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[ES] Funcionalización directa del polietileno con ésteres de diferentes longitudes y formas, adición de carbenos y posterior transesterificación, para el estudio de sus diferentes estabilidades hidrolíticas.

[ES] La cicloadición 1,3-dipolar entre alquinos y azidas ("Click Chemistry") catalizada por cobre (I), para formar 1,2,3-triazoles, es una de las reacciones más populares debido a su fiabilidad, especificidad y biocompatibilidad. Este tipo de mecanismos tienen el potencial de acortar los procedimientos y optimizarlos consiguiendo una economía atómica del 100%, además tienen la posibilidad de llevar a cabo la reacción en distintas condiciones y en un gran número de disolventes distintos, incluyendo el agua. Esta combinación de factores hace que las reacciones tipo "click" sean de gran utilidad para el diseño y la síntesis de una gran variedad de compuestos en condiciones óptimas de reacción. Un gran avance sería el descubrimiento de una reacción tipo "click" para amidas y esteres, que son compuestos químicos que se encuentran tanto en la naturaleza como en los laboratorios y de los cuales se conocen numerosos métodos sintéticos, sin embargo, estos no suelen ser sostenibles y generalmente requieren de reactivos peligrosos y condiciones violentas de reacción. Por estos motivos, en este trabajo se ha propuesto la síntesis de esteres y amidas a partir de la apertura de anillo de derivados de la ciclopropenona en presencia de aminas y alcoholes según los mecanismos de "Click Chemistry", utilizando distintas condiciones de reacción (temperatura, disolventes, catalizadores, etc.)., [EN] 1,3-dipolar cycloaddition between alkynes and azides catalyzed by copper (I) (click reaction), to form 1,2,3-triazoles, is one of the most popular reactions due to its reliability, specificity, and biocompatibility. Click reactions have the potential to perform shorter procedure and optimize them, achieving an atomic economy of 100%, and operate in different conditions and in many conventional solvents, including water. This combination of factors makes click reactions of great utility for the design and synthesis of a plethora compounds under optimal reaction conditions. A great advance would be the discovery of a click reaction for amides and esters synthesis, which are common chemicals in Nature, industry and academic laboratories. Indeed, a plethora of synthetic methods have been developed over the years, however, these methods are not sustainable and generally require harsh reagents or reaction conditions. For these reasons, in this work has been proposed the synthesis of esters and amides form the ring-opening of cyclopropenones derivatives in the presence of amines and alcohols according to the mechanisms of Click Chemistry.

