Ring-opening polymerization of L-lactide with rare earth aryloxides substituted by various alkyl groups

<正>Rare earth aryloxides substituted by various alkyl groups[Ln(OAr)_3]such as methyl,isopropyl and tertbutyl,were used as single component catalysts to affect ring-opening polymerization of L-lactide(LLA).The catalytic activity, polymerization characteristics,polymerization kinetics and the mechanism were studied.It was found that the catalytic activity of rare earth aryloxides is influenced by both the structure and the number of alkyl groups on the phenyl ring.The stronger the electron-donation ability of the alkyl group,the higher the catalytic activity will be.An increase in the number of the substitute group will result in a higher catalytic activity.Lanthanum tris(2,4,6-tri-tert-butylphenolate)[La(OTTBP)_3] exhibits the highest activity among all lanthanum aryloxides.According to the ~1H-NMR data,it was proposed that the LLA polymerization proceeded via a coordination-insertion mechanism involving cleavage of acyl-oxygen bond of the lactide.     

三氟甲磺酸稀土催化ε-己内酯开环聚合

采用三氟甲磺酸稀土(镧、钕、铒)作为单组分催化剂催化了ε-己内酯的本体开环聚合反应. 考察了稀土元素种类、催化剂浓度、聚合时间及温度对单体转化率和聚合产物分子量的影响. 该类催化剂在催化聚合过程中具有单一活性中心, 且催化活性较高. 此聚合反应可能是通过阳离子活性末端链聚合机理进行的.     

Polymerization of n-Hexyl Isocyanate Initiated by Novel Rare Earth Tris （2,6-di-tert-butyl-4-methylphenolate）

The polymerization of n-hexyl isocyanate (HNCO) was carried out in the presence of a novel single initiator, rare earth tris (2,6-di-tert-butyl-4-methylphenolate) [Ln(OAr)3]. The influences of reaction conditions such as the monomer concentration, the polymerization temperature and time, and the types of solvents on the polymerization of HNCO were studied. Polymerizations of phenyl, i-propyl, p-tolyl, n-butyl and n-octyl isocyanates with La(OAr)3 were also examined.     

Homo-and Copolymerization of ε-Caprolactone and 2,2-Dimethyltrimethylene Carbonate by Rare Earth Initiators

ＩｎｔｒｏｄｕｃｔｉｏｎＡｌｉｐｈａｔｉｃｐｏｌｙｅｓｔｅｒｓａｎｄｐｏｌｙｃａｒｂｏｎａｔｅｓｈａｖｅａｔｔｒａｃｔ ｅｄｇｒｏｗｉｎｇｉｎｔｅｒｅｓｔｆｏｒｔｈｅｉｒｅｘｃｅｌｌｅｎｔｐｒｏｐｅｒｔｉｅｓｏｆｂｉｏｄｅｇｒａｄａｂｉｌｉｔｙ ,ｂｉｏｃｏｍｐａｔｉｂｉｌｉｔｙａｎｄｌｏｗｔｏｘｉｃｉｔｙ .Ｔｈｅｉｒｅｘｐｅｃｔｅｄｕｓｅｓｉｎｃｌｕｄｅｄｒｕｇｄｅｌｉｖｅｒｙｍｅｄｉｕｍ ,ｓｕｒｇｉｃａｌｓｕ ｔｕｒｅｓ ,ｂｏｄｙｉｍｐｌａｎｔｍａｔｅｒｉａｌｓ ,ｃｅｌｌｃｕｌｔｕｒｅｓｕｂｓｔ…     

Rare earth complexes [Ln(EDBP)<Subscript>2</Subscript>(DME)Na(DME)<Subscript>3</Subscript>] as catalysts for the polymerization of 2,2-dimethyltrimethylene carbonate

The biphenol based discrete ion-pair rare earth complexes,[Ln（EDBP）₂（DME）Na（DME）₃][Ln=Er（1）,Yb（2）, Sm（3）],were prepared and used as catalysts for the ring-opening polymerization（ROP）of 2,2-dimethyltrimethylene carbonate（DTC）.Three complexes show moderate activities for the polymerization,and the catalytic activities increase in the following sequence:（Yb2 elimination was prepared.     

Ln2O3/Al2O3催化酯化合成邻苯二甲酸二辛酯

Ｌｎ_２Ｏ_３／Ａｌ_２Ｏ_３催化酯化合成邻苯二甲酸二辛酯陈其瑞，张凤美，罗明润，焦肇林（安徽师范大学化学系，芜湖２４１０００）关键词稀土氧化物，担载催化剂，催化酯化，邻苯二甲酸二辛酯邻苯二甲酸二（２－乙基己醇用酯（Ｄｉｏｃｔｙｌｐｈｔｈａｌａｔｅ）是一...     

