bluuebunny/crossref_metadata_2025 huggingface dataset:
Photo‐CIDNP in the Vacuum‐UV: Di‐tert‐butyl Ether and 2,2,5,5‐Tetramethyltetrahydrofuran in Aqueous Solution
Authors: Hildenbrand Knut , Schuchmann Heinz‐Peter , von Sonntag Clemens
Published: December 2003

Homolytic bond cleavages and photoionization occur upon irradiation of the title compounds in O2‐free D2O. In order to monitor the photochemical reactions spectroscopically, photo‐CIDNP experiments with laser excitation were carried out (ArF‐excimer laser, λ = 193 nm). In the case of tBu2O the products CH3D and C2H6 could be detected. This finding enables formulation of a reaction sequence, which starts with formation of the radical cation tBu2O⊙ ⊕. Non‐aqueous solutions of the title compounds and aqueous solutions of primary, secondary and monotertiary ethers showed no polarized NMR signals upon illumination.
Shortened CC Bonds and Antiplanar OCOH Torsion Angles in 1,4‐Cubanedicarboxylic Acid
Authors: Ermer Otto , Lex Johann
Published: December 2003

Larger bond angles—shorter bond lengths: This interrelationship gained further confirmation by the X‐ray structure analysis of 1,4‐cubanedicarboxylic acid. Whereas the exocyclic CC bonds (bond angle ca. 125°) are shortened to about 1.48 Å, the endocyclic CC bonds are stretched to about 1.57 Å. Moreover, the antiplanar OCOH partial conformation found in half of the molecule, which could be favored by the layer‐packing of the cubanedicarboxylic acid molecules, is very rare.
Quino[7,8‐h]quinoline, a New Type of “Proton Sponge”
Authors: Zirnstein Michael A. , Staab Heinz A.
Published: December 2003

So far, “proton sponges” have been defined as bis(dialkylamino)arenes whose dialkylamino groups are in close spatial proximity.[1] The unusual basicity of these compounds is ascribed to the destabilizing overlap of the lone electron pairs on the nitrogen atoms, to the formation of especially strong hydrogen bonds in the monoprotonated diamines, and to the hydrophobic shielding of these hydrogen bonds. In order to differentiate and assess the relative importance of these factors, we were interested in quino[7,8‐h]quinoline 1, whose nitrogen atoms exhibit a mutual orientation similar to that in 1,8‐bis(dimethylamino)naphthalene 2 (“proton sponge”). In contrast to 2, however, 1 lacks the hydrophobic shielding of the hydrogen bonds of its monoprotonated derivative. This shielding is considered to be responsible for the low rates of proton transfer, which make the “proton sponges” reported so far unsuitable as auxiliary bases in chemical reactions.
Amavadin, an Example for Selective Binding of Vanadium in Nature: Studies of Its Complexation Chemistry and a New Structural Proposal
Authors: Bayer Ernst , Koch Eckhard , Anderegg Giorgio
Published: December 2003

The selective enrichment of metals in nature is of great interest.[1] For example, the concentration of vanadium in the blood of tunicates is a millionfold higher than in sea water.[2–4] Fly agaric (Amanita muscaria) also concentrates vanadium.[5,6]The structure of the vanadium compound of tunicates has not yet been elucidated.[7,8] However, a structure (3) has been proposed[9] for the vanadium compound of fly agaric, amavadin.[9‐11] The structural elucidation and synthesis of the organic ligand 1b[9b] allows, for the first time, the specificity of a naturally occurring vanadium ligand to be investigated. Amavadin can be prepared from VIVO salts and synthetic 1b.[9b] Since the ligand 1b was previously unknown and since all attempts to obtain crystals of amavadin suitable for an X‐ray structure analysis failed, a detailed investigation of the complex formation of 1b should also provide an answer to the question of the arrangement of the ligands around the central atom in amavadin.
Cs3Mo5P6O25: a Novel Molybdenum Phosphate Containing a Cubane‐like Mo4O4 Cluster with Six Molybdenum‐Molybdenum Bonds
Authors: Lii Kwang‐Hwa , Haushalter Robert C. , O'Connor Charles J.
Published: December 2003

For corrigendum see DOI:10.1002/anie.198708041
Structural Dynamic of Collagen Fibers Cross‐Linked with Isocyanates; Application of Synchrotron Radiation in Macromolecular Chemistry
Authors: Mosler Erika , Dieringer Hans , Fietzek Peter P. , Folkhard Waltraud , Knörzer Ernst , Koch Michel H. J. , Nemetschek Theobald
Published: December 2003

The differentiation between intermolecular and Interfibrillar cross‐linking has been achieved experimentally for collagen fibers for the first time. Decisive for this success was the use of a diisocyanate instead of dialdehydes to carry out the cross‐linking as well as the use of synchrotron radiation. The extent of intermolecular cross‐linking depends on the reaction time. These results should be applicable not only to collagen fibers but also to other fibrous biological polymers and high polymers whose structural dynamics can be studied by X‐ray diffraction analysis.
Superconductivity—a Chemical Phenomenon?
Authors: Simon Arndt
Published: December 2003

The discovery of the oxidic high‐temperature superconductors has not only opened up scores of new applications but has also provided the chemist with straightforward relationships between the phenomenon of superconductivity and the more common concepts of oxidation number, changes in coordination, etc. The formation of Cooper pairs in oxocuprates is ascribed to valence fluctuations between Cu+ and Cu3+. The oxygen, owing to its variable polarizability, thereby plays a crucial role—as in oxidic ferroelectric substances.
Ag[MF6]2 (M  Nb, Ta), Ternary fluorides of Divalent Silber
Authors: Müller Bernd G.
Published: December 2003

