Ruthenium Allenylidene Complexes Research Articles

Syntheses, characterizations and structures of ruthenium carbene and allenylidene complexes supported by 1,4,7-trimethyl-1,4,7-triazacyclononane (Me3tacn) ligands

Treatment of ruthenium(II) precursor [(Me3tacn)Ru(dmso)Cl2] (Me3tacn = 1,4,7-trimethyl-1,4,7-triazacyclononane, dmso = dimethylsulfoxide) (1) with concentrated HCl in the presence of air afforded the ruthenium(III) complex [(Me3tacn)RuCl3·H2O] (2), from which a series of bipyridine-ruthenium(II) complexes [(Me3tacn)Ru(R-bpy)(H2O)](PF6)2 (bpy = 2,2′-bipyridine) was obtained according to our previous work. Reactions of [(Me3tacn)Ru(R-bpy)(H2O)](PF6)2 and 1,1-diphenylpropargyl alcohol afforded ruthenium(II) methoxycarbene complexes [(Me3tacn)(R-bpy)Ru=C(OMe)CHCPh2](PF6)2 (R = H,3; 4,4′-Me2, 5; 5,5′-Me2, 7; 4,4′-di-tBu, 9) and ruthenium(II) allenylidene complexes [(Me3tacn)(R-bpy)Ru=C=CCPh2](PF6)2 (R = H,4; 4,4′-Me2, 6; 5,5′-Me2, 8; 4,4′-di-tBu, 10) under different solvent conditions. Complexes 3‒10 were well characterized by infrared, UV/Vis, mass spectrometry, and NMR spectroscopies. The molecular structures of complexes 5, 7, and 8 have been also established by single-crystal X-ray diffraction.

Hexa-peri-hexabenzocoronene decorated with an allenylidene ruthenium complex - almost a flyswatter.

Carbon-rich ruthenium allenylidene complexes bearing either a hexaarylbenzene (HAB) or a hexa-peri-hexabenzocoronene (HBC) substituent were synthesised. This was achieved via the corresponding propargyl alcohols with HAB and HBC substituents, which were accessible via 3 or 4 step reaction cascades. Reaction of the propargyl alcohols HC[triple bond, length as m-dash]C(OH)Ph(HAB) and HC[triple bond, length as m-dash]C(OH)Ph(HBC) with [RuCl(η5-C5H5)(PPh3)2] yielded the complexes [Ru(η5-C5H5)([double bond, length as m-dash]C[double bond, length as m-dash]C[double bond, length as m-dash]C(HAB)(Ph))(PPh3)2]PF6 and [Ru(η5-C5H5)([double bond, length as m-dash]C[double bond, length as m-dash]C[double bond, length as m-dash]C(HBC)(Ph))(PPh3)2]PF6. The latter of which shows interesting π-π-stacking behaviour in the solid state as well as aggregation in solution.

Carbon-rich cyclopentadienyl ruthenium allenylidene complexes

Ruthenium allenylidene complexes based on carbon-rich polyaromatic moieties have been synthesized with interesting intermolecular π-interactions.

ChemInform Abstract: Recent Advances in Catalytic Stereocontrolled Cycloaddition with Terminal Propargylic Compounds

AbstractReview: [30 refs.

Recent Advances in Catalytic Stereocontrolled Cycloaddition with Terminal Propargylic Compounds

Terminal propargylic compounds containing an alkyne unit and an alcohol or ester group in the propargylic position have a fairly acidic acetylenic hydrogen atom; this makes them versatile substrates for further chemical transformation. Some transition metals such as ruthenium or copper exhibit specific affinity for terminal propargylic compounds, generating dielectrophilic ruthenium– or copper–allenylidene complexes that show high potential for stereoselective cycloaddition with various bis-nucleophiles. In this review, we highlight this emerging field of catalytic stereoselective cycloaddition with terminal propargylic compounds. Examples of ruthenium-, copper-, palladium-, and gold-catalyzed cycloaddition are given in the article, along with mechanistic considerations. 1 Introduction 2 Ruthenium–Allenylidene Complexes in Enantioselective Cycloaddition 3 Copper–Allenylidene Complexes in Enantioselective Cycloaddition 4 Palladium–π-Propargyl Complexes in Stereoselective Cycloaddition 5 Gold–Carbenoid Complexes in Stereoselective Cycloaddition 6 Summary and Outlook