芳氧基稀土化合物引发开环聚合的活性

综述了近十年来芳氧基稀土化合物在引发内酯、丙交酯和环碳酸酯开环聚合的研究进展,在整理聚合条件、聚合产物收率和分子量、聚合反应动力学和机理的基础上,比较了苯环上不同位置不同取代基的芳氧基配体对开环聚合反应活性的影响,得到以下结论:(1) 三(2,6-二叔丁基-4-甲基苯氧基)稀土化合物[Ln(26B4M)3]的活性最高,无取代基芳氧基稀土化合物(La(P)3)没有活性;(2)邻位叔丁基能提高活性,一个叔丁基与两个甲基效果相近;(3)甲基影响作用相对叔丁基较小,甲基越多活性越大.     

Anionic lanthanide phenoxide complexes as novel single‐component initiators for the polymerization of ε‐caprolactone and trimethylene carbonate

The anionic lanthanide‐sodium‐2,6‐di‐tert‐butyl‐phenoxide complexes [Ln(OAr)₄][Na(DME)₃]·DME (Ln = Nd 1 (neodymium), Sm 2 (samarium), or Gd 3 (gadolium); DME = dimethoxyethane) were synthesized by the reaction of anhydrous LnCl₃ with 4 equiv of sodium‐2,6‐di‐tert‐butyl‐phenoxide NaOAr in high yields and structurally characterized. These complexes showed high catalytic activity in the ring‐opening polymerizations of ?‐caprolactone (?‐CL) and trimethylene carbonate (TMC). The catalytic activity profoundly depended on the lanthanide metals. The active order of Gd < Sm < Nd for the polymerization of ?‐CL and TMC was observed. The polymers obtained with these initiators all showed a unimodal molecular weight distribution, indicating that the [Ln(OAr)₄][Na(DME)₃]·DME anionic complexes could be used as single‐component initiators. The anionic complex was more efficient than the corresponding neutral complex, Ln(OAr)₃(THF)₂. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1210–1218, 2007     

[(μ-CF~3CO~2)~2Ln(μ-CF~3CHO~2)AlR~2.2THF]~2的合成和表征及其对某些极性单体的催化活性

通过(CF~3CO~2)~3Ln(Ln=Nd、Y和Eu)和R^1AlR~2(R^1=H, R=i-C~4H~9;R^1=R=C~2H~5), 反应首次合成和培养出Nd-Al、Y-Al和Eu-Al三种新的双金属稀土配合物和晶体, 并用X射线衍射法测定出它们的晶体结构, 然后再用二维波谱技术, 进一步证实和完善了晶体结构中的价态和非共面现象。由此确定这三种稀土配合物分子式的通式为: [(μ-CF~3CO~2)~2Ln(μ-CF~3CHO~2)AlR~2.2THF]~2。根据实验结果还提出了通过烷基化、β-消除(或氢化)、氢转移、键合及缔合等五个步骤生成这些配合物的反应机理。这些配合物单独可使MMA和ECH催化聚合, 前者可获得主要以间同结构聚合物, 后者聚合催化活性较高, 在极少量的ECH存在下,还可使THF开环聚合, 并通过PTHF端基分析, 提出了羊离子聚合反应机理。     

Ring-Opening Copolymerization of 2,2-Dimethyltrimethylene Carbonate and ε-Caprolactone Using Rare Earth Aryloxides Substituted by Various Alkyl Groups

A variety of single component rare earth aryloxides substituted by various alkyl groups [Ln(OAr)₃] such as methyl, isopropyl, tert‐butyl have been surveyed in the ring‐opening copolymerization of 2,2‐dimethyltrimethylene carbonate (DTC) and ε‐caprolactone (ε‐CL). It was worthwhile to note that activity of the catalyst varied with both the ligands' structure and the number of alkyl groups on phenyl ring. The stronger ability of electron‐donation of alkyl groups on phenyl ring, and the more numbers of alkyl groups on phenyl ring, the higher catalytic activity. The experimental results show that lanthanum tris(2,4,6‐tri‐tert‐butylphenolate) [La(OTTBP)₃] exhibits highest activity in all lanthanum aryloxides. ¹H NMR spectral data of copolymer obtained showed that the polymerization mechanism is in agreement with the coordination insertion mechanism.     

