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排序方式: 共有1103条查询结果,搜索用时 31 毫秒
111.
Oracio Serrano 《Journal of organometallic chemistry》2011,696(10):2217-2219
The nickel (0) compound Ni(COD)(GaAr′)2 (Ar′ = C6H3-2,6-(C6H3-2,6-i-Pr2)2), 1, was synthesized by the reaction of Ni(COD)2 (COD = 1,5-cyclooctadiene) with (GaAr′)2. Compound 1 reacted with ethylene at 25 °C and at 1 atm pressure to give the bimetallic cluster [Ni2(GaAr′)2(η1:η1-μ2-C2H4)], 2, through the incorporation of one molecule of ethylene and displacement of COD. The structure of 2 featured an unusual Ni2Ga2C2 core bicyclic structure in which the C2H4 moiety bridges the Ga···Ga edge of a Ga2Ni2 tetrahedron. The galliums each carry an η1-bonded Ar′ substituent which complexes the nickel atom by an η6-π interaction with one of its flanking Ar’ rings. 相似文献
112.
Sonia Aguado-Ullate Octavio González-del Moral Alberto Hernán-Gómez Miguel Mena Cristina Santamaría 《Journal of organometallic chemistry》2011,696(25):4011-4017
The ability of the oxonitride [{Ti(η5-C5Me5)(μ-O)}3(μ3-N)] (1) to act as an organometallic ligand has been studied from both theoretical and experimental points of view. DFT calculations have allowed understanding the electronic structure of 1, and rationalizing its chemical behavior by comparison with the electronic structures of isoelectronic species [{Ti(η5-C5Me5)(μ-O)}3(μ3-CH)] and [{Ti(η5-C5Me5)(μ-NH)}3(μ3-N)]. Reactions of 1 with different inorganic molecules such as [Mo(CO)3(1,3,5-Me3C6H3)] or AlEt3 have confirmed the possibility of 1 to act as a tridentate or monodentate ligand to give the [{(CO)3Mo}(μ3-O)3{Ti3(η5-C5Me5)3(μ3-N)}] (2) and [{Et3Al}(μ3-O){(μ-O)2Ti3(η5-C5Me5)3(μ3-N)}] (3) complexes, respectively. Surprisingly, reactions of 1 with [M(CO)6] (M = Cr, Mo, W) complexes led to activate the μ3-N unit in 1 to afford the new compounds [Ti3(η5-C5Me5)3(μ-O)4{(NC)M(CO)5}]2 [M = Cr (4), Mo (5), W (6)]. Molecular structures of complexes 2-6 have been established by single crystal X-ray analysis. 相似文献
113.
Akira Miura Michael Lowe Chinmayee V. Subban Shinichi Kikkawa Richard G. Hennig Francis J. DiSalvo 《Journal of solid state chemistry》2011,184(1):7-11
A new silver nitride, AgTaN2, was synthesized from NaTaN2 by a cation-exchange reaction, using a AgNO3-NH4NO3 flux at 175 °C. Its crystal structure type is delafossite (R3¯m) with hexagonal lattice parameters of a=3.141(3) Å, c=18.81(2) Å, in which silver is linearly coordinated to nitrogen. Energy dispersive X-ray analysis and combustion nitrogen/oxygen analysis gave a composition with atomic ratios of Ag:Ta:N:O as 1.0:1.2(1):2.1(1):0.77(4), which is somewhat Ta rich and indicates some oxide formation. The X-ray photoelectron spectroscopy analysis showed a Ta- and O-rich surface and transmission electron microscope observation exhibited aggregates of ca. 4-5 nm-sized particles on the surface, which are probably related to the composition deviation from a AgTaN2. The lattice parameters of stoichiometric AgTaN2 calculated by density functional theory agree with the experimental ones, but the possibility of some oxygen incorporation and/or silver deficiency is not precluded. 相似文献
114.
Sandra Chouzier Tivadar Czeri Magalie Roy-Auberger Christophe Pichon Christophe Geantet Michel Vrinat Pavel Afanasiev 《Journal of solid state chemistry》2011,184(10):2668-2677
Decomposition of ammonium heptamolybdate–hexamethylentetramine (HMTA) complex (HMTA)2(NH4)4Mo7O24·2H2O was studied as a function of treatment conditions in the range 300–1173 K. The evolution of solid products during decomposition was studied by thermal analysis and in situ EXAFS. Depending on the nature of the gas used for treatment, single phases of highly dispersed nitrides Mo2N, carbide Mo2C, or oxide MoO2 can be obtained. The nature of the products obtained was explained by qualitative thermodynamical considerations. Morphology of the solids considerably depends on such preparation parameters as temperature and mass velocity of the gas flow. For the nitride-based materials, catalytic activity was evaluated in the model thiophene HDS reaction. It was demonstrated that NH3-treated samples showed better catalytic activity than N2-treated ones due to cleaner surface and better morphology. Transmission microscopy, XRD and XPS studies showed that MoS2 is formed on the surface during HDS reaction or sulfidation with H2S. Optimized nitride-derived catalysts showed mass activity several times higher than unsupported MoS2 or MoS2/Al2O3 reference catalyst. 相似文献
115.
