bluuebunny/crossref_metadata_2025_split huggingface dataset:
Molecular Structure of a Binuclear Copper(II) Complex: [Cu2L2DMF2]·DMF·2ClO4 (LH = 4‐Methyl‐2,6‐Bis(indazol‐2‐Ylmethyl)phenol)
Authors: Chang Wen‐Kuen , Lee Gene‐Hsiang , Wang Yu , Oliver Su Y. , Ho Tong‐Ing , Lin Yuan‐Chuan 
Published: May 2015

AbstractThe molecular structure of a binuclear copper(II) complex [Cu2L2DMF2]·DMF·2ClO4 in which LH is 4‐methyl‐2,6‐bis (indazol‐2‐ylmethyl)phenol and DMF is N,N‐dimethylformamide is reported. The structure of the crystal was characterized by X‐ray diffraction: monoclinic, space group P21/C, Z = 2, a = 15.863(4), b = 20.642(3),c = 19.598(5) Å, β = 113.05(2)°. The final R and Rw values are 0.060 and 0.061, respectively, for 4777 reflections with I > 2σ(I). Each copper(II) is penta coordinate, with two N atoms from the indazole ring, two O atoms from phenolate in ligands and another O atom from DMF to form a distorted square‐pyramid. The mean value of the lengths of the four Cu‐N bonds is 1.987(6) Å and the Cu ⃛Cu distance is 3.094(1) Å No EPR signal was detected, and the magnetic moment has a small value μ = 1.17 per copper. These results indicate strong antiferromagnetic interaction between the two copper(II) ions.
Photoaddition of Tertiary Amines to 2‐Cyclopentylidenecyclopentanone
Authors: Huang Tian‐Chyuan , Ho Tong‐Ing 
Published: May 2015

AbstractPhotochemical reactions of 2‐cyclopentylidenecyclopentanone with diisopropylmethylamine, diisopropylethylamine, dimethylaniline, triethylamine, isopropyldimethylamine and dimethylbutylamine in acetonitrile were studied. Besides the addition product, a novel 3+2 cycloaddition adduct 3a‐hydroxytrispiro(octahydropentalene‐1,1′:2,1″:3,1‴‐triscyclopentane)‐2‴‐one was isolated. The quantum yield and Stern‐Volmer parameters with triplet quencher piperylene are reported. From these kinetic studies of mechanism photo‐induced electron transfer and proton transfer is proposed for formation of the novel 3+2 cycloadduct of 2‐cyclopentylidenecyclopentanone.
Anionic Polymerization of Methyl(3,3,3‐Trifluoropropyl)cyclotrisiloxane
Authors: Yang Mei‐Hui , Yang Cheng‐Kan , Chou Chyuan 
Published: May 2015

AbstractMethods based on anionic ring‐opening polymerization, using n‐butyl lithium as an initiator, were developed to prepare monodispersed (Mw/Mn < 1.2) poly[methyl(3,3,3‐trifluoropropyl)siloxane] (PMFPS) from methyl(3,3,3‐trifluoropropyl)cyclotrisiloxane (F3) in high yield. The resulting polymers have the molecular weights ranged from 4 k to 190 k (k = 1000). Each polymer was characterized by GPC and DSC. The absolute molecular weight (Mw) of each monodispersed PMFPS was determined by means of universal calibration with GPC/DV (coupled differential viscometry‐GPC) technique. Factors that affect the narrowly distributed linearly extended polymer chain, such as solvent, temperature, promoter, monomer concentration etc., were discussed in terms of molecular weight, molecular weight distribution, polymer conversion and the cyclic oligomer content through GPC and GC analyses. Back‐biting occurred either in the bulk or the solution process. However, the presence of a promoter (DMSO or THF) in a proper proportion accelerated the polymerization, and the reaction went to completion in either process before serious backbiting and chain transfer occurred.
Preparations and Reactions of 2‐Cyanoindole Derivatives
Authors: Lin Chih‐Da , Fang Jim‐Min 
Published: May 2015

