Ruthenium Atoms Research Articles

Band gap effect of TiO2 on supported Ru single-atom catalysts for CO2 methanation by DFT calculations

The influence of TiO2 band gap on structure and reactivity of the supported single ruthenium (Ru1) atom was studied by density functional theory calculations, utilizing Ru1/2L-TiO2 and Ru1/3L-TiO2 as model catalysts for CO2 methanation. The supports have band gaps of 2.39 eV and 1.48 eV, respectively. The band gap plays a significant role in electronic metal-support interactions (EMSIs) and the position of the d-band center of the Ru1 on the TiO2. The Ru1/3L-TiO2, the Ru1 catalyst supported on the 3L-TiO2 with a narrower band gap, shows enhanced EMSIs and a d-band center that is positioned farther from Fermi level, leading to lower charge density on the Ru1 and weaker adsorption of H2, CO2, and CO compared to the Ru1/2L-TiO2. CO2 methanation followed CO pathway, with the hydrogenation of CO* to HCO* identified as the rate-determining step on the Ru1/nL-TiO2. The Ru1 catalyst supported on TiO2 with a narrower band gap is more favorable kinetically and thermodynamically for CO2 methanation, despite the band gap not altering the reaction pathway. Enhanced hydrogen mobility and a pronounced promotional effect of hydrogen on CO adsorption, due to the narrower band gap support, are key factors facilitating the easier hydrogenation of CO* on the Ru1/3L-TiO2.

α,β‐C—C—C Agostic Bonding Interactions in Ruthenacyclobutane and π‐Complex Assisted Olefin Metathesis Catalyzed by Ruthenium‐Alkylidene Complexes

ABSTRACTComputational aspects of concerted [2+2] oxidative‐retrocycloaddition‐cycloreversion reaction through ruthenium alkylidene π‐complexes and ruthenacyclobutane with α,β‐(C—C—C) agostic bonding interactions in olefin metathesis are presented. d6‐Ruthenium carbene complexes, with ruthenium in the oxidation state +2, undergo successive [2+2] cycloaddition and cycloreversion steps, through associative, dissociative, or interchange mechanisms. This process involves coordination of the olefin to 16‐electron Ru complex followed by phosphine dissociation, or first phosphine dissociation then coordination of the olefin to the 14‐electron Ru complex with rearrangement to a ruthenacyclobutane intermediate, followed by symmetrical reverse steps. Donation of σ‐electron density from the two C—C σ‐bonds to the metal center leads to α,β‐(C—C—C) agostic bonds, which stabilized metallacyclobutane as a formally 16‐electron complex, with lower energy than the corresponding π‐complex. In the transformation from π‐complex to ruthenacyclobutane the ruthenium atom is formally oxidized to Ru(IV). The most efficient ligands are those that stabilize the high‐oxidation state metallacyclobutane (IV) intermediate relative to the ruthenium carbene.

Ruthenium Single-Atom Modulated Protonated Iridium Oxide for Acidic Water Oxidation in Proton Exchange Membrane Electrolysers.

Proton exchange membrane water electrolysers promise to usher in a new era of clean energy, but they remain a formidable obstacle in designing active and durable electrocatalysts for the acidic oxygen evolution reaction (OER). In this study, a protonated iridium oxide embedded with single-atom dispersed ruthenium atoms (H3.8Ir1- xRuxO4) that demonstrates exceptional activity and stability in acidic water oxidation is introduced. The single Ru dopants favorably induce localized oxygen vacancies in the Ir─O lattice, synergistically strengthening the adsorption of OOH* intermediates and enhancing the intrinsic OER activity. In addition, the preferential oxidation of Ru and the electronegativity of the oxygen vacancies significantly stabilize the Ir─O active sites, improving the OER stability. Consequently, the H3.8Ir1─ xRuxO4 catalyst shows an overpotential of 255mV at 10mA cm-2 and displays exceptional catalytic endurance in acidic electrolytes, surpassing 1100 h, representing a remarkable one-order-of-magnitude increase in stability compared to that of pristine H3.8IrO4. A proton exchange membrane electrolyser utilizing the H3.8Ir1- xRuxO4 catalyst as an anode exhibits stable performance for more than 1280 h under a high current density of 2 A cm-2.

