Ruthenium Precursor Research Articles

Influence of ruthenium precursor on catalytic activity of Ru/Al2O3 catalyst in selective isomerization of linoleic acid to cis-9,trans-11- and trans-10,cis-12-conjugated linoleic acid

Selective double bond isomerization of linoleic acid to cis-9,trans-11-conjugated linoleic acid and trans-10,cis-12-conjugated linoleic acid (CLA) was performed batchwise under kinetic control at 165°C in an n-decane solution. Commercial H2-preactivated Ru/Al2O3 catalyst (6.19wt.% Ru) and two H2-preactivated Ru/Al2O3 catalyst samples that were prepared by incipient wetness impregnation of γ-Al2O3 with two different precursors of ruthenium, i.e. ruthenium(III) chloride trihydrate (RuCl3·3H2O, 3.27wt.% Ru) and ruthenium(III) acetylacetonate (Ru(acac)3, 2.97wt.% Ru), were investigated to study the effect on catalytic activity and isomerization selectivity of residues remaining on the catalyst surface from the impregnation step. Catalyst characterization was done by nitrogen adsorption, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy–energy dispersive X-ray analysis (SEM–EDX), and temperature programmed desorption of hydrogen techniques. Impregnation of γ-Al2O3 with ruthenium(III) acetylacetonate resulted in a remarkably higher selectivity towards the desired cis-9,trans-11- and trans-10,cis-12-conjugated linoleic acid isomers compared to that shown by impregnation of γ-Al2O3 with ruthenium(III) chloride trihydrate.

The capacitive performance of activated carbon–ruthenium oxide composites for supercapacitors: effects of ultrasonic treatment in NaOH and annealing in air

The utilization of electrode materials could be greatly promoted by the employment of a mesh-type stainless steel (SS) current collector in comparison with a plate-type one. The capacitive behavior of activated carbon (AC) and AC–ruthenium (AC–Ru) composites fabricated by the wet impregnation were systematically investigated in 0.1 M H 2SO 4 by cyclic voltammetry (CV) and chronopotentiometry (CP). The specific capacitance of AC reached a maximum (ca. 117 F g −1) through a combination of the impregnation of ruthenium precursors and the chemical conversion of the chloride precursors into hydroxides in an ultrasonic bath of NaOH for 30 min (AC–Ru(OH) x ). The stability of AC–Ru(OH) x composites was greatly promoted by annealing in air at 240 °C although a significant loss in total capacitance was found. The crystalline information and chemical environment of the impregnated oxy-hydroxyl-Ru species with annealing was, respectively, obtained from the X-ray diffraction (XRD) patterns and X-ray photoelectron spectra (XPS). The specific surface area and pore size distribution of these composites were analyzed by the Brunauer–Emmett–Teller (BET) method.

Dispersion and Distribution of Ruthenium on Carbon-Coated Ceramic Monolithic Catalysts Prepared by Impregnation

Carbon-coated monolithic catalysts were prepared by dipcoating a cordierite substrate in a Furan resin, after which the ruthenium was incorporated by impregnation with a [RuCl5]2- complex. Immobilization of the precursor proceeded particularly via weak physisorption. Since the carbon-coated monolithic supports have a broad pore-size distribution, redistribution of the ruthenium precursor occurred upon drying due to capillary forces, resulting in low dispersion. A significant amount of ruthenium is present on the surface of the carbon inclusions located deep in the cordierite walls, making the diffusion path of the reactants to the active ruthenium sites considerably larger than the average carbon-coating thickness. For successful application of the carbon-coated monolithic catalysts in gas–liquid reactions, the deposition of carbon in the walls of the monolith should be prevented and maldistribution of ruthenium upon drying should be solved.

Templated synthesis of a rotaxane with a [Ru(diimine)3]2+ core.

