Tridentate iminopyrrolyl nickel complexes and their use as catalysts for the reaction of polymerisation of ethylene to hyperbranched polyethylene

Abstract

The present invention relates to the preparation of novel nickel complexes containing iminopyrrolyl-type ligands, having the general molecular structure (I), and to their use as active catalysts in the polymerisation reaction of ethylene to hyperbranched polyethylene. The structure of the ligand precursor is such that it allows the occurrence of a cyclometallation reaction by the activation of a C—H bond, in the coordination reaction to the metal centre, generating a C,N,N′-tridentate complex.

Claims

1. A tridentate iminopyrrolyl nickel complex represented by general molecular formula (I), in which a chelating iminopyrrolyl ligand is bonded to the nickel centre in a tridentate fashion, through a subsequent cyclometallation reaction by an intramolecular CH activation, wherein general molecular formula (I) has the structure: ##STR00002## a) Ar represents an aryl group or a substituted aryl group, having one or both ortho positions of an aromatic ring substituted with C1-C4 alkyl groups, unsubstituted or substituted alkoxy or aryl groups; b) R1 represents a hydrogen atom or a C1-C4 alkyl group; c) R2 represents a hydrogen atom or a C1-C4 alkyl group or a substituted or unsubstituted aryl group; d) R3 represents a methylene group; e) R4 and R5 represent hydrogen atoms; f) R6 represents a hydrogen atom, a C1-C11 alkyl group, an unsubstituted or substituted aryl group or a halogen; g) L represents a neutral coordinating ligand selected from the group consisting of triphenylphosphine, tri(C1-C6 alkyl)phosphine, tricycloalkylphosphine, diphenylalkylphosphine, dialkylphenylphosphine, trialkylamine, arylamine, and a nitrile or equivalents.

2. The tridentate iminopyrrolyl nickel complex of claim 1, wherein Ar represents a phenyl, biphenyl, naphthyl and equivalents, or a substituted aryl group.

3. The tridentate iminopyrrolyl nickel complex of claim 2, wherein the substituted aryl group represented by Ar is a substituted phenyl group.

4. The tridentate iminopyrrolyl nickel complex of claim 2, wherein a substituted aryl group substituted on one or more of the ortho positions of an aromatic ring of the substituted aryl group represented by Ar comprises C1 alkyl or trifluoromethyl groups in meta positions.

5. The tridentate iminopyrrolyl nickel complex of claim 1, wherein the substituted or unsubstituted aryl group represented by R2 is phenyl.

6. The tridentate iminopyrrolyl nickel complex of claim 1, wherein R6 is a hydrogen atom.

7. The tridentate iminopyrrolyl nickel complex of claim 1, wherein the arylamine is pyridine.

8. The tridentate iminopyrrolyl nickel complex of claim 1, wherein the nitrile is acetonitrile.

9. A process of polymerising ethylene to hyperbranched polyethylene from a solution of a tridentate iminopyrrolyl nickel complex defined in claim 1, comprising mixing the tridentate iminopyrrolyl nickel complex in a solvent at a temperature between 25 and 50° C. to form the solution, wherein the solution is continuously pressurized by ethylene monomer at a pressure between 3 and 15 bar, during a period between 2 and 6 hours, wherein the tridentate iminopyrrolyl nickel complex acts as a catalyst to effect polymerisation of the ethylene monomer.

10. The process according to claim 9, further comprising addition of a co-catalyst, wherein the co-catalyst is [Ni(COD).sub.2].

11. The process according to claim 9, wherein the solvent used is selected from: xylene, toluene, chlorobenzene, o-dichlorobenzene, pentane, hexane, or heptane.

