- Email: [email protected]
Synthesis, characterization of potassium bulky phenolate and application in ring-opening polymerization of L-lactide
Inorganic Chemistry Communications 13 (2010) 376–379
Contents lists available at ScienceDirect
Inorganic Chemistry Communications journal homepage: www.elsevier.com/locate/inoche
Synthesis, characterization of potassium bulky phenolate and application in ring-opening polymerization of L-lactide Xiaobo Pan, Ai Liu, Xiaozhe Yang, Jincai Wu *, Ning Tang * Key Laboratory of Nonferrous Metal Chemistry and Resources Utilization of Gansu Province, State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000, People’s Republic of China
a r t i c l e
i n f o
Article history: Received 30 November 2009 Accepted 28 December 2009 Available online 4 January 2010 Keywords: Potassium complex Lactide Ring-opening polymerization Isotactic selectivity
a b s t r a c t The reaction of 2,20 -ethylidenebis(4,6-di-tert-butylphenol) (EDBP-H2) with potassium gives [EDBPH K(THF)2] (1) in 92% yield. Experimental results show that potassium complex 1 is an efficient catalyst for the ring-opening polymerization of lactide in controlled fashion, yielding polymers with expectative molecular weight and low polydispersity indexes. Furthermore, the complex 1 has isotactic selectivity for the ring-opening polymerization of rac-lactide. Ó 2010 Published by Elsevier B.V.
Polylactide (PLA) is one of the most important synthetic biodegradable and biocompatible polymer investigated for a wide range of biomedical and pharmaceutical applications such as controlled drug delivery, resorbable sutures, medical implants, and scaffolds for tissue engineering [1]. An effective method for the synthesis of polylactides is the ring-opening polymerization (ROP) of lactides. Owing to the advantages of well controlled molecular weight and low polydispersity (PDI), many metal complexes have been used to initiate/catalyze ring-opening polymerization of lactides [2]. Although heavy metal compounds such as zinc [3], tin [4], and lanthanide [5] derivatives are effective lactone/lactide ROP initiators affording polymers with high molecular weights in high yield, which are difficult to remove from the resultant polymer and limited utility owing to toxicity of metal cation [6]. Efforts to address this issue have resulted in recent sodium [7], magnesium [8], calcium [9], iron [10] and highly active metal-free [11] catalysts that are competent for the ROP of lactide. Recently some EDBP supported metal complexes are reported as excellent catalysts with good controlled features for ROP of cyclic ester [3,7,8,12]. EDBPH2 is an attractive ligand because it has been approved as an indirect food additive (as an antioxidant in polymer packaging) by the US Food and Drug Administration [13]. Sodium and potassium cations are nontoxic and are essential to life, therefore EDBP sodium and potassium complexes attract our interesting. EDBP-Na [7] has been reported as a good initiator for ROP of lactide. Herein we report one
* Corresponding authors. Fax: +86 931 8912582. E-mail addresses: [email protected] (X. Pan), [email protected] (J. Wu). 1387-7003/$ - see front matter Ó 2010 Published by Elsevier B.V. doi:10.1016/j.inoche.2009.12.027
new potassium EDBP complex to catalyze ring-opening polymerization of lactide and results show it is an efficient catalyst. The reaction of 2,20 -ethylidenebis(4,6-di-tert-butylphenol)(EDBP-H2) with potassium in THF gives complex of [EDBPH K(THF)2] (1) [14] (Scheme 1) in 92% yield. And fine colorless crystals [15] were obtained by crystallization from THF/hexane (10 mL:5 mL). The ORTEP drawing of 1 is given in Fig. 1. The [EDBPHK(THF)2] (1) complex is crystallized in monoclinic space group P2(1)/c. Two potassium atoms in this complex are equivalent. K1 is surrounded by two oxygen atoms of O1, O2 from one EDBP ligand and two