Catalyst system based on an iron complex and use thereof for the polymerization of conjugated dienes

Abstract

The invention relates to the use, within a catalyst system, of an iron complex with the formula (I) Fe(N(R)2)2, in which the R symbols, which may be the same or different, represent a hydrogen atom, a C1-C20 branched or linear aliphatic radical, which may be substituted or unsubstituted, a C3-C20 cycloaliphatic radical, which may be substituted or unsubstituted, a C6-C20 aromatic radical, which may be substituted or unsubstituted, or a silyl radical with the formula -Si(R')3, in which the R' symbols, which may be the same or different, represent a hydrogen atom, a C1-C20 branched or linear aliphatic radical, which may be substituted or unsubstituted, a C3-C20 cycloaliphatic radical, which may be substituted or unsubstituted, or a C6-C20 aromatic radical, which may be substituted or unsubstituted; for the polymerization of conjugated dienes, in particular the stereospecific polymerization of 1,3-dienes, especially butadiene and isoprene.

Description

[0001] Catalytic system based on an iron complex and its use for the polymerization of conjugated dienes

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to the use of an iron complex in processes for the polymerization of conjugated dienes. In particular, the present invention relates to a catalytic system based on an iron complex and its preparation process, as well as its use for the polymerization of conjugated dienes.

[0004] TECHNOLOGICAL BACKGROUND

[0005] Stereospecific polymerization of conjugated dienes using metal compound-based catalytic systems is known and widely described in the literature.

[0006] From an industrial perspective, the main metals commonly used for butadiene polymerization are Ni, Ti, Co, and Nd. Recent developments in industrial butadiene polymerization systems have focused on neodymium-based systems. However, neodymium is a rare earth whose natural resources are limited, more so than other metals used for catalytic polymerization. In addition, apart from its use for industrial butadiene polymerization, neodymium is also widely used for the manufacture of permanent magnets, particularly in wind turbines, hard drives, electric motors for hybrid cars, etc. It has therefore become necessary to find economically viable alternatives to continue producing high-quality polybutadiene on an industrial scale.

[0007] Aware of this problem, various research groups have previously proposed turning to stereospecific synthesis methods for conjugated diene polymers that are less expensive and more environmentally friendly. Conjugated diene polymerization systems based on abundant, recyclable, and inexpensive metals have thus been developed. Iron is one of these metals.

[0008] For example, US20140011971A1 describes the preparation of polyisoprene using a catalyst system based on an iron complex comprising a bidentate amino ligand. Also, document CN112442092A describes iron complexes comprising a bidentate amino ligand and its use for the stereospecific polymerization of conjugated diene, in particular butadiene.

[0009] The article "Cis-1,4 Specific Polymerization of 1,3-butadiene using PNP-pincer Ligated Iron(ll) Complexes" by Ryo Tanaka, Kenshi Ikeda, Yuushou Nakayama, and Takeshi Shiono in Chemistry Letters, 2019 (48), pp 525-28, describes another type of iron complex for the stereospecific polymerization of butadiene, this one comprising a PNP-type "pincer" ligand.

[0010] The iron complex-based catalytic systems proposed so far rely on complex ligand chemistries that are often incompatible with industrial exploitation. These iron complexes are also generally poorly soluble in aliphatic solvents useful for the polymerization of conjugated dienes on an industrial scale. It is a constant concern to find new methods for the stereospecific synthesis of conjugated dienes that have a limited environmental footprint while remaining economically attractive for the industrial production of polydienes, in particular butadiene or isoprene polymers.

[0011] Continuing their efforts to research a less expensive and more virtuous industrial polymerization of conjugated dienes, the Applicants have discovered that the use of a particular iron compound makes it possible to polymerize conjugated dienes efficiently in aliphatic solvents, usually used on an industrial scale, and to obtain stereoregular polymers. This iron complex has the advantage of using an abundant, recyclable and inexpensive metal, an advantage coupled with simple ligand chemistry with few synthesis steps.

[0012] BRIEF DESCRIPTION OF THE INVENTION

[0013] A first subject of the invention is the use of an iron complex of formula (I) Fe(N(R)2)2(I) in which the symbols R, identical or different, represent a hydrogen atom, a linear or branched C1-C20 aliphatic radical, substituted or not, a cycloaliphatic radical in C3-C20, substituted or not, an aromatic radical in C6-C20, substituted or not, or a silyl radical of formula -Si(R')3 in which the symbols R', identical or different, represent a hydrogen atom, a linear or branched C1-C20 aliphatic radical, substituted or not, a cycloaliphatic radical in C3-C20, substituted or not, or an aromatic radical in C6-C20, substituted or not, for the polymerization of conjugated dienes.

[0014] A second subject of the invention is a catalytic system comprising such an iron complex, a solvent, a cationizing agent and an alkylating agent.

[0015] A third object of the invention is a method for synthesizing a diene polymer using such a catalytic system.

[0016] DEFINITIONS

[0017] In this description, the following terms have the following meanings, unless otherwise indicated:

[0018] The expression "in Cx-Cy" for a hydrocarbon radical means that said radical comprises x to y carbon atoms.

[0019] The terms "radical", "group" and "grouping" are equivalent and interchangeable.

[0020] “aliphatic radical” means a saturated or unsaturated, acyclic or cyclic hydrocarbon radical, excluding aromatic radicals, preferably comprising 1 to 20 carbon atoms. The aliphatic radical may be linear or branched. Examples of linear or branched aliphatic radicals include C1-C20 alkyl groups, C2-C20 alkenyl groups and C2-C20 alkynyl groups.

