Due to the presence of ambidentate ligands coordination compounds show isomerism. Palladium complexes of the type Pd( C6H5 )2(NCS)2 and Pd(C6H5)2(SCN)2 are

1. Linkage isomers   
2. Coordination isomers
3. Ionization isomers 
4. Geometrical isomers

The ligand(s) which has two different bonding sites are known as ambident ligands

e.g., NCS, NO2 etc.

Here, NCS has two binding sites at N and S,

Hence, NCS (thiocyanate) can bind to the metal ion in two ways


Thus, coordination compounds containing NCS as a ligand can show linkage

isomerism i.e.Pd(C6H5)2(SCN)2 and Pd(C6H5)2(NCS)2 ]are linkage isomers,

Hence, correct choice is (a).