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The dihydrogen complex Ru(H

The authors acknowledge the EPSRC (grant EP/J009962/1, DTA) for financial support The efficient and highly selective room temperature hydrodefluorination (HDF) of fluoroarenes by the trans-[Ru(IMe4)4H2] catalyst, 3 , is reported. Mechanistic studies show 3 acts directly in catalysis without any ligand dissociation and DFT calculations indicate a concerted nucleophilic attack mechanism. The calculations fully account for the observed selectivities which corroborate earlier predictions regarding the selectivity of HDF. Postprint

The photochemistry of Ru(H)2(CO)(PPh3)3 (1) has been reinvestigated employing laser and conventional light sources in conjunction with NMR spectroscopy and IR spectroscopy. The sensitivity of NMR experiments was enhanced by use of p-H2-induced polarization (PHIP), and a series of unexpected reactions were observed. The photoinduced reductive elimination of H2 was demonstrated (a) via NMR spectroscopy by the observation of hyperpolarized 1 on pulsed laser photolysis in the presence of p-H2 and (b) via nanosecond time-resolved infrared (TRIR) spectroscopy studies of the transient [Ru(CO)(PPh3)3]. Elimination of H2 competes with photoinduced loss of PPh3, as demonstrated by formation of dihydrogen, triphenylarsine, and pyridine substitution products which are detected by NMR spectroscopy. The corresponding coordinatively unsaturated 16-electron intermediate [Ru(H)2(CO)(PPh3)2] exists in two isomeric forms according to TRIR spectroscopy that react with H2 and with pyridine on a nanosecond time scale. These two pathways, reductive elimination of H2 and PPh3 loss, are shown to occur with approximately equal quantum yields upon 355 nm irradiation. Low-temperature photolysis in the presence of H2 reveals the formation of the dihydrogen complex Ru(H)2(η2-H2)(CO)(PPh3)2, which is detected by NMR and IR spectroscopy. This complex reacts further within seconds at room temperature, and its behavior provides a rationale to explain the PHIP results. Furthermore, photolysis in the presence of AsPh3 and H2 generates Ru(H)2(AsPh3)(CO)(PPh3)2. Two isomers of Ru(H)2(CO)(PPh3)2(pyridine) are formed according to NMR spectroscopy on initial photolysis of 1 in the presence of pyridine under H2. Two further isomers are formed as minor products; the configuration of each isomer was identified by NMR spectroscopy. Laser pump-NMR probe spectroscopy was used to observe coherent oscillations in the magnetization of one of the isomers of the pyridine complex; the oscillation frequency corresponds to the difference in chemical shift between the hydride resonances. Pyridine substitution products were also detected by TRIR spectroscopy.

In this work, we study the hydrogenation of CO2 via the direct addition of hydride to CO2 on Ru(II) complexes to make clear the influences of two key factors, the nature of Ru–H bond and the effect...

Heterogeneous Ru/H-BEA catalysts are suitable catalysts for the one-pot transformation of citronellal to menthols, which requires a combined cyclization-hydrogenation step. Here, we report the role of different preparation conditions-namely the choice of the Ru-precursor (Ru(NO)(NO 3 ) 3 ), Ru(acac) 3 , RuCl 3 and Ru 3 (CO) 12 ) as well as the reduction temperature (523–923 K) of the catalyst. Using Ru(NO)(NO 3 ) 3 as precursor the highest activity was obtained, while the product distribution was not strongly affected by the choice of the precursor. On the contrary the reduction temperature leads to very different product distributions: Increasing it from 623 K to 923 K for a 1%Ru/H-BEA-25 catalyst the competitive hydrogenation of citronellal was diminished, which leads to an increased selectivity to menthols from 77% to 87% and additional the activity increases with a factor of 3.4. This behaviour might be due to a dealumination of the zeolite during reduction at higher temperatures. Moreover, in combination with appropriate reaction conditions a yield to menthols of 92% can be reached.

Bifunctional ruthenium catalysts supported on H-Beta zeolite were designed and applied in the hydrodeoxygenation of lignin-derived phenolic compounds for bio-oil upgrading. The oxygen-containing groups in lignin-derived phenolic monomers and dimers could be efficiently removed through aqueous phase hydrodeoxygenation catalyzed by Ru/H-Beta under very mild conditions, i.e. at 413 K and 4 MPa H2. Characterization results revealed that ruthenium species existed in the form of highly dispersed nanoparticles on H-Beta zeolite, while the presence of both Bronsted and Lewis acid sites in zeolite was crucial for the remarkable hydrodeoxygenation activity. The effects of reaction conditions and catalyst constitution on the catalytic performance of Ru/H-Beta in hydrodeoxygenation were systematically investigated. The hydrodeoxygenation pathway of diphenyl ether as a model compound catalyzed by optimized 0.5%Ru/H-Beta was discussed and the structure-activity relationship in hydrodeoxygenation was proposed.

