bluuebunny/crossref_metadata_2025 huggingface dataset:
Lise Meitner: Her Life and Times—On the Centenary of the Great Scientist's Birth
Authors: Krafft Fritz
Published: December 2003

Cooperation between the three scientists Lise Meitner, Otto Hahn, and Fritz Strassmann in the study of the “transuranics” (1934—1938) prepared the way for the chemical identification of a first fission product of uranium by Otto Hahn and Fritz Strassmann at the end of 1938. Together with her nephew Otto Robert Frisch, she also gave the first theoretical interpretation of that experimental finding (barium instead of the expected radium) and suggested the inert gas krypton to be the second fission products, which Hahn and Strassmann subsequently identified (besides xenon) among the products. But she was kept from direct participation in the experiments conducted at the Kaiser Wilhelm Institute for Chemistry at Berlin—and therefore from the unrestricted claim to being co‐discoverer of uranium fission—because she was an Austrian “Jewess”. Thus after the “annexation” of Austria by the German Reich, the Nazi racial laws also applied to her and precluded her continuing to work in Germany. She therefore emigrated illegally via Holland to Sweden in the middle of 1938. There she continued to work on problems of nuclear physics under less favorable conditions untill 1960. Work on radioactivity already started at Vienna had also brought her together with Hahn at Berlin in 1907, and she continued the work at the Kaiser Wilhelm Institute studying α‐, β‐, and γ‐radiation and related nuclear processes. Not only because of her descent, but also because of her status of a woman in science, her fate was molded by the circumstances prevailing in Germany prior to World War II. On November 7, 1978 Lise Meitner would have celebrated her hundredth birthday, reason enough for recalling her lot as a woman scientist in Germany against the background of her times, which should stand as a warning to us. To that end contemporary documents could be quoted which till now were largely unknown.
C6H5Sb[Mn(CO)2C5H5]2—The first Compound Containing Trigonal‐Planar Coordinated Antimony(I)
Authors: von Seyerl Joachim , Huttner Gottfried
Published: December 2003

Stabilization of phenylstibanediyl (C6H5Sb) is accomplished by coordination to two groups containing transition metals. X‐Ray structure analysis shows the SbI atom to have a trigonal‐planar environment in compound (1).
equation image
A Stable σ/π‐Organometallic Radical of Vanadium: (η5‐C5Me4Et)2 VCCC6H2Me3
Authors: Köhler Frank H. , Prössdorf Wolfram , Schubert Ulrich , Neugebauer Dietmar
Published: December 2003

The stabilization of vanadocene Cp2VR with a σ‐bonded ligand proves possible on complete alkylation of the cyclopentadienyl groups. X‐Ray structure analysis of the title compound (1) permitted the first determination of the length of the VIIICsp bond (203.2 pm). The paramagnetic 1H‐NMR spectrum shows that (1) contains two unpaired electrons.
Systematic Formation of Metal Complexes Containing Isocyanide Bridging Ligands: [η5‐C5H5Fe(CNC6H5)(μ‐CNC6H5)]2
Authors: Fehlhammer Wolf Peter , Mayr Andreas , Christian Götz
Published: December 2003

Stable complexes with isocyanide bridges can be synthesized on joint application of the two strategies “isocyanide bridge formation” and “isocyanide transfer.” This promising method, proceeding under especially mild conditions, permitted the synthesis of the dimer (1).
equation image
Multistage Organic Redox Systems—A General Structural Principle
Authors: Deuchert Klaus , Hünig Siegfried
Published: December 2003

A general structural principle for organic compounds that have the capacity for two‐stage electron transfer is based on the following reaction sequence:equation imageIn this scheme one or both of the entities X may be replaced by Y⊖. The radical partners in these systems often have very high thermodynamic stability. The choice of the end groups X and Y, (partial) inclusion of n‐systems in rings, alteration of the number of vinylene groups, and aza‐substitution make many variations possible. By means of this general structural principle numerous known compounds are brought together and new redox systems are simultaneously set up. The aim of the present review is to demonstrate the broad applicability of this principle, to indicate its significance for science and industry, and to describe some reactions.
Pore Sizes of Solids
Authors: Halász István , Martin Kornél
Published: December 2003

A new, fast, and simple method based on size exclusion chromatography permits determination of the volumes of open and closed pores of rigid solids such as silica or porous glasses, together with the specific surface and the pore‐size distribution for pore diameters ranging from 10 to 4000Å. The results are in good agreement with those obtained by classical methods (capillary condensation, mercury porosimetry).
Carbonyl(pyridine)iron(II) Tetrabenzporphyrin π‐Radical Cation
Authors: Vogler Arnd , Rethwisch Birgit , Kunkely Horst , Hüttermann Jürgen
Published: December 2003

“Oxidation state isomerism” exists between porphyrins which differ only in the localization of their electrons. Such a system is that of the title compound [FeII(TBP+)(CO)(py)]⊕, in which one electron is removed from the porphyrin ring, and the corresponding (unknown) FeIII porphyrin.
New Applications of Computers in Chemistry
Authors: Ugi Ivar , Bauer Johannes , Brandt Josef , Friedrich Josef , Gasteiger Johann , Jochum Clemens , Schubert Wolfgang
Published: December 2003

