Thesis (Ph. D.)--University of Texas at El Paso, 2009. / Title from title screen. Vita. CD-ROM. Includes bibliographical references. Also available online.

Thesis (Ph. D.)--University of Texas at Austin, 2008. / Vita. Includes bibliographical references.

Includes bibliographical references.

Thesis (Ph. D.)--University of Alberta, 2010. / Title from pdf file main screen (viewed on June 28, 2010). A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Doctor of Philosophy, Department of Chemistry, University of Alberta. Includes bibliographical references.

xx, 204 p. A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number. / Efforts toward developing improved methods of synthesizing acrylamides are ongoing. Several homogeneous organometallic and coordination complexes have proven useful in catalytic acrylonitrile hydration; however, none of these complexes have been tested in the hydration of cyanohydrins used to synthesize substituted acrylamides. This dissertation describes the reactivity of molybdocene and Pt phosphinito nitrile hydration catalysts toward cyanohydrin substrates and the effect of Cp ring substituents on aqueous molybdocene chemistry. Chapter I identifies the motivation for developing a transition metal-catalyzed process for cyanohydrin hydration and the strategy used to improve on the reactivity of molybdocene catalysts. Chapter II reports the effect of cyclopentadienyl ring substituents on the electronic and geometric structure, solution behavior, and hydrolytic activity of molybdocenes. To examine the effect of Cp ring substituents, ansa -molybdocenes containing the fragment {C 2 Me 4 (C 5 H 4 ) 2 }Mo 2+ were compared to non-bridged molybdocenes containing (C 5 H 5 ) 2 Mo 2+ and (C 5 H 4 Me) 2 Mo 2+ . Addition of a tetramethylethylene-bridge decreases the electron density on the Mo center and exerts a small effect on the structure of the metallocene. However, the catalytic activity of the molybdocene catalysts is unchanged or slowed because of counteractive effects on the bound nucleophile and electrophile. Although adding substituents to the Cp rings did not change the catalytic activity of the molybdocene, the substituents led to significant changes in the equilibrium behavior. The equilibria have practical consequences that warrant investigation. Chapters III and IV chronicle the effect of Cp ring substituents on the monomer-dimer equilibria and the acidity of the molybdocene complexes, respectively. Interestingly, the monomer-dimer equilibrium established by ansa -{C 2 Me 4 (C 5 H 4 ) 2 }Mo(OH)(OH 2 ) + exhibits a strong solvent dependence. New equilibrium schemes are reported for the ansa and non- ansa complexes. Chapter V describes the reactivity of the molybdocene and Pt phosphinito catalysts toward cyanohydrins. Both catalysts gave unsatisfactory results; however, the à à à à à ±-hydroxy substituent of cyanohydrins facilitates nitrile hydration. The low reactivity exhibited by these systems was due to liberation of hydrogen cyanide from the cyanohydrin leading to acute poisoning of either catalyst. As discussed in Chapter VI, this study will expedite the innovation of new catalysts that are better suited to overcome the challenges associated with cyanohydrin hydration. This dissertation includes previously published and unpublished co-authored material. / Adviser: David R. Tyler

