Process for the preparation of (co)polymers of conjugated dienes in the presence of a catalytic system comprising an oxo-nitrogenated complex of cobalt

Abstract

Process for the preparation of (co) polymers of conjugated dienes which comprises polymerizing at least one conjugated diene in the presence of a catalytic system comprising at least one oxo-nitrogenated complex of cobalt having general formula (I), wherein: R.sub.1 and R.sub.2, equal to or different from each other, represent a hydrogen atom; or they are selected from linear or branched C.sub.1-C.sub.20, preferably C.sub.1-C.sub.15, alkyl groups, optionally halogenated; cycloalkyl groups optionally substituted; aryl groups optionally substituted; Y represents an oxygen atom; or a group NR.sub.3 wherein R.sub.3 represents a hydrogen atom, or it is selected from linear or branched C.sub.1-C.sub.20 preferably C.sub.1-C.sub.15, alkyl groups, optionally halogenated, cycloalkyl groups optionally substituted-; aryl groups optionally substituted; or, when Y represents a group NR.sub.3, R.sub.2 and R.sub.3 can be optionally bound to each other to form, together with the other atoms to which they are bound, a cycle containing from 3 to 6 carbon atoms, saturated, unsaturated, or aromatic, optionally substituted with linear or branched C.sub.1-C.sub.20 preferably C.sub.1-C.sub.15, alkyl groups, said cycle optionally containing heteroatoms such as, for example, oxygen, sulfur, nitrogen, silicon, phosphorous, selenium; X.sub.1 and X.sub.2, equal to or different from each other, represent a halogen atom such as, for example, chlorine, bromine, iodine; or they are selected from linear or branched C.sub.1-C.sub.20 preferably C.sub.1-C.sub.15, alkyl groups, OCOR.sub.4 groups or OR.sub.4 groups wherein R.sub.4 is selected from linear or branched C.sub.1-C.sub.20 preferably C.sub.1-C.sub.15, alkyl groups. ##STR00001##

Claims

1. A process for the preparation of (co)polymers of conjugated dienes which comprises polymerizing at least one conjugated diene in the presence of a catalytic system comprising at least one oxo-nitrogenated complex of cobalt having general formula (I): ##STR00009## wherein: R.sub.1 and R.sub.2, independently, represent a hydrogen atom, linear or branched C.sub.1-C.sub.20 alkyl groups optionally halogenated, cycloalkyl groups optionally substituted, or aryl groups optionally substituted; Y represents an oxygen atom, or a group NR.sub.3 wherein R.sub.3 represents a hydrogen atom, branched C.sub.1-C.sub.20 alkyl groups optionally halogenated, cycloalkyl groups optionally substituted, or aryl groups optionally substituted; R.sub.2 and R.sub.3 are optionally bound to each other to form, together with the other atoms to which they are bound, a cycle containing from 3 to 6 carbon atoms, saturated, unsaturated, or aromatic, optionally substituted with linear or branched C.sub.1-C.sub.20 alkyl groups, said cycle optionally containing heteroatoms; X.sub.1 and X.sub.2, independently, represent a halogen atom, or linear or branched C.sub.1-C.sub.20 alkyl groups, OCOR.sub.4 groups, or OR.sub.4 groups wherein R.sub.4 is selected from linear or branched C.sub.1-C.sub.20 alkyl groups.

2. The process for the preparation of (co)polymers of conjugated dienes according to claim 1, wherein said catalytic system comprises at least one co-catalyst (b) selected from organic compounds of an element M different from carbon, said element M being selected from elements belonging to groups 2, 12, 13 or 14, of the Periodic Table of Elements.

3. The process for the preparation of (co)polymers of conjugated dienes according to claim 2, wherein said co-catalyst (b) is selected from (b.sub.1) aluminium alkyls having general formula (II):
Al(X).sub.n(R.sub.5).sub.3-n(II) wherein X represents a halogen atom; R.sub.5 is 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 or germanium atoms; and n is an integer ranging from 0 to 2.

4. The process for the preparation of (co)polymers of conjugated dienes according to claim 2, wherein said co-catalyst (b) is selected from (b.sub.2) organo-oxygenated compounds of an element M different from carbon belonging to groups 13 or 14 of the Periodic Table of Elements.

5. The process for the preparation of (co)polymers of conjugated dienes according to claim 2, wherein said co-catalyst (b) is selected from (b.sub.3) organometallic compounds or mixtures of organometallic compounds of an element M different from carbon capable of reacting with the oxo-nitrogenated complex of cobalt having general formula (I), further comprising extracting X.sub.1 or X.sub.2 of the oxo-nitrogenated complex -bound to form at least one neutral compound and an ionic compound, the ionic compound including a cation containing the metal (Co) coordinated by a ligand and a non-coordinating organic anion containing the metal M, wherein the negative charge is delocalized on a multicentric structure.

6. A process for the preparation of (co)polymers of conjugated dienes according to claim 1, wherein said conjugated dienes are selected from: 1,3-butadiene, 2-methyl-1,3-butadiene (isoprene), 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene, cyclo-1,3-hexadiene, or mixtures thereof.

7. The process for the preparation of (co)polymers of conjugated dienes according to claim 1, wherein in said oxo-nitrogenated complex of cobalt having general formula (I): R.sub.1 and R.sub.2, independently, represent a hydrogen atom; or linear or branched C.sub.1-C.sub.20 alkyl groups; Y is an oxygen atom or a group NR.sub.3 wherein R.sub.3 is selected from phenyl groups substituted with linear or branched C.sub.1-C.sub.20 alkyl groups; X.sub.1 and X.sub.2, the same as each other, are a halogen atom.

