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We report on the synthesis and characterization of new ruthenium indenylidene complexes bearing two unsymmetrical N-heterocyclic carbene (NHC) ligands denoted as RuCl2(3-phenyl-1-indenylidene)bis(1-mesityl-3-R-4,5-dihydroimidazole-2-ylidene) in which R is methyl 7a and cyclohexyl 7b. Complexes 7a and 7b were analyzed using single-crystal X-ray diffraction analysis, elemental analysis, IR, NMR spectroscopy, and HRMS. The catalytic activities of complexes 7a and 7b were evaluated in olefin metathesis reactions: ring-opening metathesis polymerization (ROMP) of cis,cis-1,5-cyclooctadiene (COD) and ringclosing metathesis (RCM) of diethyl diallyl malonate (DEDAM) as well as in the isomerization of allylic alcohols. Complexes 7a and 7b failed to initiate the reactions at room temperature in all tested reactions, which might be due to the high thermal stability and low degree of lability of the Ru-CNHC bonds. At 80 °C, the complex 7a showed the best performance due to an increased initiation and a decreased steric obstruction towards the incoming substrates.

The Ru-catalyzed intramolecular oxidative amidation (lactamization) of aromatic alkynylamines with 4-picoline N-oxide as an external oxidant has been developed. This chemoselective process is very efficient to achieve medium-sized ε- and ζ-lactams (seven- and eight-membered rings) but not for the formation of common δ-lactams (six-membered rings). DFT studies unveiled the capital role of the chain length between the amine and the alkyne functionalities: the longer the connector, the more favored the lactamization process vs hydroamination. This work has received financial support from MICINN (projects PID2020-118048GB-I00, PID2020-116861GB-I00, and ORFEO-CINQA network RED2018-102387-T), the Xunta de Galicia (project ED431C 2022/27, Centro singular de investigación de Galicia accreditation 2019-2022, ED431G 2019/03), and the European Union (European Regional Development Fund) SI

Natural and synthetic β-lactam derivatives constitute an interesting class of compounds due to their diverse biological activity. Mostly used as antibiotics, they were also found to have antitubercular, anticancer and antidiabetic activities, among others. In this investigation, six new 3,3-dichloro-β-lactams prepared in a previous work were evaluated for their hemolytic and cytotoxic properties. The results showed that the proposed compounds have non-hemolytic properties and exhibited an interesting cytotoxic activity toward squamous cell carcinoma (A431 cell line), which was highly dependent on the structure and concentration of these β-lactams. Among the molecules tested, 2b was the most cytotoxic, with the lowest IC50 values (30–47 µg/mL) and a promising selectivity against the tumor cells compared with non-tumoral cells.

γ-Valerolactone (GVL) is readily obtained by the hydrogenation of levulinic acid (LA) and is considered a sustainable platform chemical for the production of biobased chemicals. Herein, the performance and stability of Ru-based catalysts (1 wt % Ru) supported on TiO 2 (P25) and ZrO 2 (monoclinic) for LA hydrogenation to GVL is investigated in the liquid phase in batch and continuous-flow reactors using water and dioxane as solvents. Particular attention is paid to the influence of possible impurities in the LA feed on catalyst performance for LA hydrogenation. Benchmark continuous-flow experiments at extended times on-stream showed that the deactivation profiles are distinctly different for both solvents. In dioxane, the Ru/ZrO 2 catalyst is clearly more stable than Ru/TiO 2, whereas the latter is slightly more stable in water. Detailed characterization studies on spent catalysts after long run times showed that the deactivation of Ru/TiO 2 is strongly linked to the reduction of a significant amount of Ti 4+ species of the support to Ti 3+ and a decrease in the specific surface area of the support in comparison to the fresh catalyst. Ru/ZrO 2 showed no signs of support reduction and displayed morphological and structural stability; however, some deposition of carbonaceous material is observed. Impurities in the LA feed such as HCOOH, H 2SO 4, furfural (FFR), 5-hydroxymethylfurfural (HMF), humins, and sulfur-containing amino acids impacted the catalyst performance differently. The results reveal a rapid yet reversible loss of activity for both catalysts upon HCOOH addition to LA, attributed to its preferential adsorption on Ru sites and possible CO poisoning. A more gradual drop in activity is found when cofeeding HMF, FFR, and humins for both solvents. The presence of H 2SO 4, cysteine, and methionine all resulted in the irreversible deactivation of the Ru catalysts. The results obtained provide new insights into the (ir)reversible (in)sensitivity of Ru-based hydrogenation catalysts to potential impurities in LA feeds, which is essential knowledge for next-generation catalyst development.

γ-Valerolactone (GVL) is readily obtained by the hydrogenation of levulinic acid (LA) and is considered a sustainable platform chemical for the production of biobased chemicals. Herein, the performance and stability of Ru-based catalysts (1 wt % Ru) supported on TiO 2 (P25) and ZrO 2 (monoclinic) for LA hydrogenation to GVL is investigated in the liquid phase in batch and continuous-flow reactors using water and dioxane as solvents. Particular attention is paid to the influence of possible impurities in the LA feed on catalyst performance for LA hydrogenation. Benchmark continuous-flow experiments at extended times on-stream showed that the deactivation profiles are distinctly different for both solvents. In dioxane, the Ru/ZrO 2 catalyst is clearly more stable than Ru/TiO 2, whereas the latter is slightly more stable in water. Detailed characterization studies on spent catalysts after long run times showed that the deactivation of Ru/TiO 2 is strongly linked to the reduction of a significant amount of Ti 4+ species of the support to Ti 3+ and a decrease in the specific surface area of the support in comparison to the fresh catalyst. Ru/ZrO 2 showed no signs of support reduction and displayed morphological and structural stability; however, some deposition of carbonaceous material is observed. Impurities in the LA feed such as HCOOH, H 2SO 4, furfural (FFR), 5-hydroxymethylfurfural (HMF), humins, and sulfur-containing amino acids impacted the catalyst performance differently. The results reveal a rapid yet reversible loss of activity for both catalysts upon HCOOH addition to LA, attributed to its preferential adsorption on Ru sites and possible CO poisoning. A more gradual drop in activity is found when cofeeding HMF, FFR, and humins for both solvents. The presence of H 2SO 4, cysteine, and methionine all resulted in the irreversible deactivation of the Ru catalysts. The results obtained provide new insights into the (ir)reversible (in)sensitivity of Ru-based hydrogenation catalysts to potential impurities in LA feeds, which is essential knowledge for next-generation catalyst development.

This account surveys the current progress on the application of intra- and intermolecular enyne metathesis as main key steps in the synthesis of challenging structural motifs and stereochemistries found in bioactive compounds. Special emphasis is placed on ruthenium catalysts as promoters of enyne metathesis to build the desired 1,3-dienic units. The advantageous association of this approach with name reactions like Grignard, Wittig, Diels–Alder, Suzuki–Miyaura, Heck cross-coupling, etc. is illustrated. Examples unveil the generality of such tandem reactions in providing not only the intricate structures of known, in vivo effective substances but also for designing chemically modified analogs as valid alternatives for further therapeutic agents.

Ru(II)/carboxylate/PPh$_3$ catalyst system enabled the preparation of highly conjugated pyrazine derivatives in water under microwave irradiation. Both nitrogen atoms efficiently dictated cleavage of the ortho-C–H bonds in both benzene rings of 2,3-diphenylpyrazine substrates through chelation assistance. In conformationally more flexible diphenyldihydropyrazine 1, the arylation of four ortho-C–H bonds was possible, while in the aromatic analog 2, the triarylation was the limit.

