Question

Arrange the complexes in order of decreasing stability.

Rank from most stable to least stable. To rank items as equivalent, overlap them.

[CuF₆]²⁺   [Ni(en)₃]²⁺   [Ni(en)(H₂O)₄]²⁺   [Ni(NH₃)₆]²⁺

Answer 1

stability decreasing order

[Ni(en)₃]²⁺   > [Ni(en)(H₂O)₄]²⁺ > [Ni(NH₃)₆]²⁺ >[CuF₆]²⁺

Explanation :

[Ni(en)₃]²⁺   in this complex three chelating ligands are present . no of chelating ligands increses complex stability also increase.

all Ni complexes are octahedral complexes and low spin complexes.

Ni+2 - d⁸ - crystal field configuration ---------t_2g6 e_g2.

               CFSE =   - 6 x 0.4 + 2 x 0.6 = -1.2

in case Cu complex oxidation state of Cu is +4   ------3d7

crystal field configuration = t⁵_2ge²_g

CFSE=   -5 x 0.4 + 2 x 0.6 = -0.8

CFSE of Ni complexes is more than Cu complex. so with in Ni complex we need to decide which is more stable.

more chelating ligands present stabilty also increase.