Element-Element-Bindungen. I. Synthese und Struktur des Tetra(tert-butyl)tetrarsetans und des Tetra(tert-butyl)tetrastibetans

Element-Element Bonds. I. Syntheses and Structure of Tetra(tert-butyl)tetrarsetane and of Tetra(tert-butyl)tetrastibetane Dilithium (tert-butyl)arsenide reacts with (tert-butyl)dichloroarsine to give tetra-(tert-butyl)tetrarsetane 1 ; homologous tetra(tert-butyl)tetrastibetane 2 is formed by reduction of (tert-butyl)dichlorostibane with magnesium. The isotypic compounds 1/2 crystallize in the monoclinic space group P2₁/c with Z = 4. The dimensions of the unit cells determined at ?45 ± 5°C are: a = 957.4(8)/1 000.2(3); b = 1 399.1(14)/1 423.9(4); c = 1 697.4(9)/1 749.8(7) pm; β = 96.02(6)/96.77(3)°. As shown by low temperature X-ray structure determinations (3 531/3 232 symmetry independent reflections; R_g = 4.0/4.6%) the four membered rings E₄ (E = As or Sb) are folded; in all-trans configuration the bulky organic substituents occupy pseudo-equatorial positions. Characteristic averaged bond distances and angles are: E? E 244/282; E? C 202/221 pm; ? E? E? E 86/85° ? E? E? C 101/99°. The dihedral angels of the bisphenoides built up by the atoms of the rings are found to be 139/133°.     

Über die Darstellung von m-Hydroxybenzonitrilen durch Reaktion von Alkalicyaniden mit Chinolacetaten

Zusammenfassung Die Einwirkung von Kaliumcyanid in alkoholischer Lösung auf o- und p-Chinolacetate mit freier 5-Stellung führt unter 1,4-Addition des Cyanids zur Bildung entsprechend substituierter m-Hydroxybenzonitrile. In manchen Fällen scheint dieser Bildungsweg anderen Darstellungsmethoden dieser Verbindungen überlegen zu sein. *** DIRECT SUPPORT *** A3615062 00004     

Investigation of the electronic and structural properties of potassium hexaboride, KB6, by transport, magnetic susceptibility, EPR, and NMR measurements, temperature-dependent crystal structure determination, and electronic band structure calculations

The electronic and structural properties of potassium hexaboride, KB(6), were examined by transport, magnetic susceptibility, EPR, and NMR measurements, temperature-dependent crystal structure determination, and electronic band structure calculations. The valence bands of KB(6) are partially empty, but the electrical resistivity of KB(6) reveals that it is not a normal metal. The magnetic susceptibility as well as EPR and NMR measurements show the presence of localized electrons in KB(6). The EPR spectra of KB(6) have two peaks, a broad ( approximately 320 G) and a narrow (less than approximately 27 G) line width, and the temperature-dependence of the magnetic susceptibility of KB(6) exhibits a strong hysteresis below 70 K. The temperature-dependent crystal structure determination of KB(6) shows the occurrence of an unusual variation in the unit cell parameter hence supporting that the hysteresis of the magnetic susceptibility is a bulk phenomenon. The line width DeltaH(pp) of the broad EPR signal is independent of temperature and EPR frequency. This finding indicates that the line broadening results from the dipole-dipole interaction, and the spins responsible for the broad EPR peak has the average distance of approximately 1.0 nm. To explain these apparently puzzling properties, we examined a probable mechanism of electron localization in KB(6) and its implications.     

Investigation of the spin exchange interactions and magnetic Structures of the CrVO4-type transition metal phosphates,sulfates, and vanadates by spin dimer analysis

The CrVO(4)-type magnetic oxides MM'O(4) consist of edge-sharing MO(4) octahedral chains condensed with M'O(4) tetrahedra and exhibit a wide variety of magnetic structures. The magnetic properties of these oxides were examined by studying their spin exchange interactions on the basis of spin dimer analysis. The nature and magnitudes of the intra- and interchain spin exchange interactions depend on the square-to-rectangle distortion in the basal planes of the MO(4) chain and on the difference between the M 3d and O 2p orbital energies. The spiral magnetic structures of beta-CrPO(4) and MnSO(4) originate from the pseudohexagonal arrangement of the MO(4) chains and the frustrated interchain antiferromagnetic interactions.     

