Idealized structure of a molecule with pentagonal-bipyramidal coordination geometry.
Structure of iodine heptafluoride, an example of a molecule with the pentagonal-bipyramidal coordination geometry.
In chemistry, a pentagonal bipyramid (or dipyramid) is a molecular geometry with one atom at the centre with seven ligands at the corners of a pentagonal dipyramid. A perfect pentagonal bipyramid belongs to the molecular point groupD5h . The pentagonal bipyramid is a case where bond angles surrounding an atom are not identical (see also Trigonal bipyramid molecular geometry). Other seven coordinate geometries include the mono-capped octahedron and mono-capped trigonal prism. A variety of transition metal complexes adopt heptacoordination, but the symmetry is usually lower than D5h.