Bridged siliconium ions

Further support comes from calculation of 1 Jch spin-spin coupling constants at IGLO-DFPT/BIII level. The data were interpreted as giving strong evidence for intramolecularly TT-stabilized silanorbomyl cation structure lacking coordination to solvent or counterion. The species can also be regarded as an almost symmetrically bridged /J-silyl carbocation with siliconium ion character. 

In summary, the silanorbomyl cations 5 and 25 are stable compounds in arene solvents at ambient temperature, lacking direct coordination to solvent or counterion. They are stabilized by intramolecular Jt-interaction and can be therefore regarded as an almost symmetrically bridged p-silyl-substituted carbocation with siliconium ion character. 

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