Angewandte Chemie International Edition in English

Cover image for Vol. 30 Issue 11

November 1991

Volume 30, Issue 11

Pages 1387–1530

Currently known as: Angewandte Chemie International Edition

    1. Cover Picture (Angew. Chem. Int. Ed. Engl. 11/1991)

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199113871

      Thumbnail image of graphical abstract

      The cover picture shows a supramolecular compound composed of a boroncontaining crown ether as the host and two guests, benzylamine and methanol. This graphic representation based on the data from an X-ray structure was generated by the Insight-II program. To illustrate the host–guest relationship better the two guests are represented as ball-and-stick models with their van der Waals surfaces depicted as violet nets (boron, green; oxygen, red; carbon, white; hydrogen, blue). The coordination of nucleophilic and electrophilic centers in one host molecule make it feasible to simultaneously bind guests of different reactivities, for example a substrate and a reagent. The realization of an important goal in supramolecular chemistry, the imitation of biocatalysts using much simpler chemistry, is now closer. Further details are reported by M. Reetz et al. on p. 1412 and 1474. The current boom in supramolecular chemistry is also documented in the review by S. Schneider (p. 1417) as well as in a number of communications including those from H. Reuter (p. 1482), Y. Kobuke et al. (p. 1496), F. Hawthorne et al. (p. 1507), and A. F. Williams et al. (p. 1490) in this issue.

    2. Graphical Abstract (Angew. Chem. Int. Ed. Engl. 11/1991)

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199113872

  1. Reviews

    1. Top of page
    2. Reviews
    3. Highlights
    4. Communications
    5. Book Reviews
    1. Chemistry and Biology of the Enediyne Anticancer Antibiotics (pages 1387–1416)

      Prof. Dr. K. C. Nicolaou and Dr. W.-M. Dai

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199113873

      Hardly four years old and yet far enough advanced for a fascinating review is the area of enediyne anticancer antibiotics. The unique molecular structure and impressive biological effects of these compounds have started a broad movement, inspiring new research in computer-supported chemistry, molecular design, the chemistry of DNA, and medicine. This review article focuses on the syntheses and the chemical and biological properties of model systems based on the natural enediyne antibiotics neocarzinostatin chromophore, the calicheamicins, esperamicins, and dynemicins.

    2. Mechanisms of Molecular Recognition : Investigations of Organic Host–Guest Complexes (pages 1417–1436)

      Prof. Dr. Hans-Jörg Schneider

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199114171

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      The quantification of noncovalent interactions is of central importance for the understanding of the phenomenon of molecular recognition. Binding studies of synthetic host–guest complexes with systematic analyses based on additive binding increments are especially useful when electrostatic interactions predominate, as in the complexation of naphthalene derivatives with the macrocyclic host 1. A surprisingly uniform value of 5 kJ mol−1 per ion-pair interaction is obtained.

    3. Protease-Catalyzed Kinetically Controlled Peptide Synthesis (pages 1437–1449)

      Dr. Volker Schellenberger and Prof. Dr. Hans-Dieter Jakubke

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199114371

      Mild reaction conditions and products with high enantiopurity are among the advantages of enzyme-catalyzed reactions. The enzyme-catalyzed, kinetically controlled linkage of peptide segments does not suffer unfavorable conformational effects since blocking of functional groups in the side chains is not necessary. Surprisingly, the course of the reaction can be described by just a few kinetic parameters, which provide information useful in the optimization of the peptide yield.

  2. Highlights

    1. Top of page
    2. Reviews
    3. Highlights
    4. Communications
    5. Book Reviews
    1. Helices, Supramolecular Chemistry, and Metal-directed Self-Assembly (pages 1450–1451)

      Dr. Edwin C. Constable

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199114501

      Their synthetic applications and potential as models, as well as simple aesthetic pleasure, are the main reasons for interest in helical compounds. The preparation of several double-helical molecules made up of complexed metal ions was previously reported. Now a triple-helical molecule, in which two metal ions with a preference for octahedral coordination are complexed with three bis-(bidentate) ligands, has been synthesized by Williams et al. The geometry dictated by the ligands in this triple helix keep the two metal atoms 8 Å apart (see also p. 1490).

