Lewis-acid and fluoride-ion donor properties of SF₄ and solid-state NMR spectroscopy of Me₃SnF

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Chaudhary, Praveen
University of Lethbridge. Faculty of Arts and Science
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Lethbridge, Alta. : University of Lethbridge, Dept. of Chemistry and Biochemistry, c2011
Trimethyltin fluoride (Me3SnF) is a useful fluorinating agent in organometallic chemistry. Its solid-state structure has been investigated by X-ray crystallography showing a polymeric fluorine-bridged structure. Disorder, however, has precluded the accurate refinement of all structural parameters. In order to obtain accurate structural information, trimethyltin fluoride was investigated using high-resolution 13C, 19F, and 119Sn solid-state NMR spectroscopy using a four-channel HFXY capability. The 119Sn{1H} solid-state NMR spectrum agrees with pentacoordination about Sn in this compound. The high-resolution 119Sn{19F, 1H}, 13C{1H,19F} and 19F{1H} NMR spectra offer unambiguous determination of 1J(119Sn-19F) and 1J(119Sn-13C) coupling constants. Furthermore, the analysis of the 119Sn{19F, 1H}, 119Sn{1H}, and 19F{1H} MAS spectra as a function of spinning speed allowed for the determination of the 119Sn CSA and J anisotropy, as well as the 119Sn-19F dipolar couplings. These were determined via SIMPSON simulations of the 13C, 19F, and 119Sn NMR spectra. Finally the 119Sn{19F, 1H} revealed fine structure as the result of 119Sn-117Sn two bond J-coupling, seen here for the first time. Sulfur tetrafluoride can act as a Lewis acid. Claims had been presented for the formation of an adduct between SF4 and pyridine, but no conclusive characterization had been performed. In the present study, adducts of SF4 with pyridine, lutidine, 4-picoline and triethylamine were prepared and characterized by low-temperature Raman spectroscopy. Sulfur tetrafluoride also acts as a fluoride-ion donor towards strong Lewis acids, such as AsF5 and SbF5, forming SF3 + salts. Variable-temperature (VT) solid-state 19F NMR spectroscopy showed that SF3 +SbF6 – exists in three phases with phase transitions at ca. –45 and –85°C, while SF3 +AsF6 – exists only as one phase between +20 and –150 °C. The phases of SF3 +AsF6 – were also characterized by VT Raman spectroscopy.
xvi, 170 leaves : ill. (some col.) ; 29 cm
Organotin compounds , Organometallic chemistry , Nuclear magnetic resonance spectroscopy , Lewis acids , Sulfur tetrafluoride , Dissertations, Academic