A rotaxane containing a ruthenium bisphenanthroline complex, acting as an axis, and a macrocycle incorporating a 2,2'-bipyridine (bpy) unit, threaded by the axis, has been synthesized. The bisphenanthroline ligand is such that its ruthenium(II) complexes possess a clearly identified axis, making such compounds ideal components of rotaxanes constructed around an octahedral ruthenium(II) center, which serves as a template. The ring is threaded by the axial ruthenium(II) precursor complex, to afford the corresponding pseudorotaxane in moderate yield. The X-ray structure analysis of this compound reveals the threaded nature of the complex. The length of the threaded ring (35 atoms in the periphery) is too short to allow easy threading of the axis through the macrocycle. As a consequence, an isomer is also obtained for which the axial ruthenium complex is attached in an exo fashion. (1)H NMR studies have been carried out, which reveal various conformational equilibria for the pseudorotaxane. Light-induced decoordination of the bpy-containing cyclic fragment was shown to be quantitative and to lead to the free ring and the axial ruthenium(II) complex, regardless of the starting compound (pseudorotaxane or exo isomer). Finally, the real rotaxane could be prepared, although it could not be separated from its exo isomer.

Synthesis and Characterization of the First Carbene Derivative of a Polyoxometalate

Reaction of the Keggin-type polyanion [PW11O39]7- with the tetrakis-carbene ruthenium precursor [RuLMe4Cl2] (LMe = 1,3-dimethylimidazolidine-2-ylidene), in water, results in the formation of Na4K9[(PW9O34)2(cis-WO2)(cis-RuLMe2)].23H2O, which is the first carbene derivative of a polyoxometalate. The oxidation state of the ruthenium is confirmed by XANES experiments.

Ammonia decomposition over the carbon-based ruthenium catalyst promoted with barium or cesium

Carbon-supported ruthenium catalysts promoted with Ba or Cs were studied in ammonia decomposition. Under the experimental conditions ( p=1 bar, H 2:N 2=3:1, 5–50% NH 3, 370–400 °C), the reaction rates over Cs–Ru/carbon were found to be higher than those over Ba–Ru/carbon, the difference being larger for the high dispersion samples. The effect of the ruthenium precursor (carbonyl, chloride) proved to be unessential for the activity. At 20% NH 3 (400 °C), TOF of NH 3 decomposition over Cs–Ru/carbon was about 3×10 2 times higher than for K–Fe/carbon, both based on H 2 chemisorption. The apparent activation energies of 134 and 158 kJ/mol were determined for Cs–Ru/carbon and Ba–Ru/carbon, respectively. The temperature-programmed desorption studies revealed that the amount of nitrogen desorbed from Ba–Ru/carbon was much smaller and the peak position was shifted to higher temperatures when compared to Cs–Ru/carbon. The promoting mechanism of both Ba and Cs is discussed.

New Tandem Catalysis: Preparation of Cyclic Enol Ethers Through a Ruthenium‐Catalyzed Ring‐Closing Metathesis—Olefin Isomerization Sequence.

Tandem reactions that proceed with a single metal catalyst precursor offer novel opportunities for developing efficient new reaction sequences. In this regard, reaction conditions have been identified that allows for a tandem ring-closing metathesis−olefin isomerization sequence catalyzed by a common ruthenium precursor. Specifically, the tandem process generates cyclic enol ethers from a variety of readily available acyclic dienes in a single reaction vessel using Grubbs' ruthenium alkylidene.

First example of mu(3)-sulfido bridged mixed-valent triruthenium complex triangle Ru(III)(2)Ru(II)(O,O-acetylacetonate)(3)(mu-O,O,gamma-C-acetylacetonate)(3)(mu(3)-S) (1) incorporating simultaneous O,O- and gamma-C-bonded bridging acetylacetonate units. Synthesis, crystal structure, and spectral and redox properties.

