A half-sandwich diimine pyridine iron complex, a preparation method thereof and an application thereof

Abstract

The present invention discloses a half-sandwich diimine pyridine iron complex, a preparation method and an application thereof. The structural formula of the half-sandwich diimine pyridine iron complex is shown as formula (I): wherein, R is hydrogen, methyl, methoxy or trifluoromethyl. The half-sandwich diimine pyridine iron catalyst provided by the present invention can highly actively catalyze ethylene polymerization at high temperature (activity is 8.84×10<supgt;7< / supgt; g / (mol Fe h)), and the prepared polyethylene wax has the advantages of high purity, low impurity content and narrow distribution, has obvious economic benefits, and can be used as a high-quality polyethylene synthetic wax.

Description

Technical Field

[0001] The present invention relates to the technical field of olefin polymerization catalysts, and particularly relates to a half-sandwich diimine pyridine iron complex and its preparation method and application. Background Art

[0002] Polyethylene wax is a kind of polyolefin wax, with an appearance of white or light yellow lumps, flakes or powdery solids, a relative molecular mass of 1000 - 10000, and has advantages such as low toxicity, no corrosiveness, high softening point, low melt viscosity, wear resistance, heat resistance, chemical resistance, as well as good lubricity, dispersibility and fluidity. Polyethylene wax has good compatibility with polyolefin resins, etc., can disperse pigments and fillers in masterbatch, and can be used as a lubricant in plastic processing. During pipe extrusion and injection molding, according to different types of extruders, it can reduce and increase the plasticization time, reduce the adhesion of thermoplastic melting, improve the gloss of the product and improve the product appearance. It can also be used as an abrasion-resistant agent for ink, and has become an indispensable important chemical raw material in industries such as plastics, rubber, ink, paint, and metal casting.

[0003] Currently, there are three production preparation methods for polyethylene wax. The first method is the polyethylene pyrolysis method, which uses thermal pyrolysis to pyrolyze high-molecular-weight polyethylene resin into low-molecular-weight polyethylene wax. This thermal pyrolysis method requires high energy consumption, and at the same time, the obtained product has a relatively wide relative molecular mass distribution, and the smell from low relative molecular mass is difficult to completely eliminate, and it is also difficult to avoid the generation of black spots. The second method is to refine the by-product - oligomers generated in polyethylene production, and finally obtain polyethylene wax products. The products obtained by this method are usually mixtures of several products with different degrees of polymerization, and it is very difficult to control the quality stability. At the same time, due to the too small relative molecular mass of the product, complex components, and poor batch stability, the possibility of precipitation in terminal applications is very high. The third is the ethylene synthesis method, which uses ethylene as a raw material and polymerizes under specific conditions to generate polyethylene wax with a certain relative molecular mass, also known as polyethylene synthetic wax. The polyethylene wax obtained by the ethylene synthesis method has high purity, small relative molecular mass distribution, narrow melting range, stable product quality and adjustable performance, and is used to produce high-quality and diversified polyethylene wax products.

[0004] At present, the catalysts used in the preparation of synthetic polyethylene wax by ethylene synthesis method mainly include Ziegler-Natta (Z-N) catalysts, metallocene catalysts, and later developed late transition metal catalysts. However, traditional Ziegler-Natta (Z-N) catalysts usually have multiple active centers, and each active center produces polymers with different molecular weights and component distributions. The distribution of the polymers is very wide, and it is not easy to control the molecular weight of the polymers. Although metallocene catalysts are single active centers and can prepare polyethylene wax with a narrow distribution; however, metallocene catalysts have strong oxygen affinity, are sensitive to water and oxygen, and have relatively strict requirements for the production environment atmosphere. Moreover, metallocene catalysts are expensive, and the industrial production cost is high. Due to the weak electrophilicity of the metal center, late transition metal nickel-palladium catalysts are more insensitive to water and oxygen. However, typical α-diimine nickel-palladium catalysts generally produce branched products during the catalytic polymerization of ethylene due to chain walking, and it is difficult to prepare completely linear polyethylene wax. Iron in late transition metals also has relatively weak oxygen affinity and is insensitive to water and oxygen. Typical diimine pyridine iron complexes are very stable; and because the iron metal element is the most abundant metal in the earth's crust, the iron catalyst is cheaper. Existing literature has reported that when a diimine pyridine iron catalyst catalyzes the polymerization of ethylene, by reducing the steric hindrance effect of the catalyst, linear polyethylene wax can be prepared. Due to the non-polarity of linear polyethylene wax, which is difficult to dissolve, when using a solution polymerization process industrially, generally high temperatures are required to improve the solubility of the product in the solvent, reduce the viscosity of the system to prevent pipeline blockage, and at the same time achieve the purpose of improving the product purity. However, when the steric hindrance of the iron catalyst is reduced, the thermal stability of the catalyst is reduced. And the polymerization activity decays severely under high-temperature polymerization conditions, and the decomposition products of the iron catalyst at high temperatures also result in high impurity content and low purity of the polyethylene wax product. Therefore, the existing iron catalysts cannot adapt to the existing high-temperature solution polymerization process conditions and are difficult to be industrially produced. Developing a high-thermal-stability iron catalyst that can catalyze the polymerization of ethylene to prepare high-purity polyethylene wax under high-temperature conditions has very important industrial significance. Summary of the Invention

[0005] The purpose of the present invention is to overcome the defects and deficiencies of the existing iron catalysts with poor high-temperature resistance, low high-temperature activity, and difficulty in adapting to the existing high-temperature solution polymerization process conditions, and to provide a half-sandwich diimine pyridine iron complex with good high-temperature resistance and high catalytic activity, which can catalyze the polymerization of ethylene to prepare high-purity polyethylene wax under the action of a cocatalyst.

