Ru Cl Research Articles

Cyclodextrin-assisted catalytic hydrogenation of hydrophobic substrates with halloysite immobilized ruthenium NPs dispersed in aqueous phase

Halloysite nanotube supported ruthenium catalyst was prepared by an easy and reproducible in situ bottom up approach. Ruthenium (III) chloride was reduced by sodium borohydride in the presence of halloysite nanotubes dispersed in water. Several analyses confirm the immobilization of ruthenium particles onto the aluminosilicate support. The synthesized catalyst was then tested in the hydrogenation of 1-hexadecene, a highly hydrophobic compound, in aqueous medium using cyclodextrins as mass transfer additives. The catalytic activity deeply depended on the nature of the cyclodextrin. Best results were obtained with randomly methylated β-cyclodextrin. The catalytic system was also evaluated in the hydrogenation of biosourced long chain alkenes such as fatty acid methyl esters and vegetable oils and showed high activities in mild reaction conditions.

Mapping Solvent Entrapment in Multiphase Systems by Electrogenerated Chemiluminescence.

The interfacial properties of multiphase systems are often difficult to quantify. We describe the observation and quantification of immiscible solvent entrapment on a carbonaceous electrode surface using microscopy-coupled electrogenerated chemiluminescence (ECL). As aqueous microdroplets suspended in 1,2-dichloroethane collide with a glassy carbon electrode surface, small volumes of the solvent become entrapped between the electrode and aqueous phase, resulting in an overestimation of the true microdroplet/electrode contact area. To quantify the contribution of solvent entrapment decreasing the microdroplet contact area, we drive an ECL reaction within the microdroplet phase using tris(bipyridine)ruthenium(II) chloride ([Ru(bpy)3]Cl2) as the ECL luminophore and sodium oxalate (Na2C2O4) as the co-reactant. Importantly, the hydrophilicity of sodium oxalate ensures that the reaction proceeds in the aqueous phase, permitting a clear contrast between the aqueous and 1,2-dichloroethane present at the electrode interface. With the contrast provided by ECL imaging, we quantify the microdroplet radius, apparent microdroplet contact area (aqueous + entrapped 1,2-dichloroethane), entrapped solvent contact area, and the number of entrapped solvent pockets per droplet. These data permit the extraction of the true microdroplet/electrode contact area for a given droplet, as well as a statistical assessment regarding the probability of solvent entrapment based on microdroplet size.

Thermodynamic properties of ruthenium (IV) chloride complex and the transport of ruthenium in magmatic-hydrothermal fluids

Thermodynamic properties of platinum-group element (PGE) coordination complexes are significant for our understanding of PGE mobilization, transport, and deposition in hydrothermal fluids. This study conducted hydrolysis experiments of ruthenium (IV) chloride complex (K2RuCl6) at temperatures of 200–600 °C and water pressure of 100 MPa, combined with related geochemical modeling, to quantitatively investigate the thermodynamic behavior of the Ru-Cl complex in magmatic-hydrothermal fluids. The results show that the hydrolysis reactions of [RuCl6]2– get equilibrium within 24 hours at 200 °C and have positive temperature dependence. The cumulative hydrolysis constants (K) calculated for the reactions fit well on a linear correlation with temperatures (T, Kelvin):lnK = (42.95 ± 4.13) – (56205 ± 2594)/T.Based on the cumulative hydrolysis constants obtained, we established a preliminary model to decipher the quantitative relationship among the temperature, pH, total chlorine concentration, and the mobility of the Ru-Cl complex in natural Cl-bearing hydrothermal fluids. The calculation results demonstrate that Ru could be mobile in the Cl-bearing (0.05–0.5 wt%), low to moderate temperature (≤550 °C), and acidic (pH ≤ 4) fluids, and be highly mobile in the Cl-rich (0.5–20 wt%), acidic - weakly alkaline fluids. The fluid’s pH and total chlorine concentration dominate the Ru-Cl complex’s stability and the Ru transport. Therefore, dilution of ambient seawater on the hydrothermal fluids and plumes related to the magmatic-hydrothermal vent systems is the geochemical barrier, which is advantageous to PGE precipitation and mineralization. Furthermore, this study highlights the importance of metal source for the PGE mobilization and deposition and suggests that the source’s deficiency substantially limits the PGE mobilization, transport, and deposition, resulting in the scarcity of hydrothermal PGE deposits in the crust.

