Selective Formation of Functionalized Disiloxanes from Terphenylfluorosilanes

The reactivity of the sterically hindered organofluorosilane 2,6-Mes2C6H3-SiF3 (1) (Mes =
2,4,6-trimethylphenyl) under hydrolytic conditions differs substantially from that of the
corresponding organo chlorosilane. During the hydrolysis of 1 the combination of thermodynamic (increased Si−F bond strengths compared to Si−Cl) and kinetic aspects (steric
hindrance) favors condensation of intermediately formed silanol over the hydrolysis to give
a silanetriol. In the course of the reaction no evidence for a silanetriol could be found, while
the corresponding difluorosilanol seems to be a key intermediate. The condensation of this
difluorosilanol leads to a tetrafluorodisiloxane, which can be isolated. Further displacement
of the remaining fluorine atoms in this siloxane is possible with organolithium reagents or
base. In the latter case the deprotonated disiloxanetetrol is formed, which due to its fourfold
silanol functionality is a suitable precursor for metallasiloxanes. The deprotonated disiloxanetetrol forms a dimeric structure in the solid state, which is stabilized by hydrogen bonding
and potassium aryl interactions