The reaction of mononuclear ruthenium precursor [Ru(II)(acac)(2)(CH(3)CN)(2)] (acac = acetylacetonate) with the thiouracil ligand (2-thiouracil, H(2)L(1) or 6-methyl -2-thiouracil, H(2)L(2)) in the presence of NEt(3) as base in ethanol solvent afforded a trinuclear triangular complex Ru(3)(O,O-acetylacetonate)(3)(mu-O,O,gamma-C-acetylacetonate)(3)(mu(3)-sulfido) (1). In 1, each ruthenium center is linked to one usual O,O-bonded terminal acetylacetonate molecule whereas the other three acetylacetonate units act as bridging functions: each bridges two adjacent ruthenium ions through the terminal O,O-donor centers at one end and via the gamma-carbon center at the other end. Moreover, there is a mu(3)-sulfido bridging in the center of the complex unit, which essentially resulted via the selective cleavage of the carbon-sulfur bond of the thiouracil ligand. In diamagnetic complex 1, the ruthenium ions are in mixed valent Ru(III)Ru(III)Ru(II) state, where the paramagnetic ruthenium(III) ions are antiferromagnetically coupled. The single crystal X-ray structure of 1 showed two crystallographically independent C(3)-symmetric molecules, Ru(3)(O,O-acetylacetonate)(3)(mu-O,O,gamma-C-acetylacetonate)(3)(mu(3)-S) (1), in the asymmetric unit. Bond distances of both crystallographically independent molecules are almost identical, but there are some significant differences in bond angles (up to 6 degrees ) and interplanar angles (up to 8 degrees ). Each ruthenium atom exhibits a distorted octahedral environment formed by four oxygen atoms, two from each of the terminal and bridging acetylacetonate units, one gamma-carbon of an adjacent acetylacetonate ligand, and the sulfur atom in the center of the complex. In agreement with the expected 3-fold symmetry of the complex molecule, the (1)H and (13)C NMR spectra of 1 in CDCl(3) displayed signals corresponding to two types of ligand units. In dichloromethane solvent, 1 exhibited three metal center based successive quasireversible redox processes, Ru(III)Ru(III)Ru(III)-Ru(III)Ru(III)Ru(II) (couple I, 0.43 V vs SCE); Ru(III)Ru(III)Ru(IV)-Ru(III)Ru(III)Ru(III) (couple II, 1.12 V); and Ru(III)Ru(III)Ru(II)-Ru(III)Ru(II)Ru(II) (couple III, -1.21 V). However, in acetonitrile solvent, in addition to the three described couples [(couple I), 0.34 V; (couple II), 1.0 V; (couple III), -1.0], one irreversible oxidative response (Ru(III)Ru(III)Ru(IV) --> Ru(III)Ru(IV)Ru(IV) or oxidation of the coordinated sulfide center) appeared at E(pa), 1.50 V. The large differences in potentials between the successive couples are indicative of strong coupling between the ruthenium ions in the mixed-valent states. Compound 1 exhibited a moderately strong charge-transfer (CT) transition at 654 nm and multiple ligand based intense transitions in the UV region. In the Ru(III)Ru(III)Ru(III) (1(+)) state, the CT band was slightly blue shifted to 644 nm; however, the CT band was further blue shifted to 520 nm on two-electron oxidation to the Ru(III)Ru(III)Ru(IV) (1(2+)) state with a reduction in intensity.

Metalorganic chemical vapor deposition of SrRuO 3 thin film and its characterization

Synthesis of conducting oxide strontium ruthenate is carried out in a hot-wall tubular reactor, using Sr(C11H19O2)2/Ru(C5H5)2/O2 reaction system. Owing to a large difference in depositing efficiency between strontium and ruthenium precursors, the stoichiometric ratio of thin film is controlled in one cycle of two consecutive depositions at different temperatures. Thin films of SrRuO3 single phase are synthesized in the subsequent 700°C annealing. Thin films of SrRuO3 with extra ruthenium oxide can also be prepared by adjusting the molar ratio of RuO2 and SrO layers. The deposition sequence of ruthenium oxide first, strontium oxide later is preferred. If the deposition sequence is reverse, the thin film is plagued with unreacted oxides even when the annealing temperature is raised to 800°C. The relative ease of preparing SrRuO3 thin films, when RuO2 is under SrO, is attributed to evaporation of ruthenium oxide in O2 and diffusion in its open columnar microstructure. The sheet resistivity of thin film decreases with the ruthenium content. The room temperature resistivity of SrRuO3 film of Ru/(Sr + Ru) = 0.5 is around 910 μohm-cm. The room-temperature resistivity of Ru/(Ru + Sr) = 0.53 decreases to 470 μohm-cm. The root mean square surface roughness of 700°C synthesized SrRuO3 thin film is 22 nm, in a 2 × 2 μm2 area of film thickness 280 nm.

