The Sulfur Monoxide-Water Complex.

The hitherto experimentally unreported chalcogen-bonded sulfur monoxide-water complex (OS···OH2), a key intermediate in atmospheric but even more so in interstellar SO chemistry, was generated through 254 nm photolysis of in situ generated metastable sulfoxylic acid (HOSOH) in argon matrices at 3.5 K. The acid was prepared in the gas phase through flash vacuum pyrolysis of tert-butylsulfinic acid (t-BuS(O)OH) at 600 °C. The characterization of HOSOH and the OS···OH2 complex was accomplished by means of matrix isolation IR and UV/vis spectroscopy and 2H-isotope labeling experiments. Focal point computations indicate the triplet sulfur monoxide-water complex with chalcogen bonding (OS···OH2) is 8.1 kcal mol-1 higher in energy than singlet sulfoxylic acid (HOSOH) and more stable than the triplet hydrogen bonding complex (SO···H2O) by 0.4 kcal mol-1 but only after inclusion of the zero-point vibrational energy correction.