Dinorah Gambino Mariana FernándezDiego Santos Gustavo A. EtcheverríaOscar E. Piro Fernando R. PavanClarice Q.F. Leite Isabel TomazFernanda Marques 《Polyhedron》2011,30(7):1360-1366
In the search for gallium bioactive compounds five Ga(III) complexes, [GaIII(L-H)2](NO3), with tridentate salicylaldehyde semicarbazone derivatives as ligands (L) have been synthesized and characterized in the solid state and in solution by different techniques. The crystal structure of [GaIII(L4-H)2](NO3)·2H2O, where L4 is 3-ethoxysalicylaldehyde semicarbazone, was solved by X-ray diffraction methods. The gallium(III) ion is in a distorted octahedral environment, coordinated to two nearly planar and mutually perpendicular 3-ethoxysalicylaldehyde semicarbazonato anions acting as tridentate ligands through their phenol and carbonyl oxygen atoms and their azomethine nitrogen atom. Their biological potential has been explored by evaluating their activity on Mycobacterium tuberculosis, causative agent of tuberculosis, and their cytotoxicity on tumor cell lines. Three different human tumor cell lines were selected that show different degrees of resistance to metallodrugs: ovarian A2780 (low resistance), breast MCF7 (medium resistance) and prostate PC3 (high resistance) cells. Although the complexes have not shown activity on M. tuberculosis, complexation with gallium has led to the enhancement of the cytotoxic potencies of the organic compounds. Those complexes that contain a bromide substituent at the phenolate ring have shown the highest cytotoxicities. In particular, [GaIII(L2-H)2](NO3), where L2 is 5-bromosalicylaldehyde semicarbazone,·has shown a remarkable cytotoxicity on A2780 tumor cell line with an IC50 value of the same order than cisplatin (IC50 Ga-L2 = 2.4 ± 0.3 μM; IC50 cisplatin = 2.0 ± 0.1 μM, 72 h incubation at 37 °C). Interestingly, this complex has also shown moderate cytotoxicity against MCF7 and PC3 cells (IC50 MCF7 = 30 ± 6; IC50 PC3 = 18 ± 3 μM). Therefore, this gallium compound could be considered a promising wide spectrum potential anti-tumor agent. 相似文献
116.
Y. Turki-Ben Ali G. Bastard R. Bennaceur 《Physica E: Low-dimensional Systems and Nanostructures》2005,26(1-4):222
The aim of this work is to analyze theoretically the correlation energies, for neutral, positive and negative excitons and bi-excitons in the III–V nitride InxGa1−xN/GaN quantum dot; where x=17.5% denotes the indium concentration. So, we propose a model consistent with experimental observations that is small InxGa1−xN truncated pyramids with circular base lying on wetting layer, both buried into GaN matrix. The correlation energies of many-body complexes X, X−, X+ and XX are investigated as a function of the quantum dot radius rc and the intrinsic electric field. 相似文献
117.
118.
Kevin A. Pears Momtchil Stavrev Alessia Scire Ralf Koepe Matthias Markert Ulrich Egger Lee Donohue 《Microelectronic Engineering》2005,81(1):156-161
Carbon hard mask structures have been used to etch a variety of materials typically used in sub 90 nm DRAM manufacture. The results indicate that carbon hard masks can be used very effectively to structure oxide, nitride and metal films giving the CD performance required for the technologies being investigated. 相似文献
119.
The processes of electron transfer and dissociative scattering are explored for collisions of hyperthermal NO+ on GaAs(110). The experiments reveal a marked angular dependence to O− emergence. A strong correlation between the O− scattering angle and the final atom-surface interaction site provides a map of the lateral dependence to reactivity. The results are modeled by sequential neutralization, dissociation, and electron attachment steps. Classical trajectory calculations, in conjunction with an empirical opacity function, accurately reproduce the experimental results. The opacity function is interpreted as the probability that an electron will attach to a departing O fragment as a function of the last surface site the atom impacts. The experiments indicate that O− emergence occurs predominantly for oxygen atoms which come in close contact with the localized dangling bond states of GaAs(110). 相似文献
120.
John J. Eisch 《Journal of organometallic chemistry》1995,500(1-2):101-115
The evolution of mechanistic insight into the nature of organometallic reactions over the last forty years is recounted from the personal perspective of a chemist trained in the empirical tradition of organometallic chemistry. Starting from the viewpoint prevailing in the 1950s of organometallics as potential carbanionic nucleophiles, this investigator has become persuaded by his researches with Group 13 organometallics of the merits of treating these reagents as organometallic electrophiles. The profound effects that a tricoordinate boron center can exert on the structure and reactivity of boracyclopolyenes is a telling illustration of such boron electrophilicity operating in an intramolecular fashion. The elucidation of the mechanisms of both the carbalumination and the hydroalumination of olefins and acetylenes has adduced cogent evidence for the rate-determining step being the electrophilic attack of tricoordinate aluminum on the carbon-carbon π-electron cloud of the substrate. Finally, in an investigation of the molecular basis for Ziegler-Natta catalysis, the Breslow-Natta soluble catalyst for the polymerization of ethylene, Cp2TiCl2-RnAlCl3−n, was examined in detail and compelling evidence has been adduced that the active catalyst site is the solvent-separated ion-pair, [Cp2TiR]+ [RnAlCl4−n]−.. Here again, the polymerization reaction is initiated by an organometallic electrophile, indeed by an even more powerful cationic electrophile. The net effect of these studies has been an Umpolung in the manner with which this chemist and many of his colleagues view organometallic reaction mechanisms. 相似文献