Question

Which one of the following complex species does not obey the $EAN$ rule?

• A. $\left[Cu\right(CN{)}_4{]}^{3-}$
• B. $\left[Cr\right(N{H}_3{)}_6{]}^{3+}$
• C. $\left[Fe\right(CN{)}_6{]}^{4-}$
• D. $\left[Ni\right(CO{)}_4]$

Answer 1

The correct option is B $\left[Cr\right(N{H}_3{)}_6{]}^{3+}$

$EAN$ stands for effective atomic number. It is used to check the stability of organometallic compounds.

For a compound to obey EAN rule, its EAN value should be equal to atomic number of nearest noble gas to the central metal atom.

$EAN=Z-O.N+2[C.N]$
$Z-$ Atomic number
$O.N-$ Oxidation number
$C.N-$ Coordination number
EAN for :
$\left[Cu\right(CN{)}_4{]}^{3-}$
$29-1+2\times 4=36$
$\left[Cr\right(N{H}_3{)}_6{]}^{3+}=33$
$24-3+2\times 6=33$
$\left[Fe\right(CN{)}_6{]}^{4-}=36$
$26-2+2\times 6=36$
$\left[Ni\right(CO{)}_4]=36$
$28-0+2\times 4=36$