1. A PNSiNP ligand has a structure shown in a formula I:

wherein R is₁、R₂Each independently selected from aryl and derivatives thereof; r₃、R₄Each independently selected from methyl, ethyl, propyl, isopropyl, n-butyl, tert-butyl, ethenyl, propenyl, cyclopentyl, cyclohexyl, phenyl, naphthyl, anthracenyl or biphenyl, preferably from methyl, ethyl, isopropyl, n-butyl, cyclohexyl.

2. The PNSiNP ligand of claim 1, wherein the formula I junction isR in the PNSiNP ligand shown in the structure₁、R₂Selected from the group consisting of phenyl, benzyl, biphenyl, naphthyl, anthracenyl, 2-methylphenyl, 4-methylphenyl, 2, 4-dimethylphenyl, 2, 6-dimethylphenyl, 2-ethylphenyl, 4-ethylphenyl, 2, 4-diethylphenyl, 2, 6-diethylphenyl, 2-isopropylphenyl, 4-isopropylphenyl, 2, 4-diisopropylphenyl, 2, 6-diisopropylphenyl, 2-butylphenyl, 4-butylphenyl, 2, 4-dibutylphenyl, 2, 6-dibutylphenyl, 4-methoxyphenyl, o-methoxyphenyl, 4-ethoxyphenyl, o-ethoxyphenyl, 2-fluorophenyl, 3-fluorophenyl, 4-fluorophenyl, 2- (trimethylsilyl) phenyl, 3- (trimethylsilyl) phenyl group, 4- (trimethylsilyl) phenyl group, 2- (tri-n-butylsilyl) phenyl group, 3- (tri-n-butylsilyl) phenyl group, 4- (tri-n-butylsilyl) phenyl group.

3. A process for the preparation of a ligand according to claim 1 or 2, characterized in that it comprises the following steps:

dissolving 2-aminopyrimidine in a solvent A under anhydrous and anaerobic conditions to obtain a reaction solution I;

adding triethylamine into the reaction liquid I under stirring at the temperature of minus 10-0 ℃, continuously adding a compound shown as a structure II into the reaction liquid I, continuously stirring for reacting for 3-6h, continuously stirring for reacting for 6-24h at room temperature, and purifying the reaction liquid to obtain a product I, namely the phosphine-nitrogen ligand; the compound of formula II has the following structure:

wherein R is₁、R₂Each independently selected from the group consisting of phenyl, benzyl, biphenyl, naphthyl, anthracenyl, 2-methylphenyl, 4-methylphenyl, 2, 4-dimethylphenyl, 2, 6-dimethylphenyl, 2-ethylphenyl, 4-ethylphenyl, 2, 4-diethylphenyl, 2, 6-diethylphenyl, 2-isopropylphenyl, 4-isopropylphenyl, 2, 4-diisopropylphenyl, 2, 6-diisopropylphenyl, 2-butylphenyl, 4-butylphenyl, 2, 4-dibutylphenyl, 2, 6-dibutylphenyl4-methoxyphenyl, o-methoxyphenyl, 4-ethoxyphenyl, o-ethoxyphenyl, 2-fluorophenyl, 3-fluorophenyl, 4-fluorophenyl, 2- (trimethylsilyl) phenyl, 3- (trimethylsilyl) phenyl, 4- (trimethylsilyl) phenyl, 2- (tri-n-butylsilyl) phenyl, 3- (tri-n-butylsilyl) phenyl, or 4- (tri-n-butylsilyl) phenyl;

dissolving a phosphine-nitrogen ligand in a solvent A under anhydrous and anaerobic conditions to obtain a reaction solution II;

adding n-butyllithium into the reaction liquid II under stirring at the temperature of between 80 ℃ below zero and 70 ℃ below zero, continuously adding the compound shown in the structure of the formula III and the catalyst into the reaction liquid II, slowly heating to room temperature, continuously reacting for 36 to 72 hours under stirring, and purifying the reaction liquid to obtain a product II, namely the PNSiNP ligand; the compound of formula III has the structure shown below:

R₃、R₄each independently selected from methyl, ethyl, propyl, isopropyl, n-butyl, tert-butyl, ethenyl, propenyl, cyclopentyl, cyclohexyl, phenyl, naphthyl, anthracenyl or biphenyl, preferably from methyl, ethyl, isopropyl, n-butyl, cyclohexyl.

4. The ligand preparation method according to claim 3, wherein the molar ratio of the 2-aminopyrimidine to triethylamine is 1: 1-1: 3, and/or the molar ratio of the 2-aminopyrimidine to the compound shown in formula II is 1: 1-1: 3; and/or the solvent A is selected from one or more of toluene, methylcyclohexane, dichloromethane, acetonitrile, cyclohexane, n-hexane and n-heptane.

5. Ligand preparation process according to claim 3 or 4, characterized in that the catalyst is selected from trifluoroacetic acid; and/or the molar ratio of the compound shown in the structure of the formula III to the phosphine-nitrogen ligand is 1: 2-1: 3, and the molar ratio of the n-butyllithium to the compound shown in the structure of the formula III is 1.5: 1-2.5: 1; the molar ratio of the catalyst to the compound shown in the structure of the formula III is 0.08: 1-0.12: 1.

6. The ligand preparation method according to any one of claims 3 to 5, wherein the purification treatment comprises subjecting the reaction solution to column chromatography purification to obtain a target product and subjecting the target product to recrystallization, the column chromatography purification uses a column height-diameter ratio of 2 to 4 and a retention time of 1 to 3min, and the recrystallization uses a mixed solvent of ethanol and ethyl acetate as a solvent.

7. An ethylene oligomerization catalyst is characterized by comprising a transition metal complex and an aluminum alkyl cocatalyst, wherein the transition metal complex comprises a transition metal compound and a PNSiNP ligand, and the PNSiNP ligand is the ligand of any one of claims 1-2 or the ligand prepared by the preparation method of any one of claims 3-6.

8. The catalyst according to claim 7, wherein the transition metal compound is selected from one or more of compounds of chromium, molybdenum, cobalt, titanium, vanadium, zirconium, nickel and palladium, preferably compounds of chromium, zirconium and nickel, and the transition metal compound comprises an organic salt, an inorganic salt, a coordination complex or an organometallic complex of a transition metal, more preferably one or more of chromium acetylacetonate, chromium chloride, chromium tris (tetrahydrofuran) trichloride, chromium (III) 2-ethylhexanoate, chromium (III) octanoate, chromium hexacarbonyl, chromium (benzene) tricarbonyl.

9. The catalyst of any one of claims 6-8, wherein the alkylaluminum cocatalyst is selected from one or more of trimethylaluminum, triethylaluminum, triisobutylaluminum, diethylethoxyaluminum, diethylaluminum monochloride, ethylaluminum dichloride, ethylaluminum sesquichloride, trioctylaluminum, Methylaluminoxane (MAO), Modified Methylaluminoxane (MMAO) or ethylaluminoxane.