oxygen atoms of O3, O4 from two THF molecules with bond lengths of K1–O3 2.618(4), K1–O4 2.751(5) Å, respectively. The distance between K1 and aromatic ring of C8A C9A C10A C11A C12A C13A is 3.062(5) Å which demonstrates strong p–p interaction between K1 and the benzene ring [16]. Two molecules are bridged through this p–p interaction between K and phenyl ring of one EDBP ligand, and the complex 1 forms a dimeric structure in the crystal structure. In this context, ROP of L-lactide employing 1 (0.02 mmol) as catalyst is systematically examined in toluene at 90 °C, as shown in Table 1. In other solvents, such as THF, CH2Cl2, the polymerization progress almost does not happen. Experimental results show that complex 1 is efficient catalyst for the ROP of L-lactide, and the polymerization went to completion within 36 hours at 90 °C with a monomer-to-complex ratio of 100. It is interesting that EDBP-Na reported by Lin [7] catalyzes the ROP of L-lactide with methanol as initiator, while complex 1 can catalyzes the reaction directly without methanol. Actually complex 1 cannot activate methanol to initiate the ROP of lactide, because methanol cannot easily coordinate to K+ owing to the low lewis acid of K+ and be
377
X. Pan et al. / Inorganic Chemistry Communications 13 (2010) 376–379
Scheme 1. Preparation of potassium complex 1.
Fig. 2. Polymerization of L-LA catalyzed by 1 in toluene at 90 °C. The relationship between Mn(j) (PDI (d)) of the polymer and the initial mole ratio [LA]0/[complex]0 is shown.
Fig. 1. Molecular structure of 1 (methyl carbons of the tert-butyl groups are omitted for clarity, hydrogen atoms omitted except for ArOH). Selected bond lengths (Å): K1–O1 2.953(3), K1–O2 2.744(3), K1–O3 2.618(4), K1–O4 2.751(5).
activated by phenoxy ligand. For the different ROP mechanism, the activity of complex 1 is lower comparing to EDBP-Na. The good polymerization control is demonstrated by the linear relationship between Mn and [LA]0/[complex]0 and the polymers with PDIs, ranging from 1.29 to 1.58 (Fig. 2). Therefore, the living character of the polymerization has been proved, which was further confirmed by are resumption experiment (entry 6) in which another portion of L-LA monomer ([LA]0/[Complex]0 = 50) was added after the polymerization of the first addition ([LA]0/[Complex]0 = 50) had gone to completion. Analysis of PLA-50 (Table 1, entry 1) produced from 1 at an initial [LA]0/[Complex]0 ratio of 50 by 1H NMR shows a characteristic
methine peak (Fig. 3) at 4.35 ppm and broad carboxyl end group peak at 3.78 ppm in CDCl3, indicating the two end groups of the polymer are the hydroxyl and carboxyl end group respectively. To further confirm the components of the end group of the polymer, Electrospray-ionization (+ESI) mass spectrum of PLA-50 was also obtained. Mass spectra analysis of a related oligomer (Table 1, entry 1) corroborated the exclusive incorporation of the protic reagent in the polymer chains. The spectrum obtained by electrospray-ionization exhibited only a set of signals corresponding to oligomers of the formula HO(COCHMeO)nHM+ (M = NH4, K) (Fig. 4). Furthermore, epimerization of the chiral centers in PLLA does not occur as observed by the homonuclear decoupled 1H NMR studies in the methine region [17]. Polymerization of rac-lactide by complex 1 was also performed, as shown in Table 1 (entry 5). The homonuclear decoupled 1H NMR spectrum at the methine region of the PLA derived from 1 is isotactic predominance with Pm = 0.64 for 1 [18]. The low selectivity may result from the insufficient bulk of the ligand, the modification of this type of ligand is now in progress in our laboratory. In conclusion, a new potassium complex has been synthesized and characterized. The potassium complex 1 is an efficient catalyst for ring-opening polymerization of lactide under controlled manner with slight isotactic selectivity.
