Vibrational spectra and intermolecular forces of mercuric halide complexes of 1,4-dioxane and tetrahydrofuran

Abstract

Infrared and Raman spectra of mercuric chloride complexes of 1,4-dioxane and 1,4-dioxane-d8 and mercuric bromide complexes of tetrahydrofuran and tetrahydrofuran-d8 were measured in a solid state at various temperatures. Optically active Raman and far-infrared bands due to the lattice vibrations and to the stretching and bending modes of the mercuric halide molecules were detected. On the basis of the observed frequency data the intra- and intermolecular force constants were evaluated by the least-squares fitting of the normal frequencies. A strong interacting force was estimated for the nearest Hg⋅⋅⋅O pairs compared with the ordinary van der Waals-type intermolecular interactions. The frequencies of the Hg–X (X is Cl or Br) stretching vibrations in the complexes are lower than those of the corresponding crystalline mercuric halides, and they increase with rising temperature. These facts suggest a coordination character of the nearest Hg⋅⋅⋅O bonding in the complexes.