Catalytic systems made of a complex of rare earths for stereospecific polymerisation of conjugated dienes

Translation of description of equivalent WO 2010125072 A1

p0001A catalyst system based on a rare earth complex for the stereospecific polymerization of conjugated dienes.

p0002The present invention relates to a usable multi-component catalyst system for the stereospecific polymerization of 1,4-cis conjugated diene. More particularly, the present invention relates to a catalyst system comprising a rare earth complex and a process for preparing said catalyst system and the use of this catalyst system for the preparation of diene elastomers having a high content of cis linkage -1.4.

p0003Boisson et al. Macromol. Chem. Phys. 1999 200 1163-1166 and Monteil et al. Polymer Int.

p00042004 53 576-581 describe the use of multi-component catalytic systems for the polymerization of butadiene comprising:

p0005"Tris type neodymium salt (amide) of formula Nd [N (TMS)₂] S, or tris [N, N-bis (trimethylsilyl) amide], neodymium

p0006"Aluminum alkyl of the formula Al (i-Bu) 3," an alkylaluminium halide of formula AlEt₂Cl.

p0007These catalysts are prepared in situ and used for the polymerization of butadiene and for the copolymerization of butadiene and styrene. The molecular weight distribution of the synthesized polybutadiene is broad and multi-modal, reflecting poor control of the polymerization. In addition, such a molecular weight distribution may be detrimental for certain applications of the diene elastomer prepared, especially such as in tires for motor vehicles.

p0008Similarly, the patent application WO2003033545 describes multi-component catalyst systems for the polymerization of conjugated diene including some based tris type neodymium salt (amide), eg Nd formula [N (TMS)₂] 3, and a co-catalyst. In embodiments, the active species formed by reaction of the neodymium salt and the co-catalyst is cationic as the co-catalyst includes a systematically aluminoxane (modified methyl - or MMAO isobutylaluminoxane - IBAO). Optionally, an alkylaluminium halide or a borane (B (C_OF_S)_S) Is added to the catalytic system illustrated. Document US 3,297,667 also describes multi-component catalytic systems based

p0009(I) a rare earth compound,

p0010(Ii) a bidentate organic ligand

p0011(Iii) a halide

p0012(Iv) an aluminum alkyl.

p0013The catalytic system is prepared by reacting (i) (ii) which leads to a chelate isolated species of the rare earth metal. This species is then put in the presence of halide and alkylaluminum. As the compound (i), the catalyst system preparation process of this document basically puts out cerium chloride. Nevertheless, rare earth chlorides may be unsatisfactory reactivity with some organic ligands (ii) present in the reaction media, because of low solubility of chlorides in these environments.

p0014Furthermore, patent document US 7,300,903 B2 discloses a method of polymerizing olefins employing a catalyst system based on:

p0015"An isolated compound based on a transition metal of formula (I) below for the full definition of which reference is made to the text of the patent,

p0016<img id="imgf000004_0001" he="34" wi="36" file="imgf000004_0001.tif" img-format="tif" img-content="drawing" orientation="portrait" inline="no" />

p0017Formula (I) wherein M is a metal belonging to Groups 3 to 11 of the periodic classification of elements, at least one compound selected among: an organometallic compound, where an organoaluminum compound containing an oxygen atom, a o compound which can react with the base of a transition metal compound to form an ion pair. According to the patent, in formula I, the preferred metal M and described in the examples mainly belongs to Group 4 is titanium, zirconium or hafnium optionally. All examples of this patent relating to copolymerization tests of ethylene and butadiene were made from catalytic systems based on titanium or zirconium. Depending on the experimental conditions and the nature of the catalytic system, these tests have enabled to obtain copolymers in which the proportion of butadiene is very low and is at most 6.6% -mol (examples 150-157). Although no test is homopolymerization of butadiene describes the low capacity of the catalyst of this patent systems to insert this monomer implies that these systems are unsuitable for the stereospecific polymerization of 1,4-cis butadiene.

p0018For an application in tire for motor vehicles and more particularly in the tread, it is essential to have specific microstructure of diene elastomers, in particular polybutadiene having a cis-linkage content 1.4 high. Furthermore, a controlled molecular weight distribution or narrow, allows to better adjust the macrostructural features of the elastomer according to the desired properties in use in the tread. Also, it is constantly in search of catalyst systems and polymerization processes that allow obtaining reproducible manner diene elastomers having microstructural characteristics and specific macrostructure, and in particular diene elastomers having a content of high cis-1,4 linkage and having a controlled molecular weight distribution.