[ES] En esta tesis se han estudiado la síntesis y aplicación de clústeres y átomos metálicos aislados de Pd y Pt. Clústeres y átomos aislados han sido sintetizados siguiendo nuevas metodologías en disolución, sin utilizar ligandos orgánicos, y soportándolos en materiales metal-orgánico estructurados (MOFs) o polímeros. Después de la síntesis, las pequeñas especies metálicas se han caracterizado con diferentes técnicas, como espectroscopias ultravioleta-visible, de emisión, de absorción de rayos X, análisis atómico de emisión por plasma de inducción acoplado, difracción de rayos X y microscopía. Los clústeres y los átomos aislados se han utilizado como catalizadores en reacciones de acoplamiento C-C, de oxidación de alcoholes y como agentes antitumorales. La síntesis de dímeros de PdII soportados dentro de las cavidades del MOF ha dado lugar a la formación de complejos supramoleculares de coordinación en los canales del MOF (SCCs@MOF). En los SCCs, los dímeros de PdII representan los centros de coordinación, y ligandos de piridina fluorados y no-fluorados son los conectores entre las unidades bimetálicas. Después de la caracterización, los SCCs@MOF se han empleado como catalizadores en reacciones de acoplamiento C-C de ácidos borónicos y/o alquinos y de oxidación de alcoholes alquílicos. Estos catalizadores se comparan con los respectivos homogéneos, como un complejo cíclico de paladio, previamente sintetizado, o el sistema Pd(OAc)2/ligandos. Además, se mostrarán algunos de los pocos ejemplos de reacciones de acoplamiento C-C y de oxidación catalizadas por SCCs. También se ha llevado a cabo la reacción de oxidación de alcohol bencílicos catalizada por átomos aislados de paladio. Estas pequeñas especies fueron preparadas in situ, dando lugar a uno de los primeros ejemplos de átomos aislados en disolución en ausencia de ligandos. Para averiguar la actividad real de los átomos aislados y poder estabilizarlos, se han soportado en un MOF basado en cisteína y se han utiliz, [CA] En la present tesi doctoral s'ha realitzat un estudi de la síntesi i aplicació de clústers metàl·lics i àtoms aïllats de Pd i Pt com a catalitzadors. Ambdós s'han sintetitzat seguint noves metodologies en dissolució, sense la utilització de lligams i suportant-los en materials metal-orgànic estructurats (MOFs) o polímers. Una vegada sintetitzats, s'ha dut a terme una caracterització minuciosa amb diferents tècniques, com espectroscòpia Ultraviolat-Visible (UV-Vis), d'emissió, d'absorció de raigs X (XAS), d'emissió atòmica per plasma d'acoblament inductiu (ICP-AES), difracció de raigs X i microscòpia. Aquests clústers i àtoms aïllats s'han utilitzat com a catalitzadors en reaccions d'acoblament C-C, en oxidacions d'alcohols i en tractaments antitumorals. Concretament, la síntesi dels dímers de PdII suportats dins de les cavitats del MOF ha donat lloc a la formació de complexos de coordinació supramoleculars dins dels canals del MOF (SCCs@MOF). En els SCCs, els dímers de PdII representen els centres de coordinació, i les diferents unitats bimetàl·liques estan connectades per lligams de piridina fluorats i no fluorats. Després de la seua caracterització, els SCCs@MOF s'han utilitzat com a catalitzadors de reaccions d'acoblament C-C d'àcids borònics i/o alquins i en reaccions d'oxidació d'alcohols alquílics. També s'ha dut a terme la comparació entre els corresponents catalitzadors homogenis, per exemple un complex cíclic de pal·ladi o del sistema Pd(OAc)2/lligams. D'altra banda, mostrem un dels pocs exemples de reaccions d'acoblament C-C i de reaccions d'oxidació catalitzades per SCCs. A més, també es descriu la reacció d'oxidació d'alcohol benzílic catalitzada per àtoms aïllats de Pd. Aquestes espècies menudes es preparen in situ, donant lloc a un dels primers exemples d'àtoms aïllats en dissolució sense lligams. A més a més, per a poder verificar la seua activitat i estabilitzar-los, s'han suportat en MOFs basats amb cisteïna, utilitzant-se en el mateix procés d, [EN] The synthesis and application of tal clusters (MCs) and single atoms catalysts (SACs) of Pd and Pt is explored in this Thesis. Both clusters and single atoms were synthesized by following novel ligand-free procedures in solution, or by supporting them on Metal-Organic Frameworks (MOFs) or on polymers. After their synthesis, these entities were deeply characterized