Compounds of hypervalent halogens

As we have seen, the second-period element, fluorine, induces hypervalency in many other p-block elements, but it does not itself display hypervalency. The third and fourth period halogens, i.e. chlorine and bromine, form trifluorides and pentafluorides, XF3 and XF5. The fifth-period element, iodine, forms an unstable trifluoride which decomposes below room temperature, a pentafluoride and a heptafluoride. Iodine also forms a solid trichloride which decomposes on evaporation as in Groups 15 and 16 we find that the greater number of hypervalent derivatives are formed by the fifth-period element. 

The three pentafluorides are aU square pyramidal with C v symmetry. Note that the valence angles spanned by the apical and one of the basal F atoms, are less than 90°. The 

Iodine heptafluoride forms a pentagonal bipyramid with five fluorine atoms in the equatorial plane [1,2]. The valence angles spanned by neighboring equatorial bonds are only 72°. The two axial bonds are longer than the five equatorial, all of them are shorter than the bond in the monofluoride. 

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