PROCESS FOR THE PREPARATION OF SYNDIOTACTIC 1,2-POLYBUTADIENE IN THE PRESENCE OF A CATALYTIC SYSTEM COMPRISING A PYRIDYL IRON COMPLEX

Abstract

Process for the preparation of syndiotactic 1,2-polybutadiene comprising polymerising 1,3-butadiene in the presence of a catalytic system comprising: at least one pyridyl iron complex having the general formula (I), in which: R.sub.1 represents a hydrogen atom; or a methyl group; R.sub.2 represents a hydrogen atom; or is selected from linear or branched C.sub.1-C.sub.10, preferably C.sub.1-C.sub.3, alkyl groups; X, identical or different to one another, represent a halogen atom such as, for example, chlorine, bromine, iodine; or are selected from linear or branched, C.sub.1-C.sub.20, preferably C.sub.1-C.sub.15, alkyl groups, OCOR.sub.3 groups or OR.sub.3 groups in which R.sub.3 is selected from linear or branched C.sub.1-C.sub.20, preferably C.sub.1-C.sub.15, alkyl groups; n is 2 or 3; at least one aluminoxane having the general formula (II), (R.sub.4).sub.2-AI-O-[-AI(R.sub.5)O-].sub.m-AI-(R.sub.6).sub.2 (ll) in which R.sub.4, R.sub.5 and R.sub.6, identical or different to one another, represent a hydrogen atom, or a halogen atom such as, for example, chlorine, bromine, iodine, fluorine; or are selected from linear or branched C.sub.1-C.sub.20 alkyl groups, cycloalkyi groups, aryl groups, said groups being optionally substituted with one or more silicon atoms or germanium; and m is an integer ranging from 0 to 1000; in which the molar ratio between the aluminium present in the aluminoxane having the general formula (II) and the iron present in the pyridyl iron complex having the general formula (I) is ranging from 5 to 20, preferably ranging from 8 to 12.

##STR00001##

Claims

1. Process for the preparation of syndiotactic 1,2-polybutadiene comprising polymerising 1,3-butadiene in the presence of a catalytic system comprising: at least one pyridyl iron complex having the general formula (I): ##STR00013## in which: R.sub.1 represents a hydrogen atom; or a methyl group; R.sub.2 represents a hydrogen atom; or is selected from linear or branched C.sub.1-C.sub.10 alkyl groups; X, identical or different to one another, represent a halogen atom; or are selected from linear or branched, C.sub.1-C.sub.20 alkyl groups, OCOR.sub.3 groups or OR.sub.3 groups in which R.sub.3 is selected from linear or branched C.sub.1-C.sub.20 alkyl groups; n is 2 or 3; at least one aluminoxane having the general formula (II):
(R.sub.4).sub.2AlO[Al(R.sub.5)O].sub.mAl(R.sub.6).sub.2(II) in which R.sub.4, R.sub.5 and R.sub.6, identical or different to one another, represent a hydrogen atom, or a halogen atom; or are selected from linear or branched C.sub.1-C.sub.20 alkyl groups, cycloalkyl groups, aryl groups, said groups being optionally substituted with one or more silicon atoms or germanium; and m is an integer ranging from 0 to 1000; in which the molar ratio between the aluminium present in the aluminoxane having the general formula (II) and the iron present in the pyridyl iron complex having the general formula (I) is ranging from 5 to 20.

2. Process for the preparation of syndiotactic 1,2-polybutadiene according to claim 1, in which in said pyridyl iron complex having the general formula (I): R.sub.1 represents a hydrogen atom; or a methyl group; R.sub.2 represents a hydrogen atom; or a methyl group, an ethyl group, an n-propyl group, an iso-propyl group; X, identical to one another, represent a halogen atom selected from chlorine, bromine, iodine; n is 2 or 3.

3. Process for the preparation of syndiotactic 1,2-polybutadiene according to claim 1, in which said aluminoxane having the general formula (II) is selected from: methylaluminoxane (MAO), ethylaluminoxane, n-butylaluminoxane, tetra-iso-butylaluminoxane (TIBAO), tert-butylaluminoxane, tetra-(2,4,4-trimethylpentyl)aluminoxane (TIOAO), tetra-(2,3-dimethylbutyl)aluminoxane (TDMBAO), tetra-(2,3,3-trimethylbutyl)aluminoxane (TTMBAO), or mixtures thereof.

4. Process for the preparation of syndiotactic 1,2-polybutadiene according to claim 1 in which: said process is carried out in the presence of at least one inert organic solvent selected from: saturated aliphatic hydrocarbons selected from butane, pentane, hexane, heptane, or mixtures thereof; saturated cycloaliphatic hydrocarbons selected from cyclopentane, cyclohexane, or mixtures thereof; mono-olefins selected from 1-butene, 2-butene, or mixtures thereof; aromatic hydrocarbons selected from benzene, toluene, xylene, or mixtures thereof; halogenated hydrocarbons selected from methylene chloride, chloroform, carbon tetrachloride, trichloroethylene, perchloroethylene, 1,2-dichloroethane, chlorobenzene, bromobenzene, chlorotoluene, or mixtures thereof; and/or in said process the concentration of 1,3-butadiene in said inert organic solvent is ranging from 5% by weight to 50% by weight, based on the total weight of the 1,3-butadiene/inert organic solvent mixture; and/or said process is carried out at a temperature ranging from 30 C. to +60 C.

