The correct order of intensity of the d-d transitions in the complexes of a 3d-transition metal ion · ABC26IN0139

Subject: Inorganic Chemistry · Chapter: Coordination Chemistry · Topic: Coordination Chemistry – General · Exam: CSIR NET 2018 · Marks: 2 · Difficulty: Hard

The correct order of intensity of the d-d transitions in the complexes of a 3d-transition metal ion
(a)cis- $\left[\mathrm{M}\left(\mathrm{H}_{2} \mathrm{O}\right)_{4} \mathrm{Cl}_{2}\right]>\operatorname{trans-}\left[\mathrm{M}\left(\mathrm{H}_{2} \mathrm{O}\right)_{4} \mathrm{Cl}_{2}\right]>\left[\mathrm{M}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{2+}$
(b)$\left[\mathrm{M}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{2+}>$ cis- $\left[\mathrm{M}\left(\mathrm{H}_{2} \mathrm{O}\right)_{4} \mathrm{Cl}_{2}\right]>\operatorname{trans}-\left[\mathrm{M}\left(\mathrm{H}_{2} \mathrm{O}\right)_{4} \mathrm{Cl}_{2}\right]$
(c)trans- $\left[\mathrm{M}\left(\mathrm{H}_{2} \mathrm{O}\right)_{4} \mathrm{Cl}_{2}\right]>$ cis- $\left[\mathrm{M}\left(\mathrm{H}_{2} \mathrm{O}\right)_{4} \mathrm{Cl}_{2}\right]>\left[\mathrm{M}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{2+}$
(d)$\left[\mathrm{M}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{2+}>$ cis- $\left[\mathrm{M}\left(\mathrm{H}_{2} \mathrm{O}\right)_{4} \mathrm{Cl}_{2}\right]>\operatorname{trans}-\left[\mathrm{M}\left(\mathrm{H}_{2} \mathrm{O}\right)_{4} \mathrm{Cl}_{2}\right]$
Answer
Answer: A ✓ checked by 4AB · confidence high
Explanation
d–d bands are Laporte-forbidden and gain intensity only when the centre of symmetry is lost. cis-[M(H₂O)₄Cl₂] has no inversion centre (most intense), trans-[M(H₂O)₄Cl₂] and [M(H₂O)₆]²⁺ are centrosymmetric, the regular octahedron being the weakest: cis > trans > hexaaqua.

Study loop for Coordination Chemistry

1. Practise the PYQsPrevious-year questions, with answers

· Browse this chapter in the app