Capture of SO3 isomers in the oxidation of sulfur monoxide with molecular oxygen
When mixing SO with O2 in N2, Ne, or Ar, an end-on complex OS–OO forms in the gas phase and can subsequently be trapped at cryogenic temperatures (2.8–15.0 K). Upon infrared light irradiation, OS–OO converts to SO3 and SO2 + O with the concomitant formation of a rare 1,2,3-dioxathiirane 2-oxide, i.e., cyclic OS(O)O. Unexpectedly, the ring-closure of 16OS–18O18O yields a ca. 2 : 1 mixture of cyclic 18OS(16O)18O and 16OS(18O)18O. The characterization of OS–OO and OS(O)O with IR and UV/Vis spectroscopy is supported by high-level ab initio computations.