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The project was concerned with studying the capability of a micellar-enhanced ultrafiltration system (MEUF) to remove platinum group metal ions namely Pt (lV) and Pd (ll) chloro anions from aqueous industrial waste effluents. South Africa has the world’s largest reserves of platinum group metals (PGMs) and other valuable metals such as manganese, chrome ores, titanium minerals etc. which are required for new automotive and other technologies, including fuel cells, catalytic converters and lighter components. The consistent loss with the industrial waste stream and the toxicological effects of these precious metals led to the need to develop new and effective methods to recover them from industrial waste effluents. With such a wide variety of fields where these PGMs are used and the failure of the traditional techniques namely sedimentation, fermentation etc. to effectively reduce or recover these highly toxic and precious metal ions prior to discharging industrial waste effluents, it is necessary to explore other techniques such as membrane technology that can be used to recover these valuable species from industrial waste streams. The present study involved the use of a cationic surfactant, viz cetylpyridinium chloride, which was introduced into an aqueous solution containing palladium and platinum metal anions. The surfactant forms charged micelles above a certain critical concentration value. The metal anions adsorb onto the available oppositely charged sites on the micelle surfaces and are then able to be retained by a suitable membrane. Hollow fibre ultrafiltration membranes with the MWCO of +/- 10 kD and +/-30nm pore size were used as a filter component in this study. For this MEUF system to be effective, it was vital that the anionic metal ion species adsorbed sufficiently onto the available oppositely charged sites of the micelles and that the micelles were retained efficiently by the membrane. Results obtained during the investigation made it possible to make certain predictions about the micellisation process. It was also found that, it was not only the metal ion: surfactant (M:S) ratio that was critical, but the presence of other electrolytes in the aqueous stream proved to have a huge impact on the capability of the MEUF system. Findings of this research study showed that the MEUF system using cetylpyridinium chloride (CPC) can be used to recover or retain Pt (lV) and Pd (ll) anions from industrial waste effluents. It was also found that PtCl6 2-, due to its greater adsorption capabilities onto the micelle surface than PdCl4 2- or PdCl3(H2O)-, was preferentially retained in neutral medium. This may be exploited as a possible means of separating the two metal ions. The developed system offers the following advantages over some traditional and current methods: simplified unit operation line flow process, smaller amounts of chemical usage and no solid toxic sludge to be disposed of. Applications of this work could be of vital importance in catalytic converter recycling, especially in Port Elizabeth where extensive automobile parts manufacturing occurs.

La N-arylation d'amines primaires et secondaires par couplages C-N palladocatalysés de Buchwald- Hartwig est une méthode efficace de synthèse d'arylamines. Jusqu'à présent, la synthèse d'arylamines en série thiophénique n'avait été que peu décrite. Nous nous sommes ainsi intéressés à la réactivité de dérivés substitués des 2- et 3-bromothiophènes dans les couplages C-N palladocatalysés. Par la suite, nous avons également étudié la réactivité d'aminothiophènes dans ces mêmes réactions de couplage. Un grand nombre d'arylamines a ainsi pu être synthétisé. La synthèse de thiénopyrimidinones a aussi été effectuée via la réalisation en "one-pot" d'une réaction de couplage C-N suivie d'une cyclisation intramoléculaire / N-Arylation of primary and secondary amines by Buchwald-Hartwig C-N cross-coupling reactions is a very convenient pathway for the synthesis of arylamines. Up to now, only few examples of arylamines synthesis were described in the thiophene series, although arylaminothiophenes generally show very interesting biological and electronic properties. Thus, we investigated the reactivity of 2- and 3- bromothiophene derivatives in palladium-catalyzed cross-coupling. Then we also studied the reactivity of aminothiophenes in those same cross-coupling reactions. Using this way, the expected diarylamines were successfully synthesized. An easy access to thienopyrimidinone derivatives was also described via a one-pot C-N coupling and intramolecular cyclization

