The major directions of this thesis involve (1) the synthesis, immobilization, and characterization of tridentate phosphine linkers on silica, (2) the study of unprecedented Si2C bond cleavage in Rh and Ir phosphine complexes, and (3) the study of performance polymers with solid2state NMR techniques. First a brief overview of solid2state NMR and its relevance to the various areas of chemistry covered in this thesis is given. Following the synthesis, immobilization, and characterization of tridentate phosphine ligands, EtOSi[(CH2)nPPh2]3 (n = 4, 7, 11) and [MeP((CH2)nPPh2)3]+I? (n = 4, 7, 11) on silica is detailed. Both, immobilization by electrostatic interactions and by a covalent siloxane bond to the support, is studied and compared. Ligand exchange with Wilkinson?s catalyst affords immobilized Rh complexes. These materials are applied to catalytic olefin hydrogenation. In either case active hydrogenation catalysts are obtained that can easily and efficiently be recycled up to 30 times. Detailed investigations reveal that irrespective of the linkage to the support the catalysts consist initially of well2defined molecular species that form supported Rh nanoparticles with a narrow size distribution in the course of the catalytic reaction. The nanoparticles are active hydrogenation catalysts as well, and no metal leaching into solution is detected. The reaction of the tridentate phosphine ligands EtOSi[(CH2)2PPh2]3 and MeSi[(CH2)2PPh2]3 with Rh and Ir complexes is investigated. This reaction does not lead to the anticipated Wilkinson2type complexes with the metal in the +I oxidation state, but instead to oxidative addition of the C(sp3)2Si bond to Rh or Ir centers to yield octahedral complexes with the metal in the +III oxidation state. These complexes are fully characterized by multinuclear NMR in solution and in the solid state. Preliminary density functional theory (DFT) calculations corroborate the preference for oxidative addition. Subsequently the study of performance thermoplastics which are important materials for the oil and gas industry is presented. The polymer morphology is studied by solid2state NMR techniques. Special attention is devoted to potential decomposition pathways at elevated temperatures for polyetheretherketone (PEEK) and polyphenylene sulfide (PPS) polymers. 13C CP/MAS (cross polarization with magic angle spinning) NMR and IR spectroscopy reveal that PEEK polymers show no detectable chemical change on the molecular level, while PPS polymers display signs of oxidation of the thioether group and branching via formation of ether, thioether, and biphenyl linkages. Furthermore, the water absorption of polybenzimidazole (PBI), polyetherketoneketone (PEKK), and their blend PEKK2PBI is studied. It is demonstrated that steam2treatment even at high temperatures and pressures does not cause chemical decomposition and that the changes, which are morphological in nature, are fully reversible.

The focus of this work is to synthesize and immobilize novel rigid tetraphosphine linkers via the formation of phosphonium groups and by direct adsorption of tetraphosphine salts on oxide surfaces. These methods offer the possibility to study the mechanism of the phosphonium formation in more detail by utilizing solid-state NMR spectroscopy. It has also been a point of interest to study the linkers and catalysts under realistic conditions, in the presence of solvents. Therefore, HRMAS (high-resolution magic angle spinning) NMR spectra of several phosphonium salts, adsorbed on SiO2, have been studied. This technique allows one to probe the leaching and mobility of the linkers on the surface. The mobilities of the linkers and the catalysts are crucial factors for the performance and design of the immobilized catalysts. Finally, since the exact mode of binding to the surface is unknown and is being discussed in the literature, for example, as hydrogen bonding between the F atoms in BF4- and surface silanol protons, the influence of the counteranion on the binding of phosphonium salts on silica surfaces is of utmost interest. For surface mobility studies a monolayer of phosphonium salts on the silica surface, both without solvent and in the presence of solvent, has been studied via 31P and 2H CP/MAS and HRMAS. Our findings show that the integrity of the tetraphosphine scaffold linkers is based upon how it is immobilized. The best system is formed when the phosphine is immobilized on the SiO2 support by adding Cl(CH2)3Si(OEt)3 to the reaction mixture. In this way, phosphonium salts are obtained, which are bound to the surface irreversibly by electrostatic interactions, as proven by solid-state NMR. In addition, leaching and mobility studies prove that the solvents play a crucial role, and the more polar solvents, such as DMSO, lead to the most extensive leaching due to the solvents' strong adsorption on the SiO2 surface. Leaching studies also show that the counteranion has an influence on the binding of the phosphoniumn salts on the SiO2 surface. The leaching proceeds in the following manner: BF4- > I- > Br- > Cl-. This is an indication that there is an additional interaction between the anion and, most probably, the surface silanol protons.