p0019The inventors have discovered in their research a new multi-component catalyst system having a satisfactory catalytic activity in the stereospecific polymerization of conjugated dienes, to obtain diene elastomers such as polybutadiene or polyisoprene having a linkage content cis-1,4 high, substantially higher than 90%. This new catalytic system is based on the combination of at least three components, namely, a rare earth complex, an alkylating agent and a compound based on an aromatic ring and having at least two hetero atoms. The present catalyst system in addition the advantage to control or reduce significantly, polydispersity index compared to a system comprising only the rare earth complex and the alkylating agent. The polydispersity index (Mw / Mn) - Mw being the weight average molecular weight and Mn mass - AT -

p0020average molar number - can be controlled or reduced, depending on the nature of the reagents and the operating conditions stake.

p0021Accordingly, a first object of the invention is a catalytic system based on at least:

p0022(I) a rare earth complex Ln (A)₃(B)_not of formula (II), in which Ln is a rare earth metal of the lanthanide or yttrium or of scandium, A is a ligand selected from the family of amides, alcoholates family, the family of alkyl, aryl or benzyl, the family of borohydrides, and the organophosphates family, B is a Lewis base and n is a numerical value ranging from 0 to 3, B and n depending on the nature of Ln and a involved in the rare earth complex matching, (ii) an alkylating agent,

p0023(Iii) a compound based on an aromatic ring and having at least two hetero atoms selected from the elements O, N, S, P, and the formula (III):

p0024<img id="imgf000006_0001" he="37" wi="49" file="imgf000006_0001.tif" img-format="tif" img-content="drawing" orientation="portrait" inline="no" />

p0025Formula III in which

p0026- The groups R are identical or different and each represents either: -a hydrogen atom,

p0027-an aliphatic alkyl, cycloaliphatic or aromatic, optionally containing one or more hetero atoms (N, O, P, S, Si) or one or more halogen atoms,

p0028-a halogen atom,

p0029-a group based on one or more hetero atom (N, O, P, S, Si); - X and y are integers between 0 and 6;

p0030- D is a group having a chemical function with one of the atoms has a non-bonding electron pairs;

p0031- L is an atom from column 1 of the periodic table; the substituents of the aromatic ring is either in the ortho, meta or para with respect to each other, (iv) optionally, a halogen donor, and (v) optionally, a preforming conjugated diene.

p0032Of course, the expression "based on" is used to define the components of the catalytic system is defined as the mixture of these constituents and / or the product of the reaction between these components.

p0033Another object of the invention is a process for preparing the multicomponent catalyst system defined above.

p0034The invention also relates to a method for preparing a diene elastomer, such as polybutadiene or polyisoprene having a high cis-1,4 linkage content and a controlled molar mass distribution, even with an index of polydispersity significantly reduced.

p0035Thus, one of the components of the catalytic multi-component system according to the invention is a rare earth complex of formula (II) Ln (A)₃(B)_notWherein Ln, A, B and n are as described above.

p0036Ln is a rare earth metal of the lanthanide family or yttrium or scandium. More specifically, Ln is chosen from the elements yttrium, neodymium, gadolinium or samarium. A preferably, Ln is yttrium or gadolinium. A Even more preferably Ln is yttrium. In the definition of B, the term Lewis base include ethers, amines, phosphates and thioethers. For example, as an amine include the family trialkylamines and aromatic amines such as pyridine or piperazine and derivatives thereof. As phosphate include for example tri-n-butyl phosphate. By way of thioether include family dialkyl sulfides such as dimethyl sulfide. As an ether, may be mentioned for example diethyl ether, 1, 2-diethoxyethane, 1,2-di-n-propoxyéthane, 1, 2-di-n-butoxyethane, tetrahydrofuran, dioxane , tetrahydropyran. Especially B is an ether, preferably tetrahydrofuran (THF). A is a ligand can be selected from the various types of above cited ligands. When A is selected from the family of amides, thereof includes dialkylamides, N, N-bis (dialkylsilyl) amides and N, N-bis (trialkylsilyl) amides, alkyl groups having 1 to 10 carbon carbons.

p0037When A is selected from dialkylamides, B is preferably THF and n is preferably 1. A is then preferably diisopropylamide and dimethylamide.

