Inner orbital complex among the following is:

(A) \([Co(NH_3)_6]^{3+}\)

(B) \([CoF_6]^{3-}\)

(C) \([Ni(CN)_4]^{2-}\)

(D) \([MnCl_6]^{3-}\)

(E) \([FeF_6]^{3-}\)

Choose the correct answer from the options given below:

(A) and (C) only

The correct answer is option 1. (A) and (C) only.

A. \([Co(NH_3)_6]^{3+}\): Inner orbital complex

In \([Co(NH_3)_6]^{3+}\), there is \(Co^{3+}\) ion for which the electronic configuration in the valence shell is \(3d^6 4s^0\).

In presence of strong field \(NH_3\) ions, all the electrons are paired up. The empty two \(3d\), \(4s\) and three \(4p\) orbitals undergo \(d^2sp^3\) hybridization to make bonds with \(NH_3\) ligands in octahedral geometry. Thus \([Co(NH_3)_6]^{3+}\) is diamagnetic. It is said to be a low spin inner orbital complex.

(B) \([CoF_6]^{3-}\) : Outer orbital complex

In \([CoF_6]^{3-}\), there is \(Co^{3+}\) ion for which the electronic configuration in the valence shell is \(3d^6 4s^0\).

In presence of weak field \(F^-\) ions, the electrons are not paired up. The empty \(4s\), three \(4p\) and two \(4d\) orbitals undergo \(sp^3d^2\) hybridization to make bonds with \(F^- \) ligands in octahedral geometry. Thus \([CoF_6]^{3-}\) is paramagnetic. It is said to be a high spin outer orbital complex.

(C) \([Ni(CN)_4]^{2-}\) : Inner orbital complex

In \([Ni(CN)_4]^{2-}\), there is \(Ni^{2+}\) ion for which the electronic configuration in the valence shell is \(3d^8 4s^0\).

In presence of strong field \(CN^-\) ions, all the electrons are paired up. The empty \(3d\), \(3s\) and two \(4p\) orbitals undergo \(dsp^2\) hybridization to make bonds with \(CN^-\) ligands in square planar geometry. Thus \([Ni(CN)_4]^{2-}\) is diamagnetic. It is said to be a low spin inner orbital complex.

(D) \([MnCl_6]^{3-}\) : Outer orbital complex

In \([Mn(Cl)_6]^{3-}\), there is \(Mn^{3+}\) ion for which the electronic configuration in the valence shell is \(3d^4 4s^0\).

In presence of weak field \(Cl^-\) ions, the electrons are not paired up. The empty \(4s\), three \(4p\) and two \(4d\) orbitals undergo \(sp^3d^2\) hybridization to make bonds with \(Cl^-\) ligands in octahedral geometry. Thus \([Mn(Cl)_6]^{3-}\) is paramagnetic. It is said to be a low spin outer orbital complex.

(E) \([FeF_6]^{3-}\) : Outer orbital complex

In \([FeF_6]^{3-}\), there is \(Fe^{3+}\) ion for which the electronic configuration in the valence shell is \(3d^5 4s^0\).

In presence of strong field \(F^-\) ions, the electrons are not paired up. The empty \(4s\), three \(4p\) and two \(4d\) orbitals undergo \(sp^3d^2\) hybridization to make bonds with \(F^-\) ligands in octahedral geometry. Thus \([FeF_6]^{3-}\) is paramagnetic. It is said to be a low spin outer orbital complex.

From the above data it is clear that the correct answer is option 1. (A) and (C) only.