8. The process for the preparation of (co)polymers of conjugated dienes according to claim 3, wherein said aluminium alkyls (b.sub.1) having general formula (II) are di-ethyl-aluminium chloride (DEAC), mono-ethyl-aluminium dichloride (EADC), or ethylaluminiumsesquichloride (EASC).

9. The process for the preparation of (co)polymers of conjugated dienes according to claim 4, wherein said organo-oxygenated compounds (b.sub.2) are selected from aluminoxanes having general formula (III):
(R.sub.6).sub.2AlO[Al(R.sub.7)O].sub.pAl(R.sub.8).sub.2(III) wherein R.sub.6, R.sub.7 and R.sub.8, independently, represent a hydrogen atom, a halogen atom, or 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 or germanium atoms; and p is an integer ranging from 0 to 1,000.

10. The process for the preparation of (co)polymers of conjugated dienes according to claim 9, wherein said organo-oxygenated compound (b.sub.2) is methylaluminoxane (MAO).

11. The process for the preparation of (co)polymers of conjugated dienes according to claim 5, wherein said organometallic compounds or organometallic mixtures of compounds (b.sub.3) are selected from organic compounds of aluminium and boron represented by the following general formulae:
[(R.sub.C).sub.WH.sub.4-W].[B(R.sub.D).sub.4].sup.;B(R.sub.D).sub.3;Al(R.sub.D).sub.3;B(R.sub.D).sub.3P;[Ph.sub.3C].sup.+.[B(R.sub.D).sub.4].sup.;[(R.sub.C).sub.3PH].sup.+.[B(R.sub.D).sub.4].sup.;[Li].sup.+.[B(R.sub.D).sub.4].sup.;[Li].sup.+.[Al(R.sub.D).sub.4].sup. wherein w is an integer ranging from 0 to 3, each group R.sub.C independently represents an alkyl group or an aryl group having from 1 to 10 carbon atoms and each group R.sub.D independently represents an aryl group partially or totally fluorinated, having from 6 to 20 carbon atoms, P represents a pyrrole radical optionally substituted.

12. The process for the preparation of (co)polymers of conjugated dienes according to claim 1, wherein said process is carried out in the presence of an inert organic solvent selected from: butane, pentane, hexane, heptane, or mixtures thereof; cyclopentane, cyclohexane, or mixtures thereof; 1-butene, 2-butene, or mixtures thereof; benzene, toluene, xylene, or mixtures thereof; methylene chloride, chloroform, carbon tetrachloride, trichloroethylene, perchloroethylene, 1,2-dichloroethane, chlorobenzene, bromobenzene, chlorotoluene, or mixtures thereof.

13. The process for the preparation of (co)polymers of conjugated dienes according to claim 12, wherein the concentration of the conjugated diene to be (co)polymerized in said inert organic solvent ranges from 5% by weight to 50% by weight with respect to the total weight of the mixture of conjugated diene and inert organic solvent.

14. The process for the preparation of (co)polymers of conjugated dienes according to claim 1, wherein said process is carried out at a temperature ranging from 70 C. to +100 C.

Description

EXAMPLES

Reagents and Materials

(1) The reagents and materials used in the following examples of the invention are indicated in the following list, together with their optional pretreatments and their supplier. cobalt dichloride (CoCl.sub.2) (Stream Chemicals): used as such; tetrahydrofuran (THF) (Carlo Erba, RPE): kept at reflux temperature on potassium/benzophenone and then distilled under nitrogen; methanol (Carlo Erba, RPE): used as such; formic acid (85%) (Carlo Erba, RPE): used as such; 2,6-diacetylpyridine (Aldrich): used as such; 2,6-diethylaniline (Aldrich): distilled on sodium (Na) in an inert atmosphere; 2,6-di-iso-propylaniline (Aldrich): used as such; toluene (Aldrich): pure, 99.5%, distilled on sodium (Na) in an inert atmosphere; 1,3-butadiene (Air Liquide): pure, 99.5%, evaporated from the container before each production, dried by passing it through a column packed with molecular sieves and condensed inside the reactor pre-cooled to 20 C.; methylaluminoxane (MAO) (toluene solution at 10% by weight) (Aldrich): used as such; dry methylaluminoxane (MAO.sub.dry): obtained by drying methylaluminoxane (MAO) (toluene solution at 10% by weight) (Aldrich), under vacuum, at room temperature; dichloromethane (99%) (Aldrich): distilled on diphosphorous pentaoxide (P.sub.2O.sub.5) in an inert atmosphere; pentane (Aldrich): pure, 99.5%, distilled on sodium (Na) in an inert atmosphere; deuterated tetrachloroethylene (C.sub.2D.sub.2Cl.sub.4) (Acros): used as such; deuterated chloroform (CDCl.sub.3) (Acros): used as such; hydrochloric acid in aqueous solution at 37% (Aldrich): used as such.

(2) The analysis and characterization methods indicated below were used.

