Non-traditional Ziegler-Natta catalysis in alpha-olefin transformations: reaction mechanisms and product design

摘要

This paper describes our recent results in the field of zirconocene-catalyzed alpha-oltfin transformations, and focuses on questions regarding the reaction mechanism, rational design of zirconocene pre-catalysts, as well as prospective uses of alpha-olefin products. It has been determined that a wide range of alpha-olefin-based products, namely vinylidene dimers, oligomers and polymers, can be prepared via catalysis by zirconocene dichlorides, activated by a minimal (10-20 eq.) amount of MAO. We assumed that in the presence of minimal quantities of MAO, various types of zirconocene catalysts form different types of catalytic particles. In the case of bis-cyclopentadienyl complexes, the reactive center is formed under the influence of R2AlCl, which makes the chain termination via beta-hydride elimination significantly easier, with alpha-olefin dimers being formed as the primary product. Bis-indenyl complexes and their heteroanalogues, form stable cationic catalytic particles and effectively catalyze the polymerization. Mono-indenyl and mono-substituted bis-cyclopentadienyl-ansa complexes catalyze alpha-olefin oligomerization. Effective catalysts of dimerization, oligomerization and polymerization of alpha-olefins in the presence of minimal MAO quantities are proposed. Prospects of using alpha-olefin dimers, oligomers and polymers in the synthesis of branched hydrocarbon functional derivatives (dimers), high quality, low viscosity motor oils (oligomers), and thickeners and absorbents (polymers) are examined.