CN114853819A - Trimetallic Schiff base complexes and their preparation methods and their application in catalyzing ring-opening copolymerization of epoxy compounds - Google Patents

Abstract

The invention belongs to the technical field of epoxy compound ring-opening copolymerization catalysis, in particular to a preparation method of a trimetal Schiff base aluminum complex. The trimetallic Schiff base aluminum complex is mainly prepared by the following steps: (1) 2,3,6,7,10,11-hexaaminotriphenylhexahydrochloride raw material is prepared by condensation reaction with salicylaldehyde raw material (2) The ligand is reacted with an aluminum source to obtain a trimetal Schiff base aluminum complex. The invention solves some of the deficiencies in the ring-opening copolymerization technology of epoxy compounds in the prior art, and provides a trimetal Schiff base-aluminum complex catalyst with the characteristics of high efficiency, high selectivity, low apparent activation energy and the like.

Description

Trimetallic Schiff base complexes and their preparation methods and their application in catalyzing ring-opening copolymerization of epoxy compounds

technical field

The invention belongs to the preparation method of Schiff base metal complexes and the application field thereof, in particular to a preparation method of a trimetal Schiff base aluminum complex, in particular to the catalyzing ring-opening of epoxy compounds, cyclic esters and acid anhydride compounds. Polymerization and its catalysis ring-opening copolymerization of epoxy compounds with carbon dioxide, acid anhydride compounds and cyclic ester compounds, and ring-opening polymerization of cyclic ester compounds.

technical background

As a bulk chemical product, polyester is closely related to our life. With the continuous development of society, the continuous progress of science and technology, the continuous improvement of people's living standards and the continuous improvement of environmental protection awareness. People's requirements for degradable chemical products are also increasing. As a common chemical product, polyester has been favored by scientific researchers in recent years because of its degradable properties. Functional polyesters prepared by ring-opening copolymerization of epoxy cyclic compounds and acid anhydride compounds have attracted much attention because of the relatively mild polymerization conditions and the diversity of polymerization products. This is due to the diversity of epoxy compounds and the diversity of acid anhydride compounds. As a derivative of petrochemical products, epoxy compounds have the characteristics of abundant product sources and low prices. at the same time

Epoxy compounds have rich structures and functional groups, large ring tension, and easy ring-opening polymerization, which provides a basis for the development of functional polymers. Like epoxy compounds, acid anhydrides have the characteristics of wide source of monomers and rich structure. The ring-opening copolymerization of epoxy compounds and acid anhydrides to prepare polyester is widely used because of its mild reaction conditions and relatively low equipment requirements. Based on the diversity of epoxy compounds and acid anhydride compounds, a series of functional polyesters with ring-opening copolymerization of epoxy compounds and acid anhydride compounds are derived, which can meet the application requirements under different conditions and provide a broad space for their related applications. .

In 1864, Hugo Schiff used aldehydes and amines to obtain compounds by condensation reaction and named them Schiff base. The compounds obtained by the condensation reaction of salicylaldehyde and its derivatives with diamine compounds are collectively referred to as Salen structures. A Schiff alkali metal complex obtained by coordinating a Salen type compound with a transition metal is called a Salen type metal complex. The Salen-M structure of Schiff alkali metal complex catalyst system has the advantages of simple synthesis method, easy operation, no complicated side reactions, and convenient purification to obtain higher purity compounds. At the same time, the raw materials are easily available, the ligands are easy to modify, and the price is relatively low, etc. Attract more and more researchers to conduct research. It has played an important role in the fields of ring-opening polymerization and ring-opening copolymerization. With the continuous development of scientific research, different kinds of Schiff base ligands and complexes of different metals have been continuously developed for the ring-opening polymerization of epoxy compounds and acid anhydride compounds. Polymetallic Schiff base metal complexes are also constantly being developed. Great progress has been made in catalyzing ring-opening polymerization and ring-opening copolymerization of epoxy compounds. With the continuous development of science and technology, people's requirements for polymer compounds are constantly increasing, and the derivative products of epoxy compounds are constantly enriched, and the demand for their products is increasing. At present, the application fields of epoxy compound-related products include surfactants, coatings, functional high-resolution films, hydrogels, etc., and are also playing an increasingly important role in medical, electronics, agriculture, construction and other industries.

