Q. Explain the electronic distribution complexes?

In majority of the cases the decrease in the number of unpaired electrons agrees well with the magnetic moment values obtained experimentally. However, it does not hold true for a number of complexes. For example a complex ion like [FeF₆]^3- gives a magnetic moment  value equal to five unpaired electrons indicating thereby that the electronic distribution on  the Fe³⁺ ion remains the same as in free ion state. Pauling suggested that instead of using the inner orbitals (3d, 4s. 4p), iron can use outer orbitals (4s. 4p, & 4d) for d²sp³ hybridisation leaving the electronic distribution the same as m free ion state. Werent authors call the two types of complexes with different names as listed below.