新型钴配合物的合成及其催化性能研究
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摘要
CO_2和环氧丙烷(PO)可以发生不对称交替共聚反应生成聚碳酸丙稀酯(PPC),由手性四齿希夫碱钴配合物(SalenCo(Ⅲ)Ⅹ)作为亲电试剂,季铵盐/有机强碱作为亲核试剂组成的双组分协同催化体系,表现出非常高的活性和聚合物选择性(聚合物含量＞99%),得到了具有完全交替结构(碳酸酯单元含量＞99%)的聚合物。但在低浓度下催化剂活性不高,聚合物的区域选择性(头尾连接单元含量)不是很高以及对映体选择性(ee值)较低等问题仍没有得到解决。
本文首先根据“分子内协同催化”的作用机理,设计并合成了一系列新型双功能钴配合物。通过在配体中引入季铵盐单元,实现了同一分子中含有亲电、亲核两种组分。其中通过三个亚甲基在配体上引入较小季铵盐阳离子的配合物可以在较低的催化剂浓度下高活性地催化CO_2和环氧丙烷的交替共聚反应,而且高温时还能保持较高的聚合物选择性,在90℃,[环氧丙烷]/[催化剂]为25000时,TOF值可达到5863 h~(-1),聚合物选择性为95%。这是目前文献报道的能在高温和高活性下同时还保持较高选择性的催化体系之一。
本文还根据“双手性诱导”的理念,合成了含有手性季铵盐单元的新型双功能钴配合物,对CO_2和环氧丙烷的不对称共聚反应进行了立体化学控制,所得聚合物的ee值为52%。本文还通过采用非手性的二胺骨架和大体积的季铵盐阳离子对配体进行修饰,对该反应进行区域化学控制,所得聚合物的头尾连接单元含量为95%。
For the asymmetric altemating copolymerization of CO_2 and propylene oxide(PO) to produce poly(propylene carbonate)(PPC),the binary catalyst system composed of the chiral tetradentate Schiff base cobalt complex(SalenCo(Ⅲ)Ⅹ) as the electrophlie and ionic ammonium salt or organic sterically hindered strong base as the nucleophile can exhibit excellent activity and＞99%carbonate linkages.But there still remain some problems to be further solved,such as the poor activity at a low catalyst concentration,the low polymer regioselectivity(head-to-tail linkage) and enantioselectivity(ee value).
In this dissertation,according to the "intramolecular cooperative catalysis" mechanism,a series of new bifunctional cobalt complexes were first synthesized,which bear both the electrophlie and the nucleophile in a molecule by introducing a quaternary ammonium salt. The complex with an anchored small quaternary ammonium cation on its ligand framework by three methylene units exhibited high activity at a low catalyst concentration and high polymer selectivity even at a high temperature for the copolymerization of CO_2 and propylene oxide.An activity of 5863 h~(-1) and up to 95%polymer selectivity were achieved at 90℃and the [PO]/[catalyst]ratio of 25000.It is one of the catalyst systems that can combine high activity and high selectivity under such high temperature.
On the basis of "double chiral induction",the cobalt complex containing a chiral quatemary ammonium salt was synthesized and applied in the asymmetric copolymerization of CO2 and propylene oxide to control the stereo-chemistry selectivity.The polymer obtained only had an ee of 52%.To control the regioselectivity,the ligand was modified by using non-chiral diamine backbones and sterically hindered quaternary ammonium cation.The produced polymer had a head-to-tail linkage of 95%.
本文首先根据“分子内协同催化”的作用机理,设计并合成了一系列新型双功能钴配合物。通过在配体中引入季铵盐单元,实现了同一分子中含有亲电、亲核两种组分。其中通过三个亚甲基在配体上引入较小季铵盐阳离子的配合物可以在较低的催化剂浓度下高活性地催化CO_2和环氧丙烷的交替共聚反应,而且高温时还能保持较高的聚合物选择性,在90℃,[环氧丙烷]/[催化剂]为25000时,TOF值可达到5863 h~(-1),聚合物选择性为95%。这是目前文献报道的能在高温和高活性下同时还保持较高选择性的催化体系之一。
本文还根据“双手性诱导”的理念,合成了含有手性季铵盐单元的新型双功能钴配合物,对CO_2和环氧丙烷的不对称共聚反应进行了立体化学控制,所得聚合物的ee值为52%。本文还通过采用非手性的二胺骨架和大体积的季铵盐阳离子对配体进行修饰,对该反应进行区域化学控制,所得聚合物的头尾连接单元含量为95%。
For the asymmetric altemating copolymerization of CO_2 and propylene oxide(PO) to produce poly(propylene carbonate)(PPC),the binary catalyst system composed of the chiral tetradentate Schiff base cobalt complex(SalenCo(Ⅲ)Ⅹ) as the electrophlie and ionic ammonium salt or organic sterically hindered strong base as the nucleophile can exhibit excellent activity and＞99%carbonate linkages.But there still remain some problems to be further solved,such as the poor activity at a low catalyst concentration,the low polymer regioselectivity(head-to-tail linkage) and enantioselectivity(ee value).