The preparation, characterization, and catalytic properties of some soluble and polymer-bound palladium and platinum complexes of ferrocene derivatives are described. Special emphasis has been placed on studies of the mixed "hard-soft" ligands such as PPFA and ISOPFA. [Formula Omitted] The soluble complexes (L-L)MC1₂ (L-L = BPPF, PPFA, ISOPFA, BPPFA; M = Pd, Pt) and [(L-L)PdS₂][C10₄]₂ (L-L = BPPF, PPFA; S = DMF, py) have been characterized by microanalyses, NMR and IR spectroscopic techniques. The cationic palladium(II) complex [(L-L)PdS₂][C10₄]₂ (L-L = PPFA, S = DMF) is an effective catalyst precursor for the hydrogenation of simple olefins at 30°C and 1 atm pressure. The rate of styrene hydrogenation depends on the substrate concentration, catalyst concentration and the solvent. The results are consistent with a homogeneous catalytic system. Platinum(II) complexes (L-L)PtCl₂ (L-L = (S,R)-PPFA, (S,R)-ISOPFA) are effective catalyst precursors for the hydrosilylation of aromatic ketones with Ph₂SiH₂. The complexes with mixed "hard-soft" ligands are better catalyst precursors than those with di(tertiary phosphine) ligands. Under the same conditions the hydrosilylation of ferrocenyl ketones results in further reduction and affords mainly the alkylferrocene products. The stable carbonium ion FcC⁺HCH₃ (Fc = Fe-(C₅H₅)(C₅H₄)-) is reduced by Ph₂SiH₂ to FcCH₂CH₃ in a thermal reaction which is catalyzed by the complex (PPFA)PtCl₂. The reaction of Ph₂SiH₂ with (L-L)PtCl₂ (L-L = PPFA, ISOPFA) yields a stable platinum(IV) hydride, which eliminates Ph₂SiHCl in solution to afford (L-L)PtHCl. The mechanistic implications of these observations are discussed. Polymers functionalized with ferrocene and ferrocene derivatives have been prepared. Mossbauer spectroscopic techniques and microanalyses are used to characterize these polymers and their palladium and platinum complexes. In a number of cases these results are confirmed by the cross-polarization/magic-angle spinning ¹³C NMR spectroscopic technique. The palladium(II) and platinum(II) derivatives of the ferrocenyl-amine and -phosphine containing polymers are effective catalysts for the hydrogenation and hydrosilylation of olefins. All the catalysts can be easily separated from the reaction mixture and can be recycled with no loss of activity. The pronounced effect of the attached ligand in the palladium based polymers indicates that free metal is not involved. However, in the case of platinum based catalysts, it is likely that reduction to platinum metal takes place. / Science, Faculty of / Chemistry, Department of / Graduate

