Angewandte Chemie International Edition in English

Cover image for Vol. 30 Issue 8

August 1991

Volume 30, Issue 8

Pages 893–1050

Currently known as: Angewandte Chemie International Edition

    1. Cover Picture (Angew. Chem. Int. Ed. Engl. 8/1991)

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199108931

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      The cover picture (center) shows a CPK model of the structure of a hemicarcerand—a global minimum calculated with the MM2 force field (with the phenylethyl groups omitted). Quite astounding transformations have been carried out in its cavity. Reactions that occur within the host are gold-colored and the one that occurs outside is blue. The golden orb in the middle shows the locations of the guests within the hemicarcerand and highlights the small portal through which the guests enter and exit the interior of the host. “Incarcerated” cyclobutadiene is stable at room temperature and above in the absence of oxygen, but reacts with oxygen that enters the “container” to give incarcerated maleinaldehyde. This new type of chemistry promises to open a whole new field involving the study of electronically and sterically unperturbed reactive species. Further details are reported by D. J. Cram et al. on p. 1024.

  1. Reviews

    1. Top of page
    2. Reviews
    3. Highlights
    4. Communications
    5. Book Reviews
    1. The Isocyanide–Cyanide Rearrangement; Mechanism and Preparative Applications (pages 893–901)

      Prof. Dr. Christoph Rüchardt, Dr. Michael Meier, Dr. Klaus Haaf, Dr. Joachim Pakusch, Dipl.-Chem. Erwin K. A. Wolber and Dipl.-Chem. Barbara Müller

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199108933

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      Optically active cyanides (1), which are synthetically useful building blocks, may be obtained from naturally occurring α-amino acids (2) in overall yields of up to 60% and with ee values of > 98%. The key feature of the approach discussed here is the isocyanide rearrangement of 3, induced by flash photolysis. Thus this rearrangement, which has long been investigated primarily in terms of mechanism, now constitutes one step in a preparatively useful procedure.

    2. Strained-Ring and Double-Bond Systems Consisting of the Group 14 Elements Si, Ge, and Sn (pages 902–930)

      Dr. Takeshi Tsumuraya, Dr. Scott A. Batcheller and Prof. Dr. Satoru Masamune

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199109021

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      Does the diverse chemistry of carbon have a counterpart in the chemistry of its homologues silicon, germanium, and tin? Without a doubt. Just consider compounds like 1–3 and the kinetic stabilization of reactive double-bond systems and three-membered rings. Despite the synthesis of such compounds, long considered impossible, further challenges remain, namely, systems containing Si, Ge, and Sn tetrahedra or triple bonds. R = 2,6-Et2C6H3, R′ = tBu, R″ = CH(SiMe3)2.

    3. The Biochemical Reactions of Organometallics with Enzymes and Proteins (pages 931–941)

      Prof. Dr. Alexander D. Ryabov

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199109311

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      Organometallic compounds as diverse as ferrocene derivatives and organomercury compounds can be transformed by enzymes. For example, bacterial enzymes catalyze the detoxification of mercury compounds and microbial enzymes are capable of hydroxylating 1 to give hydroxyketone 2.

    4. Lise Meitner and Fission: Fallout from the Discovery (pages 942–953)

      Dr. Ruth Lewin Sime

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199109421

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      A stimulating lecture on Lise Meitner at the International Congress for the History of Science in Munich in 1989 has reawakened much interest in this great German scientist. In fact, Lise Meitner is the first woman to be honored with a bust in the Ehrensaal of the Deutsches Museum. The bust (shown on the right), sculptured by Chrysille Schmitthenner, was unveiled at a ceremony on July 4, 1991 and now stands among those of 39 men. The lecture by Ruth Sime, the motivating force behind this development, is printed here in an expanded version.

  2. Highlights

    1. Top of page
    2. Reviews
    3. Highlights
    4. Communications
    5. Book Reviews
    1. Toward the Understanding of Immunosuppression (pages 954–955)

      Prof. Dr. Horst Kessler, Dr. Dale F. Mierke, Dr. David Donald and Dr. Mark Furber

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199109541

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      Cyclosporin, FK506, and rapamycin exhibit astounding immunosuppressive effects. The first of these is a cyclic undecapeptide, the second a peptide macrolide. In the cytosol they bind to proteins that exhibit rotamase activity. Presumably, therefore, these immunosuppressives inhibit the ubiquitous rotamases. Much information has been obtained recently on the structures of FK506 and its complex with the FK506 binding protein, and the mechanism of action of these compounds is beginning to emerge.