New tandem catalysis: preparation of cyclic enol ethers through a ruthenium-catalyzed ring-closing metathesis-olefin isomerization sequence.

Tandem reactions that proceed with a single metal catalyst precursor offer novel opportunities for developing efficient new reaction sequences. In this regard, reaction conditions have been identified that allows for a tandem ring-closing metathesis-olefin isomerization sequence catalyzed by a common ruthenium precursor. Specifically, the tandem process generates cyclic enol ethers from a variety of readily available acyclic dienes in a single reaction vessel using Grubbs' ruthenium alkylidene.

Synthesis of a Linear Assembly Consisting of a Central Ru(Phen)32+ Derivative and Two Peripheral Porphyrins

A ruthenium(II) precursor complex containing a bis-phenanthroline ligand, leading to a controlled helical structure around the metal centre, and a third phenanthroline-type ligand has been prepared. The spatial arrangement of the system is such that two chemical groups are disposed trans to one another on an axis running through the Ru centre. By appropriate functional group transformation, these two groups can be attached to monosubstituted zinc(II) porphyrins (PZn) to afford a linear array consisting of a central ruthenium(II) complex and two peripheral PZn motifs. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

Ligand-stabilized ruthenium nanoparticles: synthesis, organization, and dynamics.

The decomposition of the ruthenium precursor Ru(COD)(COT) (1, COD = 1,5-cyclooctadiene; COT = 1,3,5-cyclooctatriene) in mild conditions (room temperature, 1--3 bar H(2)) in THF leads, in the presence of a stabilizer (polymer or ligand), to nanoparticles of various sizes and shapes. In THF and in the presence of a polymer matrix (Ru/polymer = 5%), crystalline hcp particles of uniform mean size (1.1 nm) homogeneously dispersed in the polymer matrix and agglomerated hcp particles (1.7 nm) were respectively obtained in poly(vinylpyrrolidone) and cellulose acetate. The same reaction, carried out using various concentrations relative to ruthenium of alkylamines or alkylthiols as stabilizers (L = C(8)H(17)NH(2), C(12)H(25)NH(2), C(16)H(33)NH(2), C(8)H(17)SH, C(12)H(25)SH, or C(16)H(33)SH), leads to agglomerated particles (L = thiol) or particles dispersed in the solution (L = amine), both displaying a mean size near 2--3 nm and an hcp structure. In the case of amine ligands, the particles are generally elongated and display a tendency to form worm- or rodlike structures at high amine concentration. This phenomenon is attributed to a rapid amine ligand exchange at the surface of the particle as observed by (13)C NMR. In contrast, the particles stabilized by C(8)H(17)SH are not fluxional, but a catalytic transformation of thiols into disulfides has been observed which involves oxidative addition of thiols on the ruthenium surface. All colloids were characterized by microanalysis, infrared spectroscopy after CO adsorption, high-resolution electron microscopy, and wide-angle X-ray scattering.

Ammonia synthesis over Ru/C catalysts with different carbon supports promoted by barium and potassium compounds

Ammonia synthesis over ruthenium catalysts supported on different carbon materials using Ba or K compounds as promoters has been investigated. Ba(NO 3) 2, KOH, and KNO 3 are used as the promoter or promoter precursor, and activated carbon (AC), activated carbon fiber (ACF), and carbon molecular sieve (CMS) are used as the support. The activity measurement for ammonia synthesis was carried out in a flow micro-reactor under mild conditions: 350–450°C and 3.0 MPa. Results show that KOH promoter was more effective than KNO 3, and that Ba(NO 3) 2 was the most effective promoter among the three. The roles of promoters can be divided into the electronic modification of ruthenium, the neutralization of surface functional groups on the carbon support and the ruthenium precursor. The catalyst with AC as the support gave the highest ammonia concentration in the effluent among the supports used, while the catalyst with ACF as the support showed the highest turnover-frequency (TOF) value. It seems that the larger particles of Ru on the carbon supports are more active for ammonia synthesis in terms of TOF value.

