Thesis (Ph. D.)--University of Wisconsin--Madison, 1969. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographies.

Thesis (M.S.)--University of Wisconsin--Madison, 1970. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph. D.)--University of Hong Kong, 2005. / Title proper from title frame. Also available in printed format.

Thesis (Ph.D.)--Texas Christian University, 2007. / Title from dissertation title page (viewed Jul. 31, 2007). Includes abstract. Includes bibliographical references.

This study focussed on two copper(II)-containing metal-organic frameworks (MOFs): Cu2Na(OH)B4C•7H2O and Cu2¼(OH)½B4C•8H2O (B4C = 1,2,4,5- benzenetetracarboxylate). They are both covalent, three-dimensional metalorganic framework polymers containing voids filled with water molecules. Both were characterised by elemental analysis, infrared spectroscopy, X-ray powder diffractometry (both in situ and regular), thermogravimetric analysis, differential scanning calorimetry and X-ray photoelectron spectroscopy. These two MOFs are essentially identical, with the only difference being the substitution of sodium by copper at every 4th site (disordered throughout the crystal). The guest inclusion properties of both MOFs were studied and compared. Although both structures collapse on dehydration, it was observed that Cu2Na(OH)B4C•7H2O is able to take up signifcant amounts of water, methanol and ethanol. All these processes are fully reversible. Car-Parrinello molecular dynamics studies suggest that it is a strong interaction between the oxygen atoms on these molecules with the sodium cation of the MOF that is responsible for this signifcant uptake. In contrast, Cu2¼ (OH)½ B4C•8H2O, the MOF without a sodium cation, did not demonstrate any methanol or ethanol uptake, but was able to take up some water. The uptake of water, however, is not a fully reversible process. The absence of sodium likely results in insuffcient energy to draw methanol and ethanol into the framework, while a subtle rotation of a carboxylate group on dehydration decreases the ability of the framework to form hydrogen bonds, thus reducing the ability to take up water. A series of hydrothermal syntheses were performed in order to develop a method of synthesis superior to the current gel-based synthesis that requires several months and has poor yields. The hydrothermal products were characterized by elemental analysis, infrared spectroscopy, X-ray powder diffractometry, thermogravimetric analysis and differential scanning calorimetry. It was shown that the MOF Cu2Na(OH)B4C•7H2O may be synthesised in almost 100% yield by using a temperature of 120°C over a period of 72 hours. It was not possible to synthesise Cu2¼ (OH)½ B4C•8H2O in a 100% yield - it was only obtained as a minor product.

