VICINAL H-2/H-1 ISOTOPE SHIFTS FOR LI-6-NMR AND THE AGGREGATION BEHAVIOR OF PHENYLLITHIUM

Vicinal deuterium-induced Li-6-NMR isotope shifts have been found for (D5)phenyllithium. These shifts are to low field, and their magnitude varies from 7 to 19 ppb with different solvents and donor molecules. On the basis of the isotopic fingerprints observed in the Li-6-NMR spectra of (C6H5Li/C6DLi)-Li-6Li-6 mixtures, the aggregation behaviour of phenyllithium under different solvent conditions and in the presence of amines as donor ligands (TMEDA, PMDTA) was studied. Tetramers and dimers are observed in Et2O, dimers as well as momomers in Et2O/TMEDA and in THF, and momomers in THF/PMDTA. The hitherto unidentified species in Et2O/TMEDA was shown to be a monomer.