Angewandte Chemie International Edition in English

Cover image for Vol. 26 Issue 11

November 1987

Volume 26, Issue 11

Pages 1059–1200

Currently known as: Angewandte Chemie International Edition

    1. Cover Picture (Angew. Chem. Int. Ed. Engl. 11/1987)

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198710591

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      The stereoprojection on the cover shows the structure of a double-helix strand in solid α-amylose. In the ball-and-stick model in the upper part, C is symbolized by pink spheres, O by orange spheres. However, what is the significance of the curved surface, one side of which is blue, the other side green, in the lower part? This surface represents a non-Euclidian, periodically curved potential surface (of the type Q*). In general, the space in crystalline mateirals is divided up by such surfaces. The structural fragments thereby obtained can be analyzed as increments with respect to their chemical significance. This results in a better understanding of the collective behavior of such substances. Further details on this fundamentally new approach to structural chemistry, whose results are also of special aesthetic appeal, are described by H. G. von Schnering and R. Nesper on P. 1059 ff.

  1. Reviews

    1. Top of page
    2. Reviews
    3. Communications
    4. Book Reviews
    1. How Nature Adapts Chemical Structures to Curved Surfaces (pages 1059–1080)

      Prof. Dr. Hans Georg von Schnering and Dr. Reinhard Nesper

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198710593

      Guided by symmetry in a natural way, periodic potential surfaces divide up the space in solid, crystalline materials. The arrangement of atoms, clusters, and molecules clearly follows the (generally) curved shape of these spatial dividers. The periodic surfaces can, in a certain sense, be viewed as inner surfaces, the knowledge of which provides new insights into the organization of crystalline substances, both inorganic and organic.

    2. Fluorides of Copper, Silver, Gold, and Palladium (pages 1081–1097)

      Priv.-Doz. Dr. Bernd G. Müller

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198710811

      The special properties of both fluorine and the coinage metals are one of the reasons for studying the coinage-metal fluorides. Despite considerable progress, our knowledge of this area of inorganic solid-state chemistry is still inadequate. On the one hand, methods are still required for purifying the compounds obtained; on the other, the growth of single crystals has proved to be extraordinarily difficult. Finally, a deeper understanding of many of the structures is still lacking. A broad field still remains for future research.

    3. Homoatomic d10–d10 Interactions: Their Effects on Structure and Chemical and Physical Properties (pages 1098–1110)

      Prof. Dr. Martin Jansen

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198710981

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      The basis of many fundamental concepts in chemistry is the differentiation between the valence electrons involved in bonding and the practically inactive core electrons. Recent findings have revealed that this oversimplification requires modifications in certain areas. Homoatomic interactions have been demonstrated, for instance, for cations having closed d10 configurations. In compounds of monovalent coinage metals, these cations form clusterlike aggregates corresponding to fragments from the structure of the metal itself. The example below shows the silver substructure of Ag6Si2O7 (I).

    4. Carbosilanes (pages 1111–1132)

      Prof. Dr. Gerhard Fritz

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198711111

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      Alternating silicon and carbon atoms characterize the molecular frameworks of carbosilanes. These kinds of compounds are formed extremely easily. For example, species such as 1, with a tetrasilaadamantane framework, can be isolated from SiMe4 pyrolysates. Directly synthesized carbosilanes have been used to demonstrate that their reactivity depends primarily on the substituents. Carbosilanes have acquired recent interest as the basis of ceramics.

  2. Communications

    1. Top of page
    2. Reviews
    3. Communications
    4. Book Reviews
    1. A Sulfene Umpolung (pages 1133–1134)

      Prof. Dr. Rudolf Allmann, Prof. Dr. Wolfgang Hanefeld, Magda Krestel and Dr. Bernd Spangenberg

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198711331

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      It has now been shown for dichlorosulfene 1 that the reaction products of sulfenes can arise from two dipolar forms. Form 1A is responsible for the typical sulfene reactions, e.g., the formation of a sulfonate from 1, indanetrione, and R3NHCl. Form 1B explains why the salt R3NHCL alone (e.g., R=Et) reacts with 1 to give the trichloromethanesulfinate 2.

