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1.
Kraikivskii P. B. Saraev V. V. Matveev D. A. Zelinskii S. N. Tkach V. S. 《Russian Journal of Coordination Chemistry》2003,29(6):431-434
Reactions of aluminium tribromide with the Ni(0) phosphine and phosphite complexes are studied by EPR method. AlBr3was found to cause the oxidation of the transition metal in the (PPh3)4Ni complex to the univalent state with the formation of the tetracoordinated (PPh3)3NiBr complex. With an excess of AlBr3, the phosphine ligands are eliminated from the coordination sphere of Ni(I), and the coordinatively unsaturated complexes are destroyed to give the colloidal nickel. In the reaction of (P(OEt)3)4Ni with AlBr3, Ni(0) is also oxidized to Ni(I), but the acido ligand is not eliminated even with a 15-fold excess of the Lewis acid. The activity of catalytic systems on the basis of the Ni(0) phosphine complexes and the Lewis acids in the low-molecular oligomerization reactions of olefines is determined by the cationic coordinatively unsaturated Ni(I) complexes formed in these systems. 相似文献
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Peter B. Kraikivskii Vitaly V. Saraev Galina V. Romanenko Dmitrii A. Matveev 《Journal of organometallic chemistry》2011,696(22):3483-3490
It has been shown that the reaction of Ni(allyl)2 with (2,6-diisopropylphenyl)diazabutadiene gives the imino-amide Ni complex (1). The imino-amide moiety of this complex undergoes some complicated rearrangements resulting in spontaneous formation of a paramagnetic π-allyl Ni(I) complex. Nickel complexes formed in the system have been studied with ESR, FTIR, 2D NMR, and mass spectrometry. The structure of complex 1 was studied with X-ray diffraction. 相似文献
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V. V. Saraev P. B. Kraikivskii V. V. Annenkov A. I. Vil'ms D. A. Matveev E. N. Danilovtseva T. G. Ermakova N. P. Kuznetsova K. Lammertsma 《Kinetics and Catalysis》2005,46(5):712-718
The interaction of the [Ni(PPh3)3]BF4 complex with styrene and the products of styrene conversion in the polymerization reaction were studied by EPR and 13C NMR spectroscopy. The structure of the σ-carbocationic complex of Ni(I) formed by the interaction of styrene with the [Ni(PPh3)3]BF4 cationic phosphine complex of Ni(I) was characterized in detail. It was found that the reaction of styrene polymerization occurred with the participation of the coordination center of the σ-carbocationic complex (coordination catalysis), whereas the reaction of telomerization occurred with the participation of the cationic center of this complex (ionic catalysis). The resulting polymer contained active terminal double bonds; it is a promising macromonomer for the synthesis of grafted copolymers. The discovered capacity of alcohols to undergo nucleophilic addition to a growing polymer chain offers strong possibilities for preparing functional polymers and block copolymers. 相似文献
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Saraev V. V. Kraikivskii P. B. Zelinskii S. N. Ratovskii G. V. Tkach V. S. Shmidt F. K. 《Russian Journal of Coordination Chemistry》2001,27(11):757-762
The reactions of the individual cationic complex [(PPh3)3Ni]BF4with unsaturated hydrocarbons (ethene, propene, and styrene), as well as the reaction of the -alkyl Ni(I) complex (PPh3)2Ni–CH(COOC2H5)2(obtained in situ) with ethene, were studied using EPR, UV, and NMR spectroscopy. It was found that stable dimeric carbocationic -alkyl Ni(I) complexes are intermediates in the reactions of unsaturated hydrocarbons with cationic Ni(I) complexes. The transformations of unsaturated hydrocarbons on cationic Ni(I) complexes were explained in terms of an experimentally justified ionic coordination mechanism. A stable mononuclear Ni(I) complex with a Ni–C -bond was synthesized and characterized using EPR. An organonickel(I) complex with - and -bonded carbon atoms was identified using EPR and NMR methods. 相似文献
