Ruthenium Vinyl Research Articles

Multistate Switching of Some Ruthenium Alkynyl and Vinyl Spiropyran Complexes.

To study the switching properties of photochromes, we undertook the synthesis and characterization of several ruthenium organometallic complexes of the type [Ru(Cp*)(dppe)(C≡C-SP)] or [Ru(CO)(dppe)(PPh3)Cl(CH═CH-SP)], where SP = spiropyran. The spectroscopic and electrochemical properties of the complexes were determined by careful cyclic voltammetric and spectroelectrochemical experiments. Whereas the mononuclear alkynyl ruthenium complexes undergo one-electron oxidations localized over the metal alkynyl moiety, the oxidation of the mononuclear vinyl ruthenium complexes is centered on the indoline moiety of the spiropyran. Through these studies, we demonstrate access to several stable redox states, in addition to switching states attained via acidochromism and/or photoisomerization.

Simultaneous Detection of Carbon Monoxide and Viscosity Changes in Cells.

A new family of robust, non‐toxic, water‐compatible ruthenium(II) vinyl probes allows the rapid, selective and sensitive detection of endogenous carbon monoxide (CO) in live mammalian cells under normoxic and hypoxic conditions. Uniquely, these probes incorporate a viscosity‐sensitive BODIPY fluorophore that allows the measurement of microscopic viscosity in live cells via fluorescence lifetime imaging microscopy (FLIM) while also monitoring CO levels. This is the first example of a probe that can simultaneously detect CO alongside small viscosity changes in organelles of live cells.

Simultaneous Detection of Carbon Monoxide and Viscosity Changes in Cells

AbstractA new family of robust, non‐toxic, water‐compatible ruthenium(II) vinyl probes allows the rapid, selective and sensitive detection of endogenous carbon monoxide (CO) in live mammalian cells under normoxic and hypoxic conditions. Uniquely, these probes incorporate a viscosity‐sensitive BODIPY fluorophore that allows the measurement of microscopic viscosity in live cells via fluorescence lifetime imaging microscopy (FLIM) while also monitoring CO levels. This is the first example of a probe that can simultaneously detect CO alongside small viscosity changes in organelles of live cells.

Cp*RuCl-Vinyl Carbenes: Two Faces and the Bifunctional Role in Catalytic Processes.

Ruthenium vinyl carbenes derived from Cp/Cp*RuCl-based complexes (Cp=cyclopentadiene, Cp*=1,2,3,4,5-pentamethylcyclopentadiene) have been routinely invoked as key intermediates in tandem reactions involving a carbene/alkyne metathesis (CAM). A priori, these intermediates resemble the Grubbs-type family of catalysts, but they exhibit a completely different reactivity pattern that few, if any, other catalytic system can reproduce so far. The reactivity of these species with α-unsubstituted and α-substituted alkynals showcases the peculiarities of these intermediates. Although Z-vinyl dihydrooxazines are preferentially obtained with the former, Z-vinyl epoxypyrrolidines are obtained with the latter. A combination of spectroscopic and computational data now prove that a η3 -coordination mode of the ruthenium vinyl carbene and the presence of a Lewis basic chloride ligand give rise to two markedly different stereoelectronic faces, which are responsible for the unconventional reactivity of these species.

Recent Advances in Ruthenium-Catalyzed Carbene/Alkyne Metathesis (CAM) Transformations

Carbene intermediates have shown versatile applications in modern synthetic chemistry. Catalytic ruthenium carbene/alkyne metathesis (CAM) with readily available substrates renders an efficient procedure for the in situ generation of ruthenium vinyl carbene intermediates. Here, recent advances in synthetic applications of ruthenium-catalyzed carbene/alkyne metathesis (CAM) are highlighted.1 Introduction2 Ruthenium Vinyl Carbenes through Carbene/Alkyne Metathesis (CAM)3 Nonpolar Transformations of Ruthenium Vinyl Carbenes4 Polar Transformations of Ruthenium Vinyl Carbenes4.1 Intramolecular Ruthenium-Catalyzed [1,5]- and [1,6]-Hydride Transfer/Cyclization4.2 Heterocyclizations of Alkynals and Alkynones4.3 Heterocyclizations of ortho-(Alkynyloxy)benzylamines5 DFT Studies on the Stereoselectivity of the CAM Reaction6 Conclusions

Oxidized divinyl oligoacene-bridged diruthenium complexes: bridged localized radical characters and reduced aromaticity in bridge cores.

