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Activation of Pentafluorophenylsilanes by Weak Lewis Bases in Reaction with Iminium Cations

Summary: Activation of Pentafluorophenylsilanes by Weak Lewis Bases in
Reaction with Iminium Cations
Alexander D. Dilman,*, Vitalij V. Levin, Miriam Karni, and Yitzhak Apeloig
N. D. Zelinsky Institute of Organic Chemistry, Leninsky prosp. 47, 119991 Moscow, Russian Federation,
and The Lise Meitner MinerVa Center for Computational Quantum Chemistry,
Technion-Israel Institute of Technology, Technion City, 32000 Haifa, Israel
ReceiVed March 30, 2006
The Lewis base mediated carbon-carbon bond forming reactions between pentafluorophenylsilanes and
iminium cations were studied theoretically and experimentally. The complexation of silanes with anionic
Lewis bases was analyzed computationally using DFT methods at the B3LYP/6-31+G(d) level. The
pentafluorophenyl group was found to exhibit a significant stabilizing effect on the formation of
pentacoordinate silicon species, with (C6F5)3SiF and C6F5SiF3 being the strongest Lewis acids. Comparison
of geometrical isomers of trigonal bipyramidal siliconates R2(C6F5)SiXY-
(R ) Me, F, Cl; X, Y ) F,
Cl, ClO4) revealed that the heteroatoms and the C6F5 group prefer to occupy apical and equatorial positions,
respectively. Calculations of C6F5 group transfer processes from silanes to N,N-dimethyliminium cation
lead to the following conclusions: (1) when employing weak Lewis bases X-
) Cl-
, ClO4


Source: Apeloig, Yitzhak - Department of Chemistry, Technion, Israel Institute of Technology


Collections: Chemistry