Des membranes polymères catalytiques ont été préparées via la polymérisation photo-amorcée de monomères acryliques à la surface de membranes support MicroPES(r). Des nanoparticules de palladium (PdNP) avec diamètre moyen compris entre 4 et 10 nm sont ensuite synthétisés et immobilisées dans ces gels polymères greffés. Cette thèse se focalise sur le greffage d'un gel de polymère neutre : (2-hydroxyethyl acrylate) (PHEA), pour négliger les contributions ioniques du réseau polymère sur la synthèse in-situ des PdNP. La stabilisation de PdNP dans le gel de PHEA greffé est possible par des moyens stériques étant donné que la distance entre des chaînes de polymère réticules (entre 0.3 à 2.5 nm) est plus petite que le diamètre moyen de PdNP. Une approche à la fois théorique et expérimentale, sur la base des mecanismes de nucléation et de croissance, permet la conception de PdNP de taille spécifique. La performance catalytique des membranes a été évaluée avec une configuration en filtration traversée. Sur la réaction de couplage de Suzuki-Miyaura, des conversions et sélectivités de 100 % ont été obtenues pour des temps de séjour de 10 secondes avec des membranes planes. Les réactions d'hydrogénation de plusieurs composés aromatiques ont également été testées. Des taux de conversion élevés ont été obtenus en quelques secondes avec des membranes planes en filtration avec des solutions saturés d'H2. Des taux de conversion élevés sont obtenus en seulement quelques minutes avec des membranes fibres creuses catalytiques en mode contacteur permettant une importante intensification du procédé. / Catalytic polymeric membranes are prepared via photo-grafting polymerization of neutral acrylic monomers onto the surface of a MicroPES(r) membrane support. Palladium nanoparticles (PdNP) of mean diameter of 4-10 nm are synthetized and immobilized within the grafted polymer gels. The research is focused on grafting a neutral polymer gel: poly (2-hydroxyethyl acrylate) (PHEA), to avoid any ionic contribution of the polymer network on the in-situ synthesis of PdNP. The stabilization of PdNP within the grafted PHEA is achieved by steric means as the distance between polymeric crosslinked chains (ca. 0.3 to 2.5 nm) is smaller than the mean diameter of PdNP. Both theoretical and experimental approaches are presented on the PdNP synthesis as an approach to conceive PdNP of specific sizes using nucleation and growth theories. Catalytic performance of the membranes is evaluated in flow-through configuration. Catalytic tests are performed on Suzuki-Miyaura cross-coupling reactions. Full conversion and selectivity within 10 seconds of residence time using flat sheet membrane are obtained. Hydrogenation of several aromatic compounds are also tested and high conversions were achieved within seconds of residence time using flat sheet membranes in flow-through configuration with H2-saturated solutions and within minutes using catalytic hollow fibers in contactor mode.

[ES] La presente tesis doctoral se desarrolla en el ámbito de la catálisis, la cual está enmarcada dentro del concepto de Química Sostenible. En concreto, la investigación se ha centrado en el desarrollo y aplicación de nuevos catalizadores basados en nanopartículas metálicas coloidales y soportadas para llevar a cabo reacciones de interés. Todas las MNPs sintetizadas en esta tesis doctoral se llevaron a cabo a partir de la aproximación organometálica, donde generalmente se descompone un precursor organometálico bajo condiciones suaves de reacción y en presencia de un agente estabilizador (molécula orgánica o soporte). En el Capítulo 4 de la tesis, se ha descrito el primer ejemplo de estabilización de Ru NPs con una nueva familia de ligandos policíclicos aromáticos no planos, denominados nanografenos (hept-HBC). Específicamente, se han utilizado dos tipos distintos de nanografeno distorsionado: i) uno funcionalizado con un grupo carbonilo, y ii) otro funcionalizado con una grupo metileno en la misma posición (Ru@1 y Ru@2, respectivamente). Gracias a la similitud con los sistemas basados en MNPs soportadas en grafeno o derivados, este material puede utilizarse como referencia para estudiar los modos de coordinación y las dinámicas de estos con la superficie de la nanopartícula. A partir de un estudio combinado teórico/experimental se ha demostrado que la curvatura de los nanografenos hept-HBC es crucial para la estabilización de las Ru NPs. Por