Process for the preparation of (co) polymers of conjugated dienes in the presence of a catalytic system comprising a bis-imine 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 bis-imine complex of cobalt having general formula (I) wherein: n is 0 or 1; Y represents a group CRR wherein R and R, equal to or different from each other, represent a hydrogen atom; or a linear or branched C.sub.1-C.sub.20, preferably C.sub.1-C.sub.15, alkyl group; or a divalent aromatic group optionally substituted; R.sub.1 and R.sub.2, equal to or different from each other, represent a hydrogen atom; or they are selected from a linear or branched Ci-C2o/preferably C.sub.1-C.sub.15, alkyl group optionally halogenated, cycloalkyl groups optionally substituted; or R.sub.1 and R.sub.2 can be optionally bound to each other to form, together with the other atoms to which they are bound, a cycle containing from 4 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; R.sub.3 and R.sub.4, equal to or different from each other, represent a hydrogen atom; or they are selected from a linear or branched Ci-C20, preferably C.sub.1-C.sub.15, alkyl groups optionally halogenated, cycloalkyl groups optionally substituted, aryl groups optionally substituted; or R2 and R4 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 Ci-C2o, preferably C1-C15 alkyl groups, said cycle optionally containing other heteroatoms such as, for example, oxygen, sulfur, nitrogen, silicon, phosphorous, selenium; or R.sub.1 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 other 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.5 groups or OR.sub.3 groups wherein R.sub.5 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 bis-imine complex of cobalt having general formula (I): ##STR00022## wherein: n is 0 or 1; Y represents a group CRR wherein R and R, equal to or different from each other, represent a hydrogen atom, or a linear or branched C.sub.1-C.sub.20 alkyl group; or a divalent aromatic group optionally substituted; R.sub.1 and R.sub.2, equal to or different from each other, represent a hydrogen atom; or they are selected from a linear or branched C.sub.1-C.sub.20 alkyl groups optionally halogenated, or cycloalkyl groups optionally substituted; or R.sub.1 and R.sub.2 can be optionally bound to each other to form, together with the other atoms to which they are bound, a cycle containing from 4 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; R.sub.3 and R.sub.4, equal to or different from each other, represent a hydrogen atom; or they are selected from a linear or branched C.sub.1-C.sub.20 alkyl groups optionally halogenated, cycloalkyl groups optionally substituted; or aryl groups optionally substituted; or R.sub.2 and R.sub.4 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 alkyl groups, said cycle optionally containing other heteroatoms; or R.sub.1 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 alkyl groups, said cycle optionally containing other heteroatoms; X.sub.1 and X.sub.2, equal to or different from each other, represent a halogen atom; or they are selected from linear or branched C.sub.1-C.sub.20 alkyl groups, OCOR.sub.5 groups or OR.sub.5 groups wherein R.sub.5 is selected from linear or branched C.sub.1-C.sub.20 alkyl groups, wherein when n=0; R.sub.1 and R.sub.3 are bound to each other to form, together with the other atoms to which they are bound, an aromatic cycle containing 5 carbon atoms; and R.sub.4 is a phenyl group, then at least one of the following occurs: R.sub.2 is selected from a linear or branched C.sub.1-C.sub.20 alkyl groups optionally halogenated, or cycloalkyl groups optionally substituted; and the R.sub.4 phenyl group is substituted with linear or branched C.sub.2-C.sub.20 alkyl groups; or wherein when n=0; R.sub.2 and R.sub.4 are bound to each other to form, together with the other atoms to which they are bound, an aromatic cycle containing 5 carbon atoms; and R.sub.3 is a phenyl group, then at least one of the following occurs: R.sub.1 is selected from a linear or branched C.sub.1-C.sub.20 alkyl groups optionally halogenated, or cycloalkyl groups optionally substituted; and the R.sub.3 phenyl group is substituted with linear or branched C.sub.2-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.6).sub.3-n(II) wherein X represents a halogen atom; R.sub.6 is selected from linear or branched C.sub.1-C.sub.20 alkyl groups, cycloalkyl groups, or 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 bis-imine complex of cobalt having general formula (I), extracting therefrom a substituent X.sub.1 or X.sub.2 -bound, to form at least one neutral compound, and an ionic compound including a cation containing the metal (Co) coordinated by a bis-imine ligand, and a non-coordinating organic anion containing the metal M, wherein the negative charge is delocalized on a multicentric structure.

