Ru Clusters Research Articles

Structural evolution of small ruthenium cluster anions.

The structures of ruthenium cluster anions have been investigated using a combination of trapped ion electron diffraction and density functional theory computations in the size range from eight to twenty atoms. In this size range, three different structural motifs are found: Ru8(-)-Ru12(-) have simple cubic structures, Ru13(-)-Ru16(-) form double layered hexagonal structures, and larger clusters form close packed motifs. For Ru17(-), we find hexagonal close packed stacking, whereas octahedral structures occur for Ru18(-)-Ru20(-). Our calculations also predict simple cubic structures for the smaller clusters Ru4(-)-Ru7(-), which were not accessible to electron diffraction measurements.

Selective aerobic oxidation of HMF to 2,5-diformylfuran on covalent triazine frameworks-supported Ru catalysts.

The selective aerobic oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-diformylfuran has been performed under mild conditions at 80 °C and 20 bar of synthetic air in methyl t-butyl ether. Ru clusters supported on covalent triazine frameworks (CTFs) allowed excellent selectivity and superior catalytic activity compared to other support materials such as activated carbon, γ-Al2 O3 , hydrotalcite, or MgO. CTFs with varying pore size, specific surface area, and N content could be prepared from different monomers. The structural properties of the CTF materials influence the catalytic activity of Ru/CTF significantly in the aerobic oxidation of HMF, which emphasizes the superior activity of mesoporous CTFs. Recycling of the catalysts is challenging, but promising methods to maintain high catalytic activity were developed that facilitate only minor deactivation in five consecutive recycling experiments.

Carbon supported Ru clusters prepared by pyrolysis of Ru precursor-impregnated biopolymer fibers

Ru clusters deposited on pyrolyzed bacterial nanocellulose (Ru/p-BNC) were prepared in a single step by controlled pyrolysis at 1250 °C (under Ar gas), starting from bacterial nanocellulose (BNC) fibers impregnated with [RuCl2(DMSO)4], which serves as a Ru precursor.

Platinum-ruthenium bimetallic clusters on graphite: a comparison of vapor deposition and electroless deposition methods.

Bimetallic Pt-Ru clusters have been grown on highly ordered pyrolytic graphite (HOPG) surfaces by vapor deposition and by electroless deposition. These studies help to bridge the material gap between well-characterized vapor deposited clusters and electrolessly deposited clusters, which are better suited for industrial catalyst preparation. In the vapor deposition experiments, bimetallic clusters were formed by the sequential deposition of Pt on Ru or Ru on Pt. Seed clusters of the first metal were grown on HOPG surfaces that were sputtered with Ar(+) to introduce defects, which act as nucleation sites for Pt or Ru. On the unmodified HOPG surface, both Pt and Ru clusters preferentially nucleated at the step edges, whereas on the sputtered surface, clusters with relatively uniform sizes and spatial distributions were formed. Low energy ion scattering experiments showed that the surface compositions of the bimetallic clusters are Pt-rich, regardless of the order of deposition, indicating that the interdiffusion of metals within the clusters is facile at room temperature. Bimetallic clusters on sputtered HOPG were prepared by the electroless deposition of Pt on Ru seed clusters from a Pt(+2) solution using dimethylamine borane as the reducing agent at pH 11 and 40 °C. After exposure to the electroless deposition bath, Pt was selectively deposited on Ru, as demonstrated by the detection of Pt on the surface by XPS, and the increase in the average cluster height without an increase in the number of clusters, indicating that Pt atoms are incorporated into the Ru seed clusters. Electroless deposition of Ru on Pt seed clusters was also achieved, but it should be noted that this deposition method is extremely sensitive to the presence of other metal ions in solution that have a higher reduction potential than the metal ion targeted for deposition.

