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111.
《Journal of Coordination Chemistry》2012,65(18):3272-3279
New cyclopentadienyltitanium aryloxide complexes, 1-phenyl-2,3,4,5-Me4CpTi(O-2,6-iPr2-4-nBu-C6H2)Cl2 (1) and [4,4′-biphenyl-(2,3,4,5-Me4Cp)2][Ti(O-2,6-iPr2-4-nBu-C6H2)Cl2]2 (2), have been prepared by treatment of cyclopentadienyltitanium trichloride complexes [PhMe4CpTiCl3 and 4,4′-biphenyl-(Me4CpTiCl3)2] with 1 or 2 equiv of lithium salt of 2,6-di-isopropyl-4-butylphenol. Complexes 1 and 2 have been characterized by elemental analysis, 1H and 13C NMR spectroscopy. The molecular structure of 1 has been determined by single-crystal X-ray diffraction. Upon activation with iBu3Al and Ph3CB(C6F5)4, 1 and 2 both exhibit good catalytic activity for ethylene polymerization, producing polyethylene with moderate molecular weight and melting point. 相似文献
112.
《Journal of Coordination Chemistry》2012,65(14):2444-2454
A 3D copper phosphate, [Cu2(PO4)(OH)] n (1), has been synthesized hydrothermally and characterized by single-crystal X-ray diffraction analysis. In [Cu2(PO4)(OH)] n , there are two types of copper centers having distorted trigonal bipyramidal geometry and distorted octahedral geometry that are connected by the μ2-bridging of each phosphate oxygen ultimately forming a η8-PO4 bridged 3D network. The compound exhibited excellent catalytic performance in olefin epoxidation. Epoxidation of styrene and substituted styrenes, as well as bulky olefins like cycloalkenes and long-chain alkenes, is efficiently catalyzed by [Cu2(PO4)(OH)] n using tert-butylhydroperoxide in acetonitrile. The results obtained in the heterogeneous catalytic reactions show that the olefins are converted to the respective epoxides in good yield with high selectivity. [Cu2(PO4)(OH)] n was catalytically more active and selective in comparison to simple copper(II) phosphate salt in heterogeneous medium. The catalyst can be recycled and reused several times without significant loss of activity. 相似文献
113.
The tentative identification of the reactive species in the condensation of Cp2 TiCl2 with salts of diacids to form titanium polysters is made. The reactive species are believed to be the same for both aqueous solution and interfacial systems, i.e., R -CO2 ? and Cp2 Ti2+ with reaction occurring in the aqueous phase. The condensation of Cp2 TiCl2 with disodium terephthalate in interfacial systems occurs via a pseudo-first-order reaction: Rate = K[Cp2 TiCl2] The rate-determining step (s) is believed to be diffusion of CP2 TiCl2 into the aqueous layer and/or hydrolysis of Cp2 TiCl2 相似文献
114.
Silver(I) and copper(I) are known to form reversible complexes with π bonds, which have been exploited in LC for separating unsaturated organic compounds. Prominent examples include the use of AgNO3‐impregnated silica gel in LC, and the use of copper(I) salts for selective extraction of alkenes from hydrocarbon mixtures. The Dewar–Chatt–Duncanson model is often invoked to explain the interaction between Ag(I) and Cu(I) and π bonds. However, it is unclear if such a reversible interaction is directly related to their d10 outer electronic configurations. Particularly, Au(I) has not been reported to separate olefins with different numbers of double bonds in LC. Also, there has not been a systematic comparison of the liquid chromatographic properties of other d10 transition metal salts (e.g., Zn(II), Cd(II)), making it difficult to fully understand the observed reversible interactions of Ag(I) and Cu(I) with π bonds. We demonstrate for the first time that silica gel impregnated with all three Group 11 transition metals with 1+ oxidation state strongly and similarly retain olefin compounds in LC, while transition metals from Groups 10 and 12 do not. We also tested a range of functionalized silica gels to improve the stability of Cu(I) and Au(I) ions on the surface of the silica. 相似文献
115.