M.Sc. / This dissertation describes the synthesis and characterization of CdSe/ZnO and Ag/ZnO core/shell nanoparticles using water as a solvent. The effects of the concentration of the shell precursor, pH, and stabilizing agents on the properties of the nanoparticles were investigated. In general, the type of capping agents had an influence on the crystallite size of the core nanocrystals. The particle size distributions which were calculated from TEM images show that thioglycolic acid as a capping agent produced larger particle sizes compared to thioglycerol. For example, thioglycolic acid produced on average 5.0 nm CdSe nanoparticles while 4.0 nm average CdSe particle size was obtained when using thioglycerol as stabilizer. This observation was confirmed by UV/Vis absorption results which showed that thioglycerol capped CdSe NCs exhibited excitonic peaks positioned at lower wavelength than thioglycolic capped CdSe NCs. XRD results showed that the capping agents used in the current work had no influence upon crystal structure of the CdSe nanocrystals as the cubic structure was obtained with both stabilizers. The effect of shell precursor concentration at pH 12 showed heterogeneous formation of ZnO nanoparticles at high shell precursor concentrations. Various ZnO morphologies including nanoflowers and nanotriangles were observed on TEM images when 50 mL and 25 mL of zinc nitrate solution were used as shell precursors. UV/Vis absorption results also confirmed the presence of ZnO absorption peaks for samples prepared with 50 mL and 25 mL of zinc nitrate solution as shell precursors. PL results showed an increase in peak intensity as a function of precursor volumes. XRD results showed diffraction patterns due to the wurtzite structure of ZnO. CdSe diffraction patterns in these samples were not detected by the XRD instrument. At low volume of the shell precursor, which was 5 mL of 0.05 M zinc nitrate, TEM results showed that spherical CdSe/ZnO core/shell nanoparticles were obtained at pH 12 with 5 mL of 0.05 M zinc nitrate solution and 0.1 M sodium hydroxide used as shell precursor solutions, and thioglycerol as a stabilizer. XRD analysis of the v sample exhibited ZnO diffraction patterns and the CdSe patterns were not detected owing to their low peak intensities compared to those of the ZnO. Similar results were obtained when thioglycolic acid was used a stabilizing agent. However, TEM images showed the hexagonal shape of the CdSe/ZnO core/shell nanoparticles. The pH level was found to influence the photoluminescence properties of the CdSe/ZnO core/shell nanoparticles. The enhanced PL intensity was obtained with CdSe/ZnO core/shell nanoparticles with pH 9 in comparison with CdSe/ZnO core/shell nanoparticles prepared at pH 12. TEM images showed the presence of a thin ZnO shell on the surface of CdSe cores for CdSe/ZnO prepared at pH 9 which could be attributed to the PL enhancement. Although EDS results confirmed the presence of elements such as Cd, Se, Zn and O for both the CdSe core and ZnO shell, the XRD results confirmed the presence of only CdSe diffraction patterns, which suggested the ZnO shell had low peak intensity or was amorphous. A similar effect of these capping agents was observed for Ag nanoparticles as thioglycerol produced average particle size of 16.0 nm whereas 31.0 nm as the average particle size was obtained with thioglycolic acid as stabilizing agent. The crystal phase of Ag NPs was independent of the type of stabilizer. The Ag NPs precipitated in face centred cubic phase. Core/shell Ag/ZnO nanoparticles were produced with 5 ml of zinc nitrate as shell precursor. Higher volumes (50 ml and 25 ml) of zinc nitrate shell precursor induced heterogeneous precipitation of ZnO nanoparticles. XRD patterns confirmed peaks due to ZnO and Ag for Ag/ZnO core/shell nanoparticles.

