Turtle-shaped nickel complex as well as preparation method and application thereof

Abstract

The invention provides a turtle-shaped nickel complex as well as a preparation method and application thereof. The preparation method of the nickel complex comprises the following steps: 1) preparing a butanedione diimine ligand; and 2) under the protection of inert gas, reacting the butanedione diimine ligand obtained in the step 1) with (DME) NiBr2 in the presence of an organic solvent at room temperature for 24 hours to obtain the turtle-shaped nickel complex. The turtle-shaped nickel complex is activated with sesquethyl aluminum chloride (EASC) and shows high activity on ethylene polymerization, polyethylene with high linearity, high molecular weight and narrow molecular weight distribution can be obtained, the highest catalytic activity can reach 1.87 * 10 < 7 > g mol <-1 > h <-1 >, and the highest molecular weight of polyethylene can reach 8.73 * 10 < 5 > g mol <-1 >.

Description

Technical Field

[0001] The present invention relates to a post-transition metal catalyst for ethylene polymerization, and in particular to a "tortoise" type nickel complex containing 5-dibenzocycloheptyl, and a preparation method and application thereof. Background Art

[0002] Polyolefins are the most important materials produced by the petrochemical industry, with polyethylene (PE) accounting for the largest market share. Polyethylene, the most widely produced general-purpose synthetic resin, primarily includes low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), high-density polyethylene (HDPE), and several products with specialized properties. These products are characterized by their low price and excellent performance, making them widely used in industry, agriculture, packaging, and everyday applications. The widespread development and application of polyethylene products is inseparable from the advancement of olefin polymerization catalysts. Recently developed high-efficiency catalysts based on late transition metal complexes for ethylene oligomerization and polymerization are not only simple to prepare, exhibit high catalytic activity, and enable control over polymer molecular weight and distribution, they have rapidly become a hot topic in applied research. Brookhart pioneered the use of α-diimine nickel catalysts for ethylene polymerization. This nickel catalyst was the first late transition metal catalyst system discovered to be capable of catalyzing ethylene polymerization. The key focus of research on these catalysts is the development of catalysts with higher activity and thermal stability. Furthermore, modifying the ligand structure can alter the coordination environment of these catalysts, thereby regulating the catalytic behavior and the structure and properties of the resulting polymers. Summary of the Invention

[0003] The purpose of the present invention is to provide a "turtle" type nickel complex and a preparation method thereof, as well as the application of such catalyst in ethylene polymerization.

[0004] The present invention provides a "turtle" type nickel complex having the following structural formula:

[0005]

[0006] wherein R is methyl or ethyl.

[0007] The present invention also provides a method for preparing the series of "turtle"-shaped nickel complexes, comprising the following steps:

[0008] (1) Preparation of ligand compound: iminobutanone with a monobasic group, aniline, and p-toluenesulfonic acid were added to a flask and dissolved in toluene; the reaction mixture was refluxed at 150° C. for 10 hours; after the reaction was completed, the solvent was removed under reduced pressure; and a yellow solid product was obtained by purification;

[0009] (2) Preparation of nickel complex: Under an inert atmosphere, anhydrous dichloromethane was added to the prepared Schlenk tube, and the ligand compound and (DME)NiBr2 were added to the Schlenk tube respectively; the resulting mixture was stirred at room temperature for 24 hours; then, the solvent was removed under reduced pressure, and the product was extracted with ether several times, filtered, and dried to obtain a dark red solid product.

[0010] In the step (1), the molar ratio of the unilateral macro-group iminobutanone and aniline is 1:1-1.5; and in the step (2), the molar ratio of the ligand compound and (DME)NiBr2 is 1:0.9-1.5.

[0011] The synthetic route is as follows:

[0012]

[0013] The present invention discloses an application of a "tortoise"-shaped nickel complex in ethylene polymerization. Specifically, the series of "tortoise"-shaped nickel complexes are used as a main catalyst, ethylaluminum sesquichloride (EASC) is used as a co-catalyst, and a composite catalyst system is formed with a molar ratio of the main catalyst to the co-catalyst of 1:200 to 1:600. The reaction temperature is controlled at 30 to 100° C. and the reaction time is 5 to 60 minutes to catalyze ethylene polymerization.