by techniques, such as Ultraviolet-Visible (UV-Vis), emission, X-ray Absorption (XAS) spectroscopies, Induced Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES), X-ray Diffraction and microscopy, among others. Finally, MCs or SACs were used as catalyst in homo- or cross-coupling reactions, in alcohol oxidation reactions, and in antitumoral treatments. Especially, the supporting of PdII dimers inside a MOF network allowed the following formation of Supramolecular Coordination Complexes (SCCs) within the MOF channels (SCCs@MOF). In the SCCs, the PdII dimers represent the pivotal centers and different pyridyl ligands, fluorinated and non-fluorinated, embody the linkers between the bimetallic units. After being characterized, the SCCs@MOF were used as catalysts in homocoupling reactions of boronic acids and alkynes, in cross-coupling reactions of alkynes and in alkyl alcohols oxidation. These catalysts were compared with its homogeneous counterparts, i.e., a pre-synthesized Pd metallacycle or the system Pd(OAc)2/ligands. Overall, we show some examples of C-C coupling and oxidation reactions catalyzed by SCCs. Moreover, benzyl alcohols oxidation reaction catalyzed by palladium single atoms is described. The small metal species were prepared in situ, leading to one of the first example of ligand-free single atoms in solution. Afterward, in order to verify the real activity of single atoms and to stabilize them, they were supported inside a cysteine-based MOF and used in the same oxidation process. Finally, the application of Pt clusters (MCs) in antitumoral treatments is portrayed. The clusters were synt

This is the peer reviewed version of the following article: C. Bilanin, E. Tiburcio, J. Ferrando-Soria, D. Armentano, A. Leyva-Pérez, E. Pardo, ChemCatChem 2021, 13, 1195, which has been published in final form at https://doi.org/10.1002/cctc.202001492. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving., [EN] The low-temperature water-gas shift reaction (WGSR, CO+H2O H-2+CO2) is considered a very promising reaction -candidate for fuel cells- despite an efficient and robust catalyst is still desirable. One of the more prominent catalysts for this reaction is based on single Pt atoms (Pt-1) on different supports, which are supposed to manifold the reaction by the accepted mechanism for the general WGSR, i. e. by addition of one H2O molecule to CO, with generation of CO2 and H-2. Here we show, experimentally, that not one but two H2O molecules are added to CO on the Pt-1 catalyst, as assessed by a combination of reactivity experiments with soluble Pt catalysts, kinetic and spectroscopic measurements, and finally by in-operando single crystal X-ray diffraction on a Pt-1-MOF, to visualize the formation of the hemiacetal intermediate on the solid catalytic site. These results confirm our previous DFT predictions and provide a paradigmatic shift in the assumed mechanism of the WGSR, which may open the debate if two H2O molecules are recurrently added during the WGSR, not only for Pt-1 catalysts but also for other metal catalysts.

This is the peer reviewed version of the following article: M. Á. Rivero-Crespo, M. Tejeda-Serrano, H. Pérez-Sánchez, J. P. Cerón-Carrasco, A. Leyva-Pérez, Angew. Chem. Int. Ed. 2020, 59, 3846, which has been published in final form at https://doi.org/10.1002/anie.201909597. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving., [EN] The carbonyl-olefin metathesis reaction has experienced significant advances in the last seven years with new catalysts and reaction protocols. However, most of these procedures involve soluble catalysts for intramolecular reactions in batch. Herein, we show that recoverable, inexpensive, easy to handle, non-toxic, and widely available simple solid acids, such as the aluminosilicate montmorillonite, can catalyze the intermolecular carbonyl-olefin metathesis of aromatic ketones and aldehydes with vinyl ethers in-flow, to give alkenes with complete trans stereoselectivity on multi-gram scale and high yields. Experimental and computational data support a mechanism based on a carbocation-induced Grob fragmentation. These results open the way for the industrial implementation of carbonyl-olefin metathesis over solid catalysts in continuous mode, which is still the origin and main application of the parent alkene-alkene cross-metathesis.

