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β-Silyl and β-Germyl Carbocations Stable at Room Temperature
Journal of Organic Chemistry (1999)
  • Joseph B. Lambert, Northwestern University
  • Yan Zhao, Northwestern University
  • Hongwei Wu, Northwestern University

Stable carbocations have been prepared at room temperature with benzene as solvent and tetrakis(pentafluorophenyl)borate (TPFPB) as anion by the addition of solvated triethylsilylium TPFPB or of tributylgermylium TPFPB to 1,1-diphenylethene. These carbocations are stabilized by σ conjugation with nonadjacent group 14 atoms and respectively constitute stable saturated β-silyl and β-germyl carbocations. NMR parameters, including the 29Si chemical shift, the 13C chemical shifts of the cationic, aryl, and methylene carbons, and the one-bond 13C−1H coupling constant of the methylene group adjacent to the group 14 element, define the distribution of positive charge between carbon and (through σ conjugation) silicon or germanium. The extent of hyperconjugation is estimated quantitatively by comparison with models. The NMR parameters indicate that the cations are open rather than bridged.

Publication Date
March, 1999
Publisher Statement
Reprinted (adapted) with permission from Journal of Organic Chemistry 64 (1999): 2729, doi:10.1021/jo982146a. Copyright 1999 American Chemical Society.
Citation Information
Joseph B. Lambert, Yan Zhao and Hongwei Wu. "β-Silyl and β-Germyl Carbocations Stable at Room Temperature" Journal of Organic Chemistry Vol. 64 Iss. 8 (1999)
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