published_or_final_version / abstract / Chemistry / Doctoral / Doctor of Philosophy

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The primary goal of this study is to develop novel metal catalyzed multicomponent reaction methods to generate imidazoles and their derivatives. This is directed towards the assembly of poly-substituted imidazoles, imidazolones and imidazole-containing pi-conjugated polymers. These products are generated in one-pot from such basic components as imines, acid chlorides, carbon monoxide, and/or organostannanes, via the use of palladium catalysis. / In Chapter 2, the design of a new palladium catalyzed synthesis of highly substituted imidazoles from imines and acid chlorides is described. This reaction involves the palladium catalyzed generation of 1, 3-oxazolium-5-oxides (Munchnones); which are trapped with N-tosyl substituted imines via a 1, 3 dipolar cycloaddition reaction to form the final products. Overall, this provides a one step method to assemble imidazoles from imines and acid chlorides with excellent regiochemical control. The versatility of this process is demonstrated by the assembly of diversely substituted imidazoles, including those with aryl, alkyl, heterocyclic and vinyl substituents. / Chapter 3 describes a new, palladium catalyzed, five component coupling of imines, chloroformates, organotin reagents, carbon monoxide and ammonium acetate to form imidazolones. The key step in this process is the efficient formation of ketocarbamates via the carbonylative cross coupling type reaction of imines, chloroformates and organostannanes. These products can be easily converted into imidazolones via a cyclocondensation with ammonium acetate. / The synthesis of pi-conjugated imidazole-containing polymers is described in Chapter 4. This process is designed based upon our previous studies on palladium catalyzed multicomponent synthesis of imidazoles, developed in Chapter 2. It is shown that bifunctional monomers such as di-imines, di-acid chlorides and di-N-tosylimines can be coupled together to assemble pi-conjugated imidazole-containing oligomers and polymers utilizing this same palladium catalyzed reaction. This approach was used to create a novel library of conjugated imidazole polymers. By modifying the substituents on the polymer structures, the UV-vis absorbance and fluorescence excitation/emission spectra of these compounds are varied over a range of 150 nm. / In Chapter 5, the palladium catalyzed multicomponent polymerization is discussed in more detail. This includes the analysis of the end groups on the polymer backbone, as well as mechanistic studies into how the polymerization is terminated. These results suggest that the sulfinate anion liberated upon N-tosylimine cycloaddition may be non-innocent in this polymerization, and its presence could lead to termination of the growing polymer chain.

Actualmente, el interés industrial de los productos carbonilados ha atraído la atención de los científicos hacia el desarrollo de nuevos sistemas catalíticos eficientes. La reacción de alcoxicarbonilación de vinil arenos ha sido considerada una ruta alternativa para la obtención de ácidos 2-aril propiónicos, la clase más importante de antiinflamatorios no esteroides. Por otro lado, los copolímeros de monóxido de carbono y olefinas son materiales de gran interés industrial debido a su aplicación potencial como termoplásticos. El concepto de economía atómica ha influenciado el desarrollo de los procesos catalíticos industriales. El máximo aprovechamiento de los reactivos y la disminución de residuos han hecho de la catálisis un proceso altamente atractivo en el marco de tecnologías de desarrollo sostenible. El conocimiento de los mecanismos operantes en las reacciones de carbonización es de gran importancia para el diseño de nuevos sistemas catalíticos altamente efectivos.Basándose en las consideraciones anteriores, el primer objetivo de esta tesis se ha centrado en el desarrollo de nuevos sistemas catalíticos de paladio y su aplicación en la metoxicarbonilación asimétrica de vinil arenos, con el fin de obtener altas regio- y enantioselectividades, simultáneamente. Un segundo objetivo, ha sido el desarrollo de nuevos catalizadores catiónicos de paladio y el estudio de su actividad catalítica en las reacciones de co- y terpolimerización