6. The process for the preparation of (co)polymers of conjugated dienes according to claim 1, wherein said conjugated diene is 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 bis-imine complex of cobalt having general formula (I): n is 0; R.sub.1 and R.sub.2; equal to or different from each other, are a hydrogen atom, or they are selected from linear or branched C.sub.1-C.sub.20 alkyl groups; R.sub.3 and R.sub.4, equal to or different from each other, are selected from phenyl groups optionally 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 1, wherein in said bis-imine complex of cobalt having general formula (I): n is 1; Y is a group CRR wherein R and R, equal to or different from each other, are a hydrogen atom; or they are selected from linear or branched C.sub.1-C.sub.20 alkyl groups; R.sub.1 and R.sub.2, equal to or different from each other, are a hydrogen atom; or they are selected from linear or branched C.sub.1-C.sub.20 alkyl groups; R.sub.3 and R.sub.4, equal to or different from each other, are selected from phenyl groups optionally 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.

9. The process for the preparation of (co)polymers of conjugated dienes according to claim 1, wherein in said bis-imine complex of cobalt having general formula (I): n is 0; R.sub.1 and R.sub.3, are bound to each other and, together with the other atoms to which they are bound, form a pyridine; R.sub.2 is selected from linear or branched C.sub.1-C.sub.20 alkyl groups; R.sub.4 is selected from phenyl groups substituted with linear or branched C.sub.2-C.sub.20 alkyl groups; X.sub.1 and X.sub.2, the same as each other, are a halogen atom.

10. The process for the preparation of (co)polymers of conjugated dienes according to claim 1, wherein in said bis-imine complex of cobalt having general formula (I): n is 1; Y is a divalent aromatic group optionally substituted; R.sub.1 and R.sub.2, equal to or different from each other, are a hydrogen atom, or they are selected from linear or branched C.sub.1-C.sub.20 alkyl groups; R.sub.3 and R.sub.4, equal to or different from each other, are selected from phenyl groups optionally 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.

11. 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, mono-ethyl-aluminium dichloride, ethylaluminiumsesquichloride (EASC).

12. 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.7).sub.2AlO[Al(R.sub.8)O].sub.pAl(R.sub.9).sub.2(III) wherein R.sub.7, R.sub.8 and R.sub.9, equal to or different from each other, represent a hydrogen atom, a halogen atom; or they are selected from linear or branched C.sub.1-C.sub.20 alkyl groups, cycloalkyl groups, or 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.

13. The process for the preparation of (co)polymers of conjugated dienes according to claim 12, wherein said organo-oxygenated compound (b.sub.2) is methylaluminoxane (MAO).

14. The process for the preparation of (co)polymers of conjugated dienes according to claim 5, wherein said compounds or 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.

15. 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.

16. The process for the preparation of (co)polymers of conjugated dienes according to claim 15, 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.

17. 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.

18. The process for the preparation of (co)polymers of conjugated dienes according to claim 1, wherein said (co)polymers of conjugated dienes are polybutadiene having a content of 1,4-cis units 98%.

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; formic acid (85%) (Carlo Erba, RPE): used as such; 2,3-butandione (Aldrich): used as such; 2-tert-butylaniline (Aldrich): used as such; 2,6-diethylaniline (Aldrich): used as such; 2,4,6-trimethylaniline (Aldrich): used as such; 2,6-di-iso-propylaniline (Aldrich): used as such; p-toluidine (Aldrich): used as such; benzene-1,3-carboxyaldehyde (Aldrich): used as such; acetylpyridine (Aldrich): used as such; glyoxal (aqueous solution at 40%) (Aldrich): used as such; toluene (Aldrich): pure, 99.5%, distilled on sodium (Na) in an inert atmosphere; pentane (Aldrich): pure, 99.5%, distilled on sodium (Na) in an inert atmosphere; methylaluminoxane (MAO) (toluene solution at 10% by weight) (Aldrich): used as such; acetylacetone (Aldrich): used as such; 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 which has been pre-cooled at 20 C.; hydrochloric acid in aqueous solution at 37% (Aldrich): used as such; p-toluenesulfonic acid (Aldrich): used as such; sodium carbonate decahydrate (Na.sub.2CO.sub.3.10H.sub.2O) (Aldrich): used as such; magnesium sulfate (MgSO.sub.4) (Aldrich): used as such; methanol (Carlo Erba, RPE): used as such; ethanol (Carlo Erba, RPE): used as such or optionally anhydrified by distillation on magnesium (Mg); dichloromethane (Carlo Erba, RPE): used as such; deuterated tetrachloroethylene (C.sub.2D.sub.2Cl.sub.4) (Acros): used as such; deuterated chloroform (CDCl.sub.3) (Acros): used as such.

