Angewandte Chemie International Edition

Cover image for Vol. 44 Issue 19

May 6, 2005

Volume 44, Issue 19

Pages 2817–2983

    1. Cover Picture: On the Remarkable Antitumor Properties of Fludelone: How We Got There (Angew. Chem. Int. Ed. 19/2005) (page 2817)

      Alexey Rivkin, Ting-Chao Chou and Samuel J. Danishefsky

      Version of Record online: 3 MAY 2005 | DOI: 10.1002/anie.200590063

      Synthetic and biological studies of epothilone B (isolated from a myxobacterium) led to the discovery of a 26-trifluoro analogue that is remarkably active in treating xenograft tumors in nude mice. These findings underscore the potential of using natural products as leads, in conjunction with directed total synthesis, in the quest for new drugs. S. J. Danishefsky and co-workers present their synthetic strategy along with biological data in their Minireview on page 2838 ff.

    2. Dendrimers: Platforms for Chemical Functionality (pages 2830–2831)

      Jean-François Nierengarten

      Version of Record online: 3 MAY 2005 | DOI: 10.1002/anie.200501226

    3. V-Shaped Molecules: New Contenders for the Biaxial Nematic Phase (pages 2834–2836)

      Geoffrey R. Luckhurst

      Version of Record online: 21 APR 2005 | DOI: 10.1002/anie.200500709

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      V for victory? Theory has suggested that V-shaped molecules may provide a route to biaxial nematic liquid crystals (see picture). The identification of a biaxial nematic phase is, however, a challenging task. Even if it is yet to be agreed that the hunt is over, it appears that this path is well worth pursuing.

    4. On the Remarkable Antitumor Properties of Fludelone: How We Got There (pages 2838–2850)

      Alexey Rivkin, Ting-Chao Chou and Samuel J. Danishefsky

      Version of Record online: 3 MAY 2005 | DOI: 10.1002/anie.200461751

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      A retrospective account of the discovery through chemical synthesis of the second-generation epothilone drug candidates the 9,10-dehydroepothilones (e.g. fludelone (1)) is presented. The importance of natural products as leads in drug development is highlighted, as well as the use of molecular editing through chemical synthesis to fine-tune the biological and pharmacodynamic properties of the natural product to develop a viable drug.

    5. Recognition of Proline-Rich Motifs by Protein–Protein-Interaction Domains (pages 2852–2869)

      Linda J. Ball, Ronald Kühne, Jens Schneider-Mergener and Hartmut Oschkinat

      Version of Record online: 3 MAY 2005 | DOI: 10.1002/anie.200400618

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      Solving the mystery of mutual attraction: Proline-mediated protein–protein interactions are involved in the regulation of numerous essential cellular processes. Analysis of the structures of complexes formed between proline-rich peptides and their respective binding domains (see figure) reveals fundamental features of this mechanism of recognition, which is highly specific, yet only requires low binding affinities.

    6. One-Nanometer-Scale Size-Controlled Synthesis of Monodisperse Magnetic Iron Oxide Nanoparticles (pages 2872–2877)

      Jongnam Park, Eunwoong Lee, Nong-Moon Hwang, Misun Kang, Sung Chul Kim, Yosun Hwang, Je-Geun Park, Han-Jin Noh, Jae-Young Kim, Jae-Hoon Park and Taeghwan Hyeon

      Version of Record online: 30 MAR 2005 | DOI: 10.1002/anie.200461665

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      Accurate to size: Monodisperse magnetic iron oxide nanoparticles with a continuous size spectrum of 6–13 nm have been synthesized by a procedure similar to seed-mediated growth and characterized by transmission electron microscopy (see picture) and magnetic measurements. This method yields monodisperse nanoparticles directly without a size-selection process.

    7. Ternary Nets formed by Self-Assembly of Triangles, Squares, and Tetrahedra (pages 2877–2880)

      Zhenqiang Wang, Victor Ch. Kravtsov and Michael J. Zaworotko

      Version of Record online: 8 APR 2005 | DOI: 10.1002/anie.200500156

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      Three not of a kind: Two metal–organic nets sustained by three different molecular building blocks, triangles, squares, and tetrahedra, are prepared and characterized. The shapes (see picture red triangles, green squares, yellow tetrahedra) reveal how appropriate combinations of vertex-linked polygons or polyhedra afford novel topologies that could be prototypal of an even wider range of organic and metal–organic compounds.