Theoretical investigation of the spin exchange interactions and magnetic properties of the homometallic ludwigite Fe(3)O(2)BO(3)

The homometallic ludwigite Fe(3)O(2)BO(3) has a complex structure made up of corner- and edge-sharing FeO(6) octahedra and exhibits a number of apparently puzzling magnetic properties. The reasons for these properties were probed by examining the trends in the spin exchange interactions of Fe(3)O(2)BO(3). To analyze the relative strengths of spin exchange interactions in such a complex magnetic solid, we first generalized the method of spin dimer analysis and then employed the resulting formulation to investigate how the magnetic properties of Fe(3)O(2)BO(3) are related to its reported crystal structures. The spin-orbital interaction energies calculated for various spin dimers of Fe(3)O(2)BO(3) provide estimates for the relative strengths of the associated spin exchange interactions, which in turn account for the observed magnetic properties of Fe(3)O(2)BO(3).     

Effect of surface composition on the flowability of industrial spray-dried dairy powders

The surface composition of four industrial spray-dried dairy powders (skim milk powder, whole milk powder, cream powder and whey protein concentrate) was estimated by electron spectroscopy for chemical analysis (ESCA), and its influence on powder flowability was studied. It was found that skim milk powder flows well compared to the other powders because the surface is made of lactose and protein with a small amount of fat, whereas the high surface fat composition inhibits the flow of whole milk, cream and whey protein powders. However, the poor flowability of the powders with high surface fat coverage was drastically improved by removal of fat present on the surface through a brief wash with petroleum ether. The results obtained indicate that, although there are several parameters including particle size, which influence the flowability of powders, the flowability of powders is strongly influenced by the surface composition of powders, particularly for fat-containing powders.     

Übergangsmetall-Chalkogensysteme, 1. Mitt.: Das System Kobalt-Selen

Zusammenfassung Das Phasendiagramm Co–Se wurde auf Grund der Resultate thermischer und röntgenographischer Untersuchungen aufgestellt. Für die thermischen Analysen wurde eine vollautomatischeDTA-Anlage mit konstanten Heiz- und Kühlgeschwindigkeiten im Bereich von 200 bis 1100 °C konstruiert. Neben der schon früher gefundenen Mischungslücke in kobaltreichen Schmelzen tritt eine weitere Mischungslücke in Schmelzen mit mehr als 70 At %Se oberhalb 952 °C auf. Die B8(NiAs)-Phase Co_1–x Se hat einen kongruenten Schmelzpunkt bei 54,0 At %Se und 1078 °C und eine maximale Phasenbreite von 50,7 At %Se (910 °C) bis 59,0 At %Se (952 °C). Das Eutektikum zwischen Co_1–x Se und -Co liegt bei 44,5 At %Se und 910 °C. CoSe₂ zerfällt peritektisch bei 938 °C in Co_1–x Se und eine Se-reiche Schmelze. Die röntgenographischen Untersuchungen bestätigten die Existenz der drei Verbindungen Co₉Se₈, Co_1–x Se und CoSe₂.

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Transition metal-chalcogen systems, I: The system cobalt-selenium

The Co–Se phase diagram was constructed using results of thermal and X-ray investigations. For the thermal analyses a fully automaticDTA-apparatus for constant heating and cooling rates in the range 200 to 1100 °C was built. In addition to the miscibility gap in liquid cobalt-rich alloys previously reported there exists another miscibility gap in melts with more than 70 at %Se above 952 °C. The B8 (NiAs) phase Co_1–x Se has a congruent melting point at 54,0 at % Se and 1078 °C and a maximal range of homogeneity between 50,7 at %Se (910 °C) and 59,0 at %Se (952 °C). The eutectic between Co_1–x Se and -Co occurs at 44,5 at %Se and 910 °C. CoSe₂ decomposes peritectically at 938 °C into Co_1–x Se and a Se-rich melt. X-ray investigations confirmed the existence of the three compounds Co₉Se₈, Co_1–x Se, and CoSe₂.

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Mit 4 Abbildungen

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Herrn Prof. Dr.O. Kratky zum 70. Geburtstag gewidmet.     

Melting characteristics of fat present on the surface of industrial spray-dried dairy powders

The melting characteristics of the fat present on the surface (surface free-fat) of two industrial spray-dried dairy powders (cream powder and whole milk powder) were investigated in comparison with those of other milk fat fractions present in the powder, such as free-fat from the interior of the powder particle (inner free-fat) and encapsulated fat. The melting characteristics of the milk fat fractions were studied by fatty acid composition, melting profile and solid fat content profile. The results indicated that all milk fat fractions including surface free-fat contained various triglycerides with melting points ranging from -40 to +40 degrees C. However, some fractionation was observed among the different milk fat fractions. The free-fat fractions (surface free-fat and inner free-fat) had a greater proportion of high-melting triglyceride species than the encapsulated fat. Furthermore, the high-melting triglyceride species present in the free-fat fractions were slightly accumulated at the surface of powder. This phenomenon was observed in both cream powder and whole milk powder and its effect on wetting time was established. This indicates that manipulation of the surface fat content during drying operation may hold the key to functionality improvement.