bluuebunny/crossref_metadata_2025 huggingface dataset:
NMR Studies of Yeasts Grown on Substrates at “Zero” Level Radioactivity
Authors: Basosi Ricardo , Rossi Clausio , Tiezzi Enzo , Valensin Gianni
Published: December 2003

The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1983, 57. DOI:10.1002/anie.198300570
A Novel Route to Thiocarbonyl Compounds
Authors: Schaumann Ernst , Wriede Ulrich , Rühter Gerd
Published: December 2003

The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1983, 63. DOI:10.1002/anie.198300630
Tellurium as Six‐Electron Donor‐Synthesis and Structure of μ3‐Te[Mn(CO)2(η5‐C5H5)]3
Authors: Herberhold Max , Reiner Dietmar , Neugebauer Dietmar
Published: December 2003

The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1983, 10. DOI:10.1002/anie.198300100
On the Description of Complex Inorganic Crystal Structures
Authors: Andersson Sten
Published: December 2003

To describe a structure is to describe chemistry. A description of structure should be simple yet also open up ways for an understanding of complex structures and their properties. Such interrelationships are gained on inspection and discussion of structures in models of interpenetrating partial structures and on application of symmetry operations to whole structures. Transition regions between interpenetrating partial structures can be approximated to periodic minimal surfaces. Chemical reactions, e.g. in ion‐exchange, in heterogeneous catalysis, or in molecular separations in complicated zeolites will take place on these minimal surfaces.
Oxidative Coupling of the Selenolate Functions in (C6H5)3PC(Se)P(C6H5)3: Crystal Structure of {[(C6H5)3P]2CSe}Fe2OCl·4CH2Cl2 Containing a Linear FeOFe Axis
Authors: Schmidbaur Hubert , Zybill Christian E. , Neugebauer Dietmar
Published: December 2003

The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1983, 169. DOI:10.1002/anie.198301690
Dicyanoketene: Flash Vacuum Thermolysis of Alkyl Dicyanoacetates
Authors: Gano James E. , Jacobson Roy H. , Wettach Richard H.
Published: December 2003

The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1983, 193. DOI:10.1002/anie.198301930
Successive Electron Transfers in Molecules with Two Electrophoric Groups: Novel Singlet, Doublet, and Triplet States
Authors: Huber Walter , Unterberg Heinz , Müllen Klaus
Published: December 2003

The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1983, 288. DOI:10.1002/anie.198302880
Reactions of N‐Methylenecarboxamides with Electrophiles: 1‐Alkoxy‐2‐azaallenium Salts and N‐Acyl(methylene)ammonium Salts
Authors: Würthwein Ernst‐Ulrich , Kupfer Rainer , Kaliba Claus
Published: December 2003

The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1983, 264. DOI:10.1002/anie.198302640
Straightforward Preparation and Stabilization of 2‐trans‐4,7: 10,13‐Diepoxy[15]annulenone
Authors: Ogawa Haru , Inoue Tadashi , Imoto Taiji , Miyamoto Izumi , Kato Hidefumi , Taniguchi Yōichi
Published: December 2003

The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1983, 243. DOI:10.1002/anie.198302430
Can Radicals Participate in Pericyclic Reactions? Model Reactions for Electron‐Transfer Induced Valence Isomerization of 1‐Arylindenes
Authors: Kiesele Herbert
Published: December 2003

The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1983, 210. DOI:10.1002/anie.198302100
Tetraethoxyallene: Equivalent of the Fictive Malonic Ester Dianion—A Versatile Synthetic Building Block
Authors: Saalfrank Rolf W. , Rost Walter
Published: December 2003

The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1983, 451. DOI:10.1002/anie.198304510
Capping of Metal Atom Triangles in Clusters by R3PAu Moieties
Authors: Roland Eckehart , Fischer Klaus , Vahrenkamp Heinrich
Published: December 2003

The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1983, 419. DOI:10.1002/anie.198304190
Modern Pulse Methods in High‐Resolution NMR Spectroscopy
Authors: Benn Reinhard , Günther Harald
Published: December 2003

The introduction of Fourier transform methods has not only remarkably enhanced the sensitivity of high‐resolution NMR spectroscopy, thus allowing measurements to be made on less sensitive nuclei of the Periodic Table, but also has paved the way for the development of a large number of new experimental techniques. On the one hand, procedures already known have been improved and can now be performed more rapidly, and, on the other, completely new experimental approaches have become available. This situation resulted mainly from the introduction of programmable pulse transmitters and the separation of the experiment into preparation, evolution, and detection. In particular, the concept of two‐dimensional spectroscopy has opened up new possibilities important for the analysis of complicated spectra and is able to provide information previously not accessible. As elsewhere, optimum application of the techniques and correct interpretation of the results require sound understanding of the underlying physical principles. Since a rigorous mathematical treatment is complicated and does not necessarily improve the comprehensibility, this article attempts to give an illustrative presentation of the new pulse techniques within the framework of the Bloch vector model. After a short introduction covering the basic principles, one‐dimensional pulse techniques that can be applied using standard experimental equipment are dealt with. The main areas of application are signal assignment, sensitivity enhancement for measurements on less abundant nuclei, and selective excitation of individual resonances. Subsequently, the various techniques of two‐dimensional NMR spectroscopy are treated: these enable shift correlations for different types of nuclei to be made, the presentation of spin multiplets without overlap, and the analysis of geometrical relations as well as of chemical exchange phenomena.
syn‐Benzene Dioxide/1,4‐Dioxocin Systems via a Diels‐Alder Route
Authors: Altenbach Hans‐Josef , Voss Burkhard , Vogel Emanuel
Published: December 2003

