MoCl5对烯烃歧化和歧化聚合的催化作用

考察了单组元 MoCl_5对己烯-1歧化和歧化聚合的催化性能,低浓度MoCl_5催化剂只有烯烃歧化活性,高浓度的既有烯烃歧化又有歧化聚合活性,而且聚合反应是主要的,同时还发现Bu_4Sn-Ph_2Si(OEt)_2对MoCl_5的烯烃聚合及歧化的催化活性有明显的影响,推测MoCl_5-PhSi(OEt)与烯可能形成钼、硅、烯配合物(实验中发现它是一个深棕色固体),这个配合物在Bu_4Sn的作用下,容易形成金属卡宾络合物,促进了歧化收率的提高。     

固载在无机载体上的烯烃歧化钨、钼催化剂

将均相歧化催化剂WCl_6-Bu_4Sn,Bu_4N[Mo(CO)_5Cl]-EtAlCl_2中的钨、钼组分分别固载在一些无机载体上,进行己烯-1的催化歧化反应,发现某些固载体系,特别是WCl_6/SiO_2-Bu_4Sn体系的反应活性和选择性大大提高。讨论了SiO_2负载的WCl_6催化剂性能提高的可能原因。     

过渡金属催化烯烃异构化的研究 Ⅵ.Cp_2TiCl_2/i-C_3H_7MgBr催化4-乙烯基环己烯异构化的研究

近年来我们用 Cp_2 TiCl_2/i-C_3 H_7 MgBr(Cp=η~5-C_5 H_5)催化体系对非共轭双烯烃的异构化进行了一系列的研究.以1,5-环辛二烯和1,5-已二烯为模型化合物的催化异构化反应结果表明,这一催化体系无论是对非共轭的环双烯还是链双烯都具有催化剂活性高,反应条件温和,产物选择性好的特点.本文用同一体系,以4-乙烯基环已烯(1)为代表,研究了     

有机钛化学 Ⅲ.1,5-环辛二烯的钛催化均相氢化

本文研究了一系列有机钛化合物(R-C_5H_4)_2TiCl_2(R=H,CH_3,C_2H_5,n-C_3H_7,CH_2-CHCH_2,CH_3CH-CHCH_2,CH_3OCH_2CH_2,C_2H_5OCH_2CH_2,cyclo-C_6H_(11)等)和还原剂((i-Bu)_3Al,LiAlH_4,i-C_3H_7MgBr)组成的低价钛催化体系对1,5-环辛二烯的均相催化氢化反应。结果表明,低价钛催化体系在温和条件下具有较好的催化活性,氢化时还同时发生异构化反应。并讨论茂环上取代基对反应的影响及催化机理。     

有机钼、钨化合物研究 ⅩⅢ六羰基钼、钨体系催化炔烃聚合及其聚合物的性质

本文首次报导M(CO)_6 CX_4(M=Mo,W;X=Cl,Br)和AlCl_3(无水)组成的体系,在光照下对各种取代炔烃的聚合催化作用.发现AlCl_3能明显地提高M(CO)_6 CX_4 hv体系的催化活性.研究了不同聚合条件对聚合反应的影响,提出和讨论了该体系催化炔烃聚合反应的机理:金属卡宾活性中心的产生、金属卡宾稳定化,催化炔烃歧化聚合反应,以及最佳聚合条件.     

四氮杂大环四烯镍(Ⅱ)配合物[Ni(TIM)]X催化BrO_3~-氧化双有机底物的振荡反应

本文报道了四氮杂大环四烯镍(Ⅱ)配合物[Ni(TIM)]X[TIM为2,3,9,10-四甲基-1,4,8,11-四氮杂环十四-1,3,8,10-四烯;X=(ClO_4)_2,ZnCl_4,(SCN)_2]催化BrO_3~-CH_2(CO_2H)_2-(CO_2H)_2-H_2SO_4体系的新型振荡化学反应.对该振荡反应体系进行了多方面的研究,并提出了简要的机理.     

过渡金属催化烯烃异构化反应的研究I.1,5-环辛二烯的催化异构化

用20多种过渡金属络合物催化体系进行了1,5-环辛二烯的催化异构化研究,发现CP_2TiCl_2/i-C_3H_7MgBr催化体系的条件温和,催化活性高。例如,当Cp_2TiCl_2与 1,5-环辛二烯克分子比为1:200时,25℃下反应1小时,1,5-环辛二烯即可定量转化为1,3-环辛二烯。深入研究了这个催化体系,并提出了[Cp_2TiH]对双键加成,然后发生 Ti—βH消除的异构化机理。     

过渡金属催化烯烃异构化反应的研究——Ⅲ.Cp2Ni/i-C3H7MgBr体系与环辛二烯的反应

1,5-环辛二烯(简称COD)是丁二烯环化二聚产物。l,3-环辛二烯是新型的有机合成中间体和高分子单体。近年来,陆续出现了一些报道用过渡金属配合物作为均相催化剂,使非共轭的1,5-COD异构化为共轭的1,3-COD,并先后提出了几种不同的反应机理。我们也曾用含Ti、Ni、Fe、Cr、Mo、Pd、Zr等过渡金属配合物的20多种催化体系对1,5-COD的催化异构化进行了研究,发现用Cp_2TiCl_2(C_p=η~5-C_5H_5)/i-     

