CN101418006A - N-aryloxy functionalized ketimine rare earth metal amido and catalytic use thereof - Google Patents

Abstract

The invention discloses N-aryloxo-functionalized beta-ketoimio rare earth metal amides containing two rare earth metals and two N-aryloxo-functionalized beta-ketoimio ligands. The N-aryloxo-functionalized beta-ketoimio rare earth metal amides can be represented by a general formula of [{ONArO}Ln[N(SiMe3)2}(THF)]2, wherein Ln is a rare earth metal selected from neodymium(Nd), samarium (Sm), ytterbium(Yb) and yttrium (Y); and [ONArO]=(2-O-5-R-C6H3)N=C(CH3)CH=CO(CH3), wherein R is selected from alkyl groups having 1 to 5 carbon atoms. The N-aryloxo-functionalized beta-ketoimio rare earth metal catalysts can serve as single component catalysts under a mild condition to catalyze ring-opening polymerization of epsilon-caprolactone actively with high efficiency to obtain plycaprolactone with high and evenly distributed molecular weight.

Description

N-aryloxy functionalized ketimine-based rare earth metal amides and their catalytic applications

technical field

The invention relates to a ketimine-based rare earth metal amide, in particular to an N-aryloxy functionalized ketimine-based rare earth metal amide and its catalytic application.

Background technique

Aliphatic polyester is a class of biodegradable polymer materials, which can be degraded under physiological conditions, and the degradation products are non-toxic. Therefore, it has been used clinically as a compatible material for biological tissues. For example, polycaprolactone, because of its high solubility, low melting point, and compatibility with various polymers, can be used as a polymer Plasticizers, etc.; polylactic acid, because of its characteristics, is widely used in drug controlled release systems, orthopedic fixation materials, and tissue engineering scaffold materials. In view of some broad application prospects of aliphatic polyesters, its research has received widespread attention.

Ring-opening polymerization is a convenient method for the synthesis of aliphatic polyesters. People have developed many catalytic systems for the ring-opening polymerization of cyclic esters. The catalysts used can be alkoxy compounds, alkyl compounds, amino compounds and borohydride compounds of main group metals, transition metals and rare earth metals, among which Some rare earth metal complexes have attracted much attention because of their definite structure and can be used as one-component catalysts, such as:

McLain et al. from DuPont Company first discovered that single-component alkoxy rare earth metal compounds Y ₅ (O)(CHMe ₂ ) ₁₃ and Y(CH ₂ CH ₂ OEt) ₃ can catalyze the ring-opening polymerization of caprolactone at room temperature, And has the characteristics of active polymerization (see: McLain, SJ; Drysdale, NE Polym. Prepr. 1992, 33, 174);

Shen Zhiquan et al reported that the triisopropoxy rare earth metal compound Ln(O ⁱ Pr) ₃ is an effective catalyst for the ring-opening polymerization of caprolactone (see: Shen, YQ; Shen, ZQ; Zhang, FY; Zhang, YFPolym.J. 1995, 27, 59), and found that [CH ₃ C(O)CHC(O)CH ₂ CH ₃ ] ₂ Ln(O ⁱ Pr) can inhibit the transesterification reaction in the polymerization process, and can catalyze the active polymerization of caprolactone (See: Shen, YQ; Shen, ZQ; Zhang, YF; Yao, KM Macromolecules 1996, 29, 8289);

Yasuda et al. have also reported that rare earth metal methyl compounds, hydrides and alkyl compounds can catalyze caprolactone active polymerization (referring to: Yamashita, M.; Takemoto, Y.; Ihara, E.; Yasuda, H.Macromolecules 1996, 29, 1798);

Other single-component rare earth metal catalysts for caprolactone ring-opening polymerization also have divalent rare earth metal complexes (referring to: Evans, WJ; Katsumata, H.Macromolecules 1994,27,2330; Evans, WJ; Katsumata, H. Macromolecules 1994, 27, 4011; Nishiura, M.; Hou, ZM; Koizumi, T.; Imamoto, T.; Wakatsuki, Y.Maromolecules 1999, 32, 8245), metacene rare earth metal amides (see: Xue Mingqiang, Mao Lisheng, Shen Qi, Ma Jiale, Applied Chemistry 1999, 16, 102; Xue Mingqiang, Shen Qi, Zhang Zhenjiang, Mao Lisheng, Chinese Journal of Rare Earth 1999, 17, 498), Ln[N(SiMe ₃ ) ₂ ] ₃ (see: Martin, E.; Dubois, P.; Jerome, R. Macromolecules 2000, 33, 1530), Sc(OTf) ₃ (see: Nomura, N.; Taira, A.; Tomioka, T.; Okuda, M. Macromolecules 2000, 33, 1497), triamidine rare earth complexes (see: Luo, YJ; Yao, YM; Shen, Q.; Sun, J.; Weng, LHJ Organomet.Chem.2002, 662, 144) and triguanidine rare earth metal Complexes (see: Zhou, LY; Sun, HM; Chen, JL; Yao, YM; Shen, QJ Polym. Sci., Part A: Polym. Chem. 2005, 43, 1778) and the like.

