CO2 – Baustein des Lebens und Treiber der globalen Erwärmung

For hundreds of millions of years, nature uses carbon dioxide in photosynthesis as a vital building block of life. The compound is also an essential part of the carbon cycle and is co‐responsible for the transport of carbon between Earth's spheres. However, over the last years CO₂ has been closely associated with global warming since the immense emissions from mainly the burning of fossil resources has led to a vast increase in atmospheric CO₂‐levels. Therefore, not only a reduction of emissions on a global scale is crucial but also a trend towards renewable resources is clearly visible and necessary due to depleting fossil resources. In this context, the use of CO₂ as an abundant resource in the chemical industry can contribute its share.     

Methan im Gashydrat. Gefangen im Wasserkäfig

This article shows the variety of gas hydrates regarding their occurrences, composition, characterization and potential usability. Synthetic clathrate hydrates are described as well as those hydrates occurring in nature. Different methods, embracing the spectrum from laboratory analytic methods to field use are described.     

Naturwirkstoffe aus Pflanzen. Biodiversitätsforschung

Due to its deepened natural material research the transdisciplinary biodiversity research offers new options to therapeutical challanges of the 21st century. Besides phytochemicals, known for centuries, these natural materials also include recently known material such as antiviral active high polymer polyphenols of Mediterranean rockroses or new kinds of antiadipos active bitter‐tasting compounds. Natural ressources are invaluable. To protect and preserve these, detailed knowledge of biodiversity on Earth and its embedding in the biogeosystem is required.     

Der 1: 2-Kobalt (III)-Komplex aus einem o-Hydroxy-o′-alkylamino-azofarbstoff im Vergleich mit dem durch Verbrückung erhaltenen analogen pentacyclischen Komplex

A pentacyclic Co^III complex is described which is comparable with the tetracyclic 1:2 Co^III complex from 2-aminophenol-4-methyl-sulphone → N-ethyl-2-naphtylamine. Formally, the two ethyl groups of this latter dyestuff are eliminated in the new compound and replaced by a propylene group joining the two amine-nitrogen atoms together. The pentacycle occurs in two forms: one with a single positive charge and one with a single negative charge. Both amine-nitrogen atoms are protonated in the cation and deprotonated in the anion. The tetracyclic 1:2 complex cannot form a corresponding cation; it decomposes in acid medium. The stability of the cationoid pentacycle results from a positive chelate effect due to the additional ring. From the comparison of the electron spectra of the pentacyclic and the tetracyclic 1:2 complexes the author concludes that in the pentacyclic complex the azo dyestoff halves have merely undergone a displacement of position but no torsion.     

Eine Boswelliasäure aus Weihrauch

3‐O‐Acetyl‐11‐keto‐β‐boswelliasäure was extracted from pulverized frankincense and purified by HPLC. All analytical spectra were recorded and are reproduced either in the main part or in the supporting information. The NMR‐ and mass‐spectra have been interpreted and compared with theoretical calculations of the ¹³C chemical shifts. The project is a follow up of the recent book “Classics in Spectroscopy” by S. Berger und D. Sicker (Wiley‐VCH 2009).     

Präkeramische Polyazane über die Sol‐Gel‐Route im Ammonosystem und aus molekularen Einkomponentenvorläufern — ein Leistungsvergleich

Preceramic Polyazanes via Sol Gel Route in the Ammono System and via Molecular Single Source Precursors — a Comparison of Performance All steps of the sol gel process in the oxo system can be transferred analogously to the ammono system. For this purpose, element alkyl amides of titanium, zirconium, tantalum and boron, have been co‐ammonolised with silicon alkyl amides in aprotic solvents. Pyrolysis of the resulting polyazanes yields multinary nitridic ceramic powders. For the model systems Si(NHMe)₄/Ti(NMe₂)₄, Si(NHMe)₄/Zr(NMe₂)₄, Si(NHMe)₄/Ta(NMe₂)₅, and Si(NHMe)₄/B(NMe₂)₃ the corresponding polymeric polyboro‐, polytitano‐, polyzirkono‐ and polytantalosilazanes were synthesised. Pyrolysis in flowing ammonia at 1000°C results in ternary amorphous silicon nitrides; further heating in nitrogen leads to partly crystalline composites. The process of pyrolysis as well as the morphology and composition of the final pyrolysis products were analysed by means of NMR, MAS‐NMR, FT‐IR, DTA‐TG‐MS, XRD, SEM, EDX, and elemental analyses. In order to verify this new and convenient access to multinary nitride ceramics, single source precursors were synthesised and, via polymer intermediates, processed to ceramic powders. A specially developed reaction sequence is generally applicable to syntheses of single source precursors for various ternary metal silicon nitrides. Dilithiated silazanes of the type Si(NMe₂)₂(NLiR)₂, with R = t‐Butyl, SiMe₃, CH₃, synthesised and structurally characterised for the first time, are good silicon synthones. While forming nitrido bridges, those compounds react with e.g. two‐ or four valent transition metal chlorides, to silicon transition metal adducts. Actually, we have analysed the reaction of Si(NMe₂)₂(NLiR)₂ and TiCl₄, ZrCl₄, TaCl₅, CrCl₃, MnCl₂, and ZnCl₂, respectively. The adducts as formed were crosslinked with ammonia and pyrolysed. In the case of the chlorides of the 4.—6. group metals, amorphous ceramics were obtained. Treatment at higher temperatures results in composites of transition metal nitride and an amorphous matrix. MnSiN₂ and a new hexagonal modification of ZnSiN₂ were obtained in the systems Mn/ Si/ N and Zn/ Si/ N. Surprisingly, during the synthesis of ZnSiN₂, ZnCN₂ was obtained as a side product.     

Pseudohalogenmetallverbindungen. LXXIV. Darstellung von Alkylisocyanid-Eisenkomplexen aus Isoblausäure-Eisenkomplexen und primären Alkoholen mittels Redox-Kondensation

Pseudohalogeno Metal Compounds. LXXIV. Preparation of Alkyl Isocyanide Iron Complexes from Isocyano Acid Iron Complexes and primary Alcohols via Redox Condensation Isocyano acid iron complexes Fe(CN)₂(CNH)₄ · 4Et₂O and Fe(bpy)(CN)₂(CNH)₂ · 2H₂O are esterificated with methanol and ethanol in the presence of triphenylphosphine and diethyl azodicarboxylate (Mitsunobu conditions) to give the isocyanide complexes Fe(CN)₂(CNR)₄ and Fe(bpy)(CN)₂(CNR)₂ · 2H₂O (R = Me, Et) which are characterized by their spectroscopic data.