BIS-IMINE TITANIUM COMPLEX, CATALYTIC SYSTEM COMPRISING SAID BIS-IMINE TITANIUM COMPLEX AND PROCESS FOR THE (CO)POLYMERIZATION OF CONJUGATED DIENES

Abstract

Bis-imine titanium complex having general formula (I): wherein: R.sub.1 and R.sub.2, mutually identical or different, represent a hydrogen atom; or are selected from linear or branched, optionally halogenated, C.sub.1-C.sub.20 alkyl groups, preferably C.sub.1-C.sub.15, optionally substituted cycloalkyl groups; R.sub.3 and R.sub.4, mutually identical or different, represent a hydrogen atom; or are selected from linear or branched, optionally halogenated, C.sub.1-C.sub.20 alkyl groups, preferably C.sub.1-C.sub.15, optionally substituted cycloalkyl groups, optionally substituted aryl groups; X.sub.1, X.sub.2, X.sub.3 and X.sub.4, mutually identical or different, represent a halogen atom such as chlorine, bromine, iodine; or are selected from linear or branched C.sub.1-C.sub.20 alkyl groups, preferably C.sub.1-C.sub.15, 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, preferably C.sub.1-C.sub.15; or represent an acetylacetonate group (acac); provided that when R.sub.1 and R.sub.2 represent a methyl group and X.sub.1, X.sub.2, X.sub.3 and X.sub.4 represent a chlorine atom, R.sub.3 and R.sub.4 are different from 2,6-di-isopropylphenyl.

##STR00001##

Claims

1. Bis-imine titanium complex having general formula (I): ##STR00022## wherein: R.sub.1 and R.sub.2, mutually identical or different, represent a hydrogen atom; or are selected from linear or branched, optionally halogenated, C.sub.1-C.sub.20 alkyl groups, preferably C.sub.1-C.sub.15, optionally substituted cycloalkyl groups; R.sub.3 and R.sub.4, mutually identical or different, represent a hydrogen atom; or are selected from linear or branched, optionally halogenated, C.sub.1-C.sub.20 alkyl groups, preferably C.sub.1-C.sub.15, optionally substituted cycloalkyl groups, optionally substituted aryl groups; X.sub.1, X.sub.2, X.sub.3 and X.sub.a, mutually identical or different, represent a halogen atom such as chlorine, bromine, iodine; or are selected from linear or branched C.sub.1-C.sub.20 alkyl groups, preferably C.sub.1-C.sub.15, 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, preferably C.sub.1-C.sub.15; or represent an acetylacetonate group (acac); provided that when R.sub.1 and R.sub.2 represent a methyl group and X.sub.1, X.sub.2, X.sub.3 and X.sub.4 represent a chlorine atom, R.sub.3 and R.sub.4 are different from 2,6-di-iso-propylphenyl.

2. A bis-imine titanium complex having general formula (I) according to claim 1, wherein: R.sub.1 and R.sub.2, mutually identical, are a hydrogen atom; or are selected from linear or branched C.sub.1-C.sub.20 alkyl groups, preferably are a methyl group; R.sub.3 and R.sub.4, mutually identical, are selected from phenyl groups optionally substituted with linear or branched C.sub.1-C.sub.20 alkyl groups, preferably substituted with one or more methyl, ethyl, iso-propyl, tert-butyl groups; X.sub.1, X.sub.2, X.sub.3 and X.sub.4, mutually identical, are a halogen atom such as chlorine, bromine, iodine, preferably chlorine.

3. Catalytic system for the (co)polymerization of conjugated dienes comprising: (a) at least one bis-imine titanium complex having general formula (I) according to claim 1; (b) at least one co-catalyst selected from organic compounds of an element M other than carbon, said M element being selected from elements belonging to groups 2, 12, 13 or 14 of the Periodic Table of the Elements, preferably from: boron, aluminum, zinc, magnesium, gallium, tin, even more preferably from aluminum, boron.

4. Catalytic system for the (co)polymerization of conjugated dienes according to claim 3, wherein said co-catalyst (b) is selected from (b.sub.1) aluminum alkyl having general formula (II):
Al(X).sub.n(R.sub.6).sub.3-n(II) wherein X represents a halogen atom such as chlorine, bromine, iodine, fluorine; R.sub.6, mutually identical or different, represent a hydrogen atom, or are selected from linear or branched C.sub.1-C.sub.20 alkyl groups, cycloalkyl groups, aryl groups, said groups being optionally substituted with one or more silicon or germanium atoms; and n is an integer ranging from 0 to 2.

5. Catalytic system for the (co)polymerization of conjugated dienes according to claim 3, wherein said co-catalyst (b) is selected from (b.sub.2) organo-oxygenated compounds of an element M other than carbon belonging to groups 13 or 14 of the Periodic Table of the Elements, preferably aluminum, gallium, tin compounds.

6. The catalytic system for the (co)polymerization of conjugated dienes according to claim 3, wherein said co-catalyst (b) is selected from (b.sub.3) compounds or mixtures of organometallic compounds of an element M other than carbon capable of reacting with the bis-imine titanium complex titanium having general formula (I), thereby extracting a -linked substituent X.sub.1, X.sub.2, X.sub.3 or X.sub.4, to form at least one neutral compound and an ionic compound consisting of a cation containing the metal (Ti) coordinated by the ligand, and an uncoordinating organic anion containing the metal M, whose negative charge is delocalized on a multicentric structure.

7. Catalytic system for the (co)polymerization of conjugated dienes according to claim 4, wherein said aluminum alkyls (b.sub.1) having general formula (II) are triethylaluminum (TEA), tri-n-propyl aluminum, tri-iso-butyl aluminum (TIBA), tri-hexyl-aluminum, di-iso-butyl aluminum hydride (DIBAH), diethyl aluminum chloride (DEAC).

8. Catalytic system for the (co)polymerization of conjugated dienes according to claim 5, wherein said organoxygenated compounds (b.sub.2) are selected from aluminoxanes having general formula (III):
(R.sub.7).sub.2AlO[-Al(R.sub.8)O].sub.p-Al(R.sub.9).sub.2(III) wherein R.sub.7, R.sub.8 and R.sub.9, mutually identical or different, represent a hydrogen atom, a halogen atom such as chlorine, bromine, iodine, fluorine; or are selected from linear or branched C.sub.1-C.sub.20 alkyl groups, cycloalkyl groups, aryl groups, said groups being optionally substituted with one or more silicon or germanium atoms; and p is an integer ranging from 0 to 1000.

9. Catalytic system for the (co)polymerization of conjugated dienes according to claim 8, wherein said organo-oxygenated compound (b.sub.2) is methylaluminoxane (MAO).

