CN117983305A

CN117983305A - Catalyst containing aromatic heterocycle-aliphatic ligand for ethylene selective tetramerization and preparation method and application thereof

Info

Publication number: CN117983305A
Application number: CN202211351177.7A
Authority: CN
Inventors: 张军; 孔维欢; 赵兴; 周涛; 左静; 王继贺
Original assignee: East China University of Science and Technology
Current assignee: East China University of Science and Technology
Priority date: 2022-10-31
Filing date: 2022-10-31
Publication date: 2024-05-07

Abstract

The invention relates to a catalyst containing aromatic heterocycle-aliphatic ligand for ethylene selective tetramerization, and a preparation method and application thereof, wherein the catalyst comprises the ligand, a transition metal compound and an activator, and the chemical structural formula of the ligand is shown as the following formula (I): wherein the groups R ¹ to R ⁴ are each independently selected from alkyl, alkoxy, alkenyl or aryl groups, R ¹ to R ⁴ are the same or different and R ¹ to R ⁴ are not simultaneously aryl groups, said A, B and D are each independently selected from NR ⁵、O、S、CR⁶ or CR ⁷, and one of them is NR ⁵, O or S, the remainder being independently selected from CR ⁶、CR⁷; the radicals R ⁵、R⁶ and R ⁷ are identical or different and are each independently selected from hydrogen, halogen, alkyl, heteroalkyl, alkenyl or aromatic radicals. Compared with the prior art, the method has the characteristics of high 1-octene selectivity, high total selectivity of 1-hexene and 1-octene, high stability, high catalytic activity and low polymer production.

Description

Catalyst containing aromatic heterocycle-aliphatic ligand for ethylene selective tetramerization and preparation method and application thereof

Technical Field

The invention relates to the technical field of ethylene oligomerization, in particular to a catalyst containing aromatic heterocycle-aliphatic ligand for ethylene selective tetramerization, a preparation method and application thereof.

Background

Linear alpha-olefin (LAO) is used as an important chemical raw material for preparing lubricating oil, surfactant and the like, wherein 1-hexene and 1-octene are indispensable comonomers in the synthesis of Linear Low Density Polyethylene (LLDPE) and High Density Polyethylene (HDPE) (the comonomer content in LLDPE is generally 8-10%, and the comonomer content in HDPE is 1-2%). Ethylene oligomerization is an important method for producing linear alpha-olefin, and has a great improvement in product quality compared with the traditional methods of wax cracking, coal extraction, extraction separation and the like, and is widely applied to industrial production.

The traditional ethylene oligomerization catalysis mainly uses metallic titanium series, zirconium series, iron series and the like, and the catalytic systems mainly follow Cossee-Arlman mechanism, namely, ethylene molecules are inserted into the catalyst metal center to linearly chain-grow, the obtained linear alpha-olefin is normally distributed, and the separation and the purification are needed in industrial application. The ethylene high-selectivity oligomerization mainly follows a metal cyclization mechanism, so that the produced alpha-olefin is in Schulz-Flory distribution, and the product at the peak has higher content, and the method provides an important path for producing the alpha-olefin with specific carbon number. In recent years, the increase in demand for 1-hexene, 1-octene has made ethylene selective oligomerization a hot spot for industrial and academic research.

At present, high-selectivity oligomerization of ethylene is mainly reported to be dimerization, trimerization and tetramerization to prepare 1-butene, 1-hexene and 1-octene. In these catalytic systems, the structural regulation of the catalyst plays a key role in the product distribution, whereas the regulation of the catalyst structure depends on the variation of the framework and substituents of the ligand. In recent years, research in this area has focused on the mechanism of ethylene selective oligomerization catalysis and ligand design, with some important achievements. In 2002, british Petroleum reported that PNP ligands with the structure of PAr ₂N(R)PAr₂ (Ar is ortho methoxy substituted aryl) were used for chromium catalyzed high selectivity ethylene trimerization to 1-hexene with selectivity up to 91.5% (chem. Commun.,2002, 858-859). In 2004, by modification of substituents, sasol successfully achieved ethylene tetramerization with 1-octene selectivities up to 70.5% using the PNP ligand/chromium catalyst system described above (j.am. Chem. Soc.,2004,126,14712-14713). In the ethylene tetramerization catalytic reaction, ethylene trimerization still occurs, and the product still contains 12.2% of 1-hexene. Therefore, the total selectivity of 1-hexene and 1-octene with high economic value is not high, only 82.7%, and still needs to be improved. In 2017, zhang et al designed and synthesized a series of thiophenic bone bridged bisphosphine ligands containing bisphenylphosphine groups (-PPh ₂) substituted for catalyzing ethylene selective tetramerization, which resulted in a 1-octene selectivity of up to 47.7% due to the presence of more 1-hexene and other high carbon number α -olefins, and exhibited low catalytic activity (Dalton trans.,2017,46,8399-8404).

Disclosure of Invention

The invention aims to overcome at least one of the defects in the prior art and provide an ethylene selective tetramerization catalyst containing aromatic heterocyclic-aliphatic ligand and taking aromatic heterocyclic as a framework, which has high 1-octene selectivity and high total selectivity of 1-hexene and 1-octene, and a preparation method and application thereof. The catalyst has the characteristics of high stability, high catalytic activity and low polymer production.

The aim of the invention can be achieved by the following technical scheme:

In order to further improve the selectivity of 1-octene and the catalytic activity of a catalytic system, one or more alkyl substituted phenyl groups are creatively introduced on the phosphorus atom of the biphosphine ligand bridged by the aromatic heterocyclic bone. By introducing less sterically hindered alkyl groups, the invention successfully improves the 1-octene selectivity of the catalytic system to 71.6% and the total selectivity of 1-hexene and 1-octene to 95.1%. Because the electron donating ability of the alkyl is stronger than that of the phenyl, the electron cloud density of the phosphorus atoms of the coordination atoms can be increased by introducing the alkyl into the ligand structure, so that the stability of the metal active center is obviously improved, the service life of the catalyst is prolonged, and the catalytic activity of the catalytic system is effectively improved. The catalyst life is prolonged, so that the degradation of the catalyst is reduced, and the polymer content in the reaction is reduced to 0.02-0.07%, and the specific scheme is as follows:

a catalyst for selective tetramerization of ethylene containing aromatic heterocycle-aliphatic ligand, which comprises ligand, transition metal compound and activator, wherein the chemical structural formula of the ligand is shown as the following formula (I):

Wherein the groups R ¹ to R ⁴ are each independently selected from alkyl, alkoxy, alkenyl, aromatic groups, R ¹ to R ⁴ are the same or different and R ¹ to R ⁴ are not simultaneously aromatic groups, said A, B and D are each independently selected from NR ⁵、O、S、CR⁶ or CR ⁷, and one of them is NR ⁵, O or S, the remainder being independently selected from CR ⁶、CR⁷; the radicals R ⁵、R⁶ and R ⁷ are identical or different and are each independently selected from hydrogen, halogen, alkyl, heteroalkyl, alkenyl, aromatic radicals.

