Question

Specify the oxidation numbers of the metals in the following coordination entities:
(i) ${\left[Co\left(H_{2}O\right)\left(CN\right)\right(en{)}_2]}^{2+}$

(ii) $K_3\left[Fe{\left(CN\right)}_6\right]$

(iii) ${\left[CoB{r}_2{\left(en\right)}_2\right]}^{+}$

(iv) $\left[Cr{\left(N{H}_3\right)}_{3}C{l}_3\right]$

(v) ${\left[PtC{l}_4\right]}^{2-}$

Answer 1

Let the oxidation number of metal be x.
(i) ${\left[Co\left(H_{2}O\right)\left(CN\right){\left(en\right)}_2\right]}^{2+}$
$\begin{array}{c}\Rightarrow x+0+(-1)+(2\times 0)=+2\\ x=2+1=+3\end{array}$

(ii) $K_3\left[Fe{\left(CN\right)}_6\right]$
$\begin{array}{c}(+1)\times 3+x+(-1)\times 6=0\\ 3+x-6=0\\ x-3=0\\ x=+3\end{array}$

(iii) ${\left[CoB{r}_2{\left(en\right)}_2\right]}^{+}$
$\begin{array}{c}x+2\times (-1)+(2\times 0)=+1\\ x=1+2=+3\end{array}$

(iv) $\left[Cr{\left(N{H}_3\right)}_{3}C{l}_3\right]$

$\begin{array}{c}x+(3\times 0)+(3\times -1)=0\\ x=+3\end{array}$

(v) ${\left[PtC{l}_4\right]}^{2-}$
$\begin{array}{c}x+(-1)4=-2\\ x-4=-2\\ x=-2+4=+2\end{array}$