[(η1-Flu)Ti(μ-OiPr)(OiPr)2]2 (1) and (η1-Flu)(η5-Flu)Ti(OiPr)2 (2) were easily prepared from FluLi and ClTi(iPrO)3 and demonstrated a remarkable thermal stability in comparison with known (fluorenyl)titanium complexes. Both complexes were characterized by X-ray analysis and temperature-dependent NMR spectroscopy. In combination with methylaluminoxane, both compounds are highly efficient initiators for styrene polymerization, producing highly syndiotactic polymers.

The aluminohydride of zirconocene Me3SiCp2ZrH3AlH2 was supported on pre‐treated SiO2, and its catalytic activity for ethylene polymerization and ethylene‐1‐hexene copolymerization was evaluated in order to compare with the corresponding activity of the complex in solution. As expected for systems based on metallocenes, the aluminohydride of zirconocene complex showed higher activity in solution than in suspension, however its thermal and kinetic stability was significantly increased. The effect of the co‐catalyst concentration (MAO) on the activity and the molecular weight of the polymers are also reported in this study, finding that in heterogeneous phase low concentrations of MAO were used to activate the pre‐catalyst. The MW of the polymers and copolymers synthesized with the supported Me3SiCp2ZrH3AlH2/SiO2 could be controlled by adding molecular hydrogen (H2) as chain transfer agent in the polymerization and copolymerization reactions.

Summary: In this work we studied the copolymerization of ethylene and different alpha-olefins (propylene, 1-butene, 1-hexene, and 1-octene) using aluminohydride zirconocene systems supported on modified silica. The copolymerization reactions were carried out in hexanes, at different Al/Zr ratios, using two different comonomer concentrations. The effect of comonomer type on catalyst activity and polymer molecular weight and chemical composition distributions (MWD and CCD) was compared. Average comonomer incorporation was determined by 13 C NMR and the CCD by crystallization elution fractionation (CEF). Most of the copolymerizations showed very high catalytic activity (up to 4000 Kg PE/mol Zr), and the molecular weight was higher for the copolymers containing 1-octene, demonstrating that aluminohydride zirconocene systems can copolymerize ethylene and alpha-olefins effectively.

Summary:Copolymerizations of ethylene and a-olefins (1-hexene and 1-octene) using a supported catalyst derived from the activation of a zirconocene aluminohydride complex with PMAO and MMAO are reported. The supported (nBu-Cp 2 ZrH 3 AlH 2 )/SiO 2 / MAO system was evaluated by high-throughput techniques, in order to find approaches to the optimal copolymerization conditions. The polymerization reactions were carried out in a parallel polymerization reactors system (PPR) by Symyx Technologies, Inc. The screening of the activity of the supported system and the molecular weight (MW) of the polymers and copolymers obtained in the PPR, allowed us to optimize copolymerization conditions, like hydrogen (H 2 ) addition to control MW and molecular weight distribution (MWD), polymerization temperature, cocatalyst ratio, and solvent type. The copolymerization reactions were scaled-up in order to validate the performance of the catalytic system at higher polymerization scales, according to the results obtained in the combinatorial phase. The scaled-up copolymerizations of ethylene with 1-hexene and 1-octene, showed high activities and MW, and low comonomer incorporation (from 0.3 to 1.3 mol-%, determined by 13 C NMR). However, the crystallinity (X c ), thermal properties (T c and T m ) and densities of the polyethylenes obtained with the supported (nBu-Cp 2 ZrH 3 AlH 2 )/SiO 2 /MAO system, were significantly modified, approaching those of metallocene linear lowdensity polyethylenes (mLLDPE).