[EN] The cyanosilylation of carbonyl compounds is a fundamental reaction in organic synthesis, to give cyanohydrins. Ketones are particularly reluctant to cyanosilane addition and require the action of a catalyst, and despite many soluble Bronsted and Lewis acids have been employed for this task, it is difficult to find in the open literature catalytic solids able to carry out the reaction. Here, we show that commercially available nanoceria catalyzes the cyanosilylation of different ketones (21 examples) at temperatures between 0 and 50 degrees C, in high yields, under solventless conditions if required. The nanoceria network atoms act in a cooperative way to provide a bifunctional acid-base solid catalyst for the cyanosilylation reaction. The amorphization of nanoceria during reaction, due to acid release, does not hamper the catalytic activity and, indeed, different types of nanoceria, even with supported metal nanoparticles on surface, are active for the reaction, enabling extensive reuses after air calcination and the use of the catalytic material for the aerobic oxidation of alcohols / cyanosilylation reaction. (C) 2020 Elsevier Inc. All rights reserved.

[EN] Zeolites are the most used catalysts worldwide in petrochemistry processes, with particular ability to stabilize carbocations. However, the use of zeolites in organic synthesis is still scarce. We show here that representative carboxonium-mediated organic reactions, such as the Nazarov cyclization and thetert-butylation of alcohols withtert-butyl acetate, typically performed with very strong acid catalysts in solution such as triflic acid, can be catalyzed by simple zeolites with high yield and selectivity. The aluminosilicate framework stabilizes the intermediate carboxonium species and overrides the need for superacid protons in solution

[EN] The exact chemical structure of non-crystallising natural products is still one of the main challenges in Natural Sciences. Despite tremendous advances in total synthesis, the absolute structural determination of a myriad of natural products with very sensitive chemical functionalities remains undone. Here, we show that a metal-organic framework (MOF) with alcohol-containing arms and adsorbed water, enables selective hydrolysis of glycosyl bonds, supramolecular order with the so-formed chiral fragments and absolute determination of the organic structure by single-crystal X-ray crystallography in a single operation. This combined strategy based on a biomimetic, cheap, robust and multigram available solid catalyst opens the door to determine the absolute configuration of ketal compounds regardless degradation sensitiveness, and also to design extremely-mild metal-free solid-catalysed processes without formal acid protons. Elucidation of the chemical structure of natural products constitutes one of the main challenges in Natural Sciences. Here, the authors show that an amino acid-based metal-organic framework exhibits hydrolase-like catalytic activity and crystallographic determination of the resulting products

[EN] The substitution of catalytic metals by p-block main elements has a tremendous impact not only in the fundamentals but also in the economic and ecological fingerprint of organic reactions. Here we show that few-layer black phosphorous (FL-BP), a recently discovered and now readily available 2D material, catalyzes different radical additions to alkenes with an initial turnover frequency (TOF0) up to two orders of magnitude higher than representative state-of-the-art metal complex catalysts at room temperature. The corresponding electron-rich BP intercalation compound (BPIC) KP6 shows a nearly twice TOF0 increase with respect to FL-BP. This increase in catalytic activity respect to the neutral counterpart also occurs in other 2D materials (graphene vs. KC8) and metal complex catalysts (Fe-0 vs. Fe2- carbon monoxide complexes). This reactive parallelism opens the door for cross-fertilization between 2D materials and metal catalysts in organic synthesis.

[EN] Supramolecular coordination compounds (SCCs) represent the power of coordination chemistry methodologies to self-assemble discrete architectures with targeted properties. SCCs are generally synthesized in solution, with isolated fully coordinated metal atoms as structural nodes, thus severely limited as metal-based catalysts. Metal-organic frameworks (MOFs) show unique features to act as chemical nanoreactors for the in situ synthesis and stabilization of otherwise not accessible functional species. Here, we present the self-assembly of Pd-II SCCs within the confined space of a pre-formed MOF (SCCs@MOF) and its post-assembly metalation to give a Pd-II-Au-III supra molecular assembly, crystallography underpinned. These SCCs@MOFs catalyze the coupling of boronic acids and/or alkynes, representative multi-site metal-catalyzed reactions in which traditional SCCs tend to decompose, and retain their structural integrity as a consequence of the synergetic hybridization between SCCs and MOFs. These results open new avenues in both the synthesis of novel SCCs and their use in heterogeneous metal-based supramolecular catalysis.