The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1983, 571. DOI:10.1002/anie.198305710
Synthesis of an [18]Annulene Dioxide: An Oxygen‐Bridged [18]Annulene Possessing Equivalent Kekulé Structures
Authors: Ogawa Haru , Sadakari Naomi , Imoto Taiji , Miyamoto Izumi , Kato Hidefumi , Taniguchi Yōichi
Published: December 2003

The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1983, 471. DOI:10.1002/anie.198304710
Synthesis of Hetero[17]annulene Dioxides and a [16]Annulene Dioxide Using Furan Building Blocks
Authors: Ogawa Haru , Fukuda Chiyuki , Imoto Taiji , Miyamoto Izumi , Kato Hidefumi , Taniguchi Yōichi
Published: December 2003

The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1983, 480. DOI:10.1002/anie.198304800
Electron Diffraction with the Transmission Electron Microscope as a Phase‐Determining Diffractometer—From Spatial Frequency Filtering to the Three‐Dimensional Structure Analysis of Ribosomes
Authors: Hoppe Walter
Published: December 2003

Chemists recognize X‐ray crystal structure analysis and electron microscopy as powerful methods of analysis. In the last 20 years the basic ideas of X‐ray diffraction analysis have been extended to the field of electron microscopy, whereby an image‐forming apparatus is converted into an electron diffractometer, and through which an old dream of crystallographers can be realized—the measurement of the phase shift of scattered waves, a prerequisite for the direct calculation of structures. Its most important area of application, like that of the X‐ray diffractometer, is in three‐dimensional structure analysis—in all fields of science. However, beyond crystallography, aperiodic structures (comparable to crystals with a single unit cell) can also be analyzed three‐dimensionally. In this progress report, the development of the first idea (spatial frequency filtering) to the analysis of ribosomal particles is outlined. Attention will be focused primarily on quantitative methods for the measurement of scattered rays, which are also usable beyond the conventional limit of resolution, down to atomic resolution. In the course of this work in 1968, the principle of the three‐dimensional analysis of native biological crystal structures using the electron microscope, as worked with today in many laboratories, was developed. In Munich, however, further research focused on the three‐dimensional analysis of aperiodic and individual (especially biological) objects. The analysis of 50S‐subunits of the procaryotic ribosome ofE. colishowed surprisingly good reproducibility of the results (although only within the same orientation), allowing the deduction of almost ideal average model structures from a limited number of particles.
Ketene‐Alkyne Conversion using Lewis Acids
Authors: Kreissl Fritz R. , Sieber Werner , Wolfgruber Mathias
Published: December 2003

The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1983, 631. DOI:10.1002/anie.198306310
Novel Nickel‐Oligomerization Catalysts with Arsenic‐Oxygen Chelate Ligands
Authors: Keim Wilhelm , Behr Arno , Limbäcker Brigitte , Krüger Carl
Published: December 2003

The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1983, 655. DOI:10.1002/anie.198306550
1,3,5,7‐Tetrazocines
Authors: Gompper Rudolf , Schwarzensteiner Marie‐Luise
Published: December 2003

The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1983, 812. DOI:10.1002/anie.198308120
1‐(1,3‐Butadienyl)triazoles from 1‐Vinyltriazoles and Electron‐Rich Alkynes‐Cleavage to “Push‐Pull” 1,3‐Butadienes
Authors: Schubert Hans , Regitz Manfred
Published: December 2003

The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1983, 726. DOI:10.1002/anie.198307260
Base‐Induced Isomerization of Cycloalkenynes in Competition with Addition Reactions
Authors: Zountsas Johannes , Kreuzer Matthias , Meier Herbert
Published: December 2003

The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1983, 851. DOI:10.1002/anie.198308510
Olefins from β‐Hydroxycarboxylic Acids—Synthesis of Isomerically Pure α‐ and β‐Asarone
Authors: Mulzer Johann , Lammer Ortrud
Published: December 2003

The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1983, 887. DOI:10.1002/anie.198308870
Ligand‐Free Metal Clusters
Authors: Ozin Geoffrey A. , Mitchell Steven A.
Published: December 2003

Recent advances in the synthesis and spectroscopic characterization of ligand‐free metal clusters immobilized in cryogenic rare gas matrices have contributed greatly to the understanding of electronic, geometric, dynamic, and chemical bonding properties of a wide range of uni‐ and bimetallic clusters as a function of nuclearity and metal type. The knowledge accumulated on molecular metal aggregates devoid of ligands and isolated on various supports will form an important data base for gauging the reliability of quantum chemical calculations on metal clusters, as well as for comprehending certain aspects of chemisorption on, and catalysis by, supported metal clusters. It can be envisaged that information on ligand‐free metal clusters entrapped in a wide range of matrix environments in conjunction with the data for these same metal clusters in the gas phase and in molecular beams will probably contribute towards understanding metal‐support interactions and to the designed synthesis of a new breed of high‐technology heterogeneous catalysts in the not too distant future.
Inclusion Complexes between a Macrocyclic Host Molecule and Aromatic Hydrocarbons in Aqueous Solution
Authors: Diederich François , Dick Klaus
Published: December 2003

The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1983, 957. DOI:10.1002/anie.198309570
A Carbene‐Complex Route to Vitamin E
Authors: Dötz Karl Heinz , Kuhn Werner
Published: December 2003

The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1983, 1045. DOI:10.1002/anie.198310450
29Si‐E(lectron)N(uclear)DO(uble)R(esonance)
Authors: Bock Hans , Hierholzer Bernhard , Kurreck Harry , Lubitz Wolfgang
Published: December 2003