12. A tridentate iminopyrrolyl nickel complex represented by general molecular formula (I), in which the iminopyrrolyl chelating ligand is bonded to the nickel centre in a tridentate fashion, through a subsequent cyclometallation reaction by a C—H intramolecular activation, wherein general molecular formula (I) has the structure: ##STR00003## a) Ar represents an aryl group or a substituted aryl group, having one or both ortho positions of an aromatic ring substituted with substituted or unsubstituted alkoxy or aryl groups; b) R1 and R2 represent together a fused aromatic ring containing the corresponding C═C bond, substituted at least in one of the ortho positions by a methylene group (R3), but which may be or not substituted in the other positions, by different or equal substituents, that can be C1-C4 alkyl, trifluoromethyl, methoxy or halogen; c) R3 represents a methylene group; d) R4 and R5 represent hydrogen atoms; e) R6 represents a hydrogen atom, a C1-C11 alkyl group, a substituted or unsubstituted aryl group or a halogen; f) L represents a neutral coordinating ligand selected from the group consisting of triphenylphosphine, tri(C1-C6 alkyl)phosphine, tricycloalkylphosphine, diphenylalkylphosphine, dialkylphenylphosphine, trialkylamine, arylamine, and a nitrile or equivalents.

13. The tridentate iminopyrrolyl nickel complex of claim 12, wherein Ar represents a phenyl, biphenyl, naphthyl and equivalents, or a substituted aryl group.

14. The tridentate iminopyrrolyl nickel complex of claim 13, wherein the substituted aryl group represented by Ar is a substituted phenyl group.

15. The tridentate iminopyrrolyl nickel complex of claim 13, wherein a substituted aryl group substituted on one or more of the ortho positions of an aromatic ring of the substituted aryl group represented by Ar comprises C1 alkyl or trifluoromethyl groups in meta positions.

16. The tridentate iminopyrrolyl nickel complex of claim 12, wherein the fused aromatic ring represented by R1 and R2 together is phenyl.

17. The tridentate iminopyrrolyl nickel complex of claim 12, wherein the arylamine is pyridine.

18. The tridentate iminopyrrolyl nickel complex of claim 12, wherein the nitrile is acetonitrile.

19. A process of polymerising ethylene to hyperbranched polyethylene from a solution of a tridentate iminopyrrolyl nickel complex defined in claim 12, comprising mixing the tridentate iminopyrrolyl nickel complex in a solvent at a temperature between 25 and 50° C. to form the solution, wherein the solution is continuously pressurized by ethylene monomer at a pressure between 3 and 15 bar, during a period between 2 and 6 hours, wherein the tridentate iminopyrrolyl nickel complex acts as a catalyst to effect polymerisation of the ethylene monomer.

20. The process according to claim 19, further comprising addition of a co-catalyst, wherein the co-catalyst is [Ni(COD).sub.2].

Description

DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows the general molecular structure (I) of the nickel complexes of this invention.

(2) FIG. 2 shows the molecular structure of the ligand precursors II (a) and III (b) used for the synthesis of the complexes I.1 and I.2, and I.3, respectively.

(3) FIG. 3 shows the .sup.1H NMR spectrum of complex I.1 in CD.sub.2Cl.sub.2, with the assignment of the different resonances and the corresponding integration values.

(4) FIG. 4 shows the evolution of the reaction of the formation of the complex I.1 with the increase of the temperature, monitored by .sup.31P{.sup.1H} NMR spectroscopy (reaction of the corresponding sodium salt II.sub.Na (R′=Me) with the trans-[NiCl(2-ClC.sub.6H.sub.4)(PPh.sub.3).sub.2] complex).

(5) FIG. 5 shows the evolution of the .sup.1H VT-NMR spectra for the reaction of the sodium salt II.sub.Na (R′=Ph) with complex trans-[NiCl(2-ClC.sub.6H.sub.4)(PPh.sub.3).sub.2].

(6) FIG. 6 shows the molecular structures of complexes I.1 (a) and I.2 (b), obtained by X-ray diffraction.

(7) FIG. 7 shows the molecular structure of complex I.3, obtained by X-ray diffraction.

(8) FIG. 8 shows the .sup.13C{H} NMR spectrum of the polyethylene obtained with the catalyst system I.1/[Ni(COD).sub.2], at 9 bar and 25° C.

(9) FIG. 9 shows the .sup.13C{.sup.1H} NMR spectrum of the polyethylene obtained with the catalyst system I.3/[Ni(COD).sub.2], at 9 bar and 25° C.

