Question

In $\left[Cr\right(CO{)}_6]$ how many $CO$ groups can be replaced by NO?

• A. All the $6CO$ groups are replaced by $6NO$ groups
• B. All the $4CO$ groups are replaced by $6NO$ groups
• C. All the $2CO$ groups are replaced by $3NO$ groups
• D. All the $6CO$ groups are replaced by $4NO$ groups

Answer 1

The correct option is D All the $6CO$ groups are replaced by $4NO$ groups

$\left[Cr\right(CO{)}_6]$
$EAN=24-0+2\times 6=36$
Number of electrons donated by ligands​ (CO) is 12.
$NO$ is $3e^{-}$ donor species so,
$6CO$ which is replaced by $4NO$ group to make EAN 36.