In this dissertation,according to the "intramolecular cooperative catalysis" mechanism,a series of new bifunctional cobalt complexes were first synthesized,which bear both the electrophlie and the nucleophile in a molecule by introducing a quaternary ammonium salt. The complex with an anchored small quaternary ammonium cation on its ligand framework by three methylene units exhibited high activity at a low catalyst concentration and high polymer selectivity even at a high temperature for the copolymerization of CO_2 and propylene oxide.An activity of 5863 h~(-1) and up to 95%polymer selectivity were achieved at 90℃and the [PO]/[catalyst]ratio of 25000.It is one of the catalyst systems that can combine high activity and high selectivity under such high temperature.
On the basis of "double chiral induction",the cobalt complex containing a chiral quatemary ammonium salt was synthesized and applied in the asymmetric copolymerization of CO2 and propylene oxide to control the stereo-chemistry selectivity.The polymer obtained only had an ee of 52%.To control the regioselectivity,the ligand was modified by using non-chiral diamine backbones and sterically hindered quaternary ammonium cation.The produced polymer had a head-to-tail linkage of 95%.
引文
[1]周家贤．二氧化碳开发利用综述[J]．化工设计,2004,14(4)：7-10．
[2]Arakawa H,Aresta M,Armor J N et al.Catalysis research of relevance to carbon management:progress,challenges,and opportunities[J].Chem.Rev.,2001,101:953-996.
[3]Throat S D,Phillips P J,Semenov V et al.Physical properties of aliphatic polycarbonates made from CO_2 and epoxides[J].J.Appl.Polym.Sci.,2003,89:1163-1176.
[4]Inoue S,Koinuma H,Tsuruta T.Copolymerization of carbon dioxide and epoxide[J].J.Polym.Sci.,Polym.Lett.,1969,7:287-292.
[5]Inoue S,Koinuma H,Tsuruta T.Copolymerization of carbon dioxide and epoxide with organometallic compounds[J].Makromol.Chem.,1969,130:210-220.
[6]Coates G W,Moore D R.Discrete metal-based catalysts for the copolymerization of CO_2 and epoxides:discovery,reactivty,optimization,and mechanism[J].Angew.Chem.Int.Ed.,2004,43:661.8-6639.
[7]Darensbourg D J,Yarbrough J C,Ortiz C et al.Comparative kinetic studies of the copolymerization of cyclohexene oxide and propylene oxide with carbon dioxide in the presence of chromium salen derivatives.In situ FTIR measurements of copolymer vs cyclic carbonate production[J].J.Am.Chem.Soc.,2003,125:7586-7591.
[8]Chishiolm M H,Zhou Z P.New generation polymers:the role of metal alkoxides as catalysts in the production of polyoxygenates[J].J.Mater.Chem.,2004,14:3081-3092.
[9]Soga K,Imai E,Hattori I.Alternating copolymerization.of carbon dioxide and propylene oxide with the catalysts prepared from zinc hydroxide and various dicarboxylic acids[J].Polym.J.,1981,13:407-410.
[10]Kruper W J,Swart D J.Carbon dioxide-oxirane copolymers prepared using double metal cyanide complexes[P].US Patent,4,500,704.1985.
[11]Chen L B.Activation and copolymerazation of carbon dioxide by macromolecule-metal complexes[J].Makromol.Chem.Macromol.Symp.,1992,59:75-82.