[0014] In the experiment of ethylene polymerization, the catalyst polymerization activity can reach up to 1.87×10 7 g mol -1 h -1 , the maximum molecular weight of polyethylene can reach: 8.73×10 5 g mol -1 .

[0015] Compared with the prior art, the advantages and effects of the present invention are as follows: the raw materials used for synthesizing the catalyst are readily available and inexpensive, and the preparation method is simple; the catalyst has high catalytic activity and good thermal stability for ethylene polymerization, and can obtain polyethylene with high linearity, high molecular weight, and narrow molecular weight distribution. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Schematic diagram of the crystal structure of nickel complex C1 prepared in Example 1. DETAILED DESCRIPTION

[0017] The following specific embodiments are given for illustration only and are not intended to limit the scope of protection of the present invention.

[0018] Example 1

[0019] Preparation of ligand compound L1: Add unilateral bulky iminobutanone (4.0 mmol), 2,4,6-trimethylaniline (4.0 mmol) and p-toluenesulfonic acid (0.1 mmol) into a flask and dissolve in toluene. Reflux the reaction mixture at 150°C for 10 hours. After the reaction is completed, remove the solvent under reduced pressure. The crude product is purified by column chromatography (hexane / ethyl acetate, 500 / 5) to obtain a yellow solid. Characterization data are as follows: L1: (R = Me) yellow solid product, yield 17%. FT-IR (KBr, cm -1 ):3061(w),3022(w),2933(w),2887(w),2362(w),2343(w),1639(ν(C=N)m),1495(m),1443(m),1388(w),1365(w),770(s),757(s),619(w). 1 H NMR(600MHz,Chloroform-d)δ7.15(d,J=9.1Hz,2H),7.09(d,J=11.4Hz,4H),7. 03(t,J=8.1Hz,4H),7.00–6.91(m,12H),6.87(d,J=12.1Hz,4H),6.54(s,2H),5 .01(s,1H),4.78(s,2H),2.79(d,J=15.6Hz,2H),2.70–2.62(m,4H),2.56–2.48 (m,2H),2.43–2.33(m,4H),2.31(s,3H),2.14(s,6H),2.00(s,3H),1.34(s,3H). 13 C NMR (151 MHz, Chloroform-d) δ 140.28, 140.09, 139.94, 139.87, 139.26, 130.86, 130.76, 130.64, 130.59, 130.52, 130.24, 129.33, 129.19, 128.72, 126.88, 126.72, 126.07, 125.89, 125.43, 124.82, 57.72, 55.92, 32.05, 31.36, 31.31, 20.71, 18.41, 16.39, 15.97. Elemental analysis: C 64 H 58 N2, theoretical value: C, 89.89; H, 6.84; N, 3.28. Actual value: C, 89.51; H, 6.54; N, 3.64.

[0020] Preparation of ligand compound L2: Add unilateral bulky iminobutanone (4.0 mmol), 2,6-diethyl-4-methylaniline (4.0 mmol) and p-toluenesulfonic acid (0.1 mmol) into a flask and dissolve in toluene. The reaction mixture was refluxed at 150°C for 10 hours. After the reaction, the solvent was removed under reduced pressure. The crude product was purified by column chromatography (hexane / ethyl acetate, 500 / 5) to obtain a yellow solid. The characterization data are as follows: L2: (R = Et) yellow solid product with a yield of 14%. FT-IR (KBr, cm -1 ):3057(w),3015(w),2963(w),2927(w),2880(w),2369(w),2327(w),1641 (ν(C=N)m),1496(m),1454(m),1441(w),1360(w),773(s),747(s),609(w). 1 H NMR(600MHz,Chloroform-d)δ7.16(d,J=9.1Hz,2H),7.10(d,J=10.1Hz,4H),7.04(t,J=7.5Hz,4H),6.96(d,J=6.0Hz,12H),6.88(d,J=17.0Hz,4H),6.55(s, 2H),5.02(s,1H),4.79(s,2H),2.83–2.75(m,2H),2.72–2.62(m,4H),2.55–2. 47(m,4H),2.45–2.33(m,9H),2.03(s,3H),1.38(s,3H),1.24(t,J=7.5Hz,6H). 13 C NMR(151MHz,Chloroform-d)δ170.25,168.02,144.92,144.82,140.37,140.24,140.10, 139.96,139.25,136.86,132.73,130.92,130.75,130.67,130.58,130.56,130.28,130.1 3,129.35,129.21,126.89,126.77,126.68,126.38,126.02,125.90,125.39,57.73,55.88,32.03,31.60,31.39,31.35,29.34,24.48,21.03,16.46,15.98,14.13,13.52. Elemental analysis: C 66 H 62N2, theoretical value: C, 89.75; H, 7.08; N, 3.17. Actual value: C, 89.35; H, 7.57; N, 3.52.

