Ruthenium Complex Ru Research Articles

Ruthenium Complex Suppresses Proliferation of Residual Hepatocellular Carcinoma after Incomplete Radiofrequency Ablation Therapy.

Radiofrequency ablation (RFA) is an effective therapy for hepatocellular carcinoma (HCC). However, incomplete radiofrequency ablation (IRFA) can promote the progression of residual cancer cells, which is a serious problem in the clinical application of RFA. Therefore, it is of great significance to explore the mechanism and countermeasures of the progression of residual tumors after IRFA. Our previous study confirmed that IRFA can activate the hypoxia/ autophagy pathway of residual tumors in mice and then induce the proliferation of residual tumor cells. Additionally, we found a metal ruthenium complex [Ru(bpy)2(ipad)](ClO4)2 (Ru, where bpy = 2,2'-bipyridine and ipad = 2-(anthracene-9,10-dione-2-yl)imidazo[4,5-f][1,10]phenanthroline) can effectively inhibit hypoxia-inducible factor (HIF-1α) and has good anti-tumor effect in a hypoxic environment; however, whether Ru could suppress the proliferation of residual tumor cells after IRFA is unknown. This study intends to evaluate the effect of Ru in suppressing the proliferation of residual hepatocellular carcinoma after IRFA in a mice model. The Hepa1-6 xenograft mouse model was established in C57BL/6 mice to simulate clinical IRFA. H&E staining was used to evaluate the biosafety of major organs in the treated mice. TUNEL assay was employed to assess the antitumor effect. Immunohistochemically and immunofluorescence staining was performed to detect the expression of HIF-1α and autophagy-related proteins. The ELISA assay was used to examine the cytokines of interferon-gamma (IFN-γ) and interleukin 10 (IL-10). Our findings revealed that the residual tumor relapsed via the HIF-1α/LC3B/P62 autophagy- related pathway after IRFA, while Ru could suppress this process. In addition, it was demonstrated that Ru could effectively activate the immune system of the mice and reverse the tumor immune suppression microenvironment after IRFA. The ruthenium complex Ru could suppress the proliferation of residual hepatocellular carcinoma cells after IRFA in the mice model. This study introduces a novel approach that combines the use of ruthenium complexes with IRFA, offering a potential solution to address the reoccurrence of residual liver cancer following IRFA in clinical settings.

Visible light induced generation of nitric oxide from designed ruthenium nitrosyl complex and studies on antibacterial activity

In this article, a chloro-bridged dinuclear ruthenium complex Ru-(a) has been synthesized, which was employed for the synthesis of a photolabile NO liberating complex Ru-(b). A newly synthesized tridentate ligand 2-methyl-6-((2-phenyl-2-(pyridin-2-yl)hydrazineylidene)methyl)pyridine with three N-atoms as donating site was used to synthesize the complex Ru-(a). The molecular structure of Ru-(a) was investigated by single-crystal X-ray crystallography and, in solution was characterized by or ESI mass spectrometry. Several spectroscopic techniques were used for the characterization of the ligand as well as complexes. To understand the electronic structure of Ru-(a) and Ru-(b), DFT computations were utilized. By the utilization of visible light, photo-liberation experiments were examined. The amount of NO released during the photodissociation experiment was measured using the Griess reagent assay technique. The photodissociated NO was fruitfully transported to reduced myoglobin (Mb). The antibacterial activity against Escherichia coli was carried out with 31.2 μg/mL concentration of Ru-(b). In the final results, we detected considerable antibacterial activity against E. coli and showed >99 % inhibition of the bacterial cells after 120 min of the experiment on exposure to visible light. These investigations proposed that Ru-(b) could be employed to treat several topical deliveries of NO for treating various topical and bacterial infections.

