Aryl-Aryl Interactions in (Aryl-Perhalogenated) 1,2-Diaryldisilanes

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.