Question

Octahedral complexes of copper (II) undergo structural distortion (Jahn-Teller). Which one of the given copper (II) complexes will show the maximum structural distortion ?

(en-ethylenediamine; H₂N - CH₂ - CH₂ - NH₂)

(A) [Cu(H₂O)₆]SO₄ 

(B) [Cu(en)(H₂O)₄]SO₄

(C) cis-[Cu(en)₂Cl₂] 

(D) trans-[Cu(en)₂Cl₂]

Answer 1

(A) [Cu(H₂O)₆]SO₄ 

There is un symmetric filling of e_g subset of Cu⁺² ion, while there is symmetrical distribution in t_2g set, if the complex has same ligand there will be equal repulsion which leads to symmetrical bond length along t_2g , but due to uneven filling of electron in e_g subset, either octahedral will be elongated or compressed.