A Novel Method for the Demetalation of Tricarbonyliron–Diene Complexes by a Photolytically Induced Ligand Exchange Reaction with Acetonitrile

The photochemical exchange of all three carbonyl ligands with acetonitrile converts tricarbonyliron–diene complexes into the very labile triacetonitrile-iron–diene complexes. These easily demetalate in high yields to the corresponding free ligands on injection of air at −30°C [Eq. (1)]. The novel demetalation procedure is applied to the tricarbonyliron complexes of cyclopentadienones, cyclohexa-1,3-dienes, and buta-1,3-dienes.     

Formation of Novel Dinuclear Mixed-Valence Rhodium Complexes by Intramolecular Migration of a Chelating Ligand

Significantly different coordination spheres are displayed by the two central atoms of 2 , the first representative of a novel type of mixed-valence dinuclear Rh⁰–Rh^II compound, which was synthesized from the stibane-bridged complex 1 . The Rh−Rh distance determined by an X-ray crystal structure analysis of 2 indicates a metal–metal interaction between the two metal centers.     

Electronic Communication in C4-Bridged Binuclear Complexes with Paramagnetic Bisphosphane Manganese End Groups

Building blocks for conducting polymers or NLO materials are the linear, unsaturated carbon chain bridged manganese complexes 1 ⁿ⁺ (n=0–2). All oxidation states were investigated spectroscopically and by X-ray structure determinations. The analytical data confirm a communication of the electrons over the C₄ chain—a prerequisite for electrical conductivity and NLO properties of oligo- or polymeric materials.     

Umweltchemie 1998

Nachdem im Trendbericht des letzten Jahres ausgewählte Beispiele aus Bereichen der Umweltchemie besprochen wurden,¹⁾ sollen in diesem Jahr Ergebnisse aus Ökotoxikologie and Humantoxikologie behandelt werden. Zunächst werden einige Arbeiten aus den Bereichen der Entsorgungsverfahren und neue Entwicklungen bei Spurenstoffen vorgestellt. Da das Gebiet der nachhaltigen Chemie immer mehr in den Brennpunkt des Interesses rückt, werden auch neue umweltfreundliche Synthesen und Produkte ausführlich diskutiert.     

A Novel Type of a Second Epoxy Bridge in Eunicellane Diterpenes: Isolation and Characterization of Massileunicellins A – C from the Gorgonian Eunicella cavolinii

Massileunicellins A ( 7 ), B ( 9 ), and C ( 11 ) – which show a novel type of a second epoxy bridge in eunicellane diterpenes – were isolated from the gorgonian Eunicella cavoliniii collected near Marseille. Structural assignments are based on NMR and MS data of these compounds and of their ketal derivatives 8 , 10 , and 12 . Negligible activity of the massileunicellins on L1210 and KB tumor cell lines, and similar results for related known compounds, cast doubt on high cytotoxicity reported for the latter by other authors.     

Microwave‐Sensitive Foamable Poly(ionic liquids) Bearing tert‐Butyl Ester Groups: Influence of Counterions on the Ester Pyrolysis

Several poly(ionic liquids) have been synthesized based on poly(1‐vinyl‐3‐tert‐butoxycarbonylmethylene imidazolium) salts with different counterions to investigate the tert‐butyl ester pyrolysis of these compounds. It is found that the counterions strongly influence the temperature of the pyrolysis. The pyrolysis temperature shifts to higher or lower temperatures depending on the nature of the counterions. The use of microwave irradiation was employed to accelerate the gas release because of the high dipolar interaction of amorphous salts with microwaves. The result of these reactions is the formation of organic foams that could be of industrial interest.

     

Polymerizable Ionic Liquid Crystals

Polymerizable vinylimidazolium ionic liquids (ILs) that contain mesogenic coumarin and biphenyl units, respectively, have been synthesized. The N‐alkylation of N‐vinylimidazole with bromoalkylated mesogenic units 7‐(6‐bromohexyloxy)coumarin ( 1 ) and 4,4′‐bis(6‐bromohexyloxy)biphenyl ( 2 ) was then carried out. The thermal behavior of the obtained ILs 3 and 4 was investigated by differential scanning calorimetry and polarizing optical microscopy. These measurements showed that the attached mesogenic units induce the self‐assembly of ILs and, therefore, the occurrence of liquid crystalline phases. Subsequently, the ionic liquid crystals (ILCs) 3 and 4 were polymerized by a free‐radical mechanism.

     

Symmetric Versus Asymmetric “Homologous” Vinylic Cross‐Linkers in Two‐Components Networks: Formation of Pseudo‐Conetworks or Pseudo‐IPNs

Radical copolymerizations of heterologous comonomers are compositionally heterogeneous, unless the reaction is performed in continuous conditions. A bicomponent network prepared from a heterogeneous reaction like the mentioned before is therefore a complex structure where chains with different compositions are linked through the cross‐linker molecules. It is theoretically shown here that the use of cross‐linkers with different structural homologies toward the two comonomers may lead to very different topologies. Thus, a mixture of symmetric cross‐linkers, each one homologous to each comonomer, tends to form interpenetrated networks (IPNs). However, the use of a single bihomologous asymmetric cross‐linker, where each of the functionalities is homologous toward each of the comonomers, tends to form conetworks. It is shown here that the higher the differential reactivity between the groups, the higher is the tendency toward these extreme structures.