Preparation of Uniform Ni-B Amorphous Alloy Catalyst on CNTs and its Performance for Acetylene Selective Hydrogenation

Carbon nanotubes (CNTs) are severely bundled and essentially insoluble in solvent. These properties are generally considered as a significant barrier toward the practical uses of CNTs. Therefore, the functionalization and solubilization of CNTs have recei…     

聚苯乙炔的伏安特性

聚苯乙炔的伏安特性周淑琴（中国科学院化学研究所北京１０００８０）关键词聚苯乙炔，伏 安特性，欧姆电导，空间电荷限制电流，高斯分布陷阱能级，陷阱态密度聚苯乙炔（ＰＰＡ）是一种具有π电子的共轭高分子聚合物，它的光电导特性引起了同行的兴趣［１］．目前高分...     

Theoretical Study of the Products of Acetylene Addition to HgCl2

The ab initio MP2 method is used with the LANL2DZ basis to calculate the mercury chloride ,-complex with two acetylene molecules (1) and various isomeric forms of mercury di()-vinyl chloride -complexes (2): cis-cis (2A), cis-trans (2B), and trans-trans (2C). The ,-complex is the most stable form of all those considered; the difference between 1 and 2A is 24.9 kcal/mole. A relation between the total energies (kcal/mole) for isomeric forms 2 is established to be 2A (0) < 2B (0.98) < 2C (1.58). Complex 1 is shown to be transformed into 2A via the intermediate formation of 3, which is a hybrid form of the complex (,-complex of mercury chloride with two acetylene molecules). The structures of the transition states for the transformations of 1 into 3 (structure 4) and of 3 into 2A (structure 5) and the corresponding transition activation energies are determined. The interaction of 2A, 2B, and 2C with the Cl^- anion as a model nucleophile is considered. It is shown that the resulting anions (6A, 6B, 6C) have a planar structure with the relative stability increasing in the series 6A<6B<6C.     

CATALYTIC ACTIVITY OF Pd-Sn COMPLEX CARBONYLATION OF ACETYLENE

The influence of different concentration of HO, SnCl2, Cl- and n-BuOH on the carbonylation of acetylene has been studied. The results show that the yield of n- butyl propionate increases with the increase of HC1 concentration and the catalytic activity is depressed when Cl" concentration increases. However, the stability of catalytic complex is promoted by Cl-. The key to the carbonylation of acetylene lies in the addition of SnCl2, which promotes the formation of the complex of C2H2, CO with catalyst and plays an important role in the hydrogen removal from n-BuOH. The hydrogen removed from n BuOH is the hydrogen source of this reaction. Meanwhile, the principle of the effect of HCl, Cl- and SnCl2 on reaction has been discussed. The reaction model has also been proposed.     

Cobalt(III)-catalyzed cycloaddition polymerization of diynes with nitriles: Synthesis of polymers containing pyridine moieties in the main chain

The synthesis of pyridine-containing polymers was carried out by the cycloaddition of diynes with nitriles in the presence of organocobalt complexes as catalysts. As a model experiment, the pyridine-formation reaction of monofunctional acetylenes with nitriles was reexamined in detail in the presence of organocobalt catalysts, from which the combination of terminal aliphatic acetylenes and aromatic nitriles was proved to be suitable for the specific pyridine-formation process. On the basis of this result, the polymerization of terminal aliphatic diynes with aromatic nitriles was carried out in the presence of the cobalt catalyst (10 mol %) to give polymers containing substituted pyridine moieties in the main chain in high yields. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1979–1986, 1999     

Internal acetylene unit linked para to the aromatic ring as a crosslink site for polyimide

Crosslinking behavior of internal acetylene units linked para to the aromatic rings was investigated by preparing polyimide from 4,4′-diaminodiphenylacetylene (p-intA) and 2,2′-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA). Polyimide was also prepared from 1,4-phenylenediamine (PDA) and 6FDA for comparison. The polymers were moderately to highly viscous at the stage of polyamide acid. Thermal imidization gave polyimide having acetylene units that are linked para to the aromatic connecting units. Differential scanning calorimetry (DSC) measurement of the polymer revealed that exotherm due to the crosslinking of the acetylene unit appeared at ca. 330°C. After thermal treatment at high temperature such as 350 and 400°C, onset of the exotherm shifted to higher temperature and the amount of the exotherm became smaller. The dynamic mechanical properties of the uncrosslinked polyimide film treated at 250°C had a glass transition temperature (T_g) at 330°C with a considerable drop in the storage modulus at this temperature. After the film was exposed to a higher temperature to induce crosslinking, the T_g was observed to increase to above 400°C and the storage modulus was maintained to higher temperatures. Tensile properties of the polyimide showed that the films had good mechanical properties. © 1996 John Wiley & Sons, Inc.     