The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1983, 1088. DOI:10.1002/anie.198310880
Secologanin, a Biogenetic Key Compound—Synthesis and Biogenesis of the Iridoid and Secoiridoid Glycosides
Authors: Tietze Lutz‐F.
Published: December 2003

The monoterpene glycoside secologanin is a key intermediate in the biosynthesis of most indole, cinchona, ipecacuanha, and pyrroloquinoline alkaloids, as well as of simple monoterpene alkaloids. More than a thousand alkaloids are formed from secologanin in vivo; this represents almost a quarter of this large group of natural products. It is also the parent compound of the secoiridoids. Many of the compounds derived from secologanin display a high degree of biological activity and are employed as pharmaceuticals, e.g., the dimeric indole alkaloid leurocristine (vincristine) which is used very successfully in the treatment of acute leukemia. A knowledge of the biosynthesis and biological reactions of secologanin provides a sound basis for the biosynthesis‐orientated classification of numerous natural products and the taxonomy of many plants. Secologanin and structurally related substances can be synthesized in a few steps by stereocontrolled photochemical and thermal cycloadditions. Its biomimetic reaction with amines and amino acids yields other natural products and compounds of pharmacological interest.
Tricyclo[4.1.0.01,3] hept‐4‐enes as Intermediates
Authors: Brinker Udo H. , Gomann Klaus , Zorn Ruth
Published: December 2003

The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1983, 1241. DOI:10.1002/anie.198312410
Resolution, Circular Dichroism, and Absolute Configuration of 1,1′‐Biazulenes
Authors: Tajiri Akio , Fukuda Masahiko , Hatano Masahiro , Morita Tadayoshi , Takase Kahei
Published: December 2003

The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1983, 1283. DOI:10.1002/anie.198312830
Reaction Control by Catalysts with Variable Specificity: Stable Palladium‐Phthalocyanine as Hydrogenation Catalyst with Three Catalytic Patterns
Authors: Eckert Heiner , Fabry Gudrun , Kiesel Yvonne , Raudaschl Gabriele , Seidel Christoph
Published: December 2003

The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1983, 1291. DOI:10.1002/anie.198312910
Synthesis and Structure of (Z)‐3‐Amino‐4‐oxo‐2‐azetidinesulfonic Acids
Authors: Hoppe Dieter , Sheldrick George M. , Egert Ernst , Kaars Petra
Published: December 2003

The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1983, 1333. DOI:10.1002/anie.198313330
Electron‐Rich Half‐Sandwich Complexes—Metal Bases par excellence
Authors: Werner Helmut
Published: December 2003

Electron‐rich, half‐sandwich complexes of the type CnRnML2 or CnRnMLL′ are built up of an aromatic five‐ or six‐membered ring, a d8‐metal, and either a pair of two‐electron donors or an equivalent chelating ligand. Such complexes behave like Lewis bases and react with a wide variety of electrophiles, El or ElX, to form products with a new metal‐element bond. According to their reactivity they are comparable to the Vaska‐type compounds. Certain of the products obtained after addition of the electrophile undergo interesting subsequent reactions in which, for example, metal complexes containing molecules that are unstable in the free state, such as CS, CSe, CH2S, CH2Se, CH2Te, CH3CHS, CH3CHSe, CH2CS, CH2CSe, and CH2CTe are formed. Moreover, cycloadditions as well as reactions with coordinatively unsaturated transition‐metal compounds which result in formation of heterometal binuclear complexes demonstrate that the metal bases CnRnML2 and CnRnMLL′ are valuable synthetic building blocks. Furthermore, very recent investigations have indicated links between metal basicity and the problem of CH activation.
Synthesis and Structure of a Diarsenechromium Complex with an Unsupported Arsenic‐Arsenic Double Bond
Authors: Cowley Alan H. , Lasch Jon G. , Norman Nicholas C. , Pakulski Marek
Published: December 2003

The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1983, 1493. DOI:10.1002/anie.198314930
Synthesis and Structure of [Na(tmeda)2]⊕[HNi2(C2H)4]⊕
Authors: Pörschke Klaus Richard , Kleimann Wolfgang , Wilke Günther , Claus Karl Heinz , Krüger Carl
Published: December 2003

The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1983, 1527. DOI:10.1002/anie.198315270
Disulfur and Diselenium as Strong Acceptor Ligands in (η5‐C5H5)Re(CO)2S2 and [η5‐C5(CH3)5]Mn(CO)2Se2
Authors: Herberhold Max , Reiner Dietmar , Thewalt Ulf
Published: December 2003

The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1983, 1343. DOI:10.1002/anie.198313430
Resonance Energy of Bridged [10]Annulenes
Authors: Roth Wolfgang R. , Böhm Manfred , Lennartz Hans‐Werner , Vogel Emanuel
Published: December 2003

The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1983, 1379. DOI:10.1002/anie.198313790
The Allyl Group as Mildly and Selectively Removable Carboxy‐Protecting Group for the Synthesis of Labile O‐Glycopeptides
Authors: Kunz Horst , Waldmann Herbert
Published: December 2003

Biologically important O‐glycopeptides contain inter alia, the acid‐ and baselabile glycosyl‐serine or glycosyl‐threonine bond; to link these bounds, it has proven useful to protect the carboxy group of the glycopeptide with an allyl group. The deblocking can be carried out selectivley, almost quantitatively, an extremely mildly with tetrakis (triphenylphosphane)palladium(0) in the presence of morpholine.
Hydrolysis Products of the Monomeric Amine Complex (C6H15N3)FeCl3: The Structure of the Octameric Iron(III) Cation of {[(C6H15N3)6Fe8(μ3‐O)2(μ2‐OH)12]Br7(H2O)}Br·8H2O
Authors: Weighardt Karl , Pohl Klaus , Jibril Ibrahim , Huttner Gottfried
Published: December 2003