Ruthenium atoms anchored on oxygen-modified molybdenum disulfide with strong interfacial coupling as efficient and stable catalysts for lithium–oxygen batteries

Rechargeable non-aqueous lithium-oxygen batteries (LOBs) have garnered increasing attention owing to their high theoretical energy density. However, their slow cathodic kinetics hinder efficient battery reactions. Nanoscale catalysts can effectively enhance electrocatalytic activity and atomic utilization efficiency. However, the agglomeration of nanoscale catalysts (such as cluster and single atoms) during continuous discharge/charge cycles leads to decreased electrochemical performance and poor cyclic stability. Herein, the ruthenium (Ru) atomic sites anchored on an O-doped molybdenum disulfide (O-MoS2) catalyst (designated as Ru/O-MoS2) was fabricated using a facile impregnation and calcination method. Strong Ru-O coupling between Ru atoms and the O-MoS2 substrate optimizes the localized electronic structure, resulting in improved electrochemical performance and enhanced resistance to Ostwald ripening. When employed as a cathode catalyst for LOBs, Ru/O-MoS2 catalyst exhibits a high reversible specific capacity (18700.5 (±59.8) mAh g−1), good rate capability, and enhanced long-term stability (115 cycles, 1200 h). This study encourages facile and efficient strategies for the development of effective and stable electrocatalysts for use in LOBs.

The effect of ion implantation and annealing temperatures on the migration behavior of ruthenium in glassy carbon

Nuclear waste storage materials are inevitable in nuclear industry for preventing the release of radioactive waste products. Glassy carbon has been considered being beneficial to be used in the dry cask needed for nuclear waste storage. Thus, we studied the migration of ruthenium implanted in glassy carbon upon annealing. Our investigations show that ruthenium implantation caused defects in the glassy carbon structure, with more defects observed in the room temperature as-implanted samples compared to those implanted at 200 °C. Annealing the as-implanted samples from 500 to 800 °C showed no significant change in the ruthenium depth profiles, indicating the non-diffusivity of ruthenium in glassy carbon at these temperatures. However, annealing at higher temperatures (from 900 and 1300 °C) resulted in an increase in the maximum depth profile peaks, accompanied by a shift towards the surface, and a decrease in the full-width at half-maximum. These changes indicate the aggregation of ruthenium atoms in the near-surface region. Additionally, more ruthenium aggregation was observed in room temperature implanted samples compared to those implanted at 200 °C. This difference is attributed to the higher concentration of defects in room temperature implanted samples, which promotes ruthenium aggregation. Moreover, the migration and aggregation of ruthenium in the near-surface region contributed to an increase in the surface roughness of the glassy carbon.

Core-shell Ru@Co2P synergistic catalyst as polysulfides adsorption-catalytic conversion mediator with enhanced redox kinetics in lithium-sulfur batteries

Lithium-sulfur batteries (LSBs) have emerged as the research hotspot due to their compelling merits, including high specific capacity (1675 mAh g−1), theoretical energy density (2600 Wh kg−1), environmental friendliness, and economic advantages. However, challenges still exist for further application due to their inherent issues such as the natural insulation, shuttle effect, and volume expansion of sulfur cathode during the continuous cycle processes. These factors obstruct the lithium ions (Li+) transfer process and sulfur utilization, resulting in significant impedance and inducing inferior battery performance. Herein, the core–shell nanocube anchoring ruthenium atoms and dicobalt phosphate (Ru@Co2P@NC) were fabricated as the effective catalyst and inhibited barrier for LSBs. On the one hand, the core–shell structure offers numerous channels to expedite Li+ diffusion. On the other hand, ruthenium (Ru) and dicobalt phosphate (Co2P) active sites facilitate the chemical capture of lithium polysulfides (LiPSs), accelerating sluggish kinetics. Ru@Co2P@NC modified cells not only exhibited a high initial specific capacity (1609.35 mAh g−1) at 0.5C and enduring stability with high specific capacity retention of 906.60 mAh g−1 at 0.5C after 400 cycles but also possessed low capacity attenuation rate of 0.07 % per cycle after 600 cycles (1C, Sulfur loading: 1.2 mg). Interestingly, the modified cells demonstrated a high specific capacity and long-cycle stability with high sulfur loading (from 1.984 to 3.137 mg), which provides a promising research approach for high-performance LSBs.