Carbon-Rich Ruthenium Allenylidene Complexes Bearing Heteroscorpionate Ligands

A series of ruthenium allenylidene complexes bearing polyaromatic substituents have been prepared starting from [Ru(bdmpza)Cl(PPh3)2] (1) (bdmpza = bis(3,5-dimethylpyrazol-1-yl)acetato). Reacting 1 with 1,1-bis(3,5-di-tert-butylphenyl)-1-methoxy-2-propyne results in the formation of two structural isomers of an allenylidene complex [Ru(bdmpza)Cl(═C═C═C(PhtBu2)2)(PPh3)] (5A/5B), as well as the related carbonyl complex [Ru(bdmpza)Cl(CO)(PPh3)] (4A/4B). Conversion of 9-ethynyl-9-fluorenol leads to the corresponding allenylidene complex [Ru(bdmpza)Cl(═C═C═(FN))(PPh3)] (7A/7B) (FN = fluorenyl). Based on anthraquinone, a new synthetic route toward 10-ethynyl-10-hydroxyanthracen-9-one via the trimethylsilyl-protected propargyl alcohol is described, and subsequent conversion of this compound to the allenylidene complex ([Ru(bdmpza)Cl(═C═C═(AO))(PPh3)] (12A/12B) (AO = anthrone) is reported. The synthetic route from 7H-benzo[no]tetraphen-7-one to the propargyl alcohol 7-ethynyl-7H-benzo[no]tetraphen-7-ol is described, which is followed by the transformation into the allenylidene complex [Ru(bdmpza)Cl(═C═C═(BT))(PPh3)] (17A/17B) (BT = benzotetraphene). The molecular structures of 4B, 7A, 7B, 12A, 12B, 13A, and 17A have been characterized by single-crystal X-ray crystallography, and these analyses suggest that 17A might function as a “metal-tuned organic field effect transistor”. The electrochemical properties of the allenylidene complexes have been studied via cyclic voltammetry, and time-dependent DFT calculations have been conducted to assign weak absorptions in the NIR region to forbidden MLCT transitions.

Diastereoselective Attack on Chiral-at-Metal Ruthenium Allenylidene Complexes To Give Alkynyl Complexes

New chiral ruthenium(II) allenylidene complexes were synthesized, and their reactivity with nucleophiles to give alkynyl complexes was investigated. The new allenylidene complex (RRu,Rax)-[Ru(Ind)(PPh3)(6){═C═C═C(t-Bu)(2-naphthyl)}]+PF6– was synthesized from the chloro precursor complex (RRu,Rax)-[RuCl(Ind)(PPh3)(6)] and the racemic propargylic alcohol HC≡CC(OH)(t-Bu)(2-naphthyl) and obtained in 96% yield, where (Rax)-6 is a chiral phosphoramidite and Ind an anionic indenyl ligand. The precursor and the allenylidene complex are chiral-at-metal, and the chiral information is completely transferred from the chloro precursor to the product allenylidene complex, both of which show the same absolute configuration, as demonstrated by X-ray diffraction. Together with the known allenylidene complex (RRu,Rax)-[Ru(Ind)(PPh3)(6)(═C═C═CPh2)]+PF6–, the attack of n-BuLi, MeLi, LiC≡CPh, and lithium 1-phenylethenolate nucleophiles on the allenylidene chain of (RRu,Rax)-[Ru(Ind)(PPh3)(6){═C═C═C(t-Bu)(2-naphthyl)}]+PF6– wa...

Etherification reactions of propargylic alcohols catalyzed by a cationic ruthenium allenylidene complex

The cationic ruthenium allenylidene complex RRuRax−[Ru(indenyl)L(PPh3)CCCPh2]+PF6 catalyzes the etherification of secondary and tertiary propargylic alcohols in a formal nucleophilic substitution reaction utilizing primary and secondary alcohols as the nucleophiles. At a catalyst loading of only 1.1mol%, the corresponding propargylic ether products were obtained in 9 to 73% isolated yields (18h reaction time at 100°C); no further additives are required. The reaction exhibits an induction period; as shown by a control reaction, the high reaction temperature may chemically change the allenylidene complex to be employed as the catalyst but does not lead to catalyst deactivation.