D.Sc. (Chemistry) / Please refer to full text to view abstract

Ph.D. / The intramolecular insertion of allylpalladium species into alkene and alkyne bonds ('metalloene' cyclisation) of acetoxy-2,7-dienes and acetoxy-2-en-7-ynes has evolved into a synthetically powerful process. Proceeding from the favourable results obtained with achiral analogues, the palladium-catalysed 'metallo-ene' reactions of acyclic carbohydrate-derived 1,1-diacetoxy-2,7-diene and 1,1-diacetoxy-2-en-7-yne compounds proceeded in a stereospecific fashion to furnish chiral, multi-functionalised five-membered carbo- and heterocyclic products. A valuable consequence of the reactions of these geminal diacetate starting materials is that the products contain enolacetate, or latent aldehyde moieties. Further elaboration of these functionalities enables the facile entry to an array of substituted five-membered ring compounds, some of which have been identified as synthons or substructures of important natural products. In the presence of carbon monoxide (1 atm) the corresponding cyclic carboxylic acid products were obtained under mild 'metallo-ene' reaction conditions. Cyclised chloro componds were obtained by exposure of the 1,1-diacetoxy-2-en-7-yne substrates to Wacker-like conditions in the presence of an excess of LiC1. The highly atom economical Trost-type cycloisomerisation ensued when these enyne starting materials were stirred in acetic acid in the presence of a palladium(0) catalyst. The mechanism of the palladium-catalysed 'metallo-ene' transformations is discussed with respect to the enantioselectivity of carbopalladation of prochiral alkenes as well as the transition states. The topological influence of pre-existing centres over developing stereogenic centres is evaluated. Following indications that n-allylpalladium complexes can be prepared by the oxidative addition of Pd(0) to an a,13-unsaturated acetal, our next strategy was based on the use of suitably substituted A 2'3-pyranoside rings as chiral templates for the construction of multi-functionalised fivemembered ring systems via Pd-catalysed 'metallo-ene' cyclisations. Enantiomerically pure bi- and/or tricyclic products of carbonyl insertion were obtained in fair to good yields when these 'metallo-ene' reactions were conducted in the presence of CO under mild reaction conditions. Subsequently, bicyclic diene products were prepared via the palladium-catalysed cyclisation of Az3-C-glycoside derivatives. Important revelations concerning the relative stereochemistry of substrates for palladium-catalysed 'metallo-ene' cyclisation/carbonylation of unsaturated C-glycoside derivatives were made. The consecutive introduction of unsaturated C-alkyl side-chains at C-4 and C-1 of selected pseudoglycals via palladium-catalysed nucleophilic allylic substitution reactions accomplished the formation of chiral dienyne compounds. Palladium-catalysed cascade cycloisomerisation of these substrates effected the smooth synthesis of enantiopure tricyclic products. Cascade cyclisation of these highly unsaturated starting materials under Wacker-like conditions afforded [5,6,6]-tricyclic dichloro compounds. A mechanism to account for the stereospecific incorporation of two chlorine atoms into, and the ring expansion of the substrate carbon framework, is proposed. Finally, the readily accessible tert-butyl 6-0-acety1-4-[bis(ethoxycarbonyl)but-3-eny1]-2,3,4- trideoxy-a-D-erythro-hex-2-enopyranoside was converted, via a domino process, into a chiral substituted dihydropyran in the presence of a Pd(II)-catalyst in acetic acid/acetonitrile. By conducting the reaction under an atmosphere of CO, a tetrahydropyran compound containing a carboxylic acid side-chain was obtained, while the corresponding chloro product was prepared when the pseudoglucal starting material was exposed to an excess of LiC1 and CuC1 2 under Wacker-like conditions.

M.Sc. (Chemistry) / Palladium-mediated carbon-earbon (and carbon-heteroatom) bond formation! is to an increasing extent playing a vital role in synthetic organic chemistry. The chemistry is usually performed under mild conditions, with the organopal1adium intermediates being formed in situ from inorganic palladium salts or complexes, and has good tolerance of functionality on the substrates. The palladium mediator may be present in the reaction in amounts ranging from stoichiometric to catalytic. Reactions requiring stoichiometric amounts of palladium may appear to be inherently uneconomical. Palladium, however, may be easily recovered in most cases, and may be converted into salts useful for catalysis, effectively offsetting the initial expense. 2 The use of polymer-bound palladium catalysts! has also been shown to be a viable method of palladium recovery. Palladium may form a- or 1r-eomplexes with organic compounds and, as with many other transition-metal complexes, a-palladium complexes are generally only stable in the presence of select ligands. Arylphosphines are most commonly used, and of these triphenylphosphine is the ligand of choice for its availability and low cost...

