过渡金属盐催化甲基丙烯酸2-(N,N-二乙氨基)乙酯的自引发自由基聚合

研究了高氧化态过渡金属盐(CuX2/L、FeX3/L,X=C1或Br;L =2,2′-联吡啶、N,N'-四甲基乙二胺、N,N,N′,N″,N″-五甲基二亚乙基三胺;CuSO4)催化甲基丙烯酸2-(N,N-二乙氨基)乙酯(DEAEMA)的自引发氧化聚合,利用气相色谱跟踪单体转化率、利用凝胶渗透色谱和多角激光光散射跟踪聚合...     

α-二亚胺镍(Ⅱ)催化甲基丙烯酸甲酯聚合

以4种不同结构的α-二亚胺镍(Ⅱ)催化剂[(t-Bu)—N CH—CH N—(t-Bu)]NiBr2(C1),[C6H5—N C(Me)—C(Me)N—C6H5]NiBr2(C2),[(2,6-C6H3(Me)2)—N C(Me)—C·(Me)N—(2,6-C6H3(Me)2)]NiBr2(C3)和[(2,6-C6H3(i-Pr)2)—N C(An)—C(An)N—(2,6-C6H3(i-Pr)2)]NiBr2(An=acenaphthyl)(C4),在甲基铝氧烷(MAO)作用下,对甲基丙烯酸甲酯(MMA)进行催化聚合.以C2为模型催化剂系统研究了Al/Ni摩尔比、单体浓度、聚合温度、聚合时间和反应溶剂对催化活性及聚合物分子量的影响.在较适合的聚合条件(催化剂用量为1.6μmol,Al/Ni摩尔比为800,MMA浓度为2.9 mol/L,甲苯为溶剂,聚合温度为60℃,聚合时间为4 h)下,讨论了催化剂结构对催化活性和聚合物分子量的影响.研究发现,催化剂C1~C3催化MMA聚合均得到富含间规结构的聚甲基丙烯酸甲酯(PMMA).催化剂结构中空间位阻增大导致催化活性降低,空间位阻最小的C1催化活性最高[达107.8 kg/(mol Ni·h)];而空间位阻最大的C4催化活性仅为7.8 kg/(mol Ni·h).催化剂结构中给电子效应增加有利于催化活性及聚合物分子量的增加.C2催化活性为62.5 kg/(mol Ni·h),所得聚合物的分子量为5.0×104;而具有较强给电子效应的C3催化活性达到96.9 kg/(mol Ni·h),并得到更高分子量的聚合物(7.6×104).     

镍体系(NiCl_2/PPh_3)催化的反向原子转移自由基聚合

以 2 ,3 二氰基 2 ,3 二苯基丁二酸二乙酯 (DCDPS) NiCl2 PPh3 为引发体系 ,首次利用Ni2 + 和Ni+ 之间的变价关系 ,研究了乙烯基单体的反向ATRP .结果表明 ,苯乙烯 (St)的聚合具有活性自由基聚合的特征 ,所得PSt的分子量随转化率的增加而增加 ,并且制得的PSt可以作为大分子引发剂进行扩链反应 .但该引发体系引发甲基丙烯酸甲酯 (MMA)聚合时没有活性自由基聚合特征 ,PMMA的分子量与转化率基本无关 ,但分子量分布窄Mw Mn=1 19     