So far, in the application of metal complexes with ketimine groups as auxiliary ligands in the catalysis of ester polymerization reported in the literature, the central metals are mainly concentrated in the main group metals magnesium, aluminum, and transition metals titanium, zirconium, nickel, niobium . In addition to our recent report that N-aryloxy-functionalized ketimine-based rare earth metal aryl oxides can catalyze the ring-opening polymerization of lactide (see: Peng, H.M.; Yao, Y.M.; Zhang, Y.; Shen, Q. Inorg.Chem.2008, 47, 9828), there is no report that other ketimine-based rare earth metal complexes are used as single-component catalysts to catalyze the polymerization of other ester monomers.

Contents of the invention

The purpose of the present invention is to provide a kind of N-aryloxy functionalized ketimine base rare earth metal amides, to improve the catalytic activity of ε-caprolactone ring-opening polymerization catalyst, make reaction conditions milder, and improve the polymerization product molecular weight.

In order to achieve the above object, the technical solution adopted in the present invention is: a kind of N-aryloxy functionalized ketimine group rare earth metal amides, containing two rare earth metals and two N-aryloxy functionalized ketimine groups The ligand can be represented by the following general formula:

[{ONArO}Ln{N(SiMe ₃ ) ₂ }(THF)] ₂ ;

Wherein Ln is a rare earth metal, selected from one of neodymium (Nd), samarium (Sm), ytterbium (Yb) or yttrium (Y); [ONArO]=(2-O-5-RC ₆ H ₃ )N =C(CH ₃ )CH=CO(CH ₃ ), wherein R is selected from C ₁ to C ₅ alkyl groups, and [ONArO]H ₂ is expressed by the following structural formula:

In a preferred technical solution, R is selected from one of methyl, ethyl, propyl or tert-butyl.

The preparation method of the above-mentioned N-aryloxy functionalized ketimine based rare earth metal amides comprises the following steps:

(1) Under anhydrous and oxygen-free conditions, dissolve the N-aryloxy functionalized ketimine ligand [ONArO]H ₂ with Ln[N(SiMe ₃ ) ₂ ] ₃ (μ-Cl)Li(THF) ₃ In a solvent, then react at 0°C to 40°C for 20 minutes;

(2) The reaction product is precipitated from the solution, and the mother liquor is removed by centrifugation. The precipitated powder is dissolved in tetrahydrofuran, concentrated and cooled to -5°C to obtain [{ONArO}Ln{N(SiMe ₃ ) ₂ }(THF)] ₂ crystals.

In the above technical scheme, the preparation methods of N-aryloxy functionalized ketimine ligand [ONArO]H ₂ and Ln[N(SiMe ₃ ) ₂ ] ₃ (μ-Cl)Li(THF) ₃ are both existing Technology, wherein the preparation method _{of N-aryloxy functionalized ketimine ligand [ONArO]H 2} see: Peng, HM; Yao, YM; Zhang, Y.; Shen, Q.Inorg.Chem.2008, 47, 9828; Preparation of Ln[N(SiMe ₃ ) ₂ ] ₃ (μ-Cl)Li(THF) ₃ See: Zhou, SL; Wang, SW; Yang, GS; Liu, XY; Sheng, EH; Zhang, KH ; Cheng, L.; Huang, ZX Polyhedron 2003, 22, 1019;

In the preferred technical scheme, N-aryloxy functionalized ketimine ligand [ONArO]H ₂ and Ln[N(SiMe ₃ ) ₂ ] ₃ (μ-Cl)Li(THF) ₃ are equimolar; the solvent is tetrahydrofuran A mixed solvent with toluene, the ratio of furan and toluene in the mixed solvent is 1:1 by volume.

The present invention also relates to the application of the N-aryloxy functionalized ketimine-based rare earth metal amides as a single-component catalyst in catalyzing the ring-opening polymerization of ε-caprolactone.

