Synthesis of [Li(CH2SiMe3)(pmdeta)] and the crystalline monomeric bulky alkyl-lithium complexes[LiR(tmeda)]and [LiR(pmdeta)][R = CH(SiMe3)2]; X-ray crystal structrue of [Li{CH(SiMe3)2}(pmdeta)]{tmeda = Me2NCH2CH2NMe2, pmdeta = Me2N[CH2]2N(Me)[CH2]2NMe2}

Abstract

Reaction of SiMe₄ or CH₂(SiMe₃)₂ in n-C₆H₁₄ with LiBuⁿ(pmdeta) affords in high yield Li( CH₂SiMe₃)-(pmdeta) or Li{CH(SiMe₃)₂}(pmdeta), (2), respectively, the latter also being available from Li{CH(SiMe₃)₂}-(tmeda), (1), and pmdeta; crystalline compound (1) and (2) are monomers (Ebullioscopy, C₆H₁₂), and for (2) this is also shown by X-ray crystallography, with the short Li–C distance [2.13(5)Å] indicative of a covalent bond.