EXAMPLES

(10) General Procedure for the Synthesis of the C,N,N′-Tridentate Iminopyrrolyl Nickel Complexes Described in the Examples

(11) The ligand precursor was suspended in THF (10 mL) and added slowly with stirring to a Schlenk tube containing the previously weighed NaH powder. When the addition was complete, the mixture was refluxed for 2 h. After cooling to room temperature, the solution was filtered, the solvent removed and the powder was dried under vacuum and then dissolved in toluene (10 mL). Complex trans-[NiCl(Ar*)(PPh.sub.3).sub.2] (Ar*=Ph or 2-ClC.sub.6H.sub.4 was suspended in toluene (30 mL) and the solution of the corresponding sodium salt added dropwise, at −20° C. The reaction mixture was heated gradually to 65° C. and stirred, for ca. 12 h under inert atmosphere, giving rise to a dark red solution. The solution was filtered and evaporated to dryness and the residue washed with n-pentane or n-hexane at low temperature (−10 to 0° C.). Subsequently, the compound was extracted with an appropriate solvent, the solution concentrated and stored at −20° C., yielding the pure complex.

Example 1

[Ni{κC,N,N′-5-[(CH.SUB.2.)C(CH.SUB.3.)C(H)]—NC.SUB.4.H.SUB.2.-2-C(H)═N-2,6-.SUP.i.Pr.SUB.2.C.SUB.6.H.SUB.3.}(PPh.SUB.3.)]

(12) As described in the general procedure, 0.52 g (1.7 mmol) of the ligand precursor 5-(2-CH.sub.3C.sub.3H.sub.3)-2-[N-(2,6-.sup.iPr.sub.2C.sub.6H.sub.3)formimino].sup.−1H-pyrrole were deprotonated with 0.05 g (2.2 mmol) of NaH and the corresponding sodium salt was added to 1.09 g (1.5 mmol) of the complex trans-[NiCl(2-ClC.sub.6H.sub.4)(PPh.sub.3).sub.2]. After washing with r-hexane and the resulting red solid was dissolved in a minimum of toluene and double-layered with n-hexane while stirring leading to the precipitation of a microcrystalline red solid. Yield: 0.5.6 g (60%). Crystals suitable for single crystal X-ray diffraction were obtained from a toluene solution at −20° C. This compound was characterised by NMR spectroscopy and elemental analysis.

(13) .sup.1H NMR (300 MHz, CD.sub.2Cl.sub.2): δ.sub.H 7.40-7.28 (m, 10H, CHN, PPh.sub.3-H.sub.para e. H.sub.ortho), 7.21-7.15 (m, 6H, PPh.sub.3-H.sub.meta), 6.93 (t, 1H, .sup.3J.sub.HH=7.7 Hz, N-Ph-H.sub.para), 6.80 (d, 1H, .sup.3J.sub.HH=3.6 Hz, H3), 6.74 (d, 2H, .sup.3J.sub.HH=7.7 Hz, N-Ph-H.sub.meta), 6.58 (s, 1H, CH═C(CH.sub.3)(CH.sub.2)), 6.2.8 (d, 1H, .sup.3J.sub.HH=3.6 Hz, H4), 3.63 (hept, 2H, .sup.3J.sub.HH=6.8 Hz, CH(CH.sub.3).sub.2), 1.89 (d, 2H, .sup.3J.sub.HP=11.5 Hz, CH═C(CH.sub.3)(CH.sub.2), 1.39 (s, 3H, CH═C(CH.sub.3)(CH.sub.2)), 1.05 (d, 6H, .sup.3J.sub.HH=6.8 Hz, CH(CH.sub.3).sub.2), 0.86 (d, 6H, .sup.3J.sub.HH=6.8 Hz, CH(CH.sub.3).sub.2. .sup.13C NMR {.sup.1H} (75 MHz, CD.sub.2Cl.sub.2): δ.sub.C 160.0 (d, .sup.3J.sub.CP=2.6 Hz, CHN), 149.4 (N-Ph-C.sub.ipso), 147.7 (d, .sup.3J.sub.CP=2.3 Hz, CH═C(CH.sub.3)(CH.sub.2)), 146.5 (d, .sup.3J.sub.CP=1.6 Hz, C5) 141.8 (N-Ph-C.sub.ortho), 140.7 (d, .sup.3J.sub.CP=1.4 Hz, C2), 134.5 (d, .sup.2J.sub.CP=11.3 Hz, PPh.sub.3-C.sub.ortho), 132.8 (d, .sup.1J.sub.CP=41.0 Hz, PPh.sub.3-C.sub.ipso), 129.0 (d, .sup.4J.sub.CP=2.1 Hz, PPh.sub.3-C.sub.para), 128.5 (d, .sup.3J.sub.CP=9.5 Hz, PPh.sub.3-C.sub.meta), 125.9 (N-Ph-C.sub.para), 123.3 (N-Ph-C.sub.meta), 118.5 (d, .sup.4J.sub.CP=1.5 Hz, C3), 117.6 (CH═C(CC(CH.sub.3)(CH.sub.2)), 109.5 (d, .sup.4J.sub.CP=3.6 Hz, C4), 28.4 (CH(CH.sub.3).sub.2), 25.8 (CH(CH.sub.3).sub.2), 25.3 (CH.sub.3), 25.2 (d, .sup.2J.sub.CP=21.3 Hz, Ni—CH.sub.2), 22.1 (CH(CH.sub.3).sub.2). .sup.31P{H} NMR (121 MHz, CD.sub.2Cl.sub.2): δ.sub.P 32.1. Anal. Calculated (%) for C.sub.39H.sub.41N.sub.2NiP: C, 74.66; H, 6.59; N, 4.46. Found: C, 74.94; H, 6.69; N, 4.28.

