ZXYW molecules

If one of the Yatoms of a planar XY3 molecule is replaced by a Z atom, the symmetry is lowered to C21 . If two of the Y atoms are replaced by two different atoms, W and Z, the symmetry is lowered to Q. As a result, the selection rules are changed, as already shown in Table 1.18. In both cases, all six vibrations become active in infrared and Raman spectra. Table 2.4c lists the vibrational frequencies of planar ZXY 2 and ZXYW molecules. 

TABLE 2.4c. Vibrational Frequencies of Planar ZXY2 and ZXYW Molecules (cm... 

The ZXYW-type molecule belongs to the Ci point group, and all six vibrations are infrared- and Raman-active. The vibrational spectra of OSClBr [666] and [XSnYZ] (X, Y,Z a halogen) have been reported [667]. For example, the Raman spectrum of the [ClSnBrl] ion in the solid state exhibits the v(SnCl), v (Sn-Br), and v (SnI) at 275,193, and 155cm respectively. 

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