(3) Elemental Analysis

(4) a) Determination of Co

(5) For the determination of the weight quantity of cobalt (Co) in the oxo-nitrogenated complexes of cobalt used for the aim of the present invention, an aliquot weighed exactly, operating in a dry-box under a nitrogen flow, of about 30-50 mg of sample, was placed in a platinum crucible of about 30 ml, together with a mixture of 1 ml of hydrofluoric acid (HF) at 40%, 0.25 ml of sulfuric acid (H.sub.2SO.sub.4) at 96% and 1 ml of nitric acid (HNO.sub.3) at 70%. The crucible was then heated on a plate, increasing the temperature until the appearance of white sulfuric fumes (about 200 C.). The mixture thus obtained was cooled to room temperature (20 C.-25 C.), ml of nitric acid (HNO.sub.3) at 70% was added and the mixture was then heated until the re-appearance of fumes. After repeating the sequence a further two times, a limpid, almost colourless solution was obtained. 1 ml of nitric acid (HNO.sub.3) and about 15 ml of water were then added; without heat, and the mixture was then heated to 80 C., for about 30 minutes. The sample thus prepared was diluted with water having a MilliQ purity up to a weight of about 50 g, weighed exactly, to obtain a solution on which analytical instrumental determination was carried out using an ICP-OES (optical detection plasma) Thermo Optek IRIS Advantage Duo spectrometer, by comparison with solutions at a known concentration. For this aim, a calibration curve was prepared for each analyte, within the range of 0 ppm-10 ppm, measuring solutions having a known titre obtained by dilution by weight of certified solutions.

(6) The solution of the sample prepared as described above was diluted again by weight so as to obtain concentrations close to those used as reference, before carrying out spectrophotometric analysis. All the samples were prepared in duplicate. The results were considered acceptable if the single data of the tests in duplicate did not differ by more than 2% relative with respect to their average value.

(7) b) Chlorine Determination

(8) For this aim, samples of the oxo-nitrogenated complexes of cobalt used for the aim of the present invention, about 30 mg-50 mg, were weighed exactly in 100 ml glasses in a dry-box under a stream of nitrogen. 2 g of sodium carbonate (Na.sub.2CO.sub.3) and 50 ml of MilliQ water were added, outside the dry-box. The mixture was brought to boiling point on a plate under magnetic stirring for about 30 minutes. It was left to cool, diluted sulfuric acid (H.sub.2SO.sub.4) was added until the reaction became acid and the mixture was titrated with silver nitrate (AgNO.sub.3) 0.1 N with a potentiometer titrator.

(9) c) Determination of Carbon, Hydrogen, Nitrogen and Oxygen

(10) The determination of the carbon, hydrogen, and nitrogen, in the oxo-nitrogenated complexes of cobalt, used for the aim of the present invention, and also in the ligands used for the aim of the present invention, was carried out by means of a Thermo Flash 2000 automatic analyzer, whereas the determination of the oxygen was carried out by means of a Thermo EA1100 automatic analyzer.

(11) .sup.13C-HMR and .sup.1H-HMR Spectra

(12) The .sup.13C-HMR and .sup.1H-HMR spectra were registered by means of a nuclear magnetic resonance spectrometer mod. Bruker Avance 400, using deuterated tetrachloroethylene (C.sub.2D.sub.2Cl.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. Polymeric solutions having concentrations equal to 10% by weight with respect to the total weight of the polymeric solution, were used for the aim.

(13) The microstructure of the polymers [i.e. content of 1,4-cis units (%)] was determined by analysis of the above spectra on the basis of what is indicated in literature by Mochel, V. D., in Journal of Polymer Science Part A-1: Polymer Chemistry (1972), Vol. 10, Issue 4, pages 1009-1018.

(14) I.R. Spectra

(15) The I.R. spectra (FT-IR) were registered by means of Thermo Nicolet Nexus 670 and Bruker IFS 48 spectrophotometers.

(16) The I.R. spectra (FT-IR) of the ligands used in the present invention, were obtained by dispersing the ligand to be analyzed in anhydrous potassium bromide (KBr) (disks of KBr), or in a suspension of nujol.

(17) The I.R. spectra (FT-IR) of the oxo-nitrogenated complexes of cobalt used in the present invention, were obtained by dispersing the oxo-nitrogenated complex of cobalt to be analyzed in anhydrous potassium bromide (KBr) (disks of KBr), or in a suspension of nujol.

(18) The I.R. spectra (FT-IR) of the polymers were obtained from polymeric films on tablets of potassium bromide (KBr), said films being obtained by deposition of a solution of the polymer to be analyzed in hot o-dichlorobenzene. The concentration of the polymeric solutions analyzed was equal to 10% by weight with respect to the total weight of the polymeric solution.

(19) Thermal Analysis (DSC)

(20) The DSC (Differential Scanning calorimetry) thermal analysis, for determining the melting point (T.sub.m) and the crystallization temperature (T.sub.a) of the polymers obtained, was carried out using a Perkin Elmer Pyris differential scanning calorimeter. For this aim, 5 mg of polymer were analyzed, with a scanning rate ranging from 1 C./min to 20 C./min; in an inert nitrogen atmosphere.

(21) The DSC (Differential Scanning calorimetry) thermal analysis, for determining the glass transition temperature (T.sub.y) of the polymers obtained was carried out by means of the above calorimeter, using the following thermal program: isotherm for 3 minutes at +70 C.; cooling from +70 C. to 90 C. at a rate of 10 C./min; isotherm for 3 min at 90 C.; heating from 90 C. to +70 C. at a rate of 10 C./min.

(22) Molecular Weight Determination

(23) The determination of the molecular weight (MW) of the polymers obtained was carried out by means of GPC (Gel Permeation Chromatography) operating under the following conditions: Agilent 1100 pump; I.R. Agilent 1100 detector; PL Mixed-A columns; solvent/eluent: tetrahydrofuran (THF); flow-rate 1 ml/min; temperature: 25 C.; molecular mass calculation: Universal Calibration method.