[0021] "alkyl" means a monovalent, linear or branched saturated hydrocarbon radical comprising from 1 to 20 carbon atoms, preferably from 1 to 10 carbon atoms, for example the methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl and decyl radicals. "alkenyl" means a monovalent hydrocarbon radical comprising at least one double bond, said radical being linear or branched and preferably comprising here from 2 to 20 carbon atoms, preferably from 2 to 6 carbon atoms, for example the ethenyl, vinyl, butenyl or 2-propen-1-yl (allyl) radical.

[0022] “alkynyl” means a monovalent hydrocarbon radical comprising at least one triple bond, said radical being linear or branched and preferably comprising here from 2 to 20 carbon atoms, preferably from 2 to 6 carbon atoms, for example the ethynyl, propynyl and butynyl radical.

[0023] “cycloaliphatic radical” means a mono- or polycyclic aliphatic radical preferably comprising here from 3 to 20 atoms, saturated or unsaturated. Examples of cycloaliphatic radicals include C3-C20 cycloalkyl groups and C3-C20 cycloalkenyl groups.

[0024] “cycloalkyl” means a monocyclic saturated hydrocarbon radical preferably comprising herein from 3 to 20 carbon atoms, preferably from 3 to 10 carbon atoms. Examples of cycloalkyl radicals include the cyclopentyl, cyclohexyl and cycloheptyl radical.

[0025] “cycloalkenyl” means a monocyclic hydrocarbon radical comprising at least one double bond and preferably comprising here from 3 to 20 carbon atoms, preferably from 3 to 10 carbon atoms.

[0026] “aromatic radical” means a mono- or polycyclic aromatic radical preferably comprising here from 5 to 20 members. Examples of aromatic radicals include aryl groups.

[0027] “aryl” means a mono- or polycyclic aromatic hydrocarbon radical preferably comprising here from 6 to 20 carbon atoms, preferably from 6 to 10 carbon atoms. Examples of aryl radicals include the phenyl radical and the naphthyl radical.

[0028] The notation "(halo)" preceding a radical means that it does or does not include a halogen atom. For example, the radical (halo)aryl includes the aryl radical and the halogenated aryl radical.

[0029] By "halogen atom" is meant an atom chosen from chlorine, bromine, iodine and fluorine.

[0030] DETAILED DESCRIPTION OF THE INVENTION

[0031] A first object of the invention is the use of an iron complex for the polymerization of conjugated dienes.

[0032] A / Iron complex

[0033] The iron complex useful for the purpose of the present invention is a compound of formula (I): Fe(N(R)2)2(I) in which the symbols R, identical or different, represent a hydrogen atom, a linear or branched C1-C20 aliphatic radical, substituted or not, a cycloaliphatic radical in C3-C20, substituted or not, an aromatic radical in C6-C20, substituted or not, or a silyl radical, substituted or not of formula -Si(R')3 in which the symbols R', identical or different, represent a hydrogen atom, a linear or branched C1-C20 aliphatic radical, substituted or not, a cycloaliphatic radical in C3-C20, substituted or not, or an aromatic radical in C6-C20, substituted or not.

[0034] Such metallic iron compounds are notably used in WO 2019008279 for their catalytic activity in the hydrosilylation and / or dehydrogenative silylation of organopolysiloxane compounds with a compound comprising at least one hydrogenosilyl function.

[0035] The aliphatic, cycloaliphatic and aromatic radicals defining R and R' may be substituted by one or more substituents independently selected from halogen atoms, C3-C6 (halo)cycloalkyls, C6-C14 (halo)aryls.

[0036] The cycloaliphatic radical and the aromatic radical defining R and R' may further or alternatively be substituted by one or more substituents independently selected from C1-C10 (halo)alkyl, C7-C12 (halo)aralkyl, C2-C10 (halo)alkenyl and C2-C10 (halo)alkynyl.

[0037] According to certain embodiments, in formula (I) above, each R represents a silyl radical of formula -Si(R')3 in which each R' independently of the other represents a hydrogen atom or a C1-C20 alkyl radical, preferably a C1-C10 alkyl radical, for example a methyl, ethyl, n-propyl, iso-propyl, n-butyl, sec-butyl, iso-butyl or tert-butyl radical.

[0038] According to certain embodiments, in formula (I) above, each R represents a trialkylsilyl radical of formula -Si(R')3 in which each R' represents a C1-C4 alkyl radical, for example a methyl radical.

[0039] According to certain embodiments, the iron complex of formula (I) is an iron (II) bis[N,N-bis(trimethylsilyl)amide], in particular iron (II) bis[N,N-bis(trimethylsilyl)amide].

[0040] Preparation of iron complex:

[0041] The iron complex of formula (I) can be prepared in a known manner by a simple process of reacting an iron halide, for example iron chloride or bromide, in the presence of THF with a lithium amide of formula Li-N(SiR3)2. Such a process is for example described in WO2013043912A2, or in the article Andersen, RA; Faegri, K.; Green, JC; Haaland, A.; Lappert, MF; Leung, WP; Rypdal, K. Inorg. Chem. 1988, Tl (10), 1782-1786, with regard to the synthesis of Fe N SiMeahh-

[0042] According to the invention, the iron complex of formula (I) is used for the polymerization of conjugated dienes, in particular 1,3-dienes, preferably butadiene, isoprene or mixtures thereof.

[0043] For the purposes of the invention, the iron complex of formula (I) is then advantageously used within a catalytic system.

[0044] B / Catalytic system

[0045] Thus, the present invention also relates to such a catalytic system which comprises: - an iron complex of formula (I) Fe(N(R)2)2(I)

[0046] - a solvent,

[0047] - a cationizing agent, and

[0048] - an alkylating agent. a) Solvent of the catalytic system

[0049] The solvent of the catalytic system is chosen so that all other components of the catalytic system are soluble in said solvent.

