Overall, the proposed cycle is outlined in Figure , proceeding via 1. Arene C-H zincation, 2. bond metathesis and 3. Protonolysis. The latter could potentially occur directly from 11 or by initial endergonic conversion of 11 into 1 which would then undergo protonolysis. remained a key question. The -bond metathesis process was of particular interest as the C-H borylation reactions were performed in chlorobenzene, where (H-BBN)2 persists in its dimeric form. Cognizant that hidden catalysis can facilitate transformations in organoboron chemistry, several species that could be present at low concentration during the catalysis were tested for their effect on the metathesis step. The addition of 5 mol% of DMT, [(DMT)H][B(C6F5)4] and Me2S-BH3 separately to the reaction between Zn-Aryl 10 and (H-BBN)2 led to no change in the rate of the metathesis reaction, indicating that these species do not catalyze this metathesis reaction. With the positive effect of catalyst loading on borylation rate determined (Table and Fig. -106), variable time normalization analysis (VTNA) was used to determine the order with respect to (H-BBN)2. This analysis gave data that was consistent with a first order in (H-BBN)2 dimer for the metathesis step (Fig. ). Some alkene hydroboration reactions using (H-BBN)2 are first order with respect to the dimer, which indicates the dissociation of the (H-BBN)2 dimer into two equivalents of (H-BBN) monomer is rate limiting. In these cases, the hydroboration reactions are zero order with respect to the other component(s). The situation here is different, as the rate is also affected by the concentration of the zinc complex and the thienyl substrate (see Table , S1 and Fig. ). This precludes (H-BBN)2 dimer dissociation into two monomers being the turnover limiting step in this zinc catalyzed arene borylation. The standard metathesis mechanism involves a monomeric hydroborane species reacting via a four membered transition state (e.g., involving M-C and H-B). However, such a process is not consistent with the above data as when one equivalent of monomeric H-BBN reacts with a substrate in the rate limiting step the reaction is 0.5 order with respect to (H-BBN)2 dimer. Therefore, computational analysis was performed to provide further insight into the mechanism.