This report is an investigation of regioselectivity in transition metal catalyzed ring-opening reactions involving unsymmetrical oxabicycles, specifically with a substituent at the C1 position. This report also provides the details of the work conducted towards the preparation of various oxanorbornadienes and their precursors. A large number of reactions have been developed using various transition metal catalysts on oxabicyclic alkenes to form functionalized organic scaffolds. However, most of the literature is limited to symmetrical substrates. Introduction of a substituent at the bridgehead carbon of the bicyclic ring makes the molecule unsymmetrical. The implications of loss of the plane of symmetry in C1 substituted oxabicyclic ring are manifested in interesting ways during various metal catalyzed reactions. The fundamental basis for the current work is to study the consequences of transition metal catalyzed ring opening reactions of unsymmetrical bicyclic alkenes. The reactivity of a wide range of C1 substituted benzoxanorbornadienes and oxanorbornadienes in palladium and nickel-catalyzed ring opening reactions was explored. The palladium catalyzed ring opening reaction of both electron rich and electron deficient C1 substituted benzoxanorbornadienes are optimized. The ring opening reactions with electron withdrawing C1 substituent resulted in formation of substituted naphthalene-1-carboxylic acid methyl ester derivatives in up to 85% yield. Electron donating substituents on the C1 position of benzoxanorbornadiene led to the formation of substituted cis-1,2-dihydronaphthol rings in excellent yields. Palladium catalyzed ring opening reactions were also explored with a wide range of aryl iodides and halobenzenes. The electronic and steric effects of the substituent at the C1 position of oxabicyles were also investigated. The nickel catalyzed ring opening reactions resulted in formation of inseparable regioisomeric mixtures of products. However, it was found that the nickel catalyzed ring opening of 1-methoxycarbonyl-7-oxabenzonorbornadiene occurred regioselectively affording a single product. A scalable procedure for preparation of large quantities of 2-bromofuran was developed. 2-Aryl furans were prepared using Suzuki cross coupling protocols of 2-bromofuran with aryl boronic acids whereas 2-alkyl furans were prepared by iron catalyzed cross coupling reaction of 2-bromofuran with various alkyl and cycloalkyl Grignard reagents. The 2-substituted furans were used for the preparation of novel C1 substituted benzoxanorbornadiene and oxanorbornadienes.

In this study a number of cage alkenes were synthesised and tested for activity towards ringopening metathesis polymerisation (ROMP) with the commercially available catalysts 55 (Grubbs-I) and 56 (Grubbs-II). The first group of monomers are derivatives of tetracyclo[6.3.0.04,1105,9]undec-2-en-6-one (1). The synthesis of these cage alkenes are summarised in Scheme 7.1. The cage alkene 126b was synthesised by a Diels-Alder reaction between 1 and hexachlorocyclopentadiene (9, Scheme 7.2). The geometry of 126b was determined from XRD data. Knowledge of the geometry of 126b also established the geometry of 127 since conformational changes during the conversion from 126b to 127 are unlikely. Synthesis of the cage alkene 125 by the cycloaddition of 9 to 118 failed. The cage alkene exo-11- hydroxy-4,5,6,7,16,16-hexachlorohexacyclo[7.6.1.03,8.02,13.010,14]hexa-dec-5-ene (124, Scheme 7.3) could therefore not be prepared. Synthesis of 125 by reduction of 126b with various reduction systems was not successful. Theoretical aspects of these reactions were investigated with molecular modelling. A possible explanation for the unreactive nature of 126b towards reduction is presented, but the lack of reactivity of 118 towards 9 eluded clear explanations. The synthesis of cage alkenes from 4-isopropylidenepentacyclo[5.4.0.02,6.03,10.05,9]-undecane-8,11- dione (23) did not meet with much success (Scheme 7.4). Numerous synthetic methods were investigated to affect the transformation from 134a/134b to 135 (Scheme 7.5). These attempts evolved into theoretical investigations to uncover the reasons for the observed reactivity. Possible explanations were established by considering the differences and similarities between the geometries and electronic structures of reactive and unreactive cage alcohols. ROMP of cage monomers based on 1 were mostly unsuccessful. Only the cage monomer 127 showed some reactivity. Endocyclic cage