Properties of chemically generated π-radical cations and molecules of (meso-phenyl-β-octaethylporphyrinato)rhenium(V) with axial molecular oxygen

Abstract

The state of existence and reactions of stable rhenium(V) complexes with β-octaethylporphin (O=Re(OPh)OEP, O=Re(Cl)OEP) and its meso-diphenyl-substituted derivatives (O=Re(Cl)5,15DPOEP) in concentrated H2SO4 at 318–348 K were studied. It was found that O=Re(Cl)5,15DPOEP undergoes slow single-electron oxidation at the aromatic ligand to give π-radical cation. The oxidation is accompanied by replacement of the axial Cl− ligand by the hydrogen sulfate ion present in excess. Full kinetic description of the intricate oxidation reaction of the complex involving atmospheric oxygen was obtained and parameters of simple reactions that constitute the intricate process were determined. In the case of O=Re(Cl)OEP and O=Re(OPh)OEP, the reaction stops after the formation of the cationic complex with axially coordinated oxygen and outer-sphere chloride ion O=Re(O2)OEP+ Cl−. The effect of the nature of axial and macrocyclic ligands in rhenium(V) porphyrins on the processes in sulfuric acid solutions of these compounds was established.