[0050] Depending on the embodiments, the solvent of the catalytic system is chosen:

[0051] - among polar aprotic solvents chosen from ethers, amines and their mixtures; or

[0052] - among aliphatic apolar solvents, aromatic apolar solvents and their mixtures.

[0053] Thus, according to certain embodiments, the solvent of the catalytic system is an aliphatic apolar solvent, an aromatic apolar solvent or a mixture of an aliphatic apolar solvent and an aromatic apolar solvent. For example, the solvent of the catalytic system may be cyclohexane, methylcyclohexane, toluene, benzene and mixtures thereof. Preferably, according to these embodiments, the solvent of the catalytic system is aromatic, more preferably then the solvent is toluene. According to these embodiments, the stereospecificity of the catalytic system promotes the insertion in the 1,4-cis position of the 1,3-diene monomers and therefore the formation of predominantly cis poly-1,3-dienes.

[0054] Also, according to other embodiments, the solvent of the catalytic system is a polar aprotic solvent chosen from ethers, amines and their mixtures, preferably then the solvent of the catalytic system is an ether, more preferably a derivative of tetrahydrofuran (THF) for example methyltetrahydrofuran. According to these embodiments, the stereospecificity of the catalytic system promotes the insertion in the 1,4-trans position of the 1,3-diene monomers and therefore the formation of predominantly trans poly-1,3-dienes. b) Alkylating agent

[0055] The catalyst system according to the invention also comprises an alkylating agent. The alkylating agent may be any alkylating agent commonly used for the polymerization of conjugated diene monomers.

[0056] More particularly, the alkylating agent may be an organometallic alkylating agent of metals from groups 1, 2, 12 and 13 of the periodic table according to IUPAC (December 2018).

[0057] Examples of such alkylating agents include alkylating agents belonging to the group consisting of magnesium alkyls, lithium alkyls, zinc alkyls, aluminum alkyls, Grignard reagents and mixtures of these constituents.

[0058] Alkylating agents belonging to the alkylaluminium group can be represented by the following formula (II): (Ra) m -AI (ORb) n -H P -X q - (II) in which: - Ra and Rb are identical or different and each represent a hydrocarbon group of 1 to 15 carbon atoms, preferably a hydrocarbon group of 1 to 4 carbon atoms;

[0059] - X is a halogen atom; and

[0060] - m', n', p' and q' are numbers satisfying the following conditions: 0 <m' = 3,

[0061] 0 = n' <3, 0 = p' <3, 0 = q' <3 and m' + n' + p' + q' = 3.

[0062] In particular, the aluminum alkyls of formula (II) may be compounds represented by the following formulas: i) (Ra) m -AI(ORb) 3.m - in which Ra and Rb are the same or different and each represents a hydrocarbon group of 1 to 15 carbon atoms, preferably a hydrocarbon group of 1 to 4 carbon atoms; and m' is preferably a number satisfying the condition of 1.5 sm' s 3; ii) (Ra)m-AIX3.m- in which Ra is a hydrocarbon group of 1 to 15 carbon atoms, preferably a hydrocarbon group of 1 to 4 carbon atoms; X is a halogen atom; and m' is preferably a number satisfying the condition of 0 <m' <3 ; iii) (Ra)mAIH3.m- dans laquelle Ra est un groupe hydrocarboné de 1 à 15 atomes de carbone, de préférence un groupe hydrocarboné de 1 à 4 atomes de carbone ; et m' est de préférence un nombre satisfaisant à la condition de 2 s m' <3 ; iv) (Ra) m -AI(ORb) n-Xq- in which Ra and Rb may be the same or different and each represents a hydrocarbon group of 1 to 15 carbon atoms, preferably a hydrocarbon group of 1 to 4 carbon atoms; X is a halogen atom; and m', n' and q' are numbers satisfying the conditions of 0 <m' s 3, 0 s n' <3, 0 s q' <3 et m' + n' + q' = 3.

[0063] Particular examples of alkylaluminum compounds include:

[0064] - tri-n-alkylaluminium, such as trimethylaluminium, triethylaluminium, tri-n-butylaluminium, tripropylaluminium, tripentylaluminium, trihexylaluminium, trioctylaluminium and tridecylaluminium;

[0065] - branched-chain trialkylaluminiums, such as triisopropylaluminium, triisobutylaluminium, tri-sec-butylaluminium, tri-tert-butylaluminium, tri-2-methylbutylaluminium, tri-3-methylbutylaluminium, tri-neopentylaluminium, tri-2-methylpentylaluminium, tri-3-methylpentylaluminium, tri-4-methylpentylaluminium, tri-2-methylhexylaluminium, tri-3-methylhexylaluminium and tri-2-ethylhexylaluminium;

[0066] - tricycloalkylaluminium, such as tricyclohexylaluminium and tricyclooctylaluminium;

[0067] - triarylaluminum, such as triphenylaluminum and tritolylaluminum;

[0068] - trialkenylaluminiums represented by the formula (i-C4H9)aAlb(C5H10)c (where a, b and c are positive numbers and c È 2X), such as isoprenylaluminium; - alkylaluminium alcoholates, such as isobutylaluminium methoxide, isobutylaluminium ethoxide and isobutylaluminium isopropoxide;

[0069] - dialkylaluminum alcoholates, such as dimethylaluminum methoxide, diethylaluminum ethoxide and dibutylaluminum butoxide;

[0070] - alkylaluminium sesquialkoxides, such as ethylaluminium sesquiethoxide and butylaluminium sesquibutoxide;

