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排序方式: 共有200条查询结果,搜索用时 15 毫秒
31.
Cyclic voltammetry has been employed to examine the electrochemistry of nickel(II) salen at a glassy carbon electrode in an ionic liquid (1-butyl-3-methylimidazolium tetrafluoroborate, BMIM+BF4−). Residual water in the ionic liquid can be eliminated by introduction of activated molecular sieves into the electrochemical cell. Nickel(II) salen exhibits a one-electron, quasi-reversible reduction to nickel(I) salen, and the latter species serves as a catalyst for the cleavage of carbon–halogen bonds in iodoethane and 1,1,2-trichlorotrifluoroethane (Freon® 113). In BMIM+BF4− the diffusion coefficient for nickel(II) salen at room temperature has been determined to be 1.8×10−8 cm2 s−1, which is more than 500 times smaller than that (1.0×10−5 cm2 s−1) in a typical organic solvent–electrolyte system such as dimethylformamide (DMF) containing 0.10 M tetramethylammonium tetrafluoroborate. 相似文献
32.
Selective Polymerization Catalysis from Monomer Mixtures: Using a Commercial Cr‐Salen Catalyst To Access ABA Block Polyesters 下载免费PDF全文
Tim Stößer Prof. Dr. Charlotte K. Williams 《Angewandte Chemie (International ed. in English)》2018,57(21):6337-6341
ABA triblock polyesters are synthesized using a commercially available chromium salen catalyst, in one pot, from monomer mixtures comprising epoxide, anhydride and lactone. The catalysis is highly selective and applies a single catalyst in two distinct pathways. It occurs first by epoxide/anhydride ring‐opening copolymerization and subsequently by lactone ring‐opening polymerization. It is used to produce various new ABA polyester polyols; these polyols can undergo post‐functionalization and chain‐extension reactions. The ability to use a commercial catalyst and switchable catalysis with monomer mixtures is expected to facilitate future explorations of new classes of block polymers. 相似文献
33.
手性SalenZn配合物的合成及对咪唑类、吡啶类客体的分子识别研究 总被引:4,自引:0,他引:4
合成并表征了手性Salen配体1及其Zn配合物2。详细讨论了配体及配合物的电 子光谱和圆二色光谱性质。用紫外—可见光谱滴定法测定了主体2与4种咪唑、5种 吡啶客体轴向配位反应的平衡常数,研究了主体分子2的分子识别行为。实验结果 表明:各种客体的缔合常数,咪吡类按K(Im)>K(2—MeIm)>K(SMIm)>K(EMIm)顺 序递减;吡啶类按K(Py)>K(3-Py)>K(3,5-Py)>K(2,4—Py)>K(2,4,6—Py)顺 序递减。测定了识别过程的△rGm^-,△rHm^-,△rSm^-,发现该反应是放热、熵减 小的过程。采用分子力学的方法考察了主客体的最低能量构象,并对该构象进行量 子化学计算,从理论上对实验事实给予较好的解释。 相似文献
34.
《Electroanalysis》2003,15(2):139-144
A highly selective and sensitive membrane electrode based on vanadyl salen complex (VS), which responds to monohydrogenphosphate (MHP) ions is described. The response of the sensor is Nernstian over the wide concentration range (1.0×10?1 ? 5.0×10?6 M) of MHP. The sensitivity of the electrode is high enough to permit the detection of as little as 0.6 μg/mL of MHP without any significant interference from high levels of other anions. The potentiometric selectivity coefficient data revealed negligible interference from 11 common anions. The electrode has a fast response time (<25 s), good slope stability at pH 8.2 for a period of at least eight weeks. It was successfully applied for the direct determination of monohydrogenphosphate in fertilizer and, as indicator electrode, in potentiometric titration of HPO42? ion with barium chloride. 相似文献
35.
Hiromichi Egami 《Tetrahedron letters》2005,46(36):6049-6052
The mechanism of aerobic oxidation of alcohols using (ON)Ru(salen) complex as catalyst under photo-irradiation was examined through studies of kinetics of the oxidation, kinetic isotope effect in the oxidation, and effect of the ligand structure on the chemoselectivity of the oxidation of primary and secondary alcohols. It was demonstrated that the aerobic oxidation includes an intramolecular hydrogen atom transfer process that is attributed to realization of efficient differentiation of primary and secondary alcohols in the oxidation. 相似文献
36.
将(1R,2R)-环己二胺与2-羟基-1-萘甲醛和3,5-二叔丁基水杨醛反应,得到非对称Salen配体H2L,然后将配体H2L与Ni(OAc)2·4H2O、Cu(OAc)2·H2O、Mn(OAc)2·4H2O进行配位反应,得到3个单核配合物[Ni(L)]·CH2Cl2(1),[Cu(L)](2),[Mn(L)(Cl)]·CH2Cl2(3),分别采用1H NMR、FT-IR和元素分析对化合物进行了表征,并通过X射线单晶衍射技术测定了配体和3个配合物的晶体结构。配体H2L属于正交晶系,P212121空间群。配合物1属于单斜晶系,P21/c空间群,而配合物2和配合物1的结构相似。配合物3属于三斜晶系,P1空间群。 相似文献
37.
38.
Asymmetric catalytic epoxidation of alkenes such as styrenes, chromenes and indene using transition metal complexes both inhomogeneous and heterogeneous phase has been discussed in this review. The various strategies to make the catalysts recyclable by introducing in-built phase transfer ability, converting these to dimeric form, exchanging into clays and supporting on polymeric or inorganic supports are discussed at length. 相似文献
39.
Five novel chiral dinuclear Salen complexes M2L (M = Fe3+Cl-, Mn3+Cl-, Co2+, Ni2+, Cu2+) and Ba2+-crown ether complex H4BaL(ClO4)2 were synthesized. The complexes were synthesized by reaction between ligand 3(H4L) and corresponding metal salts (FeCl3, Mn(OAc)2·4H2O, Co(OAc)2·4H2O, Ni(OAc)2·4H2O, Cu(OAc)2·H2O, Ba(ClO4)2·2H2O). The chiral two discrete Salen ligand 3 was condensed from 3,3′-[Oxybis(2,l-ethanediyloxy)]bis(2-hydroxybenzaldehyde) and (R,R)-1,2-diamino-cyclohexane. The structure of complexes is two discrete Salen unit bridged with crown ether from two sides. We found that ligand 3 had three complex cites. The two N2O2 cavities can found complexes with d-metals (compound 4), while the O10 cavity can found complex with alkali metals and alkaline-earth metals (compound 5). The compounds were characterized by elemental analyses, 1H NMR, Mass-spectra, FT-IR, UV-Vis and CD spectra. The FT-IR, UV-Vis and CD spectra property of complexes were minutely analyzed. 相似文献
40.
A new type of chiral cobalt salen complexes bearing BF3 Lewis acid proved to be reactive and enantioselective in the hydrolytic resolution of terminal epoxides. The polymer type salen catalysts also showed a high enantioselectivity in the same reaction. 相似文献