Angewandte Chemie International Edition

Cover image for Vol. 43 Issue 41

October 18, 2004

Volume 43, Issue 41

Pages 5417–5553

    1. Cover Picture: Molecular Gyroscopes: {Fe(CO)3} and {Fe(CO)2(NO)}+ Rotators Encased in Three-Spoke Stators; Facile Assembly by Alkene Metatheses (Angew. Chem. Int. Ed. 41/2004) (page 5417)

      Takanori Shima, Frank Hampel and J. A. Gladysz

      Version of Record online: 13 OCT 2004 | DOI: 10.1002/anie.200490142

      Three-fold alkene metatheses are used to access the family of molecular gyroscopes shown in the cover picture. As described by J. A. Gladysz and co-workers in their Communication on page 5537 ff. the gyroscopes consist of a phosphorus–iron–phosphorus axis, an {Fe(CO)3} or {Fe(CO)2(NO)}+ “rotator”, and three (CH2)n “spokes” that connect the phosphorus termini. These are believed to be the first systems that rigorously duplicate the connectivity and symmetry of toy gyroscopes (shown in the background).

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      An Amphotericin B–Fluorescein Conjugate as a Powerful Probe for Biochemical Studies of the Membrane (page 5428)

      Andreas Zumbuehl, Damien Jeannerat, Scott E. Martin, Marc Sohrmann, Pasquale Stano, Tamas Vigassy, Daniel D. Clark, Stephen L. Hussey, Mathias Peter, Blake R. Peterson, Ernö Pretsch, Peter Walde and Erick M. Carreira

      Version of Record online: 13 OCT 2004 | DOI: 10.1002/anie.200490144

    3. Molecular Motors. Edited by Manfred Schliwa. (pages 5432–5433)

      Christoph G. Baumann

      Version of Record online: 13 OCT 2004 | DOI: 10.1002/anie.200485002

    4. Nucleophilic Catalysis by 4-(Dialkylamino)pyridines Revisited—The Search for Optimal Reactivity and Selectivity (pages 5436–5441)

      Alan C. Spivey and Stellios Arseniyadis

      Version of Record online: 17 SEP 2004 | DOI: 10.1002/anie.200460373

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      A complex interplay between catalyst structure, acylating agent, auxiliary base, and solvent governs the reactivity and selectivity in 4-(dialkylamino)pyridine-catalyzed esterification reactions (see scheme). This highlight attempts a rationalization of the complicated mechanism and puts forward some explanations for seemingly contradictory experimental observations.

    5. Unveiling Reliable Catalysts for the Asymmetric Nitroaldol (Henry) Reaction (pages 5442–5444)

      Claudio Palomo, Mikel Oiarbide and Antonia Mielgo

      Version of Record online: 28 SEP 2004 | DOI: 10.1002/anie.200460506

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      Conceptually different chiral catalysts ranging from polymetallic complexes to Lewis acids and organocatalysts have emerged for solving the long-standing problem of stereocontrol in the Henry reaction, a fundamental C[BOND]C bond-forming process (see scheme). New catalyst systems with improved selectivity have increased the synthetic value of this reaction considerably.

    6. Using Hydrogen Bonds to Direct the Assembly of Crowded Aromatics (pages 5446–5453)

      Mark L. Bushey, Thuc-Quyen Nguyen, Wei Zhang, Dana Horoszewski and Colin Nuckolls

      Version of Record online: 16 SEP 2004 | DOI: 10.1002/anie.200301678

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      Columnar superstructures are formed from the assembly of crowded aromatics. The design, synthesis, and self-assembly of this new class of aromatics (see picture) is detailed in this Minireview. The assembly of these subunits produces helical and polar stacks that can be directed with electric fields. In concentrated solutions, these self-assembled rods exhibit superhelices.

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      Snapshot Magnetic Resonance Imaging (Nobel Lecture) (pages 5456–5464)

      Peter Mansfield

      Version of Record online: 21 SEP 2004 | DOI: 10.1002/anie.200460078

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      Modern medicine relies heavily on magnetic resonance imaging. Sir Peter Mansfield was awarded the 2003 Nobel price in Physiology or Medicine for his investigations on theory and instrumental setup (see picture), which made this method a versatile diagnostic tool, and for the development of ultrahigh-speed techniques.