Table 1 Ring-opening polymerization of lactide using complexa.
a b c d
Entry
[LA]0/[Complex]0
Time (h)
PDI
Mn (obsd)b
Mn (calcd)c
Conversion (%)
1 2 3 4 5 6
50:1 100:1 125:1 150:1 100:1d 50(50):1
24 36 48 48 36 48
1.34 1.44 1.58 1.43 1.29 1.40
15,200 23,400 27,700 34,600 17,700 30,000
6400 11,400 14,300 19,400 11,650 13,100
87.1 78.5 79.2 89.4 80.3 90.6
(8800) (13,500) (16,100) (20,000) (10,300) (17,400)
Conditions: 0.02 mmol of complex, 10 mL of toluene, 90 °C. Obtained from GPC analysis, and calibrated by polystyrene standard (corrected values listed in brackets). Calculated from the molecular weight of L-lactide times [LA]0/[Complex]0 times conversion yield plus the molecular weight of H2O. At 90 °C, 10 mL of toluene and rac-lactide were used.
378
X. Pan et al. / Inorganic Chemistry Communications 13 (2010) 376–379
Fig. 3. 1H NMR PLA-50 (from table 1, entry 1) in CDCl3.
Fig. 4. +ESI mass spectrum of PLA-50.
X. Pan et al. / Inorganic Chemistry Communications 13 (2010) 376–379
Acknowledgments Financial support from the National Natural Science Foundation of China (No. 20601011), the Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Education Ministry, Science Foundation of Gansu Province of China (0803RJZA103) are gratefully acknowledged.
[3] [4] [5] [6] [7] [8]
Appendix A. Supplementary material Supplementary data associated with this article can be found, in the online version, at doi:10.1 016/j.inoche.2009.12.027.
[9] [10] [11] [12]
References [13] [1] (a) R.P. Lanza, R. Langer, J. Vacanti, Principles of Tissue Engineering, second ed., Academic Press, San Diego, CA, 2000; (b) K. Nakano, N. Kosaka, T. Hiyama, K. Nozaki, J. Chem. Soc. Dalton Trans. (2003) 4039; (c) O. Dechy-Cabaret, B. Martin-Vaca, D. Bourissou, Chem. Rev. 104 (2004) 6147; (d) J.C. Wu, T.-L. Yu, C.-T. Chen, C.-C. Lin, Coord. Chem. Rev. 250 (2006) 602; (e) A.J. Chmura, C.J. Chuck, M.G. Davidson, M.D. Jones, M.D. Lunn, S.D. Bull, et al., Angew Chem. Int. Ed. 46 (2007) 2280; (f) R.H. Platel, L.M. Hodgson, C.K. Williams, Chem. Rev. 48 (2008) 11. [2] (a) C.K. Williams, L.E. Breyfogle, S.K. Choi, W.-W. Nam, Jr.V.G. Young, M.A. Hillmyer, W.B. Tolman, J. Am. Chem. Soc. 125 (2003) 11350; (b) M.H. Chisholm, J.C. Gallucci, K. Phomphrai, Chem. Commun. (2003) 48; (c) N. Nimitsiriwat, E.L. Marshall, V.C. Gibson, M.R.J. Elsegood, S.H. Dale, J. Am. Chem. Soc. 126 (2004) 13598; (d) H. Li, C.H. Wang, F. Bai, J. Yue, H.-G. Woo, Organometallics 23 (2004) 1411; (e) J.C. Wu, B.H. Huang, M.L. Hsueh, S.L. Lai, C.-C. Lin, Polymer 46 (2005) 9784; (f) Z. Tang, V.C. Gibson, Eur. Polym. J. 43 (2007) 150; (g) H. Du, X. Pang, H. Yu, C.X. Zhuang, D. Cui, Macromolecules 40 (2007) 1904;