10. Catalytic system for the (co)polymerization of conjugated dienes according to claim 6, wherein said compound(s) or mixtures of compounds (b.sub.3) are selected from organic aluminum compounds and especially boron, such as those represented by the following general formulae:
[(R.sub.C).sub.WH.sub.4-W].[B(R.sub.D).sub.4]; B(R.sub.D).sub.3; Al(R.sub.D).sub.3; B(R.sub.D).sub.3Pir; [Ph.sub.3C]+.[B(R.sub.D).sub.4]; [(R.sub.C).sub.3PirH]+.[B(R.sub.D).sub.4]; [Li]+.[B(R.sub.D).sub.4]; [Li]+.[Al(R.sub.D).sub.4] wherein w is an integer ranging from 0 to 3, each R.sub.C group, independently represents an alkyl group or an aryl group having from 1 to 10 carbon atoms and each R.sub.D group represents, independently, a partially or totally, preferably totally-fluorinated, aryl group having from 6 to 20 carbon atoms, Pyr represents an optionally substituted pyrrole radical.

11. Process for the (co)polymerization of conjugated dienes, characterized in that it uses the catalytic system according to claim 4.

12. Process for the (co)polymerization of 1,3-butadiene characterized in that it uses the catalytic system according to claim 4.

Description

EXAMPLES

Reagents and Materials

[0087] The list below reports the reagents and materials used in the following examples of the invention, any pre-treatments thereof and their manufacturer: [0088] titanium tetrachloride (TiCl.sub.4) (Aldrich): pure, 99.9%, distilled and stored in an inert atmosphere; [0089] o-toluidine (Aldrich): distilled at reduced pressure and stored in an inert atmosphere; [0090] p-toluidine (Aldrich): distilled at reduced pressure and stored in an inert atmosphere; [0091] 2-tert-butylaniline (Aldrich): distilled at reduced pressure and stored in an inert atmosphere; [0092] 2,6-dimethylaniline (Aldrich): distilled at reduced pressure and stored in an inert atmosphere; [0093] 2,6-di-iso-propylaniline (Aldrich): distilled at reduced pressure and stored in an inert atmosphere; [0094] 2,4,6-trimethylaniline (Aldrich): distilled at reduced pressure and stored in an inert atmosphere; [0095] aniline (Aldrich): distilled at reduced pressure and stored in an inert atmosphere; [0096] 2,3-butanedione (Aldrich): used as such; [0097] formic acid (85% by weight aqueous solution) (Carlo Erba, RPE): used as such; [0098] methanol (Carlo Erba, RPE): used as such; [0099] glyoxal (40% by weight aqueous solution) (Aldrich): used as such; [0100] toluene (Fluka): pure, 99.5%, refluxed over sodium (Na) in an inert atmosphere for about 8 hours and subsequently distilled and maintained in said atmosphere, at 4 C., on molecular sieves; [0101] heptane (Aldrich): pure, 99%, refluxed over sodium (Na) in an inert atmosphere for about 8 hours and subsequently distilled and maintained in said atmosphere, at 4 C., on molecular sieves; [0102] tetrahydrofuran (THF) (Aldrich): refluxed over sodium (Na) in an inert atmosphere for about 8 hours and subsequently distilled and maintained in said atmosphere, at 4 C., on molecular sieves; [0103] titanium tetrachloride:tetrahydrofuran complex (1:2) [TiCl.sub.4(THF).sub.2]: prepared from titanium tetrachloride (TiCl.sub.4) and tetrahydrofuran (THF) (molar ratio 1:2), in dichloromethane, at ambient temperature, according to the methodology reported by Manzer L. E. et al, in Inorganic Syntheses (1982), t. 2, Vol. 21, pg. 135-140; [0104] 1,3-butadiene (Air Liquide): pure, 99.5%, evaporated from the container before each production, dried by passing it through a molecular sieve packed column and condensed inside the reactor that was pre-cooled to 20 C.; [0105] methylaluminoxane (MAO) (toluene solution 10% in weight) (Aldrich): used as such; [0106] hydrochloric acid (37% by weight aqueous solution) (Aldrich): used as such; [0107] hydrofluoric acid (HF) (40% by weight aqueous solution) (Aldrich): used as such; [0108] sulfuric acid (H.sub.2SO.sub.4) (96% by weight aqueous solution) (Aldrich): used as such, or diluted with distilled water (1/5); [0109] nitric acid (HNO.sub.3) (70% by weight aqueous solution) (Aldrich): used as such; [0110] sodium carbonate (Na.sub.2CO.sub.3) (Aldrich): used as such; [0111] silver nitrate (AgNO.sub.3) (Aldrich): used as such; [0112] deuterated tetrachloroethylene (C.sub.2D.sub.2Cl.sub.4) (Acros): used as such; [0113] hexamethyldisilazane (HMDS) (Acros): used as such; [0114] deuterated chloroform (CDCl.sub.3) (Aldrich): used as such; [0115] tetramethylsilane (TMS) (Acros): used as such; [0116] o-dichlorobenzene (Aldrich): used as such. [0117] The analysis and characterization methodologies reported below were used.

Elementary Analysis

a) Determination of Titanium (Ti)

[0118] For the determination of the quantity by weight of titanium (Ti) in the bis-imine titanium complexes object of the present invention, an exactly weighed aliquot, operating in dry-box under nitrogen flow, of about 30 mg-50 mg of sample, was placed in a 30 ml platinum crucible, together with a 1 ml mixture of hydrofluoric acid (HF) (40% by weight aqueous solution), 0.25 ml of sulfuric acid (H.sub.2SO.sub.4) (96% by weight aqueous solution) and 1 ml of nitric acid (HNO.sub.3) (70% by weight aqueous solution). The crucible was then heated on a hot plate increasing the temperature until white sulfur fumes appeared (about 200 C.). The mixture thus obtained was cooled to ambient temperature and 1 ml of nitric acid (HNO.sub.3) (70% by weight aqueous solution) was added, then it was left again until fumes appeared. After repeating the sequence another two times, a clear, almost colorless, solution was obtained. 1 ml of nitric acid (HNO.sub.3) (70% by weight aqueous solution) and about 15 ml of water were then added cold, then heated to 80 C., for about 30 minutes. The sample thus prepared was diluted with MilliQ pure water until it weighed about 50 g, precisely weighed, to obtain a solution on which the instrumental analytical determination was carried out using a Thermo Optek IRIS Advantage Duo ICP-OES (plasma optical emission) spectrometer, for comparison with solutions of known concentration. For this purpose, for every analyte, a calibration curve was prepared in the range 0 ppm-10 ppm, measuring calibration solutions by dilution by weight of certified solutions.