An extraordinary cation with eight FeIII centres is contained in the title compound. It has been characterized X‐ray crystallographically as the first FeIII‐oligomer with more than three centres. Besides the strong bridging by oxo‐ and hydroxo‐groups the “hydrophobization” of the surface by the six amine ligands is worthy of note. In the crystal, seven of the eight Br⊖ ions and a H2O molecule are associated with the cation—it can thus be regarded as a bromide‐ion bearing complex monocation.
Photochemical Hole Burning: A Spectroscopic Study of Relaxation Processes in Polymers and Glasses
Authors: Friedrich Josef , Haarer Dietrich
Published: December 2003

Photochemical hole burning is a special type of saturation spectroscopy in the optical domain having many analogies with NMR methods. The holes, which are burnt with laser irradiation, appear as small indentations in the absorption spectra of dye molecules which are doped into a polymer or glass in minute concentrations. Based on their narrow line width, photochemical holes can be regarded as highly sensitive spectroscopic probes. They can be used to detect small perturbations of the system by external parameters, giving rise to line‐shifts and broadenings. Besides the many well documented, spectroscopic applications of hole burning, it may offer interesting future developments for the spectroscopy of biomolecules and for high‐density data storage.
Aliphatic Polyethers, Basic Building Blocks from Naturally Occurring Humic Substances: Detection by Solid State 13C‐NMR Spectroscopy
Authors: Bayer Ernst , Albert Klaus , Bergmann Wolf , Jahns Kuno , Eisener Wolfram , Peters Hans‐Konrad
Published: December 2003

The structure of humic substances has long been a subject of controversy. In particular, their higher oxygen content could not be explained. Studies in solution did little to help. CP‐MAS‐13C‐NMR spectroscopy of the substances in the solid state has now permitted precise assignment of the structural elements. Aliphatic part‐structures comprise the framework of humic substances; of the oxygen‐containing groups, aliphatic ethers dominate.—These findings are also of importance in understanding the genesis of fossil fuels.
ENDOR Spectroscopy — A Promising Technique for Investigating the Structure of Organic Radicals
Authors: Kurreck Harry , Kirste Burkhard , Lubitz Wolfgang
Published: December 2003

The name “ENDOR” has been known since biblical times and denotes a small town close to the Sea of Galilee (ca. 1000 B.C., 1 Sam. 28 : 7 ff). The acronym “ENDOR” (Electron Nuclear DOuble Resonance) characterizes the extension of electron spin resonance to electron‐nuclear double resonance spectroscopy, a method that has opened up new dimensions for the investigation of complicated paramagnetic molecules. Only ENDOR spectoscopy, which has achieved technical perfection in the last decade, overcomes the resolution limitations of EPR spectroscopy, thus allowing interesting applications in the field of biochemistry. ENDOR investigations of the primary process of photosynthesis, of the mode of action of derivatives of vitamin E and K, and of the mechanism of the enzymatic catalysis of flavoenzymes in biological redox‐chains have opened up new vistas. ENDOR and its extension to the triple resonance experiment TRIPLE offer, for example, the potential for a precise determination of hyperfine coupling constants, including their signs, which are frequently especially interesting. In addition to protons, a multiple of magnetic nuclei can be studied by ENDOR, such as e.g. 2H, 13C, and 14N. The ENDOR techniques is not restricted to monoradicals, but can also be applied to polyradicals in spin states of higher multiplicities (triplet, quartet, or quintet state). The experimental data accessible from ENDOR yield information about spin and charge density distributions, and about the geometrics of radicals and their internal dynamics; they also provide an excellent test for the accuracy of quantum mechanical calculations.
Electrochemiluminescence of Tetrakis(diphosphonato)diplatinate(II)
Authors: Vogler Arnd , Kunkely Horst
Published: December 2003

Important information about the mechanism of redox reactions can be obtained from investigations of the electrochemiluminescence (ECL). So far, very few studies of this kind have been carried out on metal complexes. The ECL specrtrum of [Pt2(P2H2O5)4]4⊖ (A4⊖) in conjunction with other observations allows, inter alia, conclusions to be drawn about the PtPt bond order in A3⊖, A4⊖, and A5⊖, about the half‐lives of the oxidized (A3⊖) and the reduced complex (A5⊖), and about the redox potentials.
Liquid Crystals: A Tool for Studies on Chirality
Authors: Solladié Guy , Zimmermann Richard G.
Published: December 2003

Nematic liquid crystals are extremely sensitive to optically active molecules, which, at very low concentration, convert them into cholesteric liquid crystals. The purpose of this report is to review recent applications of liquid crystals to chirality studies. A brief discussion of the structure and properties of liquid crystals is followed by a survey of the methods currently being employed for the determination of the pitch and handedness of cholesteric liquid crystals. Of special interest in the formation of induced‐cholestric phases are the twisting powers of optically active compounds and the structural relationships between dopants and nematics. Liquid crystals can be used, inter alia, for the detection of small optical activities and for the determination of thermal racemization barriers and absolute configurations.
Mixed Crystals Containing the Diamagnetic Complex [Mo2(SO2)(S2)(CN)8]4⊖ and the Paramagnetic Complex [Mo2(SO2)(S2)(CN)8]5⊖
Authors: Müller Achim , Eltzner Werner , Jostes Rainer , Bögge Hartmut , Diemann Ekkehard , Schimanski Jürgen , Lueken Heiko
Published: December 2003

