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21.
S.V. Devyatkin 《Journal of solid state chemistry》2004,177(2):407-409
Powder and coatings of metal-like refractory compounds (MLRC) can be produced by electrochemical synthesis from molten salts. The stoichiometry of the deposited MLRC was found to correlate with the molar ratio of MLRC component ions in the melts. The system Ti-Si-B is of particular interest in terms of electrochemical synthesis since the titanium, silicon and boron potentials in the melt are close together. The electrochemical synthesis has been investigated in the system NaCl-KCl-NaF-K2TiF6-K2SiF6-KBF4 at 700°C. The opportunity of deposition of new ternary compound in the system Ti-Si-B is shown by the electrochemical synthesis from molten salts. 相似文献
22.
Heinz Günter Viehe Zdenek Janousek 《Angewandte Chemie (International ed. in English)》1973,12(10):806-818
Dichloromethylenammonium salts, particularly dichloromethylenedimethylammonium chloride, occupy a unique place as stable but reactive building blocks for synthesis. They contain three mobile chlorine atoms activated by an amino group on the same carbon atom. These salts can be regarded as chlorinated Vilsmeier or Mannich reagents and are thus at a higher oxidation level. As in the Mannich or Vilsmeier reaction, the carbon condenses here as an electrophile with formation of C? C or C? hetero atom bonds in a variety that is still far from being exhausted. 相似文献
23.
24.
Eva BeckerChristian Slugovc Eva RübaChristina Standfest-Hauser Kurt MereiterRoland Schmid Karl Kirchner 《Journal of organometallic chemistry》2002,649(1):55-63
The synthesis and some reactions of the Ru(II) and Ru(IV) half-sandwich complexes [RuCp(EPh3)(CH3CN)2]+ (E=P, As, Sb, Bi) and [RuCp(EPh3)(η3-C3H5)Br]+ have been investigated. The chemistry of this class of compounds is characterized by a competitive coordination of EPh3 either via a RuE or a η6-arene bond, where the latter is favored when the former is weaker, that is in going down the series. Thus in the case of Bi, the starting material [RuCp(CH3CN)3]+ does not react with BiPh3 to give [RuCp(BiPh3)(CH3CN)2]+ but instead gives only the η6-arene species [RuCp(η6-PhBiPh2)]+ and [(RuCp)2(μ-η6,η6-Ph2BiPh)]2+. Similarly, the EPh3 ligand can be replaced by an aromatic solvent or an arene substrate. Thus, the catalytic performance of [RuCp(EPh3)(CH3CN)2]+ for the isomerization of allyl-phenyl ethers to the corresponding 1-propenyl ethers is best with E=P, while the conversion drops significantly using the As and Sb derivatives. By the same token, only [RuCp(PPh3)(CH3CN)2]+ is stable in a non-aromatic solvent, whereas both [RuCp(AsPh3)(CH3CN)2]+ and [RuCp(SbPh3)(CH3CN)2]+ rearrange upon warming to [RuCp(η6-PhEPh2)]+ and related compounds. In addition, the potential of [RuCp(EPh3)(CH3CN)2]+ as precatalysts for the transfer hydrogenation of acetophenone and cyclohexanone has been investigated. Again aromatic substrates are clearly less suited than non-aromatic ones due to facile η6-arene coordination leading to catalyst's deactivation. 相似文献
25.
Anna M. Maj Albert Demonceau Alfred F. Noels 《Journal of organometallic chemistry》2007,692(14):3048-3056
A range of new imidazolium and imidazolinium chlorides bearing biphenyl units on their nitrogen atoms was synthesized. They differed by the electron-withdrawing or -donating nature and the steric bulk of the substituents on their aromatic rings. These various N-heterocyclic carbene (NHC) precursors were combined with the [RuCl2(p-cymene)]2 dimer and potassium tert-butoxide to generate the corresponding ruthenium-arene complexes [RuCl2(p-cymene)(NHC)] in situ. The catalytic activity of these species was investigated in the photoinduced ring-opening metathesis polymerization (ROMP) of cyclooctene. The results obtained confirmed the necessity of blocking the ortho-positions of the phenyl rings in the vicinity of the metal center in order to attain high catalytic efficiencies. They also showed that changing the steric and electronic properties of the substituents on the remote phenyl rings of the biphenyl units had no significant influence on the outcome of the polymerization. 相似文献
26.
