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A well-defined NHC-Ir(iii) catalyst provides access to a wide range of aryl- and heteroarylsilanes by intermolecular dehydrogenative C–H bond silylation., A well-defined NHC–Ir(iii) catalyst, [Ir(H)2(IPr)(py)3][BF4] (IPr = 1,3-bis-(2,6-diisopropylphenyl)imidazol-2-ylidene), that provides access to a wide range of aryl- and heteroaryl-silanes by intermolecular dehydrogenative C–H bond silylation has been prepared and fully characterized. The directed and non-directed functionalisation of C–H bonds has been accomplished successfully using an arene as the limiting reagent and a variety of hydrosilanes in excess, including Et3SiH, Ph2MeSiH, PhMe2SiH, Ph3SiH and (EtO)3SiH. Examples that show unexpected selectivity patterns that stem from the presence of aromatic substituents in hydrosilanes are also presented. The selective bisarylation of bis(hydrosilane)s by directed or non-directed silylation of C–H bonds is also reported herein. Theoretical calculations at the DFT level shed light on the intermediate species in the catalytic cycle and the role played by the ligand system on the Ir(iii)/Ir(i) mechanism.

Trabajo presentado al XXXVI GEQO Congress Organometallic Chemistry Group, celebrado en Zaragoza (España) del 5 al 7 de septiembre de 2018.

Resumen del trabajo presentado a la XXVIII International Conference on Organometallic Chemistry, celebrada en Florencia (Italia) del 15 al 20 de julio de 2018.

Resumen del trabajo presentado a la XXVIII International Conference on Organometallic Chemistry, celebrada en Florencia (Italia) del 15 al 20 de julio de 2018.

Resumen del trabajo presentado a la XXVIII International Conference on Organometallic Chemistry, celebrada en Florencia (Italia) del 15 al 20 de julio de 2018.

Resumen del trabajo presentado a la 17th International Conference on X-Ray Absorption Fine Structure (XAFS), celebrada en Kraków (Polonia) del 22 al 27 de julio de 2018., We here report an x-ray absorption spectroscopic (XAS) study of a set of hybrid catalysts with Rh. This task focuses on the development and characterization of new effective heterogeneous catalysts, easily recoverable, of great interest for industrial processes. In particular, the hydrosilylation of multiple C-C bonds what is one of the most direct and efficient ways of preparing functionalized alkyl/alkenylsilanes. These silanes are quite versatile intermediate compounds in organic synthesis and represent a more sustainable alternative to stannanos or boranes due to its non-toxic nature. Rh(I) complexes based on N-heterocyclic carbenes showed a high efficiency in the hydrosilylation of terminal alkynes. However, this was a homogeneous system with a consequent difficulty in separating the catalyst for later uses. Therefore, the development of heterogeneous catalysts with similar activity would be a breakthrough in these processes. Our strategy to achieve this goal was to anchor Rh-NHC carbenes in functionalized graphene oxides (GO) through a three steps procedure. First, the azolium salts were linked to the GO walls directly through a C-N bond obtained by reaction of the carbon material with azide groups, and secondly, the azolium salts formed by reaction with alkynes were the precursors of these mesoinic NHC-carbenes bonded to the rhodium by a posterior third reaction. Different salts were tested in order to modify the complex solubility in water. Room temperature x-ray absorption measurements at the Rh K-edge were carried at the Claess beam line of the Alba synchrotron facility (Barcelona, Spain). The energy resolution ΔE/E was estimated to be about 8 × 10−5 at the Rh K-edge, and a foil of Rh metal was simultaneously measured for energy calibration. Different homogeneous and heterogeneous catalysts were measured to determine changes in the local structure around Rh atoms. The extended X-ray absorption fine structure (EXAFS) spectra were analyzed using the ARTEMIS program. The fits were carried out in R space using a Hanning window for filtering purposes. Our XAS results confirms an oxidation state of Rh(I) in both, homogeneous and heterogeneous materials. We were successful in refining the local structure from EXAFS spectra and we have related the catalytic activity to the changes of the ligands surrounding the Rh atoms. One surprising result was the fragility of the catalysts made using azolium salts. In spite of the high activity of those hetereogeneous catalysts based on 1,2,3-triazole ligands supported on graphene oxides in hydrosilylation of unsaturated compounds, our measurements revealed a continuous diminution of the supported Rh after each catalytic cycle.