5. Shoe soles comprising the syndiotactic 1,2-polybutadiene obtained by the process according to claim 1.

6. Process for the preparation of syndiotactic 1,2-polybutadiene according to claim 1, in which in said pyridyl iron complex having the general formula (I): R.sub.1 represents a hydrogen atom; or a methyl group; R.sub.2 represents a hydrogen atom; or a methyl group or an iso-propyl group; X, identical to one another, represent a chlorine atom; n is 2 or 3.

Description

EXAMPLES

Reactants and Materials

[0073] The following list shows the reactants and materials used in the subsequent examples of the invention, any optional pretreatments and the manufacturers thereof: [0074] iron powder (Fe) (Aldrich): purity 99%, used as such; [0075] iron trichloride (FeCl.sub.3) (Aldrich): purity 99.9%, used as such; [0076] iron dichloride (FeCl.sub.2) (Aldrich): purity 97%, used as such; [0077] iron dichloride:tetrahydrofuran complex (1:1.9) [FeCl.sub.2(THF).sub.1.9]: prepared from iron powder (Fe) and iron trichloride (FeCl.sub.3), in tetrahydrofuran (THF) with heat, according to the method reported by Cotton F. A. et al., in Inorganic Chimica Acta (1991), vol. 179, pp. 11-15; [0078] methylaluminoxane (MAO) (10% by weight solution in toluene) (Crompton): used as such; [0079] aniline (Aldrich): distilled under reduced pressure and stored under an inert atmosphere; [0080] hydrochloric acid, 37% aqueous solution (Aldrich): used as such; [0081] o-toluidine (Aldrich): distilled under reduced pressure and stored under an inert atmosphere; 2-iso-propylaniline (Aldrich): used as such; [0082] 2-pyridinecarboxaldehyde (Aldrich): used as such; 2-acetylpyridine (Aldrich): used as such; [0083] ethyl acetate (Aldrich): used as such; [0084] p-toluenesulfonic acid monohydrate (Aldrich): 98.5%, used as such; [0085] heptane (Aldrich): pure, 99%, distilled over sodium (Na) under an inert atmosphere; [0086] pentane (Aldrich): pure, 99%, distilled over sodium (Na) under an inert atmosphere; [0087] methanol (Carlo Erba, RPE): used as such; [0088] toluene (Aldrich): pure, 99.5%, distilled over sodium (Na) under an inert atmosphere; [0089] cobalt dichloride (CoCl.sub.2) (Strem Chemicals): used as such; di-triphenylphosphine (Strem Chemicals): used as such; [0090] ethanol (Carlo Erba, RPE): used as such; 1,3-butadiene (Air Liquide): pure, 99.5%, evaporated from the container before each production, dried by being passed through a column packed with molecular sieves and condensed inside the reactor which has been pre-cooled to 20 C.; [0091] formic acid (HCOOH) (Aldrich): purity 95%, used as such; [0092] hydrochloric acid (HF) (40% aqueous solution) (Aldrich): used as such; [0093] sulfuric acid (H.sub.2SO.sub.4) (96% aqueous solution) (Aldrich): used as such, or diluted with distilled water (1:5); [0094] nitric acid (HNO.sub.3) (70% aqueous solution) (Aldrich): used as such; [0095] sodium carbonate (Na.sub.2CO.sub.3) (Aldrich): used as such; [0096] silver nitrate (AgNO.sub.3) (Aldrich): used as such; [0097] deuterated tetrachloroethylene (C.sub.2D2Cl.sub.4) (Acros): used as such; [0098] hexamethyldisiloxane (HMDS) (Acros): used as such; [0099] deuterated chloroform (CDCl.sub.3) (Acros): used as such; tetramethylsilane (TMS) (Acros): used as such.

[0100] The analysis and characterisation methods stated below were used.

Elemental Analysis

a) Determination of Fe

[0101] The quantity by weight of iron (Fe) in the pyridyl iron complexes used for the purpose of the present invention was determined by placing an accurately weighed aliquot, working in a dry box under a stream of nitrogen, of approx. 30 mg-50 mg of sample in an approx. 30 ml platinum crucible, together with a mixture of 1 ml of 40% hydrofluoric acid (HF), 0.25 ml of 96% sulfuric acid (H.sub.2SO.sub.4) and 1 ml of 70% nitric acid (HNO.sub.3). The crucible was then heated on a plate, increasing the temperature until white sulfuric fumes appeared (approx. 200 C.). The mixture obtained was cooled to room temperature, 1 ml of 70% nitric acid (HNO.sub.3) was added and then heated again until fumes appeared. Once the sequence had been repeated twice, a clear, almost colourless solution was obtained. 1 ml of nitric acid (HNO.sub.3) and approx. 15 ml of water were then added cold and the temperature was raised to 80 C. for approx. 30 minutes. The sample so prepared was diluted with MilliQ purity water to an accurately weighed weight of approx. 50 g, in order to obtain a solution on which an instrumental analytical determination was performed by means of a Thermo Optek IRIS Advantage Duo ICP-OES spectrometer (plasma with optical detection) by comparison with solutions of known concentration. For this purpose, a calibration curve in the range from 0 ppm-10 ppm was prepared for each analyte by measuring solutions of known titre obtained by weight dilution of certified solutions.