(24) The weight average molecular weight (M.sub.w) and polydispersion Index (PDI) corresponding to the M.sub.w/M.sub.n ratio (M.sub.n=number average molecular weight), are specified.

(25) Determination of the Branching

(26) The determination of the branching of the polymers obtained was carried out by means of the GPC/MALLS technique obtained by coupling a multi-angle light scattering detector (MALLS) with a traditional SEC/RI elution, operating under the following conditions: Agilent 1050 pump; I.R. Agilent 1050 detector; MALLS Dawn-DSP Wyatt detectorTechnology, =632.8 nm; PL GEL Mixed-A (4) columns; solvent/eluent: tetrahydrofuran (THF); flow-rate 1 ml/min; temperature: 25 C.

(27) Operating as described above, the absolute measurement can be contemporaneously carried out of the molecular weight and gyration radius of the macromolecules that are separated by the chromatographic system: the quantity of light scattered from a macromolecular species in solution can in fact be used directly for obtaining its molecular weight, whereas the angular variation in the scattering is directly correlated to its average dimensions. The fundamental relation which is used is represented by the following equation (1):

(28) $\begin{array}{cc}\frac{K*c}{R_{}}=\frac{1}{M_w{P}_{}}+2A_{2}c& \left(1\right)\end{array}$
wherein:
K* is the optical constant which depends on the wave-length of the light used, on the refraction index (dn/dc) of the polymer, on the solvent used;
M.sub.w is the weight average molecular weight;
c is the concentration of the polymeric solution;
R.sub. is the intensity of the light scattered, measured at the angle (excess Rayleigh factor);
P.sub. is the function describing the variation of the light scattered with the angle at which it is measured, equal to 1 for an angle equal to 0;
A.sub.2 is the second virial coefficient.

(29) For very low concentrations (typical of a GPC system), the equation (1) indicated above is reduced to the following equation (2):

(30) $\begin{array}{cc}\frac{K*c}{R_{}}=\frac{1}{M_w{P}_{}}& \left(2\right)\end{array}$
wherein K*, c, R.sub., M.sub.w and P.sub., have the same meanings defined above, and by carrying out the measurement on several angles, the extrapolation at angle null of the function K*c/R.sub. in relation to sen.sup.2/2 directly provides the molecular weight of the intercept value and the gyration radius of the slope.

(31) Furthermore, as this measurement is carried out for every slice of the chromatogram, it is possible to obtain a distribution of both the molecular weight and the gyration radius.

(32) The macromolecular dimensions in solution are directly correlated to their branching degree: for the same molecular weight, the smaller the dimensions of the macromolecule with respect to the linear correspondent, the higher the branching degree will be.

(33) Informations relating to the macrostructure of the polymer is qualitatively deduced from the value of the parameter , which represents the slope of the curve which correlates the gyration radius with the molecular weight: when, under the same analysis conditions, this value decreases with respect to a macrostructure of the linear type, there is the presence of a polymer having a branched-type macrostructure. The typical value of the parameter for linear polybutadiene having a high content of 1,4-cis units, in tetrahydrofuran (THF), is equal to 0.58-0.60.

Example 1

Synthesis of the Ligand Having Formula (L2)

(34) ##STR00004##

(35) 2.48 mg (14 mmoles) of 2,6-di-iso-propylaniline were introduced into a reaction flask together with 5 ml of methanol, obtaining a limpid solution. 0.25 ml of formic acid and 20 ml of methanol containing 1.96 g (12 mmoles) of 2,6-diacetylpyridine were subsequently added dropwise to said solution, at room temperature. After about 1 hour, the precipitation of a yellow microcrystalline solid product was obtained: said yellow solid was recovered by filtration, washed with cold methanol and dried, under vacuum, at room temperature, obtaining 2.4 g of a light yellow solid product (yield=62%) having formula (L2).

(36) Elemental analysis [found (calculated)]: C, 77.80% (78.22%); H, 8.24% (8.13%); N, 8.51% (8.69%); O, 4.91% (4.96%).

(37) Molecular weight (MW): 322.45.

(38) FT-IR (nujol): 1700 cm.sup.1 .sub.(CO); 1648 cm.sup.1 .sub.(CN).

(39) .sup.1H-NMR ( shift from TMS): 1.16 (d, 12H), 2.27 (s, 3H), 2.73 (m, 2H), 2.80 (s, 3H), 7.17 (m, 3H), 7.95 (t, 1H), 8.15 (d, 1H), 8.57 (d, 1H).

Example 2

Synthesis of the Ligand Having Formula (L6)

(40) ##STR00005##

(41) 1.96 g (12 mmoles) of 2,6-di-acetylpyridine were introduced into a reaction flask together with 5 ml of methanol and 5 drops of formic acid, obtaining a solution. 5 ml of methanol containing 1.34 g (9 mmoles) of 2,6-diethylaniline were subsequently added dropwise to said solution, at room temperature. After 48 hours, the mixture was cooled to 4 C., obtaining the precipitation of a whitish microcrystalline solid product: said whitish solid product was recovered by filtration, washed with cold methanol and dried, under vacuum, at room temperature, obtaining 1.8 g of a whitish solid product (yield=67%) having formula (L6).

(42) Elemental analysis [found (calculated)]: C, 77.58% (77.52%); H, 7.50% (7.53%); N, 9.60% (9.52%); O, 5.30% (5.43%).

