EXO,EXO-[1,3-BIS(TRIMETHYLSILYL)ALLYL]LITHIUM N,N,N',N'-TETRAMETHYLETHYLENEDIAMINE COMPLEX - CRYSTAL-STRUCTURE AND DYNAMICS IN SOLUTION

The X-ray structure of the title compound (1-TMEDA) shows that the essentially symmetrical allyl anion moiety is perturbed by complexation with TMEDA in a twisted conformation. The NMR-observed symmetrization of both the allyl end carbons and all the TMEDA methyl groups at higher temperatures is best modeled by molecular orbital calculations when two mechanisms (ligand rotation and ligand twisting) are assumed. These are calculated to have nearly the same barrier and. are in accord with the experimental value.