Insertion of CS2 into the Ru-H bond of Cp′Ru(PTA)(PR3)H, where Cp′ = Cp (C5H5−); Cp* (C5Me5−); Dp (C8H9−); Ind (C9H7−); or Tp ([HB(C3N2H3)3]−) and PR3 = PTA (1,3,5-triaza-7-phosphaadamantane) or PPh3, resulted in a series of air-stable Cp′Ru(PTA)(PR3)(SC(S)H) complexes. All compounds were characterized by multinuclear (1H, 13C, 31P{1H}) NMR spectroscopy, IR, and HRMS. The synthesis, isolation, and X-ray crystal structures of the CS2 insertion products TpRu(PTA)(PPh3)(SC(S)H) and CpRu(PTA)2(SC(S)H) are described. The rate of CS2 insertion for the series of Cp′Ru(PTA)(PPh3)H complexes varied with the Cp′ ligand with the order found to be Cp* > Tp > Dp ∼ Cp >> Ind. The insertion of the structurally similar CO2 was also explored; however, the products, Cp′Ru(PTA)2(OC(O)H) (Cp′ = Cp, Dp), were unstable relative to the loss of CO2 and concomitant reversion of the starting ruthenium hydride.

Treatment of CpRuH(PP) (PP=dppm, dppe) with TlPF6 produced [CpRu(H)(Tl)(PP)]PF6 . X-ray diffraction and computational studies suggest that the complexes contain a Ru-H-Tl 3c-2e bond and can be viewed as the first σ-complexes of period 6 main-group hydrides [CpRu{η2 -(H-Tl)}(PP)]PF6 or [Tl{η2 -H-RuCp(PP)}]PF6 . The complexes can be stored as a solid at room temperature for days without appreciable decomposition, but are unstable in solution and evolved to the trimetallic complexes [{CpRu(PP)}2 (μ-Tl)]PF6 .

The one-pot transformation of citronellal to menthol requires a combined cyclization–hydrogenation step for which Ru/H-BEA catalysts were identified as highly active and selective catalysts. After identifying zeolite H-BEA as the most promising heterogeneous catalyst for the cyclization of citronellal to the intermediate isopulegol, bifunctional metal/H-BEA catalysts were investigated in the one-pot transformation of citronellal to menthols. Using Pd undesired defunctionalization prevailed, while using Pt and Ru, the formation of menthols predominated. Finally, for Ru/H-BEA catalysts, the effect of catalyst composition (Si:Al ratio, Ru content) and reaction conditions (temperature, hydrogen pressure, and solvent) was investigated to diminish citronellal hydrogenation, dimerization, and defunctionalization. Accordingly, with a 1%Ru/H-BEA-25 catalyst (Ru particle size = 1 nm) in dioxane at 15 bar hydrogen pressure and 373 K, a very high selectivity to menthols of 93% at nearly full conversion was obtained. The catalyst is also highly diastereoselective producing 79% of the desired (±)-menthol.

Temperature, pressure, and concentration variation experiments were conducted in the one-pot-transformation of citronellal to menthol with 1%Ru/H-BEA-25 as bifunctional catalyst. This reaction requires a combination of a cyclization and hydrogenation step, therefore the product distribution strongly depends on reaction conditions, especially on the reaction temperature. At lower temperatures the consecutive hydrogenation of citronellal prevails, whereas at high temperatures defunctionalization of menthols is favored leading to a maximum menthol yield at 373 K. A kinetic model was proposed based on a Langmuir–Hinshelwood mechanism and different active sites for cyclization and hydrogenation reactions. Kinetic parameters (reaction constants, activation energies, and adsorption coefficients) were estimated by using nonlinear regression.

Binary Alloy Phase Diagrams, 2nd edition, a comprehensive collection of alloy phase diagrams for 2159 binary systems, was published in 1990 (T.B. Massalski, H. Okamoto, P.R. Subramanian, and L. Kacprzak., ASM International, Materials Park, OH [Massalski2]). This review intends to provide more recent information on the binary phase diagrams for the Bi-Ga, Bi-Y, Ca-H, Cd-Fe, Cd-Mn, Cr-La, Ge-Ru, H-Li, Mn-Sr, Ni-Sr, Sm-Sn, and Sr-Ti systems that have become available after 1990. The criteria for selecting such information for inclusion in this review are (1) systems for which no phase diagram was given in [Massalski2], (2) complete diagrams that are substantially different from the earlier version, and (3) partial diagrams that alter or clarify the earlier version. Thermodynamic consistency of the new phase diagrams was checked based on phase rules and the diagrams were modified if necessary. However, each updated phase diagram has not gone through the ordinary evaluation process. Accordingly, a newer phase diagram is not always a better diagram, especially when there is too little published data on a system. For convenience, reaction tables and crystal structure data have been added when new information was available.