(43) Molecular weight (MW): 294.40.

(44) FT-IR (nujol): 1648 cm.sup.1 .sub.(CN); 1702 cm.sup.1 .sub.(CO).

Example 3

Synthesis of CoCl2(L2) [Sample GL545]

(45) ##STR00006##

(46) Anhydrous cobalt dichloride (CoCl.sub.2) (0.401 g; 3.09 mmoles) was introduced into a 100 ml reaction flask together with tetrahydrofuran (THF) (40 ml). The whole was kept under stirring, at room temperature, for a few minutes and the ligand having formula (L2) (1.20 g; 3.7 mmoles; molar ratio L2/Co=1.2) obtained as described in Example 1, was subsequently added. Upon the addition of the ligand, a dark blue-coloured suspension was immediately formed, which was kept under stirring, at room temperature, for 1 day. The solvent was then removed under vacuum and the residue obtained was dried under vacuum, at room temperature, and subsequently charged onto the porous septum of a hot extractor for solids and was extracted, in continuous, with pentane at boiling point, for 24 hours, in order to remove the non-reacted ligand. Subsequently, the residue remaining on the porous septum was extracted again, in continuous, with dichloromethane at boiling point, for hours, obtaining a green-coloured solution. The dichloromethane was removed under vacuum and the solid residue remaining on the porous septum was recovered and dried under vacuum, at room temperature, obtaining 1.25 g of a dark green solid product corresponding to the complex CoCl.sub.2(L2), equal to a conversion of 89.4% with respect to the cobalt dichloride charged.

(47) Elemental analysis [found (calculated)]: C, 55.20% (55.77%); H, 5.50% (5.79%); Cl, 15.30% (15.68%); Co, 12.80% (13.03%); N, 5.90% (6.19%); O, 3.20% (3.54%).

(48) Molecular weight (MW): 452.28

(49) FT-IR (nujol): 1648 cm.sup.1 .sub.(CO); 1590 cm.sup.1 .sub.(CN), 334 cm.sup.1 .sub.(CoCl).

Example 4

Synthesis of CoCl2(L6) [Sample GL926]

(50) ##STR00007##

(51) Anhydrous cobalt dichloride (CoCl.sub.2) (0.832 g; 6.41 mmoles) was introduced into a 100 ml reaction flask together with tetrahydrofuran (THP) (70 ml). The whole was kept under stirring, at room temperature, for a few minutes and the ligand having formula (L6) (2.07 g; 7.03 mmoles; molar ratio L6/Co=1.1) obtained as described in Example 2, was subsequently added. Upon the addition of the ligand, a green-coloured suspension was immediately formed, which was kept, under stirring, at room temperature, for 1 day. The solvent was then removed under vacuum and the residue obtained was dried under vacuum, at room temperature, and subsequently charged onto the porous septum of a hot extractor for solids and was extracted, in continuous, with pentane at boiling point, for 24 hours, in order to remove the non-reacted ligand. Subsequently, the residue remaining on the porous septum was extracted again, in continuous, with dichloromethane at boiling point, for 24 hours, obtaining a green-coloured solution. The dichloromethane was removed under vacuum and the solid residue remaining on the porous septum was recovered and dried under vacuum, at room temperature, obtaining 2.31 g of a dark green solid product corresponding to the complex CoCl.sub.2(L6), equal to a conversion of 85% with respect to the cobalt dichloride charged.

(52) Elemental analysis [found (calculated)]: C, 53.40% (53.79%); H, 4.90% (5.23%); Cl, 16.30% (16.71%); Co, 13.40% (13.89%); N, 6.30% (6.60%); O, 3.50% (3.77%).

(53) Molecular weight (MW): 424.23

(54) FT-IR (nujol): 1685 cm.sup.1 .sub.(CO); 1590 cm.sup.1 .sub.(CN), 334 cm.sup.1 .sub.(CoCl).

(55) FIG. 1 shows the FT-IR spectrum of the complex CoCl.sub.2(L6) obtained (the nujol bands having been subtracted).

Example 5

Synthesis of CoCl2(L4) [Sample GL922]

(56) ##STR00008##

(57) Anhydrous cobalt dichloride (CoCl.sub.2) (0.413 g; 3.18 mmoles) was introduced into a 100 ml reaction flask together with tetrahydrofuran (THF) (70 ml). The whole was kept under stirring, at room temperature, for a few minutes and the ligand having formula (L4) (i.e. 2,6-di-acetylpyridine) (0.571 g; 3.50 mmoles; molar ratio L4/Co=1.1), was subsequently added. Upon the addition of the ligand, a green-coloured suspension was immediately formed, which was kept, under stirring, at room temperature, for 1 day. The solvent was then removed under vacuum and the residue obtained was dried under vacuum, at room temperature, and subsequently charged onto the porous septum of a hot extractor for solids and was extracted, in continuous, with pentane at boiling point, for 24 hours, in order to remove the non-reacted ligand. Subsequently, the residue remaining on the porous septum was extracted again, in continuous, with dichloromethane at boiling point, for hours, obtaining a green-coloured solution. The dichloromethane was removed under vacuum and the solid residue remaining on the porous septum was recovered and dried under vacuum, at room temperature, obtaining 0.82 g of a light green solid product corresponding to the complex CoCl.sub.2(L4), equal to a conversion of 88% with respect to the cobalt dichloride charged.

