8.2 sp3d & sp3d2 Hybridization

Hybrids involving d orbitals

In atoms that are below those in the first complete row of the periodic table, the simple octet rule begins to break down. For example, we have seen that PCl₃ does conform to the octet rule but PCl₅ does not. We can describe the bonding in PCl₃ very much as we do NH₃: four sp³-hybridized orbitals, three of which are shared with electrons from other atoms and the fourth containing a nonbonding pair.

D. Sp³d & sp³d² Hybridization

There are five d orbitals that can also take part in hybridization

Figure 8.33 d-orbitals

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Sp³d hybridization

Pentagonal bipyramid molecules: sp³d hybridization

Figure 8.34 sp3d Hybrid Orbitals in PCl₅

Ref: Commons.wikimedia.org

In order to understand the bonding in phosphorus pentachloride PCl₅, we have to consider the d orbitals in addition to the s– and p types. When d orbitals are energetically close to the outmost s– and p orbitals, additional hybrid types can be built. In the case of PCl₅ we need five hybrid orbitals, and these can be constructed by adding two d-orbital functions to the mathematical mixture of one s– and two p-orbitals, resulting in five sp³d hybrid orbitals directed toward the corners of a trigonal bipyramid, as is predicted by VSEPR theory.

Figure 8.35 Electronic Arrangement of sp3d Hybrid Orbitals in PCl₅

The shapes of molecules with trigonal bipyramidal electron group arrangements are rationalized with VB theory through similar arguments. The difference is that molecules have central atoms from period 3 or higher so that s, p and d orbitals are mixed up to form hybrid orbitals.

For the shape of PCl5, VB model proposes one 3s, three 3p and one of the five 3d orbitals of the central P atom mix and form five sp3d hybrid

E. sp³d² hybridization

To rationalize the shape of SF6, the VB model proposes that the one, 3s, the three 3p and two of the five 3d orbitals of the central S atom mix and foem sp3d2 hybrid orbitals which point to the vertices of an octahedron. Each hybrid orbital overlaps a 2p orbital of an F atom, and the six valence electrons of S, together with  one from each of the six F atom.

SF6 Hybridization-QUORA

https://www.quora.com/What-is-the-hybridization-of-SF6

Octahedral coordination: sp³d² hybridization

The molecule sulfur hexafluoride SF₆ exemplifies one of the most common types of d-orbital hybridization. The six bonds in this octahedrally-coordinated molecule are derived from mixing six atomic orbitals into a hybrid set. The easiest way to understand how these come about is to imagine that the molecule is made by combining an imaginary S⁶⁺ ion (which we refer to as the S(VI) valence state) with six F^– ions to form the neutral molecule. These now-empty 3s and 3p orbitals then mix with two 3d orbitals to form the sp³d² hybrids.

Figure 8.36 Electronic Arrangement of sp3d2 Hybrid Orbitals in SF₆

Some of the most important and commonly encountered compounds, which involve the d orbitals in bonding, are the transition metal complexes. The term “complex” in this context means that the molecule is composed of two or more kinds of species, each of which can have an independent existence.

Figure 8.37 Formation of sp3d2 Hybrid Orbitals in PCl₅

Figure 8.38 Charge distribution of sp3d2 Hybrid Orbitals in SF₆

Ref: Commons.wikimedia.org/

In summary, square planar and square pyramidal molecules have lone pairs in one

Six electron pairs (ortahedral geo)sp3d2

Five electron pairs ( trigonal bipyramidal) sp3d

Four electron pair (tetrahedral) sp3

Three electron pair (Trigonal planar) sp2

Two electron pair (linear) sp

Figure 8.39 Shapes of all Hybrid Orbitals

Ref: Commons.wikimedia.org/

The following video is about sp3d and sp3d2 hybridization model.

Hybridization of atomic orbitals. sp3d and sp3d2