Trinuclear μ3-Silyl Complexes of Ruthenium and Group 9 Metals Having 3c-2e Interactions and Transformation of a μ3-Silyl Complex of Ru2Ir into μ-Silyl and μ3-Silylene Complexes

μ3-Silyl complexes (Cp*Ru)2(Cp*M)(μ3-H2SiR)(μ-H)3 (4, M = Co; 5, M = Rh; 6, M = Ir) were synthesized by the reaction of trinuclear heterometallic clusters of Ru and group 9 metals, (Cp*Ru)2(Cp*M)(μ-H)3(μ3-H) (1, M = Co; 2, M = Rh; 3, M = Ir), with primary silanes. The unprecedented coordination mode of primary silanes on a trimetallic plane was unambiguously confirmed by means of multinuclear NMR spectroscopy, IR spectroscopy, and X-ray diffraction studies. The μ-silane complex (Cp*Ru)2(Cp*Ir)(μ-H2SiHtBu)(μ-H)4 (7), which is a plausible intermediate en route to the μ3-silyl complex, was obtained by the reaction of 3 with tBuSiH3. The μ3-silyl complex 6a was transformed into the μ-silyl complex (Cp*Ru)2(Cp*Ir)(μ-H2SiPh)(tBuNC)(μ-H)3 (8) upon treatment with tBuNC. Complex 6a also reacted with CO to afford the μ3-silylene complex (Cp*Ru)2(Cp*Ir)(μ3-HSiPh)(μ-CO)(μ-H)2 (10) via the formation of the μ-silyl complex (Cp*Ru)2(Cp*Ir)(μ-H2SiPh)(CO)(μ-H)3 (9).

Improvement on electrochemical performance by partial replacement of Ru@Pt core-shell nanocatalyst by temperature modification

In this paper, the homemade open-loop reduction system (OLRS), and redox transmetalation method were utilized to produce the core-shell Ru (ruthenium)/Pt (platinum) catalysts on the carbon cloth (CC) for direct methanol fuel cell (DMFC) application. By adjusting pH value and heating to proper temperature of the ionized reduction environment, Pt4+ can be first converted into Pt2+ to allow partial Ru replacement with Pt by redox transmetalation and produce Ru@Pt core-shell nanostructures[1]. And we change the reduction temperature to see how it affects the efficiency of the DMFC.The scanning electron microscopic (SEM) top-view micrographs showing that the apparent Ru@Pt nanoparticles successfully deposited on both the inner and outer surfaces of the hydrophilically-treated CC. At high SEM magnification, the small size and high-density distribution of the Ru@Pt nanoparticles were clearly observed on the hydrophilically-treated CC, and much more Pt@Ru catalyst deposit on the CC surface with the sample of 80 °C. The electrosorption charges of hydrogen ion (QH) and the peak current density (IP) of the samples in the cyclic voltammetry (CV) curves. The magnitude of peak current density is positive correlation to the temperature. However, the CO tolerance, indicated that the better CO tolerance contributed to the less Pt replace on Ru cluster, which allow the Ru oxidizing CO to CO2 efficiently, is negative correlation-- to the temperature. The sample of 50 °C shows the better combination catalyst efficiency between the CO tolerance and the electrochemical performance.

Magnetic properties of small ruthenium clusters in fullerene cage — A DFT study

Encapsulation of small clusters in fullerene cages provides a stable environment for their application in nanoscale functional devices. In this paper, first principles study of Ruthenium as an endohedral dopant in buckminsterfullerene has been carried out using density functional theory. Ruthenium atom has three stable dopant sites inside C 60, with three possible values of magnetic moment (4, 2 and 0 μB). The doping position of Ru atom can be seen to have an effect on HOMO–LUMO gap, formation energy, binding energy and magnetic moment of the fullerene cage. The interaction between Ru and C atoms in different conformations can be explained in terms of Mulliken analysis and density of states analysis. It is also possible to encapsulate more than one Ru atoms in the C 60 cage ( Ru n@ C 60, n = 2–6); encapsulation up to six atoms has been analyzed, after which the process is energetically unfavorable. The geometry of the lowest energy structures, compared to the isolated Ru n clusters, is found to change as a result of encapsulation (e.g., in Ru 3@ C 60 and Ru 5@ C 60). A reduction in magnetic moment of Ru clusters inside fullerene cage as compared to isolated clusters also occurs due to hybridization and confinement effects. The varied magnetic moments of Ru -encapsulated C 60 molecules reveal its applications in molecular magnetic devices and quantum peapods.

