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The thesis describes a study of the catalytic hydrogenation of an olefinic substrate by the complex hydridochlorobis(triphenylphosphine) ruthenium(II) and an investigation of the complex in the solid state and in solution. The visible spectra of the complex, (HRuCl(PPh₃)₂)₂, at a series of concentrations showed that Beer's law is not obeyed, and that in solution a dissociative equilibrium exists: (1) (HRuCl(PPh₃)₂)₂ K ⇆ (2HRuCl(PPh₃)₂ The complex in N,N-dimethylacetamide solution was found to be an effective catalyst for the homogeneous hydrogenation of hex-l-ene. A detailed kinetic study on this system revealed a mechanism involving initial formation of a σ-alkyl intermediate which then reacts with molecular hydrogen to produce the saturated product and regenerate the catalyst: (2) HRuCl(PPh₃)₂ + olefin k₁ ⇆ k₋₁ RuCl(PPh₃)₂(alkyl) (3) HRuCl(PPh₃)₂(alkyl) + H₂ k₂→ HRuCl(PPh₃)₂ + alkane. The mechanism is quite different from that reported for the same catalyst system but using acrylamide as substrate, thereby showing that the nature of the substrate can have a pronounced affect on the course of hydrogenation. Addition of triphenylphosphine and lithium chloride to the (HRuCl(PPh₃)₂)₂- hex-l-ene system were found to decrease and increase the rate of hydrogenation, retrospectively. The added phosphine likely competes with the olefinic substrate for a coordination site; the role of the chloride ion is more uncertain, but a more active catalyst containing more than one chloride ligand is the most obvious rationale. To enhance the solubility of this hydridophosphine type catalyst the tri-p-tolylphosphine analogue of the triphenylphosphine complex was prepared; the variable temperature ¹H and ³¹P{¹H}-solution n.m.r. of the (HRuCl(P(p-tolyl)₃)₂)₂ complex showed the presence of both monomer and fluxional dimer. Addition of dimethyl maleate to the complex in order to obtain a Ru-alkyl species (equation (2)) gave very complex spectra which could not be interpreted in terms of a single species, but there was some evidence for a hydrido(olefin) species rather than an alkyl. An x-ray analysis of the p-tolyl complex confirmed the expected chloro-bridged dimeric structure of these hydridochlorobis(phosphine) species. There is a square pyramidal coordination geometry about each ruthenium atom, and two such centres share a basal edge, but the molecule has no symmetry as a result of the small hydride ligands allowing distortion. / Science, Faculty of / Chemistry, Department of / Graduate

New cis-dichloro ruthenium-based pre-catalysts for olefin metathesis reaction were synthesised. This work was inspired by the report of complex cis-Caz-1 in 2010, a 2nd generation-type pre-catalyst displaying latent character and acknowledged as state-of-the-art for challenging transformation in olefin metathesis. The stability and the reactivity of such species led us to investigate the possibility to perform the catalysis in air with reagent-grade solvents, so that olefin metathesis reaction can be easily carried out in synthetic laboratories avoiding restricting inert conditions (Chapter 2). Next, further modifications of the original scaffold were attempted. Pre-catalyst cis-Caz-1 was reacted with different silver salts leading to new cis-complexes. The first examples of Ru-F species for olefin metathesis reaction are reported in Chapter 3. The phosphite ligand plays a very important role in the cis-Caz-1 scaffold and allowed the formation of the mono and the difluoro complexes selectively. Other silver salts were then employed such as trifluoroacetate, acetate, benzoate and pivalate. In all the studies involving silver salts, the anionic exchange reactions occurring among cis-Ruspecies in solution was observed. Electronic properties rather than sterics were responsible for the selective formation of the mixed complex trifluoroacetate/acetate 55 (Chapter 4). The results obtained with 2nd generation systems prompted us to evaluate triisopropyl phosphite as ligand in 1st generation-type complexes. Similar synergistic effects to complex cis-Caz-1 were observed. The mixed PCy3/P(OiPr)3 complex 56 displayed cis-geometry, high thermal stability and latent character compared to the bis-phosphine analogue Ind-I (Chapter 5). Last, a catalytic and structural study of commercially available pre-catalysts M51TM and M52TM in collaboration with Umicore was carried out together with the Grela group (Chapter 6). These Hoveyda-Grubbs type pre-catalysts showed an interesting activity in ring closing metathesis, allowing the isolation of di- and tri- substituted ring-products at room temperature, as well as in cross metathesis, where some examples of biologically active compounds were obtained.