10. The catalyst of any one of claims 6-9, wherein the molar ratio of transition metal compound to PNSiNP ligand is 1: 1-3, preferably 1: 1-2; the molar ratio of aluminum alkyl cocatalyst to transition metal compound is 50-2000:1, preferably 90-800:1, based on the molar ratio of aluminum element to transition metal element.

11. Use of a catalyst according to any one of claims 6 to 10 for the oligomerization of ethylene.

12. The application of the method as claimed in claim 11, wherein the reaction kettle is heated to 110-160 ℃ before reaction, vacuumized for 1-4h, replaced by nitrogen, cooled to room temperature, replaced by ethylene, the solvent B and the alkyl aluminum cocatalyst are added, then the transition metal compound and the PNSiNP ligand are added, and after the temperature reaches the reaction temperature, the reaction is started by sequentially introducing 0-0.8MPa hydrogen and 2MPa-7MPa ethylene, wherein the reaction temperature is 35-90 ℃, preferably 40-70 ℃, and the reaction time is 10-240 min, preferably 20-100 min.

Background

Linear alpha-olefin is an important chemical raw material and can be used as polyolefin comonomer, PVC plasticizer, surfactant, lubricating oil additive and other fields. The consumption of the comonomer accounts for more than half of the consumption of the alpha-olefin, and the polyolefin products of the 1-octene and the 1-hexene have good mechanical properties and excellent processability, so that the polyolefin products have a large amount of demands in industrial production. The production method of linear alpha-olefin mainly includes ethylene oligomerization process, wax cracking process, alkane dehydrogenation process, coal chemical extraction process, alkane catalytic cracking process, extraction separation method, fatty alcohol dehydrogenation method and the like. The products of different production processes are distributed differently, wherein the product of the ethylene oligomerization process has high linearization degree and good product quality, and is the most important industrial production method.

In recent years, the selective oligomerization of ethylene to produce 1-octene and 1-hexene has received increasing attention. Bollmann et al (J.AM. CHEM. SOC.2004,126,14712-14713), from Sasol corporation, for the first time, have achieved highly selective oligomerization of ethylene to produce 1-octene and 1-hexene. A Cr/PNP/MAO catalytic system is adopted, the catalyst consists of a trivalent chromium precursor and a PNP ligand, MAO is taken as a cocatalyst, toluene or alkane is taken as a solvent, the reaction temperature is 45 ℃, and the ethylene pressure is 4.5 MPa. Octene-1 selectivity 70%, hexene-1 selectivity 13%, catalyst activity about 300kg product/(gCr). Sasol company applies a series of ethylene oligomerization patents CN105263890A, CN104220402A, CN105228973A, CN105228974A, CN101052605A and the like, and realizes the industrial production of 1-octene through ethylene selective tetramerization in 2014.

The ligand framework used in the ethylene selective oligomerization catalyst comprises monodentate N ligands, multidentate PNP, PCCP, PCICP, PNCN and various derived ligands, and the steric hindrance effect and the electron donating effect of the ligands have great influence on the activity and the selectivity. Patents US8609924B2, CN105562096A, CN105562095A, CN105562097A, CN105562099A, CN105566036A, CN105566045A, CN105566037A, CN105566046A, CN104415790A and the like disclose a series of oligomerization catalysts of ligands with different PCCP skeleton structures, wherein the oligomerization activity of the PCCP ligands is similar to that of the PNP ligands of Sasol, but the products have more isoolefins, poor economy and more polymers, which are not favorable for the long-period operation of the device.

On the premise of ensuring the catalytic activity, the product selectivity of the existing catalytic systems such as PNP, PCCP and the like is only about 80 percent, and the space for promotion is still provided. Meanwhile, the P framework structure is influenced by substituents on nitrogen/carbon, the selectivity of the polymer is generally more than 0.2 wt%, and the long-period operation of the device is influenced. In view of the problems of low selectivity and high polymer yield of the conventional ligand structure catalyst, the development of a novel ligand structure catalyst is urgently needed.

Disclosure of Invention

The invention aims to provide a novel PNSiNP ligand and a preparation method thereof.

The invention also aims to provide an ethylene oligomerization catalyst and application thereof in ethylene oligomerization reaction. The catalyst improves the selectivity of 1-hexene and 1-octene in the ethylene oligomerization reaction process, the polymer production is lower, the invention can improve the selectivity of 1-hexene and 1-octene to more than 88 wt%, the polymer production is reduced to less than 0.1 wt%, and the activity is as high as 1600000 g/(gCr.h).

In order to achieve the above purpose, the technical scheme of the invention is as follows:

the invention provides a PNSiNP ligand, which has a structure shown in a formula I:

wherein R is₁、R₂Each independently selected from aryl and derivatives thereof. R₃、R₄Each independently selected from methyl, ethyl, propyl, isopropyl, n-butyl, tert-butyl, ethenyl, propenyl, cyclopentyl, cyclohexyl, phenyl, naphthyl, anthracenyl or biphenyl, preferably from methyl, ethyl, isopropyl, n-butyl, cyclohexyl.

Preferably, R in the PNSiNP ligand shown in the structure of the formula I₁，R₂Selected from the group consisting of phenyl, benzyl, biphenyl, naphthyl, anthracenyl, 2-methylphenyl, 4-methylphenyl, 2, 4-dimethylphenyl, 2, 6-dimethylphenyl, 2-ethylphenyl, 4-ethylphenyl, 2, 4-diethylphenyl, 2, 6-diethylphenyl, 2-isopropylphenyl, 4-Isopropylphenyl, 2, 4-diisopropylphenyl, 2, 6-diisopropylphenyl, 2-butylphenyl, 4-butylphenyl, 2, 4-dibutylphenyl, 2, 6-dibutylphenyl, 4-methoxyphenyl, o-methoxyphenyl, 4-ethoxyphenyl, o-ethoxyphenyl, 2-fluorophenyl, 3-fluorophenyl, 4-fluorophenyl, 2- (trimethylsilyl) phenyl, 3- (trimethylsilyl) phenyl, 4- (trimethylsilyl) phenyl, 2- (tri-n-butylsilyl) phenyl, 3- (tri-n-butylsilyl) phenyl or 4- (tri-n-butylsilyl) phenyl.

The invention also provides a preparation method of the ligand, which comprises the following steps:

dissolving 2-aminopyrimidine in a solvent A under anhydrous and anaerobic conditions to obtain a reaction solution I;

and (2) dropwise adding triethylamine into the reaction liquid I under stirring at-10-0 ℃, continuously adding a compound shown as a structure II into the reaction liquid I, reacting for 3-6h under stirring, continuously reacting for 6-24h under stirring at room temperature, and purifying the reaction liquid to obtain a product I, namely the phosphine-nitrogen ligand. The compound of formula II has the following structure:

wherein R is₁、R₂Each independently selected from the group consisting of phenyl, benzyl, biphenyl, naphthyl, anthracenyl, 2-methylphenyl, 4-methylphenyl, 2, 4-dimethylphenyl, 2, 6-dimethylphenyl, 2-ethylphenyl, 4-ethylphenyl, 2, 4-diethylphenyl, 2, 6-diethylphenyl, 2-isopropylphenyl, 4-isopropylphenyl, 2, 4-diisopropylphenyl, 2, 6-diisopropylphenyl, 2-butylphenyl, 4-butylphenyl, 2, 4-dibutylphenyl, 2, 6-dibutylphenyl, 4-methoxyphenyl, o-methoxyphenyl, 4-ethoxyphenyl, o-ethoxyphenyl, 2-fluorophenyl, 3-fluorophenyl, 4-fluorophenyl, 2- (trimethylsilyl) phenyl, o-methoxyphenyl, 4-fluorophenyl, and mixtures thereof, 3- (trimethylsilyl) phenyl group, 4- (trimethylsilyl) phenyl group, 2- (tri-n-butylsilyl) phenyl group, 3- (tri-n-butylsilyl) phenyl group, 4- (tri-n-butylsilyl) phenyl group.