    2. Energetic and Constitutional Hysteresis in Bistable Molecules (pages 956–958)

      Prof. Dr. Ulrich Kölle

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199109561

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      A macrocycle containing [Ru(NH3)5]S and [Ru(NH3)5]SO functions (shown on the right) was recently employed by Taube and Sano as a bistable system, which, like the key components of digital electronic devices, switches from one state to another when triggered by a signal. On going from RuII to RuIII, Ru[BOND]SO can isomerize to Ru[BOND]OS. Using cyclic voltammetry, Taube and sano were thus able to prepare both the SO and the OS isomer by selective redox triggering, depending on whether they started from the completely oxidized or reduced complex.

    3. Dyes for Visual Distinction between Enantiomers: Crown Ethers as Optical Sensors for Chiral Compounds** (pages 958–960)

      Prof. Dr. Fritz Vögtle and Dr. Peter Knops

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199109581

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      A fascinating idea of modern organic chemistry, the discrimination between enantiomers of an optically active substance by the use of differently colored host–guest complexes, has now been realized by systematically applying what has been learned about supramolecular chemistry. The enantiomers of optically active ammonium salts as guests can be distinguished visually after they are allowed to react with the steroid crown ether host 1 and the host–guest complex is embedded in a cholesteric liquid-crystal matrix.

  3. Communications

    1. Top of page
    2. Reviews
    3. Highlights
    4. Communications
    5. Book Reviews
    1. Polyacetylene in Polyacrylonitrile Matrix: Novel Soluble Matrix Polyacetylenes by Ylide-Nickel Catalysis (pages 961–962)

      Dr. K. Alexander Ostoja Starzewski and Dr. Günter M. Bayer

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199109611

      In its crude form, polyacetylene is black, insoluble, nonprocessible, and unstable. Now, ylide-nickel catalysts have opened up an approach to the preparation of novel polyacetylenes in a stabilizing polyacrylonitrile matrix. These were characterized by IR and UV spectroscopy. The composition of the polymers can be controlled; the degree of polyene conjugation is dependent on the choice of ligand. Even for polyacetylene contents over 50%, the polymers are soluble and easily processed.

    2. Thiadistannirane, 1,2-Dithiadistannetane, and Selenadistannirane: Small Rings with Tin–Tin Bonds (pages 962–964)

      Dr. Annemarie Schäfer, Prof. Dr. Manfred Weidenbruch, Dipl.-Chem. Wolfgang Saak, Prof. Dr. Siegfried Pohl and Prof. Dr. Heinrich Marsmann

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199109621

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      The reaction of sulfur and selenium with the distannene 1 (Ar = 2,4,6-iPr3C6H2) gives the ring systems 2 and 3, respectively, which were obtained together with the respective 1,3-dichalcogenadistannetanes. The thiadistannirane 4, which is not accessible in this way, is smoothly formed by reaction of 1 with methylthiirane.

    3. Light Absorption as well as Crystal and Molecular Structure of N,N-Dimethylindigo : An Example of the Use of Synchrotron Radiation (pages 964–967)

      Dr. Gerhard Miehe, Prof. Dr. Peter Süsse, Prof. Dr. Vladimir Kupcik, Prof. Dr. Ernst Egert, Martin Nieger, Dipl.-Chem. Gerold Kunz, Ralf Gerke, Dr. Burkhard Knieriem, Dr. Matthias Niemeyer and Prof. Dr. Wolfgang Lüttke

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199109641

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      The determination of physically meaningful thermal ellipsoids for hydrogen from X-ray diffraction data was achieved in the X-ray structure analysis of N, N′-dimethylindigo (1) by synchrotron radiation. Owing to the steric interactions of the CH3 groups with the carbonyl O atoms, the molecule is slightly twisted. This explains the bathochromic absorption of 1 in comparison to that of indigo and was also predicted from calculations.

