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Persistent bissilylated arenium ions
Rita Meyer1, Karla Werner, Thomas Müller
1Institut für Anorganische Chemie, Goethe Universität-Frankfurt, Marie Curie-Str. 11, 60439 Frankfurt/Main, Germany.
Chemistry (Weinheim an Der Bergstrasse, Germany)
|March 14, 2002
Summary
Researchers synthesized stable bissilylated arenium ions using hydride abstraction. These novel silicon-containing carbocations exhibit unusual stability due to silyl group electronic effects and non-nucleophilic conditions.
Area of Science:
- Organosilicon Chemistry
- Carbocation Chemistry
- Computational Chemistry
Background:
- Arenium ions are transient intermediates in organic reactions.
- Silyl substituents can influence carbocation stability.
- Synthesis of stable, isolable arenium ions remains a challenge.
Purpose of the Study:
- To synthesize novel bissilylated arenium ions.
- To investigate the electronic and stabilizing effects of silyl groups on arenium ions.
- To characterize the stability and reactivity of these new compounds.
Main Methods:
- Synthesis via hydride abstraction from 2-aryl-substituted 2,6-dimethyl-2,6-disilaheptanes.
- Characterization using NMR spectroscopy (29Si, 13C).
- Quantum mechanical calculations (B3LYP) for structural, energetic, and magnetic properties.
Main Results:
- Successful synthesis of a series of bissilylated arenium ions.
- NMR data confirmed the structures, showing characteristic shifts for silicon and carbon.
- Calculations revealed significant charge dispersal and stabilization by silyl groups, with the bissilylated benzenium ion being 37.6 kcal/mol more stable than the parent.
Conclusions:
- Bissilylated arenium ions are unusually stable in solution at room temperature.
- Thermodynamic stabilization by beta-silyl substituents and non-nucleophilic conditions contribute to their stability.
- These ions react with stronger nucleophiles, leading to desilylation.