The mathematical model of constitutional chemistry described here is based on a concept of isomerism which has been extended from molecules to ensembles of molecules. A chemical reaction is the conversion of an ensemble of molecules into an isomeric ensemble. An ensemble of molecules is representable by an atomic vector and an associated bond and electron (BE)‐ matrix, and a reaction by a reaction (R)‐matrix. These BE‐and R‐matrices serve as a basis for computer programs for the deductive solution of chemical problems. We present here algorithms and computer programs based on the theory of BE‐ and R‐matrices. They enable the classification and documentation of structrues, substructures and reactions, the prognosis of reaction products,the design of syntheses, the construction of networks of mechanistic and synthetic pathways and the prediction of chemical reactions.
Synthesis of the Mast Cell Degranulating (MCD) Peptide from Bee Venom
Authors: Birr Christian , Wengert‐Müller Margot
Published: December 2003

Potential value in the therapy of rheumatism and other inflammation processes could attach to the MCD peptide from bee venom if it were available in larger quantities. The peptide consists of 22 amino acids and contains two disulfide bridges. Its first total synthesis has now been accomplished.
Long‐Chain Alkylammonium Ions as Phase Transfer Reagents for the Synthesis of Mixed‐Ligand Complexes of the Platinum Metals
Authors: Shukla Ashok Kumar , Preetz Wilhelm
Published: December 2003

Phase transfer reactions have great preparative potential in inorganic chemistry. Thus the first halo complexes of Os, Ir, Pt, and Re have now been synthesized in the presence of [(C12H25)3NH]HSO4; they contain not only fluorine but also bromine and iodine as ligands. The following anions are examples (XCL or Br):
equation image
Anchimerically Accelerated Bond Homolyses
Authors: Reetz Manfred T.
Published: December 2003

Radical reactions of the type R1abR2→•abR1 + •R2 are feasible if the new bond formed between b and R1 is considerably stronger than the old bond between a and R1. Furthermore, both the radical fragments formed must be resonance stabilized. An example of this reaction type is the thermolysis of benzyl trimethylsilylmethyl ethers, in which the trimethylsilyl group (with empty orbitals) migrates to the oxygen atom (with lone pairs). Assumption of a cyclic reactive intermediate with pentacoordinated silicon explains the observed intramolecular nature and the negative entropy of activation of such homolyses.
Elemental Sulfur/Alkali Metal Hydroxide/Dimethyl Sulfoxide—A New “Reagent” for Preparing Organic Sulfur compounds
Authors: Jończyk Andrzej
Published: December 2003

The introduction of the alkylthio group into oraganic compounds previously involved several reaction steps or reagents with RS groups. The reaction shown below proceeds in single step, and S/NaOH(or KOH)/DMSO/RS serves as “reagent”.
equation image
η5‐Cyclopentadienyl(trinitrosyl)vanadium Hexafluorophosphate, [CpV(NO)3]PF6
Authors: Herberhold Max , Klein Reinhard , Smith Paul D.
Published: December 2003

The series of isosteric half‐sandwich compounds of type [CpML3]+ (LCO or NO) has now been complied by the synthesis of (1) and is thus available for comparative studies.
equation image
Alkenediazonium Salts: A New Chapter of Classical Organic Chemistry
Authors: Bott Kaspar
Published: December 2003

Whereas the protonation of α‐diazo‐β‐diketones and α‐diazo‐β‐oxo esters with hydrogen chloride and antimony pentachloride yields the corresponding hydroxyalkenediazonium hexachloroantimonates, the “acid‐sensitive” α‐diazomonocarbonyl compounds can be transformed into resonance‐stabilized alkenediazonium salts by an analogous O‐alkylation with triethyloxonium hexachloroantimonate. A general route for synthesizing these compounds consists in the transformation of the p‐toluenesulfonylhydrazones of α‐halogenated aldehydes and ketones with Lewis acids. Alkenediazonium ions which are not resonance stabilized can be isolated at room temperature only if their decomposition at higher temperatures leads, via evolution of nitrogen, to vinyl cations in particularly high energy levels. Facile substitution reactions at the CC double bond with anisole and methanol demonstrate the strongly electrophilic nature of alkenediazonium salts. When electron‐donating substituments are attached to C2 of an ethylenediazonium ion, the bond order of the NN triple bond can be reduced to a level comparable with that in diazoacetic ester.
Polymer Alloys—Their Structure, Morphology, and Properties
Authors: Schmitt Burghard J.
Published: December 2003

Polymeric materials with novel properties for new technological applications are increasingly obtained by combining existing polymers, while the synthesis of new monomers has receded into the background. These polymer combinations or “alloys” (polyblends) are characterized by their chemical composition, the conformation of the chain molecules, and the morphology, i.e. the state of order at supramolecular level. Multiphase constitution is a typical characteristic of these substances, with a decisive influence on their macroscopic properties. The morphology of multiphase polymer alloys can be controlled to a limited extent via the chemical composition of their components when homopolymers are mixed in the melt or as dispersions. Graft copolymerization, on the other hand, makes it possible to achieve the desired morphology at a given chemical composition. Furthermore, transprent two‐phase polymer alloys can be obtained under certain conditions. In multiphase polymers the reduction of stress without fracture, caused by mechanical loading will be treated using models. Certain combinations of properties such as hardness and toughness are connected with the coexistence of disperse and continuous phases. Equilibrium thermodynamical criteria for liquid mixtures wil be used to explain demixing phenomena in polymers. In the last few years it has become possible to determine the chain conformation experimentally using neutron scattering.
Unsymmetrical Binuclear Complexes of Tungsten with Three OR Bridges, η3‐C7H7(CO)2W(OR)3W(CO)2‐η4‐C7H8
Authors: Schulze Wolfgang , Weidenhammer Klaus , Ziegler Manfred L.
Published: December 2003

