Chemistry - A European Journal

Cover image for Vol. 9 Issue 20

October 17, 2003

Volume 9, Issue 20

Pages 4841–5164

    1. Cover Picture: Aromaticity and Electron Affinity of Carbok-[3]radialenes, k=0, 1, 2 (Chem. Eur. J. 20/2003) (page 4841)

      Christine Lepetit, Mogens Brøndsted Nielsen, François Diederich and Remi Chauvin

      Article first published online: 10 OCT 2003 | DOI: 10.1002/chem.200390253

    2. Structure and Reactivity of Ziegler–Natta Catalyst Intermediates (pages 4854–4860)

      Piotr Sobota

      Article first published online: 19 SEP 2003 | DOI: 10.1002/chem.200304735

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      Findings from unexpected reactions were often observed from our attempts to prepare new polynuclear procatalysts and to understand the chemistry of their formation. These could then be applied to syntheses of well-defined heterogeneous olefin polymerization catalysts. We have shown that in the reaction of [Mg4(thffo)8] with AlMe3 the magnesium–methylalumoxane [Al3Mg(μ3-O)(thffo)3(Me)6] (shown here) is formed which is a good methylation agent and support for metallocenes.

    3. Formation of Quaternary Stereocenters by Copper-Catalyzed Michael Reactions with L-Valine Amides as Auxiliaries (pages 4862–4867)

      Jens Christoffers

      Article first published online: 19 SEP 2003 | DOI: 10.1002/chem.200304937

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      The combination of choice in Michael reactions for constructing quaternary stereocenters with excellent selectivities at ambient temperature is copper(II) salts and L-valine amides.

    4. “Janus” Supermolecular Liquid Crystals—Giant Molecules with Hemispherical Architectures (pages 4869–4877)

      Isabel M. Saez and John W. Goodby

      Article first published online: 19 SEP 2003 | DOI: 10.1002/chem.200305100

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      Two chemically different faces! Giant “Janus” liquid crystals are supermolecular materials designed to have two chemically different faces, one chiral and the other achiral (see diagram). The syntheses and physical properties of these materials, which self-organise like proteins, are described.

    5. Photochromism of Diarylethenes Linked by Hydrogen Bonds in the Single-Crystalline Phase (pages 4878–4886)

      Satoshi Yamamoto, Kenji Matsuda and Masahiro Irie

      Article first published online: 19 SEP 2003 | DOI: 10.1002/chem.200304947

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      Hydrogen-bonded linear chain structures of photochromic diarylethenes have been prepared (see picture). The diarylethenes show photochromism in solution as well as in the single-crystalline state. This photochromic behavior has been shown to be dependent on the supramolecular structure.

    6. Stereoselective Aldol Additions Catalyzed by Dihydroxyacetone Phosphate-Dependent Aldolases in Emulsion Systems: Preparation and Structural Characterization of Linear and Cyclic Iminopolyols from Aminoaldehydes (pages 4887–4899)

      Laia Espelt, Teodor Parella, Jordi Bujons, Conxita Solans, Jesús Joglar, Antonio Delgado and Pere Clapés

      Article first published online: 19 SEP 2003 | DOI: 10.1002/chem.200304966

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      Emulsion systems are useful reaction media for enzyme-catalyzed aldol reactions. The L-fructose-1,6-bisphosphate aldolase (RAMA) and recombinant L-rhamnulose-1-phosphate aldolase from E. coli (RhuA) catalyzed stereoselective aldol additions between DHAP and N-Cbz aminoaldehydes (see scheme). A description of the reactivity of the aldolases in emulsions and a detailed stereochemical analysis of both linear and cyclic iminocylitols is presented.