Polymerization and polymer properties of (p-tert-butyl-o,o-dimethylphenyl)acetylene

(p-tert-Butyl-o,o-dimethylphenyl)acetylene (BDMPA) polymerized in high yields in the presence of W and Mo catalysts. Especially the W(CO)₆–CCl₄–hv catalyst quantitatively produced a polymer totally soluble in toluene and chloroform. The weight-average molecular weight of this polymer exceeded 2 × 10⁶. Poly(BDMPA) was a dark brown solid, and had alternating double bonds along the main chain. The weight loss of the polymer in air occurred only above 300°C, indicating a fairly high thermal stability. A free-standing film could be fabricated by solution casting. The electrical conductivity of the polymer at 25°C was 1 × 10⁻¹³ S cm⁻¹. The oxygen permeability coefficient and the separation factor of O₂ vs. N₂ of the polymer at 25°C were 67 barrers and 3.2, respectively. © 1996 John Wiley & Sons, Inc.     

Polymerization of 1-chloro-2-β-naphthylacetylene by Mo catalysts and polymer properties

1-Chloro-2-β-naphthylacetylene (ClβNA) polymerized in good yields in the presence of MoCl₅-based catalysts. The highest weight-average molecular weight of poly(ClβNA) reached about 3 × 10⁵. The polymer was a yellow solid (absorption cutoff in CHCl₃ 450 nm). It was soluble in toluene, chloroform, etc., and provided a tough film by the solvent casting method. The polymer retained its weight up to 300°C in air; it was thermally less stable than poly(1-chloro-2-phenylacetylene) but more stable than poly(β-naphthylacetylene). The oxygen permeability coefficient (P_O2) of this polymer was 19 barrers (25°C), which is fairly small for a substituted polyacetylene. © 1996 John Wiley & Sons, Inc.     

Terminal and Internal Alkyne Complexes and Azide-Alkyne Cycloaddition Chemistry of Copper(I) Supported by a Fluorinated Bis(pyrazolyl)borate

Copper plays an important role in alkyne coordination chemistry and transformations. This report describes the isolation and full characterization of a thermally stable, copper(I) acetylene complex using a highly fluorinated bis(pyrazolyl)borate ligand support. Details of the related copper(I) complex of HC≡CSiMe₃ are also reported. They are three-coordinate copper complexes featuring η²-bound alkynes. Raman data show significant red-shifts in C≡C stretch of [H₂B(3,5-(CF₃)₂Pz)₂]Cu(HC≡CH) and [H₂B(3,5-(CF₃)₂Pz)₂]Cu(HC≡CSiMe₃) relative to those of the corresponding alkynes. Computational analysis using DFT indicates that the Cu(I) alkyne interaction in these molecules is primarily of the electrostatic character. The π-backbonding is the larger component of the orbital contribution to the interaction. The dinuclear complexes such as Cu₂(μ-[3,5-(CF₃)₂Pz])₂(HC≡CH)₂ display similar Cu-alkyne bonding features. The mononuclear [H₂B(3,5-(CF₃)₂Pz)₂]Cu(NCMe) complex catalyzes [3 + 2] cycloadditions between tolyl azide and a variety of alkynes including acetylene. It is comparatively less effective than the related trinuclear copper catalyst {μ-[3,5-(CF₃)₂Pz]Cu}₃ involving bridging pyrazolates.     

An Ab Initio Study of C2H2.H2, C2H2.N2, and C2H2.Ar Complexes

Ab initio calculations at the post Hartree–Fock level were performed on complexes of acetylene with hydrogen, nitrogen, and argon. Total energies, optimum geometries, and binding energies were calculated, using the 6-311G** and the 6-31+G(2df,2pd) basis sets. Calculations showed the complexes to be more stable than the separate entities, with the exception of the acetylene–hydrogen complex.