A series of bimetallic ruthenium vinyl complexes 1-5 bridged by oligoacenes were synthesized and characterized in this study. Comparative cyclic voltammetry results from 1-5 indicated that the first oxidation potential decreased gradually with the extension of conjugate ligands. Upon oxidation to singly oxidized species 1+-5+, rather small ν(CO) changes in the infrared (IR) spectra and the characteristic bands of metal-to-ligand charge transfer absorptions in the near IR (NIR) region predicted via time-dependent DFT calculations suggested that strong bridged ligands participate in redox processes. NIR absorptions were not observed in complexes 4+ and 5+ possibly because of instability in their twisted and noncoplanar geometry. Electron paramagnetic resonance results and spin density distribution demonstrated that the bridged localized degrees of 1+-5+ successively increased with the extension of oligoacene from benzene to tetracene. Further comparative analysis of neutral molecules and monocations to the aromaticity and π-electron density of bridge cores indicated a step-by-step transformation process from an aromatic to quinoidal radical upon oxidation.

Synthesis and Application of Ruthenium(II) Alkenyl Complexes with Perylene Fluorophores for the Detection of Toxic Vapours and Gases.

A series of new ruthenium(II) vinyl complexes has been prepared incorporating perylenemonoimide (PMI) units. This fluorogenic moiety was functionalised with terminal alkyne or pyridyl groups, allowing attachment to the metal either as a vinyl ligand or through the pyridyl nitrogen. The inherent low solubility of the perylene compounds was improved through the design of poly-PEGylated (PEG=polyethylene glycol) units bearing a terminal alkyne or a pyridyl group. By absorbing the compounds on silica, vapours and gases could be detected in the solid state. The reaction of the complexes [Ru(CH=CH-PerIm )Cl(CO)(py-3PEG)(PPh3 )2 ] and [Ru(CH=CH-3PEG)Cl(CO)(py-PerIm )(PPh3 )2 ] with carbon monoxide, isonitrile or cyanide was found to result in modulation of the fluorescence behaviour. The complexes were observed to display solvatochromic effects and the interaction of the complexes with a wide range of other species was also studied. The study suggests that such complexes have potential for the detection of gases or vapours that are toxic to humans.

Heterotrimetallic complexes of iron and ruthenium based on vinyliminium dithiocarboxylate ligands

The diiron vinyliminium compounds [Fe2{μ-η1:η3-C(R2) = C(H)C=N(Me)R1}(μ-CO)(CO)(Cp)2]OSO2CF3 (R1 = Xyl = 2,6-C6H3Me2, R2 = Me; R1 = Me, R2 = CO2Me) provide a versatile entry point for many subsequent transformations, such as their reaction with carbon disulfide to provide zwitterionic dithiocarboxylate products. These compounds react with the coordinatively-unsaturated ruthenium vinyl precursors [Ru(CH=CHR3)Cl(CO)(PPh3)2] (R3 = C6H4Me-4, 1-Pyrenyl) to yield heterotrimetallic Fe2Ru compounds, exhibiting vinyl moieties at both iron and ruthenium centres. The emission associated with the pyrenyl unit is enhanced in the diiron vinyliminium ruthenium pyrenyl complex compared to the diethyldithiocarbamate analogue.

Ex Vivo Tracking of Endogenous CO with a Ruthenium(II) Complex.

A two-photon fluorescent probe based on a ruthenium(II) vinyl complex is capable of selectively detecting carbon monoxide in cells and ex vivo using mice with a subcutaneous air pouch as a model for inflammation. This probe combines highly selective and sensitive ex vivo detection of endogenous CO in a realistic model with facile, inexpensive synthesis, and displays many advantages over the widely used palladium-based systems.