(2) The analyses and characterization methods indicated hereunder, were used.

(3) Elemental Analysis

(4) a) Determination of Co

(5) For the determination of the weight quantity of cobalt (Co) in the bis-imine 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 mg-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.), 1 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 bis-imine 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) 1/5 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 and Nitrogen

(10) The determination of the carbon, hydrogen and nitrogen, in the bis-imine 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 Carlo Erba automatic analyzer Mod. 1106.

(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 bis-imine complexes of cobalt used in the present invention, were obtained by dispersing the bis-imine 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.c) 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.g) 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 of the 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) The informations relating to the macrostructure of the polymer are 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 (L5)

(34) ##STR00006##

(35) A few drops of formic acid were added to a solution of 13.49 g (90 mmoles) of 2-tert-butylaniline in 50 ml of methanol, obtaining a yellow solution. A solution of 2,3-butandione (3.875 g45 mmoles) in 30 ml of methanol were added, dropwise, under stirring, to said solution.

(36) The whole was left, under stirring, at room temperature, for about 2 hours, until the formation of a yellow precipitate had been observed. The whole was left to rest for 14 hours and was subsequently filtered and dried under vacuum, at room temperature, obtaining 14.1 g of a yellowish solid product (yield=90%) having formula (L5).

(37) FT-IR (nujol): 1636 cm.sup.1 .sub.(CN).

(38) Molecular weight (MW): 348.53.

(39) Elemental analysis [found (calculated)]: C, 81.95% (82.71%); H, 9.26% (9.25%); N, 8.02% (8.01%).

Example 2

Synthesis of the Ligand Having Formula (L7)

(40) ##STR00007##

(41) A few drops of formic acid were added to a solution of 21.81 g (180 mmoles) of 2,6-diethylaniline in 80 ml of methanol, obtaining a yellow solution. A solution of 2,3-butandione (7.75 g90 mmoles) in 100 ml of methanol were added, dropwise, under stirring, to said solution.

(42) The whole was left, under stirring, at room temperature, for about 2 hours, until the formation of a yellow precipitate had been observed. The whole was left to rest for 14 hours and was subsequently filtered and dried under vacuum, at room temperature, obtaining 27 g of a yellowish solid product (yield=86%) having formula (L7).

(43) FT-IR (nujol): 1644 cm.sup.1 .sub.(CN).

(44) Molecular weight (MW): 348.53.

(45) Elemental analysis [found (calculated)]: C, 82.6% (82.71%); H, 9.29% (9.25%); N, 8.04% (8.04%).

Example 3

Synthesis of the Ligand Having Formula (L8)

(46) ##STR00008##

(47) A few drops of formic acid were added to a solution of 15.96 g (90 mmoles) di 2,6-di-iso-propylaniline in 80 ml of methanol, obtaining a yellow solution. A solution of 2,3-butandione (3.875 g45 mmoles) in 80 ml of methanol were added, dropwise, under stirring, to said solution.

(48) The whole was left, under stirring, at room temperature, for about 2 hours, until the formation of a yellow precipitate had been observed. The whole was left to rest for 14 hours and was subsequently filtered and dried under vacuum, at room temperature, obtaining 15.4 g of a yellowish solid product (yield=84%) having formula (L8).

(49) FT-IR (nujol): 1640 cm.sup.1 .sub.(CN).