de CO/etileno/propileno. Para alcanzar el primer objetivo, se ha planteado la exploración de complejos de paladio modificados con fosfinas monodentadas y fosfinas bidentadas. Con el fin de conocer mejor ambos sistemas e identificar algunos intermedios de reacción, se llevó a cabo un estudio de la metoxicarbonilación de estireno bajo condiciones similares a las catalíticas. Para lograr el segundo objetivo, se han sintetizado nuevos catalizadores de paladio catiónicos modificados con difosfinas derivadas de D-(+)-xilofuranosa. Los nuevos complejos se aplicaron en las reacciones de copolimerización de CO/etileno y CO/propileno, así como, en la terpolimerización CO/etileno/propileno. Después de revisar los antecedentes bibliográficos en la introducción y planteados los objetivos, en el Capítulo 2 "Palladium complexes bearing monodentate ligands in asymmetric methoxycarbonylation of vinyl arenes" se presenta la síntesis y caracterización de complejos de paladio modificados con fosfinas cíclicas quirales, tales como, fosfetanos, fosfolanos y fosfepinos. Estos nuevos complejos se aplican en la metoxicarbonilación asimétrica de vinil arenos, mostrando que la actividad decrece a medida que aumenta el número de miembros del ciclo fosforado.En el Capítulo 3 "Palladium complexes bearing bidentate ligands in asymmetric methoxycarbonylation of styrene" se describe la aplicación de complejos de paladio neutros y catiónicos modificados con ligandos bidentados, en la metoxicarbonilación asimétrica de estireno. Los ligandos ultilizados en este capítulo presentan propiedades estéricas y electrónicas diferentes. En términos generales, para los sistemas neutros y catiónicos, la presencia de sustituyentes electroatractores en los grupos fenilos del ligando, tiene una gran influencia sobre la regioselectividad de la reacción hacia el producto ramificado. En el Capítulo 4 "Mechanistic aspects of the methoxycarbonylation of styrene" se discuten algunos aspectos mecanísticos de la metoxicarbonilación de estireno, utilizando complejos de paladio modificados con ligandos monodentados y bidentados. La reactividad de los complejos con los diferentes componentes del sistema catalítico, se llevó a cabo paso a paso y mediante experimentos in situ en condiciones similares a las empleadas en la catálisis.Finalmente en el Capítulo 5 "Cationic palladium complexes bearing xylofuranose-derivative diphosphines in CO/ethene/propene co- and terpolymerisation reactions" se describe la síntesis de una difosfina derivada de la D-(+)-xilofuranosa, así como la síntesis y caracterización de nuevos complejos neutros y catiónicos. Los resultados obtenidos han sido comparados con los complejos análogos modificados con dppp y o-MeO-dppp, con el fin de discutir cómo afectan los efectos electrónicos y la rigidez del ligando en la copolimerización perfectamente alternada. / Nowadays the industrial interest of the carbonylated products has attracted the attention of scientists towards the development of new efficient catalytic systems. The alcoxycarbonylation of vinyl arenes has been considered an alternative route to obtain 2-aryl propionic acids, the most important class of non-steroidal anti-inflammatory drugs. Copolymers formed by carbon monoxide and alkenes are materials of industrial interest due to their potential application as engineering thermoplastics. The concept of atomic economy has influenced the development of industrial catalytic processes. The waste diminishing by the complete conversion of reagents into the desired product in a catalytic process introduce the homogeneous catalysis as an attractive sustainable technology. The knowledge of the carbonylation mechanisms is of great importance for the design of new highly efficient catalytic systems.Based on these considerations, the first objective of this thesis was to develop new catalytic palladium systems and its application in the asymmetric methoxycarbonylation of vinyl arenes, in order to obtain high regio-and enantioselectivities simultaneously. The second objective was to synthesise new cationic palladium complexes and to study the activity in the copolymerisation reaction. To achieve the first objective, palladium complexes modified with monodentate and bidentate phosphine ligands were explored. In order to know more about the influence of the nature of