ИСТИНА

Проект направлен на создание новых катализаторов на основе полусэндвичевых комплексов переходных металлов с двумя типами нидо-карборановых лигандов: с симметричными нейтральными нидо-карборановыми производными с заместителем по атому бора и с углеродзамещенными анионными соединениями нидо-карборана, в которых заместитель связан с карборановым ядром через атом серы.

Catalysis is one of the most important and actual directions of chemistry development in the last few decades. Catalytic reactions make it possible to obtain the necessary products with high yields and the desired purity, as well as to carry out the regio- and sterioselective reactions. In this regard, the search for new catalysts for a different processes of laboratory and industrial organic synthesis remains one of the most important and actual academic tasks. Modern catalysts must comply with a number of requirements such as high rate of catalyzed reactions, the high yield of required products, low cost, environmental safety, etc. The using of metal complexes in catalytic systems has begun in the early 1990s. Since then, a large number of ligands with different steric, electronic and chemical properties have been obtained. Most of them were based on the derivatives with one or more carbon atoms. At the same time, it was found out that the compounds with boron atoms can also be used as ligands. In this regard, the ligands based on carboranes with 1-2 carbon atoms and 9-10 boron atoms (depending on the cluster) in their structure are of great interest. Carboranes represent the compounds with a number of unique properties that are often "unavailable" for organic ligands. In addition to the high thermal and chemical stability, due to the boron atoms included in the carborane structure and the presence of two-electronic three-centered bonds, there is a delocalization of the electron density, which causes a number of specific reactions that are possible only for the carborane system. For instance, in 1,2-dicarba-closo-dodecaborane the hydrogen atoms at two carbon atoms have the acidic character and can be substituted by various organic substituents. The obtained derivatives can then be converted to anionic nido-form by the deboronotion reaction of one boron vertex. It produces the C-substituted derivatives of 7,8-dicarba-nido-undecaborate anion that are the three-dimensional analogues of cyclopentadienyl and can give the metal complexes with a wide range of transition metals. At the same time, the 7,8-dicarba-nido-undecaborate anion itself is characterized by the reactions only at boron atoms on the open pentagonal face of the boron cluster. Previously, we found out that nido-carborane reacts with nitriles by the electrophilic-induced nucleophilic substitution mechanism. This leads to the formation of symmetrical neutral (charge-compensated) nitrilium derivatives of nido-carborane with the boron-quaternary nitrogen bond (-В-N+≡CR). This bond is very stable due to the negative charge on the boron cluster that is almost impossible to achieve in organic chemistry. Also we have shown that the nitrilium derivatives of nido-carborane enter the reactions of nucleophilic addition at the triple bond with the formation of symmetrical charge-compensated compounds of nido-carborane with a stable boron-quaternary nitrogen bond -В-N+(Н)=C(R)XR’ (X=O, S, N). In this project it is planned to obtain by this method the new neutral ligands based on nido-carborane, including the ligands with the extra nucleophilic atoms in the side substituent, such as nitrogen and oxygen, which can give the additional chelated effect in the formation of complexes with transition metals. Also we plan the synthesis of ligands through the alkylation of mercapto-derivative of closo-carborane followed by the conversion to nido-form that will allow obtaining the carbon-substituted ligands based on nido-carborane with the additional nucleophilic centers in the alkyl substituents that will be associated with the carborane cluster through a sulfur atom. The complexation reactions of all obtained ligands with a number of transition metals, such as cobalt, nickel, palladium, rhodium, ruthenium, titanium, etc., will be investigated. This will allow obtaining the new half-sandwich complexes of transition metals based on nido-carborane.