Among the following complexes, the one which shows zero crystal field stabilization energy (CFSE) is

Options

A. `[Mn(H_(2)O)_(6)]^(3+)`
B. `[Fe(H_(2)O)_(6)]^(3+)`
C. `[Co(H_(2)O)_(6)]^(2+)`
D. `[Co(H_(2)O)_(6)]^(3+)`

Answer

B

Explanation

`H_(2)O` is a weak field ligand. Hence,
`Delta_(0) lt` pairing energy.
CFSE = `(-0.4x+0.6y) Delta_(0)`
where x and y are no. of electrons occupying `t_(2g)` and `e_(g)` orbitals respectively.
For `[Fe(H_(2)O)_(6)]^(3+)` complex ion, `Fe^(3+)(3d^(5)) = t_(2g)^(3) e_(g)^(2)`
`therefore CFSE=-0.4xx3+0.6xx2=0Dq`