    8. Reversible Photoinduced Magnetic Properties in the Heptanuclear Complex [MoIV(CN)2(CN[BOND]CuL)6]8+: A Photomagnetic High-Spin Molecule (pages 5468–5471)

      Juan Manuel Herrera, Valérie Marvaud, Michel Verdaguer, Jérôme Marrot, Marguerite Kalisz and Corine Mathonière

      Version of Record online: 3 SEP 2004 | DOI: 10.1002/anie.200460387

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      Metastable up to 280 K, {MoVCuICuII5} (S=3) forms as a result of intramolecular electron transfer from the MoIV center to one of the CuII termini of the [MoIV(CN)2(CN-CuII(L))6]8+ complex, (1; L=tris(2-aminoethyl)amine) upon light excitation (see picture: Mo yellow; C black; N blue; Cu purple). This process is thermally reversible. Compound 1 shows the magnetic properties of six independent CuII ions (S=1/2).

    9. Electrophilic Double-Sandwiches Formed by Interaction of [Cp2Fe] and [Cp2Ni] with the Tridentate Lewis Acid [(o-C6F4Hg)3] (pages 5471–5474)

      Mason R. Haneline and François P. Gabbaï

      Version of Record online: 13 OCT 2004 | DOI: 10.1002/anie.200461152

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      A sandwich in a sandwich: Electrophilic double-sandwich compounds are readily formed by interaction of ferrocene and nickelocene with the tridentate Lewis acid 1 (see scheme; C gray, F light green, Hg orange, M dark green). These new supramolecules result from π interactions between the mercury centers of 1 and the C5H5 rings of the metallocenes. Surprisingly, the nickelocene derivative is dark red and air stable.

    10. Rhodium Silyl Boryl Hydride Complexes: Comparison of Bonding and the Rates of Elimination of Borane, Silane, and Dihydrogen (pages 5474–5477)

      Kevin S. Cook, Christopher D. Incarvito, Charles Edwin Webster, Yubo Fan, Michael B. Hall and John F. Hartwig

      Version of Record online: 13 OCT 2004 | DOI: 10.1002/anie.200460430

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      Spoilt for choice: a silane, dihydrogen, borane, or hydridoborate complex? The silyl boryl hydride complex [Cp*Rh(H2)(Et3Si)(Bpin)] (Bpin=(pinacolato)boryl) could adopt any of these structures, but it appears to contain stronger B[BOND]H bonding than Si[BOND]H or H[BOND]H bonding and undergoes elimination of pinacolborane faster than of silane or hydrogen (see scheme). The bonding situation is studied by experimental and theoretical methods.

    11. Hemibuckminsterfullerene C30H12: X-ray Crystal Structures of the Parent Hydrocarbon and of the Two-Dimensional Organometallic Network {[Rh2(O2CCF3)4]3⋅(C30H12)} (pages 5477–5481)

      Marina A. Petrukhina, Kristian W. Andreini, Lingqing Peng and Lawrence T. Scott

      Version of Record online: 13 OCT 2004 | DOI: 10.1002/anie.200460855

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      Bringing together two C30hemispheres by coordinating their concave faces to a monometal template or metal cluster represents the first step in an appealing strategy for the controlled synthesis of endohedral fullerene complexes by laboratory methods. A crystalline transition metal complex of this structural type (see picture; Rh blue, O red, C gray; H, F omitted) has now been prepared from hemibuckminsterfullerene C30H12 and [Rh2(O2CCF3)4].

    12. Rationalization of Supramolecular Chirality in a Bisporphyrin System (pages 5481–5485)

      Victor V. Borovkov, Isao Fujii, Atsuya Muranaka, Guy A. Hembury, Takeyuki Tanaka, Arnout Ceulemans, Nagao Kobayashi and Yoshihisa Inoue

      Version of Record online: 13 OCT 2004 | DOI: 10.1002/anie.200460965

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      A sign of the times: A 1:1 tweezer complex consisting of an achiral bis(zinc porphyrin) and (R,R)-1,2-diaminocyclohexane has been characterized by X-ray crystallographic analysis (see picture, Zn red, N blue). This has enabled a full and unambiguous rationalization of the highly efficient transfer of chirality information from an optically active guest to an achiral host in a supramolecular system based on a bisporphyrin to be carried out.

    13. Mono- and Multidecker Sandwich-Like Complexes of the Tetraazacyclobutadiene Aromatic Ring (pages 5485–5488)

      Jose M. Mercero, Jon M. Matxain and Jesus M. Ugalde

      Version of Record online: 13 OCT 2004 | DOI: 10.1002/anie.200460498

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      Sandwich structures are readily formed with the aromatic N42− anion. The complexes, which form with early- and late-transition-metal centers are described and their properties analyzed. These sandwich complexes can oligomerize or polymerize to form multidecker chains.