[0006] The purpose of the present invention is to provide a half-sandwich diimine pyridine iron complex, and the structural formula of the half-sandwich diimine pyridine iron complex is shown in formula (I):

[0007]

[0008] Among them, R is hydrogen, methyl, methoxy or trifluoromethyl.

[0009] In some embodiments of the present invention, R is methyl or methoxy.

[0010] The design principle of the half-sandwich diimine pyridine iron complex provided by the present invention is as follows: The half-sandwich diimine pyridine iron complex has a semi-open axial steric hindrance. On the one hand, an imine group substituted with a naphthyl group has no axial steric hindrance effect on the metal center, which is conducive to the chain transfer reaction during ethylene polymerization to obtain low-molecular-weight polyethylene wax; on the other hand, a substituted naphthyl imine contains a substituted phenyl group that is almost perpendicular to the axial direction of the metal center, which plays a good shielding role for the axial space and shows a large steric hindrance. At the same time, according to the single crystal structure data of the complex, the included angle between the benzene ring where the substituent is located and the pyridine ring is less than 11°, which confirms the existence of π-π stacking between the benzene ring where the substituent is located and the pyridine ring, and can improve the stability of the catalyst. Therefore, the half-sandwich diimine pyridine iron catalyst obtained from the half-sandwich diimine pyridine iron complex has good high-temperature stability and can adapt to the high-temperature solution polymerization process to prepare high-purity polyethylene synthetic wax.

[0011] Another object of the present invention is to provide a preparation method of the half-sandwich diimine pyridine iron complex, which includes the following steps:

[0012] S1. A substituted aromatic amine and 2,6-diacetylpyridine react to obtain a monoimine pyridine

[0013] S2. The monoimine pyridine and 1-naphthylamine react to obtain a diimine pyridine ligand

[0014] S3. The diimine pyridine ligand and FeCl2 react to obtain the half-sandwich diimine pyridine iron complex

[0015] In some embodiments of the present invention, in S1, the molar ratio of 2,6-diacetylpyridine to the substituted aromatic amine is 1.1-1.5:1.

[0016] In some embodiments of the present invention, in S2, the molar ratio of naphthylamine to monoimine pyridine is 1.4-2.4:1.

[0017] In some embodiments of the present invention, in S2, the molar ratio of naphthylamine to monoimine pyridine is 1.4:1.

[0018] In some embodiments of the present invention, in S3, the molar ratio of the diimine pyridine ligand to FeCl2 is 1.05 - 1.5:1.

[0019] In some embodiments of the present invention, in S3, the molar ratio of the diimine pyridine ligand to FeCl2 is 1.2:1.

[0020] Another object of the present invention is to provide a half - sandwich diimine pyridine iron catalyst, which includes a main catalyst and a co - catalyst, and the main catalyst is the above - mentioned half - sandwich diimine pyridine iron complex.

[0021] In some embodiments of the present invention, the co - catalyst includes at least one of methylaluminoxane (MAO), modified methylaluminoxane (MMAO), diethylaluminum chloride, and dichloroethylaluminum.

[0022] In some embodiments of the present invention, the co - catalyst includes methylaluminoxane (MAO) or modified methylaluminoxane (MMAO).

[0023] In some embodiments of the present invention, the molar ratio of the main catalyst to the co - catalyst is 1:500 - 2500.

[0024] In some embodiments of the present invention, the molar ratio of the main catalyst to the co - catalyst is 1:500 - 1500.

[0025] Another object of the present invention is to provide a polyethylene wax, which is prepared by catalytic ethylene polymerization using the above - mentioned half - sandwich diimine pyridine iron catalyst.

[0026] The half - sandwich diimine pyridine iron catalyst provided by the present invention belongs to a late - transition metal diimine pyridine iron catalyst. There is no chain - walking process similar to nickel - palladium catalysts during the catalytic ethylene polymerization. Therefore, the polyethylene wax prepared by catalytic ethylene polymerization has the characteristics of narrow distribution and high purity, and can be used as a high - quality polyethylene synthetic wax.

[0027] In some embodiments of the present invention, the weight - average molecular weight of the polyethylene wax is 1 - 10 kg / mol, PDI ≤ 3, and the melting point is 118 - 128 °C.

[0028] In some embodiments of the present invention, the pressure of ethylene is 1 - 20 atm.

[0029] In some embodiments of the present invention, the pressure of ethylene is 10 - 15 atm.

[0030] In some embodiments of the present invention, the temperature of the polymerization reaction is 80 - 120 °C, and the time of the polymerization reaction is 5 - 30 min.

[0031] In some embodiments of the present invention, the temperature of the polymerization reaction is 80 - 100 °C.

[0032] In some embodiments of the present invention, the time of the polymerization reaction is 5 - 10 min.

[0033] In some embodiments of the present invention, the solvent for the polymerization reaction includes at least one of toluene, p-xylene, hexane, cyclohexane, and heptane.