    7. The Effect of Hydrogen Bonding on Allylic Alkylation and Isomerization Reactions in Ionic Liquids (pages 4900–4906)

      James Ross and Jianliang Xiao

      Article first published online: 10 OCT 2003 | DOI: 10.1002/chem.200304895

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      Allylic alkylation is considerably slowed down when performed in an imidazolium ionic liquid due to trapping of in situ generated base by hydrogen bonding with the solvent cations (see scheme). This phenomenon can be exploited to suppress unwanted allylic isomerization depending on the choice of catalyst.

    8. Efficient Transport of Saccharides through a Liquid Membrane Mediated by a Cyclodextrin Dimer (pages 4907–4910)

      Hiroshi Ikeda, Akiyuki Matsuhisa and Akihiko Ueno

      Article first published online: 10 OCT 2003 | DOI: 10.1002/chem.200304816

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      A new efficient transport system for saccharides through a liquid membrane was constructed. The transport rates of saccharides were accelerated by a cyclodextrin dimer such as depicted, whereas a cyclodextrin monomer was not effective for the transport of saccharides.

    9. The Hetero-Diels–Alder Addition of Sulfur Dioxide: The Pseudo-Chair Conformation of a 4,5-Dialkylsultine (pages 4911–4915)

      Dean Markovic, Elena Roversi, Rosario Scoppelliti, Pierre Vogel, Rubén Meana and José A. Sordo

      Article first published online: 10 OCT 2003 | DOI: 10.1002/chem.200304932

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      Even unsubstituted butadiene adds to sulfur dioxide in the hetero-Diels–Alder mode at low temperature (see scheme). The first example of a non-fluorinated sultine has been crystallized and analyzed by X-ray diffraction. The data confirmed the prediction based on quantum chemical calculations.

    10. Structure and Reactivity of Homoleptic Samarium(II) and Thulium(II) Phospholyl Complexes (pages 4916–4923)

      Daniela Turcitu, François Nief and Louis Ricard

      Article first published online: 10 OCT 2003 | DOI: 10.1002/chem.200305107

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      The first stable homoleptic TmIIcomplex (see picture) was isolated by using a bulky phospholyl ligand. This compound and analogous samarium(II) phospholyl complexes display remarkably low reactivity. Bulky phospholyl ligands thus are promising for the stabilisation of other metals in unusually low oxidation states.

    11. A New Family of Insulin-Mimetic Vanadium Complexes Derived from 5-Carboalkoxypicolinates (pages 4924–4935)

      Jessica Gätjens, Beate Meier, Tamás Kiss, Eszter M. Nagy, Peter Buglyó, Hiromu Sakurai, Kenji Kawabe and Dieter Rehder

      Article first published online: 10 OCT 2003 | DOI: 10.1002/chem.200305019

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      The 5-carboalkoxypicolinato complexes [VO(H2O)(5 ROpic)2] (R=Me, Et, iPr, sBu) have been characterised by X-ray structure analysis (see picture), solution speciation in the presence of low molecular mass biogenic ligands, insulin-mimetic behaviour (stimulation of glucose uptake by modified fibroblasts; inhibition of fatty acid release by adipocytes), and uptake by fibroblasts. The most effective complex is the methyl ester, possibly because of a balanced lipo-/hydrophilicity.

    12. Characterisation of Four New Two-Dimensional Lithium Beryllofluoro-Layered Compounds (pages 4936–4942)

      Lee A. Gerrard and Mark T. Weller

      Article first published online: 10 OCT 2003 | DOI: 10.1002/chem.200304991

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      By using different amine templates, two 2D lithium beryllofluoride sheets (see picture), of the stoichiometry [LiBeF4], have been synthesised. Both types of material contain terminal, doubly and triply bridged anions that link BeF4 and LiF4 through solely corner-sharing tetrahedra.

