Borohydride metallocene complex of a lanthanide, catalytic system including said complex, polymerization method using same and ethylene/butadiene copolymer obtained using said method
A borohydride metallocene complex of a lanthanide, its process of preparation, a catalytic system incorporating a borohydride metallocene complex and a process for the copolymerization of olefins employing this catalytic system. Such a complex corresponds to one or other of the following formulae A and B: where, in the formula A, two ligands Cp 1 and Cp 2 , each composed of a cyclopentadienyl group, are connected to the lanthanide Ln, such as Nd, and where, in the formula B, a ligand molecule, composed of two cyclopentadienyl 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, where p is an integer equal to or greater than 1 and where y is an integer which is equal to or greater than 0.
1. 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.
2. The catalytic system according to claim 1 , wherein the cocatalyst is butyloctylmagnesium.
3. A process for the copolymerization of at least two olefinic monomers, such as a monoolefin and/or a diolefin, by reaction of a catalytic system 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.
4. The copolymerization process according to claim 3 , wherein the lanthanide metallocene complex corresponds to the formula B′:
where Cp 1 and Cp 2 are chosen from identical or different and substituted or unsubstituted cyclopentadienyl groups, it being possible in addition for Cp 2 to represent a substituted or unsubstituted fluorenyl group, and x is an integral or non-integral number greater than 0.
5. The copolymerization process according to claim 4 , wherein Cp 1 and Cp 2 , each representing a cyclopentadienyl group, are substituted by a trimethylsilyl group.
6. The copolymerization process according to claim 3 , further comprising the copolymerization of ethylene and butadiene.
7. The copolymerization process according to claim 3 , wherein the molar level of units resulting from butadiene in the copolymer is greater than 24%.
8. The process according to claim 3 , wherein the molar level of units resulting from butadiene in the copolymer is equal to or greater than 45%.
9. The copolymerization process according to claim 3 , wherein the cocatalyst/complex molar ratio is equal to 10.
10. The copolymerization process according to claim 9 , wherein the cocatalyst/complex molar ratio is chosen to be equal to 5.
11. The copolymerization process according to claim 3 , comprising:
(i) a preliminary preparation of the catalytic system by reacting the complex with the cocatalyst, then
(ii) a reaction in suspension or in solution in a hydrocarbon solvent, and at a temperature of between −20° C. and 120° C. of the catalytic system obtained in (i) in the presence of the monomers to be polymerized.