Kohlenstoff-haltige ternäre Phasen (Nb3Al2C und Ta3Al2C)

Ohne Zusammenfassung     

Trimerisierung von Dicyanamid-Ionen C2N3– im Festkörper – Synthesen,Kristallstrukturen und Eigenschaften von NaCs2(C2N3)3 und Na3C6N9 · 3 H2O

Trimerization of Dicyanamide Ions C₂N₃^– in the Solid – Syntheses, Crystal Structures, and Properties of NaCs₂(C₂N₃)₃ und Na₃C₆N₉ · 3 H₂O The Tricyanomelaminate Na₃C₆N₉ · 3 H₂O is obtained by heating NaC₂N₃ to 500 °C and subsequent crystallization from water. According to the single-crystal structure determination (Na₃C₆N₉ · 3 H₂O: P62c; a = 1023.53(8), c = 650.85(15) pm, Z = 2, R1 = 0.0276, wR2 = 0.0710) in the solid cyclic C₆N₉^3– ions occur. Partial ion exchange and crystallization from water yields anhydrous NaCs₂(C₂N₃)₃. The X-ray structure determination (NaCs₂(C₂N₃)₃: P6₃/m, a = 700.01(4), c = 1449.29(7) pm, Z = 2, R1 = 0.0173, wR2 = 0.0432) reveals C₂N₃^– ions in the solid. Calorimetric investigations and detailed IR spectroscopy of NaC₂N₃, Na₃C₆N₉, Na₃C₆N₉ · 3 H₂O, as well as NaCs₂(C₂N₃)₃ reveal in combination with the structure analyses that NaC₂N₃ transforms to Na₃C₆N₉ above 380 °C by trimerization of the C₂N₃^– ions in the solid. Above 180 °C the hydrate Na₃C₆N₉ · 3 H₂O reversibly dehydrates.     

Die Kristallstruktur von Co3Al3Si4 und Co2AlSi2 und der Aufbau einiger Monosilicidsysteme von Übergangsmetallen

Zusammenfassung Im Dreistoff: Co-Al-Si werden zwei ternäre Phasen festgestellt, deren Zusammensetzung bei Co₃Al₃Si₄ bzw. Co₂AlSi₂ liegt. Die erstgenannte kristallisiert im Ir₃Ge₇-Typ mit einer Gitterkonstante von:a _w =8,07₅ kX·E., die zweite ist mit der Ni₂Al₃-Struktur isotyp und besitzt einen geringen homogenen Bereich. Die Gitterkonstanten sind:a=3,86₂–3,90₂;c=4,74₀ bis 4,78₁ kX·E.CrSi und MnSi bilden miteinander und mit den Monosiliciden von Eisen und Kobalt lückenlose Mischreihen (B 20-Typ). MnSi vermag 70 Mol% NiSi aufzunehmen, NiSi (B 31) nur etwa 5 Mol% MnSi. CrSi löst rd. 40 Mol% NiSi, dagegen ist CrSi in NiSi praktisch unlöslich.Mit 2 AbbildungenHerrn Prof. Dr.A. Zinke zu seinem 70. Geburtstag in Verehrung gewidmet.     

Intermetallische Phasen mit β-Wolfram-Struktur (V3Pb,Nb3Pb und V3Cd)

Zusammenfassung Neue Phasen mit -Wolfram-Struktur (Cr₃O-Typ) werden in den Systemen V–Pb, Nb–Pb und V–Cd hergestellt und deren Gitterparameter bestimmt.     

Die Zersetzungsreaktion des Dialan-Radikalanions [R2Al-AlR2]·− in DME: I. Kristallstrukturen von R2Al(Me)OC2H4OMeK(DME) und R2Al(OC2H4OMe)2K (R  CH(SiMe3) 2)

Tetrakis[bis(trimethylsilyl)methyl]dialane(4) (1) reacts as recently reported with potassium in 1,2-dimethoxyethane (DME) to yield after purification the surprisingly stable radical monoanion [R₂AlAlR₂]·⁻ [K(DME)₃]⁺ (2) (R  CH(SiMe₃)₂). With a longer reaction time of some days at room temperature and an excess of potassium, however, complete decomposition occurs under cleavage of ether molecules and formation of several new products. One of these compounds was identified as R₂AlMe(OC₂H₄OMe)K(DME) (3) and characterized by a crystal structure determination. Two further derivatives were synthesized and their spectroscopic data compared to the decomposition products: R₂Al(OC₂H₄OMe)₂K (6), also characterized by crystal structure determination, and [R₂AlMe₂]⁻ [K(DME)₆]⁺ (9), but due to the NMR characterization only 9 could be a component of the above-mentioned reaction mixture. In both aluminium alcoholates (3 and 6) the potassium ion is bound in a chelating manner by oxygen atoms of the aluminate unit, probably for this reason they are very soluble in non-polar solvents. In the solid state 3 polymerizes by intermolecular K…H₃CAl bridges forming one-dimensional chains along a crystallographic glide plane, and 6 forms dimers via KOK bridges and fourfold coordinated oxygen atoms.     

