A trimethyl-, triethyl-, or triisopropylsilyl group attached to the meta position of toluene retards the rate of permutational H/metal interconversion with butyllithium in the presence of K tert-butoxide by factors of 1.7, 3, and 7, resp. Although remote from the reaction center, the substituents sterically impede the coordination of K to the arene electron sextet. p-Arene/metal bonding may play a major role in modulating chem. and, by extension, biochem. reactivity. [on SciFinder (R)]