[0119] The solution of sample prepared as above was then diluted again by weight in order to obtain concentrations close to the reference ones, before carrying out spectrophotometric measurement. All the samples were prepared in double quantities. The results were considered acceptable if the individual repeated test data did not have a relative deviation of more than 2% relative to their mean value.

b) Determination of Chlorine (Cl)

[0120] For said purpose, samples of bis-imine titanium complexes object of the present invention, about 30 mg-50 mg, were precisely weighed in 100 ml glass beakers in dry-box under nitrogen flow. 2 g of sodium carbonate (Na.sub.2CO.sub.3) were added and, outside the dry-box, 50 ml of MilliQ water. It was brought to the boil on the hot plate, under magnetic stirring, for about 30 minutes. It was left to cool, then sulfuric acid (H.sub.2SO.sub.4) (96% by weight aqueous solution), diluted 1/5 with distilled water, was added, until acid reaction and was then titrated with 0.1 N silver nitrate (AgNO.sub.3) with a potentiometric titrator.

c) Determination of Carbon (C), Hydrogen (H) and Nitrogen (N)

[0121] The determination of carbon (C), hydrogen (H) and nitrogen (N), in the bis-imine titanium complexes object of the present invention, like the ligands used for the purpose of the present invention, was carried out through a Carlo Erba automatic analyzer Mod. 1106.

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

[0122] The .sup.13C-HMR and .sup.1H-HMR spectra were recorded using a nuclear magnetic resonance spectrometer mod. Bruker Avance 400, using deuterated tetrachloroethylene (C.sub.2D.sub.2Cl.sub.4) at 103 C., and hexamethyldisilazane (HMDS) as internal standard, or using deuterated chloroform (CDCl.sub.3), at 25 C., and tetramethylsilane (TMS) as internal standard. For this purpose, polymeric solutions were used with concentrations equal to 10% by weight with respect to the total weight of the polymeric solution.

[0123] The microstructure of the polymers [i.e. 1,4-cis (%) and 1,2 unit content], was determined through the analysis of the aforementioned spectra based on what reported in the literature by Mochel, V. D., in Journal of Polymer Science Part A-1: Polymer Chemistry (1972), Vol. 10, Issue 4, pg. 1009-1018.

FT-IR Spectra (Solid StateUATR)

[0124] The FT-IR spectra (solid stateUATR) were recorded using a Bruker IFS 48 spectrophotometer equipped with a Thermo Spectra-Tech horizontal ATR connection. The section wherein the samples to be analyzed are placed is a Fresnel ATR accessory (Shelton, Conn., USA) which uses crystals of zirconium selenide (ZnSe) with an angle of incidence of 45 in the horizontal direction.

[0125] The FT-IR spectra (solid stateUATR) of the bis-imine titanium complexes object of the present invention, were obtained by inserting samples of the bis-imine titanium complex to be analyzed into said section.

I.R. Spectra

[0126] The I.R. (FT-IR) spectra were recorded through Thermo Nicolet Nexus 670 and Bruker IFS 48 spectrophotometers.

[0127] The I.R. (FT-IR) spectra of the ligands used in the present invention, were obtained by dispersing the ligand to be analyzed in anhydrous potassium bromide (KBr) (KBr disks), or in Nujol solution.

[0128] The I.R. (FT-IR) spectra of the polymers were obtained from polymeric films on potassium bromide (KBr) tablets, said films being obtained through the deposition of a solution in hot o-dichlorobenzene of the polymer to be analyzed. The concentration of the polymeric solutions analyzed was equal to 10% by weight with respect to the total weight of the polymeric solution.

Determination of the Molecular Weight

[0129] The determination of the molecular weight (MW) of the polymers obtained was carried out through GPC (Gel Permeation Chromatography), using the Waters Alliance GPCN 2000 System by Waters Corporation which uses two detection lines: Refractive Index [0130] RI and Viscometer operating under the following conditions: [0131] two PLgel Mixed-B columns; [0132] solvent/eluent: o-dichlorobenzene; [0133] flow rate: 0.8 ml/min; [0134] temperature: 145 C.; [0135] molecular mass calculation: Universal Calibration method. [0136] The weight-average molecular weight (M.sub.w) and the Polydispersion Index (PDI) are reported, corresponding to the ratio M.sub.w/M.sub.n (M.sub.n=number-average molecular weight).

Example 1

Synthesis of Ligand Having Formula (L1)

[0137] ##STR00005##

[0138] A solution of 10.72 g (100 mmol) of o-toluidine in methanol (50 ml) was added, drop by drop, to a solution of 7.26 g (50 mmol) of glyoxal (40% by weight aqueous solution), cooled to 0 C. and kept under stirring and, subsequently some drops of formic acid (85% by weight aqueous solution): the reaction mixture obtained was left, under stirring, in a water/ice bath, until the formation of a precipitate was noted. Subsequently, everything was left to return to ambient temperature and the precipitate was filtered, washed with methanol and vacuum dried, at ambient temperature, obtaining 9.92 g of a yellow powder (yield=84%) corresponding to the ligand having formula (L1).

[0139] FT-IR (nujol): 1605 cm.sup.1 v.sub.(C=N).

[0140] Molecular weight (MW): 236.32.

[0141] Elementary analysis [found (calculated) for C.sub.16H.sub.16N.sub.2]: C: 81.28% (81.32%); H: 6.80% (6.82%); N: 11.83% (11.85%).

[0142] FIG. 1 shows the FT-IR (solid stateUATR) spectrum of the ligand (L1) obtained.

Example 2

Synthesis of Ligand Having Formula (L2)

[0143] ##STR00006##

[0144] A solution of 10.72 g (100 mmol) of p-toluidine in methanol (50 ml) was added, drop by drop, to a solution of 7.26 g (50 mmol) of glyoxal (40% by weight aqueous solution), cooled to 0 C. and kept under stirring and, subsequently some drops of formic acid (85% by weight aqueous solution): the reaction mixture obtained was left, under stirring, in a water/ice bath, until the formation of a precipitate was noted. Subsequently, everything was left to return to ambient temperature and the precipitate was filtered, washed with methanol and vacuum dried, at ambient temperature, obtaining 9 g of a yellow powder (yield=76%) corresponding to the ligand having formula (L2).

[0145] FT-IR (nujol): 1608 cm.sup.1 v.sub.(C=N).

[0146] Molecular weight (MW): 236.32.

[0147] Elementary analysis [found (calculated) for C.sub.16H.sub.16N.sub.2]: C: 81.29% (81.32%); H: 6.82% (6.82%); N: 11.87% (11.85%).

[0148] .sup.1H-NMR (CDCl.sub.3, 5 ppm): 8.42 (s, 2H, CH), 7.23 (s, 8H, ArH), 2.39 (s, 6H, ArCH.sub.3).

[0149] FIG. 2 shows the FT-IR (solid stateUATR) spectrum of the ligand (L2) obtained.

[0150] FIG. 3 shows the .sup.1H-NMR spectrum of the ligand (L2) obtained.

