Thesis (M.S.)--University of Wyoming, 2008. / Title from PDF title page (viewed on July 16, 2009). Includes bibliographical references.

Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2004. / Includes bibliographical references. Also available in electronic version. Access restricted to campus users.

Yes / The synthesis, characterisation, and evaluation of the in vitro cytotoxicity of five maleonitriledithiolate-based ruthenium metal complexes bearing various phosphine ligands towards two ovarian cancer cell lines (A2780 and A2780cisR), one non-small-cell lung cancer cell line (H460) and one normal prostate cell line (PNT2) are presented herein. These 18-electron complexes were designed with four water-soluble phosphine ligands to increase the water-solubility character of the corresponding electron-deficient ruthenium complex which showed great in vitro promises, and triphenylphosphine for comparison. The complexes with triphenylphosphine-3,3',3''trisulfonic acid and triphenylphosphine present similar cytotoxicity compared to the 16-electron precursor, with equal cytotoxicity to both A2780 and A2780cisR. Hints at the mechanism of action suggest an apoptotic pathway based on ROS production. No toxicity was observed in preliminary in vivo pilot studies for these two complexes in subcutaneous A2780 and A2780cisR xenograft models, with some evidence of tumour growth delay. / The support of the Royal Society (University Research Fellowship No. URF150295, and RGF\EA\201001), the Academy of Medical Sciences/ The Wellcome Trust/ The Government Department of Business, Energy and Industrial/ The British Heart Foundation Springboard Award (SBF003\1170), and the CNRS is acknowledged. LRP is supported by a PhD studentship funded by the University of Bradford.

In this study, an attempt was made to identify the electronic and steric properties of the precatalyst ligands that determine the characteristics of phosphine ligated Grubbs-type precatalysts for alkene metathesis by means of molecular modelling. It was found from studying the literature that the possibilities for synthesising a wide range of phosphine ligands are almost unlimited. Additionally, it was found that there is no easy method to determine the electronic and steric properties of the precatalyst ligands in existence. Molecular modelling might provide a method to study potential ligands and precatalysts before tedious synthesis methods are attempted. It was found that the theoretically calculated structures of the commercially available precatalysts compared well with the experimental data reported in literature. It is also shown that the energy profiles for alkene metathesis of simplified model systems do not compare well with non-simplified systems. Correlations between these simplified model systems and experimental work have to be regarded as serendipitous at best. When the energy profiles of the various new and commercially available precatalysts are compared, similarities in the energy trends for 1-octene metathesis are observed. These similarities raise questions about the significance of the differences in the energy barriers. In an effort to better understand this, two low activity precatalysts were also investigated in an attempt to identify the area or trend of poor catalysis. Instead of providing the desired different result, trends very similar to that of the highly active precatalysts were observed. This led to the observation that, without a sufficiently large dataset, great care should be taken before conclusions are drawn from theoretical work. Since the electronic investigation did not provide the desired result of finding a fast and effective method of determining which ligand merits further investigation, some steric aspects were studied. Once again, the precatalysts proved to be remarkably similar and no definitive answer for the observed differences in the various precatalysts could be determined. A preliminary experimental study into the feasibility of the synthesis of the new potential ligands was done. The multi-step synthesis route resulted in low yields in some cases, with the need for large volumes of solvents to purify the products. The toxicity of phenylphosphine also has to be taken into account when considering these types of ligands. A new precatalyst obtained by using a new ligand should show a remarkable improvement over the current commercially available precatalysts to justify the additional cost to synthesise a new ligand. It would seem that for future projects more consideration should be given to the deactivation mechanism of the Grubbs-type precatalysts, since this seems to be the logical starting point to look for the answers to the experimentally observed differences. A deeper understanding of the mechanism of alkene metathesis can only be obtained if all aspects are investigated in as much detail as possible. While the results did not provide the initially expected outcome, some valuable insights were gained that challenge the current way of thinking about the alkene metathesis mechanism. It is also clear that to oversimplify a very complex reaction and using limited data will lead to false assumptions being made. / PhD (Chemistry), North-West University, Potchefstroom Campus, 2014

