and ClF6 – are all octahedral, but and IF6 – are distorted, with a lone pair on the...

and ClF₆ ^– are all octahedral, but and IF₆ ^– are distorted, with a lone pair on the central atom apparently influencing the shape. Suggest a reason for the difference in shape of these two groups of ions. (See J. Pilmé, E. A. Robinson, R. J. Gillespie, Inorg. Chem ., 2006 , 45 , 6198.)