Although the related ring-opening polymerization products of epoxy compounds are becoming more and more important in our daily life, the practical application efficiency of ring-opening polymerization of epoxy compounds is not very high at present. Efficiency and high cost limit the industrialization of new catalysts. Therefore, the focus of this field is to develop catalysts with high efficiency, high selectivity, and low cost, thereby reducing the cost of ring-opening copolymerization of epoxy compounds and acid anhydrides. The catalyst systems that have been developed so far mainly include non-metallic catalysts and metal catalysts, and metal catalysts include double metal cyanide catalysts, Schiff alkali metal coordination catalysts (Salen-M) and so on. Among them, Schiff base metal coordination catalysts are favored by scientific researchers due to their excellent catalytic performance, high cost performance, easy synthesis, and easy purification.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a trimetallic Schiff base complex and its application in catalyzing the ring-opening copolymerization of epoxy compounds and acid anhydride compounds. Some deficiencies in the prior art catalyzed ring-opening copolymerization of epoxy compounds are solved, and a trimetal Schiff base complex catalyst with high selectivity, high catalytic performance, low unsaturation, and low cost is obtained. .

In order to achieve the above object, the present invention adopts the following technical solutions:

A kind of trimetallic Schiff base complex, its structural formula is as follows:

，

,

Wherein, R ₁ and R ₂ are -H, ^-t Bu, -Br, -Cl, -OCH ₃ , -OC ₂ H ₅ , -N(C ₂ H ₅ ) ₂ and other groups, and X is -CH ₃ , -NO ₃ , -Cl, -OCH(CH ₃ ) ₂ and other groups, wherein R ₁ and R ₂ can be different. M is a metal such as Co, Fe, Al, Zn, Cr, Ni, and Mo.

The preparation method of above-mentioned trimetallic Schiff base complex comprises the following steps:

(1) Condensation of 2,3,6,7,10,11-hexaaminotriphenylhexahydrochloride with salicylaldehyde or salicylaldehyde derivative, and react at 50-80℃ for 6-12h.

(2) The Schiff base ligand obtained in (1) is subjected to a coordination reaction with a metal source (preferably an aluminum source), and the reaction is carried out at 25-80 ° C for 4-12 h to obtain a trimetallic Schiff base complex, wherein the metal It is Co, Al, Zn, Cr, Ni or Mo.

Further, the salicylaldehyde derivatives are: 3,5-di-tert-butyl salicylaldehyde, 3,5-diethylamino salicylaldehyde, o-vanillin, 3,5-dichlorosalicylaldehyde any of the following.

Further, the solvent of the condensation reaction in step (1) is preferably methanol or a mixed solution of methanol and dimethyl sulfoxide;

Further, in step (1), the molar ratio of 2,3,6,7,10,11-hexaaminotriphenylhexahydrochloride to salicylaldehyde or salicylaldehyde derivative is preferably 1:6-8;

Further, the condition of the condensation reaction in step ( ₁ ) is preferably carried out in an N atmosphere;

Further, the solvent of the coordination reaction in step (2) is preferably a toluene solvent;

Further, the reaction conditions of the coordination reaction in step (2) are preferably carried out in an atmosphere of N ₂ ;

Further, in step (2), the molar ratio of the Schiff base ligand to the aluminum source in the coordination reaction is preferably 1:3-6;

Further, the aluminum source of the coordination reaction in step (2) is preferably trimethylaluminum or diethylaluminum chloride.

The beneficial effects of the present invention are:

(1) The trimetal Schiff base complex of the present invention is used in the ring-opening copolymerization reaction of epoxy compounds, and is used as a catalyst for catalyzing the ring-opening copolymerization reaction of epoxy compounds and acid anhydride compounds.