Ruthenium(II)‐Catalyzed Enantioselective Synthesis of 1,2‐trans‐Disubstituted PhSO2CF2‐containing Cyclopropanes

AbstractThe direct diastereo‐ and enantioselective Ru(II)‐ catalyzed cyclopropanation reaction of alkenes with ((2‐diazo‐1,1‐difluoroethyl)sulfinyl)benzene was described. The desired enantioenriched PhSO2CF2‐cyclopropanes were obtained in high yields with high diastereo‐ and enantioselectivities in the presence of a chiral ruthenium complex Ru(II)‐Pheox (17–94% yields, >20:1 d.r. and 83:17–98:2 e.r.). The robustness of the approach was showcased and This methodology gave access to chiral 1,2‐trans difluoro‐methylcyclopropanes.

Nanoencapsulation of Ruthenium Complex Ru(ThySMet): A Strategy to Improve Selective Cytotoxicity against Breast Tumor Cells in 2D and 3D Culture Models.

Ruthenium complexes have shown promise in treating many cancers, including breast cancer. Previous studies of our group have demonstrated the potential of the trans- [Ru(PPh3)2(N,N-dimethylN'-thiophenylthioureato-k2O,S)(bipy)]PF6 complex, the Ru(ThySMet), in the treatment of breast tumor cancers, both in 2D and 3D culture systems. Additionally, this complex presented low toxicity when tested in vivo. Improve the Ru(ThySMet) activity by incorporating the complex into a microemulsion (ME) and testing its in vitro effects. The ME-incorporated Ru(ThySMet) complex, Ru(ThySMet)ME, was tested for its biological effects in two- (2D) and three-dimensional (3D) cultures using different types of breast cells, MDAMB- 231, MCF-10A, 4T1.13ch5T1, HMT-3522 and Balb/C 3T3 fibroblasts. An increased selective cytotoxicity of the Ru(ThySMet)ME for tumor cells was found in 2D cell culture, compared with the original complex. This novel compound also changed the shape of tumor cells and inhibited cell migration with more specificity. Additional 3D cell culture tests using the non-neoplastic S1 and the triple-negative invasive T4-2 breast cells have shown that Ru(ThySMet)ME presented increased selective cytotoxicity for tumor cells compared with the 2D results. The morphology assay performed in 3D also revealed its ability to reduce the size of the 3D structures and increase the circularity in T4-2 cells. These results demonstrate that the Ru(ThySMet)ME is a promising strategy to increase its solubility, delivery, and bioaccumulation in target breast tumors.

Cellular Mechanistic Considerations on Cytotoxic Mode of Action of Phosphino Ru(II) and Ir(III) Complexes

AbstractTwo piano‐stool ruthenium(II) complexes Ru(η6‐p‐cymene)Cl2PPh2CH2OH (RuPOH) and Ru(η6‐p‐cymene)Cl2P(p‐OCH3Ph)2CH2OH (RuMPOH) and two half‐sandwich iridium(III) complexes Ir(η5‐Cp*)Cl2PPh2CH2OH (IrPOH) and Ir(η5‐Cp*)Cl2P(p‐OCH3Ph)2CH2OH (IrMPOH) have been studied in terms of potential anticancer activity on previously selected cell line (human lung adenocarcinoma). Based on experimental results obtained in monoculture in vitro model mechanistic considerations on the possible cellular modes of action have been carried out. ICP‐MS analysis revealed the higher cellular uptake for less hydrophobic Ir(III) complexes in comparison to the corresponding Ru(II) compounds. Cytometric analysis showed a predominance of apoptosis over the other types of cell death for all complexes. The apoptotic pathway was confirmed by a decrease in mitochondrial membrane potential and the activation of caspases‐3/9 for both Ru(II) and Ir(III) complexes. It was concluded that in the case of Ru(II) complexes the intense ROS generation is mainly responsible for the resulting cytotoxicity. The corresponding Ir(III) complexes trigger simultaneously at least three different cytotoxic pathways i. e., depletion of mitochondrial potential, activation of caspases‐dependent apoptosis, and ROS‐associated oxidation. Thus, it can be assumed that the final accumulation of toxic effects over time via parallel activation of different pathways results in the highest cytotoxicity in vitro exhibited by Ir(III) complexes when compared with Ru(II) complexes.