[0102] The solution of the sample prepared as above was again weight-diluted in such a manner as to obtain concentrations close to the reference concentrations prior to carrying out spectrophotometric detection. All samples were prepared in duplicate. The results were considered acceptable if the individual results of the duplicate tests differed by no more than 2% relative with respect to the mean value thereof.

b) Determination of Chlorine

[0103] To this end, approx. 30 mg-50 mg samples of the pyridyl iron complexes used for the purpose of the present invention were accurately weighed into 100 ml glass beakers in a dry box under a stream of nitrogen. 2 g of sodium carbonate (Na.sub.2CO.sub.3) were added and, outside the dry box, 50 ml of MilliQ water. The mixture was brought to the boil on a plate and stirred with a magnetic stirrer for approx. 30 minutes. The mixture was left to cool, sulfuric acid (H.sub.2SO.sub.4) diluted to 1:5 was added until an acidic reaction was obtained and titration was performed with 0.1 N silver nitrate (AgNO.sub.3) with a potentiometric titrator.

c) Determination of Carbon, Hydrogen, Nitrogen and Phosphorus

[0104] Carbon, hydrogen and nitrogen were determined in the pyridyl iron complexes used for the purpose of the present invention, and in the ligands used for the purpose of the present invention, using a Carlo Erba model 1106 automatic analyser.

.sup.13C-HMR and .sup.1H-HMR Spectra

[0105] The .sup.13C-HMR and .sup.1H-HMR spectra were recorded with a Bruker Avance 400 nuclear magnetic resonance spectrometer using deuterated tetrachloroethylene (C.sub.2D2Cl.sub.4) at 103 C. and hexamethyldisiloxane (HDMS) as internal standard, or using deuterated chloroform (CDCl.sub.3) at 25 C. and tetramethylsilane (TMS) as internal standard. Polymer solutions having concentrations of 10% by weight based on the total weight of the polymer solution were used for this purpose.

[0106] The microstructure of the polymers [i.e. content of 1,4-cis (%) and 1,2(%) units and content of syndiotactic triads (rr %)] was determined by analysing the above-stated spectra on the basis the description in the literature by Mochel, V. D., in Journal of Polymer Science Part A-1: Polymer Chemistry (1972), vol. 10, issue 4, pp. 1009-1018.

FT-IR Spectra (Solid State, UATR)

[0107] The FT-IR spectra (solid state, UATR) were recorded by means of a Bruker IFS 48 spectrophotometer equipped with a Thermo Spectra-Tech horizontal ATR attachment. The section in which the samples are placed for analysis is a Fresnel ATR accessory (Shelton, Conn., USA) which uses zirconium selenide crystals (ZnSe) with an angle of incidence of 45 in the horizontal direction.

[0108] The FT-IR spectra (solid state, UATR) of the pyridyl iron complexes used for the purpose of the present invention were obtained by inserting samples of the pyridyl iron complex for analysis into said section.

IR Spectra

[0109] The IR (FTIR) spectra were recorded by means of Thermo Nicolet Nexus 670 and Bruker IFS 48 spectrophotometers.

[0110] The IR (FTIR) spectra of the polymers were obtained from polymer films on potassium bromide (KBr) pellets, said films being obtained by deposition of a solution of the polymer for analysis in hot 1,2-dichlorobenzene. The concentration of the analysed polymer solutions was 10% by weight based on the total weight of the polymer solution.

Determination of Molecular Weight

[0111] The molecular weight (MW) of the polymers obtained was determined by GPC (Gel Permeation Chromatography) using a Waters Alliance GPCN 2000 System from Waters Corporation which uses two detection lines: refractive index (RI) and viscometer working under the following conditions: [0112] two PLgel Mixed-B columns; [0113] solvent/eluent: o-dichlorobenzene (Aldrich); [0114] flow rate: 0.8 ml/min; [0115] temperature: 145 C.; [0116] calculation of molecular mass: Universal Calibration method.

[0117] The weight-average molecular weight (M.sub.w) and polydispersity index (PDI) corresponding to the ratio M.sub.w/M.sub.n (M.sub.n=number-average molecular weight) are reported.

X-Ray Diffractometry (XRD) X-Ray Spectrum

[0118] To this end, samples of the polymers obtained in powder form (approx. 100 mg), were analysed by X-ray diffractometry (XRD) using a Bruker P4 diffractometer equipped with a HiStar 2D detector using graphite-monochromatised Cu KR radiation () (1.54179 ) and a sample-detector distance of 10 cm.

Thermal Analysis (DSC)

[0119] DSC (Differential Scanning Calorimetry) thermal analysis for the purpose of determining the melting point (T.sub.m) and crystallisation temperature (T.sub.a) of the polymers obtained was carried out using a Perkin Elmer Pyris differential scanning calorimeter. To this end, 5 mg of polymer were analysed at a scanning speed ranging from 1 C./min to 20 C./min under an inert nitrogen atmosphere.

Example 1

Synthesis of the Ligand Having the Formula (L1)

[0120] ##STR00004##

[0121] 2-Pyridinecarboxaldehyde (30 g; 280 mmol) and a few drops of formic acid were added to a solution of aniline (26.1 g; 280 mmol) in methanol (250 ml), in a 500 ml reaction flask: the mixture obtained was left to stand, under stirring, at room temperature, for 48 hours. The solvent was then removed by vacuum evaporation and the residue obtained was purified by elution on a silica gel chromatographic column [eluent: 99/1 (vol/vol) heptane/ethyl acetate mixture], 38 g of a pale yellow solid (yield=74.5%) corresponding to the ligand having the formula (L1), being obtained.

[0122] Molecular weight (MW): 182.22.

[0123] Elemental analysis [found (calculated for C.sub.12H.sub.10N.sub.2)]: C: 80.00% (79.10%); H: 5.83% (5.53%); N: 15.71% (15.37%).

