Angewandte Chemie International Edition

Cover image for Vol. 42 Issue 13

April 4, 2003

Volume 42, Issue 13

Pages 1427–1549

    1. Cover Picture: Cyanide-Bridged Iron(III)–Cobalt(II) Double Zigzag Ferromagnetic Chains: Two New Molecular Magnetic Nanowires (Angew. Chem. Int. Ed. 13/2003) (page 1427)

      Rodrigue Lescouëzec, Jacqueline Vaissermann, Catalina Ruiz-Pérez, Francesc Lloret, Rosa Carrasco, Miguel Julve, Michel Verdaguer, Yves Dromzee, Dante Gatteschi and Wolfgang Wernsdorfer

      Version of Record online: 7 APR 2003 | DOI: 10.1002/anie.200390367

      Magnetic nanowires are among new objects that chemists can design with a view to magnetic information storage. The cover picture shows views of an ordered bimetallic double chain of iron(III) and cobalt(II) ions, bridged by cyanide groups. Each chain has remarkable anisotropic magnetic properties (axes of easy magnetization are shown) and shows slow relaxation of the magnetization. Find out more about these nanowires in the Communication by M. Julve, M. Verdaguer et al. on page 1483 ff.

    2. Reactions between Organomagnesium Reagents and Nitroarenes: Past, Present, and Future (pages 1444–1446)

      Alfredo Ricci and Mariafrancesca Fochi

      Version of Record online: 7 APR 2003 | DOI: 10.1002/anie.200201618

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      Grignard reagents display useful diversity in their reactions with nitroarenes. Depending on the organomagnesium species used, these reactions, the results of which can be predicted from mechanistic studies, may lead to significantly diverse products (see scheme), and can be tailored towards the synthesis of substituted nitroarenes, indoles, and diarylamines. FG=functional group.

    3. Gemini Surfactants: New Synthetic Vectors for Gene Transfection (pages 1448–1457)

      Anthony J. Kirby, Patrick Camilleri, Jan B. F. N. Engberts, Martin C. Feiters, Roeland J. M. Nolte, Olle Söderman, Mark Bergsma, Paul C. Bell, Matthew L. Fielden, Cristina L. García Rodríguez, Philippe Guédat, Andreas Kremer, Caroline McGregor, Christele Perrin, Gaël Ronsin and Marcel C. P. van Eijk

      Version of Record online: 7 APR 2003 | DOI: 10.1002/anie.200201597

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      The powerful combination of the superior surfactant properties of gemini surfactants with the cationic character necessary for binding and compacting DNA has led to a new class of gene transfection agents (e.g. 1). The compounds are derived from natural metabolites and combine high transfection activity with low cell toxicity.

    4. Anion-Templated Synthesis (pages 1460–1477)

      Ramón Vilar

      Version of Record online: 7 APR 2003 | DOI: 10.1002/anie.200200551

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      Anion templates in vogue: In contrast to the well-studied templating properties of cationic and neutral species until very recently only a handful of anion-templated syntheses had been reported. That this is beginning to change is evident from the number of anion-templated assemblies—such as macrocycles (see scheme), cages, helicates, rotaxanes, and extended structures—that have emerged over the past few years. Such systems are summarized in this review.

    5. Efficient Heterogeneous Aerobic Oxidation of Amines by a Supported Ruthenium Catalyst (pages 1480–1483)

      Kazuya Yamaguchi and Noritaka Mizuno

      Version of Record online: 7 APR 2003 | DOI: 10.1002/anie.200250779

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      An inexpensive supported ruthenium catalyst (Ru/Al2O3) can be used to convert a broad range of primary (see scheme) and secondary amines into the corresponding nitriles and imines in high yields using either dioxygen or air as oxidants. The catalyst can be recycled and reused with no detectable loss of ruthenium and without an observed reduction in catalytic activity.

