This work set out to develop synthetic routes to transition metal complexes containing the ligands of general type [PPh₂(X)][PPh₂(Y)][PPh₂(Z)]CH and [PPh₂(X)][PPh₂(Y)][PPh₂(Z)]C⁻, where X, Y, Z = various combinations of O, S, Se and electron pairs. The aim would then be to fully characterise the complexes by various spectroscopic methods to determine the modes of coordination of the ligands and rationalise any dynamic processes which may be occurring in solution. Finally the complexes would be investigated in terms of chemical reactivity, especially with regards to potential catalytic activity. The synthesis and characterisation of a series of rhodium, iridium, platinum, and palladium complexes containing the phosphine chalcogenide ligands, [CH(P(S)Ph₂)₃]/[C(P(S)Ph₂)₃]⁻ and [CH (PPh₂)(P(S)Ph₂)₂]/[C(PPh₂)(P(S)Ph₂)₂]⁻, are described.The crystal structures of seven of these complexes plus that of the ligand, [CH(PPh₂)(P(S)Ph₂)₂], have been determined. These structures include [Pd(n³-C₄H₇){CH(PPh₂)(P(S)Ph₂)₂-P,S}]BF₄ 2H₂O, [Pd(n³-QH₇){CH(P(S)Ph₂)₃-S,S,S]BF4, [Rh(cod){C(P(S)Ph₂)₃-S,S}], [Ir(CO)3 {C(P(S)Ph₂)3 -S,S}], [Rh(cod){C(PPh₂(P(S)Ph₂)₂-P,S}] CH₂Cl₂. [Rhl₂CBuNC)₂ {C(PPh₂)(P(S)Ph₂)₂-P,S}], and [Ir(cod){CH(PPh₂)(P(S)Ph₂)₂-P,S}]BF₄ CH₂Cl₂, which are all discussed in detail. The [CH(P(S)Ph₂)₃] ligand coordinates in an n³ mode to metal centres. The anionic ligand [C(P(S)Ph₂)₃]⁻ coordinates to metals in an n² mode using two of its sulphur atoms, leaving a -P(S)Ph₂ group dangling. The ligand, [CH(PPh₂)(P(S)Ph₂)₂], can either coordinate in an n² P,S mode, using a phosphorus and a sulphur atom, or in an n³ P.S.S mode using a phosphorus and two sulphur atoms. The anionic ligand, [C(PPh₂)(P(S)Ph₂)₂], acts as a four electron donor, using one phosphorus and one sulphur atom, to metal centres. The reaction of [Ir(cod){C(P(S)Ph₂)₃-S,S}] with CO to give [Ir(CO)₂{C(P(S)Ph₂)₃-S,S}] is described. The reaction of [Rh(cod){C(PPh₂)(P(S)Ph₂)₂-P,S}] with tBuNC to give [Rh(tBuNC)₂{C(PPh₂)(P(S)Ph₂)₂-P,S}] is discussed. The subsequent oxidative additions of I₂ and benzyl bromide, to give isomeric mixtures of [RhI₂(tBuNC)₂{C(PPh₂)(P(S)Ph₂-P,S}] and [RhBr)(Bz)(tBuNC)₂ {C(PPh₂)(P(S)Ph₂)₂-P,S}] respectively, are also presented. The fluxional behaviours of [Pd(n³-C₄H₇){CH(PPh₂(P(S)Ph₂)₂-P,S}]BF₄, [Pd(n³-₄H₇){C(P(S)Ph₂)3-S,S}, [Pt(MeOcod){C(P(S)Ph₂)₃-S,S}], and [Rh(cod){C(P(S)Ph₂)₃}] are discussed in detail.The two -Ph₂P=S groups in the above complexes undergo a rapid intramolecular site exchange at ambient temperature in solution. Line shape analysis of variable temperature ³¹P{¹H} NMR data gives the following ΔG° for this dynamic exchange of coordinated and noncoordinated sulphur at 298 K. [Pd(n³-C₄H₇){CH(PPh₂)(P(S)Ph₂)₂-P,S)}]BF₄ 48 kJ/mol [Pd(n³-C₄H₇ ){C(P(S)Ph₂)₃-S,S}] 38 kJ/mol [Pt(MeOcod){C(P(S)Ph₂)₃-S,S}] 48 kJ/mol [Rh(cod){C(P(S)Ph₂)₃-S,S}] 46 kJ/mol / Graduate