Example 3

Synthesis of Ligand Having Formula (L3)

[0151] ##STR00007##

[0152] A solution of 14.92 g (100 mmol) of 2-tert-butylaniline in methanol (100 ml) was added, drop by drop, to a solution of 7.26 g (50 mmol) of glyoxal (40% by weight aqueous solution), cooled to 0 C. and kept under stirring and, subsequently some drops of formic acid (85% by weight aqueous solution): the reaction mixture obtained was left, under stirring, in a water/ice bath, until the formation of a precipitate was noted. Subsequently, everything was left to return to ambient temperature and the precipitate was filtered, washed with methanol and vacuum dried, at ambient temperature, obtaining 12 g of a yellow powder (yield=75%) corresponding to the ligand having formula (L3).

[0153] FT-IR (nujol): 1608 cm.sup.1 v.sub.(C=N).

[0154] Molecular weight (MW): 320.48.

[0155] Elementary analysis [found (calculated) for C.sub.22H.sub.28N.sub.2]: C: 82.42% (82.45%); H: 8.80% (8.81%); N: 8.76% (8.74%).

[0156] FIG. 4 shows the FT-IR (solid stateUATR) spectrum of the ligand (L3) obtained.

Example 4

Synthesis of Ligand Having Formula (L4)

[0157] ##STR00008##

[0158] A solution of 12.12 g (100 mmol) of 2,6-dimethylaniline in methanol (100) was added, drop by drop, to a solution of 7.26 g (50 mmol) of glyoxal (40% by weight aqueous solution), cooled to ambient temperature and kept under stirring and, subsequently some drops of formic acid (85% by weight aqueous solution): the reaction mixture obtained was left, under stirring, in a water/ice bath, until the formation of a precipitate was noted. Subsequently, everything was left to return to ambient temperature and the precipitate was filtered, washed with methanol and vacuum dried, at ambient temperature, obtaining 12 g of a yellow powder (yield=90%) corresponding to the ligand having formula (L4).

[0159] FT-IR (nujol): 1610 cm.sup.1 v.sub.(C=N).

[0160] Molecular weight (MW): 264.37.

[0161] Elementary analysis [found (calculated) for C.sub.18H.sub.20N.sub.2]: C: 81.72% (81.78%); H: 7.61% (7.63%); N: 10.63% (10.60%).

[0162] FIG. 5 shows the FT-IR (solid stateUATR) spectrum of the ligand (L4) obtained.

Example 5

Synthesis of Ligand Having Formula (L5)

[0163] ##STR00009##

[0164] A solution of 17.73 g (100 mmol) of 2,6-di-iso-propylaniline in methanol (50 ml) was added, drop by drop, to a solution of 7.26 g (50 mmol) of glyoxal (40% by weight aqueous solution) in methanol and distilled water (30 ml+10 ml, respectively), cooled to 0 C. and kept under stirring, and, subsequently some drops of formic acid (85% by weight aqueous solution): the reaction mixture obtained was left, under stirring, at ambient temperature, until the formation of a precipitate was noted, which was filtered, washed with methanol, and vacuum dried, at ambient temperature, obtaining 14 g of a yellow powder (yield=74%) corresponding to the ligand having formula (L5).

[0165] FT-IR (nujol): 1614 cm.sup.1 v.sub.(C=N).

[0166] Molecular weight (MW): 376.59.

[0167] Elementary analysis [found (calculated) for C.sub.26H.sub.36N.sub.2]: C: 82.88% (82.93%); H: 9.85% (9.64%); N: 7.99% (7.44%).

[0168] .sup.1H-NMR (CDCl.sub.3, ppm): 1,22 (d, 24H, CH(CH.sub.3).sub.2); 2.95 (m, 4H, CH(CH.sub.3).sub.2); 7.19-7.22 (m, 6H C.sub.6H.sub.3); 8.11 (s, 2H, NCH).

[0169] FIG. 6 shows the FT-IR (solid stateUATR) spectrum of the ligand (L5) obtained.

[0170] FIG. 7 shows the .sup.1H-NMR spectrum of the ligand (L5) obtained.

Example 6

Synthesis of Ligand Having Formula (L6)

[0171] ##STR00010##

[0172] A solution of 13.52 g (100 mmol) of 2,4,6-trimethylaniline in methanol (50 ml) was added, drop by drop, to a solution of 7.26 g (50 mmol) of glyoxal (40% by weight aqueous solution) in methanol (50 ml), cooled to ambient temperature and kept under stirring and, subsequently some drops of formic acid (85% by weight aqueous solution): the reaction mixture obtained was left, under stirring, in a water/ice bath, until the formation of a precipitate was noted. Subsequently, everything was left to return to ambient temperature and the precipitate was filtered, washed with methanol and vacuum dried, at ambient temperature, obtaining 12 g of a yellow powder (yield=82%) corresponding to the ligand having formula (L6).

[0173] FT-IR (nujol): 1616 cm.sup.1 v.sub.(C=N).

[0174] Molecular weight (MW): 292.442.

[0175] Elementary analysis [found (calculated) for C.sub.20H.sub.24N.sub.2]: C: 82.0% (82.15%); H: 8.28% (8.27%); N: 9.51% (9.58%).

[0176] .sup.1H-NMR (CDCl.sub.3, ppm): 2.15 (s, 12H, 2,6-(CH.sub.3).sub.2C.sub.6H.sub.2), 2.29 (s, 6H, 4-CH.sub.3-C.sub.6H.sub.2), 6.90 (s, 4H, C.sub.6H.sub.2), 8.09 (s, 2H, NCH).

[0177] FIG. 8 shows the FT-IR (solid stateUATR) spectrum of the ligand (L6) obtained.

Example 7

Synthesis of Ligand Having Formula (L7)

[0178] ##STR00011##

[0179] Sequentially and under stirring, a solution of 9.3 g (100 mmol) of aniline in methanol (80 ml), a solution of 4.3 g (50 mmol) of 2,3-butandione in methanol (50 ml) and some drops of formic acid (85% by weight aqueous solution) were loaded into a 500 ml reactor. Everything was left, under stirring, at ambient temperature, for about 2 hours, until the formation of a precipitate was noted, which was left to rest for 14 hours, at ambient temperature. Subsequently, the precipitate obtained was filtered, washed with methanol and vacuum dried, at ambient temperature, obtaining 12 g of a yellow powder (yield=98%) corresponding to the ligand having formula (L7).

[0180] FT-IR (nujol): 1634 cm.sup.1 v.sub.(C=N).

[0181] Molecular weight (MW): 292.42.

[0182] Elementary analysis [found (calculated) for C.sub.16H.sub.16N.sub.2]: C: 81.42% (81.32%); H: 6.33% (6.82%); N: 11.92% (11.85%).

[0183] .sup.1H NMR (CDCl.sub.3 ppm) 7.06 (m, 2H); 7.29 (m, 4H); 6.85 (m, 4H); 2.19 (s, 6H).