Dissolving a phosphine-nitrogen ligand in a solvent A under anhydrous and anaerobic conditions to obtain a reaction solution II;

dropwise adding n-butyllithium into the reaction liquid II under stirring at the temperature of between 80 ℃ below zero and 70 ℃ below zero, continuously adding the compound shown in the structure of the formula III and the catalyst, slowly heating to room temperature, continuously reacting for 36 to 72 hours under stirring, and purifying the reaction liquid to obtain a product II, namely the PNSiNP ligand.

The compound of formula III has the structure shown below:

R₃、R₄each independently selected from methyl, ethyl, propyl, isopropyl, n-butyl, tert-butyl, ethenyl, propenyl, cyclopentyl, cyclohexyl, phenyl, naphthyl, anthracenyl or biphenyl, preferably from methyl, ethyl, isopropyl, n-butyl, cyclohexyl.

In the preparation method of the ligand, the solvent A is selected from one or more of toluene, methylcyclohexane, dichloromethane, acetonitrile, cyclohexane, n-hexane and n-heptane. The molar ratio of the 2-aminopyrimidine to the triethylamine is 1: 1-1: 3, preferably 1: 2.2; the molar ratio of the 2-aminopyrimidine to the compound shown in the formula II is 1: 1-1: 3, preferably 1: 2.2. wherein solvent A is used in excess.

In the preparation method of the ligand, the catalyst is selected from trifluoroacetic acid. Preferably, the molar ratio of the compound shown in the structure of the formula III to the phosphine-nitrogen ligand is 1: 2-1: 3, and the molar ratio of the n-butyllithium to the compound shown in the structure of the formula III is 1.5: 1-2.5: 1; the molar ratio of the catalyst to the compound represented by the structure of formula III is 0.08: 1-0.12: 1.

The purification treatment comprises the steps of carrying out column chromatography purification on the reaction liquid to obtain a target product and carrying out recrystallization on the target product, wherein the height-diameter ratio of a chromatographic column used for the column chromatography purification is 2-4, the retention time is 1-3min, and a solvent used for the recrystallization is a mixed solvent of ethanol and ethyl acetate.

The invention provides an ethylene oligomerization catalyst, which comprises a transition metal complex and an alkyl aluminum cocatalyst, wherein the transition metal complex comprises a transition metal compound and a PNSiNP ligand.

The transition metal compound is one or more than two of compounds of chromium, molybdenum, cobalt, titanium, vanadium, zirconium, nickel and palladium, preferably compounds of chromium, zirconium and nickel, and the transition metal compound comprises organic salt, inorganic salt, coordination complex or organic metal complex of transition metal, preferably one or more than two of chromium acetylacetonate, chromium chloride, chromium tris (tetrahydrofuran) trichloride, chromium (III) 2-ethylhexanoate, chromium (III) octanoate, chromium hexacarbonyl and chromium (benzene) tricarbonyl.

The alkyl aluminum cocatalyst disclosed by the invention is selected from one or more than two of trimethylaluminum, triethylaluminum, triisobutylaluminum, diethyl aluminum ethoxide, diethyl aluminum monochloride, ethyl aluminum dichloride, aluminum sesquiethyl chloride, trioctylaluminum, Methylaluminoxane (MAO), Modified Methylaluminoxane (MMAO) or ethylaluminoxane.

In the catalyst, the molar ratio of the transition metal compound to the PNSiNP ligand is 1: 1-3, preferably 1: 1-2; the molar ratio of aluminum alkyl cocatalyst to transition metal compound is from 50 to 2000:1, preferably from 90 to 800:1, in terms of the molar ratio of aluminum element to transition metal element.

The invention also provides the application of the catalyst, which is used for ethylene oligomerization.

In some preferred embodiments of the present invention, the ethylene oligomerization process comprises: heating the reaction kettle to 160 ℃ for 110-160 ℃ before reaction, vacuumizing for 1-4h, replacing by nitrogen, cooling to room temperature, replacing ethylene, adding a solvent B and an alkyl aluminum cocatalyst, then adding a transition metal compound and a PNSiNP ligand, and introducing 0-0.8MPa hydrogen and 2MPa-7MPa ethylene in sequence to start reaction after the temperature reaches the reaction temperature, wherein the reaction temperature is 35-90 ℃, preferably 40-70 ℃, and the reaction time is 10-240 min, preferably 20-100 min.

The catalyst composition is applied to ethylene oligomerization, the ethylene oligomerization reaction solvent B is one or more than two of n-butane, isobutane, n-pentane, cyclopentane, methylcyclopentane, methylene cyclopentane, n-hexane, cyclohexane, methylcyclohexane, n-heptane, n-octane, n-nonane, benzene, toluene and xylene, and the solvent B is used in excess.

In a more specific embodiment, the polymerization process of the catalyst composition of the present invention is as follows: polymerization was carried out in a 300mL autoclave, and the purified alkane was used as solvent C. Before the reaction, the reaction kettle is heated to 130 ℃, vacuumized for 1-3h, and replaced by nitrogen for three times. Cooling to room temperature, replacing ethylene twice, adding 150ml of dehydrated and deoxidized solvent C and quantitative alkyl aluminum cocatalyst, then adding a metal chromium compound and a PNSiNP ligand, and introducing 0.2-0.7MPa hydrogen and 2MPa-7MPa ethylene in sequence to start reaction when the temperature is constant near the reaction temperature. The reaction temperature is 35-90 ℃, preferably 40-70 ℃, and the reaction time is 10min-240min, preferably 20min-100 min. After the reaction is finished, closing the ethylene inlet valve, rapidly cooling by using ice water bath or liquid nitrogen, slowly releasing pressure, and discharging the kettle to obtain an ethylene oligomerization product.

Compared with the prior art, the ethylene oligomerization catalyst system has the activity for ethylene oligomerization of over 1600000 g/(gCr.h), the total selectivity of 1-hexene and 1-octene of 90 percent and the PE selectivity of less than 0.05 percent by weight, can reduce the production cost and has high economic added value.

Detailed Description

The following specific examples are merely illustrative of the present invention, but these examples are only part of the present invention and do not limit the application of the present invention in other fields.

The starting materials used in the examples are conventional in the art and the purity specifications used are either analytically or chemically pure.