[0124] .sup.1H-NMR (CDCl.sub.3, ppm) 8.70 (m, 1H, HPy), 8.41 (m, 1H, HPy), 8.80 (tds, 1H CHN), 8.19 (d, 1H, HPy), 7.77 (dt, 1H, HPy), 7.23-7.42 (m, 1H, HPy; m, 5H, Ar).

Example 2

Synthesis of the Ligand Having the Formula (L2)

[0125] ##STR00005##

[0126] 2-Acetylpyridine (9.1 g; 75 mmol) and a few drops of formic acid were added to a solution of o-toluidine (8 g; 75 mmol) in methanol (100 ml), in a 250 ml reaction flask: the mixture obtained was left to stand, under stirring, at room temperature, for 48 hours. The solvent was then removed by vacuum evaporation and the residue obtained was purified by elution on a silica gel chromatographic column [eluent: 99/1 (vol/vol) heptane/ethyl acetate mixture], 6.5 g of a yellowish oil (yield=40%) corresponding to the ligand having the formula (L2), being obtained.

[0127] Molecular weight (MW): 210.28.

[0128] Elemental analysis [found (calculated for C.sub.14H.sub.14N.sub.2)]: C: 80.00% (79.97%); H: 6.77% (6.71%); N: 13.41% (13.32%).

[0129] .sup.1H-NMR (CDCl.sub.3, ppm): 8.70 (m, 1H, HPy), 8.41 (m, 1H, HPy), 8.80 (td, 1H, HPy), 7.39 (dt, 1H, HPy), 7.27-7.18 (m, 2H, Ph), 7.02 (m, 1H, Ph), 6.69 (d, 1H, Ph), 2.30 (s, 3H, NCCH.sub.3), 2.10 (s, 3H, Ph-CH.sub.3).

Example 3

Synthesis of the Ligand Having the Formula (L3)

[0130] ##STR00006##

[0131] 2-Acetylpyridine (3.78 g; 31.1 mmol) and p-toluenesulfonic acid monohydrate (0.15 g; 0.81 mmol) were added to a solution of 2-iso-propylaniline (4.20 g; 31.1 mmol) in toluene (20 ml), in a 500 ml reaction flask: the mixture obtained was refluxed for 2 hours. The solvent was then removed by vacuum evaporation and the residue obtained was purified by distillation under vacuum, 5.89 g of an orange oil (yield=79%), corresponding to the ligand having the formula (L3), being obtained.

[0132] FT-IR (Nujol): (cm.sup.1): 1637 (v.sub.C=N).

[0133] Molecular weight (MW): 238.

[0134] Elemental analysis [found (calculated for C.sub.16H.sub.18N.sub.2)]: C: 80.17% (80.63%); H: 7.80% (7.61%); N: 11.91% (11.75%).

[0135] FT-IR (solid state, UATR) (cm.sup.1): 1637 (v.sub.C=N).

[0136] .sup.1H-NMR (CDCl.sub.3, ppm) 8.71 (d, 1H), 8.37 (d, 1H), 7.81 (t, 1H), 7.38 (m, 2H), 7.22 (t, 1H), 7.15 (t, 1H), 6.67 (d, 1H), 3.05 (sept, 1H), 2.39 (s, 3H), 1.23 (d, 6H).

Example 4

Synthesis of FeCl.SUB.2.(L1) [Sample MG82A]

[0137] ##STR00007##

[0138] The iron dichloride:tetrahydrofuran (1:1.9) complex [FeCl.sub.2(THF).sub.1.9] (171 mg; 0.65 mmol) was added to a solution of the ligand having the formula (L1) (118 mg; 0.65 mmol; molar ratio L1/Fe=1), obtained as described in Example 1, in toluene (20 ml) in a 100 ml reaction flask: the mixture obtained was left to stand, under stirring, at 100 C., for 3 hours. The supernatant was then removed by evaporation under reduced pressure and the residue obtained was washed with heptane (215 ml) and dried under vacuum, at room temperature, 156 mg of a blue solid product corresponding to the FeCl.sub.2(L1) complex being obtained, this amounting to conversion of 78% based on the introduced iron dichloride:tetrahydrofuran (1:1.9) complex [FeCl.sub.2(THF).sub.1.9].

[0139] Molecular weight (MW): 308.97.

[0140] Elemental analysis [found (calculated for C.sub.12H.sub.10Cl.sub.2FeN.sub.2)]: C: 46.01% (46.65%), H: 3.02% (3.26%), N: 9.58% (9.07%), Cl: 22.03% (22.95%), Fe: 16.05% (16.89%).

[0141] FIG. 1 shows the FT-IR spectrum (solid state, UATR) of the FeCl.sub.2(L1) complex obtained.

Example 5

[0142] Synthesis of FeCl.sub.2(L2) [sample MG215]

##STR00008##

[0143] Iron dichloride (FeCl.sub.2) (319 mg; 2.51 mmol) was added to a solution of the ligand having the formula (L2) (527 mg; 2.51 mmol; molar ratio L2/Fe=1), obtained as described in Example 2, in toluene (20 ml), in a 100 ml reaction flask: the mixture obtained was left to stand, under stirring, at 100 C., for 3 hours. The supernatant was then removed by evaporation under reduced pressure and the residue obtained was washed with heptane (215 ml) and dried under vacuum, at room temperature, 521 mg of a pale blue solid product corresponding to the FeCl.sub.2(L2) complex being obtained, this amounting to conversion of 62% based on the introduced iron dichloride (FeCl.sub.2).

