Kostyukovich Alexander Yu, Burykina Julia V, Eremin Dmitry B, Ananikov Valentine P
Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Leninsky Prospect 47, Moscow 119991, Russia.
The Bridge@USC, University of Southern California, 1002 Childs Way, Los Angeles, California 90089-3502, United States.
Inorg Chem. 2021 May 17;60(10):7128-7142. doi: 10.1021/acs.inorgchem.1c00173. Epub 2021 May 5.
The Mizoroki-Heck reaction is one of the most known and best studied catalytic transformations and has provided an outstanding driving force for the development of catalysis and synthetic applications. Three out of four classical Mizoroki-Heck catalytic cycle intermediates contain Pd-C bonds and are well known and studied in detail. However, a simple palladium hydride (which is formed after the product-releasing β-H-elimination step) is a kind of elusive intermediate in the Mizoroki-Heck reaction. In the present study, we performed a combined theoretical and mass spectrometry (MS) study of palladium hydride complexes [PdXH] (X = Cl, Br, and I), which are reactive intermediates in the Mizoroki-Heck reaction. Static and molecular dynamic calculations revealed that these species have a T-shaped structure with a trans-arrangement of halogen atoms. Other isomers of [PdXH] are unstable and easily rearrange into the T-shaped form or decompose. These palladium hydride intermediates were detected by MS in precatalyst activation using NaBH, EtN, and a solvent molecule as reducing agents. Online MS monitoring allowed the detection of [PdXH] species in the course of the Mizoroki-Heck reaction.
宫泽-赫克反应是最知名且研究最深入的催化转化反应之一，为催化作用和合成应用的发展提供了强大动力。经典宫泽-赫克催化循环的四种中间体中有三种含有钯-碳键，且已为人们所熟知并得到了详细研究。然而，一种简单的氢化钯（在产物释放的β-氢消除步骤之后形成）在宫泽-赫克反应中是一种难以捉摸的中间体。在本研究中，我们对氢化钯配合物[PdXH]（X = Cl、Br和I）进行了理论与质谱（MS）相结合的研究，这些配合物是宫泽-赫克反应中的活性中间体。静态和分子动力学计算表明，这些物种具有T形结构，卤素原子呈反式排列。[PdXH]的其他异构体不稳定，容易重排成T形或分解。在使用硼氢化钠、乙腈和溶剂分子作为还原剂的预催化剂活化过程中，通过质谱检测到了这些氢化钯中间体。在线质谱监测能够在宫泽-赫克反应过程中检测到[PdXH]物种。