In this study, an attempt was made to identify the electronic and steric properties of the precatalyst ligands that determine the characteristics of phosphine ligated Grubbs-type precatalysts for alkene metathesis by means of molecular modelling. It was found from studying the literature that the possibilities for synthesising a wide range of phosphine ligands are almost unlimited. Additionally, it was found that there is no easy method to determine the electronic and steric properties of the precatalyst ligands in existence. Molecular modelling might provide a method to study potential ligands and precatalysts before tedious synthesis methods are attempted. It was found that the theoretically calculated structures of the commercially available precatalysts compared well with the experimental data reported in literature. It is also shown that the energy profiles for alkene metathesis of simplified model systems do not compare well with non-simplified systems. Correlations between these simplified model systems and experimental work have to be regarded as serendipitous at best. When the energy profiles of the various new and commercially available precatalysts are compared, similarities in the energy trends for 1-octene metathesis are observed. These similarities raise questions about the significance of the differences in the energy barriers. In an effort to better understand this, two low activity precatalysts were also investigated in an attempt to identify the area or trend of poor catalysis. Instead of providing the desired different result, trends very similar to that of the highly active precatalysts were observed. This led to the observation that, without a sufficiently large dataset, great care should be taken before conclusions are drawn from theoretical work. Since the electronic investigation did not provide the desired result of finding a fast and effective method of determining which ligand merits further investigation, some steric aspects were studied. Once again, the precatalysts proved to be remarkably similar and no definitive answer for the observed differences in the various precatalysts could be determined. A preliminary experimental study into the feasibility of the synthesis of the new potential ligands was done. The multi-step synthesis route resulted in low yields in some cases, with the need for large volumes of solvents to purify the products. The toxicity of phenylphosphine also has to be taken into account when considering these types of ligands. A new precatalyst obtained by using a new ligand should show a remarkable improvement over the current commercially available precatalysts to justify the additional cost to synthesise a new ligand. It would seem that for future projects more consideration should be given to the deactivation mechanism of the Grubbs-type precatalysts, since this seems to be the logical starting point to look for the answers to the experimentally observed differences. A deeper understanding of the mechanism of alkene metathesis can only be obtained if all aspects are investigated in as much detail as possible. While the results did not provide the initially expected outcome, some valuable insights were gained that challenge the current way of thinking about the alkene metathesis mechanism. It is also clear that to oversimplify a very complex reaction and using limited data will lead to false assumptions being made. / PhD (Chemistry), North-West University, Potchefstroom Campus, 2014

The research reported in this thesis was carried out in Brisbane, Australia and Calgary, Canada. The aim of the research conducted in Brisbane was to prepare a series of copper(I) and ruthenium(II) based complexes incorporating a hemilabile phosphine ligand and to determine whether or not these compounds possessed catalytic activity. The history, uses, properties and recent work incorporating hemilabile phosphine ligands is discussed in detail as well as the application of hemilabile ligands to atom transfer radical polymerization (ATRP) and the usefulness of the 'windscreen wiper' action of these ligands in polymerization. The literature synthesis and characterization of four hemilabile phosphine ligands is reported with modifications. The (2-chlorophenyl)diphenylphosphine ligand was prepared via a Grignard reaction giving a 11% yield. The (2-bromophenyl) diphenylphosphine ligand was prepared by reaction of 2-bromoiodobenzene with Ph2PSiMe3 in the presence of a palladium catalyst (MeCN)2PdCl2 which yielded 50% product. The 1-chloro-2-diphenylphosphinoethane ligand was prepared following the generation of a lithium diphenylphosphide which was added to 1,2-dichloroethane to give a 43% yield of product. The (2-benzoic-acid)diphenylphosphine ligand was prepared by hydrolysis of (2-methyl-ester-phenyl)diphenylphosphine. Following acidification of the methyl ester phosphine with HCl, the desired product was isolated in 88% yield. The synthesis and characterization of a series of copper(I) based complexes incorporating the prepared phosphine ligands involved reaction in CH3CN of the appropriate ligand with copper halides as starting material. Solution state 31P NMR and mass spectrometry were used to study many of these complexes in the solution state, whilst microanalysis, 31P CP MAS NMR and single crystal X-ray diffraction studies were used to study their solid state properties. The complexes of the type bis(2-halophenyl)diphenylphosphine copper halide were found to be three coordinate with non-chelating ligands and to be isostructural with the previously studied bis(2-methylphenyl)diphenylphosphine copper halide complexes. The synthesis and characterization of ruthenium(II) based complexes incorporating hemilabile phosphine ligands involved reaction of the appropriate ligands in MeOH with RuCl3.3H2O or RuCl2(DMSO)4 as the ruthenium source. Modes of characterization included solution state 31P NMR, mass spectrometry, microanalysis and single crystal X-ray diffraction studies. All ruthenium(II) based complexes were found to incorporate the hemilabile ligands in a chelating mode resulting in 6 coordinate structures. The preliminary polymerization testing of MMA in the presence of the copper(I) and ruthenium(II) based complexes has been reported. All complexes successfully polymerized the monomer and the resulting polyMMA showed polydispersity values ranging from moderate (3.1) to very high (6.7). Chapter 7 discusses research conducted over a 6 month period at the University of Calgary, Canada under an International Resident Fellowship award. This work involved the synthesis and characterization of scandium(III) and yttrium(III) based complexes incorporating a chelating amido-imine ligand, as potential olefin polymerization catalysts.

