Synthesis and Properties of Silylium Ions Incorporated into Pentaselenylphenyl Platforms

We report the synthesis of silylium salts incorporated into σ-delocalized systems arising from interactions between lone-pair electrons on non-bonded selenium atoms. The cationic silicon center is coordinated by an adjacent selenium atom to form a silylselenonium structure, as evidenced by quantum-chemical calculations. The silylselenonium salt undergoes exchange of a coordinating selenium atom through the symmetric transition state with a very small energy barrier. The silylselenonium salt retains reactivity as a silylium salt and reacted with tetrafluoroborate to afford a fluorinated silane. The Lewis acidity of the silylselenonium salt is evaluated using 4-fluorobenzonitrile.