[14]
[15]
[16] [17] [18]
379
(h) E. Grunova, E. Kirillov, T. Roisnel, J.-F. Carpentier, Organometallics 27 (2008) 5691. B.M. Chamberlain, M. Cheng, D.R. Moore, T.M. Ovitt, E.B. Lobkovsky, G.W. Coates, J. Am. Chem. Soc. 123 (2001) 3229. K.B. Aubrecht, M.A. Hillmyer, W.B. Tolman, Macromolecules 35 (2002) 644. H. Ma, T.P. Spaniol, J. Okuda, Dalton Trans. (2003) 4770. K.E. Uhrich, S.M. Cannizzaro, R.S. Langer, K.M. Shakesheff, Chem. Rev. 99 (1999) 3181. H.-Y. Chen, J.B. Zhang, C.-C. Lin, J.H. Reibenspies, S.A. Miller, Green Chem. 9 (2007) 1038. T.-L. Yu, C.-C. Wu, C.-C. Chen, B.-H. Huang, J.C. Wu, C.-C. Lin, Polymer 46 (2005) 5909. M.H. Chisholm, J.C. Gallucci, K. Phomphrai, Inorg. Chem. 43 (2004) 6717. B.J. O’Keefe, L.E. Breyfogle, M.A. Hillmyer, W.B. Tolman, J. Am. Chem. Soc. 124 (2002) 4384. R.C. Pratt, B.G.G. Lohmeijer, D.A. Long, R.M. Waymouth, J.L. Hedrick, J. Am. Chem. Soc. 128 (2006) 4556. (a) B.-T. Ko, C-C. Lin, J. Am. Chem. Soc. 123 (2001) 7973; (b) B.-H. Huang, B.-T. Ko, T. Athar, C.-C. Lin, Inorg. Chem. 45 (2006) 7348; (c) W.-C. Hung, C.-C. Lin, Inorg. Chem. 48 (2009) 728. U.S.F.D.A. Code of Federal Regulations, Title 21, Volume 3, Section 178. 2010, Revised April 1, 2006; Federal Register, 51(193) (1986) 35511; Federal Register, 48(132) (1983) 31382; Federal Register, 47(101, Bk. 1) (1982) 22512. Potassium complex: Yield 0.57 g (92%). 1H NMR (CDCl3, ppm): d 7.04 (s, 4H, Ph), 7.02(s, 4H, Ph), 4.79 (s, 2H, CH(CH3)), 3.74 (s, 16H, O–CH2), 1.85 (s, 16H, CH2), 1.68 (s, 6H, CH(CH3)), 1.37 (s, 36H, C(CH3)3), 1.26 (s, 36H, C(CH3)3). Anal. calcd for C76H122K2O8: C, 73.50; H, 9.90%. Found: C, 73.24; H, 9.58%. Crystal data for potassium complex: C38H61KO4, M = 620.97, monoclinic, space group P2(1)/c, a = 12.8666(3) Å, b = 16.6906(4) Å, c = 18.0583(5) Å, a = 90.00, b = 98.6890(10), c = 90.00, V = 3833.53(17) Å3, T = 293(2) K, Z = 4, Dc = 1.076 g/ cm3, F000 = 1360, 2hmax = 26.56, 22532 reflections collected, 7974 unique (Rint = 0.0466), no. of observed reflections 3962 (I > 2r(I)); R1 = 0.0715, wR2 = 0.2061. P.C. Andrews, A.R. Kennedy, R.E. Mulvey, C.L. Raston, B.A. Roberts, R.B. Rowlings, Angew. Chem. Int. Ed. 39 (2000) 1960. M. Diekmann, G. Bockstiegel, A. Lützen, M. Firedemann, W. Saak, D. Haase, R. Beckhaus, Organometallics 25 (2006) 339. (a) H.R. Kricheldorf, C. Boettcher, K.-U. Tönnes, Polymer 33 (1992) 2817; (b) M.T. Zell, B.E. Padden, A.J. Paterick, K.A.M. Thakur, R.T. Kean, M.A. Hillmyer, E.J. Munson, Macromolecules 35 (2002) 7700.