Linking of phosphinidene-capped triruthenium carbonyl clusters with diphosphine ligands

A phosphinidene-capped triruthenium cluster Ru3(CO)9(μ-H)2(μ3-PMes) (1, Mes=mesityl=2,4,6-trimethylphenyl) reacted with diphosphines to afford linked clusters [Ru3(CO)8(μ-H)2(μ3-PMes)]2(μ-dppe) (2a, dppe=1,2-bis(diphenylphosphino)ethane), [Ru3(CO)8(μ-H)2(μ3-PMes)]2(μ-dppa) (2b, dppa=bis(diphenylphosphino)acetylene), and [Ru3(CO)8(μ-H)2(μ3-PMes)]2(μ-dppf) (2c, dppf=1,1′-bis(diphenylphosphino)ferrocene) in high yields. The molecular structures of 2a and 2c were confirmed by single-crystal X-ray diffraction.

Backbone Modified Small Bite-Angle Diphosphines: Synthesis, Structure, Fluxionality and Regioselective Thermally-Induced Transformations of Ru3(CO)10{µ-Ph2PCH(Me)PPh2}

The synthesis of Ru3(CO)10{µ-Ph2PCH(Me)PPh2} (1) has been achieved from the radical-catalysed reaction of Ru3(CO)12 with 1,1′-bis(diphenylphosphino)ethane and the fluxionality, protonation and regioselective thermally-induced on-metal transformations of the small bite-angle diphosphine have been studied. Cluster 1 is fluxional in solution and variable temperature 13C{1H} NMR spectroscopy shows that the six carbonyls on the phosphine-bound metal centers interconvert rapidly on the NMR timescale. Protonation of 1 is facile at room temperature and affords the cationic-hydride [Ru3(CO)10{µ-Ph2PCH(Me)PPh2}(μ-H)][BF4] (1H +) which is fluxional, the hydride migrating between bridged and non-bridged ruthenium–ruthenium vectors, location across an unbridged metal–metal bond being thermodynamically favoured. Thermolysis of 1 in heptane affords moderate amounts of the expected benzene-CO elimination product, Ru3(CO)8(µ-CO){µ3-PhPCH(Me)PPh(C6H4)} (2), along with smaller amounts of Ru3(CO)10{μ-PhP(CHMe)(C6H4)PPh} (3) containing a novel doubly-bridged diphosphine ligand. Hydrogenation of 1 in refluxing cyclohexane affords the hydride cluster Ru3(CO)9{μ3-PhPCH(Me)PPh2}(μ-H) (4), the same species also being obtained when 2 was treated with hydrogen under similar conditions. All thermally-induced transformations are regioselective, with only a single isomer being generated. In light of the observed regioselectivity a mechanism is proposed for the formation of 2 from 1 which results from an intermediate in which the methyl-group is held over the triruthenium framework. Cluster Ru3(CO)10{µ-Ph2PCH(Me)PPh2} has been synthesized from the radical-catalysed reaction between Ru3(CO)12 and 1,1′-bis(diphenylphosphino)ethane and the fluxionality, protonation and regioselective thermally-induced on-metal transformations of the small bite-angle diphosphine have been investigated.

Experimental and computational studies on the reaction of silanes with the diphosphine-bridged triruthenium clusters Ru3(CO)10(μ-dppf), Ru3(CO)10(μ-dppm) and Ru3(CO)9{μ3-PPhCH2PPh(C6H4)}