Trinuclear and Tetranuclear Ruthenium Carbonyl Nitrosyls: Oxidation of a Carbonyl Ligand by an Adjacent Nitrosyl Ligand.

Trinuclear and tetranuclear ruthenium carbonyls of the types Ru3(CO)n(NO)2, Ru3(N)(CO)n(NO), Ru3(N)2(CO)n, Ru3(N)(CO)n(NCO), Ru3(CO)n(NCO)(NO), Ru4(N)(CO)n(NO), Ru4(N)(CO)n(NCO), and Ru4(N)2(CO)n related to species observed experimentally in the chemistry of Ru3(CO)10(µ-NO)2 have been investigated using density functional theory. In all cases, the experimentally observed structures have been found to be low-energy structures. The low-energy trinuclear structures typically have a central strongly bent Ru-Ru-Ru chain with terminal CO groups and bridging nitrosyl, isocyanate, and/or nitride ligands across the end of the chain. The low-energy tetranuclear structures typically have a central Ru4N unit with terminal CO groups and a non-bonded pair of ruthenium atoms bridged by a nitrosyl or isocyanate group.

The investigation on the synthesis, characterization and anticancer activity of Ru-based chelating diphosphine ligand compounds

Compound trans-[RuIII(dmpe)2Cl2]2(PF6)2 (2) (dmpe = 1, 2 - bis (dimethylphosphino) ethane) was obtained by directly reaction of trans-[RuII(dmpe)2Cl2] (1) with [Cp2FeIII(PF6)]. trans-[RuIII(dmpe)2Cl2]2(FeIIIX4)2 (X = Cl, 3; X = Br, 4) were prepared by reaction of compound 1 with FeX3 (X = Cl, Br), respectively. Compounds 2-4 were characterized by IR, electronic absorption spectra, elemental analysis and Single-crystal X-ray diffraction, respectively. Single-crystal X-ray diffraction studies indicate that the ruthenium atoms in compounds 2-4 all define a slightly distorted octahedron with a [RuP4Cl2] coordination core, and the iron atoms in anion FeX4− of compounds 3 and 4 displays the expected tetrahedron with a [FeX4]− coordination core. Both metal-to-ligand charge-transfer (MLCT) and ligand-to-metal charge-transfer (LMCT) transitions exhibit in the lectronic absorption spectra of compounds 2-4. The in vitro activity of compounds 1-4 was evaluated in A549 and HeLa as well as MCF7 cell lines. The relative cell viability of compounds 2-4 on A549, HeLa and MCF7 cancer cells is in the order of 2>3>4 >1 by CCK-8 method. Compounds 2-4 have better activity than that of cisplatin in higher concentration, especially compound 2.

Hydrogenation of hexene catalyzed by a ruthenium (II) complex with N‐heterocyclic carbene ligands

AbstractIn this study, we investigated the mechanism of the inactivated hexene hydrogenation reaction catalyzed by a ruthenium (II) complex containing “N‐heterocyclic carbene” (NHC) ligands, specifically SIMes and CBA, using DFT calculations. Our focus was on RuH(OSO2CF3)(CO)(SIMes)(CBA), which exhibits excellent catalytic behavior. We tested the B3LYP‐D3, cam‐B3LYP, and TPSSh functionals. The hydrogenation reaction is initiated by the release of SIMes rather than CBA due to the lower associated dissociation energy. Our findings indicate a reaction mechanism consisting of two consecutive steps, each involving one hydrogen atom migration. The first step, considered as the kinetically limiting transition state, exhibits a Gibbs free activation barrier of 12.9 kcal mol−1. This step involves two asynchronous processes. The first one describes the migration of the ruthenium hydride to the internal carbon of the olefine function, transitioning from π to σ coordination mode, which promotes the formation of a bond between ruthenium and the terminal olefinic carbon. The second process involves the oxidation of ruthenium from Ru(II) to Ru(IV). This oxidation is crucial as it enables the decomposition of the H2 molecule into two hydrogen atoms bonded to the ruthenium atom. The geometrical structures of the Hidden Reaction Intermediate Ru(II) complex and the quasi‐transition state of the second process have been determined by means of the RIRC technique. The second step entails the migration of one of the newly formed hydrides of the Ru(IV) complex to the terminal olefinic carbon, resulting in the release of hexane with a weak activation Gibbs free energy of .8 kcal mol−1. Lastly, we explored the use of dichloromethane as a solvent, considering the PCM model. The presence of the solvent significantly decreases the energy dissociation of SIMes from 17.9 to 9.0 kcal mol−1, providing notable benefits.