Abstract2‐Cyano‐1‐phenylsulfonylindole (1a) and 2‐cyano‐1‐methylindole (1b) were prepared by chemical and electrolytic methods in modest yields. Nucleophiles such as sodium benzenethiolate, butyllithium and lithium dimethylcuprate attacked the sulfonyl group of 1a, whereas they attacked the cyano group of 1b. 1,3‐Dipolar cycloadditions of 1a and 1b with 2,4,6‐trimethylbenzonitrile oxide occurred at the cyano groups. Electrophilic reactions of 1b with N‐bromosuccinimide, Vilsmeir reagent and acetyl chloride afforded the corresponding 3‐bromo‐, 3‐formyl‐ and 3‐acetylindole derivatives in modest or high yields, albeit less rapidly than the reactions of 1‐methylindole. Photochemical addition of dimethyl acetylenedicarboxylate to 1b was followed by cleavage of the cyclobutene intermediate to give dimethyl (2‐cyano‐1‐methylbenzazepine)‐3,4‐dicarboxylate.
3‐Substituted 2‐Cyclopentenones from Cyclopentadienes
Authors: Lin Chu‐Chung , Hsia Ket‐Shang , Wu Hsien‐Jen 
Published: May 2015

AbstractOxidation of cyclopentadienes 1a‐1j, which were prepared by alkylation of cyclopentadienyl anion with the corresponding alkyl bromides, with pyridinium chlorochromate (PCC) gave the 2‐cyclopentenones 2a‐2j respectively in 10–15% yields. Reaction of 3 and 5 with PCC gave the spiro compounds 4 and 6 respectively in 75–80% yields.
Dehalogenation and Halogenation of Sydnone Compounds with Duet Electrosynthesis
Authors: Hung Wei‐Jing , Tien Hsien‐Ju 
Published: May 2015

AbstractCathodic dehalogenation of 4‐halosydnones was conducted with a mercury electrode at a constant potential (−0.5 – −1.0 vs SCE). The combination of cathodic dedromination of 4‐bromosydnones on a mercury electrode with anodic bromination/chlorination of 3‐substituted sydnones with a platinum electrode in a divided electrolytic cell produced sydnone derivatives with a total current yield 87 ∼ 168%.
Radical‐Induced Ring Opening of Epoxysilane in the Synthesis of (±)‐Supinidine and (±)‐Trachelanthamidine
Authors: Tsai Yeun‐Min , Ke Bor‐Wen 
Published: May 2015

AbstractAn α‐(2‐silyloxiranyl)carbinyl radical fused to a pyrrolizidine skeleton was generated from the corresponding bromide 4. This radical underwent rearrangements followed by hydrogen abstraction to give silyl allyl ether 8 and silyl enol ether 9. The mixture was converted to (±)‐supinidine 1 and (±)‐trachelanthamidine 3. When triethylborane/oxygen was used to initiate the radical reaction, an α,β‐unsaturated aldehyde 15 was obtained, thus to accomplish a formal synthesis of (±)‐1.
Crown Ether As The Phase‐Transfer Catalyst for Free Radical Polymerization of Hydrophobic Vinyl Monomers
Authors: Tarng Jeng‐Yu , Shih Jeng‐Shong 
Published: May 2015

AbstractVarious crown ethers were used as phase‐transfer catalysts for free radical polymerizations of some water‐insoluble vinyl monomers such as acrylonitrile, methylmethacrylate and styrene with persulfate as initiator. The catalytic abilities of these crown ethers for free radical polymerization of acrylonitrile with S2O82−ion as an initiator were in the order: 18‐crown‐6 > 15‐crown‐4 > 12‐crown‐4 > benzo‐15‐crown‐5 > dibenzo‐18‐crown‐6. Among various persulfates such as Na2S2O8 K2S2O8 and (NH4)2S2O8, ammonium persulfate was the optimum initiator for the polymerization of acrylonitrile catalyzed by 18‐crown‐6 or 15‐crown‐5. Among the organic solvents used, chloroform seems to be the best solvent for the catalytic polymerization of acrylonitrile. An apparent activation energy of 72.9 kJ mol−1 was observed for the polymerization of acrylonitrile. The catalytic reaction rates of free radical polymerization for these hydrophobic vinyl monomers were in the order: acrylonitrile > methylmethacrylate > styrene > isoprene. Effects of concentrations of crown ether, initiator, and nitrogen on the polymerization of these vinyl monomers were investigated.
Crystal Structure of L‐Quebrachitol
Authors: Huang Keh‐Feng , Luo Wen‐Lih 
Published: May 2015