monomers with a tetracycloundecane (TCU) framework showed no reactivity. The results from NMR experiments verified the experimental results. Hexacyclo[8.4.0.02,9.03,13.04,7.04,12]tetradec-5-en-11,14-dione (3) exhibited notable ROMP reactivity. Examination of the orbitals of the cage alkenes used in this study suggested that the reactivity of 1 and 3 could possibly be enhanced by removal of the carbonyl groups. Decarbonylation of 1 and 3 yielded the cage hydrocarbons 159 and 175, respectively. ROMP tests revealed that 175 is an excellent monomer, but 159 was unreactive. The results obtained for the ROMP reactions in this study was rationalised by considering aspects such as ring strain, energy profiles, steric constraints, and frontier orbital theory. The concept of ring strain is less useful when describing the reactivity of cage alkenes towards ROMP and therefore the concepts of fractional ring strain and fractional ring strain energy (RSEf) were developed. A possible link between RSEf and the ROMP reactivity of cage alkenes was also established. The following criteria were put forth to predict the reactivity or explain the lack of reactivity of cage alkenes towards ROMP reactions with Grubbs-I and Grubbs-II. The criteria for ROMP of cage monomers: 1. Sufficient fractional ring strain energy (RSEf). 2. A reasonable energy profile when compared to a reference compound such as cyclopentene. 3. Ability to form a metallacyclobutane intermediate with reasonable distances between different parts of the cage fragment. 4. Sufficient ability of the polymer fragment to take on a conformation that exposes the catalytic site. 5. Sufficient size, shape, orientation and energy of HOMO and/or NHOMO at the alkene functionality of the cage monomer and of the LUMO at the catalytic site. / Thesis (Ph.D. (Chemistry))--North-West University, Potchefstroom Campus, 2012

<p>Numerous methodologies for efficient formation of carbon-nitrogen bonds have been developed over the decades due to the widespread importance of nitrogen containing compounds in pharmaceuticals and bulk commercial chemicals. Among many methods, hydroamination, especially, has attracted enormous attention because of its atom-economical characteristic to synthesize amine moieties. As a result, numerous publications have been reported relating the hydroamination reaction using various metal catalysts. However, the hydroamination of unactivated alkenes still remains a challenge task because of the low reactivity of the CC double bond. Recent development of superior gold(I) catalysis in many organic transformations stimulated us to develop efficient gold(I)-catalyzed methods for enantioselective intra- and intermolecular hydroamination of unactivated alkenes. </p><p>A gold(I)-catalyzed system for enantioselective intramolecular hydroamination of unactivated alkenes has been developed. For the effective gold(I)-catalyzed method, various gold(I)-catalysts have been synthesized and tested. Among the catalysts, bis(gold) complexes containing an axially chiral bis(phosphine) ligand catalyze the enantioselective intramolecular hydroamination of unactivated alkenes with carboxamide derivatives, most effectively. The method was effective for both carbamates and ureas to form pyrrolidine derivatives with up to 85 % ee.</p><p>The first enantioselective intermolecular hydroamination of unactivated alkenes was realized by a gold(I)-catalyzed method. The gold(I) catalyst system adds cyclic ureas to unactivated 1-alkenes to produce corresponding enantiomerically enriched hydroamination product in good yield with enantioselectivity up to 78 % ee. </p><p>Polymer-embedded ligands have been synthesized to demonstrate proofs of concepts for fluxional mechanocatalysis. We applied a certain shear stress using a rheometer in the course of palladium-catalyzed asymmetric allylic alkylation to examine catalytic reactivity change under the mechanical force.</p> / Dissertation