[ES] En la presente tesis doctoral se ha llevado a cabo la búsqueda de catalizadores heterogéneos para sustituir catalizadores homogéneos de Fe en reacciones químicas de interés industrial y/o sintético. En primer lugar, se sintetizaron nanopartículas planas de FeOx en la superficie de diferentes óxidos inorgánicos ácidos mediante un proceso redox en one-pot a temperatura ambiente, las cuales catalizan la semi-hidrogenación de alquinos con altos rendimientos y selectividad. Esta reacción había sido descrita con complejos de Fe en disolución. Estos óxidos mixtos de Fe2,3+ son capaces de disociar y transferir H2 a alquinos de forma quimio- y estereoselectiva asistidos por los grupos hidroxilo del soporte del óxido inorgánico, el cual, por tanto, está involucrado en el mecanismo de la reacción. Este mecanismo se asemeja al que usan las enzimas de Fe hidrogenasas en la naturaleza para disociar H2. Además, sitios aislados de FeIII-O en sólidos catalizan de manera quimioselectiva la hidrogenación del acetileno en corrientes de etileno, en condiciones industriales front-end. Para corroborar la naturaleza del centro activo, se preparó un MOF con sitios de FeIII accesibles dentro de sus poros, mediante la funcionalización post-sintética por metátesis de catión en los cristales, lo que permitió resolver la estructura del sólido por difracción de rayos X de monocristal, confirmando que el centro catalítico es FeIII-O. Por otra parte, se llevó a cabo la reacción radicalaria ATRA entre alquenos y halogenuros de carbono con complejos de Fe de baja valencia y también con fosforeno, un material bidimensional de fósforo análogo al grafeno. Los compuestos de Fe en disolución y el fosforeno tienen en común que son ricos en electrones disponibles para iniciar la reacción radicalaria, por lo que presentan una actividad mucho mayor que sus compuestos análogos en estados de oxidación más altos, incluso a temperatura ambiente. Y por último, se llevó a cabo la metátesis de carbonilo-olefina, [CA] En la present tesi doctoral s'ha dut a terme la recerca de catalitzador heterogenis per a substituir catalitzadors homogenis de Fe en reaccions químiques d'interès industrial i/o sintètic. En primer lloc, es sintetitzaren nanopartícules planes de FeOx en la superfície de diferents òxids inorgànics àcids mitjançant un procés redox en one-pot a temperatura ambient, les quals catalitzen la semi-hidrogenació d'alquins amb alts rendiments i selectivitat. Aquesta reacció havia sigut descrita amb complexes de Fe en dissolució. Aquests òxids mixtes de Fe2,3+ són capaços de dissociar i transferir H2 a alquins de forma quimio- i estereoselectiva assistits pels grups hidroxil del suport de l'òxid inorgànic, el qual, per tant, està involucrat en el mecanisme de la reacció. Aquest mecanisme s'assembla al que utilitzen les enzimes de Fe hidrogenases en la natura para dissociar H2. A més a més, llocs aïllats de FeIII-O en sòlids catalitzen de manera quimioselectiva la hidrogenació del acetilè en corrents de etilè, en condicions industrials front-end. Per a corroborar la natura del centre actiu, es va preparar un MOF amb llocs de FeIII accessibles dins dels seus porus, mitjançant la funcionalització post-sintètica per metàtesis de catió en els cristalls, el que va permetre resoldre l'estructura del sòlid per difracció de rajos X de monocristall, confirmant que el centre catalític és FeIII-O. Per altra banda, es va dur a terme la reacció radicalaria ATRA entre alquens i halogenurs de carboni amb complexos de Fe de baixa valència i també amb fosforè, un material bidimensional de fòsfor anàleg al grafè. Els compostos de Fe en disolució i el fosforè tenen en comú que són rics en electrons disponibles per a iniciar la reacció radicalaria, per el qual presenten una activitat molt major que els seus compostos anàlogues en estats d'oxidació més alts, inclòs a temperatura ambient. I per últim, es va realitzar la metàtesis de carbonil-olefina intermolecular entre aldehids aromàtics i èt, [EN] In the present doctoral thesis, the search of heterogeneous catalysts to substitute homogeneous Fe catalysts in chemical reactions of industrial and/or synthetic interest has been carried out. First, planar FeOx nanoparticles were synthesized on the surface of different acidic inorganic oxides using a one-pot redox process at room temperature, which catalyze the semi-hydrogenation of alkynes with high yields and selectivity. This reaction had been described previously only with Fe complexes in solution. These mixed Fe2,3+ oxides are capable to dissociate and transfer H2 to alkynes in chemo- and stereoselective manner assisted by the hydroxyl groups of the inorganic oxide support, which, as a result, is involved in the mechanism of the reaction. This mechanism resembles that used by the Fe hydrogenases enzymes in nature to dissociate H2. In addition, FeIII-O isolated sites in solids catalyze chemo- and stereoselectively the hydrogenation of acetylene in ethylene streams under front-end industrial conditions. To corroborate the nature of the active center, a MOF with accessible FeIII sites within its pores was prepared by post-synthetic metathesis of cations in crystals, which allowed resolving the structure of the solid by single crystal X-ray diffraction, confirming that the catalytic center is FeIII-O. On the other hand, the ATRA radical reaction between alkenes and carbon halides was carried out with low-valent Fe complexes and also with phosphorene, a phosphorous based two-dimensional material analogous to graphene. The compounds of Fe in solution and phosphorene have in common that they are rich in electrons available to initiate the radical reaction, so they have a much higher activity than their analogs in higher oxidation states and are active even at room temperature. Finally, the intermolecular carbonyl-olefin metathesis between aromatic aldehydes and vinyl ethers was carried out catalyzed by conventional Brönsted or Lewis acids in batch (including Fe

