Isolable Silyl and Germyl Radicals Lacking Conjugation with π-Bonds:  Synthesis, Characterization, and Reactivity

• Published in: Journal of the American Chemical Society 2002-08, Vol.124 (33), p.9865-9869
• Main Authors: Sekiguchi, Akira, Fukawa, Tomohide, Nakamoto, Masaaki, Lee, Vladimir Ya, Ichinohe, Masaaki
• Format: Article
• Language: English
• Subjects: Chemistry; Condensed matter: structure, mechanical and thermal properties; Exact sciences and technology; Free radicals chemistry; Organic chemistry; Organic compounds; Organometalloidal and organometallic compounds; Physics; Reactivity and mechanisms; Structure of solids and liquids; crystallography; Structure of specific crystalline solids
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja0126780

The one-electron oxidation reaction of tris[di-tert-butyl(methyl)silyl]silyl and -germyl anions with dichlorogermylene−dioxane complex results in the formation of stable tris[di-tert-butyl(methyl)silyl]silyl and -germyl radicals 1 and 2, representing the first isolable radical species of heavier Group 14 elements lacking stabilization by conjugation with π-bonds. The crystal structures of both silyl and germyl radicals 1 and 2 showed a completely planar geometry around the radical centers. The ESR spectra of 1 and 2 showed strong signals with characteristic satellites due to the coupling with the 29Si and 73Ge nuclei. The small values of the hyperfine coupling constants a(29Si) and a(73Ge) clearly indicate the π-character of both radicals, corresponding to a planar geometry and sp2 hybridization of the radical centers. Both 1 and 2 easily undergo halogenation reactions with carbon tetrachloride, 1,2-dibromoethane, and benzyl bromide to form the corresponding halosilanes and halogermanes.