    2. Valence Isomerization between 1-Phosphanorcaradienes and 1-Phospha-2H-tropylidenes (2H-Phosphepines) (pages 1134–1141)

      Prof. Dr. Gottfried Märkl, Dipl.-Chem. Hans J. Beckh, Prof. Dr. Manfred L. Ziegler and Dr. Bernd Nuber

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198711341

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      λ3σ3 and λ3σ2 phosphorus can be interconverted in pericyclic reactions. This conclusion is supported by the identity of the products obtained from the reaction of 1 with diazoalkanes. Whereas 2 is the expected phosphanorcaradiene, the formation of 4 can only be explained by 1,3-dipolar cycloaddition of a second molecule of diazoalkane to 3, the valence isomer of 2 (Ph2 [RIGHTWARDS DOUBLE ARROW] H, R; R=H, Me).

    3. Stereoselective Synthesis of β-Amino Alcohols from Optically Active α-Amino Acids (pages 1141–1143)

      Prof. Dr. Manfred T. Reetz, Mark W. Drewes and Alfred Schmitz

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198711411

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      Effective use of the “chiral pool” of natural L-amino acids is achieved by means of the easily accessible derivatives 1. Depending on the reagent, 1 reacts stereoselectively under either chelate or non-chelate control to give 2 or 3, respectively. Three examples for R = Me: the ratio 2 : 3 is 3 : 97 with PhMgBr, 4 : 96 with allylTi(NEt2)3, and 94 : 6 with CH3TiCl3.

    4. High Stereoselectivity in Lewis-Acid-Catalyzed and Uncatalyzed Diels–Alder Reactions of the Fumarate of (S)-Ethyl Lactate (pages 1143–1145)

      Dipl.-Chem. Horst Hartmann, Abdel Fattah Abdel Hady, Karina Sartor, Dr. John Weetman and Prof. Dr. Günter Helmchen

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198711431

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      Enantiomeric diastereomers can be selectively obtained from the fumarate 1 and dienes. For instance, the uncatalyzed Diels-Alder reaction of 1 with cyclopentadiene gives preferentially the diastereomer 2a (2a : 2b = 98 :2); with TiCl4 as catalyst, on the other hand, 2b is the main product (2a : 2b = 5 :95). Analogous results were obtained for less reactive dienes [R*[BOND]OH = (S)-ethyl lactate].

    5. Estimation of the Configurational Stability of Chiral Organometallic Reagents (pages 1145–1146)

      Prof. Dr. Reinhard W. Hoffmann, Dipl.-Chem. Joachim Lanz, Dr. Rainer Metternich, Dipl.-Chem. Gerhard Tarara and Prof. Dr. Dieter Hoppe

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198711451

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      The relative rates of racemization of chiral organometallic reagents can be obtained by reaction of the racemic reagent with a chiral aldehyde–in one experiment, racemic, in the other, enantiomerically pure [Eq. (a)]. The greater the configurational stability of the reagent, the larger the difference in the product ratios for the racemic and the enantiomerically pure aldehyde.

    6. Isovalent and Mixed-Valent Ylide Complexes of Gold: The Synthesis of Trinuclear Compounds Having Double Paddlewheel Structure (pages 1146–1148)

      Prof. Dr. Hubert Schmidbaur, Dipl.-Chem. Christoph Hartmann, Dipl.-Chem. Gabriele Reber and Dr. Gerhard Müller

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198711461

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      The first organo trigold complex, the title compound 1, X = CL, Br, I, is characterized by several unique structural features. In 1, AuIII serves as a spiro atom; its square-planar coordination is expanded to a pseudooctahedral coordination by two flanking Au I centers. Complex 1 is colorless and air-stable.