Raw material source information:

2-aminopyrimidine: 99%, Bailingwei Tech Co Ltd

Triethylamine: not less than 99.5% (GC), Shanghai Aladdin Biotechnology Ltd

Diphenyl phosphine chloride: 97% of Alfa Angsa chemical Co Ltd

Dichlorodimethylsilane: 98.5% (GC), Shanghai Aladdin Biotechnology Ltd

Tert-butylmethyldichlorosilane: 95% Shanghai Aladdin Biotechnology Ltd

Isopropyl methyl dichlorosilane: 96% Shanghai Aladdin Biotechnology Ltd

Cyclohexyl methyl dichlorosilane: 95% Shanghai Aladdin Biotechnology Ltd

N-butyl lithium: 15% Hexane solution (1.6mol), Shanghai Aladdin Biotech Co., Ltd

Chloro (2-fluorophenyl) (phenyl) phosphine: 97%, Shanghai Xinkai medicine science and technology Limited

Chloro (3-fluorophenyl) (phenyl) phosphine: 97%, Shanghai Xinkai medicine science and technology Limited

Chloro (4-fluorophenyl) (phenyl) phosphine: 97%, Shanghai Xinkai medicine science and technology Limited

Chlorobis (4-methylphenyl) phosphine: more than 97%, Shanghai Aladdin Biotechnology Ltd

Chlorobis (4-methoxyphenyl) phosphine: 98% of Alfa Sha (China) Chemicals Co., Ltd

4- (trimethylsilyl) phenylphosphonium chloride: 97% Jiangsu Xinnoco catalyst Co., Ltd

4- (tri-n-butylsilyl) phenyl phosphine chloride: 97% Jiangsu Xinnoco catalyst Co., Ltd

Ethyl acetate: 99.9% by Bailingwei Tech Co Ltd

Ethanol: chemical reagent of analytical pure, national drug group Co Ltd

MMAO-3 a: the molar concentration of Al was 1.75mol/L (7 wt% Al, n-heptane solvent), Jiangsu Xinnoco catalyst Co., Ltd

MAO Al molar concentration 1.5mol/L (10 wt% AL, toluene solvent), Jiangsu Xinnaoko catalyst Co., Ltd

The Al/M of the oligomerization reaction is the molar ratio of the aluminum alkyl to the metal center.

The oligomerization catalyst activity is defined as the mass of 1-octene and 1-hexene produced per gram of metal per hour. The mass of 1-octene and 1-hexene was determined by qualitative and quantitative analysis of each component in the reaction solution using the following conditions for the GC analyzer:

the instrument model is as follows: shimadzu GC2010

A chromatographic column: DB-5(30m 0.25mm 0.25 μm)

Column temperature procedure: the temperature was first maintained at 35 ℃ for 10min and then raised to 250 ℃ at a rate of 10 ℃/min, and maintained at this temperature for 10 min.

Detector temperature: 300 deg.C

Carrier gas: 1bar

Air: 0.3bar

Fuel gas (H2): 0.3bar

The sample quality analysis was performed using an internal standard method. The following should be mentioned:

wherein m1 is the mass of a certain product, m is the mass of an internal standard substance, a1 is the peak area of the product detected in a gas chromatogram, and a is the peak area of the internal standard substance. k is a correction factor associated with the substance to be measured and the detection condition.

Example 1

Preparation of PNSiNP ligand: the relevant solvent is soaked by a molecular sieve for removing water before use.

Preparation of phosphine-nitrogen ligand: dissolving 100mmol of 2-aminopyrimidine in 200ml of dichloromethane under anhydrous and anaerobic conditions to obtain a reaction solution I; and (2) dropwise adding 220mmol of triethylamine into the reaction liquid I under stirring at-5 ℃, slowly adding 110mmol of a compound (diphenyl phosphine chloride) shown as the structure II into the reaction liquid I, adding the rest 110mmol of diphenyl phosphine chloride when the solution is stable and does not release heat continuously, reacting for 3 hours under stirring, removing the low-temperature constant-temperature reaction bath, and stirring for 12 hours at room temperature. Purifying the reaction liquid by using column chromatography (tetrahydrofuran is used for leaching, the height-diameter ratio is 2), then recrystallizing at 78 ℃ (the solvent is ethanol: ethyl acetate: 5:1), and treating the reaction liquid to obtain a product I, namely the phosphine-nitrogen ligand L^a，L^aThe structure of the compound (A) is shown as follows:

the above ligand (L)^a) The nuclear magnetic data for (c) are as follows:¹H NMR(400MHz，CDCl₃)：8.45(s，2H)，7.38～7.45(m，20H)，6.93(s，1H)

preparation of PNSiNP ligand: 50mmol of phosphine-nitrogen ligand L under anhydrous and oxygen-free conditions^aDissolving the mixture in 180ml of dichloromethane to obtain a reaction solution II; 40mmol of n-butyllithium was added dropwise to the reaction solution II under stirring at-78 deg.C, 20mmol of the compound represented by the formula III (dichlorodimethylsilane) and 2.5mmol of trifluoroacetic acid were further added thereto, the temperature was slowly raised to room temperature, and the reaction was continued for 50 hours under stirring. Purifying the reaction liquid by using column chromatography (tetrahydrofuran is used for leaching, the height-diameter ratio is 2), then recrystallizing at 78 ℃ (the solvent is ethanol: ethyl acetate: 5:1), and treating the reaction liquid to obtain a product, namely the PNSiNP ligand L1, wherein the structure of L1 is shown as the following formula:

the nuclear magnetic data for the above ligand (L1) are as follows:¹H NMR(400MHz，CDCl₃)：8.47(s，4H)，7.36～7.48(m，40H)，0.14(s，6H)

oligomerization of ethylene:

before reaction, a 300ml reaction kettle is heated to 150 ℃, vacuumized for 3 hours and replaced by nitrogen for three times. After the temperature is cooled to room temperature, ethylene is replaced twice, 100ml of dehydrated and deoxidized solvent methylcyclohexane and 1ml of MMAO-3a (7 wt% Al, n-heptane) (Al/Cr molar ratio is 500) are added, then 4.2 mu mol of PNSiNP ligand L1 and 3.5 mu mol of chromium acetylacetonate are added, and after the temperature is kept constant at 45 ℃, 0.5Mpa hydrogen and 5MPa ethylene are sequentially introduced to start the reaction. The reaction temperature is 45 ℃ and the reaction time is 60 min. After the reaction is finished, closing the ethylene inlet valve, using ice water bath or quickly cooling to below 5 ℃, slowly releasing pressure, and discharging the reactor to obtain the ethylene oligomerization product.

The product was analyzed by GC, for an activity of 1623kg/gCr.h, a selectivity of (1-hexene + 1-octene) of 88.6 wt% and a polymer selectivity of 0.09 wt%.

Example 2

Preparation of PNSiNP ligand: the relevant solvent is soaked by a molecular sieve for removing water before use.