    2. Erythromycin Synthesis—A Never-ending Story? (pages 1452–1454)

      Prof. Johann Mulzer

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199114521

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      The most extensive single project in the history of organic chemistry—the total synthesis of erythromycin A and B—has received new impetus from biosynthetic studies (see related Highlight in the last edition) as well as from a new approach for the final steps of the chemical synthesis. The sequence of first lactonization, then glycosidation has been assumed incontestable; however, the reversed order of reactions recently led to considerable success. The story continues…

  3. Communications

    1. Top of page
    2. Reviews
    3. Highlights
    4. Communications
    5. Book Reviews
    1. [3-Bromo-2-lithio-1-phenylsulfonylbenzofuran Diisopropyl Ether]2 and 3-Fluoro-2-lithio-1-phenyl-sulfonylbenzene · Pentamethyldiethylenetriamine : Crystal Structures of Compounds with Lithium and Halogen on Neighboring Carbon Atoms (pages 1455–1457)

      Ferdinand Bosold, Dipl.-Chem. Peter Zulauf, Michael Marsch, Dr. Klaus Harms, Dipl.-Chem. John Lohrenz and Prof. Dr. Gernot Boche

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199114551

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      The crystal structures and reactivities in solution correlate for the title compounds. The β-elimination of lithium and halide to the corresponding (hetero)aryne does not occur in the case of bromobenzofuran 1, in which the C[BOND]Br bond length is that same as in its nonlithiated counterpart; LiF elimination does occur in compound 2, whose C[BOND]F bond is lengthened in comparison to the neutral fluoroarene. This implies that the elimination is structurally predetermined. PMDETA = N, N, N′, N″, N″-pentamethyldiethylenetriamine.

    2. Extension of Free Energy Correlations to Gas-Phase Ionic Reactions. Competitive Alkylation of Substituted Benzonitriles by (CH3)2Cl+ Ions (pages 1457–1459)

      Dr. Marina Attinà, Prof. Dr. Fulvio Cacace and Dr. Andreina Ricci

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199114571

      Hammett equations are now possible for ionic reactions in the gas phase. The combination of mass spectrometry and high pressure radiolysis techniques make it possible to set up a linear free energy relationship for reaction (a), which is analogous to the Hammett system. The value of the reaction constant ρ, -1.9, verifies that the C(CH3)2Cl+ ion is a typical though rather indiscriminant electrophile. Because investigations of ion–molecule reactions in the gas phase suffer no disruptive solvent effects, a direct correlation with theoretical findings is possible:

      • equation image
    3. Observation of a Direct Sn[BOND]Li Bond; The Crystal and Molecular Structure of Monomeric [Ph3SnLi · PMDETA] and the Detection of 119, 117Sn[BOND]7Li NMR Coupling in Solution (pages 1459–1460)

      Dr. David Reed, Dr. Dietmar Stalke and Dr. Dominic S. Wright

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199114591

      Thumbnail image of graphical abstract

      The metalation of Ph3SnH with nBuLi in the presence of the tridentate amine ligand N, N, N′, N″, N″-pentamethyldiethylenetriamine (PMDETA) provides the title compound. Crystal structure analysis shows this to be monomeric in the solid state and to contain a direct Sn[BOND]Li bond. This structure is preserved in solution, as demonstrated in low-temperature 7Li NMR studies.