AbstractL‐Quebrachitol (1) isolated from the root of Elaeagnus formosana Nakai (Elaeagnaceae) has not been reported before for any species of the genus of Elaeasnus. Its structure was established from spectral data and was completely characterized by single‐crystal X‐ray analysis. L‐Quebrachitol crystallizes in the monoclinic system, space group P21, with cell parameters are a = 6.702(4), b = 7.207(4), c = 8.758(5) Å, β = 90.24(5)° and Z = 2.
Design and Construction of a Pulsed Field‐Gradient NMR Probe for a High‐Field Superconducting Magnet
Authors: Price William S. , Chang Wen‐Tsung , Kowk Wai‐Ming , Hwang Lian‐Pin 
Published: May 2015

AbstractWe describe the design and construction of a high‐resolution pulsed field‐gradient NMR probe for use in a high‐field superconducting magnet. Overview and details of the design and construction of the probe case, rf circuitry, temperature control and shielded gradient coils for a heteronuclear probe suitable for a spectrometer (Bruker MSL‐300) equipped with a wide bore (i.e., 89 mm) magnet (Oxford) are given. The interior of the probe is designed so mat it may be easily moved to variable height so as to accept easily various gradient coils. A design for a novel jig for the winding of saddle‐geometry rf coils is given.
Reactivity of [Te6Fe8(CO)24]2− and Its Conversion to [Te4Fe5(CO)14]2−
Authors: Shieh Minghuey , Chen Pao‐Fei , Peng Shie‐Ming , Lee Gene‐Hsiang 
Published: May 2015

AbstractWhereas reaction of [PhCH2NMe3]2|Te6Fe8(CO)24] (1) in refluxing CH2CI2 forms Fe2(CO)6(μ0‐) TeCH2Te), treatment of 1 with Ph2SnCl 2 or Mel gave the oxidation product Te2Fe3(CO)9. Oxidation of 1 with [Cu(CH3CN)4]BF4 afforded Te2Fe3(CO)9 in good yield. Cluster 1 was converted to [PhCH2NMe3][Te4Fe5(CO)14] (2) in MeOH/CH2Cl2 solution. Cluster 2 was structurally characterized by single‐crystal X‐ray diffraction and spectral methods. Complex 2 is composed of two Te2Fe2(CO)6 fragments linked by one Fe(CO)2 group. 2 crystallizes in the orthorhombic space group Pbcn with a = 13.351 (4) Å, b = 13.417 (4) Å, c = 26.077 (3) Å, V = 4671 (2) Å 3, Z = 4.
Kinetics and Thermodynamics of Synthesis of Tertiary‐Amyl Methyl Ether Catalyzed by Ion‐Exchange Resin
Authors: Hwang Wen‐Shwong , Wu Jung‐Chung 
Published: May 2015

AbstractSynthesis of tertiary‐amyl methyl ether (TAME) was carried out in the temperature range 40–70 ° Cusing a sulfonic acid resin as the catalyst. Thermodynamic data were calculated from the equilibrium concentration of the components in a stirred batch reactor by the Unifac method. The enthalpy change of TAME formation was calculated to be (−20.4 ± 0.8) kJ/mol and the equilibrium constant is expressed as Ka = 3.94 × 10−4 exp (20400/RT). For the kinetic tests, a homogeneous solution system was selected to interpret experimental results. The activation energy of the forward reaction was calculated to be (94.0 ± 1.5) kJ/mol and the rate constant is expressed as k2 = 5.31 × 1011 exp (−94000/RT). The validity of this kinetic model was verified by fitting experimental data.
Determination of Enantiomeric Purity and Absolute Configuration of β‐Lactams by High‐Performance Liquid Chromatography on Chiral Columns
Authors: Lee Chih‐Shone , Chen Hsiu‐Ho 
Published: May 2015