(50) Molecular weight (MW): 404.64.

(51) Elemental analysis [found (calculated)]: C, 82.86% (83.11%); H, 9.97% (9.96%); N, 6.94% (6.92%).

Example 4

Synthesis of the Ligand Having Formula (L9)

(52) ##STR00009##

(53) A few drops of formic acid were added to a solution of 24.34 g (180 mmoles) of 2,4,6-trimethylaniline in 60 ml of methanol, obtaining a yellow solution. A solution of 2,3-butandione (7.75 g90 mmoles) in 100 ml of methanol were added, dropwise, under stirring, to this solution.

(54) The whole was left, under stirring, at room temperature, for about 2 hours, until the formation of a yellow precipitate had been observed. The whole was left to rest for 14 hours and was subsequently filtered and dried under vacuum, at room temperature, obtaining 27.25 g of a yellowish solid product (yield=94.5%) having formula (L9).

(55) FT-IR (nujol): 1637 cm.sup.1 .sub.(CN).

(56) Molecular weight (MW): 320.48.

(57) Elemental analysis [found (calculated)]: C, 81.62% (82.45%); H, 8.80% (8.81%); N, 8.66% (8.74%).

Example 5

Synthesis of the Ligand Having Formula (L12)

(58) ##STR00010##

(59) 14.924 g (100 mmoles) of 2-tert-butylaniline were dissolved in a mixture of methanol and distilled water (50 ml+100 ml). 7.26 g (50 mmoles) of glyoxal (40% by weight of aqueous solution) were added, under vigorous stirring, to the solution thus obtained, cooled to 0 C. with a water/ice bath. The yellow solution obtained was left, under stirring, at room temperature, until the precipitation of a solid had been obtained, which was filtered, washed with methanol, re-crystallized from pentane and dried under vacuum, at room temperature, obtaining 12 g of a yellow microcrystalline product (yield=75%) having formula (L12).

(60) FT-IR (nujol): 1608 cm.sup.1 .sub.(CN).

(61) Molecular weight (MW): 320.47.

(62) Elemental analysis [found (calculated)]: C, 82.42% (82.45%); H, 8.80% (8.81%); N, 8.76% (8.74%).

Example 6

Synthesis of the Ligand Having Formula (L13)

(63) ##STR00011##

(64) 13.52 g (100 mmoles) of 2,4,6-trimethylaniline were dissolved in a mixture of methanol and distilled water (50 ml+100 ml). 7.26 g (50 mmoles) of glyoxal (40% by weight of aqueous solution) were added, under vigorous stirring, to the solution thus obtained, cooled to 0 C. with a water/ice bath. The yellow solution obtained was left, under stirring, at room temperature, until the precipitation of a solid had been obtained, which was filtered, washed with methanol, re-crystallized from pentane and dried under vacuum, at room temperature, obtaining 12 g of a yellow microcrystalline product (yield=82%) having formula (L13).

(65) FT-IR (nujol): 1616 cm.sup.1 .sub.(CN).

(66) Molecular weight (MW): 292.42.

(67) Elemental analysis [found (calculated)]: C, 82.0% (82.15%); H, 8.28% (8.27%); N, 9.5% (9.58%).

Example 7

Synthesis of the Ligand Having Formula (L20)

(68) ##STR00012##

(69) 1 g (7.4 mmoles) of benzene-1,3-carboxyaldehyde (diisophthalaldehyde) was dissolved in 20 ml of anhydrous ethanol. 1.75 g of p-toluidine (16.3 mmoles) and a few drops of formic acid were added to the solution thus obtained. The yellow solution obtained was left, under stirring, at room temperature, for 4 hours, obtaining the precipitation of a solid, which was filtered, washed with ethanol and pentane and dried under vacuum, at room temperature, obtaining 2 g of a yellow solid product (yield=86%) having formula (L20).

(70) FT-IR (nujol): 1625 cm.sup.1.sub.(CN).

(71) Molecular weight (MW): 312.41.

(72) Elemental analysis [found (calculated)]: C, 84.4% (84.58%); H, 6.4% (6.45%); N, 9.0% (8.97%).

