Synthesis and Crystal Structure of a Silyl‐Stabilized Allyl Cation Formed by Disruption of an Arene by a Protonation–Hydrosilylation Sequence

Sly silyl caught in the act : Protonation of a mesitylene ring by the strongly acidic arenium carborane [CH₃C₆H₆]‐ [CHB₁₁Me₅Br₆] initiates a cascade reaction that results in a stable β‐silyl allyl cation (see picture, H yellow, C blue, silyl allyl group red). Remarkably, the driving force in the reaction suffices to disrupt a stable aromatic ring in favor of a cationic reactive intermediate.

     

Superacidity of Boron Acids H2(B12X12) (X=Cl,Br)

Acid remarks : The anhydrous diprotic boron acids H₂(B₁₂X₁₂) (X=Cl, Br; see picture, B orange, X green) are the first examples of diprotic superacids and may be the strongest acids yet isolated. Both protons protonate benzene to give benzenium ion salts that are stable at room temperature. These acids owe their existence to the stability of the icosahedral B₁₂ cluster with its dinegative charge buried beneath a layer of halide substituents.

     

Synthesis of onio-, dionio-, and trionio-substituted phosphines; the nucleophilic behavior of DBN and DBU toward main group electrophiles

1,5-Diazabicyclo[4.3.0]non-5-ene (DBN) and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) react with chloro- and dichloro-phosphines leading to onio- and dionio-substituted phosphines. Similarly, onio-substituted silicon and tin derivatives are prepared; they are used as onio-substituent transfer reagents in the synthesis of a trionio-substituted phosphine.     

ChemInform Abstract: Tetrakis(tetramethylammonium) Tricarbonatodioxidouranate Octahydrate.

Single crystals of (Me₄N)₄ [UO₂(CO₃)₃]·8H₂O are grown by slow evaporation (25 °C, 6 weeks) of an aqueous solution of uranyl 1‐hydroxyethane‐1,1‐diphosphonate and Me₄NOH.     

Monitoring kinetic processes in polymer solutions with time dependent static light scattering (TDSLS)

An overview of recent developments in TDSLS and auxiliary techniques is given. This includes background theory, and examples of results and applications for online monitoring of polymerization reactions, kinetics and structural determinations from degrading polymers, aggregation, and dissolution of dry polymer powders. Also, automatic dilution techniques allow for continuous characterization of the equilibrium states of multi-component solutions. Illustrations are given for the case where the change in polyelectrolyte dimensions, interactions and hydrodynamics can be probed.