(i) In
[CoF6]3− ion, the oxidation state of cobalt is +3 .
Co3+ ion
Formation of
[CoF6]3+
Here,
F− ion provides a weak ligand field and is unable to pair up the unpaired electrons of the
3d -orbitals. Thus, it is highly paramagnetic.
(ii) In
[Co(NH3)6]3+ ion,
NH3 provides a strong field ligand and the electrons of metal are made to pair up, so the complex will be diamagnetic.
Formation of [Co (NH
3)6]3+
(iii) Similarly in
[Ni(NH3)4]2+,NH3 is a strong field ligand and the complex is diamagnetic.
(iv)
[Ni(CN)4]2− has
Ni in the +2 oxidation state and
dsp2 hybridisation. Thus it is also diamagnetic.
(v) In [Fe(CN)
6]4− ions, oxidation state of Fe is +2 and
CN− ligand is a strong field ligand. Thus the resulting complex ion involves
d2sp3 hybridisation and diamagnetic as it does not contain any unpaired electrons.
∵ Magnetic moment
=√n(n+2) where,
n= no. of unpaired electrons
∴[CoF6]3− has maximum magnetic moment.