Inside Cover: Perfluoropentaphenylborole (Angew. Chem. Int. Ed. 16/2009)

Perfluoroaryl boranes are an important class of organometallic Lewis acids. The synthesis of perfluorinated compounds brings special challenges to tried‐and‐true synthetic methodologies. In their Communication on page 2955 ff., W. E. Piers and co‐workers present the synthesis of a new, fully fluorinated heterocyclic borane that is also a member of the rare antiaromatic borole class of compounds. The route relies on normally facile transmetallation reactions made more difficult by the electron‐withdrawing C₆F₅ groups of the target product.

     

Gas‐Phase versus Liquid‐Phase Structures by Electrospray Ionization Mass Spectrometry

Preferred protonation : Does electrospray ionization mass spectrometry produce gas‐phase or liquid‐phase structures? The preferred protonation site in p‐aminobenzoic acid depends upon the medium, and the structure of its conjugate acid varies with the solvent used during spraying.

     

Platinum(II)‐Catalyzed Intramolecular Cyclization of o‐Substituted Aryl Alkynes through sp3 C?H Activation

Ring leader : PtCl₂ catalyzes intramolecular cyclization of o‐isopropyl or o‐benzyl aryl alkynes to give substituted indene derivatives with good yields and high selectivity. This reaction appears to proceed through an sp³ C? H activation and 1,4‐hydrogen migration pathway (see scheme).

     

Room‐Temperature C?H Bond Activation of Methane by Bare [P4O10].+

No need for a metal : A combination of mass spectrometry and computational studies (density functional theory and coupled‐cluster methods) shows that [P₄O₁₀]^.+ is the first polynuclear nonmetal oxide cation that is capable of activating the C? H bond of methane at room temperature (see picture). This process represents a further example in the reactivity of oxygen‐centered radicals.

     

Structural Link between Giant Molybdenum Oxide Based Ions and Derived Keggin Structure: Modular Assemblies Based on the [BW11O39]9− Ion and Pentagonal {M′M5} Units (M′=W; M=Mo,W)

Linked to the Pentagon : The addition of molybdate to [HBW₁₁O₃₉]^8? ions leads to the formation of mixed pentagonal units {W(Mo₅)} and {W(WMo₄)} trapped as linkers in the resulting modular assemblies, thus establishing the first link between the conventional Keggin ion derivatives and the giant molybdenum oxide and keplerate ions.

     

How Much Water Does Calcined Gypsum Contain?

Ordered water : Gypsum has been used for construction for millennia. The structure and water content of calcined gypsum, CaSO₄?0.5 H₂O, has been under discussion until now: single‐crystal structure analysis (see picture: S yellow, Ca gray, O blue, H red) provides an ordered model that is confirmed by DFT calculations.

     

Combining RAFT Radical Polymerization and Click/Highly Efficient Coupling Chemistries: A Powerful Strategy for the Preparation of Novel Materials

This paper highlights the powerful combination of reversible addition–fragmentation chain transfer (RAFT) radical polymerization and various click/coupling chemistries. This is not an exhaustive review but rather an overview demonstrating the impressive possibilities that the “marriage” of these two synthetic approaches offers in modern macromolecular design and synthesis.

     

3 D Characterization of Gold Nanoparticles Supported on Heavy Metal Oxide Catalysts by HAADF‐STEM Electron Tomography

Living on the edge : Three‐dimensional reconstructions from electron tomography data recorded from Au/Ce_0.50Tb_0.12Zr_0.38O_2?x catalysts show that gold nanoparticles (see picture; yellow) are preferentially located on stepped facets and nanocrystal boundaries. An epitaxial relationship between the metal and support plays a key role in the structural stabilization of the gold nanoparticles.

     

Über geordnete Perowskite mit Kationenfehlstellen. X. Verbindungen vom Typ ABB□1/4MVIO6 ≙ ABIIB□MO24 mit AII,BII = Ba,Sr, Ca und MVI = U,W

On Ordered Perovskites with Cationic Vacancies. X. Compounds of Type A B B □_1/4M^VIO₆ ? A B^IIB □M O₂₄ with A^II, B^II = Ba, Sr, Ca and M^VI = U, W Perovskites of type Ba₈B^IIB₂^III□UO₂₄ show polymorphic phase transformations of order disorder type. An 1:1 ordered orthorhombic HT form is transformed into a higher ordered LT modification with a fourfold cell content (four formula units Ba₈B^IIB□U₄O₂₄), compared to cubic 1:1 ordered perovskites A₂BMO₆. In the series Ba₈BaB□W₄O₂₄ and Sr₈SrB□W₄O₂₄ different ordering phenomena are observed. In comparison with 1:1 ordered cubic perovskites A₂BMO₆, the cell contains eight formula units AB^IIB□W₄O₂₄. The higher ordered cells with U^VI and W^VI are face centered, which has its origin in an ordering of cationic vacancies.     