[0184] FIG. 9 shows the FT-IR (solid stateUATR) spectrum of the ligand (L7) obtained.

Example 8

Synthesis of Ligand Having Formula (L8)

[0185] ##STR00012##

[0186] Sequentially and under stirring, a solution of 13.43 g (90 mmol) of tert-butylaniline in methanol (50 ml), and some drops of formic acid (85% by weight aqueous solution) were loaded into a 500 ml reactor obtaining a solution. A solution of 3.87 g (45 mmol) of 2,3-butanedione in methanol (30 ml) was added to said solution drop by drop, under stirring. Everything was left, under stirring, at ambient temperature, for about 2 hours, until the formation of a precipitate was noted, which was left to rest for 14 hours, at ambient temperature. Subsequently, the precipitate was filtered, washed with methanol and vacuum dried, at ambient temperature, obtaining 14.1 g of a yellow powder (yield=90%) corresponding to the ligand having formula (L8).

[0187] FT-IR (nujol): 1636 cm.sup.1 v.sub.(C=N).

[0188] Molecular weight (MW): 348.52.

[0189] Elementary analysis [found (calculated) for C.sub.24H.sub.32N.sub.2]: C: 81.95% (82.71%); H: 9.26% (9.25%); N: 8.02% (8.01%).

[0190] NMR (CDCl.sub.3 ppm) 7.42 (dd, 2H); 7.19 (m, 2H); 7.08 (m, 2H); 6.51 (dd, 2H); 2.21 (s, 6H); 1.36 (s 18H).

[0191] FIG. 10 shows the FT-IR (solid stateUATR) spectrum of the ligand (L8) obtained.

Example 9

Synthesis of TiCl.SUB.4.(L1) [Sample MG270]

[0192] ##STR00013##

[0193] In a 100 ml Schlenk tube, titanium tetrachloride (TiCl.sub.4) (121 mg; 0.63 mmoles; molar ratio L1/Ti=1) was added to a solution of the ligand having formula (L1) (150 mg; 0.63 mmoles), obtained as described in Example 1, in toluene (20 ml): the mixture obtained was left, under stirring, at ambient temperature, for 18 hours. The suspension obtained was vacuum dried, at ambient temperature, and the solid obtained was washed with heptane (210 ml) and vacuum dried, at ambient temperature, obtaining 224 mg of an orange solid product corresponding to the complex TiCl.sub.4(L1), equal to an 83% conversion with respect to the titanium tetrachloride (TiCl.sub.4) loaded.

[0194] Elementary analysis [found (calculated) for C.sub.16H.sub.16C.sub.14N.sub.2Ti]: C: 45.61% (45.11%); H: 3.56% (3.79%); N: 6.08% (6.58%); Cl: 33.00% (33.29%); Ti: 10.95% (11.24%).

[0195] FIG. 11 shows the FT-IR spectrum of the complex TiCl.sub.4(L1) obtained.

Example 10

Synthesis of TiCl.SUB.4.(L2) [Sample MG291]

[0196] ##STR00014##

[0197] In a 100 ml Schlenk tube, the titanium tetrachloride:tetrahydrofuran complex (1:2) [TiCl.sub.4(THF).sub.2] (231 mg; 0.69 mmoles; molar ratio L2/Ti=1) was added to a solution of the ligand having formula (L2) (163 mg; 0.69 mmoles), obtained as described in Example 2, in toluene (20 ml): the mixture obtained was left, under stirring, at ambient temperature, for 18 hours. The suspension obtained was vacuum dried, at ambient temperature, and the solid obtained was washed with heptane (210 ml) and vacuum dried, at ambient temperature, obtaining 268 mg of a brown solid product corresponding to the complex TiCl.sub.4(L2), equal to a 91% conversion with respect to the titanium tetrachloride:tetrahydrofuran complex (1:2) [TiCl.sub.4(THF).sub.2].

[0198] Elementary analysis [found (calculated) for C.sub.16H.sub.16C.sub.14N.sub.2Ti]: C: 45.73% (45.11%); H: 4.05% (3.79%); N: 6.32% (6.58%); Cl: 32.95% (33.29%); Ti: 10.87% (11.24%).

[0199] FIG. 12 shows the FT-IR spectrum of the complex TiCl.sub.4(L2) obtained.

Example 11

Synthesis of TiCl.SUB.4.(L3) [Sample MG274]

[0200] ##STR00015##

[0201] In a 100 ml Schlenk tube, titanium tetrachloride (TiCl.sub.4) (119 mg; 0.63 mmoles; molar ratio L3/Ti=1) was added to a solution of the ligand having formula (L3) (200 mg; 0.62 mmoles), obtained as described in Example 3, in toluene (20 ml): the mixture obtained was left, under stirring, at ambient temperature, for 18 hours. The suspension obtained was vacuum dried, at ambient temperature, and the solid obtained was washed with heptane (210 ml) and vacuum dried, at ambient temperature, obtaining 236 mg of an ochre solid product corresponding to the complex TiCl.sub.4(L3), equal to a 75% conversion with respect to the titanium tetrachloride (TiCl.sub.4) loaded.

[0202] Elementary analysis [found (calculated) for C.sub.22H.sub.28Cl.sub.4N.sub.2Ti]: C: 51.46% (51.80%); H: 5.23% (5.53%); N: 5.75% (5.49%); Cl: 27.20% (27.80%); Ti: 8.98% (9.38%).

[0203] FIG. 13 shows the FT-IR spectrum of the complex TiCl.sub.4(L3) obtained.

Example 12

Synthesis of TiCl.SUB.4.(L3) [Sample MG290]

[0204] ##STR00016##

[0205] In a 100 ml Schlenk tube, the titanium tetrachloride:tetrahydrofuran complex (1:2) [TiCl.sub.4(THF).sub.2] (246 mg; 0.74 mmoles; molar ratio L3/Ti=1) was added to a solution of the ligand having formula (L3) (236 mg; 0.74 mmoles), obtained as described in Example 3, in toluene (20 ml): the mixture obtained was left, under stirring, at ambient temperature, for 18 hours. The suspension obtained was vacuum dried, at ambient temperature, and the solid obtained was washed with heptane (210 ml) and vacuum dried, at ambient temperature, obtaining 236 mg of a brown solid product corresponding to the complex TiCl.sub.4(L3), equal to a 61% conversion with respect to the titanium tetrachloride:tetrahydrofuran complex (1:2) [TiCl4(THF).sub.2].

[0206] Elementary analysis [found (calculated) for C.sub.22H.sub.28Cl.sub.4N.sub.2Ti]: C: 51.00% (51.80%); H: 4.92% (5.53%); N: 5.29% (5.49%); Cl: 26.98% (27.80%); Ti: 9.01% (9.38%).

[0207] FIG. 14 shows the FT-IR spectrum of the complex TiCl.sub.4(L3) obtained.