    4. d-Electron Density in Formal d0 Systems from Multiplet Splitting in the Photoelectron Spectrum of Permanganates (pages 967–969)

      Dipl.-Chem. Michael Schmalz, Prof. Dr. Robert Schöllhorn and Prof. Dr. Robert Schlögl

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199109671

      A total of 3.5 electrons are present in the formally empty d orbitals of manganese in MnOmath image. This was found by analysis of the multiplet splitting in the Mn 3 s photoelectron spectrum. The appearance of this splitting is itself a proof that d electrons are present. As a consequence, the charge at the oxygen ions must be substantially less than − 2. These results are of importance for the description of the charge distribution in high-temperature superconductors of the oxometallic type.

    5. The cyclo-P4 Ligand as 12-Electron Donor (pages 969–971)

      Dr. Manfred Scheer, Prof. Dr. Eckhard Herrmann, Doz. Dr. Joachim Sieler and Dipl.-Chem. Matthias Oehme

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199109691

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      White phosphorus and a suitable metal complex fragment are always good for surprises. Reaction of [W(CO)5thf] with P4 in THF affords the complex shown on the right, in which the square-planar P4 ligand serves as a 12-electron donor. The analogous chromium complex is also accessible in this way.

    6. Synthesis and Structure of the Pentaisopropylcyclopentadienyl Radical (pages 971–973)

      Dr. Helmut Sitzmann and Dr. Roland Boese

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199109711

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      The reaction of FeCl2 with C5iPr5Na does not yield a ferrocene derivative but instead the surprisingly stable radical C5iPrmath image. Apparently, the bulky isopropyl substituents interfere with the formation of a sandwich structure. In the crystal, the cyclopentadienyl units are stacked along the crystallographic x axis to give a “metal-free polydecker” (shown on the right).

    7. Synthesis of Sterically Hindered Tellurophenols and the Structure of [Cd(μ-TeC6H2M3)2] (pages 973–975)

      Dr. Manfred Bochmann, Dr. Andrew P. Coleman, Kevin J. Webb, Prof. Michael B. Hursthouse and Dr. Muhammed Mazid

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199109731

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      Useful starting compounds for the synthesis of metal complexes are provided by the thermally sensitive and photosensitive tellurophenols 1 (R = Me, iPr, tBu). For instance, the methyl-substituted compound 1 reacts with [Cd{N(SiMe3)2}2] to give [Cd(TeC6H2Me3)2], whose linear one-dimensional chain structure is due to the spatial bulk of the mesityl groups.

    8. Thermal and Light-Induced Spin Crossover to a Metastable Low-Spin State in [Fe(mtz)6](CF3SO3)2 (pages 975–977)

      Prof. Dr. Philipp Gütlich and Dr. Peter Poganiuch

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199109751

      Irradiation by red light at T ≲ 40 K induces the transition of the stable high-spin state of 1 to a metastable low-spin state, which, at T < 40 K, has a lifetime of days to weeks, The transition occurs via double intersystem crossing, 5T2 [RIGHTWARDS ARROW] 5E [RIGHTWARDS ARROW] 3T1 [RIGHTWARDS ARROW] 1A1. Compound 1 is only the second compound to show this effect.

      • equation image
    9. Rubyrin: A New Hexapyrrolic Expanded Porphyrin (pages 977–980)

      Prof. Jonathan L. Sessler, Takashi Morishima and Dr. Vincent Lynch

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199109771

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      The intense bright red color of the diprotonated derivatives of rubyrin (1), the largest expanded porphyrin to be characterized so far, is the source of the compound's name. A diprotonated alkyl derivative of 1 was synthesized efficiently. The molecule is nearly planar in the crystal—not unexpected for a large porphyrin-like aromatic macrocycle.

    10. The Synthesis and Structure of the Yellow and Green Forms of [Nb(O)Cl3(PMe3)3] and the Orange and Green Forms of [Nb(S)Cl3(PMe3)3]; Examples of Perfectly Matched Bond-Stretch Isomers? (pages 980–982)

      Alan Bashall, Dr. Vernon C. Gibson, Terence P. Kee, Prof. Mary McPartlin, Oliver B. Robinson and Alan Shaw

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199109801

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      Four sevenfold coordinated isostructural and isomorphic NbV complexes were isolated as two pairs of pure bond-stretch isomers (a, long Nb[BOND]E bond; b, short Nb[BOND]E bond). Good characterization by IR spectroscopy and X-ray analysis of this new “material” have added fuel to the heated discussion on bond-stretch isomerism.

