Triggered Exchange of Anionic for Neutral Guests inside a Cationic Coordination Cage

Molecular encapsulation processes under the control of an external trigger play a major role in biological signal transduction processes and enzyme catalysis. Here, we present an artificial mimic of a controllable host system that forms via self-assembly from a simple bis-monodentate ligand and Pd­(II) cations. The resulting interpenetrated double cage features three consecutive pockets which initially contain one tetrafluoroborate anion, each. Activation of this host system with two halide anions triggers a conformational change that renders the central pocket susceptible to the uptake of small neutral guest molecules. Thereby, the pentacationic cage expels the central anion and replaces it with a neutral molecule to give a hexacationic species. The cage structures prior and after the halide triggered binding of benzene were examined by X-ray crystallography, ESI MS, and NMR techniques. The kinetics and thermodynamics of the encapsulation of benzene, cyclohexane, and norbornadiene are compared

Triggered Exchange of Anionic for Neutral Guests inside a Cationic Coordination Cage

Molecular encapsulation processes under the control of an external trigger play a major role in biological signal transduction processes and enzyme catalysis. Here, we present an artificial mimic of a controllable host system that forms via self-assembly from a simple bis-monodentate ligand and Pd­(II) cations. The resulting interpenetrated double cage features three consecutive pockets which initially contain one tetrafluoroborate anion, each. Activation of this host system with two halide anions triggers a conformational change that renders the central pocket susceptible to the uptake of small neutral guest molecules. Thereby, the pentacationic cage expels the central anion and replaces it with a neutral molecule to give a hexacationic species. The cage structures prior and after the halide triggered binding of benzene were examined by X-ray crystallography, ESI MS, and NMR techniques. The kinetics and thermodynamics of the encapsulation of benzene, cyclohexane, and norbornadiene are compared

One-Electron-Mediated Rearrangements of 2,3-Disiladicarbene

A disiladicarbene, (Cy-cAAC)₂Si₂ (<b>2</b>), was synthesized by reduction of Cy-cAAC:SiCl₄ adduct with KC₈. The dark-colored compound <b>2</b> is stable at room temperature for a year under an inert atmosphere. Moreover, it is stable up to 190 °C and also can be characterized by electron ionization mass spectrometry. Theoretical and Raman studies reveal the existence of a SiSi double bond with a partial double bond between each carbene carbon atom and silicon atom. Cyclic voltammetry suggests that <b>2</b> can quasi-reversibly accept an electron to produce a very reactive radical anion, <b>2</b>^{<b>•–</b>}, as an intermediate species. Thus, reduction of <b>2</b> with potassium metal at room temperature led to the isolation of an isomeric neutral rearranged product and an anionic dimer of a potassium salt via the formation of <b>2</b>^{<b>•–</b>}