Question

Why is $\left[ Ni ( en )_{3}\right]^{2^{+}}$, nearly $10^{10}$ times more stable than $\left[ Ni \left( NH _{3}\right)_{6}\right]^{2^{+}} ?($ en $=$ enthlene diamine $)$

• A. $NH _{3}$ is the weakest ligand
• B. 'en' is a chelating ligand and forms thermody namically more stable complexes
• C. six $NH _{3}$ ligands cause steric hindrance around the $Ni ^{2^{+}}$centre
• D. $NH _{3}$ evaporates easily and causes instability to the $\left[ Ni \left( NH _{3}\right)_{6}\right]^{2+}$ complex

Answer 1

Answer: (B)

Option (C) is correct. $\left[ Ni ( en )_{3}\right]^{2+}$, is nearly $10^{10}$ times more stable then $\left[ Ni \left( NH _{3}\right)_{6}\right]^{2+}$ because 'en' is a chelating ligand and forms thermodynamically more stable complexes while ammonia is a weak ligand.
In general cases, a cyclic or chelate complex is more stable than open complex due to chelating effect or macrocyclic effect.