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Question: Which of the following pairs represents linkage isomers? (A) \([Cu{(N{H_3})_4}][PtC{l_4}]\) and \(...

Which of the following pairs represents linkage isomers?
(A) [Cu(NH3)4][PtCl4][Cu{(N{H_3})_4}][PtC{l_4}] and [Pt(NH3)][CuCl4][Pt(N{H_3})][CuC{l_4}]
(B) [Pd(PPh3)2(NCS)2][Pd{(PP{h_3})_2}{(NCS)_2}] and [Pd(PPh3)2(SCN)2][Pd{(PP{h_3})_2}{(SCN)_2}]
(C) [Co(NH3)5NO3]SO4[Co{(N{H_3})_5}N{O_3}]S{O_4} and [Co(NH3)5SO4]NO3[Co{(N{H_3})_5}S{O_4}]N{O_3}
(D) [PtCl2(NH3)4]Br2[PtC{l_2}{(N{H_3})_4}]B{r_2} and [PtBr2(NH3)4]Cl2[PtB{r_2}{(N{H_3})_4}]C{l_2}

Explanation

Solution

Any metal complex that has ambidentate ligands may show linkage isomerism. When a ligand is bound to metal with two different atoms in different complexes, then both the complexes are called linkage isomers.

Complete step by step solution:
We are given four pairs of metal complexes and we need to find which of the pair shows linkage isomerism. Let’s know what linkage isomerism is.
- Isomers are the compounds that have the same chemical formula but have different properties. We know that isomerism is broadly divided into two categories; structural isomerism and stereoisomerism. Linkage isomerism is a type of a structural isomerism.
- Linkage isomerism is seen in the complexes which involves ambidentate ligand. Ambidentate ligand is a ligand which can donate the electrons to metal from more than one atom.
- The ligands Cl−,Br−,PPh3,NH3,NO3− and SO42−C{l^ - },B{r^ - },PP{h_3},N{H_3},N{O_3}^ - {\text{ and S}}{{\text{O}}_4}^{2 - } can only donate electrons from one site. So, in option (A), (C) and (D) the ligands present are not ambidentate. So, they cannot show linkage isomerism.
- In option (B), one of the ligands are NCS− and SCN−NC{S^ - }{\text{ and SC}}{{\text{N}}^ - }. These ligands are ambidentate because they can donate electrons from S-atoms as well as N-atoms.
- So, we can see that in one complex, the bond is like M-SCN and in another complex the bond is like M-NCS. So, it is clear that the same ligand is donating electrons from different atoms. Therefore linkage isomerism is present in this pair.

So, the correct answer to this question is (B).

Note: Do not get confused with coordination isomerism. It actually involves interchange of ligands between anionic and cationic species of different metal ions present in the metal complex.