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

The unbridged complexes bis(eta(5)-(1-para-fluoro benzyl)indenyl) MCl2 (2: M = Hf; 3: M = Zr) as well as their ethylene bridged analogues bis[(eta(5)-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.