Example 8

Synthesis of the Ligand Having Formula (L18)

(73) ##STR00013##

(74) 15.96 g (90 mmoles) of 2,6-di-isopropylaniline were introduced into a flask together with 50 ml of methanol and 0.25 ml of formic acid. 50 ml of methanol containing 10.9 g (90 mmoles) of acetylpyridine were added dropwise, at room temperature, to the solution thus obtained. The solution obtained was left under stirring, at room temperature, until the precipitation of a solid was obtained, which was filtered, washed with cold methanol and dried under vacuum, at room temperature, obtaining 12.6 g of a white microcrystalline, product (yield=53%) having formula (L18).

(75) FT-IR (nujol): 1652 cm.sup.1 .sub.(CN).

(76) Molecular weight (MW): 280.41.

(77) Elemental analysis [found (calculated)]: C, 81.52% (81.38%); H, 8.57% (8.63%); N, 9.90% (9.99%).

Example 9

Synthesis of the Ligand Having Formula (L21)

(78) ##STR00014##

(79) A mixture of p-toluidine (2.68 g, 25 mmoles), 2,4-pentadione (1.24 g, 12 mmoles) and p-toluenesulfonic acid (2.13 g) in toluene (35 ml), was heated to reflux temperature, for 24 hours, in a Dean-Stark apparatus. At the end, the toluene was decanted and the residue obtained was treated with diethylether (30 ml), water (25 ml) and sodium carbonate decahydrate (Na.sub.2CO.sub.3.10H.sub.2O). The mixture obtained was left, under stirring, at room temperature, for 30 minutes and, the ether layer was subsequently separated from the aqueous layer and anhydrified with magnesium sulfate (MgSO.sub.4). The solvent was then removed by vacuum evaporation. The residue obtained was dried under vacuum, at 100 C., and subsequently re-crystallized from hexane, obtaining 2.7 g of a microcrystalline product (yield=78%), having formula (L21).

(80) FT-IR (nujol): 1611 cm.sup.1 .sub.(CN).

(81) .sup.1H-NMR (CDCl.sub.3): =12.66 (s, 1H), 7.10 (d, 4H, ArH), 6.86 (d, 4H), 4.85 (s, 1H), 2.30 (s, 6H), 1.98 (s, 6H) ppm.

(82) Molecular weight (MW): 278.41.

(83) Elemental analysis [found (calculated)]: C, 81.80% (81.97%); H, 7.90% (7.96%); N, 10.20% (10.60%).

Example 10

Synthesis of CoCl2(L8) [Sample GL648]

(84) ##STR00015##

(85) Cobalt dichloride (CoCl.sub.2) (0.334 g; 2.577 mmoles) was introduced into a 100 ml reaction flask together with 70 ml of tetrahydrofuran (THF). The whole was kept, under stirring, at room temperature, for a few minutes and the ligand having formula (L8) (1.25 g; 3.08 mmoles; molar ratio L8/Co=1.2) obtained as described in Example 3, was subsequently added. A green suspension was immediately formed, which was kept, under stirring, at room temperature, for 24 hours. The solvent was then removed under vacuum and the solid dark green 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. The residue remaining on the porous septum was subsequently extracted again, in continuous, with toluene at boiling point, for 24 hours, obtaining a green-coloured solution. The toluene was removed under vacuum and the solid residue remaining on the porous septum was recovered and dried under vacuum, at room temperature, obtaining 1.03 g of a light green solid product corresponding to the complex CoCl.sub.2(L8), equal to a conversion of 75% with respect to the cobalt dichloride charged.

(86) Elemental analysis [found (calculated)]: C, 62.30% (62.92%); H, 7.44% (7.54%); N, 5.36% (5.24%); Cl, 12.80% (13.27%); Co, 10.90% (11.03%).

(87) Molecular weight (MW): 534.47.

(88) FT-IR (nujol): 1639 cm.sup.1 .sub.(CN); 1585 cm.sup.1 .sub.(CN).

(89) FIG. 1 shows the FT-IR spectrum of the complex CoCl.sub.2(L8) obtained (the nujol bands having been subtracted).

