Abstract:
The synthesis of complex and robust organosilicon compounds in a controlled fashion is a steadily developing area of research. Largely surpassed by the well-developed chemistry of carbon-based polymers, main-group polymers such as polysilanes are beginning to emerge as interesting compounds with unique chemical properties and potential applications from ceramics to semi-conducting materials. The Leitao research group has begun contributing to this field via the synthesis of bridged (or bridgeable) disilanes to reinforce the Si-Si bond and thus, present a new class of monomers for polysilane formation. A focus of this work has been investigating the synthetic routes toward the formation of Si-Si and Si-element (Si-E) linkages, to deepen the understanding of the chemistry of complex Si-containing compounds. Chapter 1 gives an overview of the known catalytic ad non-catalytic synthetic routes to polysilanes and a brief description of their properties. This is followed by a summary of current literature on the preparation of Si-Si and Si-E bonds. The second chapter reports the synthesis of model molecules to assess the feasibility of creating bridgeable and bridged disilanes. Novel disilane compounds were successfully synthesized and the discoveries have pointed this research toward understanding the challenges and conditions for preparing reactive organosilicon fragments. Chapters 3 and 4 describe the synthesis, characterization and electronic properties of naphthalene- and ferrocene-bridged disilanes, respectively. The results suggest that the Si-Si bond is highly susceptible to oxidation and that absolute removal of moisture is necessary in catalytic dehydrocoupling reactions. These findings led to research on the synthesis of designer siloxanes catalyzed by (C6F5)3B(OH2) which is discussed in Chapter 5. Studies on the recyclability of the catalyst is also reported to demonstrate the efficiency of this protocol relative to the traditional methods of synthesizing siloxanes. Overall, the work undertaken has expanded the current body of knowledge of synthetic routes available to access bridged disilane monomers. This work has also improved the understanding of the chemistry and properties of these monomers and has provided groundwork to develop routes to a new class of polysilanes. Furthermore, this research has presented a new protocol to provide an easy route to a wide variety of structured siloxanes.