(2) The trimetal Schiff base complex of the present invention is a catalyst for ring-opening copolymerization of epoxy compounds with excellent performance. When the trimetal Schiff base complex of the invention is used in the catalytic reaction, the amount of the required catalyst is small and the catalytic activity is high, and a novel trimetal Schiff base aluminum complex is provided for the ring-opening copolymerization of epoxy compounds. catalyst.

(3) When the trimetal Schiff base complex of the present invention catalyzes the ring-opening copolymerization of epoxy cyclohexane and maleic anhydride, it has lower apparent activation energy.

(4) The trimetal Schiff base complex of the present invention has a potential synergistic effect between metal aluminums, which can reduce the polymerization reaction time and further improve the catalytic effect of the trimetal Schiff base complex.

Description of drawings

Figure 1: hydrogen nuclear magnetic spectrum (HNMR) of the Schiff base aluminum complex of Example 1;

Figure 2: Infrared spectrum (FTIR) of Example 1 Schiff base ligand and Schiff base aluminum complex;

Figure 3: Triple quadrupole time-of-flight mass spectrum (MS) of the Schiff base aluminum complex of Example 1;

Fig. 4: the X-ray photoelectron spectroscopy (XPS) of embodiment 1 Schiff base aluminum complex;

Figure 5: Synthesis scheme of the Schiff base aluminum complex of Example 1.

Detailed ways:

The present invention will be further described below in conjunction with specific examples. It should be understood that the following examples are only used to illustrate the present invention and not to limit the scope of the present invention.

Example 1

The preparation method of the trimetal Schiff base aluminum complex catalyst for the ring-opening copolymerization of the catalyzed epoxy compound and the acid anhydride compound of the present embodiment is as follows:

(1) Dissolve 2,3,6,7,10,11-hexaaminotriphenylhexahydrochloride (0.20g 0.37mmol) in a mixed solution of methanol (20ml) and dimethyl sulfoxide (4ml), The above solution was slowly added dropwise ( _1-2 drops per second) in 3,5-di-tert-butylsalicylaldehyde (0.70 g, 2.98 mmol, 8 eq.) methanol ( 20ml) solution. The reaction was stirred at 50 °C under nitrogen protection for 18 h. After the reaction was completed, it was cooled to room temperature, filtered with suction and washed with a large amount of cold methanol solution to obtain a yellow solid powder, which was the trimetallic site Schiff base ligand.

(2) The ligand (0.56g, 0.35mmol, 1eq.) was dissolved in toluene (50ml) solution, and trimethylaluminum (4ml, 1M in hexane, 4eq.) was slowly added under an ice-water bath in a nitrogen atmosphere, Slow reaction at room temperature for 24h. Most of the solvent was removed by rotary evaporation, centrifuged and washed with a large amount of toluene to obtain an orange-red solid powder, which is the final product-a trimetallic Schiff base aluminum complex, which was dried in a vacuum drying oven at 50°C for 12h.

Example 2

(1) Dissolve 2,3,6,7,10,11-hexaaminotriphenylhexahydrochloride (0.20g 0.37mmol) in a mixed solution of methanol (20ml) and dimethyl sulfoxide (4ml), The above solution was slowly added dropwise ( _1-2 drops per second) in 3,5-diethylammonium salicylaldehyde (0.78 g, 2.98 mmol, 8 eq.) methanol ( 20 ml) solution. The reaction was stirred at 50 °C under nitrogen protection for 18 h. After the reaction is completed, it is cooled to room temperature, filtered with suction and washed with cold methanol to obtain a solid powder which is a Schiff base ligand at a trimetallic site.

(2) The ligand (0.63g, 0.35mmol, 1eq.) was dissolved in toluene (50ml) solution, and trimethylaluminum (4ml, 1M in hexane, 4eq.) was slowly added under an ice-water bath in a nitrogen atmosphere, Slow reaction at room temperature for 24h. Most of the solvent was removed by rotary evaporation, centrifuged and washed with a large amount of toluene to obtain a solid powder which is the final product-a trimetallic Schiff base aluminum complex, which was dried in a vacuum drying oven at 50°C for 12h.

