Ruthenium Carbonyl Clusters Research Articles

GeRu6(CO)18HI]: A Germanium-Centered Ruthenium Carbonyl Cluster with Aromatic Ring Current.

The carbonyl cluster compound [GeRu6(CO)18HI] is unique in regard to its structure and bonding with a GeRu6 cluster core, a planar GeRu4HI unit, extensive multi-center bonding, and an aromatic ring current similar to benzene (9-10nAT-1). The open-shell cluster core is a Ge-centered five-membered Ru4(Ru2) ring with CO ligands and an additional H and I atom, each bridging two Ru atoms on opposite sides of the cluster core. The compound is prepared at 130°C in a weakly-coordinating ionic liquid.

The growth of higher nuclearity carbonyl clusters of ruthenium and osmium

In this review the synthetic and structural chemistry of osmium and ruthenium clusters is described with emphasis on the studies carried out during the 1980s and 1990s when research in the area was prolific. The methods of cluster synthesis are discussed as are the techniques used to characterise the complexes. The electron counting methods that are used to predict and rationalise the cluster structures are highlighted. Emphasis is placed on the synthetic methods used to build high nuclearity carbonyl clusters of osmium and ruthenium, namely vacuum pyrolysis, the linking of cluster fragments with bridging ligands, and the development of methodologies used to build higher nuclearity mixed-metal clusters.

Synthesis of ruthenium carbonyl cluster complexes containing bis(2′-pyridylethynyl)benzene derivatives: Construction of an extended Zero-valent ruthenium chain

The reactions of Ru3(CO)12 in a refluxing acetonitrile-toluene solution with a half equivalent of the ligand 1,3-bis(pyridin-2-ylethynyl)benzene afforded Ru3(CO)7(μ-CO)[μ-(2-PyCCH)(1,3-C6H3)(2-PyCC)]Ru4(CO)12 (compound 1) and Ru3(CO)7(μ-CO)[μ-(2-PyCCH)(1,3-C6H2)(2-PyCCH)]Ru3(CO)8 (compound 2). Separately, Ru3(CO)12 was treated with a half equivalent of 1,4-bis(pyridin-2-ylethynyl)benzene in a refluxing acetonitrile-toluene solution to generate Ru3(CO)7(μ-CO)[μ-(2-PyCCH)(1,4-C6H3)(2-PyCC)]Ru4(CO)12 (compound 3) and Ru3(CO)8Ru(CO)2[μ-(2-PyCCH)(1,4-C6H2)(2-PyCCH)]Ru3(CO)8 (compound 4). Compounds 1–4 were characterized by FT-IR, NMR, ESI-HRMS and single-crystal X-ray diffraction. The structure of compound 2 was found to contain two triruthenium triangular frameworks, and compound 1 was found to be an intermediate of compound 2. Compounds 1 and 3 were shown to consist of triruthenium and tetraruthenium frameworks. Both compounds 1 and 3 exhibited two types of fluxional behavior in solution due to degenerate rearrangement of the acetylide ligand and restricted rotation. This assumption was confirmed by the variable-temperature 1H NMR, COSY and NOESY spectra. Noticeably, compound 4 possessed a quasilinear pentaruthenium structure, and compound 3 was shown to be an intermediate to compound 4.

Chemical Bonding Topology of Metal-Centered Polygonal Wheels: Two-Dimensional Analogues of Metallaboranes Related to Benzene and Cyclopentadienide.

