Synthesis and Catalytic Activity of Dinuclear Rare-Earth Metal Complexes with Nitrogen-Containing Bridged Dipyrrolyl Ligand towards Ring-Opening Polymerization of e-Caprolactone

Jie Wu Xiuli Zhang Lijun Zhang Yun Wei Shuangliu Zhou

Citation:  Wu Jie, Zhang Xiuli, Zhang Lijun, Wei Yun, Zhou Shuangliu. Synthesis and Catalytic Activity of Dinuclear Rare-Earth Metal Complexes with Nitrogen-Containing Bridged Dipyrrolyl Ligand towards Ring-Opening Polymerization of e-Caprolactone[J]. Chinese Journal of Organic Chemistry, 2020, 40(3): 801-805. doi: 10.6023/cjoc201908010 shu

含氮原子桥联吡咯基稀土金属双核配合物的合成及催化e-己内酯的开环聚合反应

    通讯作者: 张丽军, zljun@ahnu.edu.cn
    周双六, slzhou@ahnu.edu.cn
  • 基金项目:

    国家自然科学基金 Nos. 21672004

    国家自然科学基金 21602004

    国家自然科学基金(Nos.21672004,21602004)资助项目

摘要: RE(CH2SiMe33(THF)2和1.5 equiv.(C4H3NHCH22NCH31)反应合成得到含氮原子桥联吡咯基稀土金属双核配合物[η1η1η1-(C4H3NCH22NCH3]RE{m-η5η5η1-(C4H3NCH22NCH3}RE[η1η1η1-(C4H3NCH22NCH3](THF)[RE=Y(2),Er(3),Yb(4)],所得配合物经过核磁共振、红外和元素分析表征,配合物24经单晶X-Ray进一步确认结构.同时研究了稀土配合物作为单一组分催化剂催化e-内酯的开环聚合反应.

English

  • Over the last two decades, polyesters have attracted considerable attention due to its biocompatibility, biodegradability and good drug penetrability.[1] The ring-opening polymerization (ROP) of lactones provides a convenient method for the synthesis of biodegradable polyesters.[2] In this aspect, organometallic complexes with adjustment of ligands play an important role not only in molecular weight and molecular weight distribution, but also in stereoregularity of polyesters. Many metal complexes including alkali metals, [3] alkaline earth metals, [4] aluminum, [5] zinc, [6] tin, [7] early transition metals, [8] and lanthanides[9] have been used as initiators for the ROP of ε-caprolactone.

    On the contrast, lanthanide catalysts have received great interest due to their high activity and capability of giving polymers with high molecular weights in narrow polydispersity without alcohol initiators. Additionally, a diversity of structurally well-defined lanthanide catalysts, such as lanthanide alkoxides or aryloxides, [10] amides, [11] alkylates, [12] and rare-earth borohydride[13] is effective initiators for living polymerization of lactones. The homoleptic amidinate[14] and amidate[15] complexes of the rare-earth metals have been extensively investigated and have been modestly successful in ROP of ε-caprolactone. Recently, we reported[16] that homoleptic tris(pyrrolyl) lanthanide complexes could be used as single-component catalysts for ε-caprolactone polymerization, indicating that lanthanide complexes without active group could also initiate the ε-caprolactone polymerization. We herein report the synthesis and characterization of dinuclear rare-earth metal complexes with nitrogen-containing bridged dipyrrolyl ligand and their catalytic activities toward ROP of ε-caprolactone.

    Treatment of RE(CH2SiMe3)3(THF)2 with 1.5 equiv. of (C4H3NHCH2)2NCH3 (1) in toluene, after workup, afforded nitrogen-containing bridged dipyrrolyl dinuclear rare-earth metal complexes [η1:η1:η1-(C4H3NCH2)2NCH3]RE{μ-η5: η1:η5:η1:η1-(C4H3NCH2)2NCH3}RE[η1:η1:η1-(C4H3NCH2)2NCH3](THF) [RE=Y (2), Er (3), Yb (4)] (Scheme 1). The complexes are sensitive to air and moisture, and they have good solubility in polar solvents such as THF, Et2O, toluene, and slight solubility in n-hexane. All the complexes were fully characterized by spectroscopic and element analyses, and the structures of complexes 2 and 4 were furtherly determined by X-ray diffraction.

