A happy ending : The germanium(II) hydride [LGeH], where L=[HC{(CMe)(2,6‐iPr2C6H3N)}2], reacts with a diazoalkane to form the hydrazone derivative (see picture). The reaction proceeds through the unprecedented end‐on nitrogen insertion of the diazo compound.
Why bigger is better : A “steric wall” created by the N‐(2,6‐diisopropylphenyl) substituent on the bulky NHC ligand IPr (1,3‐bis(2,6‐diisopropylphenyl)imidazol‐2‐ylidene) guides the reactants to and from the Pd center through weak, fleeting (IPr)H–Pd interactions that help the oxidative addition intermediate escape “the anti‐trap”. The alternative “side” approach leads to transmetalation (the rate‐limiting step) for which a novel Pd–Zn interaction was identified.
A light touch is all that is required to cleave a maleimide C? N bond to effect a [5+2] photocycloaddition with a sterically encumbered C?N moiety (see scheme).
From zero to hero? Sulfoxides are generally not considered useful ligand entities in asymmetric metal catalysis. However, a chiral disulfoxide as a chelating ligand in the rhodium‐catalyzed 1,4‐addition of aryl boronic acids to cyclic, α,β‐unsaturated ketones and esters gives impressive catalytic results, thus opening the door to future applications of this new chiral ligand class.
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).
The fungus Rhizopus microsporus …? ; shown in the micrograph on the cover picture, harbors the endosymbiotic bacteria Burkholderia rhizoxinica that produces the antimitotic polyketide macrolide rhizoxin (see structure). In their Communication on page 5001 ff. , C. Hertweck and co‐workers show that the enzyme rhizoxin polyketide synthase is uniquely capable of introducing a β branch (highlighted by the magnifying glass) by a Michael‐type addition of a malonyl unit to an acryloyl intermediate.
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.
Ring any bells? The differential capacitance curve of Au(100) in neat [BMI]BF4 (BMI=1‐butyl‐3‐methylimidazolium) ionic liquid has a bell‐shaped feature (see picture). The adsorption of BMI+ shows a disorder–order transition and depends on the structure of the surface. Ordered adsorption in a micelle‐like structure stabilizes the underlying Au surface.
Custom built : A promising new approach towards more efficient self‐assembled cage receptors through computer‐aided design is demonstrated. The resulting M4L6 tetrahedral cage, internally functionalized with accurately positioned urea hydrogen‐bonding groups (see structure; yellow: predicted, blue: experimental, space‐filling: SO42?), proved to be a remarkably strong sulfate receptor in water.
Doped up : The incorporation of Zn2+ dopants in tetrahedral sites leads to the successful magnetism tuning of spinel metal ferrite nanoparticles (see picture). (Zn0.4Mn0.6)Fe2O4 nanoparticles exhibit the highest magnetization value among the metal ferrite nanoparticles. Such high magnetism results in the largest MRI contrast effects (r2=860 mm?1 s?1) reported to date and also huge hyperthermic effects.
Fleetingly formyl : A new rhodium‐catalyzed hydroformylation reaction of N‐allyl oxazolidines, carried out under a CO/H2 atmosphere, followed by a diastereoselective deformylative cyclization affords hexahydropyrrolo[2,1‐b]oxazoles in good yields. The reaction proceeds by a unique hydroformylation–deformylation sequence in which the formyl group virtually substitutes for the {CH2? O} fragment of the oxazolidine heterocycle.
Novel conjugated carbazole polymers based on the alkyne‐linked 1,8‐carbazole structure are synthesized in high yield by the Sonogashira cross‐coupling reaction and acetylenic oxidative coupling reaction. The polymers are thermally stable and highly soluble in common organic solvents such as CHCl3, CH2Cl2, and THF. As compared to ethynylene‐linked polymer, the butadiynylene‐linked polymer display a bathochromic shift in the absorption maximum and end absorption position. In addition, the fluorescence behaviors in CH2Cl2 are almost identical for both polymers. Electrochemical measurements indicate that the ethynylene‐linked polymer possesses a lower first oxidation potential than the butadiynylene‐linked one.
Easy come, easy go? Transport resistances on particle surfaces are important for mass transfer in nanoporous materials and bulk diffusion in crystals. Interference microscopy and IR micro‐imaging are shown to be excellent tools for determining such transport resistances. By studying short‐chain‐length alkane guest molecules in crystals of the metal–organic framework compound Zn(tbip) a data collection of surface permeabilities is established.
?The biggest challenge facing scientists is finding a way to make clean energy. If I could have dinner with three famous scientists from history, they would be Marie Curie, Dmitri Mendeleev, and Henri Moissan. …?“ This and more about Véronique Gouverneur can be found on page 3559.
Are you in? Bimetallic PtRu nanoparticles have been selectively confined inside or deposited outside carbon nanotubes (see picture). The confined nanoparticles display significantly higher selectivity and catalytic activity in hydrogenation reactions.
Forces to reckon with : Supramolecular complexes, such as the one shown, are normally based on a combination of different interactions such as ion pairing, hydrogen bonds, and stacking interactions. The not always simple characterization of the nature and strength of intermolecular forces provides assistance to the understanding of biomimetic systems, as well as for the design of synthetic receptors, drugs, and intelligent materials.