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Computational fluid dynamics, where simulations require largecomputation times, is one of the areas of application of highperformance computing. Schemes such as the SIMPLE (semi-implicitmethod for pressure-linked equations) algorithm are often usedto solve the discrete Navier-Stokes equations. Generally theseschemes take a short time per iteration but require a largenumber of iterations. For simple geometries (or coarser grids)the overall CPU time is small. However, for finer grids or morecomplex geometries the increase in the number of iterationsmay be a drawback and the decoupling of the differential equationsinvolved implies a slow convergence of rotationally dominatedproblems that can be very time consuming for realistic applications.So we analyze here another approach, DIRECTO, that solves theequations in a coupled way. With recent advances in hardwaretechnology and software design, it became possible to solvecoupled Navier-Stokes systems, which are more robust but implyincreasing computational requirements (both in terms of memoryand CPU time). Two approaches are described here (band blockLU factorization and preconditioned GMRES) for the linear solverrequired by the DIRECTO algorithm that solves the fluid flowequations as a coupled system. Comparisons of the effectivenessof incomplete factorization preconditioners applied to the GMRES(generalized minimum residual) method are shown. Some numericalresults are presented showing that it is possible to minimizeconsiderably the CPU time of the coupled approach so that itcan be faster than the decoupled one. 相似文献
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Rare earth element substituted bismuth ferrites (BiFeO3) are of enormous importance as magnetoelectric materials. The polycrystalline samples of Bi
x
La1−x
FeO3 (x=0, 0.2, 0.4, 0.6, 0.8) were prepared by solid-state reaction using standard ceramic method. The single-phase formation of
these compounds was confirmed by X-ray diffraction (XRD) studies. The samples with x=0, 0.2, 0.4, 0.6 are found to be orthorhombic while the sample with x=0.8 is triclinic. The dielectric constant (ε′) and dissipation factor (tan δ) were measured in the frequency range 100 Hz
to 1 MHz at room temperature and as a function of temperature at certain fixed frequencies (1 kHz, 10 kHz, 100 kHz, 1 MHz).
All the samples showed dielectric dispersion. The dielectric constant with temperature shows a broad peak; the peak temperature
shifts with frequency which reflects the relaxor-type behavior. The peak above 600 K in the measured temperature range corresponds
to antiferromagnetic ordering temperature (Néel temperature). The broadness of the peak changes with composition. The ac conductivity
as well as ε′ are found to be maximum for the sample x=0.2 at room temperature. 相似文献
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Saraev VV Kraikivskii PB Svoboda I Kuzakov AS Jordan RF 《The journal of physical chemistry. A》2008,112(48):12449-12455
The compound [Ni(PPh(3))(3)][BF(4)] x BF(3) x OEt(2) was isolated in crystalline form from the olefin oligomerization catalyst system Ni(PPh(3))(4)/BF(3) x OEt(2) and structurally characterized by X-ray diffraction. The influence of vibronic coupling on the EPR parameters of three-coordinate metal complexes with a 3d(9) electronic configuration was investigated within the framework of ligand field theory. Analytical expressions for g-tensor components and isotropic hyperfine coupling constants with ligand nuclei were obtained using first-order perturbation theory. It has been shown that the account of the vibronic interaction in the excited state predicts the existence of three-axial anisotropy of the g-tensor even at the level of first-order perturbation theory; two axes of the g-tensor located in a plane of three-coordinate structure can rotate about the main z axis when a compound is distorted by motion of ligands. It has been shown that in three points of the potential energy surface minimum, for which linear and quadric constants of the vibronic interactions have an identical signs, the HFS isotropic constant from one ligand is larger than HFS constants from the other two; for different vibronic constant signs the ratio between HFS constants varies on opposite. This theoretical researches are in the quality consent with experimental data for a three-coordinate Ni(I) and Cu(II) flat complexes. 相似文献