Example 3

Dissolve 2,3,6,7,10,11-hexaaminotriphenylhexahydrochloride (0.20g 0.37mmol) in a mixed solution of methanol (20ml) and dimethyl sulfoxide (4ml) under _N2 Under protective conditions, the above solution was slowly added dropwise (1-2 drops per second) to 3,5-diethylammonium salicylaldehyde (0.78g, 2.98mmol, 8eq.) methanol (20ml) using a constant pressure dropping funnel in the solution. The reaction was stirred at 50 °C under nitrogen protection for 18 h. After the reaction is completed, it is cooled to room temperature, filtered with suction and washed with cold methanol to obtain a solid powder which is a Schiff base ligand at a trimetallic site.

(2) Dissolve the ligand (0.63g, 0.35mmol, 1eq.) in a mixed solution of methanol and dichloromethane (50ml), slowly add cobalt acetate (0.17g, 1.40mmol, 4eq.), and slowly react at room temperature 24h. Most of the solvent was removed by rotary evaporation, centrifuged and washed with a large amount of toluene to obtain the final product - trimetallic Schiff base cobalt complex, which was dried in a vacuum drying oven at 50°C for 12h.

Application example 1

The catalyst used in this example is the trimetal Schiff base aluminum complex prepared in Example 1, and the step of catalyzing the ring-opening copolymerization of epoxy compound and acid anhydride compound is as follows:

Add a stirrer to the Schlenk tube, and add three catalysts in sequence according to the ratio of catalyst: cocatalyst (bis(triphenylphosphoranyl) ammonium chloride): epoxy cyclohexane: maleic anhydride = 1:3:3000:900 Metal Schiff base aluminum complex (5.70 mg), bis(triphenylphosphoranyl)ammonium chloride (5.70 mg), epoxycyclohexane (1.00 ml), maleic anhydride (0.29 g). Freeze-pump-thaw method was used to remove the air in the airtight Schlenk tube under nitrogen protection. Add it to a pre-set 80°C oil bath and stir for 7 hours. After the reaction is complete, stop stirring and heating, cool to room temperature, take out the copolymerization product, dissolve the product with a small amount of dichloromethane, filter to remove the residual catalyst, and then precipitate with methanol and separate it. , the obtained product was vacuum-dried at 50 °C to constant weight to obtain a copolymerized product. The number-average molecular weight Mn was measured to be 8.20KDa, and the PDI was 1.24.

Comparative Example 1

The method for the ring-opening copolymerization of epoxy compound and acid anhydride compound catalyzed by the single metal Schiff base aluminum complex of the present embodiment, the steps are as follows:

Add a stirrer to the Schlenk tube, and in turn, add monosodium glutamate in the ratio of catalyst: cocatalyst (bis(triphenylphosphoranyl) ammonium chloride): epoxy cyclohexane: maleic anhydride = 1:1:1000:300 Metal Schiff base aluminum complex (4.10 mg), bis(triphenylphosphoranyl)ammonium chloride (5.65 mg), epoxycyclohexane (1.00 ml), maleic anhydride (0.29 g). Freeze-pump-thaw method was used to remove the air in the airtight Schlenk tube under nitrogen protection. Add it to a pre-set oil bath at 80°C and stir for 9 hours. After the reaction is complete, stop stirring and heating, cool to room temperature, take out the copolymerized product, dissolve the product with a small amount of dichloromethane, filter to remove the residual catalyst, and then precipitate with methanol and separate it. , the obtained product was vacuum-dried at 50 °C to constant weight to obtain a copolymerized product. The number-average molecular weight Mn was measured to be 6.70KDa, and the PDI was 1.53.

