Cooperative Noble Base Metal Catalysis

协同贵贱金属催化

• 批准号: EP/X019306/1
• 负责人: Oriol Planas
• 金额: $ 60.51万
• 依托单位: Queen Mary University of London
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2023
• 资助国家: 英国
• 起止时间: 2023 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FX019306%2F1
• 关键词: Cooperative; Noble; Base; Metal; Catalysis

In the UK, the chemicals sector is a key contributor to the UK economy. It adds close to £20 billions of value to the country's economy every year and has an annual turnover of approximately £60 billion, sustaining more than half a million jobs. Within this sector, the manufacture of most chemicals involves the use of a catalyst, which is usually based on the rarest elements on the Earth's crust, such as noble metals (Pd, Rh or Ir). The limited supply of these group of privileged metals, together with their huge environmental footprint (e.g. obtaining 1 kg of pure metallic Rh produces near 32t of carbon dioxide) blocks the development of truly sustainable processes. This is pushing chemists towards the discovery of catalysts based on inexpensive, abundant, and benign base metals (e.g. Ni, Co and Fe). However, reactivity on BM centres often proceeds through one-electron events, resulting in difficulties controlling and maintaining the catalyst function, thus preventing the development of sustainable, efficient, and predictable catalysts. Among all the strategies employed to control the chemistry of base metals, we were attracted by chemical metal-ligand cooperation, in which actor ligands participate in bond-forming and breaking events. Based on this, our strategy to tame two-electron catalytic cycles and develop predictable catalytic methods with BM will exploit low-valent aluminium-based ligands. Thus, our aim will be furnishing ambiphilic Al-BM units that are capable of (1) binding substrates to the highly electrophilic Al centre and (2) activate them using a nucleophilic base metal centre. Using Al as binding site is not a random choice: this group 13 element is not only benign, but the most abundant metal in the Earth's crust. Furthermore, in its +1 oxidation state presents interesting properties as ligand, becoming a powerful sigma-donor with an empty and accessible p-orbital. These properties have been recently exploited in the field of noble metal catalysis. Nonetheless, heterobimetallic complexes in which Al(I) is paired with another earth-abundant metal remain under-explored and currently limited to stoichiometric activation of small molecules. In these examples, however, the integrity of the Al-BM bond is lost. This represents a major challenge for their implementation in catalytic processes, as ligand dissociation leads to disruption of their cooperative activation ability, resulting in catalytic deactivation. To overcome this issue and achieve rigid and stable structures and Al-BM bonds, we will establish a rational design strategy to obtain bespoke Al-BM complexes that will be built by a delicate selection of ligand backbone, anchor arms, and base metal centre (Co, Ni, Fe). These complexes will be studied using a bottom-up approach based on a stoichiometric-to-catalytic strategy: employing the knowledge gathered from stoichiometric activation studies, infusing nobility to Al-BM units in a catalytic fashion will be within reach. The implementation of Coop-NBM will represent a greener and cheaper alternative to functionalise organic molecules compared to noble metal catalysis, allowing the achievement of environmentally friendly approaches with potential to be applied at industry.Overall, the importance of this research proposal lies in its potential to provide catalysts based on the most abundant elements of our planet, e.g. Al and Fe. Catalytic use of base metals combined with subvalent Al ligands remains an uncharted territory and an exceptional opportunity to establish a new chemical space that could lead to a dramatic reduction of the environmental footprint of countless organic transformations currently performed by noble metal catalysis. This will certainly make the UK take centre stage in the development of sustainable technologies aiming at retiring noble metals as workhorses of chemical industry.

在英国，化工行业是英国经济的主要贡献者。它每年为国家经济增加近200亿英镑的价值，年营业额约为600亿英镑，维持了50多万个工作岗位。在这一领域，大多数化学品的制造都涉及到催化剂的使用，催化剂通常是基于地壳上最稀有的元素，如贵金属（Pd、Rh或Ir）。这些特殊金属的有限供应，以及它们巨大的环境足迹（例如，获得1公斤纯金属Rh会产生近32吨二氧化碳）阻碍了真正可持续过程的发展。这促使化学家们朝着发现基于廉价、丰富和无害的贱金属（如镍、钴和铁）的催化剂的方向发展。然而，BM中心的反应性通常通过单电子事件进行，导致难以控制和维持催化剂功能，从而阻碍了可持续、高效和可预测催化剂的发展。在所有用于控制贱金属化学性质的策略中，我们被化学金属-配体合作所吸引，在化学金属-配体合作中，行为体参与成键和断裂事件。基于此，我们的策略是驯服双电子催化循环并开发可预测的BM催化方法，将利用低价铝基配体。因此，我们的目标是提供两亲性的Al- bm单元，它能够(1)将底物与高度亲电的Al中心结合，(2)使用亲核的贱金属中心激活它们。使用Al作为结合位点并不是一个随机的选择：这种13族元素不仅是无害的，而且是地壳中最丰富的金属。此外，在+1氧化态下，它作为配体表现出有趣的性质，成为一个强大的sigma供体，具有一个空的和可接近的p轨道。这些性质最近在贵金属催化领域得到了开发。尽管如此，Al(I)与另一种地球上丰富的金属配对的杂双金属配合物仍未得到充分探索，目前仅限于小分子的化学计量活化。然而，在这些例子中，Al-BM键的完整性丢失了。这是它们在催化过程中实现的一个主要挑战，因为配体解离导致它们的协同活化能力被破坏，从而导致催化失活。为了克服这一问题并获得刚性和稳定的结构和Al-BM键，我们将建立一个合理的设计策略来获得定制的Al-BM配合物，该配合物将通过精心选择配体主链、锚臂和贱金属中心（Co, Ni, Fe）来构建。这些配合物将采用基于化学计量到催化策略的自下而上的方法进行研究：利用从化学计量活化研究中收集的知识，以催化方式向Al-BM单元注入贵族将是可以实现的。与贵金属催化相比，Coop-NBM的实施将代表一种更环保、更便宜的有机分子功能化替代方案，使环保方法的实现具有应用于工业的潜力。总的来说，这项研究计划的重要性在于它有可能提供基于我们星球上最丰富的元素（如Al和Fe）的催化剂。贱金属与亚价铝配体的催化使用仍然是一个未知的领域，也是一个建立新的化学空间的绝佳机会，可以大大减少目前由贵金属催化进行的无数有机转化的环境足迹。这肯定会使英国在可持续发展技术的发展中处于中心地位，旨在使贵金属不再是化学工业的主力。