Example 2

[Ni{κ.SUP.3.C,N,N′-5-[(CH.SUB.2.)C(C.SUB.6.H.SUB.5.)═C(H)]—NC.SUB.4.H.SUB.2.-2-C(H)═N-2,6-.SUP.i.Pr.SUB.2.C.SUB.6.H.SUB.3.}(PPh.SUB.3.)]

(14) As described in the general procedure, 0.56 g (1.5 mmol) of the ligand precursor 5-(2-PhC.sub.3H.sub.4)-2-[N-(2,6-.sup.iPr.sub.2C.sub.6H.sub.3)formimino]-1H-pyrrole were deprotonated with 0.05 g (2.0 mmol) of NaH and the corresponding sodium salt was added to 0.88 g (1.2 mmol) of the complex trans-[NiCl(2-ClC.sub.6H.sub.4)(PPh.sub.3).sub.2]. After washing with n-hexane and the remaining red solid extracted with diethyl ether, the resulting solution was further concentrated and stored at −20° C., giving red crystals suitable for single crystal X-ray diffraction. Yield: 0.46 g (55%). This compound was characterised by NMR spectroscopy and elemental analysis.

(15) .sup.1H NMR (300 MHz, CD.sub.2Cl.sub.2): δ.sub.H 7.41 (s, 1H, CHN), 7.35-7.29 (m, 6H, PPh.sub.3-H.sub.ortho), 7.24-7.19 (m, 3H, PPh.sub.3-H.sub.para), 7.10-7.05 (m, 7H, PPh.sub.3-H.sub.meta e. CH═C(CH.sub.2)(Ph)), 7.01-6.99 (m, 3H, Ph-H.sub.ortho and Ph-H.sub.para), 6.94-6.86 (m, 4H, Ph-H.sub.meta, N-Ph-H.sub.para e H3), 6.73 (d, 2H, .sup.3J.sub.HH=7.7 Hz, N-Ph-H.sub.meta), 6.49 (d, 1H, .sup.3J.sub.HH=2.8 Hz, H4), 3.62 (hept, 2H, .sup.3J.sub.HH=7.0 Hz, CH(CH.sub.3).sub.2), 2.28 (d, 2H, .sup.3J.sub.HP=11.2 Hz, CH═C(Ph)(CH)), 1.06 (d, 6H, .sup.3J.sub.HH=6.7 Hz, CH(CH.sub.3).sub.2), 0.89 (d, 6H, .sup.3J.sub.HH=6.7 Hz, CH(CH.sub.3).sub.2). .sup.13C{.sup.1H} NMR (75 MHz, CD.sub.2Cl.sub.2): δ.sub.C 160.3 (d, .sup.3J.sub.CP=2.6 Hz, CHN), 149.2 (N-Ph-C.sub.ipso), 148.2 (d, .sup.3J.sub.CP=2.1 Hz, CH═C(Ph)(CH.sub.2)), 146.4 (d, .sup.3J.sub.CP=1.5 Hz, C5), 144.6 (Ph-C.sub.ipso), 141.7 (N-Ph-C.sub.ortho), 141.2 (d, .sup.3J.sub.CP=1.2 Hz, C2), 134.4 (d, .sup.2J.sub.CP=11.2 Hz, PPh.sub.3-C.sub.ortho), 132.3 (d, .sup.1J.sub.CP=41.1 Hz, PPh.sub.3-C.sub.ipso), 129.8 (d, .sup.4J.sub.CP=2.0 Hz, PPh.sub.3-C.sub.para), 128.4 (d, .sup.3J.sub.CP=9.5 Hz, PPh.sub.3-C.sub.meta), 127.9 (Ph-C.sub.ortho), 126.9 (Ph-C.sub.meta), 126.2, (Ph-C.sub.para), 126.1 (N-Ph-C.sub.para), 123.3 (N-Ph-C.sub.meta), 118.9 (CH═C(Ph)(CH.sub.2)), 118.6 (d, .sup.4J.sub.CP=1.4 Hz, C3), 111.6 (d, .sup.4J.sub.CP=3.5 Hz, C4), 28.5 (CH(CH.sub.3).sub.2), 25.8 (CH(CH.sub.3).sub.2), 22.3 (d, .sup.2J.sub.CP=20.0 Hz, Ni—CH.sub.2), 22.0 (CH(CH.sub.3).sub.2). .sup.31P{.sup.1H} NMR (121 MHz, CD.sub.2Cl.sub.2): δ.sub.P 32.4. Anal. Calculated (%) for C.sub.44H.sub.43N.sub.2NiP: C, 76.65; H, 6.29; N, 4.06. Found: C, 76.19; H, 6.01; N, 3.78.

