Carbon–silicon hyperconjugation: X-ray structural study of N-methyl-4-trimethylsilylmethylpyridinium triflate

Hyperconjugation between the CH2Si bond and the charged pyridinium π system in the N-methyl 4-trimethylsilylmethyl pyridinium ion (8), manifests in the crystal structure as lengthening of the CH2Si bond, shortening of the CH2Cipso bond and smaller but systematic effects on the CC bond distances within the pyridinium ring. The structural effects are supported in solution by systematic effects on the 29Si–13C and 13C–13C one-bond coupling constants.