Dit wil voorkom asof metallasiekels ‘n betreklike nuwe generasie van kataliste is, wat nie volkome vir gebruik in die industrie bestudeer is nie. Meeste van die bekende metallasiekels is fosfor, en tot ‘n mindere mate, swael gebasseerde mono- en bidentate metallasiekels. Relatief min is bekend oor die ooreenkomstige stikstof gebasseerde metallasiekels. Die doelwit van hierdie studie was om vas te stel of metallasiekels van stikstof en swael ligande vergelykbaar is met metallasiekels van fosfor ligande en of enige van dié vergelyk kan word met die standaard palladium en fosfor kataliste wat gewoonlik in situ berei word. ‘n Paar probleme wat ondervind is met organometaal literatuur was, onderandere, ‘n gebrek aan volledige eksperimentele prosedures vir metallasiekel sintese asook ‘n tekort aan volledige karakteriseringsdata. Metallasiekelvorming behels die insersie van ‘n metal in ‘n geaktiveerde C-H binding. Organometaal literatuur beskou metallasiekel vorming as oksidatiewe addisie gevolg deur redutiewe eliminasie. Meganisties gesproke het hierdie terme nie veel betekenis nie. Dit is egter moontlik om die reaksie te rasionaliseer in terme van suur/basis interaksies asook elektrofiliese substitusie wat nie die metal se oksidasie toestand verander nie. Die kritiese afhanklikheid van palladasiekel vorming op die reaksiekondisies het duidelik geword gedurende die studie. Die vorming van metallasiekels van palladium is altyd in kompetisie met ander prosesse soos kompleksasie en reduksie van palladium(II). Direkte metallering met palladium asetaat was net suksesvol met fosfor ligande, terwyl palladium chloried weer net suksesvol met stikstof ligande was. Die asetaatioon speel ‘n baie belangrike rol, naamlik om as basis op te tree. Palladium chloried het nie sulke sterk basiese eienskappe nie en dus misluk palladasiekel vorming met fosfor ligande. Wanneer hierdie feite in ag geneem word, is dit duidelik hoekom dit so moeilik was om die swak beskryfde literatuur metodes te volg. Sommige metallasiekels kan nie deur direkte insersie berei word nie en moet dus deur oksidatiewe addisie van halogeen verbindings gevorm word. Kermerkende verskille tussen die KMR spektra van die metallasiekel en sy vry ligand maak dit moontlik om te onderskei tussen die vorming van eenvoudige komplese en die metallasiekel. FAB-MS karakterisering is ook ‘n goeie metode om die verloop van metallering to moniteer. Die bereide metallasiekels en die standaard Pd(OAc)2/PPh3 sisteem is met mekaar vergelyk as katalisatore in die Heck reaksie. Met ‘n ariel jodied as, toon die stikstof palladasiekels hoër aktiviteit as die fosfor palladasiekels, terwyl hul aktiviteit vergelykbaar is met die standaard nie-palladasiekel kataliste. Die pinser komplese het amper geen aktiviteit onder hierdie kondisies getoon nie. Wat die meganisme van die reaksie betref, is bewyse vir die omsetting van die palladasiekel na ‘n palladium(0) spesie al aangevoer, maar meeste outeurs verkies ‘n meganisme wat ‘n Pd(II)/Pd(IV) oksidatiewe verandering behels. Twee tipes reaksies wat van groot belang is vir Sasol is isomerisasie en hidroformilering/alkoksikarbonilering van alkene. Daar is gevind dat palladasiekels oneffektief is in die reaksies met koolstof monoksied, omdat hulle gereduseer word na palladium(0). Die moontlikheid dat hierdie verbindings kan optree as kataliste in hidrogenasie reaksies is dus onwaarskynlik. Palladasiekels hou tog belofte in as kataliste vir olefien isomerisasie. Wanneer die katalitiese eienskappe van metallasiekels bestudeer word, is dit duidelik dat metallasiekels ‘n verandering in oksidasie toestand ondergaan as deel van die katalitiese siklus. In gevalle waar ‘n Pd(II) na Pd(IV) oksidasietoestand verandering moet plaasvind, sal dit noodwendig ‘n baie hoë energie proses wees. Dit sal dan die lae tempo van kataliese verklaar. Dus is dit amper seker dat metallasiekels beperkte toepassing sal vind in die industrie. Die vermoë van metallasiekels om as kataliste op te tree in reaksies waar ‘n verandering in oksidasie toestand nie nodig is nie, is to dusver nog nie ondersoek nie. / Prof. C.W. Holzapfel

In this study polar ligands that would be suitable for use in homogenous catalysis in aqueous-organic and/or ionic liquid systems were designed and synthesised. Initially an attempt was made to design a synthetic route that would incorporate an imidazolium into a phosphorus compound which would then allow the variation of the alkyl group on the imidazole or of the anion, thereby producing a series of ionic ligands with wide range of anticipated chemical and physical properties. This approach was partially successful: phosphines containing imidazolium moieties were synthesised by incorporating N-methyl imidazolium into bi- and tri-aryl phosphine compounds. As these ligands contain imidazolium residues, the retention of the catalyst in the ionic liquid to be used in the catalytic transformation would be enhanced. Water-soluble ligands that are suitable to aqueous-organic systems were also synthesised. The ligands were synthesised by first performing a Michael type reaction with diphenyl phosphine and a Michael acceptor, in this case, malonate esters. These were reduced and subsequently reacted with 1,4-butanesultone. The addition of butane sultone to these phosphorus compounds made them sufficiently water-soluble and therefore ideal for catalysis in aqueous biphasic or ionic solutions. Several water-soluble/ionic ligands were synthesised by incorporating dimethylphosphoryl chloride into di- and tri-aryl phosphine ligands in high yields followed by subsequent hydrolysis of the phosphonate groups. All the ligands produce were tested in transition metal-catalysed reactions, namely the Heck reaction, the Suzuki cross coupling and the Hydroformylation reaction. Test reactions were carried out under conditions selected to show the effectiveness of the ligands in the reaction, and they were performed in organic and aqueous-organic systems, as well as in ionic liquids for the Heck reaction. The results of these reactions were compared to the benchmark triphenylphosphine and it was found that the new ligands produced results that were similar to the triphenylphosphine but there were numerous instances where the new ligands produced better results. This study, therefore allowed for the synthesis for a range of polar phosphine ligands that would be suitable for homogenous catalysis using aqueous and/or ionic liquid systems, and these ligands were shown to influence transition metal-catalysed reactions. / Prof. D.B.G. Williams

