Enium Ions of Other Group 16 Elements

In the synthesis of cation 277 the cation 278 was also isolated as a byproduct. 13C NMR data show that all three cyclopentenemethyl substituents are equivalent at the NMR time scale, suggesting a dynamic equilibrium between bisalkene 

The tin analog of ion 267a [see Eq. (4.168)] has been prepared and a 119Sn NMR chemical shift at 8119Sn -2219 was reported.701 

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