Rare Earth Complex Initiated Ring-Opening Polymerization of 2,2-Dimethyltrimethylene Carbonate

Aliphatic polycarbonate is a series of useful biodegradable materials attracting more interests recently. Poly(2,2-dimethyltrimethylene carbonate) (polyDTC) has been studied for a long time. Polymerization of DTC can be catalyzed by alkyl metals1, trifluoromethanesulfonic acid and its esters2, alcohol/methylaluminum diphenolate system3 and etc. Herein tris(2,6-di-tert-butyl-4-methylphenoxo) lanthanides (Ln(OAr)3, Ln=La, Nd) are firstly applied to initiate the polymerization of DTC. Ln(O…     

RING-OPENING POLYMERIZATION OF 1,4-DIOXAN-2-ONE INITIATED BY LANTHANUM TRIS（ 2,6-DI-TERT-BUTYL-4-METHYLPHENOLATE）

The ring-opening polymerization of 1,4-dioxan-2-one （PDO） was carried out by lanthanum tris（2,6-di-tert-butyl-4- methylphenolate） （La（OAr）3） as novel single component initiaLor. The influences of polymerization reaction temperature and the molar ratio of monomer to initiator on the monomer conversion and molecular weight of poly（1,4-dioxan-2-one） （PPDO） were explored. PPDO with high viscosity average molecular weight of 1.95×10^5 can be prepared at 40℃ when [PDO]/ [La（OAr）3] molar ratio was 800. Mechanism investigation shows that the polymerization proceeds through a ＂coordination- insertion＂ mechanism with selective rupture of acyl-oxygen be,nd of PDO.     

RING-OPENING POLYMERIZATION OF 1,4-DIOXAN-2-ONE INITIATED BY LANTHANUM TRIS( 2,6-DI- TERT-B UTYL-4-METHYLPHENOLATE)

The ring-opening polymerization of 1,4-dioxan-2-one (PDO) was carried out by lanthanum tris(2,6-di-tert-butyl-4-methylphenolate) (La(OAr)3) as novel single component initiator. The influences of polymerization reaction temperature and the molar ratio of monomer to initiator on the monomer conversion and molecular weight of poly(1,4-dioxan-2-one) (PPDO) were explored. PPDO with high viscosity average molecular weight of 1.95 × 105 can be prepared at 40℃ when [PDO]/ [La(OAr)3] molar ratio was 800. Mechanism investigation shows that the polymerization proceeds through a "coordinationinsertion" mechanism with selective rupture of acyl-oxygen bond of PDO.     

Synthesis and reactivity of rare earth metal alkyl complexes stabilized by anilido phosphinimine and amino phosphine ligands

Anilido phosphinimino ancillary ligand H(2)L(1) reacted with one equivalent of rare earth metal trialkyl [Ln{CH(2)Si(CH(3))(3)}(3)(thf)(2)] (Ln=Y, Lu) to afford rare earth metal monoalkyl complexes [L(1)LnCH(2)Si(CH(3))(3)(THF)] (1 a: Ln=Y; 1 b: Ln=Lu). In this process, deprotonation of H(2)L(1) by one metal alkyl species was followed by intramolecular C--H activation of the phenyl group of the phosphine moiety to generate dianionic species L(1) with release of two equivalnts of tetramethylsilane. Ligand L(1) coordinates to Ln(3+) ions in a rare C,N,N tridentate mode. Complex l a reacted readily with two equivalents of 2,6-diisopropylaniline to give the corresponding bis-amido complex [(HL(1))LnY(NHC(6)H(3)iPr(2)-2,6)(2)] (2) selectively, that is, the C--H activation of the phenyl group is reversible. When 1 a was exposed to moisture, the hydrolyzed dimeric complex [{(HL(1))Y(OH)}(2)](OH)(2) (3) was isolated. Treatment of [Ln{CH(2)Si(CH(3))(3)}(3)(thf)(2)] with amino phosphine ligands HL(2-R) gave stable rare earth metal bis-alkyl complexes [(L(2-R))Ln{CH(2)Si(CH(3))(3)}(2)(thf)] (4 a: Ln=Y, R=Me; 4 b: Ln=Lu, R=Me; 4 c: Ln=Y, R=iPr; 4 d: Ln=Y, R=iPr) in high yields. No proton abstraction from the ligand was observed. Amination of 4 a and 4 c with 2,6-diisopropylaniline afforded the bis-amido counterparts [(L(2-R))Y(NHC(6)H(3)iPr(2)-2,6)(2)(thf)] (5 a: R=Me; 5 b: R=iPr). Complexes 1 a,b and 4 a-d initiated the ring-opening polymerization of d,l-lactide with high activity to give atactic polylactides.     

