Making Plastics from Carbon Dioxide: Copolymerization of Epoxides and CO 2

Size: px

Start display at page:

Download "Making Plastics from Carbon Dioxide: Copolymerization of Epoxides and CO 2"

Arnold Garrison
5 years ago
Views:

Making Plastics from Carbon Dioxide: Copolymerization of Epoxides and C 2 Contents: I Global warming II Utilization of C 2 III Copolymerization of epoxides and C 2 a Background of copolymerization of

1 Making Plastics from Carbon Dioxide: Copolymerization of Epoxides and C 2 Contents: I Global warming II Utilization of C 2 III Copolymerization of epoxides and C 2 a Background of copolymerization of epoxides and C 2 b First example of copolymerization of epoxides and C 2 c Salen metal complexe as catalysts 1 Cr salen complex 2 Co salen complex d Zinc catalysts 1 Coates 's β-diiminate zinc catalysts 2 Asymmetric copolymerization using zinc catalysts IV utlook Review: 1 Chem. Rew. 2001, 101, Angew. Chem. Int. Et. 2004, 43, Chem. Rew. 2007, 107, /3/12, Z. Chen (D1)

predicted to be exhausted within the next century at the current rate of consumption, there is a growing effort to develop new chemical processes using biorenewable

2 I Global warming! Fig 1 sea-level rise caused by global warming Fig 2: Desertification Fig 3 The major reason of global warning n the other hand, since petroleum resources are predicted to be exhausted within the next century at the current rate of consumption, there is a growing effort to develop new chemical processes using biorenewable resources. C 2 is an abundant, inexpensive, and nontoxic biorenewable resource. C 2 might be an attrative raw material! II Utilization of C 2 a Situation in Japan: 1997 Kyoto Protocol; 2008 TYAK Summit Conference. Fig 4 Immobilization of C 2 in Japan Let's concentrant on immobilization of C 2 by chemical methods! 1/11

3 b Reduction of C 2 Methods: Electrochemical reduction; Metal-catalyzed hydrogenation; Photochemical reduction and so on Scheme 2 Example of metal catalyzed: Cu/Zr 2 heterogeneous catalytic hydrogenation of C 2 to methanol Scheme 1 Example of electrochemical reduction: c Chemical transformation of C 2 Scheme 3 Chemical transformations of C 2 Example of chemical transfromation of C 2 : Mori miwako group, JACS 2002, 124, ovel Catalytic C 2 Incorporation Reaction: ickel-catalyzed Regio- and Stereoselective Ring-Closing Carboxylation of Bis-1,3-dienes Scheme 4 i-catalyzed ring-closing carboxylation Scheme 5 Possible reaction mechanism ne of the most efficient way to immobilize C 2 is polymerzation of C 2 C MR 2 M n R Eq 1 or C 2 n Eq 2 So far it is very difficult! Today let me introduce copolymeriztion of epoxides and C 2 to you. 2/11

4 III Copolymerization of epoxides and C 2 or CH: cyclohexene oxide P: propylene oxide a Background of copolymerization of epoxides and C 2 Scheme 6 The basic mechanism of epoxide and C 2 copolymerization and the formation of cycli carbonates backbiting Major by-product (Thermodynamically more stable than polycarbonates) Scheme 7 Qualitative, ideal free-energy profile depicting alternating copolymerization of propylene oxide and C 2, as well as potential side-reactions. Scheme 8 Regiochemistry of PPC low temperature is better! Chiral center! least hindered C- bond ther key point of this reaction: 1 TF 2 Pressure(C 2 ) 3 temperature 4 M n 5 M w /M n 3/11

5 b First example: Inoue group (aluminum catalysts) Makromol. Chem. 1978, 179, Scheme 10 ther alumium catalysts: Macromolecules 1982, 15, : Aluminuim calix-4-arene (Kuran, 1998) Scheme 9 Alumium porphyrins for copolymerization 4,5,6: Aluminum alkoxides complex (Beckman, 1999, 2000) of epoxide and C 2 Cocatalysts: phosphonium salts 20 o C, 8 atm C 2, 0.3 h -1 TF C Salen metal complex: 1 Cr Salen complex i Jacobsen group: JACS 1995, 117, First example of copolymerization of Salen complex: Jacobsen PCTInt. Appl. W00/09463, ii ther groups developed the salen complex system with cocatalysts: 2001, guyen: Cat 9d/MeIm 2002, Darensbourg: Cat 10/P t Bu , Rieger: Cat 11/DMAP 80 o C, 55 atm C 2, 12 h -1 TF 80 o C, 60 atm C 2, 32.2 h -1 TF, 100% carbonate linkages. 75 o C, 35 atm C 2, 226 h -1 TF, 98% carbonate linkages. iii Proposed mechanism with cocatalyst in the initiation step: (intermolecular) (intarmolecular) uc: cocatalyst 4/11

