It should be noted that thiosulfoxides have been invoked previously in a number of mechanisms involving reactions of di-, tri-, and tetrasulfides. While these reactive intermediates are challenging to observe directly, there is spectroscopic evidence for the S=S bond in sulfur monofluoride (F2S2), which can exist as both the linear disulfide (FSSF) and the thiosulfoxide isomer (F2S=S). The S=S bond of a cyclic thiosulfite has also been characterized by X-ray crystallography. Previous theoretical studies by Steudel have indicated thiosulfoxides are highly polar, and should be stabilized in polar solvents. Invoking a thiosulfoxide intermediate may also help explain the metathesis inhibition by water, alcohols, and acids: these species may hydrogen bond to the thiosulfoxide and attenuate its reactivity. Inhibition of metathesis by anhydrides and TEMPO might also be due to reaction with the thiosulfoxide by acylation and oxidation, respectively. We also note that the thiosulfoxide isomer of the 5-member cyclic trisulfide would be strained in its conversion to a 4-member ring, which explains why these substrates do not undergo spontaneous ring-opening S-S metathesis in DMF (S186-S189).