Tethered cyclopentadienyl-stannylene ligands for C-H activation

在一个化石燃料日益减少的世界里，科学家和工程师必须利用他们的专业知识来有效地利用我们剩下的资源。燃烧化石燃料（通常是不活泼的碳氢化合物）是将其作为资源利用的最简单方法。然而，这将它们转化为二氧化碳和水，增加了全球二氧化碳水平，而它们可以用于制造材料和其他有用的化学品。更好的利用化石燃料的方法是直接将其转化为有用的产品，而不是燃烧。多年来，这一目标一直是化学工业的基础，但随着需求的增加和不同原料的开发，需要开发新的化学品来跟上这些变化。碳氢化合物含有许多碳氢键，通常不活泼，难以利用。使这些键更具反应性被称为“C-H活化”，并有可能彻底改变我们利用化石燃料作为资源的方式，使我们能够将非常不活泼的化合物转化为更有用的化合物。然后，这些化合物可以转化为基本材料，如塑料，原料化学品和药物，这些材料的价值远远高于用于制造它们的起始材料。C-H活化通常需要结合过渡金属的催化剂，但由于C-H活化是化学中相对较新的发现，我们还远未了解如何改善导致这种惊人反应性的金属络合物。因此，该提议将探索C-H活化化学，这是由一种全新的催化剂促进的。新的C-H活化剂将由三个部分组成：一个在以前的C-H活化反应中已被证明有用的后过渡金属中心，一个稳定的支持平台，用于含有C-H片段的络合物，以及一个含有锡原子的高度非常规部分。这种非传统的碎片提供了广泛的未开发的机会，包括：i）将两个C-H活化中心靠近在一起的桥接模式，ii）配体主动参与反应循环和物理参与键断裂步骤的能力，和iii）利用半不稳定性，该性质可以在反应性过渡金属中心附近产生空位并允许反应有效地发生。从这项研究中，影响C-H激活的因素将被确定，帮助这个新过程的长期发展成为一个有用的工具。

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.