Gas-phase chemistry of the silaformyl anion, HSiO-

Article abstract of DOI:10.1021/ja00159a016

The silaformyl anion, HSiO^-, has been prepared by collisionally induced dissociation (CID) of H₃SiO in a tandem flowing afterglow selected ion flow tube (FA-SIFT). The chemistry of the silaformyl anion has been studied in detail. Reactions with CO₂, COS, CS₂, SO₂, O₂, acetic acid, nitromethane, and hexafluorobenzene reveal a rich chemistry. For example, the silaformyl anion reacts with CO₂ by both an oxidative pathway giving HSiO₂^- and CO and a reductive path giving SiO and HCO₂^-. Typically, the silaformyl anion, which could have several sites of reactivity, behaves both as an oxygen nucleophile and as a hydride donor. Detailed mechanistic studies have been carried out on many of these reactions with isotopically labeled H²⁹SiO^- and HSi¹⁸O^-. In addition to its reaction chemistry, the heat of formation of the silaformyl anion, its basicity, and the heat of formation of its parent compound have been estimated. Ab initio computations on the silaformyl anion have been carried out and demonstrate that HSiO^- is more than 40 kcal/mol more stable than HOSi^-.