Allenylidene Complexes Based on Pentacenequinone

Stable ruthenium–allenylidene complexes based on pentacenequinone have been synthesized. The complexes show an electronic absorption in the NIR region that arises from forbidden MLCT transitions, as explained by DFT calculations. The crystal structure reveals promising features for the formation of metal-influenced organic FETs.

Reactions of Ruthenium-Allenylidene Complexes Tethering a Cyclopropyl Group

Two cyclopropyl allenylidene complexes [Ru]=C=C=C(R)(C(3)H(5)) ([Ru]=[RuCp(PPh(3))(2)], Cp=Cyclopentadienyl; R=thiophene (2a) and R=Ph (2b)) are prepared from the reactions of [Ru]Cl with the corresponding 1-cyclopropyl-2-propyn-1-ol in the presence of KPF(6). Thermal treatment, halide-anion addition, and palladium-catalyzed reactions of 2a and 2b all lead to a ring expansion of the cyclopropyl group, giving the vinylidene complexes 4a and 4b, respectively, each with a five-membered ring. This ring expansion proceeds by C-C bond formation between Cβ of the cumulative double bond and a methylene group of the cyclopropyl ring. In the reaction of 2a with pyrrole, consecutive formation of two C-C bonds, one between C-2 of pyrrole and Cγ of 2a and the other between C-3 of pyrrole and Cα, results in the formation of 6a. The reaction proceeds by addition of pyrrole and 1,3-proton shifts. The hydrogenation of 2a by NaBH(4) is carried out in different solvents. The cumulative double bonds are reduced regioselectively to give a mixture of 7a and 8a. Interestingly, use of different solvents leads to different ratios of 7a and 8a. Presence of a protic solvent like methanol in dichloromethane or chloroform solution increases the yield of 8a, thus revealing that both the rates of hydroboration and deboronation increase. The structures of two new complexes 4a and 6a have been firmly established by X-ray diffraction analysis.

Synthesis and Structural Characterization of a Series of New Chiral‐at‐Metal Ruthenium Allenylidene Complexes

AbstractNew chiral‐at‐metal ruthenium indenyl PPh3 phosphoramidite allenylidene complexes have been synthesized and structurally characterized. Through thermal ligand‐exchange reactions with [RuCl(Ind)(PPh3)2], the phosphoramidite ligands (R)‐binol‐N,N‐dimethylphosphoramidite (5a), (R)‐binol‐N,N‐dibenzylphosphoramidite (5b), (R,S)‐binol‐N‐benzyl‐N‐α‐methylbenzylphosphoramidite (5c), and (R)‐catechol‐2‐methylpyrrolidinephosphoramidite [(R)‐10] were converted into the complexes [RuCl(Ind)(PPh3)(L)] [L = 5a, 79 %; 5b, 87 %; 5c, 80 %, (R)‐10, 67 %]. The complexes [RuCl(Ind)(PPh3)(5b)] and [RuCl(Ind)(PPh3)(5c)] were obtained diastereomerically pure and, by reaction with propargylic alcohols, subsequently converted into the allenylidene complexes [Ru(Ind)(PPh3)(5b)(=C=C=CRR′)]+ PF6– (R = R′ = Ph, 85 %; R = Ph, R′ = Me, 66 %; R = 2‐furyl, R′ = Me, 94 %; R = R′ = 4‐fluorophenyl, 76 %; R = 4‐methoxyphenyl, R′ = Me, 66 %) and [Ru(Ind)(PPh3)(5c)(=C=C=CRR′)]+ PF6– (R = R′ = Ph, 91 %; R = Ph, R′ = Me, 72 %; R = 2‐furyl, R′ = Me, 93 %), which were also obtained diastereomerically pure. Complex [RuCl(Ind)(PPh3)(5b)] and three of the new allenylidene complexes were characterized structurally, which showed that the chiral information was transferred from the precursor complex to the corresponding allenylidenes. Dynamic NMR experiments showed that during the synthesis of allenylidene complexes only one diastereomer was formed. The research presented herein has an impact on the chemistry of chiral allenylidene complexes as catalysts and as potential intermediates in propargylic substitution reactions.