M.Sc. / There were two main objectives of the research presented m this dissertation. Firstly, the synthesis of bulky electron withdrawing phosphine-alkene ligands for classic ligand testing in the Suzuki cross-coupling reaction was performed. Previously, a range of electron deficient phosphine-alkenes was prepared from 2- ( diphenylphosphino )benzaldehyde, using both Wittig and Knoevenagel chemistry. These were tested for catalysis and gave high yields for the Suzuki reaction. In the present instance, 2-( di-otolylphosphino) benzaldehyde was synthesised making use of Grignard technology from acetyl protected 2-bromobenzaldehyde and chloro(di-o-tolyl)phosphine (itself prepared from PCh. And the appropriate o-tolyl Grignard reagent. This material served as a building block for the generation of P-alkene ligands which were synthesised making use of Wittig, Knoevenagel and transesterification chemistry. These o-tolyl analogues of the P-alkene ligands prepared in the previous study were used in ligand testing experiments in the Pd-catalysed Suzuki cross-coupling reaction. The results of the catalysis showed an enhanced activity with these ligands over the previous cases The second part of this dissertation involved determining the role (influence on activity) of the non coordinating counterion in the catalyst system in the methoxycarbonylation reaction. To this end discrete Pd complexes were synthesised and used directly in the methoxycarbonylation reaction. There have been a few reports on the role of the non-coordinating counterions of the catalyst systems in the methoxycarbonylation reaction. The catalyst is typically a palladium compound in the presence of a Bmnsted acid co-catalyst. Changes to the Bmnsted co-catalyst cause two variables to change, namely the acidity of the acid and the nature of the counterion that the acid provides. The work presented in this dissertation shows the results of only one variable being changed (that of the counterion) and as such allowed the specific role of the counterion in the outcome of the reaction to be determined. Previous work done in our laboratories made use of the Lewis acid Al(OTf)3 to co-catalyse the methoxycarbonylation reaction with rates and high yields being observed. In the present instance discrete Pd complexes were synthesised from Pd(OAc)2 using p-TsOH, MsOH and TfOH as the acids containing the weakly coordinating counterions. These Bnmsted acids have the ability to displace the OAc- anion from the Pd and as such formed the discrete L2PdX2complexes (L = PPh3; X = Mso-, p-Tso-, TfO} Synthesis of these discrete complexes was impeded by a lack of knowledge of the specific conditions under which to prepare the complexes and many avenues were pursued before successful isolation of these complexes was achieved. These discrete catalysts were used in the methoxycarbonylation reaction co-catalysed by Al(OT£)3. Here, the Al(OTt)3 forms the basis of a constant acid cocatalyst allowing only the counterion to be changed with the view to determining its role in these reactions. It was found that the counterion appears to play no role at all (Aco-, p-Tso-, Mso-, TfO-) in the outcomes of these reactions under the conditions employed. A comparative study is also detailed herewithin of the effects of both ex situ and in situ catalyst generation on the activity in the methoxycarbonylation reaction, which provides some insightful results.

Eight rare earth complexes with bis(2-pyridylmethyl)amine (DPA) were synthesised and recrystallised, under air-sensitive or low moisture conditions. The crystal structures were successfully determined, via SC-XRD, and the asymmetric units of five complexes (1, 3, 5, 6 and 7) were submitted for DFT molecular modelling calculations, which involved geometry optimisation and frequency calculations. The neutral complexes obtained were bis(bis(2-pyridylmethyl)amine)-trichloro-lanthanum(III) [LaCl3(DPA)2] (1), bis(bis(2-pyridylmethyl)amine)-trichloro-cerium(III)) [CeCl3(DPA)2] (2), bis(μ2-chloro)-diaqua-tetrachloro-bis(bis(2-pyridylmethyl)amine)-di-praseodymium(III) [PrCl2(μ-Cl)(DPA)(OH2)]2 (3) and bis(μ2-methoxo)-bis(bis(2-pyridylmethyl)amine)- tetrachloro-di-dysprosium(III) [DyCl2(μ-OCH3)(DPA)]2 (4). The cationic complexes obtained in this study were dichloro-bis(bis(2-pyridylmethyl)amine)- neodymium(III) chloride methanol solvate [NdCl2(DPA)2]Cl·CH3OH (5), dichloro-bis(bis(2- pyridylmethyl)amine)-dysprosium(III) chloride methanol solvate [DyCl2(DPA)2]Cl·CH3OH (6), dichloro-bis(bis(2-pyridylmethyl)amine)-yttrium(III) chloride methanol solvate [YCl2(DPA)2]Cl·CH3OH (7) and dichloro-bis(bis(2-pyridylmethyl)amine)-lutetium(III) chloride methanol solvate [LuCl2(DPA)2]Cl·CH3OH (8). The ‘Quantum theory of atoms in molecules’ approach was used to investigate the electron density topology, primarily in order to investigate the hydrogen and coordination bonds for three of the eight complexes. Two of the neutral complexes contain the ‘early’ rare earth elements lanthanum and praseodymium and one cationic complex contains the ‘late’ lanthanide element dysprosium. Noncovalent interaction analysis was also performed on the aforementioned complexes in order to gain a deeper understanding of the intra-molecular stereo-electronic interactions. Spin density analysis was used to investigate the distribution of unpaired electron density at and around the metal centres of the aforementioned paramagnetic Pr- and Dy-complexes. A ligand conformation search for DPA was undertaken and 32 low energy conformers were identified and their relative energies were determined using two DFT functionals, namely M06 and M06-2X.