Orientador: Ronaldo Aloise Pilli Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Quimica Doutorado Química Orgânica Doutor em Química

Orientador: Antonio Jose Gomez Cobo, Adler Gomes Moura Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica Resumo: A hidrogenação parcial do benzeno é uma reação química de grande interesse científico e industrial, uma vez que o cicloexeno formado pode ser empregado na obtenção de diversos produtos, em razão da sua dupla ligação altamente reativa. O presente trabalho tem como objetivo principal estudar os efeitos do cloro em catalisadores de Ru/CeO2, destinados à hidrogenação parcial do benzeno. Com o intuito de verificar a influência da natureza do suporte, catalisadores de Ru/Al2O3 também foram estudados, como referência, uma vez que a alumina é um suporte não redutível. Para tal, catalisadores com uma fração mássica de metal de cerca de 5 % foram preparados através do método de impregnação a seco. Após a adição do precursor clorado RuCl3xH2O ao suporte, os catalisadores foram submetidos a tratamentos térmicos consecutivos de redução direta a 573K. Os sólidos obtidos foram caracterizados através das técnicas de adsorção de N2 (método B.E.T.), microscopia eletrônica de varredura com microssonda para análise espectrométrica de raios X (MEV + EDX), espectrometria de fotoelétrons excitados por raios X (XPS) e redução à temperatura programada (TPR). O desempenho dos catalisadores foi avaliado nas reações de hidrogenação do benzeno e de hidrogenação do cicloexeno, empregando-se um reator Parr do tipo "slurry". A reação foi conduzida à pressão de hidrogênio constante de 5 Mpa e à temperatura de 373 K, em meio reacional trifásico contendo água. Em alguns testes catalíticos realizados, soluções aquosas de TiCl3, NaCl, ZnCl2 ou HCl foram adicionadas ao meio reacional. Os resultados da caracterização revelam que o cloro, oriundo do precursor clorado, praticamente não é eliminado do catalisador Ru/CeO2, mesmo após os sucessivos tratamentos de redução. Na reação de hidrogenação do benzeno, o catalisador Ru/CeO2, reduzido duas vezes consecutivas, apresenta os maiores rendimentos de cicloexeno, tanto na ausência, quanto na presença de TiCl3 no meio reacional. Dentre os aditivos empregados no meio reacional, o TiCl3 conduz aos maiores rendimentos de cicloexeno Abstract: The partial hydrogenation of the benzene is a chemical reaction of great scientific and industrial interest, since the produzed cyclohexeno can be used in the attainment of diverse products, in reason of its highly reactive double bond. The present work has as main objective to study the effect of chlorine in Ru/CeO2 catalysts, destined to the partial hydrogenation of the benzene. With intention to verify the influence of the nature of the support, Ru/Al2O3 catalysts have been also studied, as reference, since that alumina is a not reducible support. For such, catalysts with a mass metal fraction of about 5 % were prepared by the wet impregnation technique. After the addition of the chloride precursor RuCl3xH2O to the support, the catalysts were submitted to consecutive thermal treatments of direct reduction at 573K. The gotten solids have been characterized by N2 adsorption (method B.E.T.), electronic scanning microscopy with energy dispersive X-ray spectroscopy analysis (MEV+EDX), X-ray photolectron spectroscopy (XPS) and temperature-programmed reduction (TPR) techniques. The performance of the catalysts have been evaluated in the reactions of benzene hydrogenation and cyclohexeno hydrogenation, using a Parr reactor of the type "slurry". The reaction has been carried out at 5 Mpa constant hydrogen pressure and 373K temperature, in a three-phase reacional system with water. In some catalysts tests, aqueous solutions of TiCl3, NaCl, ZnCl2 or HCl have been added to the reacional system. The results of the characterization show that the chlorine, from the chloride precursor, is practically not eliminated of the Ru/CeO2 catalyst, after the successive treatments of reduction. In the benzene hydrogenation reaction, the Ru/CeO2 catalyst, reduced two consecutive times, presents the biggest yields of cyclohexeno, as in the absence, as in the presence of TiCl3 in the reacional system. Among additives used in the reacional system, the TiCl3 leads to the biggest yields of cicloexeno Mestrado Sistemas de Processos Químicos e Informática Mestre em Engenharia Química

Orientador: Antonio José Gomez Cobo Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química Resumo: Com foco na sustentabilidade alinhada à obtenção de produtos de maior valor agregado, as indústrias químicas vêm investindo em pesquisas que viabilizem o processamento de matérias primas renováveis. Em particular, o sorbitol é um poliálcool proveniente da glicose, que pode ser convertido a etileno glicol e propileno glicol, derivados químicos de forte demanda industrial. Nesse contexto, o presente trabalho tem por objetivo estudar os efeitos dos suportes SiO2 kieselguhr, ?-Al2O3 e carvão ativado, assim como do método de impregnação, sobre o desempenho de catalisadores de Ru, destinados à hidrogenólise do sorbitol. Para tanto, catalisadores com uma fração mássica de 5 % de metal foram preparados através de impregnação incipiente ou úmida, a partir do precursor RuCl3.xH2O. Os sólidos preparados por impregnação incipiente foram submetidos a uma redução direta a 473 K (200 °C), sob fluxo de H2. A impregnação úmida foi realizada a 273 K (0 ºC), utilizando-se formaldeído como agente redutor. Suportes e catalisadores foram caracterizados através de técnicas para determinação da distribuição granulométrica, de titulação potenciométrica, adsorção de N2, porosimetria de Hg, microscopia eletrônica de varredura e redução à temperatura programada. Os desempenhos dos catalisadores foram avaliados na reação de hidrogenólise do sorbitol, conduzida em reatores trifásicos do tipo "slurry" e "trickle-bed". Durante os testes catalíticos, a temperatura e a pressão de H2 nos reatores foram mantidas constantes, entre 473 e 573 K (200 e 300 ºC) e entre 5 e 7 MPa (50 e 70 atm), respectivamente. Os resultados revelam que os catalisadores de Ru suportados em carvão ativado apresentam melhores desempenhos que aqueles suportados em SiO2 ou Al2O3. Maiores rendimentos de etileno glicol e propileno glicol são obtidos quando o catalisador de Ru/C é preparado por impregnação úmida Abstract: Focusing on sustainability aligned to obtain products with higher added value, the chemical industries are investing in research that enables the processing of renewable raw materials. In particular, sorbitol is a polyalcohol derived from the glucose, which can be converted to ethylene glycol and propylene glycol, commodity chemical of strong industrial demand. In this context, the present work aims to study the supports effects SiO2 kieselguhr, ?-Al2O3 and activated carbon as well as the impregnation method on the performance of Ru catalysts for the hydrogenolysis of sorbitol. For this purpose, catalysts with a total fraction of 5 %wt. of metal were prepared by incipient or wet impregnation from the RuCl3.xH2O precursor. The solids prepared by incipient impregnation underwent direct reduction at 473 K (200 ° C) under flow H2. The wet impregnation was conducted at 273 K (0 ° C) using formaldehyde as reducing agent. Supports and catalysts were characterized by techniques for determination of particle size distribution, potentiometric titration, N2 adsorption, Hg porosimetry, scanning electron microscopy and temperature programmed reduction. The performances of the catalysts were evaluated though the sorbitol hydrogenolysis reaction, conducted in three phase reactors such as "slurry" and "trickle-bed". During the catalytic tests the temperature and H2 pressure in the reactors were kept constant between 473 and 573 K (200 to 300 ° C) and between 5 and 7 MPa (50 to 70 atm), respectively. The results indicate that the Ru catalysts supported on activated carbon have better performance than those supported on SiO2 or Al2O3. Higher yields of ethylene glycol and propylene glycol are obtained when the catalyst Ru/C is prepared by wet impregnation Mestrado Sistemas de Processos Químicos e Informática Mestra em Engenharia Química

Olefin metathesis is one of the most powerful C–C double-bond-forming reactions. Metathesis reactions have had a tremendous impact in organic synthesis, enabling a variety of applications in polymer chemistry, drug discovery and chemical biology. Although challenging, the possibility to perform aqueous metatheses has become an attractive alternative, not only because water is a more sustainable medium, but also to exploit biocompatible conditions. This review focuses on the progress made in aqueous olefin metatheses and their applications in chemical biology.

This study reveals the effect of the catalytic 1D supports (carbon, ceria, alumina and titanate) for ruthenium particles on the low temperature release of hydrogen from ammonia. While the state-of-art literature presents Ru/carbon nanotubes (CNT) as the most active catalyst, we found in this work that ruthenium supported on ceria nanorods (Ru/CeO2) catalyst exhibited activity over 8 times higher than the Ru/CNT counterpart system. This enhanced activity is believed to be related to a strong metal-support interaction on the Ru/CeO2 catalysts promoting the formation of small (~ 3 nm) Ru particles. Addition of sodium as a promoter leads to the formation of smaller Ru particle sizes in addition to the modification of the electronic environment of Ru, enhancing the ammonia decomposition activity at low temperatures. This effect is particularly noticeable in the Ru–Na/CNT catalysts, facilitated by the high conductivity of the support, allowing distant electronic modification of the Ru active sites. This work provides novel insights in designing catalysts for hydrogen production from ammonia in our effort to enable the long-term energy storage in chemical bonds.

