shapeof the molecule [IF6]- ionis destoid octahedral according to NCERT XIIwithout reason,why it is not pentagonal pyramidal shape,while angle 72*is less then 90*?(*=degree)

Dear Student,
The shape of a molecule is attained by keeping in track of lp-lp , lp-bp and bp-bp repulsions (VSEPR theory)
I has 8electons in IF6- molecule
If shape is pentagonal pyramidal angle is 72* which is low than the angle in distorted octahedral. Therefore to minimise the repulsions such shape is attained.