A method for catalyzing the ring-opening polymerization of ε-caprolactone, comprising the following steps:

Under anhydrous and oxygen-free conditions, mix the solvent and ε-caprolactone monomer, add the solution of the catalyst under vigorous stirring, the molar ratio of ε-caprolactone and the catalyst is 50:1～800:1; after the polymerization is completed, use Containing the alcohol termination of volume fraction 5% hydrochloric acid;

Wherein, the polymerization temperature is 0° C. to 120° C., and the pKa value of the solvent is smaller than the pKa value of the ligand coordinated with the rare earth ion.

The preferred technical solution is that the polymerization temperature is 25°C to 70°C, and the solvent is selected from toluene, benzene, tetrahydrofuran or ethylene glycol dimethyl ether.

In the above, the polymerization system must remove oxygen and water, and be protected with an inert gas. The inert gas can be argon or nitrogen; the solvent used should not contain active hydrogen, that is, its pKa value is lower than the pKa of the ligand coordinated with the rare earth metal ion value.

The molecular weight and molecular weight distribution measuring method of polymer among the present invention comprise the following steps: polymer is made into the tetrahydrofuran solution of required concentration, measure molecular weight and molecular weight distribution on the PL-50 type gel permeation chromatograph produced by PL company. Test conditions: temperature 40°C, tetrahydrofuran as eluent, flow rate of eluent 1.0 ml/min, polystyrene standard sample for molecular weight calibration.

Due to the use of the above-mentioned technical solutions, the present invention has the following advantages compared with the prior art:

1. The N-aryloxy functionalized ketimine-based rare earth metal catalysts provided by the present invention can be used as single-component catalysts under mild conditions to catalyze the ring-opening polymerization of ε-caprolactone with high activity to obtain high molecular weight (Mn> 10 ⁴ ), polycaprolactone with moderate molecular weight distribution (Mw/Mn=1.47～2.28)

2. The synthesis process of the catalyst of the present invention is simple and the yield is high.

Detailed ways

The present invention will be further described below in conjunction with embodiment:

Example 1: Synthesis of [{ONArO}Ln{N(SiMe ₃ ) ₂ }(THF)] ₂ ; the substituent at the 5th position on the aromatic ring is a methyl group) (taking Ln=Sm as an example)

Add 2.70 mmol of Sm[N(SiMe ₃ ) ₂ ] ₃ (μ-Cl)Li(THF) ₃ (1.81 g) in tetrahydrofuran to 2.70 mmol of [ONArO]H ₂ (0.55 g) in toluene , the reaction system immediately became clear, the color was brownish yellow, stirred and reacted at 0°C for 20 minutes, yellow powder gradually precipitated in the clear solution, concentrated slightly, centrifuged, separated the precipitated powder from the mother liquor, dissolved with an appropriate amount of tetrahydrofuran, and kept in the refrigerator overnight , 1.31 g (1.12 mmol) of a large number of yellow crystals were precipitated, and the yield was 83%.

Example 2: Synthesis of [{ONArO}Ln{N(SiMe ₃ ) ₂ }(THF)] ₂ ; the 5-position substituent on the aromatic ring is methyl) (taking Ln=Y as an example)

Add 1.68 mmoles of Y[N(SiMe ₃ ) ₂ ] ₃ (μ-Cl)Li(THF) ₃ (1.02 g) in tetrahydrofuran to 1.68 mmoles of [ONArO]H ₂ (0.34 g) in toluene , the reaction system immediately became clear, the color was dark yellow, stirred and reacted at 0°C for 20 minutes, yellow powder gradually precipitated from the clear solution, concentrated slightly, centrifuged, separated the precipitated powder from the mother liquor, dissolved with an appropriate amount of tetrahydrofuran, and stood at room temperature , 0.74 g (0.71 mmol) of a large number of yellow crystals were precipitated, and the yield was 85%.

Example 3: Synthesis of [{ONArO}Ln{N(SiMe ₃ ) ₂ }(THF)] ₂ ; the 5-position substituent on the aromatic ring is methyl) (taking Ln=Yb as an example)

Add 2.10 mmol of Yb[N(SiMe ₃ ) ₂ ] ₃ (μ-Cl)Li(THF) ₃ (1.45 g) in tetrahydrofuran to 2.10 mmol of [ONArO]H ₂ (0.43 g) in toluene , the reaction system immediately became clear, the color was dark yellow, stirred and reacted at 0°C for 20 minutes, yellow powder gradually precipitated from the clear solution, concentrated slightly, centrifuged, separated the precipitated powder from the mother liquor, dissolved with an appropriate amount of tetrahydrofuran, and stood at room temperature , 1.12 g (0.92 mmol) of a large number of yellow crystals were precipitated, and the yield was 88%.