    11. trans-[Mo(η2-O,C-PhNCO)(η2-C,N-PhNCO)-(syn-Me8[16]aneS4)]; Novel Discrimination of the C[DOUBLE BOND]O and C[DOUBLE BOND]N Bonds of PhNCO at Stereochemically Different Axial Sites (pages 982–984)

      Prof. Dr. Toshikatsu Yoshida, Tomohiro Adachi, Kenji Kawazu, Akira Yamamoto and Nobuyoshi Sasaki

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199109821

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      Two coordination possibilities for the phenylisocyanate ligand are realized in the thio crown ether complex 1. Crucial are only the stereochemically different environments of the axial positions at the metal center. Such discrimination of the potentially coordinating parts of the polyfunctional phenylisocyanate ligand is also of interest in connection with metal-induced transformations of isocyanates.

    12. Unusual Mode of Addition of 1,2-Alkadienylidene Carbenes to 1,3-Dienes: 1,4 Addition to Rigid and Flexible 1,3-Dienes (pages 984–986)

      Hikaru Sugita, Dr. Kazuhiko Mizuno, Toshiki Mori, Dr. Kakuzo Isagawa and Prof. Dr. Yoshio Otsuji

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199109841

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      Surprisingly large amounts of the 1,4-adducts 5 are formed in the reaction of 3,3-diphenyl-1,2-propadienylidene (2)—generated from 1 under phase-transfer conditions—with the diene 3. Compounds 4 and 5 (overall yield 37%) are formed in a ratio of 78 : 22. The overall yield and product ratio in such reactions are dependent on both the carbene and the diene.

    13. An Imide Radical Anion which Assembles into π-Stacks in Solution (pages 986–987)

      Dr. Jean-François Penneau and Prof. Larry L. Miller

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199109861

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      The radical anion 1⊙⊖ is present as a monomer in dimethylformamide, as a dimer in aqueous dimethylformamide, and as stacks in aqueous NaCl solution according to ESR and UV/VIS spectra. The “π stacks” of 1⊙⊖—actually a trianion—are soluble models for conducting organic charge-transfer compounds. Thin, black, lustrous films of 1⊙⊖ exhibit a conductivity of 0.1 S cm−1.

    14. Enantiomer Separation on Immobilized Chirasil-Metal and Chirasil-Dex by Gas Chromatography and Supercritical Fluid Chromatography (pages 987–989)

      Prof. Dr. Volker Schurig, Dipl.-Chem. Dieter Schmalzing and Dipl.-Chem. Michael Schleimer

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199109871

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      It takes less than half a minute to separate the enantiomers of 2-methyltetrahydrofuran and 2-methyloxetane on the immobilized chiral stationary phase 1. The same column proved suitable for chromatographic enantiomer separation using supercritical CO2, as was shown for 1-phenyl- and 1-(2-naphthyl)ethanol.

    15. Syndiotactic Poly(1-oxo-2-phenyltrimethylene): On the Mode of the Chain Growth under Palladium Catalysis (pages 989–991)

      Dr. Marco Barsacchi, Prof. Dr. Giambattista Consiglio, Lorenzo Medici, Dr. Giorgio Petrucci and Prof. Dr. Ulrich W. Suter

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199109891

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      Selection between the enantiotopic faces of an olefin occurs in the sterically controlled carbonylation of styrene with [Pd(phen)(p-CH3C6H4SO3)2] as catalyst to give the title compound 1. The identification of the polymer end groups and the parallel reactions with other catalytic systems shed light on the mechanism of the reaction.

    16. Oxidation of Alkanes by [Fe(O)OH] in the Gas Phase—the Role of Iron Oxidation State in C[BOND]H Activations (pages 991–993)

      Dipl.-Chem. Detlef Schröder and Prof. Dr. Helmut Schwarz

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199109911

      Under the conditions of Fourier transform ion cyclotron resonance, the FeIV oxide [O[DOUBLE BOND]FeOH] was induced to react with methane, ethane, n-butane, and isobutane. These reactions between mass-selected cations of metal oxides and organic compounds in the gas phase allow control of the stoichiometry and the oxidation states of metal oxides. In order to investigate the reaction mechanisms involved in C[BOND]H activation, these experiments were also carried out with deuterated compounds.

