用~(13)C-NMR研究 1,2-聚丁二烯的分子运动——1,2-聚丁二烯分子运动对微观结构的依赖性

本工作用200兆赫脉冲傅里叶变换 NMR 波谱仪测定了一系列1,2-聚丁二烯样品在溶液中~13C核自旋-晶格弛豫时间(T_1)和核Overhauser效应(NOE)。较系统地研究了1,2-聚丁二烯的分子运动与化学结构、序列结构和大分子链节构成的关系,分析了乙烯基的内旋转运动。实验结果表明,顺1,4-链节中各碳的nT_1值比1,2-链节中相应各碳的nT_1值长1倍左右;对于相同的链节,当其两旁由1,2-链节变为顺1,4-链节时,其各类碳的nT_1值都大大增加;随着1,2-链节增加,各类碳的nT_1值都明显缩短。乙烯基叔碳的nT_1值大于端碳,经计算表明,引起乙烯基叔、端碳的nT_1值不相等的主要因素是乙烯基在垂直于主链的平面上的摆动。     

Anionic Polymerization and Copolymerization of Hydrocarbon Monomers Catalyzed by Organobarium Initiators

The barium salt of the dimeric dianion of 1,1-diphenylethylene (Ba-DPhE) initiates polymerization and copolymerization of monomers capable of anionic polymerization (butadiene, isoprene, styrene) in ethereal and hydrocarbon solvents. Ba-DPhE is more stereospecific in butadiene polymerization (up to 70% of cis-1, 4-units in hydrocarbon medium) than initiators based on other metals of Groups I and II. The relative reactivity of monomers in copolymerization processes in THF decreases in an order typical for anionic polymerization: styrene > butadiene > isoprene. The most interesting feature of organobarium initiators is their ability to form random butadiene-styrene copolymers with high cis-1,4-butadiene unit content when copolymerization proceeds in a hydrocarbon medium.

A new phenomenon in anionic polymerization, the dependence of diene units structure on copolymer composition, was observed. Thus an increase of styrene content in butadienestyrene copolymer leads to conversion of cis-1,4-butadiene units into trans-1,4-units (in benzene) or to conversion of 1,4-units to 1,2-units (in THF). Similarly, an increase of butadiene content in its copolymer with isoprene (in benzene) leads to conversion of cis-1,4-isoprene units into trans-1,4-units.

Spectrophotometric, conductometric, and viscometric methods were used to study organobarium active centers. Certain anomalies connected with the formation of specific aggregates due to coupling of bifunctional hydrocarbon chains with bivalent counterions were observed.     

用Co(naph)2-Al2(C2H5)3Cl3-P(OPh)3催化体系合成中乙烯基液体聚丁二烯

为获得适中乙烯基含量的液体聚丁二烯为目的, 对Co(naph)2-Al2(C2H5)3Cl3-P(OPh)3催化体系进行了较为系统的研究, 考察了该体系的催化剂配比、浓度及供电子试剂对分子量、微观结构和转化率的影响. 实验结果表明, 该体系在一定的条件下可以制备出分子量在700~3500、1,2结构含量在35%~40%且转化率高于55%的液体聚丁二烯.     

结晶3,4-聚异戊二烯的合成

<正> 非结晶的3,4-聚异戊二烯的合成已有一些报道,本文则采用合铁的三元催化体系:三乙酰基丙酮铁-含氮给电子试剂-三异丁基铝,可使异成二烯聚合得到高3,4-链节含量,高分子量以及高熔点的结晶聚合物。 1.试剂及聚合反应 异戊二烯为聚合级产品,用前经常压蒸馏除去阻聚剂后,用活性氧化铝浸泡48小时     

Microstructure of polyisoprenes synthesized with titanium- and neodymium-containing catalytic systems

Polyisoprenes predominantly composed of cis-1,4-units are studied by the methods of NMR spectroscopy (600 MHz), GPC, and DSC. A comparative investigation of synthetic polyisoprene and natural rubbers shows that a small (up to 3?C4 mol %) amount of polymer-chain disruptions, such as inverse additions of cis-1,4 units and units occurring in 3,4- and trans-1,4-configurations, has no effect on the local conformational structure of the polymer.     

