Raman and infrared spectra of6Li2C2O4 and7Li2C2O4

Raman and infrared spectra of polycrystalline⁶Li₂C₂O₄ and⁷Li₂C₂O₄ have been investigated in the wavenumber region from 1,800 to 40 cm^–1. The internal C₂O₄ ^–2 vibrations have been studied on the basis of a D_2h molecular structure and the correlation field splittings have been found to be about 40 cm^–1 for the stretching modes and about 15 cm^–1 for the bending modes. The external vibrations of the Li⁺ and C₂O₄ ^–2 sites have been discussed by considering the results of the factor group analysis and the⁶Li/⁷Li isotope effect on the normal vibrations.

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Raman- und Infrarot-Spektren von⁶Li₂C₂O₄ und⁷Li₂C₂O₄

Zusammenfassung Es wurdenRaman- und IR-Spektren von polykristallinem⁶Li₂C₂O₄ und⁷Li₂C₂O₄ im Bereich der Wellenzahlen von 1800 bis 40 cm^–1 untersucht. Die internen Schwingungen wurden auf der Basis einer D_2h Molekülstruktur analysiert. Für die Streckschwingungen wurde eine Korrelationsaufspaltung von etwa 40 cm^–1 gefunden, für die Deformationsschwingungen etwa 15 cm^–1. Die Diskussion der externen Schwingungen von Li⁺ und C₂O₄ ^–2 erfolgte unter Berücksichtigung der Resultate der Faktorgruppenanalyse und des⁶Li/⁷Li Isotopeneffekts auf die Normalschwingungen.

     

Topotactic formation and exchange reactions of hydrated layered tin sulfides A x (H2O) y SnS2

Reduction of tin disulfide SnS₂ leads in a reversible topotactic reaction to the formation of layered hydrated phases A _x ⁺ (H₂O)_y[SnS₂]^x–. The latter exhibit polyelectrolyte character, i. e. ion exchange and solvent exchange reactions as a consequence of the high mobility of the interlayer species. Structure and properties of the tin sulfide hydrates are closely related to those of transition metal dichalcogenide hydrates.

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Topotaktische Bildung und Austauschreaktionen von hydratisierten Zinnsulfiden A_x(H₂O)_ySnS₂ mit Schichtstruktur

Zusammenfassung Die Reduktion von Zinndisulfid führt in einer reversiblen topotaktischen Reaktion zur Ausbildung von hydratisierten Phasen A _x ⁺ (H₂O)_y[SnS₂]^x– mit Schichtengitterstruktur. Diese weisen Polyelektrolytcharakter auf, d.h. sie zeigen Ionenaustausch- und Lösungsmittelaustausch-Reaktionen als eine Folge der großen Beweglichkeit der Moleküle zwischen den Schichten. Struktur und Eigenschaften der Zinnsulfid-Hydrate stehen denen der Übergangsmetalldichalkogenid-Hydrate sehr nahe.

     

Die Systeme Tl3SbS3-Tl3AsS3 und TlSbS2-TlAsS2

The influence of structural relationships between the components of (pseudo)binary systems with no intermediate compounds on the type of phase diagram was investigated. Structurally and chemically closely related Tl₃SbS₃ and Tl₃AsS₃ form a complete solid solution series whereas crystallographically different TlSbS₂ and TlAsS₂ constitute an eutectic type system.

     

The vibrational spectra of linear and branched perchlorosilanes Si n Cl2n+2 and their simulation using a local symmetry force field

Infrared andRaman vibrational spectra ofn-Si₄Cl₁₀,n-Si₅Cl₁₂,neo-Si₅Cl₁₂ and [(SiCl₃)₃Si]₂ have been measured and assigned. A local symmetry force field has been developed to simulate vibrational spectra of all (noncyclic) perchlorosilanes Si _n Cl_2n+2 known today (n=2, 3, 4, 5, 8). The observed spectra are reproduced satisfactorily

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Die Vibrationsspektren linearer und verzweigter PerchlorsilaneSi _n Cl _2n+2 und deren Simulierung mittels eines lokalen Symmetrie-Kraftfeldes

