[LI-4(CH2NME2)(4)(THF)(4)] - AN UNUSUAL TETRAMERIC BUT NOT TETRAHEDRAL SIGMA-ORGANOLITHIUM COMPOUND

Recrystallization of unsolvated LiCH2NMe2 (1) from n-hexane\THF\diethy l ether gave [Li-4(CH2NMe2)(4)(THF)(4)] (2), which lost THF easily in vacuo to regenerate compound 1. In the solid state, 2 is tetrameric (C -i symmetry). There are two different (N,N-dimethylamino)methyl ligand s with a 1,2 kappa C:3 kappa N and 1,3 kappa-C:1 kappa N coordination, respectively. Two Lithium centers are pentacoordinated by Li, N and t hree C atoms, and the other two adopt tetrahedral coordination, define d by C, N, and two O atoms. The structure of 2 can be understood as th at of an opened Li-4 tetrahedron.