Ruthenium macrocycles bearing pyridine bis(carboxamide): synthesis, structure, and catalytic activity for hydrosilylation

Ruthenium complexes Ru(MC33)(CO)n(L)2−n (L = H2O, PPh3, P(OEt)3; n = 1, 2) with a pincer-type macrocyclic ligand MC33 with a cavity were synthesized and characterized.

Metabolomics of Escherichia coli Treated with the Antimicrobial Carbon Monoxide-Releasing Molecule CORM-3 Reveals Tricarboxylic Acid Cycle as Major Target

In the last decade, carbon monoxide-releasing molecules (CORMs) have been shown to act against several pathogens and to be promising antimicrobials. However, the understanding of the mode of action and reactivity of these compounds on bacterial cells is still deficient. In this work, we used a metabolomics approach to probe the toxicity of the ruthenium(II) complex Ru(CO)3Cl(glycinate) (CORM-3) on Escherichia coli By resorting to 1H nuclear magnetic resonance, mass spectrometry, and enzymatic activities, we show that CORM-3-treated E. coli accumulates larger amounts of glycolytic intermediates, independently of the oxygen growth conditions. The work provides several evidences that CORM-3 inhibits glutamate synthesis and the iron-sulfur enzymes of the tricarboxylic acid (TCA) cycle and that the glycolysis pathway is triggered in order to establish an energy and redox homeostasis balance. Accordingly, supplementation of the growth medium with fumarate, α-ketoglutarate, glutamate, and amino acids cancels the toxicity of CORM-3. Importantly, inhibition of the iron-sulfur enzymes glutamate synthase, aconitase, and fumarase is only observed for compounds that liberate carbon monoxide. Altogether, this work reveals that the antimicrobial action of CORM-3 results from intracellular glutamate deficiency and inhibition of nitrogen and TCA cycles.

Stability of the oxidized form of RuLL′(NCS)2 dyes in acetonitrile in the presence of water and pyridines – Why the dye-sensitized solar cell electrolyte should be dry

The detrimental effect of electrolyte water contamination on the light-soaking lifetime of Dye-sensitized Solar Cells (DSCs) prepared with RuLL′(NCS)2 dyes and N-additives like 4-tert-butylpyridine (TBP) is not well understood. A new explanation is presented based on investigation of the stability of the ruthenium(III) complexes Ru(bipy)2(NCS)2+ (1+) and RuLL′(NCS)2+ (L = 4,4′-dicarboxy-2,2′-bipyridine, L′= 4,4′-nonyl-2,2′-bipyridine) (Z907+) in acetonitrile in the presence of water and pyridines covering a large variation in basicity. 1+ reacts with small amounts of water in the acetonitrile containing a pyridine base (X) according to the overall reaction: 6Ru(bipy)2(NCS)2+ + 4H2O + 8X → 5Ru(bipy)2(NCS)2 + Ru(bipy)2(NCS)(CN) + SO42− + 8XH+. The reaction mechanism of 1+ (and Z907+) is proposed to be initiated by an attack of OH− giving Ru(bipy)2(NCS)(NCS-OH). The stronger the base the faster the reaction. Extrapolating the life time of Z907+ to a typical TBP concentration of 0.5 M in the DSC gives a degradation rate around 7 s−1. Z907+ bound to a layer of nano crystalline TiO2 surface reacted fast too, when inserted in an acetonitrile solution containing 4-tert-butylpyridine. In a “wet” electrolyte, containing more than 500 mM of water the light-soaking lifetime of a DSC prepared with Z907 is predicted to be about 10 days at out-door light soaking conditions, whereas trace amounts of water (<25 mM) in a “dry” electrolyte is used up by consumption of only 10% of the Z907 in a typical DSC. Therefore, the DSC is expected to have a long light-soaking lifetime with a “dry” electrolyte.

