The low frequency infra-red and Raman spectra of some diaryltellurium dihalides

Abstract

Assignments are suggested for the low-frequency i.r. and Raman bands of the isomorphous series Ph₂TeX₂(X = Cl, Br, I). Resonance enhancement of the intensity of ν₈(TeX) is noted for X = Br, I. The vibrational spectra of R₂TeX₂(R =p-tolyl, o-tolyl, p-MeOC₆H₄, C₆F₅; X = Cl, Br, I) are also reported and assignments of ν(TeX) are suggested. It is concluded that all these compounds have ψ-trigonal bipyramidal structures with axial halogen atoms regardless of the nature of the substituents in the aryl ring. In all cases ν₈(TeCl) is assigned at higher frequency than ν_as(TeCl) but for the bromo- and iodo-compounds the asymmetric mode occurs at the higher frequency.