    8. Fabrication of Chemical Microarrays by Efficient Immobilization of Hydrazide-Linked Substances on Epoxide-Coated Glass Surfaces (pages 2881–2884)

      Myung-ryul Lee and Injae Shin

      Version of Record online: 12 APR 2005 | DOI: 10.1002/anie.200462720

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      Fixed to the spot: A new, efficient, and simple immobilization technique for the construction of chemical microarrays has been developed. This technique is applicable to the site-selective attachment of diverse substances, including small molecules, carbohydrates, and peptides, to glass slides (see picture). The chemical microarrays fabricated by using this method were applied to screening peptide and small-molecule binding to proteins.

    9. Structure and Unique Interactions with DNA of a Cationic Trans-Platinum Complex with the Nonplanar Bicyclic Piperidinopiperidine Ligand (pages 2885–2887)

      Yousef Najajreh, Dmitri Prilutski, Yael Ardeli-Tzaraf, Jose Manuel Perez, Elena Khazanov, Yechezkel Barenholz, Jana Kasparkova, Viktor Brabec and Dan Gibson

      Version of Record online: 8 APR 2005 | DOI: 10.1002/anie.200462389

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      Circumventing cisplatin resistance: The trans-[PtCl2(NH3)(pip-pip)]+ ion (see structure; red Pt, blue N, green Cl, gray C) is a cytotoxic compound with a cationic piperidinopiperidine ligand. The piperidine ring that is removed from the PtII center is fluxional and acts as a hydrogen-bond donor. The complex binds calf thymus DNA directly and rapidly (t1/2=11 min) without prior hydrolysis and circumvents cisplatin resistance in ovarian cancer cells.

    10. Nanoporous Polyelectrolyte Spheres Prepared by Sequentially Coating Sacrificial Mesoporous Silica Spheres (pages 2888–2892)

      Yajun Wang, Aimin Yu and Frank Caruso

      Version of Record online: 7 APR 2005 | DOI: 10.1002/anie.200462135

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      A hole load of spheres: Nanoporous polyelectrolyte (PE) spheres are prepared through layer-by-layer deposition of oppositely charged poly(acrylic acid) and poly(allylamine hydrochloride) onto mesoporous silica spheres (with cross-linking by heating in each step), and the subsequent removal of the silica templates by hydrofluoric acid (HF; see scheme).

    11. Engineering Virus Functionalities on Colloidal Polyelectrolyte Lipid Composites (pages 2892–2895)

      Martin Fischlechner, Olaf Zschörnig, Jörg Hofmann and Edwin Donath

      Version of Record online: 13 APR 2005 | DOI: 10.1002/anie.200460763

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      Engineered from the inside out: Polyelectrolyte-multilayered colloids were prepared employing the layer-by-layer technology. A lipid bilayer was then added, and finally rubella-like particles were fused. Immunofluorescence studies demonstrate that the colloidal biocomposites have a virus-like surface. Indeed, they were taken up into cells, while particles with an outer lipid layer were rarely found inside cells.

    12. Direct Organocatalytic and Highly Enantio- and Diastereoselective Mannich Reactions of α-Substituted α-Cyanoacetates (pages 2896–2899)

      Thomas B. Poulsen, Carlos Alemparte, Steen Saaby, Marco Bella and Karl Anker Jørgensen

      Version of Record online: 13 APR 2005 | DOI: 10.1002/anie.200500144

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      Metal-free catalysis: Highly functionalized molecules with two contiguous stereocenters are easily accessed in high yield with high enantio- and diastereoselectivity by using a commercially available organocatalyst ((DHQD)2PYR, see scheme). The easily removed Boc protecting group in the product is an added value to this method as an important tool in asymmetric synthesis.

    13. A Calix[4]imidazolium[2]pyridine as an Anion Receptor (pages 2899–2903)

      Kavitha Chellappan, N. Jiten Singh, In-Chul Hwang, Jung Woo Lee and Kwang S. Kim

      Version of Record online: 6 APR 2005 | DOI: 10.1002/anie.200500119

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      An effective macrocyclic ionophore for F ions that contains an array of positively charged imidazolium units has been prepared. The calix[4]imidazolium[2]pyridine cation formed a complex with F ions in a 1:1 stoichiometry, as shown by binding studies using 1H NMR spectroscopic analysis, X-ray crystallographic determination (see structure), and density functional calculations.