the ligand on the mechanism, a mechanistic study under similar conditions to those used in the catalysis was performed. To achieve the second objective new cationic palladium complexes modified with diphosphine ligands derived from D-(+)-xylofuranose were synthesised. The new complexes were tested in the CO/ethene, CO/propene copolymerisation reaction, as well as in the CO/ethene/propene terpolymerisation process. Chapter 2 "Palladium complexes bearing monodentate ligands in asymmetric methoxycarbonylation of vinyl arenes" shows the use of chiral monodentate cyclic phosphines, such as phosphetane, phospholane and binepine, in the palladium-catalysed asymmetric methoxycarbonylation of vinyl arenes. New neutral palladium complexes are synthesised and characterised by multinuclear NMR spectroscopy. This new complexes were showed a decreased in the catalytic activity when increased the number of the phosphorus membered ring.Chapter 3 "Palladium complexes bearing bidentate ligands in asymmetric methoxycarbonylation of vinyl arenes" describes the synthesis of neutral and cationic complexes bearing bidentate ligands with different electronic and steric properties and its application in the methoxycarbonylation of vinyl arenes. In general terms, it was observed that the presence of electron withdrawing groups in the phenyl moiety of the ligand has an influence on the regioselectivity of the reaction to the branched ester. Chapter 4 "Mechanistic aspects of the methoxycarbonylation of styrene" discusses mechanistic aspects of the methoxycarbonylation reaction. In situ studies are performed under similar conditions to those used in the catalytic studies. The studies are focuses in palladium systems modified with mono- and bidentate ligands, in order to establish comparison between them. The characterisation of some species by NMR spectroscopy is showed.Finally in Chapter 5 "Cationic palladium complexes bearing xylofuranose-derivative diphosphines in CO/ethene/propene co- and terpolymerisation reactions" it was discussed the electronic effects of xylose-derivatives diphosphines ligands in the CO/ethene/propene co- and ter-polymerisation processes. The new diphosphines o-MeO-xylophos is synthesised. A series of new neutral and cationic palladium complexes bearing xylophos and o-MeO-xylophos were synthesised and fully characterised by multinuclear NMR techniques. The catalytic polymerisation reactions were performed in methanol using the cationic complexes and are compared to the reaction catalysed by analogous complexes bearing dppp and o-MeO-dppp to determine the electronic effects and the backbone rigidity on the perfectly alternating copolymerisation.

Enormous efforts have been made to optimize the Pd-catalyzed Suzuki-Miyaura reaction, but there is to date no generally useful protocol and forcing conditions are often required. One reaction variable that has often been neglected is the extent to which the supposed catalysts, bisphosphinepalladium(0) complexes, are actually formed from the variety of popular precatalysts used. There is in fact little evidence that these precursors produce bis-ligated Pd(0) complexes and it is possible that the rate limiting factor may be catalyst formation. If so, then the development of an optimized method for forming these catalytic species would be a significant contribution to this field. The following work describes research efforts to determine the optimum conditions to generate PdL2 (L = PCy3, PMeBut2, PBut3) cleanly and quantitatively from Pd(3-C3H5)(5-C5H5) and Pd(3-1-Ph-C3H5)(5-C5H5). Furthermore, the conditions under which PdL3 species may exist in equilibrium with the PdL2 species are defined. NMR studies indicate that while Pd(PBut3)2 shows no inclination to increase its coordination number, Pd(PCy3)2 and Pd(PMeBut2)2 react with added phosphine to form 3:1 compounds. Equilibrium constants for dissociation of the PdL3 compounds were measured over a range of temperatures, yielding the thermodynamic parameters of dissociation and estimated Pd-P bond dissociation energies. Additionally, the generation of heteroleptic species serve to confirm the existence of 3:1 compounds. A kinetic study of the oxidative addition of PhBr to Pd(PCy3)2 was also performed. It was found that oxidative addition was first order in palladium, but that added bromide had no effect on the rate of oxidative addition. Added PCy3 inhibited oxidative addition, possibly due to the conversion of palladium(0) into the less active 3:1 compound. The formation of the catalytically less active 3:1 compounds has serious implications for many catalytic cross-coupling processes which involve catalyst formation via the slow reduction of palladium(II) in the presence of excess phosphine; for many systems, relatively little of the added palladium may actually be present as the active bisphosphinepalladium(0) compound. / Thesis (Ph.D, Chemistry) -- Queen's University, 2008-12-08 13:24:50.825