活性正离子聚合制备聚(异丁烯-b-α-甲基苯乙烯)嵌段共聚物

以2-氯-2,4,4-三甲基戊烷(TMPCl)/TiCl4/质子捕捉剂(DtBP)为引发剂体系,引发异丁烯聚合,随后加入1,1-二(4-甲基苯基)乙烯作为封端剂稳定末端碳正离子,再引入四异丙醇钛(Ti(OiPr)4),降低Lewis酸性,继续引发α-甲基苯乙烯聚合,实现活性正离子聚合制备聚(异丁烯-b-α-甲基苯乙烯)嵌段共聚物.考察了α-甲基苯乙烯聚合时间对单体转化率、产物的dn/dc值、分子量及其分布的影响以及四异丙醇钛对聚合速率的影响.并通过体积排斥色谱法/紫外检测器/示差折光指数/多角激光光散射、1H-NMR以及DSC以对产物进行表征.实验结果表明,嵌段共聚物分子量分布窄(MWD≤1.2),单体转化率与分子量呈线性关系,聚合速率对单体浓度呈一级动力学关系,具有活性聚合的特征.Ti(OiPr)4能有效稳定活性中心,降低聚合速率.聚(异丁烯-b-α-甲基苯乙烯)嵌段共聚物的DSC测试发现明显的两个Tg,表明存在微相分离结构.     

甲基丙烯酸(N,N-二甲氨基)乙酯的自引发催化氧化聚合

作为一种自身还原性单体,甲基丙烯酸(N,N-二甲氨基)乙酯(DMAEMA)可与部分氧化剂构成氧化还原引发剂体系,并引发自身的聚合.为验证该假设,进行了以CuCl2络合物催化DMAEMA的本体氧化聚合.动力学研究表明,所得聚合物的分子量随着聚合时间的延长而逐渐增加.核磁波谱分析表明,低转化率下所得低聚物同时含有甲基丙烯酸酯末端和C-Cl端基,显示DMAEMA的二甲氨基(N-CH3)被CuCl2氧化成单体自由基(N-CH2·),并通过原子转移自由基聚合(ATRP)机理形成聚合物.由于叔胺广泛地用作ATRP的络合物,由此可见,在传统ATRP体系中,来自CuCl2/叔胺的氧化还原引发不可忽略.     

某些添加物对丁二烯在(C_2H_5)_2AlCl-CoCl_2·4Py系统中聚合的影响

研究了某些含氧、氮及硫的化合物对丁二烯在催化系统(C_2H_5)_2AlCl-CoCl_2·4Py中聚合的影响。结果表明,加入乙醚或乙醛等含氧化合物及某些合氮化合物,如呲啶、苯胺和三乙胺等,都导致单体转化率和聚合物中凝胶量及分子量的降低,而对聚合物链中顺式-1,4链节的含量几乎没有什么影响。依据于添加物的性貭,在D/Al克分子比为0.5-1.0时(D-添加物),完全抑制聚合过程的进行。加入对二乙基氯化铝为过量的噻吩不影响转化率,但导致分子量的改变。在研究聚丁二烯的苯溶液与C_2H_5AlCl_2及催化系统(C_2H_5)_2AlCl-H_2O或(C_2H_5)_2AlCl-HCl的作用基础上,提出了在聚合过程中生成凝胶的可能作用机理。     

N_2O在Cu_xFe_(1-x)Fe_2O_4和Ni_xFe_(1-x)Fe_2O_4复合氧化物催化剂上的分解反应

用共沉淀法制备了一组具有尖晶石结构的Cu-Fe和Ni-Fe复合氧化物,用于有氧条件下催化分解N2O,考察了催化剂组成对催化活性的影响.用N2物理吸附(BET)、X射线衍射(XRD)、H2程序升温还原(H2-TPR)等技术对催化剂进行了结构表征.结果表明:在不同组成的Cu-Fe、Ni-Fe系列复合氧化物催化剂中,Cu Fe2O4和Ni Fe2O4对于N2O分解反应的初活性较高,这是因为Cu Fe2O4和Ni Fe2O4的比表面积较高、晶粒较小,而且其表面氧物种与金属(Cu2+、Fe3+)的化学作用较弱,氧物种易脱除、脱氧量较高.相比较而言,Ni Fe2O4催化剂上的N2O分解活化能低于Cu Fe2O4,Ni Fe2O4的初活性优于Cu Fe2O4.500℃连续反应100 h,Cu Fe2O4上的N2O转化率降至84.9%,而Ni Fe2O4上的N2O转化率一直保持99%,Ni Fe2O4有较高的催化稳定性.     

