| abstract |
The present invention relates to a borohydride metallocene complex of a lanthanide, to its process of preparation, to a catalytic system incorporating it, to a process for the copolymerization of olefins employing this catalytic system and to an ethylene/butadiene copolymer obtained by this process, the butadiene units of which comprise 1,2-cyclohexane or 1,2- and 1,4-cyclohexane links. n A complex according to the invention corresponds to one or other of the following formulae A and B: n n n n n n n n n n n n where, in the formula A, two ligand molecules Cp 1 and Cp 2 , each composed of a fluorenyl group, are connected to the lanthanide Ln, such as Nd, and where, in the formula B, a ligand molecule, composed of two fluorenyl groups Cp 1 and Cp 2 which are connected to one another via a bridge P of formula MR 1 R 2 , where M is an element from group IVa, such as Si, 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 the lanthanide Ln, where L represents an alkali metal, such as Li, where N represents a molecule of a complexing solvent, such as THF, where x is an integral or non-integral number greater than 0 and where p is an integer equal to or greater than 1. |