Pentagonal bipyramidal molecular geometry explained

Examples:	,
Symmetry Group:	D5h
Atom Direction:	7
Bond Angle:	90°, 72°
Mu:	0

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.^{[1] [2]}

Pentagonal bipyramids are claimed to be promising coordination geometries for lanthanide-based single-molecule magnets, since (a) they present no extradiagonal crystal field terms, therefore minimising spin mixing, and (b) all of their diagonal terms are in first approximation protected from low-energy vibrations, minimising vibronic coupling.^[3]

Examples

• Iodine heptafluoride (IF₇) with 7 bonding groups
• Rhenium heptafluoride (ReF₇)
• Peroxo chromium(IV) complexes, e.g. [Cr(O₂)₂(NH₃)₃] where the peroxo groups occupy four of the planar positions.
• and ^{[4] [5]}

External links

• http://www.ch.ic.ac.uk/rzepa/bpr/Figure-5.html – Images of IF₇
• 3D Chem – Chemistry, Structures, and 3D Molecules
• IUMSC – Indiana University Molecular Structure Center

Notes and References

1. Seven-coordination. A molecular orbital exploration of structure, stereochemistry, and reaction dynamics. Roald. Hoffmann. Barbara F. Beier. Earl L. Muetterties. Angelo R. Rossi. Inorganic Chemistry. 1977. 16. 3. 511–522. 10.1021/ic50169a002.
2. Wells A.F. (1984) Structural Inorganic Chemistry 5th edition Oxford Science Publications
3. Duan . Yan . Rosaleny . Lorena E. . Coutinho . Joana T. . Giménez-Santamarina . Silvia . Scheie . Allen . Baldoví . José J. . Cardona-Serra . Salvador . Gaita-Ariño . Alejandro . 2022-12-09 . Data-driven design of molecular nanomagnets . Nature Communications . en . 13 . 1 . 7626 . 10.1038/s41467-022-35336-9 . 36494346 . 9734471 . 2022NatCo..13.7626D . 2041-1723.
4. "Non-VSEPR" Structures and Bonding in d(0) Systems. Martin. Kaupp. Angew Chem Int Ed Engl. 2001. 40. 1. 3534–3565. 10.1002/1521-3773(20011001)40:19<3534::AID-ANIE3534>3.0.CO;2-#. 11592184.
5. Stereochemistry of Seven-Coordinate Main Group and d0 Transition Metal Molecules. Zhenyang Lin. Ian Bytheway. Inorganic Chemistry. 1996. 35. 3. 594–603. 10.1021/ic950271o.