Phosphaniminato-Komplexe des Iods. Synthese und Kristallstrukturen von Ph3PNIO2 und Ph3PNSiMe3 · I2

Phosphoraneiminato Complexes of Iodine. Syntheses and Crystal Structures of Ph₃PNIO₂ and Ph₃PNSiMe₃ · I₂ Ph₃PNIO₂ has been prepared as yellow crystals by the reaction of Ph₃PNSiMe₃ with I₂O₅ in boiling acetonitrile, whereas the molecular complex Ph₃PNSiMe₃ · I₂ is formed as brown crystals by the reaction of Ph₃PNSiMe₃ with iodine in acetonitrile solution. Both complexes were characterized by crystal structure determinations. Ph₃PNIO₂: Space group P2₁/n, Z = 4, 2 858 observed unique reflections, R = 0.039. Lattice dimensions at 19°C: a = 972.8(2), b = 1 743.4(3), c = 1 073.7(2) pm, β = 115.46(3)°. The compound forms monomeric molecules with pyramidal geometry at the iodine atom. The bond angle PNI (126.9°) is unusually small; the PN bond length of 159.2 pm corresponds with a double bond. Ph₃PNSiMe₃ · I₂: Space group P1 , Z = 2, 3 560 observed unique reflections, R = 0.033. Lattice dimensions at 19°C: a = 941.2(2), b = 1 041.7(2), c = 1 287.4(3) pm, α = 78.34(1)°, β = 72.00(2)°, γ = 86.08(2)°. The compound forms monomeric molecules, in which the I₂ molecule and the nitrogen atom of the phosphoraneimine molecule realize a linear N? I? I axis with a bond length N? I of 243.2 pm.     

Synthese und Kristallstruktur von [ReNCl(NPPh2C6H4)]2 · [Ph3PNH2]Cl · CH3CN,einem rheniumorganischen Nitrido-Phosphaniminato-Komplex

Synthesis and Crystal Structure of [ReNCl(NPPh₂C₆H₄)]₂ · [Ph₃PNH₂]Cl · CH₃CN, a Rhenium Organic Nitrido Phosphoraneiminato Complex The title compound is synthesized by the reaction of ReNCl₄ with Me₃SiNPPh₃ in boiling acetonitrile, forming colourless crystals, which are characterized by an X-ray structure determination. Space group P1 , Z = 2, 4 037 observed unique reflections, R = 0.043. Lattice dimensions at 19°C: a = 1 005.5; b = 1 695.2; c = 1 744.7 pm, α = 105.86°; β = 101.49°; γ = 104.45°. The structure consists of dimeric molecules [ReNCl(NPPh₂C₆H₄)]₂, triphenylphosphorane ammoniumchloride and included acetonitrile molecules. In the nitrido phosphoraneiminato complex the rhenium atoms are μ₂-bridged via the N-Atoms of the phosphoraneiminato ligands. Because of this bridging and a Re? Re bond, one terminal nitrido ligand, one terminal chloro ligand, and a Re? C bond of an -C-atom of one phenylene group of Re-atoms attain co-ordination number six.     

Optimization of molecular geometries in the PCILO and CNDO/2 formalism. The barrier to internal rotation in thioacetaldehyde

The barrier to internal rotation in thioacetaldehyde was investigated within the PCILO and CNDO/2 framework using standard and optimized geometries. The optimized geometries give for the barrier of PCILO a value closer to the experimental one (1.06 kcal mol^?1) whereas the CNDO/2 results yield a qualitatively wrong conformational behavior.     

Solution and solid-state structure of the anion [Ag(2)[closo-CB(11)H(12)](4)](2-)

Addition of the carbene 1,3-dimesitylimidazol-2-ylidene (IMes) to a toluene solution of Ag[closo-CB(11)H(12)] results in the formation of the complex [(IMes)(2)Ag](2)[Ag(2)[closo-CB(11)H(12)](4)], the anionic component of which contains two silver(I) centers bridged by two carboranes in addition to one terminally bound carborane on each metal, in the solid-state. Comparison of the observed (11)B[(1)H] NMR chemical shifts of [(IMes)(2)Ag](2)[Ag(2)[closo-CB(11)H(12)](4)] or Ag[closo-CB(11)H(12)] with [NBu(4)][closo-CB(11)H(12)] in CD(2)Cl(2) demonstrates that the silver ion interacts significantly with the cage in solution. Theoretical investigations using the ab initio/GIAO/NMR method of [closo-CB(11)H(12)](-) and Na[closo-CB(11)H(12)] as model geometries for the silver salts support experimental evidence for these Ag...[BH] interactions in solution.     

Detection of stress whitening in plastics with the help of X-ray dark field imaging

The processing of thermoplastics can induce a wide range of defects such as stress whitening, cavitation and porosity, which can adversely affect the reliability of the final products. Hence, fast and effective non-destructive detection methods for such defects are highly important for quality assurance on production lines. In this paper, X-ray dark field imaging is presented as a new non-destructive testing method that allows the visualization of stress whitening or cavitation efficiently. The performance of the method is demonstrated for the case of an injection-moulded polyvinylidene fluoride part that exhibits stress whitening. Whereas the stress whitening could not be detected by conventional X-ray imaging, it was localized by an X-ray dark field image acquired within a few minutes. Once the precise location of the stress whitening was known, it was possible to verify the result by local micro X-ray computed tomography and by a micro section image.     

On Fundamental Domains and Volumes of Hyperbolic Coxeter–Weyl Groups

We present a simple method for determining the shape of fundamental domains of generalized modular groups related to Weyl groups of hyperbolic Kac?CMoody algebras. These domains are given as subsets of certain generalized upper half planes, on which the Weyl groups act via generalized modular transformations. Our construction only requires the Cartan matrix of the underlying finite-dimensional Lie algebra and the associated Coxeter labels as input information. We present a simple formula for determining the volume of these fundamental domains. This allows us to re-produce in a simple manner the known values for these volumes previously obtained by other methods.