High‐pressure fluorination (p ≈ 3 kbar) of Ag2O/Ta2O3 mixtures afforded brilliant‐blue single crystals of Ag[TaF6]2. The crystal structure is surprisingly simple: three isolated and noticeably elongated AgF6 octahedra are each coupled cis with one another above and below the (100) plane via TaF6 octahedra. The magnetic behavior—paramagnetism—is understandable, but F‐bridges, through which magnetic interactions could take place, are lacking.
Structure Elucidation of a New Icosapeptide from Human Semen
Authors: Schneider Klaus , Reiner Josef , Spiteller Gerhard
Published: December 2003

Only 300 μg of the new oligopeptide 1 was available for a structure determination. The sequence could be determined by a combination of liquid secondary ion mass spectrometry (LSIMS) and Edman degradation. Crucial for this success was the observation that the sample used for the mass spectrometric analysis could be eluted unchanged from the target and subsequently used for an Edman degradation.
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Triphosgene, a Crystalline Phosgene Substitute
Authors: Eckert Heiner , Forster Barbara
Published: December 2003

Thermally stable, not very volatile, easy to transport and to store, accurately dosable—these are the advantages of bis(trichloromethyl) carbonate 1 as a substitute for phosgene. In addition, stoichiometric amounts of 1 suffice for chloroformylations, carbonylations, chlorinations, and dehydrations, which, moreover, proceed in good to very good yields.
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Nonaphenyltristiboxane‐1,5‐diyl Disulfonates
Authors: Rüther Robert , Huber Friedo , Preut Hans
Published: December 2003

Tristiboxanes were hitherto inaccessible. Reaction (a) now enables the synthesis of the tristiboxane 1, which presumably is present in equilibrium with other phenylantimony species in solution. The considerable dissymmetry within the bent SbOSb bridges of 1a can be attributed to the positive partial charge of the external antimony atoms and the stronger interaction resulting therefrom with the lone pair of the bridge oxygen atom.
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Dimanganese Heptoxide for the Selective Oxidation of Organic Substrates
Authors: Trömel Martin , Russ Manuel
Published: December 2003

Stable solutions of Mn2O7, which is explosive in the pure form, have been prepared. These solutions—in CCl4 or Freon 113—can be used to oxidize primary alcohols to carboxylic acids [reaction (a)], secondary alcohols to ketones, alkenes to carboxylic acids (CC cleavage), and ethers to esters (or lactones). The reactions proceed in aprotic medium at low temperatures to afford good yields of products; the workup is simple.
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cis‐ and trans‐1,2‐Dilithioethylene
Authors: Maercker Adalbert , Graule Thomas , Demuth Wolfgang
Published: December 2003

By double mercury‐lithium exchange using tert‐butyllithium, it has been possible for the first time to prepare both cis‐ and trans‐1,2‐dilithioethylene. Both compounds are unstable and lose lithium hydride; however, the cis compound reacts more rapidly than the trans compound. The title compounds were identified by reaction with dimethyl sulfate.
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IR Emission Analysis of Temperature Profiles in Pt/SiO2 Catalysts during Exothermic Reactions
Authors: Georgiades George , Self Valerie A. , Sermon Paul A.
Published: December 2003

During H2 oxidation and cyclohexene hydrogenation on Pt/SiO2 heterogenous catalysts, the temperature of the Pt crystallite can be much higher than that of the SiO2 support. The extent of this temperature rise depends on the reaction. There is a wide range of temperatures on the catalyst particles, but these temperatures remain stable during the reaction. These findings, obtained by IR emission spectroscopy, are of importance for the kinetic analysis of heterogeneously catalyzed reactions.
Lithium‐Tellurium Exchange: A New Entry to Organolithium Compounds
Authors: Hiiro Tomoki , Kambe Nobuaki , Ogawa Akiya , Miyoshi Noritaka , Murai Shinji , Sonoda Noboru
Published: December 2003

Compounds of the type Rli, with R PhC°C, PhCH2 Ph, CH2  CHCH2, alkyl, Me3SiCH2, PhCH2OCH2, etc., can be generated in an indirect way by the route shown below. In a one‐pot procedure, the tellurides are formed directly from alkyl halides and tellurolates RTeLi. The procedure particularly valuable when conventional lithium‐halogen exchange is not possible.
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Control of the Superconducting Properties of YBa2Cu3O7 by Topotactic Redox Reactions
Authors: Eickenbusch Heinz , Paulus Werner , Gocke Elmar , March Joachim Friedrich , Koch Hans , Schöllhorn Robert
Published: December 2003

The critical temperature of the phase transition normal conductivity/superconductivity can be controlled continuously and reversibly between 93 K and 30 K for the high‐temperature superconductor YBa2Cu3O7 over a nonstoichiometric range Yba2Cu3Ox (7 ≥ x ≥ 6.5) by means of topotactic oxygen intercalation and deintercalation. Hydrogen and lithium can also be inserted into the lattice of the superconductor at low temperatures. 7Li‐NMR investigations revealed a high mobility of the Li ions at room temperature.
Modern NMR Spectroscopy of Organolithium Compounds
Authors: Günther Harald , Moskau Detlef , Bast Peter , Schmalz Dietmar
Published: December 2003

