Polymerization of olefins catalyzed by a dichloride complex of titanium with a dioxolane dicarbonate ligand: The promoting effect of LiCl and MgCl2

The polymerizations of propylene and ethylene with two postmetallocene catalysts (4R,5R)-2,2-dimethyl-α,α,α′,α′-tetra(perfluorophenyl)-1,3-dioxolane-4,5-dimethanol]TiCl₂ · MgCl₂ and (4R,5R)-2,2-dimethyl-α,α,α′,α′-tetra-(perfluorophenyl-1,3-dioxolane-4,5-dimethanol]TiCl₂· (LiCl)₂ are studied. The first catalyst shows higher activity in both reactions and forms a lower molecular mass PP. This PP is characterized by a wide molecular-mass distribution that can be described by a set of five or six Flory components with different average molecular masses. Along with heterogeneity with respect to kinetic parameters, there is heterogeneity with respect to stereospecificity. Some of the sites form a high-molecular-mass highly isotactic polymer whose melting point is ≥150°C, whereas other sites produce syndiotactic and atactic PPs. For the most isospecific sites, a stereocontrol mechanism similar to the mechanism typical for metallocene catalysts with C ₁-symmetry is advanced. The catalysts under study are composed of the (4R,5R)-2,2-dimethyl-α,α,α′,α′-tetra(perfluorophenyl)-1,3-dioxolane-4,5-dimethanol]TiCl₂ complex supported on LiCl and MgCl₂, respectively.