    17. Chemo- and Stereoselective Cobalt-Mediated [2 + 2 + 2]Cycloaddition of Alkynes with Uracil Derivatives. A Novel Synthetic Entry to Modified Nucleosides (pages 993–994)

      Dr. Roland Boese, Dr. Jean Rodriguez and Prof. Dr. K. Peter C. Vollhardt

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199109931

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      The incorporation of the 5,6 double bond of uracil derivatives in the [2 + 2 + 2] cyclization with triple bonds—whether those of alkyne substituents on a heterocycle or those of free alkynes—was accomplished by the proven CpCo route, even though the analogous reaction with other heterocycles had failed earlier. Reaction of 1 with 2 to give 3 reveals interesting possibilities, especially with respect to the synthesis of new active substances (R1 = H, CH3; R2 = CH3; sugar moiety, n = 1–3).

    18. Arsenic Compounds in Organic Synthesis: Pentamethinium Salts from Aminoarsanes and Pyrylium Salts (pages 994–996)

      Dr. Yves Madaule, Myriam Ramarohetra, Dr. Jean-Gérard Wolf, Prof. Dr. Jean-Paul Declercq and Dr. Antoine Dubourg

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199109941

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      Pentamethinium salts such as 1 are formed in high yields in a surprisingly easy way from the correspondingly substituted pyrylium salts and aminoarsanes. This reaction is a striking example of the high synthetic potential of organoarsenic compounds, which so far have been considered rather exotic in preparative organic chemistry.

    19. Effect of Intramolecular Coordination on Tantalum-Alkylidene-Centered Reactions: Synthesis and Structure of a Tantalum-Olefin Adduct and a Tantalum-Zinc-Alkylidene Complex (pages 996–998)

      Hendrikus C. L. Abbenhuis, Nantko Feiken, Henk F. Haarman, Dr. David M. Grove, Dr. Ernst Horn, Huub Kooijman, Dr. Anthony L. Spek and Prof. Dr. Gerard van Koten

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199109961

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      An asymmetrically bridging aryldiamine ligand is the salient structural feature of the binuclear complex 1, formed from the corresponding alkylidenetantalum complex and neopentylzinc chloride with elimination of neopentane. The structural data indicate that the Ta[BOND]C[BOND]Zn bridge lies midway in character between a three-center two-electron bond and a combination of a Ta[BOND]C σ bond and a coordinative C[RIGHTWARDS ARROW]Zn bond.

    20. Coupling of Alkynes with Carbene Ligands to Tungsten-coordinated Cyclopropenes and Their Stereoselective Isomerization to Vinylcarbene Complexes (pages 998–999)

      Prof. Dr. Helmut Fischer, Dr. Josef Hofmann and Dipl.-Chem. Elvira Mauz

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199109981

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      The synthesis of cyclopropene complexes, not by ligand-displacement reactions but rather by coupling a carbene ligand with an alkyne at the metal, was accomplished for the first time for 1, R = H, Me. At temperatures above − 40°C, 1 undergoes stereoselective rearrangement to give the vinylcarbene complex 2.

    21. Ammoniumyl Salt-Induced Diels-Alder Reaction of Ketenes—Control of [2 + 2] vs. [4 + 2] Selectivity (pages 999–1001)

      Dr. Michael Schmittel and Dipl.-Chem. Heinke von Seggern

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199109991

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      The [2 + 4] cycloaddition products 4 are formed from 1 and 2 when the ammoniumyl salt 3 is added as initiator. The reaction is complete in only a few minutes at 0°C. In the absence of 3, compounds 1 and 2 only react at 80°C over two days, leading to [2 + 2] cycloadducts. An acid-catalyzed side reaction also produces cycloheptadienone. R = p-tolyl, p-anisyl.

    22. The Structure of the Trimethylenemethane Dianion and the Question of Y-Aromaticity (pages 1001–1003)

      Alberto Gobbi, Dr. Preston J. MacDougall and Prof. Dr. Gernot Frenking

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199110011

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      Neither delocalization nor “Y-aromaticity” explains the stability of the trimethylenemethane dianion 1, but rather the optimal separation of the lone pairs on the terminal C atoms. This was shown by quantum-chemical calculations, according to which the planar form of 1 (1a) corresponds to a higher-order saddle point, whereas the lower-energy structure 1 b displays strongly pyramidalized CH2 groups and only two of the three lone pairs are situated on the same side of the molecular plane.

