Investigation of Bis(Perfluoro-tert-Butoxy) Halogenates(I/III)

A systematic study of halogenate(I/III) anions with polyatomic ligands is presented. The bis(perfluoro-tert-butoxy) halogenates(I) [X(OC₄F₉)₂]⁻, X=Cl, Br, I, of chlorine, bromine, and iodine are prepared as their tetraethylammonium salts and characterized with IR, Raman, and NMR spectroscopic methods, as well as single-crystal X-ray diffraction analyses. Spectroscopical data are supported by quantum-chemical calculations. Additionally, the bonding situation of the species in question are analyzed and discussed. Furthermore, the oxidation to the corresponding halogenate(III) derivatives was studied. For [Br(OC₄F₉)₂]⁻, oxidation with elemental fluorine gave [BrF₂(OC₄F₉)₂]⁻. Iodide was directly oxidized by ClOC₄F₉ to the I^III species [I(OC₄F₉)₄]⁻, which is a surprisingly inert anion that might be used as a weakly coordinating anion (WCA) in the future. For [Cl(OC₄F₉)₂]⁻, the decomposition products of the synthetic approaches towards a chlorine(III) system were analyzed.     

Controlled radical polymerization in the presence of N‐oxyls

Recent development in controlled radical polymerization has provided a tool to combine a relatively robust radical polymerization technique with structural control. This contribution focuses on stable free radical polymerization in the presence of nitroxides. The influence of 2,2,6,6‐tetramethyl‐piperidine‐N‐oxyl (TEMPO) and temperature on the copolymerization of styrene and acrylonitrile will be discussed. In the second part a new class of nitroxide stable free radicals will be presented that shows enhanced performance in styrene polymerizations.     

Raman microscopic identification of gunshot residues

Raman microscopy was used to identify unambiguously the anions of lead and barium in gunshot residues (ca. 5 μm in size) deposited on cellulosic substrates. It was found that most of the particles consist of mixtures of oxides, sulphate and carbonate (along with carbon). In particular, there is strong evidence for the formation of mixed oxides of iron but only relatively little evidence for oxides of antimony. The Raman technique has been shown to be able to identify individual or mixed components and to confirm the presence of microcrystalline particles with a particular crystal structure (e.g. orthorhombic lead oxide). © 1998 John Wiley & Sons, Ltd.