Crystal structure of [Li(tmen) ₂ ][Li{C(SiMe ₃ ) 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′-tetramethylethylenediamine) shows that it crystallises with the ionic structure [Li(tmen)2][Li{C(SiMe3)3}2] but that the anions pack with different orientations from those in crystalline [Li(thf)4][Li{C(SiMe3)3}2](thf = tetrahydrofuran). The 1H, 7Li, 13C and 29Si NMR spectra of (Me3Si)3CLi·2thf and (Me3Si)3CLi·tmen in thf and toluene, and 7Li, 13C and 29Si NMR spectra of the solids are described. Spectra obtained from solutions below ca. 25 °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 with further species which appear to be different in thf and toluene. Spectra from solutions at higher temperatures show inter-species exchange on the NMR timescale.