Thesis (MSc)--University of Stellenbosch, 2011. / ENGLISH ABSTRACT: In this thesis the synthesis of a wide range of model and siloxane functionalized N-(n-propyl)-1-(2-pyridyl and quinolyl)-imine ligands (L1-L6) are described. Functionalized ligands (L4-L6) were obtained by the reaction of the pyridyl and quinolyl aldehydes with 3-aminopropyltriethoxysilane. Model ligands were characterized by FT-IR and 1H NMR spectroscopy while 13C{1H} NMR spectroscopy was additionally used for functional ligand characterization. Functionalized complexes of both Pd(II) and Cu(I) were found to be more thermally stable than their model counterparts. Overall the model Pd(II) complexes showed a higher thermal stability than the model Cu(I) complexes. Ligands (L1-L6) were reacted with either Pd(II) or Cu(I) metal precursors to produce both the model and functionalized Pd(II) (C1-C6) and Cu(I) (C7-C12) metal complexes. These metal complexes were all characterized by FT-IR spectroscopy, 1H NMR and UV/Vis spectroscopy for the model Cu(I) complexes. Functionalized complexes were additionally characterized with 13C{1H} NMR spectroscopy. Siloxane functionalized complexes of Pd(II) and Cu(I) were immobilized on MCM-41 and SBA-15 silica materials to produce heterogenized immobilized catalysts. These immobilized catalysts were characterized by a wide range of solid state techniques including: BET nitrogen adsorption/desorption, scanning electron microscopy (SEM), thermal gravimetric analysis (TGA), ICP-AES, FT-IR spectroscopy, powder XRD and solid state 13C{1H} NMR spectroscopy. ICP-AES and BET surface analysis showed that better complex immobilization occurred for SBA-15 supported materials despite SBA-15 having a significantly lower surface area than MCM-41. This higher immobilization was ascribed to the larger pore sizes of SBA-15 (50 Å) vs. that of MCM-41 (26 Å). Immobilized catalysts were tested for the oxidation of benzyl alcohol to benzaldehyde. Immobilization had a positive effect on the catalytic activity of the Pd(II) complexes with higher conversions being observed for immobilized Pd(II) catalysts when compared to their model analogues. Overall the MCM-41 immobilized Pd(II) catalysts showed a higher increase in activity than SBA-15 immobilized catalysts. For Ti-doped supports a generally higher activity was seen for the Ti-SBA-15 system. The Cu(I) systems however were not as effective in the oxidation reactions. / AFRIKAANSE OPSOMMING: In hierdie tesis word die sintese van `n wye reeks model sowel as gefunksioneerde N-(n-propiel)-1-(2-piridiel en kinoliel)-imien ligande (L1-L6) beskryf. Gefunksioneerde ligande (L4-L6) is gevorm deur die reaksie van piridiel en kinoliel aldehied met 3-amniopropieltriëtoksiesilaan. Model ligande is gekaraktariseer deur FT-IR en 1H KMR spektroskopie terwyl 13C{1H} KMR spektroskopie addisioneel gebruik is vir die karaktarisering van die gefunksioneerde ligande. Ligande (L1-L6) is gereageer met Pd(II) of Cu(I) metaal voorgangers om beide model sowel as gefunksioneerde Pd(II) (C1-C6) en Cu(I) (C7-C12) metaal komplekse op te lewer. Hierdie metaal komplekse is almal gekaraktariseer deur FT-IR, 1H KMR en UV/Vis spektroskopie vir die model Cu(I) komplekse. Gefunksionalseerde komplekse is addisioneel gekaraktariseer deur gebruik te maak van 13C{1H} KMR spektroskopie. Dit is gevind dat gefunksionaliseerde komplekse van beide Pd(II) sowel as Cu(I) termies meer stabiel was as hulle ooreenstemmende model komplekse. Oor die algemeen het die Pd(II) komplekse hoër termiese stabiliteit as die Cu(I) komplekse getoon. Siloksaan gefunksioneerde komplekse van Pd(II) en Cu(I) is geimmobiliseer op MCM-41 en SBA-15 silika materiale om heterogene geimmobiliseerde katalisatore