AbstractEnantiomers of β‐lactams bearing aryl, furyl or styryl substituents in the 4‐position were chromatographically separated by means of high‐performance liquid chromatography on chiral column packed with amino acid‐derived chiral stationary phase. Separation factors are generally modest. To improve further the resolution of enantiomers, the rings of these β‐lactams were opened with octanol in acidic conditions and converted into N‐3,5‐ dinitrobenzoyl ester derivatives of the resulting β‐amino acids. Enantiomers of these derivatives are efficiently separated on an amide‐derived chiral stationary phase. The chromatographic separations enable accurate determination of optical purity of the chiral β‐ lactams, prepared from homochiral ester enolate‐imine condensation. The absolute configuration of the major enantiomer of the β‐amino acid derivatives was determined from elution order on a chiral column.
Synthesis of 4H‐Pyrrolo[2,1‐C][1,4]benzothiazines and 3‐(Methylthio)oxindoles
Authors: Wang Huey‐Min , Lin Meng‐Chiao , Chen Ling‐Ching 
Published: May 2015

AbstractThe Pummerer reaction was carried out with α‐acylsulfides and phenyl iodosyl bis(trifluoroacetate) instead of α‐acylsulfoxides to prepare 4H‐pyrrolo[2,1‐c][1,4]benzothiazines and 3‐(methyIthio)oxindoles.
Vibrational Spectroscopy of Surface Adsorbates by Sum Frequency Generation (SFG)
Authors: Hirose Chiaki , Watanabe Nobuyuki , Yamamoto Hiroyoshi , Wada Akihide , Domen Kazunari , Ohtake T. , Mino Norihisa 
Published: May 2015

AbstractThe vibrational spectroscopy by way of vibrational sum‐frequency generation (VSFG) has been made of formic acid adsorbed on MgO(001) surface and of n‐alkyltrichlorosilanes chemisorbed on quartz plates. It was revealed that the species on the MgO surface was formate ion (HCOO+) with CH bonds standing vertical to the surface and that the different adsorption sites showed up on repeated cycles of adsorption‐desorption processes. The results of chemisorbed films indicated that the g‐t and/or g‐t‐g′ conformational scquences of n‐alkyl chains occurred more frequently by the length of alkyl chain and that the surface hydroxyls, which are the sites of chemisorption, are ripped off by pre‐exposure of substrate to oxygen plasma.
Antineoplastic Alkaloids From Chinese Medicinal Plants and Their Analogs
Authors: Lee Kuo‐Hsiung , Sun Li , Wang Hui‐Kang 
Published: May 2015

AbstractThe Chinese medicinal plant‐derived antineoplastic alkaloids and their analogs are reviewed with emphasis on those discovered from the authors' laboratory. The active compounds include camptothecin, colchicine, ellipticine, harringtonine, Vinca alkaloids, indirubin, (‐)‐sophocarpine, lycobetaine, monocrotaline, d‐tetrandrine, indicine N‐oxide, maytansine, aporphine type alkaloids, palmatine, murrapanine, emarginatine alkaloids, and the alkaloids from Securinega virosa. The compounds are discussed briefly with the recent advances concerning their antitumor activity, structure‐activity relationships and mechanisms of action.
Rhenium(V) Complexes of N,N′‐Ethylenebis(2‐mercaptopropanamide). Synthesis, Characterization, and X‐ray Crystal Structures
Authors: Liao Fen‐Ling , Wang Sue‐Lein , Lin Cheng‐Hsien , Huang Shih‐Tsorng 
Published: May 2015

