A group of scientists from Russia and Germany demonstrated a new catalytic system based on the simplest nickel salts and a photoactive additive. Under the influence of visible light and added reagents in such a catalyst, the structure and degree of oxidation of the metal spontaneously change, which ensures maximum efficiency of the chemical process. With the help of a cheap and affordable catalyst, the authors were able to obtain and describe more than 250 products, including precursors of drugs, pesticides and other useful compounds. The results of the work supported by grants from the Russian Science Foundation (RNF) are published in the journal Nature.
Transition metals, capable of changing their degree of oxidation, often become the basis of catalysts for organic synthesis, including medical substances and various chemicals. Despite the many works devoted to catalysis by complexes of copper, palladium, nickel and other metals, the selection of optimal conditions for the most efficient reaction remains a non-trivial task. So, it is necessary to change the external conditions — temperature, pressure, solvent; to select the ligands surrounding the metal atom and helping it to interact with reagents with accuracy to small side groups; to take into account the structure of the catalyst and substrate (reagents) and much more. It is possible to calculate something on a computer, but a lot of work lies in experiments - sometimes quite expensive and time—consuming. As a result, it is possible to choose a more or less optimal reaction system, at best relevant for a class of compounds or type of reactions. When setting a new task, even if it is close enough to the one already solved, everything has to be repeated from the beginning.
Researchers from the laboratory of metal-complex and Nanoscale catalysts of the Institute of Organic Chemistry named after N.D. Zelinsky (Moscow) and the University of Regensburg (Germany) have proposed a universal catalytic system in which there are no expensive or rare components. It is based on the simplest nickel salts and a cheap photoactive additive. It was possible to adjust the catalytic properties under the influence of visible light (that is, expensive lasers or powerful ultraviolet lamps are not needed) with the help of commonly used organic bases – special organic "adapters". The last component of the system is the substrate, that is, the reagent from which the product will be synthesized. All three components are in the same state, liquid, — such a catalysis is called homogeneous.
Thus, under the influence of light, a photochemical reaction and the process of formation of a wide variety of complexes from a nickel core and "adapters"-bases begin. However, how the catalytically active particle will be arranged among the many available options depends on the substrate: its geometry, chemical properties, and other things. In fact, the system itself "chooses" which type of catalytic particles will be most effective in each case.
The universality of the proposed approach was demonstrated by scientists using the example of cross-combination reactions accompanied by the formation of nine different types of bonds. The authors managed to obtain more than 250 different products, the structure of which can be predicted in the case of each of the substrates.
"The distinctive features of our photocatalytic system are its accessibility and the softness of the process conditions. For comparison: in cross-combination reactions, expensive complexes of palladium or other metals are usually used — cheaper, but working at high temperatures. On the other hand, the minimum set of initial parameters of an adaptive catalytic system makes it predictable and potentially attractive for building a more advanced model using artificial intelligence," says Valentin Ananikov, head of the project supported by a grant from the Russian Academy of Sciences, Academician of the Russian Academy of Sciences, Head of the Department of IOH RAS, Professor of the Faculty of Chemistry of Moscow State University.
PHOTO: Illustration of dynamic adaptive catalysis. Source: Valentin Ananikov
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