Catalytic system based on a metallocene and a diorganomagnesium
A catalytic system based on at least one metallocene and on a diorganomagnesium compound of formula R B —Mg—R A is provided, R B being different from R A and comprising a benzene nucleus substituted with a 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 an alkyl, a cycloalkyl or a benzyl, which may be substituted or unsubstituted. The catalytic system makes it possible to increase the functional group content in the synthesis of a functional polymer.
1 . A catalytic system based at least:
on a metallocene of formula (Ia) or (Ib),
on a diorganomagnesium compound as co-catalyst,
{P(Cp 1 )(Cp 2 )Y} (Ia)
Cp 3 Cp 4 Y (Ib)
Y denoting a group including a metal atom which is a rare-earth metal,
Cp 1 , Cp 2 , Cp 3 and Cp 4 , which may be 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 diorganomagnesium compound being an asymmetric compound of formula (II)
R B —Mg—R A (II)
R B being different from R A ,
R B comprising a benzene nucleus substituted with a 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 neighbor 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, and
R A being an alkyl, a cycloalkyl or a benzyl, which may be substituted or unsubstituted.
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 2 , in which Cp 1 and Cp 2 each represent an unsubstituted fluorenyl group of formula C 13 H 8 .
4 . The catalytic system according to claim 1 , in which the symbol Y represents the group Met-G, with Met denoting a metal atom which is a rare-earth metal 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.
5 . The catalytic system according to claim 4 , 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.
6 . The catalytic system according to claim 5 , in which N represents diethyl ether or tetrahydrofuran.
7 . 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.
8 . The catalytic system according to claim 7 , in which the rare-earth metal is neodymium.
9 . 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 may be identical or different, each representing an alkyl group comprising from 1 to 20 carbon atoms.
10 . The catalytic system according to claim 9 , in which R 1 and R 2 each represent methyl.
11 . 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.
12 . 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.
13 . 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.
14 . The catalytic system according to claim 1 , in which the diorganomagnesium compound is of formula (IV)
R 1 and R 5 , which may be identical or different, represent a methyl or an ethyl,
R 2 , R 3 and R 4 , which may be identical or different, being a hydrogen atom or an alkyl,
R A being an alkyl, a cycloalkyl or a benzyl, which may be substituted or unsubstituted.
15 . The catalytic system according to claim 1 , in which R A represents an alkyl containing from 2 to 10 carbon atoms.
16 . The catalytic system according to claim 1 , in which the ratio between the number of moles of Mg of the co-catalyst and the number of moles of rare-earth metal of the metallocene ranges from 1 to 100.
17 . A process for preparing a polymer, which comprises a step of polymerization of a monomer M chosen from the group of monomers consisting of conjugated dienes, ethylene, α-monoolefins and mixtures thereof in the presence of the catalytic system defined in claim 1 .
18 . The process according to claim 17 , in which the monomer M is a mixture of a 1,3-diene and of ethylene.
19 . The process according to claim 18 , said process comprising, after the polymerization step, the addition of a functionalizing agent to functionalize the polymer, the functionalizing agent being an alkoxysilane.
20 . The process according to claim 18 , wherein the 1,3-diene is 1,3-butadiene, isoprene, myrcene, β-farnesene or mixtures thereof.
21 . The catalytic system according to claim 1 , wherein the metallocene is of formula (Ia).
22 . The catalytic system according to claim 1 , in which the two carbon atoms of the benzene nucleus of R B ortho to the magnesium are not substituted with an isopropyl.