| abstract |
The invention relates to a borohydride metallocene complex of a lanthanide, the preparation method thereof, a catalytic system including said borohydride metallocene complex, a method for the copolymerisation of olefins using said catalytic system and an ethylene/butadiene copolymer obtained using said method, having butadiene units with 1,2-cyclohexane or 1,2 and 1,4-cyclohexane chains. The inventive complex has one of the following formulas (A and B), wherein, in formula A, two molecules of ligands Cp<SUB>1</SUB> and Cp<SUB>2</SUB> are linked to the lanthanide Ln, such as Nd, said ligand molecules each consisting of a fluorenyl group, and, in formula B, a ligand molecule is linked to the lanthanide Ln, said ligand molecule consisting of two fluorenyl groups Cp<SUB>1</SUB> and Cp<SUB>2</SUB>which are interlinked by means of a bridge P having formula MR<SUB>1</SUB>R<SUB>2</SUB>, in which M is an element from column IVA, such as Si, and R<SUB>1</SUB> and R<SUB>2</SUB>, which may be identical or different, represent an alkyl group having between 1 and 20 carbon atoms. According to the invention, L represents an alkali metal, such as Li, N represents a molecule of a complexing solvent, such as THF, x is an integer or a non-integer which is greater than 0 and p is an integer which is equal to or greater than 1. |