The anion [Au@Ru5(CO)15(μ-CO)4]- has a pentagonal wheel structure that can be derived from a hypothetical pentagonal ruthenium carbonyl cluster Ru5(CO)20 by insertion of a gold atom in the center, thereby splitting the original Ru5 pentagon in Ru5(CO)20 into five AuRu2 triangles. The six electrons used to form 3c-2e bonds in three of the five AuRu2 triangles suggest a relationship to the aromatic sextet of the likewise pentagonal cyclopentadienide anion. Furthermore, the pentagonal wheel framework of [Au@Ru5(CO)15(μ-CO)4]- can be derived from a pentagonal bipyramid, such as that found in the deltahedral borane anion B7H72-, by bringing the two C5 axial vertices together at the center of the equatorial pentagon. Similarly, the hexagonal wheel complexes Ni@P6R6 and Pd@Pd6(μ-N═CtBu2)6 with six triangular faces can be derived from a hexagonal bipyramid, such as that found in the dirhenaborane (η5-Me5C5)2Re2B6H4Cl2, by bringing the two C6 axial vertices together at the center of the equatorial hexagon. A reasonable chemical bonding model for the hexagonal wheel complexes has three-fold symmetry with 3c-2e bonds in three of these six triangular faces analogous to the C═C double bonds in a Kekulé structure of benzene.

In Search of Multi-Stage Mutation Resistant HIV Drugs: A DFT Study

Aims: Searching of highly active (activity at the pico molar level) multi-stage, mutation registrant HIV-1 drug through theoretical and computational methodologies. Background: Recent advances of computational methodology to predict the important properties of a drug, like IC50, LogP, CC50, etc., assist in model and in-silico characterization of compounds as drug for variant deadly diseases. The drug potency of thio-propionate derivatives of iron, ruthenium and osmium carbonyl clusters are reported as less toxic,water-soluble, easy metabolic and effective as cancer drugs. Objective: The study of the drug-like activity of organo-metallic clusters of group-8 metals as HIV drug using the latest computational aids is the objective of the present research. Method: Quantum computational methodologies are used to predict the IC50, and LogP, CC50 of the modeled compounds. Density Functional Theory (DFT) calculations are used where it is required. Molecular docking methods are used for the study of the metabolic probability of the compound which has the best activity as an HIV drug. Result: It is observed that IC50 of Ru5(CO)14(µ−H)(µ−S(CH2)2COO−)Na+ is only 220 pico-mole as HIV-1 capsid -A inhibitor. Its inhibition activities in other enzymatic processes involved in the HIV life cycle in the human body are also studied and compared with the most used market available drugs. This modeled compound has supreme activity and less toxicity compared to the FDA approved drugs chosen for the comparison. Conclusion: From this study, it could be concluded that this modeled compound would be a multi-stage, mutation resistant HIV drug. Other: These findings would enrich the HIV drug search. Funding Statement: None to declare Declaration of Interests: None to declare

Aerobic oxidation of primary benzylic amines to amides and nitriles catalyzed by ruthenium carbonyl clusters carrying N,O-bidentate ligands.

Four trinuclear ruthenium carbonyl clusters, (6-BrPyCHRO)2Ru3(CO)8 (R = 4-OCH3C6H4, 1a; R = 4-BrC6H4, 1b) and (2-OC6H4-HC[double bond, length as m-dash]N-C6H4R)2Ru3(CO)8 (R = 4-OCH3, 2a; R = 4-Br, 2b), were synthesized from the reactions of Ru3(CO)12 with the corresponding N,O-bidentate ligands (two pyridyl alcohols and two Schiff bases) respectively in a ratio of 1 : 2. Three new complexes 1b, 2a and 2b have been fully characterized by elemental analysis, FT-IR, NMR and X-ray crystallography. The catalytic activity of these ruthenium complexes for the aerobic oxidation of primary benzylic amines to amides and nitriles in the presence of t-BuOK was investigated, of which the Schiff base complex 2a was found to exhibit the highest activity.

