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101.
Two novel heterometallic trinuclear incomplete cubane-like clusters [(CH3CH2)4N][{M2CuS4}(edt)2(PPh3)] (M = Mo, W) have been synthesized by reaction of [(CH3CH2)4N]2[M2S4(edt)2] (M = Mo, W) with Cu(PPh3)2(dtp) [where edt is 1,2-ethane-dithiolato ligand, dtp is S2P(OCH2CH3)2−]. The two crystals are isomorphous in space group P1 (No. 1). The unit cell contains two independent molecules, but the two discrete anions have the same orientation for the PPh3 ligands along one axis so the space group is undoubtedly non-centrosymmetric. The discrete anion contains two edt ligands and one PPh3 ligand attached to one incomplete cubane-like cluster core {M2CuS4}3+ (M = Mo, W). The bond lengths of Mo---Mo[W---W] and the two Mo---Cu[W-Cu] are 2.852(2)[2.844(1)], 2.802(2)[2.765(3)], 2.760(2)[2.762(3)] Å, respectively. The M 2S4(edt)2 (M = Mo, W) moiety remains almost unchanged, except that for the compound 1 the Mo=S double bond length elongates from av. 2.10 to av. 2.165 Å. The title clusters provide a new type of unsymmetric μ2-bridging sulphido ligand. The incomplete cubane-like cluster core {Mo2CuS4}3+ of compound 1 is distorted because the two Cu---μ2---S bond lengths are significantly different (2.313 Å and 2.409 Å), but the core {W2CuS4}3+ of compound 2 has approximately Cs symmetry. The IR spectra of the two title clusters and two starting materials are assigned. 相似文献
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Ye Qing Li Ming Lu Chun Xu Lu Sai Jian Zhu Qi Fa Liu 《中国化学快报》2007,18(11):1313-1315
A novel and simple procedure for synthesis of azanucleoside by Mitsunobu reaction between N-(p-nitrobenzyloxycarbonyl)- trans-4-hydroxy-D-proline methyl ester obtained from trans-4-hydroxy-L-proline after six-step reaction and 2-fluoro-6-azidopurine is described,and azanucleoside is fluorinated by new fluridizer 2,2-difluoro-1,3-dimethylimidazolidine (DFI).All reactions could be carded out under mild condition. 相似文献
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Modified modeling of the effect of pH and viscosity on the mass transfer in hydrophobic hollow fiber membrane contactors 总被引:3,自引:0,他引:3
This paper studied the effect of pH and the viscosity of feed solution on the mass transfer in two different specifications of hydrophobic hollow fiber membrane contactors. Experimental results showed that the pH of the feed had a significant effect on the rate of mass transfer, the flux and the removal efficiency of easily ionized volatile compounds (VCs), such as ammonia. In unbuffered feed solutions, both the resistance of membrane and the resistance of feed side were affected by the pH of feed and both of them had contributions to the overall mass transfer. A model, , was proposed to predict the effect of pH and gave good agreement with the experimental data for the two contactors. The relationship between viscosities and the mass transfer coefficient could be described by . Based on our experiments, the change of the viscosities in the concentration range of ammonia from 50 to 10,000 mg l−1 caused about 3–4% variation of the mass transfer coefficients. Moreover, it may be more suitable to use the equilibrium concentrations of volatile species instead of the total concentrations of VCs to estimate mass transfer coefficients, removal efficiency and flux. Experimental results also revealed that the choice of the pH of feed might be one of the most crucial factors for removing easily ionized VCs, such as ammonia, from water and wastewater. 相似文献
107.
[structure: see text] The cephalosporin antibiotic Cefadroxil can be epimerized at the alpha-carbon of its amino acid side chain using pyridoxal as the mediator. By clathration with 2,7-dihydroxynaphthalene, the desired diastereomer can be selectively withdrawn from the equilibrating mixture of epimers. In this way, an asymmetric transformation of Cefadroxil can be accomplished. This opens the possibility of the production of Cefadroxil starting from racemic p-hydroxyphenylglycine, in contrast to the current industrial synthesis that employs the D-amino acid in enantiopure form. 相似文献
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Shuang‐Jun Lin Chang‐Heng Tan Shan‐Hao Jiang Yi‐Ming Li Da‐Yuan Zhu 《Helvetica chimica acta》2006,89(11):2789-2793
Four new iridoids, buergerinins B–E ( 1 – 4 ), along with three known iridoids, were isolated from the roots of Scrophularia buergeriana. Their structures were identified on the basis of spectroscopic analysis. 相似文献