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Thesis (Doctoral)--Rijksuniversiteit te Utrecht, 1983. / Summary in Dutch. "Stellingen" ([2] p.) inserted. Includes bibliographical references.

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Substituent effects in eta5-cyclopentadienyl (Cp) transition metal complexes have been intensely studied since the discovery of the first such complex, ferrocene. Modifications of the Cp ligand framework effect changes in the physical properties and chemical reactivity of the coordinated transition metal. This concept is useful when applied to catalysis mediated by Cp complexes, because the performance of the catalyst can be markedly improved using well-chosen ligand substituents. Studies of electronic substituent effects ideally employ a wide range of electron-donating and electron-withdrawing groups. Unfortunately, most of the available electron-withdrawing groups suffer from problems with Cp ligand synthesis, Cp anion stability, and electron-withdrawing group stability under catalytic conditions. This dissertation shows that the pentafluorophenyl (C6F5) substituent is highly electron-withdrawing but avoids all of these problems. Several new C6F5-substituted cyclopentadienes are prepared by the reaction of sodium cyclopentadienide and hexafluorobenzene (C6F6) under varying conditions. Corresponding C6F5-substituted cyclopentadienyl ligands (sodium salts) are obtained upon deprotonating the dienes with NaH. Complexes of Mn(I), Re(I), Fe(II), Co(II), Zr(IV) are synthesized by reacting these ligands with transition metal halides. The acidities of several C6F5- and C5F4N-substituted cyclopentadienes and indenes are measured using 19F NMR spectroscopy. The electron-withdrawing fluorinated aryl groups have a substantial acidifying effect. The identity and number of substituents (C6F5, C5F4N, CH3, and t-Bu), the position of the substituents on the cyclopentadiene, and the intramolecular (vicinal) steric effects also influence acidity. The electron-withdrawing ability of the C6F5 group is also characterized by infrared spectroscopic analysis of substituted CpM(CO)3 (M = Mn(I) and Re(I)) and electrochemical analysis of substituted ferrocenes. X-ray crystal structures of several C6F5-substituted Cp complexes reveal interesting structural motifs, including pi-stacking of the C6F5 substituents, Cp-M bond elongation, and CO-C6F5 interactions. In addition, dynamic Cp-C6F5 and Cp-M rotational barriers are measured by variable temperature NMR spectroscopy. Finally, ethylene polymerizations and ethylene/1-hexene copolymerizations are conducted using C6F5- and C6H5-substituted zirconocene dichlorides as catalysts. Contrary to findings published elsewhere, this study shows that substituent electronic effects induce substantial changes in comonomer incorporation. / Ph. D.

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

The purpose of this research was to synthesize the constrained geometry catalyst Ti[(C5Me4)SiMe2(tBuN)]Cl2 (1) with MAO as a cocatalyst for ethylene homopolymerization and copolymerizations with 1-TMSO-alkenes to produce a copolymer with polar functionality. Three 1-alkenols of varying length were purchased and derivatized and used for the copolymerization experiments: 2-propen-1-ol, 3-buten-1-ol and 9-decen-1-ol. Several variables were tested to determine their effects on comonomer incorporation such as temperature, equivalents of comonomer, equivalents of MAO and two different solvents. Higher catalytic activities were correlated with fewer equivalents of polar comonomer, lower temperatures, and no fewer than 1000 equivalents of MAO. Toluene was found to be a far more effective reaction solvent than dichloromethane, as polymer yields were on average thirteen times higher. All polymer samples were analyzed by high temperature 1H NMR spectroscopy and selected samples were analyzed by DSC and IR spectroscopy. DSC determined that the polyethylene produced by 1 was substantially linear HDPE with long chain branching and that comonomer incorporation reduced the Tc and Tm, probably due to increased short chain branching. 1-TMSO-9-Decene was the most effective comonomer, as it had the highest incorporation rates (8.0 mol%) of all three of the polar comonomers. The two shorter comonomers exhibited no incorporation at all. This confirmed the hypothesis that polar comonomers with longer chains would be less prone to poisoning the electrophilic catalyst. / Thesis (Master, Chemistry) -- Queen's University, 2009-04-27 10:16:46.356