Orientador: Raphael Soeiro Suppino Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química Resumo: O estudo de catalisadores suportados para uso em reações químicas de conversão do furfural, molécula plataforma proveniente da biomassa, abre caminho para o desenvolvimento de novos processos inseridos no conceito de biorrefinarias. O álcool furfurílico, produto da hidrogenação do furfural, possui importantes aplicações industriais, sobretudo na fabricação de resinas. Metais nobres e básicos podem compor a fase ativa do catalisador, dentre os quais foram escolhidos Ni, Cu, Pd e Ru para esta pesquisa. A escolha da nióbia (Nb2O5) como suporte se dá por suas propriedades químicas e estruturais, notadamente sua acidez natural e área superficial específica, além de apresentar elevada disponibilidade em território nacional. Portanto, este trabalho teve como objetivo avaliar o desempenho de catalisadores de metais suportados em Nb2O5 na hidrogenação de furfural a álcool furfurílico em fase líquida. Os catalisadores foram sintetizados por impregnação úmida, com prévia calcinação do suporte. O teor metálico do catalisador de Ni foi variado entre 5 e 20%. Metais básicos (Ni e Cu) foram reduzidos sob fluxo de H2 e metais nobres (Pd e Ru) foram reduzidos utilizando-se formaldeído em sua preparação. As reações foram conduzidas em um reator Parr do tipo slurry, sob pressão de H2 de 5 MPa, temperatura de 150°C e 2-propanol foi utilizado como solvente. Com o intuito de correlacionar os resultados obtidos com as propriedades físico-químicas dos materiais, o suporte e os catalisadores foram caracterizados por fisissorção de N2, EDS, DRX, TPR, TPD-NH3 e XPS. A temperatura de calcinação do suporte permitiu a síntese de materiais não-cristalinos e com alta área superficial específica. Há indícios de que a redução por formaldeído evitou o agregamento de partículas nos metais nobres, enquanto a exposição ao fluxo de H2 permitiu um elevado grau de redução para metais básicos. A elevação do teor metálico em catalisadores de Ni intensificou o bloqueio dos poros, principalmente no sólido 15% Ni/Nb2O5, mas de modo geral contribuiu para o aumento da atividade catalítica. Catalisadores de Ni e Cu apresentaram alta seletividade a álcool furfurílico, porém o sólido Cu/Nb2O5 apresentou uma conversão de furfural de apenas 15% devido à perda de sítios ativos na superfície. Catalisadores de Pd e Ru forneceram altas taxas iniciais de reação e possibilitaram a conversão completa do furfural, porém enquanto Pd/Nb2O5 apresentou seletividade crescente a álcool tetraidrofurfurílico, Ru/Nb2O5 possibilitou a formação de álcool furfurílico nas primeiras 2 horas de reação. A presença de sítios ácidos na superfície catalítica favoreceu a formação de subprodutos, especialmente éter difurfurílico Abstract: The study of supported catalysts applied in chemical reactions for the conversion of furfural, a platform molecule obtained from biomass, enables the development of new processes inserted in the concept of biorefineries. Furfuryl alcohol, a furfural hydrogenation product, has important industrial applications, especially in the manufacturing of resins. Noble and base metals may constitute the active phase of the catalyst, of which Ni, Cu, Pd and Ru have been chosen for this research. The choice of niobia (Nb2O5) as support is due to its chemical and structural properties, especially its natural acidity and specific surface area, besides being highly available in national territory. Therefore, this research aimed to evaluate the performance of metal catalysts supported on Nb2O5 in the hydrogenation of furfural to furfuryl alcohol in liquid phase. The catalysts were synthesized by wet impregnation, with prior calcination of the support. The metal loading of the Ni catalyst was varied between 5 and 20 wt%. Base metals (Ni and Cu) were reduced under H2 flow and noble metals (Pd and Ru) were reduced using formaldehyde in their preparation. The reactions were conducted in a slurry Parr reactor under H2 pressure of 5 MPa, temperature of 150°C and 2-propanol was used as solvent. In order to correlate the obtained results with the physicochemical properties of the materials, support and catalysts were characterized by N2 physisorption, EDS, XRD, TPR, TPD-NH3 and XPS. The calcination temperature of the support allowed the synthesis of non-crystalline materials with high specific surface area. There are indications that the reduction by formaldehyde prevented particle aggregation in noble metals, while the exposure to H2 flow allowed a high degree of reduction for base metals. The increase of metal loading on Ni catalysts intensified pore blockage, mainly in the solid 15% Ni/Nb2O5, but in general it contributed to an increase in catalytic activity. Ni and Cu catalysts showed high selectivity to furfuryl alcohol, however the solid Cu/Nb2O5 presented a furfural conversion of only 15% due to the loss of active sites on the surface. Pd and Ru catalysts provided high initial reaction rates and enabled complete furfural conversion, but while Pd/Nb2O5 showed increasing selectivity to tetrahydrofurfuryl alcohol, Ru/Nb2O5 enabled the formation of furfuryl alcohol in the first 2 hours of reaction. The presence of acid sites on the catalytic surface favored the formation of by-products, especially difurfuryl ether Mestrado Mestra em Engenharia Química CNPQ 130783/2019-6 CAPES 001 FAPESP 2015/20630-4

International audience; Discovered in 2005, cyclic (alkyl)(amino)carbenes (CAACs) have led to numerous discoveries in the field of ruthenium olefin metathesis, until then largely dominated by the well-known N-heterocyclic carbenes (NHCs). In comparison to the latter, CAACs are simultaneously more nucleophilic (σ-donating) and electrophilic (π-accepting), which leads to very strong metal-carbene bonds. Consequently, (CAAC)ruthenium complexes are very robust, which leads to enhanced catalytic activities, as exemplified by the industrially relevant ethenolysis of unsaturated fatty acids (TONs of up to 390000). Herein, we provide a comprehensive overview of the effect of CAAC ligands in olefin metathesis, including results which are described in patents.

Carbon xerogels were synthesised and used as support of ruthenium-based catalysts for the ammonia decomposition reaction. To improve their physical-chemical properties, carbon xerogels were either activated in carbondioxide atmosphere (for 1 and 5 h), or doped with nitrogen via co-precursor method, using urea as nitrogen source. Un-promoted and sodium-promoted ruthenium catalysts were prepared by incipient wetness impregnation. All catalysts were tested during the ammonia decomposition reaction (1 atm, 100–600 ◦C), showing high catalytic activity. The 5 h carbon dioxide activation treatment resulted in a decrease in oxygen surface groups (i.e. by 11 wt%) on carbon xerogels surface, and in an increase in the structure crystallinity (i.e. by 15% in the TBurn) of carbon xerogels, resulting in a higher ammonia decomposition reaction rate (i.e. 3.5-fold at 450 ◦C). Similarly, nitrogen addition to carbon xerogels had a positive effect on the catalysts basicity, enhancing their catalytic performance (i.e. triple reaction rate at 450 ◦C). The addition of sodium conferred an enhancement in the performance of each catalyst (i.e. reaction rate up to 9 times higher at 450 ◦C). Two ammonia decomposition reaction runs were performed for all catalysts, to test the performance reproducibility of the catalysts. It was found that un-promoted catalysts exhibited higher reaction rates (i.e. up to 3.5 times at 450 ◦C) during the second run of reaction due to the larger ruthenium particle size, whereas sodium-promoted catalysts exhibited similar catalytic activity in both reaction runs due to the presence of sodium oxide avoiding the sintering of ruthenium particles.

The synthesis of two novel enol esters, namely hex-1-en-2-yl indole-2-carboxylate and hex-1-en-2-yl 1-(hex-1-en-2-yl)-indole-2-carboxylate, is presented. Both compounds were generated by addition of indole-2-carboxylic acid to 1-hexyne employing [RuCl2(η6-p-cymene)(PPh3)] and [AuCl(PPh3)]/AgPF6, respectively, as catalysts.