Cyclization Accompanied with 1,2-Phenyl Migration in the Protonation of Ruthenium Acetylide Complex Containing an Allenyl Group

Reaction of the ruthenium allenylidene complex [Ru]═C═C═CPh2 (1, [Ru] = Cp(PPh3)2Ru) with the propargylic Grignard reagent R-C≡CCH2MgBr (R = CH3, CH2CH3, Ph) yielded a mixture of two acetylide complexes. The major products, [Ru]C≡CCPh2C(R)═C═CH2 (2a, R = CH3; 2b, R = CH2CH3; 2c, R = Ph), have an allenyne moiety, and the minor ones, [Ru]C≡CCPh2CH2C≡CR (3a, R = CH3; 3b, R = CH2CH3; 3c, R = Ph), have a diyne ligand. The reaction of similar propargyl Grignard reagent HC≡CCH2MgBr with 1 yielded only the diyne complex 3d. Treatment of complexes 2a−2c with HBF4 afforded the cyclization complexes 5a−5c, respectively, proceeding via a vinylidene intermediate. The cyclization of the allenyl and the vinylidene groups is accompanied with a phenyl group migration. Complex 5b is fully characterized by a single-crystal X-ray diffraction analysis. Similar cyclization of complexes 2a and 2b, catalyzed by a Au phosphine complex, gave the ruthenium vinylidene complexes 6a and 6b, respectively, with different selectivity from that of the protonation reaction. Au-catalyzed cyclization of the diyne complex 3d yielded 6d, which is fully characterized by a single-crystal X-ray diffraction analysis.

ChemInform Abstract: Development of Novel Catalytic Reactions via Ruthenium—Allenylidene Complexes as Key Intermediates

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Ruthenium-Catalyzed Enantioselective Intramolecular Propargylation of Thiophenes with Propargylic Alcohols

Ruthenium-catalyzed enantioselective cyclization of propargylic alcohols bearing a thiophene moiety affords the corresponding propargylated thiophenes in good to high yields with a high enantioselectivity (up to 97% ee). This catalytic reaction is proposed to proceed via chiral ruthenium-allenylidene complexes as key intermediates.

ルテニウム-アレニリデン錯体を鍵中間体として経由する新規触媒反応の開発

Our recent studies on catalytic reactions via ruthenium-allenylidene complexes are reviewed from the viewpoint of organic synthesis. Thiolate-bridged diruthenium complexes work as efficient catalysts to promote a variety of novel organic transformations, especially propargylic substituion reactions, via allenylidene complexes as key intermediates. The asymmetric version of these reactions is also described together with some mononuclear ruthenium complex-catalyzed related reactions by other groups.

A DFT Study on the Reaction Pathways for CarbonCarbon Bond‐Forming Reactions between Propargylic Alcohols and Alkenes or Ketones Catalyzed by Thiolate‐Bridged Diruthenium Complexes

The reaction pathways of two types of the carbon-carbon bond-forming reactions catalyzed by thiolate-bridged diruthenium complexes have been investigated by density-functional-theory calculations. It is clarified that both carbon-carbon bond-forming reactions proceed through a ruthenium-allenylidene complex as a common reactive intermediate. The attack of pi electrons on propene or the vinyl alcohol on the ruthenium-allenylidene complex is the first step of the reaction pathways. The reaction pathways are different after the attack of nucleophiles on the ruthenium-alkynyl complex. In the reaction with propene, the carbon-carbon bond-forming reaction proceeds through a stepwise process, whereas in the reaction with vinyl alcohol, it proceeds through a concerted process. The interactions between the ruthenium-allenylidene complex and propene or vinyl alcohol have been investigated by applying a simple way of looking at orbital interactions.

A ruthenium(II) allenylidene complex with a 4,5-diazafluorene functional group: A new building-block for organometallic molecular assemblies

The synthesis of the new ruthenium(II) allenylidene complex [ClRu(dppe) 2 C C C 11H 6N 2][OTf] ( 4) (dppe = 1,2-bis(diphenylphosphino)ethane) terminated with a 4,5-diazafluorene ligand is reported. Further coordination of that metal allenylidene to ruthenium and rhenium moieties leads to the bimetallic adducts [ClRu(dppe) 2 C C C 11H 6N 2{Ru(bpy) 2}][B(C 6F 5) 4] 3 ( 5a), [ClRu(dppe) 2 C C C 11H 6N 2{Ru( t Bu-bpy) 2}][PF 6] 3 ( 5b) and [ClRu(dppe) 2 C C C 11H 6N 2{Re(CO) 3Cl}][OTf] ( 6). Their optical and electrochemical properties show that the allenylidene moiety is an attractive molecular clip for the access to larger original redox-active homo/heteronuclear multi-component supramolecular assemblies. The X-ray crystal structure of the allenylidene metal building block is also described.

