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 it, a process for the copolymerization of olefins employing this catalytic system and 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. This complex corresponds to one or other of the following formulae A and B : 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.
1. A borohydride metallocene complex of a lanthanide that corresponds to formula B:
where Ln represents the lanthanide having an atomic number of between 57 and 71 inclusive,
where, in the formula B, a ligand composed of two identical or different fluorenyl groups Cp 1 and Cp 2 which are substituted or unsubstituted and which are connected to one another via a bridge P corresponding to the formula MR 1 R 2 , where M is an element from Group IVa of the Periodic Table of the Elements 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 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, and
where p is an integer equal to 1 or 2.
2. The complex according to claim 1 , wherein L represents lithium.
3. The complex according to claim 1 , wherein N represents tetrahydrofuran.
4. The complex according to claim 1 , wherein x is equal to 1 and in that p is equal to 2, the complex being a dimer.
5. The complex according to claim 1 , wherein Cp 1 and Cp 2 are each composed of the same unsubstituted fluorenyl group which corresponds to formula C 13 H 8 .
6. The complex according to claim 1 , wherein the element M included in the bridge P of formula MR 1 R 2 is silicon.
7. The complex according to claim 1 , wherein the complex corresponds to the formula:
where Flu represents an unsubstituted fluorenyl group of formula C 13 H 8 ,
where Me represents a methyl group,
where Si is silicon, Nd is neodymium, Li is lithium and THF is tetrahydrofuran.
8. The complex according to claim 1 wherein the complex corresponds to the formula:
where Flu represents a fluorenyl group substituted by an alkyl group comprising from 1 to 20 carbon atoms,
where Me represents a methyl group,
where Si is silicon, Nd is neodymium, Li is lithium and THF is tetrahydrofuran,
where x is an integer ranging from 0 to 3.
9. The complex according to claim 1 , wherein the complex is in the form of single crystals.
10. The complex according to claim 9 , wherein the single crystals is a monoclinic lattice system.
11. The complex according to claim 9 , wherein the single crystals is a triclinic lattice system.
12. A process for the preparation of a complex according to claim 1 , wherein the process comprises reacting a ligand salt of formula P-Cp 1 Cp 2 -L 2 with a solution of lanthanide Ln tris(borohydride) of formula Ln(BH 4 ) 3 N 3 .
13. The process for the preparation of a complex according to claim 12 , wherein the ligand salt is represented by formula Me 2 SiFlu 2 -Li 2 and the lanthanide tris(borohydride) is represented by formula Nd(BH 4 ) 3 (THF) 3 where THF is tetrahydrofuran.
14. The process for the preparation of a complex according to claim 12 , wherein the step of reacting comprises adding the ligand salt dissolved in a solvent, into the solution of lanthanide tris(borohydride) at ambient temperature.
15. A catalytic system for the copolymerization of at least one olefin and of at least one conjugated diene, comprising a metallocene complex of a lanthanide and a cocatalyst chosen from the group consisting of an alkylmagnesium, an alkyllithium, a Grignard reagent and a mixture of an alkyllithium and of an alkylaluminium, wherein said complex is a borohydride metallocene complex of a lanthanide as defined in claim 1 .
16. The catalytic system according to claim 15 , wherein said cocatalyst is butyloctylmagnesium.
17. A process for the copolymerization of olefins employing a catalytic system, wherein the process comprises copolymerizing ethylene and butadiene in the presence of a catalytic system according to claim 16 in order to obtain a copolymer in which the units resulting from butadiene comprise links in the form of 1,2-cyclohexane.
18. The copolymerization process according to claim 17 , wherein the molar level of units resulting from butadiene in the copolymer is greater than 10%.
19. The copolymerization process according to claim 17 , wherein the molar level of the 1,2-cyclohexane links in the units of the copolymer which results from butadiene is equal to or greater than 20%.
20. The copolymerization process according to claim 19 , wherein the molar level of the 1,2-cyclohexane links in the units of said copolymer which result from butadiene is equal to or greater than 25%.
21. A process for the copolymerization of olefins, comprising the copolymerization of ethylene and butadiene using the catalytic system according to claim 16 in order to obtain a copolymer in which the units resulting from butadiene comprise links in the form of 1,4-cyclohexane.
22. A process for the copolymerization of olefins wherein the process comprises copolymerization of ethylene and butadiene using the catalytic system according to claim 16 in order to obtain a copolymer in which the units resulting from butadiene comprise links in the form of 1,2-cyclohexane and 1,4-cyclohexane links.
23. The copolymerization process according to claim 17 , wherein the cocatalyst/complex molar ratio is chosen to be less than or equal to 10.
24. The copolymerization process according to claim 23 , wherein the cocatalyst/complex molar ratio is chosen to be less than or equal to 5.
25. The copolymerization process according to claim 24 , wherein the cocatalyst/complex molar ratio is chosen to be less than or equal to 2 and in that the polymerization is carried out under a pressure equal to or greater than 8 bar in order to obtain a number-average molecular weight Mn of the copolymer which is equal to or greater than 200 000 g/mol.
26. The copolymerization process according to claim 17 , comprising:
(i) reacting the complex with the cocatalyst to prepare the catalytic system, and
(ii) carrying out the compolymerizing step in a suspension or a solution comprising a hydrocarbon solvent at a temperature of between −20° C. and 120° C. in the presence of the catalytic system obtained in step (i).