In chemistry, T-shaped molecular geometry describes the structures of some molecules where a central atom has three

ligand In coordination chemistry, a ligand is an ion or molecule ( functional group) that binds to a central metal atom to form a coordination complex. The bonding with the metal generally involves formal donation of one or more of the ligand's elec ...

s. Ordinarily, three-coordinated compounds adopt trigonal planar or pyramidal geometries. Examples of T-shaped molecules are the halogen trifluorides, such as ClF₃. According to

VSEPR theory Valence shell electron pair repulsion (VSEPR) theory ( , ), is a model used in chemistry to predict the geometry of individual molecules from the number of electron pairs surrounding their central atoms. It is also named the Gillespie-Nyholm the ...

, T-shaped geometry results when three ligands and two lone pairs of electrons are bonded to the central atom, written in AXE notation as AX₃E₂. The T-shaped geometry is related to the

trigonal bipyramidal molecular geometry In chemistry, a trigonal bipyramid formation is a molecular geometry with one atom at the center and 5 more atoms at the corners of a triangular bipyramid. This is one geometry for which the bond angles surrounding the central atom are not iden ...

for AX₅ molecules with three equatorial and two axial ligands. In an AX₃E₂ molecule, the two lone pairs occupy two equatorial positions, and the three ligand atoms occupy the two axial positions as well as one equatorial position. The three atoms bond at 90° angles on one side of the central atom, producing the T shape. The trifluoroxenate(II) anion, , has been investigated as a possible first example of an AX₃E₃ molecule, which might be expected by VSEPR reasoning to have six electron pairs in an

octahedral In geometry, an octahedron (plural: octahedra, octahedrons) is a polyhedron with eight faces. The term is most commonly used to refer to the regular octahedron, a Platonic solid composed of eight equilateral triangles, four of which meet a ...

arrangement with both the three lone pairs and the three ligands in a ''mer'' or T-shaped orientations. Although this anion has been detected in the gas phase, attempts at synthesis in solution and experimental structure determination were unsuccessful. A computational chemistry study showed a distorted planar Y-shaped geometry with the smallest F–Xe–F bond angle equal to 69°, rather than 90° as in a T-shaped geometry.

References

External links

Chem, Chemistry, Structures, and 3D Molecules

Indiana University Molecular Structure Center

{{MolecularGeometry Molecular geometry

See also

References

External links