Dans le cadre de nos travaux, nous avons développé une méthode extrêmement douce et particulièrement efficace d’accès à des γ-butyrolactones possédant un centre stéréogène quaternaire en α à partir d’énols carbonates d’allyle cycliques et exocycliques en utilisant la réaction d’alkylation allylique asymétrique décarboxylante pallado-catalysée (Pd-DAAA). Remarquablement, cette méthode a permis d’étendre l’utilisation de l’allylation asymétrique décarboxylante à des substrats sans précèdent dans la littérature, tels que les énols carbonates allyliques exocycliques. Cette réaction a été utilisée comme étape clé dans la synthèse des spirolactones chirales qui ont été obtenues avec de bons rendements et d’excellentes énantiosélectivités. Une nouvelle méthode catalytique robuste et hautement énantiosélective permettant d’accéder à des isoxazolidinones possédant un centre stéréogène quaternaire en α a été développée. Ce protocole repose sur une alkylation allylique asymétrique catalysée par des complexes de palladium chiraux (Pd-AAA) et amène aux produits désirés avec de bons rendements et d’excellents excès énantiomériques. Par ailleurs, nous avons également mis au point des conditions permettant de convertir ces isoxazolidinones α,α-disubstituées en acides β2,2 aminés et en β-lactames. / The development of a palladium-catalyzed decarboxylative allylic alkylation protocol (Pd DAAA) applied to cyclic and exocyclic allyl enol carbonates has allowed a highly enantioselective access to a range of γ butyrolactones bearing an all-carbon α quaternary stereogenic center. Remarkably, this approach allowed the extension of this reaction to substrates with no precedent in the literature, such as the exocyclic allyl enol carbonates. The Pd-DAAA process was eventually used for the synthesis of chiral spirolactones, which were readily obtained in high yields and in high optical purity. The synthesis of different isoxazolidin-5-ones bearing highly stereodefined all carbon α quaternary center was accomplished by palladium-catalyzed asymmetric allylic alkylation (Pd-AAA) of 4 substituted isoxazolidin-5-ones with an array of 2 substituted allyl acetates. The reaction proceeded in both excellent enantioselectivity and yield with isoxazolidin-5-ones containing an α-aryl substituents or an α heteroaryl moieties. This robust and highly enantioselective method allowed the access to valuable β2,2-amino acids and β lactams.

Les tétrahydropyrazines et les morpholines sont des hétérocycles à six chaînons comportant deux hétéroatomes en position 1,4. Les objectifs de cette thèse ont été la mise au point de nouvelles méthodes pour leur synthèse. Des tétrahydropyrazines orthogonalement protégée ont ainsi été synthétisées à partir des diamines correspondantes, grâce à l’utilisation de triméthylsilyl-benziodoxolone (TMS-EBX) comme donneur d’alcyne. Ce dérivé d’iode hypervalent s’est par ailleurs révélé être un agent alcynylant chimiosélectif des sulfonamides par rapport aux carbamates. Une approche synthétique différente a été utilisée pour le synthèse des morpholines. En s’appuyant sur les précédents résultats obtenus au laboratoire, une hétérocyclisation catalysée au Fe(III) a été mise au point. En présence d’une quantité catalytique de FeCl3.6H2O, des morpholines 2,6- et 3,5-disubstituées ont été obtenues avec de bons rendements et des diastéréosélectivités toujours en faveur des composés cis. Afin d’améliorer cette méthode pour la rendre encore plus éco-compatible, une méthode monotope a été ensuite développée, menant, à l’aide d’une catalyse séquentielle Pd(0)/Fe(III), à une diversité de morpholines à partir de vinyloxiranes et d’amino-alcools facilement synthétisables. Le changement des substrats de départ permet de faire varier la substitution des morpholines finales sans avoir à modifier les conditions réactionnelles. L’obtention majoritaire des composés de configuration relative cis a été rationalisés à partir des stabilités supposées des différents diastéréoisomères et un mécanisme hypothétique est présenté. / Tetrahydropyrazines and morpholines are six-membered heterocycles including two heteroatoms in positions 1 and 4. The objectives of this thesis were to develop new methods for their synthesis. Orthogonnaly protected tetrahydropyrazines were thus synthesized from the corresponding diamines, thank to the use of trimethylsilyl-benziodoxolone (TMS-EBX) as an alkyne donnor. This hypervalent iodine derivative was also found to be an efficient and chemoselective alkynylating agent of sulfonamides versus carbamates. A different synthetic approach was used for the synthesis of morpholines. Relying on previous results obtained in the laboratory, an iron(III)-catalyzed heterocylization was developped. In the presence of a catalytic amount of FeCl3.6H2O, 2,6- and 3,5-disubstituted morpholines were obtained with good yields and diastereoselectivities in favor of the cis compounds. To improve this method and make it more environnementally friendly, a one-pot method was next designed, leading, with a sequential Pd(0)/Fe(III)-catalyzed process, to a diversity of morpholines from readily available vinyloxiranes and amino-alcohols. A simple switch in the starting materials gives diverse morpholines without any change in the reaction conditions. The cis-compound predominance was rationnalized from the putative stabilities of different diastereoisomeres and a hypothetical mechanism is proposed.