    14. The Lone-Pair Cation I5+ in a Hexagonal Tungsten Oxide-Like Framework: Synthesis, Structure, and Second-Harmonic Generating Properties of Cs2I4O11 (pages 5489–5491)

      Kang Min Ok and P. Shiv Halasyamani

      Version of Record online: 13 OCT 2004 | DOI: 10.1002/anie.200460367

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      The layered iodate Cs2I4O11 has been synthesized and characterized. Its hexagonal tungsten oxide-like framework consists of six-membered rings of corner-sharing IO5 polyhedra with three lone pairs pointing inward and three lone pairs pointing outward (depicted for central ring). Capping of the layer by asymmetric IO3 polyhedra on one side results in a noncentrosymmetric material with highly efficient second-harmonic generating properties.

    15. Supramolecular Assemblies of Starlike and V-Shaped PB–PEO Amphiphiles (pages 5491–5496)

      Jun Xu and Eugene R. Zubarev

      Version of Record online: 13 OCT 2004 | DOI: 10.1002/anie.200460906

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      A star is born in the form of a polybutadiene–poly(ethylene oxide) amphiphile 1. The molecule exhibits remarkable self-assembly properties: it forms regular and reverse micelles in water and hexane, respectively. Comparison of 1 with a V-shaped precursor revealed a profound influence of molecular architecture on the self-assembly behavior of the amphiphiles.

    16. Cucurbit[8]uril-Mediated Redox-Controlled Self-Assembly of Viologen-Containing Dendrimers (pages 5496–5499)

      Kwangyul Moon, Jodi Grindstaff, David Sobransingh and Angel E. Kaifer

      Version of Record online: 13 OCT 2004 | DOI: 10.1002/anie.200460179

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      The dimerization of dendrimers that contain a single 4,4′-bipyridinium (viologen) unit, upon one-electron reduction, is strongly enhanced by the presence of the host cucurbit[8]uril. This behavior is attributed to the formation of a stable inclusion complex between the host and two π-stacked viologen radical-cation guests—the one-electron-reduced form of viologen (see scheme).

    17. Control of Nanoparticle Assembly by Using DNA-Modified Diatom Templates (pages 5500–5503)

      Nathaniel L. Rosi, C. Shad Thaxton and Chad A. Mirkin

      Version of Record online: 13 OCT 2004 | DOI: 10.1002/anie.200460905

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      Microorganisms point the way: The silica cell walls of various diatoms were covalently functionalized with DNA by using straightforward chemical procedures and then used as templates for the sequence-specific assembly and 3D hierarchical arrangement of prefabricated DNA-modified gold nanoparticles. The DNA was used to further direct the assembly of multiple nanoparticle layers onto the diatom templates (see picture).

    18. Reversibly Addressing an Allosteric Catalyst In Situ: Catalytic Molecular Tweezers (pages 5503–5507)

      Nathan C. Gianneschi, So-Hye Cho, SonBinh T. Nguyen and Chad A. Mirkin

      Version of Record online: 13 OCT 2004 | DOI: 10.1002/anie.200460932

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      Abiotic allosteric regulation: The design, synthesis, and application of novel, reversible allosteric catalytic molecular tweezers that contain a structural metal, addressable in situ, and two functional catalytic metals are reported (see picture). Kinetic and selectivity data reflect a significant decrease in cooperativity upon opening of the “arms” of the catalyst caused by reactions occurring at the hinge.

    19. Highly Enantioselective Direct Organocatalytic α-Chlorination of Ketones (pages 5507–5510)

      Mauro Marigo, Stephan Bachmann, Nis Halland, Alan Braunton and Karl Anker Jørgensen

      Version of Record online: 13 OCT 2004 | DOI: 10.1002/anie.200460462

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      AC2-symmetric diamine serves as the organocatalyst in an asymmetric α-chlorination reaction of simple ketones (e.g., cyclohexanone, diethyl ketone). Optically active α-chloroketones are formed with excellent enantioselectivities using N-chlorosuccinimide (NCS) as the chlorine source (see scheme). These products have broad synthetic utility, in particular for pharmaceutical applications.

