Dynamic Ligands for Sustainable Molecular Catalysis

该研究项目名为“可持续分子催化的动态配体”，目标是合成高价值有机化合物的创新催化剂。催化剂开发的进展将通过扩展基本设计参数和合作配体的原理来实现。这些配体的过渡金属络合物将被用于高度原子经济的催化过程中，这些催化过程使用无毒和丰富的原料（即水、氧和第一行金属）。具体来说，我们的目标烯丙基氧化和水合反应。这些新的催化体系在有机合成的学术和工业领域都有着重要的应用。 催化剂结构利用协同特性，其中金属中心的反应性通过次级过程或功能被放大或调节。这些协同关系包括表现出响应性触觉（动态协调）或第二协调领域过程的配体。后者包括参与氢键或分子内质子转移的官能团。这些合作关系为反应性或选择性开辟了新的途径，这些途径是通过传统的过渡金属活化底物无法达到的。这项工作的一个主要目标是获得这些过程的分子水平的理解，以及它们是如何改变配体设计的变化。这一见解对于开发高性能催化剂至关重要。 该研究计划分为三个主要研究分支。 1)后金属配合物的动态混合给体配体。我们正在开发一种新的配体家族P-AzA，该家族由中性磷化氢和阴离子1-氮杂烯丙基片段组成。配体具有以多种模式结合金属的潜力，并且这种配位在系统的响应条件下发生变化（即引入其他辅助配体或试剂）。通过详细的光谱和反应性研究，这些系统得到了透彻的理解，其结果是必要的催化系统的发展。这种独特的配体框架的催化测试有望揭示前所未有的活性和选择性。 2)双功能镍配合物介导的选择性氧化。分子氧是理想的氧化剂和O原子源，因为它非常丰富，如果控制得当，会产生环境友好的副产品。控制是一个主要的挑战，这可以通过独特设计的金属配合物来实现。我们的目标镍-NHC络合物，含有相邻的氢键供体，但不连接到金属中心（NHC = N-杂环卡宾）。我们假设，这些次级相互作用将改变反应性，从失活或分解的产品转移。反应活性的研究将为好氧氧化催化剂的开发提供基础。 3)用于炔的反马氏水合的高性能催化剂。用环境友好的水将炔转化为醛是100%原子经济的。需要在较低催化剂负载、较低温度和较快速率下操作的催化系统。质子转移是催化循环中的关键步骤，并且通过促进分子内运动的配体显著地辅助。一个非常有前途，但开发不足的系统是PR2NR '2配体家族。几种变体（R/R '= Ph、Ar、Cy、Bn、tBu）的催化和化学计量研究将揭示促进快速和选择性产物形成的最佳膦供体强度和胺碱性。

The research program, 'Dynamic Ligands for Sustainable Molecular Catalysis', targets innovative catalysts for the synthesis of high-value organic compounds. Advances in catalyst development will be achieved by expanding the fundamental design parameters and principles of cooperative ligands. Transition-metal complexes of these ligands will be exploited in catalytic processes that are highly atom-economic and that use non-toxic and abundant feedstocks (i.e. water, oxygen and first-row metals). Specifically, we target allylic oxidation and hydration reactions. The new catalytic systems will be powerful in applications of organic synthesis in both the academic and industrial realms. Catalysts structures exploit cooperative characteristics, where reactivity at the metal centre is amplified or modulated by a secondary process or functionality. These synergistic relationships include ligands that demonstrate responsive hapticity (dynamic coordination) or second-coordination sphere processes. The latter includes functionalities that participate in hydrogen-bonding or intramolecular proton transfer. These cooperative relationships open new pathways for reactivity or selectivity that are inaccessible through traditional activation of substrates with transition metals. A main objective of this work is to gain a molecular-level understanding of these processes and how they are altered with changes in ligand design. This insight is crucial to the development of high-performance catalysts. The research program is divided between three main research branches. 1) Dynamic Mixed-Donor Ligands for Late-Metal Complexes. We are developing a new ligand family P-AzA that is comprised of a neutral phosphine and an anionic 1-azaallyl fragment. The ligand has the potential to bind to metals in a variety of modes and this coordination shift in response conditions of the system (i.e. introduction of other ancillary ligands or reagents). A thorough understanding of these systems is attained through detailed spectroscopic and reactivity studies, the results of which are necessary for the development of catalytic systems. Catalytic testing of this unique ligand framework is expected to uncover unprecedented activity and selectivity. 2) Selective Oxidation Mediated by Bifunctional Nickel Complexes. Dioxygen is an ideal oxidant and O-atom source as it is highly abundant and, if properly controlled, generates environmentally benign by-products. Control is a major challenge, which can be achieved with uniquely designed metal complexes. We target nickel-NHC complexes that contain hydrogen-bond donors adjacent, but not attached, to the metal centre (NHC = N-heterocyclic carbene). We postulate that these secondary interactions will alter reactivity, diverting away from deactivated or decomposed products. Reactivity studies will provide the groundwork for the development of aerobic oxidation catalysts. 3) High-Performance Catalysts for the Anti-Markovnikov Hydration of Alkynes. Conversion of alkynes to aldehydes with environmentally benign water is 100% atom-economic. Catalytic systems are needed that operate at lower catalyst loadings, lower temperatures and at faster rates. Proton transfer is a key step in the catalytic cycle and is dramatically assisted by ligands that promote intramolecular movement. An extremely promising, but underexploited system is the PR2NR'2 ligand family. Catalytic and stoichiometric studies of several variants (R/R' = Ph, Ar, Cy, Bn, tBu) will uncover the optimal phosphine donor strength and amine basicity for promoting rapid and selective product formation.