In situ Neutron Powder Diffraction on Intermediate Hydrides of MgPd3 in a Novel Sapphire Gas Pressure Cell

A novel gas pressure cell for in situ neutron powder diffraction has been developed. It is based on a single crystal sapphire tube as a sample holder, allows a 360° unobstructed access by the neutron beam and has little background contribution. This device was used to study the hydrogenation of α‐MgPd₃, which undergoes a hydrogen driven rearrangement from a ZrAl₃ to a AuCu₃ type structure. Deuterium could be located and a strong preference of [Pd₆] voids was found in α‐MgPd₃D_0.79 under 5 bar and in α‐MgPd₃D_0.94 under 20 bar deuterium pressure. The crystal structure may be described as a new defect superstructure variant of the NaCl type. In situ thermal analysis under 5 bar hydrogen pressure showed that both the hydrogen uptake of α‐MgPd₃, which is complete at temperatures below 450 K, and the transformation to the hydride of cubic β‐MgPd₃, starting around 550 K, are exothermic. This completion of the hydrogenation‐dehydrogenation series of MgPd₃ suggests, that the rearrangement of the metal structure proceeds by a hydrogen assisted gliding mechanism with a shift vector of [110]. This is also supported by quantum chemical calculations, which show a decohesion of the intermetallic structure upon hydrogenation accompanied by the appearance of Pd–H bonding interactions.     

SAMBADENA Hyperpolarization of 13C-Succinate in an MRI: Singlet-Triplet Mixing Causes Polarization Loss

The signal enhancement provided by the hyperpolarization of nuclear spins of biological molecules is a highly promising technique for diagnostic imaging. To date, most ¹³C-contrast agents had to be polarized in an extra, complex or cost intensive polarizer. Recently, the in situ hyperpolarization of a ¹³C contrast agent to >20 % was demonstrated without a polarizer but within the bore of an MRI system. This approach addresses some of the challenges of MRI with hyperpolarized tracers, i. e. elevated cost, long production times, and loss of polarization during transfer to the detection site. Here, we demonstrate the first hyperpolarization of a biomolecule in aqueous solution in the bore of an MRI at field strength of 7 T within seconds. The ¹³C nucleus of 1-¹³C, 2,3-²H₂-succinate was polarized to 11 % corresponding to a signal enhancement of approximately 18.000. Interesting effects during the process of the hydrogenation reaction which lead to a significant loss of polarization have been observed.     

Simulation einer Fabrik für synthetischen Gummi — eine Fallstudie

Zusammenfassung Die Fallstudie behandelt das Problem der Dimensionierung der verschiedenen Teile einer sehr komplexen Anlage für mehrstufige Produktion. Die Programmierung erfolgte in FORTRAN. Anhand der Fallstudie werden einige wesentliche Punkte herausgearbeitet, die für den Erfolg von Simulationsprojekten wesentlich sind, nämlich: klare Zielsetzung, Simulation von Teilbereichen, so daß in kürzester Zeit Resultate vorliegen.

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Summary The case-study deals with the problem of the size of various parts of a very complex plant lay-out for multi-step production. The programming was done in FORTAN. Based on the case-study a few points were worked out which are essential for the success of simulation-projects, to wit: clear statement of purpose; simulation of partial scopes, which produce short-term results.

     

New Ionic Liquid Compounds Based on Tantalum Pentachloride TaCl5: Synthesis,Structural, and Spectroscopic Elucidation of the (μ‐Oxido)‐Chloridotantalates(V) [BMPy][TaCl6], [BMPy]4[(TaCl6)2(Ta2OCl10)], and [EMIm]2[Ta2OCl10]

1‐Butyl‐4‐methylpyridinium hexachloridotantalate(V), [BMPy][TaCl₆] ( 1 ), tetrakis(1‐butyl‐4‐methylpyridinium) bis(hexachloridotantalate(V) (μ‐oxido)‐decachloridotantalate(V), [BMPy]₄[(TaCl₆)₂(Ta₂OCl₁₀)] ( 2 ), and bis(1‐ethyl‐3‐methylimidazolium)‐(μ‐oxido)‐decachloridoditantalate(V), [EMIm]₂[Ta₂OCl₁₀] ( 3 ) were synthesized and characterized by single‐crystal X‐ray diffraction and vibrational spectroscopy. Compounds 1 and 3 crystallize in the monoclinic space group P2₁/c (no. 14), whereas compound 2 crystallizes in the triclinic space group P (no. 2). All compounds are built up by the mentioned bulky organic cations and octahedral [TaCl₆]^– respective linear [Ta₂OCl₁₀]^2– anions. Coulomb interactions are dominant between the ionic species. FT‐IR and FT‐Raman spectra were recorded and interpreted, especially with respect to the inorganic species [TaCl₆]^– (O_h) and [Ta₂OCl₁₀]^2– (C_i symmetry, approximately D_4h). The melting temperatures of compounds 1 – 3 are given.     

Oligosilane‐ and Oligosiloxane‐bridged Phosphines – Synthesis,Structures, and Metalation

The range of molecular silicon phosphorus compounds has been extended by some new species containing oligosilane ((R₂Si)_n; n ≥ 2) or oligosiloxane ((R₂SiO)_mSiR₂; m ≥ 1) fragments bound to phosphorus atoms. Primary and secondary compounds of these types allow for the synthesis of metal derivatives. Such metalated species usually form oligomers and exhibit a versatile structural chemistry with cyclic, polycyclic, and cage‐like patterns. The main results obtained in the field of oligosilane‐ and oligosiloxane‐bridged phosphines will be presented below and the structures of the metal derivatives will be discussed. Moreover, the synthesis of an inorganic ligand on the basis of siloxane‐bridged phosphines will be presented. This compound opens up a new chapter in host‐guest chemistry.