[0071] - partially alkoxylated alkylaluminiums having an average composition represented by Ra2.5AI(ORb)0.5;; also called aluminoxanes, for example methylaluminoxane (MAO), ethylaluminoxane, isobutylaluminoxane, triisobutylaluminoxane; and

[0072] - dialkylaluminum aryloxides, such as diethylaluminum phenoxide, diethylaluminum (2,6-di-t-butyl-4-methylphenoxide), ethylaluminumbis (2,6-di-t-butyl-4-methylphenoxide), diisobutylaluminum (2,6-di-t-butyl-4-methylphenoxide) and isobutylaluminum bis (2,6-di-t-butyl-4-methylphenoxide);

[0073] - dialkylaluminium halides, such as dimethylaluminium chloride, diethylaluminium chloride, dibutylaluminium chloride, diethylaluminium bromide and diisobutylaluminium chloride;

[0074] - alkylaluminium sesquihalides, such as ethylaluminium sesquichloride, butylaluminium sesquichloride and ethylaluminium sesquibromide;

[0075] -partially halogenated alkylaluminiums, such as ethylaluminium dichloride, propylaluminium dichloride and butylaluminium dibromide;

[0076] - dialkylaluminum hydrides, such as diethylaluminum hydride and diisobutylaluminum hydride;

[0077] - partially hydrogenated alkylaluminiums, for example alkylaluminium dihydrides, such as ethylaluminium dihydride and propylaluminium dihydride; and

[0078] - partially alkoxylated and halogenated alkylaluminiums, such as ethylaluminium ethoxychloride, butylaluminium butoxychloride and ethylaluminium ethoxybromide.

[0079] Alkylating agents belonging to the group of magnesium alkyls, zinc alkyls or Cd alkyls (group 2 or group 12) may be represented by the following formula: RaRbM, in which Ra and Rb may be the same or different and each represents a hydrocarbon group of 1 to 15 carbon atoms, preferably a hydrocarbon group of 1 to 4 carbon atoms; and M is Mg, Zn or Cd.

[0080] According to certain embodiments, the alkylating agent is an aluminum alkyl of formula (II) as defined above. Examples of preferred aluminum alkyls include:

[0081] - aluminoxanes, such as methylaluminoxane (MAO), ethylaluminoxane, isobutylaluminoxane, triisobutylaluminoxane;

[0082] - tri-alkylaluminum of formula AI(Cl-C10-alkyl)3, such as trimethylaluminum, triethylaluminum, tri-n-propylaluminum, tri-isopropylaluminum, tri-n-butylaluminum, tri-isobutylaluminum (TiBA), tri-t-butylaluminum, tri-n-pentylaluminum, tri-neopentylaluminum, tri-n-hexyl-aluminum, tri-cyclohexylaluminum, tri-n-octylaluminum, preferably tri-isobutylaluminuim;

[0083] - dialkylaluminium hydrides of formula (AI(Cl-C10-alkyl)2H), such as diethylaluminium hydride (HDiBA), diisopropylaluminium hydride, di-n-propylaluminium hydride, di-isobutylaluminium hydride, di-n-butylaluminium hydride, di-n-octylaluminum hydride, preferably diisobutylaluminium hydride;

[0084] - alkylaluminium monohalides, such as diethylaluminium chloride (DEAC).

[0085] In some embodiments, the alkylating agent is a tri-alkyl aluminum of formula AI(C1-C10-alkyl)3, such as trimethylaluminum, triethylaluminum, tri-n-propylaluminum, tri-isopropylaluminum, tri-n-butylaluminum, tri-isobutylaluminum (TiBA), tri-t-butylaluminum, tri-n-pentylaluminum, tri-neopentylaluminum, tri-n-hexyl-aluminum, tri-cyclohexylaluminum, tri-n-octylaluminum, preferably tri-isobutylaluminum.

[0086] In some embodiments, the alkylating agent is a dialkylaluminum hydride of formula (AI(Cl-C10-alkyl)2H), such as diethylaluminum hydride, diisopropylaluminum hydride, di-n-propylaluminum hydride, di-isobutylaluminum hydride, di-n-butylaluminum hydride, di-n-octylaluminum hydride, preferably diisobutylaluminum hydride.

[0087] The above-mentioned alkylating agents can be used alone or in mixtures of two or more.

[0088] According to certain embodiments, the molar ratio (alkylating agent) / (iron complex) is preferably greater than or equal to 5 / 1.

[0089] Those skilled in the art will understand that there is no maximum limit to the range of values ​​of this molar ratio. Indeed, there is no maximum value, even a preferential one, for this molar ratio (alkylating agent) / (iron complex) which is imposed by a deactivation of the catalytic system in the processes for the polymerization of conjugated dienes. c) Cationizing agent

[0090] The catalytic system according to the invention also comprises a cationizing agent. The cationizing agent may be any cationizing agent commonly used for the polymerization of olefins.

[0091] According to certain embodiments, the co-catalyst may be a cationizing agent of the following formula (III): [Q] + [B(Ri)4]' (III), in which

[0092] - [QJ +is a proton, a carbonium cation or one of its substituted derivatives (primary, secondary or tertiary carbocation), an ammonium cation or one of its substituted derivatives (primary, secondary, tertiary, quaternary ammonium), an oxonium cation or one of its substituted derivatives, a phosphonium cation, a cycloheptyltrienyl cation, a metallocenium cation of a transition metal such as a ferrocenium cation, or the like;

[0093] - B is the symbol for boron;

[0094] - each Ri represents, independently of one another, a linear or branched C1-C20 aliphatic radical, substituted or not, a C3-C20 cycloaliphatic radical, substituted or not, or a C6-C20 aromatic radical, substituted or not.

