7Li solid-state NMR spectroscopic study of cyclopentadienyllithium complexes

Eighteen cyclopentadienyllithium complexes were studied by solid-state Li-7 NMR spectroscopy. It is shown that the chemical shift gives information on the type of complex, i.e. whether the complex is a contact ion pair, a solvent-separated ion pair, a sandwich structure or a polymeric material. These shift differences are due to the ring current of the aromatic anion. In order to obtain information about the solvation of the lithium cation, the quadrupolar coupling constant chi has to be determined. The chi value depends on the number and type of donor atoms in the ligand, where the nitrogen-containing ligands give rise to higher chi values than the oxygen analogues. (C) 1998 John Wiley & Sons, Ltd.