Catalytic Racemization of tris(Ethylenediamine)Cobalt(III) Ion

Abstract

ALTHOUGH the optical isomers of the tris(ethylenediamine)cobalt(III) ion, ([Coen₃]³⁺), are stable indefinitely in aqueous solution at 100° C., complete racemization can be effected at 90° C. in 2 min. in the presence of activated carbon¹. It has been proposed that racemization is a surface phenomenon, and no decomposition of the complex cation occurs¹. More recently², the isomerization of lævo-tris(l-propylenediamine)cobalt(III) ion to the equilibrium mixture of the d and l forms of the complex cation was arried out with activated carbon in aqueous solution at 20° C. in 15 min. These reactions are obviously of the same nature as the rapid equilibration of mixtures of cobalt(III) complexes in various preparative procedures^3,4 brought about by activated carbon, for which no satisfactory explanation has yet been proposed.