Reactions of allenylphosphonates with 1,2-diaminoethane

The reactions of dialkyl 3-methylbuta-1,2-dien-1-ylphosphonates with 1,2-diaminoethane lead to the formation of symmetrical N,N′-bis(1-dialkoxyphosphoryl-3-methylbut-1-en-2-yl)-1,2-diaminoethanes.     

Reaction of hydroxyiminoacetophenone withp-toluenesulfonyl chloride and an X-ray diffraction study of the reaction product

2-Benzoyloxy-2-phenylmalononitrile is formed instead of the expected oxime tosylate in the reaction of hydroxyiminoacetophenone withp-toluenesulfonyl chloride. The structure of the product was confirmed unambiguously by X-ray diffraction analysis. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 872–874, April, 1997.     

X-ray diffraction study of the structure of carboxymethylcellulose-cationic surfactant complexes.

We have investigated dilute aqueous solutions of an anionic polymer (carboxymethylcellulose) mixed with cationic surfactants of different chain lengths (dodecyl to octadecyl trimethylammonium bromides: DTAB, TTAB, CTAB and OTAB). The structures of the concentrated phases formed above the precipitation threshold were studied by X-ray diffraction. Different body-centred cubic structures with space groups Pm3n were observed in the presence of surfactant with a short aliphatic chain (DTAB), despite the fact that the polymer persistence length is comparable to the repeat distance of the structure (5 nm). For larger surfactant chain lengths (TTAB and CTAB), the structure of the precipitates can be either cubic (Pm3n) or 2D hexagonal depending on the initial surfactant and polymer concentrations. For still larger chain length (OTAB), the structure becomes lamellar. This structural evolution from micellar cubic towards 2D hexagonal and lamellar is attributed to the decrease of the local curvature of the surfactant aggregates, as observed for flexible synthetic polymers and short DNA fragments under similar conditions. Furthermore, the structure of the bulk complexes formed just below the precipitation threshold anticipates the structure seen in the precipitated phases.     

Acylation of pyrrolyltricarbonylmanganese. Structure of the acylation product

The acylation of pyrrolyltricarbonylmanganese (PTM) is studied. The reaction proceeds in an unusual manner; introduction of an acetyl group into the α-position of the PTM pyrrolyl ligand is accompanied by extensive rearrangement of bonds resulting in the formation of a binuclear complex (π-C₄H₄N)Mn(CO)₃(CH₃COC₄H₃N)Mn(CO)₃ (I)Coordination of the acetylpyrrolyl ligand to the manganese atom is of the chelate type and involves atoms of heterocyclic nitrogen and of acetyl oxygen. The ligand, therefore, is not a five-electron but a three-electron donor. The manganese atom is additionally coordinated to three carbonyl groups and one molecule of the initial PTM (by a donor—acceptor bond through a nitrogen atom), thus acquiring a 18-electron shell. A scheme for complex I formation is proposed.     

X-ray diffraction study of the structure of Al-Co melts

The structure of Al-Co melts with 0 at.%, 10 at.%, 18 at.%, 23.5 at.%, 26 at.%, 80.7 at.%, and 100 at.% Co has been studied by X-ray diffraction. Inverse Monte Carlo simulation using the experimental curves of the structural factor was employed to reconstruct the models of melts, analyzed by the Voronoi-Delaunay technique. The dependence of parameters that define short-and longer range ordering of atoms is nonmonotonous in the range 85–74 at.% Al and is extremal in the vicinity of a melt with 76.5 at.% Al. In the stated range of concentrations, the cobalt atoms basically lie at distances of ≈4.2 Å in the pentagonal rings of icosahedral type polytetrahedral clusters. Therefore one can speak about correlation in the character of atomic ordering in melts and corresponding periodic and quasiperiodic phases.     

X-ray diffraction study of Raney nickel catalyst structure

X-ray diffraction studies have revealed that the modification of Raney nickel catalysts by iron leads to formation of Ni–Fe solid solution, whereas modification by chromium and titanium produces Cr₂O₃ and TiO₂. The higher dispersity of chromium — and especially of titanium-promoted catalysts is ascribed to the interaction of nickel with oxide components.

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, Ni–Fe, Cr₂O₃ TiO₂-, . , , .

     

The structure of benzoyldimedone from X-ray diffraction analysis

The structure of benzoyldimedone was established by X-ray diffraction analysis. The only tautomer was found. In this tautomer, the enol proton is covalently bound to the oxygen atom that is remote from the phenyl group. The role of steric and electronic factors in stabilization of the enol structure is analyzed. The geometric characteristics of the ring formed through an intramolecular hydrogen bond are discussed. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1074–1076, June, 2000.     

