Mechanism and Catalyst Design in Ru-Catalyzed Alkene Hydrophosphination
Mechanism and Catalyst Design in Ru-Catalyzed Alkene Hydrophosphination
复制标题
DOI：
10.1021/acscatal.1c05636
复制
发表时间：
2022-05-06
期刊：
影响因子：
12.9
通讯作者：
Rosenberg, Lisa
中科院分区：
文献类型：
--
作者：
Belli, Roman G.;Yang, Jin;Rosenberg, Lisa
研究了一系列半夹心结构钌茚基配合物[Ru（eta（5）-indenyl）（PPh 2）（L）（PPh 3）（L = PPh 2 H，CO，NCPh）]在丙烯酸叔丁酯的二苯基膦氢膦化反应中的催化性能，为该重要的P-C键形成反应设计活性和稳定的催化剂提供了有价值的经验.从反应监测（H-1和P-31 NMR）、动力学分析、化学计量控制反应以及关键中间体、催化剂失活产物和非循环副产物的分离和光谱鉴定中收集了相关催化循环中每个基本步骤的证据。对于L = PPh 2 H，两个不同的催化循环都依赖于Ru-PPh 2配体在缺电子烯烃上的外球共轭加成。这些循环的P-H活化步骤不同（分子内与分子间），但通过共同的静止状态[Ru（eta（5）-茚基）（PPh 2）P-2，其中P是氢膦化产物Ph 2 PCH 2CH 2CO 2But]连接。与L = CO的配合物是惰性的取代PPh 2 H，这排除了两个共轭加成催化循环之一。该催化剂以光谱鉴定的磷酸烯醇化物中间体的形式提供了共轭加成步骤的关键证据，磷酸烯醇化物中间体是参与竞争的非循环烯烃低聚的长寿命物质。腈不稳定性允许具有L = NCPh的络合物获得对于具有L = PPh 2 H的络合物观察到的相同的两个缀合物加成循环。然而，“自由”苯甲腈既抑制催化作用，又参与形成含有1-azaallyl片段的失活产物，该片段已被分离和晶体学表征。总的来说，这些结果表明了一个令人惊讶的复杂性，可以从一个简单的机械前提金属介导的氢膦化，并证明了各种辅助配体对催化的影响。他们强调了设计特征，使我们能够开发出半夹心Ru Cp* 催化剂[Ru（eta（5）-Cp*）（PPh 2）（PPh 2 H）（2）]，其氢膦化活性提高了30倍。
A thorough experimental examination of a series of half-sandwich Ru indenyl complexes [Ru(eta(5)-indenyl)(PPh2)(L)(PPh3) (L = PPh2H, CO, NCPh)] in the catalytic hydrophosphination of ter[ butyl acrylate by diphenylphosphine provides valuable lessons for the design of active and robust catalysts for this important P-C bond-forming reaction. Evidence for each fundamental step in the relevant catalytic cycles was gathered from reaction monitoring (H-1 and P-31 NMR), kinetic analyses, stoichiometric control reactions, and the isolation and spectroscopic identification of key intermediates, catalyst deactivation products, and off-cycle byproducts. For L = PPh2H, two distinct catalytic cycles each rely on the outer-sphere, conjugate addition of the Ru-PPh2 ligand at the electron-deficient alkene. The cycles differ in their P-H activation steps (intra- vs intermolecular) but are connected by a common resting state [Ru(eta(5)-indenyl)(PPh2)P-2, where P is the hydrophosphination product Ph2PCH2CH2CO2But]. The complex with L = CO is inert to substitution by PPh2H, which precludes one of the two conjugate addition catalytic cycles. This catalyst provides critical evidence for the conjugate addition step in the form of a spectroscopically identified phospha-enolate intermediate, a long-lived species that participates in competing, off-cycle alkene oligomerization. Nitrile lability allows the complex with L = NCPh to access the same two conjugate addition cycles observed for the complex with L = PPh2H. However, the "free" benzonitrile both inhibits catalysis and participates in the formation of a deactivation product containing the 1-azaallyl fragment, which has been isolated and crystallographically characterized. Collectively, these results indicate a surprising complexity that can arise from a simple mechanistic premise for metal-mediated hydrophosphination, and demonstrate a variety of impacts of ancillary ligands on catalysis. They highlight design features that allowed us to develop a half-sandwich Ru Cp* catalyst [Ru(eta(5)-Cp*)(PPh2)(PPh2H)(2)] that exhibits a 30-fold increase in hydrophosphination activity.