Ruthenium Precursor Research Articles

Photoinduced Self-assembly: An Alternative Strategy for the Construction of Coordination Oligomers and Polymers.

Self-assembled oligonuclear and polynuclear complexes have numerous functionalities and potential applications. Generally, such compounds have been constructed by thermal substitution reactions with bridging ligands. Herein, we report bottom-up and photochemical construction of functional coordination oligomers and polymers by photosubstitution-induced self-assembly. The photosubstitution reactions of a ruthenium precursor complex with bridging ligands having pyrazole moieties afford mono-, di-, tri-, tetra-, and pentanuclear ruthenium complexes, Ru1-Ru5, which have one-dimensional architectures. Intramolecular hydrogen bonding between each bridging ligand is a key to construct the molecular nanowires. All the complexes have been isolated and thoroughly characterized. The photochemically synthesized ruthenium complexes act as synthons for longer metal-complex-based nanowires with a length of the order of tens-of nanometers. The multinuclear complexes are generated by photoinduced self-assembly in the presence of a base, and they undergo photoinduced disassembly in the presence of acid.

Metallic nanofilms on Si(100) and SiO2 grown with a ruthenium precursor

Ruthenium (Ru) nanofilms (<3 nm) were prepared using tricarbonyl(trimethylenemethane)ruthenium, Ru(TMM)(CO)3 at 230 °C. We show that the surface morphology and electrical conductance of Ru nanofilms are substantially different on H:Si(100) and SiO2/Si(100) substrates. Two-dimensional (2D) Ru nanofilms (∼1 nm) were formed on H:Si(100), while thick (∼3 nm) granular Ru films were formed on SiO2 substrate under the same growth conditions, as confirmed by cross-sectional transmission electron microscopy and X-ray photoelectron spectroscopy. Using scanning probe microscopy, the metallic conductance of Ru grains on H:Si(100) substrates was recognized. On ultrathin (1 nm) SiO2/Si(100) substrates, the spatial separation of Ru grains facilitates the single electron tunneling (SET) phenomenon in the double barrier tunnel junction structure. The results emphasized the difference in carrier transport in Ru nanofilms on Si and SiO2 substrates.

DLPNO-CCSD(T) and DFT study of the acetate-assisted C-H activation of benzaldimine at [RuCl2(p-cymene)]2: the relevance of ligand exchange processes at ruthenium(II) complexes in polar protic media.

To gain mechanistic insights into the acetate-assisted cyclometallations of arylimines promoted by [RuCl2(p-cymene)]2 in polar protic media, DFT geometry optimizations (with M06 and ωB97X-D3 functionals and the cc-pVDZ-PP[Ru] basis set) followed by DLPNO-CCSD(T)/CBS energy evaluations were performed using benzaldimine as a model substrate and methanol as the solvent (with CPCM or SMD models). The calculation results show that coordination of the imine to an acetate ruthenium precursor is followed by anion (chloride or acetate) dissociation as the rate-determining step of the process. H-Bonding of two explicit MeOH to the anion reduces the calculated activation energy to ca. 23 kcal mol-1, in good agreement with the experimental half-life at room temperature. Subsequent AMLA/CMD C-H activation of the intermediate cationic complexes is a faster, reversible process. Alternative reaction pathways involving neutral diacetate ruthenium complexes offer AMLA/CMD transition state structures of lower energy but are precluded due to higher energy barriers for the initial ligand exchange processes at ruthenium. Solvent assistance accelerates the final chloride/acetate exchange processes on the cycloruthenate intermediates, particularly when compression in the condensed phase is taken into consideration. The performance of six DFT functionals (with the aug-pVTZ-PP[Ru] basis set) was assessed using the DLPNO-CCSD(T)/CBS reference energies. Neutral diacetate ruthenium complexes were incorrectly predicted as being kinetically relevant when using hybrid DFT methods (PBE0-D3(BJ), M06-2X or ωB97M-V). Good agreement between the calculated barrier heights and our benchmark energy results was obtained by using double-hybrid DFT methods. PWPB95 with D3(BJ) or D4 dispersion energy corrections was found to be the most accurate (ΔG≠ MUE of ca. 1 kcal mol-1). This study may aid our understanding of and help with further experimental investigations of synthetically useful carboxylate-assisted C-H bond functionalizations involving (N,C)-cyclometallated (p-cymene)Ru(II) intermediate complexes in sustainable polar protic solvents.