Modern methods of NMR spectroscopy, in particular the two‐dimensional techniques, offer new chances for structure determinations in the field of organolithium compounds, where the combination of 1H‐, 13C‐, and 6(7)Li‐NMR spectroscopy is an especially useful feature. Chemical shift correlations which also include the lithium nuclei allow a complete assignment of the 1H‐, 13C‐, and 6Li‐NMR spectra and thereby a better characterization of the various aggregates and complexes present in solution. Spatial proximities of 6Li and 1H can be detected by nuclear Overhauser experiments, and 6(7)Li‐NMR exchange spectroscopy can provide new information with regard to the mechanisms and energetics of dynamic processes like aggregate interchange and complexation. After a short resumé of the experimental aspects of the NMR spectroscopy of organolithium compounds and a discussion of the NMR parameters of these systems, new experimental techniques are presented. Areas of application of these newly conceived one‐ and two‐dimensional NMR experiments are illustrated with selected examples. The results show that even more detailed information about the structure and reactivity of organolithium compounds, which are so important for organic synthesis, can be expected in the future.
Superconductivity—a New Classification of the Chemical Bonding in the Solid Allows to Understand Its Occurrence
Authors: Urland Werner
Published: December 2003

The interplay of electron delocalization, localization and correlationwith about equal energy contributions is decisive for the occurrence of superconduction. As further development of the concepts of other scientists (particularly those of Wooley and Anderson) a kind of phase diagram is presented in which the solid states are classified according to the energies of the three electronic interactions EDel, ELoc and ECorr. In this way superconductors are found to be grouped in the neighborhood of the “triple point”.
Clusters of Valence Electron Poor Metals—Structure, Bonding, and Properties
Authors: Simon Arndt
Published: December 2003

Metals in low oxidation states are capable of forming metal–metal bonds. An attempt has been made to classify the numerous phases and structures occurring in such metal‐rich systems of valence electron poor metals in some sort of order from a rather general point of view. With this purpose in mind, clusters of these elements, their different types of interconnections, and their condensation via shared metal atoms, which finally leads to extended MM bonded structures, are described. Interstitial atoms play an important role in stabilizing electron deficient clusters, and can actually lead to the loss of all MM bonds. Surprising similarities emerge between apparently very different systems as the metal‐rich oxides of alkali metals, the oxides, halides, and chalcogenides of d transition metals, and the halides and carbide halides of the lanthanoids.
Tetrahedrane and Cyclobutadiene
Authors: Maier Günther
Published: December 2003

Tetra‐tert‐butyltetrahedrane—a useless molecule? In the first part of this progress report an attempt is made to answer this provoking question in order that the reader can evaluate why it is worthwhile to track such an esoteric molecule. An account of the unusual properties of tetra‐tert‐butyltetrahedrane, the only tetrahedrane unequivocally identified so far, and the most highly strained saturated hydrocarbon of all, is followed by a summary of attempts to synthesize the parent compound. The emphasis in these two sections is on our own research achievements. Since any discussion of the tetrahedranes must necessarily include the corresponding cyclobutadienes, it was found appropriate to organize the article at the same time as a final account of the cyclobutadiene problem. Masamune[8c] characterized his excellent report in 1980 in the journal Tetrahedron as a comma in the history of cyclobutadiene. Meanwhile, the significant questions have been answered. The time is now ripe to replace the comma by a full stop.
Oxo‐Bridged Polyiron Centers in Biology and Chemistry
Authors: Lippard Stephen J.
Published: December 2003

The functions of iron in biology are often associated with heme or iron‐sulfur proteins. But dioxygen transport, reduction of ribo‐ to deoxyribonucleotides, acid phosphatase activity, oxidation of methane to methanol, and iron storage are amont the growing list of biological phenomena known or believed to be associated with a newly emerging class of proteins having oxo‐bridged di‐ or polyiron aggregates at their metallic cores. The recognition of these iron–oxo proteins as a separate class has stimulated efforts on the part of inorganic chemists to prepare and characterize model compounds that replicate the physical properties and functions of the polymetallic protein cores. As a consequence, a variety of new oxo‐bridged di‐, tri‐, tetra‐, hexa‐, octa‐, and undecairon aggregates has been synthesized. These novel molecules promise not only to provide insight into the detailed characteristics of the metal centers in iron–oxo proteins, but also to serve as a focal point for preparing new materials, including oxidation catalysts and corrosion inhibitors, for the evolution of new theories to describe their physical properties, for developing new strategies for the treatment of iron‐related disease, and for building links between the chemistry of the biosphere and the geosphere.
The Reagent Diphenyldiselane/Iodine: No Phenylselenenyl Iodide but a Charge Transfer Complex with Cyclic Moieties
Authors: Kubiniok Silvia , du Mont Wolf‐Walther , Pohl Siegfried , Saak Wolfgang
Published: December 2003

Eight‐membered, slightly puckered rings [Se(Ph)Se(Ph)IISe(Ph)Se(Ph)II] are present in the crystalline title compound 3c; in analogy to the bulky subsituted species 2a, b, the structure PhSeI had been expected. 3c, with its hypervalent iodine and selenium atoms, acts as “frozen‐in intermediate” of the dismutation of seleniumselenium bonds with iodine. The rapidly established equilibria between the reactants 1 and the products 2 and 3 provide an explanation for the iodine‐catalyzed crystallization of rigid selenium melts.
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Two‐Dimensional NMR Spectroscopy: Background and Overview of the Experiments [New Analytical Methods (36)]
Authors: Kessler Horst , Gehrke Matthias , Griesinger Christian
Published: December 2003