Further, the ligand shown in the formula (I) comprises ligands shown in the formulas (I.a), (I.b), (I.c), (I.d), (I.e) and (I.f):

Further, the alkyl group is a C ₁-C₃₀ alkyl group including methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, sec-pentyl, isopentyl, cyclopentyl, n-hexyl, sec-hexyl, isohexyl, cyclohexyl, n-heptyl, cycloheptyl, n-octyl, n-decyl, 2-methylcyclopentyl, or 2, 6-dimethylcyclohexyl;

The alkoxy is C ₁-C₂₀ alkoxy, including methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, tert-butoxy, cyclohexyloxy or cyclopentyloxy;

The heteroalkyl is C ₁-C₂₀ heteroalkyl, including methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, tert-butoxy, cyclohexyloxy, cyclopentyloxy, dimethylamino, diethylamino, diisopropylamino, diphenylamino, trimethylsilyl, triethylsilyl, or triphenylsilyl;

The alkenyl is a C ₁-C₃₀ alkenyl group including vinyl, allyl, 1-propenyl, 1-butenyl, 2-butenyl, 3-butenyl, 1-methyl-2-butenyl, 2-methyl-1-butenyl, 3-methyl-2-butenyl, 5-hexenyl, 2-cyclohexenyl, 3-cyclohexenyl, or 2-methyl-2-cyclohexenyl;

The aromatic group is aryl of C ₄-C₃₀ and its derivatives, including phenyl, p-fluorophenyl, o-fluorophenyl, m-fluorophenyl, p-chlorophenyl, o-chlorophenyl, m-chlorophenyl, 2, 6-difluorophenyl, 2, 5-difluorophenyl, 2, 4-difluorophenyl, 2, 3-difluorophenyl, 3, 4-difluorophenyl, 3, 5-difluorophenyl, 2, 6-dichlorophenyl, 2, 5-dichlorophenyl, 2, 4-dichlorophenyl, 2, 3-dichlorophenyl, 3, 4-dichlorophenyl, 3, 5-dichlorophenyl, p-ethylphenyl, o-ethylphenyl, m-ethylphenyl, 2, 4-dimethylphenyl, 2, 4-diisopropylphenyl, 2, 4-di-tert-butylphenyl, 2, 6-dimethylphenyl, 2, 6-diisopropylphenyl, 3, 5-dimethylphenyl, 3, 5-di-tert-butylphenyl, 2,4, 6-trimethylphenyl, naphthyl, anthracenyl, biphenyl, 7-fluoro-1-naphthyl, 7-chloro-1-8-chloro-1-anthracenyl, 1-chloro-8-anthracenyl or anthracenyl-1-8-chloro-1-chloro-8-anthracenyl;

the halogen is fluorine, chlorine, bromine or iodine; fluorine, chlorine or bromine are preferred.

Further, at least one of R ¹ to R ⁴ is selected from alkyl or alkenyl; the alkyl group includes ethyl or isopropyl, and the alkenyl group includes vinyl. The aromatic group comprises phenyl or substituted phenyl, and the substituted phenyl comprises m-fluorophenyl and p-tert-butylphenyl.

Further, the group R ⁵ includes alkyl groups, R ⁶ and R ⁷ include hydrogen or heteroalkyl groups; the alkyl is tertiary butyl, and the heteroalkyl is trimethylsilyl or triphenylsilyl.

The transition metal in the catalyst system of the present invention may be a transition metal compound commonly used in the art, and a metal atom in the transition metal compound is a metal active center, which plays an important role in the catalytic process. Further, the transition metal in the transition metal compound is selected from one of iron, cobalt, nickel, copper, titanium, vanadium, chromium, manganese, molybdenum, tungsten, nickel or palladium; preferably, the transition metal in the transition metal compound is selected from one of chromium, cobalt, titanium, iron, nickel or palladium. More preferably, the transition metal in the transition metal compound is selected from chromium, in particular, the corresponding transition metal compound is any chromium compound that enables oligomerization, and the optional chromium compound includes a compound represented by the general formula CrR _n, wherein R _n is an organic anion or a neutral molecule, R _n generally contains 1 to 15 carbon atoms, n is an integer of 0 to 6, and the valence of Cr is 0 to 6. The specific R _n group is an organic matter containing carboxyl, beta-diketone and hydrocarbon groups or other groups. From the viewpoint of ease of dissolution and handling, preferred chromium compounds include one of chromium trichloride-tris (tetrahydrofuran) complex, (benzene) chromium tricarbonyl, chromium (III) octoate, chromium hexacarbonyl, chromium (III) acetylacetonate, chromium (III) naphthenate, chromium (III) 2-ethylhexanoate, chromium (III) acetate, chromium (III) 2, 6-tetramethylheptanedione and chromium (III) chloride. Preferably, the chromium compound is selected from chromium trichloride-tris (tetrahydrofuran) complex, chromium (III) acetylacetonate, chromium (III) 2-ethylhexanoate.

The activator in the catalyst system of the present invention acts as an activator in the catalyst system. Activators useful in the present invention may be any compound that when mixed with a ligand and a transition metal compound forms an active catalyst. The activators may be used alone or in combination. The activator comprises one or more of alkyl aluminum compound, aluminoxane compound and organic boron compound; the molar ratio of the ligand to the transition metal element in the transition metal compound is (0.01-100): 1; the mole ratio of the activator to the transition metal element in the transition metal compound is (1-10000): 1. Further, the aluminoxane compound specifically comprises a modified methylaluminoxane MMAO-3A; the mole ratio of the activator to the transition metal element in the transition metal compound is (400-700): 1, preferably (500-700): 1.

Further, the activator comprises one or a mixture of several of alkyl aluminum compound, aluminoxane compound, organic boron compound, inorganic acid or inorganic salt.

Specifically, the activator may be an alkylaluminum compound, which may be various trialkylaluminums such as trimethylaluminum, triethylaluminum, triisobutylaluminum, tri-n-butylaluminum, tri-n-hexylaluminum or tri-n-octylaluminum; the alkylaluminum compound may also be an alkylaluminum halide, alkylaluminum hydride or alkylaluminum sesquichloride, such as diethylaluminum chloride (AlEt ₂ Cl) and triethylaluminum chloride (Al ₂Et₃Cl₃).

Specifically, the activator may be an aluminoxane compound, which can be generally prepared by mixing water with an alkylaluminum compound (e.g., trimethylaluminum). The aluminoxane oligomer compound prepared may be a linear compound, a cyclic compound, a cage compound, or a mixture thereof. Suitable aluminoxane compounds can be selected from Methylaluminoxane (MAO), ethylaluminoxane, isobutylaluminoxane, modified aluminoxane, methylaluminoxane DMAO from which volatile components have been removed, and the like.

Specifically, suitable boron compounds may include boroxine, triethylborane, triphenylborane, tris (pentafluorophenyl) borane, and the like. The organoboron compound may be used in a form of a mixture with the organoaluminum compound.

Preferably, the activator may be selected from Methylaluminoxane (MAO), ethylaluminoxane, isobutylaluminoxane and Modified Methylaluminoxane (MMAO).

Further, the aluminoxane compound specifically comprises a modified methylaluminoxane MMAO-3A.

Further, the molar ratio of the ligand to the transition metal element in the transition metal compound is (0.01-100): 1, preferably (0.1-10): 1, more preferably (0.5-2): 1;

The molar ratio of the activator to the transition metal element in the transition metal compound is (1-10000): 1, preferably (1-2000): 1, more preferably (600-1000): 1.

A process for preparing a catalyst for the selective tetramerisation of ethylene comprising an aromatic heterocyclic-aliphatic ligand as described above, which process comprises: the ligand, the transition metal compound and the activator are pre-mixed or directly added into a reaction system for in-situ synthesis, thus obtaining the catalyst containing the aromatic heterocycle-aliphatic ligand for ethylene selective tetramerization.

