Conjugation in Isomeric Cyclosilane Thioethers

Conjugation in thioether-functionalized cyclosilanes
depends on
both conformation and connectivity. Borane-catalyzed dehydrocoupling
of thiophenols with partially hydrogenated cyclosilanes proceeded
with high chemoselectivity for Si–H bonds in the presence of
Si–Si bonds. Isomeric 1,3- and 1,4-functionalized cyclosilanes
afforded isomeric cyclosilane thioethers that also differed in preference
for chair or twist-boat conformations as demonstrated by both X-ray
crystal structures and density functional theory (DFT) calculations.
The confounding effects of different conformations and connectivity
could be distinguished with time-dependent DFT (TD-DFT) calculations
and validated with experimentally obtained UV–vis spectra.