Filler-polymer interactions in filled polybutadiene compounds

Bound rubber in a filled rubber compound is formed by physical adsorption and chemisorption between the rubber and filler. Polybutadiene (PB) is composed of three components of 1,2-, cis-1,4-, and trans-1,4-units. Filler-polymer interactions in PB compounds filled with carbon black or silica were studied by analyzing microstructures of the bound rubbers with pyrolysis-gas chromatography. Differences in the filler-polymer interactions of the 1,2-, cis-1,4-, and trans-1,4-units were investigated. The filler-polymer interaction of the 1,2-unit is stronger than those of the cis-1,4- and trans-1,4-units. The interaction of the 1,2-unit with silica is stronger than with carbon black. Bound rubber content is decreased by treatment with ammonia. Change of the bound rubber composition after the ammonia treatment was also studied.     

Considering factors on determination of microstructures of SBR vulcanizates using pyrolytic analysis

Properties of styrene-butadiene rubbers (SBRs) are depending on their microstructures (contents of 1,4-unit, 1,2-unit, and styrene), but it is hard to determine the microstructures of SBR vulcanizates. Pyrolytic method such as pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) has been used for microstructures of cured rubbers without pretreatment. Microstructure of SBRs can be estimated using the major pyrolysis products (butadiene, 4-vinylcyclohexene (VCH), and styrene). In this study, considering factors for determination of microstructures of SBR vulcanizates using Py-GC/MS were investigated. The principal considering factors were found to be change of the major pyrolysis products due to radicals formed in carbon backbone and sulfur by dissociation of sulfide crosslinks in SBR vulcanizates. Relative abundances of the major pyrolysis products of raw and cured SBRs were different due to rearrangements of the radicals. Influencing factors on pyrolysis behaviors of SBR vulcanizates were found to be 1,2-unit block, alternating sequence of 1,4- and 1,2-units, styrene-1,4-unit and styrene-1,2-unit sequences, and location of the radicals. Especially, the 1,2-unit block influenced on change of the VCH/butadiene ratio, while the styrene-1,2-unit sequence affected change of the styrene/(butadiene + VCH) one.     

氯化稀土乙二醇二甲醚配合物催化丁二烯聚合

以Nd2O3、(CH3)3SiCl和乙二醇二甲醚(DME)为原料,合成了NdCl3·2DME配合物,并将其用于催化丁二烯聚合。 考察了助催化剂种类与用量、陈化温度和聚合时间对聚合的影响。 结果表明,以烷基铝与MAO共同作为助催[JP2]化剂时具有高聚合活性,而单独以烷基铝或甲基铝氧烷(MAO)为助催化剂时聚合活性很低。 当n(Nd)∶n(AlR3)∶n(MAO)=1∶30∶45时,催化活性最高。 陈化温度对聚合活性、聚合物结构及相对分子质量均有较大的影响。 陈化温度过低或者过高,聚合活性、聚丁二烯cis-1,4含量和相对分子质量均降低;陈化温度为50 ℃时,具有最高聚合活性和最高cis-1,4含量。 NdCl3·2DME催化体系所得聚丁二烯的cis-1,4含量高达98.7%（IR）,而1,4-结构总含量高达99.6%（1H NMR）。     

Polymerization of butadiene and isoprene in the presence of a titanium catalytic system under ultrasonic irradiation

The ultrasonic irradiation of the reaction mixture during its formation in the polymerization of butadiene and isoprene with a microheterogeneous titanium catalytic system causes acceleration of the process. In this case, the multicenter titanium catalytic system is transformed into a quasi-single-center system and the type of operating center depends on the nature of a polymerizing diene. During the polymerization of butadiene, this effect leads to an increase in the amount of trans-1,4-units and to a decrease in the average molecular masses. In the case of isoprene, the resulting polymer contains a higher amount of cis-1,4-units.     

Binary boron-rich borides of magnesium: single-crystal investigations and properties of MgB(7) and the new boride Mg(∼5)B(44)