Ruthenium‐Catalyzed Synthesis of α‐Alkylated Ketones and Quinolines in an Aqueous Medium via a Hydrogen‐Borrowing Strategy Using Ketones and Alcohols

AbstractHerein, we report a simple, efficient, and sustainable method for the synthesis of α‐alkylated ketones and quinolines using a hydrogen‐borrowing strategy, which has emerged as a greener alternative in organic transformation reactions. Synthesis of a range of α‐alkylated ketones and quinoline derivatives was achieved by using the water‐soluble [Ru(8‐AQ)Cl(p‐cym.)]+Cl− [Ru]‐1 (AQ=aminoquinoline) catalyst with water as the reaction medium. By adopting this strategy, we have synthesized α‐alkylated ketones and quinolines using ketones or secondary alcohols as starting materials and the primary alcohol as a green and naturally abundant alkylating agent.

Tracking of fluorescent antibiotic conjugate in planta utilizing fluorescence lifetime imaging.

Excited state lifetime-based separation of fluorophore-tagged antibiotic conjugate emission from the spectrally broad plant autofluorescence enables in planta tracking of the translocation of systemic cargo such as antibiotics via fluorescence lifetime imaging. The efficacy of antibiotic treatments in citrus crops is uncertain due to mixed results from in-field experiments and a lack of study on their systemic movement. As of yet there has been an inability to track treatments using traditional fluorescence microscopy due to treatments having little fluorescence characteristics, and signal convolution due to plant autofluorescence. In this study, we used streptomycin sulfate, a commercially available antibiotic, and conjugated it to a modified tris(bipyridine) ruthenium (II) chloride, a dye with an excited state lifetime magnitudes higher than other commonly used organic fluorescent probes. The resultant is a fluorescence lifetime imaging (FLIM) trackable antibiotic conjugate, covalently attached via an amide linkage that is uniquely distinguishable from plant autofluorescence. Characterization of the fluorescent antibiotic conjugate showed no mitigation of excited state lifetime, and a distinct IR peak not found in any synthetic components. Subsequent tracking using FLIM in citrus tissue was achieved, with identification of movement through citrus plant vasculature via tissue localization in xylem and phloem. Results indicated upwards systemic movement of the conjugate in both xylem and phloem after 48h of incubation. However, the conjugate failed to move down towards the root system of the plant by 168h. Mechanistically, it is likely that xylem contributes heavily in the translocation of the conjugate upwards; however, phloem led flow due to growth changes could act as a contributor. This proof-of-concept sets groundwork for subsequent studies regarding antibiotic localization and movement in citrus.

Ruthenium-Catalyzed Coupling Reactions of CO2 with C2 H4 and Hydrosilanes towards Silyl Esters.

A series of in situ-prepared catalytic systems incorporating RuII precursors and bidentate phosphine ligands has been probed in the reductive carboxylation of ethylene in the presence of triethylsilane as reductant. The catalytic production of propionate and acrylate silyl esters was evidenced by high-throughput screening (HTS) and implemented in batch reactor techniques. The most promising catalyst systems identified were made of Ru(H)(Cl)(CO)(PPh3 )3 and 1,4-bis(dicyclohexylphosphino)butane (DCPB) or 1,1'-ferrocene-diyl-bis(cyclohexylphosphine) (DCPF). A marked influence of water on the acrylate/propionate selectivity was noted. Turnover numbers [mol mol(Ru)-1 ] up to 16 for acrylate and up to 68 for propionate were reached under relatively mild conditions (20 bar, 100 °C, 0.5 mol % Ru, 40 mol % H2 O vs. HSiEt3 ). Possible mechanisms are discussed.

