铂配位的腺嘌呤质子化的理论研究

用量子化学从头算研究一系列平面四方金属配体作用于腺嘌呤N₇位点对其质子化的影响。计算结果表明气相中，配合物质子化能力主要受长程静电效应影响，不同金属离子的影响差别甚微。综合考虑极性溶剂影响后长程静电效应影响显著降低。NBO电荷布居分析表明质子化位点电子云密度的变化直接影响该位点质子化能力。     

An efficient Stille cross-coupling reaction catalyzed by Pd(OAc)2/DAB-Cy catalytic system

An efficient palladium-catalyzed Stille cross-coupling reaction has been developed. In the presence of 3 mol% of Pd(dba)₂ and 6 mol% of DAB-Cy (1,4-dicyclohexyl-diazabutadiene), various aryl halides (iodides and bromides) were coupled with organotin compounds to afford the corresponding biaryls and alkyne in good to excellent yields. Furthermore, high TONs [turnover numbers, TONs up to 950,000 for the reaction of 1-iodo-4-nitrobenzene and tributyl(phenyl)stannane] for the Stille cross-coupling reaction were observed.     

Redox troponization of (η5-cyclopentadienyl)(η4-4-menthyl-4-exo-trichloromethylcyclohexa-2,5-dien-1-one)rhodium as a novel approach to the synthesis of metal-coordinated nonbenzenoid aromatics of the tropone seriesas a novel approach to the synthesis of metal-coordinated nonbenzenoid aromatics of the tropone series

The possibility of redox troponization of a gem-polyhalomethylated semiquinoid system, π-coordinated to a metal atom, was shown in relation to the reaction of (η⁵-cyclopentadienyl)(η⁴-4-menthyl-4-exo-trichloromethylcyclohexa-2,5-dien-1-one)rhodium with Pd(PPh₃)₄. The reaction occurs with retention of the metal coordination affording a sevenmembered organometallic derivative of the nonbenzoid aromatic series, namely, (η⁵-cyclopentadienyl)(η⁴-4-chloro-5-menthylcyclohepta-2,4,6-trien-1-one)rhodium, whose structure was established by means of elemental analysis, NMR, and mass-spectral data. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1255–1256, June, 1998.     

Probing depth of the low energy cascade electrons from a transition metal

A surface probing depth of only 2 layers for low energy cascade electrons excited with a 3.2 keV primary electron beam is clearly demonstrated by model experiments with non-magnetic overlayers of Ta on magnetic substrates of Fe/Ni₈₀Fe₂₀. This result establishes a short probing depth of low energy electrons in transition metals generalizing the previously observed short magnetic probing depth for spin-polarized electrons in ferromagnets. The short probing depth sheds new light on a number of spectroscopic observations on ferromagnetic transition metals, and has important implications concerning surface magnetic properties and scattering processes of hot electrons in transition metals.     

新型Ni—Pd/碳化树脂催化剂的制备及在微量测定有机氧元素中的应用

本文报道一种新型Ni—Pd／碳化树脂催化剂的制备方法，用该法制备的催化剂具有高金属分散度和高机械强度，用于库仑法微量测定有机氧元素取得满意结果。文中对Ni和Pd颗粒在催化剂上表面形貌和分布、催化活性等作了初步探讨。     

Synthesen und Kristallstrukturen von [Pd9As8(PPh3)8] und [Pd9Sb6(PPh3)8]

Syntheses and Crystal Structures of [Pd₉As₈(PPh₂)₈] and [Pd₉Sb₆(PPh₃)₈] [PdCl₂(PPh₃)₂] reacts with As(SiMe₃)₃ to give the new cluster [Pd₉As₈(PPh₃)₈] ( 4 ). 4 has been characterized by X-ray crystal structure analysis. It is a molecule in which four [Pd₂(PPh₃)₂]-units are bridged by As₂-units. A further Pd atom is located in the centre of the cluster. 4 crystallizes in the space group C2/c with four formula units per unit cell. The lattice constants at 200 K are: a = 3 970.6(3), b = 1 648.90(16), c = 3 266.30(20) pm, β = 131,44(4)°. The reaction of [PdCl₂(PPh₃)₂] with Sb(SiMe₃)₃ yields [Pd₉Sb₆(PPh₃)₈] ( 5 ). 5 consists of a body centred cubic Pd₉-cluster. All of the cube faces are capped by μ₄-Sb-ligands. 5 crystallizes in the space group Pn3 with two formula units per unit cell. The lattice constants at 200 K are: a = b = c = 1 995.4(2) pm.     

The first example of anodic corrosion of Pd in aqueous ethylenediamine with formation of colloidal palladium

For the first time, corrosion of a Pd anode was detected during electrolysis in a weakly alkaline aqueous solution of ethylenediamine. The kinetics and mechanism of the process were investigated by the methods of cyclic voltammetry and gravimetry. Scanning electron microscopy showed corrosion of the Pd anode and deposition of Pd on the cathode surface, while the formation of colloidal Pd in the working solution was identified by transmission electron microscopy.     

Recent progress and current applications of Sonogashira coupling reaction in water

The use of aqueous media in palladium‐catalyzed reactions has become popular because water‐based synthetic processes are inherently safer as well as being inexpensive. Moreover, it does not require dry solvents, and the products may easily be isolated by extraction, which greatly facilitates the operation. Thus the use of water in palladium‐catalyzed reactions represents one of the most economically and environmentally viable options for many organic transformations. In this review, recent developments of Sonogashira reaction in water or aqueous media will be disclosed. Copyright © 2013 John Wiley & Sons, Ltd.     

Synthesis and characterization of Pd(II) complexes of 2‐ and 3‐thiophenecarbaldehyde immobilized on silica obtained from sepiolite

Silica obtained by acid treatment of sepiolite was used as a support for catalysts consisting of palladium complexes of 2‐ and 3‐thiophenecarbaldehyde. The support and the catalysts were characterized by X‐ray diffraction, and solid‐state ²⁹Si and ¹³C nuclear magnetic resonance spectroscopies. The supported palladium catalysts were used in the Suzuki reaction of bromobenzene with phenylboronic acid. Copyright © 2013 John Wiley & Sons, Ltd.     

Influence of High Peroxide Concentration on the Mechanical Properties of Cross-Linked Low Density Polyethylene

In this paper are presented the static and dynamic mechanical investigation of chemically cross-linked low density polyethylene (XLPE) prepared in our laboratory. This polymer has been tested mechanically at different frequencies, amplitudes, and temperatures as a function of cross-link density which is indicated to some extent by the amount of peroxide used in the cross-linking. The main findings can be described as follows: mechanical damping in XLPE at the α-relaxation point as a function of peroxide concentration is different for shear and compression modes of deformation. Moreover, the dynamic investigation at very small amplitudes indicated two relatively rigid structures. One structure at low concentration of peroxide is attributed to excessive crystallinity; the other one at the high peroxide concentration is probably due to the very regular and perfect polyethylene network. These two interesting structures are not detected by dynamical testing with large amplitudes. As far as Young's modulus as a function of peroxide concentration is concerned, we conclude that in this polymer this factor does not depend on the crystallinity but on changes of the so-called hard amorphous phase. These findings are consistent with our previous structural investigation.