último, se ha evaluado la actividad catalítica de estas Ru NPs en la hidrogenación de multitud de sustratos aromáticos, observándose diferencias significativas en función del ligando estabilizador utilizado. En el Capítulo 5 se ha investigado la formación de MNPs a través de la aproximación organometálica utilizando el óxido de grafeno reducido dopado con átomos de nitrógeno (NH2-rGO) como soporte. En la primera parte del capítulo, sintetizamos Ru NPs soportadas sobre NH2-rGO (Ru@NH2-rGO) y rGO (Ru@rGO), con la intención de investigar el rol de los átomos de N en la estabilización de las MNPs, así como en su actividad catalítica. Para ello, se estudió la hidrogenación del ácido palmítico a 1-hexadecanol, siendo el Ru@NH2-rGO el catalizador heterogéneo monometálico de Ru más activo y selectivo reportado hasta la fecha (99% conversión y 93 % selectivo). En la segunda parte del capítulo, generamos PtRu NPs con distintas composiciones atómicas (5:1, 1:1 y 1:5) sobre NH2-rGO, siguiendo la aproximación organometálica. La misma velocidad de descomposición de los precursores Pt(NBE)3 y Ru(COD)(COT) nos permitió generar las NPs de tipo aleación. Estos sistemas bimetálicos (PtxRuy@NH2-rGO) se estudiaron en la hidrogenación de multitud de compuestos con grupos polares (C=O), observándose diferencias significativas en función del soporte utilizado y la composición atómica de las MNPs. Por último, en el Capítulo 6 se investigó el uso de nanopartículas magnéticas (MagNPs) para emitir calor por pérdidas de histéresis en presencia de un campo magnético oscilante de alta frecuencia. En primer lugar, se generaron nuevos agentes calefactores basados en MagNPs bimetálicas de tipo "core-shell" de CoNi encapsuladas en carbono (Co@Ni@C), con el objetivo de hidrogenar selectivamente el CO2 a CO (RWGS) obteniéndose excelentes resultados catalíticos. Por último, también presentamos la síntesis de una nueva MagNP de tipo "core-shell" (FeCo@Ni) para su aplicación en catálisis inducida magnéticamente en disolución, siendo capaz de modular su selectividad al producto de la hidrogenación o de la hidrodesoxigenación del HMF en función del campo magnético aplicado. Además, después de su encapsulación en carbono (FeCo@Ni@C) han demostrado ser activas, selectivas y estables en la reducción de multitud de sustratos oxigenados derivados de la biomasa en medio acuoso, siendo el primer ejemplo reportado hasta la fecha de catálisis magnética realizada en agua. / [CAT] La present Tesi Doctoral es desenvolupa en l'àmbit de la catàlisi, la qual està emmarcada dins del concepte de Química Sostenible. Concretament, la investigació s'ha centrat en el desenvolupament i aplicació de nous catalitzadors basats en nanopartícules metàl·liques col·loïdals i suportades per dur a terme reaccions d'interès. Totes les MNPs sintetitzades en aquesta tesi doctoral es van dur a terme a partir de l'aproximació organometàl·lica, on generalment es descompon un precursor organometàl·lic sota condicions suaus de reacció i en presència d'un agent estabilitzador (molècula orgànica o suport). En el Capítol 4 de la Tesi, s'ha descrit el primer exemple d'estabilització de Ru NPs amb una nova família de lligands policíclics aromàtics no plans, denominats nanografens (hept-HBC). Específicament, s'han utilitzat dos tipus diferents de nanografen distorsionat: i) un funcionalitzat amb un grup carbonil, i un altre ii) funcionalitzat amb un grup metilè en la mateixa posició (Ru@1 i Ru@2, respectivament). Gràcies a la similitud amb els sistemes basats en MNPs suportades en grafè o derivats, aquest material pot utilitzar-se com a referència per a estudiar els modes de coordinació i dinàmiques d'aquests amb la superfície de la nanopartícula. A partir d'un estudi combinat teòric/experimental s'ha demostrat que la curvatura dels nanografens hept-HBC és crucial per a l'estabilització de les Ru NPs. Finalment, s'ha avaluat l'activitat catalítica d'aquestes Ru NPs en la hidrogenació de multitud de substrats aromàtics, observant diferències significatives en funció del lligand estabilitzador utilitzat. En el Capítol 5 s'ha investigat la formació de MNPs a través de l'aproximació organometàl·lica utilitzant l'òxid de grafè reduït dopat amb àtoms de nitrogen (NH2-rGO) com a suport. En la primera part del capítol, vam sintetitzar Ru NPs suportades sobre NH2-rGO (Ru@NH2-rGO) i rGO (Ru@rGO), amb l'intenció d'investigar el paper dels àtoms de N en l'estabilització de