Characterization of iminothiosulfine-type ions [HNCS2]+/− and their neutral counterparts by mass spectrometry and computational chemistry

Electron ionization of rhodanine yields iminothiosulfine ions H–NC–S–S+,1b+, which readily communicate with the higher energy cyclic isomer H–NCS2+,1a+. CBS-QB3 and Gaussian-2 model chemistries predict that one electron reduction reverses the stability order but that the (singlet) neutrals remain connected via a negligible energy barrier. Neutralization–reionization (NR) experiments demonstrate that singlet 1a and its heterocumulene isomer 1b are stable species in the gas-phase. However, the co-generated triplet species readily dissociate into 3S2++HNC. Confirmatory experimental evidence comes from charge reversal (CR) and NR experiments on the cyclic anion H–NCS2−,1a−.