Some interesting structural chemistry of lithium

The lithium salt of alpha-carboline, Li carb, (for which the systematic nam e is 1H-pyrido[2,3-b]indole), has been prepared and crystallized from both tetrahydrofuran and toluene. In each case the molecule is tetranuclear, wit h a distorted tetrahedron of lithium atoms, and in each case, the ligands a re arranged in a Li-4(carb)(4) assembly having S-4 point symmetry. In the c ompound crystallized from tetrahydrofuran, each lithium atom is coordinated by three nitrogen atoms and an oxygen atom, whereas in the compound obtain ed from toluene each lithium atom is only three-coordinate. The structures are topologically the same, but differ in the spatial orientations of the c arboline planes. (C) 2000 Elsevier Science S.A. All rights reserved.