Process for the preparation of an olefinic copolymer having polar groups and the products obtained therefrom

Abstract

The present invention concerns a process for the preparation of a copolymer comprising the steps of copolymerizing under suitable reaction conditions at least one first type of olefin monomer and at least one second type of functionalized olefin monomer using a catalyst system to obtain a polyolefin main chain having one or multiple functionalized short chain branches, the catalyst system comprising: i) a single-site catalyst or catalyst precursor comprising a metal selected from Ti3+ or Cr3+; ii) a co-catalyst; iii) optionally a scavenger.

Claims

1. A process comprising copolymerizing at least one olefin monomer and at least one functionalized olefin monomer with a catalyst system to obtain a polyolefin main chain having one or multiple functionalized short chain branches, the catalyst system comprising: i) a single-site catalyst or catalyst precursor comprising a metal selected from Ti3+ or Cr3+; ii) a co-catalyst; iii) optionally a scavenger, wherein the molar ratio of the functionalized olefin monomer to catalyst is at least 300.

2. The process according to claim 1, wherein the first olefin monomer has the following structure according to Formula I-A: ##STR00005## wherein C is carbon and wherein R.sup.1a, R.sup.1b, R.sup.1c, and R.sup.1d are each independently selected from the group consisting of Hand hydrocarbyl with 1 to 16 carbon atoms.

3. The process according to claim 1, wherein the first olefin monomer is selected from ethylene or propylene.

4. The process according to claim 1, wherein the functionalized olefin monomer has the following structure according to Formula I-B: ##STR00006## wherein C is carbon, wherein R.sup.2, R.sup.3, and R.sup.4 are each independently selected from the group consisting of H and hydrocarbyl with 1 to 16 carbon atoms, wherein R.sup.5—X—H is a heteroatom-containing functional group, R.sup.5 is either —C(R.sup.7a)(R.sup.7b)— or a plurality of —C(R.sup.7a)(R.sup.7b)— groups, wherein R.sup.7a and R.sup.7b are each independently selected from the group consisting of H and hydrocarbyl with 1 to 16 carbon atoms.

5. The process according to claim 4, wherein said heteroatom from said heteroatom-containing group X is chosen from —O—, —S—, —NR.sup.6a—, —CO.sub.2— or one or more combinations thereof.

6. The process according to claim 1, wherein the functionalized monomers are selected from the group allyl alcohol, 3-buten-1-ol, 3-buten-2-ol, 5-hexene-1-ol, 10-undecene-1-ol, 5-norbornene-2-methanol and undecenoic acid.

7. The process according to claim 1, wherein the molar ratio of the second functionalized olefin monomer to catalyst is at least 500.

8. The process according to claim 1, wherein a scavenger is present, which is selected from trialkyl aluminum complexes.

9. The process according to claim 1, wherein a scavenger is present and wherein the molar amount of scavenger is at least the same molar amount of the functionalized olefin monomer.

10. The process according to claim 1, wherein the catalysts or catalyst precursors are selected from the group consisting the single-site catalysts according to Formula (I) and Formula (II), ##STR00007## wherein in the compound of Formula (I) M.sup.1 is titanium or chromium; each of the substituents X, which are the same as or different from each other, are monoanionic sigma ligands selected from the group consisting of hydrogen, halogen, R.sup.8, OR.sup.8, OCOR.sup.8, SR.sup.8, NR.sup.8.sub.2 and PR.sup.8.sub.2, wherein each R.sup.8 is the same as or different from each other, and are hydrogen or C.sub.1-C.sub.40 hydrocarbyl radicals optionally containing one or more heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; L.sup.1 is a divalent bridge connecting the two nitrogen atoms wherein the bonds connecting the two nitrogen atoms with the bridge L.sup.1 is single bonds or double bonds; each R.sup.9 is the same as or different from each other, and are C.sub.1-C.sub.40 hydrocarbyl radicals optionally containing one or more heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; m ranges from 0 to 2; when m is 0 the group T.sup.1 does not exist; T.sup.1 is a Lewis base he group T.sup.1 can also be bonded to the group R.sup.9; or wherein in the compound of Formula (II) M.sup.1 is titanium or chromium; X is as in the compound of Formula (I); R.sup.12, R.sup.13, R.sup.14 and R.sup.15 are each the same as or different from each other, and are hydrogen atoms, halogen atoms, or C.sub.1-C.sub.40 hydrocarbon radicals optionally containing one or more heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; or two adjacent R.sup.12, R.sup.13, R.sup.14 and R.sup.15 form one or more C.sub.3-C.sub.7-membered ring optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; L.sup.2 is a divalent bridging group selected from C.sub.1-C.sub.20 alkylidene, C.sub.3-C.sub.20 cycloalkylidene, C.sub.6-C.sub.20 arylidene, C.sub.7-C.sub.20 alkylarylidene, or C.sub.7-C.sub.20 arylalkylidene radicals optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements, and a silylidene radical containing up to 5 silicon atoms; A.sup.1 is an optional group, and when A.sup.1 is absent L.sup.2 is a hydrogen or a hydrocarbyl, and when A.sup.1 is present, then A.sup.1 is a Lewis base functionality.