In some embodiments, the ligand of formula (I), the transition metal compound, and the activator may be mixed simultaneously or in any order in the presence or absence of a solvent to provide an active catalyst. The mixing of the catalyst components can be carried out at a temperature of from-20 to 250 ℃ and the presence of the olefin typically exhibits a protective effect during the mixing of the catalyst components, thereby providing improved catalytic performance. Further, the mixing of the catalyst components may be performed at a temperature in the range of about 20-100 ℃.

In some embodiments, the detachable metal-ligand complex may be prepared in situ from the transition metal compound and the ligand of formula (I). The metal-ligand complex is then added to the reaction medium. Alternatively, the chromium compound and the ligand may be separately added to the reactor, thereby preparing the chromium-ligand complex in situ. In situ preparation of the complex means that the complex is prepared in the medium in which the catalytic reaction takes place and finally the activator is added.

Use of a catalyst for the selective tetramerisation of ethylene containing an aromatic heterocyclic-aliphatic ligand as described above, for the selective tetramerisation of ethylene to 1-octene, the reaction being carried out in an inert solvent at a temperature of 0 to 200 ℃ and a pressure of 10 to 5000psig, the concentration of transition metal in the transition metal compound in the inert solvent being 0.01 to 10000 μmol/L; the inert solvent comprises one or more of alkane, arene, alkene or ionic liquid. Typical solvents include, but are not limited to, benzene, toluene, xylene, cumene, chlorobenzene, dichlorobenzene, fluorobenzene, n-heptane, n-hexane, methylcyclohexane, cyclohexane, 1-hexene, 1-octene, and the like, with toluene, methylcyclohexane being preferred.

Further, the reaction is carried out in an inert solvent at a temperature of 0 to 200 ℃, preferably 10 to 120 ℃, more preferably 15 to 100 ℃, still more preferably 20 to 80 ℃, a reaction pressure of 10 to 5000psi, preferably 100 to 2000psi, preferably 300 to 1000psi, and a concentration of the transition metal in the transition metal compound in the inert solvent of 0.01 to 10000. Mu. Mol/L, preferably 1 to 500. Mu. Mol/L.

Further, the temperature of the reaction is 65-85 ℃, preferably 75-85 ℃; the pressure is 635-835psi, preferably 735-835psi.

Compared with the prior art, the invention creatively introduces one or more alkyl substituted phenyl groups on the phosphorus atom of the biphosphine ligand bridged by the aromatic heterocyclic bone. By introducing less sterically hindered alkyl groups, the invention successfully improves the 1-octene selectivity of the catalytic system to 71.6% and the total selectivity of 1-hexene and 1-octene to 95.1%. Because the electron donating ability of the alkyl is stronger than that of the phenyl, the electron cloud density of the phosphorus atoms of the coordination atoms can be increased by introducing the alkyl into the ligand structure, so that the stability of the metal active center is obviously improved, the service life of the catalyst is prolonged, and the catalytic activity of the catalytic system is effectively improved. The increase in catalyst life also reduces catalyst degradation, thereby reducing the polymer content in the reaction to 0.02-0.07%.

Detailed Description

The following describes in detail the examples of the present invention, which are implemented on the premise of the technical solution of the present invention, and detailed embodiments and specific operation procedures are given, but the scope of protection of the present invention is not limited to the following examples. The term "mass% is not specifically defined but may be regarded as mass%.

Catalyst for ethylene selective tetramerization containing aromatic heterocycle-aliphatic ligand and preparation method and application thereof, wherein the preparation method is as follows: the ligand, the transition metal compound and the activator are pre-mixed or directly added into a reaction system for in-situ synthesis, thus obtaining the catalyst containing the aromatic heterocycle-aliphatic ligand for ethylene selective tetramerization.

The catalyst is used for ethylene selective tetramerization reaction to generate 1-octene, the reaction is carried out in an inert solvent, the temperature of the reaction is 0-200 ℃, the pressure is 10-5000psig, and the concentration of transition metal in the transition metal compound in the inert solvent is 0.01-10000 mu mol/L; the inert solvent comprises one or more of alkane, arene, alkene or ionic liquid. In some embodiments, the temperature of the reaction is 65-85 ℃, preferably 75-85 ℃; the pressure is 635-835psi, preferably 735-835psi.

Wherein the chemical structural formula of the ligand is shown as the following formula (I):

Wherein the groups R ¹ to R ⁴ are each independently selected from alkyl, alkoxy, alkenyl, aromatic groups, R ¹ to R ⁴ are the same or different and R ¹ to R ⁴ are not simultaneously aromatic groups, said A, B and D are each independently selected from NR ⁵、O、S、CR⁶ or CR ⁷, and one of them is NR ⁵, O or S, the remainder being independently selected from CR ⁶、CR⁷; the radicals R ⁵、R⁶ and R ⁷ are identical or different and are each independently selected from hydrogen, halogen, alkyl, heteroalkyl, alkenyl, aromatic radicals. Ligands of formula (I) include ligands of formula (i.a), (I.b), (I.c), (i.d), (I.e), (I.f):

At least one of R ¹ to R ⁴ is selected from alkyl or alkenyl; the alkyl group includes ethyl or isopropyl, and the alkenyl group includes vinyl. The aromatic group comprises phenyl or substituted phenyl, and the substituted phenyl comprises m-fluorophenyl and p-tert-butylphenyl. The group R ⁵ includes alkyl groups, R ⁶ and R ⁷ include hydrogen or heteroalkyl groups; the alkyl is tertiary butyl, and the heteroalkyl is trimethylsilyl or triphenylsilyl.

The transition metal in the transition metal compound is selected from one of iron, cobalt, nickel, copper, titanium, vanadium, chromium, manganese, molybdenum, tungsten, nickel or palladium; the activator comprises one or more of alkyl aluminum compound, aluminoxane compound and organic boron compound; the molar ratio of the ligand to the transition metal element in the transition metal compound is (0.01-100): 1; the mole ratio of the activator to the transition metal element in the transition metal compound is (1-10000): 1. In some embodiments, the aluminoxane compound specifically comprises a modified methylaluminoxane MMAO-3A; the mole ratio of the activator to the transition metal element in the transition metal compound is (400-700): 1, preferably (500-700): 1.

Example 1

The preparation of complex 1 is as follows:

(1) Preparation of 3-bromo-4- (diphenylphosphino) thiophene

In a 50mL Schlenk flask, which was filled with argon, 3, 4-dibromothiophene (2.42 g,10.0 mmol), diethyl ether (10 mL), were added, stirred and cooled to-78deg.C, and n-butyllithium (4.0 mL,2.5M in hexane, 10.0 mmol) was added dropwise to the solution, and reacted at that temperature for 4 hours. Ph ₂ PCl (2.21 g,10.0 mmol) was then added dropwise, and after the addition was complete the mixture was warmed to room temperature and the reaction continued for 1 hour. After the completion of the reaction, the reaction was quenched by adding water (10 mL), the mixture was separated, the aqueous phase was extracted with diethyl ether, the organic phases were combined, the organic phases were dried over anhydrous magnesium sulfate, filtered, and volatiles were removed under reduced pressure to give a crude product, which was purified by separation with a silica gel column to give a white solid product (3.30 g, 95.0%).

