Observation of Water Complexes of the Sulfur-Nitrogen Compounds HNS and HSN

The simplest sulfur imide (HNS) and isomeric thiazyl hydride (HSN) are prototype sulfur-nitrogen compounds that have been studied by numerous theoretical calculations; however, their existence remains hitherto elusive. Herein, we report the generation of HNS as a hydrogen-bonded water complex through 254 nm photolysis of the novel aminosulfenic acid (NH₂SOH → HNS···H₂O) in an Ar-matrix at 10 K, and the latter was synthesized in the gas phase by high-vacuum flash pyrolysis of tert-butyl(amino)sulfoxide at ca. 700 K. Upon photoexcitation at 193 nm, HNS···H₂O rearranges to yield the less stable HSN···H₂O with concomitant dehydrogenation to form water complex of nitrogen monosulfide (^•NS···H₂O). The characterization of these water complexes with matrix-isolation IR spectroscopy is supported by D- and ¹⁵N-isotope labeling experiments and theoretical calculations at the B3LYP-D3/6-311++G(3df,3pd) level of theory.