JEE Main · 2023 · 11 Apr 2023 · Shift 2 · Coordination Compounds

With the weak-field ligands chloride and bromide, $\mathrm{N}{\mathrm{i}}^{2+}$ ($3d^8$) forms a tetrahedral complex that is paramagnetic and, as a tetrahedral $\mathrm{M}{\mathrm{A}}_2{\mathrm{B}}_2$ species, shows no geometrical isomerism. Changing the metal to $\mathrm{P}{\mathrm{t}}^{2+}$, a $5d$ ion, gives a square planar complex that is diamagnetic and now exhibits cis-trans geometrical isomerism, while both complexes stay optically inactive. Thus the geometry, the geometrical isomerism and the magnetic behaviour all change on going from nickel to platinum.