Capped octahedral molecular geometry

In chemistry, the capped octahedral molecular geometry describes the shape of compounds where seven atoms or groups of atoms or ligands are arranged around a central atom defining the vertices of a gyroelongated triangular pyramid. This shape has C_3v symmetry and is one of the three common shapes for heptacoordinate transition metal complexes, along with the pentagonal bipyramid and the capped trigonal prism.^[1][2]

Capped octahedral molecular geometry
Examples	MoF− 7
Point group	C3v
Coordination number	7

Examples of the capped octahedral molecular geometry are the heptafluoromolybdate (MoF⁻
₇) and the heptafluorotungstate (WF⁻
₇) ions.^[3][4]

The "distorted octahedral geometry" exhibited by some AX₆E₁ molecules such as xenon hexafluoride (XeF₆) is a variant of this geometry, with the lone pair occupying the "cap" position.

References

1. Roald. Hoffmann; Barbara F. Beier; Earl L. Muetterties; Angelo R. Rossi (1977). "Seven-coordination. A molecular orbital exploration of structure, stereochemistry, and reaction dynamics". Inorganic Chemistry. 16 (3): 511–522. doi:10.1021/ic50169a002.
2. Wells A.F. (1984) Structural Inorganic Chemistry 5th edition Oxford Science Publications ISBN 0-19-855370-6
3. Kaupp, Martin (2001). ""Non-VSEPR" Structures and Bonding in d(0) Systems". Angew Chem Int Ed Engl. 40 (1): 3534–3565. doi:10.1002/1521-3773(20011001)40:19<3534::AID-ANIE3534>3.0.CO;2-#. PMID 11592184.
4. Zhenyang Lin; Ian Bytheway (1996). "Stereochemistry of Seven-Coordinate Main Group and d0 Transition Metal Molecules". Inorganic Chemistry. 35 (3): 594–603. doi:10.1021/ic950271o.