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.

Este trabalho foi desenvolvido com o propósito de investigar as reações de polimerização por metátese via abertura de anel (ROMP) assistidas pelos catalizadores desenvolvidos pelo grupo do Prof. Dr. Benedito dos Santos de Lima Neto do Instituto de Química de São Carlos (IQSC-USP), usando métodos computacionais de mecânica quântica. Portanto, este projeto foi uma combinação de resultados teóricos e experimentais. No capítulo 1, foi elucidado o mecanismo principal da reação de ROMP de norborneno por meio do iniciador catalítico [RuCl2(PPh3)2(piperidina)]. O estudo mostrou que a primeira etapa da reação implica numa associação entre o complexo iniciador e o diazoetanoato de etila (EDA), resultando na formação de uma ligação metalcarbeno. Então, essa espécie perde duas moléculas de trifenilfosfina nos passos subsequentes, sendo que a etapa determinante da velocidade da reação está associada com a saída da segunda molécula de PPh3 devido ao sinergismo eletrônico envolvendo este ligante e a molécula de piperidina. Logo após a etapa determinante da velocidade, ocorre a coordenação de uma molécula de norborneno e um similar efeito trans-sinérgico entre este monômero e o ligante piperidina ativa a catálise. No capítulo 2 está descrito o estudo do mecanismo de uma série de complexos de fórmula [RuCl2(PPh3)2(amina)] (amina = pirrolidina, piperidina, azepano, azocano). Estas aminas cíclicas possuem volumes moleculares que aumentam no sentido da pirrolidina ao azocano. A troca dessas aminas afeta substancialmente o comportamento termodinâmico desses complexos através da combinação de efeitos eletrônicos e estéricos. A investigação realizada para os compostos dessa série levou ao mesmo mecanismo elucidado para o complexo contendo piperidina e com os mesmos processos mais relevantes que são as saídas dos ligantes trifenilfosfinas. Notou-se que a formação do isômero PBQ fica comprometida ao passo que a amina no complexo [RuCl2(PPh3)2(amina)] vai ficando mais volumosa devido ao maior espaço ocupado ao redor do metal na posição apical da pirâmide de base quadrada (PBQ) e que representa uma tensão considerável na estrutura do complexo que tende a se converter, preferencialmente, à geometria bipirâmide trigonal (BpT), como acontece com o complexo iniciador [RuCl2(PPh3)2(azocano)]. Observou-se também que a saída da primeira fosfina é influenciada pelo efeito estérico provocado pela amina. Em contrapartida, a saída da segunda já é um processo regido eletronicamente e é influenciado pela capacidade doadora da amina trans-posicionada ao ligante PPh3 em um dos intermediários que é formado durante a reação. No capítulo 3 está descrita a investigação da reação de ROMP com o complexo iniciador [RuCl2(PPh3)2(piperidina)] usando as moléculas diazoetanoato de etila (EDA), diazoetanoato de benzila (BDA) e diazoetanoato de terc-butila (TDA) como fontes de carbeno para gerar a espécie in situ [Ru(=CHR)Cl2(PPh3)2(piperidina)]. Curiosamente, a troca dos carbenos também não afetou o mecanismo proposto inicialmente para a série das aminas. Os perfis termodinâmicos traçados para esses diferentes carbenos mostram que o complexo contendo o carbeno etanoato de benzila-1-ilideno (EBI) foi o que mais se diferiu, seguindo uma tendência termodinâmica distinta para a saída dos ligantes trifenilfosfina. Para as demais etapas, os três complexos apresentaram um comportamento bastante similar. O estudo dessa série mostrou-se ser mais intricado do que a série das aminas, pois esses carbenos podem afetar tanto eletrônico quanto estericamente a estrutura dos compostos em diferentes etapas do mecanismo que ainda não foram investigadas minunciosamente. / This work was developed with the purpose of investigating the ring-opening metathesis polymerization (ROMP) with catalysts developed in the research group of Prof. Dr. Benedito dos Santos Lima Neto of the Institute of Chemistry of São Carlos (IQSC-USP) by computational methods of quantum mechanics. Therefore, this project was a combination of theoretical and experimental results. In Chapter 1, the main mechanism of ROMP reaction of norbornene by the initiator complex [RuCl2(PPh3)2(piperidine)] was elucidated In this investigation, the first reaction step involves an association between