Synthetic Applications of Vinyl Ruthenium Carbenes Derived from Diazoalkanes and Alkynes

AbstractRuthenium‐catalyzed C–C bond forming reactions between diazoalkanes and alkynes have gained much attention in recent years due to their unique ways for the formation of various synthetic scaffolds via an electrophilic vinyl ruthenium carbene intermediate. These 16‐electron species are isoelectronic with the Grubbs type ruthenium‐benzylidene catalyst, but their structural geometry and ligand liability make them more innovative in catalytic reactions. Recent advances in this field with respect to vinyl ruthenium carbenes and their coupling partners, thus leading to a step‐economical access to versatile molecular architectures, are discussed herein in a sustainable manner.magnified image

Polyelectrochromic Vinyl Ruthenium-Modified Tritylium Dyes

A series of four mononuclear and one dinuclear ruthenium styryl complexes with redox active triarylmethylium ligands were prepared. All new compounds were characterized by NMR spectroscopy, MS spectrometry, cyclic voltammetry, and in various oxidation states by IR and UV/vis/NIR and EPR spectroscopy. The increase in conjugation length by the introduction of the vinyl ruthenium entity pushes the electronic absorption to low energy, almost into the near-infrared region. Electrochemical and spectroscopic properties are strongly influenced by the para substituents at the triarylmethylium ligands. The complexes were characterized in up to four different oxidation states up to the trication level and show pronounced electrochromism. The oxidized mixed-valent diruthenium complex 52+ shows a moderate degree of charge and spin delocalization over the styryl ruthenium sites.

2 + 1] Cycloaddition of Catalytic Ruthenium Vinyl Carbenes: A Stereoselective Controlled Access to (Z)- and (E)-Vinyl Epoxypyrrolidines

Aza-alkynals undergo a cyclization reaction with diazo compounds in the presence of catalytic amounts of Cp*RuCl(cod) to afford vinyl epoxypyrrolidines, valuable building blocks for the synthesis of biologically active molecules. Ruthenium vinyl carbene intermediates have been invoked to explain the overall [2 + 1] cycloaddition (epoxy-annulation reaction). The reaction proceeds under mild conditions and in short reaction times (5–80 min) with complete (Z)- or (E)-stereoselectivity on the vinyl substituent, depending on the nature of the diazo compound used. Theoretical calculations support a mechanistic rationale to explain this controlled process.

Isolation of ruthenium formyl complexes: Insight into the metal-mediated cleavage reaction of carbon-carbon triple bond

We describe a simple and efficient ruthenium-catalyzed reaction in which propargylic alcohol HCCC(Ph)2OH is split into carbon monoxide CO, formaldehyde H2CO and ketone (Ph)2CO via cleavage of carbon-carbon triple and single bonds. A plausible reaction mechanism is proposed on the basis of ruthenium vinyl and formyl intermediates

Tuning the molecular weight of ROMP polymers by using Grubbs type catalysts and terminal alkynes

In this study, ruthenium vinyl carbene derivatives were obtained in situ by reacting Grubbs 1st and 2nd generation catalysts with terminal alkynes in toluene at 85 °C. These active species were used in ROMP of norbornene derivatives. The effect of alkyne/Ru (mol/mol) ratio and alkyne substituent on number average molecular weights (Mn) of ROMP polymers were investigated in detail. ROMP polymers with Mn values between 75 and 680 kDa were synthesized by varying alkyne/Ru (mol/mol) ratio in the presence of Grubbs type catalysts. The mechanism of the reaction and the role of alkyne in ROMP reactions were investigated in detail by 1H NMR.

DFT and Kinetic Monte Carlo Study of TMS-Substituted Ruthenium Vinyl Carbenes: Key Intermediates for Stereoselective Cyclizations

Mechanistic pathways for the cyclization of 1,5-alkynylacetal with N2CHTMS in the presence of Cp- and Cp*RuCl(cod) to afford (Z)- and (E)-(trimethylsilyl)vinyl spiroacetals have been calculated. Calculations show the presence of three conformers in equilibrium for the initially formed ruthenium carbenes. Differences in the stabilities and reactivities of the conformers, depending on the use of a Cp or Cp* ruthenium catalyst, are responsible for the favorable active reaction pathways in each case, even though the geometry of the resulting product is the same regardless of the catalyst used. Kinetic Monte Carlo (KMC) simulations with rate coefficients, including tunneling probabilities for the hydride transfer step, were used to model the evolution of reactants, intermediates, and products for all calculated pathways. It was shown that one path is almost exclusively active for each catalyst. Finally, the energetic span model of Kozuch and Shaik was used to calculate the energetic span (δE), the TOF-determining transition state (TDTS), the TOF-determining intermediate (TDI), and the TOF value for each of the feasible mechanistic pathways.