Regulation of electrons between Ru and VN for high performance HER of low-level Ru doping in vanadium-nitrogen doped carbon catalysts

Transition metal nitrides (TMNs) have garnered significant attention for their catalytic activity similar to noble metals, attributed to their distinctive electronic structures. However, the sluggish reaction kinetics have hindered the progress in TMN development. In this study, an alloying approach was employed to create Ru@VN/C catalysts by uniformly dispersing low levels of ruthenium (Ru) in vanadium-nitrogen doped carbon (VN/C) on carbon spheres. Through alloying, the electronic structures of ruthenium and vanadium atoms were further adjusted, leading to exceptional catalytic activity resulting from unique electron transfer between the atoms. The Ru@VN/C catalyst demonstrated a low overpotential of 5 mV and a Tafel slope of 27 mV·dec−1 at 10 mA·cm−2 in alkaline seawater solution, as well as superior performance in alkaline and simulated seawater solutions. The interatomic synergistic interactions, driven by charge redistribution as confirmed by density functional theory calculations and experimental data, play a crucial role in expanding the applications of TMNs in green hydrogen production.

Oxophilic vanadium and deprotonated ruthenium atoms on tungsten carbide with accelerated intermediate migration for high-performance seawater hydrogen evolution

Compared with traditional freshwater electrolysis, the seawater electrolysis process is confronted with low activity and poor stability problems due to the deposition of insoluble hydroxides and corrosion of chloride species; thus, engineering efficient catalysts for seawater electrolysis are extremely desirable but remain challenging. Herein, we have developed an efficient and robust electrocatalyst by engineering oxophilic vanadium and deprotonated ruthenium atoms on tungsten carbide (WC-RuV) as a highly active and anti-poisoning cathode material for superior seawater electrolysis. Benefiting from the high oxophilicity and electron transfer ability of V, the interaction between the OH* generated via water dissociation and Ru sites is weakened, which facilitates the OH* transfer process and consequently attenuates the formation of insoluble hydroxides. Notably, when working in simulated seawater electrolytes, the WC-RuV requires an ultralow overpotential, and the WC-RuV@carbon cloth can maintain high activity and stability even at 200 mA cm−2. The assembled WC-RuV||RuO2 anion exchange membrane (AEM) electrolyzer realizes long-term stability at the current of 100 mA cm−2 and achieves continuous operation powered by commercially available solar panels. This work provides an efficient strategy for modulating the water dissociation process and offers a new perspective for designing high-performance catalysts for the forthcoming application of seawater electrolysis.

Selective cross-metathesis of cellobiose derivatives with amido-functionalized olefinic structures: A model study for synthesis of cellulosic diblock copolymers

