Octahedral shape hybrid orbitals

Although the spatial arrangement of six electron pairs round I-atom is octahedral, due to the presence of two lone pairs of electrons in the axial hybrid orbitals, the shape of IC14- ion gets distorted and becomes square planar as shown in Fig. 

The octahedral [SiF6]2 molecular ion, and a simple valence bond approach to explaining its formation. Overlap of a p orbital containing two electrons on each of the six fluoride anions with one of six empty hybrid orbitals on the Si(IV) cation, arranged in an octahedral array, generates the octahedral shape with six equivalent covalent a bonds. 

Solution. The shapes of the FMOs for both compounds are shown below. Both species have a two-electron vacancy in one of their hybrid orbitals. Because most square planar compounds are 16-electron species and most octahedral compounds obey the 18-electron rule, a square planar compound will be isolobal with an octahedral molecule that has two greater valence electrons. 

For third-row elements and larger atoms, especially those in the p block, the existence of d orbitals introduces other possible hybridization schemes where the d orbitals themselves participate. The inclusion of one d orbital with the s and the three p orbitals yields five sp d hybrid orbitals, which collectively have an overall trigonal bipyramidal shape (like in PCI5). The inclusion of two d orbitals with the s and p orbitals yields six sp cf hybrid orbitals, which collectively have an octahedral shape (like in SFg). 

FIGURE 16.36 I1ie tear-shaped objects are representations of the six ligand atomic orbitals that are used to build the molecular orbitals of an octahedral complex in ligand field theory. They might represent s- or p-orbitals on the ligands or hybrids of the two. 

Sp d Hybridization The VB model proposes that molecules with shapes having the octahedral electron-group arrangement also nse d orbitals to form hybrids. 

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