High Antiproliferative Activity of Hydroxythiopyridones over Hydroxypyridones and Their Organoruthenium Complexes

Hydroxypyr(id)ones are a pharmaceutically important class of compounds that have shown potential in diverse areas of drug discovery. We investigated the 3-hydroxy-4-pyridones 1a–1c and 3-hydroxy-4-thiopyridones 1d–1f as well as their Ru(η6-p-cymene)Cl complexes 2a–2f, and report here the molecular structures of 1b and 1d as determined by X-ray diffraction analysis. Detailed cell biological investigations revealed potent cytotoxic activity, in particular of the 3-hydroxy-4-thiopyridones 1d–1f, while the Ru complexes of both compound types were less potent, despite still showing antiproliferative activity in the low μM range. The compounds did not modulate the cell cycle distribution of cancer cells but were cytostatic in A549 and cytotoxic in NCI-H522 non-small lung cancer cells, among other effects on cancer cells.

Platinoid effects on human plasmatic coagulation kinetics: a viscoelastic analysis.

In recent years a variety of metals (cadmium, chromium, copper, iron) have been demonstrated to modulate coagulation in vitro and in vivo. One group of metals, the platinoids, have not been assessed, and such investigation is justified given the thromboembolic phenomena associated with platinum-based chemotherapy. Thus, the goal of the present investigation was to assess the effects of carboplatin, cisplatin (platinum compounds), NAMI-A, and ruthenium chloride (ruthenium compounds) on human plasmatic coagulation. Human plasma was exposed to clinically relevant, equimolar concentrations of the aforementioned platinum and ruthenium compounds, with changes in plasmatic coagulation assessed via thrombelastography. The first series of experiments demonstrated no significant modulation of coagulation by the platinum compounds, while NAMI-A demonstrated mild hypercoagulability and ruthenium chloride exerted marked hypercoagulability. A second series of experiments utilizing a variety of specialized modifications of thrombelastography focused on ruthenium chloride revealed that this compound enhances prothrombin activation. While the hypercoagulability associated with platinum compounds in vivo do not appear to have a basis in plasmatic biochemistry, it appears that ruthenium compounds can exert procoagulant properties by enhancing the common pathway of human plasmatic coagulation. Future investigation of Ru based chemotherapeutic agents in development to assess procoagulant activity as part of evaluating their potential clinical safety is warranted.

A new bis-pyrazolylpyridine ruthenium(III) complex as a potential anticancer drug: in vitro and in vivo activity in murine colon cancer.

We synthesized and characterized the ruthenium(iii) pincer-type complex [RuCl3(H2Lt-Bu] (H2Lt-Bu = 2,6-bis(5-tert-butyl-1H-pyrazol-3-yl)pyridine, 1) by elemental analysis, IR and UV-Vis spectroscopy, and the mass spectrometry (MS) method ESI Q-TOF. For comparison reasons, we also studied ruthenium(iii) terpyridine complexes of the general formula [Ru(N-N-N)Cl3], where N-N-N = 4'-chloro-terpyridine (Cl-tpy; 2) or 4'-chlorophenyl-terpyridine (Cl-Ph-tpy; 3). A kinetic study of the substitution reactions of 1-3 with biomolecules showed that the rate constants depend on the properties of the spectator ligand and the nature of the entering nucleophile. The DNA/HSA binding study showed that in comparison to complex 1 (bis-pyrazolylpyridine), the other two (2 and 3) terpyridine complexes had a slightly better binding affinity to calf thymus DNA (CT DNA), while in the case of human serum albumin (HSA), complex 1 exhibited the strongest quenching ability. We demonstrated that 1 possesses significant in vitro cytotoxic activity against mouse colon carcinoma CT26 cells and in vivo antitumor activity in murine heterotopic colon carcinoma. Complex 1 induced G0/G1 cell cycle arrest and apoptotic death in CT26 cells. Additionally, 1 showed antiproliferative activity, as evaluated by the detection of the expression levels of the Ki67 protein. Furthermore, the in vivo results showed that 1 reduced primary tumour growth and the number and growth of lung and liver metastases, significantly prolonging the treated mice's survival rate. This study highlighted that 1 does not show hepato- and nephrotoxicity. Our data demonstrated the considerable antitumor activity of the ruthenium(iii) pincer complex against CT26 tumour cells and implicated further investigations of its role as a potential chemotherapeutic agent for colon carcinoma.