(2) Preparation of ligand L ¹

In a 50mL Schlenk tube filled with argon, the above white solid product (1.00 g,3 mmol) and tetrahydrofuran (10 mL) were added, stirred and cooled to-78deg.C, and n-butyllithium (1.20 mL,2.5M in hexane, 3.0 mmol) was added dropwise to the solution and reacted at this temperature for 1 hour. Et ₂ PCl (0.37 g,3.0 mmol) was then added dropwise, and after the addition the mixture was warmed to room temperature and the reaction continued for 3 hours. After the reaction, adding water (10 mL) to the mixture to quench the reaction, separating the solution, extracting the aqueous phase with diethyl ether, mixing the organic phases, drying the organic phases with anhydrous magnesium sulfate, filtering, removing volatile substances under reduced pressure to obtain a crude product, and separating and purifying the crude product with a silica gel column to obtain a white solid product (0.80g,75.0％).¹H NMR(400MHz,CDCl₃)δ＝7.76(s,2H),7.50-7.34(m,6H),7.21-7.09(m,4H),1.75-1.59(m,4H),0.93(t,6H).

(3) Preparation of Complex 1

Ligand L ¹ (205.25 mg,0.5 mmol) and CrCl ₃(THF)₃ (185.8 mg,0.5 mmol) were added to a dry and argon filled Schlenk reaction tube, and redistilled toluene (10 mL) was added thereto and stirred at 80℃for 6 hours. After completion of the reaction, the mixture was filtered, and the filtrate was dried to give a solid which was washed with n-hexane (5 mL. Times.3), and dried to give 249.4mg (0.42 mmol, 85%) of a blue powder.

Example 2

The preparation of complex 2 is as follows:

(1) Preparation of ligand L ²

Preparation method of reference ligand L ¹ by using diisopropyl phosphorus chloride to replace diethyl phosphorus chloride to obtain white solid product (0.75g,65.1％).¹H NMR(400MHz,CDCl₃)δ＝7.73(s,2H),7.47-7.38(m,6H),7.19-7.11(m,4H),1.63-1.59(m,2H),0.92(d,12H).

(2) Preparation of Complex 2

Ligand L ² (192.2 mg,0.5 mmol) and CrCl ₃(THF)₃ (185.8 mg,0.5 mmol) were added to a dry and argon filled Schlenk reaction tube, and redistilled toluene (10 mL) was added thereto and stirred at 80℃for 6 hours. After completion of the reaction, the mixture was filtered, and the filtrate was dried to give a solid which was washed with n-hexane (5 mL. Times.3), and dried to give 217.1mg (0.40 mmol, 80%) of a blue powder.

Example 3

The preparation of complex 3 is as follows:

(1) Preparation of ligand L ³

In a 100mL Schlenk tube filled with argon, L ¹ (1.07 g,3 mmol) above, tetrahydrofuran (45 mL) were added, stirred and cooled to 0deg.C, and n-butyllithium (2.25 mL,1.6M in hexane, 3.6 mmol) was added dropwise to the solution and reacted at this temperature for 20 minutes. Me ₃ SiCl (0.39 g,3.6 mmol) was then added dropwise, and after the addition the mixture was warmed to room temperature and the reaction continued for 6 hours. After the reaction is finished, volatile matters are removed under reduced pressure to obtain a crude product, and the crude product is separated and purified by a silica gel column to obtain a pure product L³(1.00g,77.5％).¹H NMR(400MHz,CDCl₃)δ＝7.49-7.41(m,7H),7.21-7.15(m,4H),1.66(q,4H),1.00(t,6H),0.91(s,9H).

(2) Preparation of Complex 3

Ligand L ³ (214.3 mg,0.5 mmol) and CrCl ₃(THF)₃ (185.8 mg,0.5 mmol) were added to a dry and argon filled Schlenk reaction tube, and redistilled toluene (10 mL) was added thereto and stirred at 80℃for 6 hours. After completion of the reaction, the mixture was filtered, and the filtrate was dried to give a solid which was washed with n-hexane (5 mL. Times.3), and dried to give 226.0mg (0.40 mmol, 77%) of a blue powder.

Example 4

The preparation of complex 4 is as follows:

(1) Preparation of ligand L ⁴

Preparation of reference ligand L ³ using Ph ₃ SiCl instead of Me ₃ SiCl gave pure product L⁴(1.21g,65.8％).¹H NMR(400MHz,CDCl₃)δ＝7.51-7.37(m,22H),7.24-7.17(m,4H),1.69(q,4H),1.03(t,6H).

(2) Preparation of Complex 4

Ligand L ⁴ (307.4 mg,0.5 mmol) and CrCl ₃(THF)₃ (185.8 mg,0.5 mmol) were added to a dry and argon filled Schlenk reaction tube, and redistilled toluene (10 mL) was added thereto and stirred at 80℃for 6 hours. After completion of the reaction, the mixture was filtered, and the filtrate was dried to give a solid which was washed with n-hexane (5 mL. Times.3) and dried to give 235.8mg (0.30 mmol, 61%) of a blue powder.

Example 5

The preparation of complex 5 is as follows:

(1) PhEtPCl preparation

In a 50mL Schlenk flask, filled with argon, phPCl ₂ (536.9 mg,3 mmol) was added, tetrahydrofuran (10 mL), stirred and cooled to-78℃and ethyl magnesium bromide (1.2 mL,2.5M in diethyl ether, 3.0 mmol) was added dropwise to the solution, after which the mixture was warmed to room temperature and the reaction continued for 1 hour. After the reaction was completed, the solvent was evacuated, the obtained solid was washed with diethyl ether (3X 10 mL), and the diethyl ether-insoluble solid was removed by filtration, and after the solvent was evacuated in vacuo, a pale yellow oily liquid was obtained, which was directly used for the next reaction.

(2) Preparation of ligand L ⁵

Preparation of reference ligand L ¹ Using the pale yellow oily liquid described above instead of Et ₂ PCl gave pure product L⁵(0.87g,72.1％).¹H NMR(400MHz,CDCl₃)δ＝7.78(s,2H),7.49-7.41(m,9H),7.19-7.13(m,6H),1.48(q,2H),0.95(t,3H).

(3) Preparation of Complex 5

Ligand L ⁵ (202.2 mg,0.5 mmol) and CrCl ₃(THF)₃ (185.8 mg,0.5 mmol) were added to a dry and argon filled Schlenk reaction tube, and redistilled toluene (10 mL) was added thereto and stirred at 80℃for 6 hours. After completion of the reaction, the mixture was filtered, and the filtrate was dried to give a solid which was washed with n-hexane (5 mL. Times.3), and dried to give 227.9mg (0.40 mmol, 81%) of a blue powder.

Example 6

The preparation of complex 6 is as follows:

(1) Preparation of (2-F-Ph) 2PCl

Magnesium powder (0.88 g,36 mmol) was placed in a Schlenk reaction tube, tetrahydrofuran (10 mL) was added under nitrogen protection, 5 drops of 1, 2-dibromoethane were added dropwise thereto, after 3 minutes of reaction, a solution of o-bromofluorobenzene (5.25 g,30 mmol) in tetrahydrofuran (40 mL) was slowly added at 0℃and reacted for 1 hour, and a solution of o-fluorophenyl magnesium bromide (30 mmol) in tetrahydrofuran was obtained as a gray black color by filtration. Phosphorus trichloride (2.06 g,15 mmol) was dissolved in tetrahydrofuran (10 mL), cooled to-78deg.C, to which was slowly added a tetrahydrofuran solution (50 mL) of the above-prepared o-fluorophenylmagnesium bromide (30 mmol), and after completion of the dropwise addition, slowly warmed to room temperature and stirred for 5 hours, the reaction was completed, the solvent was drained, diethyl ether (40 mL) was dissolved, filtered anhydrous and anaerobic, and the solvent was drained to give a pale yellow oily product.