(58) Elemental analysis [found (calculated)]: C, 36.60% (36.89%); H, 2.90% (3.10%); Cl, 24.0% (24.20%); Co, 19.90% (20.11%); N, 4.50% (4.78%); O, 10.70% (10.92%).

(59) Molecular weight (MW): 293.01

(60) FT-IR (nujol): 1666 cm.sup.1 .sub.(CO); 330 cm.sup.1 .sub.(CoCl).

(61) FIG. 2 shows the FT-IR spectrum of the complex CoCl.sub.2(L4) obtained (the nujol bands having been subtracted).

Example 6

GL639

(62) 2 ml of 1,3-butadiene equal to about 1.4 g were condensed at a low temperature (20 C.) in a 25 ml test-tube. 7.45 ml of toluene were then added, and the temperature of the solution thus obtained was brought to 20 C. Methylaluminoxane (MAO) in a toluene solution (6.3 ml; 110.sup.2 moles, equal to about 0.58 g) was then added, and subsequently the complex CoCl.sub.2(L2) [sample GL545] (2.25 ml of a toluene solution at a concentration equal to 2 mg/ml; 110.sup.5 moles, equal to about 4.5 mg) obtained as described in Example 3. The whole was kept, under magnetic stirring, at 20 C., for 30 minutes. The polymerization was then quenched by the addition of 2 ml of methanol containing a few drops of hydrochloric acid. The polymer obtained was then coagulated by the addition of 40 ml of a methanol solution containing 4% of Irganox 1076 antioxidant (Ciba), obtaining 1.19 g of polybutadiene having a content of 1,4-cis units equal to 97.6%: further characteristics of the process and of the polybutadiene obtained are indicated in Table 1.

(63) FIG. 3 shows the FT-IR spectrum of the polybutadiene obtained.

Example 7

GL664

(64) 2 ml of 1,3-butadiene equal to about 1.4 g were condensed at a low temperature (20 C.) in a 25 ml test-tube. 7.45 ml of toluene were then added, and the temperature of the solution thus obtained was brought to 0 C. Methylaluminoxane (MAO) in a toluene solution (6.3 ml; 110.sup.2 moles, equal to about 0.58 g) was then added, and subsequently the complex CoCl.sub.2(L2) [sample GL545] (2.25 ml of a toluene solution at a concentration equal to 2 mg/ml; 110.sup.5 moles, equal to about 4.5 mg) obtained as described in Example 3. The whole was kept, under magnetic stirring, at 20 C., for 30 minutes. The polymerization was then quenched by the addition of 2 ml of methanol containing a few drops of hydrochloric acid. The polymer obtained was then coagulated by the addition of 40 ml of a methanol solution containing 4% of Irganox 1076 antioxidant (Ciba), obtaining 0.672 g of polybutadiene having a content of 1,4-cis units equal to 98.1%: further characteristics of the process and of the polybutadiene obtained are indicated in Table 1.

(65) FIG. 3 shows the FT-IR spectrum of the polybutadiene obtained.

Example 8

GL682

(66) 2 ml of 1,3-butadiene equal to about 1.4 g were condensed at a low temperature (20 C.) in a 25 ml test-tube. 7.45 ml of toluene were then added, and the temperature of the solution thus obtained was brought to 20 C. Dry methylaluminoxane (MAO.sub.dry) in a solution of methylene chloride (6.3 ml; 110.sup.2 moles, equal to about 0.58 g) was then added, and subsequently the complex CoCl.sub.2(L2) [sample GL545] (2.25 ml of a toluene solution at a concentration equal to 2 mg/ml; 110.sup.5 moles, equal to about 4.5 mg) obtained as described in Example 3. The whole was kept, under magnetic stirring, at 20 C., for 8 minutes. The polymerization was then quenched by the addition of 2 ml of methanol containing a few drops of hydrochloric acid. The polymer obtained was then coagulated by the addition of 40 ml of a methanol solution containing 4% of Irganox 1076 antioxidant (Ciba), obtaining 0.66 g of polybutadiene having a content of 1,4-cis units equal to 97.0%: further characteristics of the process and of the polybutadiene obtained are indicated in Table 1.

(67) FIG. 3 shows the FT-IR spectrum of the polybutadiene obtained.

Example 9

B251

(68) 15 ml of 1,3-butadiene equal to about 10.5 g were condensed at a low temperature (20 C.) in a 250 ml glass reactor. 100 ml of benzene were then added, and the temperature of the solution thus obtained was brought to 20 C. Methylaluminoxane (MAO) in a toluene solution (9.95 ml; 1.5810.sup.2 moles, equal to about 0.92 g) was then added, and subsequently the complex CoCl.sub.2(L2) [sample GL545] (3.55 ml of a toluene solution at a concentration equal to 2 mg/ml; 1.5810.sup.5 moles, equal to about 7.1 mg) obtained as described in Example 3. The whole was kept, under magnetic stirring, at 20 C., for 240 minutes. The polymerization was then quenched by the addition of 2 ml of methanol containing a few drops of hydrochloric acid. The polymer obtained was then coagulated by the addition of 100 ml of a methanol solution containing 4% of Irganox 1076 antioxidant (Ciba), obtaining 5.37 g of polybutadiene having a content of 1,4-cis units equal to 96.7%: further characteristics of the process and of the polybutadiene obtained are indicated in Table 1.

