Chemistry - A European Journal

Cover image for Vol. 9 Issue 18

September 22, 2003

Volume 9, Issue 18

Pages 4273–4572

    1. Cover Picture: Assembly of Hybrid Organic–Organometallic Materials through Mechanochemical Acid–Base Reactions (Chem. Eur. J. 18/2003) (page 4273)

      Dario Braga, Lucia Maini, Marco Polito, Laurent Mirolo and Fabrizia Grepioni

      Version of Record online: 11 SEP 2003 | DOI: 10.1002/chem.200390246

    2. Multicomponent Coupling Reactions for Organic Synthesis: Chemoselective Reactions with Amide–Aldehyde Mixtures (pages 4286–4294)

      Axel Jacobi von Wangelin, Helfried Neumann, Dirk Gördes, Stefan Klaus, Dirk Strübing and Matthias Beller

      Version of Record online: 1 SEP 2003 | DOI: 10.1002/chem.200305048

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      A highly prolific source of diverse reactants for irreversible follow-up reactions is provided by the acid-catalyzed condensation chemistry of simple amides and aldehydes. These have successfully been employed in multicomponent syntheses of N-acyl α-amino acids (via palladium-catalyzed amidocarbonylation) and various cyclohexene, cyclohexadiene, and benzene derivatives (via the amide–aldehyde–dienophile (AAD) reaction) as per the scheme.

    3. C[BOND]C versus C[BOND]H Activation and versus Agostic C[BOND]C Interaction Controlled by Electron Density at the Metal Center (pages 4295–4300)

      Mark Gandelman, Linda J. W. Shimon and David Milstein

      Version of Record online: 1 SEP 2003 | DOI: 10.1002/chem.200304972

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      The influence of π-accepting ligands on the selectivity of C[BOND]C versus C[BOND]H activation was studied and a remarkable degree of control over C[BOND]C versus C[BOND]H bond activation and versus formation of an agostic C[BOND]C complex was demonstrated by choice of cationic Rh(CO)n-based (n=0, 1, 2) precursors (see scheme). Moreover, conversion of the C[BOND]C-activated and agostic C[BOND]C complexes into the C[BOND]H activated one can be achieved by simple reaction with CO, by an unprecedented sequence of 1,2-methyl shift, agostic interaction, and C[BOND]H activation processes.

    4. Progressive Studies on the Novel Samarium-Catalyzed Diastereoselective Tandem Semipinacol Rearrangement/Tishchenko Reduction of Secondary α-Hydroxy Epoxides (pages 4301–4310)

      Chun-An Fan, Xiang-Dong Hu, Yong-Qiang Tu, Bao-Min Wang and Zhen-Lei Song

      Version of Record online: 1 SEP 2003 | DOI: 10.1002/chem.200304782

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      A novel tandem reaction of secondary α-hydroxy epoxides is promoted by substoichiometric amounts of SmI2 (see scheme). Interestingly, the reaction is influenced by significant steric and electronic effects of the reductant aldehydes. The sequence could also be developed to efficiently construct 2-quaternary 1,3-diol units with an hydroxymethyl group attached to the diastereogenic quaternary carbon center.

    5. Relevance of the Electronegativity of Boron in η5-Coordinating Ligands: Regioselective Monoalkylation and Monoarylation in Cobaltabisdicarbollide [3,3′-Co(1,2-C2B9H11)2] Clusters (pages 4311–4323)

      Isabel Rojo, Francesc Teixidor, Clara Viñas, Raikko Kivekäs and Reijo Sillanpää

      Version of Record online: 1 SEP 2003 | DOI: 10.1002/chem.200304970

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      Monoalkyl and monoaryl cobaltabisdicarbollide derivatives, such as depicted, have been successfully synthesized from Cs[8-I-3,3′-Co(1,2-C2B9H10)(1′,2′-C2B9H11)] by cross-coupling reactions between a B[BOND]I fragment and an appropriate Grignard reagent in the presence of a Pd catalyst and CuI. The derivates allow the influence of boron in metallocene-type ligands and the effect of alkyl and aryl substituents on boron in anionic clusters to be studied.

