Catalysis using earth abundant and environmentally benign s-block metals

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Project background (identification of the problem and its importance and relevance to sustainability)There is an irrefutable need for the chemical industry to become more sustainable. Catalysis is fundamental to the worlds chemical industry, and catalysis-based synthesis accounts for around 90 % of all current processes. For many years, organometallic complexes of precious noble metals have been at the heart of homogeneous catalysis. These elements are expensive and their geological paucity results in particular sensitivity to global supply restrictions. Despite the near ubiquitous employment of catalytic reagents being a positive step towards realising the 12 principles of green chemistry, the exhaustive use of these rare, expensive and often toxic metals is in direct contradiction to many of the other key principles.In response to these issues, there have been major global efforts towards chemical synthesis using complexes of earth abundant and benign metals as replacements for traditional catalytic methods. The lighter s-block metals are experiencing a significant amount of attention as ideal replacements, particularly sodium, potassium, magnesium and calcium, due to their high relative abundance in the Earth's crust. These metals are readily available, cheap and environmentally benign. Such complexes have shown clear promise in catalysing a range of reactions, affording products and selectivities not seen for traditional catalysts. Thus, they represent clear potential to create sustainable, economic and green catalytic frameworks.Proposed solution and methodologyRecent research in the Kays group has shown that chelating and pincer ligands can be used to stabilise complexes of cheap, abundant and environmentally benign alkali and alkaline earth metals in high yields, which can act as efficient highly active catalysts for amine-borane dehydrocoupling and hydroelementation reactions.1,2 The development of this catalysis, in particular for the extension of this chemistry to new substrates and organic transformations, is essential if homogeneous catalysts based on the s-block are to become broadly applicable and widely adopted. As a result, this proposal suggests further design and development of robust s-block complexes for use as catalysts in a wide variety of reactions in the valorisation of small molecules for the synthesis of new chemicals. This project will design and develop active, stable and robust magnesium complexes, which will be investigated for their use as precatalysts in a range of reactions such as hydroelementation, cross-coupling and dehydrocoupling of small molecules. First, these catalysts will be employed in the hydroboration of both simple and complex nitriles to provide a route to key synthetic intermediates with labile N-B bonds which can be conveniently transformed into various functionalities such as amines, alcohols and halides. Preparation of these compounds will also be demonstrated within this work. We will also investigate how to make these catalytic reactions more sustainable and environmentally benign, through use of green solvents and optimisation of the reaction conditions. In parallel with this, the investigation of the mechanisms of these reactions through detailed kinetic analyses will inform catalyst improvements and future design. This chemistry will be extended to a wide variety of substrates such as inter- and intramolecular hydroelementation reactions, other multiple bonds, investigating the functional group tolerance of these catalysts and catalytic processes in conjunction with the applicability of these reactions in organic synthesis.