The synthesis method of this single metal Schiff base aluminum complex is as follows: (1) Dissolve o-phenylenediamine (0.27 g, 2.50 mmol) in methanol solution (50 ml), slowly add o-phenylenediamine methanol solution dropwise to 3 , 5-Di-tert-butylsalicylaldehyde (1.19 g, 5.10 mmol) in methanol (50 ml). The reaction was carried out at 70 °C for 8 h, and the yellow solid was obtained by filtration, which was washed 2-3 times with cold methanol solution. Dry in a vacuum oven at 50 °C for 12 h to obtain a single metal site Schiff base intermediate. (2) Dissolve the single metal site Schiff base intermediate (1.35 g, 2.50 mmol) in toluene (50 ml) solution, and slowly add trimethylaluminum (3.00 ml, 1M in hexane) under an ice-water bath in a nitrogen atmosphere. , 3.00 mmol), and reacted slowly for 24 h at room temperature. Most of the solvent was removed by rotary evaporation, centrifuged and washed with a large amount of toluene to obtain a solid powder, which is the final product-monometallic Schiff base aluminum complex, which was dried in a vacuum drying oven at 50 °C for 12 h.

As shown in application example 1 and comparative example 1: comparing the single-metal Schiff base aluminum complex catalyst and the trimetal Schiff base aluminum complex catalyst, the unit metal activation center corresponds to the same catalytic ratio, temperature, monomer, etc. The same reaction condition. It can be seen that the trimetal Schiff base aluminum complex has better catalytic effect than the single metal Schiff base aluminum complex. Specifically, the catalyzed ring-opening copolymerization of epoxycyclohexane and maleic anhydride has higher number average molecular weight, lower polydispersity, and shorter time required to complete the reaction. This is due to the synergistic effect between the three metals in the trimetal Schiff base aluminum complex, which improves the catalytic performance.

Application example 2

The catalyst used in this example is the trimetal Schiff base aluminum complex prepared in Example 1, and the step of catalyzing the ring-opening copolymerization of epoxy compound and acid anhydride compound is as follows:

Add a stirrer to the Schlenk tube, and sequentially add trimetallic catalyst in the ratio of catalyst: cocatalyst (bis(triphenylphosphoranyl) ammonium chloride): epoxy cyclohexane: NA anhydride = 1:3:3000:900 Schiff base aluminum complex (5.70 mg), bis(triphenylphosphoranyl)ammonium chloride (5.70 mg), epoxycyclohexane (1.00 ml), NA anhydride (0.49 g). Freeze-pump-thaw method was used to remove the air in the airtight Schlenk tube under nitrogen protection. Add it to a pre-set 80°C oil bath and stir for 12 hours. After the reaction is complete, stop stirring and heating, cool to room temperature, take out the copolymerized product, dissolve the product with a small amount of dichloromethane, filter to remove the residual catalyst, and then separate it after precipitation with methanol. , the obtained product was vacuum-dried at 50 °C to constant weight to obtain a copolymerized product. The number-average molecular weight Mn was measured to be 3.30KDa, and the PDI was 1.31.

Application example 3

The catalyst used in this example is the trimetal Schiff base aluminum complex prepared in Example 1, and the step of catalyzing the ring-opening copolymerization of epoxy compound and acid anhydride compound is as follows:

Add a stirrer to the Schlenk tube, and then add trimetal Schiff base in the ratio of catalyst: cocatalyst (bis(triphenylphosphoranyl) ammonium chloride): AGE: maleic anhydride = 1:3:3000:900 Aluminum complex (5.70 mg), bis(triphenylphosphoranyl)ammonium chloride (5.70 mg), allyl glycidyl ether (1.17 ml), maleic anhydride (0.29 g). Freeze-pump-thaw method was used to remove the air in the airtight Schlenk tube under nitrogen protection. Add a pre-set 80 ℃ oil bath to stir the reaction for 12 hours. After the reaction is completed, stop stirring and heating, cool to room temperature, take out the copolymerization product, dissolve the product with a small amount of dichloromethane, filter to remove the residual catalyst, and then precipitate with methanol and then separate, The obtained product was vacuum dried at 50°C to constant weight to obtain a copolymerized product. The number-average molecular weight Mn was measured to be 7.10KDa, and the PDI was 1.44.

