Intramolekulare π‐π‐Wechselwirkungen in flexibel verbrückten, teilweise fluorierten Bisarenen in der Gasphase

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Three 1,2‐diaryltetramethyldisilanes X5C6‐(SiMe2)2‐C6X5 with two C6H5, C6F5, or C6Cl5 groups were studied concerning the importance of London dispersion driven interactions between their aryl groups. They were prepared from 1,2‐dichlorotetramethyldisilane by salt elimination. Their structures were determined in the solid state by X‐ray diffraction and for free molecules by gas electron‐diffraction. The solid‐state structures of the fluorinated and chlorinated derivatives are dominated by aryl–aryl interactions. Unexpectedly, Cl5C6‐(SiMe2)2‐C6Cl5 exists exclusively as an eclipsed syn‐conformer in the gas phase with strongly distorted Si‐C6Cl5 units due to strong intramolecular interactions. In contrast, F5C6‐(SiMe2)2‐C6F5 reveals weaker interactions. The contributions to the total interaction energy were analyzed by SAPT calculations.

mentioning

confidence: 99%

Aryl–Aryl Interactions in (Aryl‐Perhalogenated) 1,2‐Diaryldisilanes

Linnemannstöns

Schwabedissen

Neumann

et al. 2020

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Inter‐ and Intramolecular Aryl–Aryl Interactions in Partially Fluorinated Ethylenedioxy‐bridged Bisarenes**

Weddeling

Vishnevskiy

Neumann

et al. 2020

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Several ethylenedioxy-bridged bisarenes with a variety of type and number of aryl groups were synthesized to study non-covalent dispersion-driven inter-and intramolecular aryl-aryl-interactions in the solid state and gas phase. Intramolecular interactions are preferably found in the gas phase. DFT calculations of dispersion-corrected energy scans for rotations around the ethylenedioxy-bridge and optimized structures show larger interacting aromatic groups to increase the dispersion energy. Single molecule structures generally adopt folded conformations with short intramolecular aryl-aryl-contacts. Gas electron diffraction experiments were performed exemplarily for 1-(pentafluorophenoxy)-2-(phenoxy)ethane. A new procedure for structure refinement was developed to deal with the conformational complexity of such molecules. The results are an experimental confirmation of the existence of folded conformations of this molecule with short-intramolecular aryl-aryl distances in the gas phase. Solid-state structures are dominated by stretched structures without intramolecular aryl-aryl-interactions but interactions with neighboring molecules.

Chalice‐Type Tridentate Silicon Lewis Acids of C₃ Symmetry in a Single Step Starting from Hexadehydrotribenzo[12]annulene

Schwartzen

Weddeling

Langosch

et al. 2020

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Tridentate Lewis acids with aligned functions were synthesized based on the rigid framework hexadehydrotribenzo[12]annulene. The backbone and its fluorinated analogue were synthesised in one‐pot syntheses, with alkyne deprotection and Sonogashira cross coupling reaction being carried out in one step. Hydrosilylation of the annulene with chlorohydrosilanes proceeded highly selectively and afforded rigid poly‐Lewis acids with three SiCl3 or SiCl2Me substituents perfectly oriented to one side of the molecule in a single step. The progress of hydrosilylation was investigated by time‐correlated NMR spectroscopic studies. The crystal structures show that the framework is symmetrically functionalised and the silyl substituents are aligned in one direction. To increase the acidity of the Lewis acids the chlorosilyl substituents were fluorinated with SbF3. Further investigation of hydrometallation reactions (M=B, Al, Ga, Sn) did not lead to corresponding structures.