    4. Investigation of the Light-Induced Charge Transfer between Covalently Linked Porphyrin and Quinone Units by Time-Resolved EPR Spectroscopy (pages 1461–1463)

      Dr. Friedhelm Lendzian, Dipl.-Phys. Jenny Schlüpmann, Dipl.-Chem. Jörg von Gersdorff, Prof. Dr. Klaus Möbius and Prof. Dr. Harry Kurreck

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199114611

      Thumbnail image of graphical abstract

      Time-resolved EPR spectroscopy was used to follow the primary triplet electron-transfer reaction of model compound 1 and its trans isomer in the 100 ns to several 10 μs range. This method allows not only the unequivocal identification of transient radical pairs but also the systematic study of their interactions, which govern the recombination dynamics in photosynthesis.

    5. Unique Reactivity of Heterodinuclear Pentacarbonyl(fulvalene)molybdenumruthenium with Alkynes: Fluxionality, Rearrangements, Structures, and First Reversible Conversion of a “Side-on”- to a Semi-Bridging Alkenylidene Ligand (pages 1463–1465)

      Prof. Dr. Roland Boese, Dr. Mark A. Huffman and Prof. Dr. K. Peter C. Vollhardt

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199114631

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      Acting as as two- and four-electron donors alkynes react with the heteronuclear fulvalene complex 1. Terminally bound alkyne ligands rearrange to alkenylidene ligands; in the course of the reaction an equilibrium between the side-on and semibridging coordination (2⇆3) can be observed. (2: R1 = C6H5, R2 = H).

    6. 1,2-Asymmetric Induction in the Ketene Claisen Rearrangement of Allyl Sulfides (pages 1465–1467)

      Dr. Udo Nubbemeyer, Dr. Reinhold Öhrlein, Dr. Jozef Gonda, Dr. Beat Ernst and Prof. Dr. Daniel Belluš

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199114651

      Thumbnail image of graphical abstract

      Optically active α-siloxycarbonates are converted to optically active allylsulfides 1. These intermediates are allowed to react with dichloroketene (generated in situ) leading to optically active α,α-dichloro-β-vinyl-γ-siloxy-substituted thioesters 2. The assumed transition state is represented by 3. This ketene-Claissen rearrangement shows complete 1,2-asymmetric induction in all of the cases examined. Reductive dechlorination of the γ-siloxy-substituted thioesters provides optically active 3,4-cis-distubstituted γ-lactones. R = Me, iPr, C2H4OTBDMS; TBDMS = tert-butyldimethylsilyl.

    7. Directed Synthesis of Peptides from α-Amino Acid Esters at Metal Centers (pages 1467–1469)

      Prof. Dr. Wolfgang Beck and Dipl.-Chem. Roland Krämer

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199114671

      Thumbnail image of graphical abstract

      Peptide esters coordinated in a chelate fashion as in 1 (M = Rh, R = Me) may be extended on the amino ends by reaction with α-amino acid esters in the presence of base. In the case of L-leucine methyl ester the resulting tripeptide ester can be cleaved from the metal center with virtually no racemization. The organometallic reagent [{(C5Me5)RhCl2}2] can be recovered.

    8. Synthesis of Ethenyl(phenyl)iodonium Triflate, [H2C[DOUBLE BOND]CHIPh][OSO2CF3], and Its Application as a Parent Vinyl Cation Equivalent (pages 1469–1470)

      Prof. Dr. Peter Stang and Dr. Jörg Ullmann

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199114691

      Thumbnail image of graphical abstract

      As a reactive, strongly electrophilic vinylating agent the title compound complements the known nucleophilic vinylation reagents. It reacts with catalytic amounts of silver triflate to give the parent vinyl triflate 1 and undergoes oxidative addition reactions with organometallic compounds. Reaction with Vaska's complex, for example, furnishes 2.

