CRYSTAL AND MOLECULAR STUDIES OF SUCCINIMIDE-LITHIUM SALT COMPLEXES

We discovered a new class of succinimide-lithium complexes with highly symmetric tetrahedral geometry that can accommodate a variety of anions. Of the seven succinimide-lithium salt complexes prepared and examined by solution- and solid-state complexation methods, three crystal structures are reported. The present results show that lithium ions strongly coordinate carbonyls of succinimide molecules. In the crystal structures of (succinimide)2LiNO3 (3), (Succinimide)2LiI (4), and (succinimide)2LiPF6 (7), the lithium ion is tetrahedrally coordinated by four carbonyls of four succinimide molecules. The anion in each structure takes part in an ion-dipole interaction with the imide N-H hydrogen atom. Other lithium salts, such as LiBF4, LiClO4, LiBr, and LiCl, are crystallographically isomorphous to (succinimide)2LiI and (succinimide)2LiPF6, differing slightly in the unit-cell dimensions. (Succinimide)2LiNO3, however, crystallizes in a lower symmetry group because the nitrate group is not spherelike but disk shaped. The X-ray crystal structures of three succinimide-lithium salt complexes [(succinimide)2LiX, X = I-, NO3-, PF6-] are examined to show how the molecular volumes and shapes of these anions affect lithium-imide complexation in the solid state.