The small-scale preparation and NMR characterization of isotopically enriched organotin compounds

• Published in: Applied organometallic chemistry Vol. 14; no. 11; pp. 691 - 700
• Main Authors: Sutton, Peter G., Harrington, Christopher F., Fairman, Ben, Evans, E. Hywel, Ebdon, Les, Catterick, Tim
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 01.11.2000; Wiley
• Subjects: 116Sn; 117Sn; Chemistry; coupling constants; Exact sciences and technology; Ge, sn, pb derivatives; isotopic analysis; NMR; Organic chemistry; Organometalloidal and organometallic compounds; organotins; Preparations and properties; synthesis; Isotope enrichment; Pollutant; Tin Isotopes; Tin 117; Tin 116; NMR spectrometry; Tin IV Organic compounds; Chemical synthesis
• ISSN: 0268-2605; 1099-0739
• DOI: 10.1002/1099-0739(200011)14:11<691::AID-AOC62>3.0.CO;2-L

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 (1H) and carbon‐13 (13C) spectra for butyltins, Bu4−nSnXn, and phenyltins, Ph4−nSnXn (X = I, Cl), allowing the assignment of ­1H and 13C chemical shifts, and 119Sn–13C and 117Sn–13C coupling constants. The 13C NMR spectroscopic analysis of 117Sn‐enriched organotin compounds has allowed the assignment of certain resonances and tin–carbon coupling constants which were previously unobservable. The spectral patterns show that Δ(1H) and Δ(13C) values are sensitive to structural changes, and that 13C shielding decreases with an increase in the electronegativity of the substituent. The tin–carbon coupling constants are also sensitive to structural changes, and for alkyl and aryl compounds the couplings decrease in the order 1J > 3J > 2J > 4J. The 13C chemical shift values and the magnitude of tin–carbon coupling constants are shown to be solvent‐dependent. The 13C 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. Copyright © 2000 John Wiley & Sons, Ltd.