M.Sc. / This study initially focused on the synthesis of a set of triaryl phosphine ligands, encompassing a broad range of electron withdrawing functionalities on the ortho-position of one of the aryl rings. These varying moieties were readily incorporated into diphenylphosphino benzaldehyde as starting material through both Wittig and Knoevenagel chemistry. The ligands produced were tested in the Pd-catalysed Suzuki reaction. The electronic as well as the steric nature of the alkene ligands largely dictated the activities observed: the more electron poor or the bulkier the ligand, the higher the activity observed in the Suzuki reaction. This is in contrast to much work in the literature stating that highly active Suzuki catalysts require a very electron rich system. At the same time, the literature indicates that co-ordinatively unsaturated Pd-complexes are also active catalysts. The activities observed were ascribed to the ability of these electron poor bulky phosphine alkene ligands to stabilise or promote the reductive elimination step of the Suzuki mechanism in preference to the oxidative addition step, which is the typical rate determining step. The study then investigated carbonylation reactions, specifically the methoxycarbonylation and hydrocarboxylation reactions, which are typically Brønsted acid co-catalysed. The alternative was the first time use of metal-triflate based Lewis acids as co-catalysts in these types of reactions. Thus, a systematic study was performed. It was found that metal trifluoromethane sulfonate (hereafter referred to as triflate) based Lewis acid co-catalysts outperformed the typical Brønsted acid co-catalysts by between one and a half to two and a half times on the rate of the methoxycarbonylation reaction, depending on the substrate used. The system was tested with Pd loadings in the region 2–0.03 mol%. A competing heat-induced styrene polymerisation reaction ultimately affected the results at such low Pd loadings. A low level kinetic analysis was performed indicating zero order kinetics on the alkene concentration of the reaction, with a fractional order dependence on the Lewis acid concentration. There was little to no effect on the linear/branched ratio of the product in response to the use of the Lewis acid. The nature of the metal within the metal triflate based co-catalyst also seemed to be critical to the reaction, with the 4+ based Zr and Hf ultimately providing the highest obtainable turn over frequencies, the 1+ and 2+ based metals providing no conversion, and reactivity in the presence of the 3+ metals depended on the specifics of the reaction. In addition to a great deal of work being performed on styrene and ethylene as substrates, reactions using phenylacetylene were also optimised. Here, it was found that the bidentate BINAP ligand and the literature preferred ligand, PyPPh2 afforded good catalyst activity. Both of these ligands offered much faster catalyst systems than PPh3 and various other bidentate ligands tested.

In an effort to study the spectral, magnetic, and stereochemical properties of vanadyl complexes, both a new series of vanadyl complexes derived from type (VII) ligands with subnormal magnetic moment and from type (VIII) ligands with normal magnetic moment are synthesized and characterized.