Coligands Controlled Reactivities of Ruthenium(II) Precursors: Antiferromagnetically Coupled Ruthenium(III)-Phenoxyl versus Ruthenium(II)-Phenoxyl Forms.

The study disclosed that the reactivities of [RuII (PPh3)3Cl2] and [RuII(PPh3)3(CO)(H)Cl] precursors toward a trimethoxyarylimino-phenol derivative are sensibly different. The former promotes methoxy demethylation reaction affording a [Phenolato-RuIII-Phenolato] unit, while the latter containing π-acidic CO and hydride as coligands leads to C-H activation reaction, generating a [Phenolato-RuII-Aryl] unit. Notably, the oxidized analogues of these two forms produce antiferromagnetically coupled [RuIII-phenoxyl] and paramagnetic [RuII-phenoxyl] forms, which exhibit diverse reactivities. Surprisingly, the magnetically coupled [RuIII-phenoxyl] form obtained from [Phenolato-RuIII-Phenolato] motif leads to coligand, PPh3 oxidation and undergoes dimerization, making a Ru-Ru bond (2.599(2) Å), while the [RuII-phenoxyl] form obtained from [Phenolato-RuII-Aryl] motif leads to C-C coupling and H abstraction reactions. The coupling reaction affords a 4,4'-dibenzosemiquinonate anion radical complex, but the H-abstraction of the phenoxyl form gives a [RuII-Phenol] complex. For comparison, [RuII(IQR0)] and [RuII(ISQR·-)] complexes were also isolated, where IQR0 and ISQR·- are p-R-o-iminobenzoquinone and p-R-o-iminobenzosemiquinonate anion radicals. However, they fail to promote any bond-formation reaction. The molecular and electronic structures of the ruthenium (II/III) complexes were confirmed by single-crystal X-ray crystallography, EPR spectroscopy, and DFT calculations.

Reducible tungsten(VI) oxide-supported ruthenium(0) nanoparticles: highly active catalyst for hydrolytic dehydrogenation of ammonia borane.

Reducible WO3 powder with a mean diameter of 100 nm is used as support to stabilize ruthenium(0) nanoparticles. Ruthenium(0) nanoparticles are obtained by NaBH4 reduction of ruthenium(III) precursor on the surface of WO3 support at room temperature. Ruthenium(0) nanoparticles are uniformly dispersed on the surface of tungsten(VI) oxide. The obtained Ru0/WO3 nanoparticles are found to be active catalysts in hydrolytic dehydrogenation of ammonia borane. The turnover frequency (TOF) values of the Ru0/WO3 nanocatalysts with the metal loading of 1.0%, 2.0%, and 3.0% wt. Ru are 122, 106, and 83 min-1, respectively, in releasing hydrogen gas from the hydrolysis of ammonia borane at 25.0 °C. As the Ru0/WO3 (1.0% wt. Ru) nanocatalyst with an average particle size of 2.6 nm provides the highest activity among them, it is extensively investigated. Although the Ru0/WO3 (1.0% wt. Ru) nanocatalyst is not magnetically separable, it has extremely high reusability in the hydrolysis reaction as it preserves 100% of initial catalytic activity even after the 5th run of hydrolysis. The high activity and reusability of Ru0/WO3 (1.0% wt. Ru) nanocatalyst are attributed to the favorable metal-support interaction between the ruthenium(0) nanoparticles and the reducible tungsten(VI) oxide. The high catalytic activity and high stability of Ru0/WO3 nanoparticles increase the catalytic efficiency of precious ruthenium in hydrolytic dehydrogenation of ammonia borane.

Synthesis of Novel Ru Precursors for Atomic Layer Depostion

Ruthenium (Ru), which has a low bulk resistivity and a high work function, is a well-known metal for electrode materials in various microelectronic applications, such as Dynamic Random Access Memories (DRAM), Ferroelectric Random Access Memories (FRAM), and metal-oxide-semiconductor field-effect transistors (MOSFET). Also, Ru thin films can be used as diffusion barrier layers to improve the electromigration resistance in interconnect systems due to the excellent adhesion characteristics between Ru and Cu. Therefore, research on Ru thin films, that can be deposited by methods such as MOCVD (Metal-Organic Chemical Vapor Deposition) and ALD (Atomic Layer Deposition), is attracting many researchers. To apply these deposition techniques, Ru precursors with volatility and thermal stability are required. In this study, for the synthesis of Ru precursors that can satisfy all conditions, new Ru precursors were designed and prepared by using Ru(η5-Tropone)(η5-CHT) (CHT = Cycloheptatriene) as a starting material, to yield five new ruthenium precursors: Ru(II)(C7H9)(C8H11O) (1), Ru(II)(C7H9)(C9H14O) (2), Ru(II)(C7H9)(C13H14O)(3), Ru(II)(C7H9)(C8H9O) (4), and Ru(II)(C7H9)(C9H11O) (5). These compounds were characterized by 1H-Nuclear Magnetic Resonance (NMR), Mass Spectrometry (MS), Fourier-transform Infrared Spectroscopy (FT-IR), Elemental Analysis (EA), Thermal Gravimetric Analysis (TGA), and single crystal X-ray diffraction.