[0095] In this definition, the linear or branched aliphatic radical, the cycloaliphatic radical and the C6-C20 aromatic radical may be substituted by one or more substituents independently selected from halogen atoms, C1-C5 alkyl groups or C1-C5 perfluoroalkyl groups. In certain embodiments, R 1 represents an aryl group which may be substituted by one or more substituents independently selected from halogen atoms, C1-C5 alkyl groups or C1-C5 perfluoroalkyl groups.

[0096] According to certain embodiments, Ri independently represents a phenyl, tolyl, mesityl, xylyl group, substituted or not, more particularly a pentafluorophenyl group.

[0097] In some embodiments, all four Ri's are identical. In some embodiments, all four Ri's are pentafluorophenyl groups.

[0098] Examples of the [B(Ri)4] anion include alkyltris(pentafluorophenyl)borate, tetrakis(pentafluorophenyl)borate, and tetrakis[3,5-bis(trifluoromethyl)phenyl]borate.

[0099] Examples of carbonium cations include, but are not limited to, tri-substituted carbonium cations, such as triphenylcarbonium cation, tri(methylphenyl)carbonium cation, and tri(dimethylphenyl)carbonium cation.

[0100] Examples of ammonium cations include, but are not limited to, primary, secondary, and tertiary ammonium cations. Examples of secondary ammonium cations include dialkylammonium and diarylammonium, for example, dimethylammonium, diethylammonium, di(isopropyl)ammonium, dicyclohexylammonium, and diphenylammonium. Examples of ternary ammonium cations include trialkylammonium, for example, trimethylammonium, triethylammonium, tripropylammonium, and tributylammonium (particularly tri(n-butyl)ammonium).Examples of ammonium cations also include anilinium cations and their derivatives, such as anilinium cation, N-alkylanilinium and N,N-dialkylanilinium cations, such as N-methylanilinium cation, N,N-dimethylanilinium cation, N,N-diethylanilinium cation, N,N-2,4,6-pentamethylanilinium cation, p-bromo-N,N-dimethylanilinium cation and p-nitro-N,N-dimethylanilinium cation.

[0101] Examples of phosphonium cations include, but are not limited to, triarylphosphonium cations, such as triphenylphosphonium cation, tri(methylphenyl)phosphonium cation, and tri(dimethylphenyl)phosphonium cation.

[0102] In some embodiments, the cation [QJ+ is a carbonium cation or an ammonium cation as described above, preferably [QJ+ is the triphenylcarbonium cation, the N,N-dimethylanilinium cation or the N,N-diethylanilinium cation.

[0103] According to certain embodiments, the cationizing agent may therefore be a trialkyl-substituted ammonium salt, an N,N-dialkylanilinium salt, a dialkylammonium salt or a tri-substituted carbonium salt.

[0104] Examples of cationizing agents of formula (III) include triethylammoniumtetra(phenyl) borate, tripropylammoniumtetra(phenyl) borate, tri(n-butyl) ammoniumtetra(phenyl) borate, trimethylammoniumtetra(p-tolyl) borate, trimethylammoniumtetra(o-tolyl) borate, tri(n-butyl)ammonium tetrakis(pentafluorophenyl) borate, tripropylammoniumtetrakis(o,p- dimethylphenyl) borate, tri(n-butyl)ammoniumtetrakis(m,m-dimethylphenyl) borate, tri(n-butyl)ammoniumtetrakis(p- trifluoromethylphenyl) borate, tri(n-butyl) ammoniumtetrakis(3,5- ditrifluoromethylphenyl) borate, tri(n-butyl) ammoniumtetra(o-tolyl) borate, N,N- dimethylaniliniumtetra(phenyl)borate, N,N-dimethylanilinium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate, N,N-diethylaniliniumtetra(phenyl)borate, N,N-2,4,6-pentamethylaniliniumtetra(phenyl)borate, di(l-propyl)ammoniumtetrakis(pentafluorophenyl)borate, dicyclohexylammoniumtetra(phenyl)borate,triphenylcarboniumtetrakis(pentafluorophenyl)borate, triphenylcarboniumtetrakis[3,5-bis(trifluoromethyl)phenyl]borate, N,N-dimethylaniliniumtetrakis(pentafluorophenyl)borate, ferroceniumtetrakis(pentafluorophenyl)borate, triphenylcarbeniumpentaphenylcyclopentadienyl, N,N-diethylaniliniumpentaphenylcyclopentadienyl.,

[0105] The cationizing agent is preferably a trialkyl-substituted ammonium salt, an N,N-dialkylanilinium salt, a dialkylammonium salt or a tri-substituted carbonium salt, preferably the cationizing agent is dimethylanilinium tetrakis(pentafluorophenyl)borate or trityl tetrakis(pentafluorophenyl)borate.

[0106] The above-mentioned cationizing agents can be used alone or in mixtures of two or more.

[0107] According to certain embodiments, the molar ratio (cationizing agent) / (iron complex) is preferably less than or equal to 2 / 1; more preferably this molar ratio is within a range of values ​​from 1 / 1 to 2 / 1.