[EN] Group 15 elements in zero oxidation state (P, As, Sb and Bi), also called pnictogens, are rarely used in catalysis due to the difficulties associated in preparing well-structured and stable materials. Here, we report on the synthesis of highly exfoliated, few layer 2D phosphorene and antimonene in zero oxidation state, suspended in an ionic liquid, with the native atoms ready to interact with external reagents while avoiding aerobic or aqueous decomposition pathways, and on their use as efficient catalysts for the alkylation of nucleophiles with esters. The few layer pnictogen material circumvents the extremely harsh reaction conditions associated to previous superacid-catalyzed alkylations, by enabling an alternative mechanism on surface, protected from the water and air by the ionic liquid. These 2D catalysts allow the alkylation of a variety of acid-sensitive organic molecules and giving synthetic relevancy to the use of simple esters as alkylating agents.

[EN] The reactive nature of carbenes can be modulated, and ultimately reversed, by receiving additional electron density from a metal. Here, it is shown that Au nanoparticles (NPs) generate an electron-rich carbene on surface after transferring electron density to the carbonyl group of an in situ activated diazoacetate, as assessed by Fourier transformed infrared (FT¿IR) spectroscopy, magic angle spinning nuclear magnetic resonance (MAS NMR), and Raman spectroscopy. Density functional theory (DFT) calculations support the observed experimental values and unveil the participation of at least three different Au atoms during carbene stabilization. The surface stabilized carbene shows an extraordinary stability against nucleophiles and reacts with electrophiles to give new products. These findings showcase the ability of catalytic Au NPs to inject electron density in energetically high but symmetrically allowed valence orbitals of sluggish molecules.

[EN] Imines are ubiquitous intermediates in organic synthesis, and the metal-mediated imination of alcohols is one of the most direct and simple methods for their synthesis. However, reported protocols lack compatibility with many other functional groups since basic supports/media, pure oxygen atmospheres, and/or released hydrogen gas are required during reaction. Here we show that, in contrast to previous metal-catalyzed methods, hexa-aqueous Ru(III) catalyzes the imination of primary alcohols with very wide functional group tolerance, at slightly acid pH and under low oxygen atmospheres. The inorganic metal complex can be supported and stabilized, integrally, within either faujasite-type zeolites (Y and X) or a metal organic framework (MOF), to give a reusable heterogeneous catalyst which provides an industrially viable process well below the flammability limit of alcohols and amines.

En la presente tesis doctoral se ha llevado a cabo un estudio de los clústeres y átomos aislados de platino como catalizadores para reacciones químicas de interés en la química industrial. En la reacción de hidrosililación de alquinos se ha demostrado que la selectividad está determinada por las especies activas de platino. Para el caso de la hidrosililación anti-Markovnikov, la más habitual, los verdaderos catalizadores son átomos aislados de platino, mientras que para la hidrosililación Markovnikov, son los clústeres de platino triatómico los responsables de la selectividad observada. Se han sintetizado un elevado número de compuestos ¿-alquenilsilanos y se ha demostrado su versatilidad como intermedios de síntesis. Además, el mecanismo de la reacción parece apuntar a la agregación de átomos de platino con moléculas de silano como parámetro clave para la selectividad de la reacción. Se pueden emplear clústeres de Pd y Pt de <10 átomos formados in situ o preformados como catalizadores para reacciones de acoplamiento cruzado (Heck, Suzuki o Sonogashira) en función de la base empleada, con elevada actividad y selectividad. Esto se debe a una mayor facilidad en la adición oxidativa, lo que permite que la reacción esté controlada por la base. Por otro lado se han empleado materiales híbridos clúster-MOF o SAC-MOF como catalizadores heterogéneos para reacciones de interés industrial. En primer lugar clústeres de Pt02 estabilizados dentro de un MOF se han empleado como catalizadores para las reacciones de formación de NH4CN, la metanación de CO2 y la hidrogenación de olefinas. También se han empleado átomos de platino con bajo estado de oxidación y estabilizadas por ligandos duros (H2O) sin retrodonación en un MOF como catalizadores para la reacción de desplazamiento de gas de agua (WGS)., In this thesis, a study of platinum clusters and single atoms as catalysts for industrially relevant chemical reactions have been carried out. Selectivity in alkyne hydrosilylation is determined by platinum active species. For anti-Markovnikov hydrosilylation, the thermodynamic product, the true catalysts are isolated platinum atoms, while for Markovnikov hydrosilylation, three atom platinum clusters are responsible for the observed selectivity. A big number of ¿-alkenylsilanes have been synthesized and their versatility as synthetic intermediates demonstrated. Reaction mechanism points to platinum-silane aggregation as key factor for reaction selectivity. Pd and Pt clusters with <10 atoms either formed in-situ or preformed can be used as catalysts for cross-coupling reactions (Heck, Suzuki and Sonogashira) depending on the base, with high activity and selectivity. This is due to an easier oxidative addition, which allows the base to control reaction. Hybrid materials cluster/SAC-MOF have been used as heterogeneous catalysts for industrially relevant reactions. First, Pt02 clusters stabilized inside a MOF catalyze NH4CN formation, CO2 methanation and olefin hydrogenation. Low valent Pt atoms stabilized by hard ligands (H2O) without retrodonation have proved to catalyze very efficiently the low-temperature water gas shift reaction., En la present tesi doctoral s'ha dut a terme un estudi dels clústers i àtoms aïllats de platí com a catalitzadors per reaccions químiques d'interès en la química industrial. En la reacció d'hidrosililació d'alquins s'ha demostrat que la selectivitat està determinada per les espècies actives de platí. Per al cas de la hidrosililació anti-Markovnikov, la més habitual, els vertaders catalitzadors són àtoms aïllats de platí, mentre que per la hidrosililació Markovnikov, són els clústers de platí triatòmic els responsables de la selectivitat observada. S'han sintetitzat un elevat nombre de compostos ¿-alquenilsilans i s'ha demostrat la seua versatilitat com intermedis de síntesi. A més, el mecanisme de la reacció pareix apuntar a la agregació d'àtoms de platí amb molècules de silà com a paràmetre clau per a la selectivitat de la reacció. Es poden emprar clústers de pal·ladi i platí de <10 àtoms formats in situ o preformats com catalitzadors per reaccions d'acoblament creuat (Heck, Suzuki o Sonogashira) en funció de la base emprada, amb elevada activitat i selectivitat. Això es deu a una major facilitat en la adició oxidativa, el que permet que la reacció estigui controlada per la base. Per altra banda s'han emprat materials híbrids clúster-MOF o SAC-MOF com catalitzadors heterogenis per reaccions d'interès industrial. En primer lloc clústers de Pt02 estabilitzats dins d'un MOF s'han emprat com catalitzadors per les reaccions de formació de NH4CN, la metanació de CO2 i la hidrogenació d'etilè. També s'han emprat àtoms de platí amb baix estat d'oxidació i estabilitzats per lligands durs (H2O) sense retrodonació en un MOF com a catalitzadors per la reacció de desplaçament de gas de agua (WGS).