No analogy between molybdenum and tungsten is observed in the reaction of η7‐C7H7M(CO)2X (1) with NaOR: (1), M = Mo, forms the paramagnetic compound (2) with two Mo centers in different oxidation states. In the case of (1), M = W, however, a C7H7 ligand is surprisingly reduced to C7H8 by H−; the 18‐electron rule applies to both W atoms in (3).
equation image
Photochemical Reactions of Surfactant Molecules in Condensed Monolayer Assemblies—Environmental Control and Modification of Reactivity
Authors: Whitten David G.
Published: December 2003

An investigation of the effects of a controlled microenvironment on reactivity has been carried out by the synthesis and study in organized monolayers of surfactant molecules containing photochemically reactive chromophores. Reactions where substantial environmental effects have been observed include the cis‐trans isomerization of olefins, ketone photoeliminations, ligand substitution processes, excimer and photodimer formation, and photoredox reactions. Both reactions occurring within the organized assemblies as well as interfacial phenomena have been investigated. Results obtained in these studies suggest possible extensions and applications for the development of new catalyst systems, biological models and controlled syntheses.
Krypton and Xenon Inclusion Compounds of Complex Metal Cyanides
Authors: Kämper Manfred , Wagner Madlon , Weiss Armin
Published: December 2003

The inclusion of noble gases in host lattices—e.g. CdPt(CN)6 takes up 1.046 Kr or 1.128 Xe per formula unit if the crystals are grown in the presence of the gas (64 bar)—corresponds to a compression (⩾118 bar). However, CdPt(CN)6 is too expensive for industrial use. The cavities of the cage structure surprisingly remain vacant on crystallization from water.
Pyrolysis of Sulfones as a Synthetic Method [New synthetic methods (28)]
Authors: Vögtle Fritz , Rossa Ludovica
Published: December 2003

Cyclic sulfoness containing structural elements such as aromtic rings, heteroatoms. functional groups, and further SO2‐groups as ring members decompose on heating with cleavage of SO2 and formation of a new CC bond. In the last decade this “sulfone pyrolysis” has been expanded into a generally applicable method even allowing the synthesis of sterically strianed medium‐membered and multi‐membered cyclic and polycyclic systems containing aromatic ring. By the pyrolysis of sulfones which are only unilateally activated by benzyl moieties, aromatic systms can be bridged by (CH2)n chains of any desired length. In addition, (CH2) chains can be split off together with two SO2 molecules, with recombination of the remaining centers, resulting in ring contraction by four to n atoms. However, sulfone pyrolysis is of importance not only as a ring‐contraction method but as a crucial final step in the synthesis of multi‐membered hydrocarbon cycles, e.g. of the phane type.
Spatial Structure Formation in Protein Gels
Authors: Bezrukov M. G.
Published: December 2003

The present article is concerned with the practical and theoretical aspects of gelation in protein systems. The processes involved are, inter alia, so complicated that several types of protein molecule assemblies and conformational changes during the association have to be considered. The gel network can be stabilized by five types of interaction: covalent crosslinking, polar interactions, hydrogen bonding, salt bridges and hydrophobic interactions. The microstructures of gels formed from fibrillated proteins (collagen) and from globular proteins (e.g. α‐ and β‐ casein) differ considerably. Of practical interest are methods of controlling the solubility of gels, including e.g. the use of cross‐linking agents and addition of salts.
Colloidal Redox Catalysts for Evolution of Oxygen and for Light‐Induced Evolution of Hydrogen from Water
Authors: Kiwi John , Grätzel Michael
Published: December 2003

Chemical utilization of the sun's radiation is very attractive aim. The evolution of oxygen and, on irradiation, hydrogen from water in the presence of redox catalysts are known, but rather slow processes. Colloidal ruthenium and other metals catalyze these reactions better than less finely divided materials.
Conformational Analysis by Photoelectron Spectroscopy
Authors: Klessinger Martin , Rademacher Paul
Published: December 2003

The conformation of organic molecules may be determined by means of photoelectron (PE) spectroscopy if there are orbital interactions present which depend on a dihedral angle. Straightforward application of the method requires that all ionization bands of interest can be assigned unambiguously and that inductive effects and secondary orbital interactions do not occur or can be accounted for appropriately. In many cases, this method complements conventional methods of conformational analysis. PE conformational analysis is particularly suited to compounds containing vicinal lone pairs or π systems.
Ion Cyclotron Resonance Studies on tert‐Butyl, 2‐Norbornyl, and 1‐ and 2‐Adamantyl Cations
Authors: Houriet Raymond , Schwarz Helmut
Published: December 2003

The discussion about “classical”/“nonclassical”cations continues. ICR studies show that the 1‐adamantyl cation is certainly not exceptionally stabilized (as has been repeatedly suspected) and that the energy of the 2‐adamantyl cation differs by only 4 kcal/mol instead the expected amount of 16 kcal/mol. The analogy with the controversial 2‐norbornyl cation/2‐methyl‐2‐norbornyl cation system cannot be overlooked.
Chromatographic Resolution of Racemates. New analytical methods (17)
Authors: Blaschke Gottfried
Published: December 2003

A number of racemates can be resolved into optically pure enantiomers by chromatography on optically active adsorbents. Synthetic polymers with optically active amide, amino acid, and crown ether groups, natural products such as starch and cellulose, and also microcrystalline triacetylcellulose are suitable for this purpose. Racemates can also be resolved by gas chromatography on optically active stationary phases.
3‐Phenylpropylamines, A New Class of Systemic Fungicides
Authors: Himmele Walter , Pommer Ernst‐Heinrich
Published: December 2003