the initiator complex and ethyl diazoacetate (EDA), resulting the formation of metalcarbene bond. Then, this species loses two triphenylphosphine ligands in the subsequent steps and the rate reaction is associated with the loss of the second molecule due to the electronic PPh3 synergism involving this ligand and the piperidine molecule. Immediately after the rate reaction step, the coordination of norborneno occurs and a similar trans synergistic effect between the monomer and piperidine ligand actives the catalysis. Chapter 2 describes the study of the mechanism of complexes type [RuCl2(PPh3)2(amine)] (amine = pyrrolidine, piperidine, azepane, azocane). These cyclic amines have molecular volumes that increase from pyrrolidine towards azocane. The exchange of amines affects substantially the thermodynamic behavior of these complexes by a combination of electronic and steric effects. The four compounds showed the same mechanism elucidated for the complex containing piperidine. It was noted that the formation of the PBQ isomer is avoided while the amine in the complex [RuCl2(PPh 3)2(amine)] becomes more voluminous. It was also observed that the loss of the first phosphine is influenced by the steric effect caused by the amine. In contrast, the loss of the second (phosphine) is already a process electronically-governed, and is influenced by the donor capacity of the amine ligand trans-positioned to PPh3 in one of the intermediate that is formed during the reaction. The Chapter 3 describes the investigation of the ROMP reaction using the initiator complex [RuCl2(PPh3)2(piperidine)] with the molecules ethyl diazoacetate (EDA), benzyl diazoacetate (BDA) and tert-butyl diazoacetate (TDA) to generate the carbene species [Ru(=CHR)Cl2(PPh3)2(piperidine)] in situ. Interestingly, the exchange of carbenes did not affect the mechanism originally proposed for the series of amines complexes. The complex containing the carbene ethanoate benzyl-1-ylidene (EBI) was what showed the most different thermodynamic profile from the others, following a distinct thermodynamic tendency for the loss of triphenylphosphine ligands. For the remaining steps, the three complexes showed a very similar behavior. The study of this series proved to be more intricate, because these carbenes may affect as much as sterically electronic structure of the compounds at different stages of the mechanism.

Ruthenium - catalyzed olefin metathesis is now an invaluable tool in organic synthesis. However, routes to the dominant metathesis catalysts, the second - generation Grubbs and Hoveyda catalysts (RuCl 2 (PCy 3 )(H 2 IMes)(=CHPh) and RuCl 2 (H 2 IMes)[= CH( o - O i Pr)C 6 H 4 ], respectively) are plagued with problems. The common reliance on in situ methods to generate the N - heterocyclic carbene H 2 IMes severely limits stoichiometric control, and results in contamination by byproducts, some of which are readily overlooked, and some of which are difficult to remove. Both can affect batch - to - batch reproducibility in catalysis. This thesis work demonstrated that widespread perceptions of the instability of free H 2 IMes are erroneous, and that the free carbene is readily handled under water - free conditions. Clean, convenient, near - quantitative routes were developed to these second - generation catalysts by ligand exchange of their first - gen eration counterparts RuCl 2 (PCy 3 ) 2 (=CHPh), RuCl 2 (PCy 3 )[= CH( o - O i Pr)C 6 H 4 ] with free H 2 IMes, with sequestration of the liberated phosphine by an ion - exchange resin. A second focus was examination of a much - debated hypothesis in olefin metathesis: that is, the extent to which the high productivity of the Hoveyda catalysts reflects re - uptake of the styrenyl ether functionality released in the initial cycle of metathesis. Current evidence for and against this "boomerang" hypothesis is critically examined, and new approaches to examining its operation are described. Specifically, the rate of decomposition, vs. re - uptake, is examined for the active species RuCl 2 (PCy 3 )(=CH 2 ), and background exchange of the parent catalyst with free styrenyl ether is measured by use of a 13 C - labelled styrenyl ether. These studies confirm the relevance of the boomerang mechanism for first - generation Hoveyda catalysts.