    Scheme 1

    Scheme 1.  Synthesis of complexes 2~4

    X-ray analyses showed that complexes 2 (Figure 1) and 4 (Figure 2) were isostructural dinuclear structure. Each of rare earth metals adopts a distorted octahedral geometry, and the two rare earth metals are coordinated by one dipyrrolyl ligand, which coordinated to one rare-earth metal in an η5:η1:η1 mode, and to another rare-earth metal in an η5:η1 mode. Except for dipyrrolyl ligand of the linked two rare earth metals, each rare earth metal was coordinated to another dipyrrolyl ligand in an η1:η1:η1 mode. Selected bond lengths and angles are listed in Table 1.

    Figure 1

    Figure 1.  Molecular structure of complex 2

    Figure 2

    Figure 2.  Molecular structure of complex 4

    Table 1

    Table 1.  Selected bond lengths ( ) and bond angles (°)
    下载: 导出CSV
    Compd. 2 4
    Bond length
    RE(1)—N(1) 0.2315(4) 0.2276(6)
    RE(1)—N(2) 0.2527(4) 0.2506(6)
    RE(1)—N(3) 0.2297(4) 0.2249(6)
    RE(1)—N(4) 0.2584(3) 0.2359(5)
    RE(1)—N(5) 0.2620(3) 0.2604(5)
    RE(1)—N(6) 0.2405(3) 0.2569(5)
    RE(1)—C(12) 0.2707(4) 0.2583(7)
    RE(1)—C(13) 0.2819(4) 0.2722(7)
    RE(1)—C(14) 0.2763(4) 0.2786(7)
    RE(1)—C(15) 0.2598(4) 0.2675(6)
    Bond angle
    RE(1)—N(4)—RE(2) 110.48(10) 108.69(17)
    RE(1)—N(6)—RE(2) 107.71(11) 111.04(18)
    Bond length
    RE(2)—N(4) 0.2457(3) 0.2691(5)
    RE(2)—N(6) 0.2720(3) 0.2413(5)
    RE(2)—N(7) 0.2318(3) 0.2277(5)
    RE(2)—N(8) 0.2524(3) 0.2505(5)
    RE(2)—N(9) 0.2291(3) 0.2280(5)
    RE(2)—O(1) 0.2369(3) 0.2364(4)
    RE(2)—C(19) 0.2752(4) 0.2666(6)
    RE(2)—C(20) 0.2765(4) 0.2684(6)
    RE(2)—C(21) 0.2747(4) 0.2711(6)
    RE(2)—C(22) 0.2702(4) 0.2675(6)
    Bond angle
    N(4)—RE(1)—N(6) 71.96(9) 71.28(16)
    N(4)—RE(2)—N(6) 68.94(9) 68.35(15)

    From Table 1, the distances between rare-earth ions with the linked nitrogens [RE(1)—N(2), RE(1)—N(5) and RE(2)—N(8)] are longer than the distances of the other σ- RE—N bonds. The average distance between lanthanide ions with the five membered pyrrolyl ring of 0.2716(5) nm in complex 2 is slightly longer than the corresponding value of 0.2683(7) nm found in complex 4, due to reflection of ionic radius from Y3+ and Yb3+. The another feacture of the complexes 2 and 4 is that the sum of the four bond angles of RE(1)—N(4)—RE(2), RE(1)—N(6)—RE(2), N(4)— RE(1)—N(6) and N(4)—RE(2)—N(6) is about 360°, indicating that RE(1), RE(2), N(4), and N(6) atoms are coplanar.

