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Pentagonal Bipyramidal and Square Antiprismatic

  1. Mar 9, 2013 #1
    What are the bond angles in a pentagonal bipyramidal molecule in general? If they vary from molecule to molecule then just the bond angles for IF7 would be ideal. I'd like the same thing for square antiprismatic molecules (any complex ion with coordination number 8 which is square antiprismatic - which I think is the general guess one makes for complex ions of coordination number 8 - would do the trick!). I simply can't find any of this info anywhere online.

    I would also appreciate if anyone has a 2D diagram (meaning bonds shown as dashes or wedges) for the square antiprismatic shape, if they could link me to it.
  2. jcsd
  3. Mar 9, 2013 #2


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    Staff: Mentor

    Its a simple geometry. Draw a pentagon - I is in the middle and its distance from all vertices is identical, so you can draw a circle around - what is the F-I-F angle in the base? Bonds to two other F atoms are just perpendicular to the pentagon surface.
  4. Mar 9, 2013 #3


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    Science Advisor

    I guess there are no ideal values for a square antiprism as the two squares rotated 45 degrees with respect to each other may have any distance from the central ion. This changes the angles between the atoms. However, often the square antiprism is conceptually obtained from the cubic coordination by rotating one of the squares. For this case it should be easy to work out the angles.
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