Contents lists available at ScienceDirect
Inorganic Chemistry Communications journal homepage: www.elsevier.com/locate/inoche
Synthesis, characterization of potassium bulky phenolate and application in ring-opening polymerization of L-lactide Xiaobo Pan, Ai Liu, Xiaozhe Yang, Jincai Wu *, Ning Tang * Key Laboratory of Nonferrous Metal Chemistry and Resources Utilization of Gansu Province, State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000, People’s Republic of China
a r t i c l e
i n f o
Article history: Received 30 November 2009 Accepted 28 December 2009 Available online 4 January 2010 Keywords: Potassium complex Lactide Ring-opening polymerization Isotactic selectivity
a b s t r a c t The reaction of 2,20 -ethylidenebis(4,6-di-tert-butylphenol) (EDBP-H2) with potassium gives [EDBPH K(THF)2] (1) in 92% yield. Experimental results show that potassium complex 1 is an efficient catalyst for the ring-opening polymerization of lactide in controlled fashion, yielding polymers with expectative molecular weight and low polydispersity indexes. Furthermore, the complex 1 has isotactic selectivity for the ring-opening polymerization of rac-lactide. Ó 2010 Published by Elsevier B.V.
Polylactide (PLA) is one of the most important synthetic biodegradable and biocompatible polymer investigated for a wide range of biomedical and pharmaceutical applications such as controlled drug delivery, resorbable sutures, medical implants, and scaffolds for tissue engineering [1]. An effective method for the synthesis of polylactides is the ring-opening polymerization (ROP) of lactides. Owing to the advantages of well controlled molecular weight and low polydispersity (PDI), many metal complexes have been used to initiate/catalyze ring-opening polymerization of lactides [2]. Although heavy metal compounds such as zinc [3], tin [4], and lanthanide [5] derivatives are effective lactone/lactide ROP initiators affording polymers with high molecular weights in high yield, which are difficult to remove from the resultant polymer and limited utility owing to toxicity of metal cation [6]. Efforts to address this issue have resulted in recent sodium [7], magnesium [8], calcium [9], iron [10] and highly active metal-free [11] catalysts that are competent for the ROP of lactide. Recently some EDBP supported metal complexes are reported as excellent catalysts with good controlled features for ROP of cyclic ester [3,7,8,12]. EDBPH2 is an attractive ligand because it has been approved as an indirect food additive (as an antioxidant in polymer packaging) by the US Food and Drug Administration [13]. Sodium and potassium cations are nontoxic and are essential to life, therefore EDBP sodium and potassium complexes attract our interesting. EDBP-Na [7] has been reported as a good initiator for ROP of lactide. Herein we report one
* Corresponding authors. Fax: +86 931 8912582. E-mail addresses: [email protected] (X. Pan), [email protected] (J. Wu). 1387-7003/$ - see front matter Ó 2010 Published by Elsevier B.V. doi:10.1016/j.inoche.2009.12.027
new potassium EDBP complex to catalyze ring-opening polymerization of lactide and results show it is an efficient catalyst. The reaction of 2,20 -ethylidenebis(4,6-di-tert-butylphenol)(EDBP-H2) with potassium in THF gives complex of [EDBPH K(THF)2] (1) [14] (Scheme 1) in 92% yield. And fine colorless crystals [15] were obtained by crystallization from THF/hexane (10 mL:5 mL). The ORTEP drawing of 1 is given in Fig. 1. The [EDBPHK(THF)2] (1) complex is crystallized in monoclinic space group P2(1)/c. Two potassium atoms in this complex are equivalent. K1 is surrounded by two oxygen atoms of O1, O2 from one EDBP ligand and two oxygen atoms of O3, O4 from two THF molecules with bond lengths of K1–O3 2.618(4), K1–O4 