JEE Main · 2021 · 17 Mar 2021 · Shift 2 · Coordination Compounds

In $[\mathrm{Co}(\mathrm{N}{\mathrm{H}}_3{)}_6][\mathrm{Cr}(\mathrm{CN}{)}_6]$ both the cation and the anion are complex ions, so the ammine and cyanide sets can be interchanged between cobalt and chromium to give a second compound of the same composition, which is coordination isomerism. In $[\mathrm{Co}(\mathrm{N}{\mathrm{H}}_3{)}_3(\mathrm{N}{\mathrm{O}}_2{)}_3]$ the nitrite ligand can attach through its nitrogen as nitro or through an oxygen as nitrito, which is linkage isomerism. In $[\mathrm{Cr}({\mathrm{H}}_2\mathrm{O}{)}_6]\mathrm{C}{\mathrm{l}}_3$ a water molecule inside the coordination sphere can trade places with a chloride ion outside it, giving solvate isomerism. The cis form of $[\mathrm{CrC}{\mathrm{l}}_2(\mathrm{ox}{)}_2{]}^{3-}$ carries two chelate rings in an arrangement that has no plane of symmetry, so it and its mirror image are non-superimposable and it shows optical isomerism.