Unexpected CNN-to-CC Ligand Rearrangement in Pincer–Ruthenium Precatalysts Leads to a Base-Free Catalyst for Ester Hydrogenation

We report the conversion of a series of CNN–pincer–ruthenium complexes Ru(CNN)HCl(CO) to a CC-chelated form Ru(CC)(PR3)2H(CO) on reaction with sodium tert-butoxide and monodentate phosphines. When the phosphine is triphenylphosphine, cis-phosphine complexes form at room temperature, which convert to the trans isomer at elevated temperatures. When the phosphine is tricyclohexylphosphine, only the trans-phosphine isomer is observed. The CC-chelated complexes are active catalysts for the hydrogenation of esters, without the need for added base. The ligand structure–activity relationship in the series of CC-chelated complexes mirrors that in the precursor CNN-Ru complexes, potentially indicating a common catalytic mechanism. Density functional theory calculations establish a plausible mechanism for the CNN-to-CC rearrangement and demonstrate that this rearrangement is potentially reversible under the conditions of ester hydrogenation catalysis.

Tunable Membrane Potential Reconstituted in Giant Vesicles Promotes Permeation of Cationic Peptides at Nanomolar Concentrations.

We investigate the influence of membrane potential on the permeation of cationic peptides. Therefore, we employ a microfluidic chip capable of capturing giant unilamellar vesicles (GUVs) in physical traps and fast exchange of chemical compounds. Control experiments with calcein proved that the vesicle membranes' integrity is not affected by the physical traps and applied shear forces. Combined with fluorescence correlation spectroscopy, permeation of fluorescently labeled peptides across vesicle membranes can be measured down to the nanomolar level. With the addition of a lipophilic ruthenium(II) complex Ru(C17)22+, GUVs consisting of mixed acyl phospholipids are prepared with a negative membrane potential, resembling the membrane asymmetry in cells. The membrane potential serves as a driving force for the permeation of cationic cell-penetrating peptides (CPPs) nonaarginine (Arg9) and the human immunodeficiency virus trans-activator of transcription (TAT) peptide already at nanomolar doses. Hyperpolarization of the membrane by photo-oxidation of Ru(C17)22+ enhances permeation significantly from 55 to 78% for Arg9. This specific enhancement for Arg9 (cf. TAT) is ascribed to the higher affinity of the arginines to the phosphoserine head groups. On the other hand, permeation is decreased by introducing an additional negative charge in close proximity to the N-terminal arginine residue when changing the fluorophore. In short, with the capability to reconstitute membrane potential as well as shear stress, our system is a suitable platform for modeling the membrane permeability of pharmaceutics candidates. The results also highlight the membrane potential as a major cause of discrepancies between vesicular and cellular studies on CPP permeation.

NNN-Ruthenium Catalysts for the Synthesis of Pyridines, Quinolines, and Pyrroles by Acceptorless Dehydrogenative Condensation

The bidentate ruthenium complex (HO-C5H3N-CO-C5H3N-C5H4N)Ru(CO)2Cl2 (2) could transform to a tridentate product (HO-C5H3N-CO-C5H3N-C5H4N)Ru(CO)Cl2 (3), which further reacted with CH3ONa in the presence of PPh3 to convert to two complexes [(OC5H3N-CO-C5H3N-C5H4N)Ru(PPh3)2(CO)]Cl– (4) and [(OC5H3N-CO-C5H3N-C5H4N)Ru(PPh3)(CO)Cl] (5), via −OH deprotonation. The catalytic coupling cyclizations of secondary alcohols with amino alcohols were investigated, and complex 3 exhibited the highest activity. The coupling reactions proceeded in air with only 0.2 mol % catalyst loading and had a broad scope for the synthesis of pyridines, quinolones, and pyrroles.