[0021] Preparation of nickel complex C1: Under inert gas protection, add 10 ml of anhydrous dichloromethane to the prepared Schlenk tube, add ligand compound L1 (0.21 mmol), add (DME)NiBr2 (0.20 mmol) in batches at low temperature, slowly return to room temperature, and stir the resulting mixture at room temperature for 24 hours. After the reaction is completed, remove the solvent under reduced pressure, and thoroughly wash with ether (3×10 ml), collect by filtration, and dry to obtain a deep red solid complex. Characterization data are as follows: C1: (R=Me) deep red solid powder, yield 95%. FT-IR (KBr, cm -1 ):3056(w),3014(w),2964(w),2928(w),2865(w),1629(ν(C=N)m),1590(w),1490(m),1436(m),1370(m),760(s),710(w),617(w). Elemental analysis: C 64 H 58 Br2N2Ni, theoretical values: C, 71.60; H, 5.45; N, 2.61. Actual values: C, 71.41; H, 5.64; N, 2.64.

[0022] Preparation of nickel complex C2: Under inert gas protection, add 10 ml of anhydrous dichloromethane to the prepared Schlenk tube, add ligand compound L2 (0.21 mmol), add (DME)NiBr2 (0.20 mmol) in batches at low temperature, slowly return to room temperature, and stir the resulting mixture at room temperature for 24 hours. After the reaction is completed, remove the solvent under reduced pressure, and thoroughly wash with ether (3×10 ml), collect by filtration, and dry to obtain a deep red solid complex. Characterization data are as follows: C2: (R=Et) deep red solid powder, yield 93%. FT-IR (KBr, cm -1 ):3063(w),3017(w),2961(w),2923(w),2878(w),1629(ν(C=N)m),1598(w),1493(m),1438(m),1373(m),765(s),728(w),619(w). Elemental analysis: C 66 H 62 Br2N2Ni, theoretical values: C, 71.95; H, 5.67; N, 2.54. Actual values: C, 71.68; H, 5.43; N, 2.58.

[0023] Example 2

[0024] Ethylene polymerization using complex C1 and different cocatalysts:

[0025] (1) Under ethylene atmosphere, 20 mL of toluene, 20 mL of a toluene solution of dissolved catalyst C1 (2 μmol), and 1.2 mL of a co-catalyst MAO (1.67 mol / L toluene solution) were added sequentially to a 250 mL stainless steel autoclave. Toluene was continued to be added until the total volume of the reaction solution reached 100 mL. At this time, Al / Ni = 1000. When the polymerization temperature reached 30°C, ethylene was added to the reactor and the polymerization reaction began. The ethylene pressure was maintained at 10 atm at 30°C and the reaction time was 30 min. The reaction solution was neutralized with an ethanol solution acidified with 5% hydrochloric acid, filtered, and the polymer precipitate was obtained. The polymer was washed several times with ethanol, dried under vacuum, and weighed. Polymerization activity: 6.32 × 10 6 g mol -1 h -1 , polymer T m =90.8℃(T m is the melting temperature of the polymer, obtained by DSC test), the polymer molecular weight M w =8.00×10 5 g·mol -1 (M w is the weight-average molecular weight of the polymer, obtained by temperature-elevated GPC testing).

[0026] (2) The method is the same as above, except that 0.8 mL of MMAO (1.93 mol / L n-heptane solution) is used as the co-catalyst, and Al / Ni is 1000. Polymerization activity: 5.81 × 10 6 g mol -1 h -1 , polymer T m =77.2℃, polymer molecular weight M w =5.49×10 5 g·mol -1 .

