Effect of modification of the axial (fifth and sixth) coordination sites on the physicochemical properties and reactivity of iridium(III) complexes with 5,10,15,20-tetraphenyl-21H,23H-porphine was studied. Oxidation reactions of (Cl)(H 2 O)IrTPP in protic solvents by atmospheric oxygen (on assistance of protons at high concentration) preceded by ligand substitution at the axial position were studied. It was found that (Cl)(H 2 O)IrTPP in 100% AcOH undergoes slow one-electron oxidation at the aromatic ligand to form π cation radical (CH 3 COO)(CH 3 COOH)IrTPP ·+ . The reaction was studied in 100% AcOH (H 2 O content 0.078%) at 288–308 K, its kinetic parameters were obtained. The (Cl)(H 2 O)IrTPP reaction product in CF 3 COOH was identified as complex (CF 3 COO) 2 Ir IV TPP oxidized at the central metal cation. It was experimentally confirmed that the reaction in 99% CF 3 COOH at 298 K proceeds in two stages: the substitution of axial Cl − and H 2 O by excess CF 3 COO − ( k eff = (1.8 ± 0.1) × 10 −3 s −1 ) and the oxidation of iridium to Ir(IV) ( k eff = (8.0 ± 0.5) × 10 −5 s −1 ). Data on similar Re(III) complexes (PhO)ReTPP and (Cl)ReTPP are presented for comparison.