    13. Unexpected Reaction Pathways in the Reaction of Alkoxyalkynylchromium(0) Carbenes with Aromatic Dinucleophiles (pages 4943–4953)

      Miguel A. Sierra, María J. Mancheño, Juan C. del Amo, Israel Fernández and Mar Gómez-Gallego

      Article first published online: 10 OCT 2003 | DOI: 10.1002/chem.200305138

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      Thermal- or SiO2-induced reactions of the Michael adducts of 1,2-aromatic dinucleophiles and alkynylchromium(0) carbene complexes form different products depending on the nature of the dinucleophile (see scheme). The use of 1,8-diaminonaphthalene promotes an unprecedented “retro-Aumann” reaction to form perimidines in good yields under mild reaction conditions.

    14. Hydrogenation versus Transfer Hydrogenation of Ketones: Two Established Ruthenium Systems Catalyze Both (pages 4954–4967)

      Valentin Rautenstrauch, Xuân Hoang-Cong, Raphaël Churlaud, Kamaluddin Abdur-Rashid and Robert H. Morris

      Article first published online: 10 OCT 2003 | DOI: 10.1002/chem.200304884

      An RuIIcatalyst redox pair that works in the enantioselective hydrogenation of ketones in iPrOH is likely to also work in the transfer hydrogenation with iPrOH as the reducing agent, because of the principle of microscopic reversibility, provided the pair is stable in the absence of H2. Conversely, a RuII catalyst redox pair that works in transfer hydrogenation should also work in hydrogenation if the reduced form H-Ru-N-H of the redox pair can be regenerated by addition of H2 to the dehydro form Ru[DOUBLE BOND]N rather than by the backward reaction with iPrOH.

    15. Modulating Charge-Transfer Interactions in Topologically Different Porphyrin–C60 Dyads (pages 4968–4979)

      Dirk M. Guldi, Andreas Hirsch, Michael Scheloske, Elke Dietel, Alessandro Troisi, Francesco Zerbetto and Maurizio Prato

      Article first published online: 10 OCT 2003 | DOI: 10.1002/chem.200304995

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      Control over the interchromophore separation, their angular relationship, and the spatial overlap of their electronic clouds in several ZnPC60 dyads is used to modulate the rates of intramolecular electron transfer (see figure).

    16. Systematic Construction of a Monotetrahydrofuran-Ring Library in Annonaceous Acetogenins by Asymmetric Alkynylation and Stereodivergent Tetrahydrofuran-Ring Formation (pages 4980–4990)

      Naoto Kojima, Naoyoshi Maezaki, Hiroaki Tominaga, Mikito Asai, Minori Yanai and Tetsuaki Tanaka

      Article first published online: 10 OCT 2003 | DOI: 10.1002/chem.200305185

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      Running rings around acetogenins: All eight diastereomers of the monoTHF-ring cores of annonaceous acetogenins have been synthesized by utilization of asymmetric alkynylation and stereodivergent one-pot THF-ring formation (see scheme). In all cases, the asymmetric alkynylation proceeded with very high diastereoselectivity to give the optically pure THF-ring cores from a common α-oxyaldehyde.

    17. Fabrication of Self-Supported Patterns of Aligned β-FeOOH Nanowires by a Low-Temperature Solution Reaction (pages 4991–4996)

      Yujie Xiong, Yi Xie, Shaowei Chen and Zhengquan Li

      Article first published online: 10 OCT 2003 | DOI: 10.1002/chem.200305118

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      Carpets of nanowires: Self-supported patterns of oriented alignment of β-FeOOH nanowires (shown here) with a diameter of 40 nm and length of 6 μm are fabricated by a simple solution reaction from the complex of [Fe(phen)3]2+ at 60 °C. The β-FeOOH nanowire alignment is expected to have potential applications in lithium batteries and semiconductor industry.

