Stability constants of tris(2,2′-bipyridine) complexes of Fe2+, Co2+, Ni2+, Cu2+ and Zn2+ in 1,2-dichloroethane saturated with water

From the extraction measurements, the equilibrium distribution constant K_D(L) for the electroneutral ligand 2,2′-bipyridine between the 1,2-dichloroethane and the aqueous phases has been determined in the form log K_D(L) = 2.03 ± 0.01, where L represents the ligand. Using known thermodynamic parameters and general relations, the stability constants of the metal chelate complexes [M(bipy)₃]²⁺ (M²⁺ = Fe²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺; bipy = 2,2′-bipyridine) in 1,2-dichloroethane saturated with water have been evaluated. It has been found that the stability constants determined in this medium are essentially higher than the corresponding stability constants of these complexes in water.