[0108] C / Preparation of the catalytic system

[0109] The process for preparing the catalytic system described above is also the subject of the invention. a) Pre-mixing

[0110] The components of the catalytic system may be pre-mixed before being brought into contact with the monomer(s) to be polymerized. The components of the catalytic system are mixed by introducing the iron complex and the cationizing agent into the solvent of the catalytic system. This mixture is then brought into contact with the alkylating agent for a time of between 0 and 120 minutes, at a temperature ranging from 10°C to 60°C, generally at room temperature (around 23°C), so as to obtain a pre-mixed catalyst. The pre-mixed catalyst thus obtained is then brought into contact with the monomer(s) to be polymerized, optionally in solution in the polymerization solvent. b) In situ preparation in two stages

[0111] The alkylating agent may initially be mixed with the monomers to be polymerized. The iron complex of formula (I), pre-mixed with the cationizing agent in the solvent of the catalytic system for a time between 0 and 120 minutes, at a temperature ranging from 10°C to 60°C, generally at room temperature (around 23°C), is then added to carry out the polymerization reaction. c) In situ preparation Initially, a solution of the iron complex of formula (I) and a solution of the cationizing agent may be added at the same time or successively to the monomers to be polymerized. Secondly, a solution of the alkylating agent is added to the medium. The solvents of the solutions of each component of the catalytic system may be identical or different and chosen from the solvents of the catalytic system defined above.

[0112] D / Polymerization

[0113] The catalytic system of the present invention can be used in processes for the polymerization of conjugated dienes. The monomers to be polymerized can then be brought into contact with the catalytic system according to the invention.

[0114] The monomers to be polymerized are chosen from the group of monomers consisting of conjugated dienes.

[0115] According to certain embodiments, the conjugated dienes used as monomers to be polymerized are preferably 1,3-dienes having from 4 to 15 carbon atoms. The use of the catalytic system according to the invention makes it possible to synthesize stereospecific 1,3-diene polymers, promoting the 1,4-cis or 1,4-trans insertion of the monomers depending on the nature of the solvent of the catalytic system.

[0116] Suitable 1,3-diene monomers are, in particular, 1,3-dienes having from 4 to 12 carbon atoms, such as, for example, butadiene, isoprene, 2,3-di(C1-C5 alkyl)-1,3-butadiene such as, for example, 2,3-dimethyl-1,3-butadiene, 2,3-diethyl-1,3-butadiene, 2-methyl-3-ethyl-1,3-butadiene, 2-methyl-3-isopropyl-1,3-butadiene, phenyl-1,3-butadiene, 1,3-pentadiene, etc.

[0117] Linear terpenes, such as linear monoterpenes (C10H16), such as myrcene, and linear sesquiterpenes (C15H24), such as farnesene, etc., are also suitable as 1,3-diene monomers.

[0118] According to certain embodiments of the invention, the conjugated diene monomer to be polymerized is butadiene or isoprene.

[0119] According to certain embodiments of the invention, the polymerization step of the process is a step of homopolymerization of a conjugated diene monomer in the presence of a catalytic system as described above.

[0120] According to certain embodiments of the invention, the polymerization step of the process is a step of copolymerization of at least one conjugated diene monomer in the presence of a catalytic system as described above. The conjugated diene monomer is then copolymerized with at least one other monomer. As another monomer, for example, a 1,3-diene monomer having 4 to 15 carbon atoms as defined above, different from the first 1,3-diene monomer, is suitable.

[0121] The polymerization step can be carried out in a known manner, continuously or batchwise, in bulk or in solution, generally and in a known manner at a temperature preferably of at least 40°C and preferably of at most 120°C, more preferably of at most The polymerization step can be carried out in an organic solvent conventionally used for the polymerization of diene monomers. By organic solvent, according to the invention, is meant an inert hydrocarbon solvent which can be for example an aliphatic or alicyclic hydrocarbon such as pentane, hexane, heptane, isooctane, cyclohexane, methylcyclohexane, or an aromatic hydrocarbon such as benzene, toluene, xylene, or mixtures of these solvents. It should be noted that non-aromatic solvents are particularly preferred. This is all the more so since the iron complex of formula (I) useful for the purposes of the invention is soluble in aliphatic and alicyclic solvents.

[0122] The catalytic system as described above according to all its embodiments is used for polymerization in a reaction medium comprising the monomers to be polymerized and, where appropriate, the polymerization solvent.

[0123] According to certain embodiments of the invention, the polymerization step of the process is preceded by a step of neutralizing the impurities in the reaction medium. In the context of the invention, this step can be carried out by adding a predetermined quantity of an organic aluminum compound of formula (II), independently of the introduction of the catalytic system used for the polymerization reaction. This organic aluminum compound can be identical to or different from the organic aluminum compound used as alkylating agent of the catalytic system.

[0124] It should be noted that the addition of this organic aluminium compound makes it possible to avoid impurities present in the polymerisation medium originating from the monomers or the polymerisation solvent, and not to penalise the activity of the catalytic system, so as to minimise the dispersion of the characteristics of the elastomer obtained, in particular the molecular masses.

[0125] Those skilled in the art will understand that when such a compound is added to the polymerization medium, it is added at least in amounts which depend on the degree of purity of the components of the polymerization medium, composed in particular of the solvent, if applicable, and of the monomers.

[0126] The above-mentioned characteristics of the present invention, as well as others, will be better understood upon reading the following description of several exemplary embodiments of the present invention, given for informational and non-limiting purposes.

[0127] EXAMPLES

[0128] Definition of abbreviations:

[0129] THF = tetrahydrofuran

[0130] Me = methyl

[0131] TBAr F = trityl tetrakis(pentafluorophenyl)borate

[0132] ABAr F = tetrakis(pentafluorophenyl)borate N,N-dimethylanilinium

[0133] MCH = methylcyclohexane

[0134] TiBA = tri-isobutylaluminium

[0135] DiBAH = diisobutylaluminum hydride

[0136] TEA = triethylaluminium diBHT = 2,6-di-tert-butyl-4-methylphenol

[0137] Measurements and tests used Performance:

[0138] The polymerization yield (denoted "q pol (%)") is calculated via the ratio between the mass of the polymer isolated at the end of the reaction and the mass of monomers introduced into the reactor.