Synthetic Lectins

Improving on Mother Nature? The carbohydrate recognition demonstrated by supramolecular systems in water can now compete with that of natural systems, both in terms of affinity and selectivity. A synthetic carbohydrate receptor displays similar affinity for N‐acetyl‐D ‐glucosamine derivatives as the lectin wheat germ agglutinin and even greater selectivity (see picture: gray C, white H, blue N, red O).

     

Addition of Dimethylaminobismuth to Aldehydes,Ketones, Alkenes,and Alkynes

Bi? O chemistry : A direct regioselective route to bismuth bis(amino)naphthalene compounds, incorporating Bi? O and Bi? C bonds is described, in which an amide precursor is treated with aldehydes, ketones, alkenes, and alkynes, leading to insertion into the Bi? NMe₂ bond.

     

When Do Interacting Atoms Form a Chemical Bond? Spectroscopic Measurements and Theoretical Analyses of Dideuteriophenanthrene

Don't rewrite the textbooks! Vibrational spectra of a selectively deuterated derivative of phenanthrene indicate that the C4H???HC5 interaction in its “bay” area should be interpreted as steric (Pauli) repulsion. These findings and the results of theoretical analysis are in conflict with interpretations that describe this interaction as strongly stabilizing.

     

P. Melchiorre

?My most exciting discovery to date has been always the last one (or better still, the next one). The biggest challenge facing scientists is the responsible use of knowledge and scientific power for the betterment of humanity. …?“ This and more about P. Melchiorre can be found on page 3389.

     

Rhodium(I)‐Catalyzed Enantioselective C?C Bond Activation

Relieving the strain : The rhodium(I)‐catalyzed activation of C C bonds in functionalized cyclobutanes opens a novel route to highly substituted carbo‐ and heterocycles. Particularly intriguing is the differentiation of enantiotopic C C bonds, which leads to the formation of highly enantiomerically enriched lactones, cyclopentanones, and cyclohexenones (see scheme).

     

Inside Cover: Bidirectional Chemo‐Switching of Spin State in a Microporous Framework (Angew. Chem. Int. Ed. 26/2009)

Bidirectional chemo‐switching of magnetism occurs in a microporous coordination polymer containing spin‐crossover subunits, as described by M. Ohba, J. A. Real, S. Kitagawa, and co‐workers in their Communication on page 4767 ff. In situ magnetic measurements reveal that most guest molecules transform the framework spin state from diamagnetic low spin (red) to paramagnetic high spin (yellow), whereas the guest CS₂ stabilizes the low‐spin state. These induced spin states are retained as a memory effect after the release of the guest.

     

Synthesis of titanium polyesters

Titanium polyesters of the form where Cp denotes cyclopentadiene, have been synthesized by utilizing both the interfacial and solution techniques. Polymer yield increases with reaction time. The reactive titanium reactant in the solution polycondensations is believed to be the Cp₂Ti⁺² cation.     

Mössbauer Spectroscopic Studies of the Hydroxofluorostannate(IV) Complexes

Mössbauer isomer shifts of ¹¹⁹Sn in a series of complexes K₂Sn(OH)_6-mF_m observed at 78 K were ?0.05, ?0.05, ?0.24, ?0.27 and ?0.40 mm s^?1, respectively, for m=0, 2, 4, 5 and 6. These IS values were linearly related to both m and (the average Pauling electronegativity of the ligands): . The IS straight line was compatible within experimental error with the one reported by Parish and Row-botham for the hexahalogenostannate complexes SnX₄Y₂², namely, The revised IS straight line including both series of complexes could be expressed by the equation Quadrupole splittings observed in the complexes of m = 2,4 and 5 were 1.16, 0.80 and 0.73 mm s^?1 respectively. They were linearly related to both m and .     

Antiferromagnetic Ground State of a C60‐Covered Si(001) Surface

Modeling magnetism: The antiferromagnetic ground state of the C₆₀/Si(001)‐c(4×4) surface is predicted by means of density functional theory calculations. Two adjacent dangling bonds (DBs) generated by the adsorption of C₆₀ are antiferromagnetically coupled with each other. This study demonstrates that magnetic Si surfaces can be prepared by engineering single Si DBs with unpaired electrons.

     

C(aryl)?O Activation of Aryl Carboxylates in Nickel‐Catalyzed Biaryl Syntheses

Crucial breakthroughs in the activation of the C(aryl)? O bond of phenol derivatives were achieved almost simultaneously by two research groups (see scheme; Cy=cyclohexyl). Garg et al. coupled a range of aryl pivalates with arylboronic acids to give unsymmetrical biaryls. Shi et al. achieved this through C(aryl)? O activation of aryl carboxylates; the best results for the coupling of aryl boroxines were again obtained with aryl pivalates.