les MNPs, així com en la seua activitat catalítica. Per a això, es va estudiar la hidrogenació de l'àcid palmític a 1-hexadecanol, sent el Ru@NH2-rGO el catalitzador heterogeni monometàl·lic de Ru més actiu i selectiu reportat fins a la data (99% conversió i 93 % selectiu). En la segona part del capítol, es van generar PtRu NPs amb diferents composicions atòmiques (5:1, 1:1 i 1:5) sobre NH2-rGO, seguint l'aproximació organometàl·lica. La mateixa velocitat de descomposició dels precursores Pt(NBE)3 i Ru(COD)(COT) ens va permetre generar les NPs de tipus aliatge. Aquests sistemes bimetàl·lics (PtxRuy@NH2-rGO) es van estudiar en la hidrogenació de multitud de compostos amb grups polars (C=O), observant-se diferències significatives en funció del suport utilitzat i la composició atòmica de les MNPs. Finalment, en el Capítol 6 es va investigar l'ús de nanopartícules magnètiques (MagNPs) per emetre calor per pèrdues d'histèresi en presència d'un camp magnètic oscil·lant d'alta freqüència. En primer lloc, es van generar nous agents calefactores basats en generar MagNPs bimetàl·liques de tipus "core-shell" de CoNi encapsulades en carbó (Co@Ni@C), amb l'objectiu d'hidrogenar selectivament el CO2 a CO (RWGS) obtenint excel·lents resultats catalítics. Finalment, també presentem la síntesi d'una nova MagNP de tipus "core-shell" (FeCo@Ni) per a la seva aplicació en catàlisi induïda magnèticament en solució, demostrant ser capaç de modular la seva selectivitat al producte de l'hidrogenació o de l'hidrodesoxigenació del HMF en funció del camp magnètic aplicat. A més, després de la seva encapsulació en carbó (FeCo@Ni@C) han demostrat ser actives, selectives i estables en la reducció de multitud de substrats oxigenats derivats de la biomassa en medi aquós, sent el primer exemple reportat fins a la data de catàlisi magnètica realitzada en aigua. / [EN] This Doctoral Thesis is developed in the field of catalysis, which is framed within the concept of Sustainable Chemistry. Specifically, the research has focused on the development and application of new catalysts based on colloidal and supported metallic nanoparticles to carry out relevant catalytic reactions. All the MNPs synthesized in this doctoral thesis were carried out from the organometallic approach, where an organometallic precursor is generally decomposed under mild conditions, room temperature and 3 bar H2, in the presence of a stabilizing agent (organic molecule, polymer, or support). The catalytic properties of MNPs are greatly influenced by the stabilizing agents used, which are capable of modifying their electronic and steric properties. Therefore, the search for new ligands capable of modulating these properties is of great scientific interest. In Chapter 4 of the Thesis, we describe the first example of Ru NPs stabilized with a new family of non-planar polycyclic aromatic ligands, called nanographenes (hept-HBC). Specifically, two different types of distorted nanographene have been used: i) one functionalized with a carbonyl group, and another ii) functionalized with a methylene group in the same position (Ru@1 and Ru@2, respectively). Thanks to the resemblance with systems based on supported-MNPs on graphene or derivatives, this material can be used as a reference to study the coordination modes and dynamics of these with the surface of the nanoparticle. A combined theoretical/experimental study revealed that the curvature of hept-HBC nanographenes is crucial for the stabilization of Ru NPs. Finally, the catalytic activity of these Ru NPs has been evaluated in the hydrogenation of multitude of arenes, observing significant differences depending on the stabilizing ligand used. In Chapter 5, the formation of MNPs through the organometallic approach was investigated using reduced graphene oxide N-doped (NH2-rGO) as support. In the first part of the chapter, Ru NPs supported on NH2-rGO (Ru@NH2-rGO) and rGO (Ru@rGO) were synthesized, with the aim of investigating the role of N atoms in the stabilization of the MNPs, as well as their catalytic activity. For this purpose, the hydrogenation of palmitic acid to 1-hexadecanol was studied, and Ru@NH2-rGO was found to be the most active and selective monometallic Ru-based heterogeneous catalyst reported to date (99% conversion and 93% selectivity). In the second part of the chapter, PtRu NPs with different atomic compositions (5:1, 1:1, and 1:5) were generated on NH2-rGO using the