2.751(5) Å, respectively. The distance between K1 and aromatic ring of C8A C9A C10A C11A C12A C13A is 3.062(5) Å which demonstrates strong p–p interaction between K1 and the benzene ring [16]. Two molecules are bridged through this p–p interaction between K and phenyl ring of one EDBP ligand, and the complex 1 forms a dimeric structure in the crystal structure. In this context, ROP of L-lactide employing 1 (0.02 mmol) as catalyst is systematically examined in toluene at 90 °C, as shown in Table 1. In other solvents, such as THF, CH2Cl2, the polymerization progress almost does not happen. Experimental results show that complex 1 is efficient catalyst for the ROP of L-lactide, and the polymerization went to completion within 36 hours at 90 °C with a monomer-to-complex ratio of 100. It is interesting that EDBP-Na reported by Lin [7] catalyzes the ROP of L-lactide with methanol as initiator, while complex 1 can catalyzes the reaction directly without methanol. Actually complex 1 cannot activate methanol to initiate the ROP of lactide, because methanol cannot easily coordinate to K+ owing to the low lewis acid of K+ and be
377
X. Pan et al. / Inorganic Chemistry Communications 13 (2010) 376–379
Scheme 1. Preparation of potassium complex 1.
Fig. 2. Polymerization of L-LA catalyzed by 1 in toluene at 90 °C. The relationship between Mn(j) (PDI (d)) of the polymer and the initial mole ratio [LA]0/[complex]0 is shown.
Fig. 1. Molecular structure of 1 (methyl carbons of the tert-butyl groups are omitted for clarity, hydrogen atoms omitted except for ArOH). Selected bond lengths (Å): K1–O1 2.953(3), K1–O2 2.744(3), K1–O3 2.618(4), K1–O4 2.751(5).
activated by phenoxy ligand. For the different ROP mechanism, the activity of complex 1 is lower comparing to EDBP-Na. The good polymerization control is demonstrated by the linear relationship between Mn and [LA]0/[complex]0 and the polymers with PDIs, ranging from 1.29 to 1.58 (Fig. 2). Therefore, the living character of the polymerization has been proved, which was further confirmed by are resumption experiment (entry 6) in which another portion of L-LA monomer ([LA]0/[Complex]0 = 50) was added after the polymerization of the first addition ([LA]0/[Complex]0 = 50) had gone to completion. Analysis of PLA-50 (Table 1, entry 1) produced from 1 at an initial [LA]0/[Complex]0 ratio of 50 by 1H NMR shows a characteristic
methine peak (Fig. 3) at 4.35 ppm and broad carboxyl end group peak at 3.78 ppm in CDCl3, indicating the two end groups of the polymer are the hydroxyl and carboxyl end group respectively. To further confirm the components of the end group of the polymer, Electrospray-ionization (+ESI) mass spectrum of PLA-50 was also obtained. Mass spectra analysis of a related oligomer (Table 1, entry 1) corroborated the exclusive incorporation of the protic reagent in the polymer chains. The spectrum obtained by electrospray-ionization exhibited only a set of signals corresponding to oligomers of the formula HO(COCHMeO)nHM+ (M = NH4, K) (Fig. 4). Furthermore, epimerization of the chiral centers in PLLA does not occur as observed by the homonuclear decoupled 1H NMR studies in the methine region [17]. Polymerization of rac-lactide by complex 1 was also performed, as shown in Table 1 (entry 5). The homonuclear decoupled 1H NMR spectrum at the methine region of the PLA derived from 1 is isotactic predominance with Pm = 0.64 for 1 [18]. The low selectivity may result from the insufficient bulk of the ligand, the modification of this type of ligand is now in progress in our laboratory. In conclusion, a new potassium complex has been synthesized and characterized. The potassium complex 1 is an efficient catalyst for ring-opening polymerization of lactide under controlled manner with slight isotactic selectivity.