Example 13

Synthesis of TiCl.SUB.4.(L4) [Sample MG271]

[0208] ##STR00017##

[0209] In a 100 ml Schlenk tube, (TiCl.sub.4) (144 mg; 0.76 mmoles; molar ratio L4/Ti=1) was added to a solution of the ligand having formula (L4) (200 mg; 0.76 mmoles), obtained as described in Example 4, in toluene (20 ml): the mixture obtained was left, under stirring, at ambient temperature, for 18 hours. The suspension obtained was vacuum dried, at ambient temperature, and the solid obtained was washed with heptane (210 ml) and vacuum dried, at ambient temperature, obtaining 236 mg of an ochre solid product corresponding to the complex TiCl.sub.4(L4), equal to an 85% conversion with respect to the titanium tetrachloride (TiCl.sub.4) loaded.

[0210] Elementary analysis [found (calculated) for C.sub.18H.sub.20C.sub.14N.sub.2Ti]: C: 48.11% (47.61%); H: 4.58% (4.44%); N: 5.95% (6.17%); Cl: 31.00% (31.23%); Ti: 9.95% (10.54%).

[0211] FIG. 15 shows the FT-IR spectrum of the complex TiCl.sub.4(L4) obtained.

Example 14

Synthesis of TiCl.SUB.4.(L5) [Sample MG284]

[0212] ##STR00018##

[0213] In a 100 ml Schlenk tube, the titanium tetrachloride:tetrahydrofuran complex (1:2) [TiCl.sub.4(THF).sub.2] (184 mg; 0.55 mmoles; molar ratio L5/Ti=1) was added to a solution of the ligand having formula (L5) (207 mg; 0.55 mmoles), obtained as described in Example 5, in toluene (20 ml): the mixture obtained was left, under stirring, at ambient temperature, for 18 hours. The suspension obtained was vacuum dried, at ambient temperature, and the solid obtained was washed with heptane (210 ml) and vacuum dried, at ambient temperature, obtaining 215 mg of a red solid product corresponding to the complex TiCl.sub.4(L5), equal to a 69% conversion with respect to the titanium tetrachloride:tetrahydrofuran complex (1:2) [TiCl.sub.4(THF).sub.2].

[0214] Elementary analysis [found (calculated) for C.sub.26H.sub.36Cl.sub.4N.sub.2Ti]: C: 53.91% (55.15%); H: 6.70% (6.41%); N: 4.50% (4.95%); Cl: 28.30% (25.04%); Ti: 7.90% (8.45%).

[0215] FIG. 16 shows the FT-IR spectrum of the complex TiCl.sub.4(L5) obtained.

Example 15

Synthesis of TiCl.SUB.4.(L6) [Sample MG288]

[0216] ##STR00019##

[0217] In a 100 ml Schlenk tube, the titanium tetrachloride:tetrahydrofuran complex (1:2) [TiCl.sub.4(THF).sub.2] (238 mg; 0.71 mmoles; molar ratio L6/Ti=1) was added to a solution of the ligand having formula (L6) (208 mg; 0.71 mmoles), obtained as described in Example 6, in toluene (20 ml): the mixture obtained was left, under stirring, at ambient temperature, for 18 hours. The suspension obtained was vacuum dried, at ambient temperature, and the solid obtained was washed with heptane (210 ml) and vacuum dried, at ambient temperature, obtaining 263 mg of a red solid product corresponding to the complex TiCl.sub.4(L6), equal to a 77% conversion with respect to the titanium tetrachloride:tetrahydrofuran complex (1:2) [TiCl.sub.4(THF).sub.2].

[0218] Elementary analysis [found (calculated) for C.sub.20H.sub.24Cl.sub.4N.sub.2Ti]: C: 49.46% (49.83%); H: 4.98% (5.02%); N: 5.38% (5.81%); Cl: 28.40% (29.42%); Ti: 9.50% (9.93%).

[0219] FIG. 17 shows the FT-IR spectrum of the complex TiCl.sub.4(L6) obtained.

Example 16

Synthesis of TiCl.SUB.4.(L7) [Sample MG402A]

[0220] ##STR00020##

[0221] In a 100 ml Schlenk tube, the titanium tetrachloride:tetrahydrofuran complex (1:2) [TiCl.sub.4(THF).sub.2] (185 mg; 0.55 mmoles; molar ratio L7/Ti=1) was added to a solution of the ligand having formula (L7) (131 mg; 0.55 mmoles), obtained as described in Example 7, in toluene (20 ml): the mixture obtained was left, under stirring, at ambient temperature, for 18 hours. The suspension obtained was vacuum dried, at ambient temperature, and the solid obtained was washed with heptane (210 ml) and vacuum dried, at ambient temperature, obtaining 152 mg of an orange/brown solid product corresponding to the complex TiCl.sub.4(L7), equal to a 65% conversion with respect to the titanium tetrachloride:tetrahydrofuran complex (1:2) [TiCl.sub.4(THF).sub.2].

[0222] Elementary analysis [found (calculated) for C.sub.16H.sub.16C.sub.14N.sub.2Ti]: C: 44.45% (45.11%); H: 3.86% (3.79%); N: 6.41% (6.58%); Cl: 32.29% (33.29%); Ti: 11.00% (11.24%).

[0223] FIG. 18 shows the FT-IR spectrum of the complex TiCl.sub.4(L6) obtained.

Example 17

Synthesis of TiCl.SUB.4.(L8) [Sample MG404A]

[0224] ##STR00021##

[0225] In a 100 ml Schlenk tube, titanium tetrachloride (TiCl.sub.4) (67 mg; 0.35 mmoles; molar ratio L8/Ti=1) was added to a solution of the ligand having formula (L8) (123 mg; 0.35 mmoles), obtained as described in Example 8, in toluene (10 ml): the mixture obtained was left, under stirring, at ambient temperature, for 18 hours. The suspension obtained was vacuum dried, at ambient temperature, and the solid obtained was washed with heptane (215 ml) and vacuum dried, at ambient temperature, obtaining 88 mg of an orange solid product corresponding to the complex TiCl.sub.4(L8), equal to a 47% conversion with respect to the titanium tetrachloride (TiCl.sub.4) loaded.

[0226] Elementary analysis [found (calculated) for C.sub.24H.sub.32Cl.sub.4N.sub.2Ti]: C: 52.99% (53.56%); H: 5.74% (5.99%); N: 5.06% (5.20%); Cl: 25.89% (26.35%); Ti: 8.59% (8.89%).

[0227] FIG. 19 shows the FT-IR spectrum of the complex TiCl.sub.4(L8) obtained.