This work describes a model study for synthesis of cellulose-based block copolymers, investigating selective coupling of peracetyl β-d-cellobiose and perethyl β-d-cellobiose at their reducing-ends by olefin cross-metathesis (CM). Herein we explore suitable pairs of ω-alkenamides that permit selective, quantitative coupling by CM. Condensation reactions of hepta-O-acetyl-β-d-cellobiosylamine or hepta-O-ethyl-β-d-cellobiosylamine with acyl chlorides afforded the corresponding N-(β-d-cellobiosyl)-ω-alkenamide derivatives with an aromatic olefin or linear olefinic structures. Among the introduced olefinic structures, CM of the undec-10-enamide (Type I olefin) and the acrylamide (Type II olefin) gave the hetero-block tetramers, N-(hepta-O-ethyl-β-d-cellobiosyl)-N′-(hepta-O-acetyl-β-d-cellobiosyl)-alkene-α,ω-diamides, with >98 % selectivity. Moreover, selectivity was not influenced by the cellobiose substituents when a Type I olefin with a long alkyl tether was used. Although the amide carbonyl group could chelate the ruthenium atom and reduce CM selectivity, the results indicated that such chelation is suppressed by sterically hindered pyranose rings or the long alkyl chain between the amido group and the double bond. Based on this model study, selective end-to-end coupling of tri-O-ethyl cellulose and acetylated cellobiose was accomplished, proving the concept that this model study with cellobiose derivatives is a useful signpost for selective synthesis of polysaccharide-based block copolymers.

Stable solvatochromic light-emitting diodes and their potential for color temperature adjustment of white LEDs

A viable technology for liquid phosphor-based light-emitting diodes (LEDs) with emission color tuneability is described. These devices are based on Tris(bipyridine)ruthenium(II) chloride but can be constructed from other similar metal coordination charge transfer complexes. The Frank-Condon excited state generated upon the absorption of blue (450 nm) pump photons has a large electric dipole moment due to intramolecular metal-to-ligand charge transfer from the ruthenium atom to one specific bipyridyl ligand. Polar solvents respond to the dipole field creating a solvatochromic shift that is solvent dependent. The devices were fully sealed in either a long path length or a short path length configuration. The latter encapsulating the luminescing medium in hollow silica spheres that can be easily applied like a slurry on top of InGaN/GaN LED dies. The devices were optically, thermally and environmentally stable. Also discussed is the possibility of using solvatochromic emitters for achieving color temperature tuneability in white LEDs.

Mid-IR and CH stretching vibrational circular dichroism spectroscopy to distinguish various sources of chirality: The case of quinophaneoxazoline based ruthenium(II) complexes.

Five diastereomers of ruthenium(II) complexes based on quinolinophaneoxazoline ligands were investigated by vibrational circular dichroism (VCD) in the mid-IR and CH stretching regions. Diastereomers differ in three sources of chirality: the planar chirality of the quinolinophane moiety, the central chirality of an asymmetric carbon atom of the oxazoline ring, and the chirality of the ruthenium atom. VCD, allied to DFT calculations, has been found to be effective in disentangling the various forms of chirality. In particular, a VCD band is identified in the CH stretching region directly connected to the chirality of the metal. The analysis of the calculated VCD spectra is carried out by partitioning the complexes into fragments. The anharmonic analysis is also performed with a recently proposed reduced-dimensionality approach: such treatment is particularly important when examining spectroscopic regions highly perturbed by resonances, like the CH stretching region.

Ca3Ru3Zn13 – a zinc-rich intermetallic phase composed of closest-packed layers

Abstract Ca3Ru3Zn13 was synthesized from the elements in a tantalum tube in a muffle furnace. The sample was annealed to 1123 K followed by slow cooling to enhance crystal growth. Ca3Ru3Zn13 was characterized through a Guinier powder pattern. The structure was refined from single crystal X-ray diffractometer data: new type, Pbcn, a = 522.92(5), b = 1792.72(14), c = 2789.6(2) pm, wR2 = 0.0590, 3451 F 2 values, 177 variables. One can describe the Ca3Ru3Zn13 structure by a stacking of closest packed layers of compositions Ca6Zn10, Ca6Zn12 and Ru6Zn15. The calcium atoms have high coordination numbers: Ca1@Zn13Ru3Ca2, Ca2@Zn15Ru4Ca, Ca3@Zn15Ru4Ca and Ca4@Zn15Ru4Ca. The shortest interatomic distances occur between the ruthenium and zinc atoms (255–273 pm). The Ru1@Zn8, Ru2@Zn10 and Ru3@Zn8 polyhedra condense via common edges to the [Ru3Zn13] substructure which hosts the calcium atoms. The zinc substructure consists of 15 crystallographically independent zinc sites with a broader range of Zn–Zn distances (255–307 pm).