11. The process according to claim 1, wherein a hindered phenol is added in an amount of between 0.1 and 5 mol. equivalents of main group metal compound(s).

12. The process according to claim 10, wherein in the compound of Formula (I), M.sup.1 is titanium or chromium in a trivalent oxidation state; R.sup.8 is a hydrogen atom, linear or branched, cyclic or acyclic, C.sub.1-C.sub.20-alkyl, C.sub.2-C.sub.20 alkenyl, C.sub.2-C.sub.20 alkynyl, C.sub.6-C.sub.20-aryl, C.sub.7-C.sub.20-alkylaryl, or C.sub.7-C.sub.20-arylalkyl radical optionally containing a silicon atom; n is 2; L.sup.1 is a divalent C.sub.1-C.sub.40 hydrocarbon group optionally containing one or more heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; R.sup.9 are hydrogen atom, linear or branched, cyclic or acyclic, C.sub.1-C.sub.20-alkyl C.sub.2-C.sub.20 alkenyl C.sub.2-C.sub.20 alkynyl C.sub.6-C.sub.20-aryl C.sub.7-C.sub.20-alkylaryl or C.sub.7-C.sub.20-arylalkyl radicals optionally containing silicon atoms; when T.sup.1 is present, T.sup.1 is tetrahydrofuran, tertiary amine, pyridine, pyrrole, furan, or thiophene; and in the compound of Formula (II), M.sup.1 is titanium or chromium in a trivalent oxidation state; R.sup.8 is the same as described in Formula (I); R.sup.12, R.sup.13, R.sup.14 and R.sup.15 are each the same as or different from each other, and are hydrogen atoms, halogen atoms or linear or branched cyclic or acyclic, C.sub.1-C.sub.20-alkyl C.sub.2-C.sub.20 alkenyl, C.sub.2-C.sub.20 alkynyl, C.sub.6-C.sub.20-aryl, C.sub.7-C.sub.20-alkylaryl or C.sub.7-C.sub.20-arylalkyl radicals optionally containing silicon atoms; or two adjacent R.sup.12, R.sup.13, R.sup.14 and R.sup.15 can form one or more C.sub.3-C.sub.7 membered ring; L.sup.2 is a divalent group (ZR.sup.16.sub.m1).sub.n1; Z being C, Si, Ge, N or P, and the R.sup.16 groups are each the same or different from each other, wherein each R.sup.16 group independently being hydrogen or a hydrocarbon group containing from 1 to 20 carbon atoms, or two R.sup.16 can form an aliphatic or aromatic C.sub.4-C.sub.7 ring; m1 is 1 or 2; n1 is an integer ranging from 1 to 4; A.sup.1 is present and is an NR.sup.8, NR.sup.8.sub.2, OR.sup.8 or an SR.sup.8 group, wherein R.sup.8 is as described in the compound of Formula (I) or R.sup.8 is connected to L.sup.2 forming an aliphatic or aromatic ring or heterocyclic structure.

