Mining the air for amines

氮素含量丰富，是哈伯博世工业流程中氨(用于百万吨化肥)和有机胺(特种、精细和医药化学品)的来源，但具有讽刺意味的是，它是最具挑战性的键之一，难以激活，从而以可持续的方式并入附加值分子中。然而，幸运的是，各种过渡金属在结合和激活氮方面相当有效，所以我们面临的挑战是利用这一点并将其发展为包括官能化。从机理的角度来看，生产氨从根本上来说仍然是有趣的，但一个主要的步骤变化将是激活氮素，并将其直接结合到含有NR3和R2N-NR2单元的有机分子中，这些单元具有广泛的附加值，从而绕过了几个氨反应后步骤的需要。阐明这些转化的机制也是实现这一目标的关键，因为在基本水平上的热力学和动力学信息对于设计新的氮素到有机胺催化循环是非常需要的。经过几十年的研究，整个元素周期表中仍然只有7种金属在分子物种中可以催化还原氮氮并将其固定到氨中，并且在过去4年中添加了5种：Ti，V，Mo，Fe，Ru，Os，Co。我们的工作是最近才介绍的(方案1左，天使。化学。内部编辑，2018，57,6314-6318)，这是因为钛在地壳丰度上排名第九，在能够激活氮素的金属中仅次于铁。现在我们已经证实了分子钛-Tren络合物可以催化将氮固定在氨上，并且还表明Flp可以裂解二氢并引入这些H原子来生成氨(方案1是对的，Angew。化学。内部编辑，2019，58,6674-6677)。我们致力于发展这门科学。我们的目标是通过官能化直接将氮还原为氨和有机胺，从而在理解氮还原化学及其固定方面取得重大进展。我们寻求通过实现以下目标来实现这一目标：将这种催化扩展到Zr和Hf；发展这一催化以包括通过C-N键形成反应直接形成NR3和R2N-NR2化合物，而不必通过氨；揭示反应机理，通过结构-反应性关联反馈到反应优化和产生新的催化循环；开发FLP方面来提供使用二氢的催化氨合成。因此，这个项目将涉及：重要的合成研究；催化；机理分析；计算模型。该项目牢固地植根于化学催化。它寻求利用STL的无机和氮气还原专业知识与DW的胺合成和机械专业知识来推导出新的化学反应和原子高效的胺类路线，这些方法可能具有生物相关性。因此，从定义上讲，它是一个解决问题的跨学科综合催化项目，旨在改变我们对催化的理解，将其与涉及氨和有机胺合成的现实世界挑战联系起来。在这个时间点上，随着两篇初步论文的发表，这个项目非常像TRL0，但我们相信这个项目将是通过ICAT和英国催化中心发展科学和与工业联系的完美工具，以便进行基础应用过渡，并将这项研究的TRL评级提高到可开发的结果。

Dinitrogen is plentiful and the source of ammonia (used in fertilizers on mega-tonne scales) and organoamines (for speciality, fine, and pharmaceutical chemicals) via Haber Bosch industrial processes, but ironically it is one of the most challenging bonds to activate and thus incorporate into added-value molecules in a sustainable way. Fortunately, however, various transition metals are quite effective at binding and activating dinitrogen, so the challenge for us is to harness that and develop it to include functionalization. Producing ammonia is still fundamentally interesting from a mechanistic perspective, but a major step-change will be to activate dinitrogen and incorporate it directly into organic molecules containing NR3 and R2N-NR2 units, that have extensive added-value, thus by-passing the need for several post-ammonia reaction steps. Elucidating the mechanism of these transformations is also critical to achieve, because this thermodynamic and kinetic information at a fundamental level is badly needed to feedback into designing new dinitrogen to organoamine catalytic cycles.After decades of research, there are still only 7 metals from the entire Periodic Table that in molecular species can catalytically reduce and fix dinitrogen into ammonia and 5 were added in the past 4 years: Ti, V, Mo, Fe, Ru, Os, Co. Ti is our work introduced only recently (Scheme 1 left, Angew. Chem. Int. Ed., 2018, 57, 6314-6318), which is appealing as Ti is 9th in crustal abundance and 2nd only to Fe for metals that can activate dinitrogen. Now we have established that a molecular Ti-Tren complex can catalytically fix dinitrogen to ammonia, and also shown that FLPs can split dihydrogen and introduce those H-atoms to produce ammonia (Scheme 1 right, Angew. Chem. Int. Ed., 2019, 58, 6674-6677). We seek to develop this science.Our aim is to make major advances in our understanding of dinitrogen reduction chemistry and its fixation by way of functionalization into ammonia and organoamines directly. We seek to achieve this aim by securing the following objectives: extend this catalysis to Zr and Hf; develop this to include direct formation of NR3 and R2N-NR2 compounds via C-N bond formation reactions without having to go via ammonia; unravel the reaction mechanisms to feedback, via structure-reactivity correlations, to reaction optimisation and generation of new catalytic cycles; develop the FLP aspect to deliver catalytic ammonia synthesis using dihydrogen.This project will thus involve: significant synthetic studies; catalysis; mechanistic analysis; computational modelling.The project is firmly rooted in chemocatalysis. It seeks to exploit the inorganic and N2 reduction expertise of STL with the amine synthesis and mechanistic expertise of DW to derive new chemical reactivity and atom-efficient routes to amines which could have biological relevance. It is therefore by definition a problem-solving, inter-disciplinary integrated catalysis project that seeks to make transformative step-changes in our understanding of catalysis that links to real-world challenges involving ammonia and organoamine syntheses. At this point in time with two preliminary papers published, this project is very much as TRL0, but we believe this project will be the perfect vehicle to develop the science and links to industry, via iCAT andthe UK Catalysis Hub, in order to make the fundamental-applied transition and raise the TRL rating of this research to exploitable outcomes.