Pentagonal bipyramidal molecular geometry

Pentagonal bipyramidal molecular geometry
File:Pentagonal-bipyramidal-3D-balls.png
Examples	IF7, ZrF3−7
Point group	D5h
Coordination number	7
Bond angle(s)	90°, 72°
μ (Polarity)	0

File:Iodine-heptafluoride-3D-vdW.png

Structure of iodine heptafluoride, an example of a molecule with the pentagonal-bipyramidal coordination geometry.

In chemistry, a pentagonal bipyramid is a molecular geometry with one atom at the centre with seven ligands at the corners of a pentagonal bipyramid. A perfect pentagonal bipyramid belongs to the molecular point group D_5h.

The pentagonal bipyramid is a case where bond angles surrounding an atom are not identical (see also trigonal bipyramidal molecular geometry). This is one of the three common shapes for heptacoordinate transition metal complexes, along with the capped octahedron and the capped trigonal prism.

Pentagonal bipyramids are claimed to be promising coordination geometries for lanthanide-based single-molecule magnets, since they present no extradiagonal crystal field terms, therefore minimising spin mixing, and all of their diagonal terms are in first approximation protected from low-energy vibrations, minimising vibronic coupling.

Examples

• Iodine heptafluoride (IF₇) with 7 bonding groups
• Rhenium heptafluoride (ReF₇)
• Peroxo chromium (IV) complexes, such as [Cr(O₂)₂(NH₃)₃], where the peroxo groups occupy four of the planar positions.
• ZrF³⁻
  ₇ and HfF³⁻
  ₇

External links

• [1] – Images of IF₇
• 3D Chem – Chemistry, Structures, and 3D Molecules
• IUMSC – Indiana University Molecular Structure Center