Describe hybridisation in the case of PCl5 and SF6. The axial bonds are longer as compared to equatorial bonds in PCl5 wherea in SF6 both axial bonds and equatorial bonds have the same bond length. Explain.
Formation of PCl5
In PCl5, phosphorus is sp3d hybridised to produce a set of five sp3d hybrid orbitals which are directed towards the five corners of a trigonal bipyramidal. These five sp3d hydrid orbitals overlap with singly occupied p-orbitals to Cl-atoms to form five P-Cl sigma bonds.
Three P-Cl bonds lie in one plane make an angle of with each other. These bonds are called equatorial bonds. The remaining two P-Cl bonds one lying above and other lying below the plane make and angle of with the equatorial plane.
These bonds are called axial bonds. Axial bonds are slightly longer than equatorial bonds because axial bond pairs suffer more repulsive interaction from the equatorial bond pairs.
Formation of SF6
In SF6, sulphur is sp3d2 hybridised to produce a set of six sp3d2 hybrid orbitals which are directed towards the six corners of a regular octahedron. These six sp3d2 hybrid orbitals overlap with simgly occupied orbitals of fluorine atoms to form six S-F sigma bonds.
Thus, SF6 molecule has a regular octahedral geometry and all S-F bonds have same bond length.