Single crystals of dark-red MgB(7) were grown from the elements in a Cu-melt. The crystal structure (Pearson symbol oI64; space group Imma; a = 10.478(2) ?, b = 5.977(1) ?, c = 8.125(2) ?, 2842 reflns, 48 params, R(1)(F) = 0.018, R(2)(I) = 0.034) consists of a hexagonal-primitive packing of B(12)-icosahedra and B(2)-units in trigonal-prismatic voids. According to the UV-vis spectra and band structure calculations MgB(7) is semiconducting with an optical gap of 1.9 eV. The long B-B distance of 2.278 ? within the B(2)-unit can be seen as a weak bonding interaction. The new Mg(～5)B(44) occurs beside the well-known MgB(12) as a byproduct. Small fragments of the black crystals are dark-yellow and transparent. The crystal structure (Pearson symbol tP196, space group P4(1)2(1)2, a = 10.380(2) ?, c = 14.391(3) ?, 4080 reflns, 251 params, R(1)(F) = 0.025, R(2)(I) = 0.037) is closely related to tetragonal boron-II (t-B(192)). It consists of B(12)-icosahedra and B(19+1)-units. With a charge of -6 for the B(19+1)-units and a Mg-content of ～20 Mg-atoms per unit cell the observed Mg content in Mg(～5)B(44) is quite close to the expected value derived from simple electron counting rules. All compositions were confirmed by EDXS. The microhardness was measured on single crystals for MgB(7) (H(V) = 2125, H(K) = 2004) and MgB(12) (H(V) = 2360, H(K) = 2459).     

Design and synthesis of 2-(1,3-dialkoxy-2-methylpropan-2-yl)-1,3-diarylpropanes as tethering units for folded H-stacking polymers

1,3-Diarylpropenes 9 having a 1,3-dialkoxy-2-methylpropan-2-yl group were designed as tethering monomers for folded H-stacking polymers, and were readily synthesized from 2-ethoxymethylidene malonate in four- or five-steps, including a facile sequential addition–elimination–addition reaction of benzyl zinc reagents. The preference for the closed (stacked) conformation in the resulting 2-substituted 1,3-diarylpropanes 9 was evaluated using MM2 calculations, ¹H NMR analyses, and fluorescence measurements. Copolymerization of the resulting monomers 9 with compounds containing π-units provided polymers with blue-shifted UV-absorptions both in solution and as films, compared with that of a model compound containing a single π-unit. This optical property is unique to H-aggregated π-units.     

Molecular structure of polybutadienes synthesized with a lithium-containing initiation system

With the use of high-resolution NMR spectroscopy (600 MHz) and gel-permeation chromatography, the products of anionic polymerization of butadiene initiated by n-butyllithium modified with sodium and magnesium alcoholates are studied. It is shown that a change in synthesis conditions makes it possible to vary the configuration and isomeric composition and molecular parameters of polybutadienes. The distribution of 1,2-, cis-1,4-, and trans-1,4-units in a chain has a pronounced statistical character and depends on the composition of the initiation system.     

Synthesis of acetimino complexes of Pt(II) and Pt(IV) and the first heteronuclear mu-acetimido complexes

The reactions of [Ag(NH=CMe2)2]ClO4 with cis-[PtCl2L2] in a 1:1 molar ratio give cis-[PtCl(NH=CMe2)(PPh3)2]ClO4 (1cis) or cis-[PtCl(NH=CMe2)2(dmso)]ClO4 (2), and in 2:1 molar ratio, they produce [Pt(NH=CMe2)2L2](ClO4)2 [L = PPh3 (3), L2= tbbpy = 4,4'-di-tert-butyl-2,2'-dipyridyl (4)]. Complex 2 reacts with PPh3 (1:2) to give trans-[PtCl(NH=CMe2)(PPh3)2]ClO(4) (1trans). The two-step reaction of cis-[PtCl2(dmso)2], [Au(NH=CMe2)(PPh3)]ClO4, and PPh3 (1:1:1) gives [SP-4-3]-[PtCl(NH=CMe2)(dmso)(PPh3)]ClO4 (5). The reactions of complexes 2 and 4 with PhICl2 give the Pt(IV) derivatives [OC-6-13]-[PtCl3(NH=CMe2)(2)(dmso)]ClO4 (6) and [OC-6-13]-[PtCl2(NH=CMe2)2(dtbbpy)](ClO4)2 (7), respectively. Complexes 1cis and 1trans react with NaH and [AuCl(PPh3)] (1:10:1.2) to give cis- and trans-[PtCl{mu-N(AuPPh3)=CMe2}(PPh3)2]ClO4 (8cis and 8trans), respectively. The crystal structures of 4.0.5Et2O.0.5Me2CO and 6 have been determined; both exhibit pseudosymmetry.     

