| beta-Acetoxyethylsilsesquoxanes, RSiO1.5 (R = CH2CH 2COOCH3; BAE), have been prepared and shown to undergo conversion to silica or organically modified silicas (Ormosils) under mild thermal or photochemical conditions. In contrast to typical alkyl or aryl silsesquioxanes, the CH2CH2OAc moiety undergoes facile extrusion of ethylene with formation of hydrolyzable groups. Subsequent rapid hydrolysis leads to condensation of the SiO2 network. BAESSQ converts largely to silica with <8% residual carbon. Smooth, crack-free, silica-rich films were prepared on silicon substrates from BAESSQ and were analyzed using techniques such as Fourier Transform Infrared Spectroscopy, Rutherford Backscattering Spectroscopy, Scanning Electron Microscopy, and Atomic Force Microscopy. Although residual carbon is detected after BAESSQ conversion, base catalyzed thermal routes in the bulk were found to not only lower carbon levels, but also to require lower processing temperatures. Fluoride catalyzed routes were also explored in the preparation of silica films and indeed found to proceed at lower temperatures, but the carbon levels were comparable to that found in uncatalyzed films.; A second major theme in this thesis is the investigation of new catalytic routes to organosilicon compounds. Arylsilanes are important intermediates in the silicone industry, but commonly used syntheses of arylsilanes have several limitations, including severe reaction conditions, modest product selectivities, and high cost. We have found that the silylation of arenes via the catalytic transfer dehydrocoupling of Et3SiH and functionalized arenes in the presence of an olefin successfully produces arylsilanes under mild conditions. It has been shown that two competing processes, intra- and intermolecular C-H activation, produce carbosilane dimer and the desired arylsilane, respectively. The carbosilane dimer, a kinetic product, is shown over time to ultimately convert to the more stable thermodynamic arylsilane product. Electron-withdrawing groups on the arene enhance C-H activation. Additionally, catalyst and temperature effects as well as regioselectivity of the reaction were investigated. During the study of the catalytic dehydrogenation of haloarenes and Et3SiH, bromo- and chlorobenzene were found to undergo reduction to benzene. Additionally, Si-C bond formation occurs yielding phenylsilane. This reaction was extended to include a more industrially applicable silane---Cl 3SiH---which is found to be more selective for phenylsilane. |