6 iv Intermolecular bimetallic pathway: four-membered transition state v Intarmolecular monometallic pathway: Darensbourg; Chem. Rew. 2007, 107, Scheme 11: X-ray structure of intermediate 4 Kim group: Angew. Chem. Int. Ed. 2000, 39, Scheme 12: The case in Cr-salen/DMAP system 3 3 Cr Cr ring opened by DMAP dimeric pyridinium alkoxy zinc derivatives Table 1 Effect of various phosphines on the rate of copolymerization of cyclohexene oxide and C 2 catalyzed by Cr Salen complex: Scheme 13 Activation of phosphines by formation of phosphonium zwitterious Sterical phosphines are effective cocatalysts 5/11

7 vi Cocatalyst as a turning tools: Table 2 Catalytic activity in the presence of PPX cocatalyst. PPCl: (C 6 H 5 ) 3 P=(Cl)=P(C 6 H 5 ) 3 -MeIm: -methylimidazole Fig 4: Cocatalyst loading Reason: Polymer Backbiting Polymer Cr X u u Cr X + u = cocatalyst 2 Co (III) Salen complex: Competition of data in carbonate linkages, TF, pressure, temperature and so on. 6/11

8 i 2003: Coates group (Co Salen complex only), Angew. Chem. Int. Ed. 2003, 42, * 1mPa = 145 psi ii 2004: Lu group (with quaternary amminium salts), Angew. Chem. Int. Ed. 2004, 43, /11

iii 2006: ozaki group (with a piperidinium end-capping arm) Angew. Chem. Int. Ed. 2006, 45, 7274.

9 iii 2006: ozaki group (with a piperidinium end-capping arm) Angew. Chem. Int. Ed. 2006, 45, Scheme 14 Catalyst design to suppress the production of cyclic carbonate Table 3: Copolymerization of epoxides with C 2 catalyzed by cobalt complex 1 Scheme 15: Synthesis of a block terpolymer 8/11

10 d Zinc catalysts: 1 Coates 's β-diiminate zinc catalysts i High-activity Zn(II)-based catalysts for the copolymerization of C 2 and cyclohexene oxide. JACS 1998, 120, JACS 2001, 123, Scheme 16 X-ray crystal structure of the dimer of β-diiminate zinc catalyst 1 Scheme 17 Synthesis of β-diiminate zinc catalyst Table 4 Results of copolymerization of C 2 and cyclohexene oxide ii Proposed copolymerization mechanism using β-diiminate zinc catalyst: Scheme 18 Insertion reaction of C 2 Scheme 19 Insertion reaction of CH JACS 2003, 125, e 9/11

Scheme 20 Proposed copolymerization mechanism and epoxide ring-opening transition state: Scheme 21 Unsymmetrical, electron-deficient β-di-zinc complex for the copolymerizaiton of propylene oxide and

11 Scheme 20 Proposed copolymerization mechanism and epoxide ring-opening transition state: Scheme 21 Unsymmetrical, electron-deficient β-di-zinc complex for the copolymerizaiton of propylene oxide and C 2 JACS 2002, 124, Scheme 22 Alternating copolymerization of limonene oxide and carbon C 2 JACS 2004, 126, Scheme 23 Ring opening of 1a and 1b during copolymerization and hydrolytic cleavage to give diaxial diol 13 iii Fromation of nanoparticles by intramoleucar cross-linking: following the reaction progess of single polymer chains JACS 2007, 129, Scheme 24 Synthesis of alkene crossing-linked polycarbonate nanoparticles 10/11

12 2 Zinc catalysts for asymmetric CH-C 2 copolymerizaiton i ozaki Group: JACS 1998, 121, Scheme 25 Synthesis of complex 2a and it's structure Scheme 26 Asymmetric alternating copolymerization of CH and C 2 recrystallization Fig 5 MALDI-TF mass specrtum to determine the end group Scheme 27 Proposed structure of copolymerization Scheme 28 Proposed mechanism Each signal = 142.2n (repeating unit) (1a) (H) (a + ion) ii Coates group: Chem. Commun. 2000, IV utlook: Remained task: 1 Completely controlled asymmetric CH-C 2 copolymerizaiton 2 Polymerzation of C 2 tbu tbu M But tbu How about? * M 1 M 2 MR C 2 M n R Metal Salen complex (Efficient catalysts for copolymerization of epoxides and C 2 ) Bimetallic Schiff base complex 11/11

11 Homogeneous Catalyst Design for the Synthesis of Aliphatic Polycarbonates and Polyesters

j343 11 Homogeneous Catalyst Design for the Synthesis of Aliphatic Polycarbonates and Polyesters Geoffrey W. Coates and Ryan C. Jeske 11.1 Introduction Synthetic polymers are more important now than at