Example 11

Synthesis of CoCl2(L5) [Sample GL649]

(90) ##STR00016##

(91) Cobalt dichloride (CoCl.sub.2) (0.369 g; 2.84 mmoles) was introduced into a 100 ml reaction flask together with 70 ml of tetrahydrofuran (THF). The whole was kept, under stirring, at room temperature, for a few minutes and the ligand having formula (L5) (1.14 g; 3.27 mmoles; molar ratio L5/Co=1.15) obtained as described in Example 1, was subsequently added. The green/light blue suspension obtained was kept under stirring, at room temperature, for 48 hours. The solvent was then removed under vacuum and the solid 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. The residue remaining on the porous septum was subsequently extracted again, in continuous, with dichloromethane at boiling point, for 24 hours, obtaining a green 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 1.107 g of a green solid product corresponding to the complex CoCl.sub.2(L5), equal to a conversion of 81.5% with respect to the cobalt dichloride charged.

(92) Elemental analysis [found (calculated)]: C, 59.80% (60.26%); H, 6.60% (6.74%); N, 5.70% (5.86%); Cl, 14.20% (14.82%); Co, 11.90% (12.32%).

(93) Molecular weight (MW): 478.36.

(94) FT-IR (nujol): 1633 cm.sup.1 .sub.(CN); 1587 cm.sup.1 .sub.(CN).

Example 12

Synthesis of CoCl2(L7) [Sample GL546]

(95) ##STR00017##

(96) Cobalt dichloride (CoCl.sub.2) (0.439 g; 3.4 mmoles) was introduced into a 100 ml reaction flask together with 70 ml of tetrahydrofuran (THF). The whole was kept under stirring, at room temperature, for a few minutes and the ligand having formula (L7) (1.4 g; 4.08 mmoles; molar ratio L7/Co=1.2) obtained as described in Example 2, was subsequently added. A dark green suspension was immediately formed, which was kept, under stirring, at room temperature, for 24 hours. The solvent was then removed under vacuum and the dark green solid 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. The residue remaining on the porous septum was subsequently extracted again, in continuous, with dichloromethane at boiling point, for 24 hours, obtaining a green 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 0.921 g of a green solid product corresponding to the complex CoCl.sub.2(L7), equal to a conversion of 56.6% with respect to the cobalt dichloride charged.

(97) Elemental analysis [found (calculated)]: C, 60.0% (60.26%); H, 6.30% (6.64%); N, 5.70% (5.86%); Cl, 13.90% (14.82%); Co, 12.10% (12.32%).

(98) Molecular weight (MW): 478.36.

(99) FT-IR (nujol): 1642 cm.sup.1 .sub.(CN); 1585 cm.sup.1 .sub.(CN).

Example 13

Synthesis of CoCl2(L9) [Sample GL651]

(100) ##STR00018##

(101) Cobalt dichloride (CoCl.sub.2) (0.444 g; 3.46 mmoles) was introduced into a 100 ml reaction flask together with 70 ml of tetrahydrofuran (THF). The whole was kept, under stirring, at room temperature, for a few minutes and the ligand having formula (L9) (1.33 g; 4.15 mmoles; molar ratio L9/Co=1.2) obtained as described in Example 4, was subsequently added. A green suspension was immediately formed, which was kept, under stirring, at room temperature, for 24 hours. The solvent was then removed under vacuum and the solid 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. The residue remaining on the porous septum was subsequently extracted again, in continuous, with dichloromethane at boiling point, for 24 hours, obtaining a green 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 1.10 g of a dark green solid product corresponding to the complex CoCl.sub.2(L9), equal to a conversion of 70% with respect to the cobalt dichloride charged.

(102) Elemental analysis [found (calculated)]: C, 58.40% (58.68%); H, 6.24% (6.27%); N, 6.45% (6.22%); Cl, 16.30% (15.75%); Co, 12.70% (13.09%).

(103) Molecular weight (MW): 450.31.

(104) FT-IR (nujol): 1635 cm.sup.1 .sub.(CN); 1585 cm.sup.1 .sub.(CN).

(105) FIG. 2 shows the FT-IR spectrum of the complex CoCl.sub.2(L9) obtained (the nujol bands having been subtracted).