Example 10

B230

(69) 15 ml of 1,3-butadiene equal to about 10.5 g were condensed at a low temperature (20 C.) in a 250 ml glass reactor. 100 ml of toluene were then added, and the temperature of the solution thus obtained was brought to 20 C. Methylaluminoxane (MAO) in a toluene solution (9.95 ml; 1.5810.sup.2 moles, equal to about 0.92 g) was then added, and subsequently the complex CoCl.sub.2(L2) [sample GL545] (3.55 ml of a toluene solution at a concentration equal to 2 mg/ml; 1.5810.sup.5 moles, equal to about 7.1 mg) obtained as described in Example 3. The whole was kept, under magnetic stirring, at 20 C. for 240 minutes. The polymerization was then quenched by the addition of 2 ml of methanol containing a few drops of hydrochloric acid. The polymer obtained was then coagulated by the addition of 40 ml of a methanol solution containing 4% of Irganox 1076 antioxidant (Ciba), obtaining 4.74 g of polybutadiene having a content of 1,4-cis units equal to 96.6%: further characteristics of the process and of the polybutadiene obtained are indicated in Table 1.

(70) FIG. 3 shows the FT-IR spectrum of the polybutadiene obtained.

Example 11

B231

(71) 15 ml of 1,3-butadiene equal to about 1.4 g were condensed at a low temperature (20 C.) in a 250 ml glass reactor. 100 ml of heptane were then added, and the temperature of the solution thus obtained was brought to 20 C. Methylaluminoxane (MAO) in a toluene solution (9.95 ml; 1.5810.sup.2 moles, equal to about 0.92 g) was then added, and subsequently the complex CoCl.sub.2(L2) [sample GL545] (3.55 ml of a toluene solution at a concentration equal to 2 mg/ml; 1.5810.sup.5 moles, equal to about 7.1 mg) obtained as described in Example 3. The whole was kept, under magnetic stirring, at 20 C., for 255 minutes. The polymerization was then quenched by the addition of 2 ml of methanol containing a few drops of hydrochloric acid. The polymer obtained was then coagulated by the addition of 100 ml of a methanol solution containing 4% of Irganox 1076 antioxidant (Ciba), obtaining 4.10 g of polybutadiene having a content of 1,4-cis units equal to 97.0%: further characteristics of the process and of the polybutadiene obtained are indicated in Table 1.

Example 12

GL967

(72) 2 ml of 1,3-butadiene equal to about 1.4 g were condensed at a low temperature (20 C.) in a 25 ml test-tube. 7.65 ml of toluene were then added, and the temperature of the solution thus obtained was brought to 20 C. Methylaluminoxane (MAO) in a toluene solution (6.3 ml; 110.sup.2 moles, equal to about 0.58 g) was then added, and subsequently the complex CoCl.sub.2(L6) [sample GL926] (2.11 ml of a toluene solution at a concentration equal to 2 mg/ml; 110.sup.5 moles, equal to about 4.2 mg) obtained as described in Example 4. The whole was kept, under magnetic stirring, at 20 C., for 60 minutes. The polymerization was then quenched by the addition of 2 ml of methanol containing a few drops of hydrochloric acid. The polymer obtained was then coagulated by the addition of 40 ml of a methanol solution containing 4% of Irganox 1076 antioxidant (Ciba), obtaining 1.04 g of polybutadiene having a content of 1,4-cis units equal to 98.9%: further characteristics of the process and of the polybutadiene obtained are indicated in Table 1.

(73) FIG. 4 shows the .sup.1H-NMR and .sup.13C-NMR spectra of the polybutadiene obtained.

Example 13

G1054

(74) 2 ml of 1,3-butadiene equal to about 1.4 g were condensed at a low temperature (20 C.) in a 25 ml test-tube. 7.65 ml of heptane were then added, and the temperature of the solution thus obtained was brought to 50 C. Methylaluminoxane (MAO) in a toluene solution (6.3 ml; 110.sup.2 moles, equal to about 0.58 g) was then added, and subsequently the complex CoCl.sub.2(L6) [sample GL926] (2.11 ml of a toluene solution at a concentration equal to 2 mg/ml; 110.sup.5 moles, equal to about 4.2 mg) obtained as described in Example 4. The whole was kept, under magnetic stirring, at 20 C., for 60 minutes. The polymerization was then quenched by the addition of 2 ml of methanol containing a few drops of hydrochloric acid. The polymer obtained was then coagulated by the addition of 40 ml of a methanol solution containing 4% of Irganox 1076 antioxidant (Ciba), obtaining 1.06 g of polybutadiene having a content of 1,4-cis units equal to 98.3%: further characteristics of the process and of the polybutadiene obtained are indicated in Table 1.

(75) FIG. 3 shows the FT-IR spectrum of the polybutadiene obtained.

Example 14

G1055

(76) 2 ml of 1,3-butadiene equal to about 1.4 g were condensed at a low temperature (20 C.) in a 25 ml test-tube. 7.65 ml of toluene were then added, and the temperature of the solution thus obtained was brought to 50 C. Methylaluminoxane (MAO) in a toluene solution (6.3 ml; 110.sup.2 moles, equal to about 0.58 g) was then added, and subsequently the complex CoCl.sub.2(L6) [sample GL926] (2.11 ml of a toluene solution at a concentration equal to 2 mg/ml; 110.sup.5 moles, equal to about 4.2 mg) obtained as described in Example 4. The whole was kept, under magnetic stirring, at 20 C., for 60 minutes. The polymerization was then quenched by the addition of 2 ml of methanol containing a few drops of hydrochloric acid. The polymer obtained was then coagulated by the addition of 40 ml of a methanol solution containing 4% of Irganox 1076 antioxidant (Ciba), obtaining 1.4 g of polybutadiene having a content of 1,4-cis units equal to 98.4%: further characteristics of the process and of the polybutadiene obtained are indicated in Table 1.

