Catalytic system based on a rare-earth metallocene and a co-catalyst having a plurality of carbon-magnesium bonds
A catalytic system based on at least one rare-earth metallocene and as co-catalyst an organomagnesium reagent of formula X—Mg—R A —Mg—X is provided. In the formula, R A is a divalent aliphatic hydrocarbon-based chain, optionally interrupted with an oxygen atom, a sulfur atom or with an arylene group, and X is a halogen atom. The catalytic system allows the synthesis of dienic and/or ethylenic telechelic polymers.
1 . A catalytic system based at least:
on a metallocene of formula (Ia) or (Ib),
on an organomagnesium reagent of formula (II) as co-catalyst,
{P(Cp 1 )(Cp 2 )Y} (Ia)
Cp 3 Cp 4 Y (Ib)
Y denoting a group including a rare-earth metal atom,
Cp 1, Cp 2, Cp 3 and Cp 4, which are identical or different, being chosen from the group consisting of fluorenyl groups, cyclopentadienyl groups and indenyl groups, the groups being substituted or unsubstituted,
P being a group bridging the two groups Cp 1 and Cp 2 and comprising a silicon or carbon atom,
X—Mg—R A —Mg—X (II)
R A being a divalent aliphatic hydrocarbon-based chain, interrupted or not with an oxygen atom, a sulfur atom or with an arylene group,
X being a halogen atom.
2 . The catalytic system according to claim 1 , in which Cp 1 and Cp 2 are identical and are chosen from the group consisting of substituted fluorenyl groups and the unsubstituted fluorenyl group of formula C 13 H 8 .
3 . The catalytic system according to claim 1 , in which the symbol Y represents the group Met-G, with Met denoting the rare-earth metal atom and G denoting a group comprising the borohydride BH 4 unit or denoting a halogen atom chosen from the group consisting of chlorine, fluorine, bromine and iodine.
4 . The catalytic system according to claim 3 , in which G denotes a chlorine atom or the group of formula (III)
(BH 4 ) (1+y) -L y -N x (III)
in which
L represents an alkali metal chosen from the group consisting of lithium, sodium and potassium,
N represents a molecule of an ether,
x, which may or may not be an integer, is greater than or equal to 0,
y, which is an integer, is greater than or equal to 0.
5 . The catalytic system according to claim 1 , in which the rare-earth metal is a lanthanide, the atomic number of which ranges from 57 to 71.
6 . The catalytic system according to claim 1 , in which the bridge P corresponds to the formula ZR 1 R 2 , Z representing a silicon or carbon atom and R 1 and R 2 , which are identical or different, each representing an alkyl group comprising from 1 to 20 carbon atoms.
7 . The catalytic system according to claim 1 , in which the metallocene is of formula (III-1), (III-2), (III-3), (III-4) or (III-5):
[Me 2 Si(Flu) 2 Nd(μ-BH 4 ) 2 Li(THF)] (III-1)
[{Me 2 SiFlu 2 Nd(μ-BH 4 ) 2 Li(THF)} 2 ] (III-2)
[Me 2 SiFlu 2 Nd(μ-BH 4 )(THF)] (III-3)
[{Me 2 SiFlu 2 Nd(μ-BH 4 )(THF)} 2 ] (III-4)
[Me 2 SiFlu 2 Nd(μ-BH 4 )] (III-5)
Flu representing the C 13 H 8 group.
8 . The catalytic system according to claim 1 , in which R A is a branched or linear alkanediyl, cycloalkanediyl or xylenediyl radical.
9 . The catalytic system according to claim 1 , in which R A contains from 3 to 10 carbon atoms.
10 . A process for preparing a first telechelic polymer, which comprises a step of polymerizing a monomer M in the presence of a catalytic system defined in claim 1 , the monomer M being chosen from the group of monomers consisting of 1,3-dienes, ethylene, α-monoolefins and mixtures thereof.
11 . The process for preparing a second telechelic polymer, which comprises a step of polymerizing a monomer M in the presence of a catalytic system defined in claim 1 , this polymerization step being followed by a step of functionalization with a modifying agent, the monomer M being chosen from the group of monomers consisting of 1,3-dienes, ethylene, α-monoolefins and mixtures thereof.
12 . The process for preparing a polymer, which comprises a step of polymerizing a monomer M in the presence of a catalytic system defined in claim 1 and a termination reaction with a protic compound, the monomer M being chosen from the group of monomers consisting of 1,3-dienes, ethylene, α-monoolefins and mixtures thereof.
13 . The preparation process according to claim 10 , in which the monomer M is ethylene or a mixture of a 1,3-diene and ethylene or else a mixture of a 1,3-diene, ethylene and an α-monoolefin, the 1,3-diene advantageously being 1,3-butadiene, isoprene or mixtures thereof.
14 . A telechelic polymer of formula (IV)
X—Mg-poly-R A -poly-Mg—X (IV)
in which R A and X are defined according to claim 1 , the name “poly” denotes a polymer chain of a 1,3-diene, of ethylene or of an α-monoolefin, or mixtures thereof.
15 . The telechelic polymer according to claim 14 , in which the polymer chain contains ethylene units, 1,3-butadiene units and cyclic units, 1,2-cyclohexane units of the following formula
16 . The catalytic system according to claim 1 , in which the metallocene is of formula (Ia).
17 . The catalytic system according to claim 2 , in which Cp 1 and Cp 2 each represent an unsubstituted fluorenyl group of formula C 13 H 8 .
18 . The catalytic system according to claim 4 , in which N represents a molecule of diethyl ether or tetrahydrofuran.
19 . The catalytic system according to claim 4 , in which the rare-earth metal is neodymium.
20 . The catalytic system according to claim 4 , in which R 1 and R 2 each represent a methyl.