An investigation into the Brønsted acidity of the perfluorinated alkoxy silanes {(F 3 C) 3 CO} 3 SiH and {(F 6 C 5 ) 3 CO} 2 Si(Cl)H.

The perfluorinated alkoxy silanes {(F 3 C) 3 CO} 3 SiH (1) and {(F 5 C 6 ) 3 CO} 2 Si(Cl)H (2) were prepared and fully characterized. Despite the high calculated Brønsted acidities, all attempts to deprotonate 1 and 2 to give the conjugate silanide ions failed due to the exceptionally short and strong Si-H bonds. In the solid state, the Si-H units are not involved in any intermolecular interactions, but instead the crystal packing consists of exceptionally short and strong F⋯F interactions. The cohesive energies are entirely comprised of London dispersion interactions, similarly as in the crystal structures of noble gases.