Base Metal Bifunctional Catalysis

贱金属双功能催化

基本信息

批准号：
RGPIN-2019-05958
负责人：
Baker, Ralph
金额：
$ 6.85万
依托单位：
University of Ottawa
依托单位国家：
加拿大
项目类别：
Discovery Grants Program - Individual
财政年份：
2021
资助国家：
加拿大
起止时间：
2021-01-01 至 2022-12-31
项目状态：
已结题

来源：
https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=738620
关键词：
Base Metal Bifunctional Catalysis

项目摘要

More than 80% of commercial chemical processes involve catalysts that decrease energy use, increase reaction selectivity and contribute to process intensification, e.g., by combining multiple steps into one. While commodity chemical manufacturing typically employs heterogeneous solid catalysts, production of higher value chemicals often involves molecular catalysts that can be rationally `tuned' to provide high yields of the desired product. Although precious metal (Ru, Rh, Ir, Pd, Pt) complex catalysts have been broadly developed over the last 50 years, there has been an intensive drive to develop more effective catalysts that include base-metals (Mn, Fe, Co, Ni, Cu) that are less toxic and more earth abundant. Some of the greatest reported successes in base metal catalysis include complexes in which the metal-coordinated ligand is able to provide an additional mechanistic role to those offered by the metal center. In several prominent examples a primary amine or amido ligand is able to function as a hydrogen bond donor or internal base that contributes to the activation of E-H bonds (E = H, B, C, N, O, Si). In catalysts modeled after Nature, the thiolate ligand can also participate in bifunctional E-H bond activation although the coordinated thiol S-H partner is typically more acidic than its N-H counterpart. Finally, a redox-active ligand can serve as an electron source or acceptor, working in tandem with the base-metal center to achieve multi-electron transformations. In this proposal we outline a program that will challenge 11 graduate and undergraduate students, using simple SNS ligands with five different base-metals to probe the fundamental properties of metal-ligand cooperativity in catalytic reactions. Over the last funding period we developed easily prepared SNS amido and thiolate ligands and investigated their coordination chemistry to compare the efficiency of `hard' N vs. `soft' S internal bases for a number of catalyzed reactions. Highlights include demonstration of bifunctional Fe catalysts for amine-borane dehydrogenation, Co catalysts for alcohol dehydrogenation and Mn catalysts for alkene hydrosilylation. An internal redox reaction on Fe, Co, and Ni SNS thiolate complexes afforded a redox non-innocent N2S2 ligand via imine C-C bond formation. Initial studies suggest that this reversible process may be involved in the M(N2S2) catalytic cycles and the presence of multiple stable redox states (3 for Fe, 4 for Co) opens up the exciting possibility of redox-dependent catalytic activity and selectivity. Objectives for the next funding period include tuning donor basicity by changing the metal and nature of the ancillary ligands and probing the cooperativity of ligand donors and redox activity. These fundamental investigations of bifunctional catalysis by a combination of experimental and computational approaches will eventually allow us to develop and optimize new `hydrogen-borrowing' tandem catalysis processes.

超过 80% 的商业化学工艺涉及可减少能源消耗、提高反应选择性并有助于工艺强化的催化剂，例如，通过将多个步骤合并为一个步骤。虽然商品化学品制造通常采用非均相固体催化剂，但更高价值化学品的生产通常涉及催化剂。尽管贵金属（Ru、Rh、Ir、Pd、Pt）络合物催化剂在过去 50 年间已得到广泛开发，但可以合理“调节”以提供高产率的分子催化剂。多年来，人们一直在大力开发更有效的催化剂，其中包括毒性较小且地球资源丰富的贱金属（Mn、Fe、Co、Ni、Cu），在贱金属催化方面最成功的报道之一包括配合物。其中金属配位配体能够为金属中心提供额外的机械作用，在几个突出的例子中，伯胺或酰氨基配体能够充当有助于活化的氢键供体或内部碱。 E-H的在以 Nature 为模型的催化剂中，硫醇配体也可以参与双功能 E-H 键活化，尽管配位的硫醇 S-H 伴侣通常比其 N-H 对应物更具酸性。，氧化还原活性配体可以作为电子源或受体，与贱金属中心协同工作以实现多电子转化。在本提案中，我们概述了一个将挑战 11 名研究生的计划。本科生使用具有五种不同贱金属的简单 SNS 配体来探讨催化反应中金属-配体协同性的基本性质。在上一个资助期间，我们开发了易于制备的 SNS 酰胺和硫醇盐配体，并研究了它们的配位化学以比较效率。一系列催化反应的“硬”N 与“软”S 内部碱的对比亮点包括用于胺-硼烷脱氢的双功能 Fe 催化剂、用于醇的 Co 催化剂的演示。 Fe、Co 和 Ni SNS 硫醇盐配合物上的脱氢和 Mn 催化剂通过亚胺 C-C 键形成提供了氧化还原非无害的 N2S2 配体。初步研究表明，这种可逆过程可能涉及 M()。 N2S2）催化循环和多种稳定氧化还原态（Fe 为 3，Co 为 4）的存在开启了令人兴奋的可能性下一个资助期的目标包括通过改变辅助配体的金属和性质来调整供体碱性，并通过实验相结合来探索配体供体和氧化还原活性的合作。计算方法最终将使我们能够开发和优化新的“借氢”串联催化过程。