Heptamethyl (aquo)(pentafluorophenylthiolate)cobyrinate perchlorate, [(H₂O)(C₆F₅S)Cob(III)7C₁ester]ClO₄, was synthesized as a B₁₂ model complex having a thiolate ligand in the axial position. The axial ligand change in heptamethyl (diaquo)cobyrinate diperchlorate, [(H₂O)₂Cob(III)7C₁ester](ClO₄)₂, from H₂O to C₆F₅S⁻ afforded the B₁₂–thiolate complex. The B₁₂–thiolate model complex was characterized by UV-vis, NMR and ESI-mass spectroscopies. The coordination of C₆F₅S⁻ to the cobalt center affected the spectroscopic properties of the corrin ring through the electronic interaction between the axial ligand (C₆F₅S⁻) and the equatorial ligand (corrin). The photolysis of the B₁₂–thiolate model complex led to the homolytic cleavage of the Co(III)–S bond to form the Co(II) complex and the phenyl thiyl radical. The thermolysis of the B₁₂–thiolate model complex also led to the homolytic cleavage of the Co(III)–S bond. Furthermore, the reactivity of the Co(III)–S bond of the B₁₂–thiolate model complex was applied to the catalytic oxidation of C₆F₅SH to C₆F₅S–SC₆F₅.