English

• The amount of plastic waste has been increasing drastically over the past decades which caused serious environmental pollution and ecological disaster. Waste plastic is usually disposed of by incineration or landfill and the treatment of plastic pollution has become a common consensus of the international community. Therefore, there is an urgent need to find environmentally friendly, reasonably priced plastics and related alternative products^[1]. Aliphatic polyester, polycarbonate and polylactic acid have attracted much attention in recent years due to their good biocompatibility and biodegradability. For example, poly(ε-caprolactone) (PCL) and poly lactide (PLA) are widely used in pharmaceutical and plastics fields due to their good permeability^[2-3]. Ring-opening polymerization (ROP) of cycloesters is considered as one of the most promising methods for preparing polyester materials. Different from traditional polycondensation catalytic reactions, the ROP has great advantages in controlling molecular weight and molecular weight distribution of the polymers^[4].

  Metal - organic compounds can efficiently initiate the ROP of cycloesters. The design and synthesis of metal - organic catalysts with appropriate substitutes become an important research direction for the preparation of polyester materials^[5]. The metal center acts as a Lewis acid to increase the positive charge of carbonyl groups of cyclic esters molecule to initiate the ROP. Previous studies showed that metal organic compounds containing different metal centers, such as Zn^[6-7], Ca^[8], Mg^[9-10], Ti^[11-12], Sn^[13-15] and Yb^[16], exhibited high performance on the ROP of lactones (or lactide). However, the trace metals are often present in the polymer products and difficult to remove completely. Organoaluminum compounds have attracted much attention due to their low toxicity, easy preparation and low cost^[17-18]. In the past decades, many kinds of aluminum alkoxides or alkyl complexes protected with different ligands, including salen, enolic salen, Schiff base, ketiminate, amidinate, and aminophenolate ligands, have been synthesized and used as catalysts in the ROP reactions^[19-24]. And most of the polymer molecular weight are lower than 10⁵ g·mol^-1. According to the results of Huang^[25-28], Wang^[29-32], Ma^[33-37] and our group^[38-39], the steric effect and electronic properties of metal-organic compounds played dominant roles in their catalytic activities for the ROP of ε-caprolactone. Further studies indicated that proper Lewis acidity of the aluminum center could improve the catalytic performance. Thus, many efforts have been devoted to the steric ligand design of the aluminum alkoxides or alkyl complexes to increase the catalyst activity, and the effect of the substituents at the metal center is usually ignored.

  In the past twenty years, β-diketimines were employed as ideal ligands to protect mental centers, and numbers of multifunctional aluminum derivatives were synthesized successfully owing to its steric feature and flexible electric properties. So, we synthesized the organoaluminum hydrogen compound supported by β - diketiminate ligand with -NMe₂ substitute at the Al center. The catalytic properties of the resultant organoaluminum hydrogen compound for the ROP of ε-caprolactone were studied in detail.

  1.   Experimental

  1.1   General procedures

  All the preparations were carried out under dry N₂ atmosphere using glovebox techniques and standard Schlenk lines. The related solvents such as toluene, THF and hexane were treated at least 6 h under Na/K alloy before distillation to use. Deuterated solvent CDCl₃ was purified over CaH₂ for 24 h and distilled under reduced pressure. ε-caprolactone was dried by 4A molecular sieves. ¹H NMR spectra was recorded on Bruker Avance 400 MHz eter. The melting point of compound 1 was measured in sealed capillaries using XT4A melting point apparatus. Elemental analysis was carried out using Vario EL Ⅲ analyser in the Analytical Instrumentation Center of the Tsinghua University. The IR spectra were recorded using Nicolet 6700 eter from 4 000 to 650 cm^-1. Gel penetration chromatography (GPC) measurements were performed by Shimadzu CTO - 20A system equipped with polystyrene gel columns using THF (HPLC grade) as an eluent (flow rate: 1.0 mL·min^-1, 25 ℃). (L)AlH₂ was synthesized as described previously^[38].