[12]Yang S Y,Fang X G,Chen L B.Biodegradability of CO_2 copolymers synthesized by using macromolecule-bimetal catalysts[J].Polym.Adv.Tech.,1996,7:605-608.
[13]Chen X H,Shen Z Q,Zhang Y F.New catalytic system for the fixation of carbon dioxide.1.copolymerization of CO_2 and propylene oxide with new rare-earth catalysts—RE(P_(204))-Al-(i-Bu)_3-R(OH)[J].Macromolecules,1991,24:5305-5308.
[14]Takeda N,Inoue S.Polymerization of 1,2-epoxypropane and copolymerization with carbon dioxide catalyzed by metalloporphyrins[J].Makromol.Chem.,1978,179:1377-1381.
[15]Aida T,IshikawaM,Inoue S.Alternating copolymerization of carbon dioxide and epoxide catalyzed by aluminum porphyrin-quaternary organic salt or triphenylphosphine system: Synthesis of polycarbonate with well-controlled molecular weight[J].Macromolecules,1986,19:8-13.
[16]Allen S D,Moore D R,Lobkovsky E B et al.Highly-activity,single-site catalysts for the alternating copolymerization of CO_2 and propylene oxide[J].J.Am.Chem.Soc.,2002,124:14284-14285.
[17]Jacobsen E N,Tokunaga M,Larrow J F.Stereoselective ring opening reactions involve reaction of a cyclic substrate with a sub stoichiometric amount of a nucleophile in the presence of a chiral catalyst[P].PCT Int.Appl.,W0200009463,2000.
[18]Darensbourg D J,Yarbrough J C.Mechanistic aspects of the copolymerization reaction of carbon dioxide and epoxides,using a chiral salen chromium chloride catalyst[J].J.Am.Chem.Soc,2002,124:6335-6342.
[19]Eberhardt R,Allmendinger M,RiegerB.DMAP/Cr(Ⅲ) catalyst ratio:The decisive factor for poly(propylene carbonate) formation in the coupling of C02 and propylene oxide[J].Macromol.Rapid.Commun.,2003,24:194-196.
[20]Darensbourg D J,Phelps A L.Effective,selective coupling of propylene oxide and carbon dioxide to poly(propylene carbonate) using(salen)CrN_3 catalysts[J].Inorg.Chem.,2005,44:4622-4629.
[21]Tokunaga M,Larrow J F,Kakiuchi F et al.Asymmetric catalysis with water:Efficient kinetic resolution of terminal epoxides by means of catalytic hydrolysis[J].Science,1997,277:936-938.
[22]Qin Z Q,Thomas C M,Lee S et al.Cobalt-based complexes for the copolymerization of propylene oxide and CO_2:Active and selective catalysts for polycarbonate synthesis[J].Angew.Chem.Int.Ed.,2003,42:5484-5487.
[23]Lu X B,Liang B,Zhang Y J et al.Asymmetric catalysis with CO_2:direct synthesis of optically active propylene carbonate from racemic epoxides[J].J.Am.Chem.Soc,2004,126:3732-3733.
[24]Lu X B,Wang Y.High activity,binary catalyst systems for the alternating copolymerization of CO_2 and epoxides under mild conditions[J].Angew.Chem.Int.Ed.,2004,43:3574-3577.
[25]Paddock R L,Nguyen S T.Alternating copolymerization of CO_2 and propylene oxide catalyzed by Co~(111)(salen)/lewis base[J].Macromolecules,2005,38:6251-6253.
[26]Cohen C T,Chu T,Coates G W.Cobalt catalysts for the alternating copolymerization of propylene oxide and carbon dioxide:combining high activity and selectivity[J].J.Am.Chem.Soc,2005,127:10869-10878.
[27]Cohen C T,Coates G W.Alternating copolymerization of propylene oxide and carbon dioxide with highly efficient and selective(salen)Co(Ⅲ) catalysts:Effect of ligand and cocatalyst variation[J].J.Polyra.Sci.Part A,2006,44:5182-5191.
[28]Lu X B,Shi L,Wang Y M et al.Design of highly active binary catalyst systems for CO_2/epoxide copolymerization:polymer selectivity,enantioselectivity,and stereochemistry control[J].J.Am.Chem.Soc.,2006,128:1664-1674.
