Catalytic system, its method for preparation, and method for preparation of a copolymer of ethylene and a conjugated diene

Method for preparing a catalytic system comprising an organometallic complex compound, which is represented by one of formula A or B:

• in which Ln represents a metal of a lanthanide, the atomic number of which is between 57 and 71;
• X represents a halogen selected from the group consisting of chlorine, fluorine, bromine wherein in formula A, two ligand molecules CPA, each a substituted cyclopentadienyl group, are bonded to metal Ln;
• and in formula B, a ligand comprising two CpB molecules, bonded to one another by a a bridge P, is bonded to metal Ln, wherein CpB is a substituted or unsubstituted cyclopentadienyl or fluorenyl group and P corresponds to formula MR2, in which M is an element in column IVA of Mendeleev's periodic classification, and R is an alkyl group having 1 to 20 carbon atoms;
• and
• a co-catalyst selected from the group consisting of a magnesium alkyl, a lithium alkyl, an aluminium alkyl, a Grignard's reagent, and mixtures thereof,
• the method comprising preparing the organometallic complex compound by
• a) reacting a hydrogenated molecule of a ligand represented by formula HCp, with a lithium alkyl to obtain a lithium salt;
• b) reacting the lithium salt in a complexing solvent with an anhydrous anthanide trihalide, represented by formula LnX3, in which X represents a halogen selected from the group consisting of chlorine, fluorine, bromine and iodine to produce a reaction product;
• c) evaporating the complexing solvent and extracting the reaction product of b) in a non-complexing solvent to produce an extracted reaction product, and, optionally;
• d) crystallizing the extracted reaction product of c) to obtain the organometallic complex compound, which is completely free from the said complexing solvent;
• and
• adding the co-catalyst selected from the group consisting a magnesium alkyl, a lithium alkyl, an aluminium alkyl, a Grignard's reagent, and mixtures thereof to the organometallic complex compound.