H-2-H-1 ISOTOPE SHIFTS FOR LI-6-NMR - 1ST EXPERIMENTAL DETECTION AND APPLICATIONS TO STRUCTURAL PROBLEMS IN THE FIELD OF ORGANOLITHIUM COMPOUNDS

Deuterium‐induced isotope effects on 6Li chemical shifts, transmitted over two bonds, 2Δ(6Li)(2H/1H), have been measured for the first time for methyllithium and the system methyllithium/lithium iodide. The observed shifts are to low field and range from 15 to 20 ppb per CD3 group. The multiplicity and intensity distribution of the 6Li signals resulting for mixtures of CH3‐ and CD3‐containing samples in the limit of slow inter‐ as well as intra‐aggregate exchange yield information about the size of the various clusters present in diethylether solution. It is expected that these isotope shifts can facilitate structural investigations of organolithium compounds. In some cases, the results of such measurements are expected to be less ambiguous then the conclusions based on multiplets that arise from scalar 13C,6Li spin‐spin coupling. Copyright © 1990 Verlag GmbH & Co. KGaA, Weinheim