    14. Application of Stereocontrolled Stepwise [3+2] Cycloadditions to the Preparation of Inhibitors of α4β1-Integrin-Mediated Hepatic Melanoma Metastasis (pages 2903–2907)

      Aizpea Zubia, Lorea Mendoza, Silvia Vivanco, Eneko Aldaba, Teresa Carrascal, Begoña Lecea, Ana Arrieta, Tahl Zimmerman, Fernando Vidal-Vanaclocha and Fernando P. Cossío

      Version of Record online: 13 APR 2005 | DOI: 10.1002/anie.200462497

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      Inhibitors of the interaction between protein VLA-4 and its natural ligand VCAM-1 have been designed, even though the structure of the protein remains unresolved. The rational design relied on the simulation of the steric and electronic properties of the active loop of VCAM-1, whose structure is known (see picture), and the inhibitors were readily prepared by stereoselective stepwise [3+2] cycloadditions.

    15. The Geometric and Electronic Structure of [(cyclam-acetato)Fe(N)]+: A Genuine Iron(V) Species with a Ground-State Spin S=1/2 (pages 2908–2912)

      Núria Aliaga-Alcalde, Serena DeBeer George, Bernd Mienert, Eckhard Bill, Karl Wieghardt and Frank Neese

      Version of Record online: 21 APR 2005 | DOI: 10.1002/anie.200462368

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      Low-spin, high-valent iron centers: A high-valent iron–nitrido species containing a FeV center is accessible by the photolysis of [(cyclam-ac)FeIIIN3]+. The identity of the resulting [(cyclam-ac)FeV(N)]+ species was verified by spectroscopic methods, magnetic susceptibility data, and DFT calculations (see picture). Unexpectedly, the analysis provides strong evidence for a low-spin d3 (S=1/2) ground-state electron configuration at the FeV center.

    16. Molecular Recognition by Calix[4]arene-Modified Gold Nanoparticles in Aqueous Solution (pages 2913–2916)

      T. Robert Tshikhudo, Domenico Demuru, Zhenxin Wang, Mathias Brust, Andrea Secchi, Arturo Arduini and Andrea Pochini

      Version of Record online: 7 APR 2005 | DOI: 10.1002/anie.200462909

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      Extremely stable, water-soluble gold nanoparticles 3 capable of specific molecular recognition of pyridinium ions in aqueous systems are prepared. The particles are stabilized and solubilized by thioalkylated oligoethylene glycol ligands 1. Specific recognition was achieved by thiol-modified calixarene ligands 2. The strongly colored gold particles also served as readily detectable optical markers for the specific binding events.

    17. Synthesis and Characterization of [exo-BH2(Cp*M)2B9H14] (M=Ru, Re), and the Conversion of the Ruthenaborane into [(Cp*Ru)2B10H16] with an Open Cluster Framework Based on a Capped Truncated Tetrahedron (pages 2916–2918)

      Sundargopal Ghosh, Bruce C. Noll and Thomas P. Fehlner

      Version of Record online: 13 APR 2005 | DOI: 10.1002/anie.200500343

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      Boron gets cornered: On heating, the exo-BH2 bridge on a {(Cp*Ru)2B9H14} framework (1; Cp*=C5Me5) inserts into the cluster framework to form a 12-vertex open-framework product [(Cp*Ru)2B10H16] (2).

    18. Host Solids Containing Nanoscale Anion-Binding Pockets and Their Use in Selective Sensing Displacement Assays (pages 2918–2922)

      María Comes, Gertrudis Rodríguez-López, M. Dolores Marcos, Ramón Martínez-Máñez, Félix Sancenón, Juan Soto, Luis A. Villaescusa, Pedro Amorós and Daniel Beltrán

      Version of Record online: 13 APR 2005 | DOI: 10.1002/anie.200461511

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      Functionalized mesoporous silica-based solids can be functionalized with e.g. guanidinium or polyol binding sites for detection of citrate and borate, respectively, in water. The solids are loaded with a dye (•; picture, left) that interacts with its binding sites. The dye is displaced by the target anions (○; right) and the corresponding anion is then detected by colorimetry.

