Silaimidazolium and silaimidazolidinium ions

Area of Science:

• Organosilicon Chemistry
• Main Group Chemistry
• N-Heterocyclic Compounds

Background:

• N-heterocyclic silylenes are reactive intermediates.
• Silyl arenium ions are Lewis acidic silicon species.
• Stable silicon-containing heterocyclic cations are of synthetic interest.

Purpose of the Study:

• To synthesize and characterize novel 2-silaimidazolium and 2-silaimidazolidinium ions.
• To investigate the stability and electronic properties of these silicon-based heterocyclic ions.
• To explore their behavior as Lewis pairs.

Main Methods:

• Lewis acid-base adduct formation between N-heterocyclic silylenes and silyl arenium ions.
• Isolation of target compounds as [B(C(6)F(5))(4)](-) salts.
• Characterization using NMR spectroscopy and density functional theory (DFT) computations.

Main Results:

• Successful synthesis and isolation of 2-silaimidazolium and 2-silaimidazolidinium ions in high yields.
• Compounds are stable at room temperature and characterized by NMR.
• DFT calculations confirmed molecular structures and NMR chemical shifts.
• NICS calculations indicated modest aromaticity for the imidazolium ions.

Conclusions:

• The synthesized silicon-containing heterocyclic ions are stable Lewis adducts.
• They behave as classical Lewis pairs, showing no unexpected reactivity despite bulky substituents.
• The study provides insights into the electronic properties and stability of silicon-based heterocyclic cations.