In this paper some synthetic procedures to obtain (η6-arene)metal derivatives are reviewed. The metal-atom-arene-vapor co-condensation technique is the most appropriate to generate complexes of polycyclic aromatic hydrocarbons or heterocycles. As far as the aluminium halide-mediated synthesis is concerned, two classes of reaction are observed. When AlX3 is used with a metal halide in the presence of an aromatic hydrocarbon in the absence of any reducing agent, AlX3 can function as a dehalogenating agent, to give ionic compounds of general formula [M(η6-arene)n](AlX4)m, or it can add across the M---X bond with formation of M(μ-X)nAlX4−n systems. In both cases the metal displays its typical oxidation state. However, the use of AlX3 in combination with aluminium (the Fischer-Hafner reducing system) affords ionic or covalent low-oxidation-state metal(η6-arene) complexes. Attention is focused on our most recent results concerning the synthesis, properties and reactivity of η6-arene derivatives of Group 4 and 5 elements, showing, inter alia, the first example of a tetraarylborate anion behaving as a 12-electron donor to one metal atom and low-valent η6-arene compounds as useful reagents in the inorganic and coordination chemistry of the corresponding metal in nonaqueous systems. 相似文献
27.
《Electroanalysis》2006,18(12):1141-1151
This paper reports a study of the factors affecting the analytical performance of gold and glassy carbon electrodes modified with the tripeptide Gly‐Gly‐His for the detection of copper ions. Gly‐Gly‐His is attached to a glassy carbon (GC) surface modified with 4‐carboxyphenyl moieties or a gold surface modified with 3‐mercaptopropionic acid by the reaction of the N‐terminal amine group of the peptide with the carboxylic acid groups of the monolayer via carbodiimide activation. X‐ray photoelectron spectroscopy was used to characterize the steps in the biosensor fabrication. It was found that the analytical performance of a sensor prepared with Gly‐Gly‐His on a GC electrode was similar to that on a gold electrode under the same conditions. The performance was greatly enhanced at higher temperature, no added salt during copper accumulation and longer accumulation time within a pH range of 7–9. Interference studies and investigations of stability of the Gly‐Gly‐His sensor are reported. Analysis of natural water samples show that the sensors measure only copper ions that can complex at the sensor surface. Strongly complexed copper in natural water is not measured. Despite greater stability of diazonium salt derived monolayers on carbon surfaces compared with alkanethiols self‐assembled monolayers on gold, the stability of the sensors was essentially the same regardless of the modification procedure. 相似文献
28.
Akihiko Kanazawa Tomiki Ikeda Takeshi Endo 《Journal of polymer science. Part A, Polymer chemistry》1993,31(2):335-343
Various polymeric phosphonium salts and the corresponding low-molecular-weight model compounds were prepared and their antibacterial activities against Staphylococcus aureus and Escherichia coli were explored by the viable cell counting method in sterile distilled water. Antibacterial activity of the polymers was found to be higher than that of the corresponding model compounds, particularly against S. aureus. Furthermore, the polymeric phosphonium salt exhibited a higher activity by 2 orders of magnitude than the polymeric quaternary ammonium salt with the same structure except the cationic part. Compounds with the longest alkyl chain (octyl) studied were found to exhibit particularly high activity, and this finding may be ascribed to the contribution of the increased hydrophobicity of the compounds to the cidal activity. © 1993 John Wiley & Sons, Inc. 相似文献
29.
Aryl nitriles ArCN were obtained by the Cu(I)/Cu(II) catalysed reaction of aryl diazonium salts with KCN in good yields. 相似文献
30.
The conditions of formation of Y, La and lanthanide (from Ce(III) to Lu) enanthates were worked out, their composition and their solubilities in water at 291 K were determined, and the conditions of their thermal decomposition were studied. They were prepared as crystalline solids with general formula Ln(C7H13O2)3·nH2O, wheren=2–10. On heating, they decompose in two or three steps. They first lose some water molecules and then decompose to the oxides directly (salts of Y and heavy lanthanides) or via the intermediate formation of Ln2O2CO3 (salts of La, Pr, Nd, Sm and Eu). Only yttrium enanthate dihydrate loses 2 water molecules on heating to form an anhydrous complex, which decomposes directly to Y2O3. The temperatures of dehydration are similar for all complexes (323–343 K), while the temperatures of oxide formation vary irregularly from 823 K for CeO2 to 1078 K for La2O3. 相似文献