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

M.Sc. / This study focussed on two areas of research in the field of organometallic chemistry. The first entails the preparation and characterisation of a number of Fischer-type carbene complexes of the general formula (C0) 5M(OR)(RI) (1 - 4). For the first group M = Cr, Mo or W, R = Et or Me and re = Ph or BiPh. A second, somewhat different group was prepared by deprotonating 4- methylthiazol-2-methyltlfioether, reacting it with M(CO) 6, where M = Cr or W, and neutralising the resulting anion with methyltriflate. Both metals afforded only one product which could be successfully purified and characterised as M(C0),{C(OCH3)(C=C(CH3)N=C(SCH3)S) (6,7). The crystal structure of the tungsten complex was solved by single crystal X-ray techniques. A similar carbene complex preparation was carried out with 5-methylthiophenilyl-2-thiomethylether and M(C0)6, M = Cr or W, as starting reagents. In addition to the expected carbene complexes M(CO)5 (C(OCH3)(CH2SHCH=C(CH3)S)), M = Cr and W (9a, 10a), deprotonation of a ring carbon yielded M(C0) 5{C(OCH3)(6=C(SCH3)SC(CH3)=CH)) M = Cr and W (9b, 10b), whereas unreacted starting material afforded the sulfide W(C0) 54-SC(SCH3)=CHCH=C(CH3) (11). The second part of the thesis describes the preparation of pentacarbonyl thione and iminocomplexes, as well as tricarbonyl imino-, sulphide and dinuclear re-sulphide complexes. 4- Methylthiazoly1-2-thiolate were used for nucleophilic attack on (C0) 5Cr--C(OR)(12. 1) (1 and 4) to yield the thione complex Cr(C0) 54-S=CN(CH3)C(CH3)=CHS (13) upon methylation. Two other products were also obtained from these reactions : Cr(C0) 54-NC=CHSCH=C(CH3) (12) and Cr(CO) 54-N=C(CH3)SCH=C(CH3) (14), which indicates incomplete reaction with sulfur during the formation of the mentioned thiolate. Three beautiful electron ligand systems were produced by reacting 4-methylthiazol-2-disulphide with (CO),W(THF) or Fe2(C0)) . A new "butterfly" bidentately coordinated tricarbonyl tungsten complex, [(C0)3 1/{N(S)SCH(CH3)) 2] (16) was obtained. The crystal structure of this complex shows many similarities to a known complex, (C0)3W(n2-PyS)2 that was prepared from ionic metalcarbonyl precursors. In addition to 16, a thione complex W(C0) 54-SHC(CIi )=CHS (17) also formed from the reaction with (CO) 5M(THF). The reaction between (CO),M(THF) and 4-methylthiazolyi-2-disulphide thus probably involves heterolytic bond cleavage and protonation on the silica gel. The reaction of Fe 2(CO)9 with the same disulphide resulted in the formation of the dinuclear compound Fe2(C0)6(SC=NC(CH3)=CHS)2 (18), possibly via the homolytic splitting of the disulphide bond. The crystal structure of this compound revealed the Fe-Fe-bond and eclipsed configuration, typical of this type of Fe-cluster complex. Finally, two thione complexesM(C0)54—S(SMe)(eHCH(Me)S), (M= Cr and W; 20,21) were found to isomerise in solution to their sulphide analogues of which only the chromium complex Cr(C0)54— SC(Me)=CHCH=C(C(=S)(SMe)) (22) could be characterised.