NMR spectroscopy of organolithium compounds. XXVI--The aggregation behaviour of methyllithium in the presence of LiBr and LiI in diethyl ether and tetrahydrofuran.

1H, 6Li and 13C NMR spectroscopy were used to determine the structure of aggregates formed in mixtures of methyllithium, H3CLi, and lithium bromide and iodide in diethyl ether and tetrahydrofuran. From the chemical shifts, the signal intensity distribution and the isotope shifts observed for partially deuterated systems, it was shown that generally tetrameric structures with different halogen contents dominate. For methyllithium-lithium bromide (1:1) in THF a considerable concentration of an H3CLi-LiBr dimer was found. For the first time, deuterium-induced 6Li isotope shifts over four bonds were observed.