Blackish violet crystals of the mixed valence Mo compound 1 were obtained on oxidation of [(MoIII)2(μ2‐S)2(CN)8]6⊖. The MoIII/IV species in 1 belongs to the rare paramagnetic binuclear complexes of the heavy transition metals; the MoIV species is diamagnetic. Although the structures of the two complex anions differ only slightly, markedly different MoMo distances of 279.0 and 268.4 pm, respectively, are observed.
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Ring‐Opening of Methylene‐Bridged Dimetal Complexes by Bases
Authors: Keim Wilhelm , Röper Michael , Strutz Heinz , Krüger Carl
Published: December 2003

For the mechanistic explanation of the Fischer‐Tropsch synthesis, model reactions at dimetallacyclopropane complexes such as 1 are of considerable interest. Base‐induced, ring‐opening has now been achieved for the first time. In this way, methylene bridges react with coordinated CO to afford the salt 2, which was isolated and fully characterized.
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Molecular Structure of a 1,3‐Diphosphaallene: (2,4,6‐tBu3C6H2)PCP(2,4,6‐tBu3C6H2), a Phosphorus Analogue of Carbon Disulfide
Authors: Karsch Hans Heinz , Reisacher Hans‐Ulrich , Müller Gerhard
Published: December 2003

The first structure determination of a phosphacumulene by X‐ray diffraction indicates that the 1,3‐diphosphaallene 1, synthesized independently, is a genuine allene analogue. Isolated molecules are present in the crystal and the bulky substituents are arranged othogonally. The PC bonds of the almost linear PCP moiety are markedly shorter (1.63 Å) than “normal” PC double bonds (1.68–1.72 Å); the CS bonds in CS2 are also shorter than the CS bonds in thioketones
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Experimental and Theoretical Nuclear Astrophysics; The Quest for the Origin of the Elements (Nobel Lecture)
Authors: Fowler William A.
Published: December 2003

The heavier chemical elements were formed–and are being formed–in stars. Substantiation of this concept necessitated, inter alia, a detailed knowledge of numerous nuclear processes. With his quantitative experimental data, W. A. Fowler (Nobel Prize for Physics 1983) was able to put the theory of formation of the elements in the interior of stars on a firm footing. Supernovae also participate in the nucleosynthesis.
Modelling the Chemistry of Zeolites by Computer Graphics
Authors: Ramdas Subramaniam , Thomas John M. , Betteridge Paul W. , Cheetham Anthony K. , Davies E. Keith
Published: December 2003

The unique structural, adsorptive, and catalytic properties of zeolites are particularly amenable to illustration by computer (especially color) graphics. The siting of cations, the accommodation of guest reactant or product species, as well as the occurrence of various kinds of intergrowths (e.g. twin planes and coincidence boundaries) within these microporous solids can all be effectively portrayed by graphical means in such a manner as to emphasize the shape‐selective character of the host zeolite. The dynamics of translational and angular motion of guest species (for example benzene) in a channel of molecular dimensions within a typical zeolitic solid (for example silicalite) can also be probed interactively using appropriate potential functions.
On Stars, Their Evolution and Their Stability (Nobel Lecture)
Authors: Chandrasekhar Subrahmanyan
Published: December 2003

That the fate of stars is determined by their masses, and thus, that not all stars end as white dwarfs, is one of the underlying principles of the work of S. Chandrasekhar (Nobel Prize for Physics 1983). Because of the relativistic increase in mass of the electron there is an upper limit for the mass of white dwarfs: about 1.4 solar masses. Stars with about 2 solar masses form neutron stars as the final state; beyond this limit, black holes are formed.
Conversion of “LiNS(F)OCMe3” into an (Li8)2 Double Cluster
Authors: Isenberg Wilhelm , Mews Rüdiger , Sheldrick George M.
Published: December 2003

Nucleophilic substitutions of thiazyl fluoride (NSF) should afford access to thiazyl derivatives RSN. On reaction of NSF with LiOCMe3, the primary product “LiNS(F)OCMe3” could be trapped for the first time as the double cluster 1 and subsequently characterized. A molar ratio of NSF: nucleophile of 1:1 is essential for the formation of 1.
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Cyclic Voltammetry—“Electrochemical Spectroscopy”. New Analytical Methods (25)
Authors: Heinze Jürgen
Published: December 2003

Polarography is still the best known classical measuring method in electroanalytical chemistry. However, in recent years its position has been challenged by cyclic voltammetry (CV). Simple diagnostic criteria and relatively easily acquired measuring techniques have hastened this development. Cyclic voltammetry has the further attraction of providing information not only on the thermodynamics of redox processes but also on the kinetics of heterogeneous electron‐transfer reactions and coupled chemical reactions. The characteristic shapes of the voltammetric waves and their unequivocal position on the potential scale virtually fingerprint the individual electrochemical properties of redox systems. For this reason the method has been labeled “electrochemical spectroscopy”.
Synthesis of a Stable Aminosilanol and a Lithium Aminosilanolate with Cubane Structure
Authors: Graalmann Onno , Klingebiel Uwe , Clegg William , Haase Martin , Sheldrick George M.
Published: December 2003

Neither inter‐ nor intramolecular NH3‐ or H2O‐cleavage takes place in the first stable aminosilanol 2, formed on reaction of the chlorosilanol 1 with ammonia. 2 reacts with BuLi to give 3, which is tetrameric in the gas phase and in the solid state.
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Ag1.8Mn8O16: Square Planar Coordinated Ag⊕ Ions in the Channels of a Novel Hollandite Variant
Authors: Chang Fung Ming , Jansen Martin
Published: December 2003

