Multimetallic (de)hydrogenation catalysed processes

The use of different metals working together in a synergistic way, allows synthetic transformations that are not achievable by other means. The metal cooperation becomes important in catalytic processes for the synthesis of sophisticated molecules or difficult transformations. A rationale design of multimetallic catalysed processes entails metal complexes and reaction conditions being compatible, which in general is not straightforward. A key feature for success found in all systems dealing with multimetallic processes is catalyst stability. The use of robust metal complexes increases the probability of success in the search of tandem catalytic processes. This microreview is based on the recent and most important findings of multimetallic catalysed processes that involved (de)hydrogenation reactions. The field constitutes a research area that is full of potential and can be foreseen that relevant applications will be described in the near future.MINECO (CTQ2015-69153-C2-2-R), Generalitat Valenciana (AICO/2015/039), Universitat Jaume I (P1.1B2015-09

Problemario de vectores, rectas, planos, sistemas de ecuaciones lineales, cónicas y esferas : con anexo

1 archivo PDF (271 páginas)Este libro de problemas pretende reforzar y agilizar la práctica para la resolución de problemas en los temas de: vectores, rectas, planos, sistemas de ecuaciones lineales, cónicas y esferas

Enhancement of gold catalytic activity and stability by immobilization on the surface of graphene

The catalytic performance of gold complexes is evaluated at the molecular level and when supported onto reduced graphene oxide (rGO). Gold complexes of general formula [(NHC)AuX] catalyse the synthesis of indoles via intramolecular hydroamination reaction of alkynes. The catalytic properties of the molecular gold complexes are highly improved when supported onto graphene. Faster reaction rates and higher catalyst stability are observed for the immobilized gold complexes. The use of graphene as support of molecular complexes has a positive benefit in the catalytic gold properties in terms of activity and stabilityThe authors thank the financial support from MINECO (CTQ2015-69153-C2-2-R), Generalitat Valenciana (AICO/2015/039) and Universitat Jaume I (P1.1B2015-09). D. V-E thanks MINECO for a FPU grant (FPU15/03011

Ruthenium molecular complexes immobilized on graphene as active catalysts for the synthesis of carboxylic acids from alcohol dehydrogenation

Ruthenium complexes containing N-heterocyclic carbene ligands functionalized with different polyaromatic groups (pentafluorophenyl, anthracene, and pyrene) are immobilized onto the surface of reduced graphene oxide. The hybrid materials composed of organometallic complexes and graphene are obtained in a single-step process. The hybrid materials are efficient catalysts for the synthesis of carboxylic acids from the dehydrogenation of alcohols in aqueous media. The catalytic materials can be recycled up to ten times without significant loss of activity. The catalytic activity of the pyrene derivative, Pyr-Ru (3) is enhanced when the ruthenium complex is anchored onto the surface of graphene. The carbonaceous material limits the degradation of the ruthenium complex resulting in increased activity and requiring lower catalyst loadings. The catalytic process of the pyrene hybrid material is heterogeneous in nature due to the strong interaction between the pyrene and graphene. The catalytic process of the anthracene and pentafluorophenyl hybrid materials is governed by the so-called ‘boomerang effect’. The ruthenium molecular complex is released from and returned to the graphene surface during the catalytic reaction. Mechanistic insight has been obtained experimentally and theoretically. The energy profile suggests that the rate-determining step is the water nucleophilic attack to a coordinated aldehyde complex to form a gem-diolate complex.The authors thank the financial support from MINECO (CTQ2015-69153-C2-2-R and CTQ2015- 67461-P), Generalitat Valenciana (AICO/2015/039), Universitat Jaume I (P1.1B2015-09) and Universidad de Zaragoza (UZ2014-CIE-01)

Reduced graphene oxides as carbocatalysts in acceptorless dehydrogenation of N-heterocycles

The catalytic properties of graphene-derived materials are evaluated in acceptorless dehydrogenation of N-heterocycles. Among them, reduced graphene oxides (rGOs) are active (quantitative yields in 23 h) under mild conditions (130 °C) and act as efficient heterogeneous carbocatalysts. rGO exhibits reusability and stability at least during eight consecutive runs. Mechanistic investigations supported by experimental evidence (i.e., organic molecules as model compounds, purposely addition of metal impurities and selective functional group masking experiments) suggest a preferential contribution of ketone carbonyl groups as active sites for this transformation.

Catalytic Dehydrogenative Coupling of Hydrosilanes with Alcohols for the Production of Hydrogen On-demand: Application of a Silane/Alcohol Pair as a Liquid Organic Hydrogen Carrier

The compound [Ru(p-cym)(Cl)2(NHC)] is an effective catalyst for the room-temperature coupling of silanes and alcohols with the concomitant formation of molecular hydrogen. High catalyst activity is observed for a variety of substrates affording quantitative yields in minutes at room temperature and with a catalyst loading as low as 0.1 mol %. The coupling reaction is thermodynamically and, in the presence of a Ru complex, kinetically favourable and allows rapid molecular hydrogen generation on-demand at room temperature, under air, and without any additive. The pair silane/alcohol is a potential liquid organic hydrogen carrier (LOHC) for energy storage over long periods in a safe and secure way. Silanes and alcohols are non-toxic compounds and do not require special handling precautions such as high pressure or an inert atmosphere. These properties enhance the practical applications of the pair silane/alcohol as a good LOHC in the automotive industry. The variety and availability of silanes and alcohols permits a pair combination that fulfils the requirements for developing an efficient LOHC

Reduced Graphene Oxides as Carbocatalysts in Acceptorless Dehydrogenation of N-Heterocycles

[EN] The catalytic properties of graphene-derived materials are evaluated in acceptorless dehydrogenation of N-heterocycles. Among them, reduced graphene oxides (rGOs) are active (quantitative yields in 23 h) under mild conditions (130 degrees C) and act as efficient heterogeneous carbocatalysts. rGO exhibits reusability and stability at least during eight consecutive runs. Mechanistic investigations supported by experimental evidence (i.e., organic molecules as model compounds, purposely addition of metal impurities and selective functional group masking experiments) suggest a preferential contribution of ketone carbonyl groups as active sites for this transformation.Supported by MCIN/AEI/10.13039/501100011033/FEDER (Grant Nos. RTI2018-098237-B-C21, RTI2018-098237-BC22, and PID2019-105881RB-I00), Generalitat Valenciana (No. PROMETEU/2020/028), and Universitat Jaume I (No. UJI-B2018-23).Mollar-Cuni, A.; Ventura-Espinosa, D.; Martin, S.; García Gómez, H.; Mata, JA. (2021). Reduced Graphene Oxides as Carbocatalysts in Acceptorless Dehydrogenation of N-Heterocycles. ACS Catalysis. 11(23):1-6. https://doi.org/10.1021/acscatal.1c04649S16112

Ecuaciones diferenciales : técnicas de solución y aplicaciones

1 archivo PDF (243 páginas)Este libro está diseñado para un curso trimestral de ecuaciones diferenciales ordinarias. Se presentan los teoremas y técnicas de solución básicos. se proporciona una buena cantidad de ejercicios resueltos, de modo que un estudiante de Ingeniería podría obtener , mediante su análisis, un nivel satisfactorio en los diferentes métodos de solución de ecuaciones diferenciales y sus aplicaciones elementales más comunes

Renaiximent : setmanari valencianiste.

Director, Manuel Espinosa Ventur