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The ligands 2-cyanocyclopentyldiphenylphosphine and 2-cyanocyclohesyldiphenylphosphine were synthesized from 1-cyanocyclopentene and 1cyanocyclohexene by addition reactions using diphenylphosphine and aqueous base as the catalyst. These ligands reacted with Pt(II) and Pd(II) salts to yield complexes of the stoichiometry MX2L2 (X = C1, Br). In these complexes the ligands were found to function as monodentate phosphines. Infrared spectroscopic evidence suggested that the platinum complex was of cis and the palladium complexes were of trans geometries.The reactions of the ligands 2-cyanocyclopentyldiphenylphosphine and 2-cyanocyclohexyldiphenylphosphine or the ligand 2-cyanoethyldiphenylphosphine with the complexes dimethyyl(cyclooctadiene)platinun(II) or methyl) (chloro) (cyclooctadiene) platinum(II) resulted in complexes of the stoichiometries Pt(CH3)2L2 and Pt(CH3)(C1)L2. In these complexes the ligands also functioned as monodentate phosphines. hmr and far infrared spectroscopic evidence suggested that the dimethylplatinuin(II) complexes were cis and the (methyl)(chloro)platinum(II) complexes were trans.A complex of the stoichiometry Pd2Cl4(Ph2PC6H10CN)2 was isolated from the reaction of a 1:1 mole ratio of PdC12 with Ph2PC6H10CN. Far infrared and Raman spectroscopic evidence 'suggested that the complex was a chlorine bridged dieter with the ligands at symmetrical positions. The nitrile groups in this complex reacted rapidly with alcohols to yield monomeric imino ether complexes.The Pt(CH3)(C1)L2 complexes reacted with AgPF6 to yield cationic salts of the stoichiometry [Pt(CH3)L2]n+n with one ligand in each [Pt(CH3)L2]+ unit presumably serving as a bridging ligand and the other as a monodentate phosphine. The coordinated nitrite groups in these complexes reacted slowly with methanol to yield amino ether complexes.

We plan to study the attachment of a cationic tetranuclear palladium II-based macrocyclic square onto a planar gold surface or a gold nanoparticle. To understand the possible mechanisms of attachment of inorganic molecular square to gold we will see if certain related salts can cause an induced aggregation of nanoparticles.The replacement of the surface-passivated citrate layer on the gold nanoparticles can be characterized by infrared spectroscopy and shifts in the surface plasmon resonance band. Consequently, if it can bond gold nanoparticles via electrostatic interactions, then it may be possible that the square can attach to a planar gold surface by a similar mechanism.Infrared spectra of the aggregated nanoparticles will be compared to those obtained using the attachment of molecular square on a planar gold surface. By comparing.infrared spectra it may be possible to determine by what mechanism the square is attaching to gold. / Department of Chemistry

The regioselectivity in Pd(0)-catalyzed direct arylation of pyrrole, thiophene, and indole can be improved by blocking some of the reactive sites with a chloride group, leading to increased yields of the desired regioisomers. Competition experiments and computational studies show that the blocking group also activates the substrates toward arylation. Due to the activated nature of chlorinated heteroaromatics, rare and sought after regioisomers, such as 3-arylthiophenes, can be obtained under mild conditions in good yields. Chlorine-bearing thiophenes arylated at C3 and C4 have the potential to undergo controlled regioregular polymerization under conditions developed in the field of polythiophene chemistry. Mechanistic studies support the hypothesis that the arylation of the substrates under investigation likely proceeds via the CMD transition state.