Orientador: Elizabete Jordão, Wagner Alves Carvalho / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química / Made available in DSpace on 2018-08-17T00:25:36Z (GMT). No. of bitstreams: 1 MartinezJorrin_Michael_M.pdf: 2708172 bytes, checksum: faa00379224d0c77aa738becd7bd1615 (MD5) Previous issue date: 2010 / Resumo: Foram avaliados os catalisadores de Ru suportados em Nióbia, Sílica e Alumina na Hidrogenólise seletiva de Glicerol para a obtenção de propanodióis (1,2 e 1,3 - Propanodiol). O método de preparação utilizado para os três catalisadores foi o de impregnação úmida partindo-se de uma solução aquosa do sal precursor RuCl3.1,37H2O cuja porcentagem em peso do metal ativo foi de 2%. Os catalisadores foram caracterizados pelo método da Área Superficial Específica (método de B.E.T) e Microscopia Eletrônica de Varredura (M.E. V) com EDX. O maior valor de área superficial específica foi alcançado pelo catalisador de Ru/SiO2 seguido pelo catalisador de Ru/Al2O3, mas isto não foi o fator determinante para escolha do melhor sistema catalítico em termos de seletividade para o 1,2-propanodiol e conversão de substrato. A reação de hidrogenólise foi conduzida em um reator Parr, em atmosfera de H2 a qual foi avaliada ás temperaturas de 120°C, 140°C e 200°C, pressão de 50 bar, 0,75 g do catalisador e uma solução aquosa de glicerol de 0,2 g/mL, durante 6 h. Foram ainda realizados testes exploratórios variando a pressão (30 bar) e a quantidade de catalisador( 1,5 g), para avaliar a sua influência. Os resultados dos testes cinéticos mostraram que com os catalisadores utilizados ocorrem reações de degradação envolvendo a ruptura de ligações C-C e conseqüente formação de produtos tais como etilenoglicol, propanol, e outros em menores quantidades tais como metanol, etanol, e metanos que não puderam ser identificados pelas técnicas analíticas utilizadas neste trabalho. O melhor desempenho foi alcançado pelo sistema catalítico Ru/Al2O3(1,5 g) com 97% de seletividade para 1,2-propanodiol e conversão de substrato de 52% à temperatura de 120ºC e pressão de 50 bar de H2 em presença de uma resina de troca iônica (Amberlyst15). Isto pode estar associado à acidez do meio proporcionada pela combinação do suporte (Al2O3) e o aditivo utilizado / Abstract: Ru/SiO2, Ru/Nb2O5 and Ru/Al2O3 catalysts were applied to the hydrogenolysis of glycerol to propanediols( 1,2 and 1,3PD). They were prepared by wet impregnation with an aqueous solution containing RuCl3.1,37H2O. The Ruthenium catalysts were loading in the range of 0,2% wt supported on silica, niobium and alumin oxide and characterized by transmission electronic microscopy(TEM-EDX) and the BET method (N2 adsorption). The Ru/SiO2 catalyst showed the higher specific surface area. Moreover, the test activity revealed that it wasn't the main factor to chose the best catalyst performance. Hydrogenolysis of glycerol was carried out in a high pressure Parr reactor. The standard procedure was as follows, the substrate, 100 mL 20wt% glycerol aqueous solution, and 0,75 g supported catalyst were used in every run. The reaction conditions were 120ºC, 140ºC and 200ºC, 50 bar hydrogen pressure and 6 h reaction time. The effect of hydrogen pressure and the catalyst weight were studied at constant reaction temperature of 120ºC, and were varied to 30 bar and 1,5 g of catalyst respectively. The reaction results indicated that Ru/Al2O3 showed higher performance (with a 97% selectivity of 1,2 PD at 52% conversion ) at reaction temperature of 120ºC, 50 bar hydrogen pressure with the use of ion-exchange resin (Amberlyst15). This may be due to the acidity produced by combination of the support (Al2O3) and the additive used. The kinetic test results showed that catalysts used promoted degradation reactions involving C-C bonds cleavage, which led to degradative products such as ethylene glycol, propanol, and others in smaller quantities such as methanol, ethanol, and methane which were impossible to indentify by the analytical techniques used in this work / Mestrado / Sistemas de Processos Quimicos e Informatica / Mestre em Engenharia Química

M.Sc. / This study focused on the synthesis and evaluation of phosphine ligands with multiple functional ities. Polar ligands suitable for use in homogeneous catalysis in aqueous/organic systems were synthesised, as were ligands incorporating a boron atom in an intramolecular Lewis acid-Lewis base interaction with the phosphorus atom. A malonate moiety was readily incorporated into a phosphorus starting material, and derivatives were obtained by reduction of the ester groups. The polar diol products were reacted with 1,4-butanesultone which made them water soluble and thus ideal for biphasic catalysis. Wittig chemistry was employed to introduce alkenes of varying electronic nature into a phosphorus-containing aldehyde starting material. The catalysed hydroboration reaction making use of diboron reagents was used to introduce a boron functionality into the resulting a, n-unsaturated ester phosphine I igands. All of the ligands produced were tested in transition metal-catalysed reactions, namely the Heck reaction, the Suzuki reaction, the Stille reaction, the carboxymethylation reaction and the hydroformylation reaction. The polar and water soluble ligands all showed comparable or improved yields to the standard benchmark triphenylphosphine ligand in organic, biphasic and ionic liquid media. The electronic nature of the alkene ligands largely dictated the activities observed in the Heck, Suzuki and Stille reactions. The electron rich ligands showed improved activities in the Heck reaction, while the electron poor ligands showed improved activities in the Suzuki reaction. In contrast, the Stille reaction seemed to be more affected by the steric demands of the ligands rather than by electronic considerations. It was also found that the boron containing ligands showed an enhanced activity in comparison to the boron free unsaturated and saturated ester ligands. This enhancement was directly ascribable to the Lewis acidic boron atom. This study allowed the synthesis of a range of functionally varying phosphine ligands which where shown to influence transition metal-catalysed reactions based specifically on the functionality present.