[EN] Catalytic cross-coupling reactions are fundamental transformations in modern organic synthesis. Traditionally based on single-atom transition metal complex catalysts, the use of sub-nanometre metal clusters with enhanced redox and coordinating properties may lead to more efficient catalysts. Recent developments and potential new directions of catalytic sub-nanometre metal clusters for cross-coupling reactions are briefly discussed here

A new approach is presented to form self-supported bimetallic nanosized solids with acid and redox catalytic properties. They are water-, air- and H-2-stable, and are able to activate demanding C-C and C-H reactions. A detailed mechanistic study on the formation of the Ag-Fe bimetallic system shows that a rapid redox-coupled sequence between Ag+, O-2 (air) and Fe2+ occurs, giving monodisperse Ag nanoparticles supported by O-bridged diatomic Fe3+ triflimides. The system can be expanded to Ag nanoparticles embedded within a matrix of Cu2+, Bi3+ and Yb3+ triflimide.

In this thesis, different solids-containing precious metals has been prepared with controlled size and electronics, and used as catalysts for hydrogenation and hydroadition reactions, among others, obtaining prod-ucts of interest in Fine Chemistry. A palladium catalyst comprising <3 nm nanoparticules supported on carbon is capable of hydrogenating different nitroderivative compounds and subsequent cross-couplings of the amine generated in the process, with high chemoselectivity and at relatively low temperatures. Furthermore, this catalyst with a Lewis acid function allows to obtain cyclohexanone oxime directly from nitrobenzene under mild reaction condi-tions with yields above 95%. A carbon-supported nanoalloy platinum-ruthenium catalyst catalyzes the hydrogenation of different types of aromatic rings such as acetophe-none, vinyl benzoic acid, anisole and butylbenzene as well as coupling re-action cascades with other nitro groups, ketones, nitriles or oximes, to ob-tain different types of secondary amines. The catalytically active species of different insoluble metallic chlo-rides for hydroadition reactions is a metallic monomer disgregated from the polymeric salt by the action of substrates and products. These active spe-cies can be mimicked by the electronic modulation of zeolite Y-supported metal solids, which are able to perform the hydroamination of alkynes with good yields and selectivity, getting a reusable catalyst operating under mild conditions. Furthermore, different NSAIDs were synthesized with the sup-ported Pt catalyst to give different in-vitro cyclooxygenase activities., En la presente tesis doctoral se han preparado diferentes sólidos con metales preciosos soportados, de tamaño y propiedades electrónicas controladas, y se han utilizado como catalizadores para reacciones de hidrogenación e hidroadición, entre otras, obteniéndose productos de interés en Química Fina. Un catalizador de Pd nanoparticulado de menos de 3 nm, soportado sobre carbón es capaz de hidrogenar distintos compuestos nitroderivados y acoplar las aminas generadas en el proceso con alta quimioselectividad y a temperaturas relativamente bajas. Además, este catalizador junto con un ácido de Lewis permite obtener oxima de ciclohexanona directamente desde nitrobenceno en condiciones de reacción suaves, y con rendimientos superiores al 95%. Un catalizador nanoaleado de RuPt soportado sobre carbón cataliza hidrogenaciones de distintos tipos de anillos aromáticos como son acetofe-nona, ácido vinilbenzoico, anisol y butilbenceno, y también acoplamientos en cascada con nitroderivados, cetonas, nitrilo u oximas, para obtener distintos tipos de aminas secundarias. La especie activa de varios cloruros metálicos insolubles para reacciones de hidroadición es un monómero metálico disgregado de la sal polimérica por la acción de los sustratos y los productos. Esta especie activa se consiguió mimetizar mediante control electrónico de especies metálicas soportadas en zeolita Y, y este nuevo sólido cataliza las reacciones de hidroaminación e hidroalcoxilación de alquinos con muy buenos rendimientos y selectividades. Además, el correspondiente catalizador de Pt soportado en zeolita Y sirve para sintetizar distintos antiinflamatorios no esteroideos con distinta actividad in-vitro para enzimas ciclooxigenasas., En la present tesi doctoral s'han preparat sòlids amb metalls precio-sos suportats de mida y electrónica controlada, i s'han utilitzat com a catalitzadors per a reaccions d'hidrogenació i hidroadició, entre altres, obtenint-se productes d'interés en Química Fina. Un catalitzador de pal·ladi nanoparticulat de menys de 3 nm, supor-tat sobre carbó és capaç d'hidrogenar diferents compostos nitroderivats i posteriorment dur a terme un acoblament creuat de les amines generades durant el procés amb elevada quimioselectivitat i a temperatures relativament baixes. A més, aquest catalitzador, juntament amb un àcid de Lewis, permet obtenir l'oxima de ciclohexanona directament des de nitrobenzé en condicions de reacció suaus, i amb rendiments superiors al 95%. Un catalitzador nanoaleat de ruteni-platí suportat sobre carbó catalitza hidrogenacions de diferents tipus d'anells aromàtics com acetofenona, àcid vinilbenzoic, anisol i butilbenzé, i també acoblaments en cascada amb nitroderivats, cetones, nitril o oximes, per a obtenir diferents tipus d'amines secundàries. L'espècie activa de clorurs metàl·lics insolubles per a reaccions d'hidroadició és un monòmer metàl·lic disgregat de la sal polimèrica per l'acció dels substrats i dels productes. Aquesta espècie activa es va acon-seguir mimetitzar amb control electronic d'espècies metàl·liques suporta-des en zeolita Y, i aquest nou catalitzador heterogeni catalitza les reac-cions d'hidroaminació i hidroalcoxilació d'alquins amb excel·lents rendiments i selectivitats. A més, aquest catalitzador de platí suportat serveix per a sintetitzar diferents tipus d'antiinflamatoris no esteroides amb diferent activitat in-vitro per a enzims ciclooxigenases.

[EN] The Pt-catalyzed hydrosilylation of alkynes is the procedure of choice to obtain vinylsilanes, and is claimed to be the most relevant application of Pt in organic synthesis. More than half a century after its discovery, only b-vinylsilanes (anti-Markovnikov addition) are obtained with simple Pt catalysts, whereas a-vinylsilanes (Markovnikov addition)remain elusive compounds.Here the catalysis of the Markovnikov hydrosilylation of terminal alkynes by Pt3clusters, in parts-per-million amounts, to give a wide variety of a-vinylsi-lanes in reasonable isolated yields and with turnover fre-quencies that can reach up to one million per hour is reported. Moreover, these a-vinylsilanes are reactive in well-stablished C@Cbond-forming cascade reactions, in which thecorresponding b-isomers are unreactive. Besides its efficiency and synthetic usefulness, this catalytic system is an excellent example of how the atom-by-atomaggregation of a catalytic metal leads to a different selectivity for a given reaction

[EN] We show a facile method to prepare surface-clean monodispersed small and stable CuOx nanoparticles with controllable average sizes from below 1 nm up to similar to 5 nm without using bulk capping agent. Structural and surface characterizations show that the chemical states of CuOx nanoparticles and their interactions with O-2 are dependent on the particle size. To show their relevance to catalysis, the well-defined monodispersed CuOx nanoparticles have been used for oxidative coupling of alkynes. While the generally used CuCl catalysts presents a reaction induction period and agglomerate into CuOx nanoparticles during the reaction, the induction period disappears when monodispersed CuOx nanoparticles (similar to 2 nm) were used as catalyst. Supported CuOx nanoparticles on TiO2 behave in the same way as monodispersed CuOx nanoparticles. Kinetic, spectroscopic, and isotopic studies show that O-2 activation is the rate-controlling step and that the nature of the oxygen species formed on supported CuOx nanoparticles is dependent on the size of CuOx and determine the catalytic properties for oxidative coupling of alkynes.

