Activated carbon as catalyst support: precursors, preparation, modification and characterization.

The preparation of activated carbon materials is discussed along selected examples of precursor materials, of available production and modification methods and possible characterization techniques. We evaluate the preparation methods for activated carbon materials with respect to its use as catalyst support and identify important parameters for metal loading. The considered carbon sources include coal, wood, agricultural wastes or biomass as well as ionic liquids, deep eutectic solvents or precursor solutions. The preparation of the activated carbon usually involves pre-treatment steps followed by physical or chemical activation and application dependent modification. In addition, highly porous materials can also be produced by salt templating or ultrasonic spray pyrolysis as well as by microwave irradiation. The resulting activated carbon materials are characterized by a variety of techniques such as SEM, FTIR, nitrogen adsorption, Boehm titrations, adsorption of phenol, methylene blue and iodine, TPD, CHNS/O elemental analysis, EDX, XPS, XRD and TGA.

Preparation of Supported Palladium Catalysts using Deep Eutectic Solvents.

Deep eutectic solvents (DESs) dissolve metal salts or oxides and are used as solvent and carbon source for the preparation of supported palladium catalysts. After dissolving of the palladium salt in the DES, the pyrolysis of the mixture under nitrogen atmosphere yields catalytically active palladium on supporting material composed of carbon, nitrogen and oxygen (CNO) by a simple single step preparation method without further activation. The catalysts were characterized by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) and CHNS/O elementary analysis. The amount of functional groups on the surface of the supporting material was determined by Boehm titrations. Moreover, the activity of the prepared catalysts was evaluated in the hydrogenation of linear alkenes and compared with a commercial Pd/C catalyst.

Preparation of Magnesium, Cobalt and Nickel Ferrite Nanoparticles from Metal Oxides using Deep Eutectic Solvents.

Natural deep eutectic solvents (DESs) dissolve simple metal oxides and are used as a reaction medium to synthesize spinel-type ferrite nanoparticles MFe2 O4 (M=Mg, Zn, Co, Ni). The best results for phase-pure spinel ferrites are obtained with the DES consisting of choline chloride (ChCl) and maleic acid. By employing DESs, the reactions proceed at much lower temperatures than usual for the respective solid-phase reactions of the metal oxides and at the same temperatures as synthesis with comparable calcination processes using metal salts. The method therefore reduces the overall required energy for the nanoparticle synthesis. Thermogravimetric analysis shows that the thermolysis process of the eutectic melts in air occurs in one major step. The phase-pure spinel-type ferrite particles are thoroughly characterized by X-ray diffraction, diffuse-reflectance UV/Vis spectroscopy, and scanning electron microscopy. The properties of the obtained nanoparticles are shown to be comparable to those obtained by other methods, illustrating the potential of natural DESs for processing metal oxides.

About the polymorphism of [Li(C4H8O)3]I: crystal structures of trigonal and tetra-gonal polymorphs.

Two new trigonal and tetra-gonal polymorphs of the title compound, iodido-tris-(tetra-hydro-furan-κO)lithium, are presented, which both include the isolated ion pair Li(THF)3 (+)·I(-). One Li-I ion contact and three tetra-hydro-furan (THF) mol-ecules complete the tetra-hedral coordination of the lithium cation. The three-dimensional arrangement in the two polymorphs differs notably. In the trigonal structure, the ion pair is located on a threefold rotation axis of space group P-3 and only one THF mol-ecule is present in the asymmetric unit. In the crystal, strands of ion pairs parallel to [001] are observed with an eclipsed conformation of the THF mol-ecules relative to the Li⋯I axis of two adjacent ion pairs. In contrast, the tetra-gonal polymorph shows a much larger unit cell in which all atoms are located on general positions of the space group I41 cd. The resulting three-dimensional arrangement shows helical chains of ion pairs parallel to [001]. Apart from van der Waals contacts, no remarkable inter-molecular forces are present between the isolated ion pairs in both structures.

Organocuprate conjugate addition: structural features of diastereomeric and supramolecular pi-intermediates.

In the reaction pathway of conjugate additions with organocuprate reagents, Cu(I) pi-complexes and Cu(III) sigma-complexes have been identified as central, NMR-detectable intermediate species. However, no experimental evidence for the structures of pi-intermediates with extensive chiral enones or the principal aggregation level and aggregate structure of pi-complexes in diethyl ether has been available so far. Furthermore, the structural characteristics of pi-complexes which are essential for their high reactivities and diastereoselectivities have not yet been rationalized experimentally. Therefore, the pi-intermediates of 4,4a,5,6,7,8-hexahydro-4a-methyl-naphthalen-2(3H)-one and Me2CuLi or Me2CuLi x LiX (X = I, CN) in diethyl ether are investigated in detail. For the first time, the formation of two intermediate cuprate enone pi-complexes on both sides of the double bond is observed. In addition, the conformation of the enone adopted in the major beta-face pi-complex rationalizes the exclusive syn addition observed in the synthetic product. For the investigation of the aggregation level and structure, a NMR screening of pi-complexes with Me2CuLi x LiX (X = I, CN) and three achiral enones is performed, which simplifies the spectra by the generation of enantiotopic pi-complexes. Thus, NMR diffusion experiments on cuprate intermediates and the detection of scalar couplings across copper without isotope labeling are possible for the first time. Extensive NMR studies, including those of cyclohexanone complexes, show that, in principle, salt-free dimethylcuprate is able to complex the carbonyl group. However, in the presence of salt, the carbonyl-complexing aggregates are composed of salt and cuprate moieties. These mixed aggregates cause the formation of large supramolecular pi-intermediate structures which control their reactivity. The pi-complexing cuprate units show a bent geometry as a general structural feature that is unaffected by the presence or kind of salt and the type of enone. Thus, the high diastereoselectivity and the reactivity of organocuprate 1,4-addition reactions are for the first time rationalized on the basis of structural characteristics of selected pi-intermediates.

Traffic accident or dumping? - Striking results of a traffic accident reconstruction.

An atypical traffic accident scenario should be investigated directly at the crash site from all concerned professions, especially police men, forensic pathologists and technical experts, to get a personal overview and impression of the situation and the opportunity for interdisciplinary discussion. We present the rare case of a fatal traffic accident on a German motorway which was initially thought to be an accidental discovery of dumping a corpse. Based on autopsy findings, the technical investigation and the accident reconstruction, this case was solved as a spectacular form of a collision between a pedestrian and a bonnet-front car, which was not described elsewhere in scientific literature to the best of our knowledge. The pedestrian was hit in an upright body position, was lifted up by the car, smashed the windscreen and flew over the car with several body rotations. His flight curve ends directly at the roof of the car during brake processing, where the body touched the roof, smashed the rear-window and landed in the trunk. Based on the technical investigation, the driver of the car was not able to hide the accident. However, the pedestrian could have avoided the collision if he did not cross the motorway on foot.

Ligand exchange reactions in Cu(III) complexes: mechanistic insights by combined NMR and DFT studies.

NMR studies of (13)C/(12)C isotopic patterns in Cu(iii) intermediates and reaction products together with DFT calculations of possible reaction pathways indicate an intermolecular S(N)2 like substitution mechanism for ligand exchange reactions in square planar Cu(iii) complexes, which is proposed to be slow compared to reductive elimination at synthetic conditions.