13. The process according to claim 12, wherein in Formula (I), X is a halogen atom or a C.sub.1-C.sub.10 alkyl radical; and in the Formula (II), X is chlorine or a C.sub.1-C.sub.10 alkyl radical; R.sup.16 is hydrogen or a linear or branched, cyclic or acyclic, C.sub.1-C.sub.20-alkyl, C.sub.2-C.sub.20 alkenyl, C.sub.2-C.sub.20 alkynyl, C.sub.6-C.sub.20-aryl, C.sub.7-C.sub.20-alkylaryl or C.sub.7-C.sub.20-arylalkyl radical; m1 is 1; n1 is 1 or 2; and R.sup.8 is a C.sub.1-C.sub.20-alkyl radical.

14. The process according to claim 13, wherein in the compound of Formula (I), X is chlorine or a methyl or an ethyl radical; in the compound of Formula (II), L.sup.2 is selected from SiMe.sub.2, SiPh.sub.2, SiPhMe, SiMe(SiMe.sub.3), CH.sub.2, (CH.sub.2).sub.2, (CH.sub.2).sub.3 or C(CH.sub.3).sub.2; m1 is 1 or 2, and more specifically it is 1 when Z is N or P and it is 2 when Z is C, Si or Ge; and A.sup.1 is an NR.sup.8 or NR.sup.82 group.

15. A process comprising copolymerizing under suitable reaction conditions at least one first type of olefin monomer and at least one second type of functionalized olefin monomer using a catalyst system to obtain a polyolefin main chain having one or multiple functionalized short chain branches, the catalyst system comprising: i) a single-site catalyst or single-site catalyst precursor comprising a metal selected from Ti3+ or Cr3+; ii) a co-catalyst; iii) optionally a scavenger, wherein the molar ratio of the second type of functionalized olefin monomer to the catalyst is at least 300; wherein the second type of functionalized olefin monomer has the following structure according to Formula I-B: ##STR00008## wherein C is carbon, wherein R.sup.2, R.sup.3, and R.sup.4 are each independently selected from the group consisting of H or hydrocarbyl with 1 to 16 carbon atoms, wherein R.sup.5—X—H is a heteroatom-containing functional group, R.sup.5 is either —C(R.sup.7a)(R.sup.7b)— or a plurality of —C(R.sup.7a)(R.sup.7b)— groups, wherein R.sup.7a, and R.sup.7b are each independently selected from the group consisting of H or hydrocarbyl with 1 to 16 carbon atoms; wherein the single-site catalyst or single-site catalyst precursor is selected from the group consisting the single-site catalysts according to formula (I) or formula (II), ##STR00009## wherein in the compound of formula (I) M.sup.1 is titanium or chromium; the substituents X, equal to or different from each other, are monoanionic sigma ligands selected from the group consisting of hydrogen, halogen, R.sup.8, OR.sup.8, OCOR.sup.8, SR.sup.8, NR.sup.8.sub.2 and PR.sup.8.sub.2, wherein R.sup.8 equal to or different from each other are hydrogen or C.sub.1-C.sub.40 hydrocarbyl radicals optionally containing one or more heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; n ranges from 0 to 3; L.sup.1 is a divalent bridge connecting the two nitrogen atoms; the bonds connecting the two nitrogen atoms with the bridge L.sup.1 can be single bonds or double bonds; R.sup.9, equal to or different from each other are C.sub.1-C.sub.40 hydrocarbyl radicals optionally containing one or more heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; m ranges from 0 to 2; when m is 0 the group T.sup.1 does not exist; T.sup.1 is a Lewis base; the group T.sup.1 can also be bonded to the group R.sup.9 or wherein in the compound of formula (II) above M.sup.1 is titanium or chromium; X has been described above R.sup.12, R.sup.13, R.sup.14 and R.sup.15, equal to or different from each other, are hydrogen atoms, halogen atoms, or C.sub.1-C.sub.40 hydrocarbon radicals optionally containing one or more heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; or two adjacent R.sup.12, R.sup.13, R.sup.14 and R.sup.15 may form one or more C.sub.3-C.sub.7-membered ring optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; L.sup.2 is a divalent bridging group selected from C.sub.1-C.sub.20 alkylidene, C.sub.3-C.sub.20 cycloalkylidene, C.sub.6-C.sub.20 arylidene, C.sub.7-C.sub.20 alkylarylidene, or C.sub.7-C.sub.20 arylalkylidene radicals optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements, and silylidene radical containing up to 5 silicon atoms; A.sup.1 is optional group, when A.sup.1 is absent L.sup.2 a hydrogen or a hydrocarbyl; when A.sup.1 is present, then A.sup.1 a Lewis basic functionality.