    7. The Recoil-Free Fraction of the γ Resonance in 197Au Mössbauer Spectroscopy; Findings from Measurements of Polynuclear, Mixed-Valent Ylide Complexes (pages 1148–1150)

      Prof. Dr. Hubert Schmidbaur, Dr. Christoph Hartmann and Prof. Dr. Friedrich E. Wagner

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198711481

      The intensities of lines in 197 Au Mössbauer spectra have so far been very hard to interpret and therefore their use in structure elucidations has not been possible. Owing to the rich variety of new gold compounds in various oxidation states and with different coordination geometries, such an interpretation has now become possible. In addition to the isomeric shift (IS) and the quadrupole coupling (QS), the recoil-free fraction (RFF) has become an important quantity for analyzing the structures of gold compounds.

    8. Conformational Transitions between Enantiomeric 310-Helices (pages 1150–1152)

      Dipl.-Chem. Rolf-Peter Hummel, Prof. Dr. Claudio Toniolo and Prof. Dr. Günther Jung

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198711501

      The 310-helix enantiotopermerization of the decapeptide Z-(Aib)10-OtBu occurs at 1200 interconversions per second at room temperature. This finding, obtained by 13C-DNMR measurements, was derived from the coalescence temperature of 265 K for this 3math image−3math image-helix interconversion, observed here for the first time. The corresponding free energy of activation is only 46 kJ mol −1. Aib is the achiral α-aminoisobutyric acid building block, which is important in drug design.

    9. A Novel Route to Cyclopentane Derivatives: A Radical Chain Reaction (pages 1152–1153)

      Prof. Dr. By Klaus Weinges and Dipl.-Chem. Wolfgang Sipos

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198711521

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      Different reactivity of the double bonds of the starting diene 1 is a precondition for its cyclization in the reaction with Hg(OAc)2 in the presence of CaO and MeOH; reduction with NaBH4 then affords 2. The radical 3 is presumed to be an intermediate in the cyclization. Compound 2 is of interest as a starting material for the synthesis of iridoids as well as for the construction of di- and triquinane frameworks.

    10. [(η5-C5Me5)2 Ti2P6], a Distorted Dimetallaphosphacubane (pages 1153–1155)

      Prof. Dr. Otto J. Scherer, Dipl.-Chem. Herbert Swarowsky, Dr. Gotthelf Wolmershäuser, Priv.-Doz. Dr. Wolfgang Kaim and Dipl.-Chem. Stephan Kohlmann

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198711531

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      Complex 1, obtained as red-brown, air-stable crystals, is formed by cothermolysis of [Cpmath imageTi(CO)2] and P4; its NMR spectra differ significantly from those of the triple-decker complexes [(Cp*M)2(μ,η6−P6)] (M [DOUBLE BOND] Mo, W, V). Complex 1 undergoes ready oxidation and ideal reversible reduction. Instead of a distorted cubane framework, the structure of 1 can be looked upon as a P6 ring in chair conformation with two Cp*Ti “caps.”

    11. Reaction of Snmath image with Single Crystal Au: Textured Fiber Epitaxial Growth of AuSn at Room Temperature (pages 1155–1156)

      Dr. Robert C. Haushalter, Dr. Michael M. J. Treacy and Dr. Stephen B. Rice

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198711551

      Transmission electron spectroscopic investigations of thin layers of AuSn on single-crystal Au foils–prepared by dipping the foils for varying lengths of time into ethylenediamine solutions of K4 Sn9–demonstrated epitaxial growth of AuSn crystallites. It has been known for a long time that Snmath image ions immediately attack gold, but this is the first close characterization of the surface species formed.

