Catalysis using earth abundant and environmentally benign s-block metals

项目背景(查明问题及其对可持续性的重要性和相关性)化学工业必须变得更加可持续，这是无可辩驳的。催化是世界化学工业的基础，基于催化的合成约占目前所有工艺的90%。多年来，贵金属有机金属络合物一直是均相催化的核心。这些元素价格昂贵，地质上的稀缺性导致它们对全球供应限制特别敏感。尽管几乎无处不在的催化试剂的使用是实现绿色化学12项原则的积极一步，但这些稀有、昂贵且往往有毒的金属的穷尽使用与许多其他关键原则直接矛盾。针对这些问题，全球已做出重大努力，使用富含稀土和良性金属的络合物代替传统的催化方法进行化学合成。较轻的S块金属作为理想的替代品正受到极大的关注，特别是钠、钾、镁和钙，因为它们在地壳中的相对丰度很高。这些金属容易获得，价格低廉，对环境无害。这类络合物在催化一系列反应方面显示出明显的前景，提供了传统催化剂所没有的产物和选择性。因此，它们代表了创建可持续、经济和绿色催化框架的明显潜力。Kays小组最近的研究表明，螯合和钳形配体可以高产率地稳定廉价、丰富和环境友好的碱金属和碱土金属的络合物，可以作为胺-硼烷脱氢和水合稀土反应的高效高活性催化剂。1，2这种催化剂的开发，特别是将这种化学扩展到新的底物和有机转化，如果基于S块的均相催化剂要得到广泛的应用和广泛采用，是必不可少的。因此，这项建议建议进一步设计和开发强大的S嵌段络合物，作为催化剂用于小分子的价态反应，以合成新的化学品。该项目将设计和开发活性、稳定和坚固的镁配合物，并将其作为前催化剂用于一系列反应，如加氢元素化、交叉偶联和小分子的脱氢偶联。首先，这些催化剂将用于简单和复杂的腈的氢硼化反应，以提供一条路线，以获得具有不稳定的N-B键的关键合成中间体，这些中间体可以方便地转化为各种官能团，如胺、醇和卤化物。这些化合物的制备也将在这项工作中演示。我们还将研究如何通过使用绿色溶剂和优化反应条件，使这些催化反应更加可持续和对环境无害。同时，通过详细的动力学分析研究这些反应的机理将为催化剂的改进和未来的设计提供参考。这一化学将扩展到广泛的底物，如分子间和分子内的氢化反应，其他多键，研究这些催化剂和催化过程的官能团耐受性，以及这些反应在有机合成中的适用性。

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.