>Magister Scientiae - MSc / This thesis reports on the syntheses of new bimetallic iminopyridyl nickel(II) and palladium(II) complexes as catalyst precursors for ethylene ligomerization/polymerization. Tetrahydrophenyl-linked iminopyridyl ligands, pyridin-2-ylmethyl-{4-[(pyridin-2-ylmethylimino)-methyl]-benzylidene}-amine (L1) and (2-pyridin-2-yl-ethyl)-{4-[(2-pyridin-2-yl-ethylimino)-methyl]-benzylidene}-amine (L2) were prepared via condensation from terephthaldehyde and 2 molar equivalents of a primary pyridylamine. Alkyl-linked iminopyridyl ligands N,N'-bis-pyridin-2-ylmethylene-propane-1,3-diamine (L3), N,N'-bispyridin- 2-ylmethylene-butane-1,4-diamine (L4) and N,N'-bis-pyridin-2-ylmethylenepentane- 1,5-diamine (L5) were prepared by condensation of 2 equivalents of 2- pyridinecarboxaldehyde and a primary diamine. The ligands were obtained as either red oils or orange solids. These ligands were characterized using Fourier-transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (NMR), mass spectrometry (MS), elemental analysis (EA), ultraviolet-visible spectrophotometry (UV-Vis) and thermal gravimetric analysis (TGA) where applicable. The tetrahydrophenyl-linked iminopyridyl ligands were subsequently used to prepare their corresponding homobimetallic palladium(II) and nickel(II) complexes. A 1:2 reaction of the ligands with PdCl2(COD), NiCl2(DME) and NiBr2(DME) gave palladium(II) and nickel(II) complexes C1-C6 in moderate to very good yields (58-94%). The palladium(II) complexes were found to be stable, but light-sensitive solids while the nickel(II) complexes were found to be stable, but light and air sensitive solids. These complexes were characterized using FTIR, NMR, EA, MS, UV-Vis and TGA. These complexes were then tested for catalytic activity of ethylene oligomerization. It was found that complexes C1 and C5 were highly active when activated by the cocatalysts methylaluminoxane (MAO) as well as ethyl aluminium dichloride (EADC). It was found that EADC gave the highest activity so the remaining catalysts (C3 and C6) were tested exclusively with EADC. All four complexes were active for ethylene oligomerization with yields of between 2.7-6.5 g, with C5 providing the highest activity and C1 the lowest. These catalysts were highly selective towards C4 oligomers with percentages ranging from 71-81%. Optimization studies were then carried out with C3 by varying the pressure and Al:Ni ratio.

Les terpènes représentent plus de 80% des essences naturelles du Maroc, sont de faible coût et très abondants dans la nature, et existent sous forme optiquement pure. Ces composés, de par leur structure qui se prête facilement à des réactions de fonctionnalisations, comportent un ou plusieurs centres de chiralité qui les placent en première ligne comme précurseurs potentiels de coordinats optiquement actifs. Nous nous sommes intéressés à la synthèse de nouveaux ligands chiraux a partir de terpènes naturels. En particulier, nous avons préparé des aminoalcools, diimino et diaminodiols à partir de d’α-pinène, et des α-aminooximes, leurs éthers ainsi que leurs diamines correspondantes à partir du limonène. Ces nouveaux coordinats chiraux ont ensuite été appliqués en catalyse asymétrique de transfert d’hydrogène sur des cétones aromatiques sur des complexes à base de métaux de transition, en particulier le ruthénium, et en présence de l’isopropanol comme source d’hydrogène. Ces ligands en comparaison avec la littérature s’avèrent performants en termes d’activité et sont à même d’induire une bonne énantiosélectivité (des excès énantiomériques de l’ordre de 80% ont été obtenu sur certains substrats). Une étude plus approfondie du mécanisme réactionnel a été réalisée avec les ligands α-aminooximes, dont ce travail présente la première application en catalyse asymétrique. / Terpenes represent more than 80% of natural oils of Morocco, are of moderate cost and very plentiful in nature. These compounds are prone to be readily functionalized, and as their backbone includes one or more chiral centers, they are therefore potential precursors for the synthesis of chiral ligands without separation of the enantiomers. In this work, we have been interested in the synthesis of novel chiral ligands from natural terpenes. In particular, we have prepared amino alcohols, diimino and diaminodiols from α-pinene, and α-aminooximes, their ethers and their corresponding diamines from limonene. These new ligands were applied in asymmetric catalysis of hydrogen transfer of aromatic ketones with complexes based on transition metals, particularly ruthenium, in the presence of isopropanol as hydrogen source. These ligands in comparison with the literature prove to be efficient in terms of activity and are shown to induce medium to good enantioselectivities (enantiomeric excesses up to 80% have been obtained on some substrates). Further study on the reaction mechanism have been carried out specifically with the α-aminooximes ligands, as this work is presenting the first application of this new series of ligands in asymmetric catalysis.