    9. Fischer Carbene Complexes Facilitate the Intramolecular Pauson-Khand Reaction (pages 1470–1472)

      Prof. Dr. Francisco Camps, Dr. Josep M. Moretó, Dr. Susagna Ricart and Dr. Josep M. Viñas

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199114701

      Thumbnail image of graphical abstract

      One of the most efficient organometallic reactions in organic synthesis, the Pauson–Khand reaction is accelerated by the incorporation of the olefin and alkyne reaction partners in a Fischer carbene complex. The bicyclic cyclopentenone derivatives 2, obtained from 1 after a few hours reaction at roomtemperature, are highly functionalized and lend themselves to further reactions.

    10. Crown Ethers with a Lewis Acidic Center: A New Class of Heterotopic Host Molecules (pages 1472–1474)

      Prof. Dr. Manfred T. Reetz, Dipl.-Chem. Christof M. Niemeyer and Dr. Klaus Harms

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199114721

      Thumbnail image of graphical abstract

      The incorporation of a Lewis acid center in a crown ether as in 1 leads to a host molecule, which may either complex a cation leaving the counter ion “outside” (monotopicity) or bind both cation and anion simultaneously, the latter with ate complexation (di- or heterotopicity). Host 1 displays a selectivity never seen before in the complexation of series of potassium salts KX (X = F, Cl, Br, I, SCN, CN, OCH3).

    11. Heterotopic Host Molecules for Binding Two Different Guests (pages 1474–1476)

      Prof. Dr. Manfred T. Reetz, Dipl.-Chem. Christof M. Niemeyer and Dr. Klaus Harms

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199114741

      Thumbnail image of graphical abstract

      Host molecules with boron-containing acceptor and crown ether donor positions like compound 1, depicted for the preceding communication, can selectively bind alcohols and amines. The Lewis acidic boron center engages with the Brønsted properties of the alcohol/amine system so that the alkoxy ion is bound to boron and the ammonium ion to the crown ether unit. This is shown schematically in the equation below. The structure of the host/guest1/guest2 is highly unusual.

    12. Naphtho[2,3-d] [1,2,3]oxadiazole (pages 1476–1477)

      Dipl.-Chem. Achim Blocher and Prof. Dr. Klaus-Peter Zeller

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199114761

      Thumbnail image of graphical abstract

      Not the o-quinone diazide 1 but the title molecule 3 results from the deprotonation of diazonium salt 2. Compound 3 is the first preparatively realized example of a 1,2,3-oxadiazole. The high likelihood of the formation of 3 is probably due to the destabilization of the o-quinone and o-quinone bismethide structures in 1, which are passed over in favor of the lower energy naphthalene unit in the transformation to 3.

    13. [{Fe(μ-‘S4’)}2(μ-S2)]: A Model Complex for [Fe[BOND]S] Enzymes with a New Type of [2 Fe[BOND]2S] Center (pages 1477–1479)

      Prof. Dr. Dieter Sellmann, Dipl.-Chem. Günter Mahr and Dr. Falk Knoch

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199114771

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      How are the [Fe–S] centers in redox enzymes constructed in systems not containing the well-known structural element of ferredoxin? Title compound 1, which assembles spontaneously from Fe2+ ions, 2,2-(ethylenedithio)-dibenzothiolate, and sulfur can certainly provide information. The magnetic properties and Fe… Fe distance of H clusters of hydrogenases in the reduced form of the protein agree exactly with those of 1, but not with those of the known [Fe–S] clusters in the ferredoxins. ∩ = C6H4.

    14. The First Persistent β-Silyl-Substituted Vinyl Cation (pages 1479–1482)

      Priv.-Doz. Dr. Hans- Ullrich Siehl, Dipl.-Chem. Frank-Peter Kaufmann, Prof. Dr. Yitzhak Apeloig, Viviana Braude, David Danovich, Prof. Dr. Armin Berndt and Nikolaos Stamatis

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199114791

      Thumbnail image of graphical abstract

      Stabilized by four β-silyl groups through hyperconjugation, 1 is the first vinyl cation without π conjugation to be detected by NMR. The 13C NMR spectrum of 1 at 130o shows separate signals for the two silyl groups on the methine C atom. Ab initio MO calculations on model systems showed that hyperconjugation controls this hindered rotation, resulting in a preference for a conformation with distortion.