The biological activity of 3‐phenylpropylamines is not exclusively determined by their structure. It could be demonstrated that the fungicidal activity of partially hydrogenated compounds of this class of substances is also substantially influenced by the conformation. An optimization of the conformational criteria—illustrated by many examples, yet constituting only a small number of those actually examined—afforded compounds with excellent properties, e.g. N‐[3‐(4‐tert‐butyl‐1‐cyclohexenyl)‐2‐methylpropyl]‐cis‐2, 6‐dimethylmorpholine.
Photochemical Rearrangements and Fragmentations of Benzene Derivatives and Annelated Arenes
Authors: Kaupp Gerd
Published: December 2003

In this article the numerous intramolecular reactions of electronically excited benezene derivatives, which in many instances are only mentioned in original papers, are systematically analyzed and arranged according to reaction types. All known reaction types can be classified, and subdivided into reactions of the benzene ring (ionization, ring opening, ring alteration), reactions with participation of side chains (α‐, β‐, γ‐cleavage, homolysis, heterolysis), reactions of substituents with side chains (cyclization, dealkylation, cleavage of protective groups), and reactions of side chains with the aromatic ring (substitution, addition, dearomatization, cyclization). The selectivity of the energetically feasible competing reactions is primarily determined by geometric factors. Applications of the empirical effects are numerous and varied in preparative organic chemistry. Many of the reactions under discussion are already utilized industrially (e.g. in photochromism, UV stabilization, photography, information storage, printing, coating and polymer technology, and pharmacy).
Exceedingly Mild Desulfurization of Thiols by Sodium Triethylhydroborate and Transition Metal Chlorides
Authors: Alper Howard , Prince Trish L.
Published: December 2003

Hydrocarbons can be obtained from thiols at room temperature/−78 °C with the new reduction system given below. The procedure is suitable for aromatic, benzylic, and aliphatic thiols; CoCl2 can be used instead of FeCl2. Other chlorides are less effective.
equation image
Thermal Degradation of Polymers to Polymeric Carbon—An Approach to the Synthesis of New Materials
Authors: Fitzer Erich
Published: December 2003

One hundred years ago, Edison succeeded in preparing carbon fibers for his incandescent lamp bulb by thermal decomposition of natural polymeric fibers. Ten years ago, progress reports about “Novel Forms of Carbon” predicted outstanding properties and promising new applications for the carbonization products of synthetic polymers. Research and development in this field have been promoted by the problems of conventional technology (shortages of raw material and energy, pollution problems). Polymeric carbon materials—prepared by thermal degradation of synthetic polymers—exhibit a special ribbon‐like microstructure. They will provide the chemist with many challenges.
“Living Polymers” on Polymerization with Extremely Productive Ziegler Catalysts
Authors: Sinn Hansjörg , Kaminsky Walter , Vollmer Hans‐Jürgen , Woldt Rüdiger
Published: December 2003

At least 10000 polyethylene molecules per zirconium atom can be obtained with a Ziegler catalyst made up of Cp2ZrMe2 and [Al(Me)O]n. Depending upon the conditions, the molecular weight of the polymer lies between 100000 and 200000. All the results available so far are in accord with the following concept: A molecule of organozirconium compound diffuses into an associate of aluminoxanes. H‐transfer leads to zirconium hydrides which add ethylene to form alkyl compounds and thus give rise to active sites.
equation image
Extreme 13C‐NMR Data as Information on Organometal Radicals
Authors: Köhler Frank H. , Doll Karl‐Heinz , Prössdorf Wolfram
Published: December 2003

The utility of 13C‐NMR spectroscopy in the study of organometallic radicals has been demonstrated for substituted nickelocenes. The shifts and halfwidths, as well as their variation, permit structural elucidation of radicals where ESR fails, and provide indications, e.g. of the number of unpaired electrons and their incorporation in various orbitals, and even of isotope effects.
Zintl Phases with Complex Anions: Sr3Si2As4 and Sr3Ge2As4
Authors: Eisenmann Brigitte , Schäfer Herbert
Published: December 2003

Sr3Si2As4 and Sr3Ge2As4 can be regarded as transition forms between salts of complex anions and ternary intermetallic compounds; they have now been synthesized for the first time. Both compounds contain differently linked one‐dimensional, infinite anions with As3SiSiAs3 and As3GeGeAs3 structural units.
Catalytic Graphite‐Intercalation with Alkali Metals in Solution
Authors: Klein Hans‐Friedrich , Gross Joachim , Besenhard Jürgen O.
Published: December 2003

A new route to graphite inclusion complexes of alkali metals utilizes the reversible reduction of cobalt(0) catalysts. Thus KC8, RbC8 and CsC8 can be synthesized from alkali metals and graphite in pentane at 25°C in the presence of Co(C2H4) (PMe3)3.
Alkali Metal‐Transition Metal π‐Complexes
Authors: Jonas Klaus , Krüger Carl
Published: December 2003

In this progress report a new principle is described for the synthesis of multimetal π‐complexes with hitherto unknown structural features. The nickel(0)‐olefin complexes 1,5,9‐cyclododecatrienenickel(0) and bis(1,5‐cyclooctadiene)nickel(0) react unexpectedly with main‐group metals, in particular alkali metals, their hydrides, and organometallic compounds, to give nickelligand species with a surplus charge. These species endeavor to transfer the excess charge onto π‐ligands such as olefins or dinitrogen. Multimetal complexes with electron rich transition metal π‐ligand units can, in addition, be prepared from metallocenes, alkali metals, and unsaturated compounds. The syntheses, structures, and reactions of this new class of substances will be summarized.
Bis(di‐tert‐butylphosphino)tellurium(II): A Derivative of Phosphinous Anhydride Exhibiting Umpolung
Authors: du Mont Wolf‐Walther
Published: December 2003