[0027] (3) The method is the same as above, except that 0.9 mL of DMAC (0.9 mol / L n-heptane solution) is used as the co-catalyst, and Al / Ni = 400. Polymerization activity: 3.92 × 10 6 g mol -1 h -1 , polymer T m =70.4℃, polymer molecular weight M w =5.15×10 5 g·mol -1 .

[0028] (4) The method is the same as above, except that 0.4 mL of DEAC (2.0 mol / L n-hexane solution) is used as the co-catalyst, and Al / Ni is 400. Polymerization activity: 7.45 × 10 6 g mol -1 h -1 , polymer T m =7.45℃, polymer molecular weight M w =4.80×10 5 g·mol -1 .

[0029] (5) The implementation method is the same as above, except that 2.0 mL of EASC (0.4 mol / L n-hexane solution) is used as the co-catalyst, and Al / Ni is 400. Polymerization activity: 9.86×10 6 g mol -1 h -1 , polymer T m =65.0℃, polymer molecular weight M w =6.18×10 5 g·mol -1 .

[0030] Example 3

[0031] Ethylene polymerization using complex C1 and cocatalyst EASC at different aluminum-nickel ratios:

[0032] (1) The implementation method is the same as that of Example 2, except that 1.0 mL of EASC (0.4 mol / L n-hexane solution) is used as the co-catalyst, and Al / Ni is 200. Polymerization activity: 8.76×10 6 g mol -1 h -1 , polymer T m =64.6℃, polymer molecular weight M w =7.06×10 5 g·mol -1 .

[0033] (2) The method is the same as above, except that 1.5 mL of EASC (0.4 mol / L n-hexane solution) is used as the co-catalyst, and Al / Ni is 300. Polymerization activity: 9.21×10 6 g mol -1 h -1 , polymer T m =66.4℃, polymer molecular weight M w =6.56×10 5 g·mol -1 .

[0034] (3) The implementation method is the same as above, except that 2.5 mL of EASC (0.4 mol / L n-hexane solution) is used as the co-catalyst, and Al / Ni is 500. Polymerization activity: 9.71×10 6 g mol -1 h -1 , polymer T m =59.0℃, polymer molecular weight M w =6.16×10 5 g·mol -1 .

[0035] (4) The implementation method is the same as above, except that 3.0 mL of EASC (0.4 mol / L n-hexane solution) is used as the co-catalyst, and Al / Ni is 600. Polymerization activity: 8.90×10 6 g mol -1 h -1 , polymer T m =65.3℃, polymer molecular weight M w =4.05×10 5 g·mol -1 .

[0036] Example 4

[0037] Ethylene polymerization reaction at different temperatures using complex C1 and cocatalyst EASC:

[0038] (1) The implementation method is the same as that of Example 2, except that 2.0 mL of EASC (0.4 mol / L n-hexane solution) is used as the co-catalyst, Al / Ni=400, and the polymerization temperature is 40°C. Polymerization activity: 6.58×10 6 g mol -1 h -1 , polymer molecular weight M w =4.80×10 5 g·mol -1 .

[0039] (2) The implementation method is the same as above, except that the polymerization temperature is 60°C. Polymerization activity: 3.72×10 6 g mol -1 h -1 , polymer molecular weight M w =4.16×10 5 g·mol -1 .

[0040] (3) The implementation method is the same as above, except that the polymerization temperature is 80°C. Polymerization activity: 2.45×10 6 g mol -1 h-1 , polymer molecular weight M w =3.83×10 5 g·mol -1 .

[0041] (4) The implementation method is the same as above, except that the polymerization temperature is 100°C. Polymerization activity: 1.51×10 6 g mol -1 h -1 , polymer molecular weight M w =3.56×10 5 g·mol -1 .

[0042] Example 5

[0043] Ethylene polymerization reaction using complex C1 and cocatalyst EASC at different times:

[0044] (1) The implementation method is the same as that of Example 2, except that 2.0 mL of EASC (0.4 mol / L n-hexane solution) is used as the co-catalyst, Al / Ni=400, and the reaction time is 5 min. Polymerization activity: 18.72×10 6 g mol -1 h -1 , polymer T m =70.9℃, polymer molecular weight M w =3.68×10 5 g·mol -1 .