The efficient and highly selective room temperature hydrodefluorination (HDF) of fluoroarenes by the trans-[Ru(IMe4)4H2] catalyst, 3, is reported. Mechanistic studies show 3 acts directly in catalysis without any ligand dissociation and DFT calculations indicate a concerted nucleophilic attack mechanism. The calculations fully account for the observed selectivities which corroborate earlier predictions regarding the selectivity of HDF.

Chiral spirocarbocyclic skeletons are ubiquitous in natural products. An intramolecular Tsuji-Trost (T-T) α-allylation of simple cyclic ketones is a reasonable approach to construct chiral spriocarbocyclic motifs; however, it has been a challenging approach despite many excellent intermolecular examples. For the first time, this has been achieved by a Ru/H

Milstein and co-workers have reported that the pincer complexes trans-[Ru(H)2(PNN)(CO)] catalyze the unprecedented homogeneous hydrogenation of dimethyl carbonate to methanol. A mechanism for this reaction was proposed on the basis of (i) carbonyl group insertion into one of the Ru–H bonds to produce the six-coordinate trans-[Ru(OCH(OMe)2)(H)(PNN)(CO)] intermediate and (ii) a metal–ligand cooperative transformation, involving proton transfer from the phosphine arm of the PNN ligand to a methoxy group of the Ru-coordinated [OCH(OMe)2]− anion along with cleavage of a C–OMe bond, to produce methanol and an O-bound methyl formate complex of the dearomatized square-pyramidal form of the catalyst, [Ru(H)(PNN)(CO)]. We investigate herein the possibility of an alternative reaction pathway proceeding as (i) an outer-sphere hydride transfer from [Ru(H)2(PNN)(CO)] to the carbonyl of dimethyl carbonate to give an ion pair of the cationic metal fragment and the [OCH(OMe)2]− anion in which the C–H bond is facing the me...

The rates of CO2 insertion into trans-Ru(dmpe)2(Me)H [1, dmpe = 1,2-bis(dimethylphosphino)ethane] and trans-Ru(dmpe)2(Me)2 (2) derivatives were monitored by in situ infrared and 1H NMR spectroscopy. The reactions are first order in both CO2 and metal complex concentrations, and CO2 insertion into the Ru–H bond of 1 occurs instantaneously at 0 °C. The reverse process, decarboxylation, was observed to occur readily at ambient temperature as revealed by 13CO2 exchange with subsequent CO2 insertion into the Ru–Me bond at higher temperatures. No further CO2 insertion into the Ru–H bond of the resulting acetate complex was observed. The activation barrier for CO2 insertion into the first Ru–Me bond of 2 was determined to have ΔH‡ and ΔS‡ values of 12.7 ± 0.6 kcal mol–1 and –31.9 ± 2.0 e.u., respectively, which are indicative of a highly ordered transition state. The rate of CO2 insertion into the second Ru–Me bond was two orders of magnitude slower at ambient temperature and resulted in the formation of trans-Ru(dmpe)2(O2CMe)2. In general, the insertion of CO2 into the Ru–H or Ru–Me bonds of trans-Ru(dmpe)2(X)R (R = H or Me) was disvavored in the presence of poorly electron-donating X ligands. For example, the insertion of CO2 into the Ru–H bond of trans-Ru(dmpe)2(Cl)H was not observed even under forcing conditions. Computational results were in excellent agreement with these observations and predict a significant enhancement in CO2 activity and resultant complex stability if dmpe is replaced with tetramethylethylenediamine (tmeda).

