Question

Consider the following complexes:
1) $Fe(CO{)}_5$
2) $Ni(CO{)}_4$
3) $K_4\left[Fe\right(CN{)}_6]$
4) $N{a}_3\left[Cu\right(SCN{)}_4]$
Which of the above complex obeys $EAN$ rule?

• A. $1$ and $2$ only
• B. $2,3$ and $4$ only
• C. $1,2,3$ and $4$ only
• D. None of these

Answer 1

The correct option is A $1$ and $2$ only

EAN rule:-

The total number of $e^{-}s$ linked with the central metal atom or ion in a complex plus the $e^{-}s$ donated by the ligand is known as Effective Atomic Number, i.e; $EAN$. It is the attainment of noble gas configuration.

$EAN=Z-x+2nL$

$Z$= atomic number of the metal in the complex ion.

$x$= oxidation state of the central metal atom.

$n$= no. of ligands.

$L$= no. of coordinate bond formed by the ligand.

EAN rule:-

The total number of $e^{-}s$ linked with the central metal atom or ion in a complex plus the $e^{-}s$ donated by the ligand is known as Effective Atomic Number, i.e; $EAN$. It is the attainment of noble gas configuration.

$EAN=Z-x+2nL$

$Z$= atomic number of the metal in the complex ion.

$x$= oxidation state of the central metal atom.

$n$= no. of ligands.

$L$= no. of coordinate bond formed by the ligand.

1) $Fe(CO{)}_5$

EAN=$26-0+2\left(5\right)\times 1$

$\Rightarrow 26+10=36$.

2) $Ni(CO{)}_4$

EAN=$28-0+2\left(4\right)\left(1\right)$

$\Rightarrow 28+8=36$.

3) $K_4\left[Fe\right(CN{)}_6]⟷[Fe(CN{)}_6{]}^{4-}$

EAN=$26+4+2\left(6\right)\times 1$

$\Rightarrow 26+16=42$.

4)$N{a}_3\left[Cu\right(SCN{)}_4]$

EAN=$29+3+2\left(1\right)\left(4\right)$

$\Rightarrow 32+8=40$.

Thus (1) and (2) follow EAN rule.