Competitive Aryl–Fluorine and Aryl–Halogen (Halogen = Cl, Br) Bond Cleavage with Iridium Porphyrin Complexes

Abstract

Base-promoted competitive Ar–F and Ar–X (X = Cl, Br) bond cleavage with iridium porphyrin complexes was investigated. Mechanistic studies suggested that Ir(ttp)− (ttp = 5,10,15,20-tetra-p-tolylporphyrinato dianion) cleaves the Ar–F bond via nucleophilic aromatic substitution and Ir2(ttp)2 cleaves the Ar–X (X = Cl, Br) bond via metalloradical ipso substitution. Therefore, a stronger base, polar solvent, lower temperature, and iridium anion precursor favor Ar–F bond cleavage, while a weaker base, nonpolar solvent, higher temperature, and Ir2(ttp)2 precursor favor Ar–X (X = Cl, Br) bond cleavage.