Hybrid Materials: Flexible Modulation of CO‐Release Using Various Nuclearity of Metal Carbonyl Clusters on Graphene Oxide for Stroke Remediation (Adv. Healthcare Mater. 5/2018)

A facile CO-release material for in-situ vasodilation as a treatment for stroke-related vascular diseases is developed by K.V. Kong, L.D. Liao and co-workers in article number 1701113. Utilizing the size dependent adsorption properties of ruthenium carbonyl clusters (Ru-CO) onto graphene oxide (GO), the rate and amount of formation of the CO release-active RuII(CO)2 species can be modulated by a simple mixing procedure. Further modulation of thermal and CO release properties can be achieved via a hybridization of medium- and high- nuclearity of Ru-CO clusters that can provide photo-thermal response for in-situ CO release in a cortical photo-thrombotic ischemia rat model.

Flexible Modulation of CO-Release Using Various Nuclearity of Metal Carbonyl Clusters on Graphene Oxide for Stroke Remediation.

Utilizing the size-dependent adsorption properties of ruthenium carbonyl clusters (Ru-carbon monoxide (CO)) onto graphene oxide (GO), a facile CO-release platform for in situ vasodilation as a treatment for stroke-related vascular diseases is developed. The rate and amount of formation of the CO-release-active RuII (CO)2 species can be modulated by a simple mixing procedure at room temperature. The subsequent thermally induced oxidation of RuII (CO)2 to RuO2 on the GO surface results in the release of CO. Further modulation of thermal and CO-release properties can be achieved via a hybridization of medium- and high-nuclearity of Ru-CO clusters that produces a RuO2 /RuII (CO)2 /6 Ru-CO-GO composite, where 6 Ru-CO-GO provides a photothermally activated reservoir of RuII (CO)2 species and the combined infrared absorption properties of GO and RuO2 provides photothermal response for in situ CO-release. The RuO2 /RuII (CO)2 /6 Ru-CO-GO composite does not produce any cytotoxicity and the efficacy of the composite is further demonstrated in a cortical photothrombotic ischemia rat model.

A rapid and highly sensitive strain-effect graphene-based bio-sensor for the detection of stroke and cancer bio-markers.

Here, we propose a highly sensitive and rapid bio-sensor for the detection of bio-markers for stroke and cancer-related diseases, based on the utilization of the adsorption properties of ruthenium carbonyl (Ru-CO) clusters on monolayer graphene (MG). A fast rate of decarbonylation of Ru-CO to form ruthenium oxide nanoparticles (RuO2 NPs) on MG was observed. The quantitative detection of matrix metalloproteinase-2 (MMP-2) (bio-marker for stroke and vascular diseases) was demonstrated by tracking the spectral shift of the characteristic G band of graphene caused by the adsorption of RuO2 NPs. A concentration as low as 17 ng mL-1 of MMP-2 was detected in a simulated clinical serum sample. This effective bio-sensor has the potential to revolutionize the biomedical field in the early detection and possible prevention of stroke and cancer diagnosis.

High-nuclearity ruthenium carbonyl cluster chemistry. 9. Ligand substitution at decaruthenium carbonyl clusters

The mono- to tri-substituted decaruthenium cluster anions [Ru10(μ-H)(μ6-C)(CO)24–x(L)x]- [L = P(C6H4Me-4)3, AsPh3, SbPh3, x = 1–3] were prepared as their [PPh4]+ salts in moderate to good yields from reaction of [PPh4][Ru10(μ-H)(μ6-C)(CO)24] with the corresponding group 15 ligands at room temperature in acetone. The tetrakis-substituted cluster Ru10(μ6-C)(μ3-CO)(μ-CO)(CO)19{P(C6H4Me-4)3}4 was obtained in high yield from [PPh4]2[Ru10(μ6–C)(CO)24] and an excess of the phosphine under the same conditions; a single-crystal X-ray diffraction study revealed that the phosphines ligate at the vertices of the “giant tetrahedral” core. Kinetics studies of the formation of [PPh4][Ru10(μ-H)(μ6-C)(AsPh3)2(CO)22] from [PPh4][Ru10(μ-H)(μ6-C)(AsPh3)(CO)23] shows that ligand substitution at these giant tetrahedral clusters proceeds via a strongly associative pathway with the likely intermediacy of a Ru-Ru bond-cleaved intermediate.

