Xavier Olonde

A useful method for the synthesis of neodymocene homogeneous catalysts for ethylene polymerization

Abstract The direct alkylation of the neodymium complex Cp 2 *NdCl 2 Li(OEt 2 ) 2 ( 1 by butylethyl-magnesium gives rise to the production of efficient homogeneous catalytic species for ethylene polymerization. The polymers are highly linear, vinyl terminated, and present narrow molecular weight distributions ( M w / M n =2). The observed molecular weights are strongly dependent on the reaction temperature and ethylene pressure. This catalytic system is shown to be more active than classical Ti/Mg heterogeneous catalysts, and even more stable in a batch reactor at 160°C and 6 bar. Experiments conducted in a pilot plant (continuous flow autoclave reactor) have been performed at 200°C and 1200 bar. These gave rise to the conclusion that the catalyst in these conditions is still able to perform the homopolymerization of ethylene with a very high productivity, even in the presence of but-1-ene in the reaction mixture.

Development of Catalytic Systems Based on Lanthanoïd Complexes for Olefin Polymerization

The use of the alkylation technique of Cp*2LnCl2Li(OEt2)2 complexes for the synthesis of lanthanocene active species which are useful for olefin polymerization, is described. Both butyl lithium and butyl-ethyl magnesium (BEM) are shown to be suitable as alkylating reagents for ethylenepolymerization. Using BEM in excess allows the synthesis of higher dialkylmagnesium compounds via a chain transfer reaction between magnesium and lanthanoide atoms following the insertion reaction of the monomer into the Ln-alkyl bond. For methyl methacrylate polymerization, using a butyl lithium/Ln ratio of 2 gives the best results, leading to the production of syndiotactic (>80%) PMMA with low molecular weight distributions (<2), in high yields and molecular weights (up to 2*105).