Angewandte Chemie International Edition in English

The Cover picture show the bright orange-colored solution of a catalyst containing the depicted phosphane–rhodium fragment (M = Rh) in pure compressed CO₂. At 24°C, that is below the critical temperature, liquid and gaseous CO₂ are in a phase equilibrium, and the catalyst dissolves in the liquid phase. At the critical point (T = 31°C) the difference between gaseous and liquid phase disappears, and the catalyst becomes distributed in the compressed medium. Above the critical point, at 36°C, a homogeneous, supercritical phase (scCO₂) exists. The high solubility of the catalysts in supercritical CO₂ is attributed to the F(CF₂)_n(CH₂)₂ side chains (shown as waved lines). Provided that a suitable substitution pattern is maintained at the aromatic ring, these chains do not change the chemical and catalytic behavior of the active center (dashed oval) in comparison to those of the unsubstituted fragment. Thus, for the first time the well-know potential of arylphosphorus compounds as ligands for homogeneous catalysis is available for application in scCO₂. More about these findings is reported by W. Leitner et al. on pages 1628 ff. Similar rhodium and iridium complexes, which can be applied in fluorous biphase catalysis with CF₃C₆F₁₁ as solvent are described by I. T. Horvéth, J. A. Gladysz et. al. on. pages 1610 ff. and 1612 ff.

Although counterintuitive, the conjecture that high-symmetry, low-entropy truncated icosahedron C₆₀ spontaneously forms out of the chaos of condensing carbon vapor proved to be true. The observation that the cluster of 60 carbon atoms is singularly chemically unreactive, as exemplified by its flagpole prominence in mass spectra, could be explained only by this hypothesis. This resulted in more conjecture, some of which proved correct, whereas others relating C₆₀ to diffuse interstellar bonds and soot formation remain speculative. Even if of questionable validity, these speculations have played a useful role in driving chemists to think about the formation of fullerenes and other carbon morphologies.

Basic research must continue to be supported! This is one of the conclusions clearly evident from the story behind the discovery of the fullerenes. The questions to which answers were originally sought would not have been posed within the current confines of programs aimed increasingly at applied research. This and the fascination associated with C₆₀ and other members of the fullerene family are the central messages in this Nobel lecture.

Bucky get the prize—eleven years after the discovery of C₆₀ in 1985, the realization that carbon makes this truncated isosahedral molecule, and larger geodesic cages, all by itself is honored with the Nobel Prize. Only with the development of laser-vaporization cluster beam methods did the particular signification of C₆₀ become apparent. Indeed the discovery process with respect to fullerenes and the properties of carbon is far from being complete.

Very large, planar, polycyclic aromatic hydrocarbons such as “supernaphthalene” and “supertriphenylene” (1) are easily constructed by a Diels–Alder reaction and subsequent cyclodehydrogenation.

Quantitative skeletal rearrangements in the intramolecular cyclodehydrogenation of oligophenylenes such as 1 lead to planar polycyclic aromatic compounds such as 2.

The “Teflon greaseball” [RhCl{P[CH₂CH₂((CF₂)₅CF₃]₃}₃] (1) is highly soluble in CF₃C₆F₁₁ and catalyzes a variety of organic transformations. The products can be extracted with organic solvents, and the solution of 1 reused. This environmentally friendly protocol is showcased for hydroboration, in which the customary oxidative workup destroys the metal catalyst. Catalyst loadings of only 0.01–0.25 mol% are effective under mild conditions (25–40°C, 1–40 h) and give turnover numbers as high as 8500.

The most highly fluorinated aliphatic species crystallized to date is 1 an exceptionally interesting molecule with regard to its structure and from a mechanistic standpoint. Four of the fluroalkyl groups form raftlike domains, which pack back-to-back in a motif that maximizes parallel chains (depicted on the right). Complex 1 and CH₃I react by a free redical chain mechanism in CF₃C₆F₁₁, as opposed to the polar pathway for Vaska's complex in organic solvents. Although O₂ is highly soluble in CF₃C₆F₁₁, its additions to 1 slower than in common organic solvents.

Chemotherapy of malignant tumors is extremely problematic because of the low selectivity of the available cytostatic agents. The now synthetically available ether 2—the first stable analogue of lactone 1, which was identified as the tumor-associated antigen—presents the possibility for an active immunization against cancer.

Thermal stability (up to 350°C) is one of the characteristics of the supramolecular mesogenic polyamide formed by self-assembly during the complexation between a phyenylbezoic acid and a nylon containing pyridyl units in its backbone. The probable structure of the hydrogen-bonded complex is shown schematically on the right.