Zusammenfassung Infrarot- undRaman-Spektren vonn-Si₄Cl₁₀,n-Si₅Cl₁₂,neo-Si₅Cl₁₂ und [(SiCl₃)₃Si]₂ wurden aufgenommen und zugeordnet. Ein lokales Symmetrie-Kraftfeld zur Simulation der Spektren aller bisher bekannten (nicht cyclischen) Perchlorsilane Si _n Cl_2n+2 (n=2, 3, 4, 5, 8) wird angegeben. Die beobachteten Spektren werden zufriedenstellend reproduziert

     

Magnetische Eigenschaften von Hf2Fe und Hf2FeH x

The weakly temperature dependent paramagnetic compound Hf₂Fe becomes ferromagnetic by hydrogen absorption, theCurie-temperature of the resulting hydrides depends on the hydrogen content.

     

Die Kristallstruktur der isotypen Verbindungen KAg(NO3)2, NH4Ag(NO3)2 und RbAg(NO3)2

KAg(NO₃)₂ crystallizes in space group P2₁/a-C _2h ⁵ ,a=13.953,b=4.955,c=8.220 Å, =97.76°,Z=4. X-ray intensities were collected with a two-circle diffractometer. The structure was solved by means of direct methods andFourier syntheses and was refined by the least squares method toR=0.034 with 1346 observed reflexions. ¹ {Ag₂(NO₃)₄}^2–-chains run parallel toy and are linked by potassium ions. Ag shows a distorted tetrahedral coordination with four relatively close O. K is irregularily surrounded by ten O. The isotypic compounds NH₄Ag(NO₃)₂ and RbAg(NO₃)₂ were refined toR=0.032 and 0.035, respectively. The coordination figures are compareable with those in KAg(NO₃)₂.

     

Kolbe-Schmitt reaction of sodium 2-naphthoxide

The mechanism of the Kolbe-Schmitt reaction of sodium 2-naphthoxide is examined by means of the B3LYP/LANL2DZ method. After the initial formation of sodium 2-naphthoxide-CO₂ complex, the carbon of the CO₂ moiety performs an electrophilic attack on the naphthalene ring. Further transformations lead to the formation of sodium 2-hydroxy-1-naphthoate. Sodium 3-hydroxy-2-naphthoate is formed by a 1,3-rearrangement of the CO₂Na group. Our findings are in good agreement with the experimental results on the carboxylation reaction of sodium 2-naphthoxide. Correspondence: Svetlana Marković, Faculty of Science, University of Kragujevac, 34000 Kragujevac, Serbia     

Die Kristallstruktur von TlFeSe2 und TlFeS2

TlFeSe₂ is monoclinic, space groupC2/m–C _2h ³ ,a=11.973 Å,b=5.490 Å,c=7.110 Å, =118.2°,Z=4.TlFeS₂ is isotypic witha=11.636 Å,b=5.304 Å,c=6.799 Å, =116.7°.The crystal structure of TlFeSe₂ has been determined from single crystal diffractometer data. Isotypy of the sulfide has been confirmed from powder diffraction data. The crystal structure containing infinite linear chains of edgesharing FeX ₄-tetrahedra, and its relationship to the thio- and selenoferrates of the alkali metals are discussed. The mineral raguinite is very probably isotypic to synthetic TlFeS₂.

     

Thermal deamination of some complexes of the type [CO(Diox·H)2 (Amine)2]X

The thermal deamination of [Co(diox·H)₂(amine)₂]X type complexes were studied in dynamic temperature conditions (diox·H₂ stands for 1,2-cycloheptanedione dioxime (heptoxime, heptox·H₂) and 1,2-cyclo-octanedione dioxime (octoxime, octox·H₂), amine for aniline and pyridine,X for Br, I and NCS). Kinetic parametersn, E and logZ have been derived for some derivatives by means of two computerized integral methods. The influence of the sample weight, heating rate and chemical constitution upon the kinetic parameters, as well as the kinetic compensation effect are discussed.

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Thermische Desaminierung einiger Komplexe des Typs [Co(Diox·H) ₂ (Amin₂]X. Über -Dioximinkomplexe der Übergangsmetalle, LXIV.

