The correct increasing order of stability of the complexes based on ( _ o ) value is : I. ( [ Mn ( CN )₆ ]³⁻ ) II. ( [ Co ( CN )₆ ]⁴⁻ ) III. ( [ Fe ( CN )₆ ]⁴⁻ ) IV. ( [ Fe ( CN )₆ ]³⁻ )

Step-by-step solution

Neglecting pairing energy I. [ Mn ( CN ) B ]³⁻ Mn ³⁺, t ₂ ~g ^4, CFSE =-0.4 4 o =-1.6 。 II. [ Co ( CN ) 8]⁴⁻ Co ²⁺, t ₂ ^6 eg ^1, CFSE =-0.4 6+0.6 1=-1.8 _ III. [ Fe ( CN )₈ ]⁴⁻ Fe ²⁺, t _ 2 g ^6 e ^0, CFSE =-0.4 6=-2.4 ₀ IV. [ Fe ( CN )₈ ]³⁻ Fe ³⁺, t _ 2 g ^5 e ^0, CFSE =-0.4 5=-2 ₀ Order of stability III > IV > II > I