Raman spectroscopic studies of halide-ion complexes of carbon tetrahalides in solution

Abstract

The Raman spectra of solutions containing tetra-alkylammonium chlorides or bromides and CCl₄ or CBr₄ in non-hydrogen bonding solvents show evidence of 1 : 1 complexes X^–,CBr₄ present in ion pairs with the cation. From Raman intensity measurements the formation constant for [Bu₄N]⁺CBr₄Cl^– at 20 °C is 4·8 l mol^–1 in MeCN and 2·0 l mol^–1 in CH₂Cl₂ solution. Evidence is presented from changes in vibration frequencies and Raman depolarization ratios of CBr₄ on complexing that in CBr₄Cl^– the chloride ion is bound to a face rather than an apex or edge of the CBr₄ tetrahedron.