Reactions of Ru3(CO)10(μ-dppf) (1) (dppf = 1,1′-bis(diphenylphosphino)ferrocene), Ru3(CO)10(μ-dppm) (2) (dppm = bis(diphenylphosphino)methane), and the orthometalated derivative Ru3(CO)9{μ3-PPhCH2PPh(C6H4)} (3) with silanes (Ph3SiH, Et3SiH, Ph2SiH2) are reported. Treatment of 1 with Ph3SiH and Ph2SiH2 at room temperature leads to facile Si–H bond activation to afford Ru3(CO)9(μ-dppf)(SiPh3)(μ-H) (4) (60% yield) and Ru3(CO)9(μ-dppf)(SiPh2H)(μ-H) (6) (53% yield), respectively. The reaction of 1 with Ph3SiH has been investigated by electronic structure calculations, and these data have facilitated the analysis of the potential energy surface leading to 4. Compound 1 does not react with Et3SiH at room temperature but reacts at 68 °C to give Ru3(CO)9(μ-dppf)(SiEt3)(μ-H) (5) in 45% yield. Reaction of 2 with Ph3SiH at room temperature yields two new products: Ru3(CO)9(μ-dppm)(SiPh3)(μ-H) (7) in 40% yield and Ru3(CO)6(μ3-O)(μ-dppm)(SiPh3)(μ-H)3 (8) in 15% yield. Interestingly, at room temperature compound 7 slowly reverts back to 2 in solution with decomposition and liberation of Ph3SiH. Complex 8 can also be prepared from the direct reaction between 7 and H2O. Similar reactions of 2 with Et3SiH and Ph2SiH2 give only intractable materials. The orthometalated compound 3 does not react with Ph3SiH, Et3SiH and Ph2SiH2 at room temperature but does react at 66 °C to give Ru3(μ-CO)(CO)7{μ3-PPhCH2PPh(C6H4)}(SiR2R1)(μ-H)](9, R = R′ = Ph, 71% yield; 10, R = R′ = Et, 60% yield; 11, R = Ph, R′ = H, 66% yield) by activation of the Si–H bond. Compounds 4 and 8–11 have been structurally characterized. In 4, both the dppf and the hydride bridge a common Ru–Ru vector, whereas NMR studies on 7 indicate that two ligands span different Ru–Ru edges. Compound 8 contains a face-capping oxo moiety, a terminally coordinated SiPh3 ligand, and three bridging hydride ligands, whereas 9–11 represent simple oxidative addition products. In all of the compounds examined, the triruthenium framework retains its integrity and the silyl groups occupy equatorial sites.

Synthesis, Characterization, and X‐ray Crystal Structures of Ru3(CO)9(dppm)AsPh3 and Ru3(CO)9(dpam)PPh3 Complexes

Abstract Clusters Ru3(CO)10(dppm) and Ru3(CO)10(dpam) on reaction with AsPh3 and PPh3 in refluxing n‐hexane afford trisubstituted clusters Ru3(CO)9(dppm)AsPh3 and Ru3(CO)9(dpam)PPh3, respectively. These two trisubstituted clusters are characterized by spectroscopic and single‐crystal X‐ray diffraction. Ru3(CO)9(dppm)AsPh3 and Ru3(CO)9(dpam)PPh3 show a triangle of ruthenium atoms, in which the bidentate and monodentate group 15 ligands occupy equatorial position and all the carbonyl units are terminally bonded. The Ru–Ru distances in Ru3(CO)9(dppm)AsPh3 are 2.8461(7) Å, 2.8495(7) Å, and 2.8930(6) Å, with the longest distance cis to the monodentate AsPh3 ligand. For Ru3(CO)9(dpam)PPh3, the Ru–Ru distances are 2.8652(2) Å, 2.8809(2) Å, and 2.8560(2) Å with the longest distance also cis to the monodenatate PPh3 ligand.

Density Functional Theory Study on the Metal–Support Interaction between Ru Cluster and Anatase TiO2(101) Surface

Density functional theory (DFT) calculations were carried out to study the nucleation and growth mechanism of Ru clusters on the TiO2(101) surface by using supported Run (n = 1–10, 20, 22) cluster models to understand the metal–support interaction and the resulting catalytic performance toward CO oxidation. The results show that the Run cluster prefers a 3D geometry when n ≥ 4 and that the Ru–TiO2 interface is predominantly composed of Ru–O and Ti–O bonds. Calculation studies based on the density of states (DOS), Hirshfeld charge analysis, and electron deformation density (EDD) demonstrate that the electronic interaction is mainly localized at the Ru–TiO2 interface through the electron transfer via the Ru–O bond. Additionally, the investigation on catalytic behavior of Run/TiO2 toward CO oxidation reveals the largely enhanced catalytic activity of the supported Run clusters, which originates from the significant reduction of the activation barrier as a result of the electron transfer from Ru to TiO2.