Terpyridine Based Heteroleptic Ruthenium Complexes: Influence of Donor and Acceptor Ligands in Photosensitization

AbstractWe report heteroleptic ruthenium complexes of terpyridine (tpy) ligands with directly linked carboxylic acid anchors. These complexes feature methyl or methoxy‐substituted 4′−Phtpy as donor ligands. We prepared these heteroleptic complexes from the ruthenium (II) precursor via a milder route to preclude the homoleptic complex formation. The donor−acceptor arrangement of tpy ligands in these ruthenium complexes renders visible light absorption giving metal and ligand‐to‐ligand charge transfer excitations at c.a. 490 nm. We evaluate the effect of the tpy donor substituents on the light‐harvesting ability in Dye‐Sensitized Solar Cells (DSSCs) and compare their photosensitizing ability with heteroleptic complexes bearing phenyl spacer at the acceptor end. Further, scrutinizing their photovoltaic performance, we studied their electron transfer kinetics in DSSCs using electrochemical impedance spectroscopy. This paper presents the structure‐photosensitization relationship of these heteroleptic ruthenium complexes through a combined experimental and computational approach.

A series of acac-ruthenium complexes with chiral Schiff base ligands: Synthesis, characterization and catalytic property

Four acac ruthenium precursors Ru(acac)2(n-PrCN)2 (acac = acetylacetonate) (1), Ru(acac)2(PhCN)2 (2), [Ru(hfac)(CH3CN)4](CF3SO3) (hfac = 1,1,1,5,5,5-hexafluoroacetylacetonate, 3), and Ru(acac)(dmso)3Cl (dmso = dimethyl sulfoxide) (4) were synthesized. Reactions of ruthenium precursor Ru(acac)2(n-PrCN)2 and chiral Schiff bases HLn afforded a series of Ru(acac)2Ln adducts (n = 1‒9) and a trinuclear ruthenium Schiff base complex (S)-(HNEt3)[(η3-O,N,O-L3)2Ru{μ-(η1-O-L3)4RuCl}Ru(η3-O,N,O-L3)2] (5). All complexes were characterized by NMR, FT-IR, HR-MS, and UV–vis spectroscopies along with electrochemistry properties. The structures of chiral Schiff base ligands (R)-HL8 and (S)-HL9, and ruthenium complexes 1–5 were unambiguously established by single-crystal X-ray diffraction. The good catalytic property of nine Ru(acac)2Ln complexes and the trinuclear ruthenium complex 5 with chiral Schiff base ligands for cyclopropanation of styrene was also presented.

Ru(II) complexes containing NOO donors of tridentate Schiff base ligands: Synthesis, characterization, crystal structure and catalytic activity in transfer hydrogenation of ketones

A new series of pincer type ruthenium(II) Schiff base complexes namely [Ru(CO)(PPh3)2(L1‒6)] (1–6) (where, L1‒6 ​= ​NOO ‒ donors of tri-dentate ligands) have been synthesized from ruthenium precursor such as [RuHCl(CO)(PPh3)3] containing tri-dentate Schiff bases ligands (H2L1‒H2L6). These ruthenium complexes were analyzed by elemental analysis and diverse characterizations such as FT‒IR, UV–Vis and NMR (1H and 31P) spectroscopy studies. The crystal structure of one of the complexes 5 ([Ru(CO)(PPh3)2L5]) was determined by single crystal X‒ray crystallography that revealed pincer type of coordination mode of complexes. Furthermore, complexes 1–6 have been utilized for transfer hydrogenation of aromatic ketones to secondary alcohols in the presence of i‒PrOH/KOH. The catalytic efficiency of complexes showed an efficient for transfer hydrogenation of ketones with alcohol as moderate to high conversions.

