Question

Briefly speculate on why many cobalt(lll) compounds are prepared by oxidizing Co(ll) salts rather than by substituting ligands in cobalt(lll) complexes.

Answer 1

This occurs because the common oxidation state of cobalt in their simple salts is II. The oxidation state III is the stable form only when cobalt is coordinated to certain ligands. Also it is appropriate from salts of cobalt II because cobalt complexes II substitution reactions occur very rapidly, whereas the reactions with cobalt complexes III are very slow. Preparations cobalt complex III is a rapid reaction between the cobalt II and ligand group, giving a cobalt II complex, which is the corresponding oxidized cobalt complex III.