The total number of possible isomers for square-planar [Pt(Cl)(NO2)(NO3)(SCN)]²⁻ is:

The square-planar complex of type [Mabcd]ⁿ⁺, where all four ligands are different, has 3 geometrical isomers. But if one of the ligands is ambidentate, then 2 × 3 = 6 geometrical isomers are possible. Here, two ligands are ambidentate, then 4 × 3 = 12 geometrical isomers are possible. In our example, both NO₂⁻ and SCN⁻ are ambidentate ligands. Hence option B is correct. The total number of possible isomers for square-planar [Pt(Cl)(NO₂)(NO₃)(SCN)]²⁻ is 12.