Preparation of phosphine-nitrogen ligand: the preparation is as in example 1, giving the phosphine-nitrogen ligand L^a。

Preparation of PNSiNP ligand: 60mmol of phosphine-nitrogen ligand L under the anhydrous and oxygen-free conditions^aDissolving the mixture in 180ml of dichloromethane to obtain a reaction solution II; at-78 ℃, 50mmol of n-butyllithium is dropwise added into the reaction liquid II under stirring, 20mmol of the compound (isopropyl methyl dichlorosilane) shown in the formula III structure and 2.4mmol of trifluoroacetic acid are continuously added into the reaction liquid II, then the temperature is slowly raised to the room temperature, and the reaction is continuously carried out for 70 hours under stirring. Purifying the reaction liquid by using column chromatography (tetrahydrofuran is used for leaching, the height-diameter ratio is 2), then recrystallizing at 75 ℃ (the solvent is ethanol: ethyl acetate: 5:1), and treating the reaction liquid to obtain a product, namely the PNSiNP ligand L2, wherein the structure of L2 is shown as the following formula:

the nuclear magnetic data for the above ligand (L2) are as follows:¹H NMR(400MHz，CDCl₃)：8.42(s，4H)，7.35～7.49(m，40H)，0.92～1.78(m，7H)，0.14(s，3H)

oligomerization of ethylene:

before the reaction, a 500ml reaction kettle is heated to 160 ℃, vacuumized for 1.5h and replaced by nitrogen for three times. After the temperature is cooled to room temperature, the ethylene is replaced twice, 200ml of dehydrated and deoxidized solvent methylcyclohexane and 1.4ml (Al/Cr ═ 612) of MMAO-3a (7 wt% Al, n-heptane) are added, then 4.8 mu mol of PNSiNP ligand L2 and 4 mu mol of tetrahydrofuran chromium chloride are added, and the reaction is started by sequentially introducing 0.4MPa hydrogen and 4.5MPa ethylene when the temperature is constant at 55 ℃. The reaction temperature is 55 ℃, and the reaction time is 40 min. After the reaction is finished, closing the ethylene inlet valve, using ice water bath or quickly cooling to below 5 ℃, slowly releasing pressure, and discharging the reactor to obtain the ethylene oligomerization product.

The product was analyzed by GC for an activity of 2278kg/gCr. h, a selectivity for (1-hexene + 1-octene) of 89.7 wt% and a polymer selectivity of 0.07 wt%.

Example 3

Preparation of PNSiNP ligand: the relevant solvent is soaked by a molecular sieve for removing water before use.

Preparation of phosphine-nitrogen ligand: the preparation is as in example 1, giving the phosphine-nitrogen ligand L^a。

Preparation of PNSiNP ligand: under the anhydrous and oxygen-free conditions, 40mmol of phosphine-nitrogen ligand L^aDissolving the mixture in 180ml of dichloromethane to obtain a reaction solution II; and (3) dropwise adding 40mmol of n-butyllithium into the reaction liquid II under stirring at-78 ℃, continuously adding 20mmol of the compound (tert-butylmethyldichlorosilane) shown in the formula III structure and 2.2mmol of trifluoroacetic acid, slowly heating to room temperature, and continuously reacting for 40 hours under stirring. Purifying the reaction liquid by using column chromatography (tetrahydrofuran is used for leaching, the height-diameter ratio is 2), then recrystallizing at 73 ℃ (the solvent is ethanol: ethyl acetate: 5:1), and treating the reaction liquid to obtain a product, namely the PNSiNP ligand L3, wherein the structure of L3 is shown as the following formula:

the nuclear magnetic data for the above ligand (L3) are as follows:¹H NMR(400MHz，CDCl₃)：8.48(s，4H)，7.36～7.50(m，40H)，0.98(s，9H)，0.14(s，3H)

oligomerization of ethylene:

before reaction, a 500ml reaction kettle is heated to 120 ℃, vacuumized for 2 hours and replaced by nitrogen for three times. After cooling to room temperature, the ethylene was replaced twice, 200ml of toluene as a dehydrated deoxygenated solvent and 0.93ml of (Al/Cr ═ 400) MAO (10 wt%, toluene) were added, then 4.2. mu. mol of PNSiNP ligand L3 and 3.5. mu. mol of tetrahydrofuran chromium chloride were added, and the reaction was started by introducing 0.3MPa of hydrogen and 4.5MPa of ethylene in this order while keeping the temperature constant at 60 ℃. The reaction temperature is 60 ℃, and the reaction time is 45 min. After the reaction is finished, closing the ethylene inlet valve, using ice water bath or quickly cooling to below 5 ℃, slowly releasing pressure, and discharging the reactor to obtain the ethylene oligomerization product.

The product was analyzed by GC, activity 1551kg/gCr. h, (1-hexene + 1-octene) selectivity 91.5 wt%, polymer selectivity 0.05 wt%.

Example 4

Preparation of PNSiNP ligand: the relevant solvent is soaked by a molecular sieve for removing water before use.

Preparation of phosphine-nitrogen ligand: the preparation is as in example 1, giving the phosphine-nitrogen ligand L^a。

Preparation of PNSiNP ligand: under the anhydrous and oxygen-free conditions, 45mmol of phosphine-nitrogen ligand L^aDissolving the mixture in 180ml of dichloromethane to obtain a reaction solution II; at-78 ℃, 34mmol of n-butyllithium is dropwise added into the reaction liquid II under stirring, 20mmol of the compound (cyclohexylmethyldichlorosilane) shown in the formula III structure and 2.2mmol of trifluoroacetic acid are continuously added into the reaction liquid II, then the temperature is slowly raised to the room temperature, and the reaction is continuously carried out for 60 hours under stirring. Purifying the reaction liquid by using column chromatography (tetrahydrofuran is used for leaching, the height-diameter ratio is 2), then recrystallizing at 70 ℃ (the solvent is ethanol: ethyl acetate: 5:1), and treating the reaction liquid to obtain a product, namely the PNSiNP ligand L4, wherein the structure of L4 is shown as the following formula:

the nuclear magnetic data for the above ligand (L4) are as follows:¹H NMR(400MHz，CDCl₃)：8.46(s，4H)，7.35～7.49(m，40H)，1.30～1.60(m，11H)，0.13(s，3H)

oligomerization of ethylene:

before the reaction, a 500ml reaction kettle is heated to 160 ℃, vacuumized for 2.5 hours and replaced by nitrogen for three times. After the temperature is cooled to room temperature, the ethylene is replaced twice, 200ml of dehydrated and deoxidized solvent toluene and 1.2ml of (Al/Cr ═ 600) MMAO-3a (7 wt% Al, n-heptane) are added, then 4.2 mu mol of PNSiNP ligand L4 and 3.5 mu mol of chromium acetylacetonate are added, and the reaction is started by sequentially introducing 0.5Mpa of hydrogen and 4.5MPa of ethylene when the temperature is constant at 45 ℃. The reaction temperature is 45 ℃ and the reaction time is 25 min. After the reaction is finished, closing the ethylene inlet valve, using ice water bath or quickly cooling to below 5 ℃, slowly releasing pressure, and discharging the reactor to obtain the ethylene oligomerization product.

The product was analyzed by GC, the activity was 1977kg/gCr. h, the (1-hexene + 1-octene) selectivity was 89.8 wt%, the polymer selectivity was 0.08 wt%.