An exact knowledge of the structure, dynamics, and reactions of molecules provides the key to understand their functions and properties. NMR spectroscopy has developed, through the introduction of two‐dimensional methods, into the most important method for the investigation of these questions in solution. A great variety of different techniques is available. However, for their successful application not only the appropriate equipment is required, but also the right choice of experiments and optimum measurement parameters, as well as a careful evaluation of the spectra. This contribution describes the necessary background for modern NMR spectroscopy. With the aid of the so‐called product operator formalism it is possible to understand pulsed Fourier transform NMR spectroscopy both qualitatively and quantitatively. Very few, readily understandable assumptions are sufficient for confident application of these methods. This article attempts to introduce in a simple manner this formalism as well as phase cycles necessary for the understanding of pulse sequences, and to train the reader through the discussion of several 2D NMR techniques. An overview of the most important techniques is given in the second part of this article.
Rhodium‐Catalyzed Reductive Carbonylation of Methyl Formate to Acetaldehyde
Authors: Vanhoye Didier , Melloul Serge , Castanet Yves , Mortreux André , Petit Francis
Published: December 2003

The title reaction provides a selective route to acetaldehyde; rhodium compounds in combination with iodide‐containing promoters serve as catalysts. Tertiary amides such as N‐methylpyrrolidone (NMP)—used here as solvent—are indispensible for achieving high activity and high selectivity (up to ca. 80%). Mainly methanol and methyl acetate are formed as by‐products.
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Controlling the Microstructure of Monomolecular Layers
Authors: Möhwald Helmuth
Published: December 2003

This review reports on the range of lateral structures which have been detected in ultrathin organic films using the newly‐developed techniques of fluorescence microscopy and X‐ray scattering, together with more conventional methods. A number of unusual low‐dimensional ordering processes have been revealed. Hexagonal, lamellar or fractal domain structures are observed and shown to result from an interplay of electrostatic forces due to molecular alignment at interfaces, line energy between different phases and growth kinetics. On a molecular level the microstructure is distinguished by low coherence length of positional order but long coherence length concerning the orientation of crystallographic axes. It is demonstrated that the ideas presented are also relevant to adsorbate structures at interfaces and to the protein arrangement in monolayers.
Somatic Generation of Immune Diversity (Nobel Lecture)
Authors: Tonegawa Susumu
Published: December 2003

How does an organism manage during its lifetime to respond to a huge number of different antigens, even though the number of antibody genes is, of necessity, limited? The Nobel Prize for Medicine was awarded to Susumu Tonegawa in 1987 for providing an answer to this question. Tonegawa discovered that not a single complete gene for an antibody peptide chain is inherited by an organism. Instead, the genetic information in the germ line is contained in several hundred gene segments. Somatic recombination of these gene segments during the differentiation of B lymphocytes results in the production of tens of thousands of complete genes. Somatic hypermutation of these genes leads to further diversification of antibody peptide chains in such a way that B cells that carry immunoglobulin receptors displaying good recognition of specific antigens are selected for in a later phase of B‐cell differentiation.
Protein Phosphorylation in Bacteria—Regulation of Gene Expression, Transport Functions, and Metabolic Processes
Authors: Deutscher Josef , Saier Milton H.
Published: December 2003

The importance of protein phosphorylation to the regulation of physiological processes in eukaryotic cells has been known for almost half a century. In contrast, the first conclusive evidence for functionally relevant protein phosphorylation in bacteria was obtained less than a decade ago. To date, only five functionally well‐characterized bacterial proteins have been shown to be regulated by reversible phosphorylation. (1) Phosphorylation of isocitrate dehydrogenase in Escherichia coli controls the relative flux of carbon through the Krebs cycle and the glyoxylate shunt. (2) In gram‐positive bacteria, phosphorylation of HPr, a phosphoryl carrier protein of the phosphoenolypyruvate‐dependent sugar phosphotransferase system, regulates carbohydrate uptake via this system. (3) Phosphorylation of glycerol kinase in Streptococcus faecalis probably serves to regulate the degradation of glycerol. (4) Phosphorylation of the nitrogen regulatory protein I (NR1) in E. coli controls expression of genes encoding the enzymes which participate in nitrogen metabolism. (5) Phosphorylation of citrate lyase ligase in Clostridium sphenoides regulates the conversion of citrate lyase from the inactive sulfhydryl form to the active acetylated form. Recent investigations have shown that more than one hundred proteins in E. coli are phosphorylated. It can therefore be anticipated that protein phosphorylation will prove to be as important to the regulation of physiological processes in bacteria as it is in eukaryotes.
Isolated, Complex Zintl Molecules in the Gas Phase
Authors: Hartmann Andreas , Weil Konrad G.
Published: December 2003

Ternary and quaternary intermetallic molecules such as Cs2InSb3 and CsSnBiSb2, respectively, can be detected in the vapor above the corresponding alloys by mass spectrometry. The composition of the compounds is in agreement with the Zintl‐Klemm‐Busmann concept, if one assumes that the alkali metal transfers an appropriate number of electrons to the elements of the third and fourth main groups in the Sb4 tetrahedra, such that these elements become isoelectronic to Sb.
Photolytic Cluster Synthesis: Synthesis and Structure of [{(Ph3P)Au}7Mo(CO)3]OH
Authors: Beuter Georg , Strähle Joachim
Published: December 2003