p0038When A is selected from N, N-bis (trialkylsilyl) amides, n is preferably 0. A is then preferably N, N-bis (trimethylsilyl) amide of the formula -N [Si (CHs) S]₂. When A is selected from N, N-bis (dialkylsilyl) amides, B is preferably THF and n is preferably equal to 2 or 3. A is then preferably N, N-bis (dimethylsilyl) amide formula -N [SiH (CH₃)₂] 2.

p0039When A is selected from the family of borohydrides, A is preferably tetrahydroborate, B is preferably THF and n is preferably 2 or 3. Where A is selected from the family of the alkoxides, the latter comprises alcoholates an alcohol or a polyol derived from an aliphatic or cyclic hydrocarbon, and especially an aliphatic hydrocarbon, linear or branched, having 1 to 10 carbon atoms in the linear chain, more particularly 4 to 8 carbon atoms. There may be mentioned for example the neo-pentanolate.

p0040When A is selected from the family of alkyl, this includes the family of (trialkylsilyl) alkyl. Among this family A is preferably the (trimethylsilyl) methyl group of formula -CH₂Si (CH₃)₃ or bis (trimethylsilyl) methyl group of formula -CH [Si (CH₃)₃]₂ ;

p0041When A is selected from the family of the aryl or benzyl, the aromatic ring is preferably substituted only by hydrogen atoms of 5 or 4 hydrogen atoms and a substituent bearing a tertiary amine or an ether function. More preferably, the group A is the formula CH dimethylaminobenzyl₂- C₆H₄[N (CH₃)₂].

p0042When A is selected from the family of organophosphate, the latter comprises the organophosphate of phosphoric acid diesters of the general formula (R'O) (R "O) PO (OH) wherein R 'and R", identical or different, represent an alkyl, aryl or alkylaryl. Among these phosphoric acid diesters, R 'and R ", identical or different, are preferably an n-butyl, isobutyl, pentyl, amyl, isopentyl, 2,2-dimethylhexyl, 1-ethylhexyl, 2-ethylhexyl, tolyl , Among the family of organophosphates, A is more preferably bis (2-ethylhexyl) phosphate. In a preferred aspect of the invention, in formula (II) of the rare earth complex, the ligand A is selected from the family of amides.

p0043Note that according to this aspect of the invention, wherein the ligand A is an amide, preferably Ln represents yttrium or gadolinium in formula (II). Even more preferably according to this preferred aspect of the invention, the rare earth complex of formula (II) is tris [N, N-bis (trimethylsilyl) amide] yttrium or tris [N, N-bis (trimethylsilyl ) amide] gadolinium, especially tris [N, N-bis (trimethylsilyl) amide] yttrium.

p0044According to one aspect of the invention, the rare earth complex may be a complex of a mixture of rare earths or a mixture of several complex of one or more rare earths.

p0045Another component of the catalytic multi-component system according to the invention is an alkylating agent. By way of suitable alkylating agents include the alkyl aluminum compounds, among which is preferred to use a compound selected from:

p0046- Trialkylaluminums, the alkyl radical being Ci-Cio, for example triisobutyl aluminum or trioctyl aluminum; - Dialkylaluminum hydrides, the alkyl radical being Ci-Cio, for example diisobutylaluminum hydride. Note that this alkylating agent is preferably constituted triisobutylaluminum.

p0047Another component of the catalytic multi-component system according to the invention is a compound based on an aromatic ring and having at least two hetero atoms selected from the elements O, N, S, P, and having the formula (III):

p0048<img id="imgf000009_0001" he="37" wi="49" file="imgf000009_0001.tif" img-format="tif" img-content="drawing" orientation="portrait" inline="no" />

p0049Formula III in which - R are identical or different and may each be either:

p0050- A hydrogen atom,

p0051- An aliphatic alkyl radical of C₁-C₂₀, Cycloaliphatic C 5 -C 20 or aromatic C₆- C20, optionally containing one or more hetero atoms (N, O, P, S, Si), preferably nitrogen or oxygen, or one or more halogen atoms, preferably chlorine,

p0052- A halogen atom, preferably selected from chlorine or bromine,

p0053- A grouping based on one or more hetero atom (N, O, P, S, Si), preferably selected from alkoxy functions, secondary amine or tertiary amine. - X and y are identical or different, are integers between 0 and 6, preferably x is 0 to 3 and y between 0 and 3, even more preferably x = y = 0;

p0054- D is a group having a chemical function with one of the atoms has a non-bonding electron pairs, such as alcohol, amine, ether, imine, phosphine, thioether, thiol;

p0055- L is an atom from column 1 of the periodic table, such as hydrogen, lithium, sodium or potassium, preferably hydrogen;

p0056Substituents (CH₂)_X - D and (CH₂)_there - O - L of the aromatic ring are preferably in the ortho or meta position relative to each other, more preferably ortho.