(77) FIG. 3 shows the FT-IR spectrum of the polybutadiene obtained.

Example 15

GL970

(78) 2 ml of 1,3-butadiene equal to about 1.4 g were condensed at a low temperature (20 C.) in a 25 ml test-tube. 8.2 ml of toluene were then added, and the temperature of the solution thus obtained was brought to 20 C. Methylaluminoxane (MAO) in a toluene solution (6.3 ml; 110.sup.2 moles, equal to about 0.58 g) was then added, and subsequently the complex CoCl.sub.2(L4) [sample GL922] (1.5 ml of a toluene solution at a concentration equal to 2 mg/ml; 110.sup.5 moles, equal to about 3.0 mg) obtained as described in Example 5. The whole was kept, under magnetic stirring, at 20 C., for 90 minutes. The polymerization was then quenched by the addition of 2 ml of methanol containing a few drops of hydrochloric acid. The polymer obtained was then coagulated by the addition of 40 ml of a methanol solution containing 4% of Irganox 1076 antioxidant (Ciba), obtaining 1.4 g of polybutadiene having a content of 1,4-cis units equal to 97.1%: further characteristics of the process and of the polybutadiene obtained are indicated in Table 1.

(79) FIG. 5 shows the .sup.1H-NMR and .sup.13C-NMR spectra of the polybutadiene obtained.

(80) FIG. 6 shows the DSC diagrams of the polybutadiene obtained.

Example 16

G1056

(81) 2 ml of 1,3-butadiene equal to about 1.4 g were condensed at a low temperature (20 C.) in a 25 ml test-tube. 8.2 ml of heptane were then added, and the temperature of the solution thus obtained was brought to 50 C. Methylaluminoxane (MAO) in a toluene solution (6.3 ml; 110.sup.2 moles, equal to about 0.58 g) was then added, and subsequently the complex CoCl.sub.2(L4) [sample GL922] (1.5 ml of a toluene solution at a concentration equal to 2 mg/ml; 110.sup.5 moles, equal to about 3.0 mg) obtained as described in Example 5. The whole was kept, under magnetic stirring, at 20 C., for 60 minutes. The polymerization was then quenched by the addition of 2 ml of methanol containing a few drops of hydrochloric acid. The polymer obtained was then coagulated by the addition of 40 ml of a methanol solution containing 4% of Irganox 1076 antioxidant (Ciba), obtaining 1.4 g of polybutadiene having a content of 1,4-cis units equal to 97.8%: further characteristics of the process and of the polybutadiene obtained are indicated in Table 1.

(82) FIG. 3 shows the FT-IR spectrum of the polybutadiene obtained.

Example 17

G1057

(83) 2 ml of 1,3-butadiene equal to about 1.4 g were condensed at a low temperature (20 C.) in a 25 ml test-tube. 8.2 ml of toluene were then added, and the temperature of the solution thus obtained was brought to 50 C. Methylaluminoxane (MAO) in a toluene solution (6.3 ml; 110.sup.2 moles, equal to about 0.58 g) was then added, and subsequently the complex CoCl.sub.2(L4) [sample GL922] (1.5 ml of a toluene solution at a concentration equal to 2 mg/ml; 110.sup.5 moles, equal to about 3.0 mg) obtained as described in Example 5. The whole was kept, under magnetic stirring, at 20 C., for 60 minutes. The polymerization was then quenched by the addition of 2 ml of methanol containing a few drops of hydrochloric acid. The polymer obtained was then coagulated by the addition of 40 ml of a methanol solution containing 4% of Irganox 1076 antioxidant (Ciba), obtaining 1.4 g of polybutadiene having a content of 1,4-cis units equal to 98.1%: further characteristics of the process and of the polybutadiene obtained are indicated in Table 1.

(84) FIG. 3 shows the FT-IR spectrum of the polybutadiene obtained.

(85) TABLE-US-00001 TABLE 1 Polymerization of 1,3-butadiene with catalytic systems comprising complexes of cobalt Con- M.sub.w Exam- Times version N.sup.(a) T.sub.m.sup.(b) T.sub.c.sup.(c) (g M.sub.w/ ples (min) (%) (h.sup.1) ( C.) ( C.) mol.sup.1) M.sub.n .sup.(e) 6 30 85 4407 11.9 43.2 333256 2.2 0.55 7 30 48 2489 9.2 38.7 230144 1.5 0.54 8 8 46 9139 11.8 37.8 659269 2.8 0.55 9 240 51.1 1573 12.0 43.5 271000 2.1 0.54 10 240 45.1 1387 12.2 44.3 610000 2.5 0.56 11 255 39 1129 13.2 46.1 285000 2.3 0.53 12 60 74.3 1926 10.5 40.4 230000 1.5 0.56 13 60 76.0 1970 15.9 61.1 180000 1.4 0.53 14 60 100 2592 16.9 59.9 210000 1.6 0.54 15 90 100 1728 12.8 45.7 134000 2.3 0.46 16 60 100 2592 16.4 62.3 131000 1.7 0.48 17 60 100 2592 17.5 64.3 132000 1.8 0.49 .sup.(a)number of moles of 1,3-butadiene polymerized per hour, per mole of cobalt; .sup.(b)melting point; .sup.(c)crystallization temperature; .sup.(e)linearity index of polybutadiene