Dispersion-Energy-Driven Wagner–Meerwein Rearrangements in Oligosilanes

The installation
of structural complex oligosilanes from linear
starting materials by Lewis acid induced skeletal rearrangement reactions
was studied under stable ion conditions. The produced cations were
fully characterized by multinuclear NMR spectroscopy at low temperature,
and the reaction course was studied by substitution experiments. The
results of density functional theory calculations indicate the decisive
role of attractive dispersion forces between neighboring trimethylsilyl
groups for product formation in these rearrangement reactions. These
attractive dispersion interactions control the course of Wagner–Meerwein
rearrangements in oligosilanes, in contrast to the classical rearrangement
in hydrocarbon systems, which are dominated by electronic substituent
effects such as resonance and hyperconjugation.