The photolytic elimination of N2 from [(Ph3P)AuN3] is the basis of a new method for preparing gold clusters. The photolysis of a mixture of [(Ph3P)AuN3] and [Mo(CO)6] in THF results in loss of N2 and CO and formation of the title compound, in which the Mo atom forms the center of a novel icosahedral fragment consisting of seven Au atoms. Only a few examples of gold clusters containing heterometal centers were previously known.
Phase Transformations of Lithium Nitride under Pressure
Authors: Beister Heinz Jürgen , Haag Sabine , Kniep Rüdiger , Strössner Klaus , Syassen Karl
Published: December 2003

The transformation of α‐Li3N to β‐Li3N occurs at 600 MPa and room temperature. The reverse transformation, however, only begins to take place above 200°C under normal pressure. β‐Li3N crystallizes as the Na3As structure type. This modification allows Li3N to be placed systematically in the structural series of alkali‐metal compounds A3B involving elements of the nitrogen group (A = Li, Na, K, Rb, Cs; B = N, P, As, Sb, Bi). Since the phase transition occurs at relatively low pressure, the formation of small amounts of β‐Li3N upon grinding with a mortar and pestle cannot be ruled out. Indeed, X‐ray powder diffractions of α‐Li3N always reveal the presence of small amounts of β‐Li3N.
Selective INADEQUATE, a Farewell to 2D‐NMR?
Authors: Berger Stefan
Published: December 2003

“SELINQUATE,” a novel abracadabra of 13C‐NMR spectroscopy? At least the coupling of all C atoms in a molecule can be determined with the pulse sequence which is concealed behind this acronym, and by which the fourth pulse of the standard INADEQUATE sequence is replaced by a frequencyselective pulse; thereby only the same number of 13C‐NMR spectra must be recorded as the number of differentiable C atoms. This can, in addition, be done with high digital resolution so that even all coupling constants can be obtained simply and accurately.
Laser Photochemistry at Surfaces—Laser‐Induced Chemical Vapor Deposition and Related Phenomena
Authors: Kompa Karl L.
Published: December 2003

The structural characterization of materials and the tailoring of their properties is an important area of chemical research. A new trend in this area is the recourse to lasers both for analytical as well as preparative purposes, exploiting the fact that lasers, by virtue of their properties (sharp energy, spatial and temporal resolution etc.), offer the most precise and selective interaction of energy and matter that we know. Furthermore, photochemical syntheses and material transformations can proceed “cold” and without causing damage to surface structures. Laser chemistry finds application in thin film deposition, in the formation of surface layers, as well as in (structuring) ablation or etching, and in the initiation and enforcing of reactions at surfaces. In the present paper an introduction to these new possibilities on the general basis of molecule‐surface interactions is followed by a brief characterization of lasers suitable for such purposes. Thereafter, four examples are discussed: gas phase deposition from volatile organometallic compounds with photoelectric activation at the surface or photochemical activation of the gaseous species (e.g. by employing molecular beams). In this way (noble) metal contacts can be deposited on various substrates. Instead of surface deposition, nucleation can occur in the gaseous medium, yielding highly disperse powders, e.g. of silicon carbide. Finally, an etching reaction is discussed where the laser does not act as an energy source but as an analytical instrument to provide diagnostic and mechanistic information.
Cs2Bi10Ca6Cl12O16: A New Type of Catalyst for Selective Oxidation Derived from Bismuth Oxychloride
Authors: Harris Kenneth D. M. , Ueda Wataru , Thomas John M. , Smith Gallienus W.
Published: December 2003

The title compound 1 is suitable for catalytic oxidative coupling of methane to give ethylene and ethane and for structural comparison with high‐temperature superconductors. Compound 1 was obtained, as shown below, in an open crucible at 800°C. As catalyst, it leads to 40% ethylene and 12% ethane for 21% conversion. Compound 1 has an interesting layer structure. The Bi3⊕ and Ca2⊕ ions can occupy the same positions, but are not randomly distributed. Similar structures have been postulated for high‐temperature super‐conductors.
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Metal‐free Carbanion Salts as Initiators for the Anionic Polymerization of Acrylic and Methacrylic Acid Esters
Authors: Reetz Manfred T. , Knauf Thomas , Minet Ulrich , Bingel Carsten
Published: December 2003

Molecular weights of up to 20 000 are attained in the polymerization of butyl acrylates with the malonates 1; the ratio of weight average molecular weight to number average molecular weight is ≤ 1.3. The likewise metal‐free salts 2 and 3 also smoothly polymerize acrylic esters in THF or toluene at room temperature. The explanation for this behavior, which differs from that of the corresponding sodium or potassium salts, could be that metal ions are necessary as activators for the typical terminating reactions of anionic polymerization. Compounds 1–3 are readily accessible and may be stored for months at 0 °C.
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Synthesis of the Heaviest Chemical Elements—Results and Perspectives
Authors: Herrmann Günter
Published: December 2003

