Question 13

1. $[Mn(NH_3)_6]^{3+}$: $Mn^{3+}$ is $3d^4$. Even with strong field ligands, $d^4$ in octahedral geometry results in unpaired electrons (Low spin: $t_{2g}^4 e_g^0$, $n=2$). Paramagnetic.
2. $[MnCl_6]^{3-}$: $Mn^{3+}$ is $3d^4$, $Cl^-$ is a weak field ligand. High spin: $t_{2g}^3 e_g^1$, $n=4$. Paramagnetic.
3. $[FeF_6]^{3-}$: $Fe^{3+}$ is $3d^5$, $F^-$ is a weak field ligand. High spin: $t_{2g}^3 e_g^2$, $n=5$. Paramagnetic.
4. $[CoF_6]^{3-}$: $Co^{3+}$ is $3d^6$, $F^-$ is a weak field ligand. High spin: $t_{2g}^4 e_g^2$, $n=4$. Paramagnetic.
5. $[Fe(NH_3)_6]^{3+}$: $Fe^{3+}$ is $3d^5$, $NH_3$ acts as a strong field ligand. Low spin: $t_{2g}^5 e_g^0$, $n=1$. Paramagnetic.
6. $[Co(en)_3]^{3+}$: $Co^{3+}$ is $3d^6$, $en$ is a strong field chelating ligand. Low spin: $t_{2g}^6 e_g^0$, $n=0$. Diamagnetic.

Only 1 species ($[Co(en)_3]^{3+}$) is diamagnetic.