Efficient polymerization of acrylonitrile catalyzed by divalent lanthanide complex/ sodium phenolate systems

Four divalent lanthanide complexes Sm(ArO)₂ - (THF)₄, Yb(ArO)₂(THF)₃, Eu(ArO)₂(THF)₃ (ArO = 2,6-di- tert-butyl-4-methylphenolate) and (Bu^tCp)₂Sm(THF)₂ were synthesized. Their catalytic activities on the polymerization of acrylonitrile were studied. The catalytic activities were influenced by the central metal ions involved. The catalytic activities of these divalent lanthanide complexes can be greatly increased by adding NaOC₆H₂-2,6-Bu^t₂-4-Me, NaOC₆H₄-4-Bu^t, or NaOC₁₀H₆-2-Me. The amount of additive has apparent effect on the catalytic activity, but the additive has no effect on the tacticity of the resulting polyacrylonitrile.     

Synthesis and characterization of N-aryloxo-functiona- lized β-ketoiminate rare-earth complexes and their catalytic activity for the polymerization of ε-caprolactone

The synthesis and characterization of dimeric rare-earth amides stabilized by a dianionic N-aryloxo functionalized ,8-ketoiminate ligand are described. Reactions of 4-（2-hydroxy-5-methyl-phenyl） imino-2-pentanone （LH2） with Ln[N（SiMe3）2]3（μ-Cl）Li（THF）3 in a 1：1 molar ratio in THF gave the dimeric rare-earth amido complexes [LLn{N（SiMe3）2}（THF）]2 [Ln = Nd （1）, Sm （2）, Yb （3）, Y （4）]. These complexes were well characterized, and the definitive molecular structures of complexes 3 and 4 were determined. It was found that complexes 1-4 can initiate the ring-opening polymerization of ε-caprolactone, and the ionic radii of the central metals have significant effect on the catalytic activity.     

Improved dehydriding property of polyvinylpyrrolidone coated Mg-Ni hydrogen storage nano-composite prepared by hydriding combustion synthesis and wet mechanical milling

In this work, polyvinylpyrrolidone(PVP) coated Mg_(95)Ni_5 nano-composites were prepared by hydriding combustion synthesis(HCS) plus wet mechanical milling(WM) with tetrahydrofuran(THF) and donated as WM-x wt% PVP(x = 1, 3, 5 and 7) respectively. The phase compositions, microstructures and dehydriding property, as well as the co-effect of PVP and THF were investigated in detail. XRD results showed that the average crystal size of MgH_2 in the milled Mg_(95)Ni_5 decreased from 23 nm without PVP to 18 nm with 1 wt% PVP. The peak temperature of dehydrogenation of MgH_2 in the milled Mg_(95)Ni_5 decreased from 293.0 ℃ without THF to 250.4 ℃ with THF. The apparent activation energy for decomposition of MgH_2 in WM-7 wt% PVP was estimated to be 66.94 kJ/mol, which is 37.70 kJ/mol lower than that of milled Mg_(95)Ni_5 without THF and PVP. PVP and THF can facilitate the refinement of particle size during mechanical milling process. Attributed to small particle sizes and synergistic effect of PVP and THF, the composites exhibit markedly improved dehydriding properties.     

Synthesis of monosubstituted N-arylamidines by divalent diaminobisphenolate ytterbium complex catalyzed addition of amines to nitriles

Divalent ytterbium complex YbL^（ONNO）（THF）2 （L^（ONNO）= Me2NCH2CH2N（CH2-2-O-3,5-C6H2（^1Bu）2）2） （1） has first been found to serve as a catalyst for addition of amines to nitriles to give monosubstituted N-arylamidine in moderate to good yields. The aromatic amines and nitriles showed better activity. The outcome of the addition reaction was greatly affected by the structure of divalent ytterbium complexes. The reaction mechanism was proposed and the benzonitrile-coordinated divalent ytterbium phenoxide Yb（OAr）2（C6H5CN）（THF）2 （Ar = 2,6-di^tBu-4-MeC6H3） was isolated as one of the intermediates.     

Well-defined bis（phenolate） lanthanide methoxides as efficient initiators for the polymerization of cyclic carbonate and lactide

Lanthanide methoxides supported by carbon-bridged bis(phenolate) ligands 2,2′-methylene-bis(6-tert- butyl-4-methylphenoxo) (MBMP2-) [(MBMP)Ln( μ-OMe)(THF)2]2 (Ln = Nd (1), Yb (2)) were synthesized in high yields by the protolysis reaction using (C5H5)3Ln(THF) as starting materials, and complex 1 was structurally characterized. The coordination geometry around the center metal can be best described as a distorted octahedron. Complexes 1 and 2 were shown to be efficient initiators for the ring-opening polymerization of 2,2-dimethyltrimethylene carbonate (DTC) and L-lactide. The mechanism of DTC polymerization was explored by the end group analysis of the oligomer.     