H_2O/TiCl_4/ED体系引发异丁烯控制正离子聚合中的影响因素研究

在亲核试剂(ED)如吡啶(Py)、N,N-二甲基乙酰胺(DMA)或三乙胺(TEA)存在下,由引发剂H2O和共引发剂TiCl4组成引发体系,在二氯甲烷/正己烷混合溶剂中进行异丁烯(IB)正离子聚合,考察了溶剂极性、聚合温度及异丁烯浓度对聚合反应转化率、产物分子量和分子量分布的影响.试验结果表明,随聚合体系溶剂极性增大,聚合速率加快,相近转化率时聚合产物的分子量分布变窄.随着聚合温度降低,聚合速率明显提高,聚合物的分子量增加,活化能为负值,活性链端发生链转移或链终止等副反应的几率减小,当聚合温度为-60℃时,可以抑制活性链端的β-H脱除反应和链转移副反应,并得到大分子链末端全部为叔氯基团的聚异丁烯(PIB).当[IB]0≤2.5mol/L时,随[IB]0增加,聚合转化率有所增加,聚合产物的GPC谱图均为单峰分布,分子量增大,而分子量分布基本保持不变,对于加入Py的聚合体系,分子量分布指数在1.33~1.45范围内,对于加入TEA的聚合体系,分子量分布指数在1.47~1.60范围内,并求出在加入Py和TEA的聚合体系中活性链向单体的链转移常数CM分别为5.5×10-4和6.6×10-4.     

负载卤化镍(NiX2/HD)催化MMA的原子转移自由基聚合

以负载卤化镍(NiX2/HD)为催化剂合成聚甲基丙烯酸甲酯(PMMA),具有反应可控、后处理简单且催化剂可以反复使用的优点。研究结果表明:卤原子、催化剂、钝化剂的类型和含量、反应温度等条件对该体系的聚合速率及可控性有重要影响。在相同条件下,NiCl2较NiBr2的催化速率快;钝化剂卤化铜/三-(N,N-二甲基氨基乙基)胺(CuX2/Me6TREN)对聚合产物分子量分布的可控性要优于卤化铁/三-(N,N-二甲基氨基乙基)胺(FeX3/Me6TREN);增大钝化剂的含量,聚合速率降低,且含量为1%时聚合的可控性较好;温度升高聚合速率加快,分子量分布指数(PDI)增大。顺磁共振检测中观察到钝化剂中过渡金属的化合价发生改变。     

大投料比下自缩合原子转移自由基共聚合中聚合物支化结构的形成与演化

研究了少量N-[4-(α-溴代异丁酰氧基)苯基]马来酰亚胺(BiBPM)与大量甲基丙烯酸-N,N-二甲氨基乙酯(DMAEMA)在CuBr/N,N,N′,N″,N″-五甲基二乙烯三胺(PMDETA)催化下的自缩合原子转移自由基共聚合(SCATRCP).分别利用气相色谱、三检测凝胶渗透色谱测定了聚合反应过程中DMAEMA的转化率、所得聚合物(PDMAEMA)的分子量与分子量分布、绝对分子量和特性黏数等随着反应时间的变化.结果表明,在以上聚合过程中,PDMAEMA的分子量随着聚合的进行而不断上升,但是支化度持续下降.由此可知,在聚合早期就形成了低分子量而高支化度的PDMAEMA,在聚合后期,主要进行DMAEMA的ATRP,导致支化度随着分子量的上升而逐渐下降.     