[0045] (2) The implementation method is the same as above, except that the reaction time is 10 min. Polymerization activity: 14.85×10 6 g mol -1 h -1 , polymer T m =68.6℃, polymer molecular weight M w =5.38×10 5 g·mol -1 .

[0046] (3) The implementation method is the same as above, except that the reaction time is 15 min. Polymerization activity: 11.82×10 6 g mol -1 h -1 , polymer T m =63.4℃, polymer molecular weight M w =6.03×10 5 g·mol -1 .

[0047] (4) The implementation method is the same as above, except that the reaction time is 45 min. Polymerization activity: 7.80×10 6 g mol -1 h -1 , polymer T m =60.2℃, polymer molecular weight M w =6.93×10 5 g·mol -1 .

[0048] (5) The implementation method is the same as above, except that the reaction time is 60 min. Polymerization activity: 6.26×10 6 g mol -1 h -1 , polymer T m =70.6℃, polymer molecular weight M w =8.73×10 5 g·mol -1 .

[0049] Example 6

[0050] Ethylene polymerization using complex C1 and cocatalyst EASC at different ethylene pressures:

[0051] (1) The implementation method is the same as that of Example 2, except that 2.0 mL of EASC (0.4 mol / L n-hexane solution) is used as the co-catalyst, Al / Ni=400, and the ethylene pressure is 1 atm. Polymerization activity: 2.11×10 6 g mol -1 h -1 , polymer molecular weight M w =3.14×10 5 g·mol -1 .

[0052] (2) The implementation method is the same as above, except that the ethylene pressure is 5 atm. Polymerization activity: 4.90×10 6 g mol -1 h -1 , polymer T m =59.1℃, polymer molecular weight M w =4.07×10 5 g·mol -1 .

[0053] Example 7

[0054] Ethylene polymerization reaction using complex C2 and cocatalyst EASC under optimal conditions:

[0055] The implementation method was the same as that of Example 2, except that 2.0 mL of EASC (0.4 mol / L n-hexane solution) was used as the cocatalyst, Al / Ni ratio was 400, polymerization temperature was 30°C, ethylene pressure was maintained at 10 atm, polymerization time was 30 min, and complex C2 was used to catalyze ethylene polymerization. Polymerization activity: 10.72 × 10 6 g mol -1 h -1 , polymer T m =64.7℃, polymer molecular weight M w =4.74×10 5 g·mol -1 .

Claims

1. A "tortoise" type nickel complex, characterized in that: It has the following structural formula: wherein R is methyl or ethyl.

2. The method for preparing the nickel complex according to claim 1, wherein The steps include: (1) Preparation of ligand compound: iminobutanone with a unilateral bulky group, aniline, and p-toluenesulfonic acid were added to a flask and dissolved in toluene; the reaction mixture was refluxed at 150° C. for 10 hours; after the reaction was completed, the solvent was removed under reduced pressure; Purification gave a yellow solid product; (2) Preparation of nickel complex: Under an inert atmosphere, anhydrous dichloromethane was added to the prepared Schlenk tube, and the ligand compound and (DME)NiBr2 were added to the Schlenk tube respectively; the resulting mixture was stirred at room temperature for 24 hours; then, the solvent was removed under reduced pressure, and the product was extracted with ether several times, filtered, and dried to obtain a dark red solid product.

3. The method according to claim 2, characterized in that In the step (1), the molar ratio of the unilateral macro-group iminobutanone and aniline is 1:1-1.5; and in the step (2), the molar ratio of the ligand compound and (DME)NiBr2 is 1:0.9-1.

5.

4. Use of a "tortoise" type nickel complex as claimed in claim 1 in ethylene polymerization.

5. The use according to claim 4, characterized in that: The method uses a "turtle" type nickel complex as a main catalyst, ethylaluminum sesquichloride (EASC) as a co-catalyst, the molar ratio of the main catalyst to the co-catalyst is 1:200 to 1:600, the reaction temperature is 30 to 100°C, the reaction time is 5 to 60 minutes, and catalyzes ethylene polymerization.

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