Reduced graphene oxide-supported ruthenium nanocatalysts for highly efficient electrocatalytic hydrogen evolution reaction

Hydrogen energy has received great attention because of its advantages such as large energy density and not producing carbon dioxide, and it is currently considered to be one of the most valuable green energy sources. Therefore, the development of efficiently hydrogen production is of great importance. Hydrogen production from water electrolysis has large application prospects due to its cleanliness and no pollution. However, how to prepare an efficient, stable and low-cost electrocatalyst for this process is still challenging. Here, we develop a reduced graphene oxide-supported ruthenium (Ru) nanoparticle electrocatalyst synthesized by a simple method. The ruthenium precursors are encapsulated and isolated with N,N-dimethylformamide (DMF) (Ru3+-DMF), which effectively inhibits the further agglomeration growth of ruthenium. After Ru3+-DMF being loaded on graphene oxide, Ru is supported on reduced graphene oxide (Ru/rGO) by the liquid phase chemical reduction method and the remaining organic solvent could be removed by calcination to form a well-dispersed Ru-based electrocatalyst. Ru/rGO shows excellent electrocatalytic activity and long-term stability for hydrogen evolution reaction (HER). In a solution of 1.0 M KOH, the overpotential of 3.0 wt%Ru/rGO for the HER at 100 mA cm−2 is only 111.7 mV, and the Tafel slope is 31.5 mV dec−1. It exhibits better HER performance compared to commercial Pt/C and other Ru/rGO catalysts with different Ru loadings. The work could give a new strategy for the synthesis of efficient electrocatalysts.

Ruthenium Complexes Bearing α-Diimine Ligands and Their Catalytic Applications in N-Alkylation of Amines, α-Alkylation of Ketones, and β-Alkylation of Secondary Alcohols.

New Ru(II) complexes encompassing α-diimine ligands were synthesized by reacting ruthenium precursors with α-diimine hydrazones. The new ligands and Ru(II) complexes were analyzed by analytical and various spectroscopic methods. The molecular structures of L1 and complexes 1, 3, and 4 were determined by single-crystal XRD studies. The results reveal a distorted octahedral geometry around the Ru(II) ion for all complexes. Moreover, the new ruthenium complexes show efficient catalytic activity toward the C–N and C–C coupling reaction involving alcohols. Particularly, complex 3 demonstrates effective conversion in N-alkylation of aromatic amines, α-alkylation of ketones, and β-alkylation of alcohols.

ZSM-5 as a support for Ru-containing catalysts of levulinic acid hydrogenation: Influence of the reaction conditions and the zeolite acidity

Levulinic acid (LA) is a substance, which can be obtained from cellulosic biomass and hydrogenated to gamma-valerolactone (GVL) – important platform chemical. This work describes the study of a ruthenium-containing catalysts synthesized by the impregnation of HZSM-5 having different silicate modulus (40, 80 or 400) with ruthenium precursor, which resulted in formation of oxidized Ru(III) and Ru(IV) species on the catalyst surface. Synthesized catalysts allowed more than 98% of LA conversion for 60 min of the reaction and 100% GVL selectivity while working at relatively mild conditions (100 °C, 1 MPa of H2) in aqueous medium. It was demonstrated that the observed catalytic activity mainly depends on two factors: (i) concentration of strong Lewis acid centers on the catalyst surface and (ii) surface content of RuO2, since the synthesized catalysts needed no preliminarily activation procedure.

Synthesis and molecular structure of arene ruthenium(II) complexes containing benzhydrazone derivative ligands with antibacterial and antioxidant properties

A suitable method for the synthesis of ruthenium(II) arene benzhydrazone complexes (1–6) of the general formula [(η6-arene)Ru(L)Cl] (arene = p-cymene or benzene; L= bidentate substituted benzhydrazone derivatives) has been described. The composition of all the complexes have been established by IR, UV-Vis and NMR spectroscopies and ESI-MS. Ruthenium precursors [(η6-arene)RuCl2]2 (arene = p-cymene or benzene) on reacting with benzhydrazone derivative ligands (L1, L2 and L3) resulted in the formation of mononuclear neutral complexes (1-6). All the neutral complexes were further reacted with NaN3 to yield azido complexes (7-12). Then, the binding modes of the benzhydrazone derivatives to the metal center for complexes (1, 5, 6, 7 and 9) have been confirmed by single-crystal X-ray diffraction studies. Further, their in-vitro antibacterial activity against gram-positive (Staphylococcus aureus) and gram-negative (Escherichia coli, Klebsiella pneumoniae) strains have been evaluated for the complexes (1-6) and their ligands. An anti-bacterial study revealed that complex 1 and complex 6 have magnificent activity against S. aureus, E. coli and K. pneumoniae. For antioxidant properties, all the complexes showed a higher percentage of DPPH radical scavenging activity than the ligands.

