Erkki Aitola

Pyridinylimine-based nickel(II) and palladium(II) complexes: preparation, structural characterization and use as alkene polymerization catalysts

Abstract Preparation of four dimeric nickel(II) complexes and three monomeric palladium(II) complexes bearing didentate pyridinylimine ligands is described. The solid-state structures of these compounds have been determined by single-crystal X-ray diffraction. After activation with methylaluminoxane (MAO) the nickel compounds were used as catalysts in ethylene polymerization producing nearly linear or primarily methyl-branched polymers. The effect of ligand environment was most evident on degree of branching, while catalytic activity and molecular weight of the polymer were more dependent on the general catalyst composition as well as reaction conditions. Activation of the dichloropalladium(II) complexes with MAO yields highly active catalysts for the polymerization of bicyclo[2.2.1]hept-2-ene (norbornene) whereas only low conversions (

Polymerization of ethylene with new diimine complexes of late transition metals

Three pyridylimine based complexes of NiII and CoII were reacted with methylaluminoxane (MAO) and tested as catalysts in ethylene polymerization. The two nickel catalysts produced mainly methyl branched polymers with good to moderate activity, while the cobalt compound showed only marginal activity. Reaction conditions strongly affect the polymer properties, such as molecular weight, melting temperature, degree of branching, and chain end unsaturation type.

para-Fluoro benzyl substituted bis(indenyl) metallocenes as catalyst precursors in ethene polymerization

Abstract The unbridged complexes bis(η5-(1-para-fluoro benzyl)indenyl) MCl2 (2: M=Hf; 3: M=Zr) as well as their ethylene bridged analogues bis[(η5-3-(1-para-fluoro benzyl)indenyl)ethane] MCl2 (4: M=Hf; 5: M=Zr) have been synthesized and the obtained rac- and meso-isomers were separated from the 1:1 isomer mixtures. Complexation was performed by converting the ligand precursors (1-para-fluoro benzyl)indene (1a) and bis(3-(1-para-fluoro benzyl)indenyl)ethane (1b) into their lithio salts and further treatment with MCl4. To study the influence of the para-fluoro benzyl substituent in ethene polymerization, the catalyst precursors 2–5 were activated with methylalumoxane (MAO) and their polymerization behavior was compared to corresponding unsubstituted metallocenes. The crystal structure of meso-like 3 was determined by means of X-ray structure analysis, showing a central/lateral:gauche-type orientation of its para-fluoro benzyl substituents in the solid state.

Influence of the polymerization conditions on the impact properties of metallocene-catalyzed copolymers of ethylene and aryl-substituted norbornenes with low exo/endo ratios

When testing copolymers of ethylene and aryl-substituted norbornenes with the Charpy impact method it was found that under certain polymerization conditions their impact properties increased with increasing polymerization time. It was also found that this improvement on impact properties was due to increasing exo/endo ratios of the incorporated aryl-substituted norbornene comonomers. This effect is important because impact-resistant copolymers can be made using aryl-substituted norbornene comonomers with low exo/endo ratios, which are more easily synthesized and purified.