p0057According to a preferred aspect of the invention, in formula (III) D represents an imine. The compound of formula (III) is then most preferably selected from those represented by the formula (IV):

p0058<img id="imgf000010_0001" he="57" wi="53" file="imgf000010_0001.tif" img-format="tif" img-content="drawing" orientation="portrait" inline="no" />

p0059formula IV wherein R, L, x and y are as defined above and R¹ and R², Identical or different, are each a hydrogen atom or an aliphatic alkyl radical of C₁-C₂₀, Cycloaliphatic C 5 -C 20 or aromatic C₆-C₂O,

p0060Even more preferably, among these compounds x = y = 0 and L is a hydrogen atom and the compound of formula (III) is selected from the family of phénoxyimines.

p0061In the family of phénoxyimines, prefer those in which the substituent hydroxyl and imine substituent is in the ortho position to each other. These preferred compounds may be represented by the formula (V):

p0062<img id="imgf000011_0001" he="32" wi="24" file="imgf000011_0001.tif" img-format="tif" img-content="drawing" orientation="portrait" inline="no" /> formula V

p0063R¹ and R² are as defined above and R³ to R⁶ have the same definition as R above. Among these compounds of formula V, more particularly include those wherein R¹ represents an aromatic radical C₆-C₂O, substituted or unsubstituted. Examples of such compounds are N-phenyl-3,5-di-tert-butylsalicylaldimine represented by the formula (VI).

p0064<img id="imgf000011_0002" he="39" wi="28" file="imgf000011_0002.tif" img-format="tif" img-content="drawing" orientation="portrait" inline="no" />

p0065Formula VI and N- (2,6-diisopropyl) phenyl-3,5-di-tert-butylsalicylaldimine of formula (VII): <img id="imgf000012_0001" he="39" wi="32" file="imgf000012_0001.tif" img-format="tif" img-content="drawing" orientation="portrait" inline="yes" />

p0066formula VII

p0067According to another embodiment of the invention, the multicomponent catalyst system can include an optional element that is a halogen donor agent. Among these agents, there may be mentioned alkylaluminium halides such as for example chloride diéthy aluminum, diethylaluminum bromide, ethylaluminum dichloride or ethylaluminum sesquichloride. Particularly preferred is diethyl aluminum chloride.

p0068According to another embodiment of the invention, the catalytic system according to the invention may also comprise a preforming conjugated diene. As a conjugated diene used for preforming preforming the catalytic system according to the invention include 1,3-butadiene, 2-methyl-l, 3-butadiene (or isoprene), 2,3-di ( alkyl Ci-Cs) -I, 3-butadiene such as, for example 2,3-dimethyl-l, 3-butadiene, 2,3-diethyl-l, 3- butadiene, 2-methyl-3-ethyl -l, 3-butadiene, 2-methyl-3-isopropyl-l, 3-butadiene, phenyl-3-butadiene, 1,3-pentadiene, 2,4-hexadiene, or any other conjugated diene having between 4 and 8 carbon atoms, 1,3-butadiene is used preferentially.

p0069Another embodiment of the invention consists of the combination of these two embodiments.

p0070A preferably, in the catalytic system according to the invention, the molar ratio (compound based on an aromatic ring / rare earth metal) can have a value between 0 and 3 (terminals excluded), more preferably from 0 , 5-2 (inclusive). A preferentially still, in the catalytic system according to the invention, the molar ratio (alkylating agent / rare earth metal) can have a value ranging from 2 to 40 (inclusive), more preferably 2 to 10.

p0071Also preferably when the catalyst system according to the invention comprises a halogen donor the molar ratio (halogen donor / rare earth metal) may have a value ranging from 1 to 3, more preferably from 2.5 to 3 .

p0072Also preferably, when the catalytic system according to the invention comprises a preforming conjugated diene molar ratio (preforming conjugated diene / rare earth metal) can have a value ranging from 10 to 70, more preferably from 20 to 60.