A stable and effective Ru/polyethersulfone catalyst for levulinic acid hydrogenation to γ-valerolactone in aqueous solution

A cross-linked sulfonated polyethersulfone supported Ru nanoparticle catalyst was prepared for highly hydrogenation of levulinic acid (LA) into γ-valerolactone (GVL) at mild conditions (3.0MPa H2 and 70°C) in aqueous solution. X-ray diffraction (XRD) and transmission electron microscopy (TEM) characterizations show the formation of highly dispersed small (∼3nm) Ru clusters on the surface of polyethersulfone. Infrared spectroscopy (IR) and acid-base titration indicate the presence of sulfonic groups without the influence of the deposition of Ru species. Polyethersulfone consisted of cross-linked electron -withdrawing group SO2, maintained its intrinsic thermal stability during the hydrogenating reaction process, and its swelling property promoted the adsorption of LA in aqueous solution. The synchronization of sulfonic groups as active sites for esterification process and metal sites for hydrogenation promoted the hydrogenation reactivity.

ChemInform Abstract: Immobilized Ru Clusters in Nanosized Mesoporous Zirconium Silica for the Aqueous Hydrogenation of Furan Derivatives at Room Temperature.

Immobilized ru clusters in nanosized mesoporous zirconium silica for the aqueous hydrogenation of furan derivatives at room temperature

Enhanced N2 Dissociation on Ru-Loaded Inorganic Electride

Electrides, i.e. salts in which electrons serve as anions, are promising materials for lowering activation energies of chemical reactions. Ab initio simulations are used to investigate the effect of the electron anions in a prototype mayenite-based electride (C12A7:e(-)) on the mechanism of N2 dissociation. It is found that both atomic and molecular nitrogen species chemisorb on the electride surface and become negatively charged due to the electron transfer from the substrate. However, charging alone is not sufficient to promote dissociation of N2 molecules. In the presence of Ru, N2 adsorbs with the formation of a cis-Ru2N2 complex and the N-N bond weakens due to both the electron transfer from the substrate and interaction with Ru. This complex transforms into a more stable trans-Ru2N2 configuration, in which the N2 molecule is dissociated, with the calculated barrier of 116 kJ mol(-1) and the overall energy gain of 72 kJ mol(-1). In contrast, in the case of the stoichiometric mayentie, the cis-Ru2N2 is ~34 kJ mol(-1) more stable than the trans-Ru2N2, while the cis-trans transition has a barrier of 192 kJ mol(-1). Splitting of N2 is promoted by a combination of the strong electron donating power of C12A7:e(-), ability of Ru to capture N2, polarization of Ru clusters, and electrostatic interaction of negatively charged N species with the surface cations.

Ru/Active Carbon Catalyst: Improved Spectroscopic Data Analysis by Density Functional Theory

We describe a DFT study on the self-organizing of ruthenium (Ru) nanoparticles deposited on a sp2 carbon layer (either of graphite type or of graphene type) using cluster models. The calculations provide insights into the nature and structure of the supported Ru clusters and the active sites of B5-type. Different sizes of Ru nanoparticles have been tested with up to 17 atoms. The carbon support has been modeled using a single sp2 carbon layer (graphene type) and double sp2 carbon layer (graphite type). Our DFT results suggest that for clusters with more than 4 Ru atoms, epitaxial growth of Ru on the carbon support is possible only in certain configurations. We were able to build and stabilize three-dimensional Ru nanoparticles with several B5-type active sites on the carbon support. Such C-supported Ru-nanoparticles exhibiting B5-type sites give potential for further molecule adsorption and reaction mechanism studies. The all investigated structures and configurations for different Ru nanoparticles are presented. The supported Ru nanoparticles have been used for interpreting valence band and EXAFS spectra of a commercial Ru/activated carbon catalyst. The Ru nanoparticles supported on graphene gives the best interpretation of the spectroscopic data.

