Stannyl Substituent Constants

With an appropriate structure, one might expect that overlap between a C-Sn a-orbital and a vacant p-orbital would be significant over a more extended framework, leading to effects further down the Greek alphabet. 

Shiner showed that the y-trimethylstannyl substituent accelerated the solvolysis of 5-(trimethylstannyl)-l-adamantyl sulfonates (3-22),38 and Lambert showed that the effect was apparent in 3-trialkylstannylcyclohexyl tosylate (3-23), but only when the two groups are cis so that the Sn-C and C-0 bonds are in a W-geometry the solvolysis in 97% CF3CH2OH was then accelerated by a factor of 2 x 103.39 

By intermolecular competition of an allylsilane and a homoallylstannane for reaction with an electrophile, the P-effect of silicon has been shown to be more effective than the y-effect of tin in activating the double bond towards addition.40 41 

In the 1,4-substituted bicyclooctyl system (3-24), the stannyl substituent shows a substantial 5-effect,42 but no evidence could be found for a -effect in (3-25)43 

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Table 3-1 Estimated values of electronic stannyl substituent constants.

Table 3-2 Estimated values of steric stannyl substituent constants.

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