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Synthesis of Hypervalent Iodonium Alkynyl Triflates for the Application of Generating Cyanocarbenes
Published on: September 8, 2013
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Cyclic silylated onium ions of group 15 elements
Matti Reissmann1, André Schäfer, Robin Panisch
1Institut für Chemie, Carl von Ossietzky Universität Oldenburg , Carl von Ossietzky Strasse 9-11, D-26129 Oldenburg, Federal Republic of Germany.
Inorganic Chemistry
|February 10, 2015
Summary
Researchers synthesized cyclic silylated onium ions using transient silylium ions. These cyclic ions, unlike frustrated Lewis pairs, showed no reactivity with molecular hydrogen due to strong silicon-element bonds.
Area of Science:
- Organosilicon Chemistry
- Main Group Chemistry
- Supramolecular Chemistry
Background:
- Cyclic silylated onium ions are of interest due to their unique electronic properties.
- Transient silylium ions are reactive intermediates that can be utilized in synthesis.
- Frustrated Lewis pairs (FLPs) are known for their ability to activate small molecules.
Purpose of the Study:
- To synthesize novel five- and six-membered cyclic silylated onium ions.
- To investigate the reactivity of these cyclic ions, particularly in comparison to FLPs.
- To understand the factors influencing the inertness of these compounds towards molecular hydrogen.
Main Methods:
- Synthesis via intramolecular cyclization of transient silylium ions.
- Preparation of silylium ions through hydride transfer reactions.
- Characterization using multinuclear NMR spectroscopy and X-ray diffraction analysis.
- Density Functional Theory (DFT) computations to study electronic structures and bonding.
Main Results:
- Successfully synthesized five- and six-membered cyclic silylated onium ions (I).
- Observed the formation of tritylphosphonium ions (IV) when smaller ring systems were targeted.
- Characterized compounds I and IV as tetrakispentafluorophenyl borate salts.
- Demonstrated the inertness of cyclic onium ions I towards molecular hydrogen.
- DFT calculations indicated that the Si-E bond strength is responsible for the observed inertness.
Conclusions:
- The synthetic approach is effective for larger cyclic silylated onium ions but not for smaller rings.
- Cyclic silylated onium ions I do not exhibit FLP-like reactivity.
- The strong Si-E linkage in cyclic onium ions I significantly hinders their interaction with molecular hydrogen.
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