    18. The Effect of Ring Nitrogen Atoms on the Homolytic Reactivity of Phenolic Compounds: Understanding the Radical-Scavenging Ability of 5-Pyrimidinols (pages 4997–5010)

      Luca Valgimigli, Giovanni Brigati, Gian Franco Pedulli, Gino A. DiLabio, Marina Mastragostino, Catia Arbizzani and Derek A. Pratt

      Article first published online: 10 OCT 2003 | DOI: 10.1002/chem.200304960

      Hydrogen-atom abstraction: Six substituted 5-pyrimidinols were synthesized, and the thermochemistry and kinetics of their reactions with free radicals were studied and compared to those of equivalently substituted phenols. To assess their potential as hydrogen-atom donors to free radicals, their O[BOND]H bond-dissociation enthalpies (BDEs) were measured by means of the radical equilibration electron paramagnetic resonance technique.

    19. Synthesis of a Hexagonal Nanosized Macrocyclic Fluorophore with Integrated Endotopic Terpyridine Metal-Chelation Sites (pages 5011–5022)

      Paul N. W. Baxter

      Article first published online: 10 OCT 2003 | DOI: 10.1002/chem.200304786

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      Sterically encumbered bis(terpyridine) nanophane 1 has been successfully prepared using a synthesis which culminates in a surprisingly efficient macrocyclisation step. The triisopropylsilyl-protected alkynes that help solubilise the structure should also allow post-synthetic modification and modulation of its materials properties. Macrocycle 1 is also a strongly fluorescent chromophore, and may thus find many potential applications such as a new class of nanosized fluorescence sensors for biological substrates and metal ions.

    20. The Evolution of [{Ph2P(CH2)nPPh2}Pt(μ-S)2Pt{Ph2P(CH2)nPPh2}] (n=2, 3) Metalloligands in Protic Acids: A Cascade of Sequential Reactions (pages 5023–5035)

      Rubén Mas-Ballesté, Gabriel Aullón, Paul A. Champkin, William Clegg, Claire Mégret, Pilar González-Duarte and Agustí Lledós

      Article first published online: 10 OCT 2003 | DOI: 10.1002/chem.200304983

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      While the richness of the chemistry of [Pt2(μ-S)2(P∩P)2] metalloligands was not unexpected, their tremendous versatility in the presence of protic acids has been evidenced by the whole set of reactions ensuing protonation of the {Pt2S2} core (see partial scheme).

    21. Synthesis and Supramolecular Properties of Trimethylene-Bridged Clips (pages 5036–5047)

      Frank-Gerrit Klärner, Matthias Lobert, Ulf Naatz, Heinz Bandmann and Roland Boese

      Article first published online: 10 OCT 2003 | DOI: 10.1002/chem.200304919

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      Repetitive stereoselective Diels–Alder reactions have been used to synthesize novel trimethylene-bridged clips (see scheme and structure). They serve as receptors for a variety of electron-deficient aromatic substrates.

    22. Chirality Transfer from Guest Chiral Metal Complexes to Inorganic Framework: The Role of Hydrogen Bonding (pages 5048–5055)

      Yu Wang, Jihong Yu, Yi Li, Zhan Shi and Ruren Xu

      Article first published online: 10 OCT 2003 | DOI: 10.1002/chem.200305040

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      The structure elucidation of a new zinc phosphate [CoII(en)3][Zn4(H2PO4)3(HPO4)2(PO4)(H2O)2], as well as several chiral cobalt complex templated metal phosphates, reveals that the chiral complex template can transfer its chirality to the inorganic host. Hydrogen bonding is responsible for a stereo-specificity between the template and the host. The picture shows the hydrogen bonds between the complex templates and nearby chiral structural motifs in [CoII(en)3][Zn4(H2PO4)3(HPO4)2(PO4)(H2O)2].

