The study of molecular motions in substituted ferrocenes by means of NMR spectroscopy

The proton magnetic resonance spectra for ferrocene derivatives have been investigated in the solid state at a frequency of 27.5 MHz and at temperatures within the range 4.2–300 K. Evidence for re-orientation in various substituent groups and cyclopentadienyl rings has been deduced on the basis of the temperature dependence of the second moment of the PMR lines. The experimentally observed decrease in the second moment has been compared with the calculated contributions of different molecular groups to the second moment thus enabling an identification of these groups. In computing the second moment, account has been taken of both intra- and intermolecular dipole-dipole interactions. It is shown that the introduction of substituents into some ferrocene rings affects the magnitude of the re-orientation energy for both the substituted and unsubstituted rings. The change of the re-orientation energy of the substituted and unsubstituted rings in substituted ferrocenes with the structure and electronic properties of the substituents is discussed.     

Stereochemical non-rigidity of N-(dimethylhalogenosilylmethyl)-N-(1-phenylethyl) acetamides in solutions

The structure and dynamic behavior of (O-Si)-chelate N-(dimethylhalogenosilyl)methyl acetamides of the type MeC(O)N(CH(Ph)Me)CH₂ SiMe₂ X, where X = F, Cl, Br with the OSiC₃X coordination set, were studied by multinuclear (¹H, ¹³C, ¹⁷O, ²⁹Si) and dynamic ¹H NMR spectroscopy. Ligand permutation at silicon was detected. The observed influence of the solvent, nucleofugacity of the X substituent and the external nucleophile on the calculated values of the free energies of activation testify to the dissociative and/or associative mechanisms of the process, but including the stages in which the regular (pseudo-rotation or ‘turnstile’) mechanism takes place. At lower temperatures (up to −90°C) the ¹H, ¹³C, ²⁹Si NMR spectra of N-(dimethylchlorosilyl)methyl acetamide contain the signals of two species of unequal intensity. This effect was explained by an equilibrium between monomers containing the intramolecular O → Si bond and dimers with a hexacoordinate silicon and the bridging chlorine atoms.     

Crystal and molecular structures of Ni[(iso-C4H9)2PS2]2 and Pd[(iso-C4H9)2PS2]2 chelates

Crystal structures of chelate compounds Ni[(iso-C₄H₉)₂PS₂]₂ (I) and Pd[(iso-C₄H₉)₂PS₂]₂ (II) have been determined by X-ray diffraction: diffractometer X8-APEX, MoK _α∔ -radiation, 1048 F _hkl , R = 0.0544 for I and CAD-4 diffractometer, MoK _α∔ -radiation, 1283 F _hkl , R = 0.0347 for II. The crystals are rhombic: a = 12.921(5) Å, b = 17.094(5) Å, c = 22.971(5) Å; V = 5074(3) ų, Z = 8, calc = 1.250 g/cm³, space group Pbca for I and a = 13.312(3) Å, b = 16.130(7) Å, c = 23.171(5) Å; V = 4975(3) ų, Z = 8, ρ_calc = 1. 208 g/cm³, space group Pbca for II. The structures of I and II are formed by discrete mononuclear molecules. Coordination cores MS₄ (M = Ni, Pd) approach planar square configurations. Original Russian Text Copyright ? 2005 by L. A. Glinskaya, T. G. Leonova, T. E. Kokina, R. F. Klevtsova, and S. V. Larionov __________ Translated from Zhurnal Strukturnoi Khimii, Vol. 46, No. 4, pp. 715–720, July–August, 2005.     

Effect of the Nature of a Sodium-Conducting Solid Electrolyte on the Impedance of Its Interface with the SmCo0.8Ti0.2O3 Oxide Electrode in an Oxygen Atmosphere

Impedance spectroscopy is employed for studying the behavior of the interface of the SmCo_0.8Ti_0.2O₃ semiconducting oxide electrode with a sodium-conducting solid electrolyte (Na⁺–SE) in atmospheres of argon and oxygen. Compounds with the susceptibility to hydration decreasing in the row Na₅TbSi₄O₁₂ Na₃Zr₂Si₂PO₁₂ Na₃Sc₂(PO₄)₃ are used as the Na⁺–SE. Only the systems containing the Na₅TbSi₄O₁₂ solid electrolyte, the grain surfaces of which acquire boundary layers formed by hydration products, are sensitive to oxygen. The exchange current of the electrode reaction O₂ (g) + e O₂ ^– increases from 1.8 to 19 mA/cm² in the temperature interval 250–300°C. The systems with Na⁺–SE that are not prone to hydration remain inactive in the oxygen atmosphere probably due to quick blocking of the active centers by nonconducting products of the secondary chemical reaction Na⁺ + O₂ ^– NaO₂.     

Formation of primary particles in stopped pion absorption reactions

The results from analyzing the yields of protons (p), deuterons (d), and tritons (t) formed in the absorption of stopped π^– mesons by intranuclear clusters are presented. The contributions from cluster absorption to the production of hydrogen isotopes in stopped pion absorption reactions are determined. Phenomenological formulas are proposed for describing the mass number (A) dependences of the yields of the primary protons with ～15% precision in the mass number range of 6 < A < 209 (and of the primary deuterons and tritons in the mass number range of 59 < A < 209). Evidence is observed of the constancy of the ratio between the elemental absorption widths for the absorption of pions by pp and pn pairs over the investigated range of mass numbers.     

3-Hydroxyphenyl derivatives of pyrazolines and tetrahydropyridazines in a catalytic decomposition reaction

The isomeric 3-(hydroxyphenyl)-1,4,5,6-tetrahydropyridazines differ from their five-membered-ring analogs, the 3-(hydroxyphenyl)-²-pyrazolines, in their behavior in catalytic-decomposition reactions. The catalytic conversion of 3- (hydroxyphenyl)-1,4,5,6-tetrahydropyridazines takes place at 120–200° C, dehydrogenation being the main reaction. The hydroxyphenylpyrazolines, under the same conditions, undergo decomposition with liberation of nitrogen and formation of the corresponding cyclopropanes.Translated from Khimiya Geterotsiklicheskikh Soedinenii, Vol. 6, No. 5, pp. 657–659, May, 1970.     

Catalytic approach to the estimation of the influence of carbon nanomaterial structures on surface functional groups

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