One mole of the metal complex with the formula $\mathrm{Co}(en{)}_2{\mathrm{Cl}}_3$  gives one mole of silver chloride on treatment with an excess silver nitrate. The secondary valency of Co in the complex is ________________ .

One mole of the metal complex with the formula $\mathrm{Co}(\mathrm{en}{)}_2{\mathrm{Cl}}_3$  gives one mole of silver chloride on treatment with an excess silver nitrate

$\left[\mathrm{Co}(\mathrm{en}{)}_2{\mathrm{Cl}}_2\right]\mathrm{Cl}+\underset{\text{ (excess) }}{{\mathrm{AgNO}}_3}\to \underset{\text{ (white ppt) }}{\mathrm{AgCl}}$

    1 mole                 1 mole             1 mole 

Since two bidentate ligands and two monodentate ligands are there, the secondary vacancy of Co in the complex is 6.