Zusammenfassung Die thermische Desaminierung einiger Komplexe des Typs [Co (Diox·H)₂(Amin)₂]X wurde bei dynamischen Temperaturbedingungen untersucht [Diox·H₂ bedeutet 1,2-Cycloheptandiondioxim, (Heptoxim, Heptox·H₂) und 1,2-Cyclooctandiondioxim (Octoxim, Octox·H₂), Amin bedeutet Anilin und Pyridin,X bedeutet Br, I, bzw. NCS]. Die kinetische Parametern, E und logZ wurden mit Hilfe von zwei computergeeigneten Integralmethoden bestimmt. Der Einfluß des Gewichtes der Proben, der Heizungsgeschwindigkeit und der chemischen Zusammensetzung auf die kinetischen Parameter, bzw. der kinetische Kompensationseffekt werden diskutiert.

     

Spectral studies on single crystal BaBr2−Sn phosphor

The absorption spectra at 300 K, the emission and excitation spectra at 77 K and 300 K of BaBr₂–Sn phosphor have been studied. The complicated structure observed in the absorption and excitation spectra was connected with transitions to the components of the¹P₁,³P₁ and³P₂ excited states in tin centers which preserve the symmetry of the basic lattice. There has also been observed a complicated structure of the emission spectrum at 77 K which unlike all alkali earth halide phosphors observed so far, manifests itself also in the visible region of the spectrum.

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Spektroskopische Untersuchungen an Einkristallen des BaBr₂–Sn-Phosphors

Zusammenfassung Die Absorptions-, Anregungs-und Emissionsspektren des Phosphors BaBr₂–Sn wurden bei 77 K und 300 K gemessen. Die komplizierte Struktur der Absorptions-und Anregungsspektren ist mit Übergängen zu Komponenten der Anregungszustände¹P₁,³P₁ und³P₂ des Sn²⁺ unter der Annahme zu verknüpfen, daß die Zinnzentren die Symmetrie des Grundgitters beibehalten. Für 77 K ist auch das Emissionsspektrum von komplexer Natur, was bis jetzt bei keinem Erdalkalihalogenid-Phosphor im sichtbaren bereich beobachtet wurde.

     

Ein Beitrag zur Kristallchemie der Kobaltoxoniobate: CoNb2O6 mit Rutilstruktur

CoNb₂O₆ can be prepared by reaction of stoichiometric amounts of CoO (thermical decomposition of cobaltoxalate) and Nb₂O₅ in argon-atmosphere up to 1,400 °C. The isolated red-brown single crystals have tetragonal symmetry (a=472.6;c=305.4 pm; space group P4₂/mnm-D _4h ¹⁴ ). Electron probe micro-analysis of the single crystals verifies the composition Co_0.33Nb_0.67O₂. Co²⁺ and Nb⁵⁺ occupy statistically the metal positions of the rutil-type structure. The differences between Co_0.5Nb_0.5O₂ (CoNbO₄AlNbO₄-type) and Co_0.38Nb_0.67O₂ (CoNb₂O₆) are discussed.

     

Thallium silver chalcogenides of the orderedanti-PbCl2-structure type

TlAgS, TlAgSe and TlAgTe crystallize with the orderedanti-PbCl₂-structure type, space group Pnma,Z=4. The lattice constants are: TlAgS:a=722.8(3).b=446.6(1),c=833.1(2)pm. TlAgSe:a=747.56(3),b=463.75(2),c=869.0(1) pm. TlAgTe:a=775.9(1),b=486.8(1),c=877.3(2) pm. The crystal structure of TlAgSe was refined from single crystal diffractometer data to a conventionalR-factor of 0.045. The relationship with the BaCu₂S₂-structure type is discussed.On leave from Institute of Inorganic Chemistry, University of Vienna A-1090, Wien, Austria     

Dampfdruckmessungen und Protonenresonanzuntersuchung an Hydriden der intermetallischen Phasen Ti2(Ni,Co) und Ti2(Ni,Fe)

