Question

The hybridisation of Fe in K4[Fe(CN)6] is)

Answer 1

Hybridization takes advantage of the VSEPR theory which states that atoms and electron pairs are arranged in such a way that repulsion is reduced.The complex K₄[Fe(CN)₆] has a cation 4K⁺ and an anion $[Fe(CN_6)]^{-4}$. Here the central atom is bonded to 6 ligands of CN⁻. That means we need 6 hybrid orbitals to account for CN⁻ electron pairs. The iron Fe metal is a transition metal found in the 4th row of the periodic table, hence it provides an extra orbital the 3d orbital . Also, this means the 1s,2s, 2p, 3s and 3p orbitals have been filled. The 4s, 4p and 3d orbital are vacant and can be hybridized to form an sp³d² hybridized orbital. This forms and octahedral complex with CN⁻ ligands at 90° angles away fro each other.