A novel self-promoted Morita-Baylis-Hillman-like dimerization

While stable in CH₂Cl₂, hexane or THF, in the presence of MeOH, self-promoted dimerization of the triarylphosphine-alkene 1, a ligand for Pd-catalyzed reactions, produced an unusual racemic bis(phosphine) 2 in high yield. The reaction of 2 with Pd(dba)₂, followed by oxidative addition of p-IC₆H₄NO₂, yielded a trans-chelated Pd(II) aryl iodide complex.     

Synthesis and characterization of carbon-bridged bis(phenolate) lanthanum alkoxides and their catalytic behavior for the polymerization of L-lactide

Four lanthanum alkoxides stabilized by a carbon-bridged bis(phenolate) ligand were synthesized and their catalytic behavior for the ring-opening polymerization of L-lactide was explored. Reactions of [(MBMP)LaCp(THF) 2 ] (MBMP 2 = 2,2′-methylene-bis(6-tert-butyl-4-methyl phenoxo)) with HOCH 2 Ph, HOCH 2 CF 3 , HOCH(CH 3 ) 2 , and HOCH 2 CH 2 N(CH 3 ) 2 , respectively, in a 1:1 molar ratio in THF gave the dimeric lanthanum alkoxo complexes [(MBMP)Ln(μ-OR)(THF) 2 ] 2 (OR = OCH 2 Ph(1), OCH 2 CF 3 (2), OCH(CH 3 ) 2 (3), OCH 2 CH 2 N(CH 3 ) 2 (4)]. These complexes were well characterized, and the definitive molecular structure of complex 1 was determined. It was found that complexes 1 to 4 are efficient initiators for the ring-opening polymerization of L-lactide. The structure of the alkoxo groups has a significant effect on the catalytic behavior, and complex 2 can initiate L-lactide polymerization in a controlled manner.     

Na(THF)2(μ2-η5-Cp)(η5,η5,η1-Cp3Yb)(THF)]n: The synthesis and X-ray structure of an anionic organolanthanidepolymer formed via self-assembly

Cp2Yb·2THF reacts with CpNa in 1：1 molar ratio in THF at 40℃ for 2 h, and the in situ generated anionic divalent complex NaYbCp3（THF）n reacts further with an excess of CpH at 40℃ for 48h, after work-up, affording the trivalent anionic ytterbium complex[Na（THF）2（μ2-η^5-Cp） （η^5, η^5,η^1-Cp3Yb）（THF）]n：（1） by oxidation reaction of Cp2Yb with CpH. Crystal structure determination reveals that complex 1 has one-dimension polymeric chains of distinct Na（THF）2（μ2-η^5-Cp） （η^5, η^5,η^1-Cp3Yb）（THF） units, which were formed by the coordination of the bridging Cp ligand with Cp3Yb＇THF and Na（THF）2 in η^5,η^5 mode via self-assembly.     

Preparation of (R)- and (S)-2-Allyl-1, 3, 2-dinaphtho (α, β) [d.f] dioxaborepin and their reactions with aldehydes

(R)- and(S)-2-Allyl-1,3,2-dinaphtho (α,β) [d.f] dioxaborepin ((R)-2 and(S)-2) have been first prepared by the reaction of(R)-(+)- or(S)-(−)-1, 1′-bi-2-naphthol and triallylborane in THF at room temperature, respectively.(S)-2 and(R)-2 are sensitive to moisture and oxygen in air and disproportionate easily to triallylborane and 1,1′-bi-2 naphthyl bis (1,1′-bi-2-naphtholborate) at ambient temperature. However, THF is a stabilizer for them. The reactions of(R)-2 or(S)-2 and some aliphetic or aromatic aldehydes in CH₂Cl₂ at −78°C for several hours afforded β-alkylenyl alcohols in up to 84.8%ee. Among them, optically active 1-(3, 5-dichlorophenyl)-3-butenol and 1-(2-methoxyphenyl)-3-butenol were first prepared Foundation item: Supported by the National Natural Science Foundation of China (29972033) Biography: Liu Dejun (1973), male, Ph. D, research direction: asymmetric synthesis     

MgFeSiO4 prepared via a molten salt method as a new cathode material for rechargeable magnesium batteries

Well-crystallized MgFeSiO₄ microparticles were synthesized at different temperatures by a simple molten salt method using KCl flux. As a new cathode for rechargeable magnesium batteries, the material shows a reversible Mg²⁺ intercalation-deintercalation process. In 0.25 mol/L Mg(AlCl₂EtBu)₂/THF electrolyte, MgFeSiO₄ synthesized at 900??C can deliver a 125.1 mAh/g initial discharge capacity and a 91.4% capacity retention on the 20th cycle at a rate of 0.1C (about 15.6 mA/g). The results show that MgFeSiO₄ could be a good host for Mg²⁺ intercalation, and a potential cathode material for high-energy rechargeable magnesium batteries.     

