阅读说明：本技术 一种大位阻镍催化剂及其合成方法和应用 (High steric hindrance nickel catalyst and synthetic method and application thereof ) 是由 赵杰 薛新巧 于 2019-08-09 设计创作，主要内容包括：本发明属于化学合成技术领域,涉及一种大位阻镍催化剂及其合成方法和应用。该大位阻镍催化剂,其结构为邻位苯基乙烯基取代的α-二亚胺镍(Ⅱ)催化剂,可作为后过渡金属催化剂用于乙烯、苯乙烯的聚合过程。该大位阻镍催化剂,通过引入大位阻基团,有效保护催化剂金属中心的电子云密度,提高催化剂的活性,使得聚乙烯具有较高的支化度,同时,能够使单体更好的有立体选择性的插入,得到高度间同的立构聚苯乙烯。(The invention belongs to the technical field of chemical synthesis, and relates to a high steric hindrance nickel catalyst, and a synthesis method and application thereof. The structure of the nickel catalyst with large steric hindrance is ortho-phenyl vinyl substituted alpha-diimine nickel (II) catalyst which can be used as a late transition metal catalyst for the polymerization process of ethylene and styrene. According to the nickel catalyst with large steric hindrance, the electron cloud density of the metal center of the catalyst is effectively protected by introducing the large steric hindrance group, the activity of the catalyst is improved, the polyethylene has higher branching degree, and meanwhile, a monomer can be inserted into the catalyst with better stereoselectivity to obtain the high syndiotactic polystyrene.)

1. A nickel catalyst with large steric hindrance is characterized in that the catalyst is an ortho phenyl vinyl substituted alpha-diimine nickel (II) catalyst, and the structure of the catalyst is as follows:

Wherein R is₁、R₂、R₃Hydrogen, alkyl, C1-C5 alkyl, phenyl or phenethyl.

2. A method for synthesizing a high steric hindrance nickel catalyst is characterized by comprising the following steps:

(1) Mixing aniline and styrene according to a molar ratio of 1 (2-4), carrying out reflux reaction in xylene by using trifluoromethanesulfonic acid as a catalyst, removing a solvent, and carrying out separation treatment to obtain a phenylvinyl-substituted aniline substance;

(2) Mixing phenyl vinyl substituted aniline substances and butanedione according to a molar ratio of (3-4): 1, performing reflux reaction in absolute ethyl alcohol by using anhydrous formic acid as a catalyst, removing a solvent, and performing separation treatment to obtain an alpha-diimine ligand with a symmetrical structure;

(3) reacting alpha-diimine ligand with NiBr₂(DME) is mixed according to the molar ratio of 1 (1-2), dichloromethane is used as a solvent under the protection of nitrogen, stirring treatment is carried out, suspension is filtered, the obtained mother liquor is subjected to solvent removal treatment, ether washing is carried out, vacuum drying is carried out, and the alpha-diimine nickel (II) catalyst containing ortho-phenyl vinyl substitution is obtained.

3. the method for synthesizing a sterically hindered nickel catalyst as claimed in claim 2, wherein in step (1), the aniline is 2, 3-dimethylaniline.

4. The method for synthesizing the sterically hindered nickel catalyst according to claim 2, wherein in the step (1), the molar mass of the trifluoromethanesulfonic acid is 1-2 times that of aniline.

5. The method for synthesizing the sterically hindered nickel catalyst as claimed in claim 2, wherein the reflux reaction in step (1) is carried out at a temperature of 240 to 280 ℃ for 24 to 48 hours.

6. The method for synthesizing the sterically hindered nickel catalyst as claimed in claim 2, wherein in the step (2), the molar mass of the anhydrous formic acid is 4 to 20 times that of the butanedione.

7. The method for synthesizing the sterically hindered nickel catalyst as claimed in claim 2, wherein the reflux reaction in step (2) is carried out at a temperature of 50 ℃ to 60 ℃ for 24 hours to 48 hours.

8. The method for synthesizing the sterically hindered nickel catalyst as claimed in claim 2, wherein in the step (1), the separation treatment is carried out by a silica gel column chromatography method using a mixed solution of ethyl acetate and petroleum ether in a volume ratio of 1 (30-50); in the step (2), the separation treatment is carried out by adopting a silica gel column chromatography method by adopting a mixed solution of ethyl acetate and petroleum ether with a volume ratio of 1: 30.

9. The method for synthesizing the sterically hindered nickel catalyst as claimed in claim 2, wherein the stirring treatment in step (3) is carried out at room temperature for 10-24 hours.

10. The application of a nickel catalyst with large steric hindrance is characterized in that the nickel catalyst is used as a late transition metal catalyst in the polymerization process of ethylene and styrene.

Technical Field

The invention belongs to the technical field of chemical synthesis, and relates to a high steric hindrance nickel catalyst, and a synthesis method and application thereof.

Background

in real life, polyethylene and polystyrene products are indispensable commercial products, and have very wide application, such as various films, food packaging, wires and cables, high-performance fibers, medical supplies and the like. Meanwhile, since the discovery of alpha-diimine nickel catalysts by Brookhart et al, great interest has been generated in the design of homogeneous nickel-based polymerizations to obtain highly active, high molecular weight polyethylenes, or linear, highly branched polymer topologies, or stereoregularity controllable polystyrenes, etc. by designing different reaction conditions. However, when the existing late transition metal catalyst is used for catalytic polymerization, the catalyst activity is insufficient, so that the branching degree of a polymerization product cannot be effectively improved, and the stereoregularity of the polymerization product is controlled, so that the catalyst is limited in the actual use process.

Disclosure of Invention

The invention aims to provide a nickel catalyst with large steric hindrance, which has a structure of ortho-phenyl vinyl substituted alpha-diimine nickel (II) and high catalytic activity.