This thesis describes the design, synthesis and application of artificial metalloenzymes for transition metal catalysed reactions not performed by natural enzymes. Unique cysteine containing protein templates were covalently modified with transition metal ligand complexes that generate catalytic activity, which allows for the use of virtually any protein template. SCP-2L was selected as template for the linear hydrophobic tunnel that traverses the protein, which has high affinity for linear aliphatic molecules. The use of catalysts based on this protein to induce increased activity in the biphasic hydroformylation of linear α-olefins is investigated in this work. For this purpose, unique cysteine containing mutants of SCP-2L were modified with phosphine ligands by application of a novel bioconjugation procedure. Application of rhodium adducts of the phosphine modified protein constructs led to up to a 100 fold increase of the turn over numbers was measured compared to a Rh/TPPTS model system which is used in industry. Furthermore, good selectivity towards the linear product was observed. If it can be confirmed that the found catalytic results truly are the result of substrate encapsulation by the protein scaffold, this system represents the first rationally designed artificial metalloenzyme which exploits the shape selectivity of the protein scaffold to direct the outcome of a catalytic reaction. In addition, a study was performed for the development of enantioselective artificial metalloenzymes. Nitrogen ligands were covalently introduced in SCP-2L and the obtained conjugates were applied in the copper catalysed Diels-Alder and Michael addition reaction. A promising 25% ee was found for the Diels-Alder reaction between azachalcone and cyclopentadiene using one of the created constructs. Further development of these catalyst systems with the use of both synthetic (e.g. optimisation of ligand structure) and biomolecular tools (e.g. optimisation of protein environment) for optimisation can lead to very efficient and enantioselective conversions in the future.

Treatment of 4,5 bis-(diphenylphosphino)-cyclopenten-1,3 dione with thiophene carboxyaldehyde in dichloromethane, in the presence of molecular sieves results in a new heterocyclic compound, 2-(2-thienylidene)-4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione (ligand), with a high yield. This product was characterized by using both IR and NMR spectroscopic techniques and the solid-state structure of the ligand was determined using X-ray crystallography. When the ligand was treated with the solvent stabilized intermediate of ReBr(CO)5 with THF, a monomeric metal complex, fac-BrRe(CO)3[2-(2-thienylidene)-4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione] was the result. The solid-state structure of the monomeric metal complex was determined using X-ray crystallography. Photolysis and thermolysis studies of the complex will be further explored.

The "Ferrocene phosphinoguanidine donors" project presented in this Thesis targeted on the synthesis, coordination chemistry and catalytic applications of a rather uncommon class of compounds combining phosphine and guanidine functional groups in their molecules. Two series of such compounds based on ferrocene backbone (henceforth fc = ferrocen-1,1΄-diyl) were studied. Firstly, a reliable synthetic route towards polar phosphinoguanidinium chlorides [R2PfcCH2NHC(NH2)2]Cl, where R = iso-propyl, cyclohexyl, phenyl and 2-furyl, was developed and these ligands were tested as supporting ligands in palladium-catalysed Suzuki-Miyaura-type reactions in biphasic aqueous mixtures and in rhodium-catalysed hydroformylation of 1-hexene. Deduced from the results, the hydrophilic guanidinium tag had a beneficial effect on the catalytic activity and, particularly, the electron-rich phosphines from this series could serve as a useful alternative to commonly used ligands for catalytic applications in polar or aqueous reaction media. Phosphinonitriles R2PfcCN obtained as intermediates during the synthesis of the abovementioned ligands were additionally used for the preparation of the dimeric complexes [Au2(µ-R2PfcCN)2][SbF6]2, in which the gold(I) centre was stabilised by nitrile coordination. These complexes proved...

Philosophiae Doctor - PhD / Cancer is one of the leading causes of death worldwide. According to the WHO, cancer accounted for 7.4 million deaths world wide in 2004. The metallo-compound cisplatin has been used for years as an effective antitumor agent for treating solid tumours such as breast, bladder, lung, oesophageal, and head and neck carcinomas. However, the use of cisplatin as an antitumor agent has been limited because of its association with problems such as lack of selectivity for cancer cells over normal cells, development of resistance to cisplatin treatment, and side effects such as nephrotoxicity. Recent studies on anticancer drugs have focussed on alternative anticancer agents such as gold compounds in both Au(I) and (III) oxidation states, which have shown to be potential anticancer drug agents because of their ability to induce apoptosis in several human cancer cells. Some gold complexes have shown to be able to selectively kill cancer cells over normal cells.