    15. Inclusion of Metal Ions within a Tin—Oxygen Cage Stabilized by Organic Residues: Crystal Structure of [(iPrSn)12O4(OH)24][Ag7I11] · NaCl · H2O · 10DMSO (pages 1482–1484)

      Dr. Hans Reuter

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199114821

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      Around a sodium atom template the spherically shaped shell of the dodecameric organotin–oxygen cation of the title compound assembles. (See polyhedral representation, right; the black dots symbolize isopropyl groups.) The [Ag7I11] anion of this novel inorganic host–guest complex is also quite remarkable. It is a one-dimensional, twisted double band of face-sharing iodine tetrahedrons, leading one to expect a high silver-ion conductivity.

    16. Ring Inversion in Sterically Hindered Arenes (pages 1484–1485)

      Prof. Dr. Günther Maier, Dipl.-Chem. Frank Fleischer, Dr. Hans-Otto Kalinowski and Priv.-Doz. Dr. Roland Boese

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199114841

      Thumbnail image of graphical abstract

      Nonplanar and as a result chiral is the extremely sterically encumbered pyridazine 1. This causes the methyl groups of the isopropyl substituents to be diastereotopic and to give rise to separate NMR signals at room temperature. At higher temperatures these signals coalesce because of rapid inversion of the deformed aromatic ring. The activation barrier for this operation is estimated at 91.5 kJ mol−1.

      = tert-butyl.

    17. [FCNF]+[AsF6], a Salt of the Linear 22-Valence Electron Cation [FCNF]+ (pages 1485–1486)

      Dipl.-Chem. Inis C. Tornieporth-Oetting, Dr. Petra Gowik and Priv.-Doz. Dr. Thomas M. Klapötke

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199114851

      Fluorination of the [HCNH]+ ion of 1 in hydrogen fluoride produces the 30-electron cation [FCNF]+ of 2. According to 19F NMR and vibrational spectra this ion has a linear structure, which is in agreement with the predictions made by ab initio calculations.

      • equation image
    18. A Metal-Ion- and Cofactor-independent Enzymatic Redox Reaction: Halogenation by Bacterial Nonheme Haloperoxidases (pages 1487–1488)

      Dipl.-Chem. Theodor Haag, Prof. Dr. Franz Lingens and Priv.-Doz. Dr. Karl-Heinz van Pée

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199114871

      Although the chemistry of the halogens is very well known, we know relatively little about biochemical halogenations. The mode of action of a bacterial non-heme haloperoxidase is explained here for the first time. These enzymes catalyze the oxidation of halide ions (chloride, bromide, iodide) with hydrogen peroxide without the participation of the metal ions of cofactors in the electron transfer. The redox reaction in these enzymes takes place on a methionine residue of the protein chain by the reaction cycle methionine [RIGHTWARDS ARROW] methionine sulfoxide [RIGHTWARDS ARROW] halogenated methionine [RIGHTWARDS ARROW] methionine.

    19. Direct Observation of the Central Atom in [C{Au[C6H5)2(pC6H4Nme2)]}6](BF4)2 by 13C NMR Spectroscopy (pages 1488–1490)

      Prof. Dr. Hubert Schmidbaur, Dipl.-Chem. Benno Brachthäuser and Dipl.-Chem. Oliver Steigelmann

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199114881

      The synthesis of the title compound in which the interstitial C atoms are mainly 13C isotopes makes the proof of these octahedral hypercoordinated atoms possible. The septet multiplicity and the coupling constants confirm the postulated surroundings and agree with the expectations regarding bonding. The chemical shift δ (13C) = 137.27 is more difficult to understand. Relativistic effects must be taken into account in the crucial theoretical calculations.