    20. Diastereoselective Synthesis of Cycloheptadienol Derivatives by a Formal [5+2] Carbocyclization Reaction of α,β,γ,δ-Diunsaturated (Methoxy)carbene Complexes with Methyl Ketone Lithium Enolates (pages 5510–5513)

      José Barluenga, Jorge Alonso, Francisco J. Fañanás, Javier Borge and Santiago García-Granda

      Version of Record online: 13 OCT 2004 | DOI: 10.1002/anie.200460547

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      Magnificent seven! Functionalized seven-membered carbocycles can be easily synthesized in a diastereoselective way by a formal [5+2] carbocyclization reaction from dienylmethoxycarbene complexes and methyl ketone lithium enolates (see scheme). Examples for R: Ph, 2-Fu, PhCH2CH2, TMSC[TRIPLE BOND]C; R1: H, Me; R2: Ph, 2-Fu are presented.

    21. Gas-Phase Reactions of the [(PHOX)IrL2]+ Ion Olefin-Hydrogenation Catalyst Support an IrI/IrIII Cycle (pages 5513–5516)

      Rolf Dietiker and Peter Chen

      Version of Record online: 13 OCT 2004 | DOI: 10.1002/anie.200460860

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      Weighing up mechanisms: Using mass spectrometry (see scheme) gas-phase reactions of ions containing the (PHOX)Ir (PHOX=chiral phosphanyloxazoline ligand, red O, light blue N, orange P, blue Ir) fragment are used to explore mechanistic pathways in the catalytic hydrogenation by related complexes. The reactions indicate that the hydrogenation proceeds by an IrI/IrIII cycle rather than by the previously proposed IrIII/IrV polyhydride route.

    22. Expanding the LnZ3/Alkali-Metal Reduction System to Organometallic and Heteroleptic Precursors: Formation of Dinitrogen Derivatives of Lanthanum (pages 5517–5519)

      William J. Evans, David S. Lee, Charlie Lie and Joseph W. Ziller

      Version of Record online: 13 OCT 2004 | DOI: 10.1002/anie.200461170

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      Dinitrogen reduction with diamagnetic trivalent lanthanum complexes is possible for the first time using a combination of a trivalent metallocene and potassium graphite. Both [(C5Me4H)3La] and [(C5Me5)2La][BPh4] are viable starting materials and reduce dinitrogen in the presence of KC8 to give [N[DOUBLE BOND]N]2− containing structures (see picture).

    23. Biotransformations in Low-Boiling Hydrofluorocarbon Solvents (pages 5519–5523)

      Simon Saul, Stuart Corr and Jason Micklefield

      Version of Record online: 13 OCT 2004 | DOI: 10.1002/anie.200460082

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      Solvent solutions: Low-boiling hydrofluorocarbons (see examples) are excellent solvents for lipase-catalyzed reactions and ideal replacements for conventional organic solvents and supercritical fluids as media for nonaqueous biotransformations. Notably increased rates, yields, and enantioselectivities were observed with the model kinetic resolution of (±)-1-phenylethanol and the desymmetrization of meso-2-cyclopentene-1,4-diol.

    24. Methacrylate Polymerization using a Dinuclear Zirconocene Initiator: A New Approach for the Controlled Synthesis of Methacrylate Polymers (pages 5523–5526)

      Goran Stojcevic, Hoon Kim, Nicholas J. Taylor, Todd B. Marder and Scott Collins

      Version of Record online: 13 OCT 2004 | DOI: 10.1002/anie.200460785

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      Tacticity tactics: The dinuclear bis(enolate) complex 1, when activated with [PhNHMe2][B(C6F5)4], is an effective initiator of living methyl methacrylate polymerization, providing partially syndiotactic poly(methyl methacrylate) with a narrow molecular-weight distribution. Mechanistic studies showed that 1 is transformed into a cationic enolate complex and this dinuclear species is involved in propagation.

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      Integrating Single-Wall Carbon Nanotubes into Donor–Acceptor Nanohybrids (pages 5526–5530)

      Dirk M. Guldi, G. M. A. Rahman, Norbert Jux, Nikos Tagmatarchis and Maurizio Prato

      Version of Record online: 13 OCT 2004 | DOI: 10.1002/anie.200461217

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      A tube for electrons: Through π–π and Coulomb interactions, a complex is obtained between carbon nanotubes grafted with pyrene+ (1) and the zinc porphyrin complex 2. Photoexcitation of the resulting donor–acceptor assembly is followed by a rapid and efficient charge separation to generate a charge-separated state that lives for microseconds.