All 17 artificially produced elements heavier than uranium were discovered by nuclear‐chemical synthesis. The three heaviest ones–elements 107, 108 and 109–were synthesized at the heavy‐ion accelerator UNILAC in Darmstadt by nuclear fusion from the heaviest stable nuclei, lead‐208 and bismuth‐209, and the most neutron‐rich stable isotopes of chromium and iron: element 107 from bismuth‐209 (atomic number Z = 83) and chromium‐54 (Z = 24), element 108 from lead‐208 (Z = 82) and iron‐58 (Z = 26), and element 109 from bismuth‐209 and iron‐58. The first isotopes detected were those with mass numbers 262 (Z = 107), 265 (Z = 108) and 266 (Z = 109); these nuclei are short‐lived α‐emitters with half‐lives of 8.2 ms, 1.8 ms and 3.4 ms, respectively. The yields of these reactions are extremely small; only three atoms of element 109 have ever been observed. Experiments to synthesize element 110 have given ambiguous results. All attempts to detect the “superheavy” elements with proton numbers near Z = 114 and neutron numbers near N = 184 have thus far failed. These elements have been predicted theoretically, and many attempts to synthesize them have been made, e.g. at UNILAC by fusion of calcium‐48 (Z = 20) with curium‐248 (Z = 96), or by transference of protons in the collision of two very heavy nuclei such as uranium‐238 (Z = 92). Surprisingly, the heaviest known nuclei are far more stable toward spontaneous fission into two fragments than was expected, but their synthesis is strongly hindered–much more than initially anticipated. It is this hindrance rather than the decreasing nuclear stability which seems to presently limit the extent of the periodic table: even heavier elements should be able to exist, but no way has yet been found to produce them.
Ketenimine Complexes from Carbene Complexes and Isocyanides: Versatile Building Blocks for Carbocycles and N‐Heterocycles [New Synthetic Methods (74)]
Authors: Aumann Rudolf
Published: December 2003

Ketenimine complexes are readily available in great variety by reaction of isocyanides with carbene complexes. They have proven to be useful building blocks in new synthetic approaches to carbocyclic and N‐heterocyclic four‐, five‐, and six‐membered rings. The reactions involve new metal‐induced bond formation patterns of the ketenimine ligands, which can be influenced across a wide range by varying the following five parameters: the metal, the ligands, and the three substituents on the NCC unit.
On the Structure of the Cation N2H with an NH ċ N Hydrogen Bond in the Monoammonia Adduct of Ammonium Iodide
Authors: Berthold Hans Joachim , Preibsch Wolfgang , Vonholdt Elke
Published: December 2003

In spite of the great importance of the NH ċ N hydrogen bridge in chemistry and biochemistry, the solid‐state structure of the simplest system containing this bond, [H3NH ċ NH3]⊕, was previously unknown. Single crystal X‐ray diffraction studies on NH4I · NH3 have shown that the interaction NH ċ NH3 leads to the formation of the cation N2H. The N  N distance determined by least squares refinement is 269(5) pm, somewhat shorter than the equilibrium distance of 273.1 pm calculated in 1982 by Scheiner and Harding.
The SF5‐Unit as Steric Protecting Group; Synthesis and Structure of F5SCSF3
Authors: Gerhardt Rolf , Gerlbig Thomas , Buschamann Jürgen , Luger Peter , Seppelt Konrad
Published: December 2003

A linear SCS unit has been demonstrated for 1 by X‐ray crystallography, while that in 2 is bent. Precursors of 1 contain two SF5 units bound to one C‐atom; this causes the rotation about the neighboring CC bond, e.g., in 3, to be so strongly hindered that even at temperatures above 25°C two separate conformers can be detected by NMR spectroscopy.
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Uniform Heterogeneous Catalysts: The Role of Solid‐State Chemistry in their Development and Design
Authors: Thomas John M.
Published: December 2003

Heterogeneous catalysts are generally assumed to be multiphasic and multicomponent; many of them are, and this is one of the resons why disentangling the factors that govern their mode of action is so difficult. But there is a large class of heterogeneous catalysts where the solid is monophasic and where the activity may be envisaged as being dispersed in a spatially uniform fashion throughout its bulk. This is true both of zeolites and many other microporous catalysts on the one hand, and of certain mixed metal oxides, where the non‐stoiohiometry is inextricably mingled with the catalysis, on the other. By recognizing this broad classification numerous operational advantages follow: the performance of existing catalysts and the design of those yet to be prepared can be placed on a rational footing; moreover, the myriad techniques of solid‐state chemistry and physics, often regarded as inapplicable to the subtle and special problems of surface chemistry, are seen to be of direct relevance as probes for the structure and properties of proven uniform heterogeneous catalysts as well as for the synthesis and development of new ones. This review, which draws analogies with and lessons from the chemistry of enzyme catalysts, focuses largely on the catalytic conversions of hydrocarbons over zeolites, clays, microporous AlPO4 and a wide range of metal oxides.
Novel Anionic Aryl Complexes of RhIII: [Rh(C6F5)5]2⊖ and [Rh(C6F5)4(CO)2]⊖
Authors: García María P. , Oro Luis A. , Lahoz Fernando J.
Published: December 2003

The RhIII complexes 2 and 3 are very stable, both in the solid state as well as in solution. The square‐pyramidal complex 2 is formed on reaction of 1 with LiC6F5, and can be carbonylated with CO to the octahedral complex 3, which is also accessible by reaction of the Rh1 complex [RhCl(CO)2]2 with LiC6F5 + BrC6F5. 2 and 3 should be suitable starting compounds for the synthesis of homo‐ and heteronuclear metal clusters.
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Rapid Detection of Manganese Deficiency in Conifer Needles by Electron Spin Resonance Spectroscopy
Authors: Laggner Peter , Mandl Ruth , Schuster Annemarie , Zechner Monika , Grill Dieter
Published: December 2003

ESR spectroscopic findings on spruce trees could form the basis of a rapid method for the detection of damage to conifers. The correlation between forrest damage and manganese deficiency in the case of conifers has already been reported. Three types of spectra (A, B, C) have now been distinguished. Types A and B are very similar to each other. They contain only weak signals; in the needles investigated, Mn contents of 20–90 and 6–30 ppm respectively were determined. Type C is the six‐line spectrum of MnII (>50 ppm Mn). Only the needles of healthy trees gave ESR spectra of type C. Manganese deficiency, as demonstrated by the absence of type C spectra, is thus a good indicator for the recognition of damage to conifers.
A Polyhedral Oligogermane: 4,8‐Dibromoocta‐tert‐butyltetracyclo[3.3.0.02,7.03,6]octagermane
Authors: Weidenbruch Manfred , Grimm Fred‐Thomas , Pohl Siegfried , Saak Wolfgang
Published: December 2003

Reductive halogen elimination from 1 offers a surprisingly simple route to the polycyclic germane 2. Compound 2 is air‐stable and decomposes above 400°C. Its C2 symmetry is revealed in the presence of only four NMR signals for the tert‐butyl protons.

