On the basic of stability of complex ion in the solution, complexes may be of two types, perfect and imperfect complexes. The stability depends upon the extent of dissociation which in turn depends upon charge on central metal atom, basic nature of ligand, chelation, and nature of metal ion and ligand according to HSAB principle.
Q Which complex is most stable?

Options

A. `[Cu(CN)_(2)]^(-) K_(d)=1xx10^(-16)`
B. `[Fe(CN)_(6)]^(4-)K_(d)=1xx10^(-37)`
C. `[Fe(CN)_(6)]^(3-) K_d=1×10^(-44)`
D. `[Ag(CN)_(2)]^(-)K_(d)=1×10^(-20)`

Answer

C