[0034] In some embodiments of the present invention, the solvent for the polymerization reaction is a combination of hexane and cyclohexane.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] (1) The half-sandwich diimine pyridine iron complex provided by the present invention has a half-sandwich structure, and there is a π-π stacking interaction between the substituted phenyl group and the pyridine ring, improving the high-temperature resistance performance (120 °C) of the iron catalyst, enabling it to adapt to the existing high-temperature solution polymerization process and having good industrialization prospects.

[0037] (2) The half-sandwich diimine pyridine iron catalyst provided by the present invention can catalyze ethylene polymerization with high activity at high temperature (the activity is 8.84×10 7 g / (molFe h)), and the prepared polyethylene wax has the advantages of high purity, low impurity content, and narrow distribution, having obvious economic benefits and can be used as high-quality polyethylene synthetic wax.

[0038] (3) The half-sandwich diimine pyridine iron catalyst provided by the present invention can simply realize the regulation of the structural properties of the product polyethylene wax through the electronic effect regulation of the substituent R and the change of polymerization conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 The single crystal structure diagram of the half-sandwich diimine pyridine iron complex Fe2 provided in Example 10.

[0040] Figure 2 The physical picture of the polyethylene wax provided in Example 27.

[0041] Figure 3 The 1H NMR spectrum of the polyethylene wax provided in Example 30;

[0042] Figure 4 The DSC spectrum of the polyethylene wax provided in Example 26.

[0043] Figure 5 The high-temperature GPC spectrum of the polyethylene wax provided in Example 28.

[0044] Figure 6 It is the molecular structural formula diagram of the diimine pyridine iron complex Fe5 provided in Comparative Example 1. Detailed implementation manners

[0045] The concept of the present invention and the technical effects produced will be clearly and completely described below in conjunction with the embodiments, so as to fully understand the purpose, features and effects of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative efforts all fall within the scope of protection of the present invention. The test methods used in the embodiments are all conventional methods unless otherwise specified; the materials, reagents, etc. used are all reagents and materials that can be obtained from commercial channels unless otherwise specified.

[0046] In the description of the present invention, the description of reference terms such as "one embodiment", "some embodiments", "schematic embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0047] The structural formulas of the half-sandwich diimine pyridine iron complexes in each embodiment are as follows:

[0048]

[0049] In formula (II), the substituent R on the benzene ring is hydrogen, methyl, methoxy or trifluoromethyl.

[0050] Specifically:

[0051] 8-aryl-1-naphthylamine A1, R is hydrogen;

[0052] 8-aryl-1-naphthylamine A2, R is methyl;

[0053] 8-aryl-1-naphthylamine A3, R is methoxy;

[0054] 8-aryl-1-naphthylamine A4, R is trifluoromethyl;

[0055] Diimine pyridine single-side product L1a, R is hydrogen;

[0056] Diimine pyridine single-side product L2a, R is methyl;

[0057] Diimine pyridine single-side product L3a, R is methoxy;

[0058] The monoimide pyridine single-side product L4a, where R is trifluoromethyl;

[0059] The diimine pyridine ligand L1, where R is hydrogen;

[0060] The diimine pyridine ligand L2, where R is methyl;

[0061] The diimine pyridine ligand L3, where R is methoxy;

[0062] The diimine pyridine ligand L4, where R is trifluoromethyl;

[0063] The half-sandwich diimine pyridine iron complex Fe1, where R is hydrogen;

[0064] The half-sandwich diimine pyridine iron complex Fe2, where R is methyl;

[0065] The half-sandwich diimine pyridine iron complex Fe3, where R is methoxy;

[0066] The half-sandwich diimine pyridine iron complex Fe4, where R is trifluoromethyl;

[0067] The half-sandwich diimine pyridine iron complex is prepared through the following reaction route:

[0068]

[0069] In the following examples, the polyethylene prepared was measured for the molecular weight and molecular weight distribution of the polymer (using trichlorobenzene as the solvent and mobile phase, concentration 1.5 g / L, flow rate 1 mL / min) by a high-temperature gel permeation chromatograph (HT-GPC), and the melting point was determined by DSC. The 8-aryl-1-naphthylamines (A1 - A4) with different substituents were prepared according to the method reported in the literature (Organometallics 2013, 32(18), 5136 - 5143).

[0070] Example 1

[0071] This example provides a diimine pyridine single-side product L1a, and its synthesis method is as follows:

[0072] 2,6-Diacetylpyridine (5.92 mmol), anhydrous methanol (50 mL), and formic acid (0.3 mL) were successively added to a 100 mL round-bottom flask and stirred, and then 8-phenyl-1-naphthylamine (A1) (5.38 mmol) dissolved in 5 mL of methanol was slowly added dropwise to the round-bottom flask. The reaction was carried out at -10 °C for 8 h. After the reaction was completed, the system was concentrated to 20 mL, filtered, and then washed with ice methanol and dried to obtain 1.843 g of a yellow solid, with a yield of 86%.

[0073] 11H NMR (CDCl3, 400 MHz) δ (ppm): 7.98 (d, 1H, H py ), 7.87 (d, 1H, H aryl ), 7.75 (d, 1H, H py ), 7.68 (m, 2H, H aryl ), 7.48 (t, 2H, H aryl ), 7.24 (d, 1H, H aryl ), 7.18 (t, 1H, H aryl ), 7.10 (d, 2H, H aryl ), 6.82 (d, 2H, H aryl ), 6.65 (d, 1H, H py ), 2.74 (s, 3H, O=C-CH3), 2.15 (s, 3H, N1=C-CH3).