NMR and hydrogen equilibrium pressure measurements were performed on hydrides of the intermetallic compounds Ti₂(Ni, Co) and Ti₂(Ni, Fe). The following values of enthalpy H and entropy S for the formation of the hydrides of the intermetallic phases Ti₂Co and Ti₂Ni were found: H(Ti₂CoH _y )=–47.6 kJ/mol H₂, H(Ti₂NiH _y )=–53.7 kJ/mol H₂; S(Ti₂CoH _y )=–119.8 J/(K·mol H₂), S(Ti₂NiH _y )=–127.5 J/(K·mol H₂). By substitution of Ni or Co by Fe, the values of H and S of the corresponding quaternary hydrides become less negative. An interpretation of the experimental results is tried by the model ofShaltiel and coworkers.Proton diffusion was investigated in a series of the intermetallic hydrides Ti₂(Ni, Co)H _x and Ti₂(Ni, Fe)H _x . The diffusion rate is lowered by increased Ni/Fe substitution. Substitution of Ni by Co scarcely effects the hopping process. The activation energies were found to be smaller for the Ti₂Ni-hydrides compared with the Ti₂Co-hydrides.

Herrn Prof. Dr.H. Nowotny zum 70. Geburtstag gewidmet.     

Reaction of titanocene dihalides with Na2H2 EDTA. Crystal structure of [Ti(EDTA)(H2O)]

Summary Titanocene complexes ([Ti(⁵-C₅H₄ R)₂ X ₂];R = H, SiMe₃;X=Cl, Br) react with Na₂H₂ EDTA in aqueous methanol to give an identical product ([Ti(EDTA)(H₂O)] by cleavage of the halogen and cyclopentadienyl ligands. The structure of [Ti(EDTA)(H₂O)] has been determined by X-ray diffraction; crystal data: monoclinica=13.923(6),b=7.048(3),c=13.252(5) Å, =90.81(1)°, space groupP2₁/c,Z=4. In this complex, Ti has a sevenfold coordination with a hexadentateEDTA ^4– ligand and a water molecule occupying an additional coordination site.

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Reaktion von Titanocen-Dihalogeniden mit Na₂H₂ EDTA. Kristallstruktur von [Ti(EDTA)(H₂O)]

Zusammenfassung Titanocenkomplexe ([Ti(⁵-C₅H₄ R)₂ X ₂];R=H, SiMe₃;X=Cl, Br) reagieren in wäßrigem Methanol mit Na₂H₂ EDTA unter Verdrängung der Halogen- und Cyclopentadienylliganden zum selben Produkt ([Ti(EDTA)(H₂O)]). Die Struktur von ([Ti(EDTA)(H₂O)]) wurde röntgenographisch bestimmt. Kristalldaten: monoklin,a=13.923(6),b=7.048(3),c=13.252(5) Å, =90.81(1)°, RaumgruppeP2₁/c,Z=4. In diesem Komplex ist das Titanatom mit einem sechszähnigenEDTA-Liganden und einem Wassermolekül, das eine zusätzliche Koordinationsstelle besetzt, siebenfach koordiniert.

     

Theoretical study of structure,vibrational and electronic spectra of isomers of methyl-3-methoxy-2-propenoate

A systematic quantum mechanical study of the possible conformations, their relative stabilities, vibrational and electronic spectra and thermodynamic parameters of methyl-3-methoxy-2-propenoate has been reported for the electronic ground (S₀) and first excited (S₁) states using time-dependent and time-independent Density Functional Theory (DFT) and RHF methods in extended basis sets. Detailed studies have been restricted to the E-isomer, which is found to be substantially more stable than the Z-isomer. Four possible conformers c′Cc, c′Tc, t′Cc, t′Tc, of which the first two are most stable, have been identified in the S₀ and S₁ states. Electronic excitation to S₁ state is accompanied with a reversal in the relative stability of the c′Cc and c′Tc conformers and a substantial reduction in the rotational barrier between them, as compared with the S₀ state. Optimized geometries of these conformers in the S₀ and S₁ states are being reported. Based on suitably scaled RHF/6-31G^** and DFT/6-311G^** calculations, assignments have been provided to the fundamental vibrational bands of both these conformers in terms of frequency, form and intensity of vibrations and potential energy distribution across the symmetry coordinates in the S₀ state. A complete interpretation of the electronic spectra of the conformers has been provided.     

