Which of the following coordination entities exhibit exactly zero unpaired electrons (diamagnetic na — Coordination Compounds Chemistry Question

💡 Solution & Explanation

(A) $[Co(NH_3)_6]^{3+}$: $Co^{3+}$ is $d^6$. $NH_3$ acts as a strong field ligand for $Co^{3+}$, causing pairing $\rightarrow$ $d^2sp^3$, $n=0$ (diamagnetic). (B) $[Fe(CN)_6]^{4-}$: $Fe^{2+}$ is $d^6$. $CN^-$ is a strong field ligand, causing pairing $\rightarrow$ $d^2sp^3$, $n=0$ (diamagnetic). (C) $[Fe(H_2O)_6]^{2+}$: $Fe^{2+}$ is $d^6$. $H_2O$ is a weak field ligand $\rightarrow$ $sp^3d^2$, $n=4$ (paramagnetic). (D) $[CoF_6]^{3-}$: $Co^{3+}$ is $d^6$. $F^-$ is a weak field ligand $\rightarrow$ $sp^3d^2$, $n=4$ (paramagnetic).