    19. 2,4-Dinitrobenzenesulfonyl Fluoresceins as Fluorescent Alternatives to Ellman's Reagent in Thiol-Quantification Enzyme Assays (pages 2922–2925)

      Hatsuo Maeda, Hiromi Matsuno, Mai Ushida, Kohei Katayama, Kanako Saeki and Norio Itoh

      Version of Record online: 8 APR 2005 | DOI: 10.1002/anie.200500114

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      Fluorescent sensor for thiols: Deprotection of nonfluorescent 1 by thiols (R′SH) proceeds rapidly and near-quantitatively in aqueous solution (pH 7.4) to produce highly fluorescent 2. Assays performed in the presence of 1 provide a rapid and simple method for the determination of inhibitory constants for inhibitors such as donepezil toward acetyl- and butyrylcholinesterases.

    20. Deterministic One-to-One Synthesis of Germanium Nanowires and Individual Gold Nanoseed Patterning for Aligned Nanowire Arrays (pages 2925–2929)

      Dunwei Wang, Ryan Tu, Li Zhang and Hongjie Dai

      Version of Record online: 7 APR 2005 | DOI: 10.1002/anie.200500291

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      Several breakthroughs in nanowire synthesis are reported for germanium nanowires grown from gold nanoparticle seeds by a low-temperature chemical vapor deposition process. Conditions were optimized to observe the formation of nanowires in near-quantitative yields, and post-growth flow-alignment was used to obtain quasi-parallel nanowires that originate from well-controlled singleparticle sites (see images).

    21. A Dramatic Spin–Orbit Effect Observed in the Vibrational Frequencies of the Chloroiodomethane Cation (pages 2929–2931)

      Mina Lee, Hyoseok Kim, Yoon Sup Lee and Myung Soo Kim

      Version of Record online: 13 APR 2005 | DOI: 10.1002/anie.200463090

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      The vibrational spectrum of [CH235ClI]+ (see formula) was recorded by mass-analyzed threshold ionization (MATI) spectrometry. Spin–orbit effects were used in density functional calculations to determine the structure of the ground state of the cation. The results suggest that spin–orbit terms should be treated the same as other relativistic effects in some cases.

    22. Quantum Tunneling of Magnetization in Lanthanide Single-Molecule Magnets: Bis(phthalocyaninato)terbium and Bis(phthalocyaninato)dysprosium Anions (pages 2931–2935)

      Naoto Ishikawa, Miki Sugita and Wolfgang Wernsdorfer

      Version of Record online: 11 APR 2005 | DOI: 10.1002/anie.200462638

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      Staircase-like structures in the hysteresis loops at 0.04 K (see picture) are shown by doped single crystals of TBA[(Pc)2equation imageequation image] (Pc=phthalocyaninato, TBA=tetrabutylammonium), the first lanthanide single-molecule magnet. They are assigned to resonant quantum tunneling of magnetization between entangled states of the electron and nuclear spin systems. The Dy complex was also studied.

    23. High-Resolution NMR Spectroscopy in Solids by Truly Magic-Angle Spinning (pages 2935–2938)

      Sasa Antonijevic and Geoffrey Bodenhausen

      Version of Record online: 7 APR 2005 | DOI: 10.1002/anie.200463049

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      Right angles: In solid-state magic-angle spinning (MAS) NMR spectra, the line widths of carbonyl carbon atoms in polycrystalline cholesteryl acetate are found to be as narrow as 0.039 ppm if the magic angle is adjusted very accurately, that is, within ±0.004° (see picture). The line broadening observed for slightly miss-set angles is mostly due to residual chemical shift anisotropy (CSA) interactions. Long spin-echo life times up to equation image=3.6 s open the way to sophisticated NMR methods.

    24. Two Faces of a Biomimetic Non-Heme HO[BOND]FeV[DOUBLE BOND]O Oxidant: Olefin Epoxidation versus cis-Dihydroxylation (pages 2939–2941)

      Arianna Bassan, Margareta R. A. Blomberg, Per E. M. Siegbahn and Lawrence Que Jr.