    26. Ansa-Cycloheptatrienyl–Cyclopentadienyl Complexes (pages 5530–5534)

      Matthias Tamm, Andreas Kunst, Thomas Bannenberg, Eberhardt Herdtweck, Peter Sirsch, Cornelis J. Elsevier and Jan M. Ernsting

      Version of Record online: 13 OCT 2004 | DOI: 10.1002/anie.200460538

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      Introduction of the Me2Si bridge and distortion of the sandwich structure facilitate the interaction of the 16-electron ansa-complex (see picture; blue Ti, yellow Si, gray C) with σ-donor/π-acceptor ligands, such as CO or isocyanides, which allows the electronic structure of this strongly bent first ansa-cycloheptatrienyl–cyclopentadienyl transition-metal complex to be studied. The complex is prepared from [(η-C7H7)Ti(η-C5H5)].

    27. Germacarboxylic Acid: An Organic-Acid Analogue Based on a Heavier Group 14 Element (pages 5534–5536)

      Leslie W. Pineda, Vojtech Jancik, Herbert W. Roesky and Regine Herbst-Irmer

      Version of Record online: 13 OCT 2004 | DOI: 10.1002/anie.200460872

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      First impressions: An oxidative addition between [LGeOH] and elemental sulfur leads to the isolation of the first germacarboxylic acid [LGe(S)OH] (L=HC{(CMe)(2,6-iPr2C6H3N)}2; see picture). In the solid state [LGe(S)OH] displays preferential of the thiono-form and formation of hydrogen-bond arrays generates dimers. This germacarboxylic acid shows how the heavier congeners of Group 14 can mimic well know organic functional groups.

    28. Molecular Gyroscopes: {Fe(CO)3} and {Fe(CO)2(NO)}+ Rotators Encased in Three-Spoke Stators; Facile Assembly by Alkene Metatheses (pages 5537–5540)

      Takanori Shima, Frank Hampel and J. A. Gladysz

      Version of Record online: 27 AUG 2004 | DOI: 10.1002/anie.200460534

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      Complexes to toy with: Ring-closing metathesis of the bis(phosphane) complexes 1 ac (n=4–6) followed by hydrogenation gives the “molecular gyroscopes” 2 ac. The crystal structure of 2 c and the NMR data for the analogous {Fe(CO)2(NO)}+ complex indicate facile rotation of the {Fe(CO)2(L)}m+ moieties within the P(CH2)14P spokes. Shorter bridges as in 2 a lock the rotators.

    29. Ca[Si2O2N2]—A Novel Layer Silicate (pages 5540–5542)

      Henning A. Höppe, Florian Stadler, Oliver Oeckler and Wolfgang Schnick

      Version of Record online: 13 OCT 2004 | DOI: 10.1002/anie.200460098

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      A corrugated [Si2O2N2]2−layer anion, which is constructed of dreier rings, forms the basis of the silicate Ca[Si2O2N2] (see picture). The unusual structure results from the fact that every N atom—unlike the O atoms in oxosilicates—links three neighboring Si tetrahedron centers within the layers, whereas all the O atoms are exclusively bonded terminally to the Si atoms.

    30. Hydroamination/Cyclization of Aminoalkenes Using Cationic Zirconocene and Titanocene Catalysts (pages 5542–5546)

      Denis V. Gribkov and Kai C. Hultzsch

      Version of Record online: 13 OCT 2004 | DOI: 10.1002/anie.200460880

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      Alternative catalysts: The hydroamination of nonactivated double bonds has been the domain of rare-earth-metal catalysts. Now alkyl zirconocene and titanocene cations, which are readily prepared from commercially available precursors, are shown to be active catalysts in the hydroamination/cyclization of secondary aminoalkenes to give tertiary pyrrolidines and piperidines.

    31. Thermodynamically Controlled Self-Assembly of Two-Dimensional Oxide Nanostructures (pages 5546–5549)

      Johannes Schoiswohl, Svetlozar Surnev, Michael Sock, Michael G. Ramsey, Georg Kresse and Falko P. Netzer

      Version of Record online: 13 OCT 2004 | DOI: 10.1002/anie.200460150

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      Seeing stars: surface-supported nanoscale oxide materials are prepared by a chemical driven self-assembly process involving a novel star-shaped [V6O12] cluster molecules (see STM image). The [V6O12] clusters are not stable units in the gas phase but form spontaneously on a metal surface. On the surface the oxide building blocks can be organized into different 2D oxide structures by adjustment of the oxygen chemical potential.

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      Preview: Angew. Chem. Int. Ed. 41/2004 (page 5553)

      Version of Record online: 13 OCT 2004 | DOI: 10.1002/anie.200490145