Table 1 Ring-opening polymerization of lactide using complexa.
a b c d
Entry
[LA]0/[Complex]0
Time (h)
PDI
Mn (obsd)b
Mn (calcd)c
Conversion (%)
1 2 3 4 5 6
50:1 100:1 125:1 150:1 100:1d 50(50):1
24 36 48 48 36 48
1.34 1.44 1.58 1.43 1.29 1.40
15,200 23,400 27,700 34,600 17,700 30,000
6400 11,400 14,300 19,400 11,650 13,100
87.1 78.5 79.2 89.4 80.3 90.6
(8800) (13,500) (16,100) (20,000) (10,300) (17,400)
Conditions: 0.02 mmol of complex, 10 mL of toluene, 90 °C. Obtained from GPC analysis, and calibrated by polystyrene standard (corrected values listed in brackets). Calculated from the molecular weight of L-lactide times [LA]0/[Complex]0 times conversion yield plus the molecular weight of H2O. At 90 °C, 10 mL of toluene and rac-lactide were used.
378
X. Pan et al. / Inorganic Chemistry Communications 13 (2010) 376–379
Fig. 3. 1H NMR PLA-50 (from table 1, entry 1) in CDCl3.
Fig. 4. +ESI mass spectrum of PLA-50.
X. Pan et al. / Inorganic Chemistry Communications 13 (2010) 376–379
Acknowledgments Financial support from the National Natural Science Foundation of China (No. 20601011), the Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Education Ministry, Science Foundation of Gansu Province of China (0803RJZA103) are gratefully acknowledged.
[3] [4] [5] [6] [7] [8]
Appendix A. Supplementary material Supplementary data associated with this article can be found, in the online version, at doi:10.1 016/j.inoche.2009.12.027.
[9] [10] [11] [12]
References [13] [1] (a) R.P. Lanza, R. Langer, J. Vacanti, Principles of Tissue Engineering, second ed., Academic Press, San Diego, CA, 2000; (b) K. Nakano, N. Kosaka, T. Hiyama, K. Nozaki, J. Chem. Soc. Dalton Trans. (2003) 4039; (c) O. Dechy-Cabaret, B. Martin-Vaca, D. Bourissou, Chem. Rev. 104 (2004) 6147; (d) J.C. Wu, T.-L. Yu, C.-T. Chen, C.-C. Lin, Coord. Chem. Rev. 250 (2006) 602; (e) A.J. Chmura, C.J. Chuck, M.G. Davidson, M.D. Jones, M.D. Lunn, S.D. Bull, et al., Angew Chem. Int. Ed. 46 (2007) 2280; (f) R.H. Platel, L.M. Hodgson, C.K. Williams, Chem. Rev. 48 (2008) 11. [2] (a) C.K. Williams, L.E. Breyfogle, S.K. Choi, W.-W. Nam, Jr.V.G. Young, M.A. Hillmyer, W.B. Tolman, J. Am. Chem. Soc. 125 (2003) 11350; (b) M.H. Chisholm, J.C. Gallucci, K. Phomphrai, Chem. Commun. (2003) 48; (c) N. Nimitsiriwat, E.L. Marshall, V.C. Gibson, M.R.J. Elsegood, S.H. Dale, J. Am. Chem. Soc. 126 (2004) 13598; (d) H. Li, C.H. Wang, F. Bai, J. Yue, H.-G. Woo, Organometallics 23 (2004) 1411; (e) J.C. Wu, B.H. Huang, M.L. Hsueh, S.L. Lai, C.-C. Lin, Polymer 46 (2005) 9784; (f) Z. Tang, V.C. Gibson, Eur. Polym. J. 43 (2007) 150; (g) H. Du, X. Pang, H. Yu, C.X. Zhuang, D. Cui, Macromolecules 40 (2007) 1904;