Synthesis,structure and catalytic behavior of yttrium complexes bearing a diaminobis（phenolate） ligand

Yttrium complexes stabilized by a diaminobis（phenolate） ligand were synthesized and their catalytic behavior was explored. Reaction of YCI3 with 1 equiv of LNa2 [L= Me2NCH2CH2N{CH2-（2-O-C6H2-^1Bu2-3,5）}2] gave the yttrium chloride LYCI（THF） （1） in 92% yield. Complex I can be used as starting material to prepare the yttrium amido derivative. Complex 1 reacted with 1 equiv of LiNPh2 in THF to afford the expected yttrium amido complex LYNPh2 （2） in high yield. Both of complexes 1 and 2 have been well detected by elemental analysis, NMR spectra and single-crystal X-ray analysis. It was found that complex 2 can efficiently initiate the ring-opening polymerization of L-lactide and ε-caprolactone, and a controlled manner is observed in the former case.     

Grafting of thermoresponsive polymer from the surfaceof functionalized multiwalled carbon nanotubes via atom transfer radical polymerization

Multiwalled carbon nanotubes were oxidized with concentrated HNO3 and H2SO4 to introduce carboxylic groups onto carbon nanotubes surfaces. The oxidized carbon nanotubes were reacted subsequently with thionyl chloride and 2-Hydroxylethyl-2＇-bromoisobutyrate, producing MWNT-based macroinitiators, MWNT-Br, for the atom transfer radical polymerization of （N-isopropylacrylamide）. FTIR, XPS, ^1H NMR, Raman and TGA were used to characterize the resulting products and to determine the content of the water-soluble poly （N-isopropylacrylamide） chains in the product. The MWNTs grafted with PNIPAM chains have good solubility in distilled water; THF and CHCl3. TEM images of the samples provide direct evidence for the formation of a nanostructure that MWNTs coated with polymer layer. The produced MWNT-g-PNIPAM has a PNIPAM shell, which is very sensitive to the change of temperature. This method would open a door for the fabrication of novel functional carbon nanotube-based nanomaterials or nanodevices with designable structure and tailor-made properties.     

Investigation on the aggregation properties of cationic [60]fullerene derivative

Fullerenes and functionalized fullerenes have at-tracted extensive attention of chemists, material scientists and biologists since the discovery of [60]fullerene (C60). Functionalized fullerenes exhibit a wide range of biologi-cal and medicinal activities, such as DNA photocleavage, antioxidants, neuroprotective agents, antiapoptotic activity, enzyme inhibition, anti-HIV activity, contrast agents and radiotracers[1—3] owing to their unique photochemical, radical-quenching and hydrophobic pr…     

Synthesis and optical properties of poly[(4-(benzoxazole-2-yl)phenyl)methyl methacrylate] with 1,8-naphthalimide end group

A series of homopolymers, poly[(4-(benzoxazole-2-yl)phenyl)methyl methacrylate] (NAPH-PMABEs) containing benzoxazole side chain and 1,8-naphthalimide end group, were prepared by atom transfer radical polymerization (ATRP) and end-group modification. The structure of NAPH-PMABE was characterized by GPC, ¹H-NMR and UV-vis spectra. The polymer has good solubility in common organic solvents, such as dichloromethane (CH₂Cl₂), tetrahydrofuran (THF), N,N-dimethylformamide (DMF), chloroform (CHCl₃), acetone and toluene. The optical properties of NAPH-PMABE were investigated. Results show that NAPH-PMABE has a composite emission spectrum comprising an ultraviolet component originating from benzoxazole side chains and a green component originating from 1,8-naphthalimide end group in both solution and film. The intensity of the two emission bands can be easily tuned by changing molecular weight. Supported by National Natural Science Foundation of China (Grant Nos. 20476066 and 20571054), Science and Technology Project in Suzhou, China (Grant No. SG0718), and Project of High Technology of Jiangsu Province, China (Grant No. BG2005021)     

Synthesis of SnO2TiO2 nanocomposite photocatalysts by supercritical fluid combination technology

Acrylic acid, acrylic ester and their ramification have developed quickly in recent years. However, their pro duction process produces a mass of waste water, which when released into the aquatic ecosystem, becomes a source of dramatic disturbance of aquat…     