Advanced applications of the Nobel Prize winning olefin metathesis reaction require user‐friendly and highly universal catalysts. From many successful metathesis catalysts, which belong to the two distinct classes of Schrock and Grubbs‐type catalysts, the subclass of chelating‐benzylidene ruthenium complexes (so‐called Hoveyda–Grubbs catalysts) additionally activated by electron‐withdrawing groups (EWGs) provides a highly tunable platform. In the Review, the origin of the EWG‐activation concept and selected applications of the resulting catalysts in target‐oriented synthesis, medicinal chemistry, as well as in the preparation of fine‐chemicals and in materials chemistry is discussed. Based on the examples, some suggestions for end‐users regarding minimization of catalyst loading, selectivity control, and general optimization of the olefin metathesis reaction are provided., Chelating‐benzylidene ruthenium complexes (so‐called Hoveyda–Grubbs catalysts) activated by electron‐withdrawing groups (EWGs) are finding practical applications in target‐oriented synthesis, medicinal chemistry, the preparation of fine‐chemicals, and in materials chemistry.

Mesoporous ruthenium catalysts (0.74–3.06 wt%) based on ordered Mobil Composition of Matter No. 41 (MCM-41) silica arrays on aluminosilicate halloysite nanotubes (HNTs), as well as HNT-based counterparts, were synthesized and tested in benzene hydrogenation. The structure of HNT core-shell silica composite-supported Ru catalysts were investigated by transmission electron microscopy (TEM), X-ray fluorescence (XRF) and temperature-programmed reduction (TPR-H2). The textural characteristics were specified by low-temperature nitrogen adsorption/desorption. The catalytic evaluation of Ru nanoparticles supported on both the pristine HNTs and MCM-41/HNT composite in benzene hydrogenation was carried out in a Parr multiple reactor system with batch stirred reactors (autoclaves) at 80 °C, a hydrogen pressure of 3.0 MPa and a hydrogen/benzene molar ratio of 3.3. Due to its hierarchical structure and high specific surface area, the MCM-41/HNT composite provided the uniform distribution and stabilization of Ru nanoparticles (NPs) resulted in the higher specific activity and stability as compared with the HNT-based counterpart. The highest specific activity (5594 h−1) along with deep benzene hydrogenation to cyclohexane was achieved for the Ru/MCM-41/HNT catalyst with a low metal content.

γ-Valerolactone (GVL) is readily obtained by the hydrogenation of levulinic acid (LA) and is considered a sustainable platform chemical for the production of biobased chemicals. Herein, the performance and stability of Ru-based catalysts (1 wt % Ru) supported on TiO2 (P25) and ZrO2 (monoclinic) for LA hydrogenation to GVL is investigated in the liquid phase in batch and continuous-flow reactors using water and dioxane as solvents. Particular attention is paid to the influence of possible impurities in the LA feed on catalyst performance for LA hydrogenation. Benchmark continuous-flow experiments at extended times on-stream showed that the deactivation profiles are distinctly different for both solvents. In dioxane, the Ru/ZrO2 catalyst is clearly more stable than Ru/TiO2, whereas the latter is slightly more stable in water. Detailed characterization studies on spent catalysts after long run times showed that the deactivation of Ru/TiO2 is strongly linked to the reduction of a significant amount of Ti4+ species of the support to Ti3+ and a decrease in the specific surface area of the support in comparison to the fresh catalyst. Ru/ZrO2 showed no signs of support reduction and displayed morphological and structural stability; however, some deposition of carbonaceous material is observed. Impurities in the LA feed such as HCOOH, H2SO4, furfural (FFR), 5-hydroxymethylfurfural (HMF), humins, and sulfur-containing amino acids impacted the catalyst performance differently. The results reveal a rapid yet reversible loss of activity for both catalysts upon HCOOH addition to LA, attributed to its preferential adsorption on Ru sites and possible CO poisoning. A more gradual drop in activity is found when cofeeding HMF, FFR, and humins for both solvents. The presence of H2SO4, cysteine, and methionine all resulted in the irreversible deactivation of the Ru catalysts. The results obtained provide new insights into the (ir)reversible (in)sensitivity of Ru-based hydrogenation catalysts to potential impurities in LA feeds, which is essential knowledge for next-generation catalyst development.

γ-Valerolactone (GVL) is readily obtained by the hydrogenation of levulinic acid (LA) and is considered a sustainable platform chemical for the production of biobased chemicals. Herein, the performance and stability of Ru-based catalysts (1 wt % Ru) supported on TiO 2 (P25) and ZrO 2 (monoclinic) for LA hydrogenation to GVL is investigated in the liquid phase in batch and continuous-flow reactors using water and dioxane as solvents. Particular attention is paid to the influence of possible impurities in the LA feed on catalyst performance for LA hydrogenation. Benchmark continuous-flow experiments at extended times on-stream showed that the deactivation profiles are distinctly different for both solvents. In dioxane, the Ru/ZrO 2 catalyst is clearly more stable than Ru/TiO 2, whereas the latter is slightly more stable in water. Detailed characterization studies on spent catalysts after long run times showed that the deactivation of Ru/TiO 2 is strongly linked to the reduction of a significant amount of Ti 4+ species of the support to Ti 3+ and a decrease in the specific surface area of the support in comparison to the fresh catalyst. Ru/ZrO 2 showed no signs of support reduction and displayed morphological and structural stability; however, some deposition of carbonaceous material is observed. Impurities in the LA feed such as HCOOH, H 2SO 4, furfural (FFR), 5-hydroxymethylfurfural (HMF), humins, and sulfur-containing amino acids impacted the catalyst performance differently. The results reveal a rapid yet reversible loss of activity for both catalysts upon HCOOH addition to LA, attributed to its preferential adsorption on Ru sites and possible CO poisoning. A more gradual drop in activity is found when cofeeding HMF, FFR, and humins for both solvents. The presence of H 2SO 4, cysteine, and methionine all resulted in the irreversible deactivation of the Ru catalysts. The results obtained provide new insights into the (ir)reversible (in)sensitivity of Ru-based hydrogenation catalysts to potential impurities in LA feeds, which is essential knowledge for next-generation catalyst development.

Ru(II)/carboxylate/PPh3 catalyst system enabled the preparation of highly conjugated pyrazine derivatives in water under microwave irradiation. Both nitrogen atoms efficiently dictated cleavage of the ortho-C&ndash, H bonds in both benzene rings of 2,3-diphenylpyrazine substrates through chelation assistance. In conformationally more flexible diphenyldihydropyrazine 1, the arylation of four ortho-C&ndash, H bonds was possible, while in the aromatic analog 2, the triarylation was the limit.

The intermittency in power generation that characterizes renewable energy sources requires a way to convert the energy surplus. Among all the possibilities, the conversion of power in hydrogen via water electrolysis and then into methane via CO2 methanation represents a competitive storage system. CO2 methanation is an exothermic reaction which requires the use of low temperatures in order to achieve sufficiently high conversions: for this reason, there is a strong need in low-temperature active catalyst. In this work, several Ru/CeO2-ZrO2 and Ru-Ni/CeO2-ZrO2 were prepared and compared with Ni/CeO2-ZrO2, in order to evaluate the effect of Ru loading and Ru precursor salt. The results showed that in monometallic formulations the higher was the Ru amount the better were the reaction performances achieved, particularly at low temperatures. In bimetallic formulations, the presence of Ru enhances the catalyst activity; in particular, the use of the Ru acetylacetonate, for the deposition of the noble metal on support, remarkably reduces the catalyst onset temperature. The effect is due to the templating effect of the precursor molecule, which allows a better dispersion of the active compounds.

The first functional cross-metathesis (CM) depolymerization of commercial (co)polydienes using a ruthenium catalyst and an acyclic bis(trialkoxysilyl) difunctionalized chain-transfer agent (CTA), [(EtO) 3 Si(CH 2 ) 3 NHC(O)OCH 2 CH ] 2 ( 1 ), towards the synthesis of low viscosity liquid α,ω-bis(trialkoxysilyl) telechelic (co)polydienes is reported. The reactivity of three commercial grades of liquid (co)polydienes ( P1 – P3 , polybutadienes (PBDs) or poly(butadiene- co -isoprene) (P(BD- co -IP))) differing in their end-functionalization, in the amount of 1,2-vinyl and in their dispersity, was explored. Operating conditions for effective production of α,ω-bis(trialkoxysilyl) telechelic PBDs or P(BD- co -IP)s with high chemoselectivity (80–90 wt%) and catalytic productivity (non-optimized TON up to 24 000) were established. The chemoselectivity of this tandem metathesis reaction was assessed in particular through detailed 2D NMR analyses. An original approach combining the CM depolymerization of PBD with the ring-opening functional metathesis polymerization (ROMP) of a cycloolefin in the presence of CTA 1 has also been next implemented affording low viscosity liquid α,ω-bis(trialkoxysilyl) telechelic copolydienes. The viscosity of the (co)polyolefins was investigated by rheological analyses.

