Question

In which of the following coordination compounds, the central metal ion is in zero oxidation state:

• A. $\left[Fe{\left(H_{2}O\right)}_6\right]{Cl}_3$
• B. $K_4\left[Fe{\left(CN\right)}_6\right]$
• C. $Fe{\left(CO\right)}_5$
• D. $\left[Fe{\left(H_{2}O\right)}_6\right]{Cl}_2$

Answer 1

The correct option is C $Fe{\left(CO\right)}_5$

Let the oxidation state of the central atom Fe in coordination species is $x$.

The oxidation number of Fe in $\left[Fe\right(H_{2}O{)}_6{]}^{3+}$ is:

$x+6\left(0\right)=+3$

$x=+3$

The oxidation number of Fe in $\left[Fe\right(CN{)}_6{]}^{4-}$ is:

$6(-1)+x=-4$

$x-6=-4$

$x=+2$

The oxidation number of Fe in $\left[Fe\right(CO{)}_5{]}^0$ is:

$x+0\left(5\right)=0$

$x=0$

The oxidation number of Fe in $\left[Fe\right(H_{2}O{)}_6{]}^{2+}$ is:
$x+6\left(0\right)=+2$
$x=+2$

Hence, option $C$ is correct.