The small-scale preparation and NMR characterization of isotopically enriched organotin compounds
✍ Scribed by Peter G. Sutton; Christopher F. Harrington; Ben Fairman; E. Hywel Evans; Les Ebdon; Tim Catterick
- Publisher
- John Wiley and Sons
- Year
- 2000
- Tongue
- English
- Weight
- 100 KB
- Volume
- 14
- Category
- Article
- ISSN
- 0268-2605
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✦ Synopsis
Synthetic methods for the small-scale laboratory preparation of isotopically enriched dibutyltin dichloride, dibutyltin di-iodide, tributyltin chloride, tributyltin iodide, diphenyltin dichloride, triphenyltin chloride and triphenyltin iodide have been successfully established. Organotin iodides were prepared from redistribution reactions between tin(IV) iodide and the corresponding tetraorganotin, with the exception of dibutyltin di-iodide, which was prepared directly from the reaction between tin metal and iodobutane. The development of novel procedures for the dealkylation/dearylation of tetraorganotins by acid hydrolysis produced superior yields of tributyltin chloride and diphenyltin dichloride in comparison with redistribution reactions. Organotin iodide redistribution reaction products were converted to their chloride analogues via the fluoride salts using an aqueous ethanolic solution of potassium fluoride. The insolubility of organotin fluoride salts was exploited to isolate and purify the isotopically enriched compounds, and to prevent losses during the purification procedure. The nuclear magnetic resonance (NMR) spectroscopic study of 'natural abundance' and isotopically enriched organotin compounds gave proton ( 1 H) and carbon-13 ( 13 C) spectra for butyltins, Bu 4 À n SnX n , and phenyltins, Ph 4 À n SnX n (X = I, Cl), allowing the assignment of 1 H and 13 C chemical shifts, and 119 Sn-13 C and 117 Sn-13 C coupling constants. The 13 C NMR spectroscopic analysis of 117 Sn-enriched organotin compounds has allowed the assignment of certain resonances and tin-carbon coupling constants which were previously unobservable. The spectral patterns show that d( 1 H) and d( 13 C) values are sensitive to structural changes, and that 13 C shielding decreases with an increase in the electronegativity of the substituent. The tincarbon coupling constants are also sensitive to structural changes, and for alkyl and aryl compounds the couplings decrease in the order 1 J b 3 J b 2 J b 4 J. The 13 C chemical shift values and the magnitude of tin-carbon coupling constants are shown to be solvent-dependent. The 13 C spectra of the isotopically enriched compounds show that the degree of isotopic enrichment and the nature of the isotope used (magnetic or non-magnetic) are reflected in the spectral pattern obtained.
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