双烯类聚合物的热分析——Ⅲ.铁与其它催化体系聚1,2-丁二烯及其衍生物的热分析

<正> 由不同催化体系制得的聚1,2-丁二烯,由于其立体规整性(如等规、间规和无规)不同,其形态、热学性质也会有所不同。关于它们的热学性质文献报道不多。我们曾报道,由三乙酰基丙酮钴-三异丁基铝-二硫化碳催化体系制备的间规聚1,2-丁二烯是晶态的;而由正丁基锂和MoCl_4OR-(i-Bu),AlOR′制得的是无规聚1,2-丁二烯;是非晶态     

Chemistry of phosphine-borane adducts at platinum centers: dehydrocoupling reactivity of Pt(II) dihydrides with P-H bonds

The reaction of the Pt(II) dihydride complex cis-[PtH2(dcype)](dcype = 1,2-bis(dicyclohexylphosphino)ethane) with the primary or secondary phosphine-borane adducts PhRPH x BH3(R = H, Ph) was found to exclusively afford the mono-substituted complexes cis-[PtH(PPhR x BH3)(dcype)](1: R = H; 2: R = Ph)via a dehydrocoupling reaction between Pt-H and P-H bonds. Similar reactivity was observed between the uncoordinated phosphines PhRPH (R = H, Ph) and cis-[PtH2(dcype)], which gave cis-[PtH(PPhR)(dcype)](4: R = H; 5: R = Ph). The complexes were characterized by 1H, 11B, 13C and 31P NMR spectroscopy, IR, MS and, in the case of 2, X-ray crystallography that confirmed the cis geometries. The di-substituted complex cis-[Pt(PhPH x BH3)2(dcype)](3) was prepared from the reaction of cis-[PtCl2(dcype)] with two equivalents of Li[PPhH x BH3]. This suggested that steric reasons alone cannot be used to explain the lack of reactivity with respect to a second dehydrocoupling reaction involving the remaining Pt-H bond in complexes 1, 2, 4 and 5.     

First metallamacrocyclic complexes of Pt(iv) with 3,3,3',3'-tetraalkyl-1,1'-phenylenedicarbonylbis(thioureas): synthesis by direct or electrolytic oxidative addition of I(2), Br(2) and Cl(2)

Elemental I(2) and Br(2) cleanly react with the 3:3 Pt(ii) metallamacrocycle of 3,3,3',3'-tetra(n-butyl)-1,1'-terephthaloylbis(thiourea)(cis-[Pt(II)(3)(L(p)(1)-S,O)(3)]3), in chloroform at room temperature, to yield oxidative addition products; (195)Pt NMR studies reveal that a stepwise oxidative addition readily occurs to each of the Pt(ii) centres in the metallamacrocycle to yield the mixed valence species cis-[Pt(II)(2)Pt(IV)I(2)(L(p)(1)-S,O)(3)] and cis-[Pt(II)Pt(IV)(2)I(4)(L(p)(1)-S,O)(3)], and the fully oxidised cis-[Pt(IV)(3)I(6)(L(p)(1)-S,O)(3)] in solution, depending on the mole ratio I(2):3. Similar results are obtained on treatment of solutions of 3 with elemental Br(2). Treatment of the corresponding 2:2 Pt(ii) complex of 3,3,3',3'-tetraethyl-1,1'-isophthaloylbis(thiourea)(cis-[Pt(II)(2)(L(m)(1)-S,O)(2)]4) with iodine, results in facile oxidative addition to yield cis-[Pt(IV)(2)(L(m)(1)-S,O)(2)I(4)], with a trans-Pt(iv)-iodo arrangement. Molecules in the crystal structure of 5 have their trans-Pt(iv)-iodo axes essentially aligned, with very close intermolecular iodide contacts (3.775(1)A), resulting in chains of weakly bound metallamacrocycles in the solid. An alternative electrolytic synthesis method, using a simple two-compartment glass cell containing 4 and a chosen halide salt in dichloromethane, led to the formation of cis-[Pt(IV)(2)(L(m)(1)-S,O)(2)Br(4)] 6 and cis-[Pt(IV)(2)(L(m)(1)-S,O)(2)Cl(4)] 7, completing characterization of a series of first-reported trans-Pt(iv)-X (X=I, Br, Cl) metallamacrocyclic complexes.     

