Question

The order of energy absorbed which is responsible for the color of complexes
(A) ${\left[Ni{\left(H_{2}O\right)}_2(en{)}_2\right]}^{2+}$
(B) ${\left[Ni{\left(H_{2}O\right)}_4(en)\right]}^{2+}$ and
(C) ${\left[Ni(en{)}_3\right]}^{2+}$

• A. (B) > (A) > (C)
• B. (A) > (B) > (C)
• C. (C) > (B) > (A)
• D. (C) > (A) > (B)

Answer 1

Answer: (D)

(A) ${\left[Ni{\left(H_{2}O\right)}_2(en{)}_2\right]}^{2+}$
(B) ${\left[Ni{\left(H_{2}O\right)}_4(en)\right]}^{2+}$
(C) ${\left[Ni(en{)}_3\right]}^{2+}$
en is SFL (strong field ligand)
As the number of en (strong ligand) increase splitting also increases.
So, ${\Delta }_0$ increases.
i.e. maximum energy will be absorbed in case of option $C$.
So the order is $C>A>B$