    In general, rare-earth complexes catalyzed the ε-caprol- actone polymerization to require the active group or additional alcohol as initiator. In our previous study, we reported the ring-opening polymerization of ε-caprolactone catalyzed by tris-iminopyrrolyl rare-earth metal complexes without additional alcohol as initiator.[16] Herein, the catalytic activities of complexes 2~4 towards ROP of ε-caprolactone were examined, and results are listed in Table 3. From Table 2, it can be seen that the solvents have a slight influence on polymerization, and complex 2 exhibited good catalytic activities on ring-opening polymerization of ε-caprolactone in toluene and THF. The Mn obtained by complex 2 in THF, Et2O and CH2Cl2 are much larger than those calculated (Entries 4~6, Table 2), and the Mn obtained by complexes 3, and 4 are also larger than those calculated (Entries 7, 8, Table 2), suggesting slow initiation followed by rapid polymerization by small quantities of catalytically active species. Furtherly, complex 2 as an initator for ROP of ε-caprolactone was examined at 10 ℃ in the monomer-to-initiator ratio ([M]/[Cat]) range of 100~500. Results revealed that the linear relationship was associated with the Mn and [M]/[Cat] ratio and the narrow polydispersity index (PDI) ranging from 1.38 to 1.62 of the polymers ([M]/[Cat.] ratio of 100~500 (Entries 2, 9~12, Table 2). The results also represented rare examples of the ring-opening polymerization of ε-caprolactone catalyzed by nitrogen-containing bridged dipyrrolyl rare-earth complexes 2~4 without additional alcohol as initiator, which was similar to our previous example of the ring-opening polymerization of ε-caprolactone catalyzed by tris-imino- pyrrolyl rare-earth metal complexes.[16] Mechanism of the ring-opening polymerization of ε-caprolactone was proposed that the ε-caprolactone firstly coordinated to the rare-earth metal, and followed by insertion of a pyrrolyl group of rare-earth metal complex into ε-caprolactone.[16]

    Table 2

    Table 2.  Ring-opening polymerization of ε-caprolactone catalyzed by complexes 2~4a
    下载: 导出CSV
    Entry Cat. [M]:[catal.] Solvent Temp./℃ Time/min Mnb/(×10-4) Mnc/(×10-4) PDIc Conv./%
    1 2 100:1 Toluene 0 3 1.08 2.41 (1.35) 1.94 95
    2 2 100:1 Toluene 10 1 1.13 2.81 (1.57) 1.38 99
    3 2 100:1 Toluene 20 1 1.13 3.23 (1.81) 1.78 99
    4 2 100:1 THF 10 1 1.12 5.98 (3.34) 1.54 98
    5 2 100:1 Et2O 10 3 0.99 3.81 (2.13) 1.41 87
    6 2 100:1 CH2Cl2 10 5 0.83 3.96 (2.22) 1.45 73
    7 3 100:1 Toluene 10 1 0.68 2.27 (1.27) 1.41 60
    8 4 100:1 Toluene 10 1 1.03 3.23 (1.81) 1.67 90
    9 2 200:1 Toluene 10 1 2.26 4.90 (2.74) 1.61 99
    10 2 300:1 Toluene 10 1 3.39 7.89 (4.41) 1.62 99
    11 2 400:1 Toluene 10 1 4.52 10.60 (5.93) 1.49 99
    12 2 500:1 Toluene 10 2 5.59 12.96 (7.25) 1.54 98
    a Solvent (5.0 mL). b Calculated from [M(ε-capralactone)×[M]/[catal.]×conversion. c Obtained from GPC analysis and calibrated by polystyrene standard, and values in parentheses are the values obtained from GPC times 0.56.

    In summary, nitrogen-containing bridged dipyrrolyl rare-earth metal complexes were synthesized via reaction of RE(CH2SiMe3)3(THF)2 with (C4H3NHCH2)2NCH3 in toluene in good yields. The X-ray diffraction analyses of the complexes indicated that the complexes were a dimeric structure and two central metals were linked through one nitrogen-containing bridged dipyrrolyl ligand in an η5:η1: η1:η5:η1 mode. The dimeric rare-earth complexes showed high catalytic activities towards the ROP of ε-caprolactone.