(2) Preparation of ligand L ⁶

Preparation of reference ligand L ¹ Using the pale yellow oily liquid described above instead of Ph ₂ PCl gives pure product L⁶(0.82g,70.1％).¹H NMR(400MHz,CDCl₃)δ＝7.71(s,2H),7.65-7.60(m,2H),7.21-7.12(m,6H),1.65(q,4H),0.99(t,6H).

(3) Preparation of Complex 6

Ligand L ⁶ (196.2 mg,0.5 mmol) and CrCl ₃(THF)₃ (185.8 mg,0.5 mmol) were added to a dry and argon filled Schlenk reaction tube, and redistilled toluene (10 mL) was added and stirred at 80℃for 6 hours. After completion of the reaction, the mixture was filtered, and the filtrate was dried to give a solid which was washed with n-hexane (5 mL. Times.3), and dried to give 184.5mg (0.34 mmol, 67%) of a blue powder.

Example 7

The preparation of complex 7 is as follows:

(1) Preparation of (2-F-Ph) PhPCl

Magnesium powder (0.44 g,18 mmol) was placed in a Schlenk reaction tube, tetrahydrofuran (5 mL) was added under nitrogen protection, 3 drops of 1, 2-dibromoethane were added dropwise thereto, after 3 minutes of reaction, a solution of o-bromofluorobenzene (2.62 g,15 mmol) in tetrahydrofuran (20 mL) was slowly added at 0℃and reacted for 1 hour, and a solution of o-fluorophenyl magnesium bromide (15 mmol) in tetrahydrofuran was obtained as a gray black color by filtration. PhPCl ₂ (2.68 g,15 mmol) was dissolved in tetrahydrofuran (10 mL) and cooled to-78deg.C, to which was slowly added a solution of o-fluorophenylmagnesium bromide (15 mmol) prepared above in tetrahydrofuran (25 mL), after the addition was completed, slowly warmed to room temperature and stirred for 5 hours, the reaction was complete, the solvent was drained, diethyl ether (40 mL) was dissolved, filtered anhydrous and anaerobic, and the solvent was drained to give a pale yellow oily product.

(2) Preparation of ligand L ⁷

Preparation of reference ligand L ¹ Using the pale yellow oily liquid described above instead of Ph ₂ PCl gives pure product L⁷(0.74g,65.8％).¹H NMR(400MHz,CDCl₃)δ＝7.72(s,2H),7.64-7.59(m,1H),7.48-7.41(m,3H),7.21-7.11(m,5H),1.69(q,4H),0.97(t,6H).

(3) Preparation of Complex 7

Ligand L ⁷ (187.2 mg,0.5 mmol) and CrCl ₃(THF)₃ (185.8 mg,0.5 mmol) were added to a dry and argon filled Schlenk reaction tube, and redistilled toluene (10 mL) was added and stirred at 80℃for 6 hours. After completion of the reaction, the mixture was filtered, and the filtrate was dried to give a solid which was washed with n-hexane (5 mL. Times.3) and dried to give 194.4mg (0.36 mmol, 73%) of a blue powder.

Example 8

The preparation of complex 8 is as follows:

(1) Preparation of 3-bromo-2- (diphenylphosphino) thiophene

In a 50mL Schlenk flask, which was filled with argon, 2, 3-dibromothiophene (2.42 g,10.0 mmol), diethyl ether (10 mL), were added, stirred and cooled to-78deg.C, and n-butyllithium (4.0 mL,2.5M in hexane, 10.0 mmol) was added dropwise to the solution, and reacted at that temperature for 4 hours. Ph ₂ PCl (2.21 g,10.0 mmol) was then added dropwise, and after the addition was complete the mixture was warmed to room temperature and the reaction continued for 1 hour. After the completion of the reaction, the reaction was quenched by adding water (10 mL), the mixture was separated, the aqueous phase was extracted with diethyl ether, the organic phases were combined, the organic phases were dried over anhydrous magnesium sulfate, filtered, and volatiles were removed under reduced pressure to give a crude product, which was purified by separation with a silica gel column to give a white solid product (3.16 g, 91.0%).

(2) Preparation of ligand L ⁸

In a 50mL Schlenk tube filled with argon, the above white solid product (1.00 g,3 mmol) and tetrahydrofuran (10 mL) were added, stirred and cooled to-78deg.C, and n-butyllithium (1.20 mL,2.5M in hexane, 3.0 mmol) was added dropwise to the solution and reacted at this temperature for 1 hour. Et ₂ PCl (0.37 g,3.0 mmol) was then added dropwise, and after the addition the mixture was warmed to room temperature and the reaction continued for 3 hours. After the reaction, adding water (10 mL) to the mixture to quench the reaction, separating the solution, extracting the aqueous phase with diethyl ether, mixing the organic phases, drying the organic phases with anhydrous magnesium sulfate, filtering, removing volatile substances under reduced pressure to obtain a crude product, and separating and purifying the crude product with a silica gel column to obtain a white solid product (0.75g,73.3％).¹H NMR(400MHz,CDCl₃)δ＝7.74(s,2H),7.49-7.32(m,6H),7.20-7.08(m,4H),1.71-1.58(m,4H),0.94(t,6H).

(3) Preparation of Complex 8

Ligand L ⁸ (178.2 mg,0.5 mmol) and CrCl ₃(THF)₃ (185.8 mg,0.5 mmol) were added to a dry and argon filled Schlenk reaction tube, and redistilled toluene (10 mL) was added thereto and stirred at 80℃for 6 hours. After completion of the reaction, the mixture was filtered, and the filtrate was dried to give a solid which was washed with n-hexane (5 mL. Times.3) and dried to give 237.7mg (0.40 mmol, 81%) of a blue powder.

Example 9

The preparation of complex 9 is as follows:

(1) Preparation of ligand L ⁹

Preparation method of reference ligand L ⁸ by using diisopropyl phosphorus chloride to replace diethyl phosphorus chloride to obtain white solid product (0.87g,75.6％).¹H NMR(400MHz,CDCl₃)δ＝7.73(s,2H),7.47-7.38(m,6H),7.19-7.11(m,4H),1.63-1.59(m,2H),0.92(d,12H).

(2) Preparation of Complex 9

Ligand L ⁹ (192.2 mg,0.5 mmol) and CrCl ₃(THF)₃ (185.8 mg,0.5 mmol) were added to a dry and argon filled Schlenk reaction tube, and redistilled toluene (10 mL) was added thereto and stirred at 80℃for 6 hours. After completion of the reaction, the mixture was filtered, and the filtrate was dried to give a solid which was washed with n-hexane (5 mL. Times.3) and dried to give 195.4mg (0.36 mmol, 72%) of a blue powder.

Example 10

The preparation of complex 10 is as follows:

(1) Preparation of ligand L ¹⁰

In a 100mL Schlenk tube filled with argon, L ⁸ (1.07 g,3 mmol) above, tetrahydrofuran (45 mL) were added, stirred and cooled to 0deg.C, and n-butyllithium (2.25 mL,1.6M in hexane, 3.6 mmol) was added dropwise to the solution and reacted at this temperature for 20 minutes. Me ₃ SiCl (0.39 g,3.6 mmol) was then added dropwise, and after the addition the mixture was warmed to room temperature and the reaction continued for 6 hours. After the reaction is finished, volatile matters are removed under reduced pressure to obtain a crude product, and the crude product is separated and purified by a silica gel column to obtain a pure product L¹⁰(0.86g,66.9％).¹H NMR(400MHz,CDCl₃)δ＝7.45-7.38(m,7H),7.23-7.16(m,4H),1.65(q,4H),0.97(t,6H),0.92(s,9H).