Le combustible nucléaire usé, constitué d’uranium, de plutonium et de produits de fission (palladium, technétium, molybdène etc.), est traité industriellement en France par le procédé PUREX. Ce procédé hydrométallurgique permet d’extraire l’uranium et le plutonium à l’aide d’une phase organique composée de tri-n-butylphosphate (TBP) dilué dans un mélange d’hydrocarbures aliphatiques (TPH). Au cours des différents cycles d’extraction, la phase organique est soumise à des phénomènes d’hydrolyse acide et de radiolyse conduisant à la formation de produits de dégradation. Afin d’assurer le recyclage du solvant organique et le bon fonctionnement du procédé industriel, un traitement approprié permet d’éliminer ces produits. Néanmoins, après plusieurs décennies de fonctionnement des usines, des encrassements de certains équipements ont été observés. Ces solides contiennent les éléments palladium, carbone, oxygène et azote. Industriellement, une solution curative a été mise en œuvre pour éliminer ces crasses. Il convient toutefois de comprendre les phénomènes qui ont conduit à leur formation. Ce travail de doctorat a pour objectif d’étudier le comportement physico-chimique du palladium dans les cycles d’extraction et les mécanismes conduisant à la formation de solides. Pour cela, un système biphasique, constitué d’une phase organique de TBP dilué dans le TPH et d’une phase aqueuse d’acide nitrique contenant du nitrate de palladium(II), a été irradié par une source externe de rayonnement gamma afin de simuler le vieillissement du solvant d’extraction. Des précipités non radioactifs contenant du palladium et représentatifs des encrassements industriels ont été obtenus. Des analyses multi-techniques de ces précipités ont montré que les solides sont constitués d’un mélange complexe de cyanure de palladium(II), de carboxylate de palladium(II) et de divers produits organiques (di-n-butylphosphate (HDBP), composés à fonctions amines et hydrazine). Les produits menant à la précipitation du palladium proviennent de la dégradation du TBP et de celle du TPH et sont présents en phase aqueuse et en phase organique.Certains produits de dégradation formés lors de l’irradiation semblent favoriser l’extraction du palladium. Pour comprendre le rôle des produits de dégradation sur l’extraction du palladium, le solvant d’extraction utilisé dans le procédé PUREX a été dopé en composés organiques. Les composés testés sont des composés commerciaux représentatifs de produits de dégradation identifiés un solvant dégradé. De plus, les espèces testées sont des composés susceptibles d’interagir avec le palladium(II) (cétone, acide carboxylique, alcool, aldéhyde et alcène). Parmi ces composés, seul le 5-dodécène conduit à une augmentation significative de l’extraction du palladium(II) par rapport à une phase organique non dopée et à la formation d’un précipité noir constitué de palladium métal. Les analyses réalisées sur la phase organique dopée en 5-dodécène ont mis en évidence la formation d’un complexe ternaire dans lequel le palladium serait entouré de molécules de TBP, de 5-dodécène et d’ions nitrate. Par ailleurs, une fraction du palladium(II) extrait dans la phase organique oxyde le 5-dodécène en cétone et est réduit en palladium métal (précipité noir). Des voies de formation des différents composés constituant les crasses ont été proposées. Les alcènes, les cétones et l’acide nitreux apparaissent comme des précurseurs dans la formation de cyanure de palladium(II). Un carboxylate de palladium(II) serait formé par réaction de palladium(II) avec l’acide carboxylique correspondant. Les amines primaires pourraient se former par hydrogénation des nitroalcanes catalysé par la présence de palladium métal tandis que l’hydrazine pourrait se former par radiolyse des amines primaires. / The spent nuclear fuel composed of uranium, plutonium and fission products (such as palladium, technetium, molybdenum, etc.) is industrially processed in France by the PUREX process. This hydrometallurgical process allows separating uranium and plutonium by using an organic phase composed of tri-n-butyl phosphate (TBP) diluted in a mixture of aliphatic hydrocarbons (TPH = tetra propylene hydrogen). During the various extraction cycles, the organic phase is subjected to acid hydrolysis and radiolysis phenomena leading to the formation of degradation products. To ensure the recycling of the organic solvent and a normal operation of the industrial process, an appropriate treatment eliminates these degradation products. Nevertheless, after several decades of industrial operation of the factories, precipitates have been observed in some equipments. These solids contain palladium, carbon, oxygen and nitrogen atoms. Industrially, a curative solution has been found and allows eliminating these cruds containing in particular palladium. However, it is important to understand the formation of palladium precipitates in the liquid-liquid extraction cycles. This thesis aims to study the behavior of palladium in the extraction cycles and the mechanisms leading to the formation of solids.For this purpose, a biphasic system containing an organic phase of TBP diluted in TPH and a aqueous phase of nitric acid containing palladium(II) nitrate has been irradiated by an external source (gamma-irradiation). This irradiation allows simulating the aging of the extraction solvent. Nonradioactive precipitates which are representative of the industrial crud were obtained. A multi-technical analysis of these inactive precipitates has shown that the solids are composed of a complex mixture: (i) palladium cyanide(II), (ii) palladium(II) carboxylate and (iii) various organic products (di-n-butyl phosphate (HDBP)), compounds with amine functions and hydrazine. Moreover, we demonstrate that the degradation products leading to the precipitation of palladium come from either TBP or TPH and are present in the aqueous phase and in the organic phase.Some degradation products formed during irradiation seem to favor the extraction of palladium(II). To understand the role of degradation products on palladium extraction, the extraction solvent used in the PUREX process was doped with organic compounds. The compounds tested are commercial compounds representative of degradation products identified a degraded solvent. In addition, the compounds tested are species which can react with palladium(II) (ketone, carboxylic acid, alcohol, aldehyde and alkene). Among these compounds, only 5-dodecene leads to a significant increase in the extraction of palladium(II) in comparison with an undoped organic phase and the formation of a black precipitate composed of palladium metal. The analyses carried out on the 5-dodecene-doped organic phase revealed the formation of a ternary complex in which the palladium would be surrounded by TBP molécules, 5-dodecene and nitrate ions. In addition, a fraction of the palladium(II) extracted in the organic phase oxidizes the 5-dodecene to ketone and is reduced to palladium metal (black precipitate).Formation pathways of the various compounds present in the nonradioactive solids have been proposed. Alkenes, ketones and nitrous acid appear as precursors in the formation of palladium cyanide(II). A palladium(II) carboxylate would be formed by reaction of palladium(II) with the corresponding carboxylic acid. Primary amines could be formed by hydrogenation of nitroalkanes catalyzed by the presence of palladium metal while hydrazine could be formed by radiolysis of primary amines.Key word: palladium, radiolysis, PUREX process, degradation products, precipitates

Les polyoxométallates (POMs) sont aujourd'hui reconnus pour leurs diverses architectures et applications. Nous nous en sommes ici servis afin de synthétiser des nanoparticules de palladium puisque le POM va jouer à la fois le rôle de réducteur du cation métallique mais aussi de surfactant des nanoparticules.Après avoir fait, dans un premier temps, l'étude électrochimique d'une série de POMs issus de la même famille, deux d'entre-eux ont été utilisés pour la synthèse de nanoparticules de palladium. D'une taille moyenne comprise entre 15 et 20 nm, ces nanoparticules ont été entièrement caractérisées et se sont avérées stables un intervalle de temps d'au moins un mois.Enfin, divers matériaux hybrides à base de palladium et/ou de cuivre ont été caractérisés par électrochimie à l'état solide et leur pouvoir catalytique vis-à-vis de la réduction des ions nitrate et de l'oxygène a été évalué. / Polyoxometalates (POMs) are known for their high diversification in terms of architectures and applications. POMs are used in this work for the synthesis of palladium nanoparticles since they act both as a reducer of metallic cation and as surfactant of nanoparticles.At first, we studied the electrochemical properties of several POMs belonging in the same family, then among this family, we chose to use two particular POMs to synthesize palladium nanoparticles. From an average size between 15 and 20 nm, these nanoparticles have been fully characterized and are stable over a month.Finally, various hybrid materials based on palladium and/or copper have been characterized by electrochemistry in solid state and their catalytic capacity towards the reduction of nitrate ions and dioxygene has been assessed.