    All syntheses and manipulations of air- and moisture- sensitive materials were carried out under an atmosphere of argon using standard Schlenk techniques or in a glovebox. THF, toluene and hexane were refluxed and distilled over sodium benzophenone ketyl under argon prior to use unless otherwise noted. ε-Caprolactone (ε-CL) was dried over finely divided CaH2, distilled before use. (C4H3NHCH2)2N- CH3[17] and RE(CH2SiMe3)3(THF)2[18] were prepared according to literature methods. 1H NMR and 13C NMR spectra for analyses of compounds were recorded on a Bruker AV-500 NMR spectrometer (500 MHz for 1H NMR, 125 MHz for 13C NMR) in d8-THF for rare-earth metal complex. Elemental analyses data were obtained on a Perkin-Elmer Model 2400 Series II elemental analyzer. IR spectra were recorded on a Shimadzu Model FTIR-8400s spectrometer (KBr pellet). Gel permeation chromatography (GPC) analyses of the polymer samples were carried out at 30 ℃ using THF as an eluent on a Waters-2414 instrument and calibrated using monodispersed polystyrene standards at a flow rate of 1.0 mL•min-1.

    To a THF (20.0 mL) solution of RE(CH2SiMe3)3(THF)2 (1.0 mmol) was added a toluene (10.0 mL) solution of (C4H3NHCH2)2NCH3 (0.29 g, 1.5 mmol) at 0 ℃. After the reaction mixture was stirred at room temperature for 3 h, the solvent was evaporated under reduced pressure. The residue was extracted with toluene/n-hexane (V:V=1:1, 20 mL). The extractions were combined and concentrated to about 10.0 mL. The complex crystals were obtained by cooling the concentrated solution at 0 ℃ for several days

    [η1:η1:η1-(C4H3NCH2)2NCH3]Y{μ-η5:η1:η5:η1:η1-(C4H3- NCH2)2NCH3}Y[η1:η1:η1-(C4H3NCH2)2NCH3](THF) (2): Colorless crystals (0.68 g, 75% yield). m.p. 173~174 ℃; 1H NMR (d8-THF, 500 MHz, 25 ℃) δ: 7.20~7.08 (m, 5H), 6.60 (s, 3H), 5.94~5.92 (m, 3H), 5.89~5.88 (m, 3H), 3.62 (t, J=3.6 Hz, 4H), 3.42 (s, 12H), 2.31 (s, 3H), 2.08 (s, 9H), 1.79 (t, J=3.6 Hz, 4H); 13C NMR (d8-THF, 500 MHz, 25 ℃) δ: 137.8, 129.3, 129.1, 128.3, 125.4, 117.0, 107.4, 107.1, 67.6, 54.3, 41.5, 25.0, 20.9; IR (KBr) ν: 3176 (m), 3122 (m), 2989 (m), 2943 (m), 2916 (s), 2835 (m), 2791 (s), 1642 (m), 1639 (s), 1516 (m), 1462 (m), 1357 (m), 1300 (m), 1176 (s), 1101 (m), 968 (m), 846 (m), 713 (m) cm-1. Anal. calcd for C37H47N9OY2•2C7H8: C 61.51, H 6.38, N 12.66; found C 61.25, H 6.73, N 12.42.

    [η1:η1:η1-(C4H3NCH2)2NCH3]Er{μ-η5:η1:η5:η1:η1-(C4H3- NCH2)2NCH3}Er[η1:η1:η1-(C4H3NCH2)2NCH3](THF) (3):Pinkcrystals, 0.85 g, 81% yield. m.p. 186~187 ℃; IR (KBr) ν: 3176 (m), 3122 (m), 3103 (m), 2989 (m), 2943 (m), 2835 (m), 2791 (s), 1462 (m), 1357 (m), 1300 (s), 1253 (s), 1176 (m), 1028 (m), 968 (m), 848 (m), 800 (m), 713 (m), 609 (m) cm-1. NMR (d8-THF) spectra of the compound were not informative due to lack of locking signals for the paramagnetic property of the erbium(III) complex 3. Anal. calcd for C37H47N9OEr2•C7H8: C 49.83, H 5.23, N 11.89; found C 49.84, H 5.33, N 11.92.