The role of metal ions as catalysts for numerous biochemical reactions has been the subject of many investigations. One of the most important classes of ligands are phosphate esters. In this thesis I describe the investigation of some phosphate ester-metal ion equilibria. Formation constants for the complexation of p-nitrophenyl phosphate, phenyl phosphate, 1-naphthyl phosphate, α-D-glucose-1'-phosphate, glycerol-2-phosphate, methyl phosphate, 8-quinolyl phosphate, 8-quinolyl methyl phosphate, triphosphate and fluorotriphosphate with protons, copper, zinc and calcium ions were determined by potentiometry. In addition, the complexation of 1-naphthyl phosphate, 8-quinolyl phosphate and 8-quinolyl methyl phosphate with nickel and cobalt ions was also studied. Protonation enthalpies and copper complexation enthalpies of p-nitrophenyl phosphate, phenyl phosphate, 1-naphthyl phosphate, α-D-glucose-1'-phosphate, glycerol-2-phosphate and methyl phosphate were determined by calorimetry. A correlation between the nucleophilicity of the ester group and the magnitude of the stability constants of the proton, copper and zinc complexes of p-nitrophenyl phosphate, phenyl phosphate, 1-naphthyl phosphate, α-D-glucose-1'-phosphate, glycerol-2-phosphate and methyl phosphate is found and explained in terms of electronic induction effects, i.e. by polarisation of the phosphate oxygens by the ester group. The calorimetric results show that the desolvation of ligand and metal ion during the complexation plays an important role. The possibility of similar correlations for complexes of triphosphates is also discussed.

The amino acid sequence determination of Phascolopsis gouldii hemerythrin in the region of the proposed iron ligand at position 58 was the main objective of this research endeavor. Generation of a large peptide was pursued by trypsin digestion of citraconylated hemerythrin producing peptide 50-113 for sequenator analysis. Detection of the phenylthiohydantoin amino acid derivatives by gas-liquid and high-performance-liquid chromatography yielded unambiguous sequence elucidation through the region of interest identifying residue 58 as glutamic acid.

A dissertation submitted to the Faculty of Science, School of Chemistry, University of the Witwatersrand, Johannesburg, in fulfilment of requirements for the degree of Master of Science. Johannesburg, 2017. / Pyridyl-imine ligands L1-L4 were prepared by condensation of pyridine-2-carboxyaldehyde with an appropriate amine. Characterization by NMR spectroscopy, infrared spectroscopy, mass spectrometry and elemental analysis confirmed successful preparation in yields of 64-88%. These ligands were used to prepare Pd(II) complexes C1-C4, from PdCl2(CH3CN)2 and the corresponding pyridyl-imine ligand. 1H-NMR, 13C-NMR, FT-IR, mass spectrometry and elemental analysis confirmed coordination. Attempts to prepare target Fe(II) complexes C5-C8 by reacting the ligands with anhydrous FeCl2 were unsuccessful. Infrared data suggested coordination of ligands to the Fe centre, however mass spectrometry and elemental analysis data revealed that target complexes were not obtained. Pd(II) complexes C1-C4 were evaluated as catalyst precursors for 1-hexene oligomerization and norbornene polymerization using methylaluminoxane (MAO) as co-catalyst. The oligomerization of 1-hexene was investigated in a neat reaction media at various Al:Pd ratios. All investigated complexes were found to be inactive for the oligomerization of 1-hexene. From 1H-NMR spectroscopy and GC-MS analysis it was observed that the product distribution was mainly a mixture of 2-hexene and 3-hexene isomers. Parameters such as temperature and time did not have any significant influence towards the productivity of 1-hexene oligomers. Norbornene polymerization studies were carried out with Pd(II) complex C4 in toluene at room temperature. This complex was found to exhibit good activity for norbornene polymerization, producing a vinyl bicyclic polymer, confirmed with infrared and solid state 13C-NMR spectroscopy. Increasing the amount of co-catalyst (MAO) and temperature did not have any significant influence on the activity and monomer conversion. However, increasing reaction time was observed to have a significant influence on the activity. / MT2017