      Version of Record online: 5 APR 2005 | DOI: 10.1002/anie.200463072

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      Reactivity along two channels is shown by the HO[BOND]FeV[DOUBLE BOND]O species responsible for Fe(tpa)-catalyzed olefin oxidation (tpa=tris(2-pyridylmethyl)amine). Attack of the oxo ligand on an olefinic carbon atom yields epoxide and attack of the hydroxo ligand affords cis-diol (see scheme). Hybrid density functional theory now demonstrates that the two processes have comparable activation energies.

    25. C[BOND]H Activated Isomers of [M(AlCp*)5] (M=Fe, Ru) (pages 2943–2946)

      Tobias Steinke, Mirza Cokoja, Christian Gemel, Andreas Kempter, Andreas Krapp, Gernot Frenking, Ulrich Zenneck and Roland A. Fischer

      Version of Record online: 12 APR 2005 | DOI: 10.1002/anie.200462834

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      What are the limits for n in the case of [M(EIR)n] (M=transition metal; E=Al, Ga, In)? Is n=5 possible, maybe n=6, or even more? A first insight is gained through the reactions of Fe0 and Ru0 precursors with excess of AlCp*, leading to C[BOND]H activated isomers of [M(AlCp*)5] (see picture for M=Fe, gray C, white H, blue Al, red Fe, Cp*=C5Me5).

    26. Cobalt(II)-Catalyzed Cross-Coupling of Polyfunctional Aryl Copper Reagents with Aryl Bromides and Chlorides (pages 2947–2951)

      Tobias J. Korn and Paul Knochel

      Version of Record online: 12 APR 2005 | DOI: 10.1002/anie.200500099

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      Polyfunctionalized biphenyl and heteroaromatic compounds were formed in the presence of [Co(acac)2], Bu4NI, and 4-fluorostyrene (3) through a smooth cross-coupling reaction between organocopper reagents 1, prepared by the transmetalation of functionalized aryl magnesium halides with CuCN⋅2 LiCl, and aryl halides 2 that bear electron-withdrawing substituents. acac=acetylacetonate, DME=1,2-dimethoxyethane, DMPU=1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone.

    27. Hydroamination/Hydrosilylation Sequence Catalyzed by Titanium Complexes (pages 2951–2954)

      Andreas Heutling, Frauke Pohlki, Igor Bytschkov and Sven Doye

      Version of Record online: 8 APR 2005 | DOI: 10.1002/anie.200462250

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      A single precatalyst is used for the sequential combination of the Ti-catalyzed hydroamination of alkynes with the Ti-catalyzed hydrosilylation of imines. In this way alkynes and primary amines are converted efficiently into secondary amines in a fully catalytic one-pot process (see scheme).

    28. A Molecular Silicon Cluster with a “Naked” Vertex Atom (pages 2954–2956)

      David Scheschkewitz

      Version of Record online: 13 APR 2005 | DOI: 10.1002/anie.200462730

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      Reaction of a disilenide with SiCl4 produces a silicon cluster with π-bonding topology reminiscent of a Möbius array, as determined by structural data and DFT calculations (see picture). Partially hydrogenated silicon clusters are important for the optical properties of many silicon materials. The availability of a derivative that is stable in the absence of surrounding Si0 yields insight into the structure of such compounds.

    29. Birnbaumin A and B: Two Unusual 1-Hydroxyindole Pigments from the “Flower Pot Parasol” Leucocoprinus birnbaumii (pages 2957–2959)

      Andrea Bartsch, Monika Bross, Peter Spiteller, Michael Spiteller and Wolfgang Steglich

      Version of Record online: 7 APR 2005 | DOI: 10.1002/anie.200500082

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      It can come as a surprise to plant lovers to find the fruit bodies of Leucocoprinus birnbaumii (see picture) in their flower pots. This fragile fungus, which is harmless to plants, owes its yellow color to the unusual alkaloids birnbaumin A and B, in which a 1-hydroxyindole-3-glyoxylic acid amide is attached through a tetramethylene unit to N-hydroxyoxamidine. N-Hydroxyoxamidines have not been described previously.

