$\left[\mathrm{Cr}{\left({\mathrm{NH}}_3\right)}_6\right]\left[\mathrm{Co}{\left(\mathrm{CN}\right)}_6\right] \mathrm{and} \left[\mathrm{Co}{\left({\mathrm{NH}}_3\right)}_6\right]\left[\mathrm{Cr}{\left(\mathrm{CN}\right)}_6\right]$are a pair of------- isomers

Isomers in which both cation and anion are complexes are called coordination isomers;

Coordination isomers are formed due the exchange of ligands between cationic complex and anionic complex;