Example 5

Preparation of PNSiNP ligand: the relevant solvent is soaked by a molecular sieve for removing water before use.

Preparation of phosphine-nitrogen ligand: phosphine-nitrogen ligand L^bThe preparation method of (3) is as in example 1. With the difference that the compound of structure II added is (2-fluorophenyl) (phenyl) phosphonium chloride; 220mmol of triethylamine is added dropwise to the first reaction solution under stirring at 0 ℃. Phosphine-nitrogen ligand L^bThe structure of (a) is as follows:

the above ligand (L)^b) The nuclear magnetic data for (c) are as follows:¹H NMR(400MHz，CDCl₃)：8.45(s，2H)，7.22～7.75(m，18H)，6.93(s，1H)

preparation of PNSiNP ligand: under the anhydrous and anaerobic conditions, 42mmol of phosphine-nitrogen ligand L^bDissolving the mixture in 180ml of dichloromethane to obtain a reaction solution II; at-78 ℃, 36mmol of n-butyllithium is dropwise added into the reaction liquid II under stirring, 20mmol of the compound (dichlorodimethylsilane) shown in the formula III structure and 2.0mmol of trifluoroacetic acid are continuously added into the reaction liquid II, then the temperature is slowly raised to the room temperature, and the reaction is continuously carried out for 65 hours under stirring. Purifying the reaction liquid by using column chromatography (tetrahydrofuran is used for leaching, and the height-diameter ratio is 2.5), then recrystallizing at 78 ℃ (the solvent is ethanol: ethyl acetate: 5:1), and treating the reaction liquid to obtain a product, namely the PNSiNP ligand L5, wherein the structure of L5 is shown as the following formula:

the nuclear magnetic data for the above ligand (L5) are as follows:¹H NMR(400MHz，CDCl₃)：8.45(s，4H)，7.21～7.73(m，36H)，0.15(s，6H)

oligomerization of ethylene:

before reaction, a 500ml reaction kettle is heated to 120 ℃, vacuumized for 4 hours and replaced by nitrogen for three times. After the temperature is cooled to room temperature, the ethylene is replaced twice, 200ml of dehydrated and deoxidized solvent cyclohexane and 0.4ml of (Al/Cr ═ 200) MMAO (7 wt% Al, n-heptane) are added, then 4.2 mu mol of phosphine-nitrogen-silicon ligand L5 and 3.5 mu mol of chromium acetylacetonate are added, and after the temperature is kept constant at 55 ℃, 0.5MPa of hydrogen and 4.5MPa of ethylene are sequentially introduced to start the reaction. The reaction temperature is 55 ℃, and the reaction time is 50 min. After the reaction is finished, closing the ethylene inlet valve, using ice water bath or quickly cooling to below 5 ℃, slowly releasing pressure, and discharging the reactor to obtain the ethylene oligomerization product.

The product was analyzed by GC for an activity of 1952kg/gCr. h, a selectivity for (1-hexene + 1-octene) of 88.8 wt% and a polymer selectivity of 0.07 wt%.

Example 6

Preparation of PNSiNP ligand: the relevant solvent is soaked by a molecular sieve for removing water before use.

Preparation of phosphine-nitrogen ligand: phosphine-nitrogen ligand L^cThe preparation method of (3) is as in example 1. With the difference that the compound of structure II added is (3-fluorophenyl) (phenyl) phosphonium chloride; and dropwise adding 220mmol of triethylamine into the reaction liquid I under stirring at-10 ℃. Phosphine-nitrogen ligand L^cThe structure of (a) is as follows:

the above ligand (L)^c) The nuclear magnetic data for (c) are as follows:¹H NMR(400MHz，CDCl₃)：8.45(s，2H)，7.15～7.45(m，18H)，6.93(s，1H)

preparation of PNSiNP ligand: under the anhydrous and anaerobic conditions, 46mmol of phosphine-nitrogen ligand L^cDissolving the mixture in 180ml of dichloromethane to obtain a reaction solution II; and (3) dropwise adding 38mmol of n-butyllithium into the reaction liquid II under stirring at-78 ℃, continuously adding 20mmol of the compound (tert-butylmethyldichlorosilane) shown in the formula III structure and 1.8mmol of trifluoroacetic acid, slowly heating to room temperature, and continuously reacting for 55 hours under stirring. Purifying the reaction solution by column chromatography (tetrahydrofuran elution with an aspect ratio of 2.5), and then purifyingRecrystallizing at 75 deg.C (solvent is ethanol: ethyl acetate: 5:1), and treating the reaction solution to obtain the product, i.e. PNSiNP ligand L6, L6 has the following structure:

the nuclear magnetic data for the above ligand (L6) are as follows:¹H NMR(400MHz，CDCl₃)：8.48(s，4H)，7.21～7.45(m，36H)，0.99(s，9H)，0.13(s，3H)

oligomerization of ethylene:

before reaction, a 500ml reaction kettle is heated to 120 ℃, vacuumized for 5 hours and replaced by nitrogen for three times. After the temperature is cooled to room temperature, the ethylene is replaced twice, 200ml of dehydrated and deoxidized solvent methylcyclohexane and 1.6ml of (Al/Cr ═ 800) MMAO-3a (7 wt% Al, n-heptane) are added, then 4.2 mu mol of phosphine-nitrogen ligand L6 and 3.5 mu mol of chromium acetylacetonate are added, and after the temperature is constant at 60 ℃, 0.5Mpa of hydrogen and 4.5MPa of ethylene are sequentially introduced to start the reaction. The reaction temperature is 60 ℃, and the reaction time is 20 min. After the reaction is finished, closing the ethylene inlet valve, using ice water bath or quickly cooling to below 5 ℃, slowly releasing pressure, and discharging the reactor to obtain the ethylene oligomerization product.

The product was analyzed by GC for an activity of 1833kg/gCr. h, a selectivity for (1-hexene + 1-octene) of 89.7 wt% and a polymer selectivity of 0.11 wt%.

Example 7

Preparation of PNSiNP ligand: the relevant solvent is soaked by a molecular sieve for removing water before use.