    [η1:η1:η1-(C4H3NCH2)2NCH3]Yb{μ-η5:η1:η5:η1:η1-(C4H3- NCH2)2NCH3}Yb[η1:η1:η1-(C4H3NCH2)2NCH3](THF) (4):Yellowcrystals, 0.83 g, 79% yield. m.p. 195~196 ℃; IR (KBr) ν: 3174 (m), 3103 (m), 2989 (m), 2943 (m), 2835 (m), 2791 (m), 1637 (s), 1562 (s), 1516 (s), 1462 (m), 1537 (m), 1300 (s), 1253 (m) 1232 (m), 1176 (m), 1039 (m), 968 (m), 887 (m), 848 (m), 800 (m), 732 (m), 609 (m) cm-1. NMR (d8-THF) spectra of the compound were not informative due to lack of locking signals for the paramagnetic property of the ytterbium(III) complex 4. Anal. calcd for C37H47N9O- Yb2•OC4H8: C 46.81, H 5.27, N 11.98. found C 46.30, H 5.36, N 11.94.

    Single crystals of complexes 2 and 4 suitable for X-ray diffraction studies were sealed in thin-walled glass capillaries under argon. Diffraction was performed on a Bruker SMART CCD area detector diffractometer using graphite- monochromated Mo Kα radiation (λ=0.071073 nm). An empirical absorption correction was applied using the SADABS program. All structures were solved by direct methods, completed by subsequent difference Fourier syntheses, refined anisotropically for all nonhydrogen atoms by full-matrix least-squares calculations on F2 using the SHELXTL program package. All hydrogen atoms were refined using a riding model. Crystal data and details of the data collection and structure refinements are given in Table S1 in supporting information. CCDC-1502991-1502992 for complexes 2 and 4 contain the supplementary crystallo- graphic data of this paper. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.

    ε-CL polymerization reactions were performed in a 50.0 mL Schlenk flask, placed in an external temperature-controlled bath on a Schlenk line or in a glovebox. In a typical procedure, the catalyst (20~50 mg) was loaded into the Schlenk flask and the solvent was added. The ε-CL was added through a gastight syringe after the external bath temperature was stabilized. The polymer product was precipitated into hydrochloric acid (0.1 mol/L, 50.0 mL), washed with 0.1 mol/L hydrochloric acid, and then dried to a constant weight in a vacuum oven at 50 ℃. The molecular weights of the polymers were analyzed by GPC techniques.

    Supporting Information    Copies of NMR of complex 2, crystallographic data and refinements for complexes 2 and 4. The Supporting Information is available free of charge via the Internet at http://sioc-journal.cn/.


    1. [1]

      (a) Müller H. M., Seebach D.Angew. Chem., Int. Ed., 1993, 32: 477.
      (b) Ni Q., Yu L.J. Am. Chem. Soc., 1998, 120: 1645.
      (c) Okada M.Prog. Polym. Sci., 2002, 27: 87.
      (d) Wiegand T., Karr J., Steinkruger J. D., Hiebner K., Simetich B., Beatty M., Redepenning J.Chem. Mater., 2008, 20: 5016.

    2. [2]

      For reviews, see: (a) Shen Q., Yao Y.Chin. J. Org. Chem., 2001, 21: 1018(in Chinese).
      (沈琪, 姚英明, 有机化学,, 2001, 21: 1018.)
      (b) Dechy-Cabaret O., Martin-Vaca B., Bourissou D.Chem. Rev., 2004, 104: 6147
      (c) Wu J. C., Yu T.-L., Chen C.-T., Lin C.-C.Coord. Chem. Rev., 2006, 250: 602.
      (d) Sutar A. K., Maharana T., Dutta S., Chen C.-T., Lin C.-C.Chem. Soc. Rev., 2010, 39: 1724.
      (e) Wei Y., Wang S., Zhou S.Dalton Trans., 2016, 45: 4471.
      (f) Zhao N.Chin. J. Org. Chem., 2017, 37: 1139(in Chinese).
      (赵宁, 有机化学,, 2017, 37: 1139.)

    3. [3]

      (a) Wang, Z; Qi C.Organometallics, 2007, 26: 2243.
      (b) Ko B.-T., Lin C.-C.J. Am. Chem. Soc., 2001, 123: 7973.
      (c) Hsueh M.-L., Huang B.-H., Wu J., Lin C.-C.Macromolecules, 2005, 38: 9482.
      (d) Bhunia M., Vijaykumar G., Adhikari D., Mandal S. K.Inorg. Chem., 2017, 56: 14459.

