Which one of the following has a square planar geometry?
`(Co=27, Ni=28, Fe=26, Pt=78)`

Options

A. (a) `[CoCl_4]^(2-)`
B. (b) `[FeCl_4]^(2-)`
C. (c) `[NiCl_4]^(2-)`
D. (d) `[PtCl_4]^(2-)`

Answer

D

Explanation

`Cl^(-)` is weak field ligand and so chloride complexes are mostly high spin, but CFSE for transition metals is in the order `3dlt4dlt5d`, so the metal belonging to higher series will prefer low spin complex. Among the given complexes, `Pt` forms low spin complex while others form high spin complex. Square planar geometry of `[PtCl_4]^(2-)` is also supported by its diamagnetic nature.
Note: All the complexes of Pd (II) ad Pt (II) are square planar.