[0074] Example 2

[0075] This example provides a monoimine pyridine single-sided product L2a, and its synthesis method is as follows:

[0076] The difference from Example 1 is only that 8-phenyl-1-naphthylamine (A1) is replaced with 8-p-tolyl-1-naphthylamine (A2) to obtain the single-sided product L2a with a yield of 86%.

[0077] 1 1H NMR (CDCl3, 400 MHz) δ (ppm): 7.98 (d, 1H, H py ), 7.87 (d, 1H, H aryl ), 7.75 (d, 1H, H py ), 7.68 (m, 2H, H aryl ), 7.48 (t, 2H, H aryl ), 7.24 (d, 1H, H aryl ), 7.10 (d, 2H, H aryl ), 6.82 (d, 2H, H aryl ), 6.65 (d, 1H, H py ), 2.74 (s, 3H, O=C-CH3), 2.15 (s, 3H, N1=C-CH3), 1.89 (s, 3H, aryl-CH3).

[0078] Example 3

[0079] This example provides a monoimine pyridine single-sided product L3a, and its synthesis method is as follows:

[0080] The difference from Example 1 is only that 8-phenyl-1-naphthylamine (A1) is replaced by 8-(4-methoxyphenyl)-1-naphthylamine (A3) to obtain the unilateral product L3a with a yield of 88%.

[0081] 1 H NMR(CDCl3,400MHz)δ(ppm):7.99(d,1H,H py ),7.87(d,1H,H aryl ),7.82(d,1H,H py ),7.68(m,2H,H aryl ),7.47(t,2H,H aryl ),7.25(d,2H,H aryl ),7.10(d,2H,H aryl ),6.65(d,1H,H py ),6.49(d,2H,H aryl ),3.41(s,3H,aryl-O-CH3),2.74(s,3H,O=C-CH3),2.15(s,3H,N1=C-CH3).

[0082] Example 4

[0083] This example provides a diimine pyridine unilateral product L4a, and its synthesis method is as follows:

[0084] The difference from Example 1 is only that 8-phenyl-1-naphthylamine (A1) is replaced by 8-(4-trifluoromethylphenyl)-1-naphthylamine (A4) to obtain the unilateral product L4a with a yield of 89%.

[0085] 1 H NMR(CDCl3,400MHz)δ(ppm):8.00(t,1H,H py ),7.93(d,1H,H aryl ),7.50(d,1H,H py ),7.66(m,2H,H aryl ),7.51(m,2H,H aryl ),7.32(d,2H,H aryl ),7.24(d,2H,H aryl ),7.20(d,1H,H aryl ),6.68(d,1H,H py ),2.71(s,3H,O=C-CH3),2.16(s,3H,N1=C-CH3).

[0086] Example 5

[0087] This embodiment provides a diimine pyridine ligand L1, and its synthesis method is as follows:

[0088] Add L1a (2.96 mmol), anhydrous methanol (50 mL) and 1-naphthylamine (5.92 mmol) into a 100 mL round-bottom flask and start stirring. Then slowly add 0.3 mL of formic acid to the round-bottom flask and react at room temperature for 6 h. Immediately filter after the reaction ends, and finally wash with ice methanol and dry to obtain 0.941 g of yellow solid, with a yield of 65%.

[0089] 1 H NMR (CDCl3, 400 MHz) δ (ppm): 8.41 (d, 1H, H py ), 7.87 (d, 2H, H aryl ), 7.80 (d, 1H, H py ), 7.70 - 7.63 (m, 4H, H aryl ), 7.47 (m, 5H, H aryl ), 7.24 (t, 1H, H py ), 7.18 (t, 1H, H aryl ), 7.12 (d, 2H, H aryl ), 6.89 (d, 2H, H aryl ), 6.84 (d, 1H, H aryl ), 6.65 (d, 1H, H aryl ), 2.34 (s, 3H, aryl-CH3), 2.16 (s, 3H, N2=C-CH3), 2.00 (s, 6H, N1=C-CH3).

[0090] 13 C NMR (Benzene-d6, 400 MHz) δ (ppm): 168.16, 164.83, 155.49 (N2=C), 155.01 (N1=C), 149.23, 148.42, 142.11, 140.32, 136.09, 135.67, 135.47, 134.90, 129.57, 129.10, 128.56, 128.54, 128.49, 128.43, 128.32, 126.56, 126.51, 126.23, 126.21, 125.79, 125.44, 124.74, 124.46, 124.04, 123.94, 123.26, 122.32, 114.96, 114.52, 20.95 (aryl-CH3), 16.64 (N2=C-CH3), 16.15 (N1=C-CH3).

[0091] Example 6

[0092] This example provides a diimine pyridine ligand L2, and its synthesis method is as follows:

[0093] The difference from Example 5 is only that L1a is replaced with L2a to obtain ligand L2 with a yield of 53%.

[0094] 1 H NMR(CDCl3,400MHz)δ(ppm):8.41(d,1H,H py ),7.87(d,2H,H aryl ),7.80(d,1H,H py ),7.70 - 7.63(m,4H,H aryl ),7.47(m,5H,H aryl ),7.24(t,1H,H py ),7.12(d,2H,H aryl ),6.89(d,2H,H aryl ),6.84(d,1H,H aryl ),6.65(d,1H,H aryl ),2.34(s,3H,aryl-CH3),2.16(s,3H,N2=C-CH3),2.00(s,6H,N1=C-CH3).

