Question

$\left[Co\right(N{H}_3{)}_{5}Br\left]S{O}_4\text{and}\right[Co\left(N{H}_3{)}_{5}S{O}_4\right]Br$ are the examples of : –

• A. Linkage isomerism
• B. Optical isomerism
• C. Geometrical isomerism
• D. Ionisation isomerism

Answer 1

The correct option is D Ionisation isomerism

$\left[Co\right(N{H}_3{)}_{5}Br\left]S{O}_{4}and\right[Co\left(N{H}_3{)}_{5}S{O}_4\right]Br$ are ionisation isomers. This form of isomerism arises when the counter ion in a complex salt is itself a potential ligand and can displace a ligand which can then become the counter ion.
Above two complex can be distinguished by test.

Aqueous solution of $\left[Co\right(N{H}_3{)}_{5}Br]S{O}_4$ will give a white ppt in $BaC{l}_2$ solution. The ppt is insoluble in conc. $HN{O}_3$ confirming presence of free $S{O}_4^{-2}$ ion. Aqueous solution of $\left[Co\right(N{H}_3{)}_{5}S{O}_4]Br$ will not give the test.
$\Rightarrow \left[Co\right(N{H}_3{)}_{5}Br]S{O}_4\leftrightharpoons [Co(N{H}_3{)}_{5}Br{]}^{2+}+S{O}_4^{-2}$
$BaC{l}_2+S{O}_4^{-2}\to BaS{O}_4\downarrow +2C{l}^{-}$
$\text{White ppt}$
$\Rightarrow \left[Co\right(N{H}_3{)}_{5}S{O}_4]Br\leftrightharpoons [Co(N{H}_3{)}_{5}S{O}_4{]}^{+}+B{r}^{-}$
$BaC{l}_2+B{r}^{-}\to \text{No ppt}$.