Cp2ZrCl2-catalyzed hydroalumination of norbornene derivatives withi-Bu2AlCl

Cp₂ZrCl₂-catalyzed (Cp = ⁵-C₅H₅) hydroalumination of substituted norbornenes withi-Bu₂AlCl was conducted, yielding higher cycloalkylhaloalanes with high yields.Institute of Organic Chemistry, Ural Branch, Russian Academy of Sciences, 450054 Ufa. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 12, pp. 2791–2798, December, 1992.     

Synthesis, XRD structure and properties of diaqua(p-toluidine-N,N-di-3-propionato)copper(II) dihydrate [Cu(p-Tdp)(H2O)2]·2H2O

The copper(II) complex [Cu(p-Tdp)(H₂O)₂]·2H₂O, where p-Tdp is the anion of p-toluidine-N,N-di-3-propionic acid (or N,N-di(2-carboxyethyl)-p-toluidine), has been synthesized and characterized by X-ray diffraction. Three crystallographically independent [Cu(p-Tdp)(H₂O)₂] molecules have a similar structure. The Cu atoms have a square pyramidal environment (4+1) with a small trigonal bipyramidal distortion. The ortho-H atom of the benzene ring blocks up the sixth coordination position of the Cu polyhedron. The basal plane is formed by the donor atoms of the tridentate ligand and by the water molecule (average bond length Cu---N 2.03, Cu---O 1.93, Cu---O_w 2.00 Å), the apex is occupied by another water molecule (Cu---O_w 2.27 Å). The Cu atoms are located 0.20–0.30 Å out of the mean planes of the four basal atoms towards the apical O_w atom. The IR and electronic absorption spectra of p-Tdp and the title compound have been described. UV–Vis reflectance spectra shows that the complex has the same square pyramidal geometry in the crystal state and in solution. The protonation constants of the ligand log K₁=6.87(2), log K₂=3.75(2), log K₃=2.57(2) and stability constants log K_CuH(p-Tdp)=2.13(5), log K_Cu(p-Tdp)=6.38(3) were determined by pH-titration at 25.0 °C and I=0.1 M KNO₃.     

The dual role of cytochrome c2 in the facultative phototrophic bacteriumRhodopseudomonas capsulata

Succinate oxidation is stimulated by addition of cytochrome c₂ in cytochrome c₂-deficient spheroplasts from the M6-mutant and from the wild type strain ofRhodopseudomonas capsulata. Inhibition of the alternative oxidase in the wild type by CO facilitates this observation. The finding confirms a dual role of cytochrome c₂, in photosynthetic and in respiratory electron transport.

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Die doppelte Rolle von Cytochrome c₂ in Rhodopseudomonas capsulata

Zusammenfassung Die Oxidation von Succinat wird durch Zugabe von Cytochrom c₂ zu Cytochrom c₂-defizienten Sphäroplasten der Mutante M6 und des Wildtyps vonRhodopseudomonas capsulata stimuliert. Die Hemmung der alternativen Oxidase durch CO im Wildtyp erleichtert diese Beobachtung. Der Befund bestätigt die Doppelrolle von Cytochrom c₂ im photosynthetischen und respiratorischen Elektronentransport.

     

Prediction of the unit cell edge length of cubic A 2 2+ BB′O6 perovskites by multiple linear regression and artificial neural networks

The unit cell edge length, a, of a set of complex cubic perovskites having the general formula A ₂ ²⁺ BB′O₆ is predicted using two methodologies: multiple linear regression and artificial neural neworks. The unit cell edge length is expressed as a function of six independent variables: the effective ionic radii of the constituents (A, B and B′), the electronegativities of B and B′, and the oxidation state of B. In this analysis, 147 perovskites of the A ₂ ²⁺ BB′O₆ type, having the cubic structure and belonging to the Fm3m space group, are included. They are divided in two sets; 98 compounds are used in the calibration set and 49 are used in the test set. Both models give consistent results and could be successfully use to predict the lattice cell parameter of new members of this series.     

Chelate complex Ni(S2C2H2)2 as a molecular model of the hydrodesulfurization active center

Electronic states of Ni atom in a square-planar complex Ni(S₂C₂H₂)₂ and its molecular adduct with H₂S were studied by means ofab initio molecular orbital calculations. H₂S adsorption stabilizes the Ni(IV) state (d⁶) in the complex with the Ni atom shifted from the plane by 0.35 ?.