Conductivity and Ion Association of Some Diastereoisomeric Salts in Water. I. Δ-[Co(NO2)2(en)2]Δ-[Co(edta)] and Λ-[Co(NO2)2(en)2]Δ-[Co(edta)] at 15, 25, and 35 °C

Abstract

Abstract Electric conductivities of the diastereoisomeric salts, Δ(−)589-[Co(NO2)2(en)2]Δ(+)546-[Co(edta)] and Λ-(+)589-[Co(NO2)2(en)2]Δ(+)546-[Co(edta)], were measured in water at 15, 25, and 35 °C. Results were analyzed in terms of the conductivity equations of Fuoss-Hsia and Pitts. The obtained values of the ion-association constant are large and decrease with increasing temperature. The results can not be entirely explained by the electrostatic theories of ion association and suggest the formation of contact ion pairs, attributable to the existence of interactions other than simple electrostatic ones between the complex ions. No appreciable difference is found in the obtained thermodynamic parameters of ion association between the two salts. Ion–solvent interactions and effective sizes of the dissolved complex ions are also discussed in connection with the estimation of the closest distance of approach of the ions.