Patent ID: 8071700

Claim:
A catalytic system for the copolymerization of at least two olefins, comprising a metallocene complex of a lanthanide and a cocatalyst chosen from the group consisting of an alkylmagnesium, an alkyllithium, and a mixture of an alkyllithium and of an alkylaluminium, wherein the complex is a borohydride metallocene complex of a lanthanide corresponding to the following formula B: where Ln is a lanthanide having an atomic number of between 57 and 71 inclusive, where, in the formula B, a ligand composed of two groups Cp 1 and Cp 2 which are chosen from identical or different and substituted or unsubstituted cyclopentadienyl or fluorenyl groups, with the proviso that Cp 1 and Cp 2 are not fluorenyl groups at the same time, and which are connected to one another via a bridge P corresponding to the formula MR 1 R 2 , where M is silicon and where R 1 and R 2 , which are identical or different, represent an alkyl group comprising from 1 to 20 carbon atoms, is connected to Ln, where L represents an alkali metal chosen from the group consisting of lithium, sodium and potassium, where N represents a molecule of a complexing solvent, where x is an integral or non-integral number which is greater than 0, where y is an integer which is equal to or greater than 0 and where p is an integer which is equal to 1 or 2.