�-Silyl carbocations of type 1 are greatly stabilized by the adjacent silyl group, as are �-silyl carbenes of type 2. We have observed that ?-silyl carbenes of type 3 also interact strongly with the adjacent trimethylsilyl group. With this in mind, the effect of the ?-trimethylsilyl group on the stability of carbocations 4-8 has been evaluated using experimental and computational methods. There are two modes by which ?-silyl cyclobutyl cations can be stabilized by silicon. Small stabilization of 4 can result from an interaction with the front lobe of the carbon-silicon bond. A much larger stabilizing interaction results from a rear lobe interaction as pictured in 5. The 7-norbornyl cation 6 is greatly stabilized by a rear lobe interaction with an endo-2-trimethylsilyl group, while cross ring interactions stabilize the cations 7 and 8.

Remote silicon effects in carbenes and carbocations

239th National Meeting (2010)

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