二(2,6-二叔丁基-4-个甲基苯氧基)钐催化丙交酯开环聚合

聚丙交酯（PLA）可以生物降解，产物无毒，可用于外科手术的缝合线、人造器官以及药物缓释等方面，因此引起了人们的广泛注意．丙交酯的开环聚合是合成聚丙交酯的一种方便方法，所用的催化剂主要是主族及副族金属的配合物，如双金属氧桥配合物［‘j，烷基金属有机化合物［‘j，异丙氧基铝［’‘以及叶琳铝「“等．最近，关于三价烷氧基稀土化合物作为单组份催化剂催化丙交酯开环聚会已有报道［’·’‘．我们发现两价芳氧基稀土化合物（ArO）。Sin（THF）。（ArO一2，已二叔丁基一个甲基苯氧基）也可以有效地催化丙文酯的开环聚合．本…     

二(芳氧基)稀土(Ⅱ)配合物催化ε-己内酯开环聚合

系统地研究了二（２，６ 二叔丁基 ４ 甲基酚基）钐［（ＡｒＯ）２Ｓｍ（ＴＨＦ）４］催化ε 己内酯的开环聚合，发现它具有很高的催化活性并显示“活性”聚合的特点，在甲苯中，当［Ｍ］／［Ｉ］＝２０００（摩尔比），６０℃，１ｈ，转化率可达９８％．并比较了不同的两价稀土化合物的催化活性．通过核磁分析末端基结构的方法，研究了（ＡｒＯ）２Ｓｍ催化己内酯开环聚合的引发机理，发现催化剂首先与己内酯反应，生成三价烯醇式稀土化合物，后者引发己内酯聚合．     

Synthesis and Crystal Structure of [(ArO)_2(THF)Sm(μ-OH)]_2·2THF(Ar=C_6H_(2-)~tBu_3-2,4,6)

1 INTRODUCTION Sm(II) chemistry has been extensively studied due to the strong reduction potential of this 4f6 ion[1]. The transformation of unsaturated substrates by Sm (II) complexes into products with unusual structures is one of the most interesting research areas. For the successful examples reported, Sm(II) starting mate- rials were restricted primarily to cyclopentadienyl complexes[2]. The reactivity of Sm(II) complex with phenolate ligands has seldom been explored. Recen- tl…     

Synthesis and Crystal Structure of [（ArO）2Sm（OPPh3）（μ—OH）]2（ArO=2,6—tBu—4—Me—C6H2O）

1 INTRODUCTION In recent years, the syntheses, structures and reactivities of aryloxo lanthanide complexes have attracted a great deal of attention due to their various applications as homogeneous catalysts for organic reactions and precursors for organolan- thanide syntheses[1]. However, the reactivity of divalent lanthanide aryloxides has seldom been studied[2]. We have previously reported that (ArO)2- Sm(THF)4 (ArO = OC6H2-2,6-di-tert-butyl-4-Me) can efficiently initiate the poly…     

Polymerization of n‐phenyl maleimide by lanthanide complexes

N‐Phenyl maleimide (N‐PMI) was successfully polymerized by divalent rare‐earth complexes (ArO)₂Sm(THF)₄ (ArO = 2,6‐di‐tert‐butyl‐4‐methyl phenoxo‐; THF = tetrahydrofuran) and (Ar′O)₂Ln(THF)₃ (Ar′O = 2,6‐di‐tert‐butyl phenoxo‐; Ln = Sm, Yb, or Eu). The central metals greatly affected the reactivity, and the reactivity order was Sm(II) > Yb(II) > Eu(II). The activity of (Ar′O)₂Sm(THF)₃ was higher than that of (ArO)₂Sm(THF)₄. The polymerization yields were higher in THF than in other solvents, and the maximum yields were obtained around 25 °C. A proposed mechanism is discussed. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3966–3972, 2005     

Synthesis and molecular structure of the cationic samarium phenoxide complex [(ArO)2Sm(DME)2][BPh4] · THF and its catalytic activity for the polymerization of ε-caprolactone

The first cationic samarium phenoxide complex, [(ArO)₂Sm(DME)₂][BPh₄] · THF (ArO = 2,6-di-tert-butyl-4-metyl-phenoxide) (1), has been synthesized by one-electron oxidation reaction of (ArO)₂Sm(THF)₃ with AgBPh₄ in high yield and structurally characterized. The complex 1 can be used as a single-component catalyst for the ring-opening polymerization of ε-caprolactone (ε-CL) with high activity. The activity of the complex 1 is much higher than that of the parent neutral complex (ArO)₃Sm(THF)₂, and is comparable to that of the divalent complex (ArO)₂Sm(THF)₃. A coordination-insertion polymerization mechanism was supposed according to the end-group analysis.     