(2) Preparation of Complex 10

Ligand L ¹⁰ (214.3 mg,0.5 mmol) and CrCl ₃(THF)₃ (185.8 mg,0.5 mmol) were added to a dry and argon filled Schlenk reaction tube, and redistilled toluene (10 mL) was added thereto and stirred at 80℃for 6 hours. After completion of the reaction, the mixture was filtered, and the filtrate was dried to give a solid which was washed with n-hexane (5 mL. Times.3) and dried to give 237.7mg (0.40 mmol, 81%) of a blue powder.

Example 11

The preparation of complex 11 is as follows:

(1) Preparation of ligand L ¹¹

Preparation of reference ligand L ¹⁰ using Ph ₃ SiCl instead of Me ₃ SiCl gave pure product L¹¹(1.21g,65.8％).¹H NMR(400MHz,CDCl₃)δ＝7.50-7.35(m,22H),7.26-7.18(m,4H),1.68(q,4H),1.00(t,6H).

(2) Preparation of Complex 11

Ligand L ¹¹ (307.4 mg,0.5 mmol) and CrCl ₃(THF)₃ (185.8 mg,0.5 mmol) were added to a dry and argon filled Schlenk reaction tube, and redistilled toluene (10 mL) was added thereto and stirred at 80℃for 6 hours. After completion of the reaction, the mixture was filtered, and the filtrate was dried to give a solid which was washed with n-hexane (5 mL. Times.3), and dried to give 239.7mg (0.30 mmol, 62%) of a blue powder.

Example 12

The preparation of complex 12 is as follows:

(1) PhEtPCl preparation

(2) Preparation of ligand L ¹²

Preparation of reference ligand L ⁸ Using the pale yellow oily liquid described above instead of Et ₂ PCl gave pure product L¹²(0.77g,63.5％).¹H NMR(400MHz,CDCl₃)δ＝7.76(s,2H),7.49-7.42(m,9H),7.21-7.14(m,6H),1.43(q,2H),0.92(t,3H).

(3) Preparation of Complex 12

Ligand L ¹² (202.2 mg,0.5 mmol) and CrCl ₃(THF)₃ (185.8 mg,0.5 mmol) were added to a dry and argon filled Schlenk reaction tube, and redistilled toluene (10 mL) was added thereto and stirred at 80℃for 6 hours. After completion of the reaction, the mixture was filtered, and the filtrate was dried to give a solid which was washed with n-hexane (5 mL. Times.3), and dried to give 216.6mg (0.38 mmol, 77%) of a blue powder.

Example 13

The preparation of complex 13 is as follows:

(1) Preparation of (2-F-Ph) 2PCl

(2) Preparation of ligand L ¹³

Preparation of reference ligand L ⁸ Using the pale yellow oily liquid described above instead of Ph ₂ PCl gives pure product L¹³(0.75g,64.0％).¹H NMR(400MHz,CDCl₃)δ＝7.73(s,2H),7.62-7.57(m,2H),7.20-7.11(m,6H),1.64(q,4H),0.96(t,6H).

(3) Preparation of Complex 13

Ligand L ¹³ (196.2 mg,0.5 mmol) and CrCl ₃(THF)₃ (185.8 mg,0.5 mmol) were added to a dry and argon filled Schlenk reaction tube, and redistilled toluene (10 mL) was added and stirred at 80℃for 6 hours. After completion of the reaction, the mixture was filtered, and the filtrate was dried to give a solid which was washed with n-hexane (5 mL. Times.3) and dried to give 187.2mg (0.34 mmol, 68%) of a blue powder.

Example 14

The preparation of complex 14 is as follows:

(1) Preparation of (2-F-Ph) PhPCl

(2) Preparation of ligand L ¹⁴

Preparation of reference ligand L ⁸ Using the pale yellow oily liquid described above instead of Ph ₂ PCl gives pure product L¹⁴(0.78g,69.3％).¹H NMR(400MHz,CDCl₃)δ＝7.69(s,2H),7.65-7.60(m,1H),7.48-7.42(m,3H),7.22-7.10(m,5H),1.68(q,4H),0.96(t,6H).

(3) Preparation of Complex 14

Ligand L ¹⁴ (187.2 mg,0.5 mmol) and CrCl ₃(THF)₃ (185.8 mg,0.5 mmol) were added to a dry and argon filled Schlenk reaction tube, and redistilled toluene (10 mL) was added and stirred at 80℃for 6 hours. After completion of the reaction, the mixture was filtered, and the filtrate was dried to give a solid which was washed with n-hexane (5 mL. Times.3) and dried to give 183.7mg (0.34 mmol, 69%) of a blue powder.

Example 15

The preparation of complex 15 is as follows:

(1) Preparation of 3-bromo-4- (diphenylphosphino) furan

In a 50mL Schlenk flask, which was filled with argon, 3, 4-dibromofuran (2.26 g,10.0 mmol), diethyl ether (10 mL) were added, stirred and cooled to-78deg.C, and n-butyllithium (4.0 mL,2.5M in hexane, 10.0 mmol) was added dropwise to the solution, and reacted at that temperature for 4 hours. Ph ₂ PCl (2.21 g,10.0 mmol) was then added dropwise, and after the addition was complete the mixture was warmed to room temperature and the reaction continued for 1 hour. After the completion of the reaction, the reaction was quenched by adding water (10 mL), the mixture was separated, the aqueous phase was extracted with diethyl ether, the organic phases were combined, the organic phases were dried over anhydrous magnesium sulfate, filtered, and volatiles were removed under reduced pressure to give a crude product, which was purified by separation with a silica gel column to give a white solid product (2.81 g, 85.0%).

(2) Preparation of ligand L ¹⁵

In a 50mL Schlenk tube filled with argon, the above white solid product (0.99 g,3 mmol) and tetrahydrofuran (10 mL) were added, stirred and cooled to-78deg.C, and n-butyllithium (1.20 mL,2.5M in hexane, 3.0 mmol) was added dropwise to the solution and reacted at this temperature for 1 hour. Et ₂ PCl (0.37 g,3.0 mmol) was then added dropwise, and after the addition the mixture was warmed to room temperature and the reaction continued for 3 hours. After the reaction, adding water (10 mL) to the mixture to quench the reaction, separating the solution, extracting the aqueous phase with diethyl ether, mixing the organic phases, drying the organic phases with anhydrous magnesium sulfate, filtering, removing volatile substances under reduced pressure to obtain a crude product, and separating and purifying the crude product with a silica gel column to obtain a white solid product (0.71g,69.3％).¹H NMR(400MHz,CDCl₃)δ＝7.70(s,2H),7.45-7.39(m,6H),7.18-7.11(m,4H),1.71-1.62(m,4H),0.99(t,6H).

(3) Preparation of Complex 15

Ligand L ¹⁵ (170.2 mg,0.5 mmol) and CrCl ₃(THF)₃ (185.8 mg,0.5 mmol) were added to a dry and argon filled Schlenk reaction tube, and redistilled toluene (10 mL) was added thereto and stirred at 80℃for 6 hours. After completion of the reaction, the mixture was filtered, and the filtrate was dried to give a solid which was washed with n-hexane (5 mL. Times.3), and dried to give 192.0mg (0.38 mmol, 77%) of a blue powder.

Example 16

The preparation of complex 1 is as follows:

(1) Preparation of ligand L ¹⁶

Preparation method of reference ligand L ⁸, using 2, 3-dibromofuran to replace 2, 3-dibromothiophene, obtaining pure product L¹⁶(0.73g,71.3％).¹H NMR(400MHz,CDCl₃)δ＝7.72(s,2H),7.43-7.31(m,6H),7.19-7.06(m,4H),1.71-1.56(m,4H),0.93(m,6H).