[0095] 13 C NMR(Benzene-d6,400MHz)δ(ppm):168.16,164.83,155.49(N1=C),155.01(N2=C),149.23,148.42,142.11,140.32,136.09,135.67,135.47,134.90,129.57,129.10,128.56,128.54,128.49,128.43,128.32,126.56,126.51,126.23,126.21,125.79,125.44,124.74,124.46,124.04,123.94,123.26,122.32,114.96,114.52,20.95(aryl-CH3),16.54(N1=C-CH3),16.25(N2=C-CH3).

[0096] Example 7

[0097] This example provides a diimine pyridine ligand L3, and its synthesis method is as follows:

[0098] It is only different from Example 5 in that L1a is replaced with L3a to obtain ligand L3 with a yield of 67%.

[0099] 1 H NMR(CDCl3,400MHz)δ(ppm):8.43(d,1H,H py ),7.87(d,2H,H aryl ),7.79(d,1H,H py ),7.73 -7.69(m,3H,H aryl ),7.63(d,1H,H py ),7.54-7.42(m,6H,H aryl ),7.50-7.42(m,5H,H aryl ),7.14(d,2H,H aryl ),6.83(d,1H,H aryl ),6.67(d,1H,H aryl ),6.58(d,2H,H aryl ),3.54(s,3H,O-CH3),2.34(s,3H,N2=C-CH3),2.17(s,3H,N1=C-CH3).

[0100] 13 C NMR(Benzene-d6,400MHz)δ(ppm):168.19,164.73,158.41,155.53(N2=C),154.98(N1=C),149.30,148.42,140.09,137.25,136.12,135.80,134.90,130.14,129.68,128.49,128.32,128.11,127.95,126.52,126.24,126.20,125.79,125.47,124.75,124.07,123.94,123.24,122.23,114.87,113.53,112.98,112.82,53.52(1C,O-CH3),16.53(1C,N2=C-CH3),16.29(1C,N1=C-CH3).

[0101] Example 8

[0102] This example provides a diimine pyridine ligand L4, and its synthesis method is as follows:

[0103] It is only different from Example 5 in that L1a is replaced with L4a to obtain ligand L4 with a yield of 80%.

[0104] 11H NMR(CDCl3, 400 MHz) δ (ppm): 8.43 (d, 1H, H py ), 7.93 (d, 1H, H aryl ), 7.86 (d, 1H, H py ), 7.78 (d, 1H, H aryl ), 7.71 (d, 1H, H aryl ), 7.69 - 7.58 (m, 3H, H aryl ), 7.50 - 7.42 (m, 5H, H aryl ), 7.36 - 7.29 (m, 4H, H aryl ), 7.20 (d, 1H, H py ), 6.81 (d, 1H, H aryl ), 6.68 (d, 1H, H aryl ), 2.31 (s, 3H, N2=C-CH3), 2.17 (d, 3H, N1=C-CH3).

[0105] 13 13C NMR(Benzene-d6, 400 MHz) δ (ppm): 167.85, 165.64, 155.35 (N2=C), 154.66 (N1=C3), 148.76, 148.48, 138.61, 136.20, 135.94, 134.90, 129.43, 129.34, 129.24, 128.43, 128.16, 127.92, 126.55, 126.24, 125.87, 125.32, 124.78, 124.19, 124.15, 124.11, 124.08, 123.93, 122.94, 122.53, 115.14, 113.46, 16.52 (N2=C-CH3), 16.16 (N1=C-CH3). 19 19F NMR(CDCl3, 400 MHz) δ (ppm): -61.80 (s, 3F, CF3).

[0106] Example 9

[0107] This example provides a half-sandwich diimine pyridine iron complex Fe1, and its synthesis method is as follows:

[0108] Under anhydrous and anaerobic conditions, ligand L1 (1.211 mmol) and FeCl2 (1.101 mmol) were added to a Schlenk tube, and then 30 mL of freshly distilled THF was quickly added with stirring at room temperature. The solution immediately turned dark green, and a dark green precipitate slowly formed. After the reaction mixture was stirred for 8 h, the system was concentrated under reduced pressure, and the dark green precipitate was precipitated with freshly distilled n-hexane (3 × 10 mL) and washed and dried to obtain the half-sandwich diimine pyridine iron complex Fe1 (dark green powder, 481.21 mg, yield 80%).

[0109] IR (KBr, cm -1 ): 1633 (ν C＝N ), 1589, 1495, 1434, 1367, 1257, 1236, 1193, 1027, 835, 771, 705.

[0110] Anal. Calcd for C 35 H 27 Cl2FeN3: C, 68.20; H, 4.42. Found: C, 68.17; H, 4.38.

[0111] Example 10

[0112] This example provides a half-sandwich diimine pyridine iron complex Fe2, and its synthesis method is as follows:

[0113] The difference from Example 9 is only that L1 is replaced with L2 to obtain the half-sandwich diimine pyridine iron complex Fe2 with a yield of 82%.

[0114] IR (KBr, cm -1 ): 1631 (ν C＝N ), 1590, 1513, 1392, 1371, 1268, 1236, 1197, 838, 821, 806, 779.

[0115] Anal. Calcd for C 36 H 29 Cl2FeN3: C, 68.59; H, 4.64. Found: C, 68.52; H, 4.60.

[0116] Example 11

[0117] This example provides a half-sandwich diimine pyridine iron complex Fe3, and its synthesis method is as follows:

[0118] The difference from Example 9 is only that L1 is replaced with L3 to obtain the half-sandwich diimine pyridine iron complex Fe3 with a yield of 89%.