    4. [4]

      (a) Shueh M.-L., Wang Y.-S., Huang B.-H., Kuo C.-Y., Lin C.-C.Macromolecules, 2004, 37: 5155.
      (b) Sarazin Y., Schormann M., Bochmann M.Organometallics, 2004, 23: 3296.
      (c) Chisholm M. H., Gallucci J. C., Phomphrai K.Inorg. Chem., 2004, 43: 6717.
      (d) Xu X., Chen Y., Zou G., Ma Z., Li G.J. Organomet. Chem., 2010, 695: 1155.
      (e) Huang Y., Wang W., Lin C.-C., Blake M. P., Clark L., Schwarzb A. D., Mountford P.Dalton Trans., 2013, 42: 9313.
      (f) Huang Y., Kou X., Duan Y., Ding F., Yin Y., Wang W., Yang Y.Dalton Trans., 2018, 47: 8121.

    5. [5]

      (a) Duda A., Penczek S.Macromolecules, 1995, 28: 5981.
      (b) Ovitt, T M., Coates G. W.J. Am. Chem. Soc., 1999, 121: 4072.
      (c) Radano C. P., Baker G. L., Smith M. R.J. Am. Chem. Soc., 2000, 122: 1552.
      (d) Liu Y.-C., Ko B.-T., Lin C.-C.Macromolecules, 2001, 34: 6196.
      (e) Gao A., Mu Y., Zhang J., Yao W.Eur. J. Inorg. Chem., 2009, 3613.
      (f) Zhang W., Wang Y., Cao J., Wang L., Pan Y., Redshaw C., Sun W.-H.Organometallics, 2011, 30: 6253.
      (g) Li W., Yao Y., Zhang Y., Shen Q.Chin. J. Chem., 2012, 30: 609.
      (h) Chen L., Li W.Yuan D., Zhang Y., Shen Q., Yao Y.Inorg. Chem., 2015, 54: 4699.
      (i) Hao P.; Yang Z., Li W., Ma X., Roesky H. W., Yang Y., Li J.Organometallics, 2015, 34: 105.
      (j) Wei Y., Wang S., Zhu X., Zhou S., Mu X., Huang Z., Hong D.Organometallics, 2016, 35: 2621.
      (k) Lee C.-L., Lin Y.-F., Jiang M.-T., Lu W.-Y., Vandavasi J. K., Wang L.-F., Lai Y.-C., Chiang M. Y., Chen H.-Y.Organometallics, 2017, 36: 1936.

    6. [6]

      (a) Hannant M. D., Schormann M., Bochmann M.Dalton Trans., 2002, 4071.
      (b) Williams C. K., Breyfogle L. E., Choi S. K., Nam W., Young V. G., Hillmyer M. A., Tolman W. B.J. Am. Chem. Soc., 2003, 125: 11350.
      (c) Chakraborty D., Chen E. Y.-X.Organometallics, 2003, 22: 769.
      (d) Chen H.-Y., Huang B.-H., Lin C.-C.Macromolecules, 2005, 38: 5400.
      (e) Chai Z.-Y., Zhang C., Wang Z.-X.Organometallics, 2008, 27: 1626.
      (f) Zhou S., Jiang Y., Xie T., Wu Z., Zhou L., Xu W., Zhang L., Wang S.Chin. J. Chem., 2012, 30: 2176.
      (g) Ma W.-A.; Wang Z.-X.Organometallics, 2011, 30: 4364.

    7. [7]

      (a) Deshayes G., Mercier F. A. G., Degée P., Verbruggen I. I., Biesemans M., Willem R., Dubois P.Chem. Eur. J., 2003, 9: 4346.
      (b) Bratton D., Brown M., Howdle S. M.Macromolecules, 2005, 38: 1190.
      (c) Dove A. P., Gibson V. C., Marshall E. L., Rzepa H. S., White A. J. P., Williams D. J.J. Am. Chem. Soc., 2006, 128: 9834.
      (d) Chagneux N., Trimaille T., Rollet M., Beaudoin E., Gérard P., Bertin D., Gigmes D.Macromolecules, 2009, 42: 9435.

