Octahedral complexes of which transition metal ions have zero CFSE. Explain.

Explanation

Octahedral complexes formed by transition metal ions with configuration `d^(0) and d^(10)` do not have crystal field stabilisation energy, i.e., CFSE = 0. For `d^(5)` system, the CFSE will be zero if the ligand is weak.

(1) CFSE does not apply to `d^(0)` - system.
(2) Electronic configuration of `d^(5)` - system in presence of weak ligand : `t_(2)^(3)e_(g)^(2). therefore CFSE =3xx(-0.4)Delta_(o)+2xx0.6Delta_(o)=0`
[In presence of a strong ligand CFSE `ne0`].
(3) Electronic configuration of a `d^(10)`- system in presence of and ligand: `t_(2)^(6)e_(g)^(4). therefore CFSE=6xx(-0.4)Delta_(o)+4xx0.6Delta_(o)=0`