Este trabalho foi desenvolvido com o propósito de investigar as reações de polimerização por metátese via abertura de anel (ROMP) assistidas pelos catalizadores desenvolvidos pelo grupo do Prof. Dr. Benedito dos Santos de Lima Neto do Instituto de Química de São Carlos (IQSC-USP), usando métodos computacionais de mecânica quântica. Portanto, este projeto foi uma combinação de resultados teóricos e experimentais. No capítulo 1, foi elucidado o mecanismo principal da reação de ROMP de norborneno por meio do iniciador catalítico [RuCl2(PPh3)2(piperidina)]. O estudo mostrou que a primeira etapa da reação implica numa associação entre o complexo iniciador e o diazoetanoato de etila (EDA), resultando na formação de uma ligação metalcarbeno. Então, essa espécie perde duas moléculas de trifenilfosfina nos passos subsequentes, sendo que a etapa determinante da velocidade da reação está associada com a saída da segunda molécula de PPh3 devido ao sinergismo eletrônico envolvendo este ligante e a molécula de piperidina. Logo após a etapa determinante da velocidade, ocorre a coordenação de uma molécula de norborneno e um similar efeito trans-sinérgico entre este monômero e o ligante piperidina ativa a catálise. No capítulo 2 está descrito o estudo do mecanismo de uma série de complexos de fórmula [RuCl2(PPh3)2(amina)] (amina = pirrolidina, piperidina, azepano, azocano). Estas aminas cíclicas possuem volumes moleculares que aumentam no sentido da pirrolidina ao azocano. A troca dessas aminas afeta substancialmente o comportamento termodinâmico desses complexos através da combinação de efeitos eletrônicos e estéricos. A investigação realizada para os compostos dessa série levou ao mesmo mecanismo elucidado para o complexo contendo piperidina e com os mesmos processos mais relevantes que são as saídas dos ligantes trifenilfosfinas. Notou-se que a formação do isômero PBQ fica comprometida ao passo que a amina no complexo [RuCl2(PPh3)2(amina)] vai ficando mais volumosa devido ao maior espaço ocupado ao redor do metal na posição apical da pirâmide de base quadrada (PBQ) e que representa uma tensão considerável na estrutura do complexo que tende a se converter, preferencialmente, à geometria bipirâmide trigonal (BpT), como acontece com o complexo iniciador [RuCl2(PPh3)2(azocano)]. Observou-se também que a saída da primeira fosfina é influenciada pelo efeito estérico provocado pela amina. Em contrapartida, a saída da segunda já é um processo regido eletronicamente e é influenciado pela capacidade doadora da amina trans-posicionada ao ligante PPh3 em um dos intermediários que é formado durante a reação. No capítulo 3 está descrita a investigação da reação de ROMP com o complexo iniciador [RuCl2(PPh3)2(piperidina)] usando as moléculas diazoetanoato de etila (EDA), diazoetanoato de benzila (BDA) e diazoetanoato de terc-butila (TDA) como fontes de carbeno para gerar a espécie in situ [Ru(=CHR)Cl2(PPh3)2(piperidina)]. Curiosamente, a troca dos carbenos também não afetou o mecanismo proposto inicialmente para a série das aminas. Os perfis termodinâmicos traçados para esses diferentes carbenos mostram que o complexo contendo o carbeno etanoato de benzila-1-ilideno (EBI) foi o que mais se diferiu, seguindo uma tendência termodinâmica distinta para a saída dos ligantes trifenilfosfina. Para as demais etapas, os três complexos apresentaram um comportamento bastante similar. O estudo dessa série mostrou-se ser mais intricado do que a série das aminas, pois esses carbenos podem afetar tanto eletrônico quanto estericamente a estrutura dos compostos em diferentes etapas do mecanismo que ainda não foram investigadas minunciosamente. / This work was developed with the purpose of investigating the ring-opening metathesis polymerization (ROMP) with catalysts developed in the research group of Prof. Dr. Benedito dos Santos Lima Neto of the Institute of Chemistry of São Carlos (IQSC-USP) by computational methods of quantum mechanics. Therefore, this project was a combination of theoretical and experimental results. In Chapter 1, the main mechanism of ROMP reaction of norbornene by the initiator complex [RuCl2(PPh3)2(piperidine)] was elucidated In this investigation, the first reaction step involves an association between the initiator complex and ethyl diazoacetate (EDA), resulting the formation of metalcarbene bond. Then, this species loses two triphenylphosphine ligands in the subsequent steps and the rate reaction is associated with the loss of the second molecule due to the electronic PPh3 synergism involving this ligand and the piperidine molecule. Immediately after the rate reaction step, the coordination of norborneno occurs and a similar trans