Un grand nombre de 3,4-bisindolylmaléimides possède une activité inhibitrice des protéine-kinases. Les 3-isothiazolone-1,(1)-(di)oxydes pouvant être considérées comme des analogues de la maléimide, la fonctionalisation des 5-chloro- et 4,5-dichloro-3-isothiazolone 1,(1)-(di)oxydes par des réactions de couplage palladocatalysé de Suzuki-Miyaura, permet d'accéder aux analogues “thia” des 3,4-bisindolylmaléimides. La synthèse de sulfonamides primaires tels que les dérivés 4-(hétéro)aryl substitués du benzènesulfonamide comme inhibiteurs potentiels de l'anhydrase carbonique, a également été envisagée dans ce travail.Une collection de matériaux hybrides constitués de nanoparticules de palladium adsorbées sur des nanostructures de carbone a été préparée et testée dans des réactions de couplages palladocatalysés, comme catalyseurs en milieu hétérogène. Le plus efficace d'entre eux, associant des nanoparticules de palladium stabilisées par le dodécanethiol et adsorbées sur des nanotubes de carbones “multi-walled”, a été employé afin de préparer vingt-quatre nouveaux dérivés 4-(hétéro)aryl substitués du benzènesulfonamide. L'échec de l'utilisation de ce catalyseur dans les reactions de fonctionalisation des isothiazolone-1,(1)-(di)oxydes nous a contraints à employer un catalyseur plus conventionnel, le PdCl2(dppf)•CH2Cl2.Le dernier volet de ce projet visait à concevoir des catalyseurs à base de nanoparticules de palladium encapsulées dans des nanofibres de carbone “grafitisées” (nanoréacteurs). Une série de nanoréacteurs a pu être préparée et nous avons étudié l'effet du confinement généré à l'intérieur de la nanofibre, sur la réaction palladocatalysée de Suzuki-Miyaura. / 3,4-bisindolylmaleimides possess an inhibitory activity against protein kinase. Because 3-isothiazolone-1,(1)-(di)oxide can be considered as maleimide analog, 5-chloro and 4,5-dichloro-3-isothiazolone-1,(1)-(di)oxide were functionalised using a palladium-catalysed Suzuki-Miyaura cross-coupling reaction achieving the “thia” analogs of 3,4-bisindolylmaleimides. We were also interested in the preparation primary sulfonamides such as 4-(hetero)aryl substituted benzenesulfonamides as carbonic anhydrases inhibitors.A series of hybrid materials comprising palladium nanoparticles adsorbed on carbon nanostructures has been prepared and tested as heterogeneous catalysts of palladium-mediated cross-coupling reactions. The best catalyst, resulting in palladium nanoparticles stabilised by dodecanethiol adsorbed on multi-walled carbon nanotubes, was employed in Suzuki-Miyaura reactions for the preparation of twenty-four new 4-(hetero)aryl substituted benzenesulfonamides. As this catalyst failed in the functionalisation of isothiazolone-1,(1)-(di)oxides, this latter was realised using a more conventional catalyst, PdCl2(dppf)•CH2Cl2.A last part of the project aimed to the conception of catalysts made of palladium nanoparticles encapsulated in graphitised carbon nanofibres (nanoreactors). We prepared a series of nanoreactors and we studied the effect of the confinement inside the nanofibre channel on the Suzuki-Miyaura cross-coupling reaction.

In the first part of the thesis, the aim was to devise a new simple catalytic system based on palladium to allow insertion of carbon monoxide in the presence of an alcohol into unsaturated systems with retention of the double bond to give an unsaturated ester. The process is known as oxidative carbonylation. To allow the process to become catalytic, the palladium needs to be reoxidised in situ. Optimal conditions for the catalytic system were developed and a wide range of substrates have been examined. Simple terminal alkenes and alkenes bearing functional group have been successfully carbonylated (yield 16%-87%). The method was applied to the synthesis of a known pharmaceutical intermediate. The aim of the second part was to develop an efficient system for the intramolecular oxidative amination of unsaturated hydrazine carboxylates to form novel vinyl oxazolidines. After optimisation of the reaction conditions, the scope and limitations of the reaction were established. Attempts were also carried out to develop an enantioselective version of the cyclisation. The method was applied to the synthesis of a known intermediate in a sequence towards (-)-kainic acid thus accomplishing a formal total synthesis of this compound.