Rectangular channels lined with methylene groups characterize the structure of the title compound. The framework is constructed from CoO₆ octahedra and CoO₄ tetrahedra that are linked through OPO bonds (structure depicted on the right). The hydrophobic channels appear suitable for the uptake of flat guest molecules.

Generation of three stereogenic centers in the angular tetracyclic framework of 3 is possible starting from enantiomerically pure naphthoquinone 1 and the substituted racemic vinylcyclohexene 2.The product 3 is formed in a one-pot domino reaction comprising Diels–Alder cycloaddition and pyrolytic elimination of the sulfoxide. The key step is the kinetic resolution of the racemic diene.

Zwitterionic species are most likely the intermediates for the formation of 1,1-diohalo-2,3-diarylbutadiens by addition of dihalocarbenes to 1,2-diarylcyclopropenes [Eq. (a)]. Bicyclobutanes can be out as intermediates for the formation of butadienes.

The presence of an aqua bridge in the active and phosphate-bound reduced form of manganese-containing catalases is the key finding from magnetization studies on these compounds. In addition several observations indicate that the phosphate group may form a second bridge. which suggests that two syn coordination sites of the active dimanganese center are occupied by easily exchangeable ligands, namely water molecules. The proposed structures are depicted on the right.

The solubility of complexes is one decisive factor for their use as homogeneous catalysis in supercritical carbon dioxide (scCO₂). Complexes with perfluoroalkyl-substituted arylphosphane ligands (shown schematically on the right), which can be prepared by a straightforward and variable synthetic methodology, exhibit high solubility in scCO₂ in contrast to unsubstituted parent compounds.

Extremely bathochromically absorbing derivatives of the halobacterial membrane protein bacteriorhodopsin(λ_max = 570 nm) form upon incorporation of merocyanine dyes of the type shown below into the protein binding site. Upon covalent attachment to the protein (through formation of a protonated Schiff base), these compounds convert in to hemicyanines in which the positive charge is distributed over the entire π system of the chromophore.

The size and shape of the molecules of the aliphatic hydrocarbon solvent have a strong influence on the magnitude of the anomalous spectral shift in the fluorescence maximum of the charge transfer (CT) state of a high-generation dendrimer (shown schematically on the right). Its molecules no longer exist in an open extended form but exhibit a compact, globular structure, and the dipole moment of the CT state in pentane is larger than in cyclohexane.

The molecular geometry is mirrored in the macroscopically ordered patterns found in a series of stiff, phenylacetylene dendrimers 1. These compounds form hexagonal columnar liquid crystalline phase with snowflake-like morphologies.

By immobilizing the cobalt complex 1 on the glycine-functionalized inner walls of mesoporous silica (MCM-41), and efficient heterogeneous catalyst for the selective oxidation of cyclohexane to cyclohexanone with tert-butyl hydroperoxide is produced. The detailed atomic structure of the active site during catalysis was determined by in-situ X-ray absorption spectroscopy. The findings are important for the design of new efficient oxidation catalysts.

Clear confirmation of recent theoretical studies concerning the structure of the endohedral complexes formed by La and C₈₀ is provided by the NMR spectroscopic investigations presented here Complex La₂@C₈₀ is present, and its structure is based on the unstable “empty” I_h isomer of C₈₀. The two La atoms circulate inside this round cage even at room temperature (shown schematically on the right).

Novel reagents for olefin amination—A new class of manganese(V) nitrides containing Schiff bases as ligands was prepared from the corresponding Mn_III complexes following a new oxidative procedure. Structures of examples of both the Mn_III starting material and the Mn_v product have been confirmed by X-ray crystallography. These MnN complexes such as 1 are potentially effective reagents for nitrogen-atom transfer, as could be demonstrated by the reaction with styrene.

The differentiated recognition of Ag¹ and Hg¹¹ can be achieved with the pentaleno crown ethers 1 by variation of the cavity through the reversible trithia-diazapentalene–trithiotriuret redox system (1⇌2). These compounds were obtained in a one-pot reaction of trithiadiazapentalenes with diamino polyethers of different chain lengths. n = 1–3, R = CH₃, CH₂C₆H₅.

Promising as a chelating agent and as a photosensitizer hemiporphycene is the third porphyrin isomer after porphycene and corrphycene with a central N₄ coordination sphere. The stable octaethyl derivative of hemiporphycene 1 was obtained by the combination of a McMurry reaction a reductive CC cleavage from a bis(tetraphyrroledialdehyde). Like its congeners. 1 possesses a planar ring skeleton.