16. A process comprising copolymerizing at least one olefin monomer and at least one functionalized olefin monomer with a catalyst system to obtain a polyolefin main chain having one or multiple functionalized short chain branches, the catalyst system comprising: i) a single-site catalyst or catalyst precursor comprising a metal selected from Ti3+ or Cr3+; ii) a co-catalyst; iii) optionally a scavenger, wherein the molar ratio of the functionalized olefin monomer to catalyst is at least 500.

Description

FIGURES

(1) FIG. 1 shows the incorporation of C.sub.1.sup.═OH as a function of the feed concentration of C.sub.11.sup.═OH.

(2) FIG. 2 shows the activity as a function of the nucleophilic comonomer to catalyst ratio for different trivalent and tetravalent catalysts.

EXAMPLES

(3) The invention is further illustrated by the following non-limiting examples merely used to further explain certain embodiments of the present invention.

Experimental Section

(4) General Considerations.

(5) All manipulations were performed under an inert dry nitrogen atmosphere using either standard Schlenk or glove box techniques. Dry, oxygen-free toluene was employed as solvent for all polymerizations. 10-undecene-1-ol, 5-hexen-1-ol, 3-buten-1-ol, 3-buten-2-ol and allyl alcohol were purchased from Sigma Aldrich and dried with 4-A molecular sieves under an inert atmosphere. Methylaluminoxane (MAO, 30 wt. % solution in toluene) was purchased from Chemtura. Triisobutyl aluminum (TiBA, 1.0 M solution in hexanes) purchased from Aldrich. 2,6-bis(1,1-dimethylethyl)-4-methylphenol (BHT) was purchased from Fisher Scientific. Catalysts 1 ([C.sub.5Me.sub.4CH.sub.2CH.sub.2NMe.sub.2]TiCl.sub.2) was prepared according to the method described in WO97/42232. Catalyst 2 (CsMe.sub.4(SiMe.sub.2NtBu)TiCl.sub.2) was prepared according to literature procedure described in Organometallics 1990, 9, 867-869 and Chem. Ber. 1990, 123, 1649-1651. Catalyst 3 (Cp(tBu.sub.3P═N)TiCl.sub.2) was prepared according to Organometallics 2005, 24, 2548-2560. Catalysts [Et.sub.2NC(N(2,6-iPr.sub.2—C.sub.6H.sub.3)]TiCl.sub.3, [2,4-(t-Bu)2,-6-(CH═NC.sub.6F.sub.5)C.sub.6H.sub.2O].sub.2TiCl.sub.2 and rac-Me.sub.2Si(2-Me-4-Ph-Ind).sub.2ZrCl.sub.2 were purchased from MCAT GmbH, Konstanz, Germany.

(6) Randomly Functionalized PE (Entry 3, Table 1).

(7) The reaction was carried out in a stainless steel Büchi reactor (300 mL). Prior to the polymerization, the reactor was dried in vacuo at 40° C. and flushed with dinitrogen. Toluene solvent (90 mL) was introduced followed by TiBA (1.0 M solution in hexanes, 20 mmol) and the functional monomer 10-undecene-1-ol (neat solution, 2 mL, 10 mmol) under an inert atmosphere. The resulting solution was stirred for 30 min followed by the addition of MAO cocatalyst (30 wt. % solution in toluene, 2.6 mL) under dinitrogen atmosphere. The polymerization reaction was started by the injection of the catalyst (6.2 mL of a catalyst solution in toluene 1 mg.Math.mL.sup.−1) into the reactor under dinitrogen atmosphere. The reactor was then pressurized to the desired pressure with ethylene (2.5 bars) and the pressure was maintained constant for 15 min. The ethylene feed was closed and the polymerization was quenched by pouring the mixture into an Erlenmeyer containing acidified methanol (5 w. %, 500 mL). The resulting suspension was filtered and thoroughly washed with demi-water and dried under reduced pressure at 60° C. for 24 hours to determine the yield. Similar procedure was applied in ethylene copolymerization with other hydroxyl alpha-olefins (allyl alcohol, 5-hexen-1-ol, 3-buten-1-ol and 3-buten-2-ol).