Abstract 5458: Antiproliferative activity of a novel 8-hydroxyquinoline ruthenium II complex against human breast cancer cell lines

Abstract Ruthenium (Ru) complexes are recognized as the most perspective chemotherapeutic agents available, because of their low general toxicity and variety of modes of action. Ru(II)-based complexes show a higher tendency for ligand exchange reactions and therefore interact with target molecules more rapidly and there cytotoxicity often correlates with the DNA binding ability. The present study was aimed to test the anti-tumor effect of a new formulated ruthenium (II) complex Bis(quinolin-8-olato)bis(triphenylphosphine)ruthenium(II) complex (Ru(quin)2) that was prepared by reaction of the precursor RuCl2(PPh3)3 with Quinolin-8-ol on two human breast cancer cell lines, estrogen receptor-positive (ER+), T-47D, and MDA-MB-231, triple negative breast cancer cell line that display different phenotypic and differentiation patterns ranging from poor to high differentiation. The two tested breast cancer cells showed a significant growth inhibition after 24 h of treatment, but the response of T47D cells to treatment was much higher than that of MDA-MB231 cells. In contrast, the near-normal mammary cell lines, MCF-10A, showed no response to Ru(quin)2 at higher doses. In tested cells, Ru(quin)2 significantly inhibited cells proliferation after 24 h treatment as evaluated by MTT assay, cell morphology alteration, and clonogenic assay. In addition, treated cells showed significant morphological and biochemical signs of apoptosis induction through releasing of histone protein, caspase-3 activation, and G2/M phase cell cycle arrest in a dose-dependent manner compared to control. In T47D cells, Ru(quin)2 significantly downregulated protein expression of STAT3, and S6 kinase1 (S6K1) and significantly upregulated LC3B expression protein, a hallmark of autophagosomes formation, after 24 h of treatment as detected by western blot analysis and immunocytochemistry. Furthermore, in established xenograft tumor model of MDA-MB231 cells in nude mice, the growth of MDA-MB231 tumors that treated with Ru(quin)2 was inhibited by 46.88% compared to the mock group (t=2.821, P&amp;lt;0.05) after three weeks of treatment. Besides, there was no cytotoxicity on both liver and kidney function tests. Collectively, our observations support the anticancer role of the novel Ru(II)- macrocyclic complex that might be through apoptosis and autophagy induction in human breast cancer cell lines. Citation Format: Amr M. Khalifa, Ahmed S. Sultan. Antiproliferative activity of a novel 8-hydroxyquinoline ruthenium II complex against human breast cancer cell lines [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5458.

Electrochemical and Spectroscopic Studies on σ-Phenyl Ruthenium Complexes Ru(CO)Cl(C6H4R-4)(PiPr3)2

A series of mononuclear σ-phenyl ruthenium complexes Ru(CO)Cl(C6H4-R)(PiPr3)2 (R = OMe, CH3, H, F, CF3) were synthesized and analyzed with respect to their electrochemical and spectroscopic properties. To these ends, cyclic voltammetry, IR, and UV/Vis/NIR spectroelectrochemistry as well as EPR spectroscopy on their one-electron oxidized radical cations were employed. Experimental work is complimented by quantum chemical calculations. Our studies reveal that the σ-phenyl ligand strongly contributes to the HOMO and actively participates in the redox processes. Despite comparatively smaller ligand contributions, the redox potentials, the position of the CO stretch as well as the oxidation induced CO band shifts are more sensitive toward the σ-Hammett parameter of the 4-substituent than for related styryl complexes with the same Ru(CO)Cl(PiPr3)2 metal coligand platform. The comparatively high spin density/positive charge at the 4-position of the phenyl ligand leads to oxidatively induced dehydrodimerization o...

Aperture-Opening Encapsulation of a Transition Metal Catalyst in a Metal–Organic Framework for CO2 Hydrogenation

The aperture-opening process resulting from dissociative linker exchange in zirconium-based metal-organic framework (MOF) UiO-66 was used to encapsulate the ruthenium complex (tBuPNP)Ru(CO)HCl in the framework (tBuPNP = 2,6-bis((di- tert-butyl-phosphino)methyl)pyridine). The resulting encapsulated complex, [Ru]@UiO-66, was a very active catalyst for the hydrogenation of CO2 to formate. Unlike the analogous homogeneous catalyst, [Ru]@UiO-66 could be recycled five times, showed no evidence for bimolecular catalyst decomposition, and was less prone to catalyst poisoning. These results demonstrated for the first time how the aperture-opening process in MOFs can be used to synthesize host-guest materials useful for chemical catalysis.