Example 14

Synthesis of CoCl2(L13) [Sample GL769]

(106) ##STR00019##

(107) Cobalt dichloride (CoCl.sub.2) (0.284 g; 2.19 mmoles) was introduced into a 0.100 ml reaction flask together with 50 ml of tetrahydrofuran (THF). The whole was kept under stirring, at room temperature, for a few minutes and the ligand having formula (L13) (0.690 g; 2.36 mmoles; molar ratio L13/Co=1.1) obtained as described in Example 6, was subsequently added. A dark green suspension was immediately formed, which was kept, under stirring, at room temperature, for 24 hours. The solvent was then removed under vacuum and the light green solid 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. The residue remaining on the porous septum was subsequently extracted again, in continuous, with dichloromethane at boiling point, for 24 hours, obtaining a green 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 0.750 g of a brown/bordeaux solid product corresponding to the complex CoCl.sub.2(L13), equal to a conversion of 81% with respect to the cobalt dichloride charged.

(108) Elemental analysis [found (calculated)]: C, 56.20% (56.89%); H, 5.60% (5.73%); N, 6.40% (6.63%); Cl, 16.20% (16.79%); Co, 13.40% (13.96%).

(109) Molecular weight (MW): 422.26.

(110) FT-IR (nujol): 1612 cm.sup.1 .sub.(CN).

Example 15

Synthesis of CoCl2(L18) [Sample GL774]

(111) ##STR00020##

(112) Cobalt dichloride (CoCl.sub.2) (0.366 g; 2.82 mmoles) was introduced into a 100 ml reaction flask together with 50 ml of tetrahydrofuran (THF). The whole was kept under stirring, at room temperature, for a few minutes and the ligand having formula (L18) (0.908 g; 3.24 mmoles; molar ratio L18/Co=1.15) obtained as described in Example 8, was subsequently added. A purple suspension was immediately formed, which was kept, under stirring, at room temperature, for 24 hours. The solvent was then removed under vacuum and the solid 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. The residue remaining on the porous septum was subsequently extracted again, in continuous, with dichloromethane at boiling point, for 24 hours, obtaining a green 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 0.824 g of a purple solid product corresponding to the complex CoCl.sub.2(L18), equal to a conversion of 71% with respect to the cobalt dichloride charged.

(113) Elemental analysis [found (calculated)]: C, 54.90% (55.63%); H, 5.80% (5.90%); N, 6.70% (6.83%); Cl, 16.90% (17.28%); Co, 13.90% (14.37%).

(114) Molecular weight (MW): 410.25.

(115) FT-IR (nujol): 1648 cm.sup.1 .sub.(CN).

Example 16

Synthesis of CoCl2(L20) [Sample GL907]

(116) ##STR00021##

(117) Cobalt dichloride (CoCl.sub.2) (0.160 g; 1.23 mmoles) was introduced into a 100 ml reaction flask together with 50 ml of tetrahydrofuran (THF). The whole was kept under stirring, at room temperature, for a few minutes and the ligand having formula (L20) (0.416 g; 1.33 mmoles; molar ratio L20/Co=1.1) obtained as described in Example 7, was subsequently added. A green/light blue suspension was immediately formed, which was kept, under stirring, at room temperature, for 24 hours. The solvent was then removed under vacuum and the solid 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. The residue remaining on the porous septum was subsequently extracted again, in continuous, with dichloromethane at boiling point, for 24 hours, obtaining a green 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 0.435 g of a green solid product corresponding to the complex CoCl.sub.2(L20), equal to a conversion of 80% with respect to the cobalt dichloride charged.

(118) Elemental analysis [found (calculated)]: C, 59.50% (59.75%); H, 4.40% (4.56%); N, 6.10% (6.33%); Cl, 15.60% (16.03%); Co, 13.0% (13.33%).

(119) Molecular weight (MW): 442.25.

(120) FT-IR (nujol): 1622 cm.sup.1 .sub.(CN).

Example 17

GL659

(121) 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. 7.05 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(L8) [sample GL648] (2.65 ml of a toluene solution at a concentration equal to 2 mg/ml; 110.sup.5 moles, equal to about 5.3 mg) obtained as described in Example 10. 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 0.985 g of polybutadiene having a content of 1,4-cis units equal to 98%: further characteristics of the process and of the polybutadiene obtained are shown in Table 1.

