$\begin{array}{l}{\left[{\left({\mathrm{NH}}_3\right)}_5\mathrm{Co}-\mathrm{O}-\mathrm{O}-\mathrm{Co}{\left({\mathrm{NH}}_3\right)}_5\right]}^{4+}\\ \frac{{\left({\mathrm{S}}_2{\mathrm{O}}_8\right]}^{2-}}{\text{ oxidise }}{\left[{\left({\mathrm{NH}}_3\right)}_5\mathrm{Co}-\mathrm{O}-\mathrm{O}-\mathrm{Co}{\left({\mathrm{NH}}_3\right)}_5\right]}^{5+}\end{array}$

The magnetic moment of the green complex is 1. 7 BM and for brown complexes magnetic moment is zero. (0-0) is the same in all respect in both complexes. The oxidation state of Co in brown complex and green complex respectively are :