    23. Aromaticity and Electron Affinity of Carbok-[3]radialenes, k=0, 1, 2 (pages 5056–5066)

      Christine Lepetit, Mogens Brøndsted Nielsen, François Diederich and Remi Chauvin

      Article first published online: 10 OCT 2003 | DOI: 10.1002/chem.200305070

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      Is the exceptional ability of doubly expanded [3]- and [4]radialenes to accommodate electrons promoted by aromaticity enhancements? This hypothesis is theoretically analyzed here by evaluating the variation of aromaticity with endocyclic and peripheral carbomeric expansion of [3]radialene (1) and its anions. Structural aromaticity was measured through the average bond length and by the corresponding bond-length equalization parameter σ(d). Magnetic aromaticity was measured by Schleyer's NICS values at the center of the rings. By the relative variation of NICS and σ(d), two classes of species could be distinguished; this distinction was related to the degeneracy scheme of the frontier orbitals of the neutral compound. Electron-localization-function analysis allowed for a weighting of relevant resonance forms, which was validated by comparison with AIM spin density.

    24. Tailoring the Catalytic Performance of Sol–Gel-Encapsulated Tetra-n-propylammonium Perruthenate (TPAP) in Aerobic Oxidation of Alcohols (pages 5067–5073)

      Rosaria Ciriminna and Mario Pagliaro

      Article first published online: 10 OCT 2003 | DOI: 10.1002/chem.200305146

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      Sol–gel encapsulation of TPAP (tetra-n-propylammonium perruthenate) in hydrophobic silica matrix affords highly efficient, versatile catalysts, which are considerably more active than unsupported TPAP in mediating the aerobic oxidation of different alcohols. A thorough examination of the polycondensation conditions is crucial in promoting the materials' reactivities. An SEM micrograph of a typical TPAP-doped ormosil is shown here.

    25. Trivalent Boron as an Acceptor in Donor–π–Acceptor-Type Compounds for Single- and Two-Photon Excited Fluorescence (pages 5074–5084)

      Zhi-qiang Liu, Qi Fang, Dong Wang, Du-xia Cao, Gang Xue, Wen-tao Yu and Hong Lei

      Article first published online: 10 OCT 2003 | DOI: 10.1002/chem.200304833

      Fluorescent boron compounds: The synthesis, structure, and fluorescence properties of a series of new donor–π–acceptor (D–π–A) type compounds, with a trivalent boron, protected by two mesityl groups, as acceptor, and with various typical donors and different π-conjugated bridges, are reported.

    26. Bisporphyrins with Bischlorin Features Obtained by Direct Anodic Coupling of Porphyrins (pages 5085–5096)

      Laurent Ruhlmann, Maurice Gross and Alain Giraudeau

      Article first published online: 10 OCT 2003 | DOI: 10.1002/chem.200304924

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      Dimeric porphyrins with one 1,2-(diphenylphosphonium)benzene as a spacer (1) were obtained selectively in a direct one-pot electrochemical oxidation of zinc mesotetraphenylporphyrin in appropriate conditions. UV-Vis and 1H NMR spectroscopic data and electrochemical behavior indicate that the positive charges carried by the two phosphonium ions are in part delocalized onto the porphyrins, this gives an unexpected bisporphyrin with bischlorin features.

    27. Transition-Metal Complexes as Enzyme-Like Reagents for Protein Cleavage: Complex cis-[Pt(en)(H2O)2]2+ as a New Methionine-Specific Protease (pages 5097–5106)

      Nebojša M. Milović, Laura-M. Dutcǎ and Nenad M. Kostić

      Article first published online: 10 OCT 2003 | DOI: 10.1002/chem.200304772

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      The complex cis-[Pt(en)(H2O)2]2+binds to the methionine side-chains in peptides and proteins, and promotes hydrolytic cleavage of every peptide bond following a methionine residue. The new PtII reagent has the same selectivity as cyanogen bromide, and cleaves even Met[BOND]Pro bonds; however, it requires milder reaction conditions. A small turnover in cleavage of a peptide likens the PtII reagent to an artificial enzyme (see picture).

