Complex(es) which has/have unpaired electron(s) that is equal to that of iron center in oxymyoglobin is/are

A. [Fe(ox)3]3−

B. [Fe(CN)6]3−

C. [NiCl4]2−

D. [Cu(NH3)4]2+

(Given: ox = oxalato)

Correct answer is

Concept:-

The structure of the oxymyoglobin complex is shown below:

Iron is in Fe⁺³ oxidation state, has \(t_2g^{5}\:eg^{0}\) configuration and one unpaired electron (n=1).

Explanation:-

[Fe(ox)3]3−

Fe³⁺(\(t_{2g}^{3}\:e_g^{2}\))=d⁵ high spin octahedral,

No. of unpaired electrons=5

[Fe(CN)6]3−      

Fe³⁺ \((t_{2g}^{5}\:e_g^{0})\) = d⁵ low spin octahedral 

No. of unpaired electrons=1

[NiCl4]2−     

Ni²⁺ \((e_{g}^{4}\:t_{2g}^{4})\)= d⁸ tetrahedral complex, \(eg^{4}\:t_2g^{4}\)

No. of unpaired electrons=2

[Cu(NH3)4]2+

Cu²⁺=d⁹ low spin, square planner

No. of unpaired electrons=1

• In case of complex(es) [Fe(CN)6]3− and [Cu(NH3)4]2+ has one unpaired electron. 
• That is exactly the same as the number of unpaired electron(s) present in the iron center in oxymyoglobin.

Conclusion:-

Therefore B and D is the correct one.