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Do Any ABn Molecules Have Anomalous Shapes? v3 of TiF4 and TiF3 and Their Relevance to the Shape of TiF2
Authors: Beatte Ian R. , Jones Peter J. , Young Nigel A.
Published: December 2003

There is no firm evidence that any first row transition element dihalides are non‐linear. This conclusion is drawn from the fact the IR bands previously assigned to “non‐linear” LiF2 definitely arise from trigonal planar TiF3. Earlier matrix isolation studies, from which a 120°‐TiF2 had been concluded, formed the cornerstone of the theory of anomalous MF2 molecules.
Correlation of the Dynamic Behavior of n‐Alkyl Ligands of the Stationary Phase with the Retention Times of Paracelsin Peptides in Reversed Phase HPLC
Authors: Pfleiderer Betting , Albert Klaus , Bayer Ernst , Lork Klaus D. , Unger Klaus K. , Brückner Hans
Published: December 2003

The retention behavior of sterically demanding molecules with defined conformation in reversed phase HPLC is strongly influenced by the mobility of the lipophilic alkyl chains of the stationary phase. This follows from a comparison of the T1pH values determined for the alkyl chains by CP/MAS 13C NMR spectroscopy as a measure of their mobility with the retention times of the four components of the natural mixture of paracelsin peptides, which are characterized by very stable helical conformations. The C4 phase was conformationally least mobile (smallest T1PH, 44.4 ms for the methyl‐C) and exhibited the longest retention times.
Much Less Strained Cubane Analogues with Si, Ge, Sn, and Pb Skeletons
Authors: Nagase Shigeru
Published: December 2003

Virtually strain‐free four‐membered rings are formed by the higher homologues of carbon, namely silicon, germanium, tin, and lead. This followed from ab initio calculations of the corresponding hetero‐cubanes, ‐prismanes, and ‐tetrahedranes. In the case of carbon the cubane skeleton exhibits the strongest strain, whereas in the case of the other four elements it is always the least strained skeleton. Thus the strain energy of perplumbacubane is ca. 100 kcal−1 smaller than that of cubane. The XX bonds of the cubanes are only ca. 0.02–0.04 Å longer than those of the cyclobutanes, and also the strain energies per ring are very similar in the case of the cubanes and cyclobutanes.
Complexation of Cesium 137 by the Cap Pigments of the Bay Boletus (Xerocomus badius)
Authors: Aumann Dieter C. , Clooth Gabriele , Steffan Bert , Steglich Wolfgang
Published: December 2003

Why is 137Cs strongly enriched in bay boletus but hardly at all in cepe? This question, which arose after the reactor accident at Chernobyl, can now be answered. It was already known that bay boletus contains the unusual pigments badione A and norbadione A in the brown pileus and that these pigments are absent in cepe. The cap pigments are present in the mushroom as potassium complexes. However, the pigments can also bind cesium. Norbadione forms a 1:1 complex with CsCl. This complex can be dissociated by exposure to a strongly acidic cation exchanger.
Chemical Modifications of Biopolymers by Quinones and Quinone Methides
Authors: Peter Martin G.
Published: December 2003

Many quinones and their precursors, which are transformed oxidatively into quinones and/or quinone methides, are important natural products. As secondary metabolites, they frequently possess antibiotic and cytotoxic activities, in addition to acting sometimes as pathogens. Several plants and animals, especially insects, use quinonoid substances for defense, often with spectacular results. On the macromolecular level, quinone methides have a key role in the plant kingdom in lignin biosynthesis; the biosynthesis of melanoproteins exemplifies the reactions of o‐quinones in the animal kingdom. In insects, cross‐linking of structural proteins through quinones and quinone methides results in the construction of the sclerotized exoskeleton. For mankind, the reactivity of quinones in biological systems has far‐reaching consequences of pharmaceutical, toxicological, and technical relevance. The examples in this review show that a common principle underlies these reactions, namely, the chemical modification of biopolymers. As demonstrated particularly well in a more detailed discussion of the chemical principles of insect cuticle sclerotization, several major and important new results have emerged from the development and applications of modern methods of sample separation and from solid‐state NMR spectroscopy.
Materials Research—Current Issues and Future Directions
Authors: Collette John W. , Miller Joel S.
Published: December 2003

Editorial Essay: Technological advances in Europe and the USA which culminated, 50 years ago, in the commercialization of Nylon opened the way for the full scale development of synthetic materials. The Advanced Materials Conference held in Wilmington, Delaware, USA, in October 1988 as part of this 50th anniversary celebration, covered a wide spectrum of issues in materials science. John Collette and Joel Miller, organizers of the conference, introduce a series of reviews based on the lectures which took place.
Improving Effectiveness in Materials Research
Authors: Wegner Gerhard
Published: December 2003