Resumen del trabajo presentado al XI Simposio Internacional: Investigación Química en la Frontera, celebrado en Tijuana (México) del 14 al 16 de noviembre de 2018.

Resumen del trabajo presentado a la X International School on Organometallic Chemistry “Marcial Moreno Mañas”, celebrada en Ciudad Real (España) del 5 al 7 de julio de 2017., Graphene surfaces as supports of homogeneous catalysts can provide special features to the catalytic systems resulting, in favorable cases, in an enhancement of both the activity and selectivity, allowing for the recycling of the catalysts. In this work, we have prepared carbene-rhodium and iridium hybrid catalysts anchored on a graphene oxide decorated with 3-methyl-4-phenyl-1,2,3-triazolium groups. Thermally reduced graphene oxide (TRGO) was functionalized with 4-phenyl-1,2,3-triazolio groups (TRGO-2) by a Huisgen cycloaddition (click reaction) between the azide groups on the functionalized graphene material (TRGO-1) and phenylacetylene. After alkylation, the triazolium salt supported on the graphene oxide TRGO-3 was treated with methoxo-bridged cyclooctadiene rhodium(I) and iridium(I) dimers, [M(μ-OMe)(cod)]2, to obtain the hybrid carbene catalysts TRGO-Rh and TRGO-Ir. The structure of the rhodium heterogeneous catalysts has been confirmed by EXAFS analysis. We have studied the catalytic activity of both catalysts in the hydrosilylation of terminal alkynes. Although the iridium hybrid catalyst shows moderate activity, the rhodium material exhibits high activity and complete selectivity to β-Z vinyl silanes. The activity compares well with that shown by the related the homogeneous complex, [Rh(1,4-diphenyl-3-methyl,1,2,3-triazole)(cod)(I)]. Unfortunately, the catalytic activity of the hybrid catalyst decreases in the recycled experiments.

Resumen del póster presentado al XIII Simposio de Investigadores Jóvenes de la Real Sociedad Española de Química Sigma-Aldrich, celebrado en Logroño del 8 al 11 de noviembre de 2016., El desarrollo de catalizadores homogéneos está asociado al diseño de ligandos capaces de modificar las propiedades del centro metálico con el objetivo de producir transformaciones más sostenibles. En este contexto, los complejos de metales de transición que contienen ligandos carbeno N-heterocíclicos (NHC) han demostrado ser la plataforma adecuada para el diseño de catalizadores en procesos químicos sostenibles. En el presente trabajo se han diseñado catalizadores de Ir con arquitecturas tipo pincer basadas en un esqueleto piridina-NHC-grupo hemilábil que tienen el potencial de activar procesos de cooperación metal-ligando a través de la aromatización/desaromatización del anillo de piridina. Esta nueva familia de catalizadores presenta una gran actividad en reacciones de autotransferencia de hidrógeno (β-alquilación y N-alquilación) con completa conversión y buena selectividad en cortos periodos de tiempo.

Resumen del póster presentado al XIII Simposio de Investigadores Jóvenes de la Real Sociedad Española de Química Sigma-Aldrich, celebrado en Logroño del 8 al 11 de noviembre de 2016., The supported homogeneous catalysts graphene surfaces can provide special features to the catalyst systems, changing activity and selectivity such as smooth reaction conditions and recycling of the catalysts. In this work, we have prepared carbene-rhodium and iridium hybrid catalysts anchoring to a graphene oxide decorated with the 1,2,3-triazolium salt: 3-methyl-4-phenyl-1,2,3-triazolium. Thermally reduced graphene oxide (TRGO) was functionalized of triazol 4-phenyl-1,2,3-triazolium groups (TRGO-2) generated by click of the graphene material functionalized with azides (TRGO-1) with phenylacetylene catalyzed by Cu (II) salts. The triazolium salt soported on the graphene oxide TRGO-3, which contains an acid proton, have been reacted with dimers of rhodium(I) and iridium(I) and 1,5-cyclooctadiene with methoxide bridges [Rh(μ-OMe)(cod)]2 and [Ir(μ-OMe)(cod)]2 to obtain the carbene-M catalysts heterogenized of rhodium and iridium, called TRGO-Rh and TRGO-Ir. We have studied the catalytic activity of these two catalysts in a model reaction: hydrosilylation of 1-octyne with diphenyl-methylsilane. It has been found that these hybrid catalysts are quite active, but unfortunately its catalytic activity decreases in the recycled materials.

