Question

Which of the following complexes show linkage isomerism?
(a) $\left[Co\right(N{H}_3{)}_5\left(N{O}_2\right){]}^{2+}$
(b) $\left[Co\right(H_{2}O{)}_{5}CO{]}^{3+}$
(c) $\left[Cr\right(N{H}_3{)}_5]SC{N}^{2+}$
(d) $\left[Fe\right(en{)}_{2}C{l}_2{]}^{+}$

Answer 1

Coordination compounds containing a ligand with more than one non-equivalent binding position (known as ambient ligand) show linkage isomerism.
For example

$\left[Co\right(N{H}_3{)}_5\left(N{O}_2\right){]}^{2+}$ contains $N{O}_2$ which have two donor sites N and O can be shown by arrow $(\to )$ as


$\left[Cr\right(N{H}_3{)}_5]SC{N}^{2+}$ contains SCN which have two different donor sites S and N can be shown by arrow $(\to )$

$\to S$ -- $C\equiv N\leftarrow$

Hence, $\left[Co\right(N{H}_3{)}_5\left(N{O}_2\right){]}^{2+}$ and $\left[Cr\right(N{H}_3{)}_5]SC{N}^{2+}$ show linkage isomerism. While $\left[Co\right(H_{2}O{)}_{5}CO{]}^{3+}$ and $\left[Fe\right(en{)}_{2}C{l}_2{]}^{+}$ has no ambient ligand. So, these two will not show linkage isomerism.
Hence, options (a) and (c) are correct choices.