    12. Generation of β-, γ-, δ-, ε-, and ζ-Zinc Ketones and Their Transition-Metal-Catalyzed Reactions with Carbon Electrophiles (pages 1157–1158)

      Dr. Yoshinao Tamaru, Dr. Hirofumi Ochiai, Tatsuya Nakamura and Prof. Dr. Zen-ichi Yoshida

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198711571

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      C[BOND]C coupling reactions at practically any distance from the carbonyl group of a ketone are made possible by the very stable zinc ketones 1 (X = alkyl, aryl; n = 2–6), which are formed by insertion of Zn into the C[BOND]I bond of the corresponding iodoketones. The reaction of 1 with electrophiles is exemplified by reaction (a). The yield is 77%.

    13. Anthracyclinone Ring C Synthesis via Chelate Carbene Complexes (pages 1158–1160)

      Prof. Dr. Karl Heinz Dötz and Dr. Michael Popall

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198711581

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      The great potential of organometallic compounds in organic synthesis is demonstrated once again in a new anthracyclinone synthesis. The carbene complex 1 reacts with the alkyne 2 to form the product 3, which contains rings A, C, and D (R1, R2 = OCH2CH2O).

    14. Methyl (E)-2-(1-Aryl-4,5-dihydro-1H-tetrazol-5-ylidene)-2-cyanoacetate from Methyl 3,3-Diazido-2-cyanoacrylate and Primary Aromatic Amines (pages 1160–1161)

      Prof. Dr. Rolf W. Saalfrank, Dipl.-Chem. Michael Fischer, Dipl.-Chem. Uwe Wirth and Priv.-Doz. Dr. Helmuth Zimmermann

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198711601

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      A 1,5′ ring closure to give 3 and N2 elimination accompanied by nitrene addition to the C[DOUBLE BOND]C bond to give 4–these are the reaction possibilities available to vinyl azides 2 if the substituent at the 4 position is an NHR′ group that can become involved in the reaction. Previously, only 1,5 and 3,5 ring-closure reactions were known for vinyl azides substituted at the 4 position with donor groups. The azides 4 are easily prepared from the methyl cyanoacrylate 1 and primary aryl amines.

    15. Simultaneous Primary and Secondary Coordination of a Neutral Guest within a Macrocyclic Complex of Rhodium(III) (pages 1162–1163)

      Prof. George Ferguson, Karen E. Matthes and Dr. David Parker

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198711621

      Thumbnail image of graphical abstract

      A remarkable coordination of a water molecule is the unique feature of the octahedral title compound 1. H2O is bound primarily to RhIII and secondarily by two stabilizing hydrogen bonds to the O atoms of the ligand. The two H atoms occupy three positions and form a third hydrogen bond to an F atom of PFmath image.

    16. Trithiodeltate: a New, Aromatic Thioxocarbon Dianion (pages 1163–1164)

      Gerhard Baum, Apotheker Franz-Josef Kaiser, Priv.-Doz. Dr. Werner Massa and Prof. Dr. Gunther Seitz

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198711631

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      C3Smath image: this structural formula corresponds to the smallest possible thioxocarbon dianion, which has now been obtained in the form of several salts, e.g., 1. The X-ray structure analysis of 1 provides useful information concerning the bonding in this dianion, which can be described in terms of delocalized π electrons.

    17. Tricyclic 2,4-Diaminovinamidines– Readily Accessible, Very Strong CHN Bases (pages 1164–1165)

      Dr. Reinhard Schwesinger

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198711641

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      Du to the constrained planarity and the extended charge delocalization of the cations 1-H and 2-H the konjugate tricyclic vinamidines 1 and 2 are very strong bases. They are therefore of interest as proton traps in aprotic solvents. The starting materials for their syntheses are inexpensive reagents such as triethylenetetramine, malonodinitrile, and ammonium chloride.

