Generation and identification of ionic and neutral dithioformic acid [HC(S)SH]<SUP>·+/o</SUP>, dimercaptocarbene [HSCSH]<SUP>·+/o</SUP>, and dithiirane [H<SUB>2</SUB>C(S<SUB>2</SUB>)]<SUP>·+/o</SUP>: a neutralization-reionization mass spectrometry and theoretical study

Results of tandem mass spectrometric experiments characterize both ionic and neutral dithioformic acid a, dimercaptocarbene b, and dithiirane c in the gas phase. Observed collisional activation spectra of the ion at m/z 78 from compounds ethyl carbamoylmethane dithioate 1, 5-amino-1,3,4-thiadiazole-2-thiol 2, and rhodanine 3 and 1,2-dithiacyclopentane 4 are most compatible with the connectivities a, b, and c, respectively. The NRMS experiments on these structurally characterized ions reveal that the neutral dithioformic acid a, dimercaptocarbene b, and dithiirane c are viable species in the gas phase. Relative energies of the CH2S2 isomers and their radical cations calculated at the B3LYP/6-31G** level support these experimental observations. Comparisons are made between the relative energies of the oxygen and sulfur analogues. The high relative energy of dioxirane g in relation to dithiirane c makes the former a difficult target for experimental observation