The Milstein's reported discovery of hydrogenation of thioesters directly toward thiols and alcohols catalyzed by a Ru-acridine complex has been studied here by DFT calculations to know the origin of the different performance depending on the nature of the substituents. Unveiling the reaction mechanism leads to a deeper understanding of the steric and electronic properties on the nature of the limiting step of the reaction. Steric maps and Conceptual DFT have been the tools to rationalize the reactivity patterns. In addition, the nature of the catalyst has been studied, replacing the substituents on the phosphorous atoms by less sterically demanding groups with the aim to move to milder reaction conditions A.P. is a Serra Húnter Fellow and ICREA Academia Prize 2019, and thanks the Spanish MINECO for projects ref. PGC2018-097722-B-I00 and CTQ2017-85341-P Open Access funding provided thanks to the CRUE-CSIC agreement with Elsevier

The past decades have witnessed rapid development in organic synthesis via catalysis, particularly the reactions through C⁻H bond functionalization. Transition metals such as Pd, Rh and Ru constitute a crucial catalyst in these C⁻H bond functionalization reactions. This process is highly attractive not only because it saves reaction time and reduces waste,but also, more importantly, it allows the reaction to be performed in a highly region specific manner. Indeed, several organic compounds could be readily accessed via C⁻H bond functionalization with transition metals. In the recent past, tremendous progress has been made on C⁻H bond functionalization via ruthenium catalysis, including less expensive but more stable ruthenium(II) catalysts. The ruthenium-catalysed C⁻H bond functionalization, viz. arylation, alkenylation, annulation, oxygenation, and halogenation involving C⁻C, C⁻O, C⁻N, and C⁻X bond forming reactions, has been described and presented in numerous reviews. This review discusses the recent development of C⁻H bond functionalization with various ruthenium-based catalysts. The first section of the review presents arylation reactions covering arylation directed by N⁻Heteroaryl groups, oxidative arylation, dehydrative arylation and arylation involving decarboxylative and sp3-C⁻H bond functionalization. Subsequently, the ruthenium-catalysed alkenylation, alkylation, allylation including oxidative alkenylation and meta-selective C⁻H bond alkylation has been presented. Finally, the oxidative annulation of various arenes with alkynes involving C⁻H/O⁻H or C⁻H/N⁻H bond cleavage reactions has been discussed.

Orientador: Andre Luiz Barboza Formiga Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Química Resumo: A busca por energias alternativas e livres de carbono é agora imprescindível para o desenvolvimento sustentável, e o uso da energia solar aparece como uma das alternativas mais promissoras através de células fotoeletroquímicas. Para tirar o máximo proveito dessa abundante fonte de energia, foram desenvolvidos dispositivos que podem realizar a chamada "fotossíntese artificial", para converter energia solar em energia química na forma de moléculas de hidrogênio, H2, que podem ser armazenadas e transportadas. Neste sentido, esta tese descreve o uso de complexos de rutênio(II) e cobre(II) como catalisadores para a reação de oxidação da água. Em particular, são descritas a síntese e caracterização do complexo de rutênio mononuclear [Ru(H2dimpy)(bpy)OH2](PF6)2, que contém o ligante 2,6-bis(1H-imidazol-2-il)piridina (H2dimpy). Este ligante possui 2 prótons dissociáveis, cujas desprotonações ocorrem a partir de aproximadamente pH 9,5 (pKa1) e 11,3 (pKa2), causando uma grande queda no par redox RuIII/RuII de 885 mV de pH 1 a pH 13. Mesmo em meio ácido (pH = 1), quando os grupos imidazóis estão protonados, o complexo apresenta um baixo potencial para o par redox RuIII/RuII (0.61 V vs Ag/AgCl). Devido à alta complexidade do sistema que envolve múltiplas transferências de prótons e elétrons acoplados, além da oxidação do ligante, um complexo de rutênio análogo, [Ru(Me2dimpy)(bpy)OH2](PF6)2, foi preparado para auxiliar no entendimento do papel da desprotonação dos grupos imidazóis no comportamento eletroquímico e fotocatalítico. [Ru(Me2dimpy)(bpy)OH2](PF6)2 foi sintetizado utilizando o ligante 2,6-Bis(1-metil-1H-imidazol-2-il)piridina (Me2dimpy), preparado pela metilação do ligante H2dimpy. Resultados de fotocatálise em pH = 7 mostraram que o complexo contendo o ligante H2dimpy demonstra melhor desempenho fotocatalítico (TOF 7.09 s¿1 e TON 10632) quando comparado ao complexo contendo o ligante mais elétron doador Me2dimpy (TOF 5.88 s¿1 e TON 8616), nas condições otimizadas. Além disso, foram estudados complexos de cobre(II) contendo uma classe de ligantes 2-(1H-imidazol-2-il)heteroaril. O uso de metais abundantes tais como cobre, ferro e níquel são cada vez mais atrativos, apresentando-se como alternativas que visam tornar factível a aplicação desses catalisadores do ponto de vista econômico. Aqui são mostrados os resultados preliminares para estes complexos de cobre com uma classe de ligantes que foi projetada para realizar um ajuste fino das propriedades eletrônicas e eletroquímicas, visando melhorar o desempenho catalítico. Um novo complexo, [(Himpa)Cu(OH2)2]2+, apresentou melhores resultados catalíticos em pH 12 quando comparado a estruturas análogas relatadas na literatura, com uma corrente catalítica "onset" de aproximadamente 1,3 V. Adicionalmente, novas informações sobre o sistema [(bpy)Cu(µ-OH)]22+ são reportadas. Nossos resultados sugerem que o acetato pode ter um papel importante na formação da espécie catalítica ativa, sendo esta informação valiosa para o planejamento da próxima geração de catalisadores a base de cobre. Por último, a síntese de nanopartículas de rutênio(0) incorporadas em TiO2 é descrita, assim como a síntese do composto orgânico 2-fenil-4-(1-napftil)quinolínico triflato, QuPh+¿NA(OTf¿), que foi utilizado como fotossensitizador. O sistema RuNPs@TiO2 foi avaliado como catalisador na reação de evolução de hidrogênio fotocatalítica em pH = 7, utilizando o fotossensitizador QuPh+¿NA e o doador sacrificial de elétrons TEOA, e mostrou boa resposta fotocatalítica e estabilidade, com um TOF de 6 µmolh¿1 e 60 horas de medição até a desativação Abstract: The search for alternative carbon-free energy is now imperative for sustainable development. The use of solar energy appears as one of the most promising alternatives through photoelectrochemical cells. To take full advantage of this abundant source of energy, devices that can perform the so-called "artificial photosynthesis" have been developed in order to convert solar energy into chemical energy in the form of hydrogen molecules, H2, which can be stored and transported. Motivated by this scenario, this thesis describes the use of molecular ruthenium(II) and copper(II) complexes as water oxidation catalysts (mol-WOC). In particular, this thesis first describes the synthesis and characterization of the mononuclear ruthenium complex [Ru(H2dimpy)(bpy)OH2](PF6)2, featuring the 2,6-bis(1H-imidazole-2-yl)pyridine (H2dimpy) ligand. This ligand has two dissociable protons, whose deprotonations occurs starting at approximately 9.5 (pKa1) and 11.3 (pKa2), causing a large drop on the RuIII/RuII redox of 885 mV from pH 1 to pH 13. Even in acid media (pH = 1), when the imidazole groups are protonated, the complex shows a very low RuIII/RuII redox couple (0.61 V vs Ag/AgCl). Due to the high complexity of the system, involving multiple proton-coupled electron transfers and ligand oxidation, an analogous ruthenium complex, [Ru(Me2dimpy)(bpy)OH2](PF6)2, was prepared to help understanding the role of imidazole deprotonation on the electrochemical behavior and catalysis. Photocatalytic results towards water oxidation in pH = 7 showed that the complex possessing the H2dimpy ligand exhibits better photocatalytic performance (TOF 7.09 s¿1 and TON 10632) when compared to the complex with the more electron-donating Me2dimpy ligand (TOF 5.88 s¿1 and TON 8616) in optimal conditions. Furthermore, mononuclear copper complexes containing a class of 2-(1H-imidazole-2-yl)heteroaryl ligands were studied. The use of earth-abundant metals such as copper, iron, and nickel is currently of great interest in order to make the application of these catalysts economically viable. Herein are shown preliminary results of the copper complex with a class of ligands that were designed to perform fine adjustment of electronic and electrochemical properties, aiming the improvement of the catalytic performance. A new complex, [(Himpa)Cu(OH2)2]2+ showed better catalytic results in pH 12 when compared to analogous structures reported in the literature, with an onset catalytic current of c.a. 1.3 V. Furthermore, new insights on the [(bpy)Cu(µ-OH)]22+ system, that was first reported to work as a water oxidation catalyst in 2012, is reported. The results reveal that the acetate may play an important role in the active catalytic species, and it is expected that this information can be useful in the improvement of the [(bpy)Cu(µ-OH)]22+ system and in the synthesis of new Cu-based catalysts molecules. Additionally, the synthesis of ruthenium(0) nanoparticles (RuNPs) incorporated onto TiO2 is described, as well as the synthesis of the organic photosensitizer 2-Phenyl-4-(1-naphthyl)quinolinium triflate, QuPh+¿NA(OTf¿). The RuNPs@TiO2 system using the QuPh+¿NA metal-free photosensitizer and TEOA as a sacrificial electron donor was tested for photocatalytic hydrogen evolution reaction at pH = 7, showing good photocatalytic activity and stability, with a TOF of 6 µmol?h¿1 and 60 hours measurement until deactivation Doutorado Química Inorgânica Doutor em Ciências CNPQ 142440/2015-9 FAPESP 2013/22127-2