Über das Mischungsverhalten von Nb3Sn mit Ti3Sn,Mo3Al und verwandten Phasen

Zusammenfassung Nb₃Sn und Mo₃Al bilden eine lückenlose Mischreihe. Nb₃Sn löst bei 1600°C rd. 60 Mol% Ti₃Sn, 30 Mol% Zr(3)Sn, 40 Mol% Hf(3)Sn bzw. 50 Mol% Nb(3)Si.Mit 5 Abbildungen     

Tieftemperatur-flüssigphasefluorierung von pentafluorphenyl-element-Verbindungen. Darstellungen und eigenschaften von (C6F5)3AsF2, (C6F5)3SbF2, (C6F5)2SeF2, (C6F5)2SeO,C6F5TeF3 und Cs[(C6F5)3EF3] (E = As,Sb) [1]

The fluorination reactions of (C₆F₅)₃E (E = As, Sb) with elemental flourine yield (C₆F₅)₃EF₂ in high yields. From the reactions of (C₆F₅)₃EF₂ with CsF the new salts Cs[(C₆F₅)₃EF₃] are obtained. (C₆F₅)₂SeF₂ and C₆F₅TeF₃ are formed for the first time by reacting (C₆F₅)₂SeF and (C₆F₅)₂TeF₂ with elemental flourine and XeF₂, respectively. (C₆F₅)₂SeF₂ rapidly reacts with glass, and the new compound (C₆F₅)₂SeO is isolated. The preparations, properties and ¹⁹F NMR spectra of the new compounds are described.     

Schwingungsspektren und Normalkoordinatenanalyse von CF3-Verbindungen—XXII. (CF3)4Ge und (CF3)6Ge2

The gas phase i.r. and liquid phase Raman spectra of (CF₃)₄ Ge and (CF₃)₆ Ge₂ are reported and assigned for T_d and D_3d symmetry respectively. A normal coordinate analysis has been performed and force constants as well as frequencies of inactive vibrations have been obtained. The CF stretching force constants were calculated to be 5,86 and 5,83, the GeC stretching force constants 2,30 and 2,29 [N cm⁻¹] for (CF₃)₄Ge and (CF₃)₆Ge₂, respectively.     

Die ma?analytische Bestimmung von Al, CeIII und Pb

Ohne Zusammenfassung     

Die Koagulationsgeschwindigkeit von Al(OH)3-Solen,gemessen an der Aenderung ihrer Zähigkeit

Ohne Zusammenfassung     

Die spektrographische Bestimmung erh?hter Gehalte von V, Nb und Zr in Uranlegierungen

Ohne Zusammenfassung     

Crystal structure of Μ2, η2, Σ2-nitrato-η2, Σ2-nitrato-bis(1-ethyltetrazole-N4)copper(II) Cu(C3H6N4)2(NO3)2 = [Cu(C3H6N4)2(NO3)(NO3)2/2]∞

The complex compound of copper(II) nitrate with 1ethyltetrazole (ettz), Cu( C₃H₆N₄)₂(NO₃)(NO₃)_2/2] is studied by Xray diffraction analysis (“Syntex P2₁” automatic diffractometer, CuK_a radiation, graphite monochromator, 6/26 scan mode with V_min = 3.91 deg/min, the total number of data collected 3544 l_hkb including 3141 nonextinct l_hkl > 0, a correction for absorption (Μ = 25.08 cm^-1) applied by integrating over the crystal faces). The parameters of the orthorhombic unit cell (space group Pccn) are a = 15.436(3), b = 20.198(5), c = 19.587(3) Å, V_cell = 6107(2) Å^{3, Z} = 16, d_calc = 1.670 g/cm³. The two crystallographically independent copper atoms have a distorted octahedral environment (coordination node is CuN₂O₄), coordination number (CN) is 6 = 4 + t2. In the equatorial plane, two nitrogen atoms of ettz and two oxygen atoms of NO ₃ ^? groups are trans to each other; Cu-N = 1.983(8), C-O_{NO 3} ^? = 1.978(7) Å (average). The nitrato groups fulfill chelate and bridging functions, complementing the coordination polyhedra of the copper atoms to distorted octahedra, where Cu-O_{NO 3} ^? = 2.517(7) Å (average). The compound has a chain structure; the chains stretching along [001] are packed pairwise according to the hexagonal law.     

Peritektische Zersetzung von YBa2Cu3O7−x

During the heating of YBCO a peritectic reaction takes place at 1020C, which can be described by: 2YBa₂Cu₃O_7–xY₂BaCuO₅+L+(1-2x)/2O₂ (1) whereL = 3BaCuO₂ +2CuO is a fluid with limited amount of yttrium.It has been reported, that many parameters can influence the reaction. From one side not only the starting size of grains but also the heating rate have an influence on the resulting Y₂BaCuO₅-phase. From the other side, there is a change of the peritectical temperature caused by changing of the partial pressure of O₂ and the presence of parasitic phase.From general kinetic consideration one can draw the conclusion, that different mechanisms (nucleation, phase-boundary reaction and diffusion) can control the reaction.Using DTA/TG measurements, the peritectic reaction has been examined. Classical kinetic methods (Kissinger and Friedman) has been used. The Friedman method has given the dependence of the activation energy from reaction degree. This suggests many steps reactions. The dependence of the DTA-peaks from the heat rate suggest a parallel steps of reaction. This assumption can be motivated by evaluation of free O₂, one solid and liquid phase formation. Amount of this phases depends on the heating rate. Additionally X-ray and microscopic methods has been used. In this way was shown, that the perovskit structure is stable up to peritectical temperature and than is dramatically destroyed. From microscopic observations has been got information about shape and size of solid phase and it's creation as a function of temperature, time and starting grain size.

Die Arbeit wurde BMBF gefördert und durch Land NRW unterschtützt.