The title compound (1)—obtained via the reaction shown below and independently from Na2 Te and tBu2PCl— is formed very readily. (1) is the first tellurium compound to contain only R2P substituents. Its reactions prompt us to consider the bonding in (1) and in other TeP compounds.
equation image
Physicochemical Principles and Applications of Supercritical Fluid Chromatography (SFC). New analytical methods (19)
Authors: van Wasen Ulrich , Swaid Issam , Schneider Gerhard M.
Published: December 2003

In supercritical fluid chromatography (SFC) compressed gases in the region of their critical temperature are used as mobile phases. SFC has important advantages over gas chromatography (GC) for the separation of low‐volatile or thermally unstable substances. Like high pressure liquid chromatography (HPLC) and gel chromatography, it is used for various special applications and preparative separations, e.g. in the petroleum industry and in the separation of oligomers. SFC is of great interest in fundamental research on fluid extraction and for the determination of the physicochemical properties of fluid systems. In this contribution the most important physicochemical, methodological, and instrumental principles of SFC are summarized; characteristic physicochemical applications are the determination of capacity ratios, partition coefficients, partial molar volumes, interaction second virial coefficients, and difusion coefficients.
Valence Changes at High Pressure in Systems Containing Lanthanoids
Authors: Jayaraman A.
Published: December 2003

Pressure‐induced valence change in samarium sulfide SmS is reminiscent of alchemy, for when the electronic transition has taken place, the originally dull looking substance glitters like gold. Although it is not the realization of the alchemist's dream in the true sense, the material in the new state exhibits extraordinarily interesting behavior. As a novel feature, the valence state of the samarium fluctuates between two electronic configurations at a very fast rate. The physical properties of systems containing lanthanoids can be profoundly altered by manipulating the valence state by pressure or by chemical substitution. These phenomena will be described and discussed in the present article.
Template Polymerization of Rhodium(I) with Rigid Bent Diisocyanide Ligands
Authors: Efraty Avi , Feinstein Irene , Wackerle Lorenz , Frolow Felix
Published: December 2003

Two‐dimensional polymeric networks of the type [Rh(Bridge) Cl−]n are present in the green polycrystalline material obtained from [Rh(CO)2Cl]2 and bridging ligands such as 1,3‐diisocyanobenzene and 4,4′‐diisocyanodiphenylmethane. These bidentate ligands cannot form chelates. Information about the structure of the polymers was derived from X‐ray powder diagrams.
N‐Sulfinylnonafluorobutanesulfonamide—A Supernucleophile
Authors: Bussas Reinhard , Kresze Günter
Published: December 2003

The transformation of a highly reactive enophile into the supernucleophile (1) has been accomplished by formal replacement of p‐tolyl by n‐C4F9. The readily accessible compound (1) is some 103 to 104 times as active as its p‐tolyl analogue.
equation image
The Significance of Isoselective Temperatures for the Existence of Linear Free‐Energy Relationships
Authors: Giese Bernd , Lee Woo‐Bung
Published: December 2003

How does the variation of reaction partners (Yj) in competition systems influence the isoselective temperature? With the aim of answering this question, the authors examined the reactions of CF2, CCl2, and CBr2 (X1) with the pairs (Yj/Yi) of methylated ethylenes and Me2CCH2. Astonishingly, the isoselective temperature does not change in such series of reactions if a common free‐energy relationship exists.
equation image
Stereospecific Polymerization of Propylene: An Outlook 25 Years after Its Discovery
Authors: Pino Piero , Mülhaupt Rolf
Published: December 2003

In 1955Nattaand his co‐workers from the Istituto di Chimica Industriale del Politecnico di Milano reported the properties of highly crystalline polypropylene and other poly‐α‐olefins[1]which posses, at least in long sections of the main chain, asymmetric carbon atoms of the same absolute configuration (isotactic poly‐α‐olefins). The discovery of the new crystalline polymers was judged at that time “revolutionary in its significance”[2]and heralded a new era in polymer science and technology. Indeed, crystalline polypropylene, because of its relatively high melting point and its outstanding mechanical properties, has found very extensive application in the field of plastics films and fibers.—25 years after this publication, it is worthwhile examining the further developments following this discovery which has had such a great scientific and industrial impact, and the problems which are still open concerning the structure of the catalytic centers and the mechanisms by which practically completely stereoregular polypropylenes are formed.
Trinuclear Clusters of the Early Transition Elements
Authors: Müller Achim , Jostes Rainer , Cotton F. Albert
Published: December 2003

Trinuclear clusters of the early transition elements, i.e. those elements situated on the left‐hand side of the transition series, represent the simplest types of clusters. They characteristically have a pronounced formation tendency and high stability; they are therefore produced under a wide variety of conditions and their triangular M3 skeleton is conserved in ligand exchange reactions. These clusters play a very important role in the chemistry of the respective elements, and especially those of the 4 d and 5 d series. Biochemical implications are of interest in connection with MoIV. This progress report presents a systematic account of the chemistry and the molecular and electronic structure of such compounds. A connection is also established with the crystal field treatment of mononuclear metal complexes.
Chemistry of Thiazyl Fluoride (NSF) and Thiazyl Trifluoride (NSF3): A Quarter Century of Sulfur‐Nitrogen‐Fluorine Chemistry
Authors: Glemser Oskar , Mews Rüdiger
Published: December 2003

Since the first sulfur‐nitrogen‐fluorine compounds were synthesized 25 years ago[2], great progress has been made in this field of covalent fluorine chemistry[3–9]. The two small molecules thiazyl fluoride (NSF) and thiazyl trifluoride (NSF3), are key substances; nearly all sulfur‐nitrogen‐fluorine compounds can be derived from them.
Proton and Hydrogen Affinity of Furan and the Site of Protonation in the Gas Phase
Authors: Houriet Raymond , Schwarz Helmut , Zummack Waltraud
Published: December 2003

