DYNAMICS INSIDE ION-PAIRS - NMR-STUDIES OF A [1-SILYLALLYL]LITHIUM WITH A PENDANT LIGAND - [1-[[[BIS(2-METHOXYETHYL)AMINO]METHYL]DIMETHYLSILYL]ALLYL]-LITHIUM

Proton and C-13 NMR studies of the title compound, 4, in THF-d8 and toluene-d8 show it to exist as an equilibrium mixture of endo-silyl and exo-silyl species in which lithium is tridentately complexed to the pendant ligand and the whole coordination moiety is bent over the plane of the allyl anion. NMR line-shape analysis, using several different resonances, establishes the DELTAH(double dagger) for rotation around the SiC1-C2 allyl bond to be 16 +/- 0.5 kcal/mol. Further, for rotation of coordinated Li+ around the Si-C1 (allyl) bond dH(double dagger) is 7 +/- 0.4 kcal/mol. This value is similar to the activation parameters for reorientation of ions within ion pairs of (silylallyl)lithiums investigated previously.