A novel anionic RSN(O)SR species, the intermediate in transnitrosation reactions, was explored computationally with B3LYP and CBS-QB3 methods. The species resembles a nitroxyl coordinated to a highly distorted disulficle, and it differs significantly from intermediates in nucleophilic acyl substitution. Reactions of the following species were computed for comparison: MeS- + MeSNO; MeO- + MeONO; MeS- + MeSCHO; MeO- + MeOCHO. The last two have very different intermediates from the first two. Mass spectrometric experimental evidence is presented that is consistent with the formation of a nitroxyl disulficle in the gas phase. The calculated proton affinity and redox potentials of the intermediate are also reported.