    23. Cyclooctatetraenylene Vinylenes (pages 1003–1006)

      Dipl.-Chem. Petra Auchter-Krummel and Prof. Dr. Klaus Müllen

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199110031

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      The replacement of phenylene units by cyclooctatetraenylene units in poly(phenylenevinylene) leads to compounds such as 1 and 2. The realization of this plan requires the synthesis of suitable cyclooctatetraenes as well as separation of the E/Z isomers of the products. The “oligo-COT” compounds may be reduced electrochemically and by alkali metals to polyanions such as 18⊖. The charge density in the COT units thereby increases unsymmetrically. Raising the temperature results, in some cases, in an intramolecular charge shift.

    24. Formation of Doubly Vinyl-Bridged Binuclear Iridium Complexes by C-H Activation (pages 1006–1008)

      Dipl.-Chem. Angelika Nessel, Dipl.-Chem. Oliver Nürnberg, Dr. Justin Wolf and Prof. Dr. Helmut Werner

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199110061

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      A terminal C[BOND]H bond in H2C[DOUBLE BOND]CHtBu can be cleaved with, for example, Na2CO3/EtOH as base in the coordination sphere of an Ir center, leading to [{CH2(C5H4)2}{Ir2(μ-CH[DOUBLE BOND]CHtBu)2}] (1), a complex with an extremely short Ir[BOND]Ir bond. Unusual are the + 2 oxidation state of the two Ir atoms, the bridging through three organic ligands, and the absence of terminal ligands. A similar structure to that of 1, although without CH2 bridges between the Cp rings, is shown on the right.

    25. Titanate-Catalyzed Enantioselective Addition of Dialkylzinc Compounds—Generated in situ from Grignard Reagents in Ether—to Aldehydes (pages 1008–1009)

      Prof. Dr. Dieter Seebach, Dipl.-Chem. Linda Behrendt and Dr. Dorothee Felix

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199110081

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      Since manipulation of alkylzinc compounds is not always safe, it is of great advantage to prepare these from Grignard reagents in situ and then to add them to aldehydes in a one-pot procedure. The resulting secondary alcohols (e.g., 1, R from Grignard reagent) are obtained with high enantiomeric excess (90–98% ee).

    26. A Homogeneous Platinum Catalyst in the Stationary BF3 · H2O Phase for the Hydrogenation of Arenes (pages 1009–1011)

      Dr. István T. Horváth

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199110091

      The advantages of homogeneous and heterogeneous catalytic systems are combined in stationary liquid-phase catalysts such as the system [PtCl2,(CH3CN)2] in BF3 · H2O on clay or silica supports, which is used here for hydrogenation of arenes. The hydrogenation can be performed under relatively mild conditions, the products are separable by simple filtration, and the hydrogenation proceeds selectively, as shown for a 1 : 1 : 1 : 1 mixture of benzene, toluene, o-xylene, and 1,2,4-trimethylbenzene.

    27. Mixed-Anion Aggregates of Metalated Organics : Preparation and Structure of the Mixed-Anion Tetramer (PhOLi · HMPA)33-HMPA · Li)NCS (pages 1011–1013)

      Dr. Paul R. Raithby, Dr. David Reed, Dr. Ronald Snaith and Dr. Dominic S. Wright

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199110111

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      Combination of the ammonium salt method and normal metalation makes it possible to construct in a controlled fashion the inorganic/organic lithium complex 1. BuLi, NH4NCS, phenol, and HMPA (4: 1 : 3 : 4) in toluene afforded the air-sensitive compound 1 in over 60% yield. Compound 1 contains three terminal HMPA ligands and one terminal NCS ligand as well as three μ3-bridging PhO ligands and one μ3-bridging HMPA ligand. The analogous complex containing four PhO ligands and no NCS ligand was also synthesized. The latter is completely inert toward water and air.

    28. Conversion of a Diatropic Bridged Annulene into a Paratropic Species on Metal Complexation (pages 1013–1015)

      Prof. Reginald H. Mitchell and Dr. Pengzu Zhou

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199110131

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      A delocalized 4n π system is present in the macrocyclic annulene unit of the metal complex 1. The existence of a paratropic ring current is revealed unambiguously by the deshielding of the “inner” methyl protons and the shielding of the protons on the benzene part as well as their 1H[BOND]1H coupling constants. Apparently, therefore, the metal complexation results in transformation of an aromatic to an antiaromatic ring system.