Thesis (Ph.D)--Chemical Engineering, Georgia Institute of Technology, 2008. / Committee Chair: Jones, Christopher; Committee Member: Koros, William; Committee Member: Lyon, Andrew; Committee Member: Nair, Sankar; Committee Member: Weck, Marcus. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Orientador: Prof. Dr. Dalmo Mandelli / Dissertação (mestrado) - Universidade Federal do ABC. Programa de Pós-Graduação em Ciência e Tecnologia/Química, 2016. / Nas últimas décadas, a oxidação de compostos orgânicos tem atraído muitos estudos. Este tipo de reação leva à obtenção de produtos de grande aplicação na indústria farmacêutica, de plásticos e fragrâncias. Com o objetivo de promover processos que reduzam a quantidade de subprodutos, resíduos de reação e elevem os rendimentos reacionais é necessário desenvolver novos catalisadores ativos e seletivos, que também possuam custo e toxicidade relativamente baixos, Assim, os oxidantes preferenciais para esses processos são oxigênio molecular e peróxido de hidrogênio. Uma área que tem ganhado mais importância na literatura moderna é a utilização de catalisadores que não possuem metais de transição na oxidação de compostos orgânicos. Neste trabalho foi estudada a oxidação de alquenos (incluindo terpenos) com H2O2, utilizando-se como catalisadores Al(NO3)3 e Ga(NO3)3, e os efeitos da adição de co-catalisadores. Os melhores resultados foram obtidos usando o Ga(NO3)3 como catalisador, obtendo um rendimento de 80% na epoxidação do cicloocteno e de 26% na epoxidação do dec-1-eno após 8 h de reação utilizando acetato de etila como solvente. Na epoxidação da carvona o produto majoritário foi o epóxido interno, próximo a carbonila, utilizando o catalisador de Ga e o THF como solvente com rendimento superior a 40%. Foram testados diferentes co-catalisadores, ácidos ou bases, para as reações de epoxidação do cicloocteno. O ácido acético levou a ligeiros incrementos no rendimento, enquanto que ácido 2-pirazinocarboxílico (PCA) e o ácido trifluoracético (TFA) aceleraram a reação e foram os mais eficientes. Na epoxidação do dec-1-eno, a adição de PCA aumentou em cerca de 15 vezes a velocidade de reação, enquanto que na epoxidação da carvona alterou drasticamente a seletividade, favorecendo a formação de epóxido externo em detrimento do interno. / In recent decades, the oxidation of organic compounds has attracted many studies. Such reaction leads to products with wide application in pharmaceutical, plastic and fragrances industry. In order to promote processes that reduce the amount of byproducts, reaction residues and to increase reaction¿s yields it is necessary to develop new active and selective catalysts, which also have relatively low cost and toxicity. Thus, preferred oxidants for these processes are molecular oxygen and hydrogen peroxide. One area that has gained more importance in modern literature is to use transition metal-free catalysts in the oxidation of organic compounds. In this work, we studied the oxidation of alkenes (including terpenes) with H2O2, using catalysts such as Al(NO3)3 and Ga(NO3)3, evaluating the effects of the addition of co-catalysts. The best result was obtained using Ga(NO3)3 as catalyst, giving a yield of 80% in the epoxidation of cyclooctene and 26% in the epoxidation of 1-decene after 8 h of reaction using ethyl acetate as solvent. In the epoxidation of carvone the major product was the internal epoxide, near to the carbonyl group, using gallium salt and THF as solvent with yields higher than 40%. Different co-catalysts were tested, either acid or basic, for the reactions of epoxidation of cyclooctene. Acetic acid led to a slight increase in the yield, while PCA and TFA accelerated the reaction and were the most efficient. In the epoxidation of dec-1-ene the addition of the PCA increased almost 15 the initial rate of the reaction, while in the epoxidation of carvone it changed the selectivity improving the yield to the external epoxide.

A importância que a catálise representa para a sociedade pode ser vista em números: 90% dos processos da indústria química e mais de 20% de todos os produtos industriais comercializados no mundo utilizam uma ou mais etapas catalíticas. Assim, desenvolver catalisadores eficientes, ativos e seletivos é a solução para criar tecnologias mais limpas e sustentáveis. Além disso, reações químicas que geram novas ligações C-C estão entre as transformações mais relevantes na química orgânica e são a base desse trabalho. Os catalisadores de ródio apresentados aqui fazem parte de um trabalho minucioso de desenvolvimento, síntese e caracterização de nanopartículas e suportes magnéticos funcionais que foram utilizados em transformações de diversas moléculas. O estudo inicial com nanopartículas de ródio suportadas, em reações de hidrogenação do cicloexeno, serviu para a compreensão de como se comportam essas nanoestruturas e da influência que diferentes ligantes orgânicos e estabilizantes podem ter em uma aplicação catalítica bastante conhecida. O sistema catalítico mostrou-se bastante ativo e reutilizável,despertando