    20. A Self-Assembling Triple-Helical Comath image Complex : Synthesis and Structure (pages 1490–1492)

      Dr. Alan F. Williams, Dr. Claude Piguet and Dr. Gérald Bernardinelli

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199114901

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      Not a simple tetradentate, but rather a bis(bidentate) coordination is revealed for L (L = bis[1-methyl-2(6-methyl-2-pyridyl)benzoimidizol-5-yl]methane) and is attributed to the inflexibility of its aromatic rings. In its reaction with cobalt(II) perchlorate an orange salt is produced, in which the three ligands wind about the Co–Co axis in a helical fashion. Both Co atoms have an octahedral coordination geometry, in which the octahedron is flattened along the C3axis. The Co2 complex is represented schematically on the right (black, Co; white, coordinated N atoms of L).

    21. Synthesis, Absolute Configuration and Specific Rotation of (+)- and (−)-Modhephene (pages 1492–1494)

      Prof. Dr. Lutz Fitjer, Dipl.-Chem. Honorato Monzó Oltra and Dr. Mathias Noltemeyer

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199114921

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      Although twelve diastereoselective syntheses of(±)-modhephene have been published, only one enantioselective approach has been reported, in which (—)-modhephene was assigned a (1R,5S,8R) configuration on the basis of comparable optical rotations. The divergent rotational value measured for a sample taken from Otanthus maritimus was ignored because reliable purity criteria were lacking. This communication proves that all the earlier results with the exception of the absolute configuration must be corrected.

    22. Synthetic Siderophores of the Tetrazolylenol Type : Iron(III) Complexes and Three-Dimensional Iron(II) Coordination Polymers (pages 1494–1496)

      Prof. Dr. Rolf W. Saalfrank, Dipl.-Chem. Claus-Jürgen Lurz, Dipl.-Chem. Klaus Schobert, Oliver Struck, Dr. Eckhard Bill and Prof. Dr. Alfred X. Trautwein

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199114941

      Thumbnail image of graphical abstract

      One electron decides whether the coordination of tetrazolenol ligands (HL) with Fe ions leads to the mononuclear complex [FeL3] (FeIII) or the three-dimensional coordination polymer [(FeL2)n] 1 (FeII). A representationof 1 is shown (right) along with its “monomer”. The linkage occurs by coordination of the CN groups. The crucial test supporting a polymeric structure for 1 was provided by Mössbauer spectroscopy. At 1.6 K a weak antiferromagnetic ordering arises, which can be attributed to cooperative spin-spin exchange processes. R = Me3CCH2.

    23. Metal-Assisted Organization rather than Preorganization for the Design of Macrocyclic Hosts (pages 1496–1498)

      Prof. Dr. Yoshiaki Kobuke, Yasutaka Sumida, Minoru Hayashi and Prof. Dr. Hisanobu Ogoshi

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199114961

      Thumbnail image of graphical abstract

      Boric acid initiates the formation of coronand 1 from 2, providing the framework necessary for the strong complexation of alkali metal ions. This approach to the synthesis of the macrocyclic host allows a greater flexibility than the standard preorganization method. A bicyclic coronand is also obtained by this strategy. M = K, Na.

    24. Antiperovskite Structure with Ternary Tetrathiafulvalenium Salts: Construction, Distortion, and Antiferromagnetic Ordering (pages 1498–1500)

      Dr. Patrick Batail, Dr. Carine Livage, Dr. Stuart S. P. Parkin, Dr. Claude Coulon, Dr. James D. Martin and Dr. Enric Canadell

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199114981

      Thumbnail image of graphical abstract

      Rhombohedral distortion caused by the shape of the organic ions is found in the antiperovskite structures of all four ternary salts 1,which were obtained by electrocrystallization of the components tetrathiafulvalene (TTF),tetrabutylammonium halohexamolybdate, and tetrabutylammonium halide. The three-fold symmetry is quite apparent in the structural representation of these salts on the right. These salts show a sharp transition to an antiferromagnetic ground state between 6 and 8 K.

