GAS-PHASE CHEMISTRY OF THE SILAFORMYL ANION, HSIO

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 HSi02 - and CO and a reductive path giving SiO and HC02 -. 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 HSi180-. 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-. © 1990, American Chemical Society. All rights reserved.