Trigonal bipyramid molecule symmetry

Lastly, we consider a system with non-equivalent positions. An example of such a system is the trigonal bipyramidal molecule AX5 with symmetry. As discussed previously, one possible scheme is the dsp3 hybridization, where dz2 is the only d orbital participating. 

When we say that a molecule has symmetry, we mean that certain parts of it can be interchanged with others without altering either the identity or the orientation of the molecule. The interchangeable parts are said to be equivalent to one another by symmetry. Consider, for example, a trigonal bipyramidal molecule such as PF5 (A5-I). The three equatorial P—F bonds, to Fj, F2, and... 

The calculations show the equilibrium structure of PHg in the electronic ground state to be a trigonal bipyramid of symmetry. The electronic structure of the molecule is discussed in terms of a set of five valence orbitals according to. ..(la ) (le ) (2e )2 (2a )2 [5]. 

Molecules of CrCl3,2Me3N are five-co-ordinated with a basically trigonal-bipyramidal geometry. The average bond lengths are Cr—Cl = 223.8 (5) and Cr—N = 215 pm two Cl—Cr—Cl angles are 124.3 (I) and the other is 111.4 (2)°, The distortion from idealized symmetry may be attributed to electronic effects since in symmetry there will be one electron in an e MO. ... 

The structure of SbX3 molecules is trigonal bipyramidal in the vapour phase (Table 20) and this symmetry is retained in the crystal state with some variations in bond lengths. In the case of the iodide the d(Sb—I) is 2.12 A (I—Sb—199°) the crystal consists of hexagonal close packed assemblies of iodine atoms with antimony in the octahedral interstices, but off-centre, giving two different d(Sb—I) distances of 2.87 and 3.32 A. 

As a second example, let us consider a molecule with the formula AB6 having the symmetry of a trigonal bipyramid Ih. The vector system is shown in Fig. 11-3.2. The set of five hybrid orbitals (or vectors) on A form a basis for a reducible representation of the point group, with the following character ... 

For each of the following molecules, determine what atomic orbitals on the central atom are allowed by symmetry to be used in the construction of sigma hybrid orbitals, a. NHj (trigonal pyramid) b. BF3 (trigonal plane) c. SF6 (octahedron) d. PF, (trigonal bipyramid)... 

Many five-coordinated complexes of Co(II) are now known, having trigonal bipyramidal or square pyramidal structures. A much used type of ligand is a tetradentate tripod-like molecule with bulky groups attached to the bonding atoms, allowing coordination at only one additional position. In this case the symmetry is a more or less distorted trigonal bipyramid (13). 

This well-known molecule assumes a trigonal bipyramidal structure with Z>3h symmetry. As in the case of SF4, PF5 also has two types of bonds, equatorial and... 

Figure 1-25 Symmetry elements for a trigonal bipyramidal AB5 molecule.

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