[0144] Molecular weight (MW): 337.03

[0145] Elemental analysis [found (calculated for C.sub.14H.sub.14C.sub.12FeN.sub.2)]: C: 49.10% (49.89%), H: 4.38% (4.19%), N: 8.21% (8.31%), Cl: 21.42% (21.04%), Fe: 16.82% (16.57%).

[0146] FT-IR (Nujol) (cm.sup.1): 1628 (v.sub.C=N).

[0147] FIG. 2 shows the FT-IR spectrum (solid state, UATR) of the FeCl.sub.2(L2) complex obtained.

Example 6

Synthesis of FeCl.SUB.2.(L3) [Sample MG212]

[0148] ##STR00009##

[0149] Iron trichloride (FeCl.sub.2) (288 mg; 2.27 mmol) was added to a solution of the ligand having the formula (L3) (540 mg; 2.27 mmol; molar ratio L3/Fe=1), obtained as described in Example 3, in toluene (20 ml), in a 100 ml reaction flask: the mixture obtained was left to stand, under stirring, at 100 C., for 3 hours. The supernatant was then removed by evaporation under reduced pressure and the residue obtained was washed with heptane (215 ml) and dried under vacuum, at room temperature, 665 mg of a pale blue solid product corresponding to the FeCl.sub.2(L3) complex being obtained, this amounting to conversion of 80% based on the introduced iron trichloride (FeCl.sub.2).

[0150] Molecular weight (MW): 3665.08.

[0151] Elemental analysis [found (calculated for C.sub.16H.sub.18C.sub.12FeN.sub.2)]: C: 52.12% (52.64%), H: 4.65% (4.96%), N: 7.26% (7.67%), Cl: 19.02% (19.42%), Fe: 15.04% (15.30%).

[0152] FIG. 3 shows the FT-IR spectrum (solid state, UATR) of the FeCl.sub.3(L1) complex obtained.

Example 7

Synthesis of FeCl.SUB.3.(L1) [Sample MG87]

[0153] ##STR00010##

[0154] Iron trichloride (FeCl.sub.3) (225 mg; 1.39 mmol) was added to a solution of the ligand having the formula (L1) (253 mg; 1.39 mmol; molar ratio L1/Fe=1), obtained as described in Example 1, in toluene (20 ml), in a 100 ml reaction flask: the mixture obtained was left to stand, under stirring, at room temperature, for 3 hours. The supernatant was then removed by evaporation under reduced pressure and the residue obtained was washed with heptane (215 ml) and dried under vacuum, at room temperature, 203 mg of a brown solid product corresponding to the FeCl.sub.3(L1) complex being obtained, this amounting to conversion of 42% based on the introduced iron trichloride (FeCl.sub.3).

[0155] Molecular weight (MW): 344.43.

[0156] Elemental analysis [found (calculated for C.sub.12H.sub.10Cl.sub.3FeN.sub.2)]: C: 41.20% (41.84%), H: 2.35% (2.92%), N: 7.88% (8.13%), Cl: 31.25% (30.88%), Fe: 15.84% (16.21%).

[0157] FIG. 4 shows the FT-IR spectrum (solid state, UATR) of the FeCl.sub.3(L1) complex obtained.

Example 8

Synthesis of FeCl.SUB.3.(L2) [Sample MG213]

[0158] ##STR00011##

[0159] Iron trichloride (FeCl.sub.3) (225 mg; 1.39 mmol) was added to a solution of the ligand having the formula (L2) (293 mg; 1.39 mmol; molar ratio L2/Fe=1), obtained as described in Example 2, in toluene (20 ml), in a 100 ml reaction flask: the mixture obtained was left to stand, under stirring, at room temperature, for 3 hours. The supernatant was then removed by evaporation under reduced pressure and the residue obtained was washed with heptane (215 ml) and dried under vacuum, at room temperature, 396 mg of a brown solid product corresponding to the FeCl.sub.3(L2) complex being obtained, this amounting to conversion of 76% based on the introduced iron trichloride (FeCl.sub.3).

[0160] Molecular weight (MW): 372.48.

[0161] Elemental analysis [found (calculated for C.sub.14H.sub.14Cl.sub.3FeN.sub.2)]: C: 45.00% (45.14%), H: 3.69% (3.79%), N: 7.69% (7.52%), Cl: 28.96% (28.55%), Fe: 15.09% (14.99%).

[0162] FIG. 5 shows the FT-IR spectrum (solid state, UATR) of the FeCl.sub.3(L2) complex obtained.

Example 9

Synthesis of FeCl.SUB.3.(L3) [Sample MG208]

[0163] ##STR00012##

[0164] Iron trichloride (FeCl.sub.3) (350 mg; 2.16 mmol) was added to a solution of the ligand having the formula (L3) (514 mg; 2.16 mmol; molar ratio L3/Fe=1), obtained as described in Example 3, in toluene (20 ml), in a 100 ml reaction flask: the mixture obtained was left to stand, under stirring, at room temperature, for 3 hours. The supernatant was then removed by evaporation under reduced pressure and the residue obtained was washed with heptane (215 ml) and dried under vacuum, at room temperature, 821 mg of a red solid product corresponding to the FeCl.sub.3(L3) complex being obtained, this amounting to conversion of 95% based on the introduced iron trichloride (FeCl.sub.3).

[0165] Molecular weight (MW): 400.35.

