Some Electrochemical Characteristics of Boron‐ and Phosphorus‐Doped Glassy Carbon Electrodes

Three glassy carbon (GC) samples: undoped and doped with boron or phosphorus, prepared at 1000 °C, were compared in respect to hydrodynamic current‐potential curves in acidic medium, cyclic voltammograms for Fe^3+/2+ and Fe(CN)₆^3?/4? and argentometric titrations of halides. Some experiments were also carried out using standard Tokai and Sigri GC and Ag electrode. It appeared that GC doped with boron and phosphorus exhibited significant increase in hydrogen evolution overpotential. As for the electrode kinetics (ΔE_p criterion), no significant difference was observed between doped and undoped electrodes. In the potentiometric titrations the phosphorus‐doped electrode was advantageous over the other GC and Ag electrodes as it enabled more precise end‐point detection.     

Metal complexes with an aminosubstituted tricarbollide ligand

The reaction of the tricarbollide salt Tl[7-tBuNH-7,8,9-C₃B₈H₁₀] (Tl1) with [(cod)Rh(THF)_x]⁺ gives the rhodium complex [1-(cod)-12-tBuNH-1,2,4,12-RhC₃B₈H₁₀] in almost quantitative yield. Analogous reactions of Tl1 with [(ring)M(THF)_x]²⁺ ((ring)M = Cp*Rh and (1,3,5-C₆H₃Me₃)Ru) afford the corresponding metallatricarbollides [1-(ring)-12-tBuNH-1,2,4,12-MC₃B₈H₁₀] in ca. 50% yield. Refluxing Tl1 with [Mn(CO)₃(MeCN)₃]⁺ in THF give the tricarbollide analogue of cymantrene, [1,1,1-(CO)₃-12-tBuNH-1,2,4,12-MnC₃B₈H₁₀], the structure of which was determined by single-crystal X-ray diffraction analysis. In all cases, the formation of the metallatricarbollide complexes is accompanied by polyhedral rearrangement leading to the maximum separation of the cage carbon atoms.     

微量元素叶面肥料中硼的测定

研究了在 pH 6 .5乙酸铵缓冲溶液中 ,硼与 3 甲氧基 甲亚胺H的显色反应条件 ,最大吸收在 4 2 0nm处 ,摩尔吸光系数为 8.1× 10 3,硼含量在 0～ 10 μg/ 10ml范围内符合比耳定律。用于微量元素叶面肥料中硼的测定 ,获得了与国标法一致的结果     

The first 1,2-dibora-[2]ferrocenophane and its dynamic behaviour in solution

1,2-Bis(dimethylamino)-1,2-dibora-[2]ferrocenophane (1) was prepared by the reaction of 1,1′-dilithioferrocene with 1,2-dichlorobis(dimethylamino)diborane(4). In addition to hindered rotation about the B-N bond (ΔG^‡ > 80 kJ mol⁻¹), another dynamic process was revealed by ¹H and ¹³C NMR in solution at low temperature, and interpreted as motion of the cyclopentadienyl rings between staggered and eclipsed conformations (ΔG_{(233 K)}^‡ = 44 ± 1 kJ mol⁻¹).     

X‐Ray Single Crystal Refinement and Superconductivity of La3Ni2B2N3

Crystalline samples of La₃Ni₂B₂N₃ were synthesized using solid state metathesis reactions from combinations of La, LaCl₃, NiCl₂ together with Li₃BN₂. The structure was determined by single crystal X‐ray diffraction (I4/mmm (No. 139), a = 372.95(2) pm, c = 2056.3(2) pm, R₁ = 0.027, wR₂ = 0.062) and confirmed earlier results from neutron powder diffraction. La₃Ni₂B₂N₃ contains BN units capping square planar Ni layers. Isolated nitrogen atoms reside in La₆ octahedra. Magnetic measurements on several bulk samples exhibit superconductivity at temperatures below 14.6 K.     

A novel zirconocene/ultradispersed diamond black powder supported catalytic system for ethylene polymerization

A novel carrier of ultradispersed diamond black powder (UDDBP) was used to support metallocene catalyst. Al₂O₃ was also used as carrier in order to compare with UDDBP. Supported catalysts for ethylene polymerization were synthesized by two different reaction methods. One way was direct immobilization of the metallocene on the support, the other was adsorption of MAO onto the support followed by addition of the metallocene. Four supported catalysts Cp₂ZrCl₂/UDDBP, Cp₂ZrCl₂/Al₂O₃, Cp₂ZrCl₂/MAO/UDDBP and Cp₂ZrCl₂/Al₂O₃/MAO were obtained. The content of the zirconium in the supported catalyst was determined by UV spectroscopy. The activity of the ethylene polymerization catalyzed by supported catalyst was investigated. The influence of Al/Zr molar ratio and polymerization temperature on the activity was discussed. The polymerization rate was also observed.     

SrO—Al2O3—SiO2：Eu^3＋,Bi^3＋发光体的溶胶—凝胶法合成

制备无机固体材料大都采用高温固相反应,1971年Dislich报导了用溶胶-凝胶法制备多组份固体材料。近年来,有报导利用此法研制玻璃、玻璃陶瓷和陶瓷。我们在过去工作的基础上,合成了SrO-Al_2O_3-SiO_2:Eu~(3 ),Bi~(3 )发光体,研究了从凝胶至发光晶体的转变过程、Eu~(3 )和Bi~(3 )在SrO-Al_2O_3-SiO_2基质中的发光性质以及Bi~(3 )对 EU~(3 )的能量传递。     

Vibronisches Spektralverhalten von Molekülen: XIV. Zum Einfluß der vibronischen Kopplung auf die S0-S1-Absorption und Fluoreszenz von ausgewählten 1,3-Diketonato-bor-komplexen im Rahmen der Herzberg-Teller-Näherung

Summary Based upon completely-optimized S₀ and S₁ molecular geometries the vibrational structures of S₀-S₁ absorption and fluorescence transitions of selected 1,3-diketonato boron complexes being differently substituted, are calculated within the Herzberg-Teller approach taking into account vibronic coupling contributions. In dependence on substituted diketone as well as on the co-ligand, the influence of vibronic coupling and the consequences of intensity borrowing on the spectral behaviour in absorption and fluorescence are found to be quite different for the studied boron complexes. Consequently, for some complexes their spectroscopic properties may be interpreted exclusively by means of the Herzberg-Teller approach. An analysis of the relevant vibrational modes is given.

     

Micrometric BN powders used as catalyst support: influence of the precursor on the properties of the BN ceramic

Thin powders and foams of boron nitride have been prepared from molecular precursors for use as noble metal supports in the catalytic conversion of methane. Different precursors originating from borazines have been tested. The best results were obtained using a precursor derived from trichloroborazine (TCB) which, after reacting with ammonia at room temperature and then thermolyzing up to 1800°C, led to BN powders with a specific area of more than 300 m² g⁻¹ and a micrometric spherical texture. Comparable results were obtained using polyborazylene under similar conditions. Aminoborazine-derived precursors did not yield such high specific area ceramics but the BN microstructure resembled a foam with a crystallized skin and amorphous internal part. These differences were related to the chemical mechanism of the conversion of the precursor into BN. Polyhaloborazines and polyborazines yielded BN through gas-solid reactions whereas aminoborazine polymers could be kept waxy up to high temperatures, which favored the glassy foam. Catalysts composed of BN support and platinum have been prepared using two routes: from a mixture of precursor or by impregnation of a BN powder leading to very different catalysts.