Example 4: Synthesis of [{ONArO}Ln{N(SiMe ₃ ) ₂ }(THF)] ₂ ; the 5-position substituent on the aromatic ring is tert-butyl) (taking Ln=Nd as an example)

Add 2.16 mmoles of Nd[N(SiMe ₃ ) ₂ ] ₃ (μ-Cl)Li(THF) ₃ (1.43 g) in tetrahydrofuran to 2.16 mmoles of [ONArO]H ₂ (0.53 g) in toluene , the reaction system immediately became clear, the color was blue, stirred and reacted at 0°C for 20 minutes, blue broken crystals gradually precipitated in the clear solution, concentrated slightly, centrifuged, separated the mother liquor and the precipitated broken crystals, dissolved with an appropriate amount of tetrahydrofuran/toluene, After overnight at room temperature, a large amount of blue crystals, 1.05 g (0.84 mmol), were precipitated, with a yield of 78%.

Example 5: Synthesis of [{ONArO}Ln{N(SiMe ₃ ) ₂ }(THF)] ₂ ; the 5-position substituent on the aromatic ring is tert-butyl) (taking Ln=Y as an example)

Add 1.84 mmol of Y[N(SiMe ₃ ) ₂ ] ₃ (μ-Cl)Li(THF) ₃ (1.12 g) in tetrahydrofuran to 1.84 mmol of [ONArO]H ₂ (0.45 g) in toluene , the reaction system immediately became clear, the color was dark yellow, stirred and reacted at 0°C for 20 minutes, yellow powder gradually precipitated in the clear solution, concentrated slightly, centrifuged, separated the precipitated powder from the mother liquor, dissolved with an appropriate amount of tetrahydrofuran/toluene, and precipitated at room temperature A large number of yellow crystals 0.85 g (0.75 mmol), yield 82%.

Example 6: Synthesis of [{ONArO}Ln{N(SiMe ₃ ) ₂ }(THF)] ₂ ; the 5-position substituent on the aromatic ring is tert-butyl) (taking Ln=Yb as an example)

Add 1.56 mmoles of Yb[N(SiMe ₃ ) ₂ ] ₃ (μ-Cl)Li(THF) ₃ (1.08 g) in tetrahydrofuran to 1.56 mmoles of [ONArO]H ₂ (0.39 g) in toluene , the reaction system immediately became clear, the color was dark yellow, stirred and reacted at 0°C for 20 minutes, yellow powder gradually precipitated in the clear solution, concentrated slightly, centrifuged, separated the precipitated powder from the mother liquor, dissolved with an appropriate amount of tetrahydrofuran/toluene, and precipitated at room temperature A large number of yellow crystals 0.85 g (0.68 mmol), yield 87%.

Example 7: [{ONArO}Sm{N(SiMe ₃ ) ₂ }(THF)] ₂ ; the substituent at the 5th position on the aromatic ring is a methyl group) catalyzed ring-opening polymerization of ε-caprolactone

Add 9.6 mg of catalyst to a dehydration and deoxygenation polymerization bottle with stirring bar, add 2.20 ml of toluene with a syringe, stir in an oil bath at 50°C for 2 minutes and dissolve, then add 0.54 ml of ε-caprolactone (4.91 mg Moore). The polymerization system was solidified in 3 minutes, kept at 50° C. for 2 hours, and terminated with alcohol containing 5% hydrochloric acid. The polymer was precipitated with denatured alcohol, and vacuum-dried to constant weight to obtain 0.56 g of polycaprolactone with a yield of 100%. The theoretical molecular weight of the polymer is 34,000 [M _n (calcd) = (M _w of ε-CL) × [ε-CL]/[Ln] × (polymer yield) = 114 × 300 × 100%], GPC measured The average molecular weight (M _n ) was 61,000, and the molecular weight distribution (M _w /M _n ) was 1.64.

Example 8: [{ONArO}Y{N(SiMe ₃ ) ₂ }(THF)] ₂ ; the 5-position substituent on the aromatic ring is methyl) catalyzed ring-opening polymerization of ε-caprolactone

Add 17.5 mg of catalyst to a polymerization bottle with a stirring bar after dehydration and deoxygenation, add 2.95 ml of toluene with a syringe, stir in an oil bath at 50°C for 2 minutes and dissolve, then add 0.74 ml of ε-caprolactone (6.69 mg Moore). The polymerization system was solidified in 3 minutes, kept at 50° C. for 2 hours, and terminated with alcohol containing 5% hydrochloric acid. The polymer was precipitated with denatured alcohol, and vacuum-dried to constant weight to obtain 0.53 g of polycaprolactone, with a yield of 69%. The theoretical molecular weight of the polymer is 16,000 [M _n (calcd) = (M _w of ε-CL) × [ε-CL]/[Ln] × (polymer yield) = 114 × 200 × 69%], GPC measured The average molecular weight (M _n ) was 67,000, and the molecular weight distribution (M _w /M _n ) was 2.24.