    8. [8]

      (a) Thomas D., Arndt P., Peulecke N., Spannenberg A., Kempe R., Rosenthal U.Eur. J. Inorg. Chem., 1998, 1351.
      (b) Takeuchi D., Nakamura T., Aida T.Macromolecules, 2000, 33: 725.
      (c) Gowda R. R., Chakraborty D., Ramkumar V.Eur. J. Inorg. Chem., 2009, 2981.
      (d) Zhou F., Lin M., Li L., Zhang X., Chen Z., Li Y., Zhao Y., Wu J., Qian G., Hu B., Li W.Organometallics, 2011, 30: 1283.
      (e) Duan Y., Hu Z., Yang B., Ding F., Wang W., Huang Y., Yang Y.Dalton Trans., 2017, 46: 11259

    9. [9]

      (a) Evans W. J., Katsumata H.Macromolecules, 1994, 27: 2330.
      (b) Nishiura M., Hou Z., Koizumi T., Imamoto T., Wakatsuki Y.Macromolecules, 1999, 32: 8245.
      (c) Kerton F. M., Whitwood A. C., Willans C. E.Dalton Trans., 2004, 2237.
      (d) Sun H., Li H., Yao C., Yao Y., Sheng H., Shen Q.Chin. J. Chem., 2005, 23: 1541
      (e) Huang J., Yu J., Wu G., Sun W., Shen Z.Chin. Chem. Lett., 2009, 20: 1357.
      (f) Clark L., Deacon G. B., Forsyth C. M., Junk P. C., Mountford P., Townley J. P.Dalton Trans., 2010, 39: 6693.
      (g) Wang L., Liang Z., Ni X., Shen Z.Chin. Chem. Lett., 2011, 22: 249.
      (h) Susperregui N., Kramer M. U., Okuda J., Maron L.Organometallics, 2011, 30: 1326.
      (i) Gu Z., Li L., Bao Q., Yuan F.Chin. J. Chem., 2015, 33: 563.

    10. [10]

      (a) Stevels W. M., Ankone M. J. K., Dijkstra P. J., Feijen J.Macromolecules, 1996, 29: 8296.
      (b) Zhang L.-F., Shen Z.-Q., Yu C.-P.Chin. J. Chem., 2003, 21: 1236.
      (c) Wang J., Yao Y., Zhang Y., Shen Q.Inorg. Chem., 2009, 48: 744.
      (d) Wang X., Brosmer J. L., Thevenon A., Diaconescu P. L.Organometallics, 2015, 34: 4700.

    11. [11]

      (a) Zhou S., Wang S., Yang G., Li Q., Zhang L., Yao Z., Zhou Z., Song H.Organometallics, 2007, 26: 3755.
      (b) Yang Y., Li S., Cui D., Chen X., Jing X.Organometallics, 2007, 26, 671.
      (c) Zhang L., Wang Y., Shen L., Zhang T.Chin. J. Chem., 2010, 28: 1019.
      (d) Zhou S., Wu S., Zhu H., Wang S., Zhu X., Zhang L., Yang G., Cui D., Wang H.Dalton Trans., 2011, 40: 9447.

    12. [12]

      (a) Gao W., Cui D., Liu X., Zhang Y., Mu Y.Organometallics, 2008, 27: 5889.
      (b) Yang J., Xu P., Luo Y.Chin. J. Chem., 2010, 28: 457.

    13. [13]

      (a) Iftner C., Bonnet F., Nief F., Visseaux M., Maron L.Organometallics, 2011, 30: 4482.
      (b) Schmid M., Guillaume S. M., Roesky P. W.Organometallics, 2014, 33: 5392.

    14. [14]

      (a) Luo Y., Yao Y., Shen Q., Sun J., Weng L.J. Organomet. Chem., 2002, 662: 144.
      (b) Villiers C., Thuery P., Ephritikhine M. A.Eur. J. Inorg. Chem., 2004, 4624.