Amides are one of the most common functional groups in biological systems and in bioactive molecules. Arguably the most direct way to form amides is via the condensation of an amine onto a carboxylic acid. This reaction is notoriously difficult and has stimulated much development, including the developments of new reagents and catalysts to perform this transformation under milder conditions. More broadly, amide formation continues to be of high importance and the incorporation of emerging transformations utilizing new disconnections are complimentary to existing routes. Isocyanates are the simplest electrophiles containing the desired NCO motif and have a large presence in the polymer (e.g. polyurethane) and paint industries. In addition, isocyanates have been utilized for amide formation with various nucleophiles in a stoichiometric and catalytic fashion, but the inherent functional group intolerance associated with the high reactivity of isocyanate largely remains. Efforts have been made to address such limitations of isocyanates, including the use of a blocking group which allow for in situ release of the isocyanate while using a bench stable masked (blocked) isocyanate precursor. Changes to the blocking group structure have direct correlations to the stability and reactivity of the precursor, which helps in suppressing common side reactions observed with free isocyanates such as polymerization or oligomerization. Incorporation of a blocking group strategy in catalytic amide forming reactions has the power to unlock the potential of isocyanates with reactivity that would not be attainable with free isocyanates. Reports imparting this strategy exemplify the power of a blocking group with increased applicability and functional group tolerance compared to reactions with the free isocyanate counterpart. The implementation of this strategy for catalytic amide formation is sparse including only two reports with a rhodium catalyst. Utilization of different metals could broaden the scope of reactivity allowing for extensions that the rhodium (I) catalyst cannot do. The development of a palladium-catalyzed amide synthesis via masked isocyanates was targeted (Chapter 2). Indeed, implementation of a blocking group strategy with alkyl and aryl isocyanates allowed for efficient synthesis of amides with electron rich and mildly deficient aryl boroxine nucleophiles. Catalysis was achieved with 1 mol% of Pd(OAc)2 and 2 mol% of SPhos at 50 ℃ with Et3N to aid in the deblocking of the isocyanate. Several control experiments were iii conducted to obtain mechanistic insight including what mechanism may be operative as well as the necessity of this blocking group strategy. Kinetic studies were performed using the variable time normalization analysis method and have yielded the following information: 1) the presence of catalyst decomposition, 2) that the rate determining step involved the catalyst, boroxine, and masked isocyanate, and 3) that the rate determining step is likely the insertion into the isocyanate. In summary, palladium catalysts can achieve catalysis with masked isocyanates to facilitate amide formation under appropriate conditions. With limited reports of masked isocyanates in catalysis, this reactivity could act as a steppingstone for developments of reactivity that are held back with the use of free isocyanates.

Thesis advisor: James P. Morken / The development of boron and palladium ligands for conjunctive cross-coupling provides access to new reactivity. Some of these advances are outlined in this dissertation. Chapter one describes an enantioselective and diastereoselective palladium catalyzed conjunctive cross-coupling of β-substituted alkenyl boron “ate” complexes to afford contiguous benzylic stereocenters. “Mac” diol was discovered as a useful boron ligand in conjunctive cross-coupling by reducing unwanted Suzuki-Miyaura cross-coupling. Chapter two describes the utilization of “mac” diol in the enantioselective conjunctive cross-coupling of α-substituted alkenyl boron “ate” complexes with carbamoyl chlorides. This transformation affords tertiary, β-boryl amides, which provide a complementary approach to Mannich, aldol, and conjugate borylation products. Water was an essential additive to enable high yield and high enantioselectivity, and its reaction role was investigated. The synthetic utility of this cross-coupling was demonstrated with the asymmetric synthesis of (+)-adalinine. Chapter three describes the thought process behind discovering a new palladium ligand for conjunctive cross-coupling. Phosphinooxazolines (PHOX) are useful and inexpensive ligands for enantioselective palladium-catalyzed conjunctive cross-coupling. A stereochemical model of this cross-coupling with this ligand was examined. / Thesis (PhD) — Boston College, 2021. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

Technetium catalyzes hydrocarbon reforming reactions of dehydrocyclization, isomerization, hydrogenolysis, and coke formation. A kinetic equation was derived and E_a and A_o evaluated for dehydrocyclization of n-heptane, isomerization of n-pentane, and dehydrogenation of methylcyclohexane and cyclohexane. The results were related to the metal, the form of the catalyst, catalyst support, and the deactivation of the catalyst. The effect of sulfur compounds was determined. No residual radioactivity in the product was observed. The ligands, acetone azine (AA) and 3,5,5-trimethyl-2- pyrazoline (Py), reacted with (C_6H_5CN)_2PdCl_2 to form adducts, L_2PdCl_2 and (LPdCl_2)_n. Their structures were characterized by spectroscopic methods and some molecular weights determined. The basicity of the ligands, as well as acetone hydrazone (AH), was determined and found to be the same order as their ligand strength. AH rapidly reduces PdCl_2 to Pd. HPy+ and Py^_2PdCl_2 were studied for their rate of Py production from AA. Heats of reactions to form AA and AH were measured.