Density functional theory analysis of methanation reaction of CO2 on Ru nanoparticle supported on TiO2 (1 0 1)

The methanation reaction of CO2 on a Ru nanoparticle supported on TiO2 catalyst has been investigated by density functional theory (DFT) using the generalized gradient approximation with periodic boundary conditions. Two plausible reaction paths were found for the transformation of CO2 to CH4 on TiO2-supported Ru nanoparticles. The origin of the high activity of the catalyst is discussed based on the overall reaction energy diagram obtained from DFT calculations. The CO2 is readily and stably adsorbed on Ru cluster at moderate temperature as compared with that on bulk Ru surface. It is due to the difference of the Ru structure between the Ru nanoparticle and the bulk Ru surface. The elementary reactions of the hydrogenation of adsorbed CO and of the production of CH4 are possible to become the rate-determining steps over the methanation reaction, because these two reactions have a higher potential energy barrier than that of other elementary reactions in the overall reaction path. These potential energy barriers for the hydrogenation of CO and the production of CH4 on TiO2-supported Ru nanoparticles were lower than those on bulk Ru surface, which explains the high activity of the Ru nanoparticle-loaded TiO2 catalyst. The lowering of these potential energy barriers can be caused by weak charge transfer between Ru atoms and adsorbed species on the TiO2-supported Ru nanoparticles. As the results, the catalytic activity of the Ru nanoparticles supported on TiO2 catalyst is characterized by the structure of Ru nanoparticles and by the weak charge transfer between Ru atoms and adsorbed species.

Syntheses and Structural Studies of Several Group 8 Metal Complexes Derived from 1, 3‐Butadiyne

AbstractAs part of an extensive investigation into the chemistry of complexes containing metal‐ligand centers linked by chains of C(sp) atoms, the preparation, characterization, and single‐crystal X‐ray diffraction molecular structure determinations of four complexes {MLn}‐C≡CC≡C‐{M′L′m} [MLn = Ru(dppe)Cp*, M′L′m = Fe(dppp)Cp* (1), Ru(dppe)Cp* (2), MLn = M′L′m = Os(PPh3)2Cp (3)], and {Cp*(dppe)Ru}C≡CC≡C{trans‐RuCl(dppe)2} (4), in which the alternating C(sp)–C(sp) bonds have values between 1.375 and 1.40 Å (single) and between 1.20 and 1.259 Å (triple), respectively, are described. In addition, a structure determination of Ru3(μ‐H){μ3‐C2C≡C[Ru(PPh3)2Cp]}(CO)9 (5) shows that the C2 fragment attached to the HRu3 cluster shows the expected lengthening [to 1.311(7) Å] and bending at the two carbon atoms [to 152.6(6) and 157.6(5)°] (resulting from back‐bonding from the Ru3 cluster into the C≡C π* orbitals) compared with the essentially linear Ru–CC– moiety [C≡C 1.222(6) Å, angles at C of 178.0(5), 172.3(6)°],

Immobilized Ru Clusters in Nanosized Mesoporous Zirconium Silica for the Aqueous Hydrogenation of Furan Derivatives at Room Temperature

Ru lonesome tonight? Immobilized ruthenium clusters (50 Ru atoms) in nanosized mesoporous zirconium silica were synthesized by using an impregnation method starting from an aqueous solution of RuCl3. The Ru cluster catalysts were thermally stable at 500 °C and showed remarkable activity for the hydrogenation of furan derivatives in water at room temperature under 5 bar hydrogen pressure.

N2 Activation by Neutral Ruthenium Clusters

The activation of nitrogen molecules when forming complexes with neutral Ru clusters in the gas phase has been investigated by probing their N–N stretching frequencies using infrared multiple photon dissociation spectroscopy. The measured frequencies for RunN2m (n = 5–16; m = 1, 2) fall in the range between 2110 and 2201 cm–1 and can be attributed to chemisorbed σ-bonded N2, which corresponds to the γ-state on metal surfaces. The band positions are not dependent on the N2 coverage, but significant variations are found depending on cluster size.