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29Si and 13C NMR spectra of permethylpolysilanes

1981; Elsevier BV; Volume: 204; Issue: 3 Linguagem: Inglês

10.1016/s0022-328x(00)80498-2

1872-8561

David A. Stanislawski, Robert West,

Molecular Spectroscopy and Structure

Abstract 29 Si, 13 C and 1 H NMR spectra are reported for the series of linear permethylpolysilanes Me(SiMe 2 ) n Me where n = 1 to 6, for the cyclic permethylpolysilanes (Me 2 Si) n where n = 5 to 8, and for a few related compounds. For linear polysilanes the 29 Si and 13 C chemical shifts can be accurately calculated from simple additivity relationships based on the number of silicon atoms in α, β, γ and δ positions. Adjacent (α) silicon atoms lead to upfield shifts in the 29 Si and 13 C resonances, whereas more remote silicon atoms lead to downfield shifts. The 29 Si chemical shifts of the polysilane chains are linearly related to the 13 C shifts of the carbon atoms attached to the silicon. The 29 Si and 13 C resonances of the cyclic silanes deviate from this relationship. Ring current effects arising from σ delocalization are suggested as an explanation for the deviations. Proton-coupled 29 Si NMR spectra are reported for Me 3 SiSiMe 3 and for (Me 2 Si) n , n = 5 to 7.