  1.2   Synthesis of (L)AlH(NMe2)

  n-BuLi (1 mmol，0.4 mL) was mixed with one equivalent of HNMe₂ (1 mmol, 2 mL) in toluene at -78 ℃, and the mixture was allowed to warm up to room temperature and kept on stirring for 12 h to generate LiNMe₂. The above mixture was transferred to the flask with (L)AlH₂ (1 mmol, 0.446 g) in toluene at -78 ℃. The reaction temperature was kept at -78 ℃ for 1 h, then the mixture was allowed to warm up to room temperature and stirred for 24 h. All the solvents were removed under vacuum, and the residue was extracted with n-hexane. Colorless crystals of compound 1 suitable for X-ray diffraction analysis were produced from a concentrated solution at 0 ℃ after three days (0.392 g, 85%). m.p. 170 ℃. IR (KBr, cm^-1): 1 873 cm^-1 (m, Al - H). Elemental analysis Calcd. for C₃₁H₄₈AlN₃(%): C 76.03, H 9.88, N 8.58; Found(%): C 75.36, H 9.72, N 8.32. ¹H NMR (400 MHz, CDCl3, 298K): δ 7.20~7.11 (m, 6 H, Ar—H), 5.13 (s, 1 H, γ- H), 3.25 (m, 4 H, CH(CH₃)₂), 1.73 (s, 6 H, C(CH₃)), 1.26 (d, 12 H, CH(CH₃)₂), 1.13 (d, 12 H, CH(CH₃)₂).

  1.3   X-ray single crystal diffraction study

  Single - crystal diffraction analysis was conducted by Bruker APEX Ⅱ DUO instrument under low temperature by utilizing graphite monochromated Mo Kα (λ =0.071 073 nm) as the incident light source. The data were integrated and corrected by SAINT^[40]. Semiempirical absorption corrections were applied with SADABS program^[41]. The crystal structure was directly resolved by SHELXL and OLEX 2^[42-43], all nonhydrogen atoms were refined by full-matrix leastsquares refinement based on F², hydrogen atoms connected to carbon and aluminum atoms were included at geometrically calculated positions and refined by using a riding model. The crystal and structure refinement parameters for compound 1 are shown in Table 1.

  表 1

  

  Table 1.  Crystal and structure refinement parameters for compound 1

  下载: 导出CSV

  Empirical formula	C31H48AlN3
  Formula weight	488.7
  Crystal system	Triclinic
  Space group	P1
  a / nm	1.047 9(2)
  b / nm	1.199 7(2)
  c / nm	1.322 8(3)
  α / (°)	68.92(3)
  β / (°)	77.53(3)
  γ / (°)	72.96(3)
  Volume / nm3	1.472 3(5)
  Z	2
  Dc / (Mg·m-3)	1.105
  Absorption coefficient / mm-1	0.092
  F(000)	536
  Crystal size / mm	0.21×0.2×0.03
  θ range for data collection / (°)	2.07~27.52
  Index ranges	-13 ≤ h ≤ 13, -15 ≤ k ≤ 15, -17 ≤ l ≤ 17
  Reflection collected	19 491
  Independent reflection	4 386 (Rint=0.072 3)
  Completeness / %	100
  Refinement method	Full-matrix least-squares on F2
  Data, restraints, parameter	6 725, 0, 332
  Goodness-of-fit on F2	1.159
  Final R indices [I>2σ(I)]	R1=0.080 4, wR2=0.193 6
  R indices (all data)	R1=0.097 6, wR2=0.215 1

  CCDC: 1542786.

  1.4   ROP of ε-caprolactone catalyzed by compound 1

  Typically, the initiator 1 (0.023 g, 0.05 mmol) and ε-caprolactone (3.42 g, 30 mmol) were dissolved in toluene (30 mL) in separate flasks. Then the monomer solution was transfered to the initiator flask at 100 ℃ and kept stirring for 2 h. The reaction was terminated with acetic acid (1 mL). All solvents were removed un- der vacuum, and the residue was dissolved with THF (30 mL). The white solid appeared immediately after n- hexane (20 mL) was added. White polymer solid was obtained in high yield (95%) after filtration, washing with hexane and removal of volatiles.

  2.   Results and discussion

  2.1   Description of compound 1

  The synthesis of aluminum amine compound 1 is shown in Scheme 1. Reaction of n-BuLi with one equivalent of HNMe₂ in toluene at -78 ℃ generated LiNMe₂. It is worth noting that the ratio control is crucial for this reaction. The lithium was transferred to the flash with one equivalent of HNMe₂ in toluene at -78 ℃ and kept for 0.5 h. Then the mixture was allowed to warm up to room temperature and kept stirring for 12 h. Compound 1 was obtained in 85% yield. Compound 1 was characterized by ¹H NMR. The spectrum showed a new resonance at δ =2.38, and the ratio to the γ-H proton (CCHC) was 6:1, which confirmed the formation of desired AlH(NMe₂) framework. The resonance for the Al-H could not be observed in the ¹H NMR because of the quadrupolar broadening by the Al nucleus. The presence of Al—H bonds in 1 was evident from the IR spectra. The broad IR bands around 1 873 cm^-1 is owing to the Al—H stretching frequency, which matches well with the value of 1 860 cm^-1 reported^[44].