[0139] [Math 1] monomers which represents the mass of monomers introduced into the reactor, m Ppolymer which represents the mass of polymer obtained.

[0140] High-resolution NMR spectroscopy

[0141] The microstructure of elastomers is characterized by high-resolution NMR spectroscopy technique.

[0142] High-resolution NMR spectroscopy of polymers was performed on a Bruker 400 Avance III spectrometer operating at 400 MHz equipped with a 5 mm BBFO probe for the proton and on a Bruker 400 Avance II spectrometer operating at 400 MHz equipped with a 10 mm PSEX 13C probe for the carbon. Acquisitions were made in a mixture of tetrachloroethylene (TCE) and deuterated chloroform (CDCU) (2 / 1 v / v) at 298 K or in chloroform. Samples were analyzed at a concentration of 1% by mass for the proton and 5% by mass for the carbon. Chemical shifts are given in ppm, relative to the proton signal of deuterated chloroform at 7.26 ppm and the carbon signal of TCE fixed at 120.65 ppm.

[0143] Measurement of the molar mass of samples

[0144] The SEC (Size Exclusion Chromatography) technique separates macromolecules in solution according to their size through columns filled with a porous gel. The macromolecules are separated according to their hydrodynamic volume, with the largest being eluted first.

[0145] Although not an absolute method, SEC allows us to understand the distribution of molar masses of a polymer. From commercial standard products, the different number-average (Mn) and weight-average (Mw) molar masses can be determined and the polymolecularity index (D = Mw / Mn) calculated.

[0146] Size exclusion chromatography analyses were performed using a Viscotek instrument (Malvern Instruments) equipped with 3 columns (SDVB, 5 μm, 300 x 7.5 mm of Polymer Standard Service), a guard column, and 3 detectors (differential refractometer and viscometer, and light scattering). 1 mL of a solution of the sample with a concentration of 5 mg mL-1 in THF was filtered through a 0.45 μm PTFE membrane. 100 pL of this solution was eluted in THF using a flow rate of 0.8 mL min-1 at a temperature of 35 °C. OmniSEC software was used for data acquisition and analysis. The number (Mn) and mass (Mw) molar masses of the polymers as well as their dispersity (D) were calculated using a calibration curve from standard polystyrenes (Mw: 1,306 to 2,520,000 g mol-1) from Polymer Standard Service (Mainz).

[0147] 1. Synthesis of iron(ll) bisamide compound: Iron bis(trimethylsilyl)amide of formula Fe N SiMeahh is synthesized according to the procedure described by Andersen, RA; Faegri, K.; Green, JC; Haaland, A.; Lappert, MF; Leung, W.

[0148] P.; Rypdal, K. Inorg. Chem. 1988, Tl (10), 1782-1786.

[0149] In the following synthetic methods, equivalents are expressed as the molar ratio of the given reactant to the prepared iron(ll) bisamide compound.

[0150] 2. Activation of iron complex and butadiene polymerization process:

[0151] Iron (II) bis[N,N-bis(trimethylsilyl)amide] stored in a glove box is weighed (40 mg, 0.108 mmol) in a Schlenk. The cationizing agent: trityl tetrakis(pentafluorophenyl)borate (TBAr F ), or N,N-dimethylaniline tetrakis(pentafluorophenyl)borate (ABA F) where appropriate, is added according to the proportions shown in Table 1 (for example for 1 eq. or 0.108 mmol: 99.6 mg TBAr F and 86.5 mg ABA F ). A volume of a dry solvent, as indicated in Table 1, is added.

[0152] Independently, 0.81 mL of an alkylaluminum solution (triisobutyl aluminum, 1.33 M, 10 eq. or diisobutylaluminum hydride 1.51 M, 10 eq.) in methylcyclohexane (MCH) is mixed with 100 mL of MCH. This mixture is introduced into an inerted reactor. The mixture is vigorously stirred for 10 min. The reactor is then placed under reduced pressure using a vane pump before adding 30 mL of butadiene (361.84 mmol, 3350 eq.) which are previously condensed in a funnel after passing through an alumina trap, then evaporated to the reactor. Once the monomer introduction is complete, the reactor is heated to 60 °C.

[0153] The solution of iron complex and cationizing agent, pre-activated after 2 hours of stirring, is introduced into the reactor. Once the catalyst is introduced, the polymerization lasts 1 to 4 hours at 60°C.

[0154] At the end of the reaction, the reaction medium is precipitated in a solution of diBHT in methanol. The polymer is then dried and stored at 4°C.

[0155] The summary of the tests and the analysis of the polybutadienes obtained are reported in Table 1.

[0156] Table 1 molar ratio [AI] / [Fe]= 10;

[0157] Monomer M= butadiene, 30 mL, 361 mmol, molar ratio [M] / [Fe]= 3350;

[0158] Cationizing agent = [CPha] [B(CsF5)4] (TBAr F ) or [HNPhMezjtB CgFsh] (ABAr F );

[0159] Polymerization temperature = 60°C n pol = polymerization yield tr = reaction time nd* = not defined, the polymer cannot be solubilized for measurement

[0160] 3. Activation of the iron complex and Isoprene polymerization process: The iron (II) bis[N,N-bis(trimethylsilyl)amide] stored in a glove box is weighed (20 mg, 0.054 mmol) in a Schlenk, it is solubilized in MCH (25 mL), likewise, 1 equivalent of TBAr F (50 mg, 0.054 mmol) is solubilized in toluene (7 mL). Both solutions are added to 27 mL of isoprene (18.4 g, 5000 eq). After a few seconds, an alkyl aluminum solution is added (TiBA, 0.59 mL, 0.91 M, 10 eq. or TEA 0.54 mL, 1 M, 10 eq.). The mixture is then stirred until the temperature indicated in Table 2, the reaction lasts 4 hours.

