Tethered cyclopentadienyl-stannylene ligands for C-H activation

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In a world of dwindling fossil fuels, it is essential that scientists and engineers use their expertise to efficiently harness the resources we have left. Burning fossil fuels, which are generally unreactive hydrocarbons, has been the simplest way to utilise them as a resource. However, this turns them into carbon dioxide and water, increasing global carbon dioxide levels, when they could be used instead for making materials and other useful chemicals. Instead of combustion, a better way to utilise fossil fuels would involve directly transforming them into useful products. This goal has been the basis of the chemical industry for many years, but as demand increases and different feedstocks are exploited, new chemistry needs to be developed to keep pace with these changes. Hydrocarbons contain many carbon-hydrogen bonds, which are generally unreactive and difficult to exploit. Making these bonds more reactive is known as "C-H activation" and has the potential to revolutionise the way we utilise fossil fuels as a resource, allowing us to transform very unreactive compounds into more useful ones. These compounds can then be converted into essential materials, such as plastics, feedstock chemicals and pharmaceuticals, which are of much greater value than the starting materials used to make them. C-H activation typically requires a catalyst incorporating a transition metal, but as C-H activation is a relatively new discovery in chemistry, we are quite far from understanding how to improve the metal complexes which are responsible for this astounding reactivity. Therefore, this proposal will explore C-H activation chemistry which is facilitated by a completely new class of catalyst. New C-H activators will be built from three parts; a late transition-metal centre of proven use in previous C-H activation reactions, a stable supporting platform for the complex containing a cyclopentadienyl fragment and a highly unconventional part which contains a tin atom. This unconventional fragment offers a wide range of unexplored opportunities including: i) bridging modes which will bring two C-H activation centres close together, ii) the ability of the ligand to actively get involved in the reaction cycle and physically participate in bond breaking steps, and iii) exploiting hemilability, a property which can generate vacant sites next to the reactive transition metal centre and allow reactions to take place efficiently. From this research, the factors which effect C-H activation will be identified aiding the long term development of this new process into a useful tool.