Question

Is ${\left[Fe{\left(H_{2}O\right)}_6\right]}^{2+}$ is an inner d-complex.
A.True
B.False

Answer 1

Hint: We have to know that if the ligands in the coordination complex are strong field ligand then the inner d orbitals would be present for hybridization due to induced pairing. For weak field ligands there would not be pairing and the outer d orbitals would take part in the hybridization.

Complete step by step answer:
We can say a strong ligand or a strong field ligand is a ligand that can result in a higher crystal field splitting.
We can say a weak ligand or a weak field ligand is a ligand that can result in a lower crystal field splitting.
In the spectrochemical series, we have to know that ligands up to water are weak-field ligands and have a tendency to result in high-spin complexes.
In the spectrochemical series, we have to know that ligands beyond water are strong-field ligands and have a tendency to result in low-spin complexes.
We can say in case of weak ligands like $F^{-}$, both ions form octahedral complexes where the ligand electrons are located in $$s{p}^3{d}^2$$ hybrid orbitals. We can also say the partially filled inner d-orbitals are not used. Such complexes are as an outer d-orbital complex.
We can say for strong ligands like $$C{N}^{-}$$ ions, spin-pairing of the inner d-electrons, take place and both ions form octahedral complexes where the ligand electrons are seen in $$d^{2}s{p}^3$$ hybrids. In other words, we can say the partially filled d-orbitals are used, and such complexes are known as an inner d-orbital complex.
We know that $H_{2}O$ is not a strong field ligand and so ${\mathrm{\Delta }}_o<P$, so the complex would be an outer d-orbital complex. ${\left[Fe{\left(H_{2}O\right)}_6\right]}^{2+}$ is an outer orbital (or) a spin free complex (or) high complex. It involves $s{p}^3{d}^2$ hybridization. So, the given statement is false.

Note:
The binding of a strong field ligand causes a higher difference between the higher and lower energy level orbitals.
Examples: $$C{N}^{-}$$ (cyanide ligands), $$N{O_2}^{-}$$ (nitro ligand) and $$CO$$ (carbonyl ligands)
The binding of a weak field ligand causes a lower difference between the higher and lower energy level orbitals since the low difference between the two orbital levels causes repulsions between electrons in those energy levels, the higher energy orbitals can be easily filled with electrons when compared to that in low energy orbitals.
Examples: $$I^{-}$$ (iodide ligand), $$B{r}^{-}$$ (bromide ligand), etc.