(122) FIG. 4 shows the FT-IR spectrum of the polybutadiene obtained.

(123) FIG. 9 shows the DSC diagrams of the polybutadiene obtained.

Example 18

GL661

(124) 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. 7.3 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(L5) [sample GL649] (2.4 ml of a toluene solution at a concentration equal to 2 mg/ml; 110.sup.5 moles, equal to about 4.8 mg) obtained as described in Example 11. 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 1.4 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 shown in Table 1.

(125) FIG. 4 shows the FT-IR spectrum of the polybutadiene obtained.

Example 19

GL640

(126) 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. 7.3 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(L7) [sample GL546] (2.4 ml of a toluene solution at a concentration equal to 2 mg/ml; 110.sup.5 moles, equal to about 4.8 mg) obtained as described in Example 12. 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 0.56 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 shown in Table 1.

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

Example 20

GL662

(128) 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(L9) [sample GL651] (2.25 ml of 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 13. 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 0.77 g of polybutadiene having a content of 1,4-cis units equal to 98.2%: further characteristics of the process and of the polybutadiene obtained are shown in Table 1.

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

Example 21

GL779

(130) 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. 7.6 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(L13) [sample GL769] (2.1 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 14. The whole was kept, under magnetic stirring, at 20 C., for 140 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 0.59 g of polybutadiene having a content of 1,4-cis units equal to 98.2%: further characteristics of the process and of the polybutadiene obtained are shown in Table 1.

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

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

(133) FIG. 7 shows the DSC diagrams of the polybutadiene obtained.

Example 22

GL820

(134) 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. 7.6 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(L13) [sample GL769] (2.1 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 14. The whole was kept, under magnetic stirring, at 50 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 1.4 g of polybutadiene having a content of 1,4-cis units equal to 98%: further characteristics of the process and of the polybutadiene obtained are shown in Table 1.

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

(136) FIG. 6 shows the .sup.1H-NMR and .sup.13C-NMR spectra of the polybutadiene obtained.

(137) FIG. 8 shows the DSC diagrams of the polybutadiene obtained.

Example 23

GL781

(138) 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(L18) [sample GL774] (2.05 ml of a toluene solution at a concentration equal to 2 mg/ml; 110.sup.5 moles, equal to about 4.1 mg) obtained as described in Example 15. The whole was kept, under magnetic stirring, at 20 C., for 360 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 0.91 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 shown in Table 1.

(139) FIG. 4 shows the FT-IR spectrum of the polybutadiene obtained.

Example 24

GL980

(140) 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. 7.5 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(L20) [sample GL907] (2.2 ml of a toluene solution at a concentration equal to 2 mg/ml; 110.sup.5 moles, equal to about 4.4 mg) obtained as described in Example 16. The whole was kept, under magnetic stirring, at 20 C., for 120 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 0.83 g of polybutadiene having a content of 1,4-cis units equal to 98%: further characteristics of the process and of the polybutadiene obtained are shown in Table 1.

(141) FIG. 4 shows the FT-IR spectrum of the polybutadiene obtained.

(142) TABLE-US-00001 TABLE 1 Polymerization of 1,3-butadiene with catalytic systems comprising complexes of cobalt. Times Conversion T.sub.m.sup.(b) T.sub.c.sup.(c) M.sub.w Example (min) (%) N.sup.(a) (h.sup.1) ( C.) ( C.) (gxmol.sup.1) M.sub.w/M.sub.n .sup.(e) 17 30 70 3648 7.7 26.5 410000 2.0 0.60 18 30 100 5185 7.9 26.3 287000 2.1 0.60 19 90 40 691 9.0 26.4 350000 1.9 0.59 20 30 55 2852 9.3 31.1 650000 2.5 0.61 21 140 42 468 12.1 34.9 630000 2.6 0.60 22 240 100 648 13.7 40.9 296000 2.4 0.59 23 360 65 281 13.2 32.2 272000 1.8 0.55 24 120 59 769 12.8 36.2 228000 2.0 0.59 .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.