[0161] At the end of the reaction, the reaction medium is precipitated in a solution of diBHT in methanol. The polymer is then dried and stored at 4°C.

[0162] [Table 2]

Claims

CLAIMS 1. Use of an iron complex of formula (I) Fe(N(R)2)2(I) in which the symbols R, which may be identical or different, represent a hydrogen atom, a linear or branched C1-C20 aliphatic radical, substituted or not, a cycloaliphatic C3-C20 radical, substituted or not, an aromatic C6-C20 radical, substituted or not, or a silyl radical of formula -Si(R')3 in which the symbols R', which may be identical or different, represent a hydrogen atom, a linear or branched C1-C20 aliphatic radical, substituted or not, a cycloaliphatic C3-C20 radical, substituted or not, or an aromatic C6-C20 radical, substituted or not, for the polymerization of conjugated dienes.

2. Use according to claim 1 in which the symbols R, identical or different, represent a silyl radical of formula -Si(R')3 in which the symbols R', identical or different, represent a C1-C10 alkyl radical, preferably a C1-C4 alkyl radical.

3. Catalytic system for the polymerization of conjugated dienes comprising: an iron complex of formula (I) Fe(N(R)2)2(I) a solvent, a cationizing agent, and an alkylating agent, in formula (I), the symbols R, identical or different, represent a hydrogen atom, a linear or branched C1-C20 aliphatic radical, substituted or not, a cycloaliphatic radical Cs-C2o, substituted or not, an aromatic radical Ce-C2o, substituted or not, or a silyl radical of formula -Si(R')3 in which the symbols R', identical or different, represent a hydrogen atom, a linear or branched C1-C20 aliphatic radical, substituted or not, a cycloaliphatic radical Cs-C2o, substituted or not, or an aromatic radical Ce-C2o, substituted or not.

4. Catalytic system according to claim 3 in which the symbols R, identical or different, represent a silyl radical of formula -Si(R')3 in which the symbols R', identical or different, represent a C1-C10 alkyl radical, preferably a C1-C4 alkyl radical, preferably a methyl radical.

5. Catalytic system according to claim 3 or 4 wherein the solvent is an aliphatic apolar solvent, an aromatic apolar solvent, or a mixture of an aliphatic apolar solvent and an aromatic apolar solvent.

6. Catalytic system according to any one of claims 3 to 5 in which the solvent is an aromatic apolar solvent, preferably toluene.

7. Catalytic system according to any one of claims 3 to 5 in which the solvent is a polar aprotic solvent chosen from ethers and amines and their mixtures, preferably the polar aprotic solvent is chosen from ethers.

8. Catalytic system according to any one of claims 3 to 7 in which the alkylating agent is chosen from aluminum alkyls represented by the following formula (II): (Ra) m AI (ORb)n HpX q , (II) in which: - Ra and Rb are identical or different and each represent a hydrocarbon group of 1 to 15 carbon atoms, preferably a hydrocarbon group of 1 to 4 carbon atoms; - X is a halogen atom; and - m', n', p' and q' are numbers satisfying the following conditions: 0 <m’ 3, 0 s n' <3, 0 s p' <3, 0 s q' <3 and m' + n' + p' + q' = 3.

9. Catalytic system according to any one of claims 3 to 8 in which the alkylating agent is chosen from trialkylaluminiums of formula AI(Ci-Cio-alkyl)3, and dialkylaluminium hydrides of formula (AI(Ci-C -alkyl)2H).

10. Catalytic system according to any one of claims 3 to 9 in which the molar ratio of (alkylating agent / iron complex of formula (I)) is greater than or equal to 5 / 1.

11. Catalytic system according to any one of claims 3 to 10 in which the cationizing agent is chosen from the compounds represented by formula (III): [Q] + [B(Ri)4]' (III), in which - [Q] + is a proton, a carbonium cation or one of its substituted derivatives (primary, secondary or tertiary carbocation), an ammonium cation or one of its substituted derivatives (primary, secondary, tertiary, quaternary ammonium), an oxonium cation or one of its substituted derivatives, a phosphonium cation, a cycloheptyltrienyl cation, a metallocenium cation of a transition metal. - B is the symbol for boron - each Ri represents, independently of one another, a linear or branched C1-C20 aliphatic radical, substituted or not, a C3-C20 cycloaliphatic radical, substituted or not, or a C6-C20 aromatic radical, substituted or not.

12. A catalytic system according to any one of claims 3 to 11 wherein the cationizing agent is a trialkyl-substituted ammonium salt, an N,N-dialkylanilinium salt, a dialkylammonium salt or a tri-substituted carbonium salt, preferably the cationizing agent is dimethylanilinium tetrakis(pentafluorophenyl) borate or trityl tetrakis(pentafluorophenyl) borate.

13. Catalytic system according to any one of claims 3 to 12 in which the molar ratio of (cationizing agent / iron complex of formula (I)) is less than or equal to 2 / 1.

14. Process for the synthesis of a diene polymer comprising the polymerization reaction of at least one conjugated diene monomer, preferably a 1,3-diene monomer, in the presence of a catalytic system as defined in any one of claims 3 to 13.

15. The method of claim 14 wherein the conjugated diene monomer is butadiene, isoprene or a mixture of butadiene and isoprene.

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