Synthesis, reactivity, and structural characterization of sodium and ytterbium complexes containing new imidazolidine-bridged bis(phenolato) ligands

A new imidazolidine-bridged bis(phenol) [ONNO]H2 ([ONNO]H2=1,4-bis(2-hydroxy-3,5-di-tert-butyl-benzyl)imidazolidine) was prepared in relatively high yield by Mannish reaction of 2,4-di-tert-butylphenol, formaldehyde, and ethylenediamine in a 2:3:1 molar ratio. Reaction of the bis(phenol) with NaH in THF, after workup, afforded the sodium bis(phenolate) {[ONNO]Na2(THF)2}2.2THF (1) as a dimeric tetranuclear complex in an almost quantitative yield. Reaction of YbCl3 with complex 1 in a 2:1 molar ratio in THF, in the presence of HMPA, produced the desired bis(phenolate) ytterbium dichloride as bimetallic complex [ONNO]{YbCl2(HMPA)}2.2.5C7H8 (2). Complex 2 can be used as a precursor for the synthesis of ytterbium derivatives by salt metathesis reactions. Reaction of complex 2 with NaOiPr in a 1:2 molar ratio in THF led to the formation of bimetallic alkoxide [ONNO]{Yb(mu-OiPr)Cl(HMPA)}2.THF (3). However, the residual chlorine atoms in complex 3 are inactive for the further substituted reaction. Further study revealed that the bulkiness of the reagent has profound effect on the outcome of the reaction. Complex 2 reacted with bulky NaOAr (ArO=2,6-di-tert-butyl-4-methylphenoxo) or NaNPh2 in a 1:2 molar ratio under the same reaction conditions, after workup, to give the ligand redistributed products, (ArO)2YbCl(HMPA)2 (4) and [ONNO]YbCl(HMPA)2 (5) for the former and complexes 5 and (Ph2N)2YbCl(HMPA)2 (6) for the latter. If the molar ratio of complex 2 to NaNPh2 decreased to 1:4, the expected ligand redistributed products [ONNO]YbNPh2(HMPA) (7) and (Ph2N)3Yb(HMPA)2.C7H8 (8) can be isolated in high yields. All of the complexes were well characterized, and the definitive molecular structures of complexes 1-4, 7, and 8 were provided by single-crystal X-ray analysis.     

配合物(ArO)2Yb(NPh2)2K(THF)4(Ar=C6H2-t-Bu3-2,4,6)的合成、分子结构和催化行为

Reaction of anhydrous YbC13 with 2 equiv, of sodium 2,4,6-tri-tert-butylphenoxide (ArONa, Ar=C6H2-t-Bu3-2,4,6) and 2 equiv, of potassium diphenyl amide in THF afforded the first bis(aryloxo) amido-lanthanide complex of (ArO)2Yb(NPh2)2K(THF)4 (1). In 1, the ytterbium and potassium were bridged via diphenyl amido ligands.The ytterbium metal center was coordinated to two oxygen atoms of aryloxide ligands and two nitrogen atoms of diphenyl amido ligands in a conventional distorted tetrahedral fashion, while the potassium interacted in η^2-fashion with two phenyl rings of the diphenyl amido ligands besides four THF molecules. 1 displayed moderate catalytic activities for the polymerization of methyl methacrylate and acrylonitrile.     