Panel Discussion: “Educate and cooperate” was the general message which came from the discussion of future trends in materials science during the meeting in Wilmington Delaware. Gerhard Wegner gives a European view of the proceedings, pointing out current trends and future aims in both the teaching of materials science and in the development and production of new materials.
Diisocyanogen or Isocyanogen?
Authors: Cederbaum Lorenz S. , Tarantelli Francesco , Weikert Hans‐Georg , Scheller Markus , Köppel Horst
Published: December 2003

This question is unequivocally answered by detailed calculation of the photoelectron spectra. The compound recently synthesized by Bickelhaupt et al. by flash vacuum thermolysis of norbornadienone azine and identified as diisocyanogen CNNC cannot be diisocyanogen on the basis of the PE spectrum. On the other hand, the experimentally measured spectrum agrees very well with that calculated for isocyanogen CNCN.
The European Materials Research Society (E‐MRS)
Authors: Krimmel Eberhard F.
Published: December 2003

Editorial Essay: Since its birth in 1986, the European MRS has been going from strength to strength. Regular interdisciplinary meetings are held and educational programs as well as European Research Networks are supported, these activities making up the basis of a thriving society. In this month's Editorial Essay a former secretary of the E‐MRS traces the society's early development, assesses its current position and looks forward to its undoubtedly bright future.
The Stereoselectivity of Intermolecular Free Radical Reactions [New Synthetic Methods (78)]
Authors: Giese Bernd
Published: December 2003

The regio‐ and chemoselectivities of free radical reactions are often high and largely predictable; systematic studies have now shown that the stereoselectivity of free radical reactions can also be directed. Examples involving five‐ and six‐membered cyclic radicals will be used to show how steric and stereoelectronic effects influence the diastereoselectivity of reactions of cyclic radicals with olefins. The temperature, the solvent, and the nature of the radical scavenger used also play a role, so that, if the correct reaction conditions are used, the stereoselectivity of reactions for cyclic reactants can be very high. Lower stereoselectivities are often observed for reactions between acyclic radicals and acyclic alkenes. However, preliminary experiments have indicated that under certain conditions such systems can also react in a stereoselective manner.
Gauge Theory—A New Outlook on Solid State Dynamics
Authors: Clough Stanley
Published: December 2003

Research News: The hitherto mysterious relationship between the quantum and classical descriptions of solid state dynamic processes has been reexamined recently. It has been found that quantum theory has been missing important features such as symmetry breaking and Berry's phase, the incorporation of which does away with the rather fuzzy Copenhagen interpretation and rationalizes solid state behavior.
Phase Equilibria under Stress
Authors: Cahn Robert W.
Published: December 2003

Research News: A slight mismatch between the lattice parameters of two intergrown “coherent” phases can cause internal stresses within a two phase alloy which can modify the shapes of the dispersed phase particles. Recent studies by both metallurgists and geologists have been aimed at understanding this and other stress related phenomena.
Joining Ceramics, Glass and Metal in Bad Nauheim
Authors: Partridge Graham
Published: December 2003

Conference Report: G. Partridge (GEC) reports on a meeting which concerned the joining of ceramics, glass, and metals and E. Marinero and T. Sizuki (IBM) on two major symposia from the spring meeting of MRS, on magnetic and magneto‐optic thin films and multilayers.
Catalytic Antibodies
Authors: Schultz Peter G.
Published: December 2003

The vast binding repertoire of the immune system has been exploited for the generation of tailor‐made biological catalysts. A number of strategies have been developed to generate catalytic antibodies that carry out a wide range of reactions with exquisite specificities. The generation and characterization of these novel catalysts is not only providing new insights into the nature of biological recognition and catalysis, but may also lead to novel catalysts for applications in chemistry, biology, and medicine.
Graphite Intercalation Compounds in Berlin
Authors: Setton Ralph
Published: December 2003

Conference Reports: Ralph Setton reports on his visit to an international symposium on graphite intercalation compounds, Hermann Schmalzried on the Annual Meeting of the German physical chemists which this year concentrated on solid state chemistry and physics, and Hans Reuter on a meeting on the sol–gel processing of ceramics.
Sol—Gel Processing in Bad Honnef
Authors: Reuter Hans
Published: December 2003

Conference Reports: Ralph Setton reports on his visit to an international symposium on graphite intercalation compounds, Hermann Schmalzried on the Annual Meeting of the German physical chemists which this year concentrated on solid state chemistry and physics, and Hans Reuter on a meeting on the sol–gel processing of ceramics.
Water‐Soluble Porphyrin Diglycosides with Photosensitizing Properties
Authors: Fülling Gerd , Schröder Doris , Franck Burchard
Published: December 2003

In the presence of oxygen, tumors and viruses can be destroyed by photosensitizing porphyrins. Indispensable for clinical applications is, inter alia, a good solubility in water. It has now been possible to prepare two porphyrin diglycosides which are water‐soluble and stable as well as equally strongly photosensitizing as Rose Bengal. With these properties they ideally fulfill the demands of a wide spectrum of photomedicinal applications.
Polymer Optical Fibers and Nonlinear Optical Device Principles
Authors: Groh W. , Lupo D. , Sixl H.
Published: December 2003

Basic principles of the present optoelectronic research activities at Hoechst AG are presented in this contribution. Within the diversified broad band spectrum of optoelectronic materials and applications our interest is focused on new types of polymer optical fibers and nonlinear optical device principles using organic Langmuir–Blodgett films and electrically poled polymers. The basic principles and the limits of the present research and development activities which have a high market potential are outlined.