    29. Synthesis and Structure of the Potassium Salts of 1,3,2-Diazaboroles (pages 1015–1016)

      Prof. Dr. Günter Schmid, Dipl.-Chem. Jürgen Lehr, Dr. Michael Polk and Dr. Roland Boese

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199110151

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      A rich coordination chemistry is promised by the potassium salts 2 obtained by metalation of the N-silylated 1,3,2-diazaboroles 1. The structure of one of these salts is remarkable. In the crystal, compound 2 with R = C(CH3)3 contains ring-shaped units consisting of 12 diazaborolyl, 18 tert-butoxide, and 6 dimethylsilanediolate anions. For charge balance, 42 (!) potassium ions are enclosed in each of these rings.

    30. A New Economical Process for the Preparation of Silver(I,III) Oxide, AgO (page 1017)

      Dr. Sabine Kielhorn, Dr. Dieter H. Buß, Prof. Dr. Oskar Glemser, Dr. Roland Gerner and Dr. Gerald Jeske

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199110171

      SO2/O2 or SOmath image/O2 are the oxidants used to precipitate AgO from AgNO3 solutions at pH 10.5. The yield of Ago is up to 97%. The overall reaction can be formulated as Equation (a).

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    31. Synthesis and Structure of an Azadistanniridine (pages 1017–1018)

      Dr. Hansjörg Grützmacher and Dr. Hans Pritzkow

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199110172

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      The stannanediyl (stannylene) 1 reacts with mesityl azide in a molar ratio of 2.5 : 1 to give the azadistanniridine 2. Compound 2 readily decomposes to 1 and the stannaneimine 3, which undergoes dimerization or is trapped in a [2 + 3] cycloaddition by mesityl azide (in excess) to give the dihydrostannatetrazole ( R′ = 2,4,6-(CF3)3C6H2).

    32. Recombination of Carbocation–Sulfinate Ion Pairs (pages 1018–1020)

      Prof. Dr. Wolfgang Kirmse and Dipl.-Chem. Ekkehard Herpers

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199110181

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      The “nonsymmetry” of the 2-bornyl cation has been demonstrated in an ion pair for the first time. The local order in the ion pairs 1 and 2 was investigated using chiral, 18O-labeled p-toluenesulfinate. In 2, neither the oxygen atoms of the sulfinate nor C-1 and C-2 are equivalent. These results are of value in understanding the partial retention of configuration in the deamination reactions and HX additions of norbornenes.

    33. Synthesis and Interconversion of New (CH)14 Isomers (pages 1020–1022)

      Dr. Wolf-Dieter Fessner and Maria Rodriguez

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199110201

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      The polycyclic triene 1 is accessible via two efficient routes from the known cyclooctatetraene-p-benzoquinone adduct. The two parallel double bonds in 1 undergo photochemical [2 + 2] cycloaddition to give 2 and thermal [3,3] shift above 80°C to give, regiospecifically, the anti-isomer 3.

    34. 1,2,3-Triphospha-4-silabicyclo[l.1.0]butanes from Activated, Stable Phosphasilenes and White Phosphorus (pages 1022–1024)

      Dr. Matthias Drieß

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199110221

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      The phosphasilenes Is2Si[DOUBLE BOND]PR (Is = 2,4,6-tri-isopropylphenyl, R = SiMe2tBu, SiiFr3) are remarkably thermally stable. At about 60°C, they react with white phosphorus to give the 1,2,3-triphospha-4-silabicyclo[ 1.1.0]butanes 1. Compounds with P3Si framework thus join the known P4, Si4, and P2Si2 heterobicyclobutanes.

    35. The Taming of Cyclobutadiene (pages 1024–1027)

      Prof. Donald J. Cram, Dr. Martin E. Tanner and Dr. Robert Thomas

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199110241

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      The taming of cyclobutadiene was accomplished in the interior of the hemicarcerand 1. Cyclobutadiene is a stable compound with a singlet ground state when it is synthesized in the interior of 1. In order to synthesize the incarcerated cyclobutadiene and to characterize its structure, one bimolecular, three photochemical, and two thermal reactions were carried out in the interior of 1. The authors consider it both realistic and useful to regard the internal phase of carcerands and hemicarcerands as a new state of matter.

