[Cp2ZrMe)(+) + Me3N + C6H6 down arrow TS2 Cp2ZrMePh + (Me3NH](+) down arrow TS3 [Cp2ZrPh](+) + Me3N + CH4 The C-D activation of bromobenzene-d(5), by [CP2*ZrMe(BrC6D5-kappa Br)][B(C6F5)(4)] to form sigma-aryl complex [Cp-2*Zr(2-BrC6D4-kappa Br-2,C)][B(C6F5)(4)] is accelerated when the decamethylzirconocene methyl cation is generated in the presence of tertiary amines. Computational studies suggest that the overall sigma-bond metathesis reaction proceeds, in the presence of tertiary amines, via initial deprotonation of bromobenzene in the coordination sphere of the metal center. In a subsequent step, the resulting neutral methyl aryl species, CP2*ZrMe(2-BrC6D4), reacts with the concurrently generated trialkylammonium cation to generate [Cp-2*Zr(2-BrC6D4-kappa Br-2,C)][B(C6F5)(4)].