This study reveals the effect of the catalytic 1D supports (carbon, ceria, alumina and titanate) for ruthenium particles on the low temperature release of hydrogen from ammonia. While the state-of-art literature presents Ru/carbon nanotubes (CNT) as the most active catalyst, we found in this work that ruthenium supported on ceria nanorods (Ru/CeO2) catalyst exhibited activity over 8 times higher than the Ru/CNT counterpart system. This enhanced activity is believed to be related to a strong metal-support interaction on the Ru/CeO2 catalysts promoting the formation of small (~3 nm) Ru particles. Addition of sodium as a promoter leads to the formation of smaller Ru particle sizes in addition to the modification of the electronic environment of Ru, enhancing the ammonia decomposition activity at low temperatures. This effect is particularly noticeable in the Ru-Na/CNT catalysts, facilitated by the high conductivity of the support, allowing distant electronic modification of the Ru active sites. This work provides novel insights in designing catalysts for hydrogen production from ammonia in our effort to enable the long-term energy storage in chemical bonds.

Active and selective Ru catalysts based on TiO2 supports have been developed for the combined hydrogenation of levulinic acid to γ-valerolactone with internal hydrogen supply via in-situ formic acid decomposition. A controlled modification of the TiO2 support by Ca2+ improved the catalytic performance in the one-pot hydrogenation, as a result of enhanced performances in both the formic acid dehydrogenation and the levulinic acid hydrogenation. The improved performances were associated to stronger Ru/support interactions with weaker CO adsorption, as well as to an increased support basicity. The performances were further exalted thanks to a one-step solar light photon-assisted synthesis method used as sustainable alternative to classical wet impregnation. It enabled the uniform dispersion of sub-nanometric metallic Ru particles with narrow distribution and fine size monitoring, and a volcano-type profile centered at 1.5 nm was demonstrated between the nanoparticle size and the activity.; Des catalyseurs Ru supporté sur TiO2 actifs et sélectifs pour l’hydrogénation de l’acide lévulinique en γ-valérolactone en présence d’acide formique comme source interne d’hydrogène ont été développés. L’élaboration d’un nouveau support, TiO2 modifié par Ca2+, permet d’améliorer la production de γ-valérolactone, grâce à la fois à une décomposition de l’acide formique plus sélective en hydrogène et à une hydrogénation de l’acide lévulinique plus efficace. Ces performances améliorées sont associées à l’existence d’interactions Ru/support plus fortes avec une adsorption du CO plus faible, et à une basicité accrue du support. Elles ont été exaltées par la mise en œuvre d’une synthèse photo-assistée sous lumière solaire comme alternative soutenable à l’imprégnation par voie humide, permettant d’obtenir des particules sub-nanométriques de distribution de taille étroite. Il a été montré qu’un profile de type volcano centré sur 1.5 nm relie l’activité catalytique à la taille des particules.

Active and selective Ru catalysts based on TiO2 supports have been developed for the combined hydrogenation of levulinic acid to γ-valerolactone with internal hydrogen supply via in-situ formic acid decomposition. A controlled modification of the TiO2 support by Ca2+ improved the catalytic performance in the one-pot hydrogenation, as a result of enhanced performances in both the formic acid dehydrogenation and the levulinic acid hydrogenation. The improved performances were associated to stronger Ru/support interactions with weaker CO adsorption, as well as to an increased support basicity. The performances were further exalted thanks to a one-step solar light photon-assisted synthesis method used as sustainable alternative to classical wet impregnation. It enabled the uniform dispersion of sub-nanometric metallic Ru particles with narrow distribution and fine size monitoring, and a volcano-type profile centered at 1.5 nm was demonstrated between the nanoparticle size and the activity., Des catalyseurs Ru supporté sur TiO2 actifs et sélectifs pour l’hydrogénation de l’acide lévulinique en γ-valérolactone en présence d’acide formique comme source interne d’hydrogène ont été développés. L’élaboration d’un nouveau support, TiO2 modifié par Ca2+, permet d’améliorer la production de γ-valérolactone, grâce à la fois à une décomposition de l’acide formique plus sélective en hydrogène et à une hydrogénation de l’acide lévulinique plus efficace. Ces performances améliorées sont associées à l’existence d’interactions Ru/support plus fortes avec une adsorption du CO plus faible, et à une basicité accrue du support. Elles ont été exaltées par la mise en œuvre d’une synthèse photo-assistée sous lumière solaire comme alternative soutenable à l’imprégnation par voie humide, permettant d’obtenir des particules sub-nanométriques de distribution de taille étroite. Il a été montré qu’un profile de type volcano centré sur 1.5 nm relie l’activité catalytique à la taille des particules.

International audience; Hydrogen interaction with ruthenium surfaces is a complex phenomenon that can play an important role in catalytic reactions such as ammonia synthesis. In this study, H-2/D-2 isotopic homomolecular exchange has been used to characterize four different catalytic surfaces, namely Ru/AC(0), Ru/AC(1), Ru-Na/AC(0) and Ru-Na/AC(1). They are composed of 2%Ru or 2%Ru-4.5%Na supported on an active carbon with (AC(0)) and without surface groups (AC(1)). The AC(1) carbon (1162 m(2) g(-1)) is obtained by treatment of AC(0) (960 m(2) g(-1)) in N-2 at 900 degrees C. Ru/AC(0) and Ru/AC(1) catalysts are prepared by impregnation of the supports with aqueous solutions of Ru(NO)( NO3)(3). Na-promoted catalysts are then prepared by impregnation of Ru catalysts with NaOH solutions. An overall picture of the surface mobility phenomena on the four different catalytic surfaces has been described. It has been demonstrated that the presence of Na promoter in Ru-Na/AC0 and Ru-Na/AC(1) catalysts inhibits the spillover of H atoms from the Ru particles to the AC surface. However, for non Na promoted catalysts, the extension of the H spillover phenomenon depends on the amount of oxygen groups present on the AC surface. Likewise, the formation of a ruthenium hydride during the reduction treatment is suggested for catalysts promoted or not by Na. Finally, this work shows how the kinetics of the H-2/D-2 isotopic exchange reaction may be related to the surface electron density of the catalyst, which allows us to better understand the effect that both promoter and support have on the metal particles.

The cross metathesis of 1,2-epoxy-5-hexene (1) with methyl acrylate and acrylonitrile was investigated as an entry to the synthesis of polyfunctional compounds. The resulting cross metathesis products were hydrogenated in a tandem fashion employing the residual ruthenium from the metathesis step as the hydrogenation catalyst. Interestingly, the epoxide ring remained unreactive toward this hydrogenation method. The saturated compound resulting from the cross metathesis of 1 with methyl acrylate was transformed by means of nucleophilic ring-opening of the epoxide to furnish a diol, an alkoxy alcohol and an amino alcohol in high yields.

