Stability constants of the binuclear species of iron(III) with pentaammine-(substituted salicylato)cobalt(III) complexes

Abstract

The stability constants of the binuclear species of iron(III) with some pentaammine(substituted salicylato)cobalt(III) complexes have been measured spectrophotometrically. At 28°C and μ = 0.6M the values of the stability constants of the species (NH₃)₅Co{CO₂C₆H₃(X)O)Fe⁴⁺ are found to be 4.22(±0.38)x10¹⁰ l. mol^-1 (X = 5-SO₃^-), 5.29(±0.79)x10¹⁰ l. mol^-1 (X = 5-Br) and 4.39 (±0.54)x10⁹ l. mol^-1 (X = 5-NO₂). Both pK_OH of the cobalt(III) substrates and the stability constants of the binuclear species are found to decrease in the order 5-Br > 5-SO₃^- > 5-NO₂.