[29]Nakano K,Kamada T,Nozaki K.Selective formation of polycarbonate over cyclic carbonate:copolymerization of epoxides with carbon dioxide catalyzed by a cobalt(Ⅲ)complex with a piperidinium end-capping arm[J].Angew.Chem.Int.Ed.,2006,45,7274-7277.
[30]Noh E K,Na S J,Sujith S et al.Two components in a molecule:highly efficient and thermally robust catalytic system for CO_2/epoxide copolymerization[J].J.Am.Chem.Soc,2007,129:8082-8083.
[31]Gomez F J,Waymouth R M.Catalysts rise to the challenge[J].Science,2002,295:635-636.
[32]Nielsen L P,Stevenson C P,Blackmond D G et al.Mechanistic investigation leads to a synthetic improvement in the hydrolytic kinetic resolution of terminal epoxide[J].J.Am.Chem.Soc,2004,126(5):1360-1362.
[33]Li B,Zhang R,Lu X B.Stereochemistry control of alternating copolymerization of CO_2 and propylene oxide catalyzed by salenCrX complexes[J].Macromolecules,2007,40:2303-2307.
[2]Arakawa H,Aresta M,Armor J N et al.Catalysis research of relevance to carbon management:progress,challenges,and opportunities[J].Chem.Rev.,2001,101:953-996.
[3]Throat S D,Phillips P J,Semenov V et al.Physical properties of aliphatic polycarbonates made from CO_2 and epoxides[J].J.Appl.Polym.Sci.,2003,89:1163-1176.
[4]Inoue S,Koinuma H,Tsuruta T.Copolymerization of carbon dioxide and epoxide[J].J.Polym.Sci.,Polym.Lett.,1969,7:287-292.
[5]Inoue S,Koinuma H,Tsuruta T.Copolymerization of carbon dioxide and epoxide with organometallic compounds[J].Makromol.Chem.,1969,130:210-220.
[6]Coates G W,Moore D R.Discrete metal-based catalysts for the copolymerization of CO_2 and epoxides:discovery,reactivty,optimization,and mechanism[J].Angew.Chem.Int.Ed.,2004,43:661.8-6639.
[7]Darensbourg D J,Yarbrough J C,Ortiz C et al.Comparative kinetic studies of the copolymerization of cyclohexene oxide and propylene oxide with carbon dioxide in the presence of chromium salen derivatives.In situ FTIR measurements of copolymer vs cyclic carbonate production[J].J.Am.Chem.Soc.,2003,125:7586-7591.
[8]Chishiolm M H,Zhou Z P.New generation polymers:the role of metal alkoxides as catalysts in the production of polyoxygenates[J].J.Mater.Chem.,2004,14:3081-3092.
[9]Soga K,Imai E,Hattori I.Alternating copolymerization.of carbon dioxide and propylene oxide with the catalysts prepared from zinc hydroxide and various dicarboxylic acids[J].Polym.J.,1981,13:407-410.
[10]Kruper W J,Swart D J.Carbon dioxide-oxirane copolymers prepared using double metal cyanide complexes[P].US Patent,4,500,704.1985.
[11]Chen L B.Activation and copolymerazation of carbon dioxide by macromolecule-metal complexes[J].Makromol.Chem.Macromol.Symp.,1992,59:75-82.
[12]Yang S Y,Fang X G,Chen L B.Biodegradability of CO_2 copolymers synthesized by using macromolecule-bimetal catalysts[J].Polym.Adv.Tech.,1996,7:605-608.
[13]Chen X H,Shen Z Q,Zhang Y F.New catalytic system for the fixation of carbon dioxide.1.copolymerization of CO_2 and propylene oxide with new rare-earth catalysts—RE(P_(204))-Al-(i-Bu)_3-R(OH)[J].Macromolecules,1991,24:5305-5308.
[14]Takeda N,Inoue S.Polymerization of 1,2-epoxypropane and copolymerization with carbon dioxide catalyzed by metalloporphyrins[J].Makromol.Chem.,1978,179:1377-1381.
[15]Aida T,IshikawaM,Inoue S.Alternating copolymerization of carbon dioxide and epoxide catalyzed by aluminum porphyrin-quaternary organic salt or triphenylphosphine system: Synthesis of polycarbonate with well-controlled molecular weight[J].Macromolecules,1986,19:8-13.