o nosso interesse ao seu aperfeiçoamento para aplicação em reações de hidroformilação. Antes da síntese de catalisadores suportados, estudos com nanopartículasnão-suportadas mostraram que um sistema modificado pela adição de fosfinas era necessário para ativação do catalisador e que o estabilizante utilizado afetava a atividade catalítica. Assim, para possibilitar o ancoramento eficiente das espécies ativas, uma modificação da superfície do suporte magnético com a metildifenilfosfina foi realizada. A fosfina funcionalizada sobre o suporte viabilizou sua interação com as espécies ativas e evitou a sua lixiviação, possibilitando o reuso do catalisador. A reação de hidroformilação do oct-1-eno atingiu 96% de conversão e 82% de seletividade para aldeídos, em 6 horas a 80°C. A carga metálica do catalisador foi de apenas 0,2%. Buscando aumentar a eficiência na etapa de imobilização do metal e uma melhor atividade catalítica que possibilitasse o uso de substratos mais complexos, o suporte magnético foi modificado com um polímero hiper-ramificado. Essa modificação possibilitou aumentar a quantidade de grupos fosfinas sobre o suporte, assim como levou a um significativo aumento na carga de metal. A reação de hidroformilação de produtos naturais foi possível e, com o composto estragol, conversões de 100% foram alcançadas em 6 horas, com seletividade de 70% para aldeídos. Mesmo com evidências que sugerem a formação de espécies ativas moleculares, o suporte modificado possibilitou que o catalisador mantivesse sua atividade e seletividade por pelo menos seis reações sucessivas. Os materiais desenvolvidos apresentaram estabilidade quando manuseados ao ar, sem prejudicar sua vida útil e fácil separação. / The importance of catalysis to society may be seen in numbers: 90% of chemical production processes and more than 20% of all industrial products sold in the world use one or more catalytic steps. Thus, the development of efficient, active, and selective catalysts is crucial for creating cleaner and sustainable technologies. In addition, chemical reactions that generate new C-C bonds are among the most important transformations in organic chemistry and are the basis of this work. Rhodium catalysts presented herein are part of a careful investigation, which included the development, synthesis and characterization of metal nanoparticles and magnetic functional supports for use in the transformation of various molecules. The initial study of supported rhodium nanoparticles in cyclohexene hydrogenation reactions has driven our understanding of the behavior of these nanostructures, and the influence that different ligands and stabilizers may have in a well-known catalytic application. The identification of a highly active and recyclable catalytic system aroused our interest for its improvement for application in hydroformylation reactions. Prior to the synthesis of supported catalysts, studies with non-supported nanoparticles revealed that a modified system with the addition of phosphines was required for activation of the catalyst and the stabilizer used affected the catalytic activity. Thus, to enable efficient immobilization of the active species, the surface of the magnetic support was modified with methyldiphenylphosphine. The catalyst preparation removed, at least partially, the stabilizer adsorbed on the nanoparticles surfaces. The phosphine-functionalized support anchored the active species and avoided their leaching, allowing the reuse of the catalyst. The hydroformylation reaction of oct-1-ene reached 96% of conversion and 82% of selectivity to aldehydes, in 6 hours at 80°C. The metal loading of the catalyst was only 0.2%. Seeking to increase the efficiency in metal immobilization step and a better catalytic activity that would enable the use of more complex substrates, the magnetic support was modified with a hyperbranched polymer, which allowed an increase in the amount of external phosphines, as well as a significant increase in metal loading on the support. The hydroformylation reaction of natural products was possible and, with the estragole compound, 100% of conversion was achieved in 6 hours with 70% of selectivity to aldehydes. Despite evidence that suggests the formation of active molecular species, the modified support has enabled the catalyst to retain its activity and selectivity for at least six successive reactions. The materials developed could be handled in air without damaging their catalytic activity, durability and separation properties.