The use of ligand in transition-metal catalysed reactions has had a considerable impact. The present manuscript aims at showing the influence of ligands in the palladium catalysed Suzuki-Miyaura cross-coupling reaction. In chapter one, the mechanism of this reaction will be described based on the numerous contribution published in the literature. It will be shown that the electronic and steric properties of the ligands have a huge repercussion on the catalytic activity of the metal. In the second chapter, the electronic and steric properties of the widely used Buchwald-phosphine ligand will be investigated. For this purpose, bis-carbonyl iridium(I) complexes were synthesized and their characterization allowed determining their TEP (Tolman electronic parameter) and their buried volume %V[subscript(bur)]. Then three next chapters of this thesis will focus on the syntheses and characterizations of new palladium complexes bearing N-heterocyclic carbenes (NHC). Their design was made in a view to obtain high activity in cross coupling reaction, particularly in the Suzuki-Miyaura cross coupling. Their activation under the catalytic conditions leads to the formation of palladium(0) species that can be mono- or bis-ligated. The influence of the ligand on the catalyst activity will be discussed. A palladium(II) precatalyst leading to mono-ligated active species will be described. Its activity in cross-coupling is very good, since activated and non-activated aryl chlorides could be coupled with aryl boronic acids at room temperature using low catalyst loadings. Unfortunately, the catalyst activity decreased with temperature. This result showed the fragility of the mono-ligated active species. In a view to obtain more robust catalysts that can perform high turnover numbers, new palladium(II) precatalysts bearing two ancillary ligands were developed. Mixed systems NHC- phosphites and NHC-phosphines are described. NHC-phosphites precatalysts displayed very good activity, but the phosphites are unfortunately sensitive to reaction conditions, limiting their role of active species shield. NHC-phosphine bearing complexes were highly active and could perform up to 10,000 turnovers with unactivated aryl chlorides. Very interestingly, these catalysts were also able to couple benzylchlorides and allyl chlorides with a wide range of boronic acids at very low catalyst loadings. These reactions had also the great advantage to proceed in aqueous solvents at very high substrate concentration. The activation mechanism of these complexes was investigated. Dichloropalladium(II) complexes were reduced under the catalytic conditions to lead palladium(0) species. Therein, it is shown that this reduction step was rate-determining in catalysis. Some palladium(0) intermediates xxiv were synthesized and showed good to excellent activities at low temperature under the exact same conditions. They displayed high reactivity towards oxygen and moisture and have to be handled under inert atmosphere. A particular complex had the ability to react with molecular dioxygen to form a stable peroxo-complex. Interestingly, this complex displayed excellent activity in water under aerobic conditions. This system was of great advantage since the reaction could be set up under air using cheap and user-friendly reagents displaying low toxicity. Moreover, the readily available distilled water used as solvent did not require prior degassing. Symmetrical and unsymmetrical bis-NHC palladium(0) complexes were successfully synthesized. They display excellent activity in the Suzuki-Miyaura cross coupling and turnover frequencies as high as 300 could be obtained at room temperature with unactivated arylchlorides and arylboronic acids. These complexes were also found excellent catalysts for the coupling of benzylchlorides with arylboronic acids. Mechanistic studies showed that no ligand dissociation occurred during the coupling suggesting as bis-ligated active species.

Thesis (MScEng (Process Engineering))--University of Stellenbosch, 2005. / An increased demand for hydrogen in recent years has led to a revival of interest in methods for hydrogen separation and purification. Palladium (Pd) and palladium composite membranes have therefore received growing attention largely due to their unique permselectivity for hydrogen and good mechanical and thermal stability. Previous research on Pd composite membranes by Keuler (2000) in the Department of Process Engineering at the University of Stellenbosch has shown that some assumptions which he made during characterisation procedures needed further investigation, such as the assumptions about the influence of support membranes on preparation of Pd composite membranes, method of precleaning before pretreatment, vacuum applied during electroless plating, and heat treatment after electroless plating. In this study, Pd composite membranes (with Pd film thickness of 1.7 μm ~ 4 μm) were prepared on the inside layer (claimed pore diameter of 200 nm) of α-alumina ceramic support membrane tubes, consisting of three layers with varying pore diameters from inside to the outside layer, via a modified electroless plating technique (with a gauge vacuum of 20 kPa applied on the shell side of the plating reactor). Bubble point tests and bubble point screening tests were performed on the support membranes before the electroless plating to investigate the influence of the substrates characteristics on the preparation of the Pd composite membranes. It was found that Pd composite membranes with a better permselectivity can be prepared on a support membrane that contains smaller pore sizes and a smoother surface. The surface pretreatment step was modified to provide a uniform Pd surface for Pd electroless plating. The membrane was first rinsed in PdCl2 solution for 15 min using a stirrer at a stirring speed of 1300 rpm, and was then dipped into distilled water 10 times (1-2 second each). Subsequently, the membrane was rinsed in SnCl2 solution for 15 min, and was then dipped into distilled water 10 times. These procedures were repeated 4 times. In addition, by using a new method of assessment for heat treatment (i.e. cutting the Pd composite membranes into two pieces and then exposing them to two different heating methods), the most effective heat treatment method could be identified without the influences of the substrates or the plating technique. The preferable procedures was to anneal the Pd composite membrane in N2 for 5 h from 20°C to 320°C, and then oxidize it in air for 2 h at 320°C, followed by annealing it in N2 for 130 min from 320°C to 450°C and then in H2 for 3 h at 450°C. Finally the membrane was cooled down in N2 to 350°C and held at this temperature for 30 min. Additional oxidation in air for more than 10 hours changes the structure of the Pd films. PdO then forms and decreases the H2 permeation through the Pd composite membrane. More detailed characterisations of the Pd composite membranes were performed by membrane permselectivity tests (from 350°C to 550 ◦C) using either H2 or N2 in single gas test, membrane morphology and structure analysis using scanning electron microscopy (SEM), energy dispersive detectors (EDS), atomic force microscopy (AFM), Brunauer-Emmett- Teller (BET) and X-ray diffraction (XRD) analysis. Hydrogen permeability between 4.5-12 μmol/(m2.Pa.s) and an average hydrogen/nitrogen permselectivity of ≥ 150 were achieved in this study. The permselectivities of the heat treated membranes were superior to Keuler’s membranes, which had an average permselectivity of ≥ 100. AFM and BET analysis showed that dense and smooth Pd films with smaller Pd crystals sizes and compact Pd layers were obtained.