催化乙烯醛化的钌羰基原子簇新体系

发现了乙烯醛化的一个有效的新催化体系,它由钌原子簇H_4Ru_4(CO)_(12)或Ru_3(CO)_(12),卤化物和碱金属阳离子促进剂组成。在碱性的四氢呋喃-水溶液中,C_2H_4,H_2和CO的分压为1:2:2(总压小于75kg/cm~2)及125～175℃的条件下,其催化活性正比于反应温度、C_2H_4、H_2和CO的分压。添加卤化物和碱金属阳离子极大地提高了催化活性并得到如下顺序:NaI/NaOH 相似文献   

乙烯线性齐聚的研究Ⅱ、ZrCl4—Et2AlCl二组分体系的催化作用

1.引言 随着石油化工和精细化工的日益发展,工业上对直链α-烯烃的需要愈来愈迫切。乙烯齐聚反应是制备直链α-烯烃的重要方法。以过渡金属锆的化合物与烷基铝化合物组成的二元Ziegler-Natta体系催化乙烯线性齐聚,其文献和专利报导较少,且以合成高碳α-烯烃为目的。我们曾报导过ZrCl_4-Et_3A1_2Cl_3体系催化乙烯齐聚,虽能得到低碳α-烯烃,但效果较差。在使用Et_2AlCl作活化剂时结果较好。     

Cobalt-catalyzed sequential cyclization/cross-coupling reactions of 6-halo-1-hexene derivatives with Grignard reagents and their application to the synthesis of 1,3-diols

Cobalt/N-heterocyclic carbene system or cobalt/diamine combination effectively catalyzes sequential cyclization/cross-coupling reactions of 6-halo-1-hexene derivatives with trialkylsilylmethyl, 1-alkynyl, and aryl Grignard reagents. The sequential cyclization/cross-coupling reactions are applied to the synthesis of 1,3-diols starting from siloxy-tethered 6-halo-1-hexene derivatives.     

N-heterocyclic carbene ligands in cobalt-catalyzed sequential cyclization/cross-coupling reactions of 6-halo-1-hexene derivatives with Grignard reagents

[reaction: see text] N-Heterocyclic carbene/cobalt systems effectively catalyze sequential cyclization/cross-coupling reactions of 6-halo-1-hexene derivatives with trialkylsilylmethyl and 1-alkynyl Grignard reagents, which phosphine and amine ligands did not promote.     

Cobalt-mediated cross-coupling reactions of primary and secondary alkyl halides with 1-(trimethylsilyl)ethenyl- and 2-trimethylsilylethynylmagnesium reagents

[reaction: see text] This paper describes cobalt-mediated cross-coupling reactions of alkyl halides with 1-(trimethylsilyl)ethenylmagnesium bromide and 2-(trimethylsilyl)ethynylmagnesium bromide, respectively. The cobalt system allows for employing secondary as well as primary alkyl halides as the substrates. The reactions offer facile formations of alkyl-alkenyl and alkyl-alkynyl bonds. The reaction mechanism would include single-electron transfer from a cobalt complex to alkyl halide to generate the corresponding alkyl radical. The cobalt system thus enables sequential radical cyclization/alkenylation and cyclization/alkynylation reactions of 6-halo-1-hexene derivatives.     

Catalytic isomerization of 1-hexene on hy zeolite

The isomerization of 1-hexene on 70/80 mesh HY zeolite was studied at 200°C. The observed reaction products are formed via a variety of processes including double bond shift, cis–trans isomerization, skeletal rearrangement, cracking, hydrogen transfer, polymerization, cyclization, and coke formation. By applying the time-on-stream theory, the products have been classified as primary, secondary, or both, according to their OPE curves on product selectivity plots. 2-Ethyl-1-butene, which is present as an impurity in the feed, is found to react about 30 times faster than 1-hexene. Both 2-hexenes and 3 hexenes are formed primarily from 1-hexene, while 3 methyl 2 pentenes and 3-methyl-1-pentene formed from 2-ethyl-1-butene. The ratio of the initial rate of deprotonation to that of hydrogen shift in these reactions is ～15 and ～100, respectively. All products of skeletal rearrangement are observed to be secondary. Cracking products are produced mainly from precoke, which is also the source of hydrogen in the formation of paraffins. A detailed reaction network along with its associated mechanisms are presented and discussed.     

水溶性钌-氢配合物催化1-已烯双键异构化反应研究

研究了水溶性钌-氢配合物RuHCl(TPPTS)3在水/有机两相体系中催化1-己烯双键异构化反应.考察了反应温度、时间、膦配体浓度、相转移催化剂CTAB浓度以及底物与催化剂摩尔比等对转化率和产物选择性的影响.在最佳条件下1-己烯转化率达到82.4%,2-己烯选择性21.2%,3-己烯61.2%,没有发现骨架异构化.催化剂可重复使用5次.     

