Synthesis, Characterization and Catalytic Studies of EDBP Supported Lithium, Sodium, Magnesium and Zinc Complexes: Efficient Catalysts for Ring-Opening Polymerization of e-Caprolactone and L-Lactide and Anionic Polymerization of Methyl Methacrylate

Abstract

Several novel zinc and magnesium aryloxides, [(EDBP)Zn(THF)]2 (1), [(EDBP)Mg(Et2O)]2 (2), and [(EDBP)Mg(THF)]2 (3), have been synthesized by the reaction of 2,2¢-ethylidenebis(4,6-di-tert-butylphenol) (EDBP-H2) with ZnEt2 or MgnBu2 in diethyl ether (Et2O) or tetrahydrofuran (THF), respectively. Experimental results show that 1-3 efficiently catalyze the ring-opening polymerization (ROP) of e-caprolactone (e-CL) and L-lactide (L-LA) in a controlled fashion, yielding polymers with very narrow polydispersity indexes (PDI) in a wide range of monomer-to-initiator ratios. The reaction of EDBP-H2 with nBuLi in THF, Et2O or hexane, gives [(EDBP-H)Li(THF)3] (4), [(EDBP-H)Li(Et2O)3] (5) or [(EDBP-H)Li]3 (6), respectively. However, the reaction of EDBP-H2 with nBuLi in the presence of benzyl alcohol (BnOH) in Et2O or THF produces compound [(EDBP-H)Li(BnOH)]2 (7) or [(EDBP-H)Li(BnOH)(THF)2] (8), respectively. Further reaction of 7 with excess of THF produces 8. Alternatively, 8 can also be prepared by the reaction of benzyl alcohol with 4 in toluene. Experimental results show that 7 and 8 efficiently initiate the ROP of L-lactide in a controlled fashion, yielding polymers with very narrow polydispersity indexes in a wide range of monomer-to-initiator ratios. Moreover, the reaction of EDBP-H2 with 2.2 equiv nBuLi in Et2O affords [(EDBP)Li2(Et2O)]2 (9). Moreover, block copolymers, polystyrene-b-poly(L-lactide), have also been prepared from the ring-opening polymerization of L-latide catalyzed by 2 and 4 using polystyrene as a macroinitiator. The unusual lithium n-butylmagnesium [(EDBP)Mg(m2-nBu)Li(Et2O)]2 (10), sodium n-butylmagnesium [(EDBP)Na(Et2O)MgnBu]2 (13), lithium ethylzinc [(EDBP)Zn(THF)]2[(m2-C2H5)Li(THF)] (14) and lithium-magnesium enolate, {(EDBP)Mg[m2-OC(Mes)CH2]Li(Et2O)}2 (11), and the sodium aggregate, [(EDBP)Na2]4 (12), have been synthesized and structurally characterized. Among them, 10, 11, 13 and 14 have been used as initiators for the polymerization of methyl methacrylate. The dimeric lithium n-butylmagnesium complex 10 was obtained from the reaction of [(EDBP)Li(Et2O)3] (5) with a stoichiometric amount of MgnBu2. Alternatively, 10 can also be prepared by the reaction of [(EDBP)Mg(Et2O)]2 (2) with a stoichiometric amount of nBuLi in Et2O. Furthermore, the reaction of 10 with 2¢,4¢,6¢-trimethylacetophenone (MesC(O)CH3, Mes = 2,4,6-Me3C6H2) produces 11. Reaction of EDBP-H2 with excess sodium metal in Et2O furnishes compound 12. In the presence of a stoichiometric amount of MgnBu2 in Et2O, 12 can be converted to the dimeric sodium-magnesium mixed-metal complex [(EDBP)Na(Et2O)MgnBu]2 (13). Moreover, 14 can be obtained by the reaction of [(EDBP)Li(THF)3] (4) with a stoichiometric amount of ZnEt2. Experimental results show that 10, 11, 13 and 14 efficiently initiate the anionic polymerization of methyl methacrylate.Abstract…………………………………………………………………....1 Chapter 1. Introduction Biodegradable Polymers……………………………………....3 Metal Complexes Supported by Salen Ligands………………5 Metal Complexes Supported by Biphenol Ligands…………...8 References…………………………………………………...11 Chapter 2. Zinc, Magnesium and Lithium Complexes Introduction……………………………………………....….15 Results and Discussion………………………………………17 Synthesis and Spectroscopic Studies of Compounds1-9…....17 Molecular Structure Studies of 1-3………………………….20 Molecular Structure Studies of 4 and 6-9……………….