Thesis (PhD)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: In order to exploit lower grade and complex platinum group metal resources, cheaper and more efficient alternatives to the conventional mill-float-smelt-refine route are being sought. Leaching of platinum and palladium with cyanide has been proposed a number of times as a promising precious group metals (PGM) process option, and although platinum extractions are problematic, progress into the understanding of cyanide leaching of PGM containing ore and concentrate has been made. The platinum and palladium leaching will typically take place at elevated temperatures, which can range from 55°C on heaps to 180°C in autoclaves, with a better degree of leaching occurring with higher temperatures. Although this process for Pt and Pd extraction is a promising process option, research regarding the feasibility of the subsequent upgrading and recovery of the pregnant PGM leach solution, however, has been lacking. Since the carrier-phase extraction of gold using activated carbon offers significant advantages over other processes in terms of simplicity, the high pre-concentration factor, rapid phase separation, and relatively low capital and operating costs, activated carbon was deemed the most suitable sorbent for a Pt and Pd adsorption and stripping process. Very little is published on the adsorption of PGM cyanides onto activated carbon and when the effect of impurities such as base metals and thiocyanate together with a suitable elution method, are considered, no information could be found in the open literature. This study was launched and in general it was found that the activated carbon process does seem to be a viable process consideration for the upgrading of PGMs in a cyanide leach stream. Adsorption rates for dilute PGM solutions (0.15mg/L Pt, 0.38 mg/L Pd, 0.1 mg/L Au) in a stirred vessel indicated a high rate of adsorption within the first 60 minutes (giving more than 98% recovery of precious metals). A comparison of the Pt isotherm (25°C) to Au isotherms from literature indicated a similar loading capacity, while that of Pd was found to be significantly lower. In common with most diffusion controlled processes, an increase in the adsorption rate of platinum, palladium and gold cyanide with an increase in temperature was observed, while experiments with consecutive contacts of the PGM cyanide solution onto the activated carbon revealed that with an increase in temperature, the amount of PGMs that were adsorbed, decreased with each loading. In the absence of free cyanide and base metals, it was found that after 4 consecutive contacts, 99% of the total amount of platinum and palladium adsorbed at 25°C, compared to 85% of the platinum and 83% of the palladium at 50°C. No difference could be seen between the adsorption of gold cyanide at 25 and 50°C after 4 contacts. It has also been established that the detrimental effect of free cyanide on the adsorption of PGMs will increase as the temperature increases. The detrimental effect of the presence of Cu and Ni was found to depend on the amount of these base metals adsorbed, which in turn will depend on the cyanide concentration and the solution temperature. Adsorption of Pt and Pd has been found to be significantly more affected by temperature, cyanide and base metals than the adsorption of gold and needs to be carefully taken into consideration with the design of a PGM adsorption circuit to ensure sufficient Pt and Pd recovery. It is therefore highly likely that an activated carbon recovery process for Pt and Pd cyanide will not be as robust as the gold CIS (carbon-in-solution) process, which is considered to be one of its main advantages. The feasibility of eluting platinum and palladium cyanide complexes from activated carbon was investigated. It was found that platinum and palladium elute from activated carbon almost to completion in 4 to 5 bed volumes (BV) at 80°C, while the elution of gold at this temperature is slow, with a significant amount of gold (≈ 55 %) still to be eluted after 16 bed volumes. An increase in Pt and Pd elution kinetics was demonstrated with an increase in temperature with 99% recovery achieved at 4 BVs with an elution temperature of 95°C. Cyanide pre-treatment has been found to have a large influence on PGM elution. The effect of the NaCN concentration shows an increase in the recovery of Pt, Pd and Au as the cyanide increases from 0 to 2 %, after which the recovery starts decreasing again as the NaCN concentration increases from 2 to 4%. The NaOH concentration was also found to affect the PGM recovery and at 0% NaCN, an increase in the recovery is seen, while at a higher cyanide concentration (2 and 3% NaCN) a decrease in the PGM recovery occurs when the NaOH concentration is increased from 0.22% to 1.65%. A general decrease in Pt, Pd and Au recovery was seen as the ionic strength of the elution water increased and is consistent with literature on Au elution. The effect of a hydrochloric acid pre-treatment, which forms part of the process to remove calcium build-up from the activated carbon, was investigated, and for all the cases the Pt and Pd recovery increased when an acid pre-treatment was performed, compared to no acid pre-treatment. In none of the cases did any of the Pt, Pd or Au elute with the acid or the following rinsing water. The acid pre-treatment performed at 70°C removed a significant 64% to 75% of the Ni present and an additional 9.1% to 10.5% in the following rinsing water step. In the presence of copper cyanide, the elution order has been found to be copper, palladium, platinum and gold, which is the opposite order of adsorption preference. The cyanide pre-treatment has also been found to have a major influence on the elution of Cu and can be explained by the difference in the absorbance strength between