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排序方式: 共有380条查询结果,搜索用时 31 毫秒
281.
G. A. Kostin V. I. Mashukov T. M. Korda S. V. Tkachev V. G. Torgov A. B. Drapailo O. V. Kas’yan V. I. Kal’chenko 《Russian Journal of Inorganic Chemistry》2007,52(11):1697-1703
Complexing [PdCl4]2? with calix[4]arenes (L) functionalized by CH2SR (R = Me (1), n-Bu (2), or p-Tol (3)) in their upper rims has been studied in toluene and CCl4. The stoichiometry of the extracted palladium species (PdCl2) n L, where n = 1 or 2 is established by spectroscopic methods (NMR spectroscopy, UV/Vis spectrophotometry, atomic absorption) and extraction. For slow coordinative extraction, the concentration constants of complex formation and extraction from chloride solutions are determined using the coupled equilibria method. The kinetic and thermodynamic laws of extraction coincide, and their parameters increase in the following row of the substituents at the sulfur atom: p-Tol < Bu < Me. 相似文献
282.
The reaction of anhydrous YCl3 with an equimolar amount of lithium N,N'-diisopropyl-N' '-bis(trimethylsilyl)guanidinate, Li[(Me3Si)2NC(Ni-Pr)2], in tetrahydrofuran (THF) afforded the monomeric monoguanidinate dichloro complex {(Me3Si)2NC(Ni-Pr)2}YCl2(THF)2 (1). Alkylation of complex 1 with 2 equiv of LiCH2SiMe3 in hexane at 0 degrees C yielded the monomeric salt-free dialkyl complex {(Me3Si)2NC(Ni-Pr)2}Y(CH2SiMe3)2(THF)2 (2). The bis(triethylborohydride) complex [(Me3Si)2NC(Ni-Pr)2]Y[(mu-H)(mu-Et)2BEt]2(THF) (5) was prepared by the reaction of complex 1 with 2 equiv of LiBEt3H in a toluene-THF mixture at 0 degrees C. The complexes 1, 2, and 5 were structurally characterized. Complex 2 as well as the systems 2-Ph3B, 2-Ph3B-MAO, and 1-MAO (MAO = methylaluminoxanes) in toluene were inactive in ethylene polymerization, while the product obtained in situ from the reaction of complex 2 with a 2-fold molar excess of PhSiH3 in toluene polymerized ethylene with moderate activity. 相似文献
283.
284.
G. A. Kostin V. I. Mashukov N. V. Kurat’eva S. V. Tkachev V. G. Torgov A. B. Drapailo 《Russian Journal of Coordination Chemistry》2008,34(5):360-366
Two novel complexes, (AuCl)4L3(I) and (PdCl2)2L3(II) (L3 is calix[4]arene-thioether), were synthesized and their structures were determined. In complex I, one thioether group of molecule L3 is coordinated to every Au atom. In complex II, the bidentate coordination of L3 to the Pd atoms is observed; two thioether groups are in the trans-positions in the Pd square surrounding. Both complexes have the layered crystal lattices. In the Au complex, the layers are more stable due to the short contacts Au-Au (3.19–3.23 Å). 相似文献
285.
286.
Structural Variability of R2C Adducts of 3a,6a‐Diaza‐1,4‐diphosphapentalene: Tuning the N→P Bonding 下载免费PDF全文
Alexander N. Kornev Vadim E. Galperin Yulia S. Panova Alla V. Arapova Evgenii V. Baranov Georgy K. Fukin Gleb A. Abakumov 《无机化学与普通化学杂志》2017,643(19):1208-1214
3a,6a‐Diaza‐1,4‐diphosphapentalene (DDP) reacts with hexachlorocyclopentadiene to form a stable adduct (ClC)4C=DDP ( 4 ). The phosphorus atom involved into coordination has a pyramidal arrangement but retains partial double bonding with carbon [1.752(3) Å]. At the same time, the P–N bond remains covalent [1.824(3) Å]. The adduct 4 is better described as a zwitterionic compound with strongly delocalized positive and negative charges. A similar zwitterionic adduct DDP=C(CN)2 was prepared by the reactions of dichloro‐DDP ( 7 ) with malononitrile in the presence of Et3N. DFT calculations showed that related structures are formed in the case of the substituents (ClC)4C=, (HC)4C=, (NC)2C=, and (MeCO)2C=, possessing electron‐delocalizing properties. Compounds with other R2C groups (R = Ph, Me, C6F5, Cl), possessing electronegative properties as well, but insufficient e‐delocalization, demonstrate the noncovalent P–N bonding and a little shorter R2C–P bond lengths (ca. 1.70 Å). 相似文献
287.