One pot tandem dual CC and CO bond reductions in the β-alkylation of secondary alcohols with primary alcohols by ruthenium complexes of amido and picolyl functionalized N-heterocyclic carbenes.

Two different classes of ruthenium complexes, namely, [1-mesityl-3-(2,6-Me2-phenylacetamido)-imidazol-2-ylidene]Ru(p-cymene)Cl (1c) and {[1-(pyridin-2-ylmethyl)-3-(2,6-Me2-phenyl)-imidazol-2-ylidene]Ru(p-cymene)Cl}Cl (2c), successfully catalyzed the one-pot tandem alcohol-alcohol coupling reactions of a variety of secondary and primary alcohols, in moderate to good yields of ca. 63-89%. The mechanistic investigation performed on two representative catalytic substrates, 1-phenylethanol and benzyl alcohol using the neutral ruthenium (1c) complex showed that the catalysis proceeded via a partially reduced CC hydrogenated carbonyl species, [PhCOCH2CH2Ph] (3'), to the fully reduced CO and CC hydrogenated secondary alcohol, [PhCH(OH)CH2CH2Ph] (3). Furthermore, the time dependent study showed that the major product of the catalysis modulated between (3') and (3) during the catalysis run performed over an extended period of 120 hours. Finally, the practical utility of the alcohol-alcohol coupling reaction was demonstrated by preparing five different flavan derivatives (13-17) related to various bioactive flavonoid natural products, in a one-pot tandem fashion.

Understanding the regioselectivity of the copper(I)- and ruthenium(II)- catalyzed [3 + 2] cycloadditions of azido derivative of ribose with terminal alkyne: a theoretical study

In the present work, the uncatalyzed, the copper(I)-catalyzed and the ruthenium(II)-catalyzed [3 + 2] cycloadditions (32CA) of azido derivative of ribose with terminal alkyne leading to 1,4- and/or 1,5- 1,2,3-triazole regioisomers have been studied at the B3LYP level of theory in combination with the LanL2DZ basis set for Cu, Ru and Cl atoms and the standard 6-31G(d) basis set for other atoms. The obtained results reveal that the uncatalyzed reaction requires high and similar activation energies, namely 18.29 and 18.80 kcal/mol for the 1,4 and 1,5 regioisomeric pathways, respectively, indicating a very limited regioselectivity in agreement with the experimental outcomes. Interestingly, for the copper(I)-catalyzed azide–alkyne cycloaddition (CuAAC), investigated using the Fokin stepwise mechanism involving two copper atoms, the 1,4 regioisomeric reaction path found to be kinetically more favored than the 1,5 regioisomeric reaction path by 9.13 kcal/mol. By contrast, for the ruthenium(II)-catalyzed azide–alkyne cycloaddition (RuAAC), investigated using the Fokin mechanism using the pentamethylcyclopentadienyl ruthenium chloride [Cp * RuCl] complex, the 1,5 regioisomeric reaction path is more favored than the 1,4 regioisomeric reaction path by 3.48 kcal/mol. The present work puts in evidence the determinant role of Cu/Ru catalysts in the regioselectivity of this click reaction.

A New Piano-Stool Ruthenium(II) P-Cymene-Based Complex: Crystallographic, Hirshfeld Surface, DFT, and Luminescent Studies