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.

Variable hydrazine coordination modes from reactions with dichlorotris(triphenylphosphine)ruthenium(II)

The reactivity of the prominent ruthenium(II) catalyst and precursor, RuCl2(PPh3)3, was explored with hydrazine and its derivatives. The reactions produced 6-coordinate ruthenium(II) products that bond with the hydrazine moiety in bridging (NH2NH2 or NH2NHMe), end-on (NH2NHMe, NH2NHPh, or NH2NMe2), or side-on (NH2NMe2) fashions. The products have been characterized by single crystal X-ray diffraction and 31P NMR spectroscopy. With NH2NH2, the dimeric product, [RuCl2(PPh3)2]2(μ-N2H4)2, was formed under all conditions used. For other hydrazines, the reaction stoichiometry governed product formation to yield either bimetallic or monomeric products. When the RuCl2(PPh3)3 to hydrazine derivative ratio was 1:1 or lower, bimetallic complexes were formed while a 1:2 ratio produced monomeric compounds. The exception to the latter occurs with the production of the monomeric compound, RuCl2(PPh3)2(η2-NH2NMe2), that forms employing a 1:1 ratio. In addition to stoichiometry, steric factors and hydrogen bonding played a significant role in dictating the bonding mode of hydrazines. The bimetallic complexes were further reacted to yield the corresponding monomeric products, adopting the form RuCl2(PPh3)2(L)2 (L = NH2NHMe, NH2NHPh, or NH2NMe2). Reactions utilizing less than a 1:2 ratio of RuCl2(PPh3)3 to NH2NMe2 produced a mixture of products that appear to be in equilibrium. DFT calculations were performed to gain insight into the reaction energetics and molecular stability.

Ruthenium Icosahedra and Ultrathin Platelets: The Role of Surface Chemistry on the Nanoparticle Structure

The control of the crystalline structure and shape (crystal habit) of nanoparticles (NPs) is the key to controlling their physical and chemical properties. Among the different metals, the crystallogenesis of ruthenium NPs has been less studied, and until recently, the Ru NP crystal structure and morphology have been considered as presenting less versatility than the face-centered cubic (fcc) metals of the platinum group. Here, we show that while the hydrogenation of [Ru(COD)(COT)] in solutions containing a long-chain amine (hexadecylamine, HDA) in large excess leads to isotropic NPs adopting the expected hexagonal close-packed (hcp) structure of bulk Ru, a long-chain carboxylic acid (lauric acid, LA) in large excess induces the formation of Ru nano-objects of two original structures: ultrathin platelets and icosahedra. The latter have never been produced so systematically by other methods. We show that carbon monoxide, produced in situ by the decarbonylation of lauric acid, plays a pivotal role in the stabilization of the Ru icosahedra. This result is supported by density functional theory (DFT) calculations, which show that above a critical surface coverage of CO, small Ru icosahedra are more stable than the Ru bipyramid polyhedra crystallizing in the hcp structure. Thus, in situ production of CO results in a competition between icosahedral and hcp seeds, which explains the mixture of icosahedra and ultrathin platelets. Another effect of the large excess of lauric acid is the stabilization of the ruthenium precursors in solution, limiting the nucleation extent and slowing down the NP growth. While the growth of the icosahedral seeds is limited because of the structural strains, the growth of the hcp seeds preferentially develops the (0001) facets, leading to ultrathin platelets and threefold stars.

High-efficiency catalysis of Ru-based catalysts assisted by triazine-based ligands containing different heteroatoms (N, O, S) for acetylene hydrochlorination

Ru/AC catalyst used in acetylene hydrochlorination reaction has several drawbacks such as poor dispersion, metal loss, serious carbon deposition, and insufficient active sites. To address these issues of traditional Ru/AC, in this study, the supported Ru-Lx/AC catalysts were synthesized by the coordination of ruthenium precursor and several structural triazine ligands. The complexation of heteroatomic structure to Ru atom formed a local active domain, which is more conducive to the synergistic adsorption and activation of the initial reactants, and further optimizes the reaction microenvironment. The spatial topological structure with conjugated structures effectively promoted the transfer of electrons between the heteroatoms and the ruthenium precursors, facilitating the stabilization of active Ru species. The newly developed synthetic process also increased dispersion of reaction components and impeded the sintering of ruthenium components promoted by the local structural forces. The optimum Ru-1,3,5-triazine/AC (Ru-L1/AC) catalyst exhibited 162% higher acetylene conversion than the benchmark Ru/AC catalyst. The significantly improved activity and stability of the optimized catalyst will have a huge application prospect in industry.