[0119] IR (KBr, cm -1 ): 1610 (ν C＝N ), 1585, 1511, 1459, 1432, 1371, 1267, 1241, 1178, 1108, 1064

[0120] (ν C-O ), 1027, 836, 809, 781.

[0121] Anal. Calcd for C 36 H 29 Cl2FeN3O: C, 66.89; H, 4.52. Found: C, 66.83; H, 4.48.

[0122] Example 12

[0123] This example provides a half - sandwich diimine pyridine iron complex Fe4, and its synthesis method is as follows.

[0124] The difference from Example 9 is only that L1 is replaced by L4 to obtain the half - sandwich diimine pyridine iron complex Fe4, with a yield of 85%.

[0125] IR (KBr, cm -1 ): 1619 (ν C＝N ), 1587, 1504, 1428, 1373, 1324 (ν C-F ), 1268, 1238, 1162, 1120, 1062, 1020, 836, 808, 775.

[0126] Anal. Calcd for C 36 H 29 Cl2F3FeN3: C, 63.18; H, 3.83. Found: C, 63.12; H, 3.80.

[0127] Examples 13 - 38 provide the preparation of polyethylene wax by the homopolymerization of ethylene catalyzed by the half - sandwich diimine pyridine iron complex. The specific reaction steps are as follows:

[0128] The ethylene polymerization reaction was carried out in a 100 mL stainless-steel high-temperature and high-pressure reactor equipped with a stirring device. Before the polymerization reaction, the reactor was vacuum-dried at 200 °C for more than 2 h. After the reactor was cooled to room temperature, freshly distilled toluene solution and cocatalyst solution were successively injected through the feed valve. Ethylene gas was introduced to 1.5 atm, the reaction system was heated to the set polymerization temperature, and stirred thoroughly for 10 minutes. Then, the toluene solution of the iron metal complex was added through the feed valve, and the volume of the whole polymerization system was maintained at 70 mL. The pressure of ethylene was increased to the set pressure and kept constant throughout the polymerization process. After the polymerization reaction reached the set time, the introduction of ethylene was stopped, the pressure was slowly released, the reactor was opened, and ethanol was added to the reactor to terminate the reaction. The product was soaked in hydrochloric acid / ethanol, filtered, washed several times with anhydrous ethanol, and then the polyethylene wax was dried in a vacuum drying oven at 60 °C to a constant weight.

[0129] Examples 13 - 16 provide the results of preparing polyethylene wax by catalyzing ethylene with different half-sandwich diimine pyridine iron catalysts. The specific polymerization conditions and polymerization results are shown in Table 1.

[0130] Table 1. Results of ethylene polymerization catalyzed by different half-sandwich diimine pyridine iron catalysts.

[0131] Example Complex Temperature (°C) Cocatalyst <![CDATA[Activity (10 7 g / (mol Fe h))]]> <![CDATA[M w (kg / mol)]]> PDI <![CDATA[T m (℃)]]> Example 13 Fe1 80 MMAO 2.92 6.83 2.6 125 Example 14 Fe2 80 MMAO 4.46 7.58 3.0 126 Example 15 Fe3 80 MMAO 3.51 7.32 2.7 126 Example 16 Fe4 80 MMAO 1.24 6.43 2.9 127

[0132] Polymerization conditions: Complex 2.4 μmol, Al / Fe = 1000, ethylene pressure 10 atm, polymerization time 5 minutes, solvent 70 mL of toluene.

[0133] As can be seen from Table 1, under the same polymerization conditions, the polymerization activity of the half-sandwich diimine pyridine iron complex Fe2 is the highest, reaching 4.46×10 7 g / (mol Fe h).

[0134] Examples 17 - 19 provide the results of preparing polyethylene wax by catalyzing ethylene with a half-sandwich diimine pyridine iron complex Fe2 under different cocatalysts. The specific polymerization conditions and polymerization results are shown in Table 2.

[0135] Table 2. Results of ethylene polymerization catalyzed by the half-sandwich diimine pyridine iron complex Fe2 under different cocatalysts.

[0136]

[0137]

[0138] Polymerization conditions: Half-sandwich diimine pyridine iron complex Fe2 2.4 μmol, Al / Fe = 1000, ethylene pressure 10 atm, polymerization time 5 minutes, solvent 70 mL of toluene.

[0139] By comparing the effects of different alkylaluminums on the catalyst performance, it was found that MMAO had the highest activity as a cocatalyst, and the resulting polymer had a PDI ≤ 3.

[0140] Examples 20 - 23 provide the results of preparing polyethylene wax by catalyzing ethylene with a half-sandwich diimine pyridine iron complex Fe2 at different Al / Fe ratios. The specific polymerization conditions and polymerization results are shown in Table 3.

[0141] Table 3. Results of preparing polyethylene wax by catalyzing ethylene with a half-sandwich diimine pyridine iron complex Fe2 at different Al / Fe ratios.