AbstractThe preparation of benzoyl‐protectcd N,N′‐ethylenebis(2‐mercaptopropanamide) (H4emp) and its ligand‐exchange reaction with ReO2(en)2Cl are described. Three diastereomers, [syn‐ReO(meso‐emp)]; [anti‐ReO(meso‐emp)]‐, and a pair of cnantiomers, [ReO(rac‐emp)]‐, were formed due to syn and anti orientation of the two methyl groups of the ligand relative to the ReO core. The diastereomers were separated by reverse phase C18 semipreparative HPLC and isolated as salts of [Ph4As][ReO‐(emp)]. The structures of [Ph4 As][ReO(meso‐emp)] were determined by single‐crystal X‐ray analyses. [Ph4As][syn‐ReO(mesocmp)]H2O crystallizes in triclinic space group Pl with a = 10.326(3) Å, b = 13.672(4) A, c = 14.023(5) Å, α = 61.20(2)°, β =74.74(3)°, γ= 75.68(2)° V = 1656.6(8) Å3, Z = 2, Dc = 1.676 gmL−1, F(000) = 824 and R = 0.0329 for 5877 unique reflections. For (he complex [Ph4As][anti‐ReO(meso‐emp)], the crystal data are: monoclinic, space group P21/n, a = 9.128(2) Å, b = 24.284(7) Å, c = 14.112(4) Å, β = 93.41(2)° V = 3122.5(15) À3, Z = 4, Dc = 1.740 gmL−1, F(000) = 1608 and R = 0.0361 for 5487 unique reflections. In both structures the rhenium atom is penta‐coordinated and in an approximately square pyramidal environment.
Flash Vacuum Thermolysis of Phenylcyclopropanecarbaldoximes and Its Methyl Ethers
Authors: Wu Pei‐Lin , Wang Wen‐Shan , Chen Chang‐Fu 
Published: May 2015

AbstractFlash vacuum thermolysis of 1‐phenylcyclopropane‐1‐carbaldoxime at 500 °C produced mainly 3‐phenylpyrrole. The products after thermolysis of its oxime methyl ether were α‐methoxymethylstyrene, α‐methylstyrene, and a dimer 2,5‐dipheny 1‐1,5‐hexadiene.
Synthesis of Thiolato Heterometalllc Clusters from the Reaction of Os3(CO)9(NCMe)(μ‐H)(μ‐SMe) with CpW(CO)3H
Authors: Tsay Chyuan‐Wu , Tu Wen‐Cheng , Chi Yun , Peng Shie‐Ming , Lee Gene‐Hsiang 
Published: May 2015

AbstractDecarbonylation of triosmium methylthiolato cluster Os3(CO)10(μ‐H)(μ‐SMe) with Me3NO in acetonitrile solution gave cluster Os3(CO)9(NCMe)(μ‐H)(μ‐SMe) (1), in which one axial CO on the non‐bridged Os atom is replaced by an acetonitrile ligand. Crystal data for 2: space group P bca, a = 14.491(1), b = 16.107(5), c = 16.639(5) Å, Z = 8; RF = 0.037, Rw = 0.033. Treatment of 2 with CpW(CO)3H in refluxing THF solution yielded two cluster compounds with formula CpWOs3(CO)11(μ‐H)2(μ3‐SMe) (2) and CpWOs3(CO)11(μ‐H)2(μ‐SMe) (3) as the principle products. The first possesses a spiked‐triangular geometry with a triply bridging thiolato ligand and the second adopts a butterfly metal core arrangement with an edge‐bridging thiolato grouping. The structure of 2 was characterized by single‐crystal X‐ray diffraction. Crystal data: space group P 1, a = 8.865(5), b = 8.959(3), c = 16.688(4) Å, α = 103.49(2), β = 93–58(3), γ = 113.03(4)°, Z = 2, RF = 0.034, Rw = 0.035.
Promotion of Oxidative Dehydrogenation by Cobalt Ions and the Synthesis of Trans‐diaqua(C‐meso‐3,5,7,7,10,12,14,14‐octamethyl‐1,4,8,11‐tetraazacyclotetradeca‐1,4,8,11‐tetraene)cobalt(II) Perchlorate
Authors: Chen Bor‐Hann , Lai Chung‐Yu , Chung Chung‐Sun , Liao Fen‐Ling , Wang Sue‐Lein 
Published: May 2015