xxii, 143 p. ; ill. (some col.) A print copy of this title is available through the UO Libraries. Search the library catalog for the location and call number. / There are compelling economic and environmental reasons for using degradable plastics in selected applications and considerable research is now devoted to devising new photodegradable polymers with improved performance. Controlling the degradation of these materials in a prescribed fashion is still a difficult problem because the parameters that influence degradation rates are not completely understood. In order to predict polymer lifetimes, to manipulate when a polymer starts to degrade, and to control the rate of degradation, it is necessary to identify the experimental parameters that affect polymer degradation rates and to understand how these parameters affect degradation. This dissertation describes the results of experiments designed to gain fundamental insight into the factors that affect the rate of polymer photodegradation. The key experimental strategy employed was the incorporation of organometallic dimers into the backbone of the polymer chains, specifically, [CpRMo(CO) 3 ] 2 (CpR = a substituted cyclopentadienyl (· 5 -C 5 H 4 R)). Incorporating these organometallic units into a polymer chain make the polymer photodegradable because the metal-metal bond can be cleaved with visible light. The photogenerated metal radicals can then be trapped by O 2 or chlorine, resulting in degradation of the polymer. Another benefit from incorporating this chromophore into the polymer backbone is that it provides the experimentalist with a convenient spectroscopic handle to monitor degradation rates. Using these model polymers, several experimental factors that can affect polymer photodegradation rates have been explored. For example, experiments showed that radical trap concentration affects degradation rates below, but not above, the polymer glass transition temperature. In addition, degradation rates as a function of irradiation temperature, tensile stress, and time-dependent morphology changes were explored for various polymers. The results of these studies suggest that the ability of the photogenerated radicals to escape the radical cage is the dominant factor in determining photodegradation efficiencies. This dissertation includes previously published and unpublished co-authored material. / Adviser: David R. Tyler

This work is concentrated on the thermodynamic and kinetic aspects of water, alcohols, alkyl halides, ethers, and lactones bound and activated by the electrophilic [Cp'Ru(N0)] +2 and [Cp’Ru (NO)(CH3)] + centers (Cp' = cyclopentadienyl group). Counterions in these systems include OSO2CF3- (OTf-) and [(3, 5-(CF3)2C6H3)4B]- ([BAr4']-). The displacement of OTf- in Cp'Ru(N0) (0Tf)2 by H20 in dichloromethane is exothermic but entropically unfavorable due to the required reorganization of the solvent cage around released triflate ions. Thermodynamic parameters are also determined for OTf displacement by chloride and tetrahydrofuran (THF) using the 19F nuclear magnetic resonance (NMR) spectroscopy. The conversion of the [Cp’Ru (NO)(OH2)2] +2 to [Cp’Ru (NO)(μ-OH)} 2 +2 in aqueous solutions is characterized thermodynamically and kinetically by potentiometric and NMR methods. The results of the study of rhodium triflato complex trans- [Rh (CO)(PPh3)2(OTf)] show that OTf coordinates to the metal center in wet dichloromethane solutions, but the compound crystallizes as a water-coordinated triflate salt trans- [Rh (CO)(PPh3)2(OH2)] [OTf]. Thermodynamic parameters for alcohol (methanol, ethanol, isopropanol) binding to the Cp*Ru(N0) (0Tf)2 are determined from the 19F NMR spectroscopic data. The kinetics of the oxidation of alcohols to aldehydes or ketones via Ru (II) >>> Ru (0) redox process is studied by NMR methods. The results of the study support {3-hydrogen elimination mechanism, comprising one of the very few mechanistic investigations on reactions of this kind. Alkyl iodides are found to bind to the [Cp*Ru (NO)(CH3)] + fragment via displacement of a THF ligand in the presence of a BAr4 •-counterion, forming alkyl halide complexes that convert to [Cp’Ru (NO)(μ-I)]2+2. The mixed ruthenium-chromium complex [CpCr (NO)2(μ-I) (Ru (Cp’) (NOW is characterized as primarily a [Ru-I >> Cr] system as opposed to a [Ru << I-Cr] model. The complex [Cp*Ru (NO)(CH3) (THF)] is found to catalyze aerobic oxidation of THF to -y-butyrolactone. The new -y-butyrolactone ruthenium complex is isolated and characterized by X-ray methods in the solid state. The mechanism of catalytic oxidation is studied by 18O-labeled infrared spectroscopic methods. Radical decomposition of the intermediate hydroperoxy-tetrahydrofuran gives 1, 6-diol-diformate [CH(O)-(CH2)6-CH(O)]. The radical mechanism for the catalytic oxidation of THF is proposed.

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