synergistic effect between the monomer and piperidine ligand actives the catalysis. Chapter 2 describes the study of the mechanism of complexes type [RuCl2(PPh3)2(amine)] (amine = pyrrolidine, piperidine, azepane, azocane). These cyclic amines have molecular volumes that increase from pyrrolidine towards azocane. The exchange of amines affects substantially the thermodynamic behavior of these complexes by a combination of electronic and steric effects. The four compounds showed the same mechanism elucidated for the complex containing piperidine. It was noted that the formation of the PBQ isomer is avoided while the amine in the complex [RuCl2(PPh 3)2(amine)] becomes more voluminous. It was also observed that the loss of the first phosphine is influenced by the steric effect caused by the amine. In contrast, the loss of the second (phosphine) is already a process electronically-governed, and is influenced by the donor capacity of the amine ligand trans-positioned to PPh3 in one of the intermediate that is formed during the reaction. The Chapter 3 describes the investigation of the ROMP reaction using the initiator complex [RuCl2(PPh3)2(piperidine)] with the molecules ethyl diazoacetate (EDA), benzyl diazoacetate (BDA) and tert-butyl diazoacetate (TDA) to generate the carbene species [Ru(=CHR)Cl2(PPh3)2(piperidine)] in situ. Interestingly, the exchange of carbenes did not affect the mechanism originally proposed for the series of amines complexes. The complex containing the carbene ethanoate benzyl-1-ylidene (EBI) was what showed the most different thermodynamic profile from the others, following a distinct thermodynamic tendency for the loss of triphenylphosphine ligands. For the remaining steps, the three complexes showed a very similar behavior. The study of this series proved to be more intricate, because these carbenes may affect as much as sterically electronic structure of the compounds at different stages of the mechanism.

Orientador: Antonio José Gomez Cobo / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química / Made available in DSpace on 2018-08-26T01:50:26Z (GMT). No. of bitstreams: 1 Queiroz_CarlaMoreiraSantos_M.pdf: 3283587 bytes, checksum: e066f63e41c49394fe6b4a9667355aab (MD5) Previous issue date: 2014 / 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 Quimicos e Informatica / Mestra em Engenharia Química

Ruthenium - catalyzed olefin metathesis is now an invaluable tool in organic synthesis. However, routes to the dominant metathesis catalysts, the second - generation Grubbs and Hoveyda catalysts (RuCl 2 (PCy 3 )(H 2 IMes)(=CHPh) and RuCl 2 (H 2 IMes)[= CH( o - O i Pr)C 6 H 4 ], respectively) are plagued with problems. The common reliance on in situ methods to generate the N - heterocyclic carbene H 2 IMes severely limits stoichiometric control, and results in contamination by byproducts, some of which are readily overlooked, and some of which are difficult to remove. Both can affect batch - to - batch reproducibility in catalysis. This thesis work demonstrated that widespread perceptions of the instability of free H 2 IMes are erroneous, and that the free carbene is readily handled under water - free conditions. Clean, convenient, near - quantitative routes were developed to these second - generation catalysts by ligand exchange of their first - gen eration counterparts RuCl 2 (PCy 3 ) 2 (=CHPh), RuCl 2 (PCy 3 )[= CH( o - O i Pr)C 6 H 4 ] with free H 2 IMes, with sequestration of the liberated phosphine by an ion - exchange resin. A second focus was examination of a much - debated hypothesis in olefin metathesis: that is, the extent to which the high productivity of the Hoveyda catalysts reflects re - uptake of the styrenyl ether functionality released in the initial cycle of metathesis. Current evidence for and against this "boomerang" hypothesis is critically examined, and new approaches to examining its operation are described. Specifically, the rate of decomposition, vs. re - uptake, is examined for the active species RuCl 2 (PCy 3 )(=CH 2 ), and background exchange of the parent catalyst with free styrenyl ether is measured by use of a 13 C - labelled styrenyl ether. These studies confirm the relevance of the boomerang mechanism for first - generation Hoveyda catalysts.

Orientador: Antonio Jose Gomez Cobo, Adler Gomes Moura / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica / Made available in DSpace on 2018-08-09T09:24:50Z (GMT). No. of bitstreams: 1 Silva_GiselliLuziaFerreirada_M.pdf: 3889907 bytes, checksum: 3303dab5e7186f9976c1867fad4c6591 (MD5) Previous issue date: 2007 / 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 Quimicos e Informatica / Mestre em Engenharia Química