Molecules with an LLP Coordination Number of Five

Although they are much more common than was at one time believed, molecules of the non-metallic elements with an LLP coordination number of greater than four are nevertheless relatively rare. They are very largely limited to the halides, particularly the fluorides, chlorides, 

The difference in the axial and equatorial bond lengths has been discussed in terms of the three-center, four-electron model (Box 9.2), but this model was postulated on the basis of the known difference in axial and equatorial bond lengths and so does not provide an explanation of this difference in bond lengths, 

One aspect of the geometry of these molecules that is of particular interest is that the CH2 and NH groups are in the axial plane. This geometry is consistent with a bent-bond 

It is interesting that among molecules with an LLPCN of five or larger, only those, such as XeF2, with an LLPCN of five are found to have as many as three lone pairs. This is pre- 

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