    18. Novel, Very Strongly Basic, Pentacyclic “Proton Sponges” with Vinamidine Structure (pages 1165–1167)

      Dr. Reinhard Schwesinger, Dipl.-Chem. Michael Mißfeldt, Dr. Karl Peters and Prof. Dr. Hans Georg von Schnering

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198711651

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      The pentacyclic compounds 1–3 are thermodynamically very strong and kinetically active “proton sponges,” which are obtainable by means of symmetric construction from 4. In addition, they exhibit a relatively high nucleophilicity. Despite a short distance (254.1 pm) between the two N atoms involved, the intramolecular hydrogen bond in 3-H is unsymmetrical.

    19. Peralkylated Polyaminophosphazenes— Extremely Strong, Neutral Nitrogen Bases (pages 1167–1169)

      Dr. Reinhard Schwesinger and Dipl.-Chem. Helmut Schlemper

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198711671

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      Probably the strongest uncharged nitrogen bases are readily accessible, unusually stable oligophosphazenes such as 1–3 (pKa(H2O)≤29–30). They are efficient dehydrohalogenating reagents for primary and secondary halides and exhibit low nucleophilicity. Their stability is revealed by, among other things, the fact that 1 only undergoes hydrolysis in D2O at 160°C and, even under these conditions, 2 and 3 remain unchanged for at least 20 h.

    20. The Synthesis and Catalytic Properties of Some Open-Sided Binuclear Complexes of RhI: The Structure of [Rh2(CO)2(CH3CN)2{CH(PPh2)3}](CF3SO3)2 (pages 1169–1171)

      Hani El-Amouri, Dr. Ali A. Bahsoun, Prof. Jean Fischer and Prof. John A. Osborn

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198711691

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      Strong donor-acceptor character is the salient feature of the Rh[BOND]Rh bond in 1, which contains two coordinatively unsaturated, neighboring Rh1 centers. The “more open” Rh center, coordinated in a square-pyramidal fashion, thereby becomes so electron poor that CO adds to the square-planar Rh center upon reaction with 1 (L = MeCN). A complex analogous to 1 catalyzes hydrogenation.

    21. MoII and Mo0 Complexes of 3,3,7,7,11,11,15,15-Octamethyl-1,5,9,13-tetrathiacyclohexadecane (pages 1171–1172)

      Prof. Dr. Toshikatsu Yoshida, Tomohiro Adachi, Tatsuo Ueda, Megumi Watanabe, Manabu Kaminaka and Prof. Dr. Taiichi Higuchi

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198711711

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      Unusually high redox potentials characterize the MoII complexes trans-[MoX2L], X = Cl, Br, which have proved to be good precursors for the synthesis of low-valent Mo complexes containing thioether ligands L. For X = Br, both the chemical (Na/Hg) and electrochemical reduction to give the Mo0 complex 1 were accomplished in high yield under CO atmosphere. L = title compound.

    22. [As3Br12]3– and [As8I28]4– – Structurally Novel, Discrete Halogenoarsenate(III) Ions (pages 1172–1174)

      Prof. Dr. William S. Sheldrick and Dipl.-Chem. Hans-Joachim Häusler

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198711721

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      EF6 octahedra can be linked in a large number of different ways, as demonstrated once again by the preparation of the two title anions, which were obtained as crystalline triethylammonium salts. In [As3Br12]3−, the central AsBr6 octahedron shares two faces having a common corner with two other AsBr6 octahedra. [As8I28,]4− (shown at right) formally consists of eight edge-bridged AsI6 octahedra.

    23. High-Pressure Synthesis and Crystal Structure of Neodymium(III) Oxide Peroxide, Nd2O2(O2) (pages 1174–1175)

      Prof. Dr. Klaus-Jürgen Range, Dr. Maximilian Stadler, Franz Rau and Dr. Ulrich Klement

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198711741

      The most oxygen-rich compound so far reported for the system neodymiumoxygen was obtained by high-pressure synthesis from Nd2O3/KO2 mixtures. Respite the composition NDO2, the X-ray crystal structure analysis revealed at a neodymium(III) oxide peroxide and not a neodymium(iv) dioxide was present. Nd2O2(O2) is remarkably stable at normal pressure and only undergoes transformation to Nd2O3 at 420°C with loss of oxygen.

