For the first time, a detailed analysis of the structure of the catalytic system for the Mizoroki-Heck reaction using liquid-phase electron microscopy was carried out at the Zelinsky Institute

The transition from molecular to nano- and microscale in chemical reactions is an important step towards understanding the mechanisms of catalytic reactions and developing new generation catalysts. Electron microscopy is a convenient method for studying the structure of complex chemical systems at the nano- and microlevels, since it allows visualizing the morphology of objects of various nature, and is also a powerful tool for tracking the dynamics of the studied samples in real time. Electron microscopy has become one of the main methods for studying the structure of heterogeneous catalysts in the solid phase, but the use of electron microscopy to analyze liquid reaction media is still a non-trivial task.

Scientists from the Laboratory of Metal Complex and Nanoscale Catalysts of the Zelinsky Institute systematically studied the palladium-catalyzed Mizoroki-Heck reaction in various ionic liquids using a combination of scanning and transmission electron microscopy. It was shown that one of the most important factors in the stabilization of active palladium particles formed during the catalytic process is the ability of the reaction system to form a microdomain structure, which is determined both by the type of ionic liquid and by the nature of the aryl halide. For the first time, a correlation was recorded between the reactivity of an aryl halide and the microdomain structure: Ar-I (well-developed microdomains) > Ar-Br (microphase present) > Ar-Cl (minor microphase). The latter observation is particularly interesting, since it was previously assumed that molecular-level factors, among which the strength of the carbon-halogen bond, were the only aspects that determine the reactivity of aryl halides in catalytic transformations. The results obtained are of great importance for the development of new generation catalysts in structured liquid media.

Source:

Alexey S. Kashin, Darya O. Prima, Daria M. Arkhipova, Valentine P. Ananikov An unusual Microdomain Factor Controls Interaction of Organic Halides with the Palladium Phase and Influences Catalytic Activity in the Mizoroki-Heck Reaction // Small 2023, 2302999. DOI: 10.1002/smll.202302999.