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排序方式: 共有230条查询结果,搜索用时 46 毫秒
1.
Pedro lvarez‐Boo Jos Sergio Casas Alfonso Castieiras María Delfina Couce Eduardo Freijanes Eva Novoa Jos Sordo 《应用有机金属化学》2003,17(9):725-729
Reaction of dichloro‐ and dibromodimethyltin(IV) with 2‐(pyrazol‐1‐ylmethyl)pyridine (PMP) afforded [SnMe2Cl2(PMP)] and [SnMe2Br2(PMP)] respectively. The new complexes were characterized by elemental analysis and mass spectrometry and by IR, Raman and NMR (1H, 13C) spectroscopies. Structural studies by X‐ray diffraction techniques show that the compounds consist of discrete units with the tin atom octahedrally coordinated to the carbon atoms of the two methyl groups in a trans disposition (Sn? C = 2.097(5), 2.120(5) Å and 2.110(6), 2.121(6) Å in the chloro and in the bromo compounds respectively), two cis halogen atoms (Sn? Cl = 2.4908(16), 2.5447(17) Å; Sn? Br = 2.6875(11), 2.7464(9) Å) and the two donor atoms of the ligand (Sn? N = 2.407(4), 2.471(4) Å and 2.360(5), 2.455(5) Å). In both cases, the Sn? N(pyridine) bond length is markedly longer than the Sn? N(pyrazole) distance. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
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DFT computational study of the mechanism of allyl halides carbonylation catalyzed by nickel tetracarbonyl 总被引:1,自引:0,他引:1
Bottoni A Miscione GP Novoa JJ Prat-Resina X 《Journal of the American Chemical Society》2003,125(34):10412-10419
A theoretical investigation at the DFT(B3LYP) level on the carbonylation reaction of allyl bromide catalyzed by nickel tetra-carbonyl Ni(CO)(4) is discussed. The computational results show the following: (i) Three main steps characterize the catalytic cycle: (a) an oxidative addition step, (b) a carbonylation step, and (c) a reductive elimination step where the acyl product is obtained and the catalyst is regenerated. (ii) Both Ni(CO)(3) and Ni(CO)(4) complexes can behave as "active" catalytic species. (iii) The oxidative addition leads to the formation of either eta(3) or eta(1)-allyl nickel complexes, which are involved in a fast equilibrium. (iv) The carbonylation occurs much more easily on the eta(1) than on the eta(3) intermediates. 相似文献
4.
Paital AR Mitra T Ray D Wong WT Ribas-Ariño J Novoa JJ Ribas J Aromí G 《Chemical communications (Cambridge, England)》2005,(41):5172-5174
Based on a combined theoretical-experimental study, we propose that substituted m-phenylene ligands (m-N-Phi-N) can act as tuneable strong ferromagnetic couplers connecting Cu(II) ions; a new complex presenting that bridge with J close to +15 cm(-1) has been suggested and synthesized. 相似文献
5.
Sanz V de Marcos S Castillo JR Galbán J 《Journal of the American Chemical Society》2005,127(3):1038-1048
In this paper an in depth study is presented of the use of the horseradish peroxidase (HRP) enzyme as a self-indicating biorecognition reagent in UV-vis molecular absorption spectrometry. The HRP/H2O2 reaction mechanism in the absence of an external substrate has been clarified, and the interaction between HRP and glucose oxidase (GOx) has been studied. It has been demonstrated that GOx can act as a substrate of HRP; in both cases the kinetic constants have been obtained and mathematical models have been developed. Second, the HRP/H2O2 reaction is used to follow a H2O2-producing enzymatic reaction, the glucose reaction with GOx being used as a model. As an application of this, two methodologies have been proposed for glucose determination: with or without previous incubation of glucose with GOx. In both cases mathematical models relating HRP absorbance changes to glucose concentration have been developed and tested; both methods have been optimized, analytically characterized, and tested for glucose determination in samples. The methodology described could be applied to other heme-proteins and to other H2O2-producing enzymatic reactions. The models permit the reaction constants to be calculated. From the analytical chemistry point of view the models allow the prediction of the method sensitivity for other analytes involved in this type of reaction if the kinetic constants are known and can be used in the design of optical sensors. 相似文献
6.
The interaction energy of a [Au{C(NHMe)2}2]+ ... [Au{C(NHMe)2}2]+ dimer is investigated using the MP2 method and the LANL2DZ basis set when isolated or embedded in ionic an [Au{C(NHMe)2}2]2anion2 aggregate, a good model for the environment that these dimers feel in ionic crystals. A repulsive interaction energy is obtained when the dimer is isolated. However, it is possible to find short AuI ... AuI separations in [Au{C(NHMe)2}2]2anion2 aggregates, because in these aggregates the sum of the cation ... anion interactions overweight the sum of the cation ... cation plus anion...anion interactions. This explains why short AuI ... AuI separations are found in ionic crystals. The AuI ... AuI interaction found in [Au{C(NHMe)2}2]2 anion2 aggregates shows the same features observed in energetically stable dimers presenting AuI... AuI bonds. This makes appropriate to use the name counterion-mediated bonds for the AuI... AuI interactions found in [Au{C(NHMe)2}2]2 anion2 aggregates and ionic crystals. 相似文献
7.
Using a multireferent MBPT method (CIPSI) the electronic affinity (EA) of F, CN and HCC is computed. Results show how UMP2 gives unbalanced truncation of the MP series, while ROMP2 has the correct (balanced) behaviour. The good agreement with the experimental EA found for some compounds is accidental and associated to an error compensation. The good agreement with the experimental data found for the ROMP2 and CIPSI EAs is analysed.This paper was presented at the International Conference on The Impact of Supercomputers on Chemistry, held at the University of London, London, UK, 13–16 April 1987 相似文献
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Maria E. Sulbaran Gerzon E. Delgado Asilo J. Mora Ali Bahsas Hector Novoa de Armas Norbert Blaton 《Acta Crystallographica. Section C, Structural Chemistry》2007,63(9):o543-o545
In the title compound, C6H8N2O2S, also known as N‐acetyl‐2‐thiohydantoin–alanine, the molecules are joined by N—H...O hydrogen bonds, forming centrosymmetric R22(8) dimers; these dimers are linked by C—H...O interactions to form R22(10) rings, thus forming C22(10) chains that run along the [101] direction. 相似文献
10.
Carvajal MA Alvarez S Novoa JJ 《Chemistry (Weinheim an der Bergstrasse, Germany)》2004,10(9):2117-2132
The nature of intermolecular interactions between dicoordinate Cu(I) ions is analyzed by means of combined theoretical and structural database studies. Energetically stable Cu(I).Cu(I) interactions are only found when the two monomers involved in the interaction are neutral or carry opposite charges, thus allowing us to speak of bonding between the components of the bimolecular aggregate. A perturbative evaluation of the components of the intermolecular interaction energies, by means the IMPT scheme of Stone, indicates that both the Coulombic and dispersion forces are important in determining the Cu(I).Cu(I) bonding interactions, because only a small part of that energy is attributable to Cu.Cu interactions, while a large component results from Cu.ligand interactions. The electrostatic component is the dominant one by far in the interaction between charged monomers, while in the interaction between neutral complexes, the electrostatic component is found to be of the same order of magnitude as the dispersion term. Bimolecular aggregates that have like charges are repulsive by themselves, and their presence in the solid state results from anion.cation interactions with ions external to this aggregate. In these cases, the short-contact Cu.Cu interactions here should be more properly called counterion-mediated Cu.Cu bonds. 相似文献