New supported ruthenium catalyst for hydrodesulfurization reaction

The effect of the kind of ruthenium precursor {Ru 3(CO) 12 or RuCl 3· nH 2O} and the activation conditions on the performance of Ru/MgF 2 preparations in thiophene hydrodesulfurization has been studied. The highest activity, higher than that of the commercially available system CoMo/Al 2O 3, was revealed by the Ru/MgF 2 catalyst sulfided in the 50% H 2S/He atmosphere. According to the results of TPR study, this preparation was characterized by exceptionally high content of RuS 2, which seems to be responsible for its high activity. As follows from the product distribution of thiophene HDS, the activation in the H 2S/He atmosphere mainly leads to the formation of saturated products (butane), while the activation in the atmosphere of H 2S/H 2, to the formation of unsaturated products (butene-1, cis- and trans-butene-2).

Synergy of ruthenium and cobalt in SiO 2-supported catalysts on ethylene hydroformylation

Dynamic hydroformylation of ethylene at atmospheric pressure and 150°C has been studied in a fixed bed reactor over ruthenium- and cobalt-containing SiO 2-supported catalysts (1% Ru loading). Any combination of ruthenium and cobalt precursors leads to significant improvement of hydroformylation activity with respect to those of monometallic catalysts. The optimal atomic ratio of Co:Ru is estimated to be 3:1 for ideal catalytic activity. A catalyst derived from Ru 3(CO) 12 and Co 2(CO) 8 is most active. A catalyst derived from metal carbonyls is generally more active than a catalyst prepared from metal salts. Metal chlorides retard the preparation of active catalysts in most cases. The catalysts studied exhibit fairly good catalytic stability. The determined rate enhancement of ethylene hydroformylation suggests a synergy of ruthenium and cobalt, which is understood as catalysis by bimetallic particles or ruthenium and cobalt monometallic particles in intimate contact. The synergy causes high ethylene hydrogenation activity while giving enhanced ethylene hydroformylation activity. Meanwhile, the potential of the ruthenium-based catalysts is evaluated from both catalytic performances and cost by comparison with the corresponding rhodium-based ones.

Studies on the interaction between ruthenium and cobalt in supported catalysts in favor of hydroformylation

The interaction between ruthenium and cobalt atoms in SiO2‐supported catalysts prepared from various precursors by H2 treatment at 350 °C has been studied by ethylene hydroformylation, temperature‐programmed reduction (TPR) technique and IR spectroscopy. Incorporation of cobalt with ruthenium gives a catalyst with remarkably enhanced hydroformylation activity with respect to those of monometallic catalysts, irrespective of the ruthenium and cobalt precursors used. The synergistic effect of ruthenium and cobalt on the catalysis is consistent with TPR and IR results. TPR analysis shows regularly a promoted reduction of cobalt due to the “hydrogen spillover” effect, which indicates that ruthenium and cobalt atoms are in intimate contact in the catalysts. CO adsorption IR study demonstrates a strong decrease of CO chemisorption on Ru in the presence of cobalt, proposing that ruthenium and cobalt atoms interact on the SiO2 surface to form Ru–Co bimetallic particles. The results suggest that the catalysts thus obtained contain Ru–Co bimetallic particles, at least atoms of the two metals in intimate contact. However, in situ surface IR spectra of ethylene hydroformylation exhibit little modification by the presence of cobalt on Ru/SiO2.

