Using CC(C)(C)[Si](C)(C)Oc1cc2c(Cl)cc(Br)cc2cc1Br, COc1ccc([Mg]Br)cc1 to produce COc1ccc(-c2c(O[Si](C)(C)C(C)(C)C)c(Br)cc3cccc(Cl)c23)cc1, please predict the agent for this reaction in SMILES notation in \boxed{$SMILES1, SMILES2, ...} format.