p0073Another object of the invention is the preparation of the catalytic system described above.

p0074According to a first method of preparing the catalytic system according to the invention, the constituents of the catalytic system are added directly to the polymerization solvent containing the monomer (s) to be polymerized, so as to obtain a catalyst formed in situ.

p0075According to a second method of preparing the catalytic system according to the invention, the constituents of the catalytic system are premixed before being contacted with the solvent containing the monomer (s) to be polymerized, by introducing into a hydrocarbon solvent inert components of the catalyst system for a time between 0 and 120 minutes, at a temperature ranging from 10⁰C to 80⁰C, optionally greater than room temperature, generally ranging from 18 ° C to 60⁰C, so as to obtain a pre-mixed catalyst. The pre-mixed catalyst thus obtained is then contacted with the solvent containing the monomer (s) to be polymerized.

p0076According to a third method of preparing the catalytic system according to the invention, once the constituents of the catalyst system contacted with each other in an inert hydrocarbon solvent, a small amount of preforming conjugated diene is added so as to obtain a preformed catalyst. Preformation reaction is carried out for a time between 0 and 120 minutes at a temperature ranging from 10⁰C to 80 ° C, optionally greater than room temperature, generally ranging from 18 ° C to 30⁰C. The preformed catalyst thus obtained is then contacted with the solvent containing the monomer (s) to be polymerized.

p0077To this end, it should be noted that the constituents of the catalytic system are preferably mixed prior to being contacted with the solvent containing the monomer (s) to be polymerized, that is to say before the reaction polymerization. The constituents, according to the order of addition and their nature, can react with each other or not.

p0078The preparation of the catalytic system according to the invention is carried out in an aliphatic or alicyclic solvent of low molecular weight, such as for example cyclohexane, methylcyclohexane, n-heptane, or a mixture of these solvents, preferably in n heptane, or in an aromatic solvent such as toluene. It should be noted that the non-aromatic solvents are particularly preferred.

p0079According to a first order of addition of the catalyst system components according to the invention, they are added as follows: in a first step, is added the solvent in the alkylating agent; in a second step, is then added rare earth complex of Formula (II); then in a third step, is added where appropriate the halogen donating agent; and, in a fourth step, is added the compound of formula (III) and optionally the preforming conjugated diene.

p0080According to a second order of addition of the catalyst system components according to the invention, they are added as follows: in a first step, the solvent is added in the rare-earth complex of the formula (II); in a second step is added the compound of formula (III); then in a third step, the alkylating agent is added and optionally, in subsequent steps, the preforming conjugated diene and finally the halogen donating agent.

p0081Another object of the invention is a process for the preparation of diene elastomers having a high cis-1,4 linkage content and a controlled molecular weight distribution, even with a polydispersity index (Mw / Mn) significantly reduced.

p0082This method according to the invention comprises reacting the catalyst system described above with the monomer (s) polymerize, to obtain a diene elastomer can be any homopolymer or copolymer obtained by homopolymerizing or copolymerizing at least one conjugated diene monomer having 4 to 12 carbon atoms, optionally with a vinyl aromatic compound.

p0083As a conjugated diene monomer suitable in particular 1,3-butadiene, isoprene, 2,3-di (Cl-Cs alkyl) -l, 3-butadienes such as, for example 2,3-dimethyl-l , 3- butadiene, 2,3-diethyl-l, 3-butadiene, 2-methyl-3-ethyl-l, 3-butadiene, 2-methyl-3- isopropyl-l, 3-butadiene, an aryl -l, 3-butadiene, 1,3-pentadiene, 2,4-hexadiene.

p0084Vinyl aromatic compounds are suitable for example, styrene, ortho-, meta-, and para-methylstyrene, the commercial mixture "vinyltoluene", para-tertiobutylstyrene, the methoxy, chlorostyrenes, vinylmesitylene, divinylbenzene, vinylnaphthalene.

p0085The polymerization is preferably effected in the presence of an inert hydrocarbon solvent which can be for example an aliphatic or alicyclic hydrocarbon such as pentane, hexane, heptane, iso-octane, isobutane, cyclohexane, methylcyclohexane or an aromatic hydrocarbon such as benzene, toluene, xylene.

p0086The polymerization can be carried out continuously or batchwise. Is generally carried out the polymerization at a temperature between 20⁰C 150⁰C and preferably close to 30⁰C to 110⁰C.