X-ray diffraction analysis of the fine structure of carbon fiber

X-ray diffraction analysis showed that the material of carbon fibers prepared from polyacrylonitrile is heterogeneous. Its component composition is determined by the fiber preparation conditions and depends on the angle at which the coherent scattering domains are oriented relative to the thread axis. The size of coherent scattering domains increases in going to components corresponding to lower d₀₀₂ values and depends on the orientation angle φ relative to the thread axis.     

X-ray diffraction investigations of the structure of concentrated ionic solutions

Concentrated aqueous solutions of inorganic salts of indium with halogen anions were investigated. The existence of a liquid-type quasi-close-packing of complexed cations is considered for interpreting the X-ray patterns of aqueous solutions for which the concentration of the salts approaches saturation at room temperature and pressure.     

An electron diffraction study of the molecular structure of 1,2-difluoroethane

The molecular structure of 1,2-difluoroethane in the gas phase has been determined by electron diffraction at room temperature. Only the gauche conformation was found, the dihedral angle F-C-C-F is 74.5°. The bond lengths r_g(1) are: r(C-C) = 1.535 Å, r(C-F) = 1.394 Å, r(C-H) = 1.13 Å. The valency angles are: α(C-C-F) = 108.3, α(C-C-H) = 108.3. The dihedral angle between the C-C-F and C-C-H planes is 113.6°.     

X-ray diffraction investigations of the structure of concentrated ionic solutions

A liquid-type quasi-close-packing of molecular aggregates [In(NO₃)₂(H₂O)₄]⁺ is suggested as a model to interpret the scattered X-ray intensity of 2.27, 1.30, and 3.96 M aqueous solutions of indium nitrate; but the existence of another packing in the less concentrated solutions may not be excluded. Three different molecular models were tested to obtain agreement between the observed and calculated intensity, from s = (4π/λ)sinθ ≈ 0.7 to 13.0 Å⁻¹ for 2.27 and 1.30 M aqueous solutions.     

Effect of concentration on the structure of aqueous solutions of gadolinium chloride and gadolinium nitrate as probed by X-ray diffraction

Aqueous solutions of gadolinium chloride and gadolinium nitrate are studied by X-ray diffraction over wide ranges of concentrations under standard temperature and pressure. Small-angle peaks on measured scattering intensity curves are interpreted. Small-angle peaks are found not only on the intensity curves for concentrated solutions, but also on those for dilute systems, and this proves that these systems retain a long-range order. Diverse types of ion-ion interactions are shown to be the major contributors to the overall scattering pattern that are responsible for the appearance of pre-peaks.     

Cascade reaction of imines with phenylsulfinylallene. X-ray structure of the product and its formation mechanism

The structure of the product derived from the reaction of a dihydropyridine derivative with phenylsulfinylallene has been clarified by a single crystal X-ray analysis and the formation mechanism is discussed on the basis of the reaction-path calculations by semiempirical and ab initio molecular orbital methods.     

Syntheses, characterization and solid state thermal studies of N-propyl-1,2-diaminoethane (L) and N-isopropyl-1,2-diaminoethane (L′) complexes of nickel(II) nitrite: X-ray single crystal structure of trans-[NiL2(NO2)2]

Linkage isomers trans-bis(N-propyl-1,2-diaminoethane)dinitronickel(II) (brown, 1), trans-bis(N-isopropyl-1,2-diaminoethane)dinitritonickel(II) (blue-violet, 2a) and trans-bis(N-isopropyl-1,2-diaminoethane)dinitronickel(II) (brown, 2b) have been synthesized from solution and X-ray single crystal structure analysis of complex (1) has been performed. Simultaneous TG-DTA analyses reveal that complex (1) exhibits two successive phase transitions before to undergo decomposition (initial temperature of decomposition, Ti = 215 °C). The first one is reversible (82–98 °C; ΔH = 1.75 kJ mol⁻¹ for heating and 93–77 °C; ΔH = −1.65 kJ mol⁻¹ for cooling) and the second one is irreversible endothermic (135–150 °C kJ mol⁻¹; ΔH = 1.80 kJ mol⁻¹) phase transition. No visual color changes are observed in any of the two transitions. The causes related to the first phase transition remain unexplored. However, on the basis of IR spectral studies the second phase transition is supposed to be due to conformational changes of the diamine chelate rings. On the other hand, complexes (2a) and (2b) undergo decomposition without showing any phase transition [Ti = 185 and 195 °C for (2a) and (2b), respectively].