Example 9: [{ONArO}Y{N(SiMe ₃ ) ₂ }(THF)] ₂ ; the 5-position substituent on the aromatic ring is tert-butyl) catalyzed ring-opening polymerization of ε-caprolactone

Add 12.6 mg of catalyst to a polymerization bottle with a stirring bar after dehydration and deoxygenation, add 1.97 ml of toluene with a syringe, stir in an oil bath at 50°C for 2 minutes and dissolve, then add 0.49 ml of ε-caprolactone (4.43 mg Moore). The polymerization system was solidified in 3 minutes, kept at 50° C. for 2 hours, and terminated with alcohol containing 5% hydrochloric acid. The polymer was precipitated with denatured alcohol, and vacuum-dried to constant weight to obtain 0.18 g of polycaprolactone, with a yield of 36%. The theoretical molecular weight of the polymer is 0.82 million [M _n (calcd) = (M _w of ε-CL) × [ε-CL]/[Ln] × (polymer yield) = 114 × 200 × 36%], GPC measured The average molecular weight (M _n ) was 55,000, and the molecular weight distribution (M _w /M _n ) was 2.11.

Example 10: [{ONArO}Yb{N(SiMe ₃ ) ₂ }(THF)] ₂ ; the substituent at the 5th position on the aromatic ring is methyl) catalyzed ring-opening polymerization of ε-caprolactone in a dehydration and deoxygenation belt with stirring Add 17.5 mg of catalyst, add 1.27 milliliters of toluene with a syringe, stir in a 50° C. oil bath for 2 minutes and then dissolve, then add 0.32 milliliters (2.89 mmol) of ε-caprolactone with a syringe. The polymerization system was solidified in 3 minutes, kept at 50° C. for 2 hours, and terminated with alcohol containing 5% hydrochloric acid. The polymer was precipitated with denatured alcohol, and vacuum-dried to constant weight to obtain 0.26 g of polycaprolactone with a yield of 78%. The theoretical molecular weight of the polymer is 0.89 million [M _n (calcd) = (M _w of ε-CL) × [ε-CL]/[Ln] × (polymer yield) = 114 × 100 × 78%], GPC measured The average molecular weight (M _n ) was 61,000, and the molecular weight distribution (M _w /M _n ) was 2.28.

Claims (5)

1. A N-aryloxy functionalized ketimine based rare earth metal amidide, characterized in that, the N-aryloxy functionalized ketimine based rare earth metal amidide adopts the following general formula to represent: [{ONArO}Ln{N(SiMe ₃ ) ₂ }(THF)] ₂ ; Wherein Ln is a rare earth metal; [ONArO]=(2-O-5-RC ₆ H ₃ )N=C(CH ₃ )CH=CO(CH ₃ ), wherein R is selected from C ₁ -C ₅ alkyl groups. 2. The N-aryloxy functionalized ketimine-based rare earth metal amides according to claim 1, characterized in that: R is selected from one of methyl, ethyl, propyl or tert-butyl. 3. The application of the N-aryloxy functionalized ketimine-based rare earth metal amides as claimed in claim 1 as a single-component catalyst in catalyzing the ring-opening polymerization of ε-caprolactone. 4. according to the application of claim 3, it is characterized in that: the method for catalyzing ε-caprolactone ring-opening polymerization comprises the following steps: Under anhydrous and oxygen-free conditions, mix the solvent and ε-caprolactone monomer, add the solution of the catalyst under vigorous stirring, the molar ratio of ε-caprolactone and the catalyst is 50:1～800:1; after the polymerization is completed, use Containing the alcohol termination of volume fraction 5% hydrochloric acid; Wherein, the polymerization temperature is 0° C. to 120° C., and the pKa value of the solvent is smaller than the pKa value of the ligand coordinated with the rare earth metal ion. 5. The application according to claim 4, characterized in that: the polymerization temperature is 25° C. to 70° C., and the solvent is selected from toluene, benzene, tetrahydrofuran or ethylene glycol dimethyl ether.