Example 3

[Ni{κ.SUP.3.C,N,N′-5-[2′-CH.SUB.2.-6′-CH.SUB.3.—C.SUB.6.H.SUB.3.]—NC.SUB.4.H.SUB.2.-2-C(H)═N-2,6-[3,5-(CF.SUB.3.).SUB.2.C.SUB.6.H.SUB.3.].SUB.2.C.SUB.6.H.SUB.3.}(PPh.SUB.3.)]

(16) As described in the general procedure, 1.05 g (1.5 mmol) of the ligand precursor 5-[2′,6′-(CH.sub.3).sub.2C.sub.6H.sub.3]-2-{N-[2,6-[3,5-(CF.sub.3).sub.2C.sub.6H.sub.3].sub.2C.sub.6H.sub.3]formimino}-1H-pyrrole were deprotonated with 0.05 g (2.0 mmol) of NaH and the corresponding sodium salt was added to 0.83 g (1.2 mmol) of the complex trans-[NiCl(Ph)(PPh.sub.3).sub.2]. After washing with n-pentane, the remaining orange solid was dried under vacuum. Since the complex is partially soluble in n-pentane, the solution resulting from the washings was concentrated and stored at −20° C., giving crystals suitable for single crystal X-ray diffraction. Yield: 0.74 g (61%). This compound was characterised by NMR spectroscopy and elemental analysis.