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

Development of selective artificial metalloenzymes by combining the biological concepts for selective recognition with those of transition metal catalysis has received much attention during the last decade. Targeting covalent incorporation of organometallic catalysts into proteins, we explored site-selective covalent coupling of phosphane and N–containing ligands. The successful approach for incorporation of phosphane ligands we report herein consists of site-specific covalent coupling of a maleimide functionalized hydrazide into proteins, followed by coupling of aldehyde functionalized phosphanes via a hydrazone linkage. Site selective incorporation of N–containing ligands was obtained by coupling maleimide functionalized N–ligands to proteins via Michael addition to the maleimide double bond. These two methods can be easily applied to virtually any protein displaying a single reactive cysteine and allows a wide range of possibilities in terms of cofactor design. Site-specific covalent incorporation of transition metal complexes of phosphane ligands into proteins was successfully obtained. The success of the approach is influenced by several factors like the metal precursor, the phosphane type and the protein scaffold. Metal complexes of 5–maleimido–1,10–phenanthroline modified proteins were formed in situ, via addition of a metal precursor to the phenanthroline modified proteins or by coupling preformed metal complexes to proteins via Michael addition of the thiol group from a cysteine residue to the maleimide double bond of the N-ligand. These successful coupling methods enable the use of a wide range of protein structures as templates for the preparation of artificial transition metalloenzymes, which opens the way to full exploration of the power of selective molecular recognition of proteins in transition metal catalysis.

The present dissertation research is largely focused on the methods to synthesize highly substituted allene derivatives from alkynes in conjugation with carbonyl-containing functional groups. A key aspect of this research involves methylcyclopentadienylmanganese dicarbonyl (MMD), an inexpensive and air-stable organometallic auxiliary linked to alkynyl carbonyls via an η2-bond. This auxiliary influences bond formation to achieve enhanced stereoselectivity without itself undergoing any chemical transformation. Chapter 1 accounts various examples of such transition metal auxiliaries including MMD. Typically conjugated alkynyl carbonyls do not isomerize to thermodynamically less favored allenes. However, with the MMD auxiliary in place, alkynyl carbonyl compounds undergo facile 1,3-proton shifts in the presence of a mild base to produce allene isomers. Although allenyl aldehydes are important building blocks, we note that direct methods to prepare them nonracemically are not known. Chapter 2 describes the development of a new cinchonine-based phase transfer catalyst to access non-racemic allenyl aldehydes from MMD-complexed alkynyl aldehydes. With the manganese auxiliary in place, nonracemic allenyl aldehydes were obtained in a weakly basic biphasic reaction system via enantioselective protonation conditions. Chapter 3 describes the second use of the MMD auxiliary to direct nucleophilic addition reactions to allenyl aldehydes for the preparation of 2,3-allenols diastereoselectively. In the absence of the MMD auxiliary, nucleophilic reactions to the carbonyl group of axially chiral allenyl aldehydes is poorly diastereoselective, which is a long-standing problem. We observed that, in addition to leading to non-racemic allenyl aldehydes, the MMD auxiliary could also be used to improve diastereoselectivity in carbonyl additions due to its proximal position on the 2,3-bond of the allenyl aldehyde. Chapter 4 describes the use of allenyl esters as metathesis quenching agents. It was observed that the addition of an allenyl ester after a metathesis reaction was complete; facilitate the removal of most ruthenium metal impurities using simple silica chromatographic purification. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2017. / FAU Electronic Theses and Dissertations Collection