Complexation of Osmium(IV) with 3-Methyl-2,6-Dimercapto-1-Thiopyrone-4 and Its Catalytic Application

The reaction of osmium(IV) with 3-methyl-2,6-dimercapto-1-thiopyrone-4 was studied by spectrometry, amperometry, and potentiometry. In a pH range of 2–4 M HCl (2 M H₂SO₄), insoluble osmium methyl thiopyrone dimercaptides formed with a metal-to-ligand ratio of 1 : 1, 1 : 2, 1 : 3, 1 : 4, and 1 : 6 in HCl solutions and of 1 : 1, 1 : 2, 1 : 3, and 1 : 5 in H₂SO₄ solutions. Conditional stability constants and molar absorption coefficients were determined for the products formed in the presence of excess reagent (n = 3, P = 0.95): logβ = 24.42 ± 0.02 and ε = (2.95 α 0.01) × 10⁴ for the 1 : 5 complex and logβ = 30.24 ± 0.10 and ε = (2.92 ± 0.01) × 10⁴ for the 1 : 6 complex. It was shown that the reagent can be used for the potentiometric titration of osmium(IV). Conditions were determined for the successive titration of components of the osmium(IV)-ruthenium(IV) mixture.