    24. Observation of an Eclipsed Cmath image-CH3 Bond in a Tricyclic Orthoamide; Experimental and Theoretical Evidence for C[BOND]H ⃛O Hydrogen Bonds (pages 1175–1177)

      Paul Seiler, Prof. Gary R. Weisman, Eric D. Glendening, Prof. Frank Weinhold, Dr. Van B. Johnson and Prof. Dr. Jack D. Dunitz

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198711751

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      The inversion of the rotational barrier of a methyl group can be accomplished by a suitable arrangement of water molecules, as shown by X-ray crystal structure investigations of the orthoamide 1. In the trihydrate, the methyl group adopts a nearly elipsed conformation, whereas in the anhydrous compound the normal staggered conformation is found. The H…O bond strengths of the C−H·O hydrogen bonds required for this inversion (ca. 1.8 kcal nol−1) were confirmed by quantum-chemical calculations only when correlation effects were taken into consideration.

    25. Aromatic Nitration at the Encounter Rate in the Gas Phase (pages 1177–1178)

      Prof. Marina Attinà, Dr. Fulvio Cacace and Dr. Giulia de Petris

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198711771

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      In the title reaction, the formation of an “early complex,” the gas-phase analogue of the “encounter” pair in solution, is rate-determining above a certain activation of the arene (nitrating agent [RNO3H], R [DOUBLE BOND] CH3, CF3CH2). This would also explain why the intermolecular selectivity between toluene and 1,2,3,5-tetramethylbenzene is small in this reaction, whereas the intramolecular selectivity in the case of benzylmesitylene 1 is large. In the latter case, 2 is formed preferentially.

    26. Photo- and Thermochromic Liquid Crystal Polysiloxanes (pages 1178–1180)

      Dr. Ivan Cabrera, Prof. Dr. Valeri Krongauz and Prof. Dr. Helmut Ringsdorf

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198711781

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      The liquid crystalline polysiloxanes 1 display a controllable range of colors. Irradiation of film with visible light results in a pale yellow color; irradiation of the yellow film with UV light results in a deep red color. If yellow film is irradiated with UV light at −20°C, it turns blue. Upon subsequent irradiation with visible light, it turns yellow once again. The blue film is stable at −20°C in the absence of light; upon warming to above −10°C, however, it turns red.

    27. Structure and Color of Pentaphenylbismuth (pages 1180–1182)

      Dipl.-Chem. Arno Schmuck, Dr. Jürgen Buschmann, Prof. Dr. Joachim Fuchs and Prof. Dr. Konrad Seppelt

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198711801

      A violet color and strong dichroism are very unusual features for a compound of a main-group element. The X-ray structure analysis performed at −96°C reveals that Bi(C6H5)5, synthesized earlier by Wittig et al., may be described as a square pyramid and is thus very similar to the (colorless!) Sb(C6H5)5. Optical investigations showed that excitation occurs in the basal plane of the square pyramid. A charge-transfer transition from a ligand to the bismuth atom was proposed.

    28. Catalytic Dehydrogenation of Cyclohexene on Silica Overlayer Films (pages 1182–1184)

      Jeffrey M. Cogen, Khosro Ezaz-Nikpay, Dr. Ronald H. Fleming, Dr. Scott M. Baumann and Prof. Dr. Wilhelm F. Maier

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198711821

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      The preparation of nobel-metal catalysts resistant to poisoning is a possibility opened up by the following experiment: On SiO2/Pt/Si layer catalysts (shown schematically below) in the presence of H2, cyclohexene undergoes reaction to give benzene and cyclohexane. The same is true when Pt/Si catalysts are used except that the activity is lower by a factor of 100. SiO2 over-layers of 0 to 30 nm lower the activity exponentially, after which the value remains constant up to 2200 nm. The results indicate that, instead of the transition-metal surface, “active hydrogen” (atomic hydrogen) is the true catalytic species.

