Catalyst 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 an organomagnesium reagent as co-catalyst of formula R B —(Mg—R A ) m —Mg—R B is provided. According to the formula, R B comprises a benzene nucleus substituted with the magnesium atom. One of the carbon atoms of the benzene nucleus ortho to the magnesium is substituted with a methyl, an ethyl or an isopropyl or forms a ring with the carbon atom which is its closest neighbour and which is meta to the magnesium. The other carbon atom of the benzene nucleus ortho to the magnesium is substituted with a methyl, an ethyl or an isopropyl. R A is a divalent aliphatic hydrocarbon-based chain, optionally interrupted with one or more oxygen or sulfur atoms or with one or more arylene groups. The m is a number greater than or equal to 1, preferably 1. 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 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, the organomagnesium reagent being a compound of formula (II)
R B —(Mg—R A ) m —Mg—R B (II)
R B being different from R A ,
R B comprising a benzene nucleus substituted with the magnesium atom, one of the carbon atoms of the benzene nucleus ortho to the magnesium being substituted with a methyl, an ethyl, an isopropyl or forming a ring with the carbon atom which is its closest neighbour and which is meta to the magnesium, the other carbon atom of the benzene nucleus ortho to the magnesium being substituted with a methyl, an ethyl or an isopropyl,
R A being a divalent aliphatic hydrocarbon-based chain, interrupted or not with one or more oxygen or sulfur atoms or with one or more arylene groups,
m being a number greater than or equal to 1.
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, if one of the two carbon atoms of the benzene nucleus of R B ortho to the magnesium is substituted with an isopropyl, the second carbon atom of the benzene nucleus of R B ortho to the magnesium is not substituted with an isopropyl.
9 . The catalytic system according to claim 1 , in which the carbon atoms of the benzene nucleus of R B ortho to the magnesium are substituted with a methyl or an ethyl.
10 . The catalytic system according to claim 1 , in which the organomagnesium reagent is of formula (IV-m)
R 1 and R 5 , which are identical or different, represent a methyl or an ethyl,
R 2 , R 3 and R 4 , which are identical or different, being a hydrogen atom or an alkyl,
R A being a divalent aliphatic hydrocarbon-based chain, interrupted or not with one or more oxygen or sulfur atoms or with one or more arylene groups,
m being a number greater than or equal to 1.
11 . The catalytic system according to claim 1 , in which R A is a branched or linear alkanediyl, cycloalkanediyl or xylenediyl radical.
12 . 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.
13 . A 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.
14 . A 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.
15 . A telechelic polymer of formula (V)
R B —Mg-poly-R A -poly-Mg—R B (V)
R A and R B being defined according to claim 1 ,
the name “poly” denoting a polymer chain of a 1,3-diene, of ethylene or of an α-monoolefin, or mixtures thereof.
16 . The catalytic system according to claim 1 , in which m is equal to 1.
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 5 , in which the rare-earth metal is neodymium.
20 . The catalytic system according to claim 6 , in which R 1 and R 2 each represent a methyl.