    6. Cyanide-Bridged Iron(III)–Cobalt(II) Double Zigzag Ferromagnetic Chains: Two New Molecular Magnetic Nanowires (pages 1483–1486)

      Rodrigue Lescouëzec, Jacqueline Vaissermann, Catalina Ruiz-Pérez, Francesc Lloret, Rosa Carrasco, Miguel Julve, Michel Verdaguer, Yves Dromzee, Dante Gatteschi and Wolfgang Wernsdorfer

      Version of Record online: 7 APR 2003 | DOI: 10.1002/anie.200250243

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      The Ising on the cake: The cyanide-bridged low-spin FeIII–high-spin CoII compounds of formula [{FeL(CN)4}2Co(H2O)2]⋅4 H2O with L=2,2′-bipyridine (bpy; see picture; Ow=water O-atom) or 1,10-phenanthroline are 1D Ising systems and the first examples of ferromagnetically coupled bimetallic chains which show slow magnetic relaxation and hysteresis effects. The compounds, therefore, behave as magnetic nanowires.

    7. Amphiphilic Dendrimers: Novel Self-Assembling Vectors for Efficient Gene Delivery (pages 1486–1490)

      Derk Joester, Myriam Losson, Raphaël Pugin, Harry Heinzelmann, Elke Walter, Hans P. Merkle and François Diederich

      Version of Record online: 7 APR 2003 | DOI: 10.1002/anie.200250284

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      A sharp maximum in the structure–activity relationship, a surprisingly strong influence of the hydrophobic part on DNA binding and transport, and an unusual serum effect on relative transfection activities were found in preliminary biological data on a series of four amphiphilic dendrimers designed as transfection agents. The lowest generation dendrimer 1 was found to be the most active.

    8. Toward Chemically Controlled Nanoscale Molecular Machinery (pages 1491–1495)

      Hsian-Rong Tseng, Scott A. Vignon and J. Fraser Stoddart

      Version of Record online: 7 APR 2003 | DOI: 10.1002/anie.200250453

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      Mechanical displacement of the ring by around 40 % along the approximately 9-nm long dumbbell-shaped component has been seen in a bistable redox-controllable [2]rotaxane. Chemical oxidation of the tetrathiafulvalene recognition station (green, see scheme) in the dumbbell-shaped component, which also contains a 1,5-dioxynaphthalene recognition station (red), results in the cyclobis(paraquat-p-phenylene) tetracation (blue) undergoing translation from the much preferred green station to the second-choice, red station.

    9. Propargylation of Aromatic Compounds with Propargylic Alcohols Catalyzed by a Cationic Diruthenium Complex (pages 1495–1498)

      Yoshiaki Nishibayashi, Youichi Inada, Masato Yoshikawa, Masanobu Hidai and Sakae Uemura

      Version of Record online: 7 APR 2003 | DOI: 10.1002/anie.200250532

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      Two metals are better than one: The cationic methanethiolate-bridged diruthenium complex 1 (Cp*=C5Me5, OTf=CF3SO3) promotes the catalytic propargylation of aromatic compounds with propargylic alcohols bearing not only terminal alkyne but also internal alkyne units, reactions that can not be carried out with some mononuclear catalysts. This reaction provides a general and environmentally friendly (atom economical, only H2O as byproduct) method for the synthesis of a variety of propargylated aromatic compounds.

    10. The First Organocatalytic Enantioselective Inverse-Electron-Demand Hetero-Diels–Alder Reaction (pages 1498–1501)

      Karsten Juhl and Karl Anker Jørgensen

      Version of Record online: 7 APR 2003 | DOI: 10.1002/anie.200250652

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      Catalyzed by chiral amines, aldehydes undergo diastereo- and enantioselective inverse-electron-demand hetero-Diels–Alder reactions with enones (see scheme; PCC = pyridine chlorochromate). The reaction has been optimized with respect to different pyrrolidine catalysts, and tested with various aldehydes and enones.

    11. Gold[BOND]Gold Interaction—Stannaborate [SnB11H11]2− Coordination Chemistry (pages 1501–1505)

      Siegbert Hagen, Ingo Pantenburg, Florian Weigend, Claudia Wickleder and Lars Wesemann

      Version of Record online: 7 APR 2003 | DOI: 10.1002/anie.200250698

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      A stannaborate bridge supports the gold[BOND]gold interaction in the product (see picture) of the reaction of [SnB11H11]2− with [(Ph3P)AuCl]. A significant preference for the dimer [(Me3P)Au(SnB11H11)]22− over the two monomers [(Me3P)Au(SnB11H11)]E=160 kJ mol−1) was demonstrated on the basis of MP2 calculations.