p0087Advantageously and as compared to a process employing a catalyst system containing no aromatic compound having at least two hetero atoms of formula (HI), the method according to the invention allows to obtain with improved catalyst activity, an elastomer diene characterized by a high cis-1,4 linkage content and a controlled molar mass distribution, even with a polydispersity index significantly reduced, as shown by the following examples. This elastomer may for example be formed of a polyisoprene (IR) or polybutadiene (BR).

p0088The aforementioned features of the present invention, as well as others, will be better understood from reading the following description of several embodiments of the invention, illustrative and not restrictive. Examples of organic and organometallic synthesis

p0089All organometallic syntheses were performed under an inert argon atmosphere using either schlenk techniques or a glovebox. All solvents used in these syntheses are dried and stored under an inert atmosphere. Pentane and THF are freshly distilled over sodium / benzophenone. All reagents were from Sigma-Aldrich, Strem and Aldrich.

p0090Synthesis of [N, N-bis (trimethylsilyl) Rare earth amidure1 Complex tris [N, N-bis (trimethylsilyl) amide] rare earth were synthesized by the method described by Bradley et al. (Bradley, D. C, Ghotra, JS, and Hart, FA, J. Chem. Soc, Dalton Trans., 1973, 1021). and modified Drink et al. (Drink, C, Sprocket, F., and Spitz, R., Macromol. Chem. Phys., 1999, 200, 1163).

p0091Synthesis of N- (2,6-diisopropyl) phenyl-3,5-di-tert-butylsalicylaldimine

p0092<img id="imgf000016_0001" he="39" wi="32" file="imgf000016_0001.tif" img-format="tif" img-content="drawing" orientation="portrait" inline="no" />

p0093N- (2,6-diisopropyl) phenyl-3,5-di-tert-butylsalicylaldimine was synthesized according to the procedure described by Cameron et al. (Cameron, PA, Gibson, V. C, Redshaw, C, Segal, JA, Solan, GA, White, AJP, and Williams, DJJ, Chemical Society, Dalton Transactions, 2001, 1472).

p0094Examples of polymerization

p0095All preparations of the catalytic systems was performed under an inert argon atmosphere using either schlenk techniques or a glovebox. All solvents used in these preparations are dry and inert atmosphere. Toluene and heptane are dried twice over molecular sieves. All reagents were from Sigma-Aldrich, Strem and Aldrich. triisobutylaluminum solutions, chloride diethyl and N- (2,6-diisopropyl) phenyl-3,5-di-tert-butylsalicylaldimine were prepared in heptane, from pure reactants, at concentrations of 0.740, 0.027 and 0.100 mol L^"1 respectively.

p0096The molar masses of the polymers are soluble in THF are determined by steric exclusion chromatography in THF. The samples were injected using a Waters 717 injector in a series of columns placed in a chamber thermostated at 45 ° C. Detection is carried out using a Waters 410 refractometer and the molecular weight polybutadienes are expressed in polystyrene equivalents (using polystyrene standards certified Polymer Laboratories). The microstructure is determined by FTIR on a Nicolet 460 FT-IR spectrometer (measurement at room temperature of 32 scans of 500-3800 cm^"1) According to the method described by Morero et al. (Morero, D., Santambrogio, A. Porri, L., and Ciampelli, F., Chem. Ind. (Milano), 1959, 41). The polymerization takes place in a disposable container glass reactor (250 ml Schott bottle), with a stainless steel stir blade. The temperature control is ensured through a thermostatically controlled water bath connected to a double-shell po Iy carbonate. This reactor has all the inputs and outputs necessary to traditional operations: (i) conditioning the reactor 80⁰C by vacuum cycles - argon, (ii) introduction of solutions to the cannula under argon purge and (iii) gaseous monomer feed.

