Infrared and electronic spectra of matrix-isolated dichlorodioxo- and dibromodioxo-molybdenum(VI) and -tungsten(VI)

Abstract

The prominent i.r. and u.v.–visible bands of the title compounds isolated as monomers in low-temperature matrices have been obtained and assigned. For MoO₂Cl₂ and MoO₂Br₂, the vibrational isotope effect on the antisymmetric stretching mode ν(MoO) leads to estimates of bond angles OMoO of 109 ± 3°, whilst for WO₂Cl₂ and WO₂Br₂, relative band intensities predict OWO = 107 ± 2° for both molecules. In the quantitative assignment of the electronic spectra, it is suggested that the positions of the charge transfer bands require somewhat lower values of χ_opt. than are appropriate for octahedral complexes.