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 CH bond, in the coordination reaction to the metal centre, generating a C,N,N-tridentate complex.

Claims

1. Tridentate iminopyrrolyl nickel complexes, wherein the general molecular formula (I), in which the chelating iminopyrrolyl ligand is bonded to the nickel centre in a tridentate fashion, through a subsequent cyclometallation reaction by an intramolecular CH activation, in which: ##STR00002## a) Ar represents an aryl group, such as phenyl, biphenyl, naphtyl and equivalents, or a substituted aryl group, especially phenyl, having one or both ortho positions of the aromatic ring substituted with alkyl groups C1-C4, unsubstituted or substituted alkoxy or aryl groups, the latter preferably having alkyl C1 or trifluoromethyl groups in meta positions; b) R1 represents a hydrogen atom or an alkyl group C1-C4; c) R2 represents a hydrogen atom or an alkyl group C1-C4 or a substituted or unsubstituted aryl group preferably phenyl; d) R3 always represents a methylene group; e) R4 and R5 represent hydrogen atoms; f) R6 represents a hydrogen atom, an alkyl group C1-C11, an unsubstituted or substituted aryl group or a halogen, but preferably a hydrogen atom; g) L represents a neutral coordinating ligand, such as triphenylphosphine, tri(C1-C6 alkyl)phosphine, tricycloalkylphosphine, diphenylalkylphosphine, dialkylphenylphosphine, trialkylamine, arylamine such as pyridine, a nitrile such as acetonitrile or equivalent.

2. Tridentate nickel complexes, wherein the 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 CH intramolecular activation, in which: a) Ar represents an aryl group, such as phenyl, biphenyl, naphtyl and equivalents, or a substituted aryl group, especially phenyl, having one or both ortho positions of the aromatic ring substituted with substituted or unsubstituted alkoxy or aryl groups, the latter preferably having C1 alkyl or trifluoromethyl groups, in meta positions; b) R1 and R2 represent together a fused aromatic ring in the corresponding CC bond, preferably a phenyl, 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 (preferably methyl, isopropyl or t-butyl) or trifluoromethyl, methoxy or halogen; c) R3 always represents a methylene group; d) R4 and R5 represent hydrogen atoms; e) R6 represents a hydrogen atom, an alkyl group C1-C11, a substituted or unsubstituted aryl group or a halogen, but preferably a hydrogen atom; f) L represents a neutral coordinating ligand, such as triphenylphosphine, tri(C1-C6 alkyl)phosphine, tricycloalkylphosphine, diphenylalkylphosphine, dialkylphenylphosphine, trialkylamine, arylamine such as pyridine, a nitrile such as acetonitrile or equivalent.

3. Process of polymerisation reaction of ethylene to hyperbranched polyethylene, from a solution of one of the complexes defined in claim 1, wherein their action as catalysts, and of a co-catalyst, both mixed in a solvent, at a temperature between 25 and 50 C., continuously pressurized by the monomer ethylene at a pressure between 3 and 15 bar, during a period between 2 and 6 hours.

4. Process, according to claim 3, wherein the co-catalyst is [Ni(COD).sub.2].

5. Process, according to claim 4, wherein solid process is free from the addition of a co-catalyst.

6. Process, according to claim 3, wherein the solvent used is selected from: xylene, toluene, chlorobenzene, o-dichlorobenzene, pentane, hexane, heptane.

Description

DESCRIPTION OF THE DRAWINGS

[0052] FIG. 1 shows the general molecular structure (I) of the nickel complexes of this invention.

[0053] 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.

[0054] 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.

[0055] 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).

[0056] 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].

[0057] FIG. 6 shows the molecular structures of complexes I.1 (a) and I.2 (b), obtained by X-ray diffraction.

[0058] FIG. 7 shows the molecular structure of complex I.3, obtained by X-ray diffraction.

[0059] 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.

[0060] 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

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

[0061] 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{C,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.)]

[0062] 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.

[0063] .sup.1H NMR (300 MHz, CD.sub.2Cl.sub.2): .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, CHC(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, CHC(CH.sub.3)(CH.sub.2), 1.39 (s, 3H, CHC(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): .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, CHC(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 (CHC(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, NiCH.sub.2), 22.1 (CH(CH.sub.3).sub.2). .sup.31P{H} NMR (121 MHz, CD.sub.2Cl.sub.2): .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{.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.)]

[0064] 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.

[0065] .sup.1H NMR (300 MHz, CD.sub.2Cl.sub.2): .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. CHC(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, CHC(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): .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, CHC(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 (CHC(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, NiCH.sub.2), 22.0 (CH(CH.sub.3).sub.2). .sup.31P{.sup.1H} NMR (121 MHz, CD.sub.2Cl.sub.2): .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{.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.)]

[0066] 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.

[0067] .sup.1H NMR (300 MHz, CD.sub.2Cl.sub.2): .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): .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, NiCH.sub.2), 23.7 (CH.sub.3). .sup.31P{.sup.1H} NMR (121 MHz, CD.sub.2Cl.sub.2): .sub.P 33.1. .sup.19F{.sup.1H} NMR (282 MHz, CD.sub.2Cl.sub.2): .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.

[0068] General Procedure for the Catalytic Polymerisation of Ethylene to Hyperbranched Polyethylene

[0069] The catalytic polymerisation reactions of ethylene to obtain hyperbranched polyethylene were carried out in 300 mL Miniclave Drive Bchi 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.

[0070] 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.

[0071] 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.