Ph.D. / This thesis deals with the synthesis of nitrogen-donor compounds and their reaction with metal ions. The first type of nitrogen-donor compounds are the unconjugated diimines (N,N´-bis(diphenylmethylene)ethylenediamine (L1) and (N,N´-bis(diphenylmethylene)propylenediamine (L2). Compounds L1 and L2 were reacted with [NiBr2(DME)] or [NiCl2·6H2O] to form complexes (2.1a), (2.2a), (2.3a) and (2.4a). These nickel complexes were characterized by IR spectroscopy, elemental analysis and mass spectrometry. When the complexes were left in chloroform for prolonged periods, hydrolysis of the diimine ligand took place, leading to the formation of nickel complexes 2.1b, 2.2b, 2.3b and 2.4b. The identity of the hydrolysed nickel complexes 2.1b and 2.2b was confirmed by single crystal X-ray crystallography. Complex 2.1b crystallised in the P21/n space group, whilst 2.2b crystallised in the P-1 space group. Compounds L1 and L2 were also reacted with [PdClMe(MeCN)2] to form the palladium complexes (3.1) and (3.2). The palladium complexes were characterized by NMR spectroscopy, elemental analysis and single crystal X-ray crystallography. Attempts to recrystallize 3.1 from a dichloromethane solution led to the formation of 3.1a. Both complexes 3.1a and 3.2 crystallised in the P21/n space group. Complexes 3.1 and 3.2 were tested as catalysts for the Heck coupling reaction of iodobenzene with methyl acrylate or butyl acrylate at 80 C. The products from the coupling reactions were characterized by GC and NMR spectroscopy. These complexes were found to be highly active with 100% conversions observed in some instances. The second type of ligands that were prepared are the benzoylpyrazolyl compounds, (3,5-dimethylpyrazol-1-yl)phenylmethanone (C1), (3,5-ditertiarybutylpyrazol-1-yl)phenylmethanone (C2), (3,5-dimethylpyrazol-1-yl)-o-toluoylmethanone (C3), (3,5-ditertiarybutylpyrazol-1-yl)-o-toluoylmethanone (C4), (2-chlorophenyl)-(3,5-dimethylpyrazol-1-yl)methanone (C5), (2-chlorophenyl)-(3,5-ditertiarybutylpyrazol-1-yl)methanone (C6), (2-flourophenyl)-(3,5-dimethylpyrazol-1-yl)methanone (C7), (2-flourophenyl)-(3,5-ditertiarybutylpyrazol-1-yl)methanone (C8). These compounds were fully characterized using NMR spectroscopy, IR spectroscopy and elemental analysis. Compounds C1, C3, C5 and C7 were reacted with [NiBr2(DME)] to form nickel complexes (4.31-4.34). These nickel complexes were found to be insoluble in all common organic solvents and hence were characterized only by IR spectroscopy and elemental analysis. Compounds C1-C8 were also reacted with [PdCl2(MeCN)2] to form palladium complexes (4.35-4.42). Complexes 4.35-4.42 were characterized using NMR spectroscopy, IR spectroscopy, elemental analysis and in selected cases single crystal X-ray crystallography. Complex 4.39 crystallised in the C2/n space group and complex 4.42 crystallised in the P21/n space group. Attempts to recrystallize 4.37a led to the formation of 4.37b, which contains both 3,5-dimethylpyrazol-1-yl)-o-toluoylmethanone and 3,5-dimethylpyrazole as ligands. Complex 4.37b was confirmed by NMR spectroscopy and single crystal X-ray crystallography. Complex 4.37b crystallised in the Pbca space group. The formation of 4.37b is attributed to hydrolysis of 3,5-dimethylpyrazol-1-yl)-o-toluoylmethanone ligand in 4.37a due to the presence of adventitious water in the solvent. The palladium complexes (4.35-4.42) were tested as catalysts for the Heck coupling reaction of iodobenzene with butyl acrylate and also for the Suzuki coupling reaction of iodobenzene with phenylboronic acid or 4-chlorophenylboronic acid. In these reactions, complexes 4.35-4.42 were found to be highly active at 120 C. The pyrazolyl nickel and palladium complexes were further tested as catalysts in ethylene oligomerization reactions using EtAlCl2 as the co-catalyst. The nickel complexes were found to be the most active reaching TONs of 10.8105 g mol-1 h-1. The palladium analogues only gave TONs of up to 3.9105 g mol-1 h-1. The oligomers were characterized by GC and NMR spectroscopy and were found to be in the C10-C16 range, with C16 the most abundant olefin.