  Scheme1

  

  Scheme1.  Synthesis of compound 1

  下载: 全尺寸图片 幻灯片

  Compound 1 suitable for X-ray crystal diffraction crystallizes in the triclinic space group P1 (Fig. 1). The structure was determined by X - ray single crystal diffraction. The aluminum atom is stabilized by —NMe₂ and —H substituents. The sum of angles around the Al center is 317.87°, which exhibits a distorted tetrahedral geometry. The Al—N bond distances (Al1—N1 0.191 9(2) nm, Al1—N2 0.191 4(2) nm) agree well with the relative coordinated bond distances (0.190 1(3) ~0.199 6(4) nm) reported in previous studies^[29-31]. The bond distance of Al1—N3 (0.180 0(2) nm) is much shorter than the coordinated Al—N distance, which is in good agreement with the single bond nature.

  图 1

  

  Figure 1.  Molecular structure of 1

  Anisotropic displacement parameters are depicted at the 30% probability level; Hydrogen atoms are omitted for clarity except for the hydrogen bonded to Al; Selected bond lengths (nm) and an⁃ gles (°): Al1—N1 0.191 9(2), Al1—N2 0.191 4(2), Al1—N3 0.180 0(2), Al1—H 0.147(3); N2—Al1—N1 95.72(9), N3— Al1—N1 110.72(10), N3—Al1—N2 111.43(11)

  下载: 全尺寸图片 幻灯片

  2.2   Catalytic performance on the ROP of ε-caprolactone

  Many organoaluminum compounds were evaluated as initiators of the ROP of ε-caprolactone. Huang et al. reported that aluminum hydrides were catalytically active in the ROP of ε-caprolactone^[45]. However, compared with those aluminum monohydrides, the polydispersity index (PDI) values of PCL initiated by aluminum dihydride were relatively broad because of the side reactions or multiple reacting sites (Al—H or Al— N). Besides, the catalytic performance of aluminum alkoxides or alkyl protected by β-diketiminate ligand were studied systematically by many groups. Generally, the polymer molecular weight is mostly in a range of 10³~ 10⁵ g·mol^{-1 [36-39]}. The steric effect was proposed as the main factor for the polymerization activity.

  The catalytic activity of compound 1 to the ROP of ε-caprolactone was studied systematically (Table 2). According to the catalytic results, the conversion of monomer increased with the increasing polymerization temperature. Meanwhile, the PDI (PDI=M_w/M_n) values of PCL also ranged from 1.21 to 2.07. (Entry 1~4 in Table 2). The molecular weight and PDI was also influenced by the ratio of the monomer to initiator (Entry 3, 5~7 in Table 2) and the reaction time (Entry 3, 8~10 in Table 2). Organoaluminum compound 1 containing —NMe₂ and —H substituents at the atom center showed excellent catalytic activity in the ROP of ε-caprolactone. Besides, we also evaluated the catalytic performance of starting material ((L)AlH₂). Similarly, the PDI values of PCL were relatively broad as the results reported by Huang's group^[45]. We estimated that the excellent catalytic activity of 1 might be attributed to the proper Lewis acid property of the Al center, which allowed the carbonyl to coordinate with the metal center and initiated the ROP reactions.

  Scheme2

  

  Scheme2.  ROP of ε-caprolactone catalyzed by compound 1

  下载: 全尺寸图片 幻灯片

  表 2

  