organometallic approach. The same decomposition rate of Pt(NBE)3 and Ru(COD)(COT) precursors allowed us to generate alloy-type NPs. These bimetallic systems (PtxRuy@NH2-rGO) were studied in the hydrogenation of a variety of compounds with polar groups (C=O), and significant differences were observed depending on the support used and the atomic composition of the MNPs. Finally, in Chapter 6 the use of magnetic nanoparticles (MagNPs) for heat generation through hysteresis losses in the presence of a high-frequency oscillating magnetic field was investigated. Firstly, new heat-generating agents based on bimetallic core-shell type CoNi MagNPs encapsulated in carbon (Co@Ni@C) were synthesized with the aim of selectively hydrogenate CO2 to CO (RWGS), obtaining excellent catalytic results. Finally, a new core-shell type MagNP (FeCo@Ni@C), the MagNPs proved to be active, selective, and stable in the reduction of several oxygenated substrates derived from biomass in aqueous media, being the first reported example of magnetic catalysis performed in water to date. In Chapter 6, the crucial role of MagNP encapsulation was demonstrated, where carbon not only limits the total oxidation of MagNPs but also prevents their sintering at high temperatures (~ 700 °C) in gas phase and avoids their aggregation in liquid phase. / Cerezo Navarrete, C. (2023). Aplicación catalítica de nuevos nanosistemas obtenidos a partir de la aproximación organometálica [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/196366

Nucleophilic additions are an important class of reactions in the preparation of several organic compounds. Metals facilitate nucleophilic additions in many cases. The present work Mechanistic Investigation of Metal Promoted Nucleophilic additions is an attempt to understand the mechanism of nucleophilic additions to imines and carbonyl compounds mediated by the transition metal complexes. Understanding the mechanism of metal promoted nucleophilic additions can facilitate the design and synthesis of more efficient catalysts. Chapter 1 provides a brief introduction to nucleophilic addition. A few named reactions that involve nucleophilic addition are described. An overview of the metal promoted nucleophilic addition reactions and their mechanisms are presented. A short note on the importance of understanding the mechanism of metal promoted nucleophilic addition is included. This section ends with the scope of the present work. Chapter 2 “Mechanistic Investigation of Titanium Mediated Reactions of Imines” deals with two reactions. The first reaction is the formation of reduced amines on reduction of imines. Amines and diamines are synthesized often from imines. A convenient route to such nitrogen containing compounds is through reduction of imines and through reductive coupling of imines respectively. Since both reactions occur in a parallel fashion, during the synthesis of diamines, amines are obtained as side products and vice versa. This problem is acute in the case of titanium based reducing agents. These reducing agents are called low valent titanium reagents because low valent titanium species are generated in situ either from titanium(IV) or titanium(III) reagents. There is no clear understanding of the nature of the low valent titanium involved in the reaction. To rectify this, a mechanistic understanding of this reaction is essential. An attempt was made to probe the mechanism of formation of amines using low valent titanium formed by using two different reducing agents namely phenylsilane and zinc. With the help of isotopic labelling studies, it was found that the mechanism of formation of an amine with phenylsilane involves a direct hydrogen transfer from phenylsilane to an imine. This was verified using deuterium labelled phenylsilane. With zinc, it follows a traditional titanacycle pathway which was verified by quenching with the deuterium oxide. A second reaction that has been probed is the alkylation of imines by Grignard reagents using chiral titanium complexes. Alkylation of imines is one of the suitable routes to prepare chiral amines. Alkylation of imines employing a Grignard reagent with Ti(OiPr)4 can proceed through two different pathways depending on the amount of the Grignard reagent used. Alkylation reaction with one equivalent of Grignard reagent can proceed through a Ti(IV) species and the alkylation reaction with two equivalents of the Grignard reagent can proceed