AbstractAerial dehydrogenation of the Iigand in (C‐meso‐3,5,7,7,10,12,14,14‐octamethyl‐1,4,8,11‐tetraazacyclotetradeca‐4, 11‐diene)cobalt(III) leads to yellow chunky crystals of trans‐diaqua(C‐meso‐3,5,7,7,10,12,14,14‐octamcthyl‐1,4,8,11‐tetraazacyclotetradeca‐1,4,8,11‐tetraene)cobait(II)(1). The crystal structure of this complex was determined by xray crystallography and a mechanism of this reaction is proposed.
Thermal Interchanges in the Relative Stabilities of the C60Ge Specles
Authors: Slanina ZdenêK , Lee Shyi‐Long 
Published: May 2015

AbstractBridging a Ge atom across the two C‐C bonds in C60 was treated according to the PM3 method. The C2v (6/6) closed isomer represents the ground state of the system, located 52 kJ/mol below the C5 (5/6) closed structure and 97 kJ/mol below the C5 (5/6) open structure. However, at high temperatures the closed 5/6 isomer becomes the most stable, whereas the ground‐state structure is the least populated component under conditions of thermodynamic equilibrium, although no isomer is negligible. The applicable characteristics indicate a reasonable absolute stability of the whole system.
Temperature Dependence of the Rate Coefficient of the Reaction OH + CF3CH2F over the Range 255‐424 K
Authors: Leu Gen‐Hou , Lee Yuan‐Pern 
Published: May 2015

AbstractThe rate coefficient of the reaction of OH with CF3CH2F at six temperatures in the range 255‐424 K was determined by means of the discharge‐flow/resonance‐fluorescence technique. The resonance fluorescence of OH, excited by emission from a gaseous mixture of H2O and He subjected to a microwave discharge, was detected by photon‐counting technique. The reaction was carried out under pseudo‐first‐order conditions with [CF3CH2F] >> [OH]; the rate coefficient was determined to be k = (3.9±0.6) × 10−15 cm3 molecule−1 s−1 at 298 K; the uncertainty represents the 95% confidence limit. The temperature dependence of the rate coefficient is expressed in the Arrhenius form, k(T) = (9.9±1.0) × 10−13 exp [‐(1640±150)/T] cm3 molecule−1 s1.
The Mn(II)‐Catalyzed Belousov‐Zhabotinsky Reaction with Methyl‐, Ethyl‐ or Butyl‐Malonic Acid
Authors: Sun Shih Sheng , Lin Hong‐Ping , Chen Ying‐Fen , Jwo Jing‐Jer 
Published: May 2015

AbstractIn a batch‐stirred experiment, the Mn(II)‐catalyzed reaction of bromate ion with methyl‐, ethyl‐ or n‐butyl‐malonic acid (MeMA, EtMA or BuMA) exhibits oscillating behavior similar to the prototype Ce(III)‐catalyzed Belousov‐Zhabotinsky (BZ) reaction with malonic acid (MA). The effects of manganese ion, bromate ion, organic substrate, sulfuric acid, and chloride ion on the oscillating pattern were investigated. Both conventional and stopped‐flow spectrophotometric methods were applied to study the kinetics of reactions of Mn(III) ion with MA, MeMA, EtMA, BuMA, bromomalonic acid (BrMA), and dibromomalonic acid (Br2MA). The order of reactivity toward Mn(III) oxidation is MA > BrMA > MeMA > Br2MA > (EtMA, BuMA). The experimental results are rationalized.
A Layer Structure Encapsuling Interlayer K+ Cations: Hydrothermal Synthesis and Crystal Structure of Vanadyl(IV) Arsenate K2[(VO)2(AsO4)(HAsO4)(H2AsO4)(H2O)].0.5H2O
Authors: Wang Sue‐Lein , Hsu Kuei‐Fang 
Published: May 2015