Manipulation of reaction pathways in redox transmetallation-ligand exchange syntheses of lanthanoid(II)/(III) aryloxide complexes

Redox transmetallation/ligand exchange reactions of lanthanoid metals (Ln), Hg(C6F5)2 and HOAr(OMe) (Ar(OMe) = C6H2-2,6-Bu(t)-4-OMe), in thf (tetrahydrofuran) gave, for Ln = Yb, [Yb(OAr(OMe))2(thf)3], and for Ln = Sm, a mixture of [Sm(II)(OAr(OMe))2(thf)3] and mainly [Sm(III)(Ar(OMe))3(thf)] x thf. X-Ray structure determinations show the divalent complexes to have distorted square-pyramidal stereochemistry with transoid thf and OAr(OMe) ligands in the basal plane. Treatment of [Yb(OAr(OMe))2(thf)3] with diethyl ether or PhMe at room temperature gave [Yb(OAr(OMe))2] or [Yb(OAr(OMe))2] x 0.5 PhMe. For lanthanoids Ln = Nd, Er or Y, the reactions with Hg(C6F5)2 and HOAr(OMe) yielded complex product mixtures, from one of which the novel erbium aryloxide fluoride cage [Er3(OAr(OMe))4(mu2-F)3(mu3-F)2(thf)4] x thf x 0.5 C6H14 was isolated. The cage core consists of a triangle of Er atoms joined to two mu3-fluoride ligands and three further mu2-fluorides bridge adjacent Er atoms. One of the Er atoms is six-coordinate with additionally two OAr(OMe) ligands whilst the other two have one OAr(OMe) and two thf ligands and are seven coordinate. Substitution of Hg(C6F5)2 by Hg(CCPh)2 in the redox transmetallation/ligand exchange reactions gave the new derivatives [Ln(OAr(OMe))3(thf)] x thf (Ln = La, Pr, Nd, Sm, Gd, Ho) in good yields whilst Ln = Yb gave [Yb(OAr(OMe))2(thf)3]. Recrystallisation of [Sm(OAr(OMe))3(thf)] x thf from dme (1,2-dimethoxyethane) yielded [Sm(OAr(OMe))3(dme)]. Structural characterisation of [Ln(OAr(OMe))3(thf)] x thf (Ln = Nd, Ho) and [Sm(OAr(OMe))3(dme)] showed monomeric four-coordinate distorted tetrahedral and five-coordinate distorted square-pyramidal complexes respectively. For the smaller lanthanoids Ln = Y, Er or Lu, reactions with Hg(CCPh)2 and HOAr(OMe) gave the mixed aryloxide/alkynide complexes [Ln(OAr(OMe))2(CCPh)(thf)2]. Oxidation of the divalent ytterbium aryloxide [Yb(OAr(OMe))2(thf)3] by Hg(CCPh)2 in thf gave the analogous [Yb(OAr(OMe))2(CCPh)(thf)2]. The erbium alkynide [Er(OAr(OMe))2(CCPh)(thf)2] x 0.25 C6H14 has distorted square-pyramidal stereochemistry with transoid OAr(OMe) and thf ligands in the basal plane and a rare (for Ln) terminal alkynide ligand in the apical position. The reactive Lu-C bond in the [Lu(OAr(OMe))2(CCPh)(thf)2] complexes could be slowly cleaved by free HOAr(OMe) in hydrocarbon solvents, yielding Lu(OAr(OMe))3 species and fortuitous partial hydrolysis of [Er(Ar(OMe))2(CCPh)(thf)2] gave the dimeric [Er(OAr(OMe))2(mu-OH)2]2.     

稀土催化四氢呋喃开环聚合

1937年Meerwein首次发现Et_3O~(+BF)可催化四氢呋喃(THF)开环聚合。到目前为止,发现能使THF开环聚合的催化剂有质子酸、Lewis酸、洋离子、正碳离子等。1990年吴健等将(Acac)_3Nd-(i-Bu)_3Al-H_2O-环氧氯丙烷催化体系应用于THF聚合,发现它和(i-Bu)_3Al-H_2O-环氧氯丙烷体系具有相同的活性,这说明稀土配合物没有参与活性中心的形成。本工作发现(CF_3CO-2)3Ln(Ln=Y,La,Ce,     

