Exploiting hemi-labile ligands in Main Group catalysis

催化剂是一种加速化学反应速率而自身不被消耗的物质。他们通过提供另一种低能量的反应机制来实现这一点，在反应发生的最后，原始催化剂被改造。它们对能源效率至关重要，因为使用它们可以在更低的温度下更快地进行反应。因此，催化剂的使用在所有类型的工业化学过程中是普遍存在的。过渡金属（元素周期表中心的元素块）是极好的催化剂，因为它们最外层的电子壳层部分被填满，可以很容易地接触到电子和每个金属原子周围的空结合位点。然而，对催化很重要的金属，如汽车催化转化器中的钯和铑，往往对生命有毒，昂贵且稀有。随着地壳中稀土储量的减少，稀土的供应和开采出现了社会和环境问题。因此，寻找替代品至关重要。属于主族的元素（在元素周期表的右侧，如铝和硅）往往对环境和经济都更加无害。从历史上看，这些元素被认为总是形成具有完整电子壳层的化合物，使它们成为糟糕的催化剂。最近的一系列发现挑战了这一观点，现在已知这些元素与具有多种分子的过渡金属发生类似的反应。正因为如此，目前人们正在探索它们作为催化剂的用途。配体是一种与中心金属原子结合（或配位）形成配位复合物的分子。半不稳定配体是含有两个或两个以上位点的配体，其中至少一个位点可以可逆地分离，而其余位点则保持紧密结合。这个空出的空间允许其他分子结合，这使得化学反应很容易发生。现在已知半不稳定配体可以促进主基团元素的“过渡金属”行为，否则就不会看到这种行为。通过利用这种行为，已经发现了一些有希望的潜在催化剂。因此，本项目旨在扩大这项工作，并为更广泛的重要反应开发有效的催化剂。最终目标是在催化过程中用主族元素取代过渡金属。潜在的影响是一个更可持续的未来，在那里，化学制造只使用丰富、廉价和无害环境的元素。该项目属于EPSRC的“制造未来”研究领域。

A catalyst is a substance which speeds up the rate of a chemical reaction without being consumed itself. They do this by offering an alternative, lower-energy mechanism by which the reaction happens, at the end of which the original catalyst is reformed. They are crucial for energy efficiency, as using them allows for reactions to be carried out quicker and at lower temperatures. As such, the use of catalysts is ubiquitous in industry for chemical processes of all types.The transition metals (the block of elements in the centre of the periodic table) make excellent catalysts, as their outermost electron shells are partially filled, allowing easy access to both electrons and empty binding sites around each metal atom. However, the metals which are important to catalysis, such as palladium and rhodium in catalytic converters for cars, tend to be toxic to life, expensive, and rare. As reserves in the Earth's crust dwindle, social and environmental difficulties have arisen with their supply and extracting them from their ores. It is vital, therefore, for replacements to be found.Elements belonging to the main group (on the right side of the periodic table, such as aluminium and silicon) tend to be much more benign environmentally and economically. Historically, these elements were thought to invariably form compounds with completed shells of electrons, making them poor catalysts. A series of more recent discoveries around this has challenged this view, and these elements are now known to undergo similar types of reaction to transition metals with a wide variety of molecules. Because of this, they are now currently being explored for use as catalysts.A ligand is a molecule which binds (or coordinates) to a central metal atom to form a coordination complex. A hemi-labile ligand is one which contains two or more sites which can coordinate, where at least one of them can reversibly dissociate, while the rest stay(s) firmlybound. This vacated space allows for other molecules to bind, which now allows a chemical reaction to easily occur.Hemi-labile ligands are now known to promote 'transition-metal' like behaviour in the main group elements where otherwise it would not be seen. A few promising potential catalysts have already been found by exploiting this behaviour. As such, this project aims expand upon this work and to develop efficient catalysts for a wider scope of important reactions.The ultimate objective is for the eventual replacement of transition metals with main group elements in catalysis. The potential impact is a more sustainable future, where chemical manufacturing is achieved solely using abundant, inexpensive, and environmentally benign elements.This project falls within the EPSRC 'Manufacturing the Future' research area.