Intensity studies on the Raman-active fundamentals of hexahalogeno-anions of second- and third-row transition and non-transition metals. The calculation of parallel and perpendicular bond polarisability derivatives

Abstract

The Raman spectra of solutions (generally aqueous acid) of the ions MF₆^2–(M = Pt or Sn), MCl₆^2–(M = Re, Os, Ir, Pd, Pt, Sn, or Pb), MCl₆^3–(M = Rh or Ir), MBr₆^2–(M = Os, Ir, Pt, or Sn) and MI₆^2–(M = Pt or Sn) have been recorded, and accurate values for the frequencies of the ν₁(a_1g), ν₂(e_g), and ν₅(t_2g) fundamentals are reported, some for the first time. The intensities of these three fundamentals of each ion were measured using the rotating sample technique at four different exciting lines and they are reported by reference to the 935 cm^–1 band of the perchlorate ion as internal standard. The results are discussed in terms of the pre-resonance Raman effect. The intensities of ν₁(a_1g) fundamentals have been used to determine values for the metal–halogen bond polarisability derivatives (_MX′) at zero exciting frequency. These _MX′ values, coupled with the relative molar intensities of the ν₁(a_1g) and ν₂(e_g) fundamentals in each case, lead to values for the parallel and perpendicular MX bond polarisability derivatives. Factors affecting the magnitudes of these quantities are discussed.