    30. Mixtures of Configurationally Stable and Fluxional Atropisomeric Monodentate P Ligands in Asymmetric Rh-Catalyzed Olefin Hydrogenation (pages 2959–2962)

      Manfred T. Reetz and Xiaoguang Li

      Version of Record online: 12 APR 2005 | DOI: 10.1002/anie.200462612

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      Mixed (pre)catalysts such as 1 arise when [Rh(cod)2]BF4 is combined with a 1:1 mixture of a BINOL-derived monodentate phosphonite or phosphite ligand and a configurationally fluxional atropisomeric phosphite with a biphenol backbone. These systems provide excellent results for the Rh-catalyzed asymmetric hydrogenation of β-acylamino acrylates. BINOL=2,2′-dihydroxy-1,1′-binaphthyl; cod=cycloocta-1,5-diene.

    31. The Influence of Mixtures of Monodentate Achiral Ligands on the Regioselectivity of Transition-Metal-Catalyzed Hydroformylation (pages 2962–2964)

      Manfred T. Reetz and Xiaoguang Li

      Version of Record online: 13 APR 2005 | DOI: 10.1002/anie.200462613

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      1+1≠2: The mixture of triphenylphosphine and phosphinine 1 with [Rh(acac)(CO)2] forms a hydroformylation catalyst that effects the preferential formation of the branched product, even though each ligand alone mediates the opposite regioselectivity. Similar effects were observed for a series of other ligand combinations.

    32. From Racemic Primary Aminoalkyl(phosphanyl)ferrocene Complexes to a Lithium–Phosphorus closo Cluster (pages 2965–2969)

      Steffen Tschirschwitz, Peter Lönnecke, Joachim Reinhold and Evamarie Hey-Hawkins

      Version of Record online: 8 APR 2005 | DOI: 10.1002/anie.200462543

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      Li12P6: The first two primary aminoalkyl(phosphanyl)ferrocene complexes 2-(N,N-Dimethylaminomethyl)phosphanylferrocene (1) and N,N-dimethyl-1-(2-phosphanylferrocenyl)ethylamine (2) are prepared. Compound 1 readily undergoes twofold deprotonation with nBuLi to form the first lithium–phosphorus cluster (see picture) which has the structure and electronic properties of a closo cluster according to Wade's rules.

    33. Rational Design of a Coordination Cage with a Trigonal-Bipyramidal Shape Constructed from 33 Building Units (pages 2969–2973)

      Iris M. Müller and Daniela Möller

      Version of Record online: 7 APR 2005 | DOI: 10.1002/anie.200463034

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      According to plan: C2- and C3-symmetric ligands are essential to the rational design of a low-symmetry coordination cage with the outer shape of a trigonal bipyramid (view along the C3 axis shown; green: Pd, red: ligand, blue: 5,5-diethylbarbiturate). The characterization of an intermediate gives insight to the mechanism of formation.

    34. Ga10Br10(4-tert-Butylpyridine)10: A Mixed-Valent Gallium(I) Subhalide as an Intermediate during the Formation of Elemental Gallium? (pages 2973–2975)

      Taike Duan, Gregor Stößer and Hansgeorg Schnöckel

      Version of Record online: 8 APR 2005 | DOI: 10.1002/anie.200462075

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      Primary steps on the way towards Ga metal: The second structurally characterized gallium(I) subhalide Ga10Br10(4-tert-butylpyridine)10 (see picture, blue Ga, yellow N, green Br) allows an insight into the intra- and intermolecular redox process during the formation of α-gallium by the disproportionation reaction of a metastable GaBr solution. During this process, metalloid clusters with an increasing number of “naked” Ga0 atoms in the core and GaX2 entities in the periphery grow.

    35. Switchable Supramolecular Organization of Structurally Defined Micelles Based on an Amphiphilic Fullerene (pages 2976–2979)

      Stephan Burghardt, Andreas Hirsch, Boris Schade, Kai Ludwig and Christoph Böttcher

      Version of Record online: 13 APR 2005 | DOI: 10.1002/anie.200462465

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      Exactly eight amphiphilic fullerene dendrimer molecules form a globular micelle spontaneously in aqueous solution. This supramolecular organization can be turned on and off by an external stimulus (pH). Owing to the remarkable structure persistence of the micelles, their three-dimensional structure could be determined from cryogenic transmission electron micrographic images and the molecular architecture was subsequently modeled (see picture).

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