Ion cyclotron resonance measurements on D‐labeled furan revealed that in the prototype electrophilic reactions—i.e. protonation—furan behaves in the gas phase as a typical arene and not as enol ether.
Thermal and Photochemical Transformations of Hetero‐1,3,5‐hexatrienes into Five‐Membered Rings—Possible Pericyclic Reactions
Authors: George Manapurathu V. , Mitra Abijit , Sukumaran Kutikat B.
Published: December 2003

Heterosubstituted 1,3,5‐hexatrienes undergo thermal and photochemical cyclizations, most of which can be viewed as pericyclic reactions. Numerous cyclizations of this type have been reported in the literature. This article presents a systematic account of such reactions, classified according to the number and nature of the heteroatoms.
Reduction of Aromatic Nitro, Nitroso, Hydroxylamino, Azo, and Azoxy Compounds with Hydrogen Telluride from Aluminum Telluride and Water
Authors: Kambe Nobuaki , Kondo Kiyoshi , Sonoda Noboru
Published: December 2003

H2Te generated in situ reduces aromatic nitrogen compounds. Nitroarenes afford arylamines; azoxybenzene, azobenzene, and nitrosobenzene are transformed into hydrazobenzene; and hydroxylamine gives aniline. Azoxybenzene, azobenzene, and nitrosobenzene are possible intermediates of the reduction of nitrobenzene.
equation image
Phosphorus Ylide Carbene Complexes of Manganese—Synthesis and Structure
Authors: Malisch Wolfgang , Blau Herbert , Schubert Ulrich
Published: December 2003

For corrigendum see DOI:10.1002/anie.198102161
Condensed Metal Clusters
Authors: Simon Arndt
Published: December 2003

The chemistry of metals in low valence states is marked by the frequent occurrence of metal clusters, which are easily recognizable when they occur as molecular units. Many metal‐rich compounds of transition metals with p‐elements (3rd to the 6th main groups) are closely related to the corresponding halides, since they are built up from metal clusters of the same type. The clusters are however, linked together (condensed) by metal‐metal bonds. This principle of construction holds particularly well in the case of the novel reduced halides of the lanthanoids.
Electrochemical Processes in Supercritical Phases
Authors: Silvestri Giuseppe , Gambino Salvalore , Filardo Giuseppe , Cuccia Carmelo , Guarino Enrico
Published: December 2003

Following investigations of supercritical carbon dioxide, bromotrifluoromethane, hydrogen chloride, and ammonia as solvents for electrochemical reactions, it has seen established that HCl and NH3 only conduct sufficiently for synthetic purposes at small electrode separation and very high density. CO2 and CBrF3 proved to be unsuitable.
(NH4)4[P4S8]·2H2O, the Salt of a “Square” Phosphoric Acid
Authors: Falius Hans , Krause Werner , Sheldrick William S.
Published: December 2003

The square arrangement of the four phosphorus atoms is the most notable structural feature of the novel cyclic thiophosphate(III) ion, which has been isolated as its ammonium salt. The anion is formed by the reaction of white phosphorus with polysulfides in organic solvents.
Oxidation of Alcohols with Benzyl(triethyl)ammonium Permanganate
Authors: Schmidt H.‐Jürgen , Schäfer Hans J.
Published: December 2003

Esters and/or acids and/or ketones are the major products of oxidation of primary and secondary alcohols with benzyl(trielhyl)ammonium permanganate, which can be safely handled below 50 °C. For primary alcohols the reagent is superior than solid carriers impregnated with KMnO4.
cyclo‐Leu5‐Enkephalin
Authors: Kessler Horst , Hölzemann Günter
Published: December 2003

The number or conformations of biologically active peptides can be reduced by cyclization, which enables more exact NMR spectroscopic studies to be made. cyclo‐Leu5‐enkephalin (2), synthesized from (1), has the γγ‐ (or βγ) conformation according to 270‐MHz 1H‐NMR data in dimethyl sulfoxide.
equation image
Ba4SiAs4, and Ba4GeAs4, Zintl Phases with Isolated SiAs and GeAs anions
Authors: Eisenmann Brigitte , Jordan Hanna , Schäfer Herbert
Published: December 2003

Examples for an extension of the Zintl‐Klemm concept to compounds whose anion partial structure is made up of two elements are the newly synthesized isolypic compounds Ba4SiAs4 and Ba4GeAs4. They contain “isolated” SiAs4 ‐or GeAs4 tetrahedra, i.e. surrounded only by Ba counterions. The title compounds are bridging members between the ternary intermetallic compounds and the salts with complex anions. A principle concerning the charge distribution found in Zintl‐phases with complex anions remains valid.
Macromolecular Chemistry Today—Aging Roots, Sprouting Branches
Authors: Mark Hermann F.
Published: December 2003

Review and Preview—sprouting roots and new branches in macromolecular chemistry—who, in the year of Hermann Staudinger's centenary, could be better equipped to comment on the state of the art in this branch of chemistry than the old and faithful “Geheimrath”?
Polymeric Antitumor Agents on a Molecular and on a Cellular Level?
Authors: Gros Leo , Ringsdorf Helmut , Schupp Hans
Published: December 2003

“Chemistry has become a mature science, with all the advantages and handicaps of maturity: harvest is abundant, but many people think future and adventure are to be found elsewhere”[1a]. This holds true—in 1981, the year ofHermann Staudinger's100th birthday—for macromolecular chemistry, too. Where can the polymer chemists seek adventures? Unsolved problems in neighboring fields like medicine and molecular biology attract his zeal. Cancer chemotherapy is such a field. Can the polymer chemist help to solve its problems?

