Journal of the American Chemical Society, Vol.122, No.51, 12819-12823, 2000
Li-7/P-31 NMR studies of lithiated arylacetonitriles in THF-HMPA solution: Characterization of HMPA-solvated monomers, dimers, and separated ion pairs
The structures of lithiated phenylacetonitrile and 1-naphthylacetonitrile were studied in THF and HMPA-THF solution. In pure THF, Li-7 NMR line width studies suggest that these species exist as contact ion pairs; HMPA titration studies confirm this conclusion. In the presence of 0.25-2 equiv of HMPA, HMPA-solvated monomeric and dimeric contact ion pairs are detected by P-31 and Li-7 NMR spectroscopy. Finally, at 4-6 equiv of added HMPA, Li-7 NMR spectra provide direct evidence for the formation of HMPA-solvated separated ion pairs.