    25. Solvated Electrons in the Synthesis of Ionic Clusters in Zeolites (pages 1501–1502)

      Dr. Paul A. Anderson, Dr. Donald Barr and Prof. Dr. Peter P. Edwards

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199115011

      Larger metal aggregates do not form when the alkali-metal ions in zeolites are reduced to low-valent ion clusters by solvated electrons. Besides the ion cluster Namath image (n = 4–6) and Kmath image (n = 3,4) previously reported, the new cluster Namath image was obtained selectively and reproducibly. The solvated electron were prepared in situ from highly purified Li granules and propyl- or butylamine. One intriguing feature of these ion clusters is the unusual nature of the valence electrons-not bound to one atom but also not completely delocalized as in a metal.

    26. Chemoenzymatic Syntheses of Sialyloligosaccharides with Immobilized Sialidase (pages 1503–1505)

      Prof. Dr. Joachim Thiem and Dipl.-Chem. Bernd Sauerbrei

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199115031

      The α-glycosidic transfer of N-acetylneuraminic acid (Neu5Ac) to the terminally bound galactose of the acceptor molecule is achieved with immobilized sialidase obtained from Vibrio cholerae. This is the first application of this enzyme in the catalysis of transglycosylation, which produces (2–6)- and (2–3)-linked sialyloligosaccharides. These molecules often cannot be prepared by feasible synthetic methods, yet their physiological importance in glycoproteins and -lipids continue to generate interest.

    27. Synthesis and Characterization of a New Binary Deca-Osmium Carbonyl Cluster Anion—An Intermediate in the Formation of Other High-Nuclearity Osmium Carbonyl Clusters; Crystal and Molecular Structure of (Ph4P)2 [Os10 (CO)26] (pages 1505–1506)

      Angelo J. Amoroso, Prof. Brian F. G. Johnson, Prof. Lord Jack Lewis, Dr. Paul R. Raithby and Wing-Tak Wong

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199115051

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      The common precursor 1 to the pyrolysis products of [Os3(CO)10(NCMe)2] (2 and 3) was isolated when the reaction was performed under less extreme conditions. The pyrolysis of 1 itself (counterion Ph4P+) at 300oC gave 2 and 3 in good yield, proving its intermediacy in the reaction. The identification of 1 is a key contribution to the understanding of cluster assembly.

    28. “[12]Mercuracarborand-4”, the First Representative of a New Class of Rigid Macrocyclic Electrophiles: The Chloride Ion Complex of a Charge-Reversed Analogue of [12]Crown-4 (pages 1507–1508)

      Dr. Xiaoguang Yang, Dr. Carolyn B. Knobler and Prof. Dr. M. Frederick Hawthorne

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199115071

      Thumbnail image of graphical abstract

      An exceptionally stable anion complex of 1 is produced in high yield from the reaction of the dilithiated carborane 1,2-C2B10H12 with HgCl2. It appears that the Cl ion acts as a template, because the coordination geometry of the Hg center is strongly distorted. The almost perfectly square-planar coordination geometry of the Cl ion is unprecedented. The anion can be extracted from the complex by Ag+ ions without causing the decomposition of the host, which suggests new possibilities in the molecular recognition of nucleophiles.

    29. Microporous Silica Films (pages 1509–1510)

      Prof. Dr. Wilhelm F. Maier, Dipl.-Chem. Michael Wiedorn and Dipl.-Chem. Herbert O. Schramm

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199115091

      A narrow range of pore radii, pore diameters of 6 ± 2 Å, and a porosity of 14% characterize the silicon dioxide films which can be made by the electron beam evaporation of quartz. Thus they offer an alternative to zeolite films for the separation of liquids and gases, and applications in nonlinear optics and microelectronic sensors.

