Reactions of sulfur(IV) with complex ions of chromium-, manganese-, iron- and cobalt(III) in aqueous medium

The reactions of sulfur(IV) with complexes of Cr(III), Mn(III), Fe(III) and Co(III) are discussed. Cr(III) forms O-sulfito complexes while Mn(III) and Fe(III) form S-bonded sulfito species. The oxygen bonded sulfito species of Co(III) are transient intermediates which undergo sulfite ligand linkage isomerization and facile redox reactions. The S-bonded sulfito Co(III) species can be photochemically isomerized to its O-bonded isomer. The ligand control on the kinetics of reversible substitution of S(IV) at Cr(III), Mn(III), Fe(III) and Co(III) centres, the redox activities and also the S(III) induced reactions of the resulting sulfito complexes are highlighted.