Synthesis and characterization of binuclear ruthenium vinyl complexes: effect of transannular substituents on their optoelectronic properties

A series of substituted dithia[3.3]paracyclophane-bridged binuclear ruthenium vinyl complexes have been synthesized by insertion reactions of [RuHCl(CO)(PPh3)3] with the appropriate dialkynes. The products have been characterized by physico-chemical and spectroscopic methods. In addition, the structure of one complex has been determined by X-ray crystallography. Electrochemical studies have shown that all of the substituted complexes exhibit smaller ΔE values relative to the unsubstituted complex. Photoluminescence studies indicated that all of the examined substituent groups act as “quenchers,” except for the methoxy group.

ChemInform Abstract: Nucleophilic Addition of Amines to Ruthenium Carbenes: ortho‐(Alkynyloxy)benzylamine Cyclizations Towards 1,3‐Benzoxazines.

A new ruthenium-catalyzed cyclization of ortho-(alkynyloxy)benzylamines to dihydro-1,3-benzoxazines is reported. The cyclization is thought to take place via the vinyl ruthenium carbene intermediates which are easily formed from [Cp*RuCl(cod)] and N2CHSiMe3. The mild reaction conditions and the efficiency of the procedure allow the easy preparation of a broad range of new 2-vinyl-2-substituted 1,3-benzoxazine derivatives. Rearrangement of an internal C(sp) in the starting material into a tetrasubstituted C(sp3) atom in the final 1,3-benzoxazine is highly remarkable.

Open-chain and crown ether-substituted bimetallic ruthenium vinyl complexes: synthesis, characterization, and electrochemical studies

Two open-chain and closed-crown ether-substituted binuclear ruthenium vinyl complexes (E,E)-[{(PMe3)3-(CO)ClRu}2(μ-HC=CH–Ar–CH = CH)], in which the 1,4-diethenylphenylene bridge bears two different crown groups at the 2,3-positions, have been prepared and characterized by spectroscopic methods and by cyclic voltammetry. In addition, the X-ray crystal structure of complex 7a was determined. The electrochemical studies showed that both complexes undergo two successive one-electron oxidation processes, and the closed-crown complex better stabilized the mixed valence bimetallic ruthenium complex.

Nucleophilic Addition of Amines to Ruthenium Carbenes: ortho‐(Alkynyloxy)benzylamine Cyclizations towards 1,3‐Benzoxazines

AbstractA new ruthenium‐catalyzed cyclization of ortho‐(alkynyloxy)benzylamines to dihydro‐1,3‐benzoxazines is reported. The cyclization is thought to take place via the vinyl ruthenium carbene intermediates which are easily formed from [Cp*RuCl(cod)] and N2CHSiMe3. The mild reaction conditions and the efficiency of the procedure allow the easy preparation of a broad range of new 2‐vinyl‐2‐substituted 1,3‐benzoxazine derivatives. Rearrangement of an internal C(sp) in the starting material into a tetrasubstituted C(sp3) atom in the final 1,3‐benzoxazine is highly remarkable.

Nucleophilic addition of amines to ruthenium carbenes: ortho-(alkynyloxy)benzylamine cyclizations towards 1,3-benzoxazines.

A new ruthenium-catalyzed cyclization of ortho-(alkynyloxy)benzylamines to dihydro-1,3-benzoxazines is reported. The cyclization is thought to take place via the vinyl ruthenium carbene intermediates which are easily formed from [Cp*RuCl(cod)] and N2 CHSiMe3 . The mild reaction conditions and the efficiency of the procedure allow the easy preparation of a broad range of new 2-vinyl-2-substituted 1,3-benzoxazine derivatives. Rearrangement of an internal C(sp) in the starting material into a tetrasubstituted C(sp(3) ) atom in the final 1,3-benzoxazine is highly remarkable.