordination modes (η(1)-O,η(1)-O'; η(1)-C1,η(1)-O'; η(3)-CCO,η(3)-O'C'C'; η(3)-CCO,η(1)-O'; η(6)-C(6),η(1)-O'), as a potential aid to further developments in late-metal BINO chemistry.

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“…Continuous efforts have been devoted to modify the catalytic properties of these systems by changes in the metal coordination sphere . The cationic 18-electron allenylidene ruthenium complexes of general formula [(η 6 - p -cymene)RuCl(CCCAr 2 )PR 3 ][X] ( 4 ) were also found to promote ring-closing metathesis (RCM) of dienes and enynes, as well as ring-opening metathesis polymerization (ROMP) of strained cycloolefins, thus providing an unprecedented example of the involvement of allenylidenes in alkene metathesis.…”

Section: Introductionmentioning

confidence: 99%

Allenylidene to Indenylidene Rearrangement in Cationicp-Cymene Ruthenium(II) Complexes: Solvent, Counteranion, and Substituent Effects in the Key Step toward Catalytic Olefin Metathesis

et al. 2010

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The reaction of [(η6-p-cymene)RuCl(PCy3)][OTf] with Ph2C(OH)CCH, at rt in benzene-d 6 or in dichloromethane-d 2, affords the allenylidene complex [(η6-p-cymene)RuCl(CCCPh2)PCy3][OTf] ({4a}), which is used in situ as a catalyst for the ring-closing metathesis (RCM) reaction of diallyltosylamide. A kinetic study is performed by 1H NMR spectroscopy in benzene-d 6 and dichloromethane-d 2. The rates of the olefin metathesis process increase with the concentration of the ruthenium complex, but are independent of the olefin concentration, due to rate-determining transformation of the allenylidene complex. The TOF values are higher in benzene-d 6 than in dichloromethane-d 2. The spontaneous or thermally induced transformations of the allenylidene complexes [(η6-p-cymene)RuCl(CCCAr2)PR3][X] (Ar = Ph, X = CF3SO3 −(OTf) ({4a}), BF4 − ({4b}), PF6 − ({4c}), SbF6 − ({4d}) ; X = OTf, Ar = p-MeOC6H4 ({4e}), Ar = p-ClC6H4 ({4f}), Ar = p-FC6H4 ({4g})), prepared in situ from the cationic precursors [(η6-p-cymene)RuCl(PCy3)][X] (X = OTf (8a), BF4 − (8b), PF6 − (8c), SbF6 − (8d) and the propargylic alcohols (4-YC6H4)2C(OH)CCH (Y = H, OMe, Cl, F), are studied by UV−visible spectroscopy by following the disappearance of the allenylidene moiety RuCCCAr2. The allenylidene to indenylidene rearrangement involves attack by the ortho-carbon of the aryl rings to the electrophilic allenylidene Cα, to form an intermediate arenium ion, and H-transfer from aryl to Cβ. Faster rates are observed in benzene than in dichloromethane in all cases. The first-order rate constants, k obs, for complexes 4a−d (Ar = Ph) depend on the counteranion nature and decrease in the order BF4 − > OTf ≫ PF6 − > SbF6 − in benzene, while they are insensitive to the counteranion nature in dichloromethane. Measurements performed at different temperatures afford the activation parameters ΔH ‡ = 22 ± 2 kcal mol−1 and ΔS ‡ = −1 ± 5 cal mol−1 K−1 for complex {4a} at 18−50 °C and ΔH ‡ = 24 ± 1 kcal mol−1 and ΔS ‡ = 1 ± 1 cal mol−1 K−1 for complex {4e} at 25−55 °C. The values of activation entropy, which do not support a rate-determining phosphine dissociation step, and the rate effects of the aryl p-substituents are consistent with an early transition state in the C−C bond forming step of the ring-closing process. Rate differences between benzene and dichloromethane are discussed in terms of counteranion interactions in the less polar aromatic solvent. The rates of the allenylidene transformation affect directly the rates of the RCM reaction, as indicated by parallel solvent, proton, counteranion, and aryl substituent effects in the two processes, thus establishing the role of allenylidene−indenylidene rearrangement in the acid-free olefin metathesis.

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Ruthenium Allenylidenes and Indenylidenes as Catalysts in Alkene Metathesis

Cited by 4 publications

References 68 publications

Electron-Poor Rhenium Allenylidenes and Their Reactivity toward Phosphines: A Combined Experimental and Theoretical Study

Electron-Poor Rhenium Allenylidenes and Their Reactivity toward Phosphines: A Combined Experimental and Theoretical Study

A Reactive Ru–Binaphtholate Building Block with Self-Tuning Hapticity

Allenylidene to Indenylidene Rearrangement in Cationicp-Cymene Ruthenium(II) Complexes: Solvent, Counteranion, and Substituent Effects in the Key Step toward Catalytic Olefin Metathesis

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