Mineralization of flue gas CO2 with coproduction of valuable magnesium carbonate by means of magnesium chloride

CO2 mineralization and utilization is a new area for reducing the CO2 emissions. By reacting with natural mineral or industrial waste, CO2 can be transformed into valuable solid carbonate （such as calcium carbonate or magnesium carbonate） with recovery of some products simultaneously. In this paper, a novel method was proposed to mineralize CO2 by means of magnesium chloride with small energy consumption. In this method, magnesium chloride was firstly transformed into magnesium hydroxide by electrolysis. The formed magnesium hydroxide showed high reactivity to mineralize CO2. In our study, even at low concentration, CO2 can be effectively mineralized by this method, which makes it possible to directly mineralize flue gas CO2, avoiding the expensive process of CO2 capture and purification. Moreover, valuable products such as hydromagnesite and nesquehonite can be recovered by this method. Because of the wide distribution of magnesium chloride in nature, largescale CO2 mineralization is potential by means of magnesium chloride.     

Immobilization of 12-phosphotungstic heteropolyacid on amine-functionalized SiO<Subscript>2</Subscript> for tetrahydrofuran polymerization

The 12-phosphotungstic heteropolyacid (HPW) was immobilized on the surface of a silica carrier modified by the amine groups of organosilane γ-aminopropyl triethoxysilane (APTES), and its catalytic performance was investigated for tetrahydrofuran (THF) ring-opening polymerization. This amine-functionalized catalyst exhibited better activity, and the polytetramethylene ether glycol (PTMG) yield was 63.7%. The 12-phosphotungstic heteropolyacid supported on aminopropyl-functionalized SiO₂ support (HPW/SiO₂-APTES) was reused four times and showed a good maintenance of activity which was better than that of the conven-tional catalyst HPW supported on SiO₂ (HPW/SiO₂). These results were obtained using infrared spectroscopy, nuclear magnetic resonance spectroscopy, nitrogen adsorption and X-ray diffraction. HPW on the HPW/SiO₂-APTES catalyst exhibited higher dispersed state and maintained a more stable structure than that of the HPW/SiO₂ sample.     

钨卡宾络合物的一种形成方法及其与醛、酮的反应

四氯氧化钨或六氯化钨与不含β Ｈ的Ｇｒｉｇｎａｒｄ试剂在无水四氢呋喃中反应，形成钨的卡宾铬合物，可与醛、酮反应得到烯烃，具有类似于Ｗｉｔｉｇ试剂的功能     

Optimization of butanol production from corn straw hydrolysate by <Emphasis Type="Italic">Clostridium acetobutylicum</Emphasis> using response surface method

Butanol is a new kind of very potential biofuels.Enzymatic hydrolysis of corn stalk was utilized in this study to produce butanol by Clostridium acetobutylicum CICC 8008.Plackett-Burman (P-B) design and Central Composite Design (CCD) were adopted to screen crucial factors during fermentation as well as the optimization of experimental conditions.The result demonstrated that among the seven factors,namely,Yeast extract,(NH 4) 2 SO 4,KH 2 PO 4,MgSO 4,FeSO 4,CuSO 4 and CaCO 3,only CaCO 3 was selected as the most critical factor.The optimization experiment results for CaCO 3 usage,temperature and reaction time by CCD were determined to be 5.04 g/L,35°C and 70 h,respectively.A corresponding mathematical model was established to predict the fermentation experiment and maximum butanol yield of 6.57 g/L was acquired.The result of verification experiment under the optimum conditions showed that 6.20 g/L was the maximum butanol yield.This demonstrated that statistical method was a powerful tool for the optimization of butanol production from enzymatic hydrolysis of corn stalk.     

MnO_2@NiCo_2O_4核-壳异质结构的构筑及电化学性能和催化性能

采用2步水热法制备出1种以NiCo_2O_4纳米线为核,MnO_2纳米颗粒为壳的三维结构MnO_2@NiCo_2O_4@Ni-foam复合材料。通过X射线衍射(XRD),扫描电子显微镜(SEM)对复合催化剂的结构和形貌进行表征;通过循环伏安法(CV),恒流充放电性能(GCD)和电化学阻抗谱(EIS)来进行表征复合材料的电化学性能;通过O_3催化降解装置对复合材料的催化性能进行研究。结果表明:MnO_2@NiCo_2O_4@Ni-foam复合材料在频率范围为0.1～10 000 Hz时阻抗较低;通过降解实验发现,MnO_2@NiCo_2O_4@Ni-foam对O_3的降解率高于50%,表现出良好的催化效果。这表明MnO_2@NiCo_2O_4@Ni-foam复合材料在降解O_3,净化空气方面有广阔的应用前景。