Base Metal Bifunctional Catalysis

贱金属双功能催化

• 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: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=748181
• 关键词: Base; Metal; Bifunctional; Catalysis

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％的商业化学过程涉及降低能量使用，提高反应选择性并有助于过程强化，例如，将多个步骤组合成一个，从而有助于催化剂。虽然商品化学制造通常采用异质固体催化剂，但高价值化学物质的产生通常涉及分子催化剂，这些催化剂可以合理地“调节”以提供所需产品的高产量。尽管贵金属（Ru，Rh，ir，Pd，Pt）复杂催化剂在过去的50年中已广泛开发，但仍有大量驱动器来开发更有效的催化剂，其中包括碱基（MN，FE，CO，CO，NI，CU），这些催化剂的毒性较小，地球较少且富含地球。碱金属催化中有一些最大的报道成功包括复合物，其中金属配体配体能够为金属中心提供的配体提供额外的机械作用。几个突出的示例原代胺或amido配体能够充当氢键供体或内部碱，从而有助于E-H键的激活（E = H，B，C，C，N，O，SI）。在以自然为模型的催化剂中，硫醇酸盐配体也可以参与双功能的E-H键激活，尽管协调的硫醇酸盐S-H伴侣通常比其N-H对应物更酸性。最后，氧化还原活性配体可以用作电子或受体，与基层中心同时工作以实现多电子转化。在此提案中，我们概述了一个计划，该计划将挑战11名毕业生和本科生，使用具有五个不同碱基的简单SNS配体来探测催化反应中金属配位配位的基本特性。在上一个资金期间，我们开发了很容易制备的SNS Amido和硫醇酸盐配体，并研究了他们的协调化学，以比较“硬” N与“软”的内部碱的效率，以进行许多催化反应。亮点包括用于胺 - 硼烷脱氢作用的双功能FE催化剂，用于酒精脱氢的CO催化剂以及用于烯烃氢化的MN催化剂。 Fe，Co和Ni SNS硫醇酸盐复合物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处以N2S2配体。最初的研究表明，这种可逆过程可能与M（N2S2）催化循环有关，并且存在多种稳定的氧化还原态（Fe为3，CO为3）为氧化还原依赖性的催化活性和选择性带来了令人兴奋的可能性。下一个资金期的目标包括通过改变辅助配体的金属和性质以及探测配体供体和氧化还原活性的协调来调整供体碱性。通过实验方法和计算方法组合对双功能催化的这些基本研究最终将使我们能够开发和优化新的“氢借入”串联催化过程。