CRYSTAL-STRUCTURE OF [LI(TMEN)2][LI(C(SIME3)3)2] - A MULTINUCLEAR MAGNETIC-RESONANCE STUDY OF TRIS(TRIMETHYLSILYL)METHYLLITHIUM TETRAHYDROFURAN(1 2) AND -N,N,N',N'-TETRAMETHYLETHYLENEDIAMINE (1/1) (TMEN)/

A single-crystal X-ray study of (Me3Si)3CLi.tmen (tmen = N,N,N',N'-tet ramethylethylenediamine) shows that it crystallises with the ionic str ucture [Li(tmen)2][Li{C(SiMe3)3}2] but that the anions pack with diffe rent orientations from those in crystalline [Li(thf)4][Li{C(SiMe3)3}2] (thf = tetrahydrofuran). The H-1, Li-7, C-13 and Si-29 NMR spectra of (MeSi)3CLi.2thf and (Me3Si)3CLi-tmen in thf and toluene, and Li-7, C- 13 and Si-29 NMR spectra of the solids are described. Spectra obtained from solutions below ca. 25-degrees-C show the presence of ion pairs [Li(thf)4][Li{C(SiMe3)3}2] or [Li(tmen)2] [Li{C(SiMe3)3}2], together w ith further species which appear to be different in thf and toluene. S pectra from solutions at higher temperatures show inter-species exchan ge on the NMR timescale.