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Endothelial dysfunction has been considered a marker for the presence of cardiovascular disease. It is characterized by decreased release of vasodilatory factors and increased of vasoconstrictors factors. Nitric oxide (NO) is the main endogenous vasodilator molecule that regulates the vascular tone and homeostasis. Decrease in the bioavailability of NO can be caused by a variaty of factors, including the increase in the production of superoxide radical O2 •-. The production of O2 •- can be stimulated by angiotensin II, by the enzyme complex of the NADPH oxidase activation. Thus, the objective of this work was to study the effects induced by ruthenium complex cis-[Ru(H-dcbpy-)2(Cl)(NO2 -)] (DCBPY) and sodium nitroprusside (SNP) in endothelial dysfunction model, as well as perform the pharmacological characterization of the dependent effects removal of O2 •- and release of nitric oxide (NO) induced by these drugs. Normotensive (2K) and hypertensive (2K-1C) wistar rats were used. Aortic rings with intact endothelium were placed in a myograph and incubated with DCBPY: 0.1; 1.0 ou 10 μM ou com SNP: 0.1; 1.0 ou 10 nM during 30 minutes. Curves concentration-effect of acetylcholine (ACh) were built where it was possible to analyze all concentrations DCBPY and NPS improved relaxation induced by ACh. NO was measured intracellular (for DAF-2DA probe) in HUVEC treated with 0.1 μM of DCBPY, 0.1 nM a SNP and 0.1 μM DETA-NO. It was not detected NO release of the compounds DCBPY [0.1 μM] and SNP [0.1 nM]. It also evaluated the release of NO compound DCBPY using an electrode selective for NO. The compound DCBPY spontaneously release NO in solution form concentrationdependent, starting from 10 μM concentration. DCBPY released more NO in the presence of cells. This could be due to the reduction of the compound by reducing cell. Intracellular detection of superoxide radical (O2 •-) was obtained by using the fluorescent probe (DHE). Our results show that treatment of cells with DCBPY [0.1 μM] and SNP [0.1 nM] decreased the fluorescence intensity cells stimulated with angiotensin II. Thus, it is suggested that DCBPY and SNP at a concentration which does not release NO, inside the cells, they are capable of attenuating endothelial dysfunction by inactivating superoxide. A disfunção endotelial tem sido considerada um marcador para a presença de doenças cardiovasculares. É caracterizada pela diminuição da liberação de fatores vasodilatadores e/ou aumento da liberação de fatores vasoconstritores. O óxido nítrico (NO) é a principal molécula vasodilatadora endógena que regula o tônus e a homeostase vascular. A diminuição na biodisponibilidade do NO pode ser causada por diversos fatores, incluindo o aumento na produção do radical superóxido O2 •-. A produção do O2 •- pode ser estimulada pela angiotensina II, pela ativação do complexo enzimático NADPH oxidase. Desta forma, o objetivo deste trabalho foi estudar os efeitos induzidos pelo complexo de rutênio cis-[Ru(H-dcbpy-)2(Cl)(NO2 -)] (DCBPY) e Nitroprussiato de Sódio (NPS) em modelo de disunção endotelial, bem como realizar a caracterização farmacológica dos efeitos dependentes da remoção do O2 •- e liberação do óxido nítrico (NO) induzidos por estas drogas. Foram utilizados ratos Wistar machos normotensos (2R) e hipertensos (2R-1C). Anéis de aortas com endotélio intacto foram colocados em um miógrafo e incubados com DCBPY: 0,1; 1,0 ou 10 μM ou com NPS: 0,1; 1,0 ou 10 nM durante 30 minutos. Curvas concentração-efeito à acetilcolina (ACh) foram construidas onde foi possível analisar que todas as concentrações de DCBPY e NPS melhoraram o relaxamento induzido pela ACh. NO intracelular foi medido (por sonda DAF-2DA) em HUVEC tratadas com 0,1 μM de DCBPY, 0,1 nM de NPS ou 0,1 μM de DETA / NO. Não foi detectada liberação de NO dos compostos DCBPY [0,1 μM] e NPS [0,1 nM]. Também foi avaliada a liberação de NO do composto DCBPY utilizando eletrodo seletivo para NO. O composto DCBPY libera NO espontaneamente em solução de forma concentração dependente a partir da concentração 10 μM. Na presença das células, houve um aumento na liberação de NO na concentração 10 μM do composto DCBPY de 1,69 vezes em comparação com a detecção sem a presença de células. Isto pode ter ocorrido devido à redução do composto por redutores celulares. A detecção intracelular do radical superóxido (O2 •-) foi obtida através da utilização da sonda fluorescente DHE. Os nossos resultados mostram que o tratamento de células com DCBPY [0,1 μM] e de NPS [0,1 nM] diminuiu a intensidade de fluorescência a DHE em células estimuladas com angiotensina II. Assim, sugere-se que DCBPY e NPS, em uma concentração que não libera NO no interior das células, são capazes de atenuar a disfunção endotelial por inativar o radical superóxido.

The interactions between [(η6-p-cymene)Ru(H2O)3]2+ and L-malic acid (H2mal), L-tartaric acid (H2tart), and their sulfur-containing analogues dl-thiomalic acid (H3thiomal) and meso-2,3-dimercaptosuccinic acid (H4dmsa) were studied by pH potentiometry, NMR spectroscopy, and ESI-MS. The hydroxycarboxylates are potent metal ion binders and prevent hydrolysis at pH 7.4 in aqueous solution. Although H2mal forms mononuclear complexes with different degrees of protonation by the involvement of the alcohol/alkoxide group in addition to the carboxylate groups, the presence of binding isomers is detected for the H2tart system. The replacement of the alcohol group by a thiolate group results in the formation of dinuclear [Ru2A2] complexes as the single species over a wide pH range. Complexes with identical binding modes with H3thiomal or polymeric species with H4dmsa are identified, and the X-ray structure of [{(η6-p-cym)Ru}2(Hthiomal)2] is reported. The stereochemistry of the chiral-at-metal complexes was explored by NMR spectroscopy and is also discussed.