David J. Hajdasz, Y. Ho, R. Squires
Nov 1, 1994
Citations
0
Influential Citations
31
Citations
Journal
Journal of the American Chemical Society
Abstract
The formation, thermochemical properties, and reactivity of gas-phase pentacoordinate silicon hydride anions are described. These ions are produced as the major products of reactions between H[sup [minus]] and alkylsilanes under flowing afterglow conditions at room temperature. Substituted silicon hydride ions are formed by addition of nucleophilic anions such as F[sup [minus]N], alkoxides, nitrile anions, and CF[sub 3][sup [minus]] to SiH[sub 4] and to primary, secondary, or tertiary alkylsilanes. The parent ion of the series, SiH[sub 5][sup [minus]], is formed by hydride transfer from alkyl silicon hydride ions to SiH[sub 4]. Pentacoordinate silicon hydride ions are shown to be reactive hydride reducing agents, transferring H[sup [minus]] to a wide variety of organic, inorganic, and transition-metal organometallic species. Silicon hydride ions undergo sequential hydride-deuteride exchange reactions with SiD[sub 4] by a mechanism analogous to protonic H/D exchange in gas-phase carbanions. Reactions with Bronsted acids lead to protolytic cleavage of an Si-H bond in the anion and formation of H[sub 2]. Depending upon the structure and acidity of the reactant acid, these reactions produce the corresponding silyl anion and both the free and silicon-complexed conjugate base anion. 61 refs.