  Table 2.  ROP of ε-caprolactone (CL) catalyzed by aluminum amine compound^a

  下载: 导出CSV

  Entry	Initiator	nCL:n1	T / ℃	t / h	Conv.b / %	Mwc / (g·mol-1)	Mnc / (g·mol-1)	PDIc
  1	1	300:1	60	2	55	10 219	8 455	1.21
  2	1	300:1	80	2	85	61 292	36 924	1.66
  3	1	300:1	100	2	96	244 595	167 582	1.46
  4	1	300:1	120	2	95	301 878	145 263	2.07
  5	1	100:1	100	2	95	91 292	73 980	1.23
  6	1	400:1	100	2	96	284 603	141 125	2.01
  7	1	500:1	100	2	96	117 262	82 046	1.43
  8	1	300:1	100	0.5	52	52 288	35 720	1.46
  9	1	300:1	100	1.5	85	206 983	129 833	1.59
  10	1	300:1	100	4	97	266 983	93 875	2.84
  11	(L)AlH2	300:1	100	1.5	99	258 843	82 754	3.13
  a Solvent: 30 mL toluene, mCL=3.42 g, temperature=60~100 ℃, reaction time=0.5~4 h, N2 atmosphere; b Conversion based on the isolated amount of solid; c Determined by GPC in THF, calibrated with standard polystyrene samples, and multiplied by the cor⁃ rection value of 0.56.

  3.   Conclusions

  In summary, aluminum amine compound supported by β - diketiminate ligand was synthesized successfully via salt elimination reaction. The lithium LiNMe₂ was synthesized using HNMe₂ and n-BuLi as precursors, and the reactant ratio and reaction temperature were strict for the formation of the aluminum amine compound. Compound 1 containing Al—NMe₂ and Al—H groups is an excellent initiator for the ROP of ε-caprolactone. Proper Lewis acid of 1 exerts important effect on the polymerization of ε-caprolactone. The above findings would enable the rational design of aluminum amine compound with proper substituents at the metal center to prepare polymer with high molecular weight and narrow molecular weight distribution.

  
  
• 1. [1]

     Arbaoui A, Redshaw C. Polym. Chem., 2010, 1(6):801-826

  2. [2]

     Nicolas J, Mura S, Brambilla D, Mackiewicz N, Couvreur P. Chem. Soc. Rev., 2013, 42(3):1147-1235

  3. [3]

     Palivan C G, Goers R, Najer A, Zhang X, Car A, Meier W. Chem. Soc. Rev., 2016, 45(2):377-411

  4. [4]

     JIA B, HAO J S, TONG H B, WEI X H, ZHOU M S, LIU D S. Chinese J. Inorg. Chem., 2017, 33(10):1876-1880 http://www.wjhxxb.cn/wjhxxbcn/ch/reader/view_abstract.aspx?file_no=20171023&flag=1

  5. [5]

     Gao J H, Zhu D Z, Zhang W J, Solan G A, Ma Y, Sun W H. Inorg. Chem. Front., 2019, 6(10):2619-2652 doi: 10.1039/C9QI00855A

  6. [6]

     Yu X F, Zhang C, Wang Z X. ChemistrySelect, 2020, 5(1):426-429

  7. [7]

     D'Auria I, D'Alterio M C, Tedesco C, Pellecchia C. RSC Adv., 2019, 9(56):32771-32779 doi: 10.1039/C9RA07133D

  8. [8]

     Bhattacharjee J, Harinath A, Nayek H P, Sarkar A, Panda T K. Chem.-Eur. J., 2017, 23(39):9319-9331 doi: 10.1002/chem.201700672

  9. [9]

     Zhang H, Dong Y L, Huang K K, Liu J S, Dong B, Wang F. Eur. Polym. J., 2019, 118:633-641 doi: 10.1016/j.eurpolymj.2019.06.029

  10. [10]

      Trott G, Garden J A, Williams C K. Chem. Sci., 2019, 10(17):4618-4627 doi: 10.1039/C9SC00385A

  11. [11]

      Gao B, Li X, Duan R L, Pang X. New J. Chem., 2015, 39(4):2404-2408

  12. [12]

      Nakayama Y, Watanabe K, Ueyama N, Nakamura A, Harada A, Okuda J. Organometallics, 2000, 19(13):2498-2503 doi: 10.1021/om990906h

  13. [13]

      Weidner S M, Kricheldorf H R. J. Polym. Sci. Part A:Polym. Chem., 2018, 56(24):2730-2738 doi: 10.1002/pola.29259

  14. [14]

      Weidner S M, Kricheldorf H R. Macromol. Chem. Phys., 2018, 219(24):1800445-1800454 doi: 10.1002/macp.201800445

  15. [15]

      Zhong M D, Yang Z, Yi Y F, Zhang D X, Sun K N, Roesky H W, Yang Y. Dalton Trans., 2015, 44(46):19800-19804 doi: 10.1039/C5DT03244J

  16. [16]

