Question

Which of the following complexes do not follow $EAN$ rule?

• A. $K_4\left[Fe\right(CN{)}_6]$
• B. $Cr(CO{)}_6$
• C. $\left[Mn\right(CO{)}_6{]}^{+}$
• D. $\left[V\right(CO{)}_6]$

Answer 1

The correct option is D $\left[V\right(CO{)}_6]$

'Effective atomic number' (EAN) :
It is the total number of electrons around the central metal ion present in a complex and calculated as the sum of the electrons on the metal ion and the number of electrons donated by the ligands. It can be calculated using the formula.
$EAN=Z-O.S+2\times C.N$
$Z=$ atomic number of the metal
$O.S=$ number of electrons lost during the formation of the metal ion from its atom
$2\times C.N=$ number of electrons donated by the ligands.
$C.N=$ coordination number of ligands.
(a)
$K_4\left[Fe\right(CN{)}_6]$
$Z=26$
$O.S=2$
$C.N=6$
$EAN=26-2+2\times 6=36$

(b) $Cr(CO{)}_6$
$Z=24$
$O.S=0$
$C.N=6$
$EAN=24-0+2\times 6=36$

(c) $\left[Mn\right(CO{)}_6{]}^{+}$
$Z=25$
$O.S=+1$
$C.N=6$
$EAN=25-1+2\times 6=36$

(d) $\left[V\right(CO{)}_6]$
$Z=23$
$O.S=0$
$C.N=6$
$EAN=23-0+2\times 6=35$