Benzimidazolines Convert Sulfur Dioxide to Bisulfate at Room Temperature and Atmospheric Pressure Utilizing Aerial Oxygen

By employing a simple strategy of reacting SO<sub>2</sub> gas with easily attainable hydride donors such as 2-substituted-1,3-dimethyl-2,3-dihydro-1<i>H</i>-benzo­[<i>d</i>]­imidazole, benzimidazoline and SO<sub>2</sub> were converted into benzimidazolium bisulfate at room temperature and atmospheric pressure. Bisulfate originated from SO<sub>2</sub> and hydride from benzimidazoline and aerial oxygen. Metastable dimers of bisulfate anions were observed in the solid state and in solution where the anions are not stabilized by encapsulation in cages but through hydrogen bonding from benzimidazolium cations. All three benzimidazolines and resulted benzimidazolium bisulfates have been characterized using <sup>1</sup>H and <sup>13</sup>C NMR spectroscopy, high-resolution electrospray ionization mass spectrometry, and single crystal X-ray diffraction techniques.