    6. Synthesis of a New Polyfluorinated Vinylogue of Tetrathiafulvalene through 1,3-Dipolar Cycloaddition of Ethyl β-Bromoperfluorodithiocrotonate with Dimethyl Acetylenedicarboxylate (pages 4324–4329)

      Vadim M. Timoshenko, Jean-Philippe Bouillon, Alexander N. Chernega, Yuriy G. Shermolovich and Charles Portella

      Version of Record online: 1 SEP 2003 | DOI: 10.1002/chem.200304839

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      A new type of vinylogue of tetrathiafulvalene is formed from the reaction of the ethyl ester of β-bromo perfluorodithiocrotonic acid with DMAD; this leads to the formation of 1,4-difluoro-2,3-bis(trifluoromethyl)-but-2-ene-1,4-diylidene-2,2′-bis(4′,5′-dicarbomethoxy-1′,3′-dithiole) (see scheme). The thermal transformations of this compound leads, depending on the temperature, to the formation of the cyclization products: 11,14-difluoro-2,3,8,9-tetra(carbomethoxy)-12,13-bis(trifluoromethyl)-1,4,7,10-tetrathiadispiro[]tetradeca-2,8,11,13-tetraene or 5,8-difluoro-6,7-bis(trifluoromethyl)-2,3-bis(carboxymethyl)-1,4-benzodithiine.

    7. Enhanced Li+ Binding Energies in Alkylbenzene Derivatives: The Scorpion Effect (pages 4330–4338)

      Otilia Mó, Manuel Yáñez, Jean-François Gal, Pierre-Charles Maria and Michèle Decouzon

      Version of Record online: 11 SEP 2003 | DOI: 10.1002/chem.200304863

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      Does an alkyl group “chelate” an alkali metal cation? In the gas phase, alkali metal cations interact quite strongly with aromatic rings. In alkyl-substituted benzenes, the lithium cation bonding is enhanced by a secondary interaction with the alkyl chain, if it is sufficiently long and flexible, as illustrated. The extra stabilization provided by the flexible alkyl chain polarized by the charge on Li+ is named the “scorpion effect”.

    8. Gold Catalysis: Efficient Synthesis and Structural Assignment of Jungianol and epi-Jungianol (pages 4339–4345)

      A. Stephen K. Hashmi, Li Ding, Jan W. Bats, Peter Fischer and Wolfgang Frey

      Version of Record online: 11 SEP 2003 | DOI: 10.1002/chem.200305092

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      Gold-catalyzed phenol synthesis (see scheme) was the key step in opening up a new short route to the sesquiterpene alcohols epi-jungianol and jungianol starting from 2-methylfuran and crotonaldehyde. Not a single protective group was needed in the entire six-step synthesis.

    9. Mechanistic Study of Bu2SnCl2-Mediated Ring-Opening Polymerization of ε-Caprolactone by Multinuclear NMR Spectroscopy (pages 4346–4352)

      Gaëlle Deshayes, Frédéric A. G. Mercier, Philippe Degée, Ingrid Verbruggen, Monique Biesemans, Rudolph Willem and Philippe Dubois

      Version of Record online: 11 SEP 2003 | DOI: 10.1002/chem.200304769

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      Besides the well-known efficiency of some covalent metal alkoxides to initiate the ring-opening polymerization of cyclic esters, advanced 119Sn NMR investigations prompt us to conclude that controlled polymerization of ε-caprolactone can also be achieved by using tin(IV) chloride derivatives, such as Bu2SnCl2, which behaves as a catalyst, while n-propanol acts as initiator (see scheme).

    10. Scope, Kinetics, and Mechanistic Aspects of Aerobic Oxidations Catalyzed by Ruthenium Supported on Alumina (pages 4353–4361)

      Kazuya Yamaguchi and Noritaka Mizuno

      Version of Record online: 11 SEP 2003 | DOI: 10.1002/chem.200304916

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      By using molecular oxygen or air and the easily prepared inexpensive supported ruthenium catalyst (Ru/Al2O3), a broad range of alcohols can be converted into the corresponding carbonyl compounds in excellent yields (see scheme). Furthermore, Ru/Al2O3 is effective for amine oxidations. The catalyst can be reused without loss of catalytic activity and selectivity for the oxidation. Kinetic and mechanistic investigations show that the Ru/Al2O3-catalyzed aerobic alcohol oxidation proceeds through an alcoholate/β-hydride elimination mechanism and that the β-hydride elimination is a rate-limiting step.