The germanides ScTGe2 (T = Fe, Co, Ru, Rh) – crystal chemistry, 45Sc solid-state NMR and 57Fe Mössbauer spectroscopy

Abstract The TiMnSi2-type (space group Pbam) germanides ScTGe2 (T = Fe, Co, Ru, Rh) were synthesized from the elements by arc-melting. Single crystals were grown by annealing sequences of the arc-melted buttons in an induction furnace. The structures of ScFeGe2, ScRuGe2 and ScRhGe2 were refined from single-crystal X-ray diffraction data. In ScRuGe2, the ruthenium atoms have distorted octahedral germanium coordination (242–268 pm Ru–Ge). Three trans-face-sharing octahedra form a sub-unit which is condensed via common edges in c direction and connected via common corners with four adjacent blocks, forming a three-dimensional [RuGe2 type] substructure. The two crystallographically independent scandium sites have coordination numbers 15 (Sc1@Ge8Ru4Sc3) and 17 (Sc2@Ge7Ru6Sc4). Electronic band structure calculations for ScCoGe2 and ScRuGe2 show a net charge transfer from the scandium to the transition metal and germanium atoms, leading to a description with polyanionic networks Sc δ+[TGe2]δ−. The two crystallographically independent Sc sites are easily distinguishable by 45Sc magic-angle spinning (MAS)-NMR spectroscopy. Isotropic chemical shift values and nuclear electric quadrupolar interaction parameters were deduced from an analysis of the triple-quantum (TQ)-MAS NMR spectra. The electric field gradient parameters deduced from these experiments are in good agreement with quantum-chemical calculations using the Wien2k code. Likewise, the two crystallographically independent iron sites in ScFeGe2 could be discriminated in the 57Fe Mößbauer spectra through their isomer shifts and quadrupole splitting parameters: δ = 0.369(1) mm s−1 and ∆E Q = 0.232(2) mm s−1 for Fe1 and δ = 0.375(2) mm s−1 and ∆E Q = 0.435(4) mm s−1 for Fe2 (data at T = 78 K).

How an Internal Supramolecular Interaction Determines the Stereochemistry of a Metal Center

The chloro-P,N-{diphenylphosphanyl-[(5-phenyl-1,3,4-oxadiazol-2-ylamino)phenyl-me- thyl]}(p-cymene)ruthenium(II) hexafluorophosphate complex (4) was obtained in two steps from diphenylphosphanyl-[(5-phenyl-1,3,4-oxadiazol-2-ylamino)phenyl-methyl] borane (2). In the first step, the oxadiazole ring coordinated with the ruthenium atom, resulting in the formation of the dichloro-N-{diphenylphosphanyl-[(5-phenyl-1,3,4-oxadiazol-2-ylamino)phenyl-methyl]borane}(p-cymene) ruthenium(II) complex (3). During the crystallization of the P,N-chelate ruthenium complex, the formation of conglomerate crystals was revealed by X-ray structure analysis. Only two stereoisomers were obtained with (S)-Ru and (R)-C configurations in the first complex and with (R)-Ru and (S)-C configurations in the second. This deracemization during crystallization is due to the formation of a hydrogen bond between the P,N-ligand and the chlorine atom (CH•••Cl). This supramolecular interaction allows the transfer of the ligand chirality to the metal center and decrees the stereochemistry of the ruthenium atom.

Atomic-scale Ru anchored on chromium-shavings as a precursor for a pH-universal hydrogen evolution reaction electrocatalyst.