[0142] Example Temperature (°C) Al / Fe <![CDATA[Activity (10 7 g / (mol Fe h))]]> <![CDATA[M w (kg / mol)]]> PDI <![CDATA[T m (℃)]]> Example 20 80 500 3.92 9.43 2.1 127 Example 14 80 1000 4.46 7.58 3.0 126 Example 21 80 1500 2.51 5.13 2.8 123 Example 22 80 2000 1.24 3.82 2.5 122 Example 23 80 2500 0.63 1.32 2.2 120

[0143] Polymerization conditions: 2.4 μmol of half-sandwich diimine pyridine iron complex Fe2, MMAO as the cocatalyst, ethylene pressure of 10 atm, polymerization time of 5 minutes, and 70 mL of toluene as the solvent.

[0144] Examples 24 - 27 provide the results of preparing polyethylene wax by catalyzing ethylene with a half-sandwich diimine pyridine iron complex Fe2 at different polymerization temperatures. The specific polymerization conditions and polymerization results are shown in Table 4.

[0145] Table 4. Results of preparing polyethylene wax by catalyzing ethylene with a half-sandwich diimine pyridine iron complex Fe2 at different polymerization temperatures.

[0146] Example Temperature (°C) Cocatalyst <![CDATA[Activity (10 7 g / (mol Fe h))]]> <![CDATA[M w (kg / mol)]]> PDI <![CDATA[T m (℃)]]> Example 14 80 MMAO 4.46 7.58 3.0 126 Example 24 90 MMAO 2.05 2.37 1.7 123 Example 25 100 MMAO 1.51 1.86 1.5 121 Example 26 110 MMAO 0.21 1.28 1.3 120 Example 27 120 MMAO 0.13 1.00 1.2 118

[0147] Polymerization conditions: 2.4 μmol of half-sandwich diimine pyridine iron complex Fe2, Al / Fe = 1000, ethylene pressure of 10 atm, polymerization time of 5 minutes, and 70 mL of toluene as the solvent.

[0148] Examples 28 - 31 provide the results of preparing polyethylene wax by catalyzing ethylene with a half-sandwich diimine pyridine iron complex Fe2 at different ethylene pressures. The specific polymerization conditions and polymerization results are shown in Table 5.

[0149] Table 5. Results of preparing polyethylene wax by catalyzing ethylene with a half-sandwich diimine pyridine iron complex Fe2 at different ethylene pressures.

[0150] Example Temperature (°C) Ethylene Pressure (atm) <![CDATA[Activity (10 7 g / (mol Fe h))]]> <![CDATA[M w (kg / mol)]]> PDI <![CDATA[T m (℃)]]> Example 28 80 1 0.83 1.62 1.3 118 Example 29 80 5 2.62 3.38 2.4 122 Example 14 80 10 4.46 7.58 3.0 126 Example 30 80 15 6.12 8.80 3.0 127 Example 31 80 20 8.84 10.0 2.9 128

[0151] Polymerization conditions: 2.4 μmol of half-sandwich diimine pyridine iron complex Fe2, MMAO as the cocatalyst, Al / Fe = 1000, polymerization time of 5 minutes, and 70 mL of toluene as the solvent.

[0152] Examples 32 - 35 provide the results of preparing polyethylene wax by catalyzing ethylene with a half - sandwich diimine pyridine iron complex Fe2 in different solvents. The specific polymerization conditions and polymerization results are shown in Table 6.

[0153] Table 6. Results of preparing polyethylene wax by catalyzing ethylene with a half - sandwich diimine pyridine iron complex Fe2 in different solvents.

[0154]

[0155] Polymerization conditions: 2.4 μmol of half - sandwich diimine pyridine iron complex Fe2, the cocatalyst is MMAO, Al / Fe = 1000, and the polymerization time is 5 minutes.

[0156] Examples 36 - 38 provide the results of preparing polyethylene wax by catalyzing ethylene with a half - sandwich diimine pyridine iron complex Fe2 at different polymerization times. The specific polymerization conditions and polymerization results are shown in Table 7.

[0157] Table 7. Results of preparing polyethylene wax by catalyzing ethylene with a half - sandwich diimine pyridine iron complex Fe2 at different polymerization times.

[0158] Example Temperature (°C) Time (min) <![CDATA[Activity (10 7 g / (mol Fe h))]]> <![CDATA[M w (kg / mol)]]> PDI <![CDATA[T m (℃)]]> Example 14 80 5 4.46 7.58 3.0 126 Example 36 80 10 4.14 7.80 3.0 126 Example 37 80 15 4.01 8.60 3.0 126 Example 38 80 30 3.89 9.62 3.0 126

[0159] Polymerization conditions: 2.4 μmol of half - sandwich diimine pyridine iron complex Fe2, the cocatalyst is MMAO, Al / Fe = 1000, and the solvent is 70 mL of toluene.

[0160] To more clearly show the half - sandwich diimine pyridine iron complex of the present invention and its effect in preparing polyethylene wax, Comparative Examples 1 - 2 provide a small - steric - hindrance diimine pyridine iron complex Fe5 (attached Figure 6 ) for catalyzing ethylene polymerization. The polymerization procedure is the same as that in Examples 13 - 38. The diimine pyridine iron complex Fe5 is prepared according to the literature report (Journal of Organometallic Chemistry 2002, 648(1–2), 55–61.).

[0161] The diimine pyridine iron complex Fe5 has activity (0.27×10 7 g / (molFeh)) at a relatively low temperature of 50 °C for catalyzing ethylene. The product distribution is broad, obvious black zero - valent iron metal can be seen in the product, the purity is low, and the impurity content is high. It has no activity at a high temperature of 80 °C and the catalyst decomposes.

[0162] Table 8. Comparison of ethylene polymerization results between the diimine pyridine iron complex Fe5 and the half - sandwich diimine pyridine iron complexes Fe1 - 4.