Molybdenum oxide decorated Ru catalyst for enhancement of lignin oil hydrodeoxygenation to hydrocarbons

Herein, the catalysts of ruthenium and molybdenum oxide nanoparticles supported on activated carbon (AC) were synthesized by precursor stepwise impregnation and employed for the hydrodeoxygenation (HDO) of lignin oil. The XRD, TEM, XPS and NH3-TPD-MS result of RuMoOx/AC catalysts confirm that the method of loading molybdenum precursor before ruthenium precursor is advantageous for the MoOx and Ru nanoparticles high dispersion and the reduction of MoOx species enhance the amount of acidity of catalyst. Meanwhile, the reduction temperature of RuMoOx/AC-1-T catalysts could effectively regulate the MoOx species that determine the activity and product distribution of HDO. The conversion of aromatic monomers/dimers were up to 96% with high selectivity of hydrocarbon over RuMoOx/AC-1-350 catalyst at 160 °C and 30 bar H2. Which is attributed to the MoO3 and Ru species possess the excellent activity of benzene ring deep hydrogenation, ether bond breaking and acid dehydration. The RuMoOx/AC-1-350 catalyst effectively converted lignin oil (from the depolymerization of cornstalk hydrolysis residue) into hydrocarbons (56.9 wt%) and cyclohexanol/ethers (18.7 wt%) under 280 °C and 3 bar H2. The durability of the RuMoOx/AC-1-350 catalyst for HDO of lignin oil was also investigated and showed that the RuMoOx/AC-1-350 catalyst had good stability, regenerability and repeatability.

Ruthenium Complex Bearing a Hydroxy Group Functionalised N‐Heterocyclic Carbene Ligand – A Universal Platform for Synthesis of Tagged and Immobilised Catalysts for Olefin Metathesis

AbstractSix olefin metathesis catalysts, based on a common ruthenium precursor featuring a hydroxy‐substituted N‐heterocyclic carbene ligand, were successfully prepared and fully characterised. As proof‐of‐concept, two of them ([Ru]isonico and [Ru]dmab) were directly immobilised on a solid support. These non‐covalently heterogenised catalysts are efficient in different metathesis reactions and sufficiently stable to be used for repeated runs under batch and continuous flow conditions. In nonpolar media such as n‐hexane, the catalytic character of the metathesis reactions is truly heterogeneous, and the contamination of the products with ruthenium is very low.

Functionalized-1,3,4-oxadiazole ligands for the ruthenium-catalyzed Lemieux-Johnson type oxidation of olefins and alkynes in water

Three arene-ruthenium(II) complexes bearing alkyloxy(5-phenyl-1,3,4-oxadiazol-2-ylamino)(4-trifluoromethylphenyl)methyl ligands were quantitatively obtained through the reaction of (E)-1-(4-trifluoromethylphenyl)-N-(5-phenyl-1,3,4-oxadiazol-2-yl)-methanimine with the ruthenium precursor [RuCl2(η6-p-cymene)]2 in a mixture of the corresponding alcohol and CH2Cl2 at 50 °C. The obtained complexes were fully characterized by elemental analysis, infrared, NMR and mass spectrometry. Solid-state structures confirmed the coordination of the 1,3,4-oxadiazole moiety to the ruthenium center via their electronically enriched nitrogen atom at position 3 in the aromatic ring. These complexes were evaluated as precatalysts in the Lemieux-Johnson type oxidative cleavage of olefins and alkynes in water at room temperature with NaIO4 as oxidizing agent. Good to full conversions of olefins into the corresponding aldehydes were measured, but low catalytic activity was observed in the case of alkynes. In order to get more insight into the mechanism, three analogue arene-ruthenium complexes were synthesized and tested in the oxidative cleavage of styrene. The latter tests clearly demonstrated the importance of the hemilabile alkyloxy groups, which may form more stable (N,O)-chelate intermediates and increase the efficiency of the cis-dioxo-ruthenium(VI) catalyst.