In the leather manufacturing industry, the management of substantial quantities of solid waste containing chrome shavings remains a formidable challenge. Concurrently, there is a pressing need for the development of pH-universal and economically viable electrocatalysts for the hydrogen evolution reaction (HER). In response to these intertwined challenges, this study proposes an innovative approach wherein the amino groups present on the surface of chrome shavings are utilized to immobilize single ruthenium atoms during pyrolysis, thereby facilitating the synthesis of hydrogen evolution electrocatalysts. The optimized sample, denoted as CN/Cr2O3/Ru-1, demonstrates exceptional electrocatalytic performance, exhibiting an ultra-low overpotential of -28 mV in 1.0 M KOH at a current density of 10 mA cm-2, and it also exhibits good performance in acidic and neutral electrolytes. Importantly, these overpotentials surpass those reported for many previous ruthenium-based catalysts. Density functional theory (DFT) calculations elucidate that both oxygen (O) and chromium (Cr) moieties within Cr2O3 can engage in favorable interactions with the coordination patterns of the ruthenium (Ru) atoms, thereby elucidating the synergistic enhancement conferred by the chromium element in CN/Cr2O3/Ru, which ultimately facilitates and promotes the catalytic activity of the ruthenium atoms serving as the catalytic center. This facile synthesis route not only presents a green solution for addressing waste chromium pollutants but also offers a promising avenue for the development of high-performance, cost-efficient electrocatalysts.

Half-sandwich ruthenium complexes with acylhydrazone ligands: synthesis and catalytic activity in the N-alkylation of hydrazides.

Novel half-sandwich ruthenium complexes termed [(p-cymene)RuClL] were synthesized by chelating arylhydrazone ligands with [(p-cymene)RuCl2]2 and were then fully characterized using different spectroscopic and analytical techniques. The crystal structure of complex 4 indicated that the hydrazone ligands bonded to the ruthenium ion in a bidentate manner through the imine nitrogen and imidazolate oxygen, exhibiting a pseudo-octahedral geometry centered by the ruthenium atom. The as-fabricated air and moisture stable half-sandwich ruthenium complexes demonstrated excellent catalytic activity towards the N-alkylation of hydrazides under mild conditions. Under the catalysis of ruthenium complexes, acyl hydrazides were reacted with different types of alcohols in a one-pot reaction, resulting in N-alkylation hydrazides with different substituents. This catalyst exhibited characteristics such as high catalytic efficiency, broad substrate scope, and mild reaction conditions, indicating that it has great potential for industrial applications.

Binuclear methylphosphinidine complexes of cyclopentadienylruthenium carbonyls: effects of the higher ligand field strength of ruthenium derivatives relative to iron derivatives.

The structures and energetics of the binuclear methylphosphinidene complexes of cyclopentadienylruthenium carbonyls of the type [MePRu2(CO)nCp2] (n = 4, 3, 2, 1) have been investigated for comparison with their previously studied iron analogues. For the tetracarbonyls and tricarbonyls [MePM2(CO)nCp2] (n = 4, 3) substituting ruthenium for iron has relatively little effect on the energetically preferred structures. Thus such structures have two-electron donor bridging MeP groups with no metal-metal bond for the tetracarbonyls and a metal-metal single bond for the tricarbonyls. This leads to favored 18-electron configurations for both ruthenium atoms in all cases. However, the higher ligand field strengths of ruthenium complexes relative to analogous iron complexes have major effects on the energetically preferred structures for the dicarbonyls and monocarbonyls [MePM2(CO)nCp2] (M = Fe, Ru; n = 2, 1). Thus the 11 lowest energy structures for the dicarbonyl [MePFe2(CO)2Cp2] are triplet or quintet spin state structures whereas the 6 lowest energy structures for the ruthenium analogue [MePRu2(CO)2Cp2] are all singlet structures. These low-energy singlet [MePRu2(CO)2Cp2] structures include species in which both ruthenium atoms attain the favored 18-electron configurations in different ways: either by a Ru-Ru single bond and an agostic C-H-Ru interaction from the methyl group, a Ru-Ru single bond and a four-electron donor bridging MeP ligand with PRu double bonds, or a formal RuRu double bond with a two-electron donor bridging MeP ligand. The 8 lowest energy structures for the diiron monocarbonyl [MePFe2(CO)Cp2] are all triplet or quintet spin structures whereas the lowest energy structure for the diruthenium monocarbonyl [MePRu2(CO)Cp2] by more than 20 kcal mol-1 is a singlet structure with a formal RuRu double bond and bridging CO and four-electron donor MeP groups. Thermochemical information predicts such monocarbonyl derivatives to be the dominant binuclear decarbonylation products of the tricarbonyls [RPRu2(CO)3Cp2] by thermal or photochemical methods.