A promising new ion‐conducting material, the title compound, can be prepared from AgMnO4 and Ag2O (1:1) at 970 °C under 5 kbar O2. The Mn8O16 framework forms channel‐like cavities of face‐sharing cubes. The Ag⊕ ions occupy the bottle‐necks of this one‐dimensional diffusion channel as regular lattice sites. This constitutes the first example of square‐planar coordinated Ag⊕‐ions.
A Novel Iron‐Sulfur Cluster with Central Fe8‐Cube: Synthesis and Structure of (Et4N)3Fe8S6I8·2CH2Cl2
Authors: Pohl Siegfried , Saak Wolfgang
Published: December 2003

An Fe8S6 dodecahedron with twelve rectangular faces and a central Fe8‐cube is present in the novel Fe8S6I⊖ ion. The synthesis of this iron‐sulfur cluster ion, the structure of which is shown on the cover page, was accomplished by reaction of [Et4N][Fe6S6I6] with iron, ammonium iodide, and iodine.
Thin Layer Chromatography with an Immobilized Azacyclophane Derivative as Analytical Agent and Probe for Host‐Guest Interactions
Authors: Schneider Hans‐Jörg , Müller Walter , Güttes Detlev
Published: December 2003

The macrocycle 1 immobilized on silica gel layers (see previous communication) provides new insights into host‐guest interactions. The selective inclusion of an organic neutral molecule in the cavity of the macrocycle rests, on the one hand, on the interaction between lipophilic moieties of host‐ and guest‐molecule and, on the other, on the electrostatic attraction between polar substituents in the substrate and the positive charges in the host.
Crown Ether Complexes of Sulfonium Salts—The X‐Ray Crystal Structures of [PhCOCH2SMe2·[18]Crown‐6]n[PF6]n and [(PhCOCHPhSMe2)2·[18]Crown‐6][PF6]2
Authors: Allwood Billy L. , Crosby John , Pears David A. , Stoddart J. Fraser , Williams David J.
Published: December 2003

The transformation of polymeric into discrete host‐guest complexes takes place on replacement of a methylene H‐atom in the sulfonium ion of the [18]‐crown‐6 (18C6) complex 1 by a bulky group such as phenyl. The dication of 2 exhibits a sort of sandwich structure (sulfonium ion‐crown ether‐sulfonium ion); the bonding between guest cations on the one hand and crown ethers on the other derives from different H‐bridges; a peculiarity is the formation of the “bifurcated” H‐bridges.
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[Ni8(μ4‐PPh)6(PPh3)4] and [Ni9(μ4‐PPh)6(PPh3)4]; Cluster with Coordinatively Unsaturated Ni‐Atoms
Authors: Fenske Dieter , Hachgenei Johannes , Rogel Friedhelm
Published: December 2003

The novel nickel‐phosphane clusters 1 and 2 have almost identical structures: In 1 the Ni atoms form a distorted cube, each face of which is roofed by a PPh ligand. The PPh3 ligands are alternatingly bound to Ni such that a coordination gap remains at four of the Ni atoms. In 2 one of the gaps is occupied by a Ni atom.—1 is formed from NiCl2, PPh3, and PhP(SiMe3)2 under specific conditions or by reduction of 3 with Na/Hg; 2 is obtained by the same reduction, but in the presence of NiCl2.
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Chemical Basis of the Action of Glyoxalase I, an Anticancer Target Enzyme
Authors: Douglas Kenneth T. , Shinkai Seiji
Published: December 2003

Although glyoxalase I was discovered in 1913 the physiological role of this ubiquitous enzyme is still far from clear. It catalyzes the reaction of α‐ketoaldehydes and glutathione to produce S‐D‐lactoylglutathione, from which D‐lactate and glutathione are produced by glyoxalase II. Argument raged for many decades about the nature of the natural substrate. Was it methylglyoxal? Was methylglyoxal ever formed metabolically or was it purely artifactual? Some of these questions have been resolved in that a number of metabolic processes which produce α‐ketoaldehydes have now been recognized. Equally unsuccessful have been attempts to ascribe a physiological role to glyoxalase. This is clearly an important question since glyoxalase I occurs in cells at all levels of evolution. Time and time again glyoxalase I has been claimed to be linked to cancer, and a number of research groups worldwide are using it as a model for designing potential anticancer drugs. In this review article the mechanism of action of the enzyme is discussed, knowledge of which enables stronger inhibitors to be synthesized. Until roughly ten years ago when powerful NMR techniques were used to study it for the first time, it was assumed that the key step in the mechanism was a hydride ion transfer. Today, the mechanism is envisaged as a proton transfer.
Crystal Structures of Potassium Ozonide and Rubidium Ozonide
Authors: Schnick Wolfgang , Jansen Martin
Published: December 2003

Bond systems with uneven numbers of electrons—such as the ozonide ion—are an exception to the rule for main group elements and have time and again attracted the attention of experimental and theoretical chemists. Nonetheless, the exact structural data for O in KO3 and RbO3 have only now been determined. The averaged bond lengths (135.7(5) and 134.1(15) pm, respectively) and bond angles (113.4(8) and 114.6(13)°, respectively) of the two ozonides agree within the standard deviations.
[CuCo(CO)4]n—Crystal Structure of a Polymer with a One‐Dimensional, Infinite Copper‐Cobalt Bonding System
Authors: Klüfers Peter
Published: December 2003

CuCo(CO)4 crystallizes dimorphically. The tetramer with a Cu4Co4 eight‐membered ring (orange‐red crystals) is known: new is the polymer with CuCo zig‐zag chains (strongly distorted yellow platelets or needles that separate into fibers). Interatomic distances and bond angles in the building blocks of the chains are almost the same as in the tetrameric modification.
Amino(imino)phosphanes as Face‐Bridging Complex Ligands
Authors: Scherer Otto J. , Walter Richard , Sheldrick William S.
Published: December 2003