Example 18 (ZG305)

[0228] 2 ml of 1,3-butadiene equal to about 1.4 g were condensed, cold (20 C.) in a 25 ml test tube. Subsequently, 7.6 ml of toluene were added and the temperature of the solution thus obtained was brought to 20 C. Then, methylaluminoxane (MAO) in toluene solution (6.3 ml; 110.sup.2 moles, equal to about 0.58 g) was added and, subsequently, the TiCl.sub.4(L1) complex [sample MG270] (2.1 ml of toluene suspension at a concentration of 2 mg/ml; 110.sup.5, equal to about 4.26 mg) obtained as described in Example 9. Everything was kept under magnetic stirring, at 25 C., for 60 minutes. The polymerization was then stopped by adding 2 ml of methanol containing some drops of hydrochloric acid (37% by weight aqueous solution). The polymer obtained was then coagulated by adding 40 ml of a methanol solution containing 4% of Irganox 1076 antioxidant (Ciba) obtaining 0.74 g of polybutadiene having a 1,4-cis unit content of 85%: further characteristics of the procedure and of the polybutadiene obtained are reported in Table 1.

[0229] FIG. 20 shows the FT-IR spectrum of the polybutadiene obtained.

Example 19 (ZG311)

[0230] 2 ml of 1,3-butadiene equal to about 1.4 g were condensed, cold (20 C.) in a 25 ml test tube. Subsequently, 7.6 ml of toluene were added and the temperature of the solution thus obtained was brought to 25 C. Then, methylaluminoxane (MAO) in toluene solution (6.3 ml; 110.sup.2 moles, equal to about 0.58 g) was added and, subsequently, the TiCl.sub.4(L2) complex [sample MG291] (2.1 ml of toluene suspension at a concentration of 2 mg/ml; 110.sup.5, equal to about 4.26 mg) obtained as described in Example 10. Everything was kept under magnetic stirring, at 25 C., for 60 minutes. The polymerization was then stopped by adding 2 ml of methanol containing some drops of hydrochloric acid (37% by weight aqueous solution). The polymer obtained was then coagulated by adding 40 ml of a methanol solution containing 4% of Irganox 1076 antioxidant (Ciba) obtaining 0.80 g of polybutadiene having a 1,4-cis unit content of 86%: further characteristics of the procedure and of the polybutadiene obtained are reported in Table 1.

[0231] FIG. 21 shows the FT-IR spectrum of the polybutadiene obtained.

Example 20 (ZG310)

[0232] 2 ml of 1,3-butadiene equal to about 1.4 g were condensed, cold (20 C.) in a 25 ml test tube. Subsequently, 7.15 ml of toluene were added and the temperature of the solution thus obtained was brought to 25 C. Then, methylaluminoxane (MAO) in toluene solution (6.3 ml; 110.sup.2 moles, equal to about 0.58 g) was added and, subsequently, the TiCl.sub.4(L3) complex [sample MG290] (2.55 ml of toluene suspension at a concentration of 2 mg/ml; 110.sup.5, equal to about 5.1 mg) obtained as described in Example 12. Everything was kept under magnetic stirring, at 25 C., for 60 minutes. The polymerization was then stopped by adding 2 ml of methanol containing some drops of hydrochloric acid (37% by weight aqueous solution). The polymer obtained was then coagulated by adding 40 ml of a methanol solution containing 4% of Irganox 1076 antioxidant (Ciba) obtaining 0.87 g of polybutadiene having a 1,4-cis unit content of 80%: further characteristics of the procedure and of the polybutadiene obtained are reported in Table 1.

[0233] FIG. 22 shows the FT-IR spectrum of the polybutadiene obtained.

Example 21 (ZG310/1)

[0234] 2 ml of 1,3-butadiene equal to about 1.4 g were condensed, cold (20 C.) in a 25 ml test tube. Subsequently, 7.15 ml of toluene were added and the temperature of the solution thus obtained was brought to 25 C. Then, methylaluminoxane (MAO) in toluene solution (6.3 ml; 110.sup.2 moles, equal to about 0.58 g) was added and, subsequently, the TiCl.sub.4(L3) complex [sample MG274] (2.55 ml of toluene suspension at a concentration of 2 mg/ml; 110.sup.5, equal to about 5.1 mg) obtained as described in Example 11. Everything was kept under magnetic stirring, at 25 C., for 60 minutes. The polymerization was then stopped by adding 2 ml of methanol containing some drops of hydrochloric acid (37% by weight aqueous solution). The polymer obtained was then coagulated by adding 40 ml of a methanol solution containing 4% of Irganox 1076 antioxidant (Ciba) obtaining 0.82 g of polybutadiene having a 1,4-cis unit content of 81%; further characteristics of the procedure and of the polybutadiene obtained are reported in Table 1.

Example 22 (ZG309)

[0235] 2 ml of 1,3-butadiene equal to about 1.4 g were condensed, cold (20 C.) in a 25 ml test tube. Subsequently, 7.4 ml of toluene were added and the temperature of the solution thus obtained was brought to 25 C. Then, methylaluminoxane (MAO) in toluene solution (6.3 ml; 110.sup.2 moles, equal to about 0.58 g) was added and, subsequently, the TiCl.sub.4(L4) complex [sample MG271] (2.3 ml of toluene suspension at a concentration of 2 mg/ml; 110.sup.5, equal to about 4.54 mg) obtained as described in Example 13. Everything was kept under magnetic stirring, at 25 C., for 30 minutes. The polymerization was then stopped by adding 2 ml of methanol containing some drops of hydrochloric acid (37% by weight aqueous solution). The polymer obtained was then coagulated by adding 40 ml of a methanol solution containing 4% of Irganox 1076 antioxidant (Ciba) obtaining 0.43 g of polybutadiene having a 1,4-cis unit content of 73%: further characteristics of the procedure and of the polybutadiene obtained are reported in Table 1.

[0236] FIG. 23 shows the FT-IR spectrum of the polybutadiene obtained.

Example 23 (ZG302)

[0237] 2 ml of 1,3-butadiene equal to about 1.4 g were condensed, cold (20 C.) in a 25 ml test tube. Subsequently, 6.9 ml of toluene were added and the temperature of the solution thus obtained was brought to 25 C. Then, methylaluminoxane (MAO) in toluene solution (6.3 ml; 110.sup.2 moles, equal to about 0.58 g) was added and, subsequently, the TiCl.sub.4(L5) complex [sample MG284] (2.81 ml of toluene suspension at a concentration of 2 mg/ml; 110.sup.5, equal to about 5.62 mg) obtained as described in Example 14. Everything was kept under magnetic stirring, at 25 C., for 30 minutes. The polymerization was then stopped by adding 2 ml of methanol containing some drops of hydrochloric acid (37% by weight aqueous solution). The polymer obtained was then coagulated by adding 40 ml of a methanol solution containing 4% of Irganox 1076 antioxidant (Ciba) obtaining 1.29 g of polybutadiene having a 1,4-cis unit content of 60%: further characteristics of the procedure and of the polybutadiene obtained are reported in Table 1.