(N2)3- radical chemistry via trivalent lanthanide salt/alkali metal reduction of dinitrogen: new syntheses and examples of (N2)2- and (N2)3- complexes and density functional theory comparisons of closed shell Sc3+, Y3+, and Lu3+ versus 4f(9) Dy3+

New syntheses of complexes containing the recently discovered (N(2))(3-) radical trianion have been developed by examining variations on the LnA(3)/M reductive system that delivers "LnA(2)" reactivity when Ln = scandium, yttrium, or a lanthanide, M = an alkali metal, and A = N(SiMe(3))(2) and C(5)R(5). The first examples of LnA(3)/M reduction of dinitrogen with aryloxide ligands (A = OC(6)R(5)) are reported: the combination of Dy(OAr)(3) (OAr = OC(6)H(3)(t)Bu(2)-2,6) with KC(8) under dinitrogen was found to produce both (N(2))(2-) and (N(2))(3-) products, [(ArO)(2)Dy(THF)(2)](2)(μ-η(2):η(2)-N(2)), 1, and [(ArO)(2)Dy(THF)](2)(μ-η(2):η(2)-N(2))[K(THF)(6)], 2a, respectively. The range of metals that form (N(2))(3-) complexes with [N(SiMe(3))(2)](-) ancillary ligands has been expanded from Y to Lu, Er, and La. Ln[N(SiMe(3))(2)](3)/M reactions with M = Na as well as KC(8) are reported. Reduction of the isolated (N(2))(2-) complex {[(Me(3)Si)(2)N](2)Y(THF)}(2)(μ-η(2):η(2)-N(2)), 3, with KC(8) forms the (N(2))(3-) complex, {[(Me(3)Si)(2)N](2)Y(THF)}(2)(μ-η(2):η(2)-N(2))[K(THF)(6)], 4a, in high yield. The reverse transformation, the conversion of 4a to 3 can be accomplished cleanly with elemental Hg. The crown ether derivative {[(Me(3)Si)(2)N](2)Y(THF)}(2)(μ-η(2):η(2)-N(2))[K(18-crown-6)(THF)(2)] was isolated from reduction of 3 with KC(8) in the presence of 18-crown-6 and found to be much less soluble in tetrahydrofuran (THF) than the [K(THF)(6)](+) salt, which facilitates its separation from 3. Evidence for ligand metalation in the Y[N(SiMe(3))(2)](3)/KC(8) reaction was obtained through the crystal structure of the metallacyclic complex {[(Me(3)Si)(2)N](2)Y[CH(2)Si(Me(2))NSiMe(3)]}[K(18-crown-6)(THF)(toluene)]. Density functional theory previously used only with reduced dinitrogen complexes of closed shell Sc(3+) and Y(3+) was extended to Lu(3+) as well as to open shell 4f(9) Dy(3+) complexes to allow the first comparison of bonding between these four metals.     

Reactivity of tris(trimethylsilyl)silane toward diarylaminyl radicals

Absolute rate constants for the reaction of tri-tert-butylphenoxyl radical (ArO*) with (TMS)(3)SiH were measured spectrophotometrically in the temperature range 321-383 K. Rate constants for the hydrogen abstraction from (TMS)(3)SiH by diarylaminyl radicals of type (4-X-C(6)H(4))(2)N* were determined by using a method in which the corresponding amines catalyze the reaction of ArO* with (TMS)(3)SiH. At 364.2 K, rate constants are in the range of 2-50 M(-)(1) s(-)(1) for X = H, CH(3), CH(3)O, and Br, whereas the corresponding value for ArO* is 3 orders of magnitude lower. A common feature of these reactions is the low preexponential factor [log(A/M(-1)s(-1)) of 4.4 and 5.2 for ArO* and Ph(2)N*, respectively], which reflects high steric demand in the transition state. A semiempirical approach based on intersecting parabolas suggests that the observed reactivity is mainly related to the enthalpy of the reaction and allowed to estimate activation energies for the reaction of (4-X-C(6)H(4))(2)N* and ArO* radicals with a variety of silicon hydrides.