Consulta en la Biblioteca ETSI Industriales (Riunet)

Consulta en la Biblioteca ETSI Industriales (Riunet)

En la presente tesis doctoral se ha realizado un estudio sobre las especies catalíticamente activas en reacciones de formación de enlace carbono-carbono y carbono-heteroátomo catalizadas por oro, paladio y cobre. En el caso de las reacciones catalizadas por oro (sales de Au+ o Au3+ complejos de Au+ o nanopartículas de Au), se ha comprobado que, independientemente del catalizador de oro de partida, las especies catalíticamente activas en algunas reacciones son clústeres atómicos de oro de entre 2 y 9 átomos, y que, dentro de este rango, las reacciones son sensibles al número de átomos de oro que forman el clúster. Estos clústeres presentan una actividad catalítica inusualmente alta para este tipo de reacciones, llegando a realizar hasta 10 millones de ciclos catalíticos por hora a temperatura ambiente. Además, se ha estudiado la estabilidad de estos clústeres frente a aniones y ligandos en disolución. En el caso de las reacciones de acoplamiento cruzado catalizadas por paladio bajo condiciones de Jeffery (sin ligandos, amida como disolvente, 130-140 oC), se ha observado la formación y actividad catalítica de clústeres de Pd de entre 3 y 4 átomos para las reacciones de acoplamiento de Heck, Sonogashira, Stille y Suzuki. Estos clústeres se estabilizan en presencia de agua o aminas y presentan una alta actividad catalítica para yoduros y bromuros de arilo. También se ha observado la formación de clústeres de Cu en reacciones de acoplamiento entre yoduros de arilo y diversos nucleófilos (amidas, fenoles, fosfinas, tioles, alquinos) en ausencia de ligandos diamina. Además, se ha podido establecer la naturaleza, mecanismo de formación y cantidad de estos clústeres de Cu formados a partir de una sal de partida. Por último, se ha comparado la actividad catalítica de los clústeres de oro, paladio y cobre para reacciones tipo donde se necesita catálisis Lewis, radicalaria o red-ox, pudiendo relacionar la naturaleza fisicoquímica de los clústeres con su actividad catalítica.

[EN] Cyanosilylation of carbonylic compounds has a great interest in organic chemistry. In the present work ketones cyanosilylation is performed catalyzed by cerium oxide in mild conditions. A kinetic study was carried out to get an insight in the deactivation of the catalyst, active sites and reaction mechanism, [ES] La cianosililación de compuestos carbonílicos es una reacción de gran interés en la química orgánica. En este trabajo se presenta la cianosililación de cetonas catalizada por óxido de cerio en condiciones suaves. Se ha realizado un estudio cinético para conocer la desactivación, los centros activos y el mecanismo de la reacción.

Insoluble precious metal chlorides in polymeric form (i.e., PtCl2, PdCl2, AuCl, RhCl3) are commonly used as catalysts for a plethora of organic reactions in solution. Here we show that only the minor soluble fraction of these precious metal chlorides (typically 5-30%) is catalytically active for the hydroamination, hydroalkoxylation, hydrosilylation, and cyclo-isomerization of alkynes and alkenes, and that the resting insoluble metal is catalytically useless. To circumvent this waste of precious metal and follow a rational design, we generate here well-dispersed Pt(II) and Pd(II) single sites on zeolite Y, with an exquisite control of the Lewis acidity, to catalyze different hydroaddition reactions to alkynes and alkenes with up to 10(4) catalytic cycles (at least 2 orders of magnitude superior to precious metal chlorides) and with high isolated yields (82-99%, >15 examples).

[EN] The generation of a carbocation with an acid depends not only on the acid strength but also on the ability of the counteranion to stabilize the positive charge left behind. Here we report that despite their relatively weak acidity, zeolites are able to generate and stabilize medium-size (molecular weight approximate to 300 Da) delocalized carbocations on their surface under mild reaction conditions, as it can be done by strong Bronsted or Lewis acids in solution. The zeolite thus acts as a soft macroanion, prolonging the lifetime of the carbocation sufficiently to perform multifunctionalization reactions with amides, thioamides, and phenols, with high yield and selectivity. Biological studies show that some of the products obtained here present significant inhibition activity against colon cancer cells, illustrating the new possibilities of zeolites to prepare complex organic molecules.

This document is the Accepted Manuscript version of a Published Work that appeared in final form in Journal of the American Chemical Society, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see [insert ACS Articles on Request author-directed link to Published Work, see http://pubs.acs.org/doi/abs/10.1021%2Fjacs.5b00222 Additional Figures S1−S20, experimental procedures, and compound characterization, including NMR spectra. This material is available free of charge via the Internet at http:// pubs.acs.org., [EN] Sub-nanometric Cu clusters formed by endogenous reduction of Cu salts and Cu nanoparticles are active and selective catalysts for C−N, C−C, C−O, C−S, and C−P bond-forming reactions. Sub-nanometric Cu clusters have also been generated within a polymeric film and stored with full stability for months. In this way, they are ready to be used on demand and maintain high activity (TONs up to 104 ) and selectivity for the above reactions. A potential mechanism for the formation of the sub-nanometric clusters and their electronic nature is presented.

Metal-catalysed chemical reactions are often controlled by steric hindrance around the metal atom and it is rare that substituents far away of the reaction site could be differentiated during reaction, particularly if they are simple alkyl groups. Here we show that a gold catalyst is able to discriminate between linear carbon alkynes with 10 or 12 atoms in the chain during the oxidative homocoupling of alkynes: the former is fully reactive and the latter is practically unreactive. We present experimental evidences, which support that the distal size selectivity occurs by the impossibility of transmetallating two long alkyl chains in an A-framed, mixed-valence digold (I, III) acetylide complex. We also show that the reductive elimination of two alkyne molecules from a single Au(III) atom occurs extremely fast, in <1 min at -78 degrees C (turnover frequency > 0.016 s(-1)).