    11. Assembly of Hybrid Organic–Organometallic Materials through Mechanochemical Acid–Base Reactions (pages 4362–4370)

      Dario Braga, Lucia Maini, Marco Polito, Laurent Mirolo and Fabrizia Grepioni

      Version of Record online: 11 SEP 2003 | DOI: 10.1002/chem.200305017

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      Grinding the organometallic complex [Fe(η5-C5H4COOH)2] as a solid polycrystalline material with a number of solid bases generates quantitatively the corresponding adducts held together by hydrogen-bonding interactions of the O[BOND]H⋅⋅⋅O, O[BOND]H⋅⋅⋅N, and O⋅⋅⋅H[BOND]N types. Crystallization from methanol in the presence of seeds of the ground sample allows the growth of single crystals of the adducts, whose structure can thus be determined and used in turn to characterize the polycrystalline materials obtained by the grinding process (see scheme).

    12. Synthesis of Five Generations of Redox-Stable Pentamethylamidoferrocenyl Dendrimers and Comparison of Amidoferrocenyl- and Pentamethylamidoferrocenyl Dendrimers as Electrochemical Exoreceptors for the Selective Recognition of H2PO4, HSO4, and Adenosine 5′-Triphosphate (ATP) Anions: Stereoelectronic and Hydrophobic Roles of Cyclopentadienyl Permethylation (pages 4371–4379)

      Marie-Christine Daniel, Jaime Ruiz, Jean-Claude Blais, Nathalie Daro and Didier Astruc

      Version of Record online: 11 SEP 2003 | DOI: 10.1002/chem.200304886

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      Redox-robust pentamethylamidoferrocenyl dendrimers of five generations with hydrophobic pentamethylcyclopentadienyl groups allow more facile recognition and sensing by voltammetric titration of H2PO4 and adenosine 5′-triphosphate anions (ATP2−) compared to their parent cyclopentadienyl analogues, which, however, are more suitable for H2SO4 sensing. The picture shows schematically the interaction of ATP2− with the 3rd generation dendrimer.

    13. Molecular Structure–Activity Relationships for the Oxidation of Organic Compounds Using Mesoporous Silica Catalysts Derivatised with Bis(halogeno)dioxomolybdenum(VI) Complexes (pages 4380–4390)

      Carla D. Nunes, Anabela A. Valente, Martyn Pillinger, João Rocha and Isabel S. Gonçalves

      Version of Record online: 11 SEP 2003 | DOI: 10.1002/chem.200304887

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      The variability in the structures of supported oxomolybdenum catalysts, determined by XAFS spectroscopy, is responsible for the diverse results obtained for the oxidation in their presence of organic compounds with tert-butyl hydroperoxide. Catalyst precursors containing isolated MoVI mononuclear centres (illustrated, left) give the best activities for olefin epoxidation, whereas precursors containing oxo-bridged dinuclear species (right) yield better results for alcohol oxidation.

    14. Crystal and Molecular Structure of Rubidium Peroxodicarbonate Rb2[C2O6] (pages 4391–4395)

      Robert E. Dinnebier, Sascha Vensky and Martin Jansen

      Version of Record online: 11 SEP 2003 | DOI: 10.1002/chem.200304914

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      By using X-ray powder diffraction, we have determined the crystal structure of rubidium peroxodicarbonate, which was synthesized by electrocrystallization at T=257 K. The conformation of the peroxodicarboante anion was found to be planar (C2h symmetry), in contrast to the staggered conformation of the peroxodicarbonate ion in the respective potassium peroxodicarbonate. The different conformation is attributed to packing effects.

    15. Car–Parrinello Molecular Dynamics Study of the Rearrangement of the Valeramide Radical Cation (pages 4396–4404)

      Marija Semialjac, Detlef Schröder and Helmut Schwarz

      Version of Record online: 11 SEP 2003 | DOI: 10.1002/chem.200305127

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      Car–Parrinello molecular dynamics studies of neutral and ionized valeramide are performed with the aim of providing a rationalization of the unusual temperature effect on the dissociation pattern of ionized valeramide as observed in mass spectrometric experiments. Two rationales for the unusual temperature effect were provided by these computations (see scheme).

