Question

Draw energy level diagram and indicate the number of electrons in each level for the complex [Cu(H₂O)₆]²⁺. Whether the complex is paramangnetic or diamagnetic ?

Answer 1

Cu in [Cu(H₂O)₆] has +2 oxidation state. Electronic configuration of Cu atom – 3d¹⁰ 4s¹ Electronic configuration of Cu²⁺ ion – 3d⁹ Distortions in Octahedral Geometry Observed in [Cu(H₂O)₆]²⁺ 

If the ground electronic configuration of a non-linear complex is orbitally degenerate, the complex will distort so as to remove the degeneracy and achieve a lower energy. This is called the Jahn – Effect.

Cu²⁺ – Two ways of filling the eg orbitals; there is degeneracy and jahn – Teller Distortion is observed Jahn – Teller Distortion in Cu(III) Complexs [Cu(H₂ O)₆]²⁺

• t_2g⁶ e_g³ 
• It contains one unpaired electron in e_g(dx² – y²orbital) 
• Hence it is paramagnetic