    29. Transition State π-Solvation by Aromatic Rings: An Electronic Contribution to Diels–Alder Reaction Diastereoselectivity (pages 1184–1186)

      Prof. David A. Evans, Dr. Kevin T. Chapman, Deborah Tan Hung and Alan T. Kawaguchi

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198711841

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      Without making any assumptions regarding the ground-state conformation, it was possible to determine the electronic contribution of the substituent R to the Diels–Alder selectivity by comparing alkylation and Diels-Alder reactions involving 1 and 2. π-Stacking interactions, which, however, do not exhibit significant charge-transfer character, are implicated. This was show in part by the observation that, for all substituents that are not capable of π-stacking for steric or electronic reasons, a linear relation was found to exist between alkylation and Diels-Alder selectivities.

    30. Natural Fecapentaene-14 and One Fecapentaene-12 Component are all-trans Stereoisomers (pages 1186–1187)

      Dr. José Baptista, Prof. Dr. Jiri J. Krepinsky and Prof. Dr. Hans Rudolf Pfaendler

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198711861

      Fecapentaenes, which are extremely sensitive chemically, are mutagens and may also be colon carcinogens. The naturally occurring compounds have now been compared with two synthetically prepared samples having a known arrangement of double bonds. HPLC and 1H-NMR and UV spectroscopy revealed that the natural components are all-trans-fecapentaene-12 1 and all-trans-fecapentaene-14 2.

      • equation image
    31. Lithium-Tellurium Exchange: A New Entry to Organolithium Compounds (pages 1187–1188)

      Tomoki Hiiro, Dr. Nobuaki Kambe, Dr. Akiya Ogawa, Dr. Noritaka Miyoshi, Dr. Shinji Murai and Prof. Dr. Noboru Sonoda

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198711871

      Compounds of the type Rli, with R[DOUBLE BOND] PhC°C, PhCH2 Ph, CH2 [DOUBLE BOND] CHCH2, alkyl, Me3SiCH2, PhCH2OCH2, etc., can be generated in an indirect way by the route shown below. In a one-pot procedure, the tellurides are formed directly from alkyl halides and tellurolates RTeLi. The procedure particularly valuable when conventional lithium-halogen exchange is not possible.

      • equation image
    32. Control of the Superconducting Properties of YBa2Cu3O7 by Topotactic Redox Reactions (pages 1188–1190)

      Heinz Eickenbusch, Dipl.-Chem. Werner Paulus, Elmar Gocke, Dr. Joachim Friedrich March, Dr. Hans Koch and Prof. Dr. Robert Schöllhorn

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198711881

      The critical temperature of the phase transition normal conductivity/superconductivity can be controlled continuously and reversibly between 93 K and 30 K for the high-temperature superconductor YBa2Cu3O7 over a nonstoichiometric range Yba2Cu3Ox (7 ≥ x ≥ 6.5) by means of topotactic oxygen intercalation and deintercalation. Hydrogen and lithium can also be inserted into the lattice of the superconductor at low temperatures. 7Li-NMR investigations revealed a high mobility of the Li ions at room temperature.

    33. Hexacarbonylzirconate(2–), [Zr(CO)6]2–: The First Binary Carbonyl Complex of Zirconium (pages 1190–1191)

      Kai Ming Chi, Scott R. Frerichs, Dr. Stephen B. Philson and Prof. Dr. John E. Ellis

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198711901

      A “pure” carbonylmetalate–containing only metal and CO – has now been obtained for zirconium as the salt 1. The synthesis of 1 could only be achieved in the presence of a complexant for alkali metals, e.g., a crown ether such as [15]crown-5 (15-C-5). The 91Zr-NMR spectrum of[Zr(13CO)6]2- (99% 13C) reveals that the anion exhibits octahedral geometry.

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