The
history of silyl cations has all the makings of a drama but with a
happy ending. Being considered reactive intermediates impossible to
isolate in the condensed phase for decades, their actual characterization
in solution and later in solid state did only fuel the discussion
about their existence and initially created a lot of controversy.
This perception has completely changed today, and silyl cations and
their donor-stabilized congeners are now widely accepted compounds
with promising use in synthetic chemistry. This review provides a
comprehensive summary of the fundamental facts and principles of the
chemistry of silyl cations, including reliable ways of their preparation
as well as their physical and chemical properties. The striking features
of silyl cations are their enormous electrophilicity and as such reactivity
as super Lewis acids as well as fluorophilicity. Known applications
rely on silyl cations as reactants, stoichiometric reagents, and promoters
where the reaction success is based on their steady regeneration over
the course of the reaction. Silyl cations can even be discrete catalysts,
thereby opening the next chapter of their way into the toolbox of
synthetic methodology.