Antiproliferative activity of ruthenium and osmium clusters with phosphine ligands

New ruthenium and osmium carbonyl clusters with 1,3,5-triaza-7-phosphatricyclo-[3.3.1.13.7]decane and 3,7-diacetyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane ligands were synthesized using Me3NO as an initiator. The data on antiproliferative activity of new compounds against ovarian carcinoma cell cultures A2780 (cisplatin-sensitive) and A2780cisR (cisplatin-resistant) are reported. The dependence of cytotoxicity on the number of phosphine ligands was demonstrated.

Reactivity of 1,3-ynone in transformation of Ru2–Ru4 clusters: Formation of ruthenoles via tetraruthenium intermediate

A robust “soft and hard” alkyne ligand, 1,3-ynone, induced the stepwise transformation of ruthenium carbonyl clusters. The thermolysis reactions of Ru3(CO)12 (1) with 1-(4-methoxyphenyl)-3-phenylprop-2-yn-1-one (2) were systematically investigated. A diverse range of products formed via finely tuning the molar ratios of the reactants. When 1 reacted with one equivalent of 2, triruthenium cluster 3 and tetraruthenium cluster 4 were isolated. Further increasing 2 led to the formation of three ruthenoles 5a, 5b and 5c, in which the ynone moieties couple in head to head, head to tail and tail to tail modes, respectively. The cluster compounds 3, 4 and 5a–b were fully characterized and their molecular structures were determined by single crystal X-ray diffraction. The crystal structures clearly demonstrated the activation of the alkyne ligand and the transformation of cluster skeletons. The fluxionality of the alkyne coordination was observed in the crystal structure of 3. It is on the tetraruthenium framework of 4 that the coordinated C–C triple bond is activated. To elucidate the formation pathway of the ruthenoles, the reaction of 2 and 1,3-ynone capped cluster 3 was investigated. The experimental results confirmed that 4 is the intermediate for three ruthenoles, which sheds light on the alkyne mediated fragmentation and formation of low-valence ruthenium carbonyl clusters.

The origin of the selectivity and activity of ruthenium-cluster catalysts for fuel-cell feed-gas purification: a gas-phase approach.

Gas-phase ruthenium clusters Ru(n)(+) (n=2-6) are employed as model systems to discover the origin of the outstanding performance of supported sub-nanometer ruthenium particles in the catalytic CO methanation reaction with relevance to the hydrogen feed-gas purification for advanced fuel-cell applications. Using ion-trap mass spectrometry in conjunction with first-principles density functional theory calculations three fundamental properties of these clusters are identified which determine the selectivity and catalytic activity: high reactivity toward CO in contrast to inertness in the reaction with CO2; promotion of cooperatively enhanced H2 coadsorption and dissociation on pre-formed ruthenium carbonyl clusters, that is, no CO poisoning occurs; and the presence of Ru-atom sites with a low number of metal-metal bonds, which are particularly active for H2 coadsorption and activation. Furthermore, comprehensive theoretical investigations provide mechanistic insight into the CO methanation reaction and discover a reaction route involving the formation of a formyl-type intermediate.

Identification of the vibrational modes in the far-infrared spectra of ruthenium carbonyl clusters and the effect of gold substitution.

High-quality far-IR absorption spectra for a series of ligated atomically precise clusters containing Ru3, Ru4, and AuRu3 metal cores have been observed using synchrotron radiation, the latter two for the first time. The experimental spectra are compared with predicted IR spectra obtained following complete geometric optimization of the full cluster, including all ligands, using DFT. We find strong correlations between the experimental and predicted transitions for the low-frequency, low-intensity metal core vibrations as well as the higher frequency and intensity metal-ligand vibrations. The metal core vibrational bands appear at 150 cm(-1) for Ru3(CO)12, and 153 and 170 cm(-1) for H4Ru4(CO)12, while for the bimetallic Ru3(μ-AuPPh3)(μ-Cl)(CO)10 cluster these are shifted to 177 and 299 cm(-1) as a result of significant restructuring of the metal core and changes in chemical composition. The computationally predicted IR spectra also reveal the expected atomic motions giving rise to the intense peaks of metal-ligand vibrations at ca. 590 cm(-1) for Ru3, 580 cm(-1) for Ru4, and 560 cm(-1) for AuRu3. The obtained correlations allow an unambiguous identification of the key vibrational modes in the experimental far-IR spectra of these clusters for the first time.

