Infrared and electronic spectra of matrix-isolated dichlorodioxo- and dibromodioxo-molybdenum(VI) and -tungsten(VI)
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 χopt. than are appropriate for octahedral complexes.