Application example 4

The catalyst used in this example is the trimetal Schiff base aluminum complex prepared in Example 1, and the step of catalyzing the ring-opening copolymerization of epoxy compound and acid anhydride compound is as follows:

Add a stirrer to the Schlenk tube, and add trimetallic mats in the ratio of catalyst: cocatalyst (bis(triphenylphosphoranyl) ammonium chloride): epichlorohydrin: maleic anhydride = 1:3:3000:900 Aluminium complex (5.70mg), bis(triphenylphosphoranyl)ammonium chloride (5.70mg), epichlorohydrin (0.86ml), maleic anhydride (0.29g). Freeze-pump-thaw method was used to remove the air in the airtight Schlenk tube under nitrogen protection. Add a pre-set 80 ℃ oil bath to stir the reaction for 12 hours. After the reaction is completed, stop stirring and heating, cool to room temperature, take out the copolymerization product, dissolve the product with a small amount of dichloromethane, filter to remove the residual catalyst, and then precipitate with methanol and then separate, The obtained product was vacuum dried at 50°C to constant weight to obtain a copolymerized product. The number-average molecular weight Mn was measured to be 2.80KDa, and the PDI was 1.42.

The above examples show and describe the basic principles and main features of the present invention and examples of applications of the present invention. Those skilled in the art should understand that the present invention is not limited by the above-mentioned implementation regulations, and the above-mentioned implementation regulations and descriptions only describe the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will Various indiscriminate improvements and tweaks. Such improvements and adjustments fall within the scope of the claimed invention. The claimed scope of the present invention is defined by the appended claims and their equivalents.

Claims (8)

1. a trimetallic Schiff base complex, is characterized in that: structural formula is as follows:

, Wherein, R ₁ and R ₂ are -H, ^-tBu , -Br, -Cl, -OCH ₃ or -N(C ₂ H ₅ ) ₂ , and X is -CH ₃ , -NO ₃ , -Cl or -OCH (CH ₃ ) ₂ , M is Co, Al, Zn, Cr, Ni or Mo. 2. a preparation method of trimetal Schiff base complex as claimed in claim 1, is characterized in that: comprise the following steps: (1) Condensation of 2,3,6,7,10,11-hexaaminotriphenylhexahydrochloride with salicylaldehyde or salicylaldehyde derivatives, and react at 50-80°C for 6-12 h; (2) The trimetallic site Schiff base ligand obtained in (1) is subjected to a coordination reaction with a metal source, and the reaction is carried out at 25-80 °C for 4-12 h to obtain a trimetallic Schiff base complex, wherein the metal is Co, Al, Zn, Cr, Ni or Mo. 3. the preparation method of trimetallic Schiff base complexes according to claim 2 is characterized in that: 2,3,6,7,10,11-hexaaminotriphenylhexahydrochloride and salicylaldehyde or water The molar ratio of the aldehyde derivative is 1:6-8. 4. the preparation method of trimetallic Schiff base complex according to claim 2, is characterized in that: described salicylaldehyde derivative is 3,5-di-tert-butyl salicylaldehyde, 3,5-di-tert-butyl salicylaldehyde Any one of ethylamino salicylaldehyde, o-vanillin and 3,5-dichlorosalicylaldehyde. 5. the preparation method of trimetallic Schiff base complex according to claim 2, is characterized in that: the mol ratio of described Schiff base ligand and metal source is 1:3-6; The solvent is toluene. 6. An application of the trimetallic Schiff base complex according to claim 1, characterized in that: it is used for the ring-opening copolymerization of epoxy compounds. 7. the application of the trimetallic Schiff base complex as claimed in claim 6, is characterized in that: multiple epoxy compounds and acid anhydride compounds are opened under the combined action of trimetallic Schiff base complex catalyst and cocatalyst. Ring copolymerization to prepare polyesters. 8 . The application of the trimetal Schiff base aluminum complex according to claim 7 , wherein the cocatalyst is bistriphenylphosphine ammonium chloride, and the ring-opening copolymerization reaction temperature is 25-110° C. 9 .

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