op te lewer. Hierdie geimmobiliseerde katalisatore is gekaraktariseer deur van `n wye reeks vaste toestand tegnieke gebruik te maak. Hierdie suit in: SEM, TGA, ICP-AES, FT-IR, poeier XRD en vaste toestand 13C{1H} KMR spektroskopie. ICP-AES en BET oppervlak analieses het getoon dat beter kompleks immobilisering vir die SBA-15 silika material plaas gevind het, ondanks die feit dat SBA-15 `n laer oppervlak area beskik. Hierdie hoër graad van immobilisering is toegeskryf aan die groter poriegrootte van SBA-15 (50 Å) teenoor die van MCM-41 (26 Å). Geimmobiliseerde katalisatore is getoets in die oksidasie van bensielalkohol na bensaldehied. Dit is gevind dat die immobilisering van die Pd(II) komplekse op die silika materiaal `n positiewe uitwerking op die aktiwiteit van die katalitiese van die komplekse gehad het. Die hoogste toename in aktiwiteit is gesien vir geimmobiliseerde Pd(II) katalisatore wanneer hulle met hul ooreenstemmende model komplekse vergelyk is. Oor die algemeen is gevind dat MCM-41 geimmobiliseerde Pd(II) katalisatore n hoër toename in aktiwiteit getoon het as die van SBA-15. Vir die Ti-gedokterde silika materiale het die Ti-SBA-15 sisteem oor die algemeen `n hoër aktiviteit getoon as die Ti-MCM-41 sisteem. Die Cu(I) sisteme was egter nie so effektief in oksidasie reaksies nie.

Regiomeric mixture of HMe2Si(CH2)3(i-Bu)6Si7O9(OH)3 (6), containing a Si-H group in one of the ligands of the silsesquioxane, was tethered onto a vinyl terminated hyperbranched poly(siloxysilane) polymer via a hydrosilation reaction to generate extremely active catalysts, P1-8 and c-P1-8. The synthesis of 6, in good yield, was accomplished via hydrosilation of CH2=CHCH2(i-Bu)7Si8O12 (1) to generate ClMe2Si(CH2)3(i-Bu)7Si8O12 (3) followed by the reduction of 3 with LiAlH4 to afford HMe2Si(CH2)3(i-Bu)7Si8O12 (4) where the base-catalyzed excision of one framework silicon was employed to generate a regiomeric mixture of 6. [Ti(NMe2){Et3Si(CH2)3(i-Bu)6Si7O12}] (7), [Ti(NMe2){HMe2Si(CH2)3(i-Bu)6Si7O12}] (8), [Ti(NMe2){(i-C4H9)7Si7O12}] (9) and [Ti(NMe2){(c-C6H11)7Si7O12}] (10) were synthesized via protonolysis of Ti(NMe2)4 with one equivalent of the trisilanol precursor in order to determine if the presence of isomers would be intrinsically different as compared to the uniformly substituted catalysts. Isomers 8 and 9, demonstrated lower activity as compared to the uniformly substituted catalysts 9 and 10, however the isomers still exhibited extremely high catalytic activity for the epoxidation of 1-octene using tert-butyl hydroperoxide (TBHP) relative to titanium catalysts used in industry. Additionally, 9, 10, P1-8 and c-P1-8 were very selective catalysts for the epoxidation of various olefins such as terminal (1-octene), cyclic (cyclohexene or 1-methylcyclohexene), and more demanding olefins (limonene or α-pinene) employing TBHP as the oxidant. Furthermore, P1-8 and c-P1-8 were recyclable with minimal loss of titanium however the catalysts could also be repaired if a loss in activity was observed. Preliminary epoxidation reactions employing P1-8 and c-P1-8 along with hydrogen peroxide (H2O2) as the oxidant were also explored using different solvents. P1-8 degraded quickly due to the hydrolysis of the titanium from the large amount of water present in the reaction mixture however c-P1-8 showed activity for the epoxidation of cyclohexene. Finally, regiomeric mixture of Ti(NMe2)(HS(CH2)3)(i-C4H9)6Si7O12) (13), was tethered onto gold nanoparticles for the conversion of propene to propylene oxide using molecular hydrogen and oxygen. While the catalysts showed low activity under our reaction conditions, numerous improvements can be investigated in order to improve upon the catalysts.