Preparation of phosphine-nitrogen ligand: phosphine-nitrogen ligand L^dThe preparation method of (3) is as in example 1. With the difference that the compound of structure II added is (4-fluorophenyl) (phenyl) phosphonium chloride, the reaction solution containing product one is purified using column chromatography (tetrahydrofuran rinse with an aspect ratio of 2.5) and then recrystallized at 75 ℃ (solvent ethanol: ethyl acetate ═ 5:1), phosphine-nitrogen ligand L^dThe structure of (a) is as follows:

the nuclear magnetic data of the above ligand (Ld) are as follows: 1H NMR (400MHz, CDCl 3): 8.45(s, 2H), 7.09-7.45 (m, 18H), 6.93(s, 1H)

Preparation of PNSiNP ligand: under the anhydrous and oxygen-free conditions, 48mmol of phosphine-nitrogen ligand L^dDissolving the mixture in 180ml of dichloromethane to obtain a reaction solution II; dropwise adding 32mmol of n-butyl lithium into the reaction liquid II under stirring at-78 ℃, continuously adding 20mmol of a compound ((cyclohexylmethyldichlorosilane) shown in the formula III structure and 2.2mmol of trifluoroacetic acid, slowly heating to room temperature, continuously reacting for 58h under stirring, purifying the reaction liquid by using column chromatography (tetrahydrofuran is used for leaching, the height-diameter ratio is 2.5), then recrystallizing at 72 ℃ (the solvent is ethanol: ethyl acetate is 5:1), and treating the reaction liquid to obtain a product, namely the PNSiNP ligand L7, wherein the structure of L7 is shown as the following formula:

the nuclear magnetic data for the above ligand (L7) are as follows:¹H NMR(400MHz，CDCl₃)：8.49(s，4H)，7.09～7.48(m，36H)，1.29～1.62(m，11H)，0.15(s，3H)

oligomerization of ethylene:

before the reaction, a 500ml reaction kettle is heated to 125 ℃, vacuumized for 3.5 hours and replaced by nitrogen for three times. After the temperature is cooled to room temperature, the ethylene is replaced twice, 200ml of dehydrated and deoxidized solvent methylcyclohexane and 1.2ml of (Al/Cr ═ 600) MMAO-3a (7 wt% Al, n-heptane) are added, then 4.2 mu mol of phosphine-nitrogen ligand L7 and 3.5 mu mol of chromium acetylacetonate are added, and after the temperature is kept constant at 55 ℃, 0.5MPa of hydrogen and 4.5MPa of ethylene are sequentially introduced to start the reaction. The reaction temperature is 55 ℃, and the reaction time is 60 min. After the reaction is finished, closing the ethylene inlet valve, using ice water bath or quickly cooling to below 5 ℃, slowly releasing pressure, and discharging the reactor to obtain the ethylene oligomerization product.

The product was analyzed by GC and had an activity of 2170kg/gCr. h, a selectivity for (1-hexene + 1-octene) of 88.9 wt% and a polymer selectivity of 0.13 wt%.

Example 8

Preparation of PNSiNP ligand: the relevant solvent is soaked by a molecular sieve for removing water before use.

Preparation of phosphine-nitrogen ligand: phosphine-nitrogen ligand L^eThe preparation of (1) was carried out as in example 1, with the difference that the compound of the structure II added was bis (4-methylphenyl) phosphonium chloride, the reaction solution containing the first product was purified using column chromatography (tetrahydrofuran elution, height to diameter ratio of 2.5), and then recrystallized at 72 ℃ (ethanol: ethyl acetate ═ 5:1) in the solvent, phosphine-nitrogen ligand L^eThe structure of (a) is as follows:

the above ligand (L)^e) The nuclear magnetic data for (c) are as follows:¹H NMR(400MHz，CDCl₃)：8.45(s，2H)，7.23～7.26(m，16H)，6.93(s，1H)，2.34(s，12H)

preparation of PNSiNP ligand: under the anhydrous and oxygen-free conditions, 44mmol of phosphine-nitrogen ligand L^eDissolving the mixture in 180ml of dichloromethane to obtain a reaction solution II; 30mmol of n-butyllithium was added dropwise to the reaction solution II under stirring at-78 deg.C, 20mmol of the compound represented by the formula III (dichlorodimethylsilane) and 2.4mmol of trifluoroacetic acid were further added thereto, the temperature was slowly raised to room temperature, and the reaction was continued for 69 hours under stirring. Purifying the reaction liquid by using column chromatography (tetrahydrofuran is used for leaching, and the height-diameter ratio is 2.5), then recrystallizing at 70 ℃ (the solvent is ethanol: ethyl acetate: 5:1), and treating the reaction liquid to obtain a product, namely the PNSiNP ligand L8, wherein the structure of L8 is shown as the following formula:

the nuclear magnetic data for the above ligand (L8) are as follows:¹H NMR(400MHz，CDCl₃)：8.42(s，4H)，7.21～7.27(m，32H)，2.33(s，24H)，0.16(s，6H)

oligomerization of ethylene:

before the reaction, a 500ml reaction kettle is heated to 155 ℃, vacuumized for 2 hours and replaced by nitrogen for three times. After the temperature is cooled to room temperature, the ethylene is replaced twice, 200ml of dehydrated and deoxidized solvent methylcyclohexane and 1.2ml of (Al/Cr ═ 600) MMAO-3a (7 wt% Al, n-heptane) are added, then 4.2 mu mol of phosphine-nitrogen ligand L8 and 3.5 mu mol of chromium acetylacetonate are added, and after the temperature is kept constant at 50 ℃, 0.5Mpa of hydrogen and 4.5MPa of ethylene are sequentially introduced to start the reaction. The reaction temperature is 50 ℃, and the reaction time is 60 min. After the reaction is finished, closing the ethylene inlet valve, using ice water bath or quickly cooling to below 5 ℃, slowly releasing pressure, and discharging the reactor to obtain the ethylene oligomerization product.

The product was analyzed by GC for an activity of 1933kg/gCr. h, a selectivity for (1-hexene + 1-octene) of 89.1 wt% and a polymer selectivity of 0.09 wt%.

Example 9

Preparation of PNSiNP ligand: the relevant solvent is soaked by a molecular sieve for removing water before use.

Preparation of phosphine-nitrogen ligand: phosphine-nitrogen ligand L^fThe preparation method of (3) is as in example 1. With the difference that the compound shown in structure II is bis (2-methoxyphenyl) phosphine chloride; the reaction solution containing the first product was purified using column chromatography (tetrahydrofuran elution with an aspect ratio of 2.5), followed by recrystallization at 70 ℃ (solvent ethanol: ethyl acetate ═ 5:1), phosphine-nitrogen ligand L^fThe structure of (a) is as follows:

the above ligand (L)^f) The nuclear magnetic data for (c) are as follows:¹H NMR(400MHz，CDCl₃)：8.45(s，2H)，6.99～7.34(m，16H)，6.93(s，1H)，3.83(s，12H)

preparation of PNSiNP ligand: under the anhydrous and anaerobic conditions, 42mmol of phosphine-nitrogen ligand L^fDissolving the mixture in 180ml of dichloromethane to obtain a reaction solution II; 32mmol of n-butyllithium was added dropwise to the reaction solution II under stirring at-78 deg.C, 20mmol of the compound represented by the formula III (dichlorodimethylsilane) and 2.2mmol of trifluoroacetic acid were further added thereto, the temperature was slowly raised to room temperature, and the reaction was continued for 68 hours under stirring. The reaction solution was purified using column chromatography (tetrahydrofuran elution,aspect ratio of 2.5), and then recrystallized at 78 deg.c (solvent is ethanol: ethyl acetate 8:1), and treating the reaction solution to obtain a product, namely the PNSiNP ligand L9, wherein the structure of L9 is shown as the following formula:

the nuclear magnetic data for the above ligand (L9) are as follows:¹H NMR(400MHz，CDCl₃)：8.40(s，4H)，6.99～7.27(m，32H)，3.83(s，24H)，0.15(s，6H)

oligomerization of ethylene:

before the reaction, a 500ml reaction kettle is heated to 160 ℃, vacuumized for 2 hours and replaced by nitrogen for three times. After the temperature is cooled to room temperature, the ethylene is replaced twice, 200ml of dehydrated and deoxidized solvent methylcyclohexane and 1.4ml of (Al/Cr ═ 700) MMAO-3a (7 wt% Al, n-heptane) are added, then 4.2 mu mol of phosphine-nitrogen ligand L10 and 3.5 mu mol of chromium acetylacetonate are added, and after the temperature is constant at 53 ℃, 0.5Mpa of hydrogen and 4.5MPa of ethylene are sequentially introduced to start the reaction. The reaction temperature is 53 ℃, and the reaction time is 60 min. After the reaction is finished, closing the ethylene inlet valve, using ice water bath or quickly cooling to below 5 ℃, slowly releasing pressure, and discharging the reactor to obtain the ethylene oligomerization product.