[0163] Example Complex Temperature (°C) <![CDATA[Activity (10 7 g / (mol Fe h))]]> <![CDATA[M w (kg / mol)]]> PDI <![CDATA[T m (℃)]]> Example 13 Fe1 80 3.92 6.83 2.6 125 Example 14 Fe2 80 4.46 7.58 3.0 126 Example 15 Fe3 80 3.51 7.32 2.7 126 Example 16 Fe4 80 1.24 8.43 2.9 127 Comparative Example 1 Fe5 80 - - - - Comparative Example 2 Fe5 50 0.27 4.24 4.5 124

[0164] Polymerization conditions: 2.4 μmol of the complex, MMAO as the cocatalyst, Al / Fe = 1000, ethylene pressure of 10 atm, polymerization time of 5 minutes, and 70 mL of toluene as the solvent.

[0165] It can be clearly found from the data in Table 8 that the half-sandwich diimine pyridine iron complexes Fe1-4 are better than the diimine pyridine iron complex Fe5 in terms of thermal stability, catalytic activity, and product distribution. This shows that the half-sandwich structure adopted by the half-sandwich diimine pyridine iron complexes Fe1-4, introducing weak π-π stacking interactions, is a very feasible design for catalytic ethylene polymerization to prepare high-quality polyethylene wax.

[0166] The properties of the polyethylene waxes prepared from Examples 24-26 and Comparative Example 2 are shown in Table 9:

[0167] Table 9. Performance analysis data of polyethylene wax.

[0168] Polyethylene Wax Temperature (°C) <![CDATA[M w (kg / mol)]]> PDI Al Content (ppm) Fe Content (ppm) Melting Point (°C) Example 24 90 2.37 1.7 17 8 123 Example 25 100 1.86 1.5 20 9 121 Example 26 110 1.28 1.3 25 10 120 Comparative Example 2 50 4.24 4.5 300 125 124

[0169] The Al and Fe contents in the polyethylene wax in Table 9 were obtained by ICP (Inductively Coupled Plasma) testing. It can be seen from the results that the catalyst Fe5 in Comparative Example 2 is unstable at high temperatures and easily decomposes to produce impurities. Compared with Fe2, the product obtained by Fe5 catalysis has more impurities. The Fe content has reached 125 ppm, and the Al content has reached 300 ppm. This indicates that the polyethylene wax prepared by Fe5 has low purity and high impurity content. While in Examples 24-26, the Fe content in the polyethylene wax obtained at 90-110 °C is lower than 10 ppm, and the Al content is lower than 25 ppm, so it can be used as high-quality polyethylene wax.

[0170] As can be seen from the above, the half-sandwich diimine pyridine iron complex provided by the present invention can be used as the main catalyst, and under the cooperation of a specific cocatalyst, it can highly actively catalyze ethylene polymerization to obtain low-molecular-weight polyethylene wax at a relatively low ethylene pressure. The conditions of the whole reaction are mild, the catalytic activity is high, the price of ethylene monomer is low, the production process is simple, the product is easy to separate, and the production cost is low. The obtained polyethylene wax has a relatively narrow distribution, stable performance, good lubricity, and can be used as high-quality polyethylene wax.

[0171] The above embodiments are the preferred embodiments of the present invention, but the embodiments of the present invention are not limited by the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A half-sandwich diimine pyridine iron complex, characterized in that, The structural formula of the half-sandwich diimine pyridine iron complex is shown in Formula (I): Formula (I) Wherein, R is hydrogen, methyl, methoxy or trifluoromethyl.

2. The preparation method of the half-sandwich diimine pyridine iron complex according to claim 1, characterized in that, It includes the following steps: S1. Substituted aromatic amine and 2,6-diacetylpyridine react to obtain a monoimine pyridine ; S2. The monoimine pyridine and 1-naphthylamine react to obtain a diimine pyridine ligand ; S3. The diimine pyridine ligand reacts with FeCl2 to obtain the half-sandwich diimine pyridine iron complex .

3. A half-sandwich diimine pyridine iron catalyst, characterized in that, It includes a main catalyst and a cocatalyst, and the main catalyst is the half-sandwich diimine pyridine iron complex described in Claim 1.

4. The half-sandwich diimine pyridine iron catalyst according to claim 3, wherein The cocatalyst includes at least one of methylaluminoxane (MAO), modified methylaluminoxane (MMAO), diethylaluminum chloride, and dichloroethylaluminum.

5. The half-sandwich diimine pyridine iron catalyst according to claim 4, characterized in that, The molar ratio of the main catalyst to the cocatalyst is 1:500 to 2500.

6. Use of the half-sandwich diimine pyridine iron catalyst according to any one of Claims 3 to 5 in the catalytic polymerization of ethylene to prepare polyethylene wax.

7. The application according to claim 6, characterized in that The polyethylene wax has a weight-average molecular weight of 1 to 10 kg / mol, PDI ≤ 3, and a melting point of 118 to 128 °C.

8. The application according to claim 6, characterized in that, The pressure of the ethylene is 1 to 20 atm.

9. The application according to claim 6, characterized in that, The temperature of the polymerization is 80 to 120 °C, and the time of the polymerization is 5 to 30 min.

10. The application according to claim 6, characterized in that, The solvent for the polymerization includes at least one of toluene, p-xylene, hexane, cyclohexane, and heptane.

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