    12. Towards the Development of Electrical Conduction and Lithium-Ion Transport in a Tetragonal Porphyrin Wire (pages 1505–1508)

      Lu-Lin Li, Chia-Jung Yang, Wei-Hung Chen and Kuan-Jiuh Lin

      Version of Record online: 7 APR 2003 | DOI: 10.1002/anie.200219523

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      One-dimensional porphyrin wires were self-assembled by solvothermal methods. The porous framework, sustained by van der Waals and electrostatic interactions, is thermally stable up to 350 °C. Encapsulation of polyaniline (PANI) filaments in the host matrix provides a pathway for electron conduction (see picture). Moreover, it exhibits a highly reversible lithium-ion cycle in a C/Li⋅PANI@porphyrin cell. These features make this material very attractive for secondary battery solid-electrolyte applications.

    13. Understanding the Role of Active-Site Residues in Chorismate Mutase Catalysis from Molecular-Dynamics Simulations (pages 1508–1511)

      Hong Guo, Qiang Cui, William N. Lipscomb and Martin Karplus

      Version of Record online: 7 APR 2003 | DOI: 10.1002/anie.200219878

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      The removal of a key residue (Arg 90) from the chorismate mutase enzyme destroys the balance of the interactions in the active site required for stabilizing the conformation of the transition state in the Claisen rearrangement of chorismate to prephenate (see picture).

    14. Compositional and Isotopologue-Induced Phase Differentiation in Supramolecular Aggregates (pages 1512–1515)

      Jaeho Lee and Sergiu M. Gorun

      Version of Record online: 7 APR 2003 | DOI: 10.1002/anie.200250200

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      The independent variation of two seemingly unrelated parameters, namely NaCl concentration and water hydrogen isotopologues, can tune the formation of both similar (P1 and P2) and dissimilar (P3) supramolecular Mn16 aggregates in aqueous solutions. Surprisingly, a structurally intermediate phase P2, however, forms in H2O, but not in D2O.

    15. pH-Dependent Self-Assembly: Micellization and Micelle–Hollow-Sphere Transition of Cellulose-Based Copolymers (pages 1516–1519)

      Hongjing Dou, Ming Jiang, Huisheng Peng, Daoyong Chen and Yan Hong

      Version of Record online: 7 APR 2003 | DOI: 10.1002/anie.200250254

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      Simply by decreasing the pH of the medium, hydroxyethyl cellulose-graft-polyacrylic acid (HEC-g-PAA) can form micelles in water. Cross-linking the PAA chains at the periphery of the micellar core can efficiently lock the integrality of the micelles (see scheme). The resultant micelles transform into hollow spheres as the pH value increases. Both the micellization and the transition from micelles to hollow spheres are reversible. The hollow spheres show “on-off” character at a pH value of about 3.

    16. Mechanistic Insights into the Conversion of Cyclohexene to Adipic Acid by H2O2 in the Presence of a TAPO-5 Catalyst (pages 1520–1523)

      Sang-Ok Lee, Robert Raja, Kenneth D. M. Harris, John Meurig Thomas, Brian F. G. Johnson and Gopinathan Sankar

      Version of Record online: 7 APR 2003 | DOI: 10.1002/anie.200250351

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      The stereochemistry of the 1,2-cyclohexanediol intermediate plays an important role with regard to both the rate and selectivity of the production of adipic acid from cyclohexene in the absence of an organic solvent. A titanium-containing aluminophosphate molecular sieve (TAPO-5) is shown to serve as a good heterogeneous catalyst for this reaction.

