Atomic number of Mn, Fe and Co are 25, 26 and 27 respectively. Which of the following inner orbital octahedral complex ions are diamagnetic -

Options

A. `[Co(NH_(3))_(6)]^(3+)`
B. `[Mn(CN)_(6)]^(4-)`
C. `[Fe(CN)_(6)]^(4-)`
D. `[Fe(CN)_(6)]^(3-)`

Answer

A, C

Explanation

All the complexes are inner orbtial octahedral cmplexes. So central metal ions are `d^(2)sp^(3)` hybridised. In presence of respective ligand, electronic configuration of metal ions are as follows :
(A) `Co^(3+)=3d^(6)=(=d^(2)d^(2)d^(2)d^(0)d^(0))`, it has no unpaired electron (diamagnetic),
(B) `Mn^(3+)[3d^(4)(d^(2)d^(1)d^(1)d^(0)d^(0)),` it has two unpaired electrons. (C) `Fe^(2+)=3d^(6)` (similar to that of `Co^(3+)`) , No unpaired electron (diamagnetic ) (D) `Fe^(3+)=3d^(5)(=d^(2)d^(2)d^(1)d^(0)d^(0))` , one upaired electron.