(17) .sup.1H NMR (300 MHz, CD.sub.2Cl.sub.2): δ.sub.H 8.06 (s, 4H, ortho-Ph-H.sub.ortho), 7.89 (s, 2H, ortho-Ph-H.sub.para), 7.32-7.04 (m, 19H, CHN, N-Ph-H.sub.meta), N-Ph-H.sub.para e PPh.sub.3), 6.99 (d, 1H, .sup.3J.sub.HH=7.3 Hz, 5-Ph-H.sub.meta.sup.CH.sub.3), 6.87-6.83 (m, 2H, H3 e H4), 6.54 (t, 1H, .sup.3J.sub.HH=7.4 Hz, 5-Ph-H.sub.para), 6.01 (d, 1H, .sup.3J.sub.HH=7.4 Hz, 5-Ph-H.sub.meta.sup.CH.sub.2), 2.61 (s, 3H, CH.sub.3), 2.13 (d, 2H, .sup.3J.sub.HP=11.1 Hz, CH.sub.2). .sup.13C{.sup.1H} NMR (75 MHz, CD.sub.2Cl.sub.2): δ.sub.C 162.4 (d, .sup.3J.sub.CP=2.6 Hz, CHN), 148.9 (N-Ph-C.sub.ipso), 147.8 (C5), 145.0 (d, .sup.3J.sub.CP=1.6 Hz, 5-Ph-C.sub.ortho.sup.CH.sub.2), 141.6 (C2), 141.3 (N-Ph-C.sub.ortho), 135.9 (5-Ph-C.sub.ortho.sup.CH.sub.3), 134.3 (d, .sup.2J.sub.CP=11.4 Hz, PPh.sub.3-C.sub.ortho), 133.6 (0.5-Ph-C.sub.ipso), 133.5 (ortho-Ph-C.sub.ipso), 131.9 (PPh.sub.3-C.sub.para), 131.7 (quart, 2J.sub.CP=33.0 Hz, ortho-Ph-C.sub.meta), 131.3 (d, .sup.3J.sub.CP=2.7 Hz, ortho-Ph-C.sub.ortho), 130.2 (br, N-Ph-C.sub.meta and N-Ph-C.sub.para), 128.6 (d, .sup.4J.sub.CP=10.4 Hz, PPh.sub.3-C.sub.meta), 127.7 (5-Ph-C.sub.meta.sup.CH.sub.3), 126.7 (d, .sup.4J.sub.CP=7.7 Hz, 5-Ph-C.sub.meta.sup.CH.sub.2). 125.2 (5-Ph-C.sub.para), 123.9 (quart, .sup.1J.sub.CF=271.3 Hz, CF.sub.3), 121.0 (sept, .sup.3J.sub.CF=3.6 Hz, ortho-Ph-C.sub.para), 120.2 (C3), 115.3 (C4), 24.8 (d, .sup.2J.sub.CP=20.9 Hz, Ni—CH.sub.2), 23.7 (CH.sub.3). .sup.31P{.sup.1H} NMR (121 MHz, CD.sub.2Cl.sub.2): δ.sub.P 33.1. .sup.19F{.sup.1H} NMR (282 MHz, CD.sub.2Cl.sub.2): δ.sub.F −63.0. Anal. Calculated (%) for C.sub.35H.sub.35F.sub.12N.sub.2NiP: C, 62.56; H, 3.47; N, 2.75. Found: C, 62.78; H, 3.20; N, 2.67.

(18) General Procedure for the Catalytic Polymerisation of Ethylene to Hyperbranched Polyethylene

(19) The catalytic polymerisation reactions of ethylene to obtain hyperbranched polyethylene were carried out in 300 mL Miniclave Drive Büchi pressure reactors with glass vessels (up to 9 bar) or stainless steel (up to 1.5 bar) vessels. The reactors were previously dried in an oven at 140° C. and degassed, and dry distilled toluene (50 mL) was added, under a pressure of 1.3 bar of nitrogen. The reactor was warmed to the desired temperature (from 25° C. to 50° C.) and allowed to equilibrate for 10 min. After a new degassing, the reactors were pressurised with ethylene and a solution of the catalyst in toluene (10.sup.−2 mmol, 1 mL) was added, followed, when 0.25 appropriate, by the addition of a solution of [Ni(COD).sub.2] in toluene (2 mL). The ethylene pressure was raised up to the desired value (3 to 15 bar) and the admission valve was maintained continuously opened during the reaction time (2 to 6 hours). At the end of the catalytic test the ethylene supply was closed, the reactor was depressurised, and the reaction medium was quenched with methanol while stirring. The formation of an oily phase was observed in almost all the tests and which was isolated through the evaporation of the volatiles at reduced pressure. The isolated products were dried until constant weight, yielding colourless oils with different densities and viscosities.

(20) All the products were characterised by GPC/SEC and .sup.1H and .sup.13C{.sup.1H} NMR spectroscopy. The NMR samples were dissolved in 0.8 mL of a mixture of 1,2,4-trichlorobenzene and C.sub.6D.sub.6 (75:25 v/v), and the spectra recorded at 90° C. Through the analysis of the .sup.1H Spectra it is possible to determine the branching degree of the polymers, N, which is the total number of branches per 1000 carbon atoms. The analysis of the .sup.13C{.sup.1H} spectra indicates the type and distribution of those branches.

(21) Blank tests were performed to analyse the catalytic activity of the [Ni(COD).sub.2] scavenger at the different conditions of temperature and pressure, which was found to be inactive in all the conditions used.