Ruthenium carbene complexes, with the general structure, [LL’Ru=CHR], are commonly known as Grubbs type catalysts, named after the discoverer of these metathesis catalysts. The discovery was quite revolutionary, since the catalysts proved to be easy to handle, tolerant towards various functional groups and more stable with regard to air and water than previous transition metal catalysts. Another important advantage was that all types of olefin metathesis reactions could be initiated without the help of co-catalysts or promoters. Today Grubbs type catalysts find wide application in especially organic and synthetic chemistry. A well-known example is the SHOP-process which produces long chain -olefins, while other important applications include the synthesis of macro-cyclic and cyclic olefins. The current study involved experimental and theoretical work to investigate various aspects comprising synthetic procedures, reactivity, kinetics, geometry and electronic properties of the complexes. Results are discussed briefly in the following paragraphs. The first aim of the project was to synthesise a Grubbs type catalyst. Initial efforts were focused on the preparation of a first generation catalyst through various methods. This included modifying the reported method for the synthesis of [(PPh3)2Cl2Ru=CH-CH=CMe2] to yield [(PPh2Cy)2Cl2Ru=CHCH= CMe2] instead; a phosphine exchange reaction with the complex [(PPh3)2Cl2Ru=CH-CH=CMe2] and free phosphine PPh2Cy; and utilising the analogue arsine ligand, AsPh3, to synthesise [(AsPh3)2Cl2Ru=CHCH=CMe2]; but unfortunately no success was achieved. However, it was possible to synthesise a novel second generation Grubbs type catalyst, [(IMesH2)(PPh2Cy)Cl2Ru=CHPh], through the phosphine exchange reaction of [(IMesH2)(NC5H5)2Cl2Ru=CHPh] and PPh2Cy. The new complex was tested in kinetic reaction studies and phosphine exchange reactions. Results showed that [(IMesH2)(PPh2Cy)Cl2Ru=CHPh] was catalytically active for the ring closing metathesis of commercial diethyl diallylmalonate. The reaction was first order with regard to the olefin, contrary to the second order kinetic results reported for similar reactions catalysed by first generation Grubbs catalysts. The phosphine exchange reactions were very successful and a rate constant could be determined. The rate constant was independent of the free phosphine concentration and activation parameters had relatively large, positive values; results indicative of a dissociative mechanism. These findings are in correlation with literature reports. A kinetic investigation was done on the catalyst-olefin coordination involving the functionalized olefins vinyl acetate, allyl acetate and allyl cyanide; and the first generation Grubbs catalyst, [(PCy3)2Cl2Ru=CHPh]. A two-step rate law, similar to an interchange mechanism, was determined. Phobcat, [(PhobCy)2Cl2Ru=CHPh], is modified first generation Grubbs type catalyst with rigid bicyclic phosphine rings which was recently developed by the Sasol Homogeneous Metathesis Group. In the current study Phobcat was compared to Grubbs1-PCy3 in the cross metathesis reaction of 1-octene. Results showed that Phobcat was up to 60% more active and had a 5 hour longer lifetime than Grubbs 1-PCy3. Theoretical studies were done on the three functionalized olefins of the earlier experimental study to gain fundamental understanding of steric and electronic influences on these catalyst-olefin systems. Without exception, coordination via the heteroatom of the olefin was significantly more favourable than coordination via the double bond functionality. This result indicates that metathesis of these olefins is highly unlikely, since the stable heteroatom coordination will suppress the parallel Ru=C/C=C interaction which is compulsory for the metathesis reaction. Orbital studies highlighted the difference between coordination of acetate and cyanide, but no trend of an electronic nature could be recognised. / Prof. A. Roodt

