Silyl Pincer Transition Metal Complexes for Challenging Bond Activation and Catalysis

过渡金属催化剂在促进将丰富的原材料资源转化为增值产品(药品、香料、香水、塑料等)的化学过程中发挥着关键作用。以有效的、有选择性的方式。长期以来，化学家们一直专注于开发均质催化剂，这些催化剂利用稀有的贵金属，如Pd、Pt、Rh和Ru。尽管这类催化剂有效，但由于后4d和5d过渡金属的可获得性下降以及相关的高成本，这些催化剂受到限制。含有这类金属的矿石的开采和加工也是高度能源密集型的，产生大量二氧化碳排放。面对开发越来越可持续的合成工艺的迫切需要，人们对富含地球的三维金属(如锰、铁、钴和镍)的反应性的兴趣显著增加，目标是发现新的有效催化剂，以补充甚至可能取代基于贵金属的技术。虽然自然界几乎完全利用3D过渡金属来催化化学反应，但在实验室中利用这种反应性是具有挑战性的。在这方面，这项建议的目标是开发广泛使用的、可持续的新型3D金属催化剂，用于原子经济型烯烃和炔氢功能化，这是一类广泛使用的反应，可将此类原料转化为消费品。我们的战略建立在我们在开发高活性贵金属硅基钳形化合物方面取得的成功的基础上。我们试图将这种连接策略扩展到3D-金属，我们预计硅基-金属在元素-氢键断裂中的协同作用可能在氢功能化催化中提供反应优势。虽然地球上丰富的3D金属催化剂是非常可取的，也将是我们的主要关注点，但贵金属络合物在定向、具有挑战性的反应性应用中的效用还不能被忽视。因此，第二个研究领域将着眼于开发由Ir硅基钳子物种促进的新的催化胺化反应。由于含氮官能团在医药和精细化学品中的普遍存在，人们对开发新的原子经济的胺化反应非常感兴趣，特别是利用氨的反应--一种廉价的商品化学品。我们的团队已经确定，Ir硅基钳形化合物可以进行具有挑战性的化学计量N-H键氧化加成反应，以裂解包括氨在内的胺的N-H键。在这项提议中，我们试图利用这种新的反应性来开发新的胺和氨的官能化催化工艺，这将在化学合成中具有广泛的适用性。这些研究将促进我们对过渡金属介导的合成的理解，将为最终用户提供实用的3D金属催化剂，并将为现代合成化学技术的研究人员提供世界级的培训。

Transition metal catalysts play a key role in facilitating chemical processes that convert abundant raw material resources into value-added products (pharmaceuticals, flavors, fragrances, plastics, etc.) in an efficient, selective manner. Chemists have long focused on developing homogeneous catalysts that utilize scarce precious metals such as Pd, Pt, Rh, and Ru. Despite their efficacy, such catalysts are limited by the decreasing availability, and associated high cost, of the late 4d- and 5d-transition metals. Mining and processing of ores containing such metals is also highly energy intensive, generating large CO2 emissions. Faced with the pressing need to develop increasingly sustainable synthetic processes, interest in the reactivity of earth-abundant 3d-metals, such as Mn, Fe, Co, and Ni has grown significantly, with the goal of discovering new, effective catalysts to complement, and possibly supplant, precious metal-based technology. While nature has utilized 3d-transition metals almost exclusively for catalyzing chemical reactivity, harnessing this reactivity has proven challenging in the laboratory. In this regard, this proposal targets the development of new classes of broadly useful, sustainable 3d-metal catalysts for atom economical alkene and alkyne hydrofunctionalization, a class of widely used reactions for converting such feedstocks into consumer products. Our strategy builds upon our established success in developing highly reactive precious metal silyl pincer complexes. We seek to extend this ligation strategy to the 3d-metals, where we anticipate that silyl-metal cooperativity in element-hydrogen bond cleavage may provide reactivity advantages in hydrofunctionalization catalysis. While earth-abundant 3d-metal catalysts are highly desirable and will be our primary focus, the utility of precious metal complexes for targeted, challenging reactivity applications cannot yet be discounted. As such, a second area of investigation will target the development of new catalytic amination reactions facilitated by Ir silyl pincer species. Due to the prevalence of N-containing functional groups in pharmaceuticals and fine chemicals, significant interest exists in developing new atom-economical amination reactions, especially reactions that utilize ammonia - an inexpensive commodity chemical. Our group has established that Ir silyl pincer complexes can undergo challenging stoichiometric N-H bond oxidative addition reactions to cleave the N-H bonds of amines, including ammonia. In this proposal, we seek to capitalize on this novel reactivity in order to develop new catalytic processes for the functionalization of amines and ammonia, which would have wide applicability in chemical synthesis. The proposed studies will advance our understanding of transition metal mediated synthesis, will provide practical 3d-metal catalysts for uptake by end-users, and will provide world-class training for researchers in modern synthetic chemistry techniques.