聚丁二烯~(13)C-NMR谱图中一个新的共振吸收峰(T_4)

<正> 最近解析锂系和铁系含乙烯基聚丁二烯的~(13)C-NMR谱图,发现并确认了一个新的共振吸收峰。即聚丁二烯反式1,4-序列的第四峰,简称T_4峰。 Furukawa等对钼系和章哲彦等对铁系等二元聚顺-1,4-1,2-丁二烯的研究都指出在聚丁二烯的~(13)C-NMR谱图上,有四个谱峰属于顺1,4-序列。本文给出其化学位     

The subtle electronic effects of alkyl groups on the conformational equilibria and intramolecular hydrogen-bond strength in cis-3-alkoxycyclohexanols

(1)H NMR data for cis-3-n-propoxycyclohexanol (cis-3-PCH) and cis-3-isopropoxy-cyclohexanol (cis-3-ICH) show that a concentration increase shifts the conformational equilibrium from the diaxial (aa) conformer, stabilized by an intramolecular hydrogen bond (IAHB), to the diequatorial (ee) conformer [X(ee)=42% and 21% (at 0.01molL(-1)) to 58% and 56% (at 0.40molL(-1)), in CCl(4,) respectively] due to intermolecular hydrogen bonds (IEHB), as confirmed by IR data. The Deltanu values, obtained by IR spectra, indicated that increasing the size of the OR group [R=CH(3), CH(2)CH(2)CH(3) and CH(CH(3))(2)], increases the IAHB strength, due to an increase in the inductive effect of R group, which makes the oxygen lone pairs more available for an IAHB with OH group, in opposition to the steric effect. The percentage of ee conformer increases with the solvent basicity for cis-3-PCH and cis-3-ICH, from 48% and 36% in CCl(4) to 97% and 96% in DMSO, respectively. Values of 4.58, 6.06 and 6.33kcalmol(-1) for the IAHB strength in cis-3-PCH, cis-3-ICH and cis-3-TCH (cis-3-tert-butoxycyclohexanol), respectively, were obtained, from the theoretical data through the CBS-4M method, confirming the experimental results and indicating that the IAHB strength increases with the increasing bulk of OR substituent in this series of compounds.     

Role of the phosphine ligands on the stabilization of monoadducts of the model nucleobases 1-methylcytosine and 9-methylguanine in platinum(II) complexes

The addition of 1-methylcytosine (1-MeCy) or 9-methylguanine (9-MeGu) to solutions of cis-(PPh3)2P(ONO2)2 (1a), in a molar ratio of 1:1, affords the monoadducts cis-[(PPh3)2Pt(1-MeCy)(ONO2)]NO3 (2a) and cis-[(PPh3)2Pt(9-MeGu)(ONO2)]NO3 (3a) and only trace amounts of the bisadducts cis-[(PPh3)2Pt(1-MeCy)2](NO3)2 (4a) and cis-[(PPh3)2Pt(9-MeGu)2](NO3)2 (5a), respectively. The X-ray structural determination of 2a and 3a indicates a strong pi-pi stacking interaction between one of the PPh3 phenyl groups and the pyrimydinic N3-platinated cytosine or the imidazole part of the N7-coordinated guanine base. The addition of a further equiv of nucleobase to the monoadducts forms quantitatively the bisadducts that have been isolated as pure compounds 4a and 5a. Under the same experimental conditions, the dinitrato analogue cis-[(PMePh2)2Pt(ONO2)2] (1b) forms the monoadducts 2b and 3b in equilibrium with a relatively high concentration (20-30%) of the bisadducts cis-[(PMePh2)2Pt(1-MeCy)2](NO3)2 (4b) and cis-[(PMePh2)2Pt(9-MeGu)2](NO3)2 (5b), which have been structurally characterized by single-crystal X-ray analysis. The characterization of the isolated complexes by multinuclear NMR spectroscopy is also described.     

不同氢化度氢化丁腈橡胶的结构表征与分子模拟

通过核磁共振波谱(¹H NMR)、 红外光谱(IR)及热分析等方法研究了不同氢化度氢化丁腈橡胶(HNBR)分子结构之间的差异, 结果表明, 在丁腈橡胶(NBR)加氢过程中, 聚丁二烯上的乙烯基加氢速率最快, 其次是反式1,4结构, 顺式1,4结构的加氢速率最慢, 而腈基基本不发生氢化反应. 采用核磁共振谱法对不同氢化度HNBR中不同链段的含量进行定量分析, 依据此结果建模并进行分子模拟计算, 得到不同氢化丁腈橡胶的密度、 内聚能密度(CED)和玻璃化转变温度(T_g)等参数, 模拟值与实验结果吻合. 实验结果表明, 随着氢化度的增加, HNBR的热氧化稳定性逐渐增加, 这主要是由于氢化度增加后分子链中双键含量逐渐减少而CED增加的缘故. 分子模拟可以有效地计算出多种结构参数, 为共聚橡胶材料的制备与加工提供基础数据及理论指导.