Regio- and Stereoselective Ring-Opening Metathesis Polymerization of Enantiomerically Pure Vince Lactam

The ring-opening metathesis polymerization (ROMP) of (+)-Vince lactam [(S)-azabicyclo[2.2.1]hept-5-en-3-one] (1) and its N-benzyl, N-trimethylsilyl (TMS), and N-tert-butoxycarbonyl (Boc) derivatives (2a–c) is reported. Highly cis-syndiotactic (st) poly(Vince lactam) was readily accessible by using the cyclometalated ruthenium complex Ru[CH(2-OiPr-Ph)](Piv)(1-mesityl-3-C4H8-imidazol-2-ylidene) (Piv =2,2-dimethylpropanoate) (4); however, small amounts of trans double bonds (ca. 5%) formed. Highly cis-st (>98%) polymers were accessible by the action of the monoaryloxide pyrrolide (MAP) type complexes W(N-2,6-iPr2C6H3)(CHCMe2Ph)(Pyr)(HMTO) (Pyr = pyrrolide, HMTO = 2,6-(2,4,6-Me3C6H2)2C6H3O) (7) and W(O)(CHCMe2Ph)(PMe2Ph)(Me2Pyr)(TPPO) (TPPO = 2,3,5,6-tetraphenylphenolate) (8). Complementary, cis-isotactic (>98% cis-it) polymers were prepared by the action of Mo(N-2,6-Me2C6H3)(CHCMe2Ph)(OBiphen) (OBiphen = 3,3′-di-tert-butyl-5,5′,6,6′-tetramethyl-1,1′-biphenyl-2,2′-diolate) (5) and its tungsten analogue W(N-2,6-Me2C6H3)(CHCMe2Ph)(OBiphen) (6). Notably, none of these Mo- and W-based initiators polymerize unprotected Vince lactam. Deprotection of poly(N-TMS Vince lactam) and poly(N-Boc Vince lactam) with neat trifluoroacetic acid allowed for the isolation of all-cis highly tactic poly(Vince lactam).

Cytotoxicity modulation of ruthenium(II) tris-bathophenanthroline complexes with systematically varied charge

A series of four ruthenium(II) complexes Ru(bp)n(bps)3-n (n = 0-3; bp = 4,7-diphenyl-1,10-phenanthroline or bathophenanthroline; and bps = disulfonated 4,7-diphenyl-1,10-phenanthroline or bathophenanthroline disulfonate) bearing different charges were synthesized and characterized. In aqueous media, all complexes displayed similar photophysical properties which makes this series ideal to study the effect of charge on the cytotoxicity of Ru(II) complexes. Ru(bp)32+ (1) and Ru(bps)34− (4) are known photosensitizers that penetrate cancer cells and possess a significant light-induced cytotoxicity. The newly conceived neutral Ru(bp)2(bps)0 (2) and dianionic Ru(bp)(bps)22− (3) were also found to have significant uptake as well as light-activation properties. Importantly, the cytotoxicity in the dark was successfully tuned upon systematic charge modulation of the complexes. The cationic complex 1 was potent against 5 out of 6 cell lines tested (MDA-MB-231, MCF-7, B16, SF and ML2) and displayed the highest cytotoxicity among the tested complexes with IC50 values of 4.0, 3.6, 1.7, 1.0 and 2.9 μM, respectively. The two anionic complexes, 3 and 4, with respective overall charges of −2 and −4, were not potent against any of the cell lines in the dark (IC50 > 200 μM), whereas the neutral molecule, complex 2, was potent against 3 out of 6 cell lines in the dark (B16, SF and ML2) and exhibited an intermediate activity with IC50 values of 12.8, 3.0 and 10.3 μM, respectively. All complexes presented significant phototoxicity when activated at 6 h post-incubation, which is consistent with their fast uptake and ability to produce singlet oxygen. The localization of complexes 1–4 within the cells was found to be dependent on the charge and photoexcitation conditions. The charge-activity relationship elucidated in this work facilitates the development of new sensitizers for photodynamic therapy.