    28. Discrimination of Peptides by Using a Molecularly Imprinted Piezoelectric Biosensor (pages 5107–5110)

      Chung-Yin Lin, Dar-Fu Tai and Tzong-Zeng Wu

      Article first published online: 10 OCT 2003 | DOI: 10.1002/chem.200304952

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      A new cross-linking monomer, (N-Acr-L-Cys-NHBn)2, has been synthesized and copolymerized with other monomers to form molecularly imprinted membrane. Based on this approach, we succeeded in developing novel chips for peptide detection by using a quartz crystal microbalance (see diagram).

    29. Remarkable Reactions of Cyclooctatetraene Diiron-Bridging Carbyne Complexes with Amino and Amido Compounds: Nucleophilic Addition to and Breaking of the Cyclooctatetraene Ring (pages 5111–5122)

      Shu Zhang, Qiang Xu, Jie Sun and Jiabi Chen

      Article first published online: 10 OCT 2003 | DOI: 10.1002/chem.200305130

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      Unprecendented breaking of the COT ring to give ring-opened COT bridging carbene complexes 1 and formation of novel N-nucleophilic-addition products 2 and COT-coordinated iron–carbene complexes 3 occur when cationic, diiron-bridging carbyne complexes [Fe2(μ-CAr)(CO)48-C8H8)]BF4 are treated with LiN(C6H5)2, dialkylamines, and arylamines, respectively, in THF at low temperature. Structurally characterized examples of 13 are presented. COT=1,3,5,7-cyclooctatetraene.

    30. Effect of Peripheral Substitution on the Electronic Absorption and Fluorescence Spectra of Metal-Free and Zinc Phthalocyanines (pages 5123–5134)

      Nagao Kobayashi, Hiroshi Ogata, Naokazu Nonaka and Eugene A. Luk'yanets

      Article first published online: 10 OCT 2003 | DOI: 10.1002/chem.200304834

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      Substituent effects on the electronic absorption and fluorescence spectra of 35 phthalocyanines (Pcs) were examined. When electron-releasing groups are bound to four α-benzo positions of the Pc skeleton, the B and Q bands shift to longer wavelength. The relative effect of introducing the same electron-releasing groups at the other four α positions amounts to about 1.6–2.0. Introduction of electron-releasing groups in the β-benzo positions of the Pc skeleton generally shifts the Q band to shorter wavelength. The effect of electron-withdrawing groups is exactly the opposite with respect to the α and β positions. The substitution patterns of the Pcs are shown here

    31. The Open-Chain Trioxide CF3OC(O)OOOC(O)OCF3 (pages 5135–5141)

      Stefan von Ahsen, Plácido García, Helge Willner, Maximiliano Burgos Paci and Gustavo A. Argüello

      Article first published online: 10 OCT 2003 | DOI: 10.1002/chem.200304942

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      Improved yields of the open-chain trioxide CF3OC(O)OOOC(O)OCF3 as the main product have been obtained by UV photolytic reaction of CF3C(O)OC(O)CF3 in an excess of CO and O2 at −40 °C. Although the trioxide decays within minutes at room temperature, it has been fully characterised spectroscopically. The most stable rotamer, according to DFT quantum chemical calculations, is depicted here.

    32. Synthetic and Structural Studies of Cobalt–Pivalate Complexes (pages 5142–5161)

      Guillem Aromí, Andrei S. Batsanov, Paul Christian, Madeleine Helliwell, Andrew Parkin, Simon Parsons, Andrew A. Smith, Grigore A. Timco and Richard E. P. Winpenny

      Article first published online: 10 OCT 2003 | DOI: 10.1002/chem.200304993

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      The seemingly simple reaction system involving cobalt ions and pivalate as the ligand is immensely complex. Reaction with protic solvents produces heterocubanes and butterflies, while oxidation in aprotic solvents generates a range of cages based on cubanes, including a tetradecanuclear cage, the core of which is shown.

    33. Preview: Chem. Eur. J. 20/2003 (page 5164)

      Article first published online: 10 OCT 2003 | DOI: 10.1002/chem.200390255