Synthesis and Structural Characterization of Ruthenium Carbonyl Cluster Complexes Containing Platinum with a Bulky N-Heterocyclic Carbene Ligand

The reaction of Ru3(CO)12 with Pt(IMes)2 in benzene solvent at room temperature afforded the monoplatinum-triruthenium cluster complex Ru3Pt(IMes)2(CO)11, 1, in 21% yield and the trigonal bipyramidal cluster complex Ru3Pt2(IMes)2(CO)12, 2, in 26% yield. The reaction of Ru(CO)5 with Pt(IMes)2 in benzene solvent at 0 °C yielded two trinuclear cluster complexes, the monoplatinum-diruthenium Ru2Pt(IMes)(CO)9, 3, and the monoruthenium-diplatinum cluster complex RuPt2(IMes)2(CO)6, 4. The reaction of 2 with hydrogen at 80 °C afforded the tetrahydrido-tetraruthenium complex Ru4(IMes)(CO)11(μ-H)4, 5, and the dihydrido-diruthenium-diplatinum complex Ru2Pt2(IMes)2(CO)8(μ-H)2, 6. All six compounds were structurally characterized by single-crystal X-ray diffraction analyses.

Synthesis and crystal structure of {Ru2(CO)6-μ2-η3-[(Ph)CC(H)C(H)NC(H)C(H)C(H)(Ph)]} — The first structurally characterized iminoallyl ruthenium carbonyl complex

The dinuclear ruthenium carbonyl cluster {Ru 2 (CO) 6 -μ 2 -η 3 -[(Ph)C C(H) C(H) N C(H) C(H) C(H)(Ph)]} is produced from the reaction of cinnamaldehyde and Ru 3 (CO) 12 in a 2.0 M solution of ammonia in ethanol. From the crystal structure it gets obvious that ammonia reacted with two molecules of cinnamaldehyde. The resulting ligand may best be described as a formally dianionic ruthenium coordinated imino-allyl-system with one exocyclic 3-phenylallylidene unit that shows no interaction with the transition metals whereas the second one is bound to ruthenium via a C H activation step in γ-position with respect to the nitrogen atom.

Performance of novel bimetallic carbonyl clusters as PEM fuel cell anodes, a comparative study

This work describes the performance of novel bimetallic catalysts, prepared from ruthenium, rhodium and iridium carbonyl clusters by a thermolysis procedure in o-dichlorobenzene. The electrochemical characterization by the rotating disk electrode technique in 0.5 mol L−1 H2SO4 showed that the RuxIry(CO)n, RuxRhy(CO)n and RhxIry(CO)n clusters are able to perform both the hydrogen oxidation reaction (HOR) and oxygen reduction reaction (ORR), even in the presence of fuel cell contaminants such as CO and methanol, respectively. These promising results led us to evaluate the new materials as electrodes in a single fuel cell, using a Fuel Cell Test System designed and built in our group. The performance results of the three bimetallic clusters as anodes in a hydrogen PEM fuel cell are presented in this work. In the tests different H2 and O2 gas flows were fed into the cell to determine the most adequate ratio for maximum power. In the absence of CO, the results showed that although the three bimetallic materials had a similar performance to that of platinum with low flows of both reactants, RuxIry(CO)n showed the best electrocatalytic parameters. When the hydrogen fuel feed was contaminated with 100 ppm and 0.5% CO, the commercial platinum activity decreased considerably or was completely lost. However, while the current density of the novel materials also decreased in the presence of CO, it was significantly above that of platinum nanoparticles, the RhxIry(CO)n and RuxIry(CO)n catalysts showing the best performance in the presence of 100 ppm CO and 0.5% CO respectively. These results are promising in the context of PEM fuel cells using reforming hydrogen.

