Solution
= Solution
Both complexes have all their $d$ <electrons> paired, so $S=0$. Their <spin-only magnetic moment> is therefore
$$
\boxed{\mu_{\rm eff}=2\sqrt{S(S+1)}\,\mu_{\rm B}=0\ \mathrm{B.M.}\quad\text{for both complexes}.}
$$
They exhibit <diamagnetism>. The formula describes the spin contribution; it does not say that a closed-shell sample has no diamagnetic response to an applied field.