[0166] Elemental analysis [found (calculated for C.sub.16H.sub.18Cl.sub.3FeN.sub.2)]: C: 48.09% (47.97%), H: 4.71% (4.53%), N: 6.65% (6.99%), Cl: 25.96% (26.55%), Fe: 14.08% (13.94%).

[0167] FIG. 6 shows the FT-IR spectrum (solid state, UATR) of the FeCl.sub.3(L3) complex obtained.

Example 10 (G1525)

[0168] 2 ml of 1,3-butadiene, equal to approx. 1.4 g, were condensed at low temperature (20 C.) in a 25 ml tube. 14.4 ml of toluene were then added and the temperature of the solution obtained in this manner was adjusted to +20 C. Methylaluminoxane (MAO) in a solution in toluene (0.063 ml; 110.sup.4 moles, equal to approx. 5.8 g) was then added, followed by the complex FeCl.sub.2(L1) [sample MG82A] (1.54 ml of suspension in toluene at a concentration of 2 mg/ml; 110.sup.5 moles, equal to approx. 3.08 mg) obtained as described in Example 3. The whole was left to stand, under magnetic stirring, at +20 C., for 45 minutes. Polymerisation was then quenched by adding 2 ml of methanol containing a few drops of hydrochloric acid. The polymer obtained was then coagulated by adding 40 ml of a methanolic solution containing 4% Irganox 1076 (Ciba) antioxidant, 1.4 g of syndiotactic 1,2-polybutadiene being obtained: further characteristics of the process and of the syndiotactic 1,2-polybutadiene obtained are shown in Table 1.

[0169] FIG. 7 shows the FT-IR spectrum of the syndiotactic 1,2-polybutadiene obtained.

[0170] FIG. 8 shows the .sup.1H-NMR (top) and .sup.13C-NMR (bottom) spectra of the syndiotactic 1,2-polybutadiene obtained.

[0171] FIG. 9 shows the DSC curve of the syndiotactic 1,2-polybutadiene obtained.

[0172] FIG. 10 shows the X-ray spectrum of the syndiotactic 1,2-polybutadiene obtained.

Example 11 (G1524)

[0173] 2 ml of 1,3-butadiene, equal to approx. 1.4 g, were condensed at low temperature (20 C.) in a 25 ml tube. 14.25 ml of toluene were then added and the temperature of the solution obtained in this manner was adjusted to +20 C. Methylaluminoxane (MAO) in a solution in toluene (0.063 ml; 110.sup.4 moles, equal to approx. 5.8 g) was then added, followed by the complex FeCl.sub.2(L2) [sample MG215] (1.69 ml of suspension in toluene at a concentration of 2 mg/ml; 110.sup.5 moles, equal to approx. 3.38 mg) obtained as described in Example 4. The whole was left to stand, under magnetic stirring, at +20 C., for 45 minutes. Polymerisation was then quenched by adding 2 ml of methanol containing a few drops of hydrochloric acid. The polymer obtained was then coagulated by adding 40 ml of a methanolic solution containing 4% Irganox 1076 (Ciba) antioxidant, 1.4 g of syndiotactic 1,2-polybutadiene being obtained: further characteristics of the process and of the syndiotactic 1,2-polybutadiene obtained are shown in Table 1.

[0174] FIG. 11 shows the FT-IR spectrum of the syndiotactic 1,2-polybutadiene obtained.

[0175] FIG. 12 shows the DSC curve of the syndiotactic 1,2-polybutadiene obtained.

[0176] FIG. 13 shows the X-ray spectrum of the syndiotactic 1,2-polybutadiene obtained.

Example 12 (IP200/1)

[0177] 2 ml of 1,3-butadiene, equal to approx. 1.4 g, were condensed at low temperature (20 C.) in a 25 ml tube. 13.5 ml of toluene were then added and the temperature of the solution obtained in this manner was adjusted to +20 C. Methylaluminoxane (MAO) in a solution in toluene (0.063 ml; 110.sup.4 moles, equal to approx. 5.8 g) was then added, followed by the complex FeCl.sub.2(L3) [sample MG212) (1.83 ml of suspension in toluene at a concentration of 2 mg/ml; 110.sup.5 moles, equal to approx. 3.65 mg) obtained as described in Example 6. The whole was left to stand, under magnetic stirring, at +20 C., for 45 minutes. Polymerisation was then quenched by adding 2 ml of methanol containing a few drops of hydrochloric acid. The polymer obtained was then coagulated by adding 40 ml of a methanolic solution containing 4% Irganox 1076 (Ciba) antioxidant, 1.4 g of syndiotactic 1,2-polybutadiene being obtained: further characteristics of the process and of the syndiotactic 1,2-polybutadiene obtained are shown in Table 1.

[0178] FIG. 14 shows the FT-IR spectrum of the syndiotactic 1,2-polybutadiene obtained.

Example 13 (G1526)

[0179] 2 ml of 1,3-butadiene, equal to approx. 1.4 g, were condensed at low temperature (20 C.) in a 25 ml tube. 14.24 ml of toluene were then added and the temperature of the solution obtained in this manner was adjusted to +20 C. Methylaluminoxane (MAO) in a solution in toluene (0.063 ml; 110.sup.4 moles, equal to approx. 5.8 g) was then added, followed by the complex FeCl.sub.3(L1) [sample MG87] (1.7 ml of suspension in toluene at a concentration of 2 mg/ml; 110.sup.5 moles, equal to approx. 3.4 mg) obtained as described in Example 5. The whole was left to stand, under magnetic stirring, at +20 C., for 45 minutes. Polymerisation was then quenched by adding 2 ml of methanol containing a few drops of hydrochloric acid. The polymer obtained was then coagulated by adding 40 ml of a methanolic solution containing 4% Irganox 1076 (Ciba) antioxidant, 1.4 g of syndiotactic 1,2-polybutadiene being obtained: further characteristics of the process and of the syndiotactic 1,2-polybutadiene obtained are shown in Table 1.