(8) Analytical techniques.

(9) .sup.1H NMR Characterization.

(10) The percentage of functionalization was determined by .sup.1H NMR analysis carried out at 130° C. using deuterated tetrachloroethane (TCE-d.sub.2) as the solvent and recorded in 5 mm tubes on a Varian Mercury spectrometer operating at a frequency of 400 MHz. Chemical shifts are reported in ppm versus tetramethylsilane and were determined by reference to the residual solvent protons.

(11) High Temperature Size Exclusion Chromatography (HT-SEC).

(12) The molecular weight in g/mol and the PDI were determined by means of high temperature size exclusion chromatography which was performed at 160° C. using a high speed GPC (Freeslate, Sunnyvale, USA). Detection: IR4 (PolymerChar, Valencia, Spain). Column set: three Polymer Laboratories 13 μm PLgel Olexis, 300×7.5 mm. 1,2,4-Trichlorobenzene (TCB) was used as eluent at a flow rate of 1 mL.Math.min.sup.−1. TCB was freshly distilled prior to use. The molecular weights and the corresponding PDI were calculated from HT-SEC analysis with respect to narrow polyethylene standards (PSS, Mainz, Germany).

(13) Differential Scanning Calorimetry (DSC).

(14) Thermal analysis was carried out on a DSC Q100 from TA Instruments at a heating rate of 5° C.min.sup.−1. First and second runs were recorded after cooling down to ca. −20° C. The melting temperatures reported correspond to second runs.

(15) TABLE-US-00001 TABLE 1 Randomly functionalized polyethylene-co-C.sub.11.sup.=OH using single-site catalysts. BHT activity.sup.b M.sub.n MAO C.sub.11.sup.=OH/ Temp (eq. to (kg/mol. (kg/mol) branch/ # catalyst Al:cat cat. ° C. MAO) h) (PDI).sup.c 1000 C. 1 1 600 0 40 0 1108 4.1 — 2 1 600 125 40 0 1350 2.5 2.0 3 1 600 500 40 0 1550 2.2 3.5 4 1 600 750 40 0 1620 1.9 5.9 5 1 600 1000 40 0 1720 0.9 23.2 6 1 700 500 40 1.0 950 26.2 15 7 1 700 500 40 2.0 425 92.9 27 8 Comparative 1 1000 0 40 0 2027 44.7 — 9 Comparative 1 1000 250 40 0 1480 17.2 7.0 10 Comparative 1 1000 500 40 0 0 16.4 — 11 Comparative 1 1000 1000 40 0 0 — — 12 Comparative 2 1000 0 40 0 2970 — — 13 Comparative 2 1000 250 40 0 1944 17.6 0.9 14 Comparative 2 1000 500 40 0 0 — — 15 Comparative 3 1000 0 40 0 1776 — — 16 Comparative 3 1000 250 40 0 940 33.4 5.0 17 Comparative 3 1000 500 40 0 0 — — 18 Comparative 3 1000 1000 40 0 0 — — 19 2 1000 0 40 0 1100 — — 20 2 1000 250 40 0 1120 — — 21 2 1000 500 40 0 1140 — — 22 2 1000 1000 40 0 1783 — — Catalyst 1: Ti(III) = [C.sub.5Me.sub.4(CH.sub.2CH.sub.2NMe.sub.2]TiCl.sub.2 Catalyst 2: Cr(III) = [C.sub.5Me.sub.4(CH.sub.2CH.sub.2NMe.sub.2]CrCl.sub.2 Comparative 1: Ti(IV) Guanidinate = [Et.sub.2NC(N(2,6-iPr.sub.2—C.sub.6H.sub.3)]TiCl.sub.3 Comparative 2: Ti(IV) Fl = [2,4-(t-Bu)2,-6-(CH═NC.sub.6F.sub.5)C.sub.6H.sub.2O].sub.2TiCl.sub.2 Comparative 3: Zirconocene = rac-Me.sub.2Si(2-Me-4-Ph-Ind).sub.2ZrCl.sub.2

(16) The series of polymerizations of Table 1 with ethylene and 10-undecene-1-ol has been carried out with a number of different catalysts as mentioned above. They contain different metals (Ti, Cr, Zr) in different oxidation states.