Polymers may be pharmacologically active as such. If used as carriers, they may, due to their intrinsic properties, influence body distribution, excretion or cell uptake of the pharmaca they carry. Hence, there is a chance for new ways in therapy, including affinity chemotherapy using synthetic macromolecules.

Our own body has a perfect biological system for affinity therapy: immune response to infection selectively attacks foreign cells, It is fascinating to observe what the immune system does to a tumor cell which could not escape immune surveillance (cf. Fig. 14). Can these specific cell‐cell interactions be mimicked? What do we have to learn for an experimental approach to this adventure? Stable membrane and cell models can be synthesized, a first step towards this goal.

Macromolecular chemistry is far from being able to offer satisfying solutions for a specific tumor therapy; striving for it, polymer chemists can learn lots of things. In order to do so, they will have to enter neighboring fields and they will have to be willing and able to cooperate.
Cells with Manipulated Functions: New Perspectives for Cell Biology, Medicine, and Technology
Authors: Zimmermann Ulrich , Scheurich Peter , Pilwat Günter , Benz Roland
Published: December 2003

Exposure to electrical fields can reversibly increase the electrical conductivity and permeability of a cell membrane, which regulates and directs the exchange of materials and information between the cell and its environment. If cell membranes (or artificial lipid membranes) are exposed to a field pulse of high intensity and short duration (ns to μs), local electrical breakdown occurs in them. This electrical breakdown is associated with a large permeability change in the membrane, which is such that substances or particles (up to the size of genes) which cannot normally permeate through the membrane, are able to traverse the membrane into the cell. The original properties of the membrane are restored within μs to min, depending on the experimental conditions and the membrane properties.

Electrical breakdown in the zone of contact between the membranes of cells (or lipid vesicles), which have been made to adhere to each other by the action of weak inhomogeneous alternating electrical fields, leads to fusion of these cells with formation of a single cell having new functional characteristics. The electrical fusion method is very mild, and the yield of fused cells is high.

The electrically induced fusion and entrapment of membrane‐impermeable substances and genes in cells provide a new tool for the productions of a wide range of cells with manipulated functions, which could be used (or are being used) for the solution of a number of problems in cell biology, medicine and technology.

The application of electrical membrane breakdown to clinical diagnostics, the development of cellular carrier systems for the selective transport of drugs to a site of action within the organism and the potential applications of electrically induced fusion for breeding salt‐tolerant crop plants for converting solar energy into ethanol, for synthesizing natural materials and manipulating genes, are described.
Separation and Determination of Sulfur Homocycles by High Pressure Liquid Chromatography—Detection of Novel Sulfur Rings
Authors: Steudel Ralf , Mäusle Hans‐Joachim , Rosenbauer Doris , Möckel Hermann , Freyholdt Torsten
Published: December 2003

Thirteen new sulfur rings can be isolated without decomposition by reverse phase HPLC and detected by UV spectroscopy. Melts of S8 contain all Sn rings with n = 6–26; the mixture obtained on reaction of SC12 or S2C12 with KI consists of Sn rings with n = 6–21 or of even‐numbered rings with up to 22 members. The separation of S8 and Se8 was accomplished in the same way.
N‐Methyl Inversion Barriers in Six‐membered Rings
Authors: Katritzky Alan R. , Patel Ranjan C. , Riddell Frank G.
Published: December 2003

Conformational conversions of N‐methylazacyclohexanes are of particular interest: they can proceed either via ring‐ or nitrogen‐inversion processes. In both procedures an equatorial N‐methyl group is converted into an axial one, and the converse. It is appropriate to dissociate the energy barriers for N‐methyl inversion into two “half‐barriers” for the steps, axial form → transition state and equatorial form → transition state, and to report both values separately.—In this article the N‐methyl inversion barriers of numerous methylated oligoazacyclohexanes, including species with oxygen or nitrogen atoms in the ring, are discussed.
Silaethene: Highly Correlated Wave Functions and Photoelectron Spectroscopic Evidence
Authors: Rosmus Pavel , Bock Hans , Solouki Bahman , Maier Günther , Mihm Gerhard
Published: December 2003

For the PE‐spcctroscopic search for H2SiCH2‐generating reactions its first ionization energy was initially estimated by quantum chemical ab initio methods. In a wide range of pyrolysis experiments no reproducible bands could be observed in the expected region. A new band with vibrational fine structure, however, occurred on thermal retrodiene cleavage of the silabicycle (1), X = H (see previous communication). The assignment is supported by further arguments.
Structure and Decay of Gaseous Organic Radical Cations Studied by Their Radiative Decay, Exemplified by the 1,3‐Pentadiyne Cation
Authors: Maier John P.
Published: December 2003

The radiative decay of over a hundred open‐shell organic radical cations has now been established. As a result, the spectral structure of such cations in their ground and excited electronic states can be probed with resolutions of the order of ⩽ 1 cm−1. This is achieved by means of emission and laser‐induced fluorescence techniques. The analysis of the emission and excitation spectra provides the vibrational frequencies of many of the totally symmetric fundamentals of the cations in the two electronic states. In order to study the relaxation behavior of these cations under “isolated conditions”, the lifetimes and fluorescence quantum fields can be obtained by means of photoelectron‐photon coincidence measurements. These data yield the radiative and non‐radiative rate constants as a function of the internal energy of the cations. The structural and decay information obtained from each of these techniques is illustrated using the 1,3‐pentadiyne radical cation as example.
Specific Separation of Products in Supported Oligonucleotide Syntheses Using the Triester Method
Authors: Seliger Hartmut , Görtz Hans‐Helmut
Published: December 2003

