title: Silylanions: inversion barriers and NMR chemical shifts.
abstract: Alpha-substituent effects on inversion barriers and NMR chemical shifts have been studied on a set of silyl anions, [X(3-n)Y(n)Si](-) (X, Y=H, CH(3), and SiH(3)). The MP2/6-31+G* optimized structures show a pattern of increasing inversion barriers with augmenting numbers of methyl substituents. The highest barrier of 48.5 kcalmol(-1) is obtained for the (CH(3))(3)Si(-) ion. The silyl group displays the opposite effect by decreasing the inversion barrier to a minimum of 16.3 kcalmol(-1) in (SiH(3))(3)Si(-). The influence of counterions on these barriers is probed by addition of a lithium or potassium cation. In most cases, a decrease of the energy barriers with respect to the bare anions is observed. The (29)Si NMR chemical shifts calculated at the IGLO-DFT and GIAO-MP2 level of theory are also analyzed in view of the substituents and counterions.
authors.affiliation: Institut für Anorganische Chemie, Technische Universität Graz, Stremayrg. 16, 8010 Graz, Austria. flock@anorg.tu-graz.ac.at
authors.forename: Michaela
authors.initials: M
authors.lastname: Flock
authors.forename: Christoph
authors.initials: C
authors.lastname: Marschner