The product was analyzed by GC for activity 1362kg/gCr. h, (1-hexene + 1-octene) selectivity 88.5 wt%, polymer selectivity 0.06 wt%.

Example 10

Preparation of PNSiNP ligand: the related solvent is soaked in a sieve for removing water before use.

Preparation of phosphine-nitrogen ligand: phosphine-nitrogen ligand L^gThe preparation of (1) is as in example 1, except that the compound of structure II is 4- (trimethylsilyl) phenylphosphine chloride is added, the reaction solution containing the first product is purified using column chromatography (tetrahydrofuran elution, aspect ratio of 2.5), and then recrystallized at 70 ℃ (solvent ethanol: ethyl acetate ═ 8:1), phosphine-nitrogen ligand L^gThe structure of (a) is as follows:

the above ligand (L)^g) The nuclear magnetic data for (c) are as follows:¹H NMR(400MHz，CDCl₃)：8.45(s，2H)，7.36～7.40(m，16H)，6.93(s，1H)，0.25(s，36H)

preparation of PNSiNP ligand: under the anhydrous and oxygen-free conditions, 44mmol of phosphine-nitrogen ligand L^gDissolving the mixture in 180ml of dichloromethane to obtain a reaction solution II; at-78 ℃, 34mmol of n-butyllithium is dropwise added into the reaction liquid II under stirring, 20mmol of the compound (isopropyl methyl dichlorosilane) shown in the formula III structure and 2.2mmol of trifluoroacetic acid are continuously added into the reaction liquid II, then the temperature is slowly raised to the room temperature, and the reaction is continuously carried out for 45 hours under stirring. Purifying the reaction liquid by using column chromatography (tetrahydrofuran is used for leaching, and the height-diameter ratio is 2.5), then recrystallizing at 75 ℃ (the solvent is ethanol: ethyl acetate: 8:1), and treating the reaction liquid to obtain a product, namely the PNSiNP ligand L10, wherein the structure of L10 is shown as the following formula:

the nuclear magnetic data for the above ligand (L10) are as follows:¹H NMR(400MHz，CDCl₃)：8.49(s，4H)，7.36～7.40(m，32H)，0.92～1.78(m，7H)，0.25(s，72H)，0.13～0.5(s，3H)

oligomerization of ethylene: the oligomerization process was as in example 1.

The product was analyzed by GC for an activity of 1939kg/gCr. h, a selectivity for (1-hexene + 1-octene) of 89.5 wt% and a polymer selectivity of 0.08 wt%.

Example 11

Preparation of PNSiNP ligand: the relevant solvent is soaked by a molecular sieve for removing water before use.

Preparation of phosphine-nitrogen ligand: phosphine-nitrogen ligand L^hThe preparation of (1) is as in example 1, with the difference that the compound of the formula II added is 4- (tri-n-butylsilyl) phenylphosphine chloride, the reaction solution containing the first product is purified by column chromatography (tetrahydrofuran elution, aspect ratio of 2.5), and then recrystallized at 70 ℃ (solvent ethanol: acetic acid)Ethyl ester 10:1), phosphine-nitrogen ligand L^hThe structure of (a) is as follows:

the above ligand (L)^h) The nuclear magnetic data for (c) are as follows:¹H NMR(400MHz，CDCl₃)：8.45(s，2H)，7.36～7.40(m，16H)，6.93(s，1H)，0.90-1.45(m，108H)

preparation of PNSiNP ligand: under the anhydrous and anaerobic conditions, 46mmol of phosphine-nitrogen ligand L^hDissolving the mixture in 180ml of dichloromethane to obtain a reaction solution II; 30mmol of n-butyllithium was added dropwise to the reaction solution II under stirring at-78 deg.C, 20mmol of the compound represented by the formula III (dichlorodimethylsilane) and 2.4mmol of trifluoroacetic acid were further added thereto, the temperature was slowly raised to room temperature, and the reaction was continued for 71 hours under stirring. Purifying the reaction liquid by using column chromatography (tetrahydrofuran is used for leaching, and the height-diameter ratio is 2.5), then recrystallizing at 70 ℃ (the solvent is ethanol: ethyl acetate: 8:1), and treating the reaction liquid to obtain a product, namely the PNSiNP ligand L11, wherein the structure of L11 is shown as the following formula:

the nuclear magnetic data for the above ligand (L11) are as follows:¹H NMR(400MHz，CDCl₃)：8.51(m，4H)，7.31～7.39(m，32H)，0.90～1.45(m，216H)，0.15(s，6H)

oligomerization of ethylene: the oligomerization process was as in example 1.

The product was analyzed by GC, with an activity of 2625kg/gCr. h, a selectivity of (1-hexene + 1-octene) of 91.7 wt% and a polymer selectivity of 0.06 wt%.

Comparative example 1:

ligand L^ISynthesis ofⁱPr-PNP)

Adding 200mL of dichloromethane (treated by a molecular sieve) into a reaction bottle under anhydrous and oxygen-free conditions, then adding 220mmol of triethylamine (anhydrous) and 100mmol of isopropylamine (under the cooling of a low-temperature constant-temperature reaction bath, firstly slowly adding about 110mmol of diphenyl phosphine chloride, when the solution is stable and does not release heat violently, adding the rest 110mmol of diphenyl phosphine chloride, removing the low-temperature constant-temperature reaction bath, and stirring at room temperature for 12 hours.

After the reaction was completed, the solvent in the reaction flask was removed by using a rotary evaporator to obtain a cream yellow solid. The remaining solid product was dissolved in an appropriate amount of the mixed solution (ethanol: ethyl acetate ═ 5: 1). Performing column chromatography with neutral alumina column with length of about 10cm, eluting with ethanol, removing insoluble substances and unreacted phosphorus compounds, removing solvent from the obtained liquid with rotary evaporator, and further drying with vacuum pump to obtain white solid target ligand.¹H NMR(400MHz，CDCl₃)：7.24～7.35(m，20H)，3.68～3.80(m，1H),1.14(d，6H)

Oligomerization of ethylene: the oligomerization process was as in example 1.

The product was analyzed by GC, activity 780kg/gCr. h, (1-hexene + 1-octene) selectivity 63.5 wt%, polymer selectivity 0.5 wt%.