As petrochemical resources become increasingly scarce and expensive, much attention has been focused on renewable resources from biomass as alternative options for producing basic building blocks for chemical manufacturing. Catalytic olefin metathesis represents a powerful tool to transform biosourced structural motifs in valuable commodity, fine, and specialty chemicals. In that respect, the appropriate choice of the catalyst is the key issue of each metathesis transformation. The current study examines the influence of different N-heterocyclic carbene (NHC) ligands containing one or two N-alkyl substituents on the efficiency of Hoveyda&ndash, Grubbs-type catalysts in the cross-metathesis reaction of ethyl oleate with cis-1,4-diacetoxy-2-butene and cross-metathesis of eugenol acetate with cis-1,4-dichloro-2-butene. Interestingly, the introduction of alkyl N-substituents in the NHC ligand was revealed as beneficial for catalytic performances in the examined cross-metathesis (CM) reactions, leading to higher activity and/or selectivity than those observed in the presence of the classical, commercially available Hoveyda&ndash, Grubbs second generation catalyst (HGII).

Ruthenium-based homogenous catalysis is a broad and extremely useful branch of transition metal catalysis. Surely, the most famous example is olefin metathesis, for which Yves Chauvin, Robert Grubbs and Richard Schrock were awarded the 2005 Chemistry Nobel Prize. Although some of the most well-known catalysts are widely used and considered benchmark catalysts, the research around this topic has not stopped. The modification of known systems to achieve better performance and better understanding of the catalytic mechanism is very important and an example of such modification is reported in this thesis. The newly synthesised catalysts were compared to the parent commercially available catalyst showing better reactivity. Ruthenium catalysis, though, is not limited to olefin metathesis and C-H activation, for example, it has become a useful approach to the functionalisation of organic molecules. In this field, the deuteration of C-H bonds is an interesting transformation, which has many applications. The synthesis of new hydridosilylruthenium complexes and their application in the deuteration of a variety of substrates is reported in this manuscript. The unprecedented synthesis of tetradeuterated Ketoprofene is also reported. Recently, ruthenium-based catalysts have found application in the dehydrogenation of suitable compounds, such as formic acid, ammonia-borane and other hydrogen-rich substances. The driving force behind these discoveries is the use of H₂ as an energy vector in place of fossil fuels. A hydrido-ruthenium catalyst was shown to catalyse the decomposition of formic acid in CO₂ and H₂ and to catalyse the reduction of olefinic substrates. The released CO₂ from the reaction did not interfere with the fuel cell due to its inertness. This property makes its employment as C1 source very challenging, although its use would also be extremely attractive because of the abundance of this gas. In these regards, both frustrated Lewis pairs (FLPs) and gold catalysts have shown interesting reactivity in the activation of CO₂. A new FLP and a silica supported gold catalyst were synthesised to test them in CO₂ activation and the results are reported in this manuscript.

International audience; A ruthenium catalyst for Z-selective olefin metathesis has been synthesized from a readily accessible N-heterocyclic carbene (NHC) ligand that is prepared using an efficient, practical, and scalable multicomponent synthesis. The desired ruthenium complex with cyclometalated NHC ligand is obtained by means of selective C(sp3)-H activation at the adamantyl fragment and X-ray diffraction analysis unambiguously confirmed the structure of the precatalyst. The catalyst demonstrated attractive catalytic performance in self- and cross-metathesis at low catalyst loading to afford the desired internal olefins with high conversion and very high Z-selectivity (up to andgt;99%). The versatility of the chelated catalyst is illustrated by the high cis-selectivity (up to andgt;98%) and high tacticity control (up to andgt;98% syndiotactic) achieved in ring-opening polymerization, allowing for the production of highly microstructurally controlled norbornene-, norbornadiene-, and cyclopropene-derived polymers.

In this first crystal structure of an Ru complex with 6′,6"-bis­(pyridin-2-yl)-2,2′:4′,4":2",2"’-quaterpyridine, a ‘half’ of the ligand (one of the two terpyridyl units) is N^N^N mer-coordinated, whereas the other is free and adopts a trans,trans conformation about the inter­annular C—C bonds. The crystal packing features π–π stacking inter­actions between tpy–tpy ligands., We report the structural characterization of [6′,6′′-bis­(pyridin-2-yl)-2,2′:4′,4′′:2′′,2′′′-quaterpyridine](2,2′-bi­pyridine)­chlorido­ruthenium(II) hexa­fluorido­phosphate, [RuCl(C10H8N2)(C30H20N6)]PF6, which contains the bidentate ligand 2,2′-bi­pyridine (bpy) and the tridendate ligand 6′,6′′-bis­(pyridin-2-yl)-2,2′:4′,4′′:2′′,2′′′-quaterpyridine (tpy–tpy). The [RuCl(bpy)(tpy–tpy)]+ monocation has a distorted octa­hedral geometry at the central RuII ion due to the restricted bite angle [159.32 (16)°] of the tridendate ligand. The Ru-bound tpy and bpy moieties are nearly planar and essentially perpendicular to each other with a dihedral angle of 89.78 (11)° between the least-squares planes. The lengths of the two Ru—N bonds for bpy are 2.028 (4) and 2.075 (4) Å, with the shorter bond being opposite to Ru—Cl. For tpy–tpy, the mean Ru—N distance involving the outer N atoms trans to each other is 2.053 (8) Å, whereas the length of the much shorter bond involving the central N atom is 1.936 (4) Å. The Ru—Cl distance is 2.3982 (16) Å. The free uncoordinated moiety of tpy–tpy adopts a trans,trans conformation about the inter­annular C—C bonds, with adjacent pyridyl rings being only approximately coplanar. The crystal packing shows significant π–π stacking inter­actions based on tpy–tpy. The crystal structure reported here is the first for a tpy–tpy complex of ruthenium.

(Cyclopentadienyl)tris(acetonitrile)ruthenium hexafluorophosphate [CpRu(CH3CN)3][PF6] in combination with pyridine-hydrazone ligands efficiently catalyzes the asymmetric decarboxylative allylic rearrangement of allyl aryl carbonates. Formation of C[BOND]O bonds with high regio- and enantioselectivity ratios (up to 95:5 and 98% ee) is obtained. Good stereocontrol of the pseudotetrahedral geometry of the CpRu moiety is achieved by the hydrazone ligand and its “electron-poor” nature is evidenced through the epimerization of the hexacoordinated TRISPHAT-N anion.

We studied the catalytic hydrogenation of levulinic acid over zirconia supported ruthenium catalysts. Four different Ru/ZrO2 catalysts were prepared by different pre-treatments and using different zirconium supports (ZrOx(OH)(4-2x) and ZrO2). Although the final compositions of the catalysts are the same, the pre-treatments strongly affect catalytic activity. Remarkably, one of the catalysts gave > 99% yield of gamma-valerolactone under mild conditions. This catalyst was also robust, and could be recycled at least four times without any loss in activity or selectivity. The activity is attributed to the presence of small ruthenium particles together with acidic sites on the catalyst.Pre-treatment changes the performance for ruthenium nanoparticles on zirconia supports, giving TONs over 3500 in the hydrogenation of levulinic acid to gamma-valerolactone with over 99% yield.

Hydrolysis of different types of nitriles, such as acrylonitrile or benzonitrile, to selectively obtain the corresponding amides, has been successfully done using ruthenium catalysts such as [RuCl2(pypz-H)(DMSO)2], which eliminates the need for a base. In order to direct further optimization of the catalyst, the mechanism by which this reaction occurs has been studied. Based on the mechanisms proposed by Solomon et al. on the study of the nitrile hydratase, several possible routes of the ruthenium catalyst have been proposed. The viability of all of them have been studied and evaluated by computational calculations, determining the internal energy and the free energy in the aqueous phase. There have also been relevant calculations to determine which ligand dissociated to allow nitrile coordination, and if this varies depending on the route. In short, the main route of this reaction has been determined, as well as three possible secondary routes that could at least be competitive to the main one. At the same time, other species potentially present in the potential energy surface have been studied in order to determine their capability of decreasing the overall reaction rate and yield. These new insights may lead to future improvements of ruthenium catalysts for the nitriles hydrolysis

International audience; Ruthenium complexes containing phosphorus-nitrogen, pincer-type (NPN) ligands show high activities and selectivities in the transfer hydrogenation of N-benzylideneaniline using propan-2-ol as the hydrogen source. Such is the case of complexes RuCl2PPh3(PPh(NHPy)(2)) (1) and RuCl2PPh3(PPh(NHPyMe)(2)) (2) which also show TOFs 5989 h(-1) and 5928 h(-1), respectively. These remarkable results were obtained after only 10 min of reaction using a 1000/1 substrate/catalyst ratio.

