The large positive ρ values obtained from Me3M− ions reacting with appropriately- substituted chloroarenes (4.1±0.1, and 2.94±0.02 for M= Sn and Si, respectively) can be accounted for the presence of a strong negative charge in the transition state of the substitution reaction. These ρ values for Me3Sn− and Me3Si− nucleophilic attack on ArX provide evidence for the overall larger selectivity of the former, compared with the more ...