Ph.D. / Compounds, 2,6-bis(3,5-dimethylpyrazol-1-ylmethyl)pyridine (L1) and 2,6-bis(3,5-ditertbutylpyrazol-1-ylmethyl)pyridine (L2) were prepared by phase transfer alkylation of 2,6-bis(bromomethyl)pyridine with two mole equivalents of the appropriate pyrazole. Ligands L1 and L2 reacted with either [PdCl2(NCMe)2] or [PdClMe(COD)] to form mononuclear palladium complexes [(PdCl2(L1)] (1), [(PdClMe(L1)] (2), [(PdCl2(L2)] (3), [(PdClMe(L2)] (4). All new compounds prepared were characterised by a combination of 1H NMR, 13C NMR spectroscopy and microanalyses. The coordination of L2 in a bidentate fashion through the pyridine nitrogen atom and one pyrazolyl nitrogen atom has been confirmed by single crystal X-ray crystallography of complex 3. Reactions of 1, 2 and 3 with the halide abstractor NaBAr4 (Ar = 3,5-(CF3)2C6H3) led to the formation of the stable tridentate cationic species [(PdCl(L1)]BAr4 (5), [(PdMe(L1)]BAr4 (6) and [(PdCl(L2)]BAr4 (7) respectively. Tridentate coordination of L1 and L2 in the cationic complexes has also been confirmed by single X-ray crystallography of complexes 5 and 6. The analogous carbonyl linker cationic species, [Pd{(3,5-Me2pz-CO)2-py}Cl]+ (9) and [Pd{(3,5-tBu2pz-CO)2-py}Cl]+ (10), prepared by halide abstraction from [Pd{(3,5-Me2pz-CO)2-py}Cl2] and [Pd{(3,5-tBu2pz-CO)2-py}Cl2] with NaBAr4, were however less stable. While cationic complexes 5-7 showed indefinite stability in solution, 9 and 10 had t1/2 of 14 and 2 days respectively. Attempts to crystallise 1 and 3 from the mother liquor resulted in the isolation of the salts [PdCl(L1)]2[Pd2Cl6] (11) and [PdCl(L2)]2[Pd2Cl6] (12). Although when complexes 1-4 xviii were reacted with modified methylaluminoxane (MMAO) or NaBAr4, no active catalysts for ethylene oligomerisation or polymerisation were formed, activation with silver triflate (AgOTf) produced active catalysts that oligomerised and polymerised phenylacetylene to a mixture of cis-transoidal and trans-cisoidal polyphenylacetylene. Compounds 2-(3,5-dimethylpyrazol-1-ylmethyl)pyridine (L3) and 2-(3,5-di-tert-butylpyrazol-1-ylmethyl)pyridine (L4) were prepared by phase transfer alkylation of 2-picolylchloride hydrochloride with one mole equivalent of the appropriate pyrazole. Compounds 2-(3,5-bis-trifluoromethyl-pyrazol-1-ylmethyl)-6-(3,5-dimethyl-pyrazol-1-ylmethyl)-pyridine (L5) and 2-(3,5-dimethyl-pyrazol-1-ylmethyl)-6-phenoxymethyl-pyridine (L6) were isolated in good yields by reacting (2-chloromethyl-6-3,5-dimethylpyrazol-1-ylmethyl)pyridine with an equivalent amount of potassium salt of 3,5-bis(trifluoromethyl)pyrazolate and potassium phenolate respectively. L3-L6 react with either [Pd(NCMe)2Cl2] or [PdClMe(COD)] to give mononuclear palladium complexes 13-18 of the general formulae [PdCl2(L)] or [PdClMe(L)] where L = is the bidentate ligands L3, L4, L5 and L6 respectively. Single crystal X-ray crystallography of complexes 13, 15 and 16 has been used to confirm the solid state geometry of the complexes. In attempts to generate active olefin oligomerisation catalysts, the chloromethyl Pd(II) complexes 14 and 16 were reacted with the halide abstractor NaBAr4 in the presence of stabilising solvents (i.e Et2O or NCMe) but no catalytic activities were observed. Decomposition was evident as observed from the deposition of palladium black in experiments using Et2O. In experiments where NCMe was used as the stabilising solvent, the formation of cationic species stabilised by NCMe was evident from 1H NMR analyses. Reaction of complex 14 with NaBAr4 on a preparative scale in a mixture of CH2Cl2 and NCMe solvent gave the cationic complex [[PdMeNCMe(L3)]BAr4 (19) in good yields. Complex 17 reacted with NABAr4 to give tridentate cationic species [[PdMe(L5)]BAr4 (20) which is inactive towards ethylene oligomerisation or polymerisation reactions. The tridentate coordination of L5 in 20 has also been established by single crystal X-ray structure of 20. Catalysts generated from 18 and 19 catalysed ethylene polymerisation at high pressures to branched polyethylene; albeit with very low activity. The Choromethyl palladium complex 14 reacted with sulfur dioxide to form complex 21. The nature of the product has been established by 1H NMR, 13C NMR and mass spectrometry to be an insertion product of SO2 into the Pd-Me bond of 14. Compounds L1-L4 reacted with the nickel salts NiCl2 or NiBr2 in a 1:1 mole ratio to give the nickel complexes [NiCl2(L1)] (22), [NiBr2(L1)] (23), [NiCl2(L2)] (24), and [NiBr2(L2)] (25), [Ni2(μ2-Cl)2Cl2(L3)2] (26), [Ni2(μ2-Br)2Br2(L3)2] (27), [NiCl2(L4)] (29) and [NiBr2(L4)] (30) in good yields. Reaction of L3 with NiBr2 in a 2:1 mole gave the octahedral complex [NiBr2(L4)2] (28) in good yields. Complexes 22-30 were characterised by a combination micro-analyses, mass spectrometry and single crystal X-ray analyses for 27 and 30. No NMR data were acquired because of the paramagnetic nature of the complexes. When complexes 22-30 were activated with EtAlCl2, highly active olefin oligomerisation catalysts were formed. In the ethylene oligomeristion reactions, three oligomers: C11, C14 xx and C16 were identified as the major products. Selectivityof 40% towards α-olefins were generally obtained. In general catalysts that contain the bidentate ligands L3 and L4 were more active than those that contain the tridentate ligands L1 and L2. Dichloride complexes exhibited relatively higher catalytic activities than their dibromide analogues. Turn over numbers (TON) for oligomer formation showed high dependence on ethylene concentration. A Lineweaver-Burk analysis of reactions catalysed by 22 and 26 showed TON saturation of 28 393 kg oligomer/mol Ni.h and 19 000 kg oligomer/mol Ni.h respectively. Catalysts generated from complexes 22-30 also catalysed oligomerisation of the higher olefins, 1-pentene, 1-hexene and 1-heptene and displayed good catalytic activities. Only two products C12 and C15 were obtained in the 1-pentene oligomerisation reactions. The 1-hexene reactions also gave two products, C12 and C18, while 1-heptene oligomerisation reactions gave predominantly C14 oligomers. Five benzoazoles were used to prepare a series of palladium complexes that were invesitigated as Heck coupling catalysts. The compounds 2-pyridin-2-yl-1H-benzoimidazole (L7) and 2-pyridin-2-yl-benzothiazole (L8) were prepared following literature procedures. The new ligands 2-(4-tert-butylpyridin-2-yl)-benzooxazole (L9) and 2-(4-tert-butyl-pyridin-2-yl)-benzothiazole (L10) were prepared by ring closure of aminophenol and aminothiophenol with tert-butyl picolinic acid respectively. The ligand 6-tert-Butyl-2-(4-tert-butyl-pyridin-2-yl)-benzothiazole (L11) was prepared by intramolecular cyclisation under basic conditions is described. Reactions of L7-L11 with either [Pd(NCMe)2Cl2] or [Pd(COD)MeCl] afforded the corresponding mononuclear palladium complexes [PdClMe(L7)] (31), [PdClMe(L8)] (32), [PdCl2(L9)] (33), [PdMeCl(L9)] (34), [PdCl2(L10)] (5), [PdMeCl(L10)] (36) and [PdMeCl(L11)] (37) as xxi confirmed by mass spectrometry and micro-analyses. The palladium complexes 31-37 were efficient Heck coupling catalysts for the reaction of iodobenzene with butylacrylate under mild conditions and showed good stability.

M.Sc. (Chemistry) / This study deals with the synthesis of nitrogen-donor pyrazole- and pyrazolylethylamine compounds, their reactions with palladium(II) and nickel(II) precursors to form complexes and the applications of theses palladium(II) and nickel(II) complexes as catalysts for ethylene oligomerization reactions and reactions of higher α-olefins in Friedel-Crafts alkylation of aromatic solvents. A series of ligands, 3,5-di-tert-butyl-1H-pyrazole (L3), 3,5-diphenyl-1H-pyrazole (L4), 5-phenyl-3-(trifluoromethyl)-1H-pyrazole (L5) were synthesized using appropriate amounts of diketones and hydrazine hydrate; while ligands, 2-(1H-pyrazol-1-yl)ethylamine (L6), 2-(3,5-dimethyl-1H-pyrazol-1-yl)-ethylamine (L7), 2-(3,5-di-tert-butyl-1H-pyrazol-1-yl)-ethylamine (L8), 2-(3,5-diphenyl-1H-pyrazol-1-yl)-ethylamine (L9) and 2-(5-phenyl-3-(trifluoromethyl)-1H-pyrazol-1-yl)ethylamine (L10) were prepared via the N sp3 alkylation of the corresponding pyrazoles with bromoethylamine Reactions of L1-L5 with [PdCl2(CNMe)2] formed five complexes of general formula [PdCl2 (L)2] {L = L1 (2.1), L2 (2.2), L3 (2.3), L4 (2.4) and L5 (2.5)}. Similarly [NiBr2(DME)] formed five complexes of general formula [NiBr2(L)2] {L = L1(2.6), L2 (2.7), L3 (2.8), L4 (2.9) and L5 (2.10)}. Complexes 2.1-2.10 were synthesized in a 2:1 mole ratio of ligand and metal precursor. Reactions of L6-L10 with [PdCl2(MeCN)2] yielded complexes 3.1-3.5 respectively. Ligands L6-L10 were also complexed with NiCl2.6H2O to give complex 3.6 while [NiCl2(DME)] and [NiBr2(DME)] gave complexes 3.7-3.8 and 3.9-3.13 respectively...