Effect of increasing the bidentate chelate ring size in Co(III) complexes on their behavior in salting-out TLC on different adsorbents

Abstract

The effect of enlargement of the chelate ring size in Co(III) complexes containing bidentate aminocarboxylato and/or diamine ligands on their R-F values in salting-out chromatography has been investigated on thin layers of silica gel, cellulose, polyacrylonitrile, and CN-modified silica gel. Salting-out was achieved with aqueous solutions of ammonium sulfate, Enlargement of the chelate ring caused a decrease in the R-F values of the complexes. By use of linear regression analysis and the theory of error propagation it was established that the logarithms of the separation factors of the pairs of compounds investigated were either unaffected or changed only slightly with changing concentration of salt in the mobile phase; this could not be established for certain on the basis of R-F values alone. Complete correlation was established between the chromatographic behavior of the complexes and the previously investigated effect of successive enlargement of the rings in cobalt(III) complexes containing hexadentate ligands of the EDTA type. The corresponding separation mechanism of the pairs of compounds investigated was also considered. It was finally established that the regularities mentioned were independent of the adsorbent used.