Question

The number of paramagnetic complexes among $[FeF_6]^{3-}, [Fe(CN)_6]^{3-}, [Mn(CN)_6]^{3-}, [Co(C_2O_4)_3]^{3-}, [MnCl_6]^{3-}$ and $[CoF_6]^{3-}$, which involved $d^2sp^3$ hybridization is ...............

Hint:

To determine paramagnetism, look for unpaired electrons in the complex. Strong field ligands usually pair up electrons, while weak field ligands leave electrons unpaired.

Answer 1

Correct Answer: 2

To determine the number of paramagnetic complexes, we need to check the number of unpaired electrons in each complex. Paramagnetic complexes have at least one unpaired electron, while diamagnetic complexes have all paired electrons. 

Step 1: Identification
1. \([FeF_6]^{3-}\): Iron in \(Fe^{3+}\) has the electron configuration \([Ar] 3d^5\). Fluoride (\(F^{-}\)) is a weak field ligand and does not cause electron pairing. \(Fe^{3+}\) undergoes \(d^2sp^3\) hybridization, leaving 5 unpaired electrons in the \(d\)-orbitals. Paramagnetic.
2. \([Fe(CN)_6]^{3-}\): Iron in \(Fe^{3+}\) has the electron configuration \([Ar] 3d^5\). Cyanide (\(CN^{-}\)) is a strong field ligand that causes electron pairing. \(Fe^{3+}\) undergoes \(d^2sp^3\) hybridization, resulting in no unpaired electrons. Diamagnetic.
3. \([Mn(CN)_6]^{3-}\): Manganese in \(Mn^{3+}\) has the electron configuration \([Ar] 3d^4\). Cyanide (\(CN^{-}\)) is a strong field ligand and causes pairing of electrons. \(Mn^{3+}\) undergoes \(d^2sp^3\) hybridization, resulting in 2 unpaired electrons. Paramagnetic.
4. \([Co(C_2O_4)_3]^{3-}\): Cobalt in \(Co^{3+}\) has the electron configuration \([Ar] 3d^6\). Oxalate (\(C_2O_4^{2-}\)) is a weak field ligand. \(Co^{3+}\) undergoes \(d^2sp^3\) hybridization, resulting in 3 unpaired electrons. Paramagnetic.
5. \([MnCl_6]^{3-}\): Manganese in \(Mn^{3+}\) has the electron configuration \([Ar] 3d^4\). Chloride (\(Cl^{-}\)) is a weak field ligand and does not cause electron pairing. \(Mn^{3+}\) undergoes \(d^2sp^3\) hybridization, leaving 4 unpaired electrons. Paramagnetic.
6. \([CoF_6]^{3-}\): Cobalt in \(Co^{3+}\) has the electron configuration \([Ar] 3d^6\). Fluoride (\(F^{-}\)) is a weak field ligand and does not cause electron pairing. \(Co^{3+}\) undergoes \(d^2sp^3\) hybridization, leaving 2 unpaired electrons. Paramagnetic.

Step 2: Conclusion.
The number of paramagnetic complexes is 2. These are:
\([FeF_6]^{3-}\) \([Mn(CN)_6]^{3-}\)
Thus, the number of paramagnetic complexes is 2.