Example 24 (ZG307)

[0238] 2 ml of 1,3-butadiene equal to about 1.4 g were condensed, cold (20 C.) in a 25 ml test tube. Subsequently, 11.5 ml of toluene were added and the temperature of the solution thus obtained was brought to 25 C. Then, methylaluminoxane (MAO) in toluene solution (3.15 ml; 510.sup.3 moles, equal to about 0.27 g) was added and, subsequently, the TiCl.sub.4(L5) complex [sample MG284] (1.4 ml of toluene suspension at a concentration of 2 mg/ml; 110.sup.6, equal to about 2.81 mg) obtained as described in Example 14. Everything was kept under magnetic stirring, at 25 C., for 60 minutes. The polymerization was then stopped by adding 2 ml of methanol containing some drops of hydrochloric acid (37% by weight aqueous solution). The polymer obtained was then coagulated by adding 40 ml of a methanol solution containing 4% of Irganox 1076 antioxidant (Ciba) obtaining 1.12 g of polybutadiene having a 1,4-cis unit content of 60%: further characteristics of the procedure and of the polybutadiene obtained are reported in Table 1.

[0239] FIG. 24 shows the FT-IR spectrum of the polybutadiene obtained.

Example 25 (ZG308)

[0240] 2 ml of 1,3-butadiene equal to about 1.4 g were condensed, cold (20 C.) in a 25 ml test tube. Subsequently, 9.1 ml of toluene were added and the temperature of the solution thus obtained was brought to 25 C. Then, methylaluminoxane (MAO) in toluene solution (1.26 ml; 210.sup.3 moles, equal to about 0.12 g) was added and, subsequently, the TiCl.sub.4(L5) complex [sample MG284] (5.64 ml of toluene suspension at a concentration of 2 mg/ml; 210.sup.5, equal to about 11.24 mg) obtained as described in Example 14.

[0241] Everything was kept under magnetic stirring, at 25 C., for 120 minutes. The polymerization was then stopped by adding 2 ml of methanol containing some drops of hydrochloric acid (37% by weight aqueous solution). The polymer obtained was then coagulated by adding 40 ml of a methanol solution containing 4% of Irganox 1076 antioxidant (Ciba) obtaining 0.68 g of polybutadiene having a 1,4-cis unit content of 62%: further characteristics of the procedure and of the polybutadiene obtained are reported in Table 1.

[0242] FIG. 25 shows the FT-IR spectrum of the polybutadiene obtained.

Example 26 (ZG312)

[0243] 2 ml of 1,3-butadiene equal to about 1.4 g were condensed, cold (20 C.) in a 25 ml test tube. Subsequently, 7.3 ml of toluene were added and the temperature of the solution thus obtained was brought to 25 C. Then, methylaluminoxane (MAO) in toluene solution (6.3 ml; 110.sup.2 moles, equal to about 0.58 g) was added and, subsequently, the TiCl.sub.4(L6) complex [sample MG288] (2.4 ml of toluene suspension at a concentration of 2 mg/ml; 110.sup.5, equal to about 4.8 mg) obtained as described in Example 15. Everything was kept under magnetic stirring, at 25 C., for 25 minutes. The polymerization was then stopped by adding 2 ml of methanol containing some drops of hydrochloric acid (37% by weight aqueous solution). The polymer obtained was then coagulated by adding 40 ml of a methanol solution containing 4% of Irganox 1076 antioxidant (Ciba) obtaining 0.43 g of polybutadiene having a 1,4-cis unit content of 76%: further characteristics of the procedure and of the polybutadiene obtained are reported in Table 1.

[0244] FIG. 26 shows the FT-IR spectrum of the polybutadiene obtained.

Example 27 (G1603)

[0245] 2 ml of 1,3-butadiene equal to about 1.4 g were condensed, cold (20 C.) in a 25 ml test tube. Subsequently, 7.57 ml of toluene were added and the temperature of the solution thus obtained was brought to 25 C. Then, methylaluminoxane (MAO) in toluene solution (6.3 ml; 110.sup.2 moles, equal to about 0.58 g) was added and, subsequently, the TiCl.sub.4(L7) complex [sample MG402A] (2.13 ml of toluene suspension at a concentration of 2 mg/ml; 110.sup.5, equal to about 4.26 mg) obtained as described in Example 16. Everything was kept under magnetic stirring, at 25 C., for 20 minutes. The polymerization was then stopped by adding 2 ml of methanol containing some drops of hydrochloric acid (37% by weight aqueous solution). The polymer obtained was then coagulated by adding 40 ml of a methanol solution containing 4% of Irganox 1076 antioxidant (Ciba) obtaining 0.799 g of polybutadiene having a 1,4-cis unit content of 82%: further characteristics of the procedure and of the polybutadiene obtained are reported in Table 1.

[0246] FIG. 27 shows the FT-IR spectrum of the polybutadiene obtained.

Example 28 (G1604)

[0247] 2 ml of 1,3-butadiene equal to about 1.4 g were condensed, cold (20 C.) in a 25 ml test tube. Subsequently, 7.0 ml of toluene were added and the temperature of the solution thus obtained was brought to 25 C. Then, methylaluminoxane (MAO) in toluene solution (6.3 ml; 110.sup.2 moles, equal to about 0.58 g) was added and, subsequently, the TiCl.sub.4(L8) complex [sample MG404A] (2.69 ml of toluene suspension at a concentration of 2 mg/ml; 110.sup.5, equal to about 5.4 mg) obtained as described in Example 17. Everything was kept under magnetic stirring, at 25 C., for 120 minutes. The polymerization was then stopped by adding 2 ml of methanol containing some drops of hydrochloric acid (37% by weight aqueous solution). The polymer obtained was then coagulated by adding 40 ml of a methanol solution containing 4% of Irganox 1076 antioxidant (Ciba) obtaining 0.334 g of polybutadiene having a 1,4-cis unit content of 79%: further characteristics of the procedure and of the polybutadiene obtained are reported in Table 1.

TABLE-US-00001 TABLE 1 Polymerization of 1,3-butadiene with catalytic systems comprising titanium complexes Time Yield Conversion 1,4-cis M.sub.w Example (min) (g) (%) (%) 1.2 (g mol.sup.1) M.sub.w/M.sub.n 18 60 0.74 52.8 85 15 101800 1.80 19 60 0.80 57.1 86 14 307603 2.21 20 60 0.87 62.1 80 20 169935 2.47 21 60 0.82 58.6 81 19 165800 2.24 22 30 0.43 30.7 73 27 297465 1.90 23 30 1.29 92.1 60 40 347000 1.88 24 60 1.12 80 60 43 317225 1.73 25 120 0.68 48.6 62 38 180660 1.82 26 25 0.43 30.7 76 24 129650 1.90 27 20 0.80 57.1 82 18 283800 2.10 28 120 0.33 23.9 79 21 305200 1.95