Formation of Three-Membered Rings by S(H)i Displacement. Reverse of Cyclopropyl Ring Opening(1)

The general methods, photoinitiated or peroxide-initiated free radical chain additions of halomethanes to olefins, yield 1,2-addition products at temperatures ranging from 20 to 100 degrees C. At lower temperatures, -42 to -104 degrees C, a competitive reaction, subsequent to the addition of CCl(2)X(*), yields alkylcyclopropanes. The reactions of 1-octene or 1-hexene and 1-methylcyclohexene with atomic hydrogen carried out in the presence of several transfer agents (CCl(4), CCl(3)Br, CCl(2)Br(2)) initiate a radical chain addition of CCl(2)X(*) and yield cyclized materials resulting from the S(H)i displacement of halogen by a carbon-centered radical. The radical displacement of a halogen on carbon, the reverse of homolytic displacement on cyclopropyl carbon, is dominant at low temperatures. The rate constants for cyclization (k(c)) vs transfer with halomethane (k(t)) showed isokinetic temperatures of -46 degrees C (CCl(4), 1-hexene); -35 degrees C (CCl(4), 1-methylcyclohexene). The isokinetic temperatures for the reactions of the two substrates carried out in the presence of BrCCl(3) were calculated as -204 degrees C (1-octene) and -109 degrees C (1-methylcyclohexene).     

DEPENDENCE OF THE DISTRIBUTION OF ACTIVE CENTERS ON MONOMER IN SUPPORTED ZIEGLER-NATTA CATALYSTS

Distribution of active centers(ACD)of ethylene or 1-hexene homopolymerization and ethylene-1-hexene copolymerization with a MgCl_2/TiCl_4 type Z-N catalyst were studied by deconvolution of the polymer molecular weight distribution into multiple Flory components.Each Flory component is thought to be formed by a certain type of active center. ACD of ethylene-1-hexene copolymer with very low 1-hexene incorporation was compared with that of ethylene homopolymer to see the effect of introducingα-olefin on eth...     

Cobalt-catalyzed cross-coupling reactions of alkyl halides with aryl Grignard reagents and their application to sequential radical cyclization/cross-coupling reactions

Reactions of alkyl halides with arylmagnesium bromides in the presence of cobalt(II)(diphosphine) complexes are discussed. Treatment of 1-bromooctane with phenylmagnesium bromide with the aid of a catalytic amount of CoCl₂(dppp) [DPPP=1,3-bis(diphenylphosphino)propane] yielded octylbenzene in good yield. The reaction mechanism would include single electron transfer from an electron-rich cobalt complex to alkyl halide to generate the corresponding alkyl radical. The mechanism was justified by CoCl₂(dppe)-catalyzed [DPPE=1,2-bis(diphenylphosphino)ethane] sequential radical cyclization/cross-coupling reactions of 6-halo-1-hexene derivatives that yielded benzyl-substituted cyclopentane skeletons.     

Effect of 1-Hexene Comonomer on Polyethylene Particle Growth and Kinetic Profiles

Summary: The polymer growth and the microstructure of the final polymer are greatly affected by mass transfer, especially in the early stages of polymerization. In the present work, the catalytic system (nBuCp)₂ZrCl₂/MAO immobilized over SiO₂-Al₂O₃ has been tested in ethylene-1-hexene copolymerizations using different amounts of comonomer. The catalytic activity shows a positive comonomer effect up to 1-hexene concentration of 0.724 mol/L since larger amounts of 1-hexene lead to a decrease in the activity. Copolymer properties analyzed by ¹³C NMR, GPC, CRYSTAF and DSC point to the presence of important amorphous regions in the growing polymer chains as the 1-hexene concentration increases. In order to study the incorporation of 1-hexene during ethylene polymerization, several experiments were performed with 0.194 mol/L of 1-hexene, 5 bar of ethylene pressure and different polymerization times. The incorporation of 1-hexene decreases slightly at polymerization times above 20 minutes. From cross-sectioned SEM images it can be concluded that the presence of 1-hexene helps catalyst fragmentation which could be related with the filter effect proposed by Fink.     

镧系金属有机配合物的研究XIV:三(环戊二烯基)稀土金属配合物-氢化钠体系对烯烃的还原反应

研究了九种稀土有机配合物CP3Ln(Ln=La,Pr,Nd,Sm,Tb,Y,Er,Yb和Lu)与氢化钠组成的一种新还原体系及与烯烃还原反应的结果.CP3Ln-NaH体系在45℃,四氢呋喃溶液中能程度不同地把1-己烯还原成己烷.还原活性与稀土金属离子的离子半径密切相关.活性顺序是轻稀土>中稀土>重稀土.以CP3Sm最高,CP3Yb最低.讨论了各种因素对还原的影响及还原机理.