C. Dupaix D. Hilhorst I. N. Kostin 《Journal of Dynamics and Differential Equations》1999,11(2):333-353
We consider the one-dimensional viscous Cahn–Hilliard equation with Dirichlet boundary conditions as the limit of a corresponding Dirichlet boundary value problem for the phase field model and we prove the convergence of the attractor. No assumption on the hyperbolicity of the stationary solutions is made. 相似文献
288.
Anna M. Timofeeva Irina A. Kostrikina Pavel S. Dmitrenok Svetlana E. Soboleva Georgy A. Nevinsky 《Molecules (Basel, Switzerland)》2021,26(18)
In contrast to many human organs, only the human liver can self-regenerate, to some degree. Some marine echinoderms are convenient objects for studying the processes of regenerations of organs and tissues. For example, sea cucumbers Eupentacta fraudatrix can completely restore within several weeks, the internal organs and the whole body after their division into two or three parts. Therefore, these cucumbers are a very convenient model for studying the general mechanisms of regeneration. However, there is no literature data yet on which biomolecules of these cucumbers can stimulate the regeneration of organs and the whole-body processes. Studying the mechanisms of restoration is very important for modern biology and medicine, since it can help researchers to understand which proteins, enzymes, hormones, or possible complexes can play an essential role in regeneration. This work is the first to analyze the possible content of very stable protein complexes in sea cucumbers Eupentacta fraudatrix. It has been shown that their organisms contain a very stable multiprotein complex of about 2000 kDa. This complex contains 15 proteins with molecular masses (MMs) >10 kDa and 21 small proteins and peptides with MMs 2.0–8.6 kDa. It is effectively destroyed only in the presence of 3.0 M MgCl2 and, to a lesser extent, 3.0 M NaCl, while the best dissociation occurs in the presence of 8.0 M urea + 0.1 M EDTA. Our data indicate that forming a very stable proteins complex occurs due to the combination of bridges formed by metal ions, electrostatic contacts, and hydrogen bonds. 相似文献
289.
290.
Tatjana S. Pochekutova Vyacheslav K. KhamylovYury A. Kurskii Georgy K. FukinBoris I. Petrov 《Polyhedron》2010
The preparation of the barium β-diketonate complexes with crown-ethers [Ba(pta)2(18-crown-6)] (1), [Ba(pta)2(18-crown-6)] (THF) (2), [Ba(pta)2(18-dibenzocrown-6)](C6H5CH3) (3), [Ba(pta)2(18-dibenzocrown-6)] (4) (pta = 1,1,1-trifluoro-5,5-dimethylhexanedionato-2,4; 18-crown-6 = 1,4,7,10,13,16-hexaoxacyclooctadecane; 18-dibenzocrown-6 = 6,7,9,10,17,18,20,21-octahydrodibenzo[b,k][1,4,7,10,13,16]-hexaoxacyclooctadecane) is described. The complexes 1 and 2 have been synthesized from reaction of metallic barium with 2 molar equiv. of Hpta and 1 molar equiv. of 18-crown-6 in toluene; the complexes 3 and 4 from reaction of Ba(OH)2·8H2O with 1 molar equiv. 18-dibenzocrown-6 and 2 molar equiv. Hpta. The complexes were characterized by elemental analyses, IR-spectroscopy, 1H NMR spectroscopy. The crystal structures of 2 and 3 were determined by means of single-crystal X-ray diffraction methods. A single-crystal X-ray study of 2 and 3 has shown it be monomeric. The coordination number of Barium cation in 2 and 3 is nine owing to nine oxygen atoms from two pta ligands and crown-ether molecule. 相似文献