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：
2020
资助国家：
加拿大
起止时间：
2020-01-01 至 2021-12-31
项目状态：
已结题

来源：
https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=715866
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催化剂，这些催化剂可以减少能源消耗、提高反应选择性并有助于工艺强化，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可以合理调整的分子催化剂，以提供高产率的所需产品。尽管贵金属（Ru、Rh、Ir、Pd、Pt）络合物催化剂在过去 50 年中得到了广泛的开发，但人们一直在大力开发包括贱金属（Mn、Fe、Co、Ni）在内的更有效的催化剂。，Cu），毒性较小且地球资源丰富。在贱金属催化方面报道的一些最伟大的成功包括络合物，其中金属配位的配体能够为金属中心提供的作用提供额外的机械作用。在几个突出的例子中，伯胺或酰胺配体能够充当氢键供体或内部碱，有助于 E-H 键的活化（E = H、B、C、N、O、Si）。在以 Nature 为模型的催化剂中，硫醇盐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 对应物酸性更强。最后，氧化还原活性配体可以充当电子源或受体，与贱金属中心协同工作以实现多电子转化。在本提案中，我们概述了一个项目，该项目将挑战 11 名研究生和本科生，使用简单的 SNS 配体与五种不同的贱金属来探索催化反应中金属-配体协同性的基本特性。在上一个资助期间，我们开发了易于制备的 SNS 酰胺基和硫醇盐配体，并研究了它们的配位化学，以比较硬 N 与软 S 内部碱在许多催化反应中的效率。亮点包括展示用于胺-硼烷脱氢的双功能铁催化剂、用于醇脱氢的钴催化剂和用于烯烃硅氢加成的锰催化剂。 Fe、Co 和 Ni SNS 硫醇盐配合物上的内部氧化还原反应通过亚胺 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，并且多个稳定氧化还原态（Fe 为 3，Co 为 4）的存在开启了氧化还原依赖性催化活性和选择性的令人兴奋的可能性。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，并探索配体供体的协同性和氧化还原活性。这些通过实验和计算方法相结合对双功能催化进行的基础研究最终将使我们能够开发和优化新的借氢串联催化过程。