A stereoselective synthesis of (5S,6S)‐6‐[(2S,5S,7R,8E,10E)‐5‐(benzyloxy)‐7‐{[(tert‐butyl)dimethylsilyl]oxy}‐11‐phenylundeca‐8,10‐dien‐2‐yl]‐5‐ethyl‐5,6‐dihydro‐2H‐pyran‐2‐one (=(+)‐9‐O‐benzyl‐11‐O‐[(tert‐butyl)dimethylsilyl]bitungolide F) is reported. The strategy involves Gilman reaction, olefin cross‐metathesis, and Horner? Wadsworth? Emmons olefination as key steps. 相似文献
116.
This paper describes the extraction of C5–C8 linear α-olefins from olefin/paraffin mixtures of the same carbon number via a reversible complexation with a silver salt (silver bis(trifluoromethylsulfonyl)imide, Ag[Tf2N]) to form room temperature ionic liquids [Ag(olefin)x][Tf2N]. From the experimental (liquid + liquid) equilibrium data for the olefin/paraffin mixtures and Ag[Tf2N], 1-pentene showed the best separation performance while C7 and C8 olefins could only be separated from the corresponding mixtures on addition of water which also improves the selectivity at lower carbon numbers like the C5 and C6, for example. Using infrared and Raman spectroscopy of the complex and Ag[Tf2N] saturated by olefin, the mechanism of the extraction was found to be based on both chemical complexation and the physical solubility of the olefin in the ionic liquid ([Ag(olefin)x][Tf2N]). These experiments further support the use of such extraction techniques for the separation of olefins from paraffins. 相似文献
117.
Stereoselective synthesis of the C21–C40 core segment of caylobolide A has been achieved following a highly efficient convergent strategy. The key reactions featured in the synthesis are Prins cyclization, reductive radical cyclization, Sharpless asymmetric epoxidation and olefin cross metathesis. 相似文献
118.
运用密度泛函方法对含酚-膦配体的半茂钛化合物催化乙烯与降冰片烯共聚合反应的详细机理进行了理论研究。计算结果表明,虽然由于配体的不同,此系列钛化合物具有两种典型结构,但其在助催化剂作用下形成的催化活性种均为相似的P-Ti成键的阳离子物种。在烯烃聚合反应中,烯烃单体的配位插入反应易于从阳离子活性种中氧原子的对位发生。由乙烯及降冰片烯聚合反应各步骤的比较可知,乙烯单体插入Ti-Me结构的初始插入步骤较插入Ti-Et结构困难得多,因而链引发步骤为乙烯均聚的决速步骤。而降冰片烯单体插入Ti-Me结构较之乙烯单体容易得多,但由于降冰片烯单体位阻较大,其连续插入十分困难。在共聚反应过程中,NBE单体的引入可以使得Et插入反应容易越过较难的插入Ti-Me结构步骤,这是NBE与Et共聚反应的反应活性远大于催化Et均聚反应的最主要原因。 相似文献
119.
Ruthenium complexes bearing bidentate Schiff base ligands as efficient catalysts for organic and polymer syntheses 总被引:1,自引:0,他引:1
Renata Drozdzak Nele Ledoux Valerian Dragutan 《Coordination chemistry reviews》2005,249(24):3055-3074
A concise overview is given on mononuclear and dinuclear, bidentate Schiff base ruthenium complexes with different additional ligands and on their applications in various chemical transformations such as Kharasch addition, enol-ester synthesis, alkyne dimerization, olefin metathesis and atom transfer radical polymerization. These new ruthenium complexes, conveniently prepared from commonly available ruthenium compounds, are very stable, exhibit a good tolerance towards organic functionalities, air and moisture and display high activity and chemoselectivity in chemical transformations. Relevant features of coordination chemistry connected with the reaction mechanism and chemoselectivity are also fully described. Since the nature of Schiff bases can be changed in a variety of ways, appealing routes for designing and preparing novel ruthenium complexes can be foreseen in the future. 相似文献
120.
Peter Heiling Helmut Hönig Klaus Hummel 《Monatshefte für Chemie / Chemical Monthly》1980,111(3):575-579
Empirical force field calculations are used to interpret the occurrence of cyclopentenyl compounds in the course of metathesis degradation of partially isomerized modified poly(1-butenylenes). 相似文献