    36. 1,4,5,8-Tetrakis(dimethylamino)naphthalene: Synthesis, Structure, “Proton Sponge” and Electron Donor Properties (pages 1028–1030)

      Dipl.-Chem. Thomas Barth, Claus Krieger, Prof. Dr. Franz A. Neugebauer and Prof. Dr. Heinz A. Staab

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199110281

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      The “double proton sponge” 1 undergoes diprotonation by strong acids (pKa(1), = 9.8, pKa(2) = 4.9; dimethyl sulfoxide scale) and is a strong electron donor (Eox = − 0.501 V; Fc/Fc = 0.0 V). X-ray structure analyses show that the pronounced twisting of 1 around the central C(4a)–C(8 a) bond (1 8.8°) is suppressed by the diprotonation and the accompanying formation of two strong N … H … N hydrogen bonds.

    37. Aromatic Systems with Polymethine-like Structures: A Structural Comparison of Bis- and Tris(dimethylamino)phenalenium Ions (pages 1030–1032)

      Prof. Dr. Heinz A. Staab, Dr. Jörg Hofmeister and Claus Krieger

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199110301

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      Very different bonding occurs in the bis- and tris(dimethylamino)phenalenium ions 1–3. Whereas 1 and 2 can be divided into polymethine-like, olefinic, and aromatic substructures on the basis of bond lengths, C3-symmetric bond delocalization is found for 3.

    38. Enediyne Compounds Equipped with Acid-, Base- and Photo-Sensitive Triggering Devices. Chemical Simulation of the Dynemicin A Reaction Cascade (pages 1032–1036)

      Prof. K. C. Nicolaou, Dr. W.-M. Dai, S. V. Wendeborn, Dr. A. L. Smith, Dr. Y. Torisawa, P. Maligres and Dr. C.-K. Hwang

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199110321

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      Even under very mild basic conditions, the NH compound 2 is generated from the enediyne 1. Compound 2 proved too labile to be isolated, but could be trapped with nucleophiles such as PhOH and PhSH, resulting in the formation of the dibenzo compounds 4 (via 3), among other products. Compounds 2—like several other newly synthesized compounds—exhibits DNA-cleaving activity.

    39. Self-Assembling [2]Pseudorotaxanes (pages 1036–1039)

      Dr. Pier Lucio Anelli, Peter R. Ashton, Dr. Neil Spencer, Alexandra M. Z. Slawin, Dr. J. Fraser Stoddart and Dr. David J. Williams

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199110361

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      The complex formed from the tetracationic cyclophane 1 and hydroquinone polyethers such as 2 resembles a string of pearls. It forms spontaneously on combination of the components in solution and is stabilized by multiple π/π stacking interactions between the aromatic rings.

    40. Self-Assembling [3]Catenanes (pages 1039–1042)

      Peter R. Ashton, Christopher L. Brown, Dr. Ewan J. T. Chrystal, Timothy T. Goodnow, Prof. Angel E. Kaifer, Dr. Keith P. Parry, Alexandra M. Z. Slawin, Dr. Neil Spencer, Dr. J. Fraser Stoddart and Dr. David J. Williams

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199110391

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      Two polyether macrocycles are “threaded” when the dication 1 is cyclized with 4,4′-dibromomethylbiphenyl (2) in the presence of these macrocycles. NMR spectroscopy revealed that the polyether macrocycles rotate around the tetracationic macrocycle formed from 1 and 2.

    41. Molecular Trains: The Self-Assembly and Dynamic Properties of Two New Catenaries (pages 1042–1045)

      Peter R. Ashton, Christopher L. Brown, Dr. Ewan J. T. Chrystal, Dr. Keith P. Parry, Dr. Marek Pietraszkiewicz, Dr. Neil Spencer and Dr. J. Fraser Stoddart

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199110421

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      The tetracationic cyclophane (the “train”) travels at high speed around the polyether macrocycle (the “track”) of the [2]catenane 1. The synthesis of the polyether macrocycle in a total yield of > 60% made possible the formation of 1 and of the analogous [3]catenane, in which the two smaller members of the chain are present on diametrically opposite hydroquinone rings according to the 1H NMR spectrum. All that remains to be done is to introduce signals to direct the train.

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