The correct option is A (a−r,t),(b−s,u)
(c−p,t),(d−p,t)
When the complex formed involves the inner `'(n-1)d'` orbital for hybridisation `(d^2sp^3)`, the complex is called inner orbital complex. They are also called as low spin complex.
When the complex formed involves the outer `'nd'` orbital for hybridisation `(sp^3d^2)`, the complex is called outer orbital complex. They are also called as high spin complex.
[Ni(CN)4]2−
The ligand is CN−
It is a strong field ligand for Ni2+
Ni2+⇒3d84s04p04d0
Pairing of electron happens due to the presence of a strong field ligand. Thus, the hybridization is dsp2 and the geometry is square plannar and it forms an inner orbital complex.
[Ni(CO)4]
The ligand is CO
It is a strong field ligand for Ni
Ni⇒3d84s24p04d0
In the presence of a strong field ligand, the electrons in `s`-orbitals gets shifted to the `d`-orbital and thus the hybridisation is sp3 and it forms an outer orbital complex.
[Co(en)3]3+
The ligand is Ethylene diammine
It is a strong field ligand for Co3+
Co3+⇒3d64s04p04d0
Pairing of electrons takes place because of the presence of a strong field ligand. Thus the hybridisation will be it d2sp3 and it forms an inner orbital complex.
[Co(Br)3(Cl)3]3−
The ligand is Cl− and Br−
They are strong field ligands for Co3+
Co3+⇒3d64s04p04d0
Pairing of electrons takes place due to the presence of strong field ligands. Thus the hybridisation will be d2sp3 and it forms an inner orbital complex .