(2) Preparation of Complex 16

Ligand L ¹⁶ (170.2 mg,0.5 mmol) and CrCl ₃(THF)₃ (185.8 mg,0.5 mmol) were added to a dry and argon filled Schlenk reaction tube, and redistilled toluene (10 mL) was added thereto and stirred at 80℃for 6 hours. After completion of the reaction, the mixture was filtered, and the filtrate was dried to give a solid which was washed with n-hexane (5 mL. Times.3), and dried to give 179.5mg (0.36 mmol, 72%) of a blue powder.

Example 17

The preparation of complex 17 is as follows:

(1) Preparation of ligand L ¹⁷

Preparation method of reference ligand L ¹, using 1-tertiary butyl-3, 4-dibromopyrrole to replace 3, 4-dibromothiophene, obtaining pure product L¹⁷(0.4g,35％).¹H NMR(400MHz,CDCl₃)δ＝7.43-7.37(m,6H),7.16-7.09(m,6H),1.68-1.59(m,4H),1.11(s,9H),0.99(m,6H).

(2) Preparation of Complex 17

Ligand L ¹⁷ (197.7 mg,0.5 mmol) and CrCl ₃(THF)₃ (185.8 mg,0.5 mmol) were added to a dry and argon filled Schlenk reaction tube, and redistilled toluene (10 mL) was added and stirred at 80℃for 6 hours. After completion of the reaction, the mixture was filtered, and the filtrate was dried to give a solid which was washed with n-hexane (5 mL. Times.3), and dried to give 221.5mg (0.40 mmol, 81%) of a blue powder.

Example 18

The preparation of complex 18 is as follows:

(1) Preparation of ligand L ¹⁸

Preparation of reference ligand L ¹⁷ using 1-tert-butyl-2, 3-dibromopyrrole instead of 1-tert-butyl-3, 4-dibromopyrrole gives pure product L¹⁸(0.5g,42％).¹H NMR(400MHz,CDCl₃)δ＝7.45-7.30(m,7H),7.19-7.12(m,4H),6.26-6.20(m,1H),1.71-1.62(m,4H),1.19(s,9H),0.99(m,6H).

(2) Preparation of Complex 18

Ligand L ¹⁸ (197.7 mg,0.5 mmol) and CrCl ₃(THF)₃ (185.8 mg,0.5 mmol) were added to a dry and argon filled Schlenk reaction tube, and redistilled toluene (10 mL) was added and stirred at 80℃for 6 hours. After completion of the reaction, the mixture was filtered, and the filtrate was dried to give a solid which was washed with n-hexane (5 mL. Times.3), and dried to give 182.8mg (0.33 mmol, 66%) of a blue powder.

Example 19

The preparation of complex 19 is as follows:

(1) Preparation of ligand L ¹⁹

The compound was synthesized using the method reported by Dalton transactions. The nuclear magnetism is consistent with literature ,¹H NMR(400MHz,CDCl₃)δ＝7.63(dd,J＝6.78,6.67Hz,6H),7.39(d,J＝1.35,1H),7.33–7.20(m,20H),7.03–6.93(m,5H),6.91–6.85(m,4H).

(2) Preparation of Complex 19

Ligand L ¹⁹ (355.4 mg,0.5 mmol) and CrCl ₃(THF)₃ (185.8 mg,0.5 mmol) were added to a dry and argon filled Schlenk reaction tube, and redistilled dichloromethane (10 mL) was added thereto and stirred at room temperature for 2h. After completion of the reaction, the mixture was filtered, and the filtrate was dried by suction to give a solid which was washed with n-hexane (5 mL. Times.3), and dried by suction to give 352.0mg (0.40 mmol, 81.0%) of a blue powder.

Example 20

A catalyst for selectively tetramerizing ethylene containing aromatic heterocycle-aliphatic ligand, its preparing process and application are disclosed, which includes the following steps:

(1) Preparation of the catalyst

In a Schlenk reaction tube which was dried and filled with argon, complex 1 (0.48 mg, 0.80. Mu. Mol) and anhydrous methylcyclohexane (30 ml) were added, and after stirring for 5 minutes, modified methylaluminoxane MMAO-3A (0.4 mmol,1.12 mol/L) was added and reacted at room temperature for 5 minutes for further use.

(2) Oligomerization of ethylene

The 350mL stainless steel high-pressure gas reaction kettle is vacuumized on an oil bath at 120 ℃ for 3 hours to ensure the anhydrous and anaerobic environment of the reaction kettle, then cooled to the reaction temperature, and the kettle is internally ventilated for three times by ethylene gas. Then immediately sucking the prepared catalyst solution by a dry glass injector, injecting the catalyst solution into a high-pressure reaction kettle, sealing the reaction kettle, starting stirring, introducing ethylene gas, regulating the pressure to be at 735psi, and stirring and reacting at 75 ℃ for 60 minutes. After the reaction is finished, an ethylene gas supply valve is closed, the temperature is cooled to 0 ℃, the pressure is released, the reaction kettle is opened, and quantitative internal standard nonane is added and stirred uniformly. The reaction was then quenched with 10wt% aqueous HCl for about 30mL and the organic phase was filtered and analyzed by GC. The remaining mixture in the reaction vessel was filtered and the solid was taken and added to 10wt% aqueous hcl and stirred for 2 hours, filtered, dried to constant weight and weighed, the data are shown in table 1.

Example 21

The difference from example 20 is that complex 1 is replaced by complex 2 (0.43 mg, 0.80. Mu. Mol) and the data are shown in Table 1.

Example 22

The difference from example 20 is that complex 1 is replaced by complex 3 (0.45 mg, 0.80. Mu. Mol) and the data are shown in Table 1.

Example 23

The difference from example 20 is that complex 1 is replaced by complex 4 (0.63 mg, 0.80. Mu. Mol) and the data are shown in Table 1.

Example 24

The difference from example 20 is that complex 1 is replaced by complex 5 (0.46 mg, 0.80. Mu. Mol) and the data are shown in Table 1.

Example 25

The difference from example 20 is that complex 1 is replaced by complex 6 (0.43 mg, 0.80. Mu. Mol) and the data are shown in Table 1.

Example 26

The difference from example 20 is that complex 1 is replaced by complex 7 (0.43 mg, 0.80. Mu. Mol) and the data are shown in Table 1.

Example 27

The difference from example 20 is that complex 1 is replaced by complex 8 (0.48 mg, 0.80. Mu. Mol) and the data are shown in Table 1.

Example 28

The difference from example 20 is that complex 1 is replaced by complex 9 (0.43 mg, 0.80. Mu. Mol) and the data are shown in Table 1.

Example 29

The difference from example 20 is that complex 1 is replaced with complex 10 (0.45 mg, 0.80. Mu. Mol) and the data are shown in Table 1.

Example 30

The difference from example 20 is that complex 1 is replaced by complex 11 (0.63 mg, 0.80. Mu. Mol) and the data are shown in Table 1.

Example 31

The difference from example 20 is that complex 1 is replaced with complex 12 (0.46 mg, 0.80. Mu. Mol) and the data are shown in Table 1.

Example 32

The difference from example 20 is that complex 1 is replaced by complex 13 (0.43 mg, 0.80. Mu. Mol) and the data are shown in Table 1.

Example 33

The difference from example 20 is that complex 1 is replaced with complex 14 (0.43 mg, 0.80. Mu. Mol) and the data are shown in Table 1.

