Cationic tetrylenes as Single-Center Ambiphile ligands for Cooperative N-H bond activation and hydroamination catalysis

胺是化学合成中不可缺少的组成部分，在工业规模上通过多步化学计量过程生产，从而产生大量浪费并使用过多的能源。克服这一问题的一个方法是将氨100%高效地添加到烯烃和炔烃中。通过氢胺化选择性合成伯胺的均相催化系统基本上是未知的，这主要是由于过渡金属（TM）中心N-H键的激活所面临的主要挑战。从伯胺和未活化的烯烃选择性合成仲胺也是极为罕见的。因此，氢胺化的这两个方面至今仍是催化领域的主要挑战。该项目旨在通过开发配体设计和键激活的新概念，即阳离子单中心两亲性配体，来解决这些具有挑战性的过程。这些配体可以同时作为σ-给体和强π-受体，在TM的配位范围内保持刘易斯酸性。这导致了在N-H键激活中独特的金属-配体合作机制，其中底物结合发生在配体而不是金属上，因此通过“非极化”键激活进行。其独特的活化机制将导致tm -氢化物配合物通过N-H键断裂，随后可与不饱和底物反应。我们将开发和定义这种独特的键激活过程，并采取措施将其用于与氨催化烯烃的氢胺化，形成伯胺，以及随后选择性生成仲胺。为了实现这一目标，目前的项目将开发一种新型的阳离子四烯，它具有作为单中心两亲性配体的能力，特别是专注于GeII和SnII，与低成本，高含量的晚期第一排过渡金属，Fe， Co和Ni结合。通过不同的金属配体组合，以及配体的立体和电子修饰，我们将开发一套广泛的、定义良好的系统，用于控制氨和高级胺中的n -氢键激活，并将其扩展到定义良好的催化过程。为了进一步定义单中心两亲体配体- tm系统的键激活机制，我们还将研究更多质子和氢化E-H底物（E = O， P， B, Si， H等）的“非极性”断裂，以及对关键催化底物（如CO和CO2）的反应性，以了解键极性对单中心两亲体系统键激活的影响。作为一个整体，该项目旨在为新的单中心两亲性配体概念奠定基础，最终开发出能够对抗胺合成常见工业过程中原子经济性差的系统。

Amines, which are indispensable building blocks in chemical synthesis, are produced on industrial scale through multi-step stoichiometric processes, thus generating considerable waste and using excessive energy. A process which overcomes this is the 100% atom efficient addition of ammonia to alkenes and alkynes. Homogenous catalytic systems for the selective synthesis of primary amines through hydroamination are essentially unknown, historically due to major challenges in the activation of N-H bonds at a transition metal (TM) center. The selective synthesis of secondary amines from primary amines and unactivated alkenes are also extremely rare on similar grounds. These two aspects of hydroamination therefore still stand as major challenges in catalysis to this day. This project aims to tackle these challenging processes through the development of a novel concept in ligand design and bond activation, namely cationic Single-Center Ambiphile ligands. These ligands can simultaneously act as σ-donors and strong π-acceptors, remaining Lewis-acidic when in the coordination sphere of a TM. This leads to a unique metal-ligand cooperative mechanism in N-H bond activation, where substrate binding occurs at the ligand as opposed to the metal, and so proceeding through an ‘Umpoled’ bond activation. The unique activation mechanism would lead to a TM-hydride complex through N-H bond scission, which can subsequently react with unsaturated substrates. We will develop and define this unique bond activation process, and take steps towards utilizing it in the catalytic hydroamination of alkenes with ammonia, to form primary amines, and in the subsequent selective generation of secondary amines. To achieve this, the present project will develop a novel class of cationic tetrylenes, which have the capacity to act as Single-Center Ambiphile ligands, specifically focusing on GeII and SnII, in conjunction with low-cost, highly abundant late first-row transition metals, Fe, Co, and Ni. Through differing metal-ligand combinations, as well as steric and electronic modifications of the ligands, we will develop a broad, well-defined set of systems for controlled N-H bond activation in ammonia and higher amines, and extend this to well-defined catalytic processes. To further define bond-activation mechanisms via which Single-Center Ambiphile ligand-TM systems can operate, we will also study the ‘Umpoled’ scission of further protic and hydridic E-H substrates (E = O, P, B, Si, H, etc.), as well as reactivity towards key catalytic substrates such as CO and CO2, in order to understand the effects of bond polarity in bond-activation by Single-Center Ambiphile systems. As a whole, this project aims to lay the foundations for the novel Single-Centre Ambiphile ligand concept, to ultimately develop systems which counter the poor atom economy of common industrial processes for amine synthesis.