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，通过多步化学计量过程在工业规模上生产，因此产生了大量的废物和过多的能源。克服这一点的一种方法是将氨与烯烃和炔烃进行100%原子效率的加成反应。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，这是因为在过渡金属(TM)中心的N-H键的活化方面存在重大挑战。基于类似的理由，从伯胺和未活化的烯烃中选择性地合成仲胺的情况也极为罕见。因此，这两个方面的氢胺化反应至今仍是催化领域的主要挑战。该项目旨在通过开发一种新的配体设计和键激活的概念，即阳离子单中心两亲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供体和强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，因此通过Umpoled键激活进行。这种独特的活化机制将通过N-H键断裂生成TM-氢化物络合物，该络合物随后可以与不饱和底物反应。我们将开发和定义这一独特的键活化过程，并采取步骤将其用于烯烃与氨的催化氢胺化反应，生成伯胺，以及随后选择性地生成仲胺。为了实现这一目标，本项目将开发一类新型的阳离子四丙烯，它们有能力充当单中心两亲配体，特别侧重于GeII和SnII，以及低成本、高度丰富的晚期第一行过渡金属Fe、Co和Ni。通过不同的金属-配体组合，以及配体的空间和电子修饰，我们将开发一套广泛的、定义明确的系统，用于在氨和高级胺中控制N-H键的激活，并将其扩展到定义明确的催化过程。为了进一步确定单中心两亲配体-TM系统的键激活机制，我们还将研究进一步的质子型和氢型E-H底物(E=O，P，B，Si，H等)的Umpoled断裂，以及对CO和CO2等关键催化底物的反应性，以了解单中心两亲性配体体系在键激活过程中的键极性的影响。作为一个整体，该项目旨在为新的单中心两亲配体概念奠定基础，最终开发出对抗胺合成常用工业过程中较差的原子经济性的系统。

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.