Electron paramagnetic resonance characterization of ruthenium-dispersed tin oxide obtained by sol–gel and impregnation methods

Ruthenium was dispersed in SnO2 by cogelation of tin and ruthenium precursor compounds: tetra(tert-butoxy)- tin(IV), [Sn(OBut)4], and tris(acetylacetonato)ruthenium(III) [Ru(acac)3]. This resulted in samples with a controlled and reproducible metal/SnO2 molar ratio (0.8). An electron paramagnetic resonance study on sample reactivity showed that: [Ru(acac)3] was included in the SnO2 gel without significant matrix-induced quali-quantitative modifications of the coordination compound; thermal treatment of [Ru(acac)3]–SnO2 in air led to oxidation of most of the Ru3+ centres to diamagnetic Ru4+ centres; reduction with CO(0.5%)–argon at 773 K reformed all the original Ru3+ centres. In the CO–argon treated samples, the Ru3+ centres were in the field of oxide ligands; lower paramagnetic oxidation states, clustering effects and paramagnetic singly ionized oxygen vacancies (VO+) were absent. It was concluded that a great many Ru4+centres could substitute Sn4+in samples prepared by cogelation, thus optimizing the intimacy of metal–semiconductor contact.

Catalytic hydrogenation of fine chemicals: sorbitol production

Historically, skeletal nickel is the catalyst of choice in the production of sorbitol on industrial scale. A disadvantage of the use of skeletal nickel in the hydrogenation of glucose containing feedstocks to sorbitol, is the fact that a part of the nickel leaches. As a consequence, purification of the sorbitol is required, which renders this process economically less attractive. To meet the demand for non-leaching catalyst systems, ruthenium on carbon catalyst are presently becoming more important. In this paper, a comparison is made between different 5% Ru on carbon catalysts in the hydrogenation of a dextrose monohydrate and a very high maltose feedstock. The influence of the carbon support, the ruthenium metal location, and the applied ruthenium precursor are investigated. For comparison reasons, both skeletal Ni and Ru catalysts have been applied in the hydrogenation of dextrose to sorbitol. The effect of reaction temperature and pressure during the hydrogenation of a very high maltose containing feedstock is also investigated. It is shown that Ru catalysts are suitable alternatives for skeletal Ni catalysts in respect to re-usability, activity and selectivity.

Changes in the activity of Ru/Fe2O3 catalysts modified with alkali metal salts in the water-gas shift reaction

A study was undertaken to determine the activity of ruthenium catalysts, obtained by deposition of Ru3(CO)12 on products of iron oxide-hydroxide calcination modified with alkali metals, in the water-gas shift reaction. The activity depends on the kind of starting iron support, the ruthenium precursor and the amount of alkali metal salts. The most active were the catalysts obtained by deposition of Ru3(CO)12 on calcination products of σ-FeOOH, both modified and unmodified with alkali metal salts, and of α-FeOOH modified with alkali metal salts.

Synthesis, Characterization, Electrochemistry, and EQCM Studies of Polyamidoamine Dendrimers Surface-Functionalized with Polypyridyl Metal Complexes

Polyamidoamine dendrimers have been surface-modified via peptide coupling with pyridyl, bipyridyl, and terpyridyl ligands to give the analogous polypyridyl dendrimer ligands in high yield. Complexation of the pendant chelating groups with appropriate ruthenium(II) precursor complexes yielded dendrimers surface-functionalized with tris(bipyridyl)ruthenium(II) or bis(terpyridyl)ruthenium(II) pendant complexes. Electrochemical studies of the dendrimer complexes show metal-centered and ligand-centered redox couples. These molecules also adsorb onto platinum electrodes, and the deposition process and the properties of the resulting films have been investigated with the electrochemical quartz crystal microbalance. The resulting films exhibit morphological changes with potential that can be attributed to the deposition or dissolution of the dendrimer and/or to ejection or incorporation of counterions and/or solvent into the film. A number of the electrodeposited films exhibited charge trapping peaks. Dendrimers containing terminal tris(bipyridyl)ruthenium(II) complexes exhibited room-temperature luminescence, while these and dendrimers with terminal bis(terpyridyl)ruthenium(II) complexes exhibited luminescence in a rigid butyronitrile matrix at 77 K.