Synthesis of a polymer–ruthenium complex Ru(pbbp)(pydic) and its catalysis in the oxidation of secondary alcohols with TBHP as oxidant

A polymer–ruthenium complex Ru(pbbp)(pydic) was synthesized from the reaction of poly-2,6-bis(benzimidazolyl)pyridine (pbbp) with RuCl3 and disodium pyridine-2,6-dicarboxylate (pydic). The Ru(pbbp)(pydic) was characterized thoroughly by spectroscopic methods. ICP analysis revealed that the percentage of complexation of 2,6-bis(benzimidazolyl)pyridine unit in pbbp was about 83%. The complex was tested as a heterogeneous catalyst for the oxidation of secondary alcohols to their corresponding carbonyl compounds in solvent-free conditions using aqueous tert-butyl hydroperoxide as oxidant. The developed catalytic system exhibited high activity and broad functional group compatibility, allowing a variety of secondary alcohols, including substituted secondary benzylic alcohols and secondary aliphatic ones, to be oxidized to the corresponding ketones in high yields. This Ru(pbbp)(pydic) could be recycled for several times, but it dissolved in part in the reaction mixture during the catalytic run leading to gradual deactivation of the catalyst with repeated runs.

ChemInform Abstract: ONO‐Pincer Ruthenium Complex‐Bound Norvaline for Efficient Catalytic Oxidation of Methoxybenzenes with Hydrogen Peroxide.

The enhanced catalytic activity of ruthenium complex-bound norvaline Boc-L-[Ru]Nva-OMe 1, in which the ONO-pincer ruthenium complex Ru(pydc)(terpy) 2 is tethered to the α-side chain of norvaline, has been demonstrated for the oxidation of methoxybenzenes to p-benzoquinones with a wide scope of substrates and unique chemoselectivity.

Reactivity of a Ruthenium-Carbonyl Complex in the Methanol Dehydrogenation Reaction.

Finding new catalysts for the release of molecular hydrogen from methanol is of high relevance in the context of the development of sustainable energy carriers. Herein, we report that the ruthenium complex Ru(salbinapht)(CO)(Pi‐Pr3) {salbinapht=2‐[({2′‐[(2‐hydroxybenzyl)amino]‐[1,1′‐binaphthalen]‐2‐yl}imino)methyl]phenolato} (2) catalyzes the methanol dehydrogenation reaction in the presence of base and water to yield H2, formate, and carbonate. Dihydrogen is the only gas detected and a turnover frequency up to 55 h−1 at 82 °C is reached. Complex 2 bears a carbonyl ligand that is derived from methanol, as is demonstrated by labeling experiments. The carbonyl ligand can be treated with base to form formate (HCOO−) and hydrogen. The nature of the active species is further shown not to contain a CO ligand but likely still possesses a salen‐derived ligand. During catalysis, formation of Ru(CO)2(H)2(P‐iPr3)2 is occasionally observed, which is also an active methanol dehydrogenation catalyst.

Immobilization of Ru(terpyridine)(2,6‐pyridinedicarboxylate) onto MCM‐41 and its catalysis in the oxidation of alcohols

The ruthenium complex Ru(terpyridine)(2,6‐pyridinedicarboxylate) was successfully grafted onto MCM‐41 using a multi‐step grafting method. The immobilized ruthenium complex was characterized thoroughly using Fourier transform infrared, Raman, UV–visible diffuse reflectance and energy‐dispersive X‐ray spectroscopies, X‐ray diffraction, N2 adsorption, scanning electron microscopy, thermogravimetric analysis and inductively coupled plasma analysis. This immobilized ruthenium complex showed excellent performance in the oxidation of various secondary alcohols to their corresponding ketones with tert‐butyl hydroperoxide as oxidant under solvent‐free conditions, and had the advantages of easy recovery and good reusability. Copyright © 2016 John Wiley &amp; Sons, Ltd.