A new complex (Ru(η6-p-cymene)(5-ASA)Cl2) (1) where 5-ASA is 5-aminosalicylic acid has been prepared by reacting the ruthenium arene precursors ((η6-arene)Ru(μ-Cl)Cl)2, with the 5-ASA ligands in a 1:1 ratio. Full characterization of complex 1 was accomplished by elemental analysis, IR, and TGA following the structure obtained from a single-crystal X-ray pattern. The structural analysis revealed that complex 1 shows a “piano-stool” geometry with Ru-C (2.160(5)- 2.208(5)Å), Ru-N (2.159(4) Å) distances, which is similar to equivalents sister complex. Density functional theory (DFT) was used to calculate the significant molecular orbital energy levels, binding energies, bond angles, bond lengths, and spectral data (FTIR, NMR, and UV–VIS) of complex 1, consistent with the experimental results. The IR and UV–VIS spectra of complex 1 were computed using all of the methods and choose the most appropriate way to discuss. Hirshfeld surface analysis was also executed to understand the role of weak interactions such as H⋯H, C⋯H, C-H⋯π, and vdW interactions, which play a significant role in the crystal environment’s stability. Moreover, the luminescence results at room temperature show that complex 1 gives a more intense emission band positioned at 465 nm upon excitation at 330 nm makes it a suitable candidate for the building of photoluminescent material.

Ruthenium-catalyzed acceptorless dehydrogenative coupling of o-aminobenzyl alcohols with ketones to quinolines in the presence of carbonate salt

A ruthenium complex bearing a functional 2,2′-bibenzimidazole ligand [(p-cymene)Ru(BiBzImH2)Cl][Cl] was designed, synthesized and found to be a general and highly efficient catalyst for the synthesis of quinolines via acceptorless dehydrogenative coupling of o-aminobenzyl alcohols with ketones in the presence of carbonate salt. It was confirmed that NH units in the ligand are crucial for catalytic activity. The application of this catalytic system for the scale-gram synthesis of biologically active molecular was also undertaken. Notably, this research exhibits new potential of metal–ligand bifuctional catalysts for acceptorless dehydrogenative reactions.

Role of ZnNb2O6 in ZnO-promoted amorphous-Nb2O5 supported Ru catalyst for the partial hydrogenation of benzene

Ruthenium catalysts supported on zinc-promoted amorphous-niobium mixed oxides were prepared, characterized, and studied in the additive-free partial hydrogenation of benzene reaction. The amorphous matrix of Nb2O5 was responsible for a highly active Ru/Nb2O5 catalyst, although less selective than those containing zinc. The ZnO-containing supports were prepared by wet impregnation technique, followed by incipient wetness of ruthenium chloride salt. The catalysts were characterized by textural analysis, X-ray fluorescence, X-ray diffraction, H2 chemisorption, temperature-programmed reduction (TPR), Scanning electron microscopy, H2 temperature-programmed desorption, and X-ray photoelectron spectroscopy (XPS) of the calcined-reduced samples. Chlorine retention was observed on zinc-containing samples. An unexpected ZnNb2O6 oxide phase, ascribed to a selectivity increase with less activity loss, was obtained for the supports at lower temperatures than those related on the literature. A very complex electronic environment of Ru- and Zn-containing species interactions was observed by TPR. The presence of surface-reduced (Ru0) and partially reduced (Ruδ+) Ru species observed by XPS justified well, respectively, the activity and selectivity achieved with every catalyst. The addition of water as a solvent resulted in very constant yield to cyclohexene, as expected, despite activity diminution due to low solubility of the reactants.

Organometallic Complex Strongly Impairs Chikungunya Virus Entry to the Host Cells.