(17) For both the Cr(III) and Ti(III) catalyst activity increases with increase of nucleophilic comonomer, while all other catalysts are poisoned due to its presence, despite protecting the OH of the polar comonomer with an Al alkyl compound. For results see FIG. 2.

(18) TABLE-US-00002 TABLE 2 Ethylene/allyl alcohol copolymerization using catalysts 1 and 4. allyl TiBA:allyl alcohol Yield Run # Cat. alcohol mmol (g) 1 1 3.0 ref 6.1 2 1 3.0 ref 6.2 5 1 3.0 1 6.3 6 1 3.0 5 8.1 7 1 3.0 15 6.9 8 Comparative 4 3.0 ref 5.2 9 Comparative 4 3.0 5 1.2 10 Comparative 4 3.0 10 Traces 11 Comparative 4 3.0 15 Traces Conditions: toluene (80 mL); ethylene: 2.5 bar; MAO (30 wt. % in toluene) = 2.2 mL; Al/Ti = 1000; time: 15 min; 40° C.; cat. = 20 μmol. Catalyst 1: trivalent titanium [C.sub.5Me.sub.4CH.sub.2CH.sub.2NMe.sub.2]TiCl.sub.2. Comparative 4: comparative examples with tetravalent titanium phosphinimide Cp(tBu.sub.3P═N)TiCl.sub.2.

(19) TABLE-US-00003 TABLE 3 Ethylene/3-buten-2-ol copolymerization using catalyst 1. TiBA:3- 3-buten-2-ol Yield Run # buten-2-ol mmol (g) 1 3.0 ref 6.1 2 3.0 ref 6.2 3 3.0 ref 5.7 4 3.0 0.5 5.1 5 3.0 5 8.1 6 3.0 10 7.3 Conditions: toluene (80 mL); ethylene: 2.5 bar; MAO (30 wt. % in toluene) = 2.2 mL; Al/Ti = 1000; time: 15 min; 40° C.; cat. = 20 μmol. Catalyst 1: trivalent titanium [C.sub.5Me.sub.4CH.sub.2CH.sub.2NMe.sub.2]TiCl.sub.2.

(20) TABLE-US-00004 TABLE 4 Ethylene/3-buten-1-ol copolymerization using catalyst 1. TiBA:3- 3-buten-1-ol Yield Run # buten-1-ol mmol (g) 1 3.0 ref 6.1 2 3.0 0.1 5.8 3 3.0 0.5 6.4 4 3.0 1.0 6.2 5 3.0 5.0 8.6 6 3.0 10.0 6.9 7 3.0 15.0 9.8 8 3.0 20.0 7.6 Conditions: toluene (80 mL); ethylene: 2.5 bar; MAO (30 wt. % in toluene) = 2.2 mL; Al/Ti = 1000; time: 15 min; 40° C.; cat. = 20 μmol. Catalyst 1: trivalent titanium [C.sub.5Me.sub.4CH.sub.2CH.sub.2NMe.sub.2]TiCl.sub.2.

(21) TABLE-US-00005 TABLE 5 Ethylene/5-hexen-1-ol copolymerization using catalyst 1. TiBA:5- 5-hexen-1-ol Yield Run # hexen-1-ol mmol (g) 1 3.0 ref 6.1 2 3.0 ref 6.2 3 3.0 0.5 4.9 4 3.0 1.0 6.1 5 3.0 5.0 7.5 6 3.0 10.0 8.9 7 3.0 15.0 5.6 8 3.0 20.0 10.5 Conditions: toluene (80 mL); ethylene: 2.5 bar; MAO (30 wt. % in toluene) = 2.2 mL; Al/Ti = 1000; time: 15 min; 40° C.; cat. = 20 μmol. Catalyst 1: trivalent titanium [C.sub.5Me.sub.4CH.sub.2CH.sub.2NMe.sub.2]TiCl.sub.2.