Ruthenium Carbene, Vinylidene, and Allenylidene Complexes with a Bis(3,5-dimethylpyrazol-1-yl)acetato Heteroscorpionate Ligand

A series of neutral ruthenium(II) carbonyl, carbene, vinylidene, and allenylidene complexes [Ru(bdmpza)(Cl)(L)(PPh3)] (L = C(OR‘)R, CCHR, CCCR2, CO) containing the bis(3,5-dimethylpyrazol-1-yl)acetato (bdmpza) ligand, an N,N,O heteroscorpionate ligand, have been prepared. Treatment of [Ru(bdmpza)(Cl)(PPh3)2] (1a) with a variety of alkynes HC⋮CR (R = Ph, Tol, Pr, Bu) afforded the vinylidene complexes [Ru(bdmpza)(Cl)(CCHR)(PPh3)] (2a−d). The carbonyl complex [Ru(bdmpza)(Cl)(CO)(PPh3)] (3) is formed via oxidative or acid-induced degradation pathways from the vinylidene complexes. Reaction of 1a with the hydroxy-functionalized alkynes HC⋮C(CH2)nOH (n = 2, 3) yielded the cyclic Fischer type carbene complexes (4a) and (4b). The ruthenium(II) allenylidene complexes [Ru(bdmpza)(Cl)(CC CR2)(PPh3)] (5a, R = Ph; 5b, R = Tol) were prepared by the reaction of 1a with propargyl alcohols HC⋮CC(R)2OH via the vinylidene intermediates [Ru(bdmpza)(Cl)(CCHCR2OH)(PPh3)]. X-ray crystal structures of one structural isomer of the vinylidene complex [Ru(bdmpza)(Cl)(CCHTol)(PPh3)] (2b), the carbonyl complex [Ru(bdmpza)(Cl)(CO)(PPh3)] (3), the carbene complex (4b-I), and two structural isomers of [Ru(bdmpza)(Cl)(CCCPh2)(PPh3)] (5a-I and 5a-II) are reported.

Ruthenium‐Catalyzed Propargylation of Aromatic Compounds with Propargylic Alcohols

AbstractReactions of propargylic alcohols bearing a terminal alkyne moiety with aromatic compounds in the presence of a catalytic amount of thiolate‐bridged diruthenium complexes give the corresponding propargylated aromatic compounds in high yields with complete selectivity. Intramolecular reactions of propargylic alcohols bearing an aromatic moiety proceed smoothly to afford the cyclized products in high yields with complete selectivity. The stoichiometric reaction of the ruthenium–allenylidene complex [Cp*RuCl(μ2‐SMe)2RuCp*(=C=C=CHPh)]BF4 (Cp* = η5‐C5Me5) with 10 equiv. 2‐methylfuran results in the formation of 2‐methyl‐5‐(1‐phenyl‐2‐propynyl)furan in 34 % yield, indicating that these catalytic reactions proceed via ruthenium–allenylidene intermediates. The reaction is considered to be an electrophilic substitution of aromatic compounds by the ruthenium‐stabilized propargyl cation. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

Ruthenium-Catalyzed Novel Carbon-Carbon Bond Forming Reactions via Ruthenium-Allenylidene Complexes

Our recent studies on novel carbon-carbon bond forming reactions using propargylic alcohols catalyzed only by thiolate-bridged diruthenium complexes are reviewed from the viewpoint of organic synthesis. The reactions are substitutions of hydroxyl group of the alcohols with a variety of carbon-centered nucleophiles such as simple ketones, cyclic 1,3-dicarbonyl compounds, aromatic and heteroaromatic compounds, phenols, naphthols, and alkenes. The asymmetric version of propargylic alkylation with acetone is also described. All of the reactions are considered to proceed via ruthenium-allenylidene complexes as key intermediates.