Chikungunya fever is a disease caused by the Chikungunya virus (CHIKV) that is transmitted by the bite of the female of Aedes sp. mosquito. The symptoms include fever, muscle aches, skin rash, and severe joint pains. The disease may develop into a chronic condition and joint pain for months or years. Currently, there is no effective antiviral treatment against CHIKV infection. Treatments based on natural compounds have been widely studied, as many drugs were produced by using natural molecules and their derivatives. Alpha-phellandrene (α-Phe) is a naturally occurring organic compound that is a ligand for ruthenium, forming the organometallic complex [Ru2Cl4(p-cymene)2] (RcP). Organometallic complexes have shown promising as candidate molecules to a new generation of compounds that presented relevant biological properties, however, there is a lack of knowledge concerning the anti-CHIKV activity of these complexes. The present work evaluated the effects of the RcP and its precursors, the hydrate ruthenium(III) chloride salt (RuCl3⋅xH2O) (Ru) and α-Phe, on CHIKV infection in vitro. To this, BHK-21 cells were infected with CHIKV-nanoluciferase (CHIKV-nanoluc), a viral construct harboring the nanoluciferase reporter gene, at the presence or absence of the compounds for 16 h. Cytotoxicity and impact on infectivity were analyzed. The results demonstrated that RcP exhibited a strong therapeutic potential judged by the selective index > 40. Antiviral effects of RcP on different stages of the CHIKV replicative cycle were investigated; the results showed that it affected early stages of virus infection reducing virus replication by 77% at non-cytotoxic concentrations. Further assays demonstrated the virucidal activity of the compound that completely blocked virus infectivity. In silico molecular docking calculations suggested different binding interactions between aromatic rings of RcP and the loop of amino acids of the E2 envelope CHIKV glycoprotein mainly through hydrophobic interactions. Additionally, infrared spectroscopy spectral analysis indicated interactions of RcP with CHIKV glycoproteins. These data suggest that RcP may act on CHIKV particles, disrupting virus entry to the host cells. Therefore, RcP may represent a strong candidate for the development of anti-CHIKV drugs.

Ratiometric fluorescence detection of melamine in milk by a zirconium-based metal-organic frameworks composite

Melamine has biological toxicity and is forbidden to be used in food processing and food additives. The long-term ingestion of melamine will cause renal malfunction and metabolic problems of the urinary system, so it is of great significance for the rapid and selective detection of melamine. Herein, a zirconium-based metal–organic frameworks (Zr-based MOFs) encapsulated tris(2,2-bipyridyl)ruthenium (II) chloride hexahydrate ([Ru(bpy)3]2+) composite, donated as UiO-66-NH2@Ru, was reported and further studied its sensing performance for melamine based on ratiometric fluorescent method. The UiO-66-NH2@Ru was prepared from ZrCl4, 2-amino-terephthalic acid (TPA-NH2) and [Ru(bpy)3]2+ by one pot reaction through solvothermal method, which exhibited dual emission signals at 445 and 595 nm from single excitation of 350 nm. The corresponding two peaks showed different responses to melamine, that was, the obvious enhancement at 445 nm and the slow decrease at 595 nm, thus achieving the “on–off” ratiometric fluorescence detection. When the concentration of melamine was in the range of 0.27 to 110 μM, the ratio of fluorescence intensity F445/F595 had a good linear relation with the correlation coefficient R2 = 0.995 and the detection limit of 90 nM. The synthetic UiO-66-NH2@Ru probe implemented rapid determination of melamine in real sample of milk powder with high sensitivity and selectivity. Compared with the reported carbon dots, quantum dots, metal nanoclusters, nanocomposites and other fluorescent sensors, MOFs-based sensor have broadened the application of nanomaterials in melamine detection for the first time. This study also demonstrates the Zr-based MOFs as a platform to encapsulate fluorescent dye for constructing ratiometric sensor in the determination of melamine is feasible and exciting.

Redox Induced Tunable Functionalization of Picolylamines on Selective Ru‐Platform

AbstractRedox induced ligand centered reactivity has garnered significant attention in recent times. In this context, the present article described intermolecular oxygenation, dehydrogenation and C−N bond cleavage processes of structurally robust picolylamine derivatives (HL) on selective {Ru(acac)2} metal platform encompassing electron rich acac (=acetylacetonate) co‐ligand. The diverse functionalization of {Ru(acac)2} coordinated β‐ketoiminate embedded picolylamines under basic condition included (i) oxygenation of methylene (Cα) position of picolyl fragment (−CH2−NH−→−CO−NH−), (ii) dehydrogenation of phenyl substituted Cα (−CH−NH−→−C=N−) and (iii) C−N bond cleavage of the picolinoyl moiety to yield picolinate (−CO−N−−→−CO−O−). Besides structural, spectroscopic (mass, 1H/13C−NMR, EPR, UV‐vis.) and electrochemical authentication of the products, correlation of the reactivity pattern was addressed via transition state (TS) calculations. Theoretical results supported the consideration of a common dianionic intermediate to address the aforementioned reactivities. The pertinent question of intramolecular cyclization versus intermolecular oxygenation of picolylamine on simple switching from {Ru(Cl)(H)(CO)(PPh3)3} (earlier work[4a]) metal fragment to {Ru(acac)2} (present report) was also elaborated by TS calculation.