    16. Catalytic Asymmetric Allylation of Aldehydes and Related Reactions with Bis(((S)-binaphthoxy)(isopropoxy)titanium) Oxide as a μ-Oxo-Type Chiral Lewis Acid (pages 4405–4413)

      Hideo Hanawa, Daisuke Uraguchi, Shunsuke Konishi, Takuya Hashimoto and Keiji Maruoka

      Version of Record online: 11 SEP 2003 | DOI: 10.1002/chem.200305078

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      Designer Lewis acids: A new, μ-oxo type chiral bis-TiIV Lewis acid (S,S)-1 has been successfully designed, and can be utilized for strong activation of aldehyde carbonyls, thereby allowing a new catalytic enantioselective allylation of aldehydes with allyltributyltin.

    17. Chiral Pyrimidine Metallacalixarenes: Synthesis, Structure and Host–Guest Chemistry (pages 4414–4421)

      Elisa Barea, Jorge A. R. Navarro, Juan M. Salas, Miguel Quirós, Michael Willermann and Bernhard Lippert

      Version of Record online: 11 SEP 2003 | DOI: 10.1002/chem.200305183

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      Enantiomerically pure metallacalixarenes with general formula cis-[a2PdL]nn+ (a2=(R,R)- or (S,S)-1,2-diaminocyclohexane) were obtained from cis-[a2Pd(H2O)2]2+ and hydroxypyrimidines LH in aqueous media. The most stable species are the tetranuclear metallacalix[4]arenes (n=4), which were obtained in all cases. Metallacalix[6]arenes were also isolated for LH=4,6-dimethyl-2-hydroxypyrimidine and were shown to undergo conversion to the corresponding metallacalix[4]arenes on heating (see scheme).

    18. Supramolecular Spintronic Devices: Spin Transitions and Magnetostructural Correlations in [Fe4IIL4]8+ [2×2]-Grid-Type Complexes (pages 4422–4429)

      Mario Ruben, Esther Breuning, Jean-Marie Lehn, Vadim Ksenofontov, Franz Renz, Philip Gütlich and Gavin B. M. Vaughan

      Version of Record online: 11 SEP 2003 | DOI: 10.1002/chem.200304933

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      The temperature-triggered spin transition in [FeII4L4]8+ grid-type complexes displays a strong dependence on the substitution pattern of the ligand L (see scheme). In particular the nature of one substitution position has been proven to be decisive for entering into the spin transition regime, while all other positions exert much less influence. The magnetic behavior of the complexes was investigated both in solution and the solid state.

    19. Anthracene–BODIPY Cassettes: Syntheses and Energy Transfer (pages 4430–4441)

      Chi-Wai Wan, Armin Burghart, Jiong Chen, Fredrik Bergström, Lennart B.-Å. Johansson, Matthew F. Wolford, Taeg Gyum Kim, Michael R. Topp, Robin M. Hochstrasser and Kevin Burgess

      Version of Record online: 11 SEP 2003 | DOI: 10.1002/chem.200304754

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      Energy transfer efficiencies in a series of BODIPY–anthracene cassettes, such as those depicted, were measured to gauge how orientation of the acceptor and donor fragments affects the UV/fluorescence properties of these compounds. The data were correlated with observations from electrochemistry and crystallography to explore the molecular characteristics that promote efficient energy transfer.

    20. Asymmetric Synthesis of Oxygen Heterocycles via Pd-Catalyzed Dynamic Kinetic Asymmetric Transformations: Application to Nucleosides (pages 4442–4451)

      Barry M. Trost, Brian S. Brown, Ernest J. McEachern and Oliver Kuhn

      Version of Record online: 11 SEP 2003 | DOI: 10.1002/chem.200304949

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      A palladium-catalyzed dynamic kinetic asymmetric transformation of racemic epoxides with unsaturated alcohols followed by ring-closing metathesis provides a facile entry into five-, six-, and seven-membered-ring oxygen heterocycles. The utility of this methodology is highlighted by a non-carbohydrate-based route to nucleosides and analogues of either enantiomeric series in only five steps (see scheme).

    21. Synthesis, Solid-State Structure, and Bonding Analysis of the Beryllocenes [Be(C5Me4H)2], [Be(C5Me5)2], and [Be(C5Me5)(C5Me4H)] (pages 4452–4461)

      M. del Mar Conejo, Rafael Fernández, Diego del Río, Ernesto Carmona, Angeles Monge, Caridad Ruiz, Antonio M. Márquez and Javier Fernández Sanz

      Version of Record online: 11 SEP 2003 | DOI: 10.1002/chem.200304876

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      A larger covalent character of the bonding in [Be(C5Me5)2] than in the unsubstituted beryllocene [Be(C5H5)2] is revealed by a constrained space orbital variations (CSOV) analysis of the beryllocenes [Be(C5Me4H)2], [Be(C5Me5)2], and [Be(C5Me5)(C5Me4H)] (see diagram), which have been prepared and structurally characterized by X-ray studies at low temperatures.

