When a transition metal ion (usually) is involved in octahedral complex formation, the five degenerate d-orbitals split into two set of degenerate orbitals `(3+2)`. Three degenerate orbitals of lower energy `(d_(xy),d_(yz),d_(zx))` and a set of degenerate orbitals of higher energy `(d_(x^(2)-y^(2)" and "d_(z^(2))`. The orbitals with lower energy are called `t_(2g)` orbitals and those with higher energy are called `e_(g)` orbitals.
In octahedral complexes, positive metal ion may be considered to be present at the centre and negative ligands at the corner of a regular octahedron. As lobes of `d_(x^(2)-y^(2)" and "d_(z^(2)` lie along the axis, i.e., along the ligands, the repulsions are more and so, high is the energy. The lobes of the remaining three d-orbitals lie between the Axis i.e., between the ligands. The repulsions between them are less, so lesser the energy. In the octahedral complexes, if metal ion has electrons more than 3, then for pairing them, the options are
(i) Pairing may start with 4th electron in `t_(2g)` orbitals.
(ii) Pairing may start normally with 6th electron when `t_(2g)" and "e_(g)` orbitals are singly filled.
Select incorrect match for the following complexes.

Options

A. `[IrF_(6)]^(3-)(Delta gt P)`
B. `[Co(H_(2)O)_(6)]^(3+)(Delta lt P)`
C. `Fe(CO)_(5)(Delta gt P)`
D. `[PdCl_(2)(SCN)_(2)]^(2-)(Delta gt P)`

Answer

B