p0097example 1

p0098A solution composed of (in order of addition) of 150 mL of heptane, triisobutylaluminum (1.9 mL - 1.4 mmol), tris [N, N-bis (trimethylsilyl) amide] gadolinium (19.2 mg - 0.03 mmol) and diethylaluminum chloride (2.2 mL - 0.06 mmol) is prepared at 23 ° C and stirred for 5 minutes. This solution is then injected under argon in a glass reactor of 250 ml. The reactor is then degassed and butadiene (10 mL - 115 mmol) was introduced. The reactor is heated to 70⁰C then the solution was stirred for 30 min. The reaction is stopped by cooling and degassing the reactor. The polymer was obtained by precipitation in a solution of ethanol (200 mL) and 2,6-ditertiarybutyl-4-methylphenol (5 mg). The polymer (2.5 g) was isolated after drying. example 2

p0099A solution composed of (in order of addition) of 150 mL of heptane, triisobutylaluminum (1.9 mL - 1.4 mmol), tris [N, N-bis (trimethylsilyl) amide] gadolinium (19.2 mg - 0.03 mmol) of diethylaluminum chloride (2.2 mL - 0.06 mmol) and N- (2,6-diisopropyl) phenyl-3,5-di-tert-butylsalicylaldimine (0.3 mL - 0.03 mmol) is prepared at 23 ° C and stirred for 5 minutes. This solution is then injected under argon in a glass reactor of 250 ml. The reactor is then degassed and butadiene (10 mL - 115 mmol) was introduced. The reactor is heated to 70⁰C then the solution was stirred for 30 min. The reaction is stopped by cooling and degassing the reactor. The polymer was obtained by precipitation in a solution of ethanol (200 mL) and 2,6-ditertiarybutyl-4-methylphenol (5 mg). The polymer (3.5 g) was isolated after drying.

p0100example 3

p0101A solution composed of (in order of addition) of 150 mL of heptane, triisobutylaluminum (3.2 mL - 2.40 mmol), tris [N, N-bis (trimethylsilyl) amide] yttrium (34, 2 mg - 0,06 mmol) and diethylaluminum chloride (4.4 mL - 0.12 mmol) is prepared at 23 ° C and stirred for 5 minutes. This solution is then injected under argon in a glass reactor of 250 ml. The reactor is then degassed and butadiene (10 mL - 115 mmol) was introduced. The reactor is heated to 70⁰C and the solution is stirred for 240 min. The reaction was stopped by degassing of Reacte heart then cooling. The polymer was obtained by precipitation in a solution of ethanol (200 mL) and 2,6-ditertiarybutyl-4-methylphenol (5 mg). The polymer (2.5 g) was isolated after drying.

p0102Example 4 A solution composed of (in order of addition) of 150 mL of heptane, triisobutylaluminum (3.2 mL - 2.40 mmol), tris [N, N-bis (trimethylsilyl) amide] yttrium ( 34.2 mg - 0.06 mmol) of diethylaluminum chloride (4.4 mL - 0.12 mmol) and N- (2,6-diisopropyl) phenyl-3,5-di-tert-butylsalicylaldimine (0 , 6 mL - 0.06 mmol) is prepared at 23 ° C and stirred for 5 minutes. This solution is then injected under argon in a glass reactor of 250 ml. The reactor is then degassed and butadiene (10 mL - 115 mmol) was introduced. The reactor is heated to 70⁰C and the solution was stirred 6Or "min. The reaction is stopped by cooling and degassing the reactor. The polymer was obtained by precipitation in a solution of ethanol (200 mL) and 2,6-ditertiarybutyl-4-methylphenol (5 mg). The polymer (3.3 g) was isolated after drying. summary results

p0103Ln Conversion%

p0104activity

p0105Example (concentration (Mn time g.mol^"1 IP g me ¹ h^"1 in mmol.L^"1) Minute)

p01061 Gd (0.2) 37 (30) 43 192000 4.0

p0107Gd 2 (0.2) 56 (30) 65 185000 * 2.8 *

3 Y (0.4) 39 (240) 3 80000 12.1

4 Y (0.4) 53 (60) 15 117000 4.9

p0110* The molecular weight distribution is bimodal; the reported data are those of the massive majority (64% area); the second mass (36% of the area) to a Mn of 11000 g mol^"1 and an IP of 1.74.

p0111Summary of the microstructure

p0112Example Microstructure (%)

p01131,4-cis-1, 4-trans 1.2

p01141 98.8 1.2 0

p01152 98.7 1.3 0

p01163 95.1 4.1 0.8

p01174 91.3 6.4 2.3

p0118The addition of an additive N- (2,6-diisopropyl) phenyl-3,5-di-tert-butylsalicylaldimine in the preparation of a catalytic system based on tris [N, N-bis (trimethylsilyl) amide ] gadolinium or yttrium can increase the catalytic activity. The stereospecificity of the catalyst is not downgraded since the rate of 1,4-cis remain high (> 90% for yttrium and> 98% for gadolinium).