the different copper cyanide complexes. The presence of Cu did not have a negative effect on the elution of the PGMs at strong pre-treatment (2% NaCN and 0.55% NaOH) conditions, but at weak pre-treatment conditions (0% NaCN) the recovery of Pt and Pd was reduced by between 10 and 18% after 5 BVs when Cu was present. The presence of 100 mg/L KSCN salt added to the leach solution during the adsorption stage, reduces the elution recovery of the PGMs at 4 BVs from 90% for Pt and Pd, when not present, to approximately 70% when present. The addition of the additional K+ ions reduced the recovery by less that 4% at 4 BV, which indicates that the possible formation of a PGM bonding with thiocyanate ([Pt(SCN)4]2- and [Pd(SCN)4]2-), which adsorb onto carbon, but doesn’t adsorb with water, cannot be ruled out completely. A maximum amount of 0.15% for Pt, 0.28% Pd and 0.6% Au was found to report to the pre-treatment solution at 25°C. For higher pre-treatment temperatures, the amount of Pt and Pd reporting to the pre-treatment solution increased significantly to approximately 8% at 80°C, while the increase in gold was marginal to 0.8% at 80°C. For the higher loading on the activated carbon (7000 mg/kg Pt and Pd), which is expected to be a better representation of plant conditions, 0.07% Pt, 0.11% Pd and 0.12% Au reported to the pre-treatment solution. The PGMs reporting to the pre-treatment solution is attributed to the distribution of the PGMs on the carbon particle, and even though very small, a certain amount of these PGMs would readily desorb or wash off the carbon. It has thus been established here that the stripping of adsorbed platinum cyanide complexes from activated carbon consists of a two step batch process, which involves the pre-treatment of the metal-loaded activated carbon with a relatively strong sodium cyanide and sodium hydroxide solution, prior to the elution step with de-ionized water at 80°C. Through the development of a mathematical model to describe this process, it was found that the rate of release of the platinum ions is governed by the amount of platinum and sodium on the activated carbon and the concentrations of these ions in the bulk of the liquid. This is mathematically described by a modified Freundlich isotherm equation and the mass transfer diffusion equation. The dependency of the platinum elution rate on the sodium concentration on the activated carbon, as suggested by gold related literature (Van Der Merwe and Van Deventer, 1990, Stange, 1990), is confirmed. Furthermore it has been found that the rate of platinum elution interchangeably depends on the equilibrium of the Pt ions at the carbon-liquid interface and the mass transfer of these Pt ions from the interface to the bulk liquid. As both of these rate-limiting factors were found to depend on the sodium concentration, the dominant platinum elution rate limiting factor shifts as the sodium concentrations change as the elution progresses. Four main time periods are used to simplify and to describe this process. The benefits of fundamentally understanding this process can ultimately lead to improved elution, better process control, shorter elution times, smaller elution columns or assist in the development of a continuous elution process. / AFRIKAANSE OPSOMMING: Nuwe prosesse om komplekse laer graad waardevolle metaal ertse te onwikkel in plaas van die konventionele maal-flotasie-smelt-raffineer proses word tans ondersoek. Loging van platinum en palladium met sianied is verskeie kere al voorgestel as n belowende proses opsie en alhoewel die ekstraksie van platinum nog 'n probleem is, is vordering al gemaak om die logings proses beter te verstaan. Die loging van platinum en palladium met sianied sal tipies plaasvind by hoër temperature wat kan wissel van 55°C in n hoop logins proses tot 180°C onder druk. Beter loging vind plaas soos wat die temperatuur styg. Alhoewel hierdie proses belowend is, is daar nog geen navorsing beskikbaar t.o.v die volgende stap in die proses wat die opgradering van die logings oplossing behels. Aangesien die gebruik van geaktiveerde koolstof in die goud industrie baie voordele inhou soos die eenvoudigheid van die proses, hoë opgraderings faktor, relatiewe vinnige adsorpsie en lae kapitaal en operationele kostes, mag hierdie tegnologie ook geskik wees vir Pt en Pd. Baie min is gepubliseer oor die adsorpsie van waardevolle metale (PGMs) met geaktiveerde koolstof en wanneer die effek van onsuiwerhede soos basis metale en thiosianied saam met n afstropings metode in ag geneem word, kon geen informasie in the literatuur gvind word nie. Hierdie studie is dus geloots en in die algemeen is daar bevind dat die geaktiveerde koolstof metode wel n geskikte oplossing bied vir die opgradering van PGMs in 'n sianied logings stroom. Adsorpsie snelheid vir verdunde PGM oplossings (0.15mg/L Pt, 0.38 mg/L Pd, 0.1 mg/L Au) in bekers wat geroer is, was vinnig vir die eerste 60 minutte (98% herwinning van die PGMs) en 'n vergelyking tussen die Pt adsorpsie isoterm en gepubliseerde Au isoterms wys op n relatiewe soorgelyke ladings kapasiteit. Die isotherm van Pd was egter laer. Soortgelyk aan meeste diffusie beheerde prosesse, het 'n verhoging van temperatuur gelei tot vinniger adsorpsie snelhede vir Pt, Pd en Au. Indien oplossings egter herhaaldelik met dieselfde koolstof in kontak gebring word, is bevind dat met 'n verhoging in temperatuur, die totale hoeveelheid PGMs wat absorbeer, met elke kontak verminder. In die afwesigheid van sianied en enige basis metale, het die totale hoeveelheid Pt en Pd wat geabsobeer is na 4 opeenvolgende kontake verminder van 99% by 25°C tot 85% adsorpsie van Pt en 83% Pd by 50°C. Daar was geen veskil tussen die adsorpsie van Au by 25°C en 50°C na 4 kontakte nie. Dit is ook vasgestel dat die negatiewe effek van vrye sianied in die oplossing, groter