(Aminomethyl)lithium compds., LiCH2NRR'.xTHF [NRR' = NMe2 (1a, x = 0), NPhMe (1b, x = 2), NPh2 (1c, x = 1.5), NC5H10 (1d, x = 0, NC5H10 = piperidino), and NC7H14 (1e, NC7H14 = 2,6-dimethylpiperidino)] were prepd. by the reaction of Bu3SnCH2NRR' with BuLi. 1A-d were isolated in solid state and characterized by NMR spectroscopy (1H, 13C, 7Li). 1E was obtained in soln. and characterized via reaction with MeOH and with benzophenone to generate MeNC7H14 and Ph2C(OH)CH2NC7H14, resp. Recrystn. of 1c and 1d from n-hexane/THF gives [Li2(CH2NPh2)2(THF)3] (1c') and [Li4(CH2NC5H10)4(THF)2] (1d'), resp., whose structures (x-ray) were detd. The dimeric compd. 1c' forms a central planar four-membered Li2C2 ring. One Li atom is four-coordinated to two methylene C atoms (d(Li-C) = 2.246(9), 2.235(9) A) and two O atoms of THF. Unusually, the 2nd Li exhibits a nearly planar coordination sphere represented by two methylene C atoms (d(Li-C) = 2.17(1) and 2.16(1) A) and by the O atom of the disordered THF mol. 1d' is a tetrameric species exhibiting a mol. C2 symmetry. The Li atoms are arranged in a distorted tetrahedron with methylene C atoms occupying each face of the tetrahedron.