Chemistry of Ketoacetals: II. β,β′-Ketodiacetal and β,β′-Hydroxydiacetals in Reactions with Amminia and Amines

β,β′-Ketodiacetal and β,β′-hydroxydiacetals react with ammonium acetate in acetic acid to afford substituted pyridine, and with aromatic amines in the presence of hydrochloric acid form substituted pentamethine salts.     

Chemical transformations of diazoles in the reactions of carboxylation, N-siloxycarbonylation, and transsilylation

The behavior of 3,5-dimethylpyrazole, 3(5)-methylpyrazole, imidazole and their trimethyl-silyl derivatives in carboxylation, N-siloxycarbonylation, and transsilylation reactions was studied. A new Nsiloxycarbonylation reagent, diazole trimethylsilyl derivative-carbon dioxide, was found. This reagent makes it possible to obtain easily O-silylurethanes starting from primary, secondary amines and hydrazine derivatives, as well as to develop a convenient one pot synthesis method for trimethylsiloxycarbonyldiazoles.     

Investigation of the structure and energetics ofΒ-diketonates. VII. Molecular structure of Ga(DPM)3 according to gas phase electron diffraction data

A combined electron diffraction and mass spectrometric study of the saturated vapor over gallium tris-dipivaloylmethanate was performed. It was found that the vapor contains only the monomeric molecules Ga(DPM)₃ of C₃ symmetry, for which the r_a, r_g,and r_a parameters were determined. The force constant f(Ga-O) was estimated from the experimental value of the vibration amplitude 1(Ga-O). 1999.     

Evolution of ( La 1 - y Pr y ) 0.7 Ca 0.3 MnO 3 crystal structure with A-cation size, temperature, and oxygen isotope substitution

The atomic structure of ( La _{1 - y} Pr _y ) _0.7 Ca _0.3 MnO ₃ compound with 0.5≤ y ≤1 has been systematically studied by neutron powder diffraction in the temperature range from 15 to 293 K. For composition with y = 0.75, the structural analysis was performed on two samples, one containing the natural mixture of oxygen isotopes and the other one 75% enriched by ¹⁸ O. The room temperature structural characteristics of the series, including cell volume, average Mn-O bond distance, and average Mn-O-Mn bond angle, are the linear functions of the < r _A >. Temperature dependencies of these parameters are quite smooth, except for the point T = T _FM , where a jump like changes occur. The isotope enriched samples have been found identical in crystal and magnetic structure down to the temperature of transition of the sample with ¹⁶ O into the metallic ferromagnetic phase. It confirms that different transport and magnetic properties of the samples with ¹⁶ O and ¹⁸ O at low temperature are driven by the different oxygen atoms dynamics solely. Temperature dependencies of the CO and AFM diffraction peak intensities and of the peak widths for compositions close to the metal-insulator boundary ( y ≈ 0.75) indicate the macroscopically phase separated AFM-dielectric + FM-metallic state below T _FM . Received 28 April 2000     

Structure and energetics of β-diketonates. IX. Molecular structure of Sr(DPM)2 according to gas phase electron diffraction data

Simultaneous electron diffraction and mass spectrometric investigation of overheated vapor of strontium dipivaloyl methanate was carned out. It was found that at 437(5)°C one molecular form, Sr(DPM)₂, prevails in the vapor. The r_a, r_g, and r_α structural parameters of the Sr(DPM)₂ monomeric molecule were determined; the molecule was found to have D_2d symmetry. The structural characteristics are compared in the series Ca(DPM)₂—Sr(DPM)₂—Ba(DPM)₂.     

Co (III) ions high-spin configuration in nonstoichiometric Co3O4 films

Optical spectra in UV, visible and near IR wave-length range have been measured and the SCF X_∝SW method calculation of Co₃O₄ electronic structure has been carried out. The nature of absorption bands observed has been revealed. As shown, the principal peculiarity of the nonstoichiometric films electronic structure compared with “bulk” samples is a stabilization of Co(III) ions high-spin configuration in Co₃O₄ spinel octahedral sublattice.