A contribution to the ternary phase diagram Co-Sb-Te

The melting behaviour, some phase boundaries and the lattice parameters in the region of the NiAs-type phase in the ternary system cobalt-antimony-tellurium have been determined by differential thermal analysis and X-ray diffraction. A projection of the liquidus surface and the phase relationships in different sections with constant antimony/tellurium ratios are presented. The peculiar variation of the lattice parameters with the composition of the nonstoichiometric NiAs-type phase is discussed in terms of the defect structure.Dedicated to Prof. K. L. Komarek on the occasion of his 65th birthday     

Asymmetric synthesis of 6-(2′,3′,4′,5′,6′-pentafluorophenyl)-δ-lactones via “allyl”boranes: application for the synthesis of fluorinated analog of key pharmacophore of statin drugs

Asymmetric “allyl”boration of pentafluorobenzaldehyde with various α-pinene based “allyl”boranes provides homoallylic alcohols in high de and ee; the alcohols have been converted into δ-lactones via acryloylation, ring-closing metathesis and hydrogenation. Pentafluorophenyl analog of key pharmacophore of statin drugs has been synthesized using diastereoselective epoxidation and regioselective reduction as key steps.     

Vinyl‐type polymerization of norbornene by nickel(II) bisbenzimidazole catalysts

Novel nickel(II) bisbenzimidazole complexes were prepared via a three‐step synthetic procedure consisting of aniline/diacid condensation, ligand N‐alkylation, and metal complexation. The complexes were characterized by X‐ray crystallography and found to possess a pseudotetrahedral geometry. Upon activation with methylaluminoxane, these nickel bisbenzimidazoles did not polymerize simple olefins (e.g., ethylene, propylene, and 1‐butene) but were found to carry out the rapid and efficient polymerization of norbornene. The polynorbornene products were characterized by gel permeation chromatography/light scattering, ¹³C NMR, and IR, and their Mark–Houwink and dn/dc parameters were determined. The molecular weights of the polynorbornenes were very high (weight‐average molecular weight = 587,000–797,000 g/mol). ¹³C NMR suggested that the polymerization occurred via vinyl addition (i.e., a 2,3‐linked polymer); no ring‐opened product was observed. Thermogravimetric analysis indicated that the polynorbornenes were stable up to 400 °C under nitrogen. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2095–2106, 2003     

Rückbezüge des Mathematikunterrichts und der Methodik des Mathematikunterrichts in der DDR auf historische Vorausentwicklungen

The author discusses at some examples exemplarily, how the pedagogy of mathematics education in the GDR from curricular and educational/psychological knowledge from the time before 1945 has developed scientifically.