Tethered cyclopentadienyl-stannylene ligands for C-H activation

在化石燃料日益减少的世界里，科学家和工程师利用他们的专业知识有效地利用我们剩下的资源是至关重要的。化石燃料通常是不反应的碳氢化合物，燃烧化石燃料是利用它们作为资源的最简单方法。然而，当它们可以用来制造材料和其他有用的化学物质时，它们会变成二氧化碳和水，增加全球二氧化碳水平。利用化石燃料的更好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，需要开发新的化学来跟上这些变化的步伐。碳氢化合物含有许多碳氢键，这些键通常不活泼，难以开采。使这些键更活跃被称为“碳氢活化”，它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跃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、原料化学品和药品，这些材料比用于制造它们的起始材料的价值要大得多。碳氢化合物活化通常需要一种含有过渡金属的催化剂，但由于碳氢化合物活化在化学中是一个相对较新的发现，我们还远远不能理解如何改善导致这种惊人反应性的金属配合物。因此，本提案将探索C-H活化化学，这是由一类全新的催化剂促进的。新的碳氢活化剂将由三部分组成；这是一种晚期过渡金属中心，在以前的碳氢活化反应中被证明是有用的，它是一个稳定的支撑平台，包含环戊二烯片段和一个高度非常规的部分，包含一个锡原子。这种非常规的片段提供了广泛的未开发的机会，包括：i)桥接模式，将两个碳氢活化中心靠近在一起，ii)配体积极参与反应周期和物理参与断键步骤的能力，以及iii)利用半半性，一种可以在活性过渡金属中心旁边产生空位点的特性，使反应有效地发生。从这项研究中，将确定影响C-H活化的因素，帮助这一新过程的长期发展成为有用的工具。

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.