…..24 ROP of e-CL Using Complex 1 as Initiator………………...33 ROP of L-LA Using Complexes 1-3 as catalysts………......37 Proposed Mechanism for ROP of L-LA Catalyzed by 1-3...44 ROP of L-LA Using Complexes 7 and 8 as Initiators…….....46 Proposed Mechanism for ROP of L-LA Catalyzed by 7…...50 Summary………...…………………………..……………....52 Experimental Section…………………………………..…....52 References………………………………..………………….58 Chapter 3. Application for the Synthesis of PS-b-PLLA Introduction………………………………………………….62 Preparation of 4-Hydroxyl-TEMPO-terminated Polystyrene …………………………………………………………….…64 Synthesis of Polystyrene-Poly(L-lactide) Diblock Copolymer ……………………………………………………....…...….67 Summary…...…………………………………………..…....70 Experimental Section…………………………………..…....70 References………………………………..………...………..71 Chapter 4. Mixed- Metal Complexes Introduction………………………………………………….73 Results and Discussion……………………………………....81 Synthesis and Spectroscopic Studies of 10-14……………...81 Molecular structure studies of 10-14………………………..83 Polymerization of MMA Using Complexes 10, 11, 13 and 14 as Initiators…………………………………………………..93 Summary………………………….…..……………………..97 Experimental Section………………………………………..97 References………………………………………………….100 Chapter 5. Conclusion………………………………………………….106 Chapter 6. General Informations NMR Spectra…………………………………....………….109 Gel Permeation Chromatography (GPC)…………………..109 X-ray Crystallographic Studies………..…..…………...….109 Differential Scanning Calorimeter (DSC)…………...…......110 Materials…………………………………………………....110 Reference…………………………………..….……….…...111 Catalog of Scheme, Figures and Tables Scheme 1…………………………………………………………….……18 Scheme 2……………………………………………………………….…45 Scheme 3……………………………………………………………….…51 Scheme 4………………………………………………………………….66 Scheme 5………………………………………………………………….82 Scheme 6……………………………………………………………...…108 Figure 1…………………………………………………………………....21 Figure 2…………………………………………………………………....21 Figure 3……………………………………………………………………25 Figure 4……………………………………………………………………25 Figure 5……………………………………………………………………29 Figure 6……………………………………………………………………29 Figure 7……………………………………………………………………32 Figure 8…………………………………………………………………....36 Figure 9……………………………………………………………………37 Figure 10…………………………………………………………………..42 Figure 11…………………………………………………………………..43 Figure 12…………………………………………………………………..49 Figure 13……………………………………………………………….….49 Figure 14…………………………………………………………………..69 Figure 15…………………………………………………………………..69 Figure 16…………………………………………………………………..85 Figure 17…………………………………………………………………..86 Figure 18…………………………………………………………………..86 Figure 19…………………………………………………………………..87 Figure 20…………………………………………………………………..87 Figure 21…………………………………………………………………..96 Table 1…………………………………………………………………….22 Table 2…………………………………………………………………….22 Table 3…………………………………………………………………….23 Table 4…………………………………………………………………….26 Table 5…………………………………………………………………….26 Table 6…………………………………………………………………….27 Table 7…………………………………………………………………….30 Table 8…………………………………………………………………….30 Table 9…………………………………………………………………….31 Table 10…………………………………………………………………...33 Table 11…………………………………………………………………...35 Table 12…………………………………………………………….…..…40 Table 13………………………………………………………………...…41 Table 14……………………………………………………….…………..48 Table 15………………………………………………………………...…66 Table 16………………………………………………………………...…68 Table 17………………………………………………………………...…88 Table 18………………………………………………………………..….88 Table 19………………………………………………………………...…89 Table 20………………………………………………………………..…90 Table 21………………………………………………………………..…91 Table 22………………………………………………………………..…92 Table 23………………………………………………………………..…9