AbstractA new vanadyl(IV) arsenate, K2[(VO)2(AsO4)(HAsO4)(H2AsO4)(H2O)].0.5H2O, has been synthesized hydrothermally at 230 °C and structurally characterized by single‐crystal X‐ray diffraction. The compound crystallizes in triclinic space group P1 with a= 6.533(2) Å, b = 9.062(3) Å, c = 12.582(5) Å, α = 106.29(3), β = 98.64(3), γ = 103.09(2)° V = 678.0(4) Å3 Z = 2 and R = 0.0428 for 2114 unique reflections. The structure consists of VIVO6 octahedra and tetrahedra of AsO43− HAsO42−, and H2AsO4− groups to form layers along the [001] direction with K+ cations between the layers. Building units of the layers are 4‐connected ribbons connected to each other by dihydrogen arsenate groups to form large tunnels perpendicular to the layers. Cations and water molecules reside in the tunnels. The title compound is isotypic with phosphate K2(VO)2(P3O9)(OH)3‐1.125H2O (Lii et al. Inorg. Chem. 1991, 30, 446), that was synthesized at 450 °C. In contrast to the phosphate, tetranedra of three groups, AsO43−, HAsO42−, and H2AsO4−, were distinctly identified in the arsenate. The sites for lattice water are essentially fully occupied due to the larger space provided by the framework of K2[(VO)2(AsO4)(HAsO4)(H2AsO4)(H2O)].0.5H2O. The structures of this arsenate and K2(VO)2(P3O9)(OH)3·1.125H2O are discussed.
Chemical Synthesis and Characterization of Superconducting YBa2Cu4O8 at Ambient Pressure
Authors: Chen Teng‐Ming , Lin Li‐Fan 
Published: May 2015

AbstractA monophasic high‐Tc superconductor YBa2Cu4O8 with Tc(onsel), 80 K and fine grain size has beeen synthesized under oxygen at 1 bar employing metal‐ethandiol/citric acid (EG/CA) polyester complex precursors. In addition to the preparation, we report the results of infrared (IR) spectra, thermogravimetric analysis (TGA), and X‐ray diffraction (XRD) relevant to preparation of the YBa2Cu4O8 superconductor. The effect of temperature of preparation and precursor compositions (i.e. EG/CA molar ratio) on the purity and superconductivity of the YBa2Cu4O8 compound was investigated. The temperature dependence of resistivity and normal‐state resistivity of the samples varied systematically with the EG/CA ratio in the precursors. Tc(onset) and the width of the superconducting transition for YBa2Cu4O8 samples were determined to be 80 K for all samples and 6 – 9 K, respectively; the latter depended on the corresponding EG/CA ratios in the precursors. The Meissner fraction of YBa2Cu4O8 samples determined from dc magnetization tests was independent of the EG/CA ratio. Polyester precursors can potentially be applied in large‐scale preparation of high Tc ceramic‐oxide superconductors and superconducting thin films.
Synthesis and Fluxional Behavior of Intramolecular η2‐Arene Complexes via Insertion of Substituted 7‐Oxanorbornene into Palladium‐Carbon Bonds
Authors: Duan Jiun‐Pey , Cheng Chien‐Hong 
Published: May 2015

AbstractThe complexes [C6H6O(CO2CH3)2R]PdI(PPh3) (R = p‐anisyl (4), m‐anisyl (5), p‐tolyl (6), phenyl (7), 1‐naphthyl (8) and 2‐thienyl (9)) were prepared by treating Pd(PPh3)2(R)I with exo‐5,6‐dicarbomethoxy‐7‐OX‐anorbornene (3) or from the reaction of Pd(PPh3)4 with the corresponding organic iodide (RI) followed by addition of 3 and methyl iodide. In complexes 4‐8, the carbon‐carbon double bond between ipso and ortho positions of the aryl ring attached to the 7‐oxanorbornyl group is weakly bound to the palladium (II) center in a η2 fashion, in addition to the three ligands‐the 7‐oxanorbornyl group, PPh3 and I−. This η2‐interaction leads to a dramatic upfield shift of 13C NMR signals of the ipso carbons by 30‐40 ppm. Variable‐temperature NMR studies indicate that complexes 4‐7 are nonrigid on the NMR time scale. Rotation of the weakly η2 bound aryl group is proposed to account for the observed fluxionai behavior. In contrast to 4‐7,8 is static at room temperature, presumably, due to the unsymmetrical nature and the large size of the naphthyl group. In complex 9, the sulfur atom in the thienyl group is coordinated to the palladium center and no intramolecular η2‐bonding is involved.