    30. Crystal Structure of Chlorine Dioxide (pages 1510–1512)

      Dipl.-Chem. Anette Rehr and Prof. Dr. Martin Jansen

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199115101

      Thumbnail image of graphical abstract

      The X-Ray structure analysis of an explosive, low-melting compound is certainly not a trivial undertaking, but it was well worth the effort. Contrary to the general belief that the ClO2 radical is not prone to dimerize, the crystal structure right shows ClO2 as head-to-tail dimers, in which the spins are paired and the intermolecular bonding interactions occur through intramolecular antibonding [RIGHTWARDS ARROW] electrons.

    31. (NH4)2[Re2S16], a Soluble Metal Sulfide with Interesting Electronic Properties and Unusual Reactivity (pages 1512–1514)

      Prof. Dr. Achim Müller, Erich Krickemeyer, Dipl.-Chem. Volker Wittneben, Dr. Hartmut Bögge and Dipl.-Chem. Michael Lemke

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199115121

      Thumbnail image of graphical abstract

      A strong transannular Re[BOND]Re interaction and reactive metal–sulfur bonds characterize the title anion 1 (shown on the right without the two chelating S4-ligands). This surprising result explained by the existence of molecular orbitials arising from Re 5d and S 3p functions of similar energy are not only Re–Re bonding but also markedly delocalized. These findings underline the importance of the role of the metal center, especially in catalytically active metal sulfides.

    32. Switch Peptides: pH-Induced α-Helix to β-Sheet Transitions of Bis-amphiphilic Oligopeptides (pages 1514–1516)

      Prof. Dr. Manfred Mutter, Dr. R. Gassmann, Dipl.-Biochem. U. Buttkus and Dr. K.-H. Altmann

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199115141

      The interconversion of two secondary structure types (α-helix ⇆ β-sheet) induced by external conditions such as pH, temperature, concentration, and solvent could be proved in a new class of amphiphilic peptides (switch peptides) in aqueous solution. The pH-dependent conformational changes were studied by CD spectroscopy. Special attention was given to the investigations of four newly synthesized peptides with similar sequences.

    33. Photolytic Cleavage of DNA by [Pt2(P2O5H2)4]4− (pages 1517–1518)

      William A. Kalsbeck, Neena Grover and Prof. H. Holden Thorp

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199115171

      Only irradiation with visible light is needed for the isomerization of the complex of the tetraanionic [Pt(P2O5H2)4]4− (1) with the super helical form I of ϕX174-DNA to the circular form II [Eq. (a) and (b)]. The reaction takes place without the direct binding of the reagent to the DNA and without the formation of high energy intermediates. Thus application in the imaging of other DNA structures is of interest.

      • equation image
    34. 7,7′-Bi(dispiro[2.0.2.l]heptylidene)—the Perspirocyclopropanated Bicyclopropylidene (pages 1518–1520)

      Dr. Stephan Zöllner, Dipl.-Chem. Herwig Buchholz, Dr. Roland Boese, Prof. Dr. Rolf Gleiter and Prof. Dr. Armin de Meijere

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199115181

      Thumbnail image of graphical abstract

      That intermediate cyclopropyl cations with two α-spirocyclopropane groups can undergo reaction without ring opening has been proven. The reaction of title compound 1 with electrophiles like HBr and Br2 leads to addition to the central double bonds and not to rearrangements. Compound 1 was prepared in three steps from 7-cyclopropylidenedispiro-[2.0.2.l]heptane (2). Compared to other bicyciopropylidenes the target molecule shows an unusually low [RIGHTWARDS ARROW] ionization energy of 8.20 eV.

  4. Book Reviews

    1. Top of page
    2. Reviews
    3. Highlights
    4. Communications
    5. Book Reviews
    1. Book Review: Microbial Polyesters. By Y. Doi (pages 1525–1526)

      Hans Michael Bürger and Hans-Martin Müller

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199115252