    17. A Trigonal-Bipyramidal Cyanide Cluster with Single-Molecule-Magnet Behavior: Synthesis, Structure, and Magnetic Properties of {[MnII(tmphen)2]3[MnIII(CN)6]2} (pages 1523–1526)

      Curtis P. Berlinguette, Derek Vaughn, Cristina Cañada-Vilalta, José Ramón Galán-Mascarós and Kim R. Dunbar

      Version of Record online: 7 APR 2003 | DOI: 10.1002/anie.200250479

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      Slow paramagnetic relaxation was observed at low temperatures from ac susceptibility measurements in the form of a frequency-dependent out-of-phase (χequation image) signal for the title complex (see picture). This provides compelling evidence that this cluster is a rare example of a cyanide-bridged single-molecule magnet.

    18. Mesoporous Aluminosilicate Materials with Superparamagnetic γ-Fe2O3 Particles Embedded in the Walls (pages 1526–1530)

      Carlos Garcia, Yuanming Zhang, Francis DiSalvo and Ulrich Wiesner

      Version of Record online: 7 APR 2003 | DOI: 10.1002/anie.200250618

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      An iron constitution: Dark superparamagnetic iron oxide nanoparticles are present within the walls of a hexagonal mesoporous aluminosilicate (as shown by the associated bright-field TEM image). The simple block-copolymer-based “one-pot” self-assembly approach enables potential applications in magnetic separation and catalyst technologies.

    19. Structure and Characterization of CI3+[Al{OC(CF3)3}4]; Lewis Acidities of CX3+ and BX3 (pages 1531–1534)

      Ingo Krossing, Angela Bihlmeier, Ines Raabe and Nils Trapp

      Version of Record online: 7 APR 2003 | DOI: 10.1002/anie.200250172

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      Where is the charge? The positive charge of the CI3+ ion in CI3+[Al{OC(CF3)3}4] is located exclusively on the I atoms (see resonance structures BD), and not on the formal carbenium center A. According to calculations and experimental findings, the Lewis acidity of the CX3+ homologues (X=F–I) versus fluoride is reversed in comparison to that of the isoelectronic boron halides BX3, and decreases from CF3+ to CI3+.

    20. The Fourth Helical Secondary Structure of β-Peptides: The (P)-28-Helix of a β-Hexapeptide Consisting of (2R,3S)-3-Amino-2-hydroxy Acid Residues (pages 1534–1537)

      Karl Gademann, Andreas Häne, Magnus Rueping, Bernhard Jaun and Dieter Seebach

      Version of Record online: 7 APR 2003 | DOI: 10.1002/anie.200250290

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      Small change with great effect! An oligomer of α-hydroxy-β-amino acids folds into a right-handed helical structure (see picture) in MeOH; in contrast, the methyl analogue has a pleated sheet structure. Including this new helix, four different helical secondary structures of β-peptides have been discovered—a structural diversity that should allow the generation of elaborate proteomimetics.

    21. Separate Spectroscopic Detection of Carbenium and Fluoronium Isomers of Protonated Fluorobenzene (pages 1537–1540)

      Nicola Solcà and Otto Dopfer

      Version of Record online: 7 APR 2003 | DOI: 10.1002/anie.200250730

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      Simply a question of the technique! Carbenium and fluoronium isomers of protonated fluorobenzene are unambiguously identified for the first time in the gas phase by spectroscopy (see scheme; blue: C-C6H6F+, red: F-C6H6F+). The C-C6H6F+ ions are detected by IR photodissociation (IRPD) spectra of weakly bound C6H6F+⋅(N2)2 complexes, whereas the F-C6H6F+ ions are selectively observed by IRPD of bare C6H6F+.

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      A Possible Prebiotic Formation of Ammonia from Dinitrogen on Iron Sulfide Surfaces (pages 1540–1543)

      Mark Dörr, Johannes Käßbohrer, Renate Grunert, Günter Kreisel, Willi A. Brand, Roland A. Werner, Heike Geilmann, Christina Apfel, Christian Robl and Wolfgang Weigand

      Version of Record online: 7 APR 2003 | DOI: 10.1002/anie.200250371

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      Teaching an old dog a new fix: Nitrogen fixation under mild conditions is still one of the most challenging tasks in chemistry. A method for the synthesis of ammonia from molecular nitrogen using hydrogen sulfide as a reductant and freshly precipitated iron sulfide as a mediator is described. The reaction (see scheme) may be a primordial inorganic ancestor of the enzyme nitrogenase.

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