word soos wat die temperatuur verhoog. Die negatiewe effek van die teenwoordigheid van Cu en Ni, hang af van die hoeveelheid van hierdie metale wat absorbeer word wat weer bepaal word deur die sianied konsentrasie asook die temperatuur van die oplossing. Die mate waar in Pt en Pd ge-absorbeer word deur koolstof, word aansienlik meer beïnvloed deur temperatuur, sianied konsentrasie en die teenwoordigheid van basis metale as wat die adsorpsie van Au beïnvloed word. Met die ontwerp van n PGM adsorpsie proses, sal dit sterk in aanmerking geneem moet word, om seker te maak dat so min as moontlik Pt en Pd verlore gaan. Dit wys ook dat 'n geaktiveerde koolstof proses vir Pt en Pd, nie so onvatbaar vir proses veranderings sal wees soos wat die Au proses is nie, wat as een van die groot voordele van die Au proses beskou word. Die afstropery van die Pt en Pd sianied komplekse is ondersoek en gevind dat by 80°C, amper al die Pt en Pd binne 4 to 5 bed volumes (BV) van die geaktiveerde koolstof gestroop kan word. Die afstropery van Au by hierdie temperatuur is stadig en sowat 55% van die Au bly nog oor op die koolstof na 16 BVs. Die snelheid waarteen die Pt en Pd afgestroop word verhoog indien die temperatuur verhoog word en by 95°C is 99% van die Pt en Pd herwin na 4 BVs. Voorafbehandeling van die gelaaide koolstof met sianied, het 'n groot uitwerking op die PGM afstroping. Soos wat die NaCN konsentrasie verhoog word vanaf 0 tot by 2%, verhoog die PGM herwinning maar daal ook weer indien die NaCN konsentrasie verder verhoog word vanaf 2% tot by 4%. Die NaOH konsentrasie het ook n invloed gehad. By 0% NaCN, het die PGM herwinning verhoog soos wat die NaOH konsentrasie verhoog is maar by hoër sianied konsentrasies van 2 en 3%, is n daling in die herwinning waargeneem soos wat die NaOH verhoog is vanaf 0.22% tot by 1.65%. N algemene daling in die Pt, Pd and Au herwinning is waargeneem soos wat die ioniese sterkte van die stropings water toegeneem het. Dit stem ooreen met gepubliseerde navorsing oor die afstroping van Au. Om kalsium van die geaktiveerde koolstof te verwyder, word die koolstof vooraf met soutsuur gewas. Hierdie stap is vir Pt en Pd ondersoek en daar is bevind dat vir al die gevalle, die herwinning hoër was wanneer die gelaaide koolstof met soutsuur behandel is teenoor geen behandeling nie. In geen van die gevalle, is Pt, Pd of Au saam met die soutsuur of die daaropvolgende was water afgestroop nie. Voorafbehandeling met soutsuur teen 70°C lei wel daartoe dat tussen 64 en 75% Ni afgestroop word saam met die soutsuur en n verdere 9.1 to 10.5% saam met die daaropvolgende was water. In die teenwoordigheid van koper sianied, word Cu eerste afgestroop met Pd, Pt en dan Au wat daarop volg. Dit is presies die teenoorgestelde orde waarin die metale geabsorbeer word. Die voorafbehandeling met sianied, het ook 'n beduidende effek op die stroping van Cu. Dit kan verduidelik kan word aan die hand van die verskillende koper sianied komplekse wat vorm wat elkeen 'n verskillende affiniteit het vir adsorpsie. Wanneer 2% NaCN en 0.6% NaOH in die vooraf behandeling stap gebruik word, het die teenwoordigheid van koper geen negatiewe invloed op die afstroping van die PGMs gehad nie maar die herwinning is wel met 10% en 18% verlaag by 5 BVs wanneer geen sianied in die voorafbehandeling stap gebruik is nie. Wanneer 100 mg/L KSCN sout by die adsorpsie stap gevoeg word, daal die herwinning van die PGMs in die stropings stap van 90% tot 70% by 4 BVs. Die addisionel K+ katione verminder die herwinning met slegs 4% by 4 BVs wat beteken dat die vorming van adisionele komplekse soos [Pt(SCN)4]2- en [Pd(SCN)4]2-, wat nie op die normale metode afgestroop kan word, 'n moontlikheid mag wees. N maksimum van 0.15% vir Pt, 0.28% Pd en 0.6% Au word in die vooraf behandelings stap af gestroop. Indien die temperatuur van hierdie stap verhoog word na 80°C, verhoog die hoeveelheid Pt en Pd wat na hierdie stroom raporteer na 'n beduidende 8% tewyl Au basies onveranderd bly by 0.8%. Vir geaktiveerde koolstof wat hoër gelaai is (7000 mg/Kg Pt en Pd) en dus 'n beter verteenwoordiging van aanleg kondisies is, het 0.07% Pt, 0.11% Pd en 0.12% Au raporteer na die vooraf behandelings stap. Dit word toegeskryf aan die verspreiding van die PGMs op die koolstof wat hoofsaaklik op die oppervlakte voorkom en alhoewel die hoeveelheid klein is, word 'n sekere hoeveelheid slegs afgewas. Dit is dus vasgestel hier, dat die afstroping van Pt 'n twee stap proses is. Die eerste stap is die voorabehandeling van die koolstof met 'n sianied oplossing en daarna volg die afstroping van die Pt met suiwer water teen ongeveer 80°C. Met die ontwikkeling van n wiskundige model, is bevind dat die snelheid waarteen die Pt afgestroop word, beïnvloed word deur die hoeveelheid Pt en Na wat op die koolstof oppervlakte is, asook die konsentrasies van die metale in die vloeistof. Dit word wiskundig beskryf deur n gemodifiseerde Freundlich isotherm vergelyking asook deur die massa diffusie vergelyking. Die Pt afstropings snelheid wat afhanklik is van die Na konsentrasie kan vergelyk word met die afstroping snelheid van Au wat ook afhanklik is van die Na konsentrasie (Van Der Merwe and Van Deventer, 1990, Stange, 1990). Verder is bevind dat die snelheid van Pt stroping afhanklik is van beide die ewewig van Pt ione by die koolstof-vloeistof grens asook die massa beweging van Pt ione van die koolstof-vloeistof grens na die vloeistof. Beide hierdie snelheids bepalende faktore word bepaal deur die Na konsentrasie en skuif soos wat die Na konsentrasie verander soos wat die afstroping plaasvind. Vier hoof tyd periodes word gebruik om hierdie verskynsel te verduidelik. Deur die proses fundamenteel te verstaan, kan uiteindelik lei tot 'n beter proses, beter beheer, korter afstropings tye, kleiner toerusting of die ontwikkeling van 'n kontinue proses.