[0180] FIG. 15 shows the FT-IR spectrum of the syndiotactic 1,2-polybutadiene obtained.

[0181] FIG. 16 shows the .sup.1H-NMR (top) and .sup.13C-NMR (bottom) spectra of the syndiotactic 1,2-polybutadiene obtained.

[0182] FIG. 17 shows the DSC curve of the syndiotactic 1,2-polybutadiene obtained.

Example 14 (G1526/1)

[0183] 2 ml of 1,3-butadiene, equal to approx. 1.4 g, were condensed at low temperature (20 C.) in a 25 ml tube. 14.24 ml of heptane were then added and the temperature of the solution obtained was adjusted to +20 C. Methylaluminoxane (MAO) in a solution in toluene (0.063 ml; 110.sup.4 moles, equal to approx. 5.8 g) was then added, followed by the complex FeCl.sub.3(L1) [sample MG87] (1.7 ml of suspension in toluene at a concentration of 2 mg/ml; 110.sup.5 moles, equal to approx. 3.4 mg) obtained as described in Example 5. The whole was left to stand, under magnetic stirring, at +20 C. for 35 minutes. Polymerisation was then quenched by adding 2 ml of methanol containing a few drops of hydrochloric acid. The polymer obtained was then coagulated by adding 40 ml of a methanolic solution containing 4% Irganox 1076 (Ciba) antioxidant, 1.4 g of syndiotactic 1,2-polybutadiene being obtained: further characteristics of the process and of the syndiotactic 1,2-polybutadiene obtained are shown in Table 1.

[0184] FIG. 18 shows the FT-IR spectrum of the syndiotactic 1,2-polybutadiene obtained.

[0185] FIG. 19 shows the .sup.1H-NMR (top) and .sup.13C-NMR (bottom) spectra of the syndiotactic 1,2-polybutadiene obtained.

[0186] FIG. 20 shows the X-ray spectrum of the syndiotactic 1,2-polybutadiene obtained.

Example 15 (G1523)

[0187] 2 ml of 1,3-butadiene, equal to approx. 1.4 g, were condensed at low temperature (20 C.) in a 25 ml tube. 14.08 ml of toluene were then added and the temperature of the solution obtained in this manner was adjusted to +20 C. Methylaluminoxane (MAO) in a solution in toluene (0.063 ml; 110.sup.4 moles, equal to approx. 5.8 g) was then added, followed by the complex FeCl.sub.3(L2) [sample MG213] (1.86 ml of suspension in toluene at a concentration of 2 mg/ml; 110.sup.5 moles, equal to approx. 3.72 mg) obtained as described in Example 6. The whole was left to stand, under magnetic stirring, at +20 C., for 45 minutes. Polymerisation was then quenched by adding 2 ml of methanol containing a few drops of hydrochloric acid. The polymer obtained was then coagulated by adding 40 ml of a methanolic solution containing 4% Irganox 1076 (Ciba) antioxidant, 1.4 g of syndiotactic 1,2-polybutadiene being obtained: further characteristics of the process and of the syndiotactic 1,2-polybutadiene obtained are shown in Table 1.

[0188] FIG. 21 shows the FT-IR spectrum of the syndiotactic 1,2-polybutadiene obtained.

[0189] FIG. 22 shows the DSC curve of the syndiotactic 1,2-polybutadiene obtained.

Example 16 (G1523/1)

[0190] 2 ml of 1,3-butadiene, equal to approx. 1.4 g, were condensed at low temperature (20 C.) in a 25 ml tube. 14.08 ml of heptane were then added and the temperature of the solution obtained was adjusted to +20 C. Methylaluminoxane (MAO) in a solution in toluene (0.063 ml; 110.sup.4 moles, equal to approx. 5.8 g) was then added, followed by the complex FeCl.sub.3(L2) [sample MG213] (1.86 ml of suspension in toluene at a concentration of 2 mg/ml; 110.sup.5 moles, equal to approx. 3.72 mg) obtained as described in Example 6. The whole was left to stand, under magnetic stirring, at +20 C., for 35 minutes. Polymerisation was then quenched by adding 2 ml of methanol containing a few drops of hydrochloric acid. The polymer obtained was then coagulated by adding 40 ml of a methanolic solution containing 4% Irganox 1076 (Ciba) antioxidant, 1.4 g of syndiotactic 1,2-polybutadiene being obtained: further characteristics of the process and of the syndiotactic 1,2-polybutadiene obtained are shown in Table 1.

[0191] FIG. 23 shows the .sup.1H-NMR (top) and .sup.13C-NMR (bottom) spectra of the syndiotactic 1,2-polybutadiene obtained.

