Infrared and electronic spectra of matrix-isolated tetrafluoro- and tetrachloro-oxo-molybdenum(VI) and -oxotungsten(VI) and tetrabromo-oxo-tungsten(VI)

Abstract

The prominent i.r. bands of the title compounds isolated as monomers in low-temperature matrices have been obtained. Some anomalies in the literature regarding the fundamentals of WOCl₄ have been resolved, and in particular, it is shown via high-resolution studies, that whilst argon matrices generally yield multiple trapping sites, nitrogen matrices typically produce only one site. Electronic spectra in N₂ matrices have been recorded for all five compounds and compared with the predictions of Xα calculations. The matrix electronic spectra are shown to be superior to gas-phase spectra in terms of resolution, the observation of vibrational fine structure, and the absence of any complications due to the possible presence of decomposition products.