Resumen del trabajo presentado al XIV Congreso Nacional de Materiales celebrado en Gijón del 8 al 10 de junio de 2016., Los compuestos de carbenos N-heterocíclicos (NHC) de iridio son capaces de reducir enlaces C=O y C=N para generar alcoholes y aminas en condiciones suaves siguiendo los mecanismos de la transferencia de hidrógeno. Las excelentes propiedades de los nanotubos de carbono (CNTs) los vuelven adecuados candidatos para el soporte de dichos compuestos organometálicos. Sin embargo, los diferentes métodos de producción de los CNTs generan impurezas metálicas y carbonosas que deben ser eliminadas. Generalmente se emplean tratamientos ácidos oxidantes, los cuales modifican los CNTs desarrollando una química superficial oxigenada. Estos grupos funcionales se pueden emplear en la unión covalente de los compuestos NHC a los materiales. En este trabajo se purificaron CNTs aplicando cuatro tratamientos de severidad oxidativa creciente, como son ácido clorhídrico, una mezcla de hidróxido amónico y peróxido de hidrógeno, ácido nítrico diluido y peróxido de hidrógeno, y una mezcla de ácidos nítrico y sulfúrico concentrados en caliente. La oxidación gradual generó una progresiva funcionalización oxigenada, junto con la introducción de defectos, a lo largo de las paredes de los CNTs. En los grupos carboxilo se anclaron compuestos NHC de iridio mediante uniones acetilo a las unidades N-metilimidazolio, con posterior fijado del metal. Se obtuvo un grado de funcionalización proporcional al grado de oxidación de los nanotubos, tanto en el contenido de nitrógeno (análisis elemental) como en el de iridio (ICP-MS). Los análisis microscópicos y de EXAFS descartaron la presencia de nanopartículas, revelando además la existencia de un enlace directo entre la química oxigenada del nanotubo y el metal. Los materiales híbridos desarrollados se ensayaron como catalizadores en la reducción de ciclohexanona a ciclohexanol siguiendo los mecanismos de la transferencia de hidrógeno, siendo la fuente de hidrógeno un medio de 2-propanol/KOH. Todas las muestras fueron activas, pero la actividad catalítica se vio fuertemente influenciada por el tipo y cantidad de grupos funcionales resultantes de los tratamientos aplicados a los nanotubos. La muestra más activa, con 100 min para obtener conversión completa, resultó aquella que fue sometida a la oxidación más severa, en claro contraste con los CNTs menos oxidados, que requirieron 900 min para alcanzar conversión completa. Por tanto, la actividad catalítica también fue proporcional al grado de oxidación del material., Los autores agradecen al Ministerio de Economia y Competitividad (Proyectos Consolider Ingenio 2010 CSD2009-00050, MAT2013-48107-C3-1-R, CTQ2013-42532-P), al Principado de Asturias (GRUPINN14-118) y a la Diputación General de Aragón (FSE-E07 and FSE-E69) el apoyo financiero.

Trabajo presentado al XXXIV Congress of the Organometallic Chemistry Specialized Group, celebrado en Girona (España) del 7 al 9 de septiermbre de 2016., Transition-metal catalyzed hydrosilylation of terminal alkynes is the most straightforward and atom-economical methodology for the preparation of vinylsilanes, which are valuable synthetic intermediates.