Thesis (MSc)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: This study comprises the preparation and characterization of various novel organometallic complexes of palladium(ll) which contain symmetric and unsymmetric (heteroatom-containing) r..-dicarbonyl-type ligands, T]3-heteroallyl ligands and T]3-coordinated trimethylsilyl-containing ligands. With the ultimate objective of preparing potential catalytic precursors similar to known catalytic precursors which exhibit hemilabile activity, the main goals of this study were the following: - • Investigate the coordination mode of the aforementioned ligand-types to the palladium of the starting compound, trans-[Pd(CeHs)CI{P(CeHshhl (1), by physical measurements. • Carry out single crystal structure determinations where possible. • Investigate the influence of the properties of the ligands on the stability of the prepared complexes. • Investigate the existence of hemilability (if any) in the prepared complex. The deprotonated symmetric and unsymmetric f!,-dicarbonyl-type ligands readily bind to the palladium of the starting compound in a bidentate fashion through the oxygens by displacing a triphenylphosphine group and producing easily removable sodium chloride. These complexes show that a negative charge can be accommodated in a delocalized fashion by the -S=O and - P=O groups of these acac--type ligands in a similar manner to the carbonyl groups of acetylacetonate. However, no evidence of hemilabile activity was found in this series of complexes. In a similar fashion, the deprotonated T]3-heteroallyl ligands, L = [PhzPS£], [PhCOz-], [PhC{NSi(CH3hhl [(Ph)zP{NSi(CH3hh-], were linked to palladium in the same starting complex, in T]3-fashion by triphenylphosphine substitution. No evidence of hemilabilty was evident in this series of complexes, but when L = [PhzPSz-], an exchange of the coordinated triphenylphosphine group with the free triphenylphosphine group was observed in the reaction mixture. Finally, the preparation, isolation and spectroscopic characterization of several T\3-allyl paliadium(lI) complexes with ligands of the type R-TeCH2CH2CQQCH3, (R = isopropyl, t-butyl ,ethyl) were attempted with the compound bis-( T\3-allyl )-di-~ -iodo-dipalladium( II), [T\3 -( CH2CHCH2J2Pd212J, which had also now been crystallographically characterized. Chelate formation by TeAQ coordination seemed possible by halide precipitation with silver tetrafluoroborate. Unfortunately the resulting compounds were too unstable to be isolated in the pure form for characterization. / AFRIKAANSE OPSOMMING: Die studie behels die bereiding en karakterisering van verskeie nuwe palladium(lI) organometaalkomplekse met inbegrip van simmetriese en onsimmetriese (heteroatoom bevattende) ~-dikarboniel-tipe ligande, 113- heteroallielligande en 113_gekoordineerdetrimetielsiliel bevattende ligande. Met die beoogde einddoel die bereiding van potensiele katalitiese voorgangers soortgelyk aan bekende katalitiese voorgangers met hemilabiele aktiviteit, sluit die hoof mikpunte van die studie die volgende in: - • 'n Ondersoek na koordinasie-wyse van die bogenoemde ligand tipes aan die palladium van die uitgangstof, trans-[Pd(C6Hs)CI{P(C6Hshhl (1), met behulp van fisiese bepalings. • Enkel kristal struktuur bepalings waar moontlike. • 'n Ondersoek na die invloed van die einskappe van die ligande op die stabilitiet van die komplekse. • 'n Ondersoek na die bestaan van hemilabiele aktiwiteit (indien enige) in die voorbereide complekse. Die gedeprotoneerde simmetriese en onsimmetriese ~-dikarboniel-tipe ligande het geredelik, bidentaat deur middel van die suurstowwe gebind aan die palladium van die uitgangstof deur die verplasing van die trifenielfosfien group en die vorming van verweiderbare natriumchloried. Hierdie komplekse dui aan dat 'n negatiewe lading wei geakkommodeer kan word deur delokalisasie by die -S=O- en -P=O-groepe van hierdie acac"-tipe Iigande, soortgelyk aan die karbonielgroep van asetielasetonaat. Geen hemilabiliteit is waargeneem in hierdie reeks komplekse nie. Die gedeprotoneerde 113-heteroalliel Iigande, L = [Ph2PS£), [PhCO£), [PhC{NSi(CH3h}£), [(PhhP{NSi(CH3hhl is op 'n soortgelyke wyse 113- gekoppel aan palladium van dieselfde uitgangstof met trifenielfosfien verplasing. Geen hemilabiliteit is waargeneem in hierdie reeks komplekse nie, maar wanneer L = [Ph2PS£], is 'n uitruiling van 'n gekoordineerde trifenielfosfien met 'n vrye trifenielfosfien in die reaksiemengsel waargeneem. Die bereiding, isolasie en spektroskopiese karakterisering van Tj3-alliel paliadium(lI) komplekse met ligande van die tipe R-TeCH2CH2COOCH3, (R = isopropiel, t-butiel ,etiel) is gepoog met die uitgangstof bis-(Tj3-alliel)-di-ll-iododipaliadium( II), [Tj3-(CH2CHCH2hPd2b], wat volledig gekarakteriseer was. Chelaat-vorming deur TeAO-koordinasie het moonlik blyk te wees deur halied presipitasie met behulp van AgBF4. Die komplekse is baie onstabiel en is dit gevolglik nie moontlik am die komplekse suiwer te isoleer en te karakteriseer nie.