The invention also aims to provide a method for synthesizing the nickel catalyst with large steric hindrance, and the ortho-phenyl vinyl substituted alpha-diimine nickel (II) catalyst is effectively synthesized through multi-step reaction.

The invention also aims to provide the application of the nickel catalyst with large steric hindrance, so that the nickel catalyst can be used as a post-transition metal catalyst for polymerizing ethylene and styrene.

The technical scheme of the invention for solving the technical problems is as follows.

a kind of big steric hindrance nickel catalyst, this catalyst is ortho phenyl vinyl substituted alpha-diimine nickel (II) catalyst, its structure is:

Wherein R is₁、R₂、R₃hydrogen, alkyl, C1-C5 alkyl, phenyl or phenethyl.

A method for synthesizing a high steric hindrance nickel catalyst comprises the following steps:

(1) Preparation of phenylvinyl-substituted anilines: mixing aniline and styrene according to a molar ratio of 1 (2-4), performing reflux reaction at 240-280 ℃ for 24-48 h by using dimethylbenzene as a solvent and trifluoromethanesulfonic acid as a catalyst, removing the solvent in vacuum after the reaction is completed, and performing separation treatment by using a silica gel column chromatography method by using a mixed solution of ethyl acetate and petroleum ether with a volume ratio of 1 (30-50) to obtain a phenylvinyl-substituted aniline substance; furthermore, the aniline is 2, 3-dimethylaniline, and the molar mass of the trifluoromethanesulfonic acid is 1-2 times that of the aniline.

(2) Preparation of an α -diimine ligand having a symmetric structure: mixing phenyl vinyl substituted aniline substances with butanedione according to a molar ratio of (3-4): 1, performing reflux reaction at 50-60 ℃ for 24-48 h by using absolute ethyl alcohol as a solvent and anhydrous formic acid as a catalyst, removing the solvent in vacuum after the reaction is completed, and separating by using a silica gel column chromatography method to obtain an alpha-diimine ligand with a symmetrical structure, wherein the volume ratio of the mixed solution of ethyl acetate and petroleum ether is 1: 30; furthermore, the molar mass of the anhydrous formic acid is 4-20 times of that of the butanedione.

(3) Preparation of a catalyst containing o-phenylvinyl substituted nickel (II) alpha-diimine: reacting alpha-diimine ligand with NiBr₂(DME) is mixed according to the molar ratio of 1 (1-2), dichloromethane is used as a solvent under the protection of nitrogen, stirring reaction is carried out for 10-24 h at room temperature, suspension is filtered, the obtained mother liquor is subjected to solvent removal treatment, ether washing is carried out, vacuum drying is carried out, and powdery solid, namely the alpha-diimine nickel (II) catalyst containing ortho-phenyl vinyl substitution is obtained.

Specifically, the principle of the above synthesis reaction is as follows.

The application of a nickel catalyst with large steric hindrance is to use the catalyst as a late transition metal catalyst in the polymerization process of ethylene and styrene. The specific polymerization process is as follows.

In carrying out the ethylene polymerization, the reaction conditions were controlled as follows: the reaction temperature is 55-65 ℃, and the reaction time is 10-30 min; when the catalyst and the reaction conditions are utilized to catalyze the ethylene polymerization, the catalyst has higher catalytic activity which can reach 10⁶The gPE/(mol. Ni. h. bar), the obtained polyethylene also has higher branching degree which is as high as (140-150) branched chains/1000C; this is becauseDue to the existence of ortho-phenyl vinyl, the electron cloud density of the metal center of the catalyst is effectively protected by introducing a large steric hindrance group, so that the activity of the catalyst is improved, and the polymer has higher branching degree.

In carrying out the styrene polymerization, the reaction conditions were controlled as follows: the reaction temperature is 60-80 ℃, and the reaction time is 30-60 min; when the catalyst and the reaction conditions are utilized to catalyze the polymerization of the styrene, the catalyst has higher catalytic activity which can reach 10⁵The polystyrene obtained also has higher syndiotactic structure; the reason is that due to the existence of ortho-phenyl vinyl, the monomer can be inserted with better stereoselectivity by introducing large steric hindrance groups, and the styrene polymerization has high activity, so that the high syndiotactic polystyrene is obtained.

The nickel catalyst with large steric hindrance and the synthesis method thereof have the advantages that the catalyst is a post-transition metal catalyst for polymerization of ethylene and styrene, compared with a pre-transition metal catalyst, the post-transition metal catalyst has high electrophilicity, and a main catalyst is easy to synthesize and has stable performance; the catalyst has a structure of alpha-diimine nickel (II) substituted by ortho-phenyl vinyl, namely, bulky group phenyl vinyl containing carbon-carbon double bonds is introduced at the ortho position of an aromatic ring of an imine nitrogen atom, the metal center of the catalyst is effectively protected by utilizing the bulky volume of the phenyl vinyl, the instability of a ground state active center is increased, the process of inserting an ethylene monomer is accelerated, and the activity of the catalyst is improved; the steric effect of the bulky ligand, namely, the steric effect of the substituent greatly reduces the transfer rate of the active chain to the monomer and inhibits the chain walking during polymerization, so that the branched polyethylene with high molecular weight is obtained, the stereoselectivity insertion of the monomer can be better controlled, the activity on the polymerization of the styrene is high, and the highly syndiotactic polystyrene with higher regularity is obtained.

Drawings

FIG. 1 is a single crystal diffractogram of the ligand prepared in example 1 in a specific embodiment;

FIG. 2 is a carbon spectrum of syndiotactic styrene polymerization prepared in example 4 of this embodiment.

Detailed Description