    22. Synthetic, Reactivity, and Structural Studies on Half-Sandwich (η5-C5Me5)Be and Related Compounds: Halide, Alkyl, and Iminoacyl Derivatives (pages 4462–4471)

      M. del Mar Conejo, Rafael Fernández, Ernesto Carmona, Richard A. Andersen, Enrique Gutiérrez-Puebla and M. Angeles Monge

      Version of Record online: 11 SEP 2003 | DOI: 10.1002/chem.200304877

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      Good synthons for other organoberyllium derivatives, the half-sandwich [(η5-C5Me5)BeX] compounds (X=Cl, Br) can be readily converted to alkyls [(η5-C5Me5)BeR] (see scheme) and the beryllocenes [Be(C5Me5)2] and [Be(C5Me5)(C5Me4H)]. The single reaction of the latter compound with CNXyl allows isolation of three isomeric iminoacyls, thereby providing chemical evidence for both the 1,5-sigmatropic shift and the molecular inversion rearrangements, responsible for the solution dynamic behavior of these metallocenes.

    23. Square-Planar Coordinated Polyanions of Palladium, Platinum, and Gold Stannaborate [SnB11H11]2− Coordination Chemistry (pages 4472–4478)

      Thiemo Marx, Bernd Mosel, Ingo Pantenburg, Siegbert Hagen, Herbert Schulze and Lars Wesemann

      Version of Record online: 11 SEP 2003 | DOI: 10.1002/chem.200304976

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      Tetrasubstituted polyanions of platinum, palladium, and gold [M(SnB11H11)4]x (x=6, M=Pd, Pt; x=5, M=Au; see picture) have been prepared and characterized. The isolated salts are stable to air and moisture and undergo reactions with phosphines to give the related substitution products.

    24. Molecular Scale Speciation of First-Row Transition Elements Bound to Ligneous Material by Using X-ray Absorption Spectroscopy (pages 4479–4484)

      Emmanuel Guillon, Patricia Merdy and Michel Aplincourt

      Version of Record online: 11 SEP 2003 | DOI: 10.1002/chem.200304920

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      Structural elucidation of transition metal–surface systems was carried out by means of EXAFS and XANES spectroscopy. Reliable information at the atomic scale are obtained for Cu, Fe and Mn surface complexes. The picture shows an example of the first derivative copper K-edge XANES spectra of the sample and reference compounds.

    25. Enantioselective Borohydride Reduction Catalyzed by Optically Active Cobalt Complexes (pages 4485–4509)

      Tohru Yamada, Takushi Nagata, Kiyoaki D. Sugi, Kiyotaka Yorozu, Taketo Ikeno, Yuhki Ohtsuka, Daichi Miyazaki and Teruaki Mukaiyama

      Version of Record online: 11 SEP 2003 | DOI: 10.1002/chem.200304794

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      Optically active cobalt complexes catalyzed the highly enantioselective borohydride reduction of aromatic ketones or imines to the corresponding alcohols and amines. Using a precisely premodified borohydride with different alcohols such as tetrahydrofurfuryl alcohol, ethanol and methanol, high enantioselectivities were realized by choosing a suitable β-ketoiminato ligand of the catalyst such as depicted. This reaction was successfully applied to the preparation of optically active 1,3-diols, the stereoselective reduction of diacylferrocenes, and dynamic and/or kinetic resolution of 1,3-dicarbonyl compounds.

    26. Synthesis, Structure and Conformation of Partially-Modified Retro- and Retro-Inverso ψ[NHCH(CF3)]Gly Peptides (pages 4510–4522)

      Alessandro Volonterio, Stefano Bellosta, Fabio Bravin, Maria Cristina Bellucci, Luca Bruché, Giorgio Colombo, Luciana Malpezzi, Stefania Mazzini, Stefano V. Meille, Massimiliano Meli, Carmen Ramírez de Arellano and Matteo Zanda

      Version of Record online: 11 SEP 2003 | DOI: 10.1002/chem.200304881

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      A hybrid between a peptide bond mimic and a proteolytic transition-state analogue describes the role of the [-CH(CF3)NH-] group which replaces the conventional retropeptide bond in a novel class of fluorine-containing peptidomimetics (see picture), whose synthesis, structure and conformational features have been investigated in this work.