[14]
[15]
[16] [17] [18]
379
(h) E. Grunova, E. Kirillov, T. Roisnel, J.-F. Carpentier, Organometallics 27 (2008) 5691. B.M. Chamberlain, M. Cheng, D.R. Moore, T.M. Ovitt, E.B. Lobkovsky, G.W. Coates, J. Am. Chem. Soc. 123 (2001) 3229. K.B. Aubrecht, M.A. Hillmyer, W.B. Tolman, Macromolecules 35 (2002) 644. H. Ma, T.P. Spaniol, J. Okuda, Dalton Trans. (2003) 4770. K.E. Uhrich, S.M. Cannizzaro, R.S. Langer, K.M. Shakesheff, Chem. Rev. 99 (1999) 3181. H.-Y. Chen, J.B. Zhang, C.-C. Lin, J.H. Reibenspies, S.A. Miller, Green Chem. 9 (2007) 1038. T.-L. Yu, C.-C. Wu, C.-C. Chen, B.-H. Huang, J.C. Wu, C.-C. Lin, Polymer 46 (2005) 5909. M.H. Chisholm, J.C. Gallucci, K. Phomphrai, Inorg. Chem. 43 (2004) 6717. B.J. O’Keefe, L.E. Breyfogle, M.A. Hillmyer, W.B. Tolman, J. Am. Chem. Soc. 124 (2002) 4384. R.C. Pratt, B.G.G. Lohmeijer, D.A. Long, R.M. Waymouth, J.L. Hedrick, J. Am. Chem. Soc. 128 (2006) 4556. (a) B.-T. Ko, C-C. Lin, J. Am. Chem. Soc. 123 (2001) 7973; (b) B.-H. Huang, B.-T. Ko, T. Athar, C.-C. Lin, Inorg. Chem. 45 (2006) 7348; (c) W.-C. Hung, C.-C. Lin, Inorg. Chem. 48 (2009) 728. U.S.F.D.A. Code of Federal Regulations, Title 21, Volume 3, Section 178. 2010, Revised April 1, 2006; Federal Register, 51(193) (1986) 35511; Federal Register, 48(132) (1983) 31382; Federal Register, 47(101, Bk. 1) (1982) 22512. Potassium complex: Yield 0.57 g (92%). 1H NMR (CDCl3, ppm): d 7.04 (s, 4H, Ph), 7.02(s, 4H, Ph), 4.79 (s, 2H, CH(CH3)), 3.74 (s, 16H, O–CH2), 1.85 (s, 16H, CH2), 1.68 (s, 6H, CH(CH3)), 1.37 (s, 36H, C(CH3)3), 1.26 (s, 36H, C(CH3)3). Anal. calcd for C76H122K2O8: C, 73.50; H, 9.90%. Found: C, 73.24; H, 9.58%. Crystal data for potassium complex: C38H61KO4, M = 620.97, monoclinic, space group P2(1)/c, a = 12.8666(3) Å, b = 16.6906(4) Å, c = 18.0583(5) Å, a = 90.00, b = 98.6890(10), c = 90.00, V = 3833.53(17) Å3, T = 293(2) K, Z = 4, Dc = 1.076 g/ cm3, F000 = 1360, 2hmax = 26.56, 22532 reflections collected, 7974 unique (Rint = 0.0466), no. of observed reflections 3962 (I > 2r(I)); R1 = 0.0715, wR2 = 0.2061. P.C. Andrews, A.R. Kennedy, R.E. Mulvey, C.L. Raston, B.A. Roberts, R.B. Rowlings, Angew. Chem. Int. Ed. 39 (2000) 1960. M. Diekmann, G. Bockstiegel, A. Lützen, M. Firedemann, W. Saak, D. Haase, R. Beckhaus, Organometallics 25 (2006) 339. (a) H.R. Kricheldorf, C. Boettcher, K.-U. Tönnes, Polymer 33 (1992) 2817; (b) M.T. Zell, B.E. Padden, A.J. Paterick, K.A.M. Thakur, R.T. Kean, M.A. Hillmyer, E.J. Munson, Macromolecules 35 (2002) 7700.