In
K3[Fe(CN)6] :
fe+3 =
3d5 CN− being a strong field ligand, it causes pairing of electrons,so only one unpaired electron. The complex is paramagnetic.
In
[Co(NH3)−6]Cl3 :
Co3+ =
3d6 NH3 being a strong field ligand it causes pairing of spins. There is no unpaired electron, hence the complex is diamagnetic.
In
Na3[Co(oxalate)3] :
Co3+ =
3d6 Oxalate being a strong field ligand it causes pairing of electron spins. There is no unpaired electron, hence the complex is diamagnetic.
In
[Ni(H2O)6]Cl2 :
Ni2+ =
3d8 Since
H2O is a weak field ligand, no pairing takes place. There are two unpaired electrons, so the complex is paramagnetic.
In
K2[Pt(CN)4] :
Pt2+ =
5d8 CN− being a strong field ligand, it causes pairing of electron spins, so no unpaired electron. Hence, the complex is diamagnetic.
In
[Zn(H2O)6(NO3)2] :
Zn2+ has
3d10 configuration. Therefore, It is a diamagnetic complex.