The mixture of homologous nucleotide fragments usually formed during carrier‐oligonucleotide synthesis can be separated chromatographically so as to isolate the desired fragment, if the latter is protected at the 5′‐end with a hexadecyloxytrityl group (see (2) in the previous communication).
The (η5‐CH3C5H4)Mn(CO)2 Moiety as Protecting Group in the Monohalogenation of Diphenylsilane
Authors: Schubert Ulrich , Wörle Barbara , Jandik Peter
Published: December 2003

Gram amounts of halosilanes Ph2Si(H)X, free of Si‐containing side products, have been prepared by a protecting‐group synthesis. In the initiating photochemical reaction only one SiH bond is cleaved (R = η5‐CH3C5H4).
equation image
High Pressure Michael Addition Catalyzed by Fluoride Ions
Authors: Matsumoto Kiyoshi
Published: December 2003

The synthesis of compounds having quaternary C atoms by Michael addition is often unsuccessful if the donor reaction center has bulky substituents. However, under high pressure conditions and fluoride catalysis even e.g. chalcone reacts with diethyl isopropylmalonate and diethyl phenylmalonate in 20 and 24% yield, respectively.
Photometry with Laser Diodes: Determination of D2O and Compounds with OH Groups
Authors: Wenzel Martin
Published: December 2003

The quantitative determination of compounds having an OH‐ or an NH‐group can be performed using a straightforward photometric procedure. The D2O content of H2O and of native serum, as well as of urine, can be measured by spectroscopy in the near IR region (1350 nm) using a laser‐diode as light source.
Synthesis of Hydrido(phenyl)osmium(II)‐ from Benzeneosmium(0)‐Complexes: Intramolecular Insertion of a Lewis Basic Metal Atom into an sp2‐CH Bond[1]
Authors: Werner Rainer , Werner Helmut
Published: December 2003

The intramolecular insertion of osmium(0) into a CH bond of complexed benzene proceeds via formation of the C6H5OsIIH partial structure. This result can be considered as a step on the route to a metal‐catalyzed synthesis of e.g. benzoic acid from benzene and CO2. The reaction (1)→(2) was also performed with (1), using propene instead of ethene.
equation image
Electro‐Enzymatic and Electro‐Microbial Stereospecific Reductions
Authors: Simon Helmut , Günther Helmut , Bader Johann , Tischer Wilhelm
Published: December 2003

The hydrogenation of prochiral α,β‐unsaturated carboxylates and aldehydes to chiral compounds can be accomplished electrochemically, both with isolated enoate reductase as well as with whole bacteria cells which contain this enzyme; methylviologen functions as electron‐transfer agent. Since NAD+ can also be reduced to NADH, in principle all substrates of NAD‐dependent enzymes can be stereospecifically hydrogenated with this method.
Bis(thimethylgermyl)magnesium, the First Organogermylmagnesium Compound Isolated
Authors: Rösch Lutz
Published: December 2003

The title compound (1) could be prepared for the first time by reaction of (Me3Ge)2Hg with Mg in dimethoxyethane, thus proving that compounds of this type are capable of existing. (1) forms colorless crystals which melt at 90 °C.
equation image
Anodic and Cathodic CC‐Bond Formation
Authors: Schäfer Hans J.
Published: December 2003

Electrolysis allows the reactivity of a substrate to be changed, or its polarity to be reversed (“redox umpolung”). The carbon skeleton and the functional groups of a synthetic building block can thus be utilized more economically, and at the same time the number of reaction steps in multistage syntheses can be reduced. The tools necessary for an electrolytic process are a cell, a power source, electrodes, and an electrolyte, the latter being chosen in accordance with the reduction or oxidation potential of the substrate. A series of electroanalytical methods provides information on the electrode reaction mechanisms. At the anode, arenes, phenolic ethers, and electron‐rich olefins dimerize via intermediate radical cations. In the Kolbe electrolysis, carboxylic acid anions decarboxylate to form radicals which can couple to forme.g.long chain alkene derivatives having pheromone activity, or add to ole‐fins. At the cathode, activated olefins hydrodimerize via radical anions or, in the presence of appropriate reagents, can be acylated, alkylated, and carboxylated. Pinacols, crossed hydrodimers, and cyclic and arylated compounds are accessible via the cathodically produced radicals, while the formation of strained small rings or the reductive addition of halides to carbonyl compounds takes place through intermediate carbanions.
Initial Steps in the Degradation of Chlorobenzene Derivatives by Pseudomonas putida
Authors: Ballschmiter Karlheinz , Scholz Charlotte
Published: December 2003

For the first step of the bacterial transformation of chlorobenzene derivatives there are two possibilities: (1) formation of a dioxetane by a dioxygenase attack, (2) formation of an oxirane by a monooxygenase attack. Evidence for a monooxygenase attack is the conversion of 1,2‐dichlorobenzene into 2,3‐, 3,4‐ and 2,6‐dichlorophenol, as is also the formation of 2,4,6‐trichlorophenol from 1,3,5‐trichlorobenzene.
Decomposition of the Yellow Form of Thiamine
Authors: Hopmann Rudolf F. W. , Brugnoni Gian Pietro
Published: December 2003

A novel mechanism is proposed for the alkali‐induced transformation of thiamine; it is based on the results of kinetic investigations. The time‐dependent UV spectra of alkaline thiamine solutions, whose yellow color rapidly disappears, reveal isosbestic points, thus indicating that no intermediate is formed in significant amounts.