Quantum-chemical study on the role of alkyl chloride Zr,Al-complexes in stereoselective alkene oligomerization

Catalytic reactions of alkene di-, oligo- and polymerization provide a variety of highly demanded products, which structure depends on the type of catalytic system. Currently, a large number of catalytic systems have been proposed, including those based on zirconocenes and organoaluminum compounds. These systems are characterized by high activity and stereoselectivity, in this regard, the establishment of the reaction mechanisms remains an urgent problem.

To identify the factors that determine the stereoselectivity of the alkene oligomerization, catalyzed with Zr complexes, in this work, we performed a series of calculations to determine the thermodynamic and activation parameters of two successive stages of propene insertion into alkyl chloride bimetallic complexes L₂ZrМеCl-AlMe₃ (where L₂ = Cp₂, Ind₂, Me₂SiInd₂), which could be considered as catalytically active sites of the reaction. The calculations were carried out using the PBE/3ζ quantum-chemical method (Priroda 6). For comparison, similar reactions were studied with the participation of the [L₂ZrR⁺] cation. In addition, the modeling of the chain termination stage was carried out taking into account the possibility of β-H elimination and the formation of vinylidene oligomers. Comparative analysis of the energy parameters of the reactions made it possible to determine the relationship between the structure of active sites and the properties of the catalytic system

Acknowledgment: The studies were performed with the use of the equipment of Collective Usage Centre “Agidel” of Ufa Research of Russian Academy of Science at the Institute Petrochemistry and Catalysis (АААА-А19-119022290004-8). This work was supported by the Russian Science Foundation, grant 19-73-10122.