Example 17 (IP204/1)

[0192] 2 ml of 1,3-butadiene, equal to approx. 1.4 g, were condensed at low temperature (20 C.) in a 25 ml tube. 13.4 ml of heptane were then added and the temperature of the solution obtained was adjusted to +20 C. Methylaluminoxane (MAO) in a solution in toluene (0.063 ml; 110.sup.4 moles, equal to approx. 5.8 g) was then added, followed by the complex FeCl.sub.3(L3) [sample MG208] (2 ml of suspension in toluene at a concentration of 2 mg/ml; 110.sup.5 moles, equal to approx. 4 mg) obtained as described in Example 9. The whole was left to stand, under magnetic stirring, at +20 C., for 30 minutes. Polymerisation was then quenched by adding 2 ml of methanol containing a few drops of hydrochloric acid. The polymer obtained was then coagulated by adding 40 ml of a methanolic solution containing 4% Irganox 1076 (Ciba) antioxidant, 1.4 g of syndiotactic 1,2-polybutadiene being obtained: further characteristics of the process and of the syndiotactic 1,2-polybutadiene obtained are shown in Table 1.

[0193] FIG. 24 shows the FT-IR spectrum of the syndiotactic 1,2-polybutadiene obtained.

Example 18

[0194] Synthesis of CoCl.sub.2(PPh.sub.3).sub.2

[0195] A solution of di-triphenylphosphine (6.08 g, 2.3210.sup.2 moles) in ethanol (70 ml), was added, dropwise, under stirring, to a solution of anhydrous cobalt dichloride (CoCl.sub.2) (1.30 g, 110.sup.2 moles) in ethanol (70 ml), in a 200 ml reaction flask, a pale blue suspension being formed. The suspension obtained was left to stand, under stirring, at room temperature, for 24 hours, and subsequently dried under vacuum at room temperature. The residue obtained was placed onto the filter of a heated extractor for solids, and extracted continuously with pentane, in such a manner as to remove any excess phosphine: extraction in toluene was then continued for a further 24 hours, blue crystals being obtained. The blue crystals obtained were separated by siphoning off the supernatant solution and further crystals were obtained by cooling the siphoned off solution. Said crystals were then dried under vacuum, at room temperature, 4.58 g of a light blue solid product corresponding to the phosphine complex CoCl.sub.2(PPh.sub.3).sub.2 and amounting to conversion of 70% based on the anhydrous cobalt dichloride (CoCl.sub.2), being obtained.

[0196] Elemental analysis [found (calculated)]: Co: 9.10% (9.01%); Cl: 10.80% (10.84%); P: 9.40% (9.47%); C: 66.20% (66.07%); H: 4.70% (4.62%).

Example 19 (G1528) (Comparative)

[0197] 2 ml of 1,3-butadiene, equal to approx. 1.4 g, were condensed at low temperature (20 C.) in a 25 ml tube. 12.4 ml of toluene were then added and the temperature of the solution obtained in this manner was adjusted to +25 C. Methylaluminoxane (MAO) in a solution in toluene (0.63 ml; 110.sup.3 moles, equal to approx. 58 g) was then added, followed by the complex CoCl.sub.2(PPh.sub.3).sub.2(2.96 ml of suspension in toluene at a concentration of 2 mg/ml; 110.sup.5 moles, equal to approx. 5.92 mg) obtained as described in Example 11. The whole was left to stand, under magnetic stirring, at +25 C., for 40 minutes. Polymerisation was then quenched by adding 2 ml of methanol containing a few drops of hydrochloric acid.

[0198] The polymer obtained was then coagulated by adding 40 ml of a methanolic solution containing 4% Irganox 1076 (Ciba) antioxidant, 1.4 g of syndiotactic 1,2-polybutadiene being obtained: further characteristics of the process and of the syndiotactic 1,2-polybutadiene obtained are shown in Table 1.

[0199] FIG. 25 shows the FT-IR spectrum of the syndiotactic 1,2-polybutadiene obtained.

[0200] FIG. 26 shows the .sup.1H-NMR (top) and .sup.13C-NMR (bottom) spectra of the syndiotactic 1,2-polybutadiene obtained.

[0201] FIG. 27 shows the DSC curve of the syndiotactic 1,2-polybutadiene obtained.

[0202] FIG. 28 shows the X-ray spectrum of the syndiotactic 1,2-polybutadiene obtained.

[0203] It is apparent from the data shown in Table 1 that the syndiotactic 1,2-polybutadiene obtained in accordance with the process provided by the present invention (Examples 10-17) exhibits characteristics similar to those of the syndiotactic 1,2-polybutadiene obtained with a process known in the art using a catalytic system based on cobalt (Example 19).

TABLE-US-00001 TABLE 1 Polymerisation of 1,3-butadiene with catalytic systems comprising pyridyl iron complexes Al/Fe Time Conversion 1,4-cis 1,2 M.sub.w T.sub.m T.sub.c Example (molar ratio) (min) (%) (%) (%) (rr %) (g mol.sup.1) M.sub.w/M.sub.n ( C.) ( C.) 10 10 45 100 16 84 69.7 355000 1.9 102.3 78.0 11 10 45 100 24 76 60.4 350000 2.0 80.9 59.1 12 10 30 100 22 78 66.8 377000 1.9 87.0 68.5 13 10 45 100 20 80 68.4 349000 2.3 88.8 68.7 14 10 35 100 15 85 70.4 337500 2.1 110.2 82.7 15 10 45 100 29 71 54.9 344000 1.9 68.1 46.0 16 10 35 100 22 78 58.1 333000 1.8 78.3 55.7 17 10 30 100 20 82 71.5 369000 1.8 106.6 79.9 19.sup.(*.sup.) 100 40 100 28 72 55.1 317000 1.9 72.0 36.0 .sup.(*.sup.)comparative