Notiz über den Chloraufschluß niobhaltiger Substanzen

In an investigation on the decomposition of oxide minerals containing Ti, Nb, Fe, U and Y mixtures of TiO₂, Nb₂O₅, Fe₂O₃, U₃O₈ and Y₂O₃ have been heated in streaming Cl₂ containing SOCl₂. In order to avoid the formation of NbOCl₃, which is highly disturbing the distribution pattern of the chlorides, the reaction boat was covered with carbon powder. TiCl₄ was absorbed in sulphuric acid; NbCl₅, FeCl₃ and UCl₄ were condensed in the reaction tube and were separated by usual methods; YCl₃ remained in the reaction boat.     

Eine Vereinfachung des hyperbolischen Parallelenaxioms

Ohne Zusammenfassung     

Electronic structure, bonding, spectra, and linear and nonlinear electric properties of Ti@C28

The potential energy surface (PES) of Ti@C(28) has been revisited, and the stationary points have been carefully characterized. In particular, the C(2v) symmetry structure considered previously turns out to be a transition state lying 2.3 kcal/mol above the ground state of C(3v) symmetry at the MP2/6-31G(d) level. A large binding energy of 181.3 kcal/mol is found at the ROMP2/6-31G(d) level. Topological analysis of the generalized Ti@C(28) density reveals four bond paths between Ti and carbon atoms of the host. The character of all four contacts corresponds to a partially covalent closed shell interaction. UV-vis, IR, and Raman spectra are calculated and compared with C(28)H(4). The dipole moment and the static electronic and double harmonic vibrational (hyper)polarizabilities have been obtained. Distortion of the fullerene cage due to encapsulation leads to nonzero diagonal components of the electronic first hyperpolarizability β, and to an increase in the diagonal components of the electronic polarizability α and second hyperpolarizability γ. However, introduction of the Ti atom causes a comparable or larger reduction in most cases due to localized bonding interactions. At the double harmonic level, the average vibrational β is much larger than its electronic counterpart, but the opposite is true for α and for the contribution to γ that has been calculated. There is also a very large anharmonic (nuclear relaxation) contribution to β which results from a shallow PES with four minima separated by very low barriers. Thus, the vibrational γ (and α) may, likewise, become much larger when anharmonicity is taken into account.     

New Tungsten Cluster Based Contrast Agents for X-ray Computed Tomography

In recognition of the seminal contributions of F. A. Cotton and A. Bino to the field of aqueous chemistry of organometallic, trinuclear cluster compounds of tungsten, we describe their modifications and use as contrast agents for X-ray computed tomography. To enable their fundamental work for an advantageous diagnostic application in medicine a new generation of polydentate W₃O₂ complexes with improved hydrolytical stability has been synthesized and characterized. The applicability as new metal based contrast agent has been demonstrated in a computed tomography angiography animal study with increased signal intensity. Especially the bis tridentate W₃O₂ complexes with their reduced stereochemical complexity represent a promising new class in the field of X-ray contrast agents.     

Mechanistic Studies on the Hexadecafluorophthalocyanine–Iron-Catalyzed Wacker-Type Oxidation of Olefins to Ketones**

The hexadecafluorophthalocyanine–iron complex FePcF₁₆ was recently shown to convert olefins into ketones in the presence of stoichiometric amounts of triethylsilane in ethanol at room temperature under an oxygen atmosphere. Herein, we describe an extensive mechanistic investigation for the conversion of 2-vinylnaphthalene into 2-acetylnaphthalene as model reaction. A variety of studies including deuterium- and ¹⁸O₂-labeling experiments, ESI-MS, and ⁵⁷Fe Mössbauer spectroscopy were performed to identify the intermediates involved in the catalytic cycle of the oxidation process. Finally, a detailed and well-supported reaction mechanism for the FePcF₁₆-catalyzed Wacker-type oxidation is proposed.     

Cobalt(III) complexes with aminothiolates

Summary This article describes some complexes of cobalt(III) with -mercaptopropylamine,N, N-dimethyl--mercaptopropylamme andN,N-dimethyl--mercaptoethylamine. The compounds are of stoichiometry [Co(ligand)₃], [Co₃(ligand)₆]_X (X=Cl or Br) and [Co(ligand)₃]X₃ (X=Cl or ClO₄). -Mercaptopropylamine yields both chelated and non-chelated compounds while theN,N-dimethyl derivatives yield only non-chelated complexes. This behaviour contrasts with the results obtained with nickel(II).