Semi-hydrogenated, asymmetric metallocene catalysts for the propylene polymerization

The hydrogenation of rac-[1-(9-eta(5)-fluorenyl)-2-(5,6-cylopenta-2-methyl-1-eta(5)-indenyl)ethane] metallocene dichlorides (1a: Zr, 1b: Hf) with PtO2 x H2O/H-2 is rgorted. The diastereoselective formation of exclusively rac-[1-(2,3,4,5,6,7,8,9-octahydro-eta(5)-fluorenyl)-2-(2-methyl-1,4,4a(R-S),5,6,7,7a(S;R),8-octahydro-s-eta(5) -indacenyl) ethane] metallocene dichlorides (2a: Zr, 2b: Hf) was shown by H-1-NMR and by X-ray analysis of 2a. Both compounds were activated in situ with triisobutylaluminum/PhC3+[B(C6F5)(4)](-) and tested as catalysts in propylene polymerization reactions. Comparison to the non-hydrogenated complexes revealed a decrease in molecular weight of the polymer and in catalyst activity. Experiments at elevated temperatures resulted in a lower stereospecificity and reduced isotacticity values indicating a polymerization mechanism analogous to C-2-symmetric catalysts.