A similar coordination behavior as isocyanide ligands is exhibited by R2NPNR ligands, since bridging isocyanide ligands are replaced by trivalent phosphazenes in the synthesis of the cluster 2 from the cluster 1. 2 represents the first cluster in which an amino(imino)phosphane is found to function as face‐bridging ligand; a μ3‐η2‐CNCMe3 ligand is also present.
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Ag2O3, a Novel Binary Silver Oxide
Authors: Standke Burkhard , Jansen Martin
Published: December 2003

Crystalline silver(III) oxide, which is stable over prolonged periods at −20°C, was obtained by anodic oxidation of AgClO4, AgBF4 or AgPF6 (not AgNO3) in aqueous solution. The oxide of definite composition Ag2O3 was hitherto unknown. It arouses interest as a possible component of the anodes in zinc/silver oxide primary cells. According to an X‐ray structure analysis, the silver atoms in Ag2O3 are coordinated by an almost square‐planar array of oxygen atoms. The AgO4 groups are coupled via common oxygen atoms to give a three‐dimensional network.
High‐Resolution X‐ray Crystallography—An Experimental Method for the Description of Chemical Bonds
Authors: Angermund Klaus , Claus Karl Heinz , Goddard Richard , Krüger Carl
Published: December 2003

By increasing the accuracy of an X‐ray analysis, results are obtained which allow one to beyond the location of hydrogen atoms and say something about the distribution of electrons in molecules. Using several examples from organic and organometallic chemistry, the methods, problems, and results of this approach are described.
η3‐Allylpalladium Compounds
Authors: Jolly Peter W.
Published: December 2003

The use of transition‐metal complexes as homogeneous catalysts for the production of organic chemicals is of considerable industrial significance. Although palladium complexes have not attained the same importance as, for example, those of rhodium or cobalt, palladium is nonetheless one of the most versatile metals for synthetic organic purposes. An understanding of the role played by the metal in these reactions is essential for their optimal utilization. This necessarily entails a detailed study of the chemistry of the palladium‐carbon bond. In this article we concentrate on η3‐allylpalladium complexes, which are frequently involved as intermediates in the Pd‐catalyzed transformations of dienes. The study of their behavior gives a deeper insight into the individual steps of a catalytic cycle.
Formation of Organoaluminium Compounds in the Mixture AlCl3TiCl4AlC2H4
Authors: Martin Heinz , Bretinger Helmut , Fürbach Fritz
Published: December 2003

In legal controversies concerning the patent rights for the Ziegler catalysts, publications of Max Fischer and of Hall and Nash have played an important role. It was claimed that the polymerization of ethylene under the given conditions was effected by a Ziegler catalyst. This claim has now been successfully disproved: no Et2AlCl is formed in the studies carried out by Fischer; the catalyst involved is therefore different from that described by Ziegler. As intermediates, the new compounds Cl2AlCH2CH2AlCl2 and (Cl2Al)2CHCH3 could be identified and synthesized.
Enzymes Hosted in Reverse Micelles in Hydrocarbon Solution
Authors: Luisi Pier Luigi
Published: December 2003

Reverse micelles are spheroidal aggregates formed by certain surfactants in apolar media. In contrast to normal micelles in water, the polar head groups of the surfactant molecules are directed towards the interior of the aggregate and form a polar core which can solubilize water (the “water pool”); the lipophilic chains are exposed to the solvent. The water of the water pool exhibits properties that (depending on the mole ratio of water to surfactant) differ from those of bulk water. Surprisingly, these reverse micelles are able to solubilize in hydrocarbon solvents hydrophilic molecules, e.g., enzymes and even plasmids, that are much larger than the original water‐pool diameter. These biopolymer‐containing reverse micelles can be viewed as novel microreactors, whose physical properties can be controlled through the water content. Remarkable is the ability of enzyme‐containing micelles to react with water‐insoluble, hydrocarbon‐soluble substrates, as in the example of lipoxygenase with linoleic acid.
Growth and Dissolution of Organic Crystals with “Tailor‐Made” Inhibitors—Implications in Stereochemistry and Materials Science
Authors: Addadi Lia , Berkovitch‐Yellin Ziva , Weissbuch Isabelle , van Mil Jan , Shimon Linda J. W. , Lahav Meir , Leiserowitz Leslie
Published: December 2003

When crystals of organic compounds are grown in the presence of growth inhibitors, there is a change in crystal morphology. A stereochemical correlation exists between the crystal structure, its modified morphology, and the molecular structure of the inhibitor. This correlation has been successfully exploited for the efficient resolution of conglomerates, the engineering of organic crystals with desired morphologies, the direct and relative assignment of the absolute configurations of chiral molecules and crystals, and for the design of a new model for the spontaneous generation of optical activity. In an analogous way dissolution of organic crystals in the presence of these growth inhibitors induces etch pits at preselected faces. The effect of solvent on crystal growth has been analyzed in some model systems. The experimental results are complemented by atom‐atom potential energy calculations.
Great Fear of Small Amounts of Elements—The Significance of Analytical Chemistry in our Modern Industrialized Community as Exemplified by Trace Element Analysis
Authors: Tölg Günther , Garten Rainer P. H.
Published: December 2003

