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Monocyclic zwitterionic lambda(5)Si-silicates with an SiO(2)FC(2) framework: syntheses and structural
R Tacke1, R Bertermann, O Dannappel
1Institut für Anorganische Chemie, Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany. r.tacke@mail.uni-wuerzburg.de
Inorganic Chemistry
|May 15, 2001
Summary
New pentacoordinate silicate zwitterions were synthesized from acyclic precursors. Structural analysis revealed distorted trigonal bipyramidal geometries, with no silicon enantiomerization observed.
Area of Science:
- Organosilicon Chemistry
- Coordination Chemistry
- Crystallography
Background:
- Pentacoordinate silicon compounds exhibit unique reactivity and structures.
- Zwitterionic silicates offer a platform for exploring novel chemical transformations.
- Understanding the stereochemistry of silicon centers is crucial in inorganic chemistry.
Purpose of the Study:
- To synthesize novel acyclic and monocyclic zwitterionic pentacoordinate silicates.
- To elucidate the solid-state structures of these compounds using X-ray diffraction.
- To investigate the solution behavior and stereochemical stability of silicon centers using NMR spectroscopy.
Main Methods:
- Reaction of acyclic zwitterionic pentacoordinate silicates with silylating agents.
- Single-crystal X-ray diffraction for structural determination.
- Nuclear Magnetic Resonance (NMR) spectroscopy (1H, 13C, 19F, 29Si) including variable temperature studies.
Main Results:
- Successful synthesis of monocyclic zwitterionic pentacoordinate silicates (11a-14a and 11b-14b).
- X-ray diffraction confirmed distorted trigonal bipyramidal coordination geometries around silicon.
- NMR data indicated the presence of chiral silicon centers existing as enantiomeric pairs, with no observed enantiomerization up to 85°C.
Conclusions:
- The synthesized monocyclic silicates adopt distorted trigonal bipyramidal structures.
- Chiral silicon centers in these zwitterions are stereochemically stable under the studied conditions.
- This work expands the library of pentacoordinate silicate structures and their stereochemical properties.