JEE Main · 2024 · 27 Jan 2024 · Shift 2 · Coordination Compounds

The complex is $[Pt(N{H}_3{)}_{2}Cl(N{H}_{2}C{H}_3)]Cl$. Inside the coordination sphere, $N{H}_3$ and $N{H}_{2}C{H}_3$ are neutral ligands and $Cl$ (coordinated) is $-1$; the complex cation must carry a $+1$ charge to balance the ionisable $C{l}^{-}$ outside the bracket, so the platinum centre is $P{t}^{2+}$.

$P{t}^{2+}$ has the configuration $[Xe]4f^{14}5d^8$ — a $d^8$ ion. With strong-field ligands such as $N{H}_3$ and amines, $d^8$ metal centres adopt square planar geometry: the large crystal field splitting pairs up all eight d-electrons in the four lower-energy d orbitals, leaving the $d_{x^2-y^2}$ orbital empty to take part in $ds{p}^2$ hybridisation.

Since every d-electron is paired, the number of unpaired electrons $n=0$, and $\mu =\sqrt{n(n+2)}=0$ B.M.