The effect of solvents on the stability of the products of electrochemical reactions of iron, ruthenium, and osmium carbonyl cluster compounds

The electrochemical reactions of carbonyl cluster compounds M3(CO)12 (M = Fe, Ru, Os) were compared with those of [Fe5C(CO)14]2− and [Fe6C(CO)16]2− in different aprotic solvents. The stability of electrochemically generated products of these clusters in the studied solvents was shown to grow in the following order: tetrahydrofuran < acetone < dichloromethane < acetonitrile.

A ruthenium carbonyl cluster containing a hydroquinone ligand: A layered structure with a polymetallic species. Structure and electrochemical characterization

The reaction of [Ru3(CO)12] with 1,4-benzoquinone, in a hydrogen atmosphere led to the formation of a product with the formula [(μ-H)Ru3(CO)10(μ2-O–C6H4OH)] which crystallizes with two molecules of free hydroquinone in the asymmetric unit with which it forms an arrangement of hydrogen bridges leading to a layered structure of trinuclear metallic and hydroquinone fragments. Electrochemical studies showed that electrode inhibition is obtained by cycling of the oxidation process of this compound.

Synthesis of Mixed Tin–Ruthenium and Tin–Germanium–Ruthenium Carbonyl Clusters from [Ru3(CO)12] and Diaminometalenes (M = Sn, Ge)

Diaminostannylenes react with [Ru(3)(CO)(12)] without cluster fragmentation to give carbonyl substitution products regardless of the steric demand of the diaminostannylene reagent. Thus, the Sn(3)Ru(3) clusters [Ru(3){μ-Sn(NCH(2)(t)Bu)(2)C(6)H(4)}(3)(CO)(9)] (4) and [Ru(3){μ-Sn(HMDS)(2)}(3)(CO)(9)] (6) [HMDS = N(SiMe(3))(2)] have been prepared in good yields by treating [Ru(3)(CO)(12)] with an excess of the cyclic 1,3-bis(neo-pentyl)-2-stannabenzimidazol-2-ylidene and the acyclic and bulkier Sn(HMDS)(2), respectively, in toluene at 110 °C. The use of smaller amounts of Sn(HMDS)(2) (Sn/Ru(3) ratio = 2.5) in toluene at 80 °C afforded the Sn(2)Ru(3) derivative [Ru(3){μ-Sn(HMDS)(2)}(2)(μ-CO)(CO)(9)] (5). Compounds 5 and 6 represent the first structurally characterized diaminostannylene-ruthenium complexes. While a further treatment of 5 with Ge(HMDS)(2) led to a mixture of uncharacterized compounds, a similar treatment with the sterically alleviated diaminogermylene Ge(NCH(2)(t)Bu)(2)C(6)H(4) provided [Ru(3){μ-Sn(HMDS)(2)}(2){μ-Ge(NCH(2)(t)Bu)(2)C(6)H(4)}(CO)(9)] (7), which is a unique example of Sn(2)GeRu(3) cluster. All these reactions, coupled to a previous observation that [Ru(3)(CO)(12)] reacts with excess of Ge(HMDS)(2) to give the mononuclear complex [Ru{Ge(HMDS)(2)}(2)(CO)(3)] but triruthenium products with less bulky diaminogermylenes, indicate that, for reactions of [Ru(3)(CO)(12)] with diaminometalenes, both the volume of the diaminometalene and the size of its donor atom (Ge or Sn) are of key importance in determining the nuclearity of the final products.