Example 34

The difference from example 20 is that complex 1 is replaced with complex 15 (0.40 mg, 0.80. Mu. Mol) and the data are shown in Table 1.

Example 35

The difference from example 20 is that complex 1 is replaced with complex 16 (0.40 mg, 0.80. Mu. Mol) and the data are shown in Table 1.

Example 36

The difference from example 20 is that complex 1 is replaced by complex 17 (0.44 mg, 0.80. Mu. Mol) and the data are shown in Table 1.

Example 37

The difference from example 20 is that complex 1 is replaced with complex 18 (0.44 mg, 0.80. Mu. Mol) and the data are shown in Table 1.

Example 38

The difference from example 23 is that the ethylene oligomerization was carried out at 85℃and the data are shown in Table 1.

Example 39

The difference from example 23 is that the ethylene oligomerization was carried out at 65℃and the data are shown in Table 1.

Example 40

The difference from example 23 is that the reaction pressure for ethylene oligomerization is 835psi and the data are shown in Table 1.

Example 41

The difference from example 23 is that the reaction pressure for ethylene oligomerization was 635psi, and the data are shown in Table 1.

Example 42

The difference from example 23 is that the amount of MMAO-3A used as cocatalyst is 0.56mmol, the data being given in Table 1.

Example 43

The difference from example 23 is that the amount of MMAO-3A used as cocatalyst is 0.32mmol, the data being given in Table 1.

Comparative example 1

The difference from example 23 is that complex 4 is replaced with complex 19 (0.70 mg, 0.80. Mu. Mol) and the data are shown in Table 1.

TABLE 1

As shown in Table 1, the catalyst provided by the invention can catalyze ethylene selective tetramerization with higher catalytic activity (the highest catalytic activity can reach 3130kg/g Cr/h) and 1-octene selectivity (the highest 1-octene selectivity can reach 71.6%). It can be seen from a comparison of example 23 provided by the present invention with comparative example 1 that by introducing an alkyl group having a smaller steric hindrance, the catalytic activity and 1-octene selectivity of the catalytic system are greatly improved, and the total selectivity of 1-hexene and 1-octene is also greatly improved. Because the electron donating ability of the alkyl is stronger than that of the phenyl, the electron cloud density of the phosphorus atoms of the coordination atoms can be increased by introducing the alkyl into the ligand structure, so that the stability of the metal active center is obviously improved, the service life of the catalyst is prolonged, the degradation of the catalyst is reduced by increasing the service life of the catalyst, and the polymer content in the reaction is reduced to 0.02-0.07%.

The above description is only a preferred embodiment of the present invention, and is not intended to limit the invention in any way, and any person skilled in the art may make modifications or alterations to the disclosed technical content to the equivalent embodiments. However, any simple modification, equivalent variation and variation of the above embodiments according to the technical substance of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A catalyst for selective tetramerization of ethylene containing aromatic heterocycle-aliphatic ligand, which is characterized in that the catalyst comprises ligand, transition metal compound and activator, wherein the chemical structural formula of the ligand is shown as the following formula (I):

Wherein the groups R ¹ to R ⁴ are each independently selected from alkyl, alkoxy, alkenyl or aryl groups, R ¹ to R ⁴ are the same or different and R ¹ to R ⁴ are not simultaneously aryl groups, said A, B and D are each independently selected from NR ⁵、O、S、CR⁶ or CR ⁷, and one of them is NR ⁵, O or S, the remainder being independently selected from CR ⁶、CR⁷; the radicals R ⁵、R⁶ and R ⁷ are identical or different and are each independently selected from hydrogen, halogen, alkyl, heteroalkyl, alkenyl or aromatic radicals.

2. The catalyst for the selective tetramerization of ethylene containing aromatic heterocyclic-aliphatic ligand according to claim 1, wherein the ligand represented by formula (I) comprises ligands represented by formula (i.a), (I.b), (I.c), (i.d), (I.e), (I.f):

3. A catalyst for the selective tetramerisation of ethylene containing an aromatic heterocyclic-aliphatic ligand according to claim 1, characterised in that the alkyl group is a C ₁-C₃₀ alkyl group comprising methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, sec-pentyl, isopentyl, cyclopentyl, n-hexyl, sec-hexyl, isohexyl, cyclohexyl, n-heptyl, cycloheptyl, n-octyl, n-decyl, 2-methylcyclopentyl or 2, 6-dimethylcyclohexyl;

4. A catalyst for the selective tetramerisation of ethylene containing aromatic heterocyclic-aliphatic ligands according to any of the claims 1-3, characterized in that at least one of R ¹ to R ⁴ is selected from alkyl or alkenyl; the alkyl group comprises a C ₁-C₄ alkyl group, particularly comprises ethyl or isopropyl, and the alkenyl group comprises a C ₂-C₄ alkenyl group, particularly comprises vinyl; the aromatic group comprises phenyl or substituted phenyl, and the substituted phenyl comprises m-fluorophenyl or p-tert-butylphenyl.

5. A catalyst for the selective tetramerisation of ethylene containing an aromatic heterocyclic-aliphatic ligand according to any one of claims 1-3, characterised in that the group R ⁵ comprises an alkyl group, R ⁶ and R ⁷ comprise hydrogen or a heteroalkyl group; the alkyl group comprises C ₁-C₄ alkyl groups, particularly comprises tertiary butyl groups, and the heteroalkyl group is trimethylsilyl or triphenylsilyl.

6. The catalyst for selective tetramerization of ethylene containing aromatic heterocyclic-aliphatic ligand according to claim 1, wherein the transition metal in the transition metal compound is one selected from the group consisting of iron, cobalt, nickel, copper, titanium, vanadium, chromium, manganese, molybdenum, tungsten, nickel and palladium; the activator comprises one or more of alkyl aluminum compound, aluminoxane compound and organic boron compound; the molar ratio of the ligand to the transition metal element in the transition metal compound is (0.01-100): 1; the mole ratio of the activator to the transition metal element in the transition metal compound is (1-10000): 1.

7. The catalyst for the selective tetramerization of ethylene containing aromatic heterocycle-aliphatic ligand according to claim 6, wherein the aluminoxane compound comprises specifically modified methylaluminoxane MMAO-3A; the mole ratio of the activator to the transition metal element in the transition metal compound is (400-700): 1, preferably (500-700): 1.

8. A process for the preparation of a catalyst for the selective tetramerisation of ethylene containing an aromatic heterocyclic-aliphatic ligand according to any one of claims 1 to 7, characterised in that the process comprises: the ligand, the transition metal compound and the activator are pre-mixed or directly added into a reaction system for in-situ synthesis, thus obtaining the catalyst containing the aromatic heterocycle-aliphatic ligand for ethylene selective tetramerization.

9. Use of a catalyst for the selective tetramerisation of ethylene containing an aromatic heterocyclic-aliphatic ligand as described in any of the claims 1-7, characterized in that the catalyst is used for the selective tetramerisation of ethylene to 1-octene, the reaction is carried out in an inert solvent, the reaction temperature is 0-200 ℃, the pressure is 10-5000psig, the concentration of transition metal in the transition metal compound in the inert solvent is 0.01-10000 μmol/L;

the inert solvent comprises one or more of alkane, arene, alkene or ionic liquid.

10. Use of a catalyst for the selective tetramerisation of ethylene with an aromatic heterocyclic-aliphatic ligand according to claim 9, characterized in that the temperature of the reaction is 65-85 ℃, preferably 75-85 ℃; the pressure is 635-835psi, preferably 735-835psi.