This article provides a fairly comprehensive overview on olefin metathesis reactions applied as pivotal steps in the total syntheses of indolizidine alkaloids belonging to the families of castanospermine, deoxycastanospermine and diastereomers thereof, natural or non-natural compounds that play multiple roles in biological processes. A well-balanced mixture of topics is proposed, covering most relevant traits of their biological activity, therapeutic applications, and structural similarities to, or differences from, other established iminosugar drugs. While mainly focussing on a critical discussion of the metathesis-based processes (RCM, CM, RRM), their promoters and conditions, their advantages and limitations, also shown is how metathesis has contributed to more efficient and shorter protocols for accessing this important class of antiviral, antitumor, antimetastatic, anti-inflammatory and immunoregulating agents. http://benthamscience.com/journal/index.php?journalID=coc

Density functional theory calculations (DFT) have been used to describe the first turnover for olefin metathesis reaction of a new in silico family of homogenous Ru-based catalysts bearing a phosphoylide ligand with ethylene as a substrate. Equal to conventional Rubased catalysts for olefin metathesis that bear a N-heterocyclic carbene (NHC) ligand, the activation of these congeners occurs through a dissociative mechanism, with a more exothermic first phosphine dissociative step. However, predicted upper energy barriers were calculated to be on average ~5 kcal/mol less beneficial with respect to the Ru-NHC based catalysed metathesis. Overall, this present computational study emphasises on advantages of bidentate ligands to replace the NHC ligand of Ru-based metathesis and gives a potential recipe for the design of efficient Ru-based olefin metathesis catalysts. The new generation of catalysts is cationic, however the addition of a chloride instead of the phosphine seems to be favourable and with better performance in terms of both kinetics and thermodynamics

In order to design improved chiral ruthenium catalysts for asymmetric olefin metathesis, enantiomeric catalysts incorporating C1-symmetric N-Heterocyclic carbenes (NHC) ligands with syn-related substituents on the backbone were synthesized starting from meso-1,2-diphenylethylenediamine. The absolute configuration of the enantiomers of the desymmetrized meso diamine was assigned by optical rotation analysis and in silico calculations, and was found to be maintained in their respective ruthenium catalysts by comparison of the relative electronic circular dichroism (ECD) spectra. The catalytic behaviour of the enantiomeric ruthenium complexes was investigated in model asymmetric metathesis transformations and compared to that of analogous complexes bearing C1-symmetric NHC ligands with an anti backbone. Modest enantioselectivities were registered and different catalyst properties depending on the nature of stereochemical relationship of substituents on the backbone were observed.

The catalytic properties of olefin metathesis ruthenium complexes bearing N-heterocyclic carbene ligands with stereogenic centers on the backbone are described. Differences in catalytic behavior depending on the backbone configurations of symmetrical and unsymmetrical NHCs are discussed. In addition, an overview on asymmetric olefin metathesis promoted by chiral catalysts bearing C₂-symmetric and C₁-symmetric NHCs is provided.

M.Sc. (Chemistry) Compounds 2-(3,5-dimethyl-1H-pyrazol-1-yl)ethyl diphenlyphosphinite (L1), 2-(3,5-di-tert-butyl-1H-pyrazol-1-yl)ethyl diphenlyphosphinite (L2), 2-(3,5-diphenyl-1H-pyrazol-1-yl)ethyl diphenylphosphinite (L3), 2-(3,5-di-tert-butyl-1H-pyrazol-1-yl)ethyl diethylphosphite (L4), 2-(3,5-di-tert-butyl-1H-pyrazol-1-yl)ethyl diethylphosphite (L5) and 2-(3,5-diphenyl-1H-pyrazol-1-yl)ethyl diethylphosphite (L6) were synthesized and characterized by 1H NMR, 31P{1H} NMR and 13C{1H} NMR spectroscopy. Reactions of L1–L6 with [Ru(p-cymene)Cl2]2 in 2:1 ratio formed six neutral complexes, [Ru(p-cymene)Cl2(L1)] (1), [Ru(p-cymene)Cl2(L2)] (2), [Ru(p-cymene)Cl2(L3)] (3), [Ru(p-cymene)Cl2(L4)] (4), [Ru(p-cymene)Cl2(L5)] (5) and [Ru(p-cymene)Cl2(L6)] (6). The neutral complexes 1–6 were converted to salts of the general formula [Ru(p-cymene)ClL]X and [NaRu(p-cymene)Cl2L]X {X = BArF- or BPh4-} (1a,1b, 2a, 2b, 3a, 4a, 4b, 5a, 5b, and 6a) by reaction of complexes 1–6 with NaBArF (BArF = 3,5-CF3(C6H3) and/or NaBPh4 in 1:1 ratio. Neutral and ruthenium complexes and their salts were characterized by a combination of 1H, 31P{1H} and 13C{1H} NMR spectroscopy, mass spectrometry, elemental analysis and in selected cases by single crystal X-ray crystallography.

A catalytic system consisting of the ruthenium(II) complex [Ru(η3-2-C3H4Me)(CO)(dppf)][SbF6] (dppf = 1,1’-bis(diphenylphosphino)ferrocene) and trifluoroacetic acid has been used to promote the coupling of secondary propargylic alcohols with 6-chloro-4-hydroxychromen-2-one. The reactions afforded unusual 2-methylene-2,3-dihydrofuro[3,2-c]chromen-2-ones in good yields.

International audience; In this minireview, we report on the state of the art concerning the cross-metathesis of acrylonitrile with olefins. A special focus is given to catalytic conditions that are suitable for medium-size and long-chain aliphatic model substrates. The recent applications of this metathesis reaction to fatty acid derivatives to generate fatty nitriles and bifunctional products are considered. They represent very attractive transformations for the access to N-containing monomers and functional intermediates for the chemical industry from renewable raw materials.

An efficient, reproducible process for the solvothermal synthesis of Ru/γ-Al2O3 nanocatalysts has been developed. This synthesis employs a low boiling point alcohol acting as solvent and reducing agent. The reaction is performed in autoclave under nitrogen overpressure, by heating the solution of metal precursor and stabilizing agent in the presence of the support. These systems show very promising performances, also with an application perspective, in the selective hydrogenation of phenol to cyclohexanone carried out at 160 °C under 5 MPa of hydrogen: a selectivity to cyclohexanone as high as 83% has been reached at a phenol conversion value of 88%.

The study of normal N-heterocyclic carbenes (NHCs), which probably represent one of the most important families of ligands in organometallic chemistry and homogeneous catalysis, has indubitably led to the usage of other related ligands beyond di-amino carbenes. So far, such species are only marginally used as ligands due to their relative novelty and stability. The following chapters describe the exciting journey into the development of new synthetic accesses of various abnormal, remote N-heterocyclic, mesoionic and carbocyclic carbene transition metal complexes. The uses of a number of these ruthenium- and copper-based complexes as catalysts in several applications are also disclosed. Halfway between the study of the electronic effect of mixed NHC/phosphite ruthenium in olefin metathesis reactions (Chapter 1) and NHC copper-catalysed transformations (Chapters 5 and 6), resides the core of this dissertation that links the book end chapters. Indeed, the NHC-Cuᴵ transfer or “transmetalation” reaction is disclosed as a powerful and reliable tool to access new transition metal catalysts in a relatively general manner. The syntheses of a series of various non-conventional NHC-Cu complexes as precursors for the transmetalation reaction are also described in Chapter 2. The dissertation finally closes with some preliminary results on what represents the first experimental and theoretical evidence for the mechanism of the NHC transfer by transmetalation. The exploration of the reaction by exchange from copper to platinum has begun to reveal what was so far unknown through the isolation of reactive intermediate species formed during the process.