Question

Which one of the following is wrongly matched

• A. $[Ni(CO)_4 ]$ - neutral ligand
• B. $[Cu(NH_3)_4]^{2-}$ - square planar
• C. $[Co (en )_3 ]^{ 3+}$ - follows EAN rule
• D. $[Fe (CN )_6 ] ^{3-} - sp^3d^2$

Answer 1

Answer: (D)

In $\left[ Cu \left( NH _{3}\right)_{4}\right]^{2+}, Cu$ is present as $Cu ^{2+}$

$Cu ^{2+}=[ Ar ] 3 d^{9} 4 s^{0}$



$\left( NH _{3}\right.$ being a strong field ligand shifts one electron from $3 d$ orbital to $4 p$ orbital.)

(b) $In \left[ Ni ( CO )_{4}\right], CO$ is a neutral ligand.

(c) In [Fe(CN) $\left._{6}\right]^{3-}$, Fe is present as $Fe ^{3+}$.

$Fe ^{3+}=[ Ar ] 3 d ^{5} 4 s^{0}$

$\left[ Fe ( CN )_{6}\right]^{3-}= [ Ar ]$



Thus, its hybridisation is $d^{2} s p^{3}$ not $s p^{3} d^{2}, i e$, it is an inner orbital complex.

(d) $\left[ Co ( en )_{3}\right]^{3+}$ contains total 36 electrons, ie, follows EAN rule.