Analytical chemistry is consolidating an important position within the framework of our modern industrial community; the frontiers of trace (and ultra‐trace) analysis have expanded into new territories, thus demanding a constant change in our mode of thinking in a substance‐related manner in analytical chemistry. An outline of the development of analytical chemistry during this century reveals a period of underdeveloped research and education followed by a current phase of impetuous advancement. However, as a result of increasingly antagonistic sectional convictions in the public mind concerning reservations against, as well as efforts towards, efficient technological progress, this advancement evokes new existential risks for analytical chemistry—viz. either to be used in an uncritical way or to fall into discredit following slogans like ‘high‐performance analytical chemistry is to blame for it all!’ A much more constructive consideration says that risks can be estimated and evaluated solely by means of a highly efficient analytical chemistry, when used with a sense of responsibility. Analysts may help to clarify and to cope with the increasing fear of decreasingly smaller amounts of trace elements—in both adverse groups in our community. Strategies necessary to gain this end are outlined with regard to a methodological as well as a political platform.
Pentacarbonylolefin‐ and Pentacarbonyldiolefinrhenium Complex Cations; Synthesis and Structure of the 2‐Butene‐1,4‐diyl‐Bridged Carbonyldirhenium Complex trans‐[(OC)5ReCH2CHCHCH2Re(CO)5]
Authors: Beck Wolfgang , Raab Klaus , Nagel Ulrich , Sacher Wolfgang
Published: December 2003

Addition of the pentacarbonylrhenate ion to the coordinated olefin in the complex cation 1 leads to formation of the complex 2, in which a σ‐η1,σ‐η1‐type C4H6‐bridge is realized for the first time. The structure of 2 has been elucidated by an X‐ray structure analysis.
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Polymerization of Propene and Butene with a Chiral Zirconocene and Methylalumoxane as Cocatalyst
Authors: Kaminsky Walter , Külper Klaus , Brintzinger Hans H. , Wild Ferdinand R. W. P.
Published: December 2003

A novel, soluble Ziegler‐Natta catalyst enables the preparation of isotactic polypropylene, which exhibits a higher degree of isotacticity than polymers that can be produced industrially with heterogeneous catalysts. Furthermore, isotactic polybutene can also be obtained with such a catalyst. The chiral, rigid zirconocene derivative 1 and methylalumoxane 2 are used for the catalysis. The polymerization activity is remarkably high.
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Syntheses with Radicals—CC Bond Formation via Organotin and Organomercury Compounds [New Synthetic Methods (52)]
Authors: Giese Bernd
Published: December 2003

CC bond formation is one of the most important synthetic steps in the construction of organic molecules. In the last few years it has been increasingly achieved by radical addition to alkenes. In such reactions the adduct radicals have to be trapped by an donor subsequent to the CC bond formation in order to prevent polymerization. This task can be accomplished with organotin and organomercury hydrides, the use of which has led to new synthetic methods. The occurrence of radical chain reactions in which reactions take place between radicals and nonradicals is decisive for the success of the synthesis. In these cases small amounts of radical initiators suffice and numerous functional groups may be used in the CC bond‐forming reactions. The yields and selectivities of these radical reactions are often very high.
Enzymes as Catalysts in Synthetic Organic Chemistry [New Synthetic Methods (53)]
Authors: Whitesides George M. , Wong Chi‐Huey
Published: December 2003

Enzymes have great potential as catalysts for use in synthetic organic chemistry. Applications of enzymes in synthesis have so far been limited to a relatively small number of largescale hydrolytic processes used in industry, and to a large number of small‐scale syntheses of materials used in analytical procedures and in research. Changes in the technology for production of enzymes (in part attributable to improved methods from classical microbiology, and in part to the promise of genetic engineering) and for their stabilization and manipulation now make these catalysts practical for wider use in large‐scale synthetic organic chemistry. This paper reviews the status of the rapidly developing field of enzyme‐catalyzed organic synthesis, and outlines both present opportunities and probable future developments in this field.
The Construction of New Proteins and Enzymes‐a Prospect for the Future?
Authors: Mutter Manfred
Published: December 2003

Only a vanishingly small proportion of the almost infinite number of possible proteins occur in nature. Can this remaining potential of structural and functional diversity be used in the construction of new proteins? Is a “second evolution” of proteins and enzymes about to occur? These questions have suddenly become of interest because the recombinant DNA technique allows the synthesis of any given amino acid sequence. Examples of enzyme models demonstrate clearly that the unusual catalytic properties of enzymes are associated with the presence of a specifically folded polypeptide chain which has a complex three‐dimensional form. The critical hurdle in the path of artificial proteins is thus the design of amino acid sequences which are able to fold into tertiary structures. — Recent studies on the topology and the mechanism of folding have provided considerable insight into the occurrence of, and the rules governing the three‐dimensional architecture of proteins. Secondary structures apparently play a key role in the folding process; helices and “β‐structures” act as nucleation centers directing folding and account for the surprisingly small number of different folding topologies. The problem of secondary structure formation can be investigated directly by means of conformational studies on model peptides. Oligopeptides with tailormade physicochemical, structural and conformational properties can already be designed. The theoretical and experimental basis for the construction of polypeptides with stable tertiary structures is therefore established. The path to macromolecules with an immense variety of novel properties lays before us.
[L2Fe(μ‐OH)(μ‐CH3CO2)2](ClO4)·H2O, a Model Compound for the Diiron Centers in Deoxyhemerythrin
Authors: Chaudhury Phalguni , Wieghardt Karl , Nuber Bernhard , Weiss Johannes
Published: December 2003

The active center of deoxyhemerythrin and the title compound 1 have similar structures and similar magnetic and spectroscopic properties. In both cases, two FeII centers are bridged by two carboxylato ligands and one hydroxo ligand.
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Do Cp(CO)2Mn Fragments Stabilize Radicals?
Authors: Gross Renate , Kaim Wolfgang
Published: December 2003

Two classes of paramagnetic manganese complexes can be differentiated by ESR spectroscopy: radical complexes 1, in which radical‐anion ligands L⊙⊖ are stabilized by Cp(CO)2Mn1 fragments, and low‐spin Mn11 compounds 2, with strongly nucleophilic ligands L.
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