1.4, respectively, suggest that the mode of activation may also impact the kinetic relevance of the C-H bond cleavage step. That is, the mode in which TTO is activated may generate distinct thianthrenium electrophiles and impact the relative barriers for C-S bond formation and C-H bond cleavage; the latter appears to be less kinetically relevant when TTO is activated by Tf2O (Scheme 5a). We also performed a DKIE analysis on the formation of tolyl(Mes)iodonium triflate, 1m-IMes, by the same method (Scheme 5b). In this case, we obtained a DKIE of 1.5, a value similar to the DKIE obtained for arene thianthrenation (Scheme 5b). These data suggest that the kinetic relevance of the C-H cleavage step is similar for thianthrenation and iodination steps and points toward the existence of a Wheland intermediate in both cases that undergoes relatively fast deprotonation. Scheme 5. DKIE analysis for the formation of aryl "onium" species.