Photorelease of Nitric Oxide in Water-Soluble Diruthenium Nitrosyl Complexes with Phosphonate Substituted Pyridylpyrrole

The diethylphosphonate ligand HL 1 substituted pyridylpyrrole was synthesized by treatment of 2-bromo-6-(1H'-pyrrol-2-yl)pyridine and diethylphosphite in presence of base triethylamine and catalyst Pd(PPh 3 ) 4 under refluxing toluene conditions. The HL 1 ligand was treated with bromotrimethylsilane and followed hydrolysis by methanol to afford diphosphonic acid ligand H 3 L 2 . Treatment of H 3 L 2 with [Ru(NO)Cl 3 ] in presence of triethylamine in refluxing thf was generated diruthenium nitrosyl complex [Ru(L 2 )(NO)(Cl)] 2 ·(Et 3 NH) 2 ([ 1 ]·(Et 3 NH) 2 ), which is water soluble. The ligands and metal complex were fully characterized by NMR, IR, ESI-MS and single crystal X-ray diffraction technology. The solid state structure analysis displays 1 2- is dinuclear species, of which two ruthenium atoms are linked by two PO 3 2- groups. Photorelease of nitric oxide from 1 2- was monitored by UV-Vis spectra and the amount of the NO was determined by Griess reaction and DPPH radical scavenging reaction.

Application of Green Solvents: PEG and scCO2 in the Mono- or Biphasic Catalytic Systems for the Repetitive Batch Coupling of Vinylsilanes with Vinyl Boronates toward 1-Boryl-1-silylethenes.

A new method for the repetitive batch silylative coupling (trans-silylation) of vinylsilanes with vinyl boronates in the presence of Ru(CO)Cl(H)(PCy3)2 immobilized in poly(ethylene glycols) (PEGs) has been developed. Three PEGs (PEG600, PEG2000, and MPEG2000) with different molecular weights and end groups (MW = 600–2000) were tested as solvents and immobilization media, while an aliphatic solvent (n-hexane or n-heptane) or supercritical CO2 was used for product extraction. By applying 2 mol % of the Ru–H catalyst, it was possible to carry out up to 15 complete runs, with the predominant formation of 1-boryl-1-silylethenes. This immobilization strategy permitted for catalyst reuse and obtaining higher TON values (approximately 660–734) compared to the reaction in conventional solvents (∼50). Detailed kinetic studies of the most effective catalytic system were performed to determine catalyst activity and stability. Moreover, the reactions were carried out in an MPEG2000/scCO2 biphasic system, positively influencing the process sustainability.

Electronic Fine‐tuning of Ruthenium(II) Transfer Hydrogenation Catalysts with Ethanol as the Hydrogen Source

AbstractA series of ruthenium(II) complexes bearing tridentate N,N’‐diallyl‐2,6‐di(5‐butylpyrazol‐3‐yl)pyridine ligands was synthesized and characterized. Introduction of substituents in the 4‐position of the pyrazole rings tune the electron density at the ruthenium center, which was proved by correlation of the 31P NMR chemical shifts with the σp parameters of the Hammett equation. The structural elucidation of a phosphine‐free ruthenium(II) complex proves that one of the allyl side‐chains undergoes chelating coordination to the ruthenium site to realize a 18 VE center. This compound is the starting point for complexes of the type (N,N,N)Ru(L)(Cl)2 bearing ligands L other than triphenylphosphine. The ruthenium(II) complexes were investigated for their activity in the transfer hydrogenation with ethanol as the hydrogen source. Here the logarithms of the measured turn‐over frequencies (TOF) correlate with the σp parameters of the Hammett equation in terms of a linear free‐energy relationship.