[16]Allen S D,Moore D R,Lobkovsky E B et al.Highly-activity,single-site catalysts for the alternating copolymerization of CO_2 and propylene oxide[J].J.Am.Chem.Soc.,2002,124:14284-14285.
[17]Jacobsen E N,Tokunaga M,Larrow J F.Stereoselective ring opening reactions involve reaction of a cyclic substrate with a sub stoichiometric amount of a nucleophile in the presence of a chiral catalyst[P].PCT Int.Appl.,W0200009463,2000.
[18]Darensbourg D J,Yarbrough J C.Mechanistic aspects of the copolymerization reaction of carbon dioxide and epoxides,using a chiral salen chromium chloride catalyst[J].J.Am.Chem.Soc,2002,124:6335-6342.
[19]Eberhardt R,Allmendinger M,RiegerB.DMAP/Cr(Ⅲ) catalyst ratio:The decisive factor for poly(propylene carbonate) formation in the coupling of C02 and propylene oxide[J].Macromol.Rapid.Commun.,2003,24:194-196.
[20]Darensbourg D J,Phelps A L.Effective,selective coupling of propylene oxide and carbon dioxide to poly(propylene carbonate) using(salen)CrN_3 catalysts[J].Inorg.Chem.,2005,44:4622-4629.
[21]Tokunaga M,Larrow J F,Kakiuchi F et al.Asymmetric catalysis with water:Efficient kinetic resolution of terminal epoxides by means of catalytic hydrolysis[J].Science,1997,277:936-938.
[22]Qin Z Q,Thomas C M,Lee S et al.Cobalt-based complexes for the copolymerization of propylene oxide and CO_2:Active and selective catalysts for polycarbonate synthesis[J].Angew.Chem.Int.Ed.,2003,42:5484-5487.
[23]Lu X B,Liang B,Zhang Y J et al.Asymmetric catalysis with CO_2:direct synthesis of optically active propylene carbonate from racemic epoxides[J].J.Am.Chem.Soc,2004,126:3732-3733.
[24]Lu X B,Wang Y.High activity,binary catalyst systems for the alternating copolymerization of CO_2 and epoxides under mild conditions[J].Angew.Chem.Int.Ed.,2004,43:3574-3577.
[25]Paddock R L,Nguyen S T.Alternating copolymerization of CO_2 and propylene oxide catalyzed by Co~(111)(salen)/lewis base[J].Macromolecules,2005,38:6251-6253.
[26]Cohen C T,Chu T,Coates G W.Cobalt catalysts for the alternating copolymerization of propylene oxide and carbon dioxide:combining high activity and selectivity[J].J.Am.Chem.Soc,2005,127:10869-10878.
[27]Cohen C T,Coates G W.Alternating copolymerization of propylene oxide and carbon dioxide with highly efficient and selective(salen)Co(Ⅲ) catalysts:Effect of ligand and cocatalyst variation[J].J.Polyra.Sci.Part A,2006,44:5182-5191.
[28]Lu X B,Shi L,Wang Y M et al.Design of highly active binary catalyst systems for CO_2/epoxide copolymerization:polymer selectivity,enantioselectivity,and stereochemistry control[J].J.Am.Chem.Soc.,2006,128:1664-1674.
[29]Nakano K,Kamada T,Nozaki K.Selective formation of polycarbonate over cyclic carbonate:copolymerization of epoxides with carbon dioxide catalyzed by a cobalt(Ⅲ)complex with a piperidinium end-capping arm[J].Angew.Chem.Int.Ed.,2006,45,7274-7277.
[30]Noh E K,Na S J,Sujith S et al.Two components in a molecule:highly efficient and thermally robust catalytic system for CO_2/epoxide copolymerization[J].J.Am.Chem.Soc,2007,129:8082-8083.
[31]Gomez F J,Waymouth R M.Catalysts rise to the challenge[J].Science,2002,295:635-636.
[32]Nielsen L P,Stevenson C P,Blackmond D G et al.Mechanistic investigation leads to a synthetic improvement in the hydrolytic kinetic resolution of terminal epoxide[J].J.Am.Chem.Soc,2004,126(5):1360-1362.
[33]Li B,Zhang R,Lu X B.Stereochemistry control of alternating copolymerization of CO_2 and propylene oxide catalyzed by salenCrX complexes[J].Macromolecules,2007,40:2303-2307.
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