Some interesting structural chemistry of lithium

The lithium salt of α-carboline, Li carb, (for which the systematic name is 1H-pyrido[2,3-b]indole), has been prepared and crystallized from both tetrahydrofuran and toluene. In each case the molecule is tetranuclear, with a distorted tetrahedron of lithium atoms, and in each case, the ligands are arranged in a Li4(carb)4 assembly having S4 point symmetry. In the compound crystallized from tetrahydrofuran, each lithium atom is coordinated by three nitrogen atoms and an oxygen atom, whereas in the compound obtained from toluene each lithium atom is only three-coordinate. The structures are topologically the same, but differ in the spatial orientations of the carboline planes.