through a Ti(II) species. The reaction proceeding through Ti(IV) is less wasteful as it only requires one equivalent of the Grignard reagent. The two pathways differ from each other in the nature of the transition state where the C-C bond is formed. To verify the favourable pathway, chiral titanium complexes were prepared and alkylation carried out. The alkylation results suggest that one equivalent of Grignard is sufficient to give good yields of the alkylated product and the reaction may proceed through a Ti(IV) promoted path. It was reported in the literature that at least three equivalents of Grignard reagent are required to get good yields of the alkylated product with zirconium complexes. This work suggests a greener alternate to alkylation of imines. Chapter 3 “Asymmetric Transfer Hydrogenation Reaction of Ketones in Water” deals with the synthesis of chiral ruthenium half-sandwich complexes employing a proline diamine ligand which has phenyl, ethyl, benzyl, or hydrogen as a substituent. These complexes were characterized by X-ray diffraction. In addition, all these complexes were obtained as single diastereoisomers. These complexes were used as catalysts for the reduction of a variety of ketones to chiral alcohols in water using sodium formate as a hydride source. Stoichiometric reaction between sodium formate and the catalysts showed the formation of hydride complexes as the active species. Based on the electronic effects observed, the key step is found to be a nucleophilic attack of hydride on the carbonyl carbon of ketones. In the transfer hydrogenation reaction with DCOONa, more of 1-phenylethanol- 1-2H1 was observed with all the ruthenium catalysts suggesting that the hydrogen from sodium formate is transformed into a metal hydride which is subsequently transferred to the ketones to form chiral alcohols. The catalysts were optimized with acetophenone as a model substrate. Only in the case of a catalyst which has a phenyl substituent, silver nitrate was found to enhance the formation of aqua complex which in turn resulted in good yields of the chiral alcohols. Among all the complexes studied, the catalyst bearing a phenyl group induces greatest enantioselectivity. It can also be recycled. Chapter 4 “On the Formation of a Ruthenium-PPh2H Complex Using 1- Phenylethane-1,2-diol” deals with the mechanism of formation of PPh2H from PPh2Cl. This unique transformation involves a ruthenium-cymene dimer, PPh2Cl and 1-phenylethane-1,2- diol. In the attempted synthesis of a ruthenium bisphosphinite complex, using the ruthenium-cymene dimer, chlorodiphenylphosphine and 1-phenylethane-1,2-diol, the formation of [Ru(η6-cymene)Cl2PPh2H] was observed in good yield. Formation of the expected ruthenium bisphosphinite complex was not observed. The reaction was carried out in the absence of 1-phenylethane-1,2-diol resulted in the formation of [Ru(η6- cymene)Cl2PPh2Cl] suggests that the diol acts as a reducing agent. To verify the source of hydrogen in the 1-phenylethane-1,2-diol, deuterated diols were prepared. The reactions with the deuterated diols revealed several interesting aspects of the formation of the Ru-PPh2H complex. Chapter 5 “Mechanistic Studies on the Diazo Transfer Reaction” deals with the synthesis of labelled azides and the labelled azidating reagent to probe the mechanism of the diazo transfer reaction. Azides are important precursors used for a variety of chemical transformations including the celebrated Cu(I) catalyzed click reaction. Azides are also used as protecting groups for amines as they can be conveniently reduced to amines. Azidation of amines usually yield azides, with retention of stereochemistry. There is a possibility that the azide formation can occur through the SNi mechanism with retention of configuration where nitrogen in the starting material will not be retained after forming an azide. The reaction was carried out with 13C and 15N labelled L-valine and L-isoleucine to probe this possibility. The resultant labelled azide has 15N retained in its position. This excluded the SNi pathway. To show where the nucleophilic amine group is attacking the azide, labelled imidazole-1¬sulfonyl azide was synthesized from NaN215N. Reactions were carried out with L-valine (labelled and unlabelled) in the presence of a metal catalyst and with unlabelled L-valine in the absence of catalyst. These results confirm the postulated pathways described in the literature.