Hydrogen Sulfide as a Scavenger of Sulfur Atomic Cation.

The well-studied hydrogen sulfide molecule is shown here for the first time to form a S-S bond barrierlessly with sulfur atomic cation to produce stable H2 SS+ , a compound for which there is nearly no literature data. Previous work has shown that the reaction of hydrogen sulfide with neutral atomic sulfur will likely only take place at high pressures. Conversely, this work shows that hydrogen sulfide will readily bind with atomic sulfur cation first through the 1 4 A″ state from association of H2 S with S+ (4 S) and then will relax to the nearly degenerate 1 2 A' or 1 2 A″ states. S+ (4 S) + H2 S lies 29.5 kcal/mol above the 1 4 A″ H2 SS+ minimum. The 1 4 A″ H2 SS+ minimum in the S-S bond is also directly intersected by the doublet potential energy surface. As the S-S bond shortens in the association, the 1 2 A' and 1 2 A″ states split, falling 33.5 and 26.4 kcal/mol, respectively, below the 1 4 A″ state. Hence, this work is opening the door for novel synthesis of S-S bonds or potential removal of the common H2 S toxin/pollutant through concatenation and subsequent precipitation.