    15. [15]

      Stanlake L. J. E., Beard J. D., Schafer L. L.Inorg. Chem., 2008, 47:8062. doi: 10.1021/ic8010635

    16. [16]

      Zhou S., Yin C., Wang H., Zhu X., Yang G., Wang S.Inorg. Chem. Commun., 2011, 14:1196. doi: 10.1016/j.inoche.2011.04.015

    17. [17]

      Li Y., Shi Y., Odom A. L.J. Am. Chem. Soc., 2004, 126:1794-. doi: 10.1021/ja038320g

    18. [18]

      Estler F., Eickerling G., Herdtweck E., Anwander R.Organometallics, 2003, 22:1212. doi: 10.1021/om020783s

  • Scheme 1  Synthesis of complexes 2~4

    Figure 1  Molecular structure of complex 2

    Figure 2  Molecular structure of complex 4

    Table 1.  Selected bond lengths ( ) and bond angles (°)

    Compd. 2 4
    Bond length
    RE(1)—N(1) 0.2315(4) 0.2276(6)
    RE(1)—N(2) 0.2527(4) 0.2506(6)
    RE(1)—N(3) 0.2297(4) 0.2249(6)
    RE(1)—N(4) 0.2584(3) 0.2359(5)
    RE(1)—N(5) 0.2620(3) 0.2604(5)
    RE(1)—N(6) 0.2405(3) 0.2569(5)
    RE(1)—C(12) 0.2707(4) 0.2583(7)
    RE(1)—C(13) 0.2819(4) 0.2722(7)
    RE(1)—C(14) 0.2763(4) 0.2786(7)
    RE(1)—C(15) 0.2598(4) 0.2675(6)
    Bond angle
    RE(1)—N(4)—RE(2) 110.48(10) 108.69(17)
    RE(1)—N(6)—RE(2) 107.71(11) 111.04(18)
    Bond length
    RE(2)—N(4) 0.2457(3) 0.2691(5)
    RE(2)—N(6) 0.2720(3) 0.2413(5)
    RE(2)—N(7) 0.2318(3) 0.2277(5)
    RE(2)—N(8) 0.2524(3) 0.2505(5)
    RE(2)—N(9) 0.2291(3) 0.2280(5)
    RE(2)—O(1) 0.2369(3) 0.2364(4)
    RE(2)—C(19) 0.2752(4) 0.2666(6)
    RE(2)—C(20) 0.2765(4) 0.2684(6)
    RE(2)—C(21) 0.2747(4) 0.2711(6)
    RE(2)—C(22) 0.2702(4) 0.2675(6)
    Bond angle
    N(4)—RE(1)—N(6) 71.96(9) 71.28(16)
    N(4)—RE(2)—N(6) 68.94(9) 68.35(15)
    下载: 导出CSV

    Table 2.  Ring-opening polymerization of ε-caprolactone catalyzed by complexes 2~4a

    Entry Cat. [M]:[catal.] Solvent Temp./℃ Time/min Mnb/(×10-4) Mnc/(×10-4) PDIc Conv./%
    1 2 100:1 Toluene 0 3 1.08 2.41 (1.35) 1.94 95
    2 2 100:1 Toluene 10 1 1.13 2.81 (1.57) 1.38 99
    3 2 100:1 Toluene 20 1 1.13 3.23 (1.81) 1.78 99
    4 2 100:1 THF 10 1 1.12 5.98 (3.34) 1.54 98
    5 2 100:1 Et2O 10 3 0.99 3.81 (2.13) 1.41 87
    6 2 100:1 CH2Cl2 10 5 0.83 3.96 (2.22) 1.45 73
    7 3 100:1 Toluene 10 1 0.68 2.27 (1.27) 1.41 60
    8 4 100:1 Toluene 10 1 1.03 3.23 (1.81) 1.67 90
    9 2 200:1 Toluene 10 1 2.26 4.90 (2.74) 1.61 99
    10 2 300:1 Toluene 10 1 3.39 7.89 (4.41) 1.62 99
    11 2 400:1 Toluene 10 1 4.52 10.60 (5.93) 1.49 99
    12 2 500:1 Toluene 10 2 5.59 12.96 (7.25) 1.54 98
    a Solvent (5.0 mL). b Calculated from [M(ε-capralactone)×[M]/[catal.]×conversion. c Obtained from GPC analysis and calibrated by polystyrene standard, and values in parentheses are the values obtained from GPC times 0.56.
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  • 发布日期:  2020-03-25
  • 收稿日期:  2019-08-06
  • 修回日期:  2019-10-13
  • 网络出版日期:  2019-11-09
通讯作者: 陈斌, bchen63@163.com
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