新型镍催化体系合成Cis-1,4聚丁二烯的研究

本文研究了以加氢汽油为溶剂的Ni(Naph)_2-Al(i-Bu)_2OR-BP_3·OEt_2及Ni(NaPh)_2-Al(i-Bu)_2OAr-BF3·OEt_2两体系对丁二烯的催化聚合活性、聚合物分子量、微观结构等。各种Al(i-Bu)_2OR或Al(i-Bu)_2OAr为助催化剂组成的新型镍催化体系对丁二烯聚合都有较高的催化活性,所得聚合物Cis-1,4含量在96％以上。磁化率和紫外可见光谱研究证明,在Al(i-Bu)_2OR体系中以Ni(Ⅰ)为主及小量未还原的Ni(Ⅱ);Al(i-Bu)_2OAr中Ni(Ⅰ)及Ni(O)共存。     

Ring opening polymerization of α‐amino acid N‐carboxyanhydrides catalyzed by rare earth catalysts: Polymerization characteristics and mechanism

Five rare earth complexes are first introduced to catalyze ring opening polymerizations (ROPs) of γ‐benzyl‐L ‐glutamate N‐carboxyanhydride (BLG NCA) and L ‐alanine NCA (ALA NCA) including rare earth isopropoxide (RE(OiPr)₃), rare earth tris(2,6‐di‐tert‐butyl‐4‐methylphenolate) (RE(OAr)₃), rare earth tris(borohydride) (RE(BH₄)₃(THF)₃), rare earth tris[bis(trimethylsilyl)amide] (RE(NTMS)₃), and rare earth trifluoromethanesulfonate. The first four catalysts exhibit high activities in ROPs producing polypeptides with quantitative yields (>90%) and moderate molecular weight (MW) distributions ranging from 1.2 to 1.6. In RE(BH₄)₃(THF)₃ and RE(NTMS)₃ catalytic systems, MWs of the produced polypeptides can be controlled by feeding ratios of monomer to catalyst, which is in contrast to the systems of RE(OiPr)₃ and RE(OAr)₃ with little controllability over the MWs. End groups of the polypeptides are analyzed by MALDI‐TOF MS and polymerization mechanisms are proposed accordingly. With ligands of significant steric hindrance in RE(OiPr)₃ and RE(OAr)₃, deprotonation of 3‐NH of NCA is the only initiation mode producing a N‐rare earth metallated NCA ( i ) responsible for further chain growth, resulting in α‐carboxylic‐ω‐aminotelechelic polypeptides after termination. In the case of RE(BH₄)₃(THF)₃ with small ligands, another initiation mode at 5‐CO position of NCA takes place simultaneously, resulting in α‐hydroxyl‐ω‐aminotelechelic polypeptides. In RE(NTMS)₃ system, the protonated ligand hexamethyldisilazane (HMDS) initiates the polymerization and produces α‐amide‐ω‐aminotelechelic polypeptides. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

希土硼氢化物的研究--Ⅴ.十二氢十二硼酸N-氧化邻二氮杂菲合希土(Ⅲ)螯合物的合成

将希土氧化物或氢氧化物同N-氧化邻二氮杂菲及十二氢十二硼酸在水—乙醇介质中反应,合成了十三个十二氢十二硼酸N-氧化邻二氮杂菲合希土螯合物。通过元素分析、红外光谱、摩尔电导率的测量。确定螯合物的化学式为[Ln(phenO)_4]_2(B_(12)H_(12))_3·nH_2O。用DTA—TG法探讨了化合物的热行为。     

Synthesis, structure and catalytic activity of complexes [Ln(EDBP)2(DME)Na(DME)3](Ln=Er, Yb, Sm) for ring-opening polymerization of ?-caprolactone

Discrete ion-pair complexes [Ln(EDBP)₂(DME)Na(DME)₃] [Ln=Er (1), Yb (2), Sm (3)] have been synthesized by the reaction between sodium salt of 2,2′-ethylidene-bis(4,6-di-tert-butylphenol)(EDBPH₂) and Ln(BH₄)₃·3THF (Ln=Er, Yb, Sm) followed by centrifugation and recrystalization. The complexes were characterized by elemental analysis and FT-IR, and the bonding model of these compounds was confirmed by X-ray single crystal diffraction for complex 1. It was found that four O atoms in two biphenol ligands as well as two O atoms in one ethylene glycol dimethyl ether (DME) molecule connect to the center rare earth metal atom, while sodium exists as counterpart cation to balance the charge. Complexes 1–3 can all be used as single component initiators for the ring-opening polymerization of ɛ-caprolactone.