    27. Scalar Coupling between the 15N Centres in Methylated 1,8-Diaminonaphthalenes and 1,6-Diazacyclodecane: To What Extent is 2HJNN a Reliable Indicator of N[BOND]N Distance? (pages 4523–4535)

      Guy C. Lloyd-Jones, Jeremy N. Harvey, Paul Hodgson, Martin Murray and Robert L. Woodward

      Version of Record online: 11 SEP 2003 | DOI: 10.1002/chem.200304890

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      Solvation not separation: that is the conclusion drawn from a study of the factors attenuating the magnitude of the experimentally determined scalar coupling (2HJNN) between the nitrogen atoms, through the intramolecular hydrogen bond, in a series of protonated and neutral diamines (R = Me, H, see figure). According to computation, external solvation of N[BOND]H units in the protonated forms strongly attenuates the 2HJNN coupling between the nitrogen centres. Increasing alkylation reduces the possibility for such interactions.

    28. Weakly Oriented Liquid-Crystal NMR Solvents as a General Tool to Determine Relative Configurations (pages 4536–4539)

      Christie Aroulanda, Valérie Boucard, François Guibé, Jacques Courtieu and Denis Merlet

      Version of Record online: 11 SEP 2003 | DOI: 10.1002/chem.200204701

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      The determination of relative configurations of asymmetric centres is an important challenge in chemistry. A new NMR method to determine the relative configuration of asymmetric centres is presented. It proceeds through the use of a weakly ordered solvent and the measurement of orientational order parameters. This method is illustrated for dihydropyridone derivatives (shown here).

    29. An Accurate Barrier for the Hydrogen Exchange Reaction from Valence Bond Theory: Is this Theory Coming of Age? (pages 4540–4547)

      Lingchun Song, Wei Wu, Philippe C. Hiberty, David Danovich and Sason Shaik

      Version of Record online: 11 SEP 2003 | DOI: 10.1002/chem.200305093

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      The barrier of the hydrogen-exchange reaction (see scheme) has been calculated accurately by the use of two VB methods, BOVB and VBCI, with only the eight classical VB structures. It is the first accurate ab initio VB barrier that matches an experimental value.

    30. Resonance-Assisted Intramolecular Chalcogen–Chalcogen Interactions? (pages 4548–4555)

      Pablo Sanz, Manuel Yáñez and Otilia Mó

      Version of Record online: 11 SEP 2003 | DOI: 10.1002/chem.200304891

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      For unsaturated compounds, chalcogen–chalcogen interactions are enhanced through a mechanism rather similar to that involved in the so called Resonance Assisted Hydrogen Bond (RAHB), that increases the strength of intramolecular hydrogen bonds in unsaturated compounds such as β-chalcogenovinylaldehydes. Unsaturation and close vicinity of the chalcogen atoms seem to be necessary conditions to envolve strong chalcogen–chalcogen interactions (see figure).

    31. Guest–Framework Interaction in Type I Inorganic Clathrates with Promising Thermoelectric Properties: On the Ionic versus Neutral Nature of the Alkaline-Earth Metal Guest A in A8Ga16Ge30 (A=Sr, Ba) (pages 4556–4568)

      Carlo Gatti, Luca Bertini, Nick P. Blake and Bo B. Iversen

      Version of Record online: 11 SEP 2003 | DOI: 10.1002/chem.200304837

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      Guest neutrality refuted: Recent claims of near charge neutrality of the guest metal atoms in A8Ga16Ge30 (A=Sr,Ba) clathrates (see picture) are contradicted by the present ab initio study, which used periodical DFT calculations and atoms in molecules analysis. This work demonstrates that the guest atoms are almost completely ionized and confirm that they act as charge donors in these clathrates, which show promising thermoelectric properties. Thus, this theoretical picture is fully consistent with the Zintl-phase view that structural chemists have of these systems.

    32. Preview: Chem. Eur. J. 18/2003 (page 4572)

      Version of Record online: 11 SEP 2003 | DOI: 10.1002/chem.200390248