      Zhang Z J, Xu X P, Sun S, Yao Y M, Zhang Y, Shen Q. Chem. Commun., 2009, 47:7414-7416

  17. [17]

      Li W Y, Wu W T, Wang Y R, Yao Y M, Zhang Y, Shen Q. Dalton Trans., 2011, 40(43):11378-11381 doi: 10.1039/c1dt11380a

  18. [18]

      XU B, YAO Y M. Chinese J. Inorg. Chem., 2011, 27(9):1805-1809 http://www.wjhxxb.cn/wjhxxbcn/ch/reader/view_abstract.aspx?file_no=20110923&flag=1

  19. [19]

      Oishi M, Ichinose Y, Iwata N, Nomura N. Organometallics, 2019, 38(21):4233-4243 doi: 10.1021/acs.organomet.9b00540

  20. [20]

      XIE Q F, CHEN Y M. Chinese J. Inorg. Chem., 2019, 35(12):2209-2216 http://www.wjhxxb.cn/wjhxxbcn/ch/reader/view_abstract.aspx?file_no=20191203&flag=1

  21. [21]

      Wang Y L, Dang Y, Pan H F, Ge Y, Jiang Z L, Xia S W, Li Y H. Chin. J. Struc. Chem., 2019, 38(10):1797-1806

  22. [22]

      Wei C Z, Han B H, Zheng D J, Zheng Q D, Liu S F, Li Z B. Organo-metallics, 2019, 38(19):3816-3823 doi: 10.1021/acs.organomet.9b00502

  23. [23]

      Wang Y, Ma H Y. Chem. Commun., 2012, 48(53):6729-6731 doi: 10.1039/c2cc31716h

  24. [24]

      WU Q, TANG Y F, ZI Q L. Chinese J. Inorg. Chem., 2019, 35(8):1477-1484 http://www.wjhxxb.cn/wjhxxbcn/ch/reader/view_abstract.aspx?file_no=20190819&flag=1

  25. [25]

      Yu R C, Hung C H, Huang J H, Lee H Y, Chen J T. Inorg. Chem., 2002, 41(24):6450-6455 doi: 10.1021/ic025785j

  26. [26]

      Hsiao H C, Datta A, Chen Y F, Chang W, Lee T Y, Lin C H, Huang J H. J. Organomet.Chem., 2016, 804:35-41 doi: 10.1016/j.jorganchem.2015.12.030

  27. [27]

      Huang W Y, Chuang S J, Chunag N T, Hsiao C S, Datta A, Chen S J, Hu C H, Huang J H, Lee T Y, Lin C H. Dalton Trans., 2011, 40(28):7423-7433 doi: 10.1039/c1dt10442j

  28. [28]

      Hsu S Y, Hu C H, Tu C Y, Lin C H, Chen R Y, Datta A, Huang J H. Eur. J. Inorg. Chem., 2014(11):1965-1973

  29. [29]

      Ma W A, Wang Z X. Dalton Trans., 2011, 40(8):1778-1786 doi: 10.1039/c0dt01001d

  30. [30]

      Ma W A, Wang L, Wang Z X. Dalton. Trans., 2011, 40(17):4669-4677 doi: 10.1039/c0dt01713b

  31. [31]

      Yu X F, Wang Z X. Dalton Trans., 2013, 42(11):3860-3868 doi: 10.1039/c2dt32520a

  32. [32]

      Zheng X X, Wang Z X. RSC Adv., 2017, 7(44):27177-27188

  33. [33]

      Altaf C T, Wang H B, Keram M, Yang Y, Ma H. Polyhedron, 2014, 81:11-20

  34. [34]

      Kan C, Ge J L, Ma H Y. Dalton Trans., 2016, 45(15):6682-6695

  35. [35]

      Gong S G, Du P, Ma H Y. Chin. J. Polym. Sci., 2017, 36(2):190-201

  36. [36]

      Gong S G, Ma H Y. Dalton Trans., 2008, 25:3345-3357

  37. [37]

      Gong S G, Du P, Ma H Y. Chin. J. Polym. Sci., 2017, 36(2):190-201

  38. [38]

      Ma X L, Yao M M, Zhong M D, Deng Z Y, Li W L, Yang Z, Roesky H W. Z. Anorg. Allg. Chem., 2017, 643(2):198-202

  39. [39]

      Hao P F, Yang Z, Li W L, Ma X L, Roesky H W, Yang Y, Li J R. Organometallics, 2014, 34(1):105-108

  40. [40]

      SAINT, Ver. 7.68A, Bruker AXS, Inc., Madison, WI, 2009.

  41. [41]

      Sheldrick G M. SADABS, Ver. 2008/1, Bruker AXs, Inc., Madison, WI, 2008.

  42. [42]

      Sheldrick G M. SHELXTL, Ver.6.14, Bruker AXs, Inc., Madison, WI, 2003.

  43. [43]

      Dolomanov O V, Bourhis L J, Gildea R J, Howard J A K, Puschmann H. J. Appl. Crystallogr., 2009, 42(2):339-341

  44. [44]

      Atwood J L, Lawrenceb S M, Raston C L. J. Chem. Soc. Chem. Commun., 1994, 1:73-74

  45. [45]

      Chang J C, Chen Y C, Datta A, Lin C H, Hsiao C S, Huang J H. J. Organomet. Chem., 2011, 696(23):3673-3680

• 

  Scheme1  Synthesis of compound 1

  下载: 全尺寸图片 幻灯片
  

  Figure 1  Molecular structure of 1

  Anisotropic displacement parameters are depicted at the 30% probability level; Hydrogen atoms are omitted for clarity except for the hydrogen bonded to Al; Selected bond lengths (nm) and an⁃ gles (°): Al1—N1 0.191 9(2), Al1—N2 0.191 4(2), Al1—N3 0.180 0(2), Al1—H 0.147(3); N2—Al1—N1 95.72(9), N3— Al1—N1 110.72(10), N3—Al1—N2 111.43(11)

  下载: 全尺寸图片 幻灯片
  

  Scheme2  ROP of ε-caprolactone catalyzed by compound 1

  下载: 全尺寸图片 幻灯片

  Table 1.  Crystal and structure refinement parameters for compound 1

  Empirical formula	C31H48AlN3
  Formula weight	488.7
  Crystal system	Triclinic
  Space group	P1
  a / nm	1.047 9(2)
  b / nm	1.199 7(2)
  c / nm	1.322 8(3)
  α / (°)	68.92(3)
  β / (°)	77.53(3)
  γ / (°)	72.96(3)
  Volume / nm3	1.472 3(5)
  Z	2
  Dc / (Mg·m-3)	1.105
  Absorption coefficient / mm-1	0.092
  F(000)	536
  Crystal size / mm	0.21×0.2×0.03
  θ range for data collection / (°)	2.07~27.52
  Index ranges	-13 ≤ h ≤ 13, -15 ≤ k ≤ 15, -17 ≤ l ≤ 17
  Reflection collected	19 491
  Independent reflection	4 386 (Rint=0.072 3)
  Completeness / %	100
  Refinement method	Full-matrix least-squares on F2
  Data, restraints, parameter	6 725, 0, 332
  Goodness-of-fit on F2	1.159
  Final R indices [I>2σ(I)]	R1=0.080 4, wR2=0.193 6
  R indices (all data)	R1=0.097 6, wR2=0.215 1

  下载: 导出CSV

  Table 2.  ROP of ε-caprolactone (CL) catalyzed by aluminum amine compound^a

  Entry	Initiator	nCL:n1	T / ℃	t / h	Conv.b / %	Mwc / (g·mol-1)	Mnc / (g·mol-1)	PDIc
  1	1	300:1	60	2	55	10 219	8 455	1.21
  2	1	300:1	80	2	85	61 292	36 924	1.66
  3	1	300:1	100	2	96	244 595	167 582	1.46
  4	1	300:1	120	2	95	301 878	145 263	2.07
  5	1	100:1	100	2	95	91 292	73 980	1.23
  6	1	400:1	100	2	96	284 603	141 125	2.01
  7	1	500:1	100	2	96	117 262	82 046	1.43
  8	1	300:1	100	0.5	52	52 288	35 720	1.46
  9	1	300:1	100	1.5	85	206 983	129 833	1.59
  10	1	300:1	100	4	97	266 983	93 875	2.84
  11	(L)AlH2	300:1	100	1.5	99	258 843	82 754	3.13
  a Solvent: 30 mL toluene, mCL=3.42 g, temperature=60~100 ℃, reaction time=0.5~4 h, N2 atmosphere; b Conversion based on the isolated amount of solid; c Determined by GPC in THF, calibrated with standard polystyrene samples, and multiplied by the cor⁃ rection value of 0.56.

  下载: 导出CSV
•