 Potassium